VPN技术及其在数字图书馆的应用

详细阐述了VPN的实现技术及VPN远程访问和网络互联的高效低价、安全可靠的解决方案,探讨了VPN对数字图书馆建设中远程访问问题的解决方案,认为SSL VPN是解决远程用户访问数字图书馆信息资源最为简捷、安全的技术。     

Registration of medical images using an interpolated closest point transform: method and validation

Image registration is an important procedure for medical diagnosis. Since the large inter-site retrospective validation study led by Fitzpatrick at Vanderbilt University, voxel-based methods and more specifically mutual information-based registration methods (see for instance [IEEE Trans. Med. Imag. 22 (8) (2003) 986] for a review on these methods) have been regarded as the method of choice for rigid-body intra-subject registration problems. In this study we propose a method that is based on the Iterative Closest Point algorithm and a pre-computed closest point map obtained with a slight modification of the fast marching method proposed by Sethian. Pre-computing the closest point map speeds up the process because at each iteration point correspondence can be established by table lookup. We also show that because the closest point map is defined on a regular grid it introduces a registration error and we propose an interpolation scheme that addresses this issue. The method has been tested both on synthetic and real images, and registration results have been assessed quantitatively using the data set provided by the Retrospective Registration Evaluation Project. For these volumes, MR and CT head surfaces were extracted automatically using a level-set technique. Results show that on these data sets this registration method leads to accuracy numbers that are comparable to those obtained with voxel-based methods.     

Reduced fields of view are neither necessary nor sufficient for distance underestimation but reduce precision and may cause calibration problems

Watt et al. (Exp Brain Res, 2000, 135:411–416) suggested that a reduced field of view causes objects to appear closer than their physical distance. This suggestion is based on the observation that individuals terminated open-loop prehension prematurely when pretending to grasp a paper rectangle initially viewed through a reduced field of view. We tested Watt et al.s suggestion in an open-loop pointing task. In experiment 1, 21 participants pointed at targets in three locations (20, 30 and 40 cm relative to the starting position) in three viewing conditions (full, 16° and 4° field of view). No difference in accuracy was found between conditions but the reduced field of view led to an increase in end-point variability across trials. We interpret these results as indicating that a reduced field of view decreases precision but does not necessarily affect object localisation. In experiment 2, we asked participants to reach-and-grasp a real object under the same three open-loop viewing conditions but without vision following movement onset. The experimental design ensured that haptic feedback was available, which could be used to calibrate reaching movements. We found that the reduced field of view caused no changes in grasp but we observed changes in the transport kinematics consistent with increased variability in the perceptual estimate of target location. Notably there were no changes in the spatial path (expected from movements to a closer location). In experiment 3, we repeated the Watt et al. design but removed vision and forced participants to rely on memory. In this condition we found the same undershoots as described by Watt et al. We conclude that a reduced field of view is neither necessary nor sufficient for underestimation and suggest that a reduced field of view decreases precision. This can cause participants to undershoot and/or alter the movement kinematics but we argue that such findings cannot be ascribed unambiguously to perceptual underestimation as they may reflect strategic alterations in behaviour.     

The effect of plyometric training on distance running performance

Previous research has reported that plyometric training improves running economy (RE) and ultimately distance-running performance, although the exact mechanism by which this occurs remains unclear. This study examined whether changes in running performance resulting from plyometric training were related to alterations in lower leg musculotendinous stiffness (MTS). Seventeen male runners were pre- and post-tested for lower leg MTS, maximum isometric force, rate of force development, 5-bound distance test (5BT), counter movement jump (CMJ) height , RE, V˙O_2max, lactate threshold (Th_la), and 3-km time. Subjects were randomly split into an experimental (E) group which completed 6 weeks of plyometric training in conjunction with their normal running training, and a control (C) group which trained as normal. Following the training period, the E group significantly improved 3-km performance (2.7%) and RE at each of the tested velocities, while no changes in V˙O_2max or Th_la were recorded. CMJ height, 5BT, and MTS also increased significantly. No significant changes were observed in any measures for the C group. The results clearly demonstrated that a 6-week plyometric programme led to improvements in 3-km running performance. It is postulated that the increase in MTS resulted in improved RE. We speculate that the improved RE led to changes in 3-km running performance, as there were no corresponding alterations in V˙O_2max or Th_la. Electronic Publication     

美国的社会团体和相关机构在远程医疗与远程医学教育中的作用

在不同的国家，远程医学教育和远程医疗的发展状况不尽相同。美国的远程医学教育和远程医疗在内容、手段、普及程度上都处于世界领先地位，这与美国的社会团体和相关机构的作用密不可分。本文主要介绍非盈利性社会团体，如泛美卫生组织、美国医学院协会、美国远程医疗协会、世界银行协会、美国继续医学教育认可委员会和政府部门，如隶属于美国卫生部的卫生资源及服务局在远程医疗和远程医学教育中发挥的作用。     

The effect of long-distance running on plasma immunoreactive glucagon levels

Summary Twelve highly conditioned long-distance runners were studied to determine the effects of marathon (42 km) and 10,000 m running on plasma immunoreactive glucagon (IRG), serum immunoreactive insulin (IRI), and serum glucose (G) levels. Blood samples were drawn just prior to and immediately upon completion of the run. Marathon running resulted in no significant change in G, IRI, or IRG levels. After running 10,000 m, plasma IRG levels did not change significantly, while IRI and G increased significantly.In evaluating the pooled data from both runs, a significant inverse correlation was observed between G and IRG. This relationship between G and IRG suggests that glucagon plays a role in maintaining normal blood glucose levels during strenuous exercise.     

後房型人工晶體植入後人工晶體與虹膜距離的臨床分析

目的白内障摘除後房型大C袢人工晶體植入術後,人工晶體與虹膜内面(後上皮層)有相應的距離,可减少術後炎癥反應及并發癥的探討.方法術後第一天裂隙燈側照觀察人工晶體與虹膜的相應距離.結果人工晶體與虹膜有距離者反應輕,并發癥少,無距離者反應重,并發癥多.結論後房型大C袢人工晶體囊袋内植入後,人工晶體光學部分後沉緊貼晶體後囊膜,使人工晶體與虹膜產生了一定的距離,房水循環通暢,且人工晶體不刺激虹膜與睫狀溝,所以反應輕并發癥少.     

基于LADT—BP算法的心电图快速分析

本文提出了一种应用LADT（Linear Approximation Distance Thresholding)压缩算法进行预处理的BP（Backpropagation)网络算法（我们称为LADT-BP算法）。实验主日新月异该算法与现有的算法相比,在运算速度及正确识别率等方面,均有大幅度的提高。     

Losing sight of the bigger picture: peripheral field loss compresses representations of space

Three experiments examine how the peripheral visual field (PVF) mediates the development of spatial representations. In Experiment 1 participants learned and were tested on statue locations in a virtual environment while their field-of-view (FOV) was restricted to 40 degrees , 20 degrees , 10 degrees , or 0 degrees (diam). As FOV decreased, overall placement errors, estimated distances, and angular offsets increased. Experiment 2 showed large compressions but no effect of FOV for perceptual estimates of statue locations. Experiment 3 showed an association between FOV size and proprioception influence. These results suggest the PVF provides important global spatial information used in the development of spatial representations.     

Distance from an Urban Sickle Cell Center and its Effects on Routine Healthcare Management and Rates of Hospitalization

The St. Jude Children’s Research Hospital (St. Jude) comprehensive sickle cell center serves a 150 mile catchment radius around Memphis, TN, USA. Full travel expenses are provided for routine and acute care visits for sickle cell disease patients living ≥35 miles from St. Jude. We compared hospitalization rates to national estimates and assessed if driving distance was a barrier to sickle cell healthcare despite the travel reimbursement policy. We evaluated the associations between hospitalizations and routine clinic visits and distance from St. Jude using negative binomial models and we conducted bias analyses by Monte Carlo simulation. We followed 545 patients (2550 patient-years) aged ≤18 years with sickle cell disease (Hb SS only) from 2007 to 2012. The hospitalization rate per patient-year was 0.65 [95% CI (confidence interval): 0.62, 0.68), significantly lower than the national rate of 1.16 (95% CI: 1.14, 1.18). Children living <35 miles from St. Jude had 1.75 (95% CI: 1.41, 2.17) times the rate of hospitalization and 1.22 (95% CI: 1.07, 1.39) times the rate of clinic visits compared to those ≥35 miles. Bias analysis suggested that under-reporting could explain the observed difference in hospitalization rates if 30.0% of patients who lived ≥35 miles from the hospital under-reported six hospitalizations over 6 years. The hospitalization rate at St. Jude in children with sickle cell disease was lower than expected from national rates. Greater distance from the sickle cell center (>35 miles) was associated with decreased hospitalization rates, despite the travel allowances that are provided for those who live ≥35 miles from the hospital.