394 research outputs found
CMB Anisotropies in the Presence of Extra Dimensions
We discuss the effect of the time evolution of extra dimensions on CMB
anisotropies and large-scale structure formation. We study the impact of scalar
fields in a low-energy effective description of a general class of brane world
models on the temperature anisotropy power spectrum. We show that when the
coupling between these scalar fields and matter evolves over cosmological
timescales, current observations of the CMB anisotropies can constrain
primordial values of the fields in a manner complementary to local, late-time
tests of gravity. We also present the effect of these fields on the
polarization anisotropy spectra and the growth of large-scale structure,
showing that future CMB observations will constrain theories of the Universe
involving extra dimensions even further.Comment: 17 pages, 15 figure
Varying Constants in Brane World Scenarios
Higher-dimensional theories imply that some constants, such as the
gravitational constant and the strength of the gauge-couplings, are not
fundamental constants. Instead they are related to the sizes of the
extra--dimensional space, which are moduli fields in the four--dimensional
effective theory. We study the cosmological evolution of the moduli fields
appearing in brane world scenarios and discuss the implications for varying
constants.Comment: 5 pages, LaTeX, 5 figures; based on a talk given by C. van de Bruck
at JENAM 2002, Porto; typos correcte
Cosmological Evolution of Brane World Moduli
We study cosmological consequences of non-constant brane world moduli in five
dimensional brane world models with bulk scalars and two boundary branes. We
focus on the case where the brane tension is an exponential function of the
bulk scalar field, . In the limit , the model reduces to the two-brane model of Randall-Sundrum, whereas larger
values of allow for a less warped bulk geometry. Using the moduli
space approximation, we derive the four-dimensional low-energy effective action
from a supergravity-inspired five-dimensional theory. For arbitrary values of
, the resulting theory has the form of a bi-scalar-tensor theory. We
show that, in order to be consistent with local gravitational observations,
has to be small (less than ) and the separation of the branes
must be large. We study the cosmological evolution of the interbrane distance
and the bulk scalar field for different matter contents on each branes. Our
findings indicate that attractor solutions exist which drive the moduli fields
towards values consistent with observations. The efficiency of the attractor
mechanism crucially depends on the matter content on each branes. In the
five-dimensional description, the attractors correspond to the motion of the
negative tension brane towards a bulk singularity, which signals the eventual
breakdown of the four-dimensional description and the necessity of a better
understanding of the bulk singularity.Comment: 18 pages, 10 figures, typos and factor of 2 corrected, version to
appear in Physical Review
Brane World Cosmology, the CMB and the Radion
Recent developments in the theory of extra dimensions have opened up avenues
to confront such theories with cosmological tests. We discuss a brane-world
model with a bulk scalar field, motivated by supergravity. The low-energy
effective action is derived and physical constraints on the parameters of the
model discussed. The cosmological evolution of the brane-world moduli is
investigated and it is shown that one of the moduli is a quintessence field.
The CMB predictions are computed. Finally, the possibility that the radion
field in brane-worlds could be a chameleon field is investigated.Comment: 11 pages, 6 figures, to appear in the proceedings of the DPU
Workshop: The Density Fluctuations in the Universe: Beyond the Inflaton
Paradigm (Athens, June 2004
Biophysical and electrochemical studies of protein-nucleic acid interactions
This review is devoted to biophysical and electrochemical methods used for studying protein-nucleic acid (NA) interactions. The importance of NA structure and protein-NA recognition for essential cellular processes, such as replication or transcription, is discussed to provide background for description of a range of biophysical chemistry methods that are applied to study a wide scope of protein-DNA and protein-RNA complexes. These techniques employ different detection principles with specific advantages and limitations and are often combined as mutually complementary approaches to provide a complete description of the interactions. Electrochemical methods have proven to be of great utility in such studies because they provide sensitive measurements and can be combined with other approaches that facilitate the protein-NA interactions. Recent applications of electrochemical methods in studies of protein-NA interactions are discussed in detail
Four--dimensional Gravity from Singular Spaces
The modification to four--dimensional Einstein gravity at low energy in two
brane models is investigated within supergravity in singular spaces. Using
perturbation theory around a static BPS background, we study the effective
four--dimensional gravitational theory, a scalar--tensor theory, and derive the
Brans--Dicke parameter when matter is present on the positive tension brane
only. We show there is an attractor mechanism towards general relativity in the
matter dominated era. The dynamics of the interbrane distance are discussed.
Finally, when matter lives on both branes, we find that there is a violation of
the equivalence principle whose magnitude is governed by the warping of the
extra dimension.Comment: 9 pages, LaTe
Self-administered questionnaire versus interview as a screening method for intimate partner violence in the prenatal setting in Japan: A randomised controlled trial
<p>Abstract</p> <p>Background</p> <p>Intimate partner violence (IPV) is a serious social issue in Japan. In order to start effective interventions for abused women, the appropriate method of screening for IPV in healthcare settings needs clarifying. The objective of this study was to compare the effectiveness of a face-to-face interview with a self-administered questionnaire. We used the Violence Against Women Screen (VAWS), a Japanese screening instrument for intimate partner violence (IPV), for identifying pregnant women who have experienced abuse.</p> <p>Methods</p> <p>We conducted a randomised controlled trial to screen participants at three points in time in a prenatal clinic in Tokyo, Japan. There were 328 consenting women between 14 and 25 weeks of pregnancy who were consecutively selected and randomly assigned to either the interview or self-administered questionnaire group. Both groups completed the same screening instrument three times during their pregnancy. The primary outcome was the total number of women identified by each screening method and the secondary outcome was the effect of the screening as measured by the women's comfort level and their expressed need to consult with the nurse.</p> <p>Results</p> <p>For all three screenings, the identification rate in the interview group was significantly lower than that for the self-administered questionnaire group (relative risk 0.66, 95% CI 0.46 to 0.97), even after controlling for smoking (adjusted odds ratio 0.59, 95% CI 0.35 to 0.98). The two groups did not differ for secondary outcomes.</p> <p>Conclusions</p> <p>The self-administered questionnaire identified more IPV than the face-to-face interview when screening pregnant women in a Japanese prenatal clinic.</p> <p>Trial Registration</p> <p>UMIN-CTRC000000353</p
Simultaneous determination of β-alanine betaine and trimethylamine in bacterial culture and plant samples by capillary electrophoresis
Vitamin D and the hepatitis B vaccine response: a prospective cohort study and a randomized, placebo-controlled oral vitamin D3 and simulated sunlight supplementation trial in healthy adults.
PURPOSE: To determine serum 25(OH)D and 1,25(OH)2D relationship with hepatitis B vaccination (study 1). Then, to investigate the effects on hepatitis B vaccination of achieving vitamin D sufficiency (serum 25(OH)D ≥ 50 nmol/L) by a unique comparison of simulated sunlight and oral vitamin D3 supplementation in wintertime (study 2). METHODS: Study 1 involved 447 adults. In study 2, 3 days after the initial hepatitis B vaccination, 119 men received either placebo, simulated sunlight (1.3 × standard-erythema dose, 3 × /week for 4 weeks and then 1 × /week for 8 weeks) or oral vitamin D3 (1000 IU/day for 4 weeks and 400 IU/day for 8 weeks). We measured hepatitis B vaccination efficacy as percentage of responders with anti-hepatitis B surface antigen immunoglobulin G ≥ 10 mIU/mL. RESULTS: In study 1, vaccine response was poorer in persons with low vitamin D status (25(OH)D ≤ 40 vs 41-71 nmol/L mean difference [95% confidence interval] - 15% [- 26, - 3%]; 1,25(OH)2D ≤ 120 vs ≥ 157 pmol/L - 12% [- 24%, - 1%]). Vaccine response was also poorer in winter than summer (- 18% [- 31%, - 3%]), when serum 25(OH)D and 1,25(OH)2D were at seasonal nadirs, and 81% of persons had serum 25(OH)D < 50 nmol/L. In study 2, vitamin D supplementation strategies were similarly effective in achieving vitamin D sufficiency from the winter vitamin D nadir in almost all (~ 95%); however, the supplementation beginning 3 days after the initial vaccination did not effect the vaccine response (vitamin D vs placebo 4% [- 21%, 14%]). CONCLUSION: Low vitamin D status at initial vaccination was associated with poorer hepatitis B vaccine response (study 1); however, vitamin D supplementation commencing 3 days after vaccination (study 2) did not influence the vaccination response. CLINICAL TRIAL REGISTRY NUMBER: Study 1 NCT02416895; https://clinicaltrials.gov/ct2/show/study/NCT02416895; Study 2 NCT03132103; https://clinicaltrials.gov/ct2/show/NCT03132103
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