New hybrid CPU-GPU solver for CFD-DEM simulation of fluidized bed

Modeling is an alternative to experiment to explore more in multiphase flows. Various modeling approaches have been developed and used from 1D models in the macro-scale to multidimensional models in the micro scale. Well-known modeling approaches for fluidization systems are TFM and CFD-DEM, both have found many practical applications in fluidization systems. The TFM considers both fluid and particulate phase as interpenetrating continua. In contrast, the CFD-DEM considers the fluid as a continuous fluid in the meso-scale (cell-scale) and the solid as discrete particles in the micro-scale. The translational and rotational motions of individual particles are described by applying Newton’s and Euler’s second laws of motion, respectively. Since the first introduction of CFD-DEM technique by Tsuji et al. (1) and Hoomans et al. (2), different aspects of this modeling approach have been being enhanced and developed. Nowadays, this modeling approach has found many applications in different engineering fields specially fluidization (3). One of the main limitations of this modeling approach is its high computational demand which makes the parallelization necessary in order to model larger systems with more details. A CFD-DEM code comprises of three computational parts: CFD, DEM and coupling. The CFD part can be efficiently parallelized using space decomposition method on the distributed-memory platform like MPI, while the DEM part, due to its low granularity, is better to be parallelized using loop-level parallelization on the shared-memory platform like CUDA. We used a combination of both platforms to speed-up the CFD-DEM code. Figure 1 shows the data transfer between different parts of the code and the platforms that are used for their implementation. As it can be seen, the CFD and coupling parts are parallelized using MPI and executed on multiple CPUs and the DEM part is parallelized using CUDA and executed on a GPU. To solve the Navier-Stokes equations, we used the open-source CFD package, OpenFOAM®, while the code for coupling and DEM calculations were developed internally. The main goal of this programing style was to benefit from the maximum computational power of CPU and GPU in a single PC equipped with a CUDA-capable GPU. This code was successfully utilized for a fluidization system containing 100,000 spherical particles with the mean size of 2200 micrometers and density of 1500 kg/m3. Particles were placed in a cylinder with inner diameter of 0.14 m and height of 1 m. Number of fluid cells in the simulation was 7,400. The superficial gas velocity was 2 m/s. The code was executed on one CPU core of an Intel® core™-i7 processor (3.6 GHz) and an NVIDIA GeForce® GTX 660 Ti GPU. The simulation was continued for 1 second and the execution time was about 1.5 hr. Snapshots of this simulation are shown in Figure 2. These snapshots show the contour of gas velocity field and particles which are colored based on their velocity. This code is in its very first stages of developments and needs optimizations in both coupling and DEM parts to gain more execution speed. Please click Additional Files below to see the full abstract

The effect of adding gentamicin to contrast media for prevention of cholangitis after biliary stenting for non-calculous biliary obstruction, a randomized controlled trial

Aim: Cholangitis is the most common infectious complication of ERCP. In vitro studies showed that addition of aminoglycosides to contrast medium was effective in reducing cholangitis but the results of clinical trials are conflicting. We studied the effect of adding gentamicin to contrast medium in reducing the rate of post-ERCP cholangitis in patients with non-calculous obstructive jaundice. Methods: All patients with non-calculous obstructive jaundice who underwent endoscopic biliary stenting at the Shariati Hospital, Tehran, between December 2009 and October 2010 were enrolled in the study. Gentamicin (10 mg) or distilled water was added to each 10 cc contrast medium during ERCP. Intravenous antibiotics were administered before and after the procedure in all patients. After ERCP and stent deployment, patients were followed for 72 h for symptoms and signs of cholangitis. Results: A total of 114 patients were eligible for the study. Of these, 57 patients were included in each group. Cholangiocarcinoma was the most prevalent diagnosis. The obstruction was relieved in all patients by stenting. Five patients in each group (8. 8 %) developed cholangitis. There was no significant difference in the incidence of cholangitis between the two groups (p = 1. 000). Conclusions: With adequate drainage of the obstructed biliary tract by proper stenting, adding gentamicin to contrast media had no significant effect on incidence of post-ERCP cholangitis. © 2012 Indian Society of Gastroenterology

The fabrication of potentiometric membrane sensors and their applications

Ionophore-incorporated PVC-membrane sensors are well-established analytical tools routinely used for the selective and direct measurement of a wide variety of different ions in complex biological and environmental samples. The key ingredient of such plasticized PVC-members is the involved ionophore, defining the selectivity of the electrodes complex formation with the cation of interest. In the past few years, the development of new ion-selective electrodes for various ions has been reported inthe literature

Effect of Bending Anisotropy on the 3D Conformation of Short DNA Loops

The equilibrium three dimensional shape of relatively short loops of DNA is studied using an elastic model that takes into account anisotropy in bending rigidities. Using a reasonable estimate for the anisotropy, it is found that cyclized DNA with lengths that are not integer multiples of the pitch take on nontrivial shapes that involve bending out of planes and formation of kinks. The effect of sequence inhomogeneity on the shape of DNA is addressed, and shown to enhance the geometrical features. These findings could shed some light on the role of DNA conformation in protein--DNA interactions

Endoscopic screening for precancerous lesions of the esophagus in a high risk area in northern Iran

Background: Esophageal squamous cell carcinoma (ESCC) is a major health problem in many developing countries, including Iran. ESCC has a very poor prognosis, largely due to late diagnosis. As a first step in developing an early detection and treatment program, we conducted a population-based endoscopic screening for ESCC and its precursor lesion, esophageal squamous dysplasia (ESD), in asymptomatic adults from Golestan Province, northern Iran (a high-risk area for ESCC) to evaluate the feasibility of such a program and to document the prevalence and risk factor correlates of ESD. Methods: This cross-sectional study was conducted among participants of the Golestan Cohort Study (GCS), a population-based cohort of 50,000 adults in eastern Golestan Province. Randomly selected GCS participants were invited by telephone. Those who accepted were referred to a central endoscopy clinic. Eligible subjects who consented were asked to complete a brief questionnaire. Detailed information about selected risk factors was obtained from the GCS main database. Endoscopic examination with was performed with Lugol's iodine staining; biopsies were taken from unstained lesions as well as the normally stained mucosa of the esophagus, and the biopsies were diagnosed by expert pathologists according to previously described criteria. Results: In total, 1906 GCS subjects were invited, of whom only 302 (15.8%) were successfully enrolled. Esophagitis (29.5%) and ESD (6.0%) were the most common pathological diagnoses. Turkmen ethnicity (adjusted OR = 8.61; 95%CI: 2.48-29.83), being older than the median age (OR = 7.7; 95% CI: 1.99-29.87), and using deep frying cooking methods (OR = 4.65; 95%CI: 1.19-18.22) were the strongest predictors for ESD. There were significant relationships between esophagitis and smoking (p-value<0.001), drinking hot tea (P value = 0.02) and lack of education (P value = 0.004). Conclusion: We observed a low rate of participation in endoscopic screening. The overall prevalence of ESD was 6.0%. Developing non-endoscopic primary screening methods and screening individuals with one or more risk factors may improve these rates

The sensitivity of land emissivity estimates from AMSR-E at C and X bands to surface properties

Microwave observations at low frequencies exhibit more sensitivity to surface and subsurface properties with little interference from the atmosphere. The objective of this study is to develop a global land emissivity product using passive microwave observations from the Advanced Microwave Scanning Radiometer – Earth Observing System (AMSR-E) and to investigate its sensitivity to land surface properties. The developed product complements existing land emissivity products from SSM/I and AMSU by adding land emissivity estimates at two lower frequencies, 6.9 and 10.65 GHz (C- and X-band, respectively). Observations at these low frequencies penetrate deeper into the soil layer. Ancillary data used in the analysis, such as surface skin temperature and cloud mask, are obtained from International Satellite Cloud Climatology Project (ISCCP). Atmospheric properties are obtained from the TIROS Operational Vertical Sounder (TOVS) observations to determine the small upwelling and downwelling atmospheric emissions as well as the atmospheric transmission. A sensitivity test confirms the small effect of the atmosphere but shows that skin temperature accuracy can significantly affect emissivity estimates. Retrieved emissivities at C- and X-bands and their polarization differences exhibit similar patterns of variation with changes in land cover type, soil moisture, and vegetation density as seen at SSM/I-like frequencies (Ka and Ku bands). The emissivity maps from AMSR-E at these higher frequencies agree reasonably well with the existing SSM/I-based product. The inherent discrepancy introduced by the difference between SSM/I and AMSR-E frequencies, incidence angles, and calibration has been assessed. Significantly greater standard deviation of estimated emissivities compared to SSM/I land emissivity product was found over desert regions. Large differences between emissivity estimates from ascending and descending overpasses were found at lower frequencies due to the inconsistency between thermal IR skin temperatures and passive microwave brightness temperatures which can originate from below the surface. The mismatch between day and night AMSR-E emissivities is greater than ascending and descending differences of SSM/I emissivity. This is because of unique orbit time of AMSR-E (01:30 a.m./p.m. LT) while other microwave sensors have orbit time of 06:00 to 09:00 (a.m./p.m.). This highlights the importance of considering the penetration depth of the microwave signal and diurnal variability of the temperature in emissivity retrieval. The effect of these factors is greater for AMSR-E observations than SSM/I observations, as AMSR-E observations exhibit a greater difference between day and night measures. This issue must be addressed in future studies to improve the accuracy of the emissivity estimates especially at AMSR-E lower frequencies

Emerging Carbapenem-Resistant Pseudomonas aeruginosa Isolates Carrying bla_IMP Among Burn Patients in Isfahan, Iran

Background: Metallo-β-lactamase (MBL)-producing Pseudomonas aeruginosa is a significant pathogen in burn patients. Objectives: The aim of this study was to determine the prevalence of carbapenem-resistant P. aeruginosa isolates, including those resistant to imipenemase (IMP), in a burn unit in Isfahan, Iran. Patients and Methods: One hundred and fifty P. aeruginosa isolates from burn patients were tested for antibiotic susceptibility by the disc diffusion method in accordance with CLSI guidelines. Production of MBL was identified with the EDTA disk method. DNA was purified from the MBL-positive isolates, and detection of the blaIMP gene was performed with PCR. Results: Fifty-seven out of 150 (38%) isolates were multi-drug resistant (MDR), and 93 (62%) were extensively-drug resistant (XDR). Among all isolates, the resistance rate to ciprofloxacin, tobramycin, imipenem, meropenem, amikacin, ceftazidime, and cefepime was higher than 90%, while the resistance rates to piperacillin/tazobactam and aztreonam were 70.7% and 86%, respectively. Colistin and polymyxin B remained the most effective studied antibiotics. All of the imipenem-resistant P. aeruginosa isolates were MBL-positive, and 107 out of 144 (74.3%) of the MBL isolates were positive for the blaIMP gene. Conclusions: The results of this study show that the rate of P. aeruginosa-caused burn wound infections was very high, and many of the isolates were resistant to three or more classes of antimicrobials. Such extensive resistance to antimicrobial classes is important because few treatment options remain for patients with burn wound infections. blaIMP-producing P. aeruginosa isolates are a rising threat in burn-care units, and should be controlled by conducting infection-control assessments

Scalability and Total Recall with Fast CoveringLSH

Locality-sensitive hashing (LSH) has emerged as the dominant algorithmic technique for similarity search with strong performance guarantees in high-dimensional spaces. A drawback of traditional LSH schemes is that they may have \emph{false negatives}, i.e., the recall is less than 100\%. This limits the applicability of LSH in settings requiring precise performance guarantees. Building on the recent theoretical "CoveringLSH" construction that eliminates false negatives, we propose a fast and practical covering LSH scheme for Hamming space called \emph{Fast CoveringLSH (fcLSH)}. Inheriting the design benefits of CoveringLSH our method avoids false negatives and always reports all near neighbors. Compared to CoveringLSH we achieve an asymptotic improvement to the hash function computation time from $\mathcal{O}(dL)$ to $\mathcal{O}(d + L\log{L})$, where $d$ is the dimensionality of data and $L$ is the number of hash tables. Our experiments on synthetic and real-world data sets demonstrate that \emph{fcLSH} is comparable (and often superior) to traditional hashing-based approaches for search radius up to 20 in high-dimensional Hamming space.Comment: Short version appears in Proceedings of CIKM 201