Biomechanical behaviour - Anisotropy of eye cornea through experimental strip tests

Abstract With the advent of research it was identified that material properties are responsible for errors in tonometry pressure (referred to as Goldmann IOP or IOPG) with the stiffening of a composite structure of corneal tissue in particular. Strip tensile tests are conducted to determine their stress–strain relationship for the purpose to study the behaviour of material properties of cornea. Specimens are taken from the superior–inferior (vertical) and temporal– nasal (horizontal) directions. Testing is performed on an Instron machine, under different rate of loading conditions. First set of experiment, with single strain rate, is executed on eyes having random population. While the second set of experiment is executed on eyes of the same animal in both directions, and different strain rates are applied each specimen. Relatively, the first set of experiment is found to be slightly different and less accurate. In general, it is found that the vertical specimen is 34% on an average stiffer than the horizontal specimen compared to Kampmeier et al. of 20% (studied in 2000) and Defu Wang of 15% (studied in 2007). Curve fitting coefficients are also evaluated for 4–degree polynomial. The anisotropy is evident by plotting the ratio of E–tangent value of vertical Ev and horizontal Eh against stresses with individual strain rates. The value of Ev/Eh increases with slightly slow rate with stresses as compared to achieved through slow strain rates.</jats:p

Localization performance evaluation of extended kalman filter in wireless sensors network

This paper evaluates the positioning and tracking performance of Extended Kalman Filter (EKF) in wireless sensors network. The EKF is a linear approximation of statistical Kalman Filter (KF) and has the capability to work efficiently in non-linear systems. The EKF is based on an iterative process of estimating current state information from the previously estimated state. Its working is based on the linearization of observation model around the mean of current state information. The EKF has small computation complexity and requires low memory compared to other Bayesian algorithms which makes it very suitable for low powered mobile devices. This paper evaluates the localization and tracking performance of EKF for (i) Position (P) model, (ii) Position-Velocity (PV) model and (iii) Position-Velocity-Acceleration (PVA) model. The EKF processes distance measurements from cricket sensors that are acquired through time difference of arrival between ultrasound and Radio Frequency (RF) signals. Further, localization performance under varying number of beacons/sensors is also evaluated in this paper. © 2014 Published by Elsevier B.V.Peer ReviewedPostprint (published version

Mid aortic syndrome correction: anaesthetic considerations and management

A twelve years old female patient presented with headache off and on and disparity between upper and lower limb pressures. On the basis of history, physical examination and magnetic resonance angiography, the patient was diagnosed as mid aortic syndrome and planned for elective aorto aortic bypass graft surgery through left thoracotomy. Double lumen endotracheal tube was placed for lung isolation and episodes of hypertension during proximal and distal cross clamp were controlled with sodium nitropruside infusion (SNP). Extra pleural catheter was put in at the end of surgery before chest wall closure for postoperative pain control. Both upper and lower limb pressures were monitored in the cardiac intensive care unit (CICU) and over a period of twenty four hours, gradient gradually reduced to 10 mm Hg

Role of Oxidative Stress in various stages of Psoriasis

Background: Psoriasis is a chronic inflammatory, immune mediated, provocative and challenging skin condition. It is a non-contagious but debilitating disease and a leading cause of socioeconomic burden on the health system. Objective: To evaluate the role of antioxidant levels, lipid peroxidation status and lipid profile in the etiology and degree of severity of psoriatic illness among psoriasis patients presenting in Dermatology department. Study Design: This study was carried out as a retrospective case control study. Place and duration of Study: It was carried out by the Department of Biochemistry, Basic Medical Sciences Institute (BMSI) in collaboration with Departmnt of Biochemistry, Khyber Medical College, Peshawar and Department of Skin and Venereal disease, Jinnah Post Graduate Medical Centre (JPMC) Karachi. Material and Methods: One hundred and twenty cases (n=130) of already diagnosed psoriasis patients were randommely and fifty healthy matched controls (n=50) of the same age and gender were included from the general population for comparison. Lipid profile including serum total cholesterol, TG, HDL-c and LDL-c levels were measured by enzyme colorimetric analysis on Micro Lab 300 (Merck &amp; Germany). Antioxidant status SOD and lipid peroxidation status MDA were measured by ELISA technique. Statistical analysis was performed using SPSS software Version 16. In this analysis, a “p” value of less than 0.05 was considered to be significant. Results: The study showed significantly elevated levels of MDA, serum TG, total cholesterol and LDL-c levels in psoriatic patients in comparison with controls, whereas SOD levels and HDL-c levels were found to be significantly lower in psoriatic patients as compared to normal healthy matched controls. Conclusion: The findings of this study support the hypothesis that an imbalance in oxidant-antioxidant system may play a role in the etiology of psoriasis and the degree of severity of its presentation. The study also concluded that dyslipidemia was an observed risk factor for the development of cardiovascular diseases in psoriatic patients.

Single lung ventilation in a young child for repair of coarctation of aorta

Single lung ventilation in small children is extremely challenging. In this case, a paediatric bronchial blocker was successfully inserted in a 19-month-old child to provide single lung ventilation using a modified insertion technique. It provided excellent working conditions during thoracotomy and our method of insertion may help in reducing the cost

gpusvcalibration: A R Package for Fast Stochastic Volatility Model Calibration Using GPUs

In this paper we describe the gpusvcalibration R package for accelerating stochastic volatility model calibration on GPUs. The package is designed for use with existing CRAN packages for optimization such as DEOptim and nloptr. Stochastic volatility models are used extensively across the capital markets for pricing and risk management of exchange traded financial options. However, there are many challenges to calibration, including comparative assessment of the robustness of different models and optimization routines. For example, we observe that when fitted to sub-minute level midmarket quotes, models require frequent calibration every few minutes and the quality of the fit is routine sensitive. The R statistical software environment is popular with quantitative analysts in the financial industry partly because it facilitates application design space exploration. However, a typical R based implementation of a stochastic volatility model calibration on a CPU does not meet the performance requirements for sub-minute level trading, i.e. mid to high frequency trading.We identified the most computationally intensive part of the calibration process in R and off-loaded that to the GPU.We created a map-reduce interface to the computationally intensive kernel so that it can be easily integrated in a variety of R based calibration codes using our package. We demonstrate that the new R based implementation using our package is comparable in performance to aC=C++ GPU based calibration code

Effect of Area Ratio on Base Pressure in a Suddenly Expanded Duct for Under Expanded Flow ft Mach 1.87

The results of an experimental investigation carried out to control the base pressure in a suddenly expanded axi-symmetric passage is presented in this paper. An active control in the form of micro jets is employed to control the base pressure. Air injection at four locations at the base, symmetric to the nozzle axis is used as the active control. The jet Mach number studied and the area ratios are 1.87, and 2.56, 3.24, 4.84, and 6.25. The L/D ratio is varied from 10 to 1. The experiments are conducted at a fixed level of under expansion (i.e. Pe/Pa = 1.5). In addition to base pressure, wall pressure field along the duct was also measured. As high as 80 percent increase in base pressure was achieved for certain combination of parameters of the present study. The minimum Length-todiameter ratio of the duct required is L/D = 2 for area ratios 6.25 and 4.84. Whereas, this requirement is L/D = 1 for area ratios 2.56 and 3.24

Prevalence of diabetic retinopathy among individuals screened positive for diabetes in five community based eye camps in northern Karachi Pakistan

Background: Population-based data on the prevalence of diabetic retinopathy in Pakistan are lacking. We determined the prevalence of diabetic retinopathy among individuals screened positive for diabetes in five community-based eye camps in northern Karachi, Pakistan. Methods: In summer 2002, five community-based eye camps were set up in Karachi, Pakistan’s largest city. All individuals aged 30 years or older who visited the camps were requested to participate in the study. Those who agreed were screened for diabetes and those found to have the disease were referred to an eye hospital for diabetic retinopathy screening. Verbal informed consent was obtained from all participants at the examination site. Our main outcome measure was diabetic retinopathy, which was classified as non-proliferative diabetic retinopathy (NPDR), severe NPDR, and proliferative diabetic retinopathy (PDR). Our grading was based on clinical examination. Results: A total of 912 subjects were screened for diabetes mellitus. Of these, 160(17.5%) had diabetes- 1.8% had type I diabetes and 15.9% had type II diabetes. One hundred and eight individuals visited the hospital for ophthalmic examination. Of them, 15.7% had diabetic retinopathy. The prevalence of diabetic retinopathy was higher among individuals with type I diabetes, with greater duration of diabetes, and among women. The commonest form of diabetic retinopathy was non-proliferative (76.5% [mild: 35.3 %, moderate: 29.4 %, and severe: 11.8 %]), followed by maculopathy (17.6 %) and proliferative diabetic retinopathy (5.9 %). Conclusion: More systematic and population-based research is needed to estimate the prevalence of and identify risk factors for diabetic retinopathy in Pakista

Grown up congenital heart disease patient presenting for non cardiac surgery: anaesthetic implications

Congenital heart disease patients surviving to adulthood have increased over the years due to various reasons. These patients are admitted in the hospital for non cardiac surgeries and other procedures more often than normal adult population. Management of grown up congenital heart disease patient presents a challenge during perioperative period for cardiologists, surgeons, intensivists and particularly for the anaesthetist. Management issues include psychological and physiological impact on the patient, complexity of defects, presence of previous palliative procedure, impact of anaesthetic agents on shunting and myocardium, endocarditis prophylaxis and associated extra cardiac anamolies