2,155 research outputs found
Inhibition of DNA ejection from bacteriophage by Mg+2 counterions
The problem of inhibiting viral DNA ejection from bacteriophages by
multivalent counterions, specifically Mg counterions, is studied.
Experimentally, it is known that MgSO salt has a strong and non-monotonic
effect on the amount of DNA ejected. There exists an optimal concentration at
which the minimum amount of DNA is ejected from the virus. At lower or higher
concentrations, more DNA is ejected from the capsid. We propose that this
phenomenon is the result of DNA overcharging by Mg multivalent
counterions. As Mg concentration increases from zero, the net charge of
DNA changes from negative to positive. The optimal inhibition corresponds to
the Mg concentration where DNA is neutral. At lower/higher
concentrations, DNA genome is charged. It prefers to be in solution to lower
its electrostatic self-energy, which consequently leads to an increase in DNA
ejection. By fitting our theory to available experimental data, the strength of
DNADNA short range attraction energies, mediated by Mg, is found to
be 0.004 per nucleotide base. This and other fitted parameters agree
well with known values from other experiments and computer simulations. The
parameters are also in aggreement qualitatively with values for tri- and
tetra-valent counterions.Comment: 17 pages, 4 figures, improved manuscript. Submitted to J. Chem. Phys
(2010
Development and Longevity: Cellular and Molecular Determinants - A Mini-Review
Across species, development and longevity are tightly linked. We discuss the relevant literature and suggest that the root for this stringent relationship is the rate of development. The basis for the relationship between rate of development and longevity lies in adaptations that have occurred through evolution at multiple levels of biological complexity: organism, organ, cellular, and molecular. Thus, the analysis of the relationship is of interest for multiple fields of biology
Temperature-Dependent X-Ray Absorption Spectroscopy of Colossal Magnetoresistive Perovskites
The temperature dependence of the O K-edge pre-edge structure in the x-ray
absorption spectra of the perovskites La(1-x)A(x)MnO(3), (A = Ca, Sr; x = 0.3,
0.4) reveals a correlation between the disappearance of the splitting in the
pre-edge region and the presence of Jahn-Teller distortions. The different
magnitudes of the distortions for different compounds is proposed to explain
some dissimilarity in the line shape of the spectra taken above the Curie
temperature.Comment: To appear in Phys. Rev. B, 5 pages, 3 figure
What is the true evidence for gender-related differences during plant and cut maneuvers? A systematic review
Purpose Female athletes have a significantly higher risk of sustaining an anterior cruciate ligament (ACL) injury than male athletes. Biomechanical and neuromuscular factors have been reported as the main cause. The purpose of this review was to critically review results of the published literature on gender differences regarding biomechanical and neuromuscular movement patterns during plant and cutting maneuvers. Methods MEDLINE (1966 to December 2008), EMBASE (1947 to December 2008) and CINAHL (1981 to December 2008) searches were performed. The seven studies meeting the inclusion criteria were analyzed. Results Biomechanical gender differences were of questionable clinical relevance. Quadriceps dominance was not found in women. Conclusion The question raises whether ACL injuries during plant and cutting maneuvers are purely gender related and whether women do have to move like men in order to reduce injury risk? Caution is warranted in making inferences as studies were heterogeneous in terms of subject and study characteristics and had low statistical power as a result of insufficient number of subjects. It is advised that future research moves beyond the isolated gender comparison and that larger sample sizes will be included. This review may aid in improving experiments to draw valid conclusions, in order to direct future ACL injury prevention programs, which might need to be more individualized
Ultrahigh Bandwidth Spin Noise Spectroscopy: Detection of Large g-Factor Fluctuations in Highly n-Doped GaAs
We advance all optical spin noise spectroscopy (SNS) in semiconductors to
detection bandwidths of several hundred gigahertz by employing an ingenious
scheme of pulse trains from ultrafast laser oscillators as an optical probe.
The ultrafast SNS technique avoids the need for optical pumping and enables
nearly perturbation free measurements of extremely short spin dephasing times.
We employ the technique to highly n-doped bulk GaAs where magnetic field
dependent measurements show unexpected large g-factor fluctuations.
Calculations suggest that such large g-factor fluctuations do not necessarily
result from extrinsic sample variations but are intrinsically present in every
doped semiconductor due to the stochastic nature of the dopant distribution.Comment: 5 pages, 3 figure
Altered cell cycle regulation helps stem-like carcinoma cells resist apoptosis
Reemergence of carcinomas following chemotherapy and/or radiotherapy is not well understood, but a recent study in BMC Cancer suggests that resistance to apoptosis resulting from altered cell cycle regulation is crucial
No acute changes in postural control after soccer heading
Background: Soccer heading has been proposed as a potential cause of cerebral dysfunction
The first resolved imaging of milliarcsecond-scale jets in Circinus X-1
We present the first resolved imaging of the milliarcsecond-scale jets in the
neutron star X-ray binary Circinus X-1, made using the Australian Long Baseline
Array. The angular extent of the resolved jets is ~20 milliarcseconds,
corresponding to a physical scale of ~150 au at the assumed distance of 7.8
kpc. The jet position angle is relatively consistent with previous
arcsecond-scale imaging with the Australia Telescope Compact Array. The radio
emission is symmetric about the peak, and is unresolved along the minor axis,
constraining the opening angle to be less than 20 degrees. We observe evidence
for outward motion of the components between the two halves of the observation.
Constraints on the proper motion of the radio-emitting components suggest that
they are only mildly relativistic, although we cannot definitively rule out the
presence of the unseen, ultra-relativistic (Lorentz factor >15) flow previously
inferred to exist in this system.Comment: Accepted for publication in MNRAS Letters. 6 pages, 4 figure
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