Homotopy analysis solutions for the asymmetric laminar flow in a porous channel with expanding or contracting walls

In this paper, the asymmetric laminar flow in a porous channel with expanding or contracting walls is investigated. The governing equations are reduced to ordinary ones by using suitable similar transformations. Homotopy analysis method （HAM） is employed to obtain the expres- sions for velocity fields. Graphs are sketched for values of parameters and associated dynamic characteristics, especially the expansion ratio, are analyzed in detail.

Analytic solution to the micropolar-fluid flow through a semi-porous channel with an expanding or contracting wall

The flow of a micropolar fluid in a semi-porous channel with an expanding or contracting wall is investigated. The governing equations are reduced to ordinary ones by using similar transformations. To get the analytic solution to the problem, the homotopy analysis method （HAM） is employed to obtain the expressions for velocity fields. Graphs are sketched and discussed for various parameters, especially the effect of the expansion ratio on velocity and micro-rotation fields.

Perturbation solution to unsteady flow in a porous channel with expanding or contracting walls in the presence of a transverse magnetic field

An incompressible flow in a porous channel with expanding or contacting walls in the presence of a transverse magnetic field is considered. Using similarity transformations, the governing equations are reduced to the nonlinear ordinary differential equations. The exact similar solutions for the different cases of the expansion ratio and the Hartmann number are obtained with a singular perturbation method, and the associated behavior is discussed in detail.

Mechanisms mediating CCK-8S-induced contraction of proximal colon in guinea pigs

AIM:To investigate the effects of sulfated cholecystokinin octapeptide (CCK-8S) on the contractile activity of guinea-pig proximal colon.METHODS:Proximal colonic smooth muscle (PCSM) strips were obtained from adult female guinea pigs and contractile response of PCSM strips was recorded using a polyphysiograph.PCSM cells were isolated by enzymatic digestion.Resting potential (RP),action potential (AP),large conductance potassium channel currents (IBKCa) and L-type calcium currents (ICa-L) were recorded by patch-clamp techniques.RESULTS:(1) CCK-8S (10-7 mol/L) enhanced the mean contractile amplitude of colonic circular muscle and longitudinal muscle (LM) strips by 56.53% ± 11.92%(P=0.038) and 65.93% ± 12.98% (P=0.019),respectively,as well as the mean frequency of LM by 31.69% ± 13.58% (P=0.023),which were significantly attenuated by pretreating strips with devazepide,nifedipine,iberiotoxin,thapsigargin (TG) and BAPTA-AM (BA) respectively;(2) CCK-8S (10-7 mol/L) increased the AP amplitude by 38.6% ± 3.2% (P=0.015),decreased AP duration by 36.9% ± 8.7% (P=0.026),and depolarized the RP from-61.3 ± 2.7 mV to-29.8 ± 5.9 mV (P=0.032);and (3) Compared with the normal control group,CCK-8S (10-7 mol/L) enhanced the peak current of IBKCa by 18.7% ± 2.1% (from 916 ± 183 pA to 1088 ± 226 pA;at +60 mV;P=0.029),which was inhibited by respective pretreatment with iberiotoxin and devazepide.Additionally,CCK-8S (10-7 mol/L) intensif ied the peak current of ICa-L by 40% (from 60 ± 8 pA to 84 ± 11 pA;at +10 mV;P=0.012),compared to the normal control group,which was apparently suppressed by respective pretreatment with nifedipine,devazepide,TG and BA.In the respective presence of heparin and staurosporine,CCK-8S did not signif icantly enhance IBKCa and ICa-L.CONCLUSION:The results suggest that CCK-8S promotes guinea-pig proximal colon contraction by CCK1 receptors,following activation of the inositol triphosphate-protein kinase C signal transduction pathway.

Effects of anti-hypertensive drugs on esophageal body contraction

AIM:To clarify the effects of anti-hypertensive drugs on esophageal contraction and determine their possi-ble relationship with gastro-esophageal reflux disease.METHODS:Thirteen healthy male volunteers were enrolled. Esophageal body peristaltic contractions and lower esophageal sphincter (LES) pressure were measured using high resolution manometry. All subjects were randomly examined on four separate occasions following administrations of nifedipine,losartan,and atenolol,as well as without any drug administration.RESULTS:Peristaltic contractions by the esophageal body were separated into three segments by two troughs. The peak peristaltic pressures in the mid and lower segments of the esophageal body under atenolol administration were signifi cantly higher than those without medication in a supine position. On the other hand,peristaltic pressures under nifedipine administration were lower than those observed without drug ad-ministration. Losartan did not change esophageal body peristalsis. Atenolol elevated LES pressure and slowed peristaltic wave transition,while the effects of nifedip-ine were the opposite. CONCLUSION:Among the anti-hypertensive drugs tested,atenolol enhanced esophageal motor activity,which was in contrast to nifedipine.

Effect of the ginsenoside Rb1 on the spontaneous contraction of intestinal smooth muscle in mice

AIM: To investigate the effect and the possible mechanism of ginsenoside Rb1 on small intestinal smooth muscle motility in mice. METHODS: Intestinal smooth muscle strips were isolated from male ICR mice (5 wk old), and the effect of ginsenoside Rb1 on spontaneous contraction was recorded with an electrophysiolograph. The effect of ginsenoside Rb1 on ion channel currents, including the voltage-gated K + channel current (IK V ), calcium-activated potassium channel currents (IK Ca ), spontaneous transient outward currents and ATP-sensitive potassium channel current (IK ATP ), was recorded on freshly isolated single cells using the whole-cell patch clamp technique. RESULTS: Ginsenoside Rb1 dose-dependently inhibited the spontaneous contraction of intestinal smooth muscle by 21.15% ± 3.31%, 42.03% ± 8.23% and 67.23% ± 5.63% at concentrations of 25 μmol/L, 50 μmol/L and 100 μmol/L, respectively (n=5,P<0.05). The inhibitory effect of ginsenoside Rb1 on spontaneous contraction was significantly but incompletely blocked by 10 mmol/L tetraethylammonium or 0.5 mmol/L 4-aminopyridine, respectively (n=5, P<0.05). However, the inhibitory effect of ginsenoside Rb1 on spontaneous contraction was not affected by 10 μmol/L glibenclamide or 0.4 μmol/L tetrodotoxin. At the cell level, ginsenoside Rb1 increased outward potassium currents, and IK V was enhanced from 1137.71 ± 171.62 pA to 1449.73 ± 162.39 pA by 50 μmol/L Rb1 at +60 mV (n=6, P<0.05). Ginsenoside Rb1 increased IK Ca and enhanced the amplitudes of spontaneous transient outward currents from 582.77 ± 179.09 mV to 788.12 ± 278.34 mV (n=5, P<0.05). However, ginsenoside Rb1 (50 μmol/L) had no significant effect on IK ATP (n=3, P<0.05). CONCLUSION: These results suggest that ginsenoside Rb1 has an inhibitory effect on the spontaneous contraction of mouse intestinal smooth muscle mediated by the activation of IK V and IK Ca , but the K ATP channel was not involved in this effect.

Effect of gingerol on colonic motility via inhibition of calcium channel currents in rats

AIM: To investigate the effect of gingerol on colonic motility and the action of L-type calcium channel currents in this process.METHODS: The distal colon was cut along the mesenteric border and cleaned with Ca^(2+)-free physiological saline solution. Muscle strips were removed and placed in Ca^(2+)-free physiological saline solution, which was oxygenated continuously. Longitudinal smooth muscle samples were prepared by cutting along the muscle strips and were then placed in a chamber. Mechanical contractile activities of isolated colonic segments in rats were recorded by a 4-channel physiograph. Colon smooth muscle cells were dissociated by enzymatic digestion. L-type calcium currents were recorded using the conventional whole-cell patch-clamp technique.RESULTS: Gingerol inhibited the spontaneous contraction of colonic longitudinal smooth muscle in a dose-dependent manner with inhibition percentages of 13.3% ± 4.1%, 43.4% ± 3.9%, 78.2% ± 3.6% and 80.5% ± 4.5% at 25 μmol/L, 50 μmol/L, 75 μmol/L and 100 μmol/L, respectively(P < 0.01). Nifedipine, an L-type calcium channel blocker, diminished the inhibition of colonic motility by gingerol. Gingerol inhibited L-type calcium channel currents in colonic longitudinal myocytes of rats. At a 75 μmol/L concentration of gingerol, the percentage of gingerolinduced inhibition was diminished by nifedipine from 77.1% ± 4.2% to 42.6% ± 3.6%(P < 0.01). Gingerol suppressed IBa in a dose-dependent manner, and the inhibition rates were 22.7% ± 2.38%, 35.77% ± 3.14%, 49.78% ± 3.48% and 53.78% ± 4.16% of control at 0 m V, respectively, at concentrations of 25 μmol/L, 50 μmol/L, 75 μmol/L and 100 μmol/L(P < 0.01). The steady-state activation curve was shifted to the right by treatment with gingerol. The value of half activation was-14.23 ± 1.12 m V in the control group and-10.56 ± 1.04 m V in the 75 μmol/L group(P < 0.05) with slope factors, Ks, of 7.16 ± 0.84 and 7.02 ± 0.93(P < 0.05) in the control and 75 μmol/L groups, respectively. However, the steady-state inactivation curve was not changed, with a half-inactivation voltage, 0.5 V, of-27.43 ± 1.26 m V in the control group and-26.56 ± 1.53 m V in the 75 μmol/L gingerol group(P > 0.05), and a slope factor, K, of 13.24 ± 1.62 in the control group and 13.45 ± 1.68(P > 0.05) in the 75 μmol/L gingerol group.CONCLUSION: Gingerol inhibits colonic motility by preventing Ca^(2+) influx through L-type calcium channels.

Numerical Studies of Turbulent Flows in Channels with Abrupt Cross-sectional Changes

The turbulent flows through the channels with abrupt cross-sectional changes are common and importantphysical process in nature.For a better prediction of the mean flow and turbulent characteristics for this problem,atwo-dimensional depth-averaged numerical model is developed.The model is robust and accurate in reproducing therecirculation flow behind a groyne and turbulent flows in channels with abrupt cross-sectional changes,when com-pared to the available experimental data of mean velocities and turbulence kinetic energy.Our results reveal that theabrupt cross-sectional change of a channel can affect the flow pattern significantly and introduces the complex turbu-lence characteristics.In particular,when the channel has an abrupt expansion,the mean flow pattern is mainly in lon-gitudinal direction with rather small transverse component.Meanwhile,a recirculating region forms behind the expan-sion position and the turbulence has very strong intensity within this region.For the flow in the channel with an ab-rupt contraction,the longitudinal component of the flow is decreased by the obstruction on one side and accelerated onthe other side,whereas the transverse velocity is small.The turbulence is extraordinarily strong in the regions adja-cent to the contraction wall in the narrow channel.In both cases of abrupt cross-sectional changes,the TKE is genera-ted dominantly by the shear of the longitudinal velocities.

低频脉冲磁场慢性暴露对健康成年股四头肌收缩力及形态的影响

背景:目前已有关于低频脉冲磁场对骨骼肌结构形态影响研究发现了骨骼肌质量变化,但对接受慢性暴露后的形态变化未见相关研究。目的:观察低频脉冲磁场慢性暴露对腿部股四头肌最大自主收缩力与形态指标的影响,为使用该技术作为肌肉功能改善策略提供组织形态变化的参考依据。方法:招募普通健康受试者70名,随机分为接受磁场刺激的试验组与进行假治疗的对照组,每组35名,试验时长共计4周,试验组受试者每隔48 h进行1次15 min的低频脉冲磁刺激干预,对照组进行假治疗,干预间隔与时长与试验组一致,干预4周后观察不同组别受试者股四头肌最大自主收缩力值变化,利用B型超声影像作为评估手段,观察肌肉厚度、肌肉横截面积及羽状角指标的变化。结果与结论:①经过4周的低频脉冲磁场慢性暴露,68名受试者完成试验,试验组受试者股四头肌最大自主收缩力测试值显著增长(P=0.000),提升幅度显著高于对照组(P=0.008);②试验组受试者的肌肉形态3项指标均显著高于试验前测(P=0.000),而对照组肌肉厚度指标呈显著性下降(P=0.020),羽状角无显著性变化,横截面积显著性提升(P=0.000);③组间对比发现,试验组关于肌肉形态的肌肉厚度(P=0.012)、羽状角(P=0.003)及横截面积(P=0.049)3项指标均显著高于对照组;④上述数据证实,健康成年受试者经过4周的低频脉冲磁场慢性暴露,股四头肌的最大自主收缩力显著提升,同时观察到试验组的肌肉厚度、横截面积及羽状角3项肌肉形态指标的显著增长,对使用该技术作为肌肉改善的运动替代与医疗策略提供了肌组织形态改善的支持依据。

干湿环境下膨胀土裂隙演化规律及渠坡变形研究

研究干湿循环效应下膨胀土裂隙发育规律对揭示膨胀土渠道边坡失稳机制有重要意义。针对目前研究中存在的不足,开展了仅考虑干湿循环效应的膨胀土裂隙演化试验,系统测量了随时间变化的水分蒸发过程及裂隙动态发育特征。基于膨胀土裂隙演化规律,通过编程将块体离散元方法应用至膨胀土渠坡变形分析中,并得到如下结论:(1)膨胀土水分蒸发过程可分为稳定蒸发阶段、减速率蒸发阶段和残余蒸发阶段;(2)随着干湿循环次数增加,膨胀土面积裂隙率逐渐增加后趋于稳定,裂隙总长度逐步增加,裂隙平均宽度不断减小并逐渐稳定,裂隙夹角由T型逐步过渡至Y型;(3)土体颗粒排布总是向稳定方向发育,颗粒间应力分布向着更优势的状态发展,胀缩裂隙分布逐步稳定;(4)将块体离散元应用至膨胀土边坡分析中,实现了考虑裂隙和吸湿膨胀的膨胀土边坡位移场-应力场耦合;(5)干湿循环效应促进了膨胀土裂隙发育,裂隙率增加导致渠坡变形增加和塑性区扩大,在膨胀土渠坡坡脚处变形显著。

农产品双渠道供应链品牌推广与保鲜努力联合策略研究

针对由一个农产品供应商和一个传统线下零售商构成的双渠道供应链,研究构建了考虑产品商誉和新鲜度的状态变量微分博弈模型。首先,对不同渠道结构下供应链成员的最优均衡策略进行了讨论分析,发现随着时间的推移,产品商誉的轨迹呈现出多变性,而农产品的新鲜度轨迹则保持单调性。其次,制定了保鲜努力与品牌推广成本分摊契约,并讨论了契约对供应链协调性的影响。最后,通过算例分析进行验证,发现通过单双渠道供应商利润的比较,传统渠道占有率越小,则双渠道情形下供应商利润越大。同时,设计的品牌推广与保鲜努力成本分担契约可以实现供应商和传统线下零售商对各自主体的利润改善,且消费者对农产品的新鲜度偏好和品牌偏好的提高,农产品供应商和传统线下零售商将更有意愿促成成本共摊的合作模式。

政府补贴下考虑风险厌恶的双渠道绿色供应链运营决策及协调契约

在政府对绿色产品提供补贴的基础上,构建以制造商为主导的供应链博弈模型,利用均值方差法分析了在双方风险中性(RN)、双方风险厌恶(RA)、仅制造商风险厌恶(MRA)和仅零售商风险厌恶(RRA)4种模式下的双渠道绿色供应链决策及效用,并设计带有转移支付的成本分担契约以实现协调。研究发现:在RRA模式下,产品绿色度与风险厌恶程度正相关;而在MRA模式和RA模式下,产品绿色度与风险厌恶程度负相关;双方效用在4种模式下均与政府补贴正相关,且在RRA模式下制造商效用受政府补贴的影响最为显著;当研发成本系数较大时,在MRA模式和RRA模式下,一方的效用与另一方的风险厌恶程度正相关,而在RA模式下双方效用与风险厌恶程度负相关。此外,通过数值分析揭示了成本分担比例与风险厌恶程度负相关、与政府补贴正相关。以上结论可为双渠道绿色供应链的决策制定及协调管理提供参考。

不同销售模式下质量投资和自有品牌侵入的交互影响

平台作为线上资源配置媒介,正改变着供应链产业结构和市场消费模式。基于不同销售契约,研究供应链质量投资和平台自有品牌侵入的交互作用。考虑消费者策略偏好,建立8种不同情形下的供应链决策模型;进一步,通过数值分析探讨了供应链销售模式选择、质量投资和渠道结构配置策略。研究表明:供应商和平台对供应链销售模式偏好具有差异性,但通过外生参数控制可以实现局部供应链帕累托改进。供应商质量投资总是可以为其带来额外的收益,但平台自有品牌侵入会提高质量投资门槛。反常识的,当消费者接受度较高时,平台不倾向引入自有品牌,只有当接受度较低时才会选择混合渠道策略。因此,供应链实行差异化产品策略能够缓解竞争、促进消费,更有利于运营。

基于钙通道及心肌收缩机制探讨强心药的应用

心力衰竭是各种心血管疾病的末期阶段,临床表现复杂,难以根治。心肌收缩功能下降是心力衰竭发生的重要原因之一。钙通道在心肌收缩舒张过程中具有关键调控作用,心肌收缩蛋白、心肌能量代谢、心肌兴奋收缩耦联在心脏疾患后期受到各种理化因素影响而出现异常,引起心肌收缩力减弱。心肌收缩功能正常对于维持人体正常生命活动具有决定性意义,临床常根据具体状况分类应用强心药以改善心肌收缩力,效果显著。随着医学技术的进步,强心药种类增多且优势更加突出,未来仍需进一步探讨。

异质性服务平台直营、转销或混合渠道结构选择

考虑异质性服务质量努力与两部定价佣金合同,构建制造商和平台构成的博弈模型,研究异质性服务平台渠道结构,识别直营、转销和混合3种渠道结构成为平台、制造商及系统最佳选择的条件。研究表明,当平台向制造商收取一定范围的固定管理费用时,异质性服务平台选择混合渠道;制造商入侵平台形成的混合渠道会提高批发价格,加剧双重边际效应;制造商服务质量努力系数增大能够减弱服务异质性,使得混合渠道中的批发价格降低,销量增加,促进制造商提升服务质量。并通过设计有效的两部定价佣金合同,使得混合渠道实现Pareto最优。

考虑企业社会责任的供应链决策与协调

考虑碳限额交易下由制造商和具有企业社会责任(CSR)的零售商组成的双渠道供应链,通过消费者效用函数构建Stackelberg博弈模型研究不同情况各主体最优均衡决策,利用MATLAB分析CSR、消费者低碳意识以及转移支付费用对均衡结果的影响。研究发现:CSR对集中决策下整体效益有利但会降低减排率,而对分散决策的影响相反;低碳意识越强对减排量、效益、消费者剩余越有利;一定条件下二部定价契约能有效缓解双重边际效应,实现整个供应链系统效益的Pareto改进。

新零售环境下基于渠道迁徙行为的农产品供应链决策优化

有别于大众化消费普遍从线下转移到线上的迁徙路径,个体异质且存在时鲜易腐的农产品消费不仅存在线下至线上的迁徙,同时不乏线上至线下的转移,农产品消费的渠道迁徙路径更加的灵活多元。基于此,分别构建传统环境、新零售环境基于渠道迁徙行为和新零售环境基于成本共担契约的农产品供应链决策模型,计算三种情形下零售商的最优订购量及最优利润水平,并进行了模型对比分析。研究表明,适当的成本共担契约能够在存在消费者渠道迁徙行为时激励提升农产品供应链的服务水平,促进提高农产品订购量并增加供应链主体的收益。

基于努力因素的供应链利益共享契约模型研究

在需求不确定且与努力水平具有相关性的前提下,建立了单供应商(或生产商)和销售商之间的利益共享契约模型,分析了努力因素对供应链协作策略的影响。通过对传统利益共享契约模式的研究,解释了此时单纯利益共享契约模式为什么无法实现供应链协作。为此,提出了基于回馈与惩罚策略的利益共享契约理论。通过在传统的利益共享契约中引入回馈与惩罚策略,解决了单纯的利益共享契约无法实现供应链协作的问题,使供应链恢复到协作状态,并给出了确定最优契约参数的方法。最后,通过数值例子对模型进行了分析比较。

皂苷提取物宫血宁缩宫作用与细胞外钙内流关系的研究

目的探讨皂苷类提取物宫血宁引起的大鼠离体子宫收缩作用与细胞外钙内流的关系。方法应用离体子宫张力测定法,观察不同Ca2+浓度及Ca2+通道阻滞剂对宫血宁引起的大鼠离体子宫收缩作用的影响。结果无钙的台氏平衡液中,宫血宁的浓度从25μg/ml增至200μg/ml都不能引起大鼠离体子宫节律性收缩;在半钙和全钙的台氏平衡液中宫血宁能引起大鼠离体子宫节律性收缩,并与宫血宁的剂量呈显著正相关;Ca2+通道阻滞剂能明显抑制宫血宁和缩宫素引起的子宫收缩,但同缩宫素相比,宫血宁引起的子宫收缩对Ca2+通道阻滞剂更敏感。结论皂苷类提取物宫血宁的缩宫作用依赖于细胞外钙的存在,其作用机制可能是通过促进平滑肌细胞外钙内流来实现的。

考虑努力及价格因素的弹性数量契约模型

在需求不确定且与努力水平和零售价格具有相关性的前提下,建立了弹性数量契约模型,通过引入回馈与惩罚策略,解决了单纯的弹性数量契约无法实现供应链协作这一问题。并重点探讨以下两个主要内容:(1)如何确保供应链协作;(2)如何确定最优的努力水平、零售价格和订购量。最后,通过数值例子对协作和分散两种模式进行了分析比较。