Background and Objective:In recent years,a number of studies focused on the choroidal venous outflow have improved our understanding of the nature of the pachychoroid spectrum disorders(PSD)and highlighted the role of...Background and Objective:In recent years,a number of studies focused on the choroidal venous outflow have improved our understanding of the nature of the pachychoroid spectrum disorders(PSD)and highlighted the role of the intervortex venous anastomoses(IVA)as a basic characteristic of vascular remodeling of the choroid.However,the imaging data,quantitative and qualitative characteristics of IVA,as well as their relationship with other choroidal parameters,have not been systematically reviewed and summarized.The objective of this review was to summarize data on the prevalence and pathophysiological role of IVA and associated vascular changes of the choroid.Methods:This was a narrative review of available literature from databases published in English before March 2025.We analyze the results of studies reporting the status of IVA and associated vascular remodeling of the choroid in healthy eyes and eyes with various retinochoroidal disorders.Key Content and Findings:We highlight imaging techniques that have been used to display the IVA in the clinical and experimental settings including indocyanine green angiography(ICGA)and en face optical coherence tomography(OCT).We report on the prevalence of IVA in healthy eyes and eyes with various retinochoroidal disorders and indicate the potential role of the sclera in the impairment of choroidal venous outflow leading to activation of the IVA.We summarize the association of IVA with a number of abnormal characteristics of the choroid including choroidal hyperpermeability and thickening,asymmetry of the running pattern of choroidal vessels,and choroidal thickness,increased diameter of large vessels,as well as the increase of choroidal vascularity.Conclusions:IVA represent one of the few biomarkers reflecting the deep pathophysiological mechanisms of PSD,closely linked to choroidal vascular remodeling.En face OCT can provide comprehensive,clinically relevant data on this biomarker.However,further standardization is required in defining,imaging,and quantifying IVA.展开更多
Since the introduction of stapling instruments in the 1970s various studies have compared the results of sutured and stapled bowel anastomoses. A literature search was performed from 1960 to 2010 and articles relating...Since the introduction of stapling instruments in the 1970s various studies have compared the results of sutured and stapled bowel anastomoses. A literature search was performed from 1960 to 2010 and articles relating to small bowel, colonic and colorectal anastomotic techniques were reviewed. References from these articles were also reviewed, and relevant articles obtained. Either a stapled or sutured gastrointestinal tract anastomosis is acceptable in most situations. The available evidence suggests that in the following situations, however, particular anastomotic techniques may result in fewer complications: A stapled side-to-side ileocolic anastomosis is preferable following a right hemicolectomy for cancer. A stapled side-to-side anastomosis is likely also preferable after an ileocolic resection for Crohn’s disease. Colorectal anastomoses can be sutured or stapled with similar results, although the incidence of strictures is higher following stapled anastomoses. Following reversal of loop ileostomy there is some evidence to suggest that a stapled side-to-side anastomosis or sutured enterotomy closure (rather than spout resection and sutured anastomosis) results in fewer complications. Non-randomised data has indicated that small bowel anastomoses are best sutured in the trauma patient. This article reviews the theory, practice and evidence base behind the various gastrointestinal anastomoses to help the practising general surgeon make evidence based operative decisions.展开更多
Endoscopic management for difficult common bile duct(CBD)stones still presents a challenge for several reasons,including anatomic anomalies,patients’individual conditions and stone features.In recent years,variable m...Endoscopic management for difficult common bile duct(CBD)stones still presents a challenge for several reasons,including anatomic anomalies,patients’individual conditions and stone features.In recent years,variable methods have emerged that have attributed to higher stone removal success rates,reduced cost and lower adverse events.In this review,we outline a stepwise approach in CBD stone management.As first line therapy,endoscopic sphincterotomy and large balloon dilation are recommended,due to a 30%-50%reduction of the use of mechanical lithotripsy.On the other hand,cholangioscopy-assisted lithotripsy has been increasingly reported as an effective and safe alternative technique to mechanical lithotripsy but remains to be reserved in special settings due to limited large-scale evidence.As discussed,findings suggest that management needs to be tailored to the patient’s characteristics and anatomical conditions.Furthermore,we evaluate the management of CBD stones in various surgical altered anatomy(Billroth II,Roux-en-Y and Roux-en-Y gastric bypass).Moreover,we could conclude that cholangioscopy-assisted lithotripsy needs to be evaluated for primary use,rather than following a failed management option.In addition,we discuss the importance of dissecting other techniques,such as the primary use of interventional endoscopic ultrasound for the management of CBD stones when other techniques have failed.In conclusion,we recognize that endoscopic sphincterotomy and large balloon dilation,mechanical lithotripsy and intraductal lithotripsy substantiate an indication to the management of difficult CBD stones,but emerging techniques are in rapid evolution with encouraging results.展开更多
The development of intestinal anastomosis techniques,including hand suturing,stapling,and compression anastomoses,has been a significant advancement in surgical practice.These methods aim to prevent leakage and minimi...The development of intestinal anastomosis techniques,including hand suturing,stapling,and compression anastomoses,has been a significant advancement in surgical practice.These methods aim to prevent leakage and minimize tissue fibrosis,which can lead to stricture formation.The healing process involves various phases:hemostasis and inflammation,proliferation,and remodeling.Mechanical staplers and sutures can cause inflammation and fibrosis due to the release of profibrotic chemokines.Compression anastomosis devices,including those made of nickel-titanium alloy,offer a minimally invasive option for various surgical challenges and have shown safety and efficacy.However,despite advancements,anastomotic techniques are evaluated based on leakage risk,with complications being a primary concern.Newer devices like Magnamosis use magnetic rings for compression anastomosis,demonstrating greater strength and patency compared to stapling.Magnetic technology is also being explored for other medical treatments.While there are promising results,particularly in animal models,the realworld application in humans is limited,and further research is needed to assess their safety and practicality.展开更多
BACKGROUND Portal vein arterialization(PVA)has been used in liver transplantation(LT)to maximize oxygen delivery when arterial circulation is compromised or has been used as an alternative reperfusion technique for co...BACKGROUND Portal vein arterialization(PVA)has been used in liver transplantation(LT)to maximize oxygen delivery when arterial circulation is compromised or has been used as an alternative reperfusion technique for complex portal vein thrombosis(PVT).The effect of PVA on portal perfusion and primary graft dysfunction(PGD)has not been assessed.All patients receiving PVA and LT at the Fundacion Santa Fe de Bogota between 2011 and 2022 were analyzed.To account for the time-sensitive effects of graft perfusion,patients were classified into two groups:prereperfusion(pre-PVA),if the arterioportal anastomosis was performed before graft revascularization,and postreperfusion(post-PVA),if PVA was performed afterward.The pre-PVA rationale contemplated poor portal hemodynamics,severe vascular steal,or PVT.Post-PVA was considered if graft hypoperfusion became evident.Conservative interventions were attempted before PVA.展开更多
Exogenous gene suture was used to achieve peripheral nerve anastomoses to probe into the feasibility that the sites of anastomoses of nerves directly transfer gene and thus enable gene to be expressed at the sites of...Exogenous gene suture was used to achieve peripheral nerve anastomoses to probe into the feasibility that the sites of anastomoses of nerves directly transfer gene and thus enable gene to be expressed at the sites of anastomoses under the condition that perfect nerve anastomoses are ensured. PCMVβ plasmid containing cytomegalovirus promoter (CMV promoter) and Escherichia coli (E.coli) β Galactosidase (β Gal) structural gene (lacZ gene) was conducted. A soaked medical 8 0nylon suture was used to perform epineurial repair of rabbit sciatic nerve. In the control group a suture soaked in sucrose PBS was used, while in the experimental group a suture soaked in PCMVβ plasmid solution was applied. The sites of anastomoses of nerves by stages were taken out, and β Gal histochemical staining was performed and β Gal enzyme activity was assayed with 5 bromo 4 chloro 3 indolyl β D galactoside. Results showed that the sites of anastomoses of nerves were taken out 2 days, 7 days, 14 days and 30 days respectively after the operation. The β Gal histochemical stains at the sites of anastomoses showed no indigo positive cells at different stages in the control group, whereas displayed indigo positive cells in the experimental group. In the control group, no β Gal enzyme activity was detected at different stages after operation, but in the experimental group, β Gal enzyme activity could be detected from the 3rd day to the 30th day after operation. It was concluded that by using exogenous gene suture, exogenous gene could be transferred to the sites of peripheral nerve and expressed the exogenous gene expression products with bioactivity, which provided the feasibility of using gene therapy to accelerate the recovery of nerve function.展开更多
The collateral circulation is crucial for the pathophysiology and outcome of acute cortical ischemia.Current understanding of collateral circulation still remains sparse,largely due to prior limitations of spatial or/...The collateral circulation is crucial for the pathophysiology and outcome of acute cortical ischemia.Current understanding of collateral circulation still remains sparse,largely due to prior limitations of spatial or/and temporal resolution in methods to evaluate these diminutive redistributive routes of cerebral blood flow(CBF)especially in leptomeningeal anastomoses that connected cortical arteries.In the study,based on a mini-stroke model,laser speckle imaging with high spatiotemporal resolution was used to assess the dynamic evolution of the collateral circulation around a mini-ischemia in the rat cortex.We found that the blood flow and diameter in the intra-arterial anastomoses were enhanced immediately after the ligation of one branch of middle cerebral artery and recovered to baseline level as arterial recirculation was performed.Whereas the communicative flow-through of the posterior cerebral artery and the middle cerebral artery anastomoses was not significant enough to be determined.This is the evidence that intra-arterial anastomoses were the primary routes to restore blood flow into the ischemic territory during the acute phase of ischemia,and laser speckle imaging method was proven as a powerful tool to be potential for subserving further investigation of the collateral circulation.展开更多
We comment on a study titled“Feasibility and safety of"bridging"pancreaticogastrostomy for pancreatic trauma in Landrace pigs”in which ten pigs were randomized to either experimental“bridging”pancreatico...We comment on a study titled“Feasibility and safety of"bridging"pancreaticogastrostomy for pancreatic trauma in Landrace pigs”in which ten pigs were randomized to either experimental“bridging”pancreaticogastrostomy(PG)or a control group with a routine mucosa-to-mucosa PG.At six months anastomoses had strictured and closed in both groups.The authors concluded that“bridging”PG is feasible and safe in damage control surgery during the early stage of pancreatic injury.In this letter we comment on the study design,specifically leaving a 2 cm gap between the pancreatic stump and the stomach and highlight the complexity of performing pancreatic anastomoses following trauma pancreaticoduodenectomy as to our experience in a high volume trauma centre.Our data emphasize that pancreatic anastomoses in trauma are complex procedures with significant postoperative morbidity and are best managed collaboratively by trauma and hepatopancreaticobiliary surgical teams with the required technical skills.展开更多
The CycloneTM System (Castlewood Surgical, Inc., Concord, MA) is a novel device that facilitates the attachment of the saphenous vein onto the ascending aorta for the purpose of creating a bypass graft during a corona...The CycloneTM System (Castlewood Surgical, Inc., Concord, MA) is a novel device that facilitates the attachment of the saphenous vein onto the ascending aorta for the purpose of creating a bypass graft during a coronary artery bypass grafting (CABG) operation. It allows the surgeon to perform a hand-sewn anastomosis with no disruption of the intima of the aorta, and no need for partial clamping. During a 36-month period 109 CABG operations were performed, and the CycloneTM System (and its predecessor, the HexalonTM) was utilized to create 138 proximal anastomoses. This study demonstrates that this is a safe and effective method of creating a clampless, no-touch proximal anastomoses during off-pump CABG.展开更多
The 270 km long section of the Upper Yellow River at the First Great Bend is comprised of single channel and multiple channel systems that alternate among anastomosing, anabranching, meandering and braided reaches. Th...The 270 km long section of the Upper Yellow River at the First Great Bend is comprised of single channel and multiple channel systems that alternate among anastomosing, anabranching, meandering and braided reaches. The sequence of downstream pattern changes is characterized as： anastomosing-anabranching, anabranching-meandering, meandering-braided and braided-meandering. Remote sensing images, DEM data and field investigations are used to assess ahd interpret controls on these reach transitions. Channel slope and bed sediment size are key determinants of transitions in channel planform. Anas- tomosing reaches have a relatively high bed slope （0.86‰） and coarser sediment bed material （d50 = 3.5 mm）. In contrast, meandering reaches have a low slope （0.30‰） and fine sediment bed material （d50 = 0.036 mm）. The transition from a meandering to braided pattern is characterized by an increase in channel width-depth ratio, indicating the important role of bank strength （i.e. cohesive versus non-cohesive versus channel boundaries）. Interestingly, the braided-meandering and meandering-braided transitions are coincident with variable flow inputs from tributary rivers （Baihe and Heihe rivers respectively）. Theoretical analysis of the meandering-braided transition highlights the key control of channel width-depth ratio as a determinant of channel planform.展开更多
BACKGROUND Anastomosing hemangioma(AH)is a rare subtype of benign hemangioma that is most commonly found in the genitourinary tract.Due to the lack of specific clinical and radiologic manifestations,it is easily misdi...BACKGROUND Anastomosing hemangioma(AH)is a rare subtype of benign hemangioma that is most commonly found in the genitourinary tract.Due to the lack of specific clinical and radiologic manifestations,it is easily misdiagnosed preoperatively.Here,we report a case of AH arising from the left renal vein that was discovered incidentally and confirmed pathologically,and then describe its imaging characteristics from a radiologic point of view and review its clinicopathologic features and treatment.CASE SUMMARY A 74-year-old woman was admitted to our department for a left retroperitoneal neoplasm measuring 2.6 cm×2.0 cm.Her laboratory data showed no significant abnormalities.A non-contrast-enhanced computed tomography(CT)scan showed a heterogeneous density in the neoplasm.Non-contrast-enhanced magnetic resonance imaging(MRI)revealed a heterogeneous hypointensity on T1-weighed images and a heterogeneous hyperintensity on T2-weighed images.On contrastenhanced CT and MRI scans,the neoplasm presented marked septal enhancement in the arterial phase and persistent enhancement in the portal phase,and its boundary with the left renal vein was ill-defined.Based on these clinical and radiological manifestations,the neoplasm was initially considered to be a neurogenic neoplasm in the left retroperitoneum.Finally,the neoplasm was completely resected and pathologically diagnosed as AH.CONCLUSION AH is an uncommon benign hemangioma.Preoperative misdiagnoses are common not only because of a lack of specific clinical and radiologic manifestations but also because clinicians lack vigilance and diagnostic experience in identifying AH.AH is not exclusive to the urogenital parenchyma.We report the first case of this neoplasm in the left renal vein.Recognition of this entity in the left renal vein can be helpful in its diagnosis and distinction from other neoplasms.展开更多
Although anastomosing fluvial rivers are given much attention recently by some research workers because the result channel sandstone of which is one typical primary reservoirs of petroleum and natural gas, of which th...Although anastomosing fluvial rivers are given much attention recently by some research workers because the result channel sandstone of which is one typical primary reservoirs of petroleum and natural gas, of which the flood plains and the interchannel wetlands are pay zones where coals had formed, the comprehension of anastomosing river is some extent limited at present. Some researchers regard that the anastomosing river river and the anabranched river are the same kind of rivers. In this paper, the sedimentary, geomorphic and hydraulic characteristics and the main controlling factors of anastomosing fluvial system are summarized systematically. Some of the characteristics are compared with others fluvial rivers. Humid climate is suitable to form anastomosing channel systems, in arid semiarid regions anastomosing river maybe develop if many befitting factors combine together. The authors of the paper think that anastomosing river is one typical channel pattern and is dissimilar to anabranched channel pattern.展开更多
Both interchannel wetlands and multi-channels are crucial geomorphologic units in an anastomosing river system.Planform characteristics and development of interchannel wetlands and multi-channels control the character...Both interchannel wetlands and multi-channels are crucial geomorphologic units in an anastomosing river system.Planform characteristics and development of interchannel wetlands and multi-channels control the characteristics of anastomosing rivers.To under-stand the role that interchannel wetlands play in the development of anastomosing rivers,a study was conducted on the Maqu Reach of the Upper Yellow River(MRUYR),a gravel-bed anastomosing river characterized by highly developed interchannel wetlands and ana-branches.Geomorphologic units in the studied reach were extracted from high resolution satellite imagery in Google Earth.The size distributions of interchannel wetlands and inter-channel wetland clusters(IWCs),a special combination of interchannel wetlands and ana-branches,were investigated.Geomorphologic parameters,including the ratio of interchannel wetland area to IWC area(P),shoreline density(DL),and node density(Dn)were used to analyze planform characteristics of IWCs and the development of multi-channels in the stud-ied reach.The results suggest that small or middle sized interchannel wetlands and large or mega sized IWCs are more common at the study site.The area of IWC(Su)is highly cor-related with other geomorphologic parameters.P increases with increasing Su,and the upper limit is about 80%,which indicates that the development of interchannel wetlands and ana-branches in the IWC is in the equilibrium stage.In contrast,D~and D,show a tendency to decrease with increasing Su due to diverse evolution processes in IWCs with different sizes.There are three main reasons leading to the formation of IWCs:varying stream power due to the meandering principal channel;development of the river corridor due to the weakening of geologic structure control;and high stability of interchannel wetlands due to conservation by shoreline vegetation.展开更多
Primary vascular tumours of the kidney are rare and may pose diagnostic difficulties because of their similar clinical,morphological,and immunohistochemical features.This article summarizes the clinical and pathologic...Primary vascular tumours of the kidney are rare and may pose diagnostic difficulties because of their similar clinical,morphological,and immunohistochemical features.This article summarizes the clinical and pathological features of primary renal angiosarcoma and anastomosing haemangioma of the kidney including epidemiology,genetics,and prognosis.Renal anastomosing haemangiomas are benign neoplasms characterized by anastomosing capillary-sized vascular channels.These tumours are rare,with about 75 cases reported in the literature.Most anastomosing haemangiomas are found incidentally on ultrasound,computed tomography,or magnetic resonance imaging.Common symptoms include abdominal pain,haematuria,and abdominal mass.Renal anastomosing haemangiomas are characterized by recurrent mutations in GNAQ and GNA14 genes.The prognosis of anastomosing haemangioma is excellent.Primary renal angiosarcomas are malignant tumours showing endothelial differentiation.To date,76 cases have been described in the literature.Primary renal angiosarcomas are frequently symptomatic.The clinical features of renal angiosarcomas are similar to those of renal anastomosing haemangiomas,including abdominal pain,haematuria,and abdominal mass.Angiogenesis-related genes and vascular-specific receptor tyrosine kinases such as KDR,TIE1,SNRK,TEK,and FLT1 are upregulated in angiosarcomas.Primary renal angiosarcomas are highly aggressive neoplasms with a poor prognosis despite surgical treatment,chemotherapy,radiotherapy,or targeted therapy.展开更多
Mid-Cretaceous strata within the Tintina Trench, 3 km west of the community of Ross River, contain evidence of deposition in two distinct, alternating, fluvial settings. Coal-bearing, mud-dominated strata are commonly...Mid-Cretaceous strata within the Tintina Trench, 3 km west of the community of Ross River, contain evidence of deposition in two distinct, alternating, fluvial settings. Coal-bearing, mud-dominated strata are commonly associated with high-constructive sandy channel systems, with extensive overbank, levee and splay deposits. Channels are between 3 and 30 m wide and 0.4-7 m thick. They show repetitive development of side and in-channel bar-forms, as well as up-channel widening of the rivers by selective erosion of associated overbank and levee deposits. Levees extended for several hundred metres away from the channels. In this setting low-angle inclined stratification and epsilon cross stratification may reflect lateral migration of crevasse channels or small streams. The paucity of exposure prevents recognition of the channels as products of multiple channel anastomosed systems or single channel high-constructive systems. Gravel-dominated strata, inter-bedded with, and overlying coal-bearing units, are interpreted as deposits of wandering gravel-bed rivers, with sinuosity approaching 1.4. In most exposures they appear to be dominated by massive and thin planar-bedded granule to small pebble conglomerates, which would traditionally be interpreted as sheet-flood or longitudinal bar deposits of a high-gradient braided stream or alluvial fan. Architectural analysis of exposures in an open-pit shows that the predominance of flat bedding is an artefact of the geometry of the roadside exposures. In the pit the conglomerates are dominated by large scale cross stratification on a scale of 1-5.5 m. These appear to have developed as downstream and lateral accretion elements on side-bars and on in-channel bars in water depths of 2-12 m. Stacking of strata on domed 3rd order surfaces suggests development of longitudinal in-channel bar complexes similar to those observed in parts of the modern Rhone River system. Mudstone preserved in some of the channels reflects intervals of channel abandonment or avulsion. Minimum channel width is from 70 to 450 m.展开更多
BACKGROUND Renal anastomosing hemangioma(AH)is a rare benign vascular tumor characterized by unique histopathological features.CASE SUMMARY We report a highly unusual case of renal AH.A male patient had undergone part...BACKGROUND Renal anastomosing hemangioma(AH)is a rare benign vascular tumor characterized by unique histopathological features.CASE SUMMARY We report a highly unusual case of renal AH.A male patient had undergone partial nephrectomy for clear cell carcinoma of the kidney four years prior.A follow-up computed tomography scan in the third postoperative year revealed a new mass near the surgical site on the same side of the kidney,raising suspicions of tumor recurrence.However,the characteristics on contrast-enhanced magnetic resonance imaging and ultrasonography were more consistent with those of a benign lesion.The patient strongly insisted on undergoing surgery due to concerns about the possibility of renal cancer recurrence.Postoperative pathology confirmed the diagnosis of renal AH.CONCLUSION This case report presents the imaging features of a patient with rare renal AH and a history of renal clear cell carcinoma,providing broader insights into the differential diagnosis of new lesions after surgery for renal cell carcinoma.展开更多
The anastomosing river that is present within the First Great Bend of the Yellow River is different from other sand-bedded rivers of this type because it contains gravel-bedded materials. It is therefore important to ...The anastomosing river that is present within the First Great Bend of the Yellow River is different from other sand-bedded rivers of this type because it contains gravel-bedded materials. It is therefore important to determine whether, or not, the specific characteristics of this anastomosing river are similar to those seen in sand-bedded forms, including the characteristics of erosion and deposition, and the stability of channel and interchannel wetlands. Four Landsat images from 1990, 2001, 2013, and 2016 alongside two Google Earth(GE) images from 2011 and 2013 were utilized in this study in tandem with field sampling and observations to select a 12 km main channel length section of the Qihama reach anastomosing river. This section was then used to determine variations in channel planform and sedimentary characteristics over a 26 year period. The results of this study show that this gravel-bedded anastomosing river has exhibited a high degree of stability overall, and that there has been no obvious channel and wetland bank erosion and deposition. Data also show that over the 26 years of this study, anastomosing belt area increased by 2.43%, while the ratio of land to water area remained almost equal. The number of wetlands has also increased along this river section at a rate as high as 62.16% because of the fragmentation of some small interchannel examples, while the talweg has alternately migrated to either the left or right over long periods of time at a relatively stable rate. Indeed, as a result of the migration of this line, there has been significant turnover in the number of islands within the main channel while bank shift has occurred at a rate of about 5 m/yr. The numerous anastomosing channels within this river section remained very stable over the course of this study, characterized by a mean annual migration rate of just 1 m/yr, while the sediments in bank columnar sections are mainly composed of fine sands or silts with a relatively high clay content. The sediment grain-size distribution curve for this river section contains multiple peaks, distinct from the muddy sediments within bank columnar sections from sand-bedded anastomosing rivers. The dense vegetation within riparian and interchannel wetlands alongside this river reach has also protected anastomosing channels from erosion and maintainedtheir stability, a key feature of this gravel-bedded system.展开更多
The Laramie River after flowing in a north direction through southeast Wyoming’s Laramie Basin abruptly turns in an east direction to flow across the north-to-south oriented Laramie Range in a bedrock-walled canyon a...The Laramie River after flowing in a north direction through southeast Wyoming’s Laramie Basin abruptly turns in an east direction to flow across the north-to-south oriented Laramie Range in a bedrock-walled canyon and eventually reaches the lower elevation Great Plains and southeast-oriented North Platte River. The North Laramie River, Bluegrass Creek, and North Sybille/Sybille Creek also flow from the Laramie Basin in separate bedrock-walled valleys into the Laramie Range before eventually joining the Laramie River. Bedrock-walled through valleys link the various Laramie Range stream and river crossing valleys and detailed topographic maps were used to determine how this anastomosing bedrock-walled canyon complex and the large escarpment-surrounded Goshen Hole basin (located just to the east of the anastomosing canyon complex) originated. Map evidence shows multiple streams of water must have diverged in the Laramie Basin from the north-oriented Laramie River to enter the Laramie Range before converging in or east of the Laramie Range and also shows how present day through valleys enabled diverging and converging streams of water to cross the Laramie Range. The anastomosing bedrock-walled valley complex studied here extends from north of the North Laramie River valley to south of the North Sybille/Sybille Creek valley. Large volumes of water flowing from the Laramie Basin to the Great Plains are interpreted to have eroded the anastomosing canyon complex and the “downstream” Goshen Hole escarpment-surrounded basin. Headward erosion of the north-oriented Sybille and Chugwater Creek valleys across large sheets of east-oriented water are interpreted to have left the Goshen Hole escarpment-surrounded basin as a large abandoned headcut. A water source was not determined, although a continental ice sheet that deeply eroded and warped the North American continent is considered to be a possible source.展开更多
Detailed topographic maps of drainage divides surrounding the Jefferson County, Montana, Boulder River drainage basin were analyzed to determine the nature of drainage systems that preceded today’s Boulder River drai...Detailed topographic maps of drainage divides surrounding the Jefferson County, Montana, Boulder River drainage basin were analyzed to determine the nature of drainage systems that preceded today’s Boulder River drainage system and how the Boulder River drainage system evolved from those earlier drainage systems. The Boulder River studied here drains in a north, east, and south direction to the Jefferson River, which at Three Forks, Montana joins the north-oriented Madison and Gallatin Rivers to form the north-oriented Missouri River. The North American east-west Continental Divide surrounds the Boulder River drainage basin western half and mountainous drainage divides with the Jefferson and Missouri Rivers surround the drainage basin’s eastern half. More than 25 deep mountain passes are notched into these drainage divides and provide evidence of the regional drainage system that preceded the present day Boulder River drainage system. Analysis of pass elevations and of orientations of valleys leading in opposite directions from those mountain passes shows that prior to Boulder River drainage system development immense volumes of south-oriented water moving in anastomosing complexes of diverging and converging channels flowed across the Boulder River drainage basin area and that the Boulder River drainage system evolved as deeper channels progressively captured flow from shallower channels. While not documented in detail crustal warping probably raised Boulder River drainage basin areas relative to adjacent valleys and basins as capture events took place. A water source was not determined, but may have been from a large North American continental ice sheet, although Boulder River drainage basin evolution probably occurred while mid Tertiary sediments were filling adjacent valleys and basins.展开更多
Drainage divides along a southern Laramie Range crest area and in the nearby southeast Wyoming Gangplank area (as observed on detailed topographic maps) suggest present-day drainage routes in the Cheyenne Tablelands r...Drainage divides along a southern Laramie Range crest area and in the nearby southeast Wyoming Gangplank area (as observed on detailed topographic maps) suggest present-day drainage routes in the Cheyenne Tablelands region originated as headward erosion of south-oriented valleys (now the downstream Lodgepole, Crow, and Lone Tree Creek valleys) from an actively eroding northeast-oriented South Platte River valley captured flood flow in the south half of a large east-oriented anastomosing channel complex while headward erosion of a north-oriented valley (now the downstream Horse Creek valley) from the southeast-oriented North Platte River valley captured the north half of the same large anastomosing channel complex. The Gangplank, which today serves as a low gradient ramp of Tertiary Ogallala Formation sediments leading from the Great Plains to the Laramie Range erosion surface, is located along the Crow Creek-Lone Tree Creek drainage divide and low points along that divide (referred to here as divide crossings) suggest, prior to headward erosion of what is now its south-oriented downstream Lone Tree Creek valley, upstream east-oriented Lone Tree Creek drainage routes were intertwined with east-oriented Crow Creek drainage routes, which today flow much further in an east direction (than east-oriented upstream Lone Tree Creek drainage routes) before also turning in a south direction to reach the South Platte River. The ability of the commonly accepted regional geomorphology paradigm to explain this topographic map evidence is then compared with a fundamentally different and new regional geomorphology paradigm’s ability to explain the same evidence. While both paradigms offer possible explanations the new paradigm, which requires headward erosion of the valleys to have occurred as massive continental ice sheet melt water floods crossed the region, explains much more of the drainage system evidence and also permits much more detailed explanations.展开更多
文摘Background and Objective:In recent years,a number of studies focused on the choroidal venous outflow have improved our understanding of the nature of the pachychoroid spectrum disorders(PSD)and highlighted the role of the intervortex venous anastomoses(IVA)as a basic characteristic of vascular remodeling of the choroid.However,the imaging data,quantitative and qualitative characteristics of IVA,as well as their relationship with other choroidal parameters,have not been systematically reviewed and summarized.The objective of this review was to summarize data on the prevalence and pathophysiological role of IVA and associated vascular changes of the choroid.Methods:This was a narrative review of available literature from databases published in English before March 2025.We analyze the results of studies reporting the status of IVA and associated vascular remodeling of the choroid in healthy eyes and eyes with various retinochoroidal disorders.Key Content and Findings:We highlight imaging techniques that have been used to display the IVA in the clinical and experimental settings including indocyanine green angiography(ICGA)and en face optical coherence tomography(OCT).We report on the prevalence of IVA in healthy eyes and eyes with various retinochoroidal disorders and indicate the potential role of the sclera in the impairment of choroidal venous outflow leading to activation of the IVA.We summarize the association of IVA with a number of abnormal characteristics of the choroid including choroidal hyperpermeability and thickening,asymmetry of the running pattern of choroidal vessels,and choroidal thickness,increased diameter of large vessels,as well as the increase of choroidal vascularity.Conclusions:IVA represent one of the few biomarkers reflecting the deep pathophysiological mechanisms of PSD,closely linked to choroidal vascular remodeling.En face OCT can provide comprehensive,clinically relevant data on this biomarker.However,further standardization is required in defining,imaging,and quantifying IVA.
文摘Since the introduction of stapling instruments in the 1970s various studies have compared the results of sutured and stapled bowel anastomoses. A literature search was performed from 1960 to 2010 and articles relating to small bowel, colonic and colorectal anastomotic techniques were reviewed. References from these articles were also reviewed, and relevant articles obtained. Either a stapled or sutured gastrointestinal tract anastomosis is acceptable in most situations. The available evidence suggests that in the following situations, however, particular anastomotic techniques may result in fewer complications: A stapled side-to-side ileocolic anastomosis is preferable following a right hemicolectomy for cancer. A stapled side-to-side anastomosis is likely also preferable after an ileocolic resection for Crohn’s disease. Colorectal anastomoses can be sutured or stapled with similar results, although the incidence of strictures is higher following stapled anastomoses. Following reversal of loop ileostomy there is some evidence to suggest that a stapled side-to-side anastomosis or sutured enterotomy closure (rather than spout resection and sutured anastomosis) results in fewer complications. Non-randomised data has indicated that small bowel anastomoses are best sutured in the trauma patient. This article reviews the theory, practice and evidence base behind the various gastrointestinal anastomoses to help the practising general surgeon make evidence based operative decisions.
文摘Endoscopic management for difficult common bile duct(CBD)stones still presents a challenge for several reasons,including anatomic anomalies,patients’individual conditions and stone features.In recent years,variable methods have emerged that have attributed to higher stone removal success rates,reduced cost and lower adverse events.In this review,we outline a stepwise approach in CBD stone management.As first line therapy,endoscopic sphincterotomy and large balloon dilation are recommended,due to a 30%-50%reduction of the use of mechanical lithotripsy.On the other hand,cholangioscopy-assisted lithotripsy has been increasingly reported as an effective and safe alternative technique to mechanical lithotripsy but remains to be reserved in special settings due to limited large-scale evidence.As discussed,findings suggest that management needs to be tailored to the patient’s characteristics and anatomical conditions.Furthermore,we evaluate the management of CBD stones in various surgical altered anatomy(Billroth II,Roux-en-Y and Roux-en-Y gastric bypass).Moreover,we could conclude that cholangioscopy-assisted lithotripsy needs to be evaluated for primary use,rather than following a failed management option.In addition,we discuss the importance of dissecting other techniques,such as the primary use of interventional endoscopic ultrasound for the management of CBD stones when other techniques have failed.In conclusion,we recognize that endoscopic sphincterotomy and large balloon dilation,mechanical lithotripsy and intraductal lithotripsy substantiate an indication to the management of difficult CBD stones,but emerging techniques are in rapid evolution with encouraging results.
文摘The development of intestinal anastomosis techniques,including hand suturing,stapling,and compression anastomoses,has been a significant advancement in surgical practice.These methods aim to prevent leakage and minimize tissue fibrosis,which can lead to stricture formation.The healing process involves various phases:hemostasis and inflammation,proliferation,and remodeling.Mechanical staplers and sutures can cause inflammation and fibrosis due to the release of profibrotic chemokines.Compression anastomosis devices,including those made of nickel-titanium alloy,offer a minimally invasive option for various surgical challenges and have shown safety and efficacy.However,despite advancements,anastomotic techniques are evaluated based on leakage risk,with complications being a primary concern.Newer devices like Magnamosis use magnetic rings for compression anastomosis,demonstrating greater strength and patency compared to stapling.Magnetic technology is also being explored for other medical treatments.While there are promising results,particularly in animal models,the realworld application in humans is limited,and further research is needed to assess their safety and practicality.
文摘BACKGROUND Portal vein arterialization(PVA)has been used in liver transplantation(LT)to maximize oxygen delivery when arterial circulation is compromised or has been used as an alternative reperfusion technique for complex portal vein thrombosis(PVT).The effect of PVA on portal perfusion and primary graft dysfunction(PGD)has not been assessed.All patients receiving PVA and LT at the Fundacion Santa Fe de Bogota between 2011 and 2022 were analyzed.To account for the time-sensitive effects of graft perfusion,patients were classified into two groups:prereperfusion(pre-PVA),if the arterioportal anastomosis was performed before graft revascularization,and postreperfusion(post-PVA),if PVA was performed afterward.The pre-PVA rationale contemplated poor portal hemodynamics,severe vascular steal,or PVT.Post-PVA was considered if graft hypoperfusion became evident.Conservative interventions were attempted before PVA.
基金a grant from the ScientificCommittee of Hebei Province(No.982 76 110 1)
文摘Exogenous gene suture was used to achieve peripheral nerve anastomoses to probe into the feasibility that the sites of anastomoses of nerves directly transfer gene and thus enable gene to be expressed at the sites of anastomoses under the condition that perfect nerve anastomoses are ensured. PCMVβ plasmid containing cytomegalovirus promoter (CMV promoter) and Escherichia coli (E.coli) β Galactosidase (β Gal) structural gene (lacZ gene) was conducted. A soaked medical 8 0nylon suture was used to perform epineurial repair of rabbit sciatic nerve. In the control group a suture soaked in sucrose PBS was used, while in the experimental group a suture soaked in PCMVβ plasmid solution was applied. The sites of anastomoses of nerves by stages were taken out, and β Gal histochemical staining was performed and β Gal enzyme activity was assayed with 5 bromo 4 chloro 3 indolyl β D galactoside. Results showed that the sites of anastomoses of nerves were taken out 2 days, 7 days, 14 days and 30 days respectively after the operation. The β Gal histochemical stains at the sites of anastomoses showed no indigo positive cells at different stages in the control group, whereas displayed indigo positive cells in the experimental group. In the control group, no β Gal enzyme activity was detected at different stages after operation, but in the experimental group, β Gal enzyme activity could be detected from the 3rd day to the 30th day after operation. It was concluded that by using exogenous gene suture, exogenous gene could be transferred to the sites of peripheral nerve and expressed the exogenous gene expression products with bioactivity, which provided the feasibility of using gene therapy to accelerate the recovery of nerve function.
基金supported by the National High Technology Research and Development Program of China(Grant No.2007AA022303)the National Natural Science Foundation of China(Grant No.30500115)+1 种基金the NSFC-FBR International Joint Research Project(Grant No.30711120171)the Program for Changjiang Scholars and Innovative Research Team in University.
文摘The collateral circulation is crucial for the pathophysiology and outcome of acute cortical ischemia.Current understanding of collateral circulation still remains sparse,largely due to prior limitations of spatial or/and temporal resolution in methods to evaluate these diminutive redistributive routes of cerebral blood flow(CBF)especially in leptomeningeal anastomoses that connected cortical arteries.In the study,based on a mini-stroke model,laser speckle imaging with high spatiotemporal resolution was used to assess the dynamic evolution of the collateral circulation around a mini-ischemia in the rat cortex.We found that the blood flow and diameter in the intra-arterial anastomoses were enhanced immediately after the ligation of one branch of middle cerebral artery and recovered to baseline level as arterial recirculation was performed.Whereas the communicative flow-through of the posterior cerebral artery and the middle cerebral artery anastomoses was not significant enough to be determined.This is the evidence that intra-arterial anastomoses were the primary routes to restore blood flow into the ischemic territory during the acute phase of ischemia,and laser speckle imaging method was proven as a powerful tool to be potential for subserving further investigation of the collateral circulation.
文摘We comment on a study titled“Feasibility and safety of"bridging"pancreaticogastrostomy for pancreatic trauma in Landrace pigs”in which ten pigs were randomized to either experimental“bridging”pancreaticogastrostomy(PG)or a control group with a routine mucosa-to-mucosa PG.At six months anastomoses had strictured and closed in both groups.The authors concluded that“bridging”PG is feasible and safe in damage control surgery during the early stage of pancreatic injury.In this letter we comment on the study design,specifically leaving a 2 cm gap between the pancreatic stump and the stomach and highlight the complexity of performing pancreatic anastomoses following trauma pancreaticoduodenectomy as to our experience in a high volume trauma centre.Our data emphasize that pancreatic anastomoses in trauma are complex procedures with significant postoperative morbidity and are best managed collaboratively by trauma and hepatopancreaticobiliary surgical teams with the required technical skills.
文摘The CycloneTM System (Castlewood Surgical, Inc., Concord, MA) is a novel device that facilitates the attachment of the saphenous vein onto the ascending aorta for the purpose of creating a bypass graft during a coronary artery bypass grafting (CABG) operation. It allows the surgeon to perform a hand-sewn anastomosis with no disruption of the intima of the aorta, and no need for partial clamping. During a 36-month period 109 CABG operations were performed, and the CycloneTM System (and its predecessor, the HexalonTM) was utilized to create 138 proximal anastomoses. This study demonstrates that this is a safe and effective method of creating a clampless, no-touch proximal anastomoses during off-pump CABG.
基金International Science ＆ Technology Cooperation Program of China, No.2011DFA20820 No.2011DFG93160+1 种基金 Tsinghua University, No.20121080027 National Natural Science Foundation of China, No.51209010 Acknowledgments We would like to thank Professor Huang Heqing for his helpful guidance in finalizing the paper.
文摘The 270 km long section of the Upper Yellow River at the First Great Bend is comprised of single channel and multiple channel systems that alternate among anastomosing, anabranching, meandering and braided reaches. The sequence of downstream pattern changes is characterized as： anastomosing-anabranching, anabranching-meandering, meandering-braided and braided-meandering. Remote sensing images, DEM data and field investigations are used to assess ahd interpret controls on these reach transitions. Channel slope and bed sediment size are key determinants of transitions in channel planform. Anas- tomosing reaches have a relatively high bed slope （0.86‰） and coarser sediment bed material （d50 = 3.5 mm）. In contrast, meandering reaches have a low slope （0.30‰） and fine sediment bed material （d50 = 0.036 mm）. The transition from a meandering to braided pattern is characterized by an increase in channel width-depth ratio, indicating the important role of bank strength （i.e. cohesive versus non-cohesive versus channel boundaries）. Interestingly, the braided-meandering and meandering-braided transitions are coincident with variable flow inputs from tributary rivers （Baihe and Heihe rivers respectively）. Theoretical analysis of the meandering-braided transition highlights the key control of channel width-depth ratio as a determinant of channel planform.
基金the People’s Livelihood Science and Technology Innovation Project of the Bureau of Science and Technology of Jiaxing City,No.2019AD32201。
文摘BACKGROUND Anastomosing hemangioma(AH)is a rare subtype of benign hemangioma that is most commonly found in the genitourinary tract.Due to the lack of specific clinical and radiologic manifestations,it is easily misdiagnosed preoperatively.Here,we report a case of AH arising from the left renal vein that was discovered incidentally and confirmed pathologically,and then describe its imaging characteristics from a radiologic point of view and review its clinicopathologic features and treatment.CASE SUMMARY A 74-year-old woman was admitted to our department for a left retroperitoneal neoplasm measuring 2.6 cm×2.0 cm.Her laboratory data showed no significant abnormalities.A non-contrast-enhanced computed tomography(CT)scan showed a heterogeneous density in the neoplasm.Non-contrast-enhanced magnetic resonance imaging(MRI)revealed a heterogeneous hypointensity on T1-weighed images and a heterogeneous hyperintensity on T2-weighed images.On contrastenhanced CT and MRI scans,the neoplasm presented marked septal enhancement in the arterial phase and persistent enhancement in the portal phase,and its boundary with the left renal vein was ill-defined.Based on these clinical and radiological manifestations,the neoplasm was initially considered to be a neurogenic neoplasm in the left retroperitoneum.Finally,the neoplasm was completely resected and pathologically diagnosed as AH.CONCLUSION AH is an uncommon benign hemangioma.Preoperative misdiagnoses are common not only because of a lack of specific clinical and radiologic manifestations but also because clinicians lack vigilance and diagnostic experience in identifying AH.AH is not exclusive to the urogenital parenchyma.We report the first case of this neoplasm in the left renal vein.Recognition of this entity in the left renal vein can be helpful in its diagnosis and distinction from other neoplasms.
文摘Although anastomosing fluvial rivers are given much attention recently by some research workers because the result channel sandstone of which is one typical primary reservoirs of petroleum and natural gas, of which the flood plains and the interchannel wetlands are pay zones where coals had formed, the comprehension of anastomosing river is some extent limited at present. Some researchers regard that the anastomosing river river and the anabranched river are the same kind of rivers. In this paper, the sedimentary, geomorphic and hydraulic characteristics and the main controlling factors of anastomosing fluvial system are summarized systematically. Some of the characteristics are compared with others fluvial rivers. Humid climate is suitable to form anastomosing channel systems, in arid semiarid regions anastomosing river maybe develop if many befitting factors combine together. The authors of the paper think that anastomosing river is one typical channel pattern and is dissimilar to anabranched channel pattern.
基金National Natural Science Foundation of China,No.41571005,No.41271027
文摘Both interchannel wetlands and multi-channels are crucial geomorphologic units in an anastomosing river system.Planform characteristics and development of interchannel wetlands and multi-channels control the characteristics of anastomosing rivers.To under-stand the role that interchannel wetlands play in the development of anastomosing rivers,a study was conducted on the Maqu Reach of the Upper Yellow River(MRUYR),a gravel-bed anastomosing river characterized by highly developed interchannel wetlands and ana-branches.Geomorphologic units in the studied reach were extracted from high resolution satellite imagery in Google Earth.The size distributions of interchannel wetlands and inter-channel wetland clusters(IWCs),a special combination of interchannel wetlands and ana-branches,were investigated.Geomorphologic parameters,including the ratio of interchannel wetland area to IWC area(P),shoreline density(DL),and node density(Dn)were used to analyze planform characteristics of IWCs and the development of multi-channels in the stud-ied reach.The results suggest that small or middle sized interchannel wetlands and large or mega sized IWCs are more common at the study site.The area of IWC(Su)is highly cor-related with other geomorphologic parameters.P increases with increasing Su,and the upper limit is about 80%,which indicates that the development of interchannel wetlands and ana-branches in the IWC is in the equilibrium stage.In contrast,D~and D,show a tendency to decrease with increasing Su due to diverse evolution processes in IWCs with different sizes.There are three main reasons leading to the formation of IWCs:varying stream power due to the meandering principal channel;development of the river corridor due to the weakening of geologic structure control;and high stability of interchannel wetlands due to conservation by shoreline vegetation.
文摘Primary vascular tumours of the kidney are rare and may pose diagnostic difficulties because of their similar clinical,morphological,and immunohistochemical features.This article summarizes the clinical and pathological features of primary renal angiosarcoma and anastomosing haemangioma of the kidney including epidemiology,genetics,and prognosis.Renal anastomosing haemangiomas are benign neoplasms characterized by anastomosing capillary-sized vascular channels.These tumours are rare,with about 75 cases reported in the literature.Most anastomosing haemangiomas are found incidentally on ultrasound,computed tomography,or magnetic resonance imaging.Common symptoms include abdominal pain,haematuria,and abdominal mass.Renal anastomosing haemangiomas are characterized by recurrent mutations in GNAQ and GNA14 genes.The prognosis of anastomosing haemangioma is excellent.Primary renal angiosarcomas are malignant tumours showing endothelial differentiation.To date,76 cases have been described in the literature.Primary renal angiosarcomas are frequently symptomatic.The clinical features of renal angiosarcomas are similar to those of renal anastomosing haemangiomas,including abdominal pain,haematuria,and abdominal mass.Angiogenesis-related genes and vascular-specific receptor tyrosine kinases such as KDR,TIE1,SNRK,TEK,and FLT1 are upregulated in angiosarcomas.Primary renal angiosarcomas are highly aggressive neoplasms with a poor prognosis despite surgical treatment,chemotherapy,radiotherapy,or targeted therapy.
基金NSERC,Lithoprobe(Snorcle) and the Government of the Yukon for providing support for this research
文摘Mid-Cretaceous strata within the Tintina Trench, 3 km west of the community of Ross River, contain evidence of deposition in two distinct, alternating, fluvial settings. Coal-bearing, mud-dominated strata are commonly associated with high-constructive sandy channel systems, with extensive overbank, levee and splay deposits. Channels are between 3 and 30 m wide and 0.4-7 m thick. They show repetitive development of side and in-channel bar-forms, as well as up-channel widening of the rivers by selective erosion of associated overbank and levee deposits. Levees extended for several hundred metres away from the channels. In this setting low-angle inclined stratification and epsilon cross stratification may reflect lateral migration of crevasse channels or small streams. The paucity of exposure prevents recognition of the channels as products of multiple channel anastomosed systems or single channel high-constructive systems. Gravel-dominated strata, inter-bedded with, and overlying coal-bearing units, are interpreted as deposits of wandering gravel-bed rivers, with sinuosity approaching 1.4. In most exposures they appear to be dominated by massive and thin planar-bedded granule to small pebble conglomerates, which would traditionally be interpreted as sheet-flood or longitudinal bar deposits of a high-gradient braided stream or alluvial fan. Architectural analysis of exposures in an open-pit shows that the predominance of flat bedding is an artefact of the geometry of the roadside exposures. In the pit the conglomerates are dominated by large scale cross stratification on a scale of 1-5.5 m. These appear to have developed as downstream and lateral accretion elements on side-bars and on in-channel bars in water depths of 2-12 m. Stacking of strata on domed 3rd order surfaces suggests development of longitudinal in-channel bar complexes similar to those observed in parts of the modern Rhone River system. Mudstone preserved in some of the channels reflects intervals of channel abandonment or avulsion. Minimum channel width is from 70 to 450 m.
文摘BACKGROUND Renal anastomosing hemangioma(AH)is a rare benign vascular tumor characterized by unique histopathological features.CASE SUMMARY We report a highly unusual case of renal AH.A male patient had undergone partial nephrectomy for clear cell carcinoma of the kidney four years prior.A follow-up computed tomography scan in the third postoperative year revealed a new mass near the surgical site on the same side of the kidney,raising suspicions of tumor recurrence.However,the characteristics on contrast-enhanced magnetic resonance imaging and ultrasonography were more consistent with those of a benign lesion.The patient strongly insisted on undergoing surgery due to concerns about the possibility of renal cancer recurrence.Postoperative pathology confirmed the diagnosis of renal AH.CONCLUSION This case report presents the imaging features of a patient with rare renal AH and a history of renal clear cell carcinoma,providing broader insights into the differential diagnosis of new lesions after surgery for renal cell carcinoma.
基金National Natural Science Foundation of China,No.41571005,No.41271027
文摘The anastomosing river that is present within the First Great Bend of the Yellow River is different from other sand-bedded rivers of this type because it contains gravel-bedded materials. It is therefore important to determine whether, or not, the specific characteristics of this anastomosing river are similar to those seen in sand-bedded forms, including the characteristics of erosion and deposition, and the stability of channel and interchannel wetlands. Four Landsat images from 1990, 2001, 2013, and 2016 alongside two Google Earth(GE) images from 2011 and 2013 were utilized in this study in tandem with field sampling and observations to select a 12 km main channel length section of the Qihama reach anastomosing river. This section was then used to determine variations in channel planform and sedimentary characteristics over a 26 year period. The results of this study show that this gravel-bedded anastomosing river has exhibited a high degree of stability overall, and that there has been no obvious channel and wetland bank erosion and deposition. Data also show that over the 26 years of this study, anastomosing belt area increased by 2.43%, while the ratio of land to water area remained almost equal. The number of wetlands has also increased along this river section at a rate as high as 62.16% because of the fragmentation of some small interchannel examples, while the talweg has alternately migrated to either the left or right over long periods of time at a relatively stable rate. Indeed, as a result of the migration of this line, there has been significant turnover in the number of islands within the main channel while bank shift has occurred at a rate of about 5 m/yr. The numerous anastomosing channels within this river section remained very stable over the course of this study, characterized by a mean annual migration rate of just 1 m/yr, while the sediments in bank columnar sections are mainly composed of fine sands or silts with a relatively high clay content. The sediment grain-size distribution curve for this river section contains multiple peaks, distinct from the muddy sediments within bank columnar sections from sand-bedded anastomosing rivers. The dense vegetation within riparian and interchannel wetlands alongside this river reach has also protected anastomosing channels from erosion and maintainedtheir stability, a key feature of this gravel-bedded system.
文摘The Laramie River after flowing in a north direction through southeast Wyoming’s Laramie Basin abruptly turns in an east direction to flow across the north-to-south oriented Laramie Range in a bedrock-walled canyon and eventually reaches the lower elevation Great Plains and southeast-oriented North Platte River. The North Laramie River, Bluegrass Creek, and North Sybille/Sybille Creek also flow from the Laramie Basin in separate bedrock-walled valleys into the Laramie Range before eventually joining the Laramie River. Bedrock-walled through valleys link the various Laramie Range stream and river crossing valleys and detailed topographic maps were used to determine how this anastomosing bedrock-walled canyon complex and the large escarpment-surrounded Goshen Hole basin (located just to the east of the anastomosing canyon complex) originated. Map evidence shows multiple streams of water must have diverged in the Laramie Basin from the north-oriented Laramie River to enter the Laramie Range before converging in or east of the Laramie Range and also shows how present day through valleys enabled diverging and converging streams of water to cross the Laramie Range. The anastomosing bedrock-walled valley complex studied here extends from north of the North Laramie River valley to south of the North Sybille/Sybille Creek valley. Large volumes of water flowing from the Laramie Basin to the Great Plains are interpreted to have eroded the anastomosing canyon complex and the “downstream” Goshen Hole escarpment-surrounded basin. Headward erosion of the north-oriented Sybille and Chugwater Creek valleys across large sheets of east-oriented water are interpreted to have left the Goshen Hole escarpment-surrounded basin as a large abandoned headcut. A water source was not determined, although a continental ice sheet that deeply eroded and warped the North American continent is considered to be a possible source.
文摘Detailed topographic maps of drainage divides surrounding the Jefferson County, Montana, Boulder River drainage basin were analyzed to determine the nature of drainage systems that preceded today’s Boulder River drainage system and how the Boulder River drainage system evolved from those earlier drainage systems. The Boulder River studied here drains in a north, east, and south direction to the Jefferson River, which at Three Forks, Montana joins the north-oriented Madison and Gallatin Rivers to form the north-oriented Missouri River. The North American east-west Continental Divide surrounds the Boulder River drainage basin western half and mountainous drainage divides with the Jefferson and Missouri Rivers surround the drainage basin’s eastern half. More than 25 deep mountain passes are notched into these drainage divides and provide evidence of the regional drainage system that preceded the present day Boulder River drainage system. Analysis of pass elevations and of orientations of valleys leading in opposite directions from those mountain passes shows that prior to Boulder River drainage system development immense volumes of south-oriented water moving in anastomosing complexes of diverging and converging channels flowed across the Boulder River drainage basin area and that the Boulder River drainage system evolved as deeper channels progressively captured flow from shallower channels. While not documented in detail crustal warping probably raised Boulder River drainage basin areas relative to adjacent valleys and basins as capture events took place. A water source was not determined, but may have been from a large North American continental ice sheet, although Boulder River drainage basin evolution probably occurred while mid Tertiary sediments were filling adjacent valleys and basins.
文摘Drainage divides along a southern Laramie Range crest area and in the nearby southeast Wyoming Gangplank area (as observed on detailed topographic maps) suggest present-day drainage routes in the Cheyenne Tablelands region originated as headward erosion of south-oriented valleys (now the downstream Lodgepole, Crow, and Lone Tree Creek valleys) from an actively eroding northeast-oriented South Platte River valley captured flood flow in the south half of a large east-oriented anastomosing channel complex while headward erosion of a north-oriented valley (now the downstream Horse Creek valley) from the southeast-oriented North Platte River valley captured the north half of the same large anastomosing channel complex. The Gangplank, which today serves as a low gradient ramp of Tertiary Ogallala Formation sediments leading from the Great Plains to the Laramie Range erosion surface, is located along the Crow Creek-Lone Tree Creek drainage divide and low points along that divide (referred to here as divide crossings) suggest, prior to headward erosion of what is now its south-oriented downstream Lone Tree Creek valley, upstream east-oriented Lone Tree Creek drainage routes were intertwined with east-oriented Crow Creek drainage routes, which today flow much further in an east direction (than east-oriented upstream Lone Tree Creek drainage routes) before also turning in a south direction to reach the South Platte River. The ability of the commonly accepted regional geomorphology paradigm to explain this topographic map evidence is then compared with a fundamentally different and new regional geomorphology paradigm’s ability to explain the same evidence. While both paradigms offer possible explanations the new paradigm, which requires headward erosion of the valleys to have occurred as massive continental ice sheet melt water floods crossed the region, explains much more of the drainage system evidence and also permits much more detailed explanations.
