4,861 research outputs found
Functionals in stochastic thermodynamics: how to interpret stochastic integrals
In stochastic thermodynamics standard concepts from macroscopic thermodynamics, such as heat, work, and entropy production, are generalized to small fluctuating systems by defining them on a trajectory-wise level. In Langevin systems with continuous state-space such definitions involve stochastic integrals along system trajectories, whose specific values depend on the discretization rule used to evaluate them (i.e. the 'interpretation' of the noise terms in the integral). Via a systematic mathematical investigation of this apparent dilemma, we corroborate the widely used standard interpretation of heat-and work-like functionals as Stratonovich integrals. We furthermore recapitulate the anomalies that are known to occur for entropy production in the presence of temperature gradients
The NASA Astrophysics Data System: Architecture
The powerful discovery capabilities available in the ADS bibliographic
services are possible thanks to the design of a flexible search and retrieval
system based on a relational database model. Bibliographic records are stored
as a corpus of structured documents containing fielded data and metadata, while
discipline-specific knowledge is segregated in a set of files independent of
the bibliographic data itself.
The creation and management of links to both internal and external resources
associated with each bibliography in the database is made possible by
representing them as a set of document properties and their attributes.
To improve global access to the ADS data holdings, a number of mirror sites
have been created by cloning the database contents and software on a variety of
hardware and software platforms.
The procedures used to create and manage the database and its mirrors have
been written as a set of scripts that can be run in either an interactive or
unsupervised fashion.
The ADS can be accessed at http://adswww.harvard.eduComment: 25 pages, 8 figures, 3 table
The NASA Astrophysics Data System: The Search Engine and its User Interface
The ADS Abstract and Article Services provide access to the astronomical
literature through the World Wide Web (WWW). The forms based user interface
provides access to sophisticated searching capabilities that allow our users to
find references in the fields of Astronomy, Physics/Geophysics, and
astronomical Instrumentation and Engineering. The returned information includes
links to other on-line information sources, creating an extensive astronomical
digital library. Other interfaces to the ADS databases provide direct access to
the ADS data to allow developers of other data systems to integrate our data
into their system.
The search engine is a custom-built software system that is specifically
tailored to search astronomical references. It includes an extensive synonym
list that contains discipline specific knowledge about search term
equivalences.
Search request logs show the usage pattern of the various search system
capabilities. Access logs show the world-wide distribution of ADS users.
The ADS can be accessed at http://adswww.harvard.eduComment: 23 pages, 18 figures, 11 table
Platelet kinetics in the pulmonary microcirculation in vivo assessed by intravital microscopy
Growing evidence supports the substantial pathophysiological impact of platelets on the development of acute lung injury. Methods for studying these cellular mechanisms in vivo are not present yet. The aim of this study was to develop a model enabling the quantitative analysis of platelet kinetics and platelet-endothelium interaction within consecutive segments of the pulmonary microcirculation in vivo. New Zealand White rabbits were anesthetized and ventilated. Autologous platelets were separated from blood and labeled ex vivo with rhodamine 6G. After implantation of a thoracic window, microhemodynamics and kinetics of platelets were investigated by intravital microscopy. Velocities of red blood cells (RBCs) and platelets were measured in arterioles, capillaries and venules, and the number of platelets adhering to the microvascular endothelium was counted. Kinetics of unstimulated platelets was compared with kinetics of thrombin-activated platelets. Velocity of unstimulated platelets was comparable to RBC velocity in all vessel segments. Unstimulated platelets passed the pulmonary microcirculation without substantial platelet-endothelial interaction. In contrast, velocity of activated platelets was decreased in all vascular segments indicating platelet margination and temporal platelet-endothelium interaction. Thrombin-activated platelets adhered to arteriolar endothelium; in capillaries and venules adherence of platelets was increased 8-fold and 13-fold, respectively. In conclusion, using intravital microscopy platelet kinetics were directly analyzed in the pulmonary microcirculation in vivo for the first time. In contrast to leukocytes, no substantial platelet-endothelium interaction occurs in the pulmonary microcirculation without any further stimulus. In response to platelet activation, molecular mechanisms enable adhesion of platelets in arterioles and venules as well as retention of platelets within capillaries. Copyright (C) 2002 S. Karger AG, Basel
The NASA Astrophysics Data System: Data Holdings
Since its inception in 1993, the ADS Abstract Service has become an
indispensable research tool for astronomers and astrophysicists worldwide. In
those seven years, much effort has been directed toward improving both the
quantity and the quality of references in the database. From the original
database of approximately 160,000 astronomy abstracts, our dataset has grown
almost tenfold to approximately 1.5 million references covering astronomy,
astrophysics, planetary sciences, physics, optics, and engineering. We collect
and standardize data from approximately 200 journals and present the resulting
information in a uniform, coherent manner. With the cooperation of journal
publishers worldwide, we have been able to place scans of full journal articles
on-line back to the first volumes of many astronomical journals, and we are
able to link to current version of articles, abstracts, and datasets for
essentially all of the current astronomy literature. The trend toward
electronic publishing in the field, the use of electronic submission of
abstracts for journal articles and conference proceedings, and the increasingly
prominent use of the World Wide Web to disseminate information have enabled the
ADS to build a database unparalleled in other disciplines.
The ADS can be accessed at http://adswww.harvard.eduComment: 24 pages, 1 figure, 6 tables, 3 appendice
Characterization of a Second Bovine Rotavirus Serotype
Bovine rotavirus (BRV) V 1005 was characterized by two-way cross-neutralization tests as a second serotype of BRV. Virions and inner shell particles of 65 nm and 55 nm diameter respectively, and empty capsids of 65 nm and 55 nm diameter were separated by density gradient centrifugation. Three polypeptides of molecular weight 60,000, 36,000 and 28,000 (minor protein) could be identified in the outer shell of virions and in the larger empty capsids. Inner shell particles contained three polypeptides of molecular weight 105,000, 83,000 and 43,000. Both sizes of empty capsids showed two polypeptides of molecular weight 75,000 and 55,000 not found in virions. Pulse-labelling of infected cells revealed eight major and three minor intracellular viral polypeptides. Viral polypeptide synthesis started at about 6 hours p.i. and correlated in time with double-stranded RNA synthesis. As soon as viral polypeptide synthesis was detectable, newly synthesized viral polypeptides were incorporated into intracellular viral particles. Radioactive viral polypeptides appeared without a longer lag period in extracellular viruses from 6 hours p.i. onward
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A Critical Examination of Policy and Practice in the Transition Experience for Students with Math Learning Disabilities in Mumbai, India
Although some research has examined the experiences of students with learning disabilities in Indian secondary schools (see Karande, Sholarpurwala, & Kulkarni, 2011; Karande, Mahajan, & Kulkarni, 2009), the role of policy in students’ transition into post-secondary education has been largely unexamined. This study is a preliminary effort at providing an investigation of special education policy in Mumbai and the impact on students’ transition to post-secondary education, especially in regards to mathematics. This study extends the current knowledge of students with learning disabilities in Mumbai by 1) taking an in-depth look at students with math learning disabilities specifically, 2) focusing on the transition between secondary and higher secondary education, and 3) examining the impact of current policies and procedures through the lens of critical pedagogy.
In this study, I gathered data on the math proficiency of secondary students with MLD and their typically achieving peers in Mumbai. Additionally, I conducted interviews with secondary students and post-college adults with MLD, as well as interviews with secondary math teachers and college lecturers in mathematics. I also observed post-secondary math classes in various colleges, collected survey data from math lecturers, and reviewed documents from educational institutions all over Mumbai.
The data from this mixed methods study revealed that, for this sample of students in Mumbai, secondary students with MLD do have gaps in their conceptual and procedural knowledge of mathematics as compared to their peers without MLD, especially in the areas of fractions, decimals, pre-algebra, and word problems. Through interview and survey data, secondary students with MLD also expressed frustration with geometry and algebra. The data also revealed that post-secondary students who take Secretarial Practice in place of math in junior college are not prepared for the degree college math course that follows. Additionally, post-secondary students with MLD expressed feelings of fear and judgment when asking for help in mathematics from college lecturers and peers. This suggests that there is a need for professional development among all educators, from primary to post-secondary, to raise awareness of MLD. Also, trying to mediate students’ difficulties at the secondary or post-secondary level is too late; early identification of MLD and early intervention are necessary.
These findings will be useful for inclusive education advocacy groups in India as they work with policy makers and enforcers at the national and state level, as they revise policy and procedures for students with learning disabilities in Maharashtra and India
The NASA Astrophysics Data System: Overview
The NASA Astrophysics Data System Abstract Service has become a key component
of astronomical research. It provides bibliographic information daily, or near
daily, to a majority of astronomical researchers worldwide.
We describe the history of the development of the system and its current
status.
We show several examples of how to use the ADS, and we show how ADS use has
increased as a function of time. Currently it is still increasing
exponentially, with a doubling time for number of queries of 17 months.
Using the ADS logs we make the first detailed model of how scientific
journals are read as a function of time since publication.
The impact of the ADS on astronomy can be calculated after making some simple
assumptions. We find that the ADS increases the efficiency of astronomical
research by 333 Full Time Equivalent (2000 hour) research years per year, and
that the value of the early development of the ADS for astronomy, compared with
waiting for mature technologies to be adopted, is 2332 FTE research years.
The ADS is available at http://adswww.harvard.edu/.Comment: 19 pages, 22 figure
Observable consequences of quantum gravity: Can light fermions exist?
Any theory of quantum gravity must ultimately be connected to observations.
This demand is difficult to be met due to the high energies at which we expect
the quantum nature of gravity to become manifest. Here we study, how viable
quantum gravity proposals can be restricted by investigating the interplay of
gravitational and matter degrees of freedom. Specifically we demand that a
valid quantum theory of gravity must allow for the existence of light (compared
to the Planck scale) fermions, since we observe these in our universe. Within
the effective theory framework, we can thus show that UV completions for
gravity are restricted, regardless of the details of the microscopic theory.
Specialising to asymptotically safe quantum gravity, we find indications that
universes with light fermions are favoured within this UV completion for
gravity.Comment: 4 pages, based on a talk given at Loops '11, Madrid, to appear in
Journal of Physics: Conference Series (JPCS
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