浅谈冷库冲霜水系统中的防冻

分析了冷库冲霜水系统中所存在的冻结问题及解决方法。     

Meniscal regeneration in the long-term after total meniscectomy?

A cohort of 39 patients (28 male, 11 female) that had undergone total meniscectomy as adolescents (mean age 16 years) underwent FISP 3D Magnetic Resonance Imaging at a mean follow up of 30 years. The presence of meniscal tissue was assessed by two independent observers blinded to the operation details. The volume of any meniscal tissue present was calculated. A posterior horn remnant was seen in 57% of medial and 45% of lateral meniscectomy cases. The mean volume of an operated medial meniscal remnant was 0.29 mL compared with a mean volume of 1.15 mL for an intact medial meniscus. The mean volume of an operated lateral meniscal remnant was 0.30 mL compared with 1.07 mL for an intact lateral meniscus. We have shown that the incidence of incomplete excision of the posterior horn is more common after total medial meniscectomy, and that at a mean follow up of 30 years there is no convincing in vivo MRI evidence of long-term meniscal regeneration.     

Transluminal balloon angioplasty, stents, and atherectomy

Arterial bypass grafting for occlusive disease is still considered the gold standard in the treatment of arterial occlusive disease. However, less invasive methods are available for select patients. Percutaneous balloon angioplasty has been shown to be effective in focal iliac artery stenosis, with patency rates of 50% to 90% at 5 years. Patency rates for femoropopliteal lesions are generally less than 50% at 2 years. Complications seen with balloon angioplasty often can be treated with arterial stents. Stents can be categorized into balloon-expandable, which provide a rigid scaffold to support the artery, self-expanding, which exert radial force to resist external compression, and thermal expanding stents, which allow for the use of a smaller introducer sheath. Another treatment option is atherectomy, in which the offending lesion is removed instead of fracturing and dilating the lumen. Although overall initial results of atherectomy have not been favorable, short lesions with eccentric atheroma or intimal hyperplasia, such as those seen in dialysis access fistulas or vein graft stenoses, may respond well.     

水利水电施工企业项目管理浅析

阐述了水利水电施工企业项目管理的特点,就本施工企业实行项目管理的实践情况作了介绍,对施工企业如何进行规范化项目管理提出了建议。     

Lithium-induced follicular hyperkeratosis

Scanning with Tc-99m labeled RBC was performed in two patients with recurrent postoperative gastrointestinal bleeding after partial colonic resection. Imaging correctly identified the source of bleeding at the anastomotic site in the large bowel, effectively contributing in the patient's treatment planning. Radionuclide scintigraphy provides a simple, noninvasive modality to diagnose and manage difficult clinical situations such as postoperative bleeding.     

An atomic model of the outer layer of the bluetongue virus core derived from X-ray crystallography and electron cryomicroscopy

BACKGROUND: Bluetongue virus (BTV), which belongs to the Reoviridae family and orbivirus genus, is a non-enveloped, icosahedral, double-stranded RNA virus. Several protein layers enclose its genome; upon cell entry the outer layer is stripped away leaving a core, the surface of which is composed of VP7. The structure of the trimeric VP7 molecule has previously been determined using X-ray crystallography. The articulated VP7 subunit consists of two domains, one which is largely alpha-helical and the other, smaller domain, is a beta barrel with jelly-roll topology. The relative orientations of these two domains vary in different crystal forms. The structure of VP7 and the organizations of 780 subunits of this molecule in the core of virus is central to the assembly and function of BTV. RESULTS: A 23 A resolution map of the core, determined using electron cryomicroscopy (cryoEM) data, reveals that the 260 trimers of VP7 are organized on a rather precise T = 13 laevo icosahedral lattice, in accordance with the theory of quasi-equivalence. The VP7 layer occupies a shell that is between 260 A and 345 A from the centre of the core. Below this radius (230-260 A) lies the T = 1 layer of 120 molecules of VP3. By fitting the X-ray structure of an individual VP7 trimer onto the cryoEM BTV core structure, we have generated an atomic model of the VP7 layer of BTV. This demonstrates that one of the molecular structures seen in crystals of the isolated VP7 corresponds to the in vivo conformation of the molecule in the core. CONCLUSIONS: The beta-barrel domains of VP7 are external to the core and interact with protein in the outer layer of the mature virion. The lower, alpha-helical domains of VP7 interact with VP3 molecules which form the inner layer of the BTV core. Adjacent VP7 trimer-trimer interactions in the T = 13 layer are mediated principally through well-defined regions in the broader lower domains, to form a structure that conforms well with that expected from the theory of quasi-equivalence with no significant conformational changes within the individual trimers. The VP3 layer determines the particle size and forms a rather smooth surface upon which the two-dimensional lattice of VP7 trimers is laid down.     

认知定位系统的自适应精度研究

为了能够实现定位精度的自适应,本文分析了认知无线电定位系统(cognitive positioning systems,CPS)的原理。该系统利用频谱及环境感知等模块中的传感器单元来获取所需的定位参数,并将其与到达时间(time of arrival,TOA)定位估计算法相结合,以克拉美罗下界(Cramer-Rao lower bound,CRLB)为准则分析最大似然(maximum likelihood,ML)定位精度自适应算法。本文还对单径和多径环境条件下定位精度自适应性能进行了比较。仿真结果表明,该算法能够实现定位精度的自适应,并能通过改善系统可用的频带带宽、分散频谱的数目、信号的调制方式等因素来提高定位精度。