221 research outputs found
Thermal decoupling and the smallest subhalo mass in dark matter models with Sommerfeld-enhanced annihilation rates
We consider dark matter consisting of weakly interacting massive particles
(WIMPs) and revisit in detail its thermal evolution in the early universe, with
a particular focus on models where the annihilation rate is enhanced by the
Sommerfeld effect. After chemical decoupling, or freeze-out, dark matter no
longer annihilates but is still kept in local thermal equilibrium due to
scattering events with the much more abundant standard model particles. During
kinetic decoupling, even these processes stop to be effective, which eventually
sets the scale for a small-scale cutoff in the matter density fluctuations.
Afterwards, the WIMP temperature decreases more quickly than the heat bath
temperature, which causes dark matter to reenter an era of annihilation if the
cross-section is enhanced by the Sommerfeld effect. Here, we give a detailed
and self-consistent description of these effects. As an application, we
consider the phenomenology of simple leptophilic models that have been
discussed in the literature and find that the relic abundance can be affected
by as much two orders of magnitude or more. We also compute the mass of the
smallest dark matter subhalos in these models and find it to be in the range of
about 10^{-10} to 10 solar masses; even much larger cutoff values are possible
if the WIMPs couple to force carriers lighter than about 100 MeV. We point out
that a precise determination of the cutoff mass allows to infer new limits on
the model parameters, in particular from gamma-ray observations of galaxy
clusters, that are highly complementary to existing constraints from g-2 or
beam dump experiments.Comment: minor changes to match published versio
Consequences of the COVID-19 Pandemic and Governmental Containment Policies on the Detection and Therapy of Oral Malignant Lesions-A Retrospective, Multicenter Cohort Study from Germany
(1) Background: In response to the global COVID-19 pandemic, governmental measures have been undertaken. The impact of the crisis on the healthcare of patients with cancer is largely unexplored. This multicenter cohort study aimed to investigate a potential screening delay and its consequences in patients with oral cancer (OC) during the pandemic. (2) Material and Methods: Data of patients who were first diagnosed with OC during different periods were collected, especially in terms of OC incidence, tumor stage/entity and time to intervention. The periods lockdown (LD) (13 March-16 June 2020), post-lockdown (PLD) (17 June-1 November 2020), and the corresponding equivalents in 2018/19 were differentiated and compared. (3) Results: There was no obvious trend towards a higher incidence of OC or higher tumor stages, whereas a trend towards a shorter time to intervention during the LD2020 could be observed. Subgroup analyses revealed an increased incidence in OC within the PLD2020 in Mainz, which might be explained by the partial closure of dental practices in this federal state during LD. (4) Conclusions: While there was no overall higher incidence of OC, we found closure of practices during LD to possibly delay cancer diagnosis. Therefore, measures must be taken to identify patients at risk and to ensure basic healthcare, especially in the context of dental screening measures
Non-canonical chemical feedback self-limits nitric oxide-cyclic GMP signaling in health and disease
Nitric oxide (NO)-cyclic GMP (cGMP) signaling is a vasoprotective pathway therapeutically targeted, for example, in pulmonary hypertension. Its dysregulation in disease is incompletely understood. Here we show in pulmonary artery endothelial cells that feedback inhibition by NO of the NO receptor, the cGMP forming soluble guanylate cyclase (sGC), may contribute to this. Both endogenous NO from endothelial NO synthase and exogenous NO from NO donor compounds decreased sGC protein and activity. This effect was not mediated by cGMP as the NO-independent sGC stimulator, or direct activation of cGMP-dependent protein kinase did not mimic it. Thiol-sensitive mechanisms were also not involved as the thiol-reducing agent N-acetyl-L-cysteine did not prevent this feedback. Instead, both in-vitro and in-vivo and in health and acute respiratory lung disease, chronically elevated NO led to the inactivation and degradation of sGC while leaving the heme-free isoform, apo-sGC, intact or even increasing its levels. Thus, NO regulates sGC in a bimodal manner, acutely stimulating and chronically inhibiting, as part of self-limiting direct feedback that is cGMP independent. In high NO disease conditions, this is aggravated but can be functionally recovered in a mechanism-based manner by apo-sGC activators that re-establish cGMP formatio
Langzeitige Ćnderungen des Salzgehaltes in der Unterweser
Anhand hundertjƤhriger MeĆreihen wurden langfristige SalzgehaltsƤnderungen in der Unterweser und ihre mƶglichen Ursachen untersucht. Dabei wurde angestrebt, die natĆ¼rlichen und die anthropogenen EinflĆ¼sse auf den Salzgehalt zu trennen. Trotz des unvollstƤndigen Datensatzes konnten der EinfluĆ des Einzugsgebietes und Salzgehaltsschwankungen des angrenzenden Meeresgebietes nahezu eliminiert werden. Wegen der langzeitigen Ćnderungen der Gezeiten in der Nordsee waren genaue Aussagen Ć¼ber die Auswirkung der in den letzten hundert Jahren in der Unterweser durchgefĆ¼hrten BaumaĆnahmen auf den Salzgehalt nicht mƶglich. Unsere Ergebnisse geben Hinweise fĆ¼r moderne MeĆnetze zur Bestimmung der WasserqualitƤt
No attenuation of gastric distress or benefit to performance with adaptation to octanoate-rich esterified oils in female cyclists
A quasi-unit cell model for Al-Ni-Co Ideal Quasicrystal based on clusters with broken 10-fold symmetry
We present new evidence supporting the quasi-unit cell description of the
decagonal quasicrystal which shows that the solid is
composed of repeating, overlapping decagonal cluster columns with broken
10-fold symmetry. We propose an atomic model which gives a significantly
improved fit to electron microscopy experiments compared to a previous proposal
by us and to alternative proposals with 10-fold symmetric clusters.Comment: 4 pages, 4 eps figures, use epsfig.sty and revtex revised text and
figure
A computational study of the effect of windscreen shape and flow resistivity on turbulent wind noise reduction
This is the published version. Copyright 2011 Acoustical Society of AmericaIn this paper, numerical simulations are used to study the turbulentwind noise reduction effect of microphone windscreens with varying shapes and flow resistivities. Typical windscreen shapes consisting of circular, elliptical, and rectangular cylinders are investigated. A turbulent environment is generated by placing a solid circular cylinder upstream of the microphone. An immersed-boundary method with a fifth-order weighted essentially non-oscillatory scheme is implemented to enhance the simulation accuracy for high-Reynolds number flow around the solid cylinder as well as at the interface between the open air and the porous material comprising the windscreen. The NavierāStokes equations for incompressible flow are solved in the open air. For the flow inside the porous material, a modified form of the ZwikkerāKosten equation is solved. The results show that, on average, the circular and horizontal ellipse windscreens have similar overall wind noise reduction performance, while the horizontal ellipse windscreen with medium flow resistivity provides the most effective wind noise reduction among all the considered cases. The vertical ellipse windscreen with high flow resistivity, in particular, increases the wind noise because of increased self-generation of turbulence
Characterization and crystal structure of the type IIG restriction endonuclease RM.BpuSI
A type IIG restriction endonuclease, RM.BpuSI from Bacillus pumilus, has been characterized and its X-ray crystal structure determined at 2.35Ć
resolution. The enzyme is comprised of an array of 5-folded domains that couple the enzyme's N-terminal endonuclease domain to its C-terminal target recognition and methylation activities. The REase domain contains a PD-x15-ExK motif, is closely superimposable against the FokI endonuclease domain, and coordinates a single metal ion. A helical bundle domain connects the endonuclease and methyltransferase (MTase) domains. The MTase domain is similar to the N6-adenine MTase M.TaqI, while the target recognition domain (TRD or specificity domain) resembles a truncated S subunit of Type I RāM system. A final structural domain, that may form additional DNA contacts, interrupts the TRD. DNA binding and cleavage must involve large movements of the endonuclease and TRD domains, that are probably tightly coordinated and coupled to target site methylation status
Carbenic nitrile imines: Properties and reactivity
Structures and properties of nitrile imines were investigated computationally at B3LYP and CCSD(T) levels. Whereas NBO analysis at the B3LYP DFT level invariably predicts a propargylic electronic structure, CCSD(T) calculations permit a clear distinction between propargylic, allenic, and carbenic structures. Nitrile imines with strong IR absorptions above ca. 2150 cm-1 have propargylic structures with a CN triple bond (RCNNSiMe 3 and R2BCNNBR2), and those with IR absorptions below ca. 2150 cm-1 are allenic (HCNNH, PhCNNH, and HCNNPh). Nitrile imines lacking significant cumulenic IR absorptions at 1900-2200 cm -1 are carbenic (R-(C:)-N=N-Rā²). Electronegative but lone pair-donating groups NR2, OR, and F stabilize the carbenic form of nitrile imines in the same way they stabilize "normal" singlet carbenes, including N-heterocyclic carbenes. NBO analyses at the CCSD(T) level confirm the classification into propargylic, allenic, and carbenic reactivity types. Carbenic nitrile imines are predicted to form azoketenes 21 with CO, to form [2+2] and [2+4] cycloadducts and borane adducts, and to cyclize to 1H-diazirenes of the type 24 in mildly exothermic reactions with activation energies in the range 29-38 kcal/mol. Such reactions will be readily accessible photochemically and thermally, e.g., under the conditions of matrix photolysis and flash vacuum thermolysis
Reduced Gluteal Expression of Adipogenic and Lipogenic Genes in Black South African Women Is Associated with Obesity-Related Insulin Resistance
CONTEXT: Black South African women are less insulin sensitive than their White counterparts, despite less central and greater peripheral fat deposition. We hypothesized that this paradox may be explained, in part, by differences in the adipogenic capacity of sc adipose tissue (SAT). OBJECTIVE: Our objective was to measure adipogenic and lipogenic gene expression in abdominal and gluteal SAT depots and determine their relationships with insulin sensitivity (S(I)) in South African women. PARTICIPANTS AND DESIGN: Fourteen normal-weight [body mass index (BMI) <25 kg/m(2)] Black, 13 normal-weight White, 14 obese (BMI >30 kg/m(2)) Black, and 13 obese White premenopausal South African women participated in this cross-sectional study. MAIN OUTCOMES: S(I) (frequently sampled iv glucose tolerance test) in relation to expression of adipogenic and lipogenic genes in abdominal and gluteal SAT depots. RESULTS: With increasing BMI, Black women had less visceral fat (P = 0.03) and more abdominal (P = 0.017) and gynoid (P = 0.041) SAT but had lower S(I) (P < 0.01) than White women. The expression of adipogenic and lipogenic genes was proportionately lower with obesity in Black but not White women in the gluteal and deep SAT depots (P < 0.05 for ethnicity Ć BMI effect). In Black women only, the expression of these genes correlated positively with S(I) (all P < 0.05), independently of age and fat mass. CONCLUSIONS: Obese Black women have reduced SAT expression of adipogenic and lipogenic genes compared with White women, which associates with reduced S(I). These findings suggest that obesity in Black women impairs SAT adipogenesis and storage, potentially leading to insulin resistance and increased risk of type 2 diabetes
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