218 research outputs found
The English are healthier than the Americans: really?
Background: When comparing the health of two populations, it is not enough to compare the prevalence of chronic diseases. The objective of this study is therefore to propose a metric of health based on domains of functioning to determine whether the English are healthier than the Americans. Methods: We analysed representative samples aged 50 to 80 years from the 2008 wave of the Health and Retirement Study (N?=?10?349) for the US data, and wave 4 of the English Longitudinal Study of Ageing (N?=?9405) for English counterpart data. We first calculated the age-standardized disease prevalence of diabetes, hypertension, all heart diseases, stroke, lung disease, cancer and obesity. Second, we developed a metric of health using Rasch analyses and the questions and measured tests common to both surveys addressing domains of human functioning. Finally, we used a linear additive model to test whether the differences in health were due to being English or American. Results: The English have better health than the Americans when population health is assessed only by prevalence of selected chronic health conditions. The English health advantage disappears almost completely, however, when health is assessed with a metric that integrates information about functioning domains. Conclusions: It is possible to construct a metric of health, based on data directly collected from individuals, in which health is operationalized as domains of functioning. Its application has the potential to tackle one of the most intractable problems in international research on health, namely the comparability of health across countries
Chemotherapy of Metastatic Renal Adenocarcinoma with a Five- Drug Regimen*
In the past, chemotherapy of renal adenocarcinoma has been relatively unsuccessful. The progestational agent, medroxy progesterone acetate (MPA), has been the most effective single agent, even though the response rate probably does not exceed 12%. This report describes the results of a program of combination therapy with MPA, cyclophosphamide, hydroxyurea, vinblastine and prednisone that was used on 42 patients, ten of whom had received prior MPA therapy. One complete remission and seven partial remissions were observed, oniyone of whom had received prior MPA therapy. Treatment of metastatic renal adenocarcinoma with combination chemotherapy should probably include MPA and adriamycin. The role of estrogen receptor (ER) and progesterone receptor (PR) as predictions of response to hormonal therapy in this disease looks encouraging, but the results reported to date have been limited
Mechanical response of random heteropolymers
We present an analytical theory for heteropolymer deformation, as exemplified
experimentally by stretching of single protein molecules. Using a mean-field
replica theory, we determine phase diagrams for stress-induced unfolding of
typical random sequences. This transition is sharp in the limit of infinitely
long chain molecules. But for chain lengths relevant to biological
macromolecules, partially unfolded conformations prevail over an intermediate
range of stress. These necklace-like structures, comprised of alternating
compact and extended subunits, are stabilized by quenched variations in the
composition of finite chain segments. The most stable arrangements of these
subunits are largely determined by preferential extension of segments rich in
solvophilic monomers. This predicted significance of necklace structures
explains recent observations in protein stretching experiments. We examine the
statistical features of select sequences that give rise to mechanical strength
and may thus have guided the evolution of proteins that carry out mechanical
functions in living cells.Comment: 10 pages, 6 figure
Development of the fully Geant4 compatible package for the simulation of Dark Matter in fixed target experiments
The search for new comparably light (well below the electroweak scale) feebly
interacting particles is an exciting possibility to explain some mysterious
phenomena in physics, among them the origin of Dark Matter. The sensitivity
study through detailed simulation of projected experiments is a key point in
estimating their potential for discovery.
Several years ago we created the DMG4 package for the simulation of DM (Dark
Matter) particles in fixed target experiments. The natural approach is to
integrate this simulation into the same program that performs the full
simulation of particles in the experiment setup. The Geant4 toolkit framework
was chosen as the most popular and versatile solution nowadays.
The simulation of DM particles production by this package accommodates
several possible scenarios, employing electron, muon or photon beams and
involving various mediators, such as vector, axial vector, scalar,
pseudoscalar, or spin 2 particles. The bremsstrahlung, annihilation or
Primakoff processes can be simulated.
The package DMG4 contains a subpackage DarkMatter with cross section methods
weakly connected to Geant4. It can be used in different frameworks.
In this paper, we present the latest developments of the package, such as
extending the list of possible mediator particle types, refining formulas for
the simulation and extending the mediator mass range. The user interface is
also made more flexible and convenient.
In this work, we also demonstrate the usage of the package, the improvements
in the simulation accuracy and some cross check validations.Comment: 17 pages, 11 figures, 1 tabl
Single Molecule Statistics and the Polynucleotide Unzipping Transition
We present an extensive theoretical investigation of the mechanical unzipping
of double-stranded DNA under the influence of an applied force. In the limit of
long polymers, there is a thermodynamic unzipping transition at a critical
force value of order 10 pN, with different critical behavior for homopolymers
and for random heteropolymers. We extend results on the disorder-averaged
behavior of DNA's with random sequences to the more experimentally accessible
problem of unzipping a single DNA molecule. As the applied force approaches the
critical value, the double-stranded DNA unravels in a series of discrete,
sequence-dependent steps that allow it to reach successively deeper energy
minima. Plots of extension versus force thus take the striking form of a series
of plateaus separated by sharp jumps. Similar qualitative features should
reappear in micromanipulation experiments on proteins and on folded RNA
molecules. Despite their unusual form, the extension versus force curves for
single molecules still reveal remnants of the disorder-averaged critical
behavior. Above the transition, the dynamics of the unzipping fork is related
to that of a particle diffusing in a random force field; anomalous,
disorder-dominated behavior is expected until the applied force exceeds the
critical value for unzipping by roughly 5 pN.Comment: 40 pages, 18 figure
Spatio-temporal dynamics of quantum-well excitons
We investigate the lateral transport of excitons in ZnSe quantum wells by
using time-resolved micro-photoluminescence enhanced by the introduction of a
solid immersion lens. The spatial and temporal resolutions are 200 nm and 5 ps,
respectively. Strong deviation from classical diffusion is observed up to 400
ps. This feature is attributed to the hot-exciton effects, consistent with
previous experiments under cw excitation. The coupled transport-relaxation
process of hot excitons is modelled by Monte Carlo simulation. We prove that
two basic assumptions typically accepted in photoluminescence investigations on
excitonic transport, namely (i) the classical diffusion model as well as (ii)
the equivalence between the temporal and spatial evolution of the exciton
population and of the measured photoluminescence, are not valid for
low-temperature experiments.Comment: 8 pages, 6 figure
Single-molecule experiments in biological physics: methods and applications
I review single-molecule experiments (SME) in biological physics. Recent
technological developments have provided the tools to design and build
scientific instruments of high enough sensitivity and precision to manipulate
and visualize individual molecules and measure microscopic forces. Using SME it
is possible to: manipulate molecules one at a time and measure distributions
describing molecular properties; characterize the kinetics of biomolecular
reactions and; detect molecular intermediates. SME provide the additional
information about thermodynamics and kinetics of biomolecular processes. This
complements information obtained in traditional bulk assays. In SME it is also
possible to measure small energies and detect large Brownian deviations in
biomolecular reactions, thereby offering new methods and systems to scrutinize
the basic foundations of statistical mechanics. This review is written at a
very introductory level emphasizing the importance of SME to scientists
interested in knowing the common playground of ideas and the interdisciplinary
topics accessible by these techniques. The review discusses SME from an
experimental perspective, first exposing the most common experimental
methodologies and later presenting various molecular systems where such
techniques have been applied. I briefly discuss experimental techniques such as
atomic-force microscopy (AFM), laser optical tweezers (LOT), magnetic tweezers
(MT), biomembrane force probe (BFP) and single-molecule fluorescence (SMF). I
then present several applications of SME to the study of nucleic acids (DNA,
RNA and DNA condensation), proteins (protein-protein interactions, protein
folding and molecular motors). Finally, I discuss applications of SME to the
study of the nonequilibrium thermodynamics of small systems and the
experimental verification of fluctuation theorems. I conclude with a discussion
of open questions and future perspectives.Comment: Latex, 60 pages, 12 figures, Topical Review for J. Phys. C (Cond.
Matt
Are We Sitting Comfortably? Domestic Imaginaries, Laptop Practices, and Energy Use
The considerable literature on domestic energy consumption practices has tended to focus on either the (re)production and contestation of normative imaginaries, or the links between escalating standards and energy use. Far less has been written which links these related areas together. Accordingly, this paper is positioned at the intersection of debates on domestic consumption, energy use, and home cultures. Through a qualitative study of laptop use in the home, we illustrate how energy-intensive practices, such as ‘always-on-ness’, and changing computer ecologies and infrastructures, are intimately bound up with the reproduction of particular domestic imaginaries of family and home. A key insight in this paper is that a purely physiological conception of comfort would fail to explain fully why practices such as always-on-ness emerge, and thus we theorise comfort as an accomplishment comprised of inseparable temporal, bodily, spatial, and material elements. Ultimately, we argue here that comfort needs to be understood as a multivalent imaginary that is itself bound up in broader idealised notions of family and home in order to comprehend shifting practices, computing ecologies, and rising energy consumption
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