Differential activity of the G protein beta5 gamma2 subunit at receptors and effectors

The G protein beta5 subunit differs substantially in amino acid sequence from the other known beta subunits suggesting that beta gamma dimers containing this protein may play specialized roles in cell signaling. To examine the functional properties of the beta5 subunit, recombinant beta5 gamma2 dimers were purified from baculovirus-infected Sf9 insect cells using a strategy based on two affinity tags (hexahistidine and FLAG) engineered into the N terminus of the gamma2 subunit (gamma2HF). The function of the pure beta5 gamma2HF dimers was examined in three assays: activation of pure phospholipase C-beta in lipid vesicles; activation of recombinant, type II adenylyl cyclase expressed in Sf9 cell membranes; and coupling of alpha subunits to the endothelin B (ETB) and M1 muscarinic receptors. In each case, the efficacy of the beta5 gamma2HF dimer was compared with that of the beta1 gamma2HF dimer, which has demonstrated activity in these assays. The beta5 gamma2HF dimer activated phospholipase C-beta with a potency and efficacy similar to that of beta1 gamma2 or beta1 gamma2HF; however, it was markedly less effective than the beta1 gamma2HF or beta1 gamma2 dimer in its ability to activate type II adenylyl cyclase (EC50 of approximately 700 nM versus 25 nM). Both the beta5 gamma2HF and the beta1 gamma2HF dimers supported coupling of M1 muscarinic receptors to the Gq alpha subunit. The ETB receptor coupled effectively to both the Gi and Gq alpha subunits in the presence of the beta1 gamma2HF dimer. In contrast, the beta5 gamma2HF dimer only supported coupling of the Gq alpha subunits to the ETB receptor and did not support coupling of the Gi alpha subunit. These results suggest that the beta5 gamma2HF dimer binds selectively to Gq alpha subunits and does not activate the same set of effectors as dimers containing the beta1 subunit. Overall, the data support a specialized role for the beta5 subunit in cell signaling.     

Numerical detection and continuation of saddle-node homoclinic bifurcations of codimension one and two

An extension of an existing truncated boundary-value method for the numerical continuation of connecting orbits is proposed to deal with homoclinic orbits to a saddle-node equilibrium. In contrast to previous numerical work by Schecter and Friedman and Doedel, the method is based on (linear) projection boundary conditions. These boundary conditions, with extra defining conditions for a saddle-node, allow the continuation of codimension-one curves of saddle-node homoclinic orbits. A new test function is motivated for detecting codimension-two points at which loci of saddle-nodes and homoclinic orbits become detached. Two methods for continuing such codim 2 points in three parameters are discussed. The numerical methods are applied to two example systems, modelling a DC Josephson junction and CO oxidation. For the former model, existing numerical results are recovered and extended; for the latter, new dynamical features are uncovered. All computations are performed using AUTO.     

Outcome of cardiac valve ring abscesses after medical treatment: attempt to identify criteria of favorable prognosis

OBJECTIVES: Identify factors predicting favorable outcome after medical management of valve ring abscesses in order to propose a surveillance schedule for conservative treatment. METHODS: A multicentric study conducted from July 1989 to February 1996 included 28 patients (mean age 64 +/- 16 years, range 26-83) hospitalized for active endocarditis and valve ring abscesses diagnosed at transthoracic or transesophageal echography. Conservative medical therapy was given because of a decision of the medico-surgical team (n = 9), high surgical risk (n = 12), or patient refusal of surgery (n = 7). Outcome was favourable in 18 patients (Group I) and unfavorable in 10 (Group II) due to death (n = 9) or subsequent surgery (n = 1). Univariate and multivariate analysis were used to determine differences between the groups in terms of clinical and laboratory data. RESULTS: Mean follow-up in Group I was 33 +/- 18 months and 15 +/- 10 months in Group II. Univariate analysis showed significant differences between Group I and II respectively for age (59 +/- 18 yr vs 72 +/- 10, p = 0.04), delay to apyrexia after antibiotics (4.3 +/- 2.8 vs 8.3 +/- 2.4 days, p < 0.0008), heart failure (5% vs 70%, p = 0.003), grade III or IV valvular regurgitation (5% vs 60%, p < 0.04), and mean surface area of the abscess (1.5 +/- 1.2 vs 5.4 +/- 6.4 cm2, p < 0.03). Independent factors at multivariate analysis were by decreasing order: lack of heart failure at admission, delay to apyrexia, abscess surface area, and age. Outcome was favorable (mean follow-up 33 +/- 10 months) in all patients with an abscess surface area < 1.5 cm2, no signs of heart failure, no grade III or IV valvular regurgitation, apyrexia after less than 8 days on antibiotics and no staphylococcus positive blood culture. CONCLUSION: Medical management of valve ring abscesses may be indicated in selected patients in care units with rigorous surveillance facilities. Further studies are needed to precisely identify surveillance and treatment criteria.     

DOA: DSR over AODV Routing for Mobile Ad Hoc Networks

We present a lightweight hierarchical routing model, Way Point Routing (WPR), in which a number of intermediate nodes on a route are selected as waypoints and the route is divided into segments by the waypoints. Waypoints, including the source and the destination, run a high-level intersegment routing protocol, while the nodes on each segment run a low-level intrasegment routing protocol. One distinct advantage of our model is that when a node on the route moves out or fails, instead of discarding the whole original route and discovering a new route from the source to the destination, only the two waypoint nodes of the broken segment have to find a new segment. In addition, our model is lightweight because it maintains a hierarchy only for nodes on active routes. On the other hand, existing hierarchical routing protocols such as CGSR and ZRP maintain hierarchies for the entire network. We present an instantiation of WPR, where we use DSR as the intersegment routing protocol and AODV as the intrasegment routing protocol. This instantiation is termed DSR over AODV (DOA) routing protocol. Thus, DSR and AODV—two well-known on-demand routing protocols for MANETs—are combined into one hierarchical routing protocol and become two special cases of our protocol. Furthermore, we present two novel techniques for DOA: one is an efficient loop detection method and the other is a multitarget route discovery. Simulation results show that DOA scales well for large networks with more than 1,000 nodes, incurring about 60 percent-80 percent less overhead than AODV, while other metrics are better than or comparable to AODV and DSR.     

热轧高强钢平整机辊径参数设计技术研究

基于高强钢平整机的生产工艺特点,结合板形与辊耗问题,将带材的出口前张力与辊间压力横向分布都均匀作为目标函数,把保证所有被平整高强钢产品的机械性能满足产品大纲要求作为约束条件,提出了一套针对热轧高强钢平整机的工作辊与支承辊辊径参数设计模型.其研究结果对指导宝钢分公司1880 mm热轧平整机的工艺参数的确定与技术谈判发挥了重要作用,并具有进一步的推广价值.     

沿江圩区排涝水文计算实例

设计排涝模数的计算是圩区排涝规划的主要内容之一,它的大小决定了排涝站的装机容量和涵闸尺寸.本文推求了安徽省马鞍山市大公圩地区的排涝模数,是沿江圩区排涝水文计算的一个应用实例.     

三种套管接头抗压缩性能研究

针对套管接头抗压缩强度问题，使用全尺寸实物试验的方法对几种不同钢级、不同螺纹形式的套管接头的抗压缩强度进行了对比试验，并借助材料力学和有限元方法对试验结果进行了分析。实物试验中出现了管体失稳和接箍跳扣两种套管接头压缩失效形式。试验结果和分析结果表明，N80、P110钢级材料的压缩屈服强度高于拉伸屈服强度；偏梯形螺纹套管接头的压缩屈服强度比同钢级、同壁厚特殊扣螺纹套管接头低6.7%～7.7%；上扣是否到位，直接影响套管接头部分的抗压缩能力，上扣不到位的特殊螺纹套管接头的抗压缩性能甚至低于偏梯形螺纹接头。同时指出，为了保证上扣质量，不应使用浮动上扣方法，管柱设计中应进行抗压缩强度设计。     

Synthesis and properties of star-like wholly aromatic polyester fibers

Novel star-like wholly aromatic copolyesters having four arms based on a tetraamine star core, p- and m- hydroxybenzoic acids and 6-hydroxy-2-naphthoic acid have been successfully synthesized and spun into fibers for the investigation of the effect of the star-like structure on improving compressive properties of the fiber. The reactivity of the star core was demonstrated using a model compound with FTIR, ¹H and ¹³C NMR spectroscopy. The ¹³C NMR spectrum of the star-like terpolymer having a molar ratio of 10:1 of the monomers to star core showed a characteristic peak at around δ62 ppm which corresponds to a tetra-substituted carbon and thereby demonstrates that the star core was really incorporated into the polymer. The star-like copolyester exhibited a clear stir opalescence and liquid crystalline morphology in the temperature range of 150-280 °C. However, no transition was observed in the DSC thermogram except a clear T_g at 110 °C. The star-like terpolymer fiber, prepared from a polymer with a molar ratio of 500:1 for the monomers to imide core, was spun in the liquid crystalline state at 180 °C. Fiber structure and properties have been studied.