The influence of the distance between the backrest of a chair and the position of the pelvis on the maximum pressure on the ischium and estimated shear force.

PURPOSE: For some people with leg disorders, the alternative to becoming bedridden is sitting in a wheelchair for long periods of time. The purpose of this study was to investigate the relation between the backrest of a chair and the position of the pelvis on the maximum pressure at the ischium and the estimated shear force encountered while sitting in a chair.METHODS: Ten healthy males aged 22.4 +/- 2.3 years without pathologies in the leg and/or trunk participated in this study. The subjects were instructed to sit in a chair and the pressure and shear forces were measured under three sitting conditions: In the standard position, a 5 cm forward position and a 10 cm forward position. The effects of the positions of the pelvis on the maximum pressure at the ischium were measured by an instrument for measuring pressure distribution and the shear forces were estimated using an experimental model proposed by us.RESULTS: Comparisons were made among the three sitting positions; the range of displacement of the maximum pressure point was not significant. The estimated shear force on the seat was 15.5 +/- 12.4 N in the standard position, 34.4 +/- 8.5 N in the 5-cm forward position, and 53.2 +/- 16.7 N in the 10 cm forward position. There were significant differences among the three values (p < 0.01).CONCLUSIONS: Displacing the pelvis forward and leaning against the backrest tends to increase the shear force and raise the risk of decubitus ulcers

Changes in Shear Force and Inward Pressure inside Plug-fit Sockets Due to Flexion and Extension of the Elbow Joint

This study measured shear force and pressure of prosthesis sockets and compared sockets made from conventional hard acrylic resin with soft material. In addition, we also examined how the acrylic resin of the socket influences the decision to put on an elbow system prosthesis. We found that the soft socket extended the range of motion of the elbow joint and permitted movement of the soft tissue to a greater extent than the hard socket. Furthermore, the movable range of the elbow joint widened as the shape of the socket itself changed

Flexible Quasi-Dyadic Code-Based Public-Key Encryption and Signature

Drawback of code-based public-key cryptosystems is that their public-key size is lage. It takes some hundreds KB to some MB for typical parameters. While several attempts have been conducted to reduce it, most of them have failed except one, which is Quasi-Dyadic (QD) public-key (for large extention degrees). While an attack has been proposed on QD public-key (for small extension degrees), it can be prevented by making the extension degree $m$ larger, specifically by making $q^(m (m-1))$ large enough where $q$ is the base filed and for a binary code, $q=2$. The drawback of QD is, however, it must hold $n << 2^m - t$ (at least $n \leq 2^{m-1}$) where $n$ and $t$ are the code lenght and the error correction capability of the underlying code. If it is not satisfied, its key generation fails since it is performed by trial and error. This condition also prevents QD from generating parameters for code-based digital signatures since without making $n$ close to $2^m - t$, $2^{mt}/{n \choose t}$ cannot be small. To overcome these problems, we propose ``Flexible\u27\u27 Quasi-Dyadic (FQD) public-key that can even achieve $n=2^m - t$ with one shot. Advantages of FQD include 1) it can reduce the publi-key size further, 2) it can be applied to code-based digital signatures, too

Influence of Active Fingertip Contact with a Stable Surface on Postural Sway and Electromyographic Activities of the Lower Extremity Muscles Immediately after Descending a Step

Recent studies have shown that active contact cues from a fingertip provide information that leads to reduced postural sway during static standing. Although the falling risk increases immediately after descending a step, little is known about the influence of active fingertip contact with a stable surface. The purpose of this study was to investigate the influence of fingertip contact on the sway and the EMG (Electromyographic) activities of lower extremity muscles immediately after descending a step. Nine healthy male volunteers participated in this study. Sway was measured by the center of pressure (COP) and compared under three conditions: (1) standing without touching, (2) standing with the right index fingertip lightly touching (<1N), and (3) standing forcefully touching (5~10N). EMG activities were measured associated with sway and compared. More areas of COP were observed while standing without touching than while standing with light or forceful touching, but there was no significant difference between the two touching conditions. No significant differences in the length of COP and the EMG activities were observed among the three conditions. The results suggested that the fingertip touch contact with a stable surface decreased sway immediately after descending a step by finely controlling the lower extremity muscles

Statistical Applications to the Management of Intensive Care and Step-down Units

This thesis proposes three contributing manuscripts related to patient flow management, server decision-making, and ventilation time in the intensive care and step-down units system. First, a Markov decision process (MDP) model with a Monte Carlo simulation was performed to compare two patient flow policies: prioritizing premature step-down and prioritizing rejection of patients when the intensive care unit is congested. The optimal decisions were obtained under the two strategies. The simulation results based on these optimal decisions show that a premature step-down strategy contributes to higher congestion downstream. Counter-intuitively, premature step-down should be discouraged, and patient rejection or divergence actions should be further explored as a viable alternative for congested intensive care units (ICUs). Secondly, an investigation of the length of stay (LOS) competition between the intensive care unit (ICU) and the step-down unit (SDU), two servers in tandem without a buffer between them was proposed using queuing games. Analysis of the competition was done under four different scenarios: (i) both servers cooperate; (ii) the servers do not cooperate and make decisions simultaneously; (iii) the servers do not cooperate but the first server, the ICU is the leader; (iv) the servers do not cooperate, the second server the SDU is the leader. Finally, a numerical analysis was performed. The results show that the length of stay decisions of each server depends critically on the payoff function’s form and the exogenous demand. Secondly, with a linear payoff function, the SDU is only beneficial to the system if the unit cost is greater than its unit reward at the ICU. Perhaps most importantly, the critical care pathway performs better under coordination and or leadership at the ICU level. Finally, first-day ventilated patients\u27 ventilation time was analyzed using survival analysis. The probabilistic behaviour of the ventilation time duration was analyzed and the predictors of the ventilation time duration were determined based on available first-day covariates. Data were obtained from the Critical Care Information System (CCIS) about patients admitted to the ICUs in Ontario between July 2015 and December 2016. The log-logistic AFT model was found to be the best to relate the association between first-day covariates and the ventilation time

Regional Analysis of Seafloor Characteristics at Reef Fish Spawning Aggregation Sites in the Caribbean

Overfishing of stock and decreasing biodiversity are grave concerns for the U.S. and the rest of the world. Understanding and applying spatial and temporal information of marine species’ reproductive ecology and critical life habitat is vital to the development of effective strategies for marine resource management. In the Caribbean, one of the critical science gaps hindering effective management is the lack of information on how environmental factors may make fish spawning aggregation (FSA) sites optimal for spawning. Understanding the patterns of seafloor characteristics of spawning aggregation sites is of great interest to managers who need a means to efficiently design marine protected areas to help rebuild regional fish stocks. The specific goals of the study were: (1) to map the seafloor at historically known grouper and snapper spawning aggregation sites in three different countries, and (2) to characterize quantitatively the geomorphology of the sites including horizontal and vertical curvature profiles of the reefs, bottom depth at spawning sites, distance between spawning sites and shelf-edges/reef promontory tips, and the shortest distance between the spawning sites and 100 m water depth. These data were field-collected with a GPS and single-beam eco-sounder that provided latitude/longitude and depth. The point data were interpolated to surfaces in GIS to determine slope, aspect, curvature, and distance from spawning sites and three-dimensional reef structures. This study revealed that all 12 known Nassau grouper spawning aggregation sites in Belize and 5 known sites in the Cayman Islands were located at convex-shaped seaward extending reefs (reef promontories) jutting into deep water, within 1 km of reef promontory tips. However, spawning aggregations did not always occur at the tips of reef promontories, though all were found along the shelf edges within 1 km of promontory tips. Sixteen sites were multi-species spawning sites. These general characteristics were used to predict an undiscovered multi-species spawning aggregation in Belize. A successful prediction in Belize, together with the compiled data from multiple sites indicate: 1) reef promontories are vital locations for transient reef fish spawning aggregations, and 2) this study provides a potential tool for prediction of unknown spawning sites in the Caribbean