3,633 research outputs found
Dry and wet interfaces: Influence of solvent particles on molecular recognition
We present a coarse-grained lattice model to study the influence of water on
the recognition process of two rigid proteins. The basic model is formulated in
terms of the hydrophobic effect. We then investigate several modifications of
our basic model showing that the selectivity of the recognition process can be
enhanced by considering the explicit influence of single solvent particles.
When the number of cavities at the interface of a protein-protein complex is
fixed as an intrinsic geometric constraint, there typically exists a
characteristic fraction that should be filled with water molecules such that
the selectivity exhibits a maximum. In addition the optimum fraction depends on
the hydrophobicity of the interface so that one has to distinguish between dry
and wet interfaces.Comment: 11 pages, 7 figure
Exoplanet Detection Techniques
We are still in the early days of exoplanet discovery. Astronomers are
beginning to model the atmospheres and interiors of exoplanets and have
developed a deeper understanding of processes of planet formation and
evolution. However, we have yet to map out the full complexity of multi-planet
architectures or to detect Earth analogues around nearby stars. Reaching these
ambitious goals will require further improvements in instrumentation and new
analysis tools. In this chapter, we provide an overview of five observational
techniques that are currently employed in the detection of exoplanets: optical
and IR Doppler measurements, transit photometry, direct imaging, microlensing,
and astrometry. We provide a basic description of how each of these techniques
works and discuss forefront developments that will result in new discoveries.
We also highlight the observational limitations and synergies of each method
and their connections to future space missions.Comment: 24 pages, 19 figures, PPVI proceedings. Appears as 2014, Protostars
and Planets VI, Henrik Beuther, Ralf S. Klessen, Cornelis P. Dullemond, and
Thomas Henning (eds.), University of Arizona Press, Tucson, 914 pp.,
p.715-73
Reproductive outcome after hysteroscopic septoplasty in patients with septate uterus - a retrospective cohort study and systematic review of the literature
<p>Abstract</p> <p>Background</p> <p>Septate uterus, one of the most common forms of congenital uterine malformations, negatively affects female reproductive health.</p> <p>Methods</p> <p>In a retrospective cohort study, we evaluated the reproductive outcome after hysteroscopic septoplasty in 64 women with septate uterus and primary or secondary infertility. We performed a systematic review of studies evaluating the reproductive outcome after hysteroscopic septoplasty.</p> <p>Results</p> <p>Sixty-four women underwent hysteroscopic septoplasty. In 2/64 (3%) women, intraoperative uterine perforation occurred. Complete follow-up was available for 49/64 (76%) patients. Mean follow-up time was 68.6 +/- 5.2 months. The overall pregnancy rate after hysteroscopic septoplasty was 69% (34/49). The overall life birth rate (LBR) was 49% (24/49). The mean time interval between surgery and the first life birth was 35.8 +/- 22.5 months. Including our own data, we identified 18 studies investigating the effect of septoplasty on reproductive outcome in 1501 women. A pooled analysis demonstrated that hysteroscopic septoplasty resulted in an overall pregnancy rate of 60% (892/1501) and a LBR of 45% (686/1501). The overall rate of intra- and postoperative complications was 1.7% (23/1324) and the overall rate of re-hysteroscopy was 6% (79/1324).</p> <p>Conclusions</p> <p>In women with septate uterus and a history of infertility, hysteroscopic septoplasty is a safe and effective procedure resulting in a pregnancy rate of 60% and a LBR of 45%.</p
Effects of stress beliefs on the emotional and biological response to acute psychosocial stress in healthy men
Background
Negative beliefs about stress (e.g., “stress is bad”) constitute an independent risk factor for increased morbidity and mortality. One potential underlying mechanism are altered responses to acute psychosocial stress. The aim of this study was to investigate whether beliefs about stress are associated with physiological and endocrine stress response patterns.
Methods
A total of N = 77 healthy adults were randomised to an experimental and a placebo control group and were subsequently exposed to the Trier Social Stress Test (TSST). Stress beliefs were measured before and after a psychological manipulation aiming at fostering more balanced stress beliefs or a placebo manipulation. Self-reported stress was measured four times before/after the TSST, heart rate was assessed continuously, and cortisol was assessed eight times before/after the TSST.
Results
There was a significant decrease in negative stress beliefs (p < .001) and increase in positive stress beliefs (p < .001) in participants in the experimental condition, which was absent in participants in the placebo condition. The participants in the experimental group had more pronounced self-reported stress reactions (p = .028) while at the same time also showing more pronounced stress recoveries (p = .036). The findings regarding cortisol were mixed.
Conclusions
More balanced stress beliefs appeared to be associated with more efficient subjective responses to acute psychosocial stress. These findings attest to a potential mechanism translating negative stress beliefs into ill health while at the same time outlining targets for psychological interventions
EEGManyPipelines: A Large-scale, Grassroots Multi-analyst Study of Electroencephalography Analysis Practices in the Wild
The ongoing reproducibility crisis in psychology and cognitive neuroscience has sparked increasing calls to re-evaluate and reshape scientific culture and practices. Heeding those calls, we have recently launched the EEGManyPipelines project as a means to assess the robustness of EEG research in naturalistic conditions and experiment with an alternative model of conducting scientific research. One hundred sixty-eight analyst teams, encompassing 396 individual researchers from 37 countries, independently analyzed the same unpublished, representative EEG data set to test the same set of predefined hypotheses and then provided their analysis pipelines and reported outcomes. Here, we lay out how large-scale scientific projects can be set up in a grassroots, community-driven manner without a central organizing laboratory. We explain our recruitment strategy, our guidance for analysts, the eventual outputs of this project, and how it might have a lasting impact on the field
Gauge invariant perturbations around symmetry reduced sectors of general relativity: applications to cosmology
We develop a gauge invariant canonical perturbation scheme for perturbations
around symmetry reduced sectors in generally covariant theories, such as
general relativity. The central objects of investigation are gauge invariant
observables which encode the dynamics of the system. We apply this scheme to
perturbations around a homogeneous and isotropic sector (cosmology) of general
relativity. The background variables of this homogeneous and isotropic sector
are treated fully dynamically which allows us to approximate the observables to
arbitrary high order in a self--consistent and fully gauge invariant manner.
Methods to compute these observables are given. The question of backreaction
effects of inhomogeneities onto a homogeneous and isotropic background can be
addressed in this framework. We illustrate the latter by considering
homogeneous but anisotropic Bianchi--I cosmologies as perturbations around a
homogeneous and isotropic sector.Comment: 39 pages, 1 figur
Heterogeneity of the Relative Benefits of TICIÂ 2c/3 over TICIÂ 2b50/2b67 : Are there Patients who are less Likely to Benefit?
PURPOSE
Incomplete reperfusion after mechanical thrombectomy (MT) is associated with a poor outcome. Rescue therapy would potentially benefit some patients with an expanded treatment in cerebral ischemia score (eTICI)Â 2b50/2b67 reperfusion but also harbors increased risks. The relative benefits of eTICIÂ 2c/3 over eTICIÂ 2b50/67 in clinically important subpopulations were analyzed.
METHODS
Retrospective analysis of our institutional database for all patients with occlusion of the intracranial internal carotid artery (ICA) or the M1/M2 segment undergoing MT and final reperfusion of ≥eTICI 2b50 (903 patients). The heterogeneity in subgroups of different time metrics, age, National Institutes of Health Stroke Scale (NIHSS), number of retrieval attempts, Alberta Stroke Programme Early CT Score (ASPECTS) and site of occlusion using interaction terms (pi) was analyzed.
RESULTS
The presence of eTICI 2c/3 was associated with better outcomes in most subgroups. Time metrics showed no interaction of eTICI 2c/3 over eTICI 2b50/2b67 and clinical outcomes (onset to reperfusion pi = 0.77, puncture to reperfusion pi = 0.65, onset to puncture pi = 0.63). An eTICI 2c/3 had less consistent association with mRS ≤2 in older patients (>82 years, pi = 0.038) and patients with either lower NIHSS (≤9) or very high NIHSS (>19, pi = 0.01). Regarding occlusion sites, the beneficial effect of eTICI 2c/3 was absent for occlusions in the M2 segments (aOR 0.73, 95% confidence interval [CI] 0.33-1.59, pi = 0.018).
CONCLUSION
Beneficial effect of eTICIÂ 2c/3 over eTICIÂ 2b50/2b67 only decreased in older patients, M2-occlusions and patients with either low or very high NIHSS. Improving eTICIÂ 2b50/2b67 to eTICIÂ 2c/3 in those subgroups may be more often futile
Polarization and Interference Effects in Ionization of Li by Ion Impact
We present initial-state selective fully differential cross sections for ionization of lithium by 24 MeV O8+ impact. The data for ionization from the 2s and 2p states look qualitatively different from each other and from 1s ionization of He. For ionization from the 2p state, to which in our study the mL=-1 substate predominantly contributes, we observe orientational dichroism and for 2s ionization pronounced interference which we trace back to the nodal structure of the initial-state wave function
Postcollision Effects in Target Ionization by Ion Impact at Large Momentum Transfer
We have measured and calculated fully differential cross sections for target ionization in 16-MeV O7++He and 24-MeV O8++Li collisions. As in previous studies, in the case of the He target we observe a pronounced forward shift in the angular distribution of the electrons relative to the direction of the momentum transfer q at small q (q \u3c 1 a.u.). An unexpected result is that we also find a strong forward shift at large q (q \u3e 2 a.u.), while at intermediate q this shift becomes very weak or even turns into a backward shift. For the Li target, in contrast, the forward shift monotonically increases with increasing q. These observations are qualitatively reproduced by our calculations. The comparison to theory suggests that at large q the forward shift is due to the postcollision interaction between the outgoing projectile and the ejected electron, but at small q it is mostly due to an interplay between the projectile-target core interaction and the electron-target core interaction
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