383 research outputs found
Host and bacterial proteases influence biofilm formation and virulence in a murine model of enterococcal catheter-associated urinary tract infection
Urinary tract infections: targeting enzymes might help Identifying bacterial and host enzymes that support biofilm formation may help prevent urinary tract infections caused by catheters. Enterococcus faecalis bacteria is a leading cause of catheter-associated urinary tract infections, the most common type of hospital-acquired infections. Michael Caparon and colleagues at Washington University School of Medicine in Missouri, USA, studied these infections in mice. They examined the effects of two protein-degrading enzymes, both from the bacterium and one can be activated by urine trypsin-like protease from the animals. Mutations that impaired either one of the enzymes had no effect on the infection, but when both the bacterial enzymes were impaired by mutation the formation of biofilms was significantly reduced. Treating the mice with chemicals that inhibited both bacterial and host enzymes dramatically reduced catheter-induced inflammation and related problems. This suggests drugs targeting these enzymes could be useful in clinical care
Regulation of p53 Translation and Induction after DNA Damage by Ribosomal Protein L26 and Nucleolin
SummaryIncreases in p53 protein levels after DNA damage have largely been attributed to an increase in the half-life of p53 protein. Here we demonstrate that increased translation of p53 mRNA is also a critical step in the induction of p53 protein in irradiated cells. Ribosomal protein L26 (RPL26) and nucleolin were found to bind to the 5′ untranslated region (UTR) of p53 mRNA and to control p53 translation and induction after DNA damage. RPL26 preferentially binds to the 5′UTR after DNA damage, and its overexpression enhances association of p53 mRNA with heavier polysomes, increases the rate of p53 translation, induces G1 cell-cycle arrest, and augments irradiation-induced apoptosis. Opposite effects were seen when RPL26 expression was inhibited. In contrast, nucleolin overexpression suppresses p53 translation and induction after DNA damage, whereas nucleolin downregulation promotes p53 expression. These findings demonstrate the importance of increased translation of p53 in DNA-damage responses and suggest critical roles for RPL26 and nucleolin in affecting p53 induction
Finite Black Hole Entropy and String Theory
An accelerating observer sees a thermal bath of radiation at the Hawking
temperature which is proportional to the acceleration. Also, in string theory
there is a Hagedorn temperature beyond which one cannot go without an infinite
amount of energy. Several authors have shown that in the context of Hawking
radiation a limiting temperature for string theory leads to a limiting
acceleration, which for a black hole implies a minimum distance from the
horizon for an observer to remain stationary. We argue that this effectively
introduces a cutoff in Rindler space or the Schwarzschild geometry inside of
which accelerations would exceed this maximum value. Furthermore, this natural
cutoff in turn allows one to define a finite entropy for Rindler space or a
black hole as all divergences were occurring on the horizon. In all cases if a
particular relationship exists between Newton's constant and the string tension
then the entropy of the string modes agrees with the Bekenstein-Hawking
formula.Comment: 17 pages, 1 figure, Florida Preprint UFIFT-HEP-94-0
Frustration of Decoherence in Open Quantum Systems
We study a model of frustration of decoherence in an open quantum system.
Contrary to other dissipative ohmic impurity models, such as the Kondo model or
the dissipative two-level system, the impurity model discussed here never
presents overdamped dynamics even for strong coupling to the environment. We
show that this unusual effect has its origins in the quantum mechanical nature
of the coupling between the quantum impurity and the environment. We study the
problem using analytic and numerical renormalization group methods and obtain
expressions for the frequency and temperature dependence of the impurity
susceptibility in different regimes.Comment: 14 pages, 5 figure
Dust from Comet 209P/LINEAR during its 2014 Return: Parent Body of a New Meteor Shower, the May Camelopardalids
We report a new observation of the Jupiter-family comet 209P/LINEAR during
its 2014 return. The comet is recognized as a dust source of a new meteor
shower, the May Camelopardalids. 209P/LINEAR was apparently inactive at a
heliocentric distance rh = 1.6 au and showed weak activity at rh < 1.4 au. We
found an active region of <0.001% of the entire nuclear surface during the
comet's dormant phase. An edge-on image suggests that particles up to 1 cm in
size (with an uncertainty of factor 3-5) were ejected following a differential
power-law size distribution with index q=-3.25+-0.10. We derived a mass loss
rate of 2-10 kg/s during the active phase and a total mass of ~5x10^7 kg during
the 2014 return. The ejection terminal velocity of millimeter- to
centimeter-sized particles was 1-4 m/s, which is comparable to the escape
velocity from the nucleus (1.4 m/s). These results imply that such large
meteoric particles marginally escaped from the highly dormant comet nucleus via
the gas drag force only within a few months of the perihelion passage.Comment: 18 pages, 4 figures, accepted on 2014 December 11 for publication in
the Astrophysical Journal Letter
Impact of Age and Body Site on Adult Female Skin Surface pH
Background: pH is known as an important parameter in epidermal barrier function and homeostasis. Aim: The impact of age and body site on skin surface pH (pH(SS)) of women was evaluated in vivo. Methods: Time domain dual lifetime referencing with luminescent sensor foils was used for pH(SS) measurements. pH(SS) was measured on the forehead, the temple, and the volar forearm of adult females (n = 97, 52.87 +/- 18.58 years, 20-97 years). Every single measurement contained 2,500 pH values due to the luminescence imaging technique used. Results: pH(SS) slightly increases with age on all three investigated body sites. There are no significant differences in pH(SS) between the three investigated body sites. Conclusion: Adult pH(SS) on the forehead, the temple and the volar forearm increases slightly with age. This knowledge is crucial for adapting medical skin care products. Copyright (C) 2012 S. Karger AG, Base
Robust automated detection of microstructural white matter degeneration in Alzheimer’s disease using machine learning classification of multicenter DTI data
Diffusion tensor imaging (DTI) based assessment of white matter fiber tract integrity can support the diagnosis of Alzheimer’s disease (AD). The use of DTI as a biomarker, however, depends on its applicability in a multicenter setting accounting for effects of different MRI scanners. We applied multivariate machine learning (ML) to a large multicenter sample from the recently created framework of the European DTI study on Dementia (EDSD). We hypothesized that ML approaches may amend effects of multicenter acquisition. We included a sample of 137 patients with clinically probable AD (MMSE 20.6±5.3) and 143 healthy elderly controls, scanned in nine different scanners. For diagnostic classification we used the DTI indices fractional anisotropy (FA) and mean diffusivity (MD) and, for comparison, gray matter and white matter density maps from anatomical MRI. Data were classified using a Support Vector Machine (SVM) and a Naïve Bayes (NB) classifier. We used two cross-validation approaches, (i) test and training samples randomly drawn from the entire data set (pooled cross-validation) and (ii) data from each scanner as test set, and the data from the remaining scanners as training set (scanner-specific cross-validation). In the pooled cross-validation, SVM achieved an accuracy of 80% for FA and 83% for MD. Accuracies for NB were significantly lower, ranging between 68% and 75%. Removing variance components arising from scanners using principal component analysis did not significantly change the classification results for both classifiers. For the scanner-specific cross-validation, the classification accuracy was reduced for both SVM and NB. After mean correction, classification accuracy reached a level comparable to the results obtained from the pooled cross-validation. Our findings support the notion that machine learning classification allows robust classification of DTI data sets arising from multiple scanners, even if a new data set comes from a scanner that was not part of the training sample
The spontaneous symmetry breaking in TaNiSe is structural in nature
The excitonic insulator is an electronically-driven phase of matter that
emerges upon the spontaneous formation and Bose condensation of excitons.
Detecting this exotic order in candidate materials is a subject of paramount
importance, as the size of the excitonic gap in the band structure establishes
the potential of this collective state for superfluid energy transport.
However, the identification of this phase in real solids is hindered by the
coexistence of a structural order parameter with the same symmetry as the
excitonic order. Only a few materials are currently believed to host a dominant
excitonic phase, TaNiSe being the most promising. Here, we test this
scenario by using an ultrashort laser pulse to quench the broken-symmetry phase
of this transition metal chalcogenide. Tracking the dynamics of the material's
electronic and crystal structure after light excitation reveals surprising
spectroscopic fingerprints that are only compatible with a primary order
parameter of phononic nature. We rationalize our findings through
state-of-the-art calculations, confirming that the structural order accounts
for most of the electronic gap opening. Not only do our results uncover the
long-sought mechanism driving the phase transition of TaNiSe, but they
also conclusively rule out any substantial excitonic character in this
instability
Impact of gastro-oesophageal reflux on microRNA expression, location and function
We have shown that miRNA expression is altered in the
oesophageal squamous mucosa from individuals with
gastro-oesophageal reflux and ulcerative oesophagitis.
These changes in miR-143, miR-145 and miR-205 expression
appear to be most pronounced in the basal
layer of the oesophageal epithelium. In the context of
gastro-oesophageal reflux these expression changes
might influence proliferation and apoptosis and thereby
regulate epithelial restoration. It is reasonable to hypothesise
that they could represent early molecular events preceding
the development of Barrett’s oesophagus, although
proving this will require further studies as described
above. Future detailed analyses of the role of these miRNAs
in progression from gastro-oesophageal reflux to
Barrett’s oesophagus, and then to oesophageal adenocarcinoma
will be valuable, and may help in efforts to control
and treat these diseases.This study was funded by a Competing Project Grant from the National Health and Medical Research Council of Australia. Cameron Smith was supported by a PROBE-NET PhD scholarship funded by a Strategic research
Partnerships Grant from the Cancer Council of New South Wales
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