Circulation characteristics associated with the Inter-Tropical Convergence Zone during northern winter

In this study, circulation characteristics associated with the ITCZ during the winter are examined by using the archives of National Centre for Medium Range Weather Forecasting (NCMRWF). To this end, some of the mean large scale basic meteorological and derived fields surrounding the ITCZ are analysed to examine the ITCZ circulation. It would be expected that during the INDOEX field phase experiment, several remote sensing and special observations be generated. To assess the impact of new remote sensing data in maintaining the structure and intensity of ITCZ circulation, an assimilation experiment is conducted using the high resolution TOVS temperature profile data of NOAA over the Indian Ocean for March 1996. An assimilation for the forthcoming INDOEX field phase duration in 1999 is planned by incorporating all satellite and observational data to be collected to study the dynamics of ITCZ

De-identifying a public use microdata file from the Canadian national discharge abstract database

<p>Abstract</p> <p>Background</p> <p>The Canadian Institute for Health Information (CIHI) collects hospital discharge abstract data (DAD) from Canadian provinces and territories. There are many demands for the disclosure of this data for research and analysis to inform policy making. To expedite the disclosure of data for some of these purposes, the construction of a DAD public use microdata file (PUMF) was considered. Such purposes include: confirming some published results, providing broader feedback to CIHI to improve data quality, training students and fellows, providing an easily accessible data set for researchers to prepare for analyses on the full DAD data set, and serve as a large health data set for computer scientists and statisticians to evaluate analysis and data mining techniques. The objective of this study was to measure the probability of re-identification for records in a PUMF, and to de-identify a national DAD PUMF consisting of 10% of records.</p> <p>Methods</p> <p>Plausible attacks on a PUMF were evaluated. Based on these attacks, the 2008-2009 national DAD was de-identified. A new algorithm was developed to minimize the amount of suppression while maximizing the precision of the data. The acceptable threshold for the probability of correct re-identification of a record was set at between 0.04 and 0.05. Information loss was measured in terms of the extent of suppression and entropy.</p> <p>Results</p> <p>Two different PUMF files were produced, one with geographic information, and one with no geographic information but more clinical information. At a threshold of 0.05, the maximum proportion of records with the diagnosis code suppressed was 20%, but these suppressions represented only 8-9% of all values in the DAD. Our suppression algorithm has less information loss than a more traditional approach to suppression. Smaller regions, patients with longer stays, and age groups that are infrequently admitted to hospitals tend to be the ones with the highest rates of suppression.</p> <p>Conclusions</p> <p>The strategies we used to maximize data utility and minimize information loss can result in a PUMF that would be useful for the specific purposes noted earlier. However, to create a more detailed file with less information loss suitable for more complex health services research, the risk would need to be mitigated by requiring the data recipient to commit to a data sharing agreement.</p

Genetic polymorphisms of the RAS-cytokine pathway and chronic kidney disease

Chronic kidney disease (CKD) in children is irreversible. It is associated with renal failure progression and atherosclerotic cardiovascular (CV) abnormalities. Nearly 60% of children with CKD are affected since birth with congenital or inherited kidney disorders. Preliminary evidence primarily from adult CKD studies indicates common genetic risk factors for CKD and atherosclerotic CV disease. Although multiple physiologic pathways share common genes for CKD and CV disease, substantial evidence supports our attention to the renin angiotensin system (RAS) and the interlinked inflammatory cascade because they modulate the progressions of renal and CV disease. Gene polymorphisms in the RAS-cytokine pathway, through altered gene expression of inflammatory cytokines, are potential factors that modulate the rate of CKD progression and CV abnormalities in patients with CKD. For studying such hypotheses, the cooperative efforts among scientific groups and the availability of robust and affordable technologies to genotype thousands of single nucleotide polymorphisms (SNPs) across the genome make genome-wide association studies an attractive paradigm for studying polygenic diseases such as CKD. Although attractive, such studies should be interpreted carefully, with a fundamental understanding of their potential weaknesses. Nevertheless, whole-genome association studies for diabetic nephropathy and future studies pertaining to other types of CKD will offer further insight for the development of targeted interventions to treat CKD and associated atherosclerotic CV abnormalities in the pediatric CKD population

A user's guide to the Encyclopedia of DNA elements (ENCODE)

The mission of the Encyclopedia of DNA Elements (ENCODE) Project is to enable the scientific and medical communities to interpret the human genome sequence and apply it to understand human biology and improve health. The ENCODE Consortium is integrating multiple technologies and approaches in a collective effort to discover and define the functional elements encoded in the human genome, including genes, transcripts, and transcriptional regulatory regions, together with their attendant chromatin states and DNA methylation patterns. In the process, standards to ensure high-quality data have been implemented, and novel algorithms have been developed to facilitate analysis. Data and derived results are made available through a freely accessible database. Here we provide an overview of the project and the resources it is generating and illustrate the application of ENCODE data to interpret the human genome

Experimental investigation of droplet velocity fields from elliptic injectors in subsonic cross flow

The flow field associated with a liquid jet injected transversely into a crossflow, also referred as transverse jet has numerous applications in industrial, environmental and natural systems. Examples of these applications include air-breathing engines (gas turbine afterburners, ramjet and scramjet combustors), rocket engines, environmental control systems and natural flows. Earliest research of a jet in a crossflow has been motivated by applications related to environmental problems such as plume dispersal from exhaust or pipe stacks or liquid effluent dispersal in streams. This method of liquid fuel/air mixture preparation enhances flame stabilization, fuel conversion efficiency, and reduction in emissions. In gas turbine applications because of the very limited residence time available for effective fuel air mixing, detailed investigations into spray characteristics of different injector configurations in a crossflow environment is desirable for identifying promising configurations with measurements in the near field to acquire reliable spray data for development of CFD models. The velocity field of a liquid jet in the near field ejecting out from an elliptic injector into a crossflow of air were investigated experimentally at conditions relevant to gas turbine applications. A rig was set up to investigate the injection of liquid jet in subsonic cross flow with a rectangular test section of cross section measuring 100 mm by 140 mm. Experiments were done with a two injector configurations a circular 0.8mm diameter plain orifice injector and a elliptic injector with an equivalent effective area of 0.7 mm (minor axis) by 0.95 mm (major axis) which was flush mounted on the bottom plate of test section. PIV technique was used to measure droplet velocity field and distributions in the near field of the spray. Measurements were performed at a distance of 5 mm from the bottom wall in the span wise plane and the results were compared with a circular injector. It was seen that no significant differences were observed in the u and v velocity components for the elliptic and circular injectors where the geometry changes are small suggesting that parameters like velocity are not significantly affected by small changes in injector exit geometry. Further for elliptic jets it was observed that increasing the crossflow velocity and maintaining the same liquid flow rate lead to an increase in the lateral spread of the spray with no significant change in the mean vorticity values

Measurements of droplet velocity fields in sprays from liquid jets injected in high-speed crossflows using piv

The present work reports the measurement of planar droplet velocity field of a plain liquid jet injected into a high-speed crossflowing airstream. PIV was employed to measure the instantaneous and average droplet velocity field in the far-field region of the spray. Water was injected from a 1-mm orifice and crossflow air velocities up to 110 m/s were investigated. The approach using PIV was validated using experimental PDPA data reported in literature. The increase of droplet velocity with axial distance was clearly observed. In the region considered for analysis, the droplet velocity showed a peak in the central region suggesting contributions primarily from surface breakup

Effect of lean primary-zone operation on emissions and stability of non-premixed combustors

Lean operation in the primary combustion zone of a gas turbine combustor is advantageous from NOx reduction point of view. The present work deals with the influence of lean primary zone operation on combustion performance, NOx emissions, and flame stability of a model gas turbine combustor with simplex atomizer. Air distribution is varied to operate the primary combustion zone from stoichiometric to leaner operating conditions (Φpri 1.04–0.61), at fixed fuel flow rate and overall air–fuel ratio. Combustor performance is quantified with the help of gas temperature profile at exit and species concentrations at the end of primary zone. It is found that a primary zone equivalence ratio of 0.79 is optimal for high combustor efficiency and low NOx emissions, with a stable flame. When the primary zone equivalence ratio approaches the lean blowout (LBO) limit (Φpri ∼ 0.5), intermittent low–frequency, high-amplitude pressure oscillations arise, especially at higher primary zone air flow rates. Inclusion of a metallic ring in the primary combustion zone widens the equivalence ratio for flame stability, with a small reduction in combustion efficiency. It also reduces the noise level and suppresses the intermittent high-amplitude oscillations close to LBO

Effect of Atomization Quality on Lean Blow-Out Limits and Acoustic Oscillations in a Swirl Stabilized Burner

The present experimental work highlights the influence of atomization quality on lean blow-out (LBO) limits and acoustic oscillations in a swirl stabilized burner with simplex atomizer. With decrease in the initial spray droplet diameter, the LBO limit shifts toward lower equivalence ratios. Reduction in droplet size also strongly influences the mode of LBO from diffusion flame to premixed lifted flame. Correlations have been developed for the LBO limit, involving mainly the time scales for evaporation, reaction and residence times for the fuel drops, as well as the gas flow. Delay in evaporation causes vapor accumulation before combustion and hence it influences both acoustic oscillations and LBO limit. The frequency of acoustic oscillations locks-in with the quarter wave frequency of the combustor duct for all initial droplet diameters considered. The amplitude of acoustic oscillations decreases with decrease in the initial droplet size

Experimental assessment on effect of lower porosities of bend skewed casing treatment on the performance of high speed compressor stage with tip critical rotor characteristics

Development of casing treatment geometries which will enhance the stable operating envelope of the compressor stage without sacrificing the efficiency is a great challenge for the designers. Bend skewed casing treatment with relatively lower porosities in the presence of plenum chamber is proven to be capable of improving the stall margin and gain in the compressor stage efficiency compared to other conventional casing treatments. Experimental investigations presented in this paper show very encouraging results with substantial improvement in the stable margin of the compressor stage with increase in the stage efficiency. The three bend skewed casing treatments designed for the experimental evaluations have porosities of 21%, 33% and 45%. The steady and transient performances of these three casing treatment geometries are evaluated at two axial extensions of 20% and 40%. Flow survey at the rotor exit shows distinct behaviors of the aerodynamic parameters in the tip region at near stall flow condition. The unsteady velocity measurements are performed with hot wire probe in the tip region ahead of the rotor leading edge to capture the fluctuations in the inlet axial velocity and the results are presented at the stall flow condition. The presence of the casing treatment changes the stalling behavior of the compressor stage. Highest porosity casing treatment results in 40.62% improvement in the stall margin with 0.88% improvement in the compressor stage efficiency at 20% axial extension