15,618 research outputs found
A Review Paper on Various Search Engines (Google, Yahoo, Altavista, Ask and Bing)
Search engines are used in the web as a tool for information retrieval. As the web is a huge repository of heterogeneous and unstructured data so to filter out relevant information from unnecessary ones search engines are needed. Search engines usually consists of crawling module, page repository, indexing module, querying module and ranking module. The inter communication between these modules describes the working methodology of a search engine. This paper aims to focus on the comparative analysis of five major search engines i.e Google, Yahoo, Altavista, Ask and Bing in a tabular form based on some features. The features include search operator, search web, search images, search videos, search news, search maps, search books, advance search, change background, change search settings, display number of results, shopping, translation services, multi-language support, questions/answers, directory, advertising programs, business services, themes, case sensitive, finance, safe search, search pad, career and preferences. Google stands out as the best search engine amongst all search engines, which works on Page Rank algorithm. Page Rank is a numeric value which determines the importance of a web page by calculating the number of backlinks
Anopheline fauna of parts of Tirap district, Arunachal Pradesh with reference to malaria transmission
In a survey on the anopheline fauna in highly malaria endemic areas of the Tirap district of Arunachal Pradesh, 7476 anophelines belonging to 17 species were collected, including seven species of anophelines which are recognized malaria vectors in India. Anopheles tessellatus and A. jamesii were recorded for the first time in this area. The parasitological survey revealed that the area was endemic for malaria particularly P. falciparum. the slide positivity rate and slide falciparum rate being 25.63 and 19.21 per cent respectively. On dissection of 10 anopheies species, malarial infection was detected in two viz., A. minimus and A. dirus
Adiabatic multicritical quantum quenches: Continuously varying exponents depending on the direction of quenching
We study adiabatic quantum quenches across a quantum multicritical point
(MCP) using a quenching scheme that enables the system to hit the MCP along
different paths. We show that the power-law scaling of the defect density with
the rate of driving depends non-trivially on the path, i.e., the exponent
varies continuously with the parameter that defines the path, up to a
critical value ; on the other hand for , the scaling exponent saturates to a constant value. We show that
dynamically generated and {\it path()-dependent} effective critical
exponents associated with the quasicritical points lying close to the MCP (on
the ferromagnetic side), where the energy-gap is minimum, lead to this
continuously varying exponent. The scaling relations are established using the
integrable transverse XY spin chain and generalized to a MCP associated with a
-dimensional quantum many-body systems (not reducible to two-level systems)
using adiabatic perturbation theory. We also calculate the effective {\it
path-dependent} dimensional shift (or the shift in center of the
impulse region) that appears in the scaling relation for special paths lying
entirely in the paramagnetic phase. Numerically obtained results are in good
agreement with analytical predictions.Comment: 5 pages, 4 figure
Quenching Dynamics of a quantum XY spin-1/2 chain in presence of a transverse field
We study the quantum dynamics of a one-dimensional spin-1/2 anisotropic XY
model in a transverse field when the transverse field or the anisotropic
interaction is quenched at a slow but uniform rate. The two quenching schemes
are called transverse and anisotropic quenching respectively. Our emphasis in
this paper is on the anisotropic quenching scheme and we compare the results
with those of the other scheme. In the process of anisotropic quenching, the
system crosses all the quantum critical lines of the phase diagram where the
relaxation time diverges. The evolution is non-adiabatic in the time interval
when the parameters are close to their critical values, and is adiabatic
otherwise. The density of defects produced due to non-adiabatic transitions is
calculated by mapping the many-particle system to an equivalent Landau-Zener
problem and is generally found to vary as , where is the
characteristic time scale of quenching, a scenario that supports the
Kibble-Zurek mechanism. Interestingly, in the case of anisotropic quenching,
there exists an additional non-adiabatic transition, in comparison to the
transverse quenching case, with the corresponding probability peaking at an
incommensurate value of the wave vector. In the special case in which the
system passes through a multi-critical point, the defect density is found to
vary as . The von Neumann entropy of the final state is shown to
maximize at a quenching rate around which the ordering of the final state
changes from antiferromagnetic to ferromagnetic.Comment: 8 pages, 6 figure
Efficient clay supported Ni0 nanoparticles as heterogeneous catalyst for solvent-free synthesis of Hantzsch polyhydroquinoline
A green and efficient multicomponent one-pot synthesis of Hantzsch polyhydroquinoline was achieved by
the condensation of aldehydes, dimedone, ethylacetoacetate and ammonium acetate at room temperature
using environmentally benign modified Montmorillonite supported Ni0-nanoparticles as catalyst. The well
dispersed Ni0-nanoparticles having a high surface to volume ratio have promising features for the reaction
such as easy removal of the catalyst, solvent-free, shorter reaction time, high product yields (about 95%)
and easy work up procedure. There is no significant effect of electron withdrawing or donating nature of
substituent on aldehydes in the formation of polyhydroquinoline derivatives
Quantum Discord in a spin-1/2 transverse XY Chain Following a Quench
We report a study on the zero-temperature quantum discord as a measure of
two-spin correlation of a transverse XY spin chain following a quench across a
quantum critical point and investigate the behavior of mutual information,
classical correlations and hence of discord in the final state as a function of
the rate of quenching. We show that though discord vanishes in the limit of
very slow as well as very fast quenching, it exhibits a peak for an
intermediate value of the quenching rate. We show that though discord and also
the mutual information exhibit a similar behavior with respect to the quenching
rate to that of concurrence or negativity following an identical quenching,
there are quantitative differences. Our studies indicate that like concurrence,
discord also exhibits a power law scaling with the rate of quenching in the
limit of slow quenching though it may not be expressible in a closed power law
form. We also explore the behavior of discord on quenching linearly across a
quantum multicritical point (MCP) and observe a scaling similar to that of the
defect density.Comment: 6 pages, 5 figure
Path dependent scaling of geometric phase near a quantum multi-critical point
We study the geometric phase of the ground state in a one-dimensional
transverse XY spin chain in the vicinity of a quantum multi-critical point. We
approach the multi-critical point along different paths and estimate the
geometric phase by applying a rotation in all spins about z-axis by an angle
. Although the geometric phase itself vanishes at the multi-critical
point, the derivative with respect to the anisotropy parameter of the model
shows peaks at different points on the ferromagnetic side close to it where the
energy gap is a local minimum; we call these points `quasi-critical'. The value
of the derivative at any quasi-critical point scales with the system size in a
power-law fashion with the exponent varying continuously with the parameter
that defines a path, upto a critical value .
For , or on the paramagnetic side no such peak is
observed. Numerically obtained results are in perfect agreement with analytical
predictions.Comment: 5 pages, 6 figure
- …