The City of Calgary’s Nose Creek Sanitary Sewer Trunk Phase B project has been constructed over several years to accommodate future population growth and open more developable lands in northern Calgary.The project wa...The City of Calgary’s Nose Creek Sanitary Sewer Trunk Phase B project has been constructed over several years to accommodate future population growth and open more developable lands in northern Calgary.The project was divided into three phases,Phase A,B,and C,with each phase delivered by a separate consultant.Phase A was the downstream section of this project and was undertaken by Stantec Consulting.Phase B was the upstream section designed by CH2MHILL(now Jacobs)and further divided into different contracts(1 through 5).Phase C was a separate sewer called the Saddleridge Trunk sewer and this was designed by Associated Engineering.This paper covers Phase B,Contract 4,which had several unique challenges and included many innovative design and procurement solutions.One procurement strategy included a two-phase qualification package,with the initial phase to select a tunnelling contractor with the experience to deliver technical installations under rail and creeks,and the second phase,a RFP(request for proposal),to select a general contractor,with broader experience in open-cut and stormwater drainage,which were other aspects included within the project.This approach ensured that The City had the most qualified team available to complete the project.Technical challenges discussed in this paper include an oblique CPKC(Canadian Pacific Kansas City)rail and Nose Creek crossing that required independent review,and CFD(computational fluid dynamics)and hydrogen sulfide modelling to confirm conditions within the trunk sewer.展开更多
Understanding crash contributing factors is essential in safety management and improvement. These factors drive investment decisions, policies, regulations, and other safety-related initiatives. This paper analyzes fa...Understanding crash contributing factors is essential in safety management and improvement. These factors drive investment decisions, policies, regulations, and other safety-related initiatives. This paper analyzes factors that contribute to crash occurrence based on two national datasets in the United States (CISS and NASS-CDS) for the years 2017-2022 and 2010-2015, respectively. Three taxonomies were applied to enhance understanding of the various crash contributing factors. These taxonomies were developed based on previous research and practice and involved different groupings of human factors, vehicle factors, and roadway and environmental factors. Statistics for grouping the different types of factors and statistics for specific factors are provided. The results indicate that human factors are present in over 95% of crashes, roadway and environmental factors are present in over 45% of crashes, and vehicle factors are present in less than 2% of crashes. Regarding factors related to human error and vehicle maintenance, speeding is involved in over 25% of crashes, distraction is involved in over 20% of crashes, alcohol and drugs are involved in over 9% of crashes, and vehicle maintenance is involved in approximately 0.45% of crashes. Approximately 4.4% of crashes involve a driver who “looked but did not see.” Weather is involved in over 13% of crashes. Conclusions: The findings indicate that, consistent with previous research, human factors or human error are present in around 95% of crashes. Infrastructure and environmental factors contribute to about 45% of crashes. Vehicle factors contribute to only 1.67% - 1.71% of crashes. The results from this study could potentially be used to inform future safety management and improvement activities, including policy-making, regulation development, safe systems and systemic safety approaches to safety management, and other engineering, education, emergency response, enforcement, evaluation, and encouragement activities. The findings could also be used in the development of future Driver Assistance Technologies (DAT) systems and in enhancing existing technologies.展开更多
In the realm of medical rarity,the convergence of infective endocarditis with the development of an aortic root abscess stands as a formidable challenge,often bearing a grim prognosis.Recognizing this perilous conditi...In the realm of medical rarity,the convergence of infective endocarditis with the development of an aortic root abscess stands as a formidable challenge,often bearing a grim prognosis.Recognizing this perilous condition requires a vigilant eye.Embolic events stemming from infective endocarditis can precipitate acute coronary syndrome,adding another layer of complexity to diagnosis and treatment.展开更多
This work addresses challenges and opportunities in the evaluation of solar power plant impacts,with a particular focus on thermal effects of solar plants on the environment and vice-versa.Large-scale solar power plan...This work addresses challenges and opportunities in the evaluation of solar power plant impacts,with a particular focus on thermal effects of solar plants on the environment and vice-versa.Large-scale solar power plants are often sited in arid or desert habitats,which tend to include fauna and flora that are highly sensitive to changes in temperature and humidity.Our understanding of both shortwave(solar)and longwave(terrestrial)radiation processes in solar power plants is complete enough to render the modeling of radiation fluxes with high confidence for most applications.In contrast to radiation,the convective environment in large-scale solar power plants is much more difficult to characterize.Wind direction,wind speed,turbulence intensity,dust concentration,ground condition,panel configuration density,orientation and distribution throughout the solar field,all affect the local environment,the balance between radiation and convection,and in turn,the performance and thermal impact of solar power plants.Because the temperatures of the two sides of photovoltaic(PV)panels depend on detailed convection-radiation balances,the uncertainty associated with convection affects the heat and mass transfer balances as well.Those balances are critically important in estimating the thermal impact of large-scale solar farms on local habitats.Here we discuss outstanding issues related with these transfer processes for utility-scale solar generation and highlight potential pathways to gain useful knowledge about the convective environment directly from solar farms under operating conditions.展开更多
BACKGROUND Hypophosphatasia(HPP)is a rare metabolic disorder caused by low tissue-nonspecific alkaline phosphatase(ALP)activity,presenting symptoms from bone demineralization to tooth loss.It affects multiple systems ...BACKGROUND Hypophosphatasia(HPP)is a rare metabolic disorder caused by low tissue-nonspecific alkaline phosphatase(ALP)activity,presenting symptoms from bone demineralization to tooth loss.It affects multiple systems and is diagnosed based on clinical symptoms,radiological findings,and lab tests.This case report empha-sizes considering HPP in patients with unexplained bone pain and low ALP levels,especially with underlying osteopenia or osteoporosis.It highlights the importance of genetic testing and counseling for early diagnosis and treatment,aiming to raise clinician awareness.CASE SUMMARY We present a case of a 65-year-old female patient who was referred to our endoc-rinology clinic for complaints of generalized bone pain and hypothyroidism.Initial evaluation revealed osteopenia,managed with calcium and vitamin D supplementation.Persistently low ALP levels and elevated vitamin B6 levels led to the diagnosis of HPP,confirmed by genetic testing identifying a pathogenic ALPL gene variant[c.119C>T(p.Ala40Val)].Despite conservative treatment,her bone density declined,although remaining in the osteopenic range.The Fracture Risk Assessment score indicated a low risk of major osteoporotic and hip fractures,not warranting immediate treatment.Plans are underway to initiate enzyme replacement therapy with asfotase alfa.CONCLUSION Recognizing HPP is crucial,as early diagnosis and treatment can significantly improve patient outcomes and prevent complications.展开更多
Rectal neuroendocrine neoplasms pose significant challenges due to their varied presentations and prognoses.Traditional prognostic models,while useful,often fall short of accurately predicting clinical outcomes for th...Rectal neuroendocrine neoplasms pose significant challenges due to their varied presentations and prognoses.Traditional prognostic models,while useful,often fall short of accurately predicting clinical outcomes for these patients.This article discusses the development and implications of a novel prognostic tool,the GATIS score,which aims to enhance predictive accuracy and guide treatment strategies more effectively than current methods.Utilizing data from a large cohort and employing sophisticated statistical models,the GATIS score integrates clinical and pathological markers to provide a nuanced assessment of prognosis.We evaluate the potential of this score to transform clinical decision-making processes,its integration into current medical practices,and future directions for its develo-pment.The integration of genetic markers and other biomarkers could further refine its predictive power,highlighting the ongoing need for innovation in the management of rectal neuroendocrine neoplasms.展开更多
Recent advances in understanding type 1 diabetes(T1D)highlight the complexity of managing hypoglycemia,a frequent and perilous complication of diabetes therapy.This letter delves into a novel study by Jin et al,which ...Recent advances in understanding type 1 diabetes(T1D)highlight the complexity of managing hypoglycemia,a frequent and perilous complication of diabetes therapy.This letter delves into a novel study by Jin et al,which elucidates the role of intestinal glucagon-like peptide-1(GLP-1)in the counterregulatory response to hypoglycemia in T1D models.The study employed immunofluorescence,Western blotting,and enzyme-linked immunosorbent assay to track changes in GLP-1 and its receptor expression in diabetic mice subjected to recurrent hypoglycemic episodes.Findings indicate a significant increase in intestinal GLP-1 and GLP-1 receptor expression,correlating with diminished adrenal and glucagon responses,crucial for glucose stabilization during hypoglycemic events.This letter aims to explore the implications of these findings for future therapeutic strategies and the broader understanding of T1D management.展开更多
Esophageal cancer(EC)continues to pose a significant clinical challenge due to the absence of a reliable early detection method,leading to late-stage diagnoses and poor patient outcomes.The recent study by Liu et al p...Esophageal cancer(EC)continues to pose a significant clinical challenge due to the absence of a reliable early detection method,leading to late-stage diagnoses and poor patient outcomes.The recent study by Liu et al presents a promising breakthrough,demonstrating that plasma DNA methylation markers-SHOX2,SEPTIN9,EPO,and RNF180-offer a non-invasive approach for early EC detection with 76.19%sensitivity and 86.27%specificity.Given the urgent need for effective screening strategies,the potential integration of this assay into clinical practice could significantly enhance early diagnosis,patient monitoring,and overall survival rates.While further validation is necessary,this advancement marks an important step toward improving EC detection and management.展开更多
In drylands,biocrusts play crucial roles in regulating ecosystem functions.The study was conducted in the hilly rangelands of the semi-arid northern Negev of Israel,where we assessed the visual,morphological,spectral,...In drylands,biocrusts play crucial roles in regulating ecosystem functions.The study was conducted in the hilly rangelands of the semi-arid northern Negev of Israel,where we assessed the visual,morphological,spectral,and soil properties of livestock trampling routes and inter-route spaces in northern and southern facing hillslopes.Overall,both hillslope aspects were visually similar,whereas the ground surface of the routes was brighter(74.4%were characterized as having a'light'color)than the inter-route spaces(86.8%were characterized as having a'dark'color).These observations were supported by morphological identification of biocrust composition,which was dominated by cyanobacteria(67%)in the routes,and by mixed cyanobacteria/moss(56%)in the inter-routes.Mean Normalized Difference Vegetation Index(NDVI)was 24%higher in the inter-routes,while the mean Brightness Index(BI)was 12%higher in the routes.At the same time,the mean Crust Index(CI)was identical in the two microhabitats.Soil quality index(SQI),calculated based on the(pedoderm)soil properties of the two microhabitats,was 6%greater in the inter-routes than in the routes.This study suggests that recurrent trampling exacerbates soil compaction and shearing along the routes,thus preventing the successional development of complex biocrust compositions.展开更多
The femtosecond laser is commonly used for high-quality micromachining of materials.However,the interaction time between the femtosecond laser and the substrate material is extremely short,making it difficult for quan...The femtosecond laser is commonly used for high-quality micromachining of materials.However,the interaction time between the femtosecond laser and the substrate material is extremely short,making it difficult for quantitative measurements and analysis through experiments.In this work,we use a two-temperature model for simulation to study the ablation process of aluminum alloy and aluminum/titanium alloy under femtosecond laser pulse mode.The temperature changes and ablation process of both alloys under femtosecond laser burst irradiation were studied.The study found that when the separation time of sub-pulses was 1 ps,the surface temperature and ablation depth rised with the increase of sub-pulse numbers.A comparison was made between these two alloy types,and enhanced ablation was observed with the heterogeneous aluminum/titanium alloy,up to 34.7%deeper compared to aluminum alloy.Moreover,the detailed theoretical explanation was also discussed.This work provided a basis for efficient ablation of materials with low laser fluence.展开更多
Artemisia ordosica Krasch. is a dominant shrub occurring mainly on stable sand dunes in the Gobi Desert of China, in the Mongolian phytogeographic region. Achenes of A. ordosica germinate in light but poorly in ...Artemisia ordosica Krasch. is a dominant shrub occurring mainly on stable sand dunes in the Gobi Desert of China, in the Mongolian phytogeographic region. Achenes of A. ordosica germinate in light but poorly in dark and light is the limiting factor regulating the achene germination in sand depth. Achenes germinate in spring or autumn with an optimal temperature of 20 ℃. Achene mucilage can absorb large amounts of water and has important ecological function. Salt concentrations and sand moisture may regulate achene germination in sand. A. ordosica, A. sphaerocephala Krasch. and A. monosperma Delile. from different climates have similar responses to light, the underground location of achene, and sand moisture. Percentage of seedling emergence from different levels of sand depth is depends on the specific, temperature and intensity of light penetrating through the sand depths, as well as on sand moisture. The desert sand habitat seems to have had a dominant influence on the evolution of the germination strategies of these 3 Artemisia species.展开更多
A multidisciplinary approach-anatomy, histochemistry and phytochemistry-was used to investigate the leaf structure, the content and the storage location of barbaloin in the leaves of Aloe vera L. var. chinensis (Haw.)...A multidisciplinary approach-anatomy, histochemistry and phytochemistry-was used to investigate the leaf structure, the content and the storage location of barbaloin in the leaves of Aloe vera L. var. chinensis (Haw.) Berg. Xeromorphic characteristics including secondary thickened epidermal cell walls, thicker cuticle, ambiguous differentiation of spongy and palisade tissues in the chlorenchyma, and well-developed aquiferous tissue could be seen in the leaves. Several large parenchymatous cells were observed at the phloem pole of the first ring of vascular bundles. The secondary ring of vascular bundles in the leaf base and the stomata, which are surrounded by five cells, have some classification significance in this species. The density of vascular bundles, the content of barbaloin and the intensity of histochemical reaction differed among leaf numbers Ll (annual leaf), L2 (biennial leaf), L3 (triennial leaf) and L4 (quadrennial leaf), and in different parts of the leaf. These three factors were highest in the youngest leaf, Ll, and top parts of all the leaves and lowest in the basal parts and the oldest leaf, L4. The density of vascular bundles had a positive correlation to the content of barbaloin. The histochemical results revealed that the small sheath cells that surrounded the bundles might be the location of barbaloin synthesis and the large parenchymatous cells beneath the sheath might be the storage places of this metabolite.展开更多
文摘The City of Calgary’s Nose Creek Sanitary Sewer Trunk Phase B project has been constructed over several years to accommodate future population growth and open more developable lands in northern Calgary.The project was divided into three phases,Phase A,B,and C,with each phase delivered by a separate consultant.Phase A was the downstream section of this project and was undertaken by Stantec Consulting.Phase B was the upstream section designed by CH2MHILL(now Jacobs)and further divided into different contracts(1 through 5).Phase C was a separate sewer called the Saddleridge Trunk sewer and this was designed by Associated Engineering.This paper covers Phase B,Contract 4,which had several unique challenges and included many innovative design and procurement solutions.One procurement strategy included a two-phase qualification package,with the initial phase to select a tunnelling contractor with the experience to deliver technical installations under rail and creeks,and the second phase,a RFP(request for proposal),to select a general contractor,with broader experience in open-cut and stormwater drainage,which were other aspects included within the project.This approach ensured that The City had the most qualified team available to complete the project.Technical challenges discussed in this paper include an oblique CPKC(Canadian Pacific Kansas City)rail and Nose Creek crossing that required independent review,and CFD(computational fluid dynamics)and hydrogen sulfide modelling to confirm conditions within the trunk sewer.
文摘Understanding crash contributing factors is essential in safety management and improvement. These factors drive investment decisions, policies, regulations, and other safety-related initiatives. This paper analyzes factors that contribute to crash occurrence based on two national datasets in the United States (CISS and NASS-CDS) for the years 2017-2022 and 2010-2015, respectively. Three taxonomies were applied to enhance understanding of the various crash contributing factors. These taxonomies were developed based on previous research and practice and involved different groupings of human factors, vehicle factors, and roadway and environmental factors. Statistics for grouping the different types of factors and statistics for specific factors are provided. The results indicate that human factors are present in over 95% of crashes, roadway and environmental factors are present in over 45% of crashes, and vehicle factors are present in less than 2% of crashes. Regarding factors related to human error and vehicle maintenance, speeding is involved in over 25% of crashes, distraction is involved in over 20% of crashes, alcohol and drugs are involved in over 9% of crashes, and vehicle maintenance is involved in approximately 0.45% of crashes. Approximately 4.4% of crashes involve a driver who “looked but did not see.” Weather is involved in over 13% of crashes. Conclusions: The findings indicate that, consistent with previous research, human factors or human error are present in around 95% of crashes. Infrastructure and environmental factors contribute to about 45% of crashes. Vehicle factors contribute to only 1.67% - 1.71% of crashes. The results from this study could potentially be used to inform future safety management and improvement activities, including policy-making, regulation development, safe systems and systemic safety approaches to safety management, and other engineering, education, emergency response, enforcement, evaluation, and encouragement activities. The findings could also be used in the development of future Driver Assistance Technologies (DAT) systems and in enhancing existing technologies.
文摘In the realm of medical rarity,the convergence of infective endocarditis with the development of an aortic root abscess stands as a formidable challenge,often bearing a grim prognosis.Recognizing this perilous condition requires a vigilant eye.Embolic events stemming from infective endocarditis can precipitate acute coronary syndrome,adding another layer of complexity to diagnosis and treatment.
基金Partial funding from the John Dove Isaacs Endowed Chair for Natural Philosophy in Engineering at UC San Diego。
文摘This work addresses challenges and opportunities in the evaluation of solar power plant impacts,with a particular focus on thermal effects of solar plants on the environment and vice-versa.Large-scale solar power plants are often sited in arid or desert habitats,which tend to include fauna and flora that are highly sensitive to changes in temperature and humidity.Our understanding of both shortwave(solar)and longwave(terrestrial)radiation processes in solar power plants is complete enough to render the modeling of radiation fluxes with high confidence for most applications.In contrast to radiation,the convective environment in large-scale solar power plants is much more difficult to characterize.Wind direction,wind speed,turbulence intensity,dust concentration,ground condition,panel configuration density,orientation and distribution throughout the solar field,all affect the local environment,the balance between radiation and convection,and in turn,the performance and thermal impact of solar power plants.Because the temperatures of the two sides of photovoltaic(PV)panels depend on detailed convection-radiation balances,the uncertainty associated with convection affects the heat and mass transfer balances as well.Those balances are critically important in estimating the thermal impact of large-scale solar farms on local habitats.Here we discuss outstanding issues related with these transfer processes for utility-scale solar generation and highlight potential pathways to gain useful knowledge about the convective environment directly from solar farms under operating conditions.
文摘BACKGROUND Hypophosphatasia(HPP)is a rare metabolic disorder caused by low tissue-nonspecific alkaline phosphatase(ALP)activity,presenting symptoms from bone demineralization to tooth loss.It affects multiple systems and is diagnosed based on clinical symptoms,radiological findings,and lab tests.This case report empha-sizes considering HPP in patients with unexplained bone pain and low ALP levels,especially with underlying osteopenia or osteoporosis.It highlights the importance of genetic testing and counseling for early diagnosis and treatment,aiming to raise clinician awareness.CASE SUMMARY We present a case of a 65-year-old female patient who was referred to our endoc-rinology clinic for complaints of generalized bone pain and hypothyroidism.Initial evaluation revealed osteopenia,managed with calcium and vitamin D supplementation.Persistently low ALP levels and elevated vitamin B6 levels led to the diagnosis of HPP,confirmed by genetic testing identifying a pathogenic ALPL gene variant[c.119C>T(p.Ala40Val)].Despite conservative treatment,her bone density declined,although remaining in the osteopenic range.The Fracture Risk Assessment score indicated a low risk of major osteoporotic and hip fractures,not warranting immediate treatment.Plans are underway to initiate enzyme replacement therapy with asfotase alfa.CONCLUSION Recognizing HPP is crucial,as early diagnosis and treatment can significantly improve patient outcomes and prevent complications.
文摘Rectal neuroendocrine neoplasms pose significant challenges due to their varied presentations and prognoses.Traditional prognostic models,while useful,often fall short of accurately predicting clinical outcomes for these patients.This article discusses the development and implications of a novel prognostic tool,the GATIS score,which aims to enhance predictive accuracy and guide treatment strategies more effectively than current methods.Utilizing data from a large cohort and employing sophisticated statistical models,the GATIS score integrates clinical and pathological markers to provide a nuanced assessment of prognosis.We evaluate the potential of this score to transform clinical decision-making processes,its integration into current medical practices,and future directions for its develo-pment.The integration of genetic markers and other biomarkers could further refine its predictive power,highlighting the ongoing need for innovation in the management of rectal neuroendocrine neoplasms.
文摘Recent advances in understanding type 1 diabetes(T1D)highlight the complexity of managing hypoglycemia,a frequent and perilous complication of diabetes therapy.This letter delves into a novel study by Jin et al,which elucidates the role of intestinal glucagon-like peptide-1(GLP-1)in the counterregulatory response to hypoglycemia in T1D models.The study employed immunofluorescence,Western blotting,and enzyme-linked immunosorbent assay to track changes in GLP-1 and its receptor expression in diabetic mice subjected to recurrent hypoglycemic episodes.Findings indicate a significant increase in intestinal GLP-1 and GLP-1 receptor expression,correlating with diminished adrenal and glucagon responses,crucial for glucose stabilization during hypoglycemic events.This letter aims to explore the implications of these findings for future therapeutic strategies and the broader understanding of T1D management.
文摘Esophageal cancer(EC)continues to pose a significant clinical challenge due to the absence of a reliable early detection method,leading to late-stage diagnoses and poor patient outcomes.The recent study by Liu et al presents a promising breakthrough,demonstrating that plasma DNA methylation markers-SHOX2,SEPTIN9,EPO,and RNF180-offer a non-invasive approach for early EC detection with 76.19%sensitivity and 86.27%specificity.Given the urgent need for effective screening strategies,the potential integration of this assay into clinical practice could significantly enhance early diagnosis,patient monitoring,and overall survival rates.While further validation is necessary,this advancement marks an important step toward improving EC detection and management.
文摘In drylands,biocrusts play crucial roles in regulating ecosystem functions.The study was conducted in the hilly rangelands of the semi-arid northern Negev of Israel,where we assessed the visual,morphological,spectral,and soil properties of livestock trampling routes and inter-route spaces in northern and southern facing hillslopes.Overall,both hillslope aspects were visually similar,whereas the ground surface of the routes was brighter(74.4%were characterized as having a'light'color)than the inter-route spaces(86.8%were characterized as having a'dark'color).These observations were supported by morphological identification of biocrust composition,which was dominated by cyanobacteria(67%)in the routes,and by mixed cyanobacteria/moss(56%)in the inter-routes.Mean Normalized Difference Vegetation Index(NDVI)was 24%higher in the inter-routes,while the mean Brightness Index(BI)was 12%higher in the routes.At the same time,the mean Crust Index(CI)was identical in the two microhabitats.Soil quality index(SQI),calculated based on the(pedoderm)soil properties of the two microhabitats,was 6%greater in the inter-routes than in the routes.This study suggests that recurrent trampling exacerbates soil compaction and shearing along the routes,thus preventing the successional development of complex biocrust compositions.
基金Project(2023YFB4604200)supported by National Key R&D Program of ChinaProjects(52475499,52222513,52075557)supported by National Natural Science Foundation of China+5 种基金Project(2021RC3011)supported by Science and Technology Innovation Program of Hunan Province,ChinaProject(2024JJ5426)supported by Natural Science Foundation of Hunan Province,ChinaProject(2023CXQD019)supported by the Central South University Innovation-Driven Research Programme,ChinaProject(ZZYJKT2023-12)supported by the State Key Laboratory of Precision Manufacturing for Extreme Service Performance,Central South University,ChinaProject(IMETKF2024018)supported by the State Key Laboratory of Intelligent Manufacturing Equipment and Technology,Huazhong University of Science and Technology,ChinaProject(2024ZZTS0102)supported by the Fundamental Research Funds for the Central Universities,China。
文摘The femtosecond laser is commonly used for high-quality micromachining of materials.However,the interaction time between the femtosecond laser and the substrate material is extremely short,making it difficult for quantitative measurements and analysis through experiments.In this work,we use a two-temperature model for simulation to study the ablation process of aluminum alloy and aluminum/titanium alloy under femtosecond laser pulse mode.The temperature changes and ablation process of both alloys under femtosecond laser burst irradiation were studied.The study found that when the separation time of sub-pulses was 1 ps,the surface temperature and ablation depth rised with the increase of sub-pulse numbers.A comparison was made between these two alloy types,and enhanced ablation was observed with the heterogeneous aluminum/titanium alloy,up to 34.7%deeper compared to aluminum alloy.Moreover,the detailed theoretical explanation was also discussed.This work provided a basis for efficient ablation of materials with low laser fluence.
文摘Artemisia ordosica Krasch. is a dominant shrub occurring mainly on stable sand dunes in the Gobi Desert of China, in the Mongolian phytogeographic region. Achenes of A. ordosica germinate in light but poorly in dark and light is the limiting factor regulating the achene germination in sand depth. Achenes germinate in spring or autumn with an optimal temperature of 20 ℃. Achene mucilage can absorb large amounts of water and has important ecological function. Salt concentrations and sand moisture may regulate achene germination in sand. A. ordosica, A. sphaerocephala Krasch. and A. monosperma Delile. from different climates have similar responses to light, the underground location of achene, and sand moisture. Percentage of seedling emergence from different levels of sand depth is depends on the specific, temperature and intensity of light penetrating through the sand depths, as well as on sand moisture. The desert sand habitat seems to have had a dominant influence on the evolution of the germination strategies of these 3 Artemisia species.
文摘A multidisciplinary approach-anatomy, histochemistry and phytochemistry-was used to investigate the leaf structure, the content and the storage location of barbaloin in the leaves of Aloe vera L. var. chinensis (Haw.) Berg. Xeromorphic characteristics including secondary thickened epidermal cell walls, thicker cuticle, ambiguous differentiation of spongy and palisade tissues in the chlorenchyma, and well-developed aquiferous tissue could be seen in the leaves. Several large parenchymatous cells were observed at the phloem pole of the first ring of vascular bundles. The secondary ring of vascular bundles in the leaf base and the stomata, which are surrounded by five cells, have some classification significance in this species. The density of vascular bundles, the content of barbaloin and the intensity of histochemical reaction differed among leaf numbers Ll (annual leaf), L2 (biennial leaf), L3 (triennial leaf) and L4 (quadrennial leaf), and in different parts of the leaf. These three factors were highest in the youngest leaf, Ll, and top parts of all the leaves and lowest in the basal parts and the oldest leaf, L4. The density of vascular bundles had a positive correlation to the content of barbaloin. The histochemical results revealed that the small sheath cells that surrounded the bundles might be the location of barbaloin synthesis and the large parenchymatous cells beneath the sheath might be the storage places of this metabolite.
