2,504 research outputs found
Simulation of Blood Flow through Stenosed Artery
Atherosclerosis is a life-threatening disease of the human circulatory system. It can lead to blockage of arteries leading to heart attacks. It is characterized by plaque formation at the walls of the artery lumen. The progression of plaque formation can lead to complete blockage of the artery. The diagnosis of atherosclerosis is very important. So, the study of parameters affecting atherosclerosis is important. We study the effect of percentage blockage and non-Newtonian nature of blood on hydrodynamic factors in an artery that is partially blocked by atherosclerotic plaque. ANSYS Fluent software is used to study these cases. We obtain the velocity profile and wall shear stress profile for 10%, 25%, 50%, and 75% blockage. We also study the effect of various blood models like Newtonian, Power law, Carreau, and Cross models on the fluid dynamic factors. Results show that the percentage of stenosis affects the wall shear stress (WSS) the most. WSS is minimum for 10% stenosis, and maximum for 75% stenosis. The fluctuation of WSS, downstream of the stenosis, is also maximum for the case of 75% stenosis and minimum for the case of 10% stenosis. There is formation of a recirculation zone, downstream of the stenosis, for all models at 50% stenosis
Concept Drift Detection in Data Stream Mining: The Review of Contemporary Literature
Mining process such as classification, clustering of progressive or dynamic data is a critical objective of the information retrieval and knowledge discovery; in particular, it is more sensitive in data stream mining models due to the possibility of significant change in the type and dimensionality of the data over a period. The influence of these changes over the mining process termed as concept drift. The concept drift that depict often in streaming data causes unbalanced performance of the mining models adapted. Hence, it is obvious to boost the mining models to predict and analyse the concept drift to achieve the performance at par best. The contemporary literature evinced significant contributions to handle the concept drift, which fall in to supervised, unsupervised learning, and statistical assessment approaches. This manuscript contributes the detailed review of the contemporary concept-drift detection models depicted in recent literature. The contribution of the manuscript includes the nomenclature of the concept drift models and their impact of imbalanced data tuples
Near Field Lenses in Two Dimensions
It has been shown that a slab of materials with refractive index = -1 behaves
like a perfect lens focussing all light to an exact electromagnetic copy of an
object. The original lens is limited to producing images the same size as the
object, but here we generalise the concept so that images can be magnified. For
two dimensional systems, over distances much shorter than the free space
wavelength, we apply conformal transformations to the original parallel sided
slab generating a variety of new lenses. Although the new lenses are not
`perfect' they are able to magnify two dimensional objects. The results apply
equally to imaging of electric or magnetic sub wavelength objects in two
dimensions. The concepts have potential applications ranging from microwave
frequencies to the visible.Comment: PDF fil
Probiotic-induced changes in the intestinal epithelium: Implications in gastrointestinal disease
There is resurgent interest in the use of probiotics to maintain gastrointestinal and systemic health, driven by recent advances in knowledge of bacterial interactions with the epithelium and innate immune system of the intestine. The effects of probiotic bacteria on the intestinal epithelium and their downstream consequences are reviewed. Probiotics prevent pathogen adherence and invasion of the epithelium, partly by blocking adherence sites but also by upregulating gene expression of MUC2 and of antimicrobial peptides. Metabolic effects of probiotics on the intestinal epithelium include production of short chain fatty acids which influence epithelial cell metabolism, turnover and apoptosis. Bacterial metabolism of unabsorbed dietary constituents with production of free radicals and phenolic metabolites can lead to DNA damage and cancer; probiotics restore eubiosis and potentially prevent this. Probiotics alter expression and redistribution of tight junction proteins and reduce intestinal permeability limiting absorption of noxious molecules from the gut lumen. Most studied are the effects of probiotics on epithelial cells which are the first line of innate immune-capable cells that encounter luminal flora. Probiotics, through secreted molecules, influence the innate inflammatory response of epithelial cells to stimuli from the gut lumen, and reduce mucosal inflammation. Through effects on dendritic, and possibly epithelial, cells they influence naïve T cells in the lamina propria of the gut and thus influence adaptive immunity. These varied effects of probiotics have implications for the treatment of several gastrointestinal diseases including antibiotic-associated colitis, acute gastroenteritis, inflammatory bowel disease, colon cancer, and irritable bowel syndrome
Aircraft interior noise reduction by alternate resonance tuning
Existing interior noise reduction techniques for aircraft fuselages perform reasonably well at higher frequencies, but are inadequate at lower frequencies, particularly with respect to the low blade passage harmonics with high forcing levels found in propeller aircraft. A method is being studied which considers aircraft fuselage lined with panels alternately tuned to frequencies above and below the frequency that must be attenuated. Adjacent panels would oscillate at equal amplitude, to give equal source strength, but with opposite phase. Provided these adjacent panels are acoustically compact, the resulting cancellation causes the interior acoustic modes to become cutoff, and therefore be non-propagating and evanescent. This interior noise reduction method, called Alternate Resonance Tuning (ART), is currently being investigated both theoretically and experimentally. This new concept has potential application to reducing interior noise due to the propellers in advanced turboprop aircraft as well as for existing aircraft configurations
On the refractive index for a nonmagnetic two-component medium: resolution of a controversy
The refractive index of a dielectric medium comprising both passive and
inverted components in its permittivity was determined using two methods: (i)
in the time domain, a finite-difference algorithm to compute the
frequency-domain reflectance from reflection data for a pulsed plane wave that
is normally incident on a dielectric half-space, and (ii) in the frequency
domain, the deflection of an obliquely incident Gaussian beam on transmission
through a dielectric slab. The dielectric medium was found to be an active
medium with a negative real part for its refractive index. Thereby, a recent
controversy in the scientific literature was resolved.Comment: manuscript submitted to Optics Communication
Power spectrum of mass and activity fluctuations in a sandpile
We consider a directed abelian sandpile on a strip of size ,
driven by adding a grain randomly at the left boundary after every
time-steps. We establish the exact equivalence of the problem of mass
fluctuations in the steady state and the number of zeroes in the ternary-base
representation of the position of a random walker on a ring of size . We
find that while the fluctuations of mass have a power spectrum that varies as
for frequencies in the range , the activity
fluctuations in the same frequency range have a power spectrum that is linear
in .Comment: 8 pages, 10 figure
Phosphorylation of ATP-citrate lyase by a cyclic AMP-independent protein kinase from a rat liver
Dynamic Vs Static Term-Expansion using Semantic Resources in Information Retrieval
Information Retrieval in a Telugu language is upcoming area of research. Telugu is one of the recognized Indian languages. We present a novel approach in reformulating item terms at the time of crawling and indexing. The idea is not new, but use of synset and other lexical resources in Indian languages context has limitations due to unavailability of language resources. We prepared a synset for 1,43,001 root words out of 4,83,670 unique words from training corpus of 3500 documents during indexing. Index time document expansion gave improved recall ratio, when compared to base line approach i.e. simple information retrieval without term expansion at both the ends. We studied the effect of query terms expansion at search time using synset and compared with simple information retrieval process without expansion, recall is greatly affected and improved. We further extended this work by expanding terms in two sides and plotted results, which resemble recall growth. Surprisingly all expansions are showing improvement in recall and little fall in precision. We argue that expansion of terms at any level may cause inverse effect on precision. Necessary care is required while expanding documents or queries with help of language resources like Synset, WordNet and other resources
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