Parathyroid hormone （PTH） secretion is characterized by an ultradian rhythm with tonic and pulsatile components. In healthy subjects, the majority of PTH is secreted in tonic fashion, whereas approximately 30% is se...Parathyroid hormone （PTH） secretion is characterized by an ultradian rhythm with tonic and pulsatile components. In healthy subjects, the majority of PTH is secreted in tonic fashion, whereas approximately 30% is secreted in low-amplitude and high-frequency bursts occurring every 10-20 min, superimposed on tonic secretion. Changes in the ultradian PTH secretion were shown to occur in patients with primary and secondary osteoporosis, with skeletal effects depending on the reciprocal modifications of pulsatile and tonic components. Indeed, pathophysiology of spontaneous PTH secretion remains an area potentially suitable to be explored, particularly in those conditions such as secondary forms of osteoporosis, in which conventional biochemical and densitometric parameters may not always give reliable diagnostic and therapeutic indications. This review will highlight the literature data supporting the hypothesis that changes of ultradian PTH secretion may be correlated with skeletal fragility in primary and secondary osteoporosis.展开更多
Aim: To determine the relationship of carotid plaque, intima media thickness (IMT), resistivity index (RI) and pulsatility index (PI) and prevalence of different risk factors with acute ischemic stroke and stroke subt...Aim: To determine the relationship of carotid plaque, intima media thickness (IMT), resistivity index (RI) and pulsatility index (PI) and prevalence of different risk factors with acute ischemic stroke and stroke subtypes in both diabetic and non-diabetic subjects. Materials and methods: 80 cases of acute ischemic strokes and 40 healthy controls were included in the study. The plaque, IMT, RI and PI were measured by carotid duplex ultrasound. Results: 31 subjects were Type 2 diabetic, 54 hypertensive while 25 were both diabetic and hypertensive. 23 cases (28.75%) had lacunar stroke (LACI), 32 (40%) stroke involving partial anterior circulation(PACI), 10(12.5%) stroke in posterior circulation (PACI) and 15(18.75%) stroke involving total anterior circulation(TACI) respectively. The mean IMT (0.88 ± 0.19mm), RI(0.76 ± 0.05) and PI(1.71 ± 0.19) of patients and mean IMT (0.6±0.09mm), RI (0.61 ± 0.06) and PI (1.53 ± 0.11) of controls were statistically significant (p-0.000). The mean values of IMT, PI and RI were significantly higher in diabetics (IMT-0.90 ± 0.16 VS 0.64 ± 0.11, p-0.013;PI-1.76 ± 0.20 VS 1.49 ± 0.09, P-0.000 and RI-0.76 ± 0.04 VS 0.59 ± 0.06, P-0.000) and similarly the mean values for IMT, PI and RI in hypertensives as compared to controls (IMT-0.88 ± 0.16 vs 0.65 ± 0.10, P-0.006;PI1.69 ± 0.18 vs 1.49 ± 0.09, P-0.000 and RI 0.76 ± 0.04 vs 0.59 ± 0.06, P-0.000). The mean IMT, PI and RI were increased significantly in smokers compared to controls (IMT-0.93 ± 0.20 vs 0.63 ± 0.06, P-0.000;PI-1.82 ± 0.22 vs 1.49 ± 0.09, P-0.000 and RI-0.77 ± 0.04 vs 0.59 ± 0.06, P-0.000). Type 3 plaque accounted for 27 (56.2%) cases and Type 2 plaque 12 (25%) cases. The total number of plaques in patients as compared to controls were significantly more (P-0.0034) and the mean plaque area was 46 mm2 for cases and 20 mm2 for control (P-0.0001). TACI was the most common type of ischemic stroke seen in DM (60%), HTN (66.6%) and smokers (66.7%). Plaques (73.3%), IMT (0.90 ± 0.12), PI(1.72 ± 0.14) and RI (0.76 ± 0.13) were more commonly associated with TACI subtype. On multivariate analysis using ANOVA, the mean PI was highly significant (0.000) in relation to types of plaque. Summary and Conclusions: IMT, RI, PI and plaque type are useful diagnostic parameters for acute ischemic stroke and its subtypes. They can be used as noninvasive tools for predicting and preventing ischemic stroke in smokers as well as subjects with DM and hypertension.展开更多
AIM： To study the changes of portal blood flow in congestive heart failure. METHODS： We studied the congestion index （CI） and portal vein pulsatility index （PI） in patients with varied degrees of congestive hear...AIM： To study the changes of portal blood flow in congestive heart failure. METHODS： We studied the congestion index （CI） and portal vein pulsatility index （PI） in patients with varied degrees of congestive heart failure using ultrasonic Doppler. Ten patients with mean right atrial pressure （RA） 〈10 mmHg were classified as group 1 and the remaining 10 patients with RA〉 10 mmHg as group 2. RESULTS： There were no difference on cardiac index （HI, P= 0.28）, aortic pressure （AO, P= 0.78）, left ventricular end-diastolic pressure （LVED, P=0.06）, maximum portal blood velocity （Vmax, P= 0.17）, mean portal blood velocity （Vmean, P=0.15） and portal blood flow volume （PBF, P= 0.95） between the two groups. Group 2 patients had higher pulmonary wedge pressure （PW, 29.9 ± 9.3 mmHg vs 14.6±7.3 mmHg, P=0.002）, pulmonary arterial pressure （PA, 46.3± 13.2 mmHg vs 25.0±8.2 mmHg, P=0.004）, RA （17.5±5.7 mmHg vs 4.7±2.4 mmHg, P〈 0.001）, right ventricular end-diastolic pressure （RVED, 18.3±5.6 mmHg vs 6.4±2.7 mmHg, P〈0.001）, CI （8.7±2.4 vs 5.8± 1.2, P=0.03）, and PI （87.8±32.3% vs 27.0±7.4%, P〈0.001） than Group 1. CI was correlated with PI （P〈0.001）, PW （P〈0.001）, PA （P〈0.001）, RA （P=0.043）, RVED （P=0.005）, HI （P〈0.001）, AO （P〈0.001）, CO （P〈0.001）, LVED （P〈0.001）, Vmax （P〈0.001）, Vmax （P〈0.001）, cross-sectional area of the main portal vein （P〈0.001） and PBF （P〈0.001）. CI could be as high as 8.3 in patients with RA〈 10 mmHg and as low as 5.9 in those with RA≥10 mmHg.CONCLUSION： Our data show that RI is a more significant indicator than CI in the clinical evaluation of high RA≥ 10 mmHg, whereas CI is better than PI in the assessment of left heart function.展开更多
BACKGROUND The incidence of multiple pregnancies has increased worldwide recently and women with a twin pregnancy are at higher risk of adverse outcomes compared with women with a singleton pregnancy.It is important t...BACKGROUND The incidence of multiple pregnancies has increased worldwide recently and women with a twin pregnancy are at higher risk of adverse outcomes compared with women with a singleton pregnancy.It is important to understand the risk factors for adverse fetal outcomes in twin pregnancy in order to guide clinical management.AIM To identify the independent risk factors,including maternal personal and family medical histories and first trimester ultrasound screening findings,for adverse fetal outcomes of twin pregnancy before 28 weeks of gestation.METHODS The data of 126 twin pregnancies in our hospital,including pregnancy outcomes,first trimester ultrasound screening findings and maternal medical history,were retrospectively collected.Twenty-nine women with adverse outcomes were included in the abnormal group and the remaining 97 women were included in the control group.RESULTS Patients in the abnormal group were more likely to be monochorionic diamniotic(13/29 vs 20/97,P=0.009),with a higher mean pulsatility index(PI,1.57±0.55 vs 1.28±0.42,P=0.003;cutoff value:1.393)or a higher mean resistance index(0.71±0.11 vs 0.65±0.11,P=0.008;cutoff value:0.683)or early diastolic notch of bilateral uterine arteries(UtAs,10/29 vs 15/97,P=0.024)or with abnormal ultrasound findings(13/29 vs 2/97,P<0.001),compared with the control group.Monochorionic diamnioticity,higher mean PI of bilateral UtAs and abnormal ultrasound findings during first trimester screening were independent risk factors for adverse fetal outcomes(P<0.05).CONCLUSION First trimester ultrasound screening for twin pregnancy identifies independent risk factors and is useful for the prediction of fetal outcomes.展开更多
To the editor:The superior semicircular canal dehiscence was first described by Minor et all in 1998 as a condition in which the superior semicircular canal lacks a bony covering and has gained constantly increasing i...To the editor:The superior semicircular canal dehiscence was first described by Minor et all in 1998 as a condition in which the superior semicircular canal lacks a bony covering and has gained constantly increasing interest since its discovery.2 The symptoms are varied but specific what is known as Minor syndrome or‘third mobile window’syndrome,'as patients may experience autophony with abnormally loud sounds like footsteps,chewing,breathing,eye movement,echoing voice,distortion of environmental sounds and pulsatile tinnitus.展开更多
Dose-dense chemotherapy is the preferred first-line therapy for triple-negative breast cancer(TNBC),a highly aggressive disease with a poor prognosis.This treatment uses the same drug doses as conventional chemotherap...Dose-dense chemotherapy is the preferred first-line therapy for triple-negative breast cancer(TNBC),a highly aggressive disease with a poor prognosis.This treatment uses the same drug doses as conventional chemotherapy but with shorter dosing intervals,allowing for promising clinical outcomes with intensive treatment.However,the frequent systemic administration used for this treatment results in systemic toxicity and low patient compliance,limiting therapeutic efficacy and clinical benefit.Here,we report local dose-dense chemotherapy to treat TNBC by implanting 3D printed devices with timeprogrammed pulsatile release profiles.The implantable device can control the time between drug releases based on its internal microstructure design,which can be used to control dose density.The device is made of biodegradable materials for clinical convenience and designed for minimally invasive implantation via a trocar.Dose density variation of local chemotherapy using programmable release enhances anti-cancer effects in vitro and in vivo.Under the same dose density conditions,device-based chemotherapy shows a higher anticancer effect and less toxic response than intratumoral injection.We demonstrate local chemotherapy utilizing the implantable device that simulates the drug dose,number of releases,and treatment duration of the dose-dense AC(doxorubicin and cyclophosphamide)regimen preferred for TNBC treatment.Dose density modulation inhibits tumor growth,metastasis,and the expression of drug resistance-related proteins,including p-glycoprotein and breast cancer resistance protein.To the best of our knowledge,local dose-dense chemotherapy has not been reported,and our strategy can be expected to be utilized as a novel alternative to conventional therapies and improve anti-cancer efficiency.展开更多
This paper represents a detailed and systematic review of one of the most ongoing applications of computational fluid dynamics(CFD)in biomedical applications.Beyond its various engineering applications,CFD has started...This paper represents a detailed and systematic review of one of the most ongoing applications of computational fluid dynamics(CFD)in biomedical applications.Beyond its various engineering applications,CFD has started to establish a presence in the biomedical field.Cardiac abnormality,a familiar health issue,is an essential point of investigation by research analysts.Diagnostic modalities provide cardiovascular structural information but give insufficient information about the hemodynamics of blood.The study of hemodynamic parameters can be a potential measure for determining cardiovascular abnormalities.Numerous studies have explored the rheological behavior of blood experimentally and numerically.This paper provides insight into how researchers have incorporated the pulsatile nature of the blood experimentally,numerically,or through various simulations over the years.It focuses on how machine learning platforms derive outputs based on mass and momentum conservation to predict the velocity and pressure profile,analyzing various cardiac diseases for clinical applications.This will pave the way toward responsive AI in cardiac healthcare,improving productivity and quality in the healthcare industry.The paper shows how CFD is a vital tool for efficiently studying the flow in arteries.The review indicates this biomedical simulation and its applications in healthcare using machine learning and AI.Developing AI-based CFD models can impact society and foster the advancement towards responsive AI.展开更多
BACKGROUND Pituitary stalk interruption syndrome(PSIS)is a rare anatomical defect of the pituitary gland falling under the spectrum of holoprosencephaly phenotypes.It is characterized by a deficiency in anterior pitui...BACKGROUND Pituitary stalk interruption syndrome(PSIS)is a rare anatomical defect of the pituitary gland falling under the spectrum of holoprosencephaly phenotypes.It is characterized by a deficiency in anterior pituitary hormones,such as growth hormone,gonadotropins,and thyroid hormones.Due to the syndrome's rarity and nonspecific manifestations,there is a lack of standardized treatment strategies.Consequently,early diagnosis through imaging and on-time intervention are crucial for improving patients’outcomes.CASE SUMMARY A 30-year-old man presented with absent secondary sexual characteristics and azoospermia.Laboratory evaluation revealed a deficiency in gonadotropins,while thyroid function was mostly within normal ranges.Magnetic resonance imaging of the pituitary gland showed pituitary stalk agenesis,hypoplasia of the anterior pituitary,and ectopic posterior pituitary,leading to the diagnosis of PSIS.Initially,the patient underwent 6 mo of gonadotropin therapy without significant changes in hormone levels and secondary sexual characteristics.Pulsatile gonadotropin-releasing hormone therapy was then administered,resulting in the detection of sperm in the semen analysis within 3 mo.After 6 mo,routine semen tests showed normal semen quality.The couple faced challenges in conceiving due to abstinence and underwent three cycles of artificial insemination,which was unsuccessful.They also attempted in vitro fertilization,but unfortunately,the woman experienced a miscarriage 10 wk after the embryo transfer.CONCLUSION Early detection,accurate diagnosis,and timely treatment are crucial in improving the quality of life and fertility of PSIS patients.展开更多
Seventy four cases of infertility were examined to study the hemodynamics of the bilateral ovarian arteries at 21st day during the corpus luteum phase by color Doppler energy(CDE) and color Doppler flow imaging (CDFI...Seventy four cases of infertility were examined to study the hemodynamics of the bilateral ovarian arteries at 21st day during the corpus luteum phase by color Doppler energy(CDE) and color Doppler flow imaging (CDFI). All the patients were verified by laparoscopy, fallopian tube patency examination and ovarian function test. Twenty two healthy women served as controls. The results showed that the difference of resistance index(RI)and pulsatility index (PI) of bilateral ovarian arteries between the infertility and the normal controls had statistical significance ( P <0.01), and the PI showed negative correlation with the thickness of endometrium (left side: r =0.724, P <0.01; right side: r =0.756, P <0.01). The results also showed that CDE was more sensitive than CDFI in displaying the ovarian arteries. It could be concluded that the elevated resistance of ovarian artery during the corpus luteum phase was one of the important factors that resulted in infertility.展开更多
OBJECTIVE:To explore the most effective parameters of Yi Zhi Chan Tuina manipulation for improving peripheral blood circulation.METHODS:A total of 45 volunteers were recruited from Pudong district in Shanghai,China,fr...OBJECTIVE:To explore the most effective parameters of Yi Zhi Chan Tuina manipulation for improving peripheral blood circulation.METHODS:A total of 45 volunteers were recruited from Pudong district in Shanghai,China,from October to December 2010,and randomly divided into nine groups using computer-generated random numbers.Participants received Yi Zhi Chan Tuina manipulation on Chengjin(BL 56) acupoint;each group received a particular combination of manipulation force and treatment time.We used a two-factor,three-level factorial design to examine the effects of force and treatment time on changes in popliteal artery average volume flow,pulsatility index,and vessel diameter to determine the optimal parameter group.Outcomes were assessed at baseline and after Tuina manipulation by interviewers blind to treatment group status.RESULTS:After manipulation,two of the nine groups showed an increase in popliteal artery volume flow.An inter-participants effect test showed that for main effect of time,F = 0.331,P = 0.720;for main effect of force,F = 2.934,P = 0.066;and for the force-time interaction effect,F = 1.072,P = 0.385,indicating no interaction between force and time.However,a pairwise comparison of the three levels of time showed that a treatment time of 10 min was significantly more effective than that of 2 min(P = 0.024).A pairwise comparison of light force,medium force,and heavy force showed a statistically significant effect for medium force(P = 0.035).CONCLUSION:Yi Zhi Chan Tuina manipulation with vertical force of 9.31 N for 10 min is most effective in improving peripheral circulation.展开更多
Objective:To assess the hemodynamic changes that occurred in the main testicular artery at two different locations such as supra and marginal ones in bulls at three different ages.Methods:Eighteen Baladi bulls were di...Objective:To assess the hemodynamic changes that occurred in the main testicular artery at two different locations such as supra and marginal ones in bulls at three different ages.Methods:Eighteen Baladi bulls were divided according to their age into three different age groups:1 year[n=6;groupⅠwith bodyweight(380±10)kg],3 years[n=6;groupⅡwith bodyweight(570±10)kg],and 6 years old[n=6;groupⅢwith bodyweight(650±10)kg]Baladi bulls.Circumference of the scrotum,thickness of the mediastinum,testicular dimensions,vascularity,and hormonal levels were measured.Testicular hemodynamics were assessed by Doppler ultrasound scanning.Results:Testicular width,length,and volume were significantly different among the three age groups,with the highest in bulls of groupⅢ(P<0.05).The bulls in groupⅢhad significantly higher mediastinal line thickness and scrotal circumference than groupⅠ(P<0.05),but there was no significant difference between groupⅡand groupⅢ.Bulls in groupⅡshowed a decline in Doppler indices(resistance and pulsatility indexes)at both testicular branches compared to the other two groups(P<0.05).Supra and marginal end diastolic velocities in the three age groups were significantly different,with the highest in groupⅡ(P<0.05).Time average velocity(cm/s)was significantly elevated in groupⅡcompared to the other two groups(P<0.05).Both testicular echotextures were significantly decreased in groupⅡ(P<0.05).Estradiol and nitric oxide metabolites were significantly high in groupⅡcompared to the other two groups(P<0.05).Meanwhile,the level of plasma testosterone was maximum in groupⅢ(P<0.05).Positive correlations were found between supratesticular artery resistance and pulsatility indexes(r=0.81;P<0.001),while both resistance and pulsatility indexes had correlated negative with estradiol(r=-0.71 and r=-0.91;P<0.001),and nitric oxide metabolites(r=-0.92 and r=-0.72;P<0.001).Conclusions:Three-year old Baladi bull has the lesser Doppler indices with lesser echotexture and greater nitric oxide with estradiol concentrations,which directs a significant ability for the thermoregulation process.These parameters will help in breeding selection.展开更多
The aim of this study was to compare lower limb blood flow in asymptomatic diabetic patients with early-stage peripheral artery disease (PAD) and non-diabetic controls using duplex ultrasound parameters. This was a co...The aim of this study was to compare lower limb blood flow in asymptomatic diabetic patients with early-stage peripheral artery disease (PAD) and non-diabetic controls using duplex ultrasound parameters. This was a comparative cohort study of lower limb blood flow in 35 Black-African diabetic patients (25 females and 10 males with early-stage PAD median age 54 [IQR, 47 - 61] years;median HbA<sub>1c</sub> 6.3 [IQR, 5.7 - 8.0]%<sub></sub>;BMI 29.2 ± 6.7;ABI 1.1 ± 0.1) and 36 non-diabetic controls (28 females and 8 males;median age 54 [IQR, 47 - 61] years;median HbA<sub>1c</sub> 6.3 [IQR, 5.7 - 8.0] %, BMI 29.2 ± 6.7;ABI 1.1 ± 0.1). Peak systolic velocity (PSV), pulsatility index (PI) and resistive index (RI), were utilised to compare blood flow in the popliteal arteries (PA), anterior tibial arteries (ATA) and posterior tibial arteries (PTA) in addition to ankle brachial index. All the ultrasound parameters showed good (ICC ≥ 0.7;0.50 - 0.85, 95% CI) to excellent (ICC = 1.0;1.0 - 1.0, 95% CI) reliability within groups as well as acceptable variability () other than pulsatility index of the anterior tibial artery within diabetic patients (11.1% CV). PSV, RI and PI were significantly and meaningfully higher (P;d ≥ 0.33), in diabetic patients compared to non-diabetic controls except for PI - PTA (P = 0.72;d = 0.11). Differences in PSV and RI highlighted the effects of early-stage PAD on lower limb blood flow of diabetic patients. In contrast, the effects of early-stage PAD on blood flow were not demonstrated in the PTA and ATA of diabetic patients by PI.展开更多
Both pulsatile gonadotropin-releasing hormone （GnRH） infusion and combined gonadotropin therapy （human chorionic gonadotropin and human menopausal gonadotropin [HCG/HMG]） are effective to induce spermatogenesis in...Both pulsatile gonadotropin-releasing hormone （GnRH） infusion and combined gonadotropin therapy （human chorionic gonadotropin and human menopausal gonadotropin [HCG/HMG]） are effective to induce spermatogenesis in male patients with congenital hypogonadotropic hypogonadism （CH H）. However, evidence is lacking as to which treatment strategy is better. This retrospective cohort study included 202 patients with CHH： twenty had received pulsatile GnRH and 182 had received HCG/HMG. Patients had received therapy for at least 12 months. The total follow-up time was 15.6 ± 5.0 months （range： 12-27 months） for the GnRH group and 28.7 ± 13.0 months （range： 12-66 months） for the HCG/HMG group. The median time to first sperm appearance was 6 months （95% confidence interval [CI]： 1.6-10.4） in the GnRH group versus 18 months （95% Ch 16.4-20.0） in the HCG/HMG group （P〈 0.001）. The median time to achieve sperm concentrations 〉5 x 106 m1-1 was 14 months （95% Ch 5.8-22.2） in the GnRH group versus 27 months （95% Ch 18.9-35.1） in the HCG/HMG group （P 〈 0.001）, and the median time to concentrations 〉10 x 106 m1-1 was 18 months （95% Ch 10.0-26.0） in the GnRH group versus 39 months （95% CI unknown） in the HCG/HMG group. Compared to the GnRH group, the HCG/HMG group required longer treatment periods to achieve testicular sizes of 〉4 ml, 〉8 ml, 〉12 ml, and 〉16 ml. Sperm motility （a ＋ b ＋ c percentage） evaluated in semen samples with concentrations 〉1 × 106 ml-1 was 43.7% ± 20.4% （16 samples） in the GnRH group versus 43.2% ± 18.1% （153 samples） in the HCG/HMG group （P= 0.921）. Notably, during follow-up, the GnRH group had lower serum testosterone levels than the HCG/HMG group （8.3 ±4.6 vs 16.2 ± 8.2 nmol 1-1, P 〈 0.001）. Our study found that pulsatile GnRH therapy was associated with earlier spermatogenesis and larger testicular size compared to combined gonadotropin therapy. Additional prospective randomized studies would be required to confirm these findings.展开更多
The influence of high-density pulsing current on the work-hardening behaviour of H0Cr17Ni6Mn3 and 1Cr18Ni9 stainless steels in wire-drawing deformation processes has been studied. It was found that the drawing stress ...The influence of high-density pulsing current on the work-hardening behaviour of H0Cr17Ni6Mn3 and 1Cr18Ni9 stainless steels in wire-drawing deformation processes has been studied. It was found that the drawing stress and the work-hardening rate of wires were significantly reduced by applying current pulses in drawing process. The work-hardening behavior of the multi-courses drawing deformation can be well described by Hollomon formula σ=κΕn. With the application of current pulses in drawing deformation, the work-hardening exponents of H0Cr17Ni6Mn3 steel wires and 1Cr18Ni9 stainless steel wires were reduced by 33% and 45%, respectively, and their work-hardening coefficients were reduced by 41% and 47%, respectively. It was also found that the work-hardening coefficient of wires was reduced with the increment of the frequency of current pulses, while the work-hardening exponents of both steels were insensitive to the pulsing frequency.展开更多
The current research on pulse continuously variable transmission（CVT） is mainly focused on reducing the pulse degree and making pulse degrees a constant value. Current research mainly confined to find out new design...The current research on pulse continuously variable transmission（CVT） is mainly focused on reducing the pulse degree and making pulse degrees a constant value. Current research mainly confined to find out new design parameters by using the method of optimization, and reduce the pulse degree of pulse CVT and its range of variation. But the fact is that the reduction of the pulse degree is not significant. This article presents a new structure of mechanical pulse CVT--the rotational swashplate pulse CVT with driven by helical gear axial meshing. This transmission is simple and compact in structure and low in pulsatile rate （it adopts 6 guide rods）, and the pulsatile degree is irrelevant to the transmission ratio. Theoretically, pulsatile rate could be reduced to zero if appropriate curved surface of the swashplate is used. Compared with the connecting rod pulse CVT, the present struc^tre uses helical gear mechanism as transmission part and it avoids unbalanced inertial force in the former model. This paper analyzes the principle of driving of this transmission, presents its mechanical structure, and discusses its motion characteristics. Experimental prototype of this type of CVT has been manufactured. Tests for the transmission efficiency（when the rotational speed of the output shaft is the maximum） and the angular velocity of the output shaft have been carried out, and data have been analyzed. The experimental results show that the speed of the output shaft for the experimental prototype is slightly lower than the theoretical value, and the transmission efficiency of the experimental prototype is about 70%. The pulse degree of the CVT discussed in this paper is less than the existing pulse CVT of other types, and it is irrelevant to the transmission ratio of the CVT. The research provides the new idea to the CVT study.展开更多
This study experimentally and numerically investigated the effect of pulsatile flow of different frequencies and outflow resistance on wall deformation in a lateral aneurysm.A method for constructing a flexible aneury...This study experimentally and numerically investigated the effect of pulsatile flow of different frequencies and outflow resistance on wall deformation in a lateral aneurysm.A method for constructing a flexible aneurysm model was developed,and a self-designed piston pump was used to provide the pulsatile flow conditions.A fluid-structure interaction simulation was applied for comparison with and analysis of experimental findings.The maximum wall displacement oscillation increased as the pulsation frequency and outflow resistance increased,especially at the aneurysm dome.There is an obvious circular motion of the vortex center accompanying the periodic inflow fluctuation,and the pressure at the aneurysm dome at peak flow increased as the pulsatile flow frequency and terminal flow resistance increased.These results could explain why abnormal blood flow with high frequency and high outflow resistance is one of the risk factors for aneurysm rupture.展开更多
The effects of the renal artery stenosis （RAS） on the blood flow and vessel walls are investigated. The pulsatile blood flow through an anatomically realistic model of the abdominal aorta and renal arteries reconstr...The effects of the renal artery stenosis （RAS） on the blood flow and vessel walls are investigated. The pulsatile blood flow through an anatomically realistic model of the abdominal aorta and renal arteries reconstructed from CT-scan images is simulated, which incorporates the fluid-structure interaction （FSI）. In addition to the investigation of the RAS effects on the wall shear stress and the displacement of the vessel wall, it is determined that the RAS leads to decrease in the renal mass flow. This may cause the activation of the renin-angiotension system and results in severe hypertension.展开更多
Pulsatile gonadotropin-releasing hormone （GnRH） may induce spermatogenesis in most patients with congenital hypogonadotropic hypogonadism （CHH） by stimulating gonadotropin production, while the predictors for a pi...Pulsatile gonadotropin-releasing hormone （GnRH） may induce spermatogenesis in most patients with congenital hypogonadotropic hypogonadism （CHH） by stimulating gonadotropin production, while the predictors for a pituitary response to pulsatile GnRH therapy were rarely investigated. Therefore, the aim of our study is to investigate predictors of the pituitary response to pulsatile GnRH therapy. This retrospective cohort study included 82 CHH patients who received subcutaneous pulsatile GnRH therapy for at least 1 month. Patients were categorized into poor or normal luteinizing hormone （LH） response subgroups according to their LH level （LH 〈2 IU 1-1 or LH P_2 IU 1-1） 1 month into pulsatile GnRH therapy. Gonadotropin and testosterone levels, testicular size, and sperm count were compared between the two subgroups before and after GnRH therapy. Among all patients, LH increased from 0.4±0.5 IUI^-1 to 7.5±4.4 IUI^-1 and follicle-stimulating hormone （FSH） increased from 1.1±0.9 IUI^-1 to 8.8±5.3 IU 1-1. A Cox regression analysis showed that basal testosterone level （6 = 0.252, P = 0.029） and triptorelin-stimulated FSH60min（13 = 0.518, P = 0.01） were two favorable predictors for pituitary response to GnRH therapy. Nine patients （9/82, 11.0%） with low LH response to GnRH therapy were classified into the poor LH response subgroup. After pulsatile GnRH therapy, total serum testosterone level was 39± 28 ng dl^-1 versus 248±158 ng d1^-1 （P=0.001）, and testicular size was 4.0±3.1 ml versus 7.9±4.5 ml （P= 0.005） in the poor and normal LH response subgroups, respectively. It is concluded that higher levels of triptorelin-stimulated FSH60min. and basal total serum testosterone are favorable predictors of pituitary LH response to GnRH therapy.展开更多
文摘Parathyroid hormone （PTH） secretion is characterized by an ultradian rhythm with tonic and pulsatile components. In healthy subjects, the majority of PTH is secreted in tonic fashion, whereas approximately 30% is secreted in low-amplitude and high-frequency bursts occurring every 10-20 min, superimposed on tonic secretion. Changes in the ultradian PTH secretion were shown to occur in patients with primary and secondary osteoporosis, with skeletal effects depending on the reciprocal modifications of pulsatile and tonic components. Indeed, pathophysiology of spontaneous PTH secretion remains an area potentially suitable to be explored, particularly in those conditions such as secondary forms of osteoporosis, in which conventional biochemical and densitometric parameters may not always give reliable diagnostic and therapeutic indications. This review will highlight the literature data supporting the hypothesis that changes of ultradian PTH secretion may be correlated with skeletal fragility in primary and secondary osteoporosis.
文摘Aim: To determine the relationship of carotid plaque, intima media thickness (IMT), resistivity index (RI) and pulsatility index (PI) and prevalence of different risk factors with acute ischemic stroke and stroke subtypes in both diabetic and non-diabetic subjects. Materials and methods: 80 cases of acute ischemic strokes and 40 healthy controls were included in the study. The plaque, IMT, RI and PI were measured by carotid duplex ultrasound. Results: 31 subjects were Type 2 diabetic, 54 hypertensive while 25 were both diabetic and hypertensive. 23 cases (28.75%) had lacunar stroke (LACI), 32 (40%) stroke involving partial anterior circulation(PACI), 10(12.5%) stroke in posterior circulation (PACI) and 15(18.75%) stroke involving total anterior circulation(TACI) respectively. The mean IMT (0.88 ± 0.19mm), RI(0.76 ± 0.05) and PI(1.71 ± 0.19) of patients and mean IMT (0.6±0.09mm), RI (0.61 ± 0.06) and PI (1.53 ± 0.11) of controls were statistically significant (p-0.000). The mean values of IMT, PI and RI were significantly higher in diabetics (IMT-0.90 ± 0.16 VS 0.64 ± 0.11, p-0.013;PI-1.76 ± 0.20 VS 1.49 ± 0.09, P-0.000 and RI-0.76 ± 0.04 VS 0.59 ± 0.06, P-0.000) and similarly the mean values for IMT, PI and RI in hypertensives as compared to controls (IMT-0.88 ± 0.16 vs 0.65 ± 0.10, P-0.006;PI1.69 ± 0.18 vs 1.49 ± 0.09, P-0.000 and RI 0.76 ± 0.04 vs 0.59 ± 0.06, P-0.000). The mean IMT, PI and RI were increased significantly in smokers compared to controls (IMT-0.93 ± 0.20 vs 0.63 ± 0.06, P-0.000;PI-1.82 ± 0.22 vs 1.49 ± 0.09, P-0.000 and RI-0.77 ± 0.04 vs 0.59 ± 0.06, P-0.000). Type 3 plaque accounted for 27 (56.2%) cases and Type 2 plaque 12 (25%) cases. The total number of plaques in patients as compared to controls were significantly more (P-0.0034) and the mean plaque area was 46 mm2 for cases and 20 mm2 for control (P-0.0001). TACI was the most common type of ischemic stroke seen in DM (60%), HTN (66.6%) and smokers (66.7%). Plaques (73.3%), IMT (0.90 ± 0.12), PI(1.72 ± 0.14) and RI (0.76 ± 0.13) were more commonly associated with TACI subtype. On multivariate analysis using ANOVA, the mean PI was highly significant (0.000) in relation to types of plaque. Summary and Conclusions: IMT, RI, PI and plaque type are useful diagnostic parameters for acute ischemic stroke and its subtypes. They can be used as noninvasive tools for predicting and preventing ischemic stroke in smokers as well as subjects with DM and hypertension.
基金Supported by the grant from the Cathay Groups,Taipei,Taiwan,China
文摘AIM： To study the changes of portal blood flow in congestive heart failure. METHODS： We studied the congestion index （CI） and portal vein pulsatility index （PI） in patients with varied degrees of congestive heart failure using ultrasonic Doppler. Ten patients with mean right atrial pressure （RA） 〈10 mmHg were classified as group 1 and the remaining 10 patients with RA〉 10 mmHg as group 2. RESULTS： There were no difference on cardiac index （HI, P= 0.28）, aortic pressure （AO, P= 0.78）, left ventricular end-diastolic pressure （LVED, P=0.06）, maximum portal blood velocity （Vmax, P= 0.17）, mean portal blood velocity （Vmean, P=0.15） and portal blood flow volume （PBF, P= 0.95） between the two groups. Group 2 patients had higher pulmonary wedge pressure （PW, 29.9 ± 9.3 mmHg vs 14.6±7.3 mmHg, P=0.002）, pulmonary arterial pressure （PA, 46.3± 13.2 mmHg vs 25.0±8.2 mmHg, P=0.004）, RA （17.5±5.7 mmHg vs 4.7±2.4 mmHg, P〈 0.001）, right ventricular end-diastolic pressure （RVED, 18.3±5.6 mmHg vs 6.4±2.7 mmHg, P〈0.001）, CI （8.7±2.4 vs 5.8± 1.2, P=0.03）, and PI （87.8±32.3% vs 27.0±7.4%, P〈0.001） than Group 1. CI was correlated with PI （P〈0.001）, PW （P〈0.001）, PA （P〈0.001）, RA （P=0.043）, RVED （P=0.005）, HI （P〈0.001）, AO （P〈0.001）, CO （P〈0.001）, LVED （P〈0.001）, Vmax （P〈0.001）, Vmax （P〈0.001）, cross-sectional area of the main portal vein （P〈0.001） and PBF （P〈0.001）. CI could be as high as 8.3 in patients with RA〈 10 mmHg and as low as 5.9 in those with RA≥10 mmHg.CONCLUSION： Our data show that RI is a more significant indicator than CI in the clinical evaluation of high RA≥ 10 mmHg, whereas CI is better than PI in the assessment of left heart function.
基金Supported by Natural Science Foundation of Shanghai,China,No.22ZR1458200Medical Ph.D Innovative Talent Base Project of Changning District,Shanghai,China,No.RCJD2021B09Key Specialty of Changning District,Shanghai,China,No.20231004.
文摘BACKGROUND The incidence of multiple pregnancies has increased worldwide recently and women with a twin pregnancy are at higher risk of adverse outcomes compared with women with a singleton pregnancy.It is important to understand the risk factors for adverse fetal outcomes in twin pregnancy in order to guide clinical management.AIM To identify the independent risk factors,including maternal personal and family medical histories and first trimester ultrasound screening findings,for adverse fetal outcomes of twin pregnancy before 28 weeks of gestation.METHODS The data of 126 twin pregnancies in our hospital,including pregnancy outcomes,first trimester ultrasound screening findings and maternal medical history,were retrospectively collected.Twenty-nine women with adverse outcomes were included in the abnormal group and the remaining 97 women were included in the control group.RESULTS Patients in the abnormal group were more likely to be monochorionic diamniotic(13/29 vs 20/97,P=0.009),with a higher mean pulsatility index(PI,1.57±0.55 vs 1.28±0.42,P=0.003;cutoff value:1.393)or a higher mean resistance index(0.71±0.11 vs 0.65±0.11,P=0.008;cutoff value:0.683)or early diastolic notch of bilateral uterine arteries(UtAs,10/29 vs 15/97,P=0.024)or with abnormal ultrasound findings(13/29 vs 2/97,P<0.001),compared with the control group.Monochorionic diamnioticity,higher mean PI of bilateral UtAs and abnormal ultrasound findings during first trimester screening were independent risk factors for adverse fetal outcomes(P<0.05).CONCLUSION First trimester ultrasound screening for twin pregnancy identifies independent risk factors and is useful for the prediction of fetal outcomes.
文摘To the editor:The superior semicircular canal dehiscence was first described by Minor et all in 1998 as a condition in which the superior semicircular canal lacks a bony covering and has gained constantly increasing interest since its discovery.2 The symptoms are varied but specific what is known as Minor syndrome or‘third mobile window’syndrome,'as patients may experience autophony with abnormally loud sounds like footsteps,chewing,breathing,eye movement,echoing voice,distortion of environmental sounds and pulsatile tinnitus.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Ministry of Science and ICT(MSIT)(No.2021R1A2C2012808)Technology Innovation Program(Alchemist Project)(No.20012378)funded by the Ministry of Trade,Industry&Energy(MOTIE),South Korea.
文摘Dose-dense chemotherapy is the preferred first-line therapy for triple-negative breast cancer(TNBC),a highly aggressive disease with a poor prognosis.This treatment uses the same drug doses as conventional chemotherapy but with shorter dosing intervals,allowing for promising clinical outcomes with intensive treatment.However,the frequent systemic administration used for this treatment results in systemic toxicity and low patient compliance,limiting therapeutic efficacy and clinical benefit.Here,we report local dose-dense chemotherapy to treat TNBC by implanting 3D printed devices with timeprogrammed pulsatile release profiles.The implantable device can control the time between drug releases based on its internal microstructure design,which can be used to control dose density.The device is made of biodegradable materials for clinical convenience and designed for minimally invasive implantation via a trocar.Dose density variation of local chemotherapy using programmable release enhances anti-cancer effects in vitro and in vivo.Under the same dose density conditions,device-based chemotherapy shows a higher anticancer effect and less toxic response than intratumoral injection.We demonstrate local chemotherapy utilizing the implantable device that simulates the drug dose,number of releases,and treatment duration of the dose-dense AC(doxorubicin and cyclophosphamide)regimen preferred for TNBC treatment.Dose density modulation inhibits tumor growth,metastasis,and the expression of drug resistance-related proteins,including p-glycoprotein and breast cancer resistance protein.To the best of our knowledge,local dose-dense chemotherapy has not been reported,and our strategy can be expected to be utilized as a novel alternative to conventional therapies and improve anti-cancer efficiency.
文摘This paper represents a detailed and systematic review of one of the most ongoing applications of computational fluid dynamics(CFD)in biomedical applications.Beyond its various engineering applications,CFD has started to establish a presence in the biomedical field.Cardiac abnormality,a familiar health issue,is an essential point of investigation by research analysts.Diagnostic modalities provide cardiovascular structural information but give insufficient information about the hemodynamics of blood.The study of hemodynamic parameters can be a potential measure for determining cardiovascular abnormalities.Numerous studies have explored the rheological behavior of blood experimentally and numerically.This paper provides insight into how researchers have incorporated the pulsatile nature of the blood experimentally,numerically,or through various simulations over the years.It focuses on how machine learning platforms derive outputs based on mass and momentum conservation to predict the velocity and pressure profile,analyzing various cardiac diseases for clinical applications.This will pave the way toward responsive AI in cardiac healthcare,improving productivity and quality in the healthcare industry.The paper shows how CFD is a vital tool for efficiently studying the flow in arteries.The review indicates this biomedical simulation and its applications in healthcare using machine learning and AI.Developing AI-based CFD models can impact society and foster the advancement towards responsive AI.
基金Weifang Fundamental Research Projects,No.WFWSJK-2023-052.
文摘BACKGROUND Pituitary stalk interruption syndrome(PSIS)is a rare anatomical defect of the pituitary gland falling under the spectrum of holoprosencephaly phenotypes.It is characterized by a deficiency in anterior pituitary hormones,such as growth hormone,gonadotropins,and thyroid hormones.Due to the syndrome's rarity and nonspecific manifestations,there is a lack of standardized treatment strategies.Consequently,early diagnosis through imaging and on-time intervention are crucial for improving patients’outcomes.CASE SUMMARY A 30-year-old man presented with absent secondary sexual characteristics and azoospermia.Laboratory evaluation revealed a deficiency in gonadotropins,while thyroid function was mostly within normal ranges.Magnetic resonance imaging of the pituitary gland showed pituitary stalk agenesis,hypoplasia of the anterior pituitary,and ectopic posterior pituitary,leading to the diagnosis of PSIS.Initially,the patient underwent 6 mo of gonadotropin therapy without significant changes in hormone levels and secondary sexual characteristics.Pulsatile gonadotropin-releasing hormone therapy was then administered,resulting in the detection of sperm in the semen analysis within 3 mo.After 6 mo,routine semen tests showed normal semen quality.The couple faced challenges in conceiving due to abstinence and underwent three cycles of artificial insemination,which was unsuccessful.They also attempted in vitro fertilization,but unfortunately,the woman experienced a miscarriage 10 wk after the embryo transfer.CONCLUSION Early detection,accurate diagnosis,and timely treatment are crucial in improving the quality of life and fertility of PSIS patients.
文摘Seventy four cases of infertility were examined to study the hemodynamics of the bilateral ovarian arteries at 21st day during the corpus luteum phase by color Doppler energy(CDE) and color Doppler flow imaging (CDFI). All the patients were verified by laparoscopy, fallopian tube patency examination and ovarian function test. Twenty two healthy women served as controls. The results showed that the difference of resistance index(RI)and pulsatility index (PI) of bilateral ovarian arteries between the infertility and the normal controls had statistical significance ( P <0.01), and the PI showed negative correlation with the thickness of endometrium (left side: r =0.724, P <0.01; right side: r =0.756, P <0.01). The results also showed that CDE was more sensitive than CDFI in displaying the ovarian arteries. It could be concluded that the elevated resistance of ovarian artery during the corpus luteum phase was one of the important factors that resulted in infertility.
基金Supported by the National Basic Research Program of China:Basic Theoretics Research on TCM Featured Therapy(973Program,No.2007CB512701)the Research Program of State Administration of Traditional Chinese Medicine:Traditional Chinese Tuina Industry Specific Research Program(No.200707013)the National Science Foundation for Distinguished Young Scholars of China:Science of Tuina(No.81025022)
文摘OBJECTIVE:To explore the most effective parameters of Yi Zhi Chan Tuina manipulation for improving peripheral blood circulation.METHODS:A total of 45 volunteers were recruited from Pudong district in Shanghai,China,from October to December 2010,and randomly divided into nine groups using computer-generated random numbers.Participants received Yi Zhi Chan Tuina manipulation on Chengjin(BL 56) acupoint;each group received a particular combination of manipulation force and treatment time.We used a two-factor,three-level factorial design to examine the effects of force and treatment time on changes in popliteal artery average volume flow,pulsatility index,and vessel diameter to determine the optimal parameter group.Outcomes were assessed at baseline and after Tuina manipulation by interviewers blind to treatment group status.RESULTS:After manipulation,two of the nine groups showed an increase in popliteal artery volume flow.An inter-participants effect test showed that for main effect of time,F = 0.331,P = 0.720;for main effect of force,F = 2.934,P = 0.066;and for the force-time interaction effect,F = 1.072,P = 0.385,indicating no interaction between force and time.However,a pairwise comparison of the three levels of time showed that a treatment time of 10 min was significantly more effective than that of 2 min(P = 0.024).A pairwise comparison of light force,medium force,and heavy force showed a statistically significant effect for medium force(P = 0.035).CONCLUSION:Yi Zhi Chan Tuina manipulation with vertical force of 9.31 N for 10 min is most effective in improving peripheral circulation.
文摘Objective:To assess the hemodynamic changes that occurred in the main testicular artery at two different locations such as supra and marginal ones in bulls at three different ages.Methods:Eighteen Baladi bulls were divided according to their age into three different age groups:1 year[n=6;groupⅠwith bodyweight(380±10)kg],3 years[n=6;groupⅡwith bodyweight(570±10)kg],and 6 years old[n=6;groupⅢwith bodyweight(650±10)kg]Baladi bulls.Circumference of the scrotum,thickness of the mediastinum,testicular dimensions,vascularity,and hormonal levels were measured.Testicular hemodynamics were assessed by Doppler ultrasound scanning.Results:Testicular width,length,and volume were significantly different among the three age groups,with the highest in bulls of groupⅢ(P<0.05).The bulls in groupⅢhad significantly higher mediastinal line thickness and scrotal circumference than groupⅠ(P<0.05),but there was no significant difference between groupⅡand groupⅢ.Bulls in groupⅡshowed a decline in Doppler indices(resistance and pulsatility indexes)at both testicular branches compared to the other two groups(P<0.05).Supra and marginal end diastolic velocities in the three age groups were significantly different,with the highest in groupⅡ(P<0.05).Time average velocity(cm/s)was significantly elevated in groupⅡcompared to the other two groups(P<0.05).Both testicular echotextures were significantly decreased in groupⅡ(P<0.05).Estradiol and nitric oxide metabolites were significantly high in groupⅡcompared to the other two groups(P<0.05).Meanwhile,the level of plasma testosterone was maximum in groupⅢ(P<0.05).Positive correlations were found between supratesticular artery resistance and pulsatility indexes(r=0.81;P<0.001),while both resistance and pulsatility indexes had correlated negative with estradiol(r=-0.71 and r=-0.91;P<0.001),and nitric oxide metabolites(r=-0.92 and r=-0.72;P<0.001).Conclusions:Three-year old Baladi bull has the lesser Doppler indices with lesser echotexture and greater nitric oxide with estradiol concentrations,which directs a significant ability for the thermoregulation process.These parameters will help in breeding selection.
文摘The aim of this study was to compare lower limb blood flow in asymptomatic diabetic patients with early-stage peripheral artery disease (PAD) and non-diabetic controls using duplex ultrasound parameters. This was a comparative cohort study of lower limb blood flow in 35 Black-African diabetic patients (25 females and 10 males with early-stage PAD median age 54 [IQR, 47 - 61] years;median HbA<sub>1c</sub> 6.3 [IQR, 5.7 - 8.0]%<sub></sub>;BMI 29.2 ± 6.7;ABI 1.1 ± 0.1) and 36 non-diabetic controls (28 females and 8 males;median age 54 [IQR, 47 - 61] years;median HbA<sub>1c</sub> 6.3 [IQR, 5.7 - 8.0] %, BMI 29.2 ± 6.7;ABI 1.1 ± 0.1). Peak systolic velocity (PSV), pulsatility index (PI) and resistive index (RI), were utilised to compare blood flow in the popliteal arteries (PA), anterior tibial arteries (ATA) and posterior tibial arteries (PTA) in addition to ankle brachial index. All the ultrasound parameters showed good (ICC ≥ 0.7;0.50 - 0.85, 95% CI) to excellent (ICC = 1.0;1.0 - 1.0, 95% CI) reliability within groups as well as acceptable variability () other than pulsatility index of the anterior tibial artery within diabetic patients (11.1% CV). PSV, RI and PI were significantly and meaningfully higher (P;d ≥ 0.33), in diabetic patients compared to non-diabetic controls except for PI - PTA (P = 0.72;d = 0.11). Differences in PSV and RI highlighted the effects of early-stage PAD on lower limb blood flow of diabetic patients. In contrast, the effects of early-stage PAD on blood flow were not demonstrated in the PTA and ATA of diabetic patients by PI.
文摘Both pulsatile gonadotropin-releasing hormone （GnRH） infusion and combined gonadotropin therapy （human chorionic gonadotropin and human menopausal gonadotropin [HCG/HMG]） are effective to induce spermatogenesis in male patients with congenital hypogonadotropic hypogonadism （CH H）. However, evidence is lacking as to which treatment strategy is better. This retrospective cohort study included 202 patients with CHH： twenty had received pulsatile GnRH and 182 had received HCG/HMG. Patients had received therapy for at least 12 months. The total follow-up time was 15.6 ± 5.0 months （range： 12-27 months） for the GnRH group and 28.7 ± 13.0 months （range： 12-66 months） for the HCG/HMG group. The median time to first sperm appearance was 6 months （95% confidence interval [CI]： 1.6-10.4） in the GnRH group versus 18 months （95% Ch 16.4-20.0） in the HCG/HMG group （P〈 0.001）. The median time to achieve sperm concentrations 〉5 x 106 m1-1 was 14 months （95% Ch 5.8-22.2） in the GnRH group versus 27 months （95% Ch 18.9-35.1） in the HCG/HMG group （P 〈 0.001）, and the median time to concentrations 〉10 x 106 m1-1 was 18 months （95% Ch 10.0-26.0） in the GnRH group versus 39 months （95% CI unknown） in the HCG/HMG group. Compared to the GnRH group, the HCG/HMG group required longer treatment periods to achieve testicular sizes of 〉4 ml, 〉8 ml, 〉12 ml, and 〉16 ml. Sperm motility （a ＋ b ＋ c percentage） evaluated in semen samples with concentrations 〉1 × 106 ml-1 was 43.7% ± 20.4% （16 samples） in the GnRH group versus 43.2% ± 18.1% （153 samples） in the HCG/HMG group （P= 0.921）. Notably, during follow-up, the GnRH group had lower serum testosterone levels than the HCG/HMG group （8.3 ±4.6 vs 16.2 ± 8.2 nmol 1-1, P 〈 0.001）. Our study found that pulsatile GnRH therapy was associated with earlier spermatogenesis and larger testicular size compared to combined gonadotropin therapy. Additional prospective randomized studies would be required to confirm these findings.
基金supported by the laboratory foundation of Tsinghua Universitythe'985'research foundation of Tsinghua University
文摘The influence of high-density pulsing current on the work-hardening behaviour of H0Cr17Ni6Mn3 and 1Cr18Ni9 stainless steels in wire-drawing deformation processes has been studied. It was found that the drawing stress and the work-hardening rate of wires were significantly reduced by applying current pulses in drawing process. The work-hardening behavior of the multi-courses drawing deformation can be well described by Hollomon formula σ=κΕn. With the application of current pulses in drawing deformation, the work-hardening exponents of H0Cr17Ni6Mn3 steel wires and 1Cr18Ni9 stainless steel wires were reduced by 33% and 45%, respectively, and their work-hardening coefficients were reduced by 41% and 47%, respectively. It was also found that the work-hardening coefficient of wires was reduced with the increment of the frequency of current pulses, while the work-hardening exponents of both steels were insensitive to the pulsing frequency.
基金supported by Beijing Municipal Natural Science Foundation of China(Grant No. 3123036)Science and Technology Project of Beijing Municipal Education Commission of China(Grant No.KM200911417010)
文摘The current research on pulse continuously variable transmission（CVT） is mainly focused on reducing the pulse degree and making pulse degrees a constant value. Current research mainly confined to find out new design parameters by using the method of optimization, and reduce the pulse degree of pulse CVT and its range of variation. But the fact is that the reduction of the pulse degree is not significant. This article presents a new structure of mechanical pulse CVT--the rotational swashplate pulse CVT with driven by helical gear axial meshing. This transmission is simple and compact in structure and low in pulsatile rate （it adopts 6 guide rods）, and the pulsatile degree is irrelevant to the transmission ratio. Theoretically, pulsatile rate could be reduced to zero if appropriate curved surface of the swashplate is used. Compared with the connecting rod pulse CVT, the present struc^tre uses helical gear mechanism as transmission part and it avoids unbalanced inertial force in the former model. This paper analyzes the principle of driving of this transmission, presents its mechanical structure, and discusses its motion characteristics. Experimental prototype of this type of CVT has been manufactured. Tests for the transmission efficiency（when the rotational speed of the output shaft is the maximum） and the angular velocity of the output shaft have been carried out, and data have been analyzed. The experimental results show that the speed of the output shaft for the experimental prototype is slightly lower than the theoretical value, and the transmission efficiency of the experimental prototype is about 70%. The pulse degree of the CVT discussed in this paper is less than the existing pulse CVT of other types, and it is irrelevant to the transmission ratio of the CVT. The research provides the new idea to the CVT study.
基金This study was supported by the National Natural Science Foundation of China(Grants 11602053 and 51576033)the Fundamental Research Funds for the Central Universities(Grant DUT18JC23).
文摘This study experimentally and numerically investigated the effect of pulsatile flow of different frequencies and outflow resistance on wall deformation in a lateral aneurysm.A method for constructing a flexible aneurysm model was developed,and a self-designed piston pump was used to provide the pulsatile flow conditions.A fluid-structure interaction simulation was applied for comparison with and analysis of experimental findings.The maximum wall displacement oscillation increased as the pulsation frequency and outflow resistance increased,especially at the aneurysm dome.There is an obvious circular motion of the vortex center accompanying the periodic inflow fluctuation,and the pressure at the aneurysm dome at peak flow increased as the pulsatile flow frequency and terminal flow resistance increased.These results could explain why abnormal blood flow with high frequency and high outflow resistance is one of the risk factors for aneurysm rupture.
文摘The effects of the renal artery stenosis （RAS） on the blood flow and vessel walls are investigated. The pulsatile blood flow through an anatomically realistic model of the abdominal aorta and renal arteries reconstructed from CT-scan images is simulated, which incorporates the fluid-structure interaction （FSI）. In addition to the investigation of the RAS effects on the wall shear stress and the displacement of the vessel wall, it is determined that the RAS leads to decrease in the renal mass flow. This may cause the activation of the renin-angiotension system and results in severe hypertension.
文摘Pulsatile gonadotropin-releasing hormone （GnRH） may induce spermatogenesis in most patients with congenital hypogonadotropic hypogonadism （CHH） by stimulating gonadotropin production, while the predictors for a pituitary response to pulsatile GnRH therapy were rarely investigated. Therefore, the aim of our study is to investigate predictors of the pituitary response to pulsatile GnRH therapy. This retrospective cohort study included 82 CHH patients who received subcutaneous pulsatile GnRH therapy for at least 1 month. Patients were categorized into poor or normal luteinizing hormone （LH） response subgroups according to their LH level （LH 〈2 IU 1-1 or LH P_2 IU 1-1） 1 month into pulsatile GnRH therapy. Gonadotropin and testosterone levels, testicular size, and sperm count were compared between the two subgroups before and after GnRH therapy. Among all patients, LH increased from 0.4±0.5 IUI^-1 to 7.5±4.4 IUI^-1 and follicle-stimulating hormone （FSH） increased from 1.1±0.9 IUI^-1 to 8.8±5.3 IU 1-1. A Cox regression analysis showed that basal testosterone level （6 = 0.252, P = 0.029） and triptorelin-stimulated FSH60min（13 = 0.518, P = 0.01） were two favorable predictors for pituitary response to GnRH therapy. Nine patients （9/82, 11.0%） with low LH response to GnRH therapy were classified into the poor LH response subgroup. After pulsatile GnRH therapy, total serum testosterone level was 39± 28 ng dl^-1 versus 248±158 ng d1^-1 （P=0.001）, and testicular size was 4.0±3.1 ml versus 7.9±4.5 ml （P= 0.005） in the poor and normal LH response subgroups, respectively. It is concluded that higher levels of triptorelin-stimulated FSH60min. and basal total serum testosterone are favorable predictors of pituitary LH response to GnRH therapy.
