Unsteady incompressible Navier-Stokes simulations on deforming domains

Mesh generation has been an important topic of research for the past four decades, primarily because it is one of the critical elements in the numerical simulation of fluid flows. One of the main current issues in this regard is mesh generation and flow solution on domains with moving boundaries. In this research, a novel scheme has been proposed for mesh generation on domains with moving boundaries, with the location of boundary nodes known at any particular time. A new set of linearized equations is derived based on a full nonlinear elliptic grid generation system. The basic assumption in deriving these new equations is that each node experiences only a small amount of disturbance when the mesh moves from one time to the next. Comparison with grids generated by the full elliptic system shows that this new method can generate high quality grids with significantly less computational cost. Inherently, the flow on such a domain will be unsteady. The Navier-Stokes equations for unsteady 2D laminar incompressible flow are expressed in the primitive variables formulation. A SIMPLE-like scheme is applied to link the pressure and velocity fields and ensure conservation of mass is satisfied. The equations are discretized in a pure finite difference formulation and solved by implicitly marching in time. The flow solver is validated against results in the literature for flow through a channel with a moving indentation along one wall

Two-Dimensional and High-Throughput Electrophoretic Separation of Proteins Using Polymeric Microchips

A major task in proteomics is to identify proteins from a biological sample using two-dimensional (2-D) separation prior to mass spectrometry of peptides generated via proteolytic digestion of the proteins. For 2-D separations, microfluidic devices are superior to bench top and capillary-based systems since they potentially provide higher separation efficiencies due to the minimal dead volumes produced during peak transfer between the two separation dimensions. In addition, fast separations can be envisioned because the column lengths are typically shorter in microfluidic platforms without scarifying peak capacity. High-throughput capabilities are extremely desirable for many types of bio-analytical analyses, such as understanding molecular interactions and the role they play in cellular functioning and drug discovery. Polymeric microchips possess a variety of physiochemical properties to match the intended application and their ease of fabrication increases the accessibility of technology to a large research base. In this dissertation, a comprehensive 2-D separation platform for proteins using a polymeric microchip with the ability to perform high performance separations within a few minutes was established. The system combined sodium dodecyl sulfate micro-capillary gel electrophoresis (SDS µ-CGE) with micellar electrokinetic chromatography (MEKC) in a poly(methyl methacrylate), PMMA, microchip and was reported with a programmed pulse injection/separation protocol with laser-induced fluorescence for detection. A novel sixteen-channel polycarbonate (PC) microfluidic device for high-throughput separations of proteins was also presented using a process to pattern gold features as microelectrode array for sixteen parallel channels on microchips. The system was able to simultaneously analyze sixteen different samples in parallel consisting of native proteins, amino acids, peptides, and oligonucleotides with conductivity. Finally, due to the diverse nature of polymer properties and the large number of potential applications for microfluidic chips, the physiochemical properties of various polymers were investigated to guide researchers in selecting the best material for a given application including protein analysis

Bone mineral density in Iranian patients: Effects of age, sex, and body mass index

Introduction: Osteoporosis is a multifactorial skeletal disease that is characterized by reduced bone mineral density (BMD). BMD values de-pend on several factors such as age, sex and age at menopause. The purpose of this study was to determine the prevalence and changes in bone mineral density in Iranian patients. Meth-ods: Three hundred patients were selected through random sampling technique in 2009. BMD was assessed by Norland (Excell) technique at the lumbar and femoral neck. Weight and height were measured through standard methods. A thorough history was taken from each patient. The data was analyzed using SPSS software version 13.0. P-values less than 0.05 were con-sidered statistically significant. Results: From among the 300 studied patients, 86.6% were fe-male. their mean age was 52.7 years. Their av-erage body mass index (BMI) was 28.14 kg/m2. Mean T-Score at lumbar spine and femoral neck was −1.07 ± 1.19 and −1.75 ± 1.33 respectively. Mean BMD value at lumbar spine and femoral neck was 0.92 ± 0.19 and 0.77 ± 0.16 respectively. The prevalence of osteoporosis at lumbar spine and femoral neck was 33.7% and 16.7, respec-tively. There was a significant correlation be-tween age, BMI and BMD values (P-Value < 0.01). Correlation between gender and BMD value at the lumbar spine and femoral neck was not sig-nificant. Conclusion: This study shows that age- ing and low BMI are risk factors associated with bone loss. it is recommended to measure BMD and implement prevention programs for high- risk people. Keywords: Bone Mineral Density; Body Mass Index;Age; Gende

Numerical Modeling of Financially Sustainable Urban Wastewater Systems

A system dynamics model first developed using the software Stella 7.0.2, which explores the complex behavior of the financially sustainable management of water distribution infrastructure, was converted here into a system of coupled non-linear algebraic differential equations (DAEs). Each differential equation involved a time derivative on a primary variable specifying the temporal evolution of the system. In addition, algebraic (secondary) equations and variables specified the non-linearity inherent in the system as well as any controls on the primary variables constraining the physical evolution of the system relevant to the problem at hand. While Stella employed a Runge-Kutta numerical strategy, the numerical DAE method used a fully-explicit, fully-implicit and Crank-Nicolson Euler scheme combined with a fixed-point iteration to resolve the non-linearity. The Runge-Kutta and numerical DAE solutions deviate markedly when the non-linearity of the system becomes pronounced. I demonstrate point-wise stability of the numerical DAE solution as the timestep is refined. Furthermore, the refined numerical DAE solution does not exhibit any of the spurious oscillations inherent in the Runge-Kutta solution and is physically correct for the problem at hand

Operating Room Scheduling in Teaching Hospitals

Operating room scheduling is an important operational problem in most hospitals. In this paper, a novel mixed integer programming (MIP) model is presented for minimizing Cmax and operating room idle times in hospitals. Using this model, we can determine the allocation of resources including operating rooms, surgeons, and assistant surgeons to surgeries, moreover the sequence of surgeries within operating rooms and the start time of them. The main features of the model will include the chronologic curriculum plan for training residents and the real-life constraints to be observed in teaching hospitals. The proposed model is evaluated against some real-life problems, by comparing the schedule obtained from the model and the one currently developed by the hospital staff. Numerical results indicate the efficiency of the proposed model compared to the real-life hospital scheduling, and the gap evaluations for the instances show that the results are generally satisfactory

One pot synthesis of 1,4-dicarboxymethyl-2,3-diphenylnaphthalene

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Properties of PS/TiO2 electrospun fibres using limonene as a solvent

Limonene, a natural solvent, has been used for producing polystyrene (PS) nanocomposite (NC) fibres. Nanocomposite fibres of PS are prepared by electrospinning of a homogeneous solution of titanium dioxide (TiO2) nanoparticles (NPs) and PS. X-ray diffraction (XRD) pattern of PS nanocomposite fibres confirms the presence of TiO2 nanoparticles in the samples. FTIR spectra of PS nanocomposite fibres obviously show that there is no chemical linkage or interaction between PS and TiO2 nanoparticles in the resulting composites fibres. The morphology of PS electrospun fibres and PS/TiO2 nanocomposite fibres is investigated by SEM and FE-SEM. FE-SEM images of electrospun fibres reveal some aggregation of TiO2 nanoparticles. The results also show that increasing TiO2 nanoparticles reduces PS electrospun fibres diameter. Also, the UV protection of PS electrospun fibres is enhanced due to the increase in TiO2 nanoparticles load. Tensile strength and elasticity modulus first show an increase up to 4 wt% of TiO2 and then a decrease at higher loading. Differential scanning calorimeter (DSC) thermograms for PS electrospun fibres indicate that the introduction of TiO2 nanoparticles decreases the glass transition temperature (Tg)

Management of ureteropelvic junction obstruction in horseshoe kidneys by an assortment of laparoscopic options

Introduction: We report our experience with laparoscopic management of ureteropelvic junction obstruction in horseshoe kidneys. Methods: Between February 2004 and March 2014, 15 patients with horseshoe kidneys and symptomatic ureteropelvic junction obstruction underwent laparoscopic management at our national referral centre. Depending on the anatomy and presence of obtrusive vessels or isthmus, we performed either dismembered, Scardino or Foley YV pyeloplasty, or Hellstrom vessel transposition. Patients were initially evaluated by ultrasonography, then diuretic scintiscan at 4 to 6 months, and followed by yearly clinical and sonographic exams. Results: This study included 11 male and 4 female patients between the ages of 4 to 51 year (average 17.7). The left kidney was involved in 12 patients (80). Operation time was 129 minutes (range: 90-186), and patients were discharged within 2.8 days (range: 1-6). Although 8 (53.3) patients had crossing vessels, of which 6 required transposing, the Hellstrom technique was solely used in 3 cases, of which notably 1 case failed to resolve and required laparoscopic Hynes within the next year. Eight cases underwent dismembered pyeloplasty, 2 Foley YV, 1 Scardino flap and 1 required isthmectomy and vessel suspension. At the mean follow-up of 60 (range: 18-120) months, the overall success rate was 93.3. Conclusions: To our knowledge, this represents the largest report on laparoscopic pyeloplasty for horseshoe kidneys, providing the longest follow-up. Our findings confirm prior reports supporting laparoscopy and furthermore show that despite the prevalence of crossing vessels, transposition alone is seldom sufficient. © 2015 Canadian Urological Association

The residual STL volume as a metric to evaluate accuracy and reproducibility of anatomic models for 3D printing: application in the validation of 3D-printable models of maxillofacial bone from reduced radiation dose CT images.

BackgroundThe effects of reduced radiation dose CT for the generation of maxillofacial bone STL models for 3D printing is currently unknown. Images of two full-face transplantation patients scanned with non-contrast 320-detector row CT were reconstructed at fractions of the acquisition radiation dose using noise simulation software and both filtered back-projection (FBP) and Adaptive Iterative Dose Reduction 3D (AIDR3D). The maxillofacial bone STL model segmented with thresholding from AIDR3D images at 100 % dose was considered the reference. For all other dose/reconstruction method combinations, a "residual STL volume" was calculated as the topologic subtraction of the STL model derived from that dataset from the reference and correlated to radiation dose.ResultsThe residual volume decreased with increasing radiation dose and was lower for AIDR3D compared to FBP reconstructions at all doses. As a fraction of the reference STL volume, the residual volume decreased from 2.9 % (20 % dose) to 1.4 % (50 % dose) in patient 1, and from 4.1 % to 1.9 %, respectively in patient 2 for AIDR3D reconstructions. For FBP reconstructions it decreased from 3.3 % (20 % dose) to 1.0 % (100 % dose) in patient 1, and from 5.5 % to 1.6 %, respectively in patient 2. Its morphology resembled a thin shell on the osseous surface with average thickness &lt;0.1 mm.ConclusionThe residual volume, a topological difference metric of STL models of tissue depicted in DICOM images supports that reduction of CT dose by up to 80 % of the clinical acquisition in conjunction with iterative reconstruction yields maxillofacial bone models accurate for 3D printing