551 research outputs found
Beyond the Horizon
Cosmic horizons arise in general relativity in the context of black holes and
in certain cosmologies. Classically, regions beyond a horizon are inaccessible
to causal observers. However, quantum mechanical correlations may exist across
horizons that may influence local observations. For the case of de Sitter
space, we show how a single particle excitation behind the horizon changes the
density matrix governing local observables. As compared to the vacuum state, we
calculate the change in the average energy and entropy per unit volume. This
illustrates what may be a generic property allowing some features of spacetime
beyond a horizon to be inferred.Comment: 9 pages, 1 figur
The layer disorders defect in coir fiber under thermal and chemical treatment
Natural coir fibers, subjectd to thermal treatments in the range of 0oC
to 200oC and alkali treatment with 5% to 30% concentration w/w, have been used in
the present investigation to determine the interlayer variability of the cellulose
planes (020), (110) and (110). Among the equatorial reflections (110), (110) and
(020), the extent of variability is found to be more with the proportion of such
affected planes less for (020) reflection in the native cellulose at lower
temperature while at higher temperature (110) and (110) become more affected by
variability defect. (110) and (1 10) planes are more affected also with alkali
treatment.The layer disorders defect in coir fiber under thermal and chemical treatment
D N Mahato*, B K Mathur and S Bhattacharjee
Department of Physics, Indian Institute of Technology,
Kharagpur-721 302, West Bengal, India
E-mail : [email protected] of Physics, Indian Institute of Technology,
Kharagpur-721 302, West Bengal, Indi
Aperiodic tumbling of microrods advected in a microchannel flow
We report on an experimental investigation of the tumbling of microrods in
the shear flow of a microchannel (40 x 2.5 x 0.4 mm). The rods are 20 to 30
microns long and their diameters are of the order of 1 micron. Images of the
centre-of-mass motion and the orientational dynamics of the rods are recorded
using a microscope equipped with a CCD camera. A motorised microscope stage is
used to track individual rods as they move along the channel. Automated image
analysis determines the position and orientation of a tracked rods in each
video frame. We find different behaviours, depending on the particle shape, its
initial position, and orientation. First, we observe periodic as well as
aperiodic tumbling. Second, the data show that different tumbling trajectories
exhibit different sensitivities to external perturbations. These observations
can be explained by slight asymmetries of the rods. Third we observe that after
some time, initially periodic trajectories lose their phase. We attribute this
to drift of the centre of mass of the rod from one to another stream line of
the channel flow.Comment: 14 pages, 8 figures, as accepted for publicatio
Biomimetic synthesis of hybrid nanocomposite scaffolds by freeze-thawing and freeze-drying
The aim of this study is to biomimetically synthesize hydroxyapatite - hydrophilic polymer scaffolds for biomedical applications. This organic-inorganic hybrid has been structurally characterized and reveals a good microstructural control as seen by the SEM analysis and the nanosize of the particulates is confirmed by AFM microscopy. The characterization of such nano-structured composites would allow researchers to design new systems, tailoring properties for different applications. © Indian Academy of Sciences
The presentation of academic self in the digital age: the role of electronic databases
A growing number of online electronic resources present academic work. We are not focusing here on specialised electronic databases that store bibliographic research data, such as Medline, PubMed, ASSIA, ERIC, JSTOR, but databases or social networking websites /platforms for academics/researchers that profile research, academic and professional activities, such as SCOPUS, WoS (Web of Science), Academia.edu, KUDOS, ORCiD, ResearchGate, LinkedIn, GoogleScholar and Mendeley. We discuss databases or platforms can promote the profile of an individual academic, highligthing their research interests, grants and publications. These databases are good outlets for Early Career Researchers (ECRs) to build, improve and promote their public profile. However, the level of efforts requires to open an account or to maintain these databases regularly can be a daunting task for some scholars. This paper outlines some of these key databases and their functions and reflects on advantages and disadvantages of engaging with the most popular ones. We remind the reader that many of these databases require academics’ attention and input, and thus create more work
Reliability of fluctuation-induced transport in a Maxwell-demon-type engine
We study the transport properties of an overdamped Brownian particle which is
simultaneously in contact with two thermal baths. The first bath is modeled by
an additive thermal noise at temperature . The second bath is associated
with a multiplicative thermal noise at temperature . The analytical
expressions for the particle velocity and diffusion constant are derived for
this system, and the reliability or coherence of transport is analyzed by means
of their ratio in terms of a dimensionless P\'{e}clet number. We find that the
transport is not very coherent, though one can get significantly higher
currents.Comment: 14 pages, 5 figure
Mapping the G-structures and supersymmetric vacua of five-dimensional N=4 supergravity
We classify the supersymmetric vacua of N=4, d=5 supergravity in terms of
G-structures. We identify three classes of solutions: with R^3, SU(2) and
generic SO(4) structure. Using the Killing spinor equations, we fully
characterize the first two classes and partially solve the latter. With the N=4
graviton multiplet decomposed in terms of N=2 multiplets: the graviton, vector
and gravitino multiplets, we obtain new supersymmetric solutions corresponding
to turning on fields in the gravitino multiplet. These vacua are described in
terms of an SO(5) vector sigma-model coupled with gravity, in three or four
dimensions. A new feature of these N=4 vacua, which is not seen from an N=2
point of view, is the possibility for preserving more exotic fractions of
supersymmetry. We give a few concrete examples of these new supersymmetric
(albeit singular) solutions. Additionally, we show how by truncating the N=4,
d=5 set of fields to minimal supergravity coupled with one vector multiplet we
recover the known two-charge solutions.Comment: 31 pages, late
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