53 research outputs found
Development of classification and regression based QSAR models to predict rodent carcinogenic potency using oral slope factor
Carcinogenicity is among the toxicological endpoints posing the highest concern for human health. Oral slope factors (OSFs) are used to estimate quantitatively the carcinogenic potency or the risk associated with exposure to the chemical by oral route. Regulatory agencies in food and drug administration and environmental protection are employing quantitative structure-activity relationship (QSAR) models to fill the data gaps related with properties of chemicals affecting the environment and human health. In this background, we have developed quantitative structure-carcinogenicity regression models for rodents based on the carcinogenic potential of 70 chemicals with wide diversity of molecular structures, spanning a large number of chemical classes and biological mechanisms. All the developed models have been assessed according to the Organization for Economic Cooperation and Development (OECD) principles for the validation of QSAR models. We have also attempted to develop a carcinogenicity classification model based on Linear Discriminant Analysis (LDA). Developed regression and LDA models are rigorously validated internally as well as externally. Our in silico studies make it possible to obtain a quantitative interpretation of the structural information of carcinogenicity along with identification of the discriminant functions between lower and higher carcinogenic compounds by LDA. Pharmacological distribution diagrams (PDDs) are used as a visualizing technique for the identification and selection of chemicals with lower carcinogenicity. Constructive, informative and comparable interpretations have been observed in both cases of classification and regression based modeling.SK thanks the Department of Science and Technology, Government of India for awarding him a Senior Research fellowship under the INSPIRE scheme. KR thanks the Council of Scientific and
Industrial Research (CSIR), New Delhi for awarding a major
research project
Geometry of deformations of branes in warped backgrounds
The `braneworld' (described by the usual worldvolume action) is a D
dimensional timelike surface embedded in a N dimensional () warped,
nonfactorisable spacetime. We first address the conditions on the warp factor
required to have an extremal flat brane in a five dimensional background.
Subsequently, we deal with normal deformations of such extremal branes. The
ensuing Jacobi equations are analysed to obtain the stability condition. It
turns out that to have a stable brane, the warp factor should have a minimum at
the location of the brane in the given background spacetime. To illustrate our
results we explicitly check the extremality and stability criteria for a few
known co-dimension one braneworld models. Generalisations of the above
formalism for the cases of (i) curved branes (ii) asymmetrical warping and
(iii) higher co-dimension braneworlds are then presented alongwith some typical
examples for each. Finally, we summarize our results and provide perspectives
for future work along these lines.Comment: 21 pages. Version matching final version. Accepted for publication in
Class. Quant. Gra
Can extra dimensional effects replace dark matter ?
In the braneworld scenario, the four dimensional effective Einstein equation
has extra terms which arise from the embedding of the 3-brane in the bulk. We
show that in this modified theory of gravity, it is possible to model
observations of galaxy rotation curves and the X-ray profiles of clusters of
galaxies, without the need for dark matter. In this scenario, a traceless
tensor field which arises from the projection of the bulk Weyl tensor on the
brane, provides the extra gravitational acceleration which is usually explained
through dark matter. We also predict that gravitational lensing observations
can possibly discriminate between the proposed higher dimensional effects and
dark matter, the deflection angles predicted in the proposed scenario being
around 75% to 80% of the usual predictions based on dark matter.Comment: 10 pages, no figures, RevTex
Gravitational lensing in braneworld gravity: formalism and applications
In this article, we develop a formalism which is different from the standard
lensing scenario and is necessary for understanding lensing by gravitational
fields which arise as solutions of the effective Einstein equations on the
brane. We obtain general expressions for measurable quantities such as time
delay, deflection angle, Einstein ring and magnification. Subsequently, we
estimate the deviations (relative to the standard lensing scenario) in the
abovementioned quantities by considering the line elements for clusters and
spiral galaxies obtained by solving the effective Einstein equations on the
brane. Our analysis reveals that gravitational lensing can be a useful tool for
testing braneworld gravity as well as the existence of extra dimensions.Comment: 20 pages, 1 figure, 2 tables. Accepted for publication in Classical
and Quantum Gravit
de Sitter branes with a bulk scalar
We propose new braneworld models arising from a scalar field in the bulk. In
these examples, the induced on--brane line element is de Sitter (or anti de
Sitter) and the bulk (five dimensional) Einstein equations can be exactly
solved to obtain warped spacetimes. The solutions thus derived are single and
two-brane models -- one with {\em thin} branes while the other one of the {\em
thick} variety. The field profiles and the potentials are obtained and analysed
for each case. We note that for the {\em thick} brane scenario the field
profile resembles a kink, whereas for one or more {\em thin} branes, it is
finite and bounded in the domain of the extra dimension. We have also addressed
the localisation of gravity and other matter fields on the brane for these
braneworld models.Comment: 18 pages, 5 figures. Substantial changes and new results. To appear
in GR
VI Jornades IET "Bretxa salarial i desigualtats de gènere en el mercat de treball"
Quantitative structure–property relationship (QSPR)
models
used for prediction of property of untested chemicals can be utilized
for prioritization plan of synthesis and experimental testing of new
compounds. Validation of QSPR models plays a crucial role for judgment
of the reliability of predictions of such models. In the QSPR literature,
serious attention is now given to external validation for checking
reliability of QSPR models, and predictive quality is in the most
cases judged based on the quality of predictions of property of a
single test set as reflected in one or more external validation metrics.
Here, we have shown that a single QSPR model may show a variable degree
of prediction quality as reflected in some variants of external validation
metrics like <i>Q</i><sup>2</sup><sub>F1</sub>, <i>Q</i><sup>2</sup><sub>F2</sub>, <i>Q</i><sup>2</sup><sub>F3</sub>, CCC, and <i>r<sub>m</sub></i><sup>2</sup> (all of which are
differently modified forms of predicted variance, which theoretically
may attain a maximum value of 1), depending on the test set composition
and test set size. Thus, this report questions the appropriateness
of the common practice of the “classic” approach of
external validation based on a single test set and thereby derives
a conclusion about predictive quality of a model on the basis of a
particular validation metric. The present work further demonstrates
that among the considered external validation metrics, <i>r<sub>m</sub></i><sup>2</sup> shows statistically significantly different numerical
values from others among which CCC is the most optimistic or less
stringent. Furthermore, at a given level of threshold value of acceptance
for external validation metrics, <i>r<sub>m</sub></i><sup>2</sup> provides
the most stringent criterion (especially with Δ<i>r</i><sub><i>m</i></sub><sup>2</sup> at highest tolerated value of 0.2) of external validation,
which may be adopted in the case of regulatory decision support processes
Physics Potential of the ICAL detector at the India-based Neutrino Observatory (INO)
The upcoming 50 kt magnetized iron calorimeter (ICAL) detector at the
India-based Neutrino Observatory (INO) is designed to study the atmospheric
neutrinos and antineutrinos separately over a wide range of energies and path
lengths. The primary focus of this experiment is to explore the Earth matter
effects by observing the energy and zenith angle dependence of the atmospheric
neutrinos in the multi-GeV range. This study will be crucial to address some of
the outstanding issues in neutrino oscillation physics, including the
fundamental issue of neutrino mass hierarchy. In this document, we present the
physics potential of the detector as obtained from realistic detector
simulations. We describe the simulation framework, the neutrino interactions in
the detector, and the expected response of the detector to particles traversing
it. The ICAL detector can determine the energy and direction of the muons to a
high precision, and in addition, its sensitivity to multi-GeV hadrons increases
its physics reach substantially. Its charge identification capability, and
hence its ability to distinguish neutrinos from antineutrinos, makes it an
efficient detector for determining the neutrino mass hierarchy. In this report,
we outline the analyses carried out for the determination of neutrino mass
hierarchy and precision measurements of atmospheric neutrino mixing parameters
at ICAL, and give the expected physics reach of the detector with 10 years of
runtime. We also explore the potential of ICAL for probing new physics
scenarios like CPT violation and the presence of magnetic monopoles.Comment: 139 pages, Physics White Paper of the ICAL (INO) Collaboration,
Contents identical with the version published in Pramana - J. Physic
Recommended from our members
Research and Design of a Routing Protocol in Large-Scale Wireless Sensor Networks
无线传感器网络,作为全球未来十大技术之一,集成了传感器技术、嵌入式计算技术、分布式信息处理和自组织网技术,可实时感知、采集、处理、传输网络分布区域内的各种信息数据,在军事国防、生物医疗、环境监测、抢险救灾、防恐反恐、危险区域远程控制等领域具有十分广阔的应用前景。 本文研究分析了无线传感器网络的已有路由协议,并针对大规模的无线传感器网络设计了一种树状路由协议,它根据节点地址信息来形成路由,从而简化了复杂繁冗的路由表查找和维护,节省了不必要的开销,提高了路由效率,实现了快速有效的数据传输。 为支持此路由协议本文提出了一种自适应动态地址分配算——ADAR(AdaptiveDynamicAddre...As one of the ten high technologies in the future, wireless sensor network, which is the integration of micro-sensors, embedded computing, modern network and Ad Hoc technologies, can apperceive, collect, process and transmit various information data within the region. It can be used in military defense, biomedical, environmental monitoring, disaster relief, counter-terrorism, remote control of haz...学位:工学硕士院系专业:信息科学与技术学院通信工程系_通信与信息系统学号:2332007115216
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