628 research outputs found
Tempering of Die-steels based on indigenous materials
This paper present studies on the effects of quenching temperature, tempering temperature and time on the hardness of three die steels of similar carbon contents but having increasing chromium percentages. While tempering in the range of 150°C to 400°C it was observed that hardness decreased as quenching temperature was raised. All the steels showed secondary hardening phenomenon in relation to the variables mentioned above. It was also observed that on tempering the steels above 450°C, after prior quenching from increasing temperatures, hardness gradually increased upto the quenching temperature of 1100°C, beyond which followed a decrease in hardness. This phenomenon was the decrease in hardness. This phenomenon was the same at all tempering temperatures upto 601°C, but the increase in hardness from low quenching temperatures to the maximum quenching temperature was less at 450°C than at the higher temperatures and attained a maximum at 600°C secondary hardening decreased with the increase of quenching temperatur
Medical research and ethics - Revisited
Ethics in the medical research is known since many years; however, there have been new developments in this area recently. A phenomenal improvement in the health-care system, leading to increased life expectancy, and thereby, newer lifestyle and other health-related diseases has opened avenues for newer drugs and health-care technology. However, these have to be tried and tested in the context of the disease epidemiology, health-care delivery and of course, medical ethics. Monitoring and evaluation of the treatment regimes of well documented effective medicines is also required. This is the core of medical research. With the ever increasing concept of evidence-based medical system, and thereby, a rapid rise in the number of clinical trials; the role of medical ethics is potentially increasing to keep the patient
Queue-length synchronization in a communication networks
We study synchronization in the context of network traffic on a
communication network with local clustering and geographic separations. The
network consists of nodes and randomly distributed hubs where the top five hubs
ranked according to their coefficient of betweenness centrality (CBC) are
connected by random assortative and gradient mechanisms. For multiple message
traffic, messages can trap at the high CBC hubs, and congestion can build up on
the network with long queues at the congested hubs. The queue lengths are seen
to synchronize in the congested phase. Both complete and phase synchronization
is seen, between pairs of hubs. In the decongested phase, the pairs start
clearing, and synchronization is lost. A cascading master-slave relation is
seen between the hubs, with the slower hubs (which are slow to decongest)
driving the faster ones. These are usually the hubs of high CBC. Similar
results are seen for traffic of constant density. Total synchronization between
the hubs of high CBC is also seen in the congested regime. Similar behavior is
seen for traffic on a network constructed using the Waxman random topology
generator. We also demonstrate the existence of phase synchronization in real
Internet traffic data.Comment: 13 Pages, 15 figure
Research and Development work on Substitute Nickel-Free Austenitic Stainless Steels
THE demands of austenitic stainless steel as what is termed as `non-magnetic' in the Indian market in sheet, plate, tube and rod forms have been multiplying during each successive Five-Year Plan.Due to severe import restrictions, acute and chronic shortage of foreign exchange, the actual import figures tend to taper off
and do not represent the actual requirements of the country including stainless sheet used specifically
for engineering, chemical and dairy industries incl-
uding utensil-making and household hardware. The engi-neering uses of the stainless steel have also multi-plied with the rising tempo of industrial growth.
Likewise, stainless steel finished items and assembled
components of composite equipment etc. represent an `invisible' demand for heavy imports in one form or
the other. About a decade back, the import of stain-
less sheet alone represented about Rs 7-8 crores
(Rs 70-80 million) of import bill in foreign exchange
annually. This figure will double or treble itself,
were import restrictions to be removed
Substitution of galvanising by aluminising of steels
ALUMINISING has been accepted by the Government of
India as it substitute for galvanising because of
the existing scarcity of zinc. Zinc resources of our country are limited whereas minerals for extraction
of aluminium are available in plenty. The Hindustan
Steel (P ) Ltd., has decided to have provision for
strip aluminising plant at Rourkela and Tata Iron
and Steel Co. Ltd., may also be going for strip alum-inising adopting the Sendzimir Process . Bokaro Steel Plant has also made provision for aluminising of steel strip
Kinetics of transcription initiation at lacP1: multiple roles of cyclic amp receptor protein
The cyclic AMP receptor protein (CRP) acts as a transcription activator at many promoters of Escherichia coli. We have examined the kinetics of open complex formation at the lacP1 promoter using tryptophan fluorescence of RNA polymerase and DNA fragments with 2-aminopurine substituted at specific positions. Apart from the closed complex formation and promoter clearance, we were able to detect three steps. The first step after the closed complex formation leads to a rapid increase of 2-aminopurine fluorescence. This was followed by another rapid step in which quenching of tryptophan fluorescence of RNA polymerase was observed. The slowest step detected by 2-aminopurine fluorescence increase is assigned to the final open complex formation. We have found that CRP not only enhances RNA polymerase binding at the promoter, but also enhances the slowest isomerization step by about 2-fold. Furthermore, potassium permanganate probing shows that the conformation of the open complex in the presence of CRP appears qualitatively and quantitatively different from that in the absence of CRP, suggesting that contact with RNA polymerase is maintained throughout the transcription initiation
Development of substitute high temperature creep resistant alloys
HIGH temperature creep resistant super strength alloys invariably contain considerable amounts of Ni,Co,W, etc. as alloying additions, in respect of which India lacks
in raw material resources. Extensive work has been
carried out on development of Cr-Mn-N type austenitic steels as substitute for 18 Cr 8 Ni austenitic stainless steel and their aging behaviour have been extensively studied at the National Metallurgical Laboratory in the last decade. The present work has been initiated to further study the high temperature creep behaviour of Cr-Mn-N type austenitic steels with a view to evolving suitable compositions and heat-treatment to obtain opti-mum high temperature creep strength and rupture ducti-
lity in these alloys. In this group of steel Mn and N
are used as the chief austenitic stabilizers besides C
Activation of PTHrP-cAMP-CREB1 signaling following p53 loss is essential for osteosarcoma initiation and maintenance
Mutations in the P53 pathway are a hallmark of human cancer. The identification of pathways upon which p53-deficient cells depend could reveal therapeutic targets that may spare normal cells with intact p53. In contrast to P53 point mutations in other cancer, complete loss of P53 is a frequent event in osteosarcoma (OS), the most common cancer of bone. The consequences of p53 loss for osteoblastic cells and OS development are poorly understood. Here we use murine OS models to demonstrate that elevated Pthlh (Pthrp), cAMP levels and signalling via CREB1 are characteristic of both p53-deficient osteoblasts and OS. Normal osteoblasts survive depletion of both PTHrP and CREB1. In contrast, p53-deficient osteoblasts and OS depend upon continuous activation of this pathway and undergo proliferation arrest and apoptosis in the absence of PTHrP or CREB1. Our results identify the PTHrP-cAMP-CREB1 axis as an attractive pathway for therapeutic inhibition in OS.Mannu K Walia, Patricia MW Ho, Scott Taylor, Alvin JM Ng, Ankita Gupte, Alistair M Chalk, Andrew CW Zannettino, T John Martin, Carl R Walkle
Effect of hydrogen on ground state structures of small silicon clusters
We present results for ground state structures of small SiH (2 \leq
\emph{n} \leq 10) clusters using the Car-Parrinello molecular dynamics. In
particular, we focus on how the addition of a hydrogen atom affects the ground
state geometry, total energy and the first excited electronic level gap of an
Si cluster. We discuss the nature of bonding of hydrogen in these
clusters. We find that hydrogen bonds with two silicon atoms only in SiH,
SiH and SiH clusters, while in other clusters (i.e. SiH,
SiH, SiH, SiH, SiH and SiH) hydrogen is bonded
to only one silicon atom. Also in the case of a compact and closed silicon
cluster hydrogen bonds to the cluster from outside. We find that the first
excited electronic level gap of Si and SiH fluctuates as a function
of size and this may provide a first principles basis for the short-range
potential fluctuations in hydrogenated amorphous silicon. Our results show that
the addition of a single hydrogen can cause large changes in the electronic
structure of a silicon cluster, though the geometry is not much affected. Our
calculation of the lowest energy fragmentation products of SiH clusters
shows that hydrogen is easily removed from SiH clusters.Comment: one latex file named script.tex including table and figure caption.
Six postscript figure files. figure_1a.ps and figure_1b.ps are files
representing Fig. 1 in the main tex
Evidence for directed percolation universality at the onset of spatiotemporal intermittency in coupled circle maps
We consider a lattice of coupled circle maps, a model arising naturally in
descriptions of solid state phenomena such as Josephson junction arrays. We
find that the onset of spatiotemporal intermittency (STI) in this system is
analogous to directed percolation (DP), with the transition being to an unique
absorbing state for low nonlinearities, and to weakly chaotic absorbing states
for high nonlinearities. We find that the complete set of static exponents and
spreading exponents at all critical points match those of DP very convincingly.
Further, hyperscaling relations are fulfilled, leading to independent controls
and consistency checks of the values of all the critical exponents. These
results lend strong support to the conjecture that the onset of STI in
deterministic models belongs to the DP universality class.Comment: Submitted to Physical Review
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