188 research outputs found
Professional Secrecy and Privileged Communication in Medical Practice
A medical professional has the faith and confidence of society in him/her. It is his utmost duty and responsibility to uphold the ethical standards of confidentiality, set forth in the Hippocratic Oath, the Declaration of Geneva, the International Code of Medical Ethics and the World Health Organization. Communication between the physician and his patient is privileged. This information can only be divulged, in part, under special circumstances
Preventing transition to turbulence: a viscosity stratification does not always help
In channel flows a step on the route to turbulence is the formation of
streaks, often due to algebraic growth of disturbances. While a variation of
viscosity in the gradient direction often plays a large role in
laminar-turbulent transition in shear flows, we show that it has, surprisingly,
little effect on the algebraic growth. Non-uniform viscosity therefore may not
always work as a flow-control strategy for maintaining the flow as laminar.Comment: 9 pages, 8 figure
Stabilization of Hydrodynamic Flows by Small Viscosity Variations
Motivated by the large effect of turbulent drag reduction by minute
concentrations of polymers we study the effects of a weakly space-dependent
viscosity on the stability of hydrodynamic flows. In a recent Letter [Phys.
Rev. Lett. {\bf 87}, 174501, (2001)] we exposed the crucial role played by a
localized region where the energy of fluctuations is produced by interactions
with the mean flow (the "critical layer"). We showed that a layer of weakly
space-dependent viscosity placed near the critical layer can have a very large
stabilizing effect on hydrodynamic fluctuations, retarding significantly the
onset of turbulence. In this paper we extend these observation in two
directions: first we show that the strong stabilization of the primary
instability is also obtained when the viscosity profile is realistic (inferred
from simulations of turbulent flows with a small concentration of polymers).
Second, we analyze the secondary instability (around the time-dependent primary
instability) and find similar strong stabilization. Since the secondary
instability develops around a time-dependent solution and is three-dimensional,
this brings us closer to the turbulent case. We reiterate that the large effect
is {\em not} due to a modified dissipation (as is assumed in some theories of
drag reduction), but due to reduced energy intake from the mean flow to the
fluctuations. We propose that similar physics act in turbulent drag reduction.Comment: 10 pages, 17 figs., REVTeX4, PRE, submitte
Unsteady flow of a nanofluid over a sphere with nonlinear Boussinesq approximation
A theoretical study is presented of transient mixed convection boundary layer flow of a nanofluid in the forward stagnation region of a heated sphere which is rotating with time dependent angular velocity. The effect of the non-linear Boussinesq approximation is taken into account. The nanofluid is treated as a two-component mixture i.e. nano-particles distributed homogenously in a base fluid (water or gas). The effects of the Brownian motion and thermophoresis are included for the nanofluid and constant wall temperature is imposed at the sphere surface. The first and second laws of thermodynamics are employed in order to study thermophysics as well as heat and mass transfer phenomena. By introducing appropriate similarity variables the governing equations are transformed into a system of dimensionless, nonlinear, coupled, ordinary differential equations which are solved numerically by applying the second-order accurate implicit finite difference Keller box method. The reliability and efficiency of the obtained numerical results are validated via comparison with the previously published results for special cases. The effects of various parameters on primary and secondary velocities, temperature, nanofluid volume fraction (concentration), primary and secondary shear stress functions, Nusselt number function (wall heat transfer rate) and Sherwood number function (wall nanoparticle mass transfer rate) are visualized. Furthermore the influence of non-linear temperature parameter, Brinkman parameter (ratio of Brinkman number to dimensionless temperature ratio), local Reynolds number and unsteadiness parameter on entropy generation number is computed. A strong elevation in entropy generation number is computed with both increasing Brinkman parameter and unsteadiness parameter. Primary and secondary surface shear stresses, Nusselt number and Sherwood number also increase with unsteadiness and rotation parameters. Primary shear stress is boosted with increasing mixed convection parameter and Brownian motion effect whereas secondary shear stress is depressed. Temperatures are suppressed with increasing nonlinear temperature parameter whereas nano-particle concentrations are elevated. Increasing thermophoresis parameter enhances both temperatures and nano-particle concentration values. The simulations find applications in rotating chemical engineering mixing systems and nano-coating transport phenomena
Nanopackaging of Silver using Spice Extract and their Characterization
The aim of the present study was to synthesize silver nanoparticles using spice extracts as reducing agents and further evaluate their anti-microbial activities. Silver has been shown to possess antimicrobial activity. The silver nanoparticles were prepared by solvent evaporation method. The silver nanoparticles were characterized by UV-Vis spectroscopy. The functional groups present in the phyto-constituents on the plant extract were determined by FT-IR studies. The particle size of the silver nanoparticles was determined by Dynamic Light Scattering and was found to be 143, 50 and 56 nm for cloves, cinnamon and neem silver nanoparticles respectively. They exhibited antibacterial property against Escherichia coli, Staphylococcus aureus and Salmonella typhi strains, tested using Well Diffusion method. Plant extracts however reduce the antimicrobial activity of the nanoparticles. In conclusion, antimicrobial activities of silver nanoparticles were reduced by plant extracts certifies vital potential in biomedical application.Keywords: Silver nanoparticles Neem Cinnamon Clove
Deep Learning Approach for Building Detection Using LiDAR-Orthophoto Fusion
© 2018 Faten Hamed Nahhas et al. This paper reports on a building detection approach based on deep learning (DL) using the fusion of Light Detection and Ranging (LiDAR) data and orthophotos. The proposed method utilized object-based analysis to create objects, a feature-level fusion, an autoencoder-based dimensionality reduction to transform low-level features into compressed features, and a convolutional neural network (CNN) to transform compressed features into high-level features, which were used to classify objects into buildings and background. The proposed architecture was optimized for the grid search method, and its sensitivity to hyperparameters was analyzed and discussed. The proposed model was evaluated on two datasets selected from an urban area with different building types. Results show that the dimensionality reduction by the autoencoder approach from 21 features to 10 features can improve detection accuracy from 86.06% to 86.19% in the working area and from 77.92% to 78.26% in the testing area. The sensitivity analysis also shows that the selection of the hyperparameter values of the model significantly affects detection accuracy. The best hyperparameters of the model are 128 filters in the CNN model, the Adamax optimizer, 10 units in the fully connected layer of the CNN model, a batch size of 8, and a dropout of 0.2. These hyperparameters are critical to improving the generalization capacity of the model. Furthermore, comparison experiments with the support vector machine (SVM) show that the proposed model with or without dimensionality reduction outperforms the SVM models in the working area. However, the SVM model achieves better accuracy in the testing area than the proposed model without dimensionality reduction. This study generally shows that the use of an autoencoder in DL models can improve the accuracy of building recognition in fused LiDAR-orthophoto data
Dynamics and nucleation of dislocations in crystals
Hydrogen-poor superluminous supernovae (SLSNe-I) have been predominantly
found in low-metallicity, star-forming dwarf galaxies. Here we identify
Gaia17biu/SN 2017egm as an SLSN-I occurring in a "normal" spiral galaxy (NGC
3191) in terms of stellar mass (several times 10^10 M_sun) and metallicity
(roughly Solar). At redshift z=0.031, Gaia17biu is also the lowest redshift
SLSN-I to date, and the absence of a larger population of SLSNe-I in dwarf
galaxies of similar redshift suggests that metallicity is likely less important
to the production of SLSNe-I than previously believed. With the smallest
distance and highest apparent brightness for an SLSN-I, we are able to study
Gaia17biu in unprecedented detail. Its pre-peak near-ultraviolet to optical
color is similar to that of Gaia16apd and among the bluest observed for an
SLSN-I while its peak luminosity (M_g = -21 mag) is substantially lower than
Gaia16apd. Thanks to the high signal-to-noise ratios of our spectra, we
identify several new spectroscopic features that may help to probe the
properties of these enigmatic explosions. We detect polarization at the ~0.5%
level that is not strongly dependent on wavelength, suggesting a modest, global
departure from spherical symmetry. In addition, we put the tightest upper limit
yet on the radio luminosity of an SLSN-I with <5.4x10^26 erg/s/Hz (at 10 GHz),
which is almost a factor of 40 better than previous upper limits and one of the
few measured at an early stage in the evolution of an SLSN-I. This limit
largely rules out an association of this SLSNe-I with known populations of
gamma-ray burst (GRB) like central engines.Comment: Accepted for publication in ApJ. Ancillary ASCII tables added:
TRL.txt -- blackbody temperature, radius and luminosity; uvw2uvm2uvw1uvu.txt
-- UV photometry; BgVri.txt -- optical photometry; zJHK.txt -- NIR photometr
Relevant Problem of a Hydraulic Jump at Diyala Weir and the Proposed Remedy
This study aims to analyze the Diyala weir problems and compares it with the safe limit and proposes the treatment for these problems. One of the most influencing problems in the site of weir was the formation of the hydraulic jump, it was found that the scour occurs due to the position of the hydraulic jump and the sequence depth of the jump is higher than the tail water depth. Some treatment procedures are suggested, these treatments cover this problem by presenting a suitable stilling basin as well as recommended to use a low weir at end of basin to produce a back water curve that should be increase the stage of tail water and ensuring the stability of a hydraulic jump
Suicide and deliberate self-harm in Pakistan: A scoping review
Background: Suicide is a major global public health problem with more than 800,000 incidents worldwide annually. Seventy-five percent of the global suicides occur in low and middle-income countries (LMICs). Pakistan is a LMIC where information on suicidal behavior is limited. The aim of the review is to map available literature on determinants, risk factors and other variables of suicidal behavior in Pakistan.Method: This study was based on Arksey and O\u27Malley\u27s methodological framework of scoping review, combining peer reviewed publications with grey literature. Ten databases including Applied Social Sciences Index and Abstracts (ASSIA), Cochrane Trials Register (CRG), Cumulative Index to Nursing and Allied Health (CINAHL), National Library of Medicine Gateway (NLMG), ExcerptaMedica (EMBASE), National Library of Medicine\u27s MEDLINE (PUBMED), PSYCHINFO, Social Science Citation Index and Science Citation Index (SCI) and Pakmedinet.com were searched from the beginning of their time frames until December 2016 using a combination of key terms. The inclusion criteria included studies of various study designs covering different aspects of suicidal behavior in English language.Results: Six hundred and twenty three articles were initially retrieved from all ten databases. Two independent reviewers screened the titles and abstracts for relevance. One hundred and eighteen articles were read in full, out of which 11 were excluded because they did not fit the eligibility criteria. One hundred and ten articles, including two student theses and one report, were included in the final review. Most studies were descriptive in nature, with only three that used a case-control design. Majority of the studies were from urban areas, and addressed determinants rather than risk factors. Gender differences and age were predominantly reported, with more males committing suicide. Suicidal behavior was more common among individuals younger than 30 years of age. The three most common methods for suicides were hanging, poisoning and use of firearms. Mental illness as a risk factor for suicides was mentioned in only three studies.Conclusions: This review is the first attempt to synthesize available literature on suicidal behavior in Pakistan. The evidence is limited, and calls for more robust analytical research designs, along with a focus on risk factors
Revealing invisible stews:New results of organic residue analyses of beveled rim bowls from the late Chalcolithic site of Shakhi Kora, Kurdistan region of Iraq
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