Effectiveness of ab initio molecular dynamics in simulating EXAFS spectra from layered systems.

The simulation of EXAFS spectra of thin films via ab initio methods is discussed. The procedure for producing the spectra is presented as well as an application to a two-dimensional material (WSe2) where the effectiveness of this method in reproducing the spectrum and the linear dichroic response is shown. A series of further examples in which the method has been employed for the structural determination of materials are given.

A numerical efficient splitting method for the solution of two dimensional susceptible infected recovered epidemic model of whooping cough dynamics: Applications in bio-medical engineering.

Background and Objective The positivity property of the non-linear dynamical systems is one of the essential features in different fields of bio-medical engineering, science and many more. The state variables, involving in the models, describing the natural phenomenon such as concentration, density and population size etc. must be positive. Therefore, the computing techniques used to solve the system of non-linear differential equations must be consisted with the continuous nature of the models. But, unfortunately there are some existing techniques in the literature that do not preserve the positivity property, especially for the multi-space dimensional models. So there is a gap in the literature that should be filled up, by constructing the positivity preserving numerical algorithms. In this study, we consider a susceptible-infected-recovered (SIR) reaction diffusion epidemic model in two space dimensions from biomedical engineering and solved numerically to observe the behavior of the model. Since the state variables involved in this system are population densities therefore we design a novel computational method which is time efficient because of its splitting structure and holds the positivity as well as other important structure of epidemic system. Methods Three different computational techniques are designed to examine the numerical solution of SIR model of infectious disease. Two approaches are well-known existing computing methods named as forward Euler finite difference (FD) method and backward Euler operator splitting finite difference (OS-FD) method. The third approach is operator splitting nonstandard finite difference (OS-NSFD) method which is devised by using the NSFD rules. Results The proposed OS-NSFD technique retains efficiently the stability of equilibria as well as the positivity. Graphical behavior depicts that the existing computing methods can not get success to preserve the structure of the epidemic system of whooping cough dynamics. At the same time OS-NSFD computing method is proven to be reliable and suitable for the system of bio-medical engineering mathematically and graphically. Conclusion A reliable and novel computing technique is developed for the solution of two dimensional reaction diffusion problem. This technique preserves all the imperative characteristics of the model under study. Also the time efficiency of this method makes it easy to find the solution of physical system in two space dimension. The comparison with other techniques shows the efficacy and reliability of the designed technique.

Spatio-temporal numerical modeling of reaction-diffusion measles epidemic system.

In this work, we investigate the numerical solution of the susceptible exposed infected and recovered measles epidemic model. We also evaluate the numerical stability and the bifurcation value of the transmission parameter from susceptibility to a disease of the proposed epidemic model. The proposed method is a chaos free finite difference scheme, which also preserves the positivity of the solution of the given epidemic model.

Big data and visual analytics in anaesthesia and health care.

Advances in computer technology, patient monitoring systems, and electronic health record systems have enabled rapid accumulation of patient data in electronic form (i.e. big data). Organizations such as the Anesthesia Quality Institute and Multicenter Perioperative Outcomes Group have spearheaded large-scale efforts to collect anaesthesia big data for outcomes research and quality improvement. Analytics--the systematic use of data combined with quantitative and qualitative analysis to make decisions--can be applied to big data for quality and performance improvements, such as predictive risk assessment, clinical decision support, and resource management. Visual analytics is the science of analytical reasoning facilitated by interactive visual interfaces, and it can facilitate performance of cognitive activities involving big data. Ongoing integration of big data and analytics within anaesthesia and health care will increase demand for anaesthesia professionals who are well versed in both the medical and the information sciences.

The Amplatzer duct occluder: experience in 209 patients.

OBJECTIVES: The aim of the study was to assess the safety and efficacy of the Amplatzer ductal occluder (ADO) in transcatheter occlusion of patent ductus arteriosus (PDA). BACKGROUND: Transcatheter closure of small to moderate sized PDAs is an established procedure. The ADO is a self-expandable device with a number of salutary features, notably its retrievability, ease of delivery via small 5F to 7F catheters and a range of sizes suitable even for the larger PDAs. METHODS: Between November 1997 and August 1999, the ADO was successfully implanted in 205 of 209 patients with PDA. The inclusion criteria for this device occlusion method were patients with clinical and echocardiographic features of moderate to large PDA, weighing > or =3.5 kg as well as asymptomatic adolescents and adults with PDA measuring > or =5.0 mm on two-dimensional (2D) echocardiogram. Occlusion was achieved via the antegrade venous approach. Follow-up evaluations were performed with 2D echocardiogram, color-flow mapping and Doppler measurement of the descending aorta and left pulmonary artery velocity at 24 h and 1, 3, 6 and 12 months after implantation. RESULTS: Two hundred and five patients had successful PDA occlusion using this device. The patients were between two months and 50 years (median 1.9) and weighed between 3.4 kg and 63.2 (median 8.4). Infants made up 26% of the total patients. The PDA measured from 1.8 to 12.5 mm (mean 4.9) at the narrowest diameter. Forty-four percent of patients achieved immediate complete occlusion. On color Doppler the closure rates at 24 h and 1 month after implant were 66% and 97%, respectively. At 6 and 12 months all except one patient attained complete occlusion. Device embolization occurred in three patients; in two this was spontaneous, and in the other it was due to catheter manipulation during postimplant hemodynamic measurement. Mild aortic narrowing was seen in an infant. CONCLUSIONS: Patent ductus arteriosus occlusion using ADO is safe and efficacious. It is particularly useful in symptomatic infants and small children with relatively large PDA. Embolization can be minimized by selection of appropriate sized devices, and caution should be exercised in infants <5 kg.

Electrocardiographic artefact with SSEP monitoring unit during scoliosis surgery.

A case of somatosensory evoked potential (SSEP) induced electrocardiographic artefact simulating supraventricular tachycardia (SVT) is described in a three year old girl with Goldenhar syndrome, during anterior thoracoscopic discectomy with posterior spinal fusion for scoliosis. Adenosine was administered for this misinterpreted EKG with coincidental cessation of SVT like trace.

The Alagille's syndrome and its anaesthetic considerations.

Alagille's syndrome is an inherited disorder affecting multiple organ systems. Most characteristic is the paucity of the interlobular bile ducts with cholestasis. The anaesthetic plan for these patients should be based on careful preoperative preparation and attention to the issues involving hepatobiliary, cardiac, neurodevelopmental, nutritional, haematological, ocular and facial abnormalities. We report the case of a five-and-a-half-year old patient with Alagille's syndrome who sustained a pathological fracture of the femur and was scheduled for closed reduction and application of a hip spica cast. Relevant anaesthetic issues are discussed.

Oral and nasotracheal light wand guided intubation after failed fibreoptic bronchoscopy.

Fibreoptic bronchoscopic guided tracheal intubation is often the first choice for clinicians familiar with the technique, when faced with a patient in whom tracheal intubation presents known or possible difficulties. Regardless of the technique chosen, anticipated and unanticipated problems may arise. We report three patients with known difficult airways that illustrate the utility of light wand guided oral and nasotracheal intubation when tracheal intubation with fibreoptic bronchoscopy proved impossible.

Serum parathyroid hormone suppression by intravenous 1,25-dihydroxyvitamin D3 in patients on maintenance haemodialysis.

Secondary hyperparathyroidism in patients with end-stage renal disease is characterised by elevated circulating levels of parathyroid hormone, due to inadequate synthesis of calcitriol, the active metabolite of vitamin D. Recent studies suggest that administration of calcitriol may directly suppress parathyroid (PTH) secretion independent of changes in serum calcium. We have studied the effect of intravenous calcitriol administration on the PTH level in 14 patients on maintenance haemodialysis with serum PTH levels above 2,000 pmol/l over a 16-week period. There was a significant reduction in the PTH level (65%) and a rise of serum calcium to the normal range. There was a significant reduction in serum PTH levels before the serum calcium concentrations increased, suggesting that calcitriol directly inhibits PTH release. In conclusion, intravenous treatment with calcitriol is of clinical importance, because it suppresses hypersecretion of PTH in uraemic patients, with minimal side effects.

The importance of the perfusion index in the evaluation of captopril renography for transplant renal artery stenosis.

Severe renal artery stenosis (RAS) is a relatively uncommon complication following renal transplantation but is a curable cause of hypertension which demands reliable early diagnosis to reduce morbidity, mortality and graft loss. Captopril renography has been used for a number of years as a method of detecting RAS mainly in native kidneys, with only a few studies concerning the transplant situation. Controversy still exists as to the diagnostic accuracy of this test and as to the most appropriate interpretation criteria with which to establish a positive result. This paper reports the evaluation of 26 captopril renography investigations on hypertensive renal transplant patients with a suspected diagnosis of RAS. Each renogram study was correlated with an arteriogram as the 'gold standard' which was undertaken within 28 days of the renography. A sensitivity of 92%, a specificity of 86% and an accuracy of 88% were achieved by including a consideration of the change in perfusion to the kidney between pre- and post-challenge studies. It is concluded that captopril renography is a useful screening test for the detection of transplant renal artery stenosis (TRAS).

Pattern of renal disease in children.

In 1992 a total of 1298 patients with renal diseases were seen in the medical outpatients department. Eight hundred and forty-seven (65.2%) had urinary tract infection and 265 (20.5%) had nephrotic syndrome. Two hundred and twenty patients required inpatient care, which constituted 3.3% of total number of patients admitted to medical wards. Sixty-four (29%) of admitted patients with renal disease had nephrotic syndrome, 29 (13.1%) had acute renal failure due to various causes including haemolytic uraemic syndrome. The average stay was 5.8 days per patient and mean bed occupancy was 3.4 beds per day. Various renal diseases in children together form an important group of disorders often requiring long term care and this should be taken into account when planning provision of child health services particularly at tertiary care level.

Quality control of dose calibrators.

Radionuclide dose calibrators are instruments that require regular checks and proper usage to ensure that they are operating correctly. The responsibility for the accuracy of the activity and the resultant estimate of the dose delivered to the patient rests with the persons administering the radiopharmaceutical. Hence, it is essential that accurate measurements of radioactivity be provided by the dose calibrator in use in every nuclear medicine department. The routine testing of the calibrator would ensure the user that the overall characteristics of the instrument are within acceptable limits. The quality control of two dose calibrators was carried out elaborately and their performance was evaluated from various aspects of quality control such as geometry effect, instrument linearity, precision test, instrument accuracy etc. It was found that one of the calibrators was having non-linear response resulting in an error of 18% from the decay-predicted activity. It also showed a saturation effect beyond 310 mCi. Hence, it needed repair or recalibration. However, the other calibrator was working satisfactorily. This study also helped us in realizing certain operational pitfalls of the dose calibrators.