220 research outputs found
THE "FREELY" FALLING TWO-LEVEL ATOM IN A RUNNING LASER WAVE
The time evolution of a two-level atom which is simultaneously exposed to the
field of a running laser wave and a homogeneous gravitational field is studied.
The result of the coupled dynamics of internal transitions and center-of-mass
motion is worked out exactly. Neglecting spontaneous emission and performing
the rotating wave approximation we derive the complete time evolution operator
in an algebraical way by using commutation relations. The result is discussed
with respect to the physical implications. In particular the long time and
short time behaviour is physically analyzed in detail. The breakdown of the
Magnus perturbation expansion is shown.Comment: 14 Pages, Late
Increased Amoxicillin–Clavulanic Acid Resistance in Escherichia coli Blood Isolates, Spain
To determine the evolution and trends of amoxicillin–clavulanic acid resistance among Escherichia coli isolates in Spain, we tested 9,090 blood isolates from 42 Spanish hospitals and compared resistance with trends in outpatient consumption. These isolates were collected by Spanish hospitals that participated in the European Antimicrobial Resistance Surveillance System network from April 2003 through December 2006
Sitagliptin improved glucose assimilation in detriment of fatty-acid utilization in experimental type-II diabetes: Role of GLP-1 isoforms in Glut4 receptor trafficking
Background: The distribution of glucose and fatty-acid transporters in the heart is crucial for energy consecution and myocardial function. In this sense, the glucagon-like peptide-1 (GLP-1) enhancer, sitagliptin, improves glucose homeostasis but it could also trigger direct cardioprotective actions, including regulation of energy substrate utilization. Methods: Type-II diabetic GK (Goto-Kakizaki), sitagliptin-treated GK (10 mg/kg/day) and wistar rats (n = 10, each) underwent echocardiographic evaluation, and positron emission tomography scanning for [ 18 F]-2-fluoro-2-deoxy-d-glucose ( 18 FDG). Hearts and plasma were isolated for biochemical approaches. Cultured cardiomyocytes were examined for receptor distribution after incretin stimulation in high fatty acid or high glucose media. Results: Untreated GK rats exhibited hyperglycemia, hyperlipidemia, insulin resistance, and plasma GLP-1 reduction. Moreover, GK myocardium decreased 18 FDG assimilation and diastolic dysfunction. However, sitagliptin improved hyperglycemia, insulin resistance, and GLP-1 levels, and additionally, enhanced 18 FDG uptake and diastolic function. Sitagliptin also stimulated the sarcolemmal translocation of the glucose transporter-4 (Glut4), in detriment of the fatty acyl translocase (FAT)/CD36. In fact, Glut4 mRNA expression and sarcolemmal translocation were also increased after GLP-1 stimulation in high-fatty acid incubated cardiomyocytes. PI3K/Akt and AMPKα were involved in this response. Intriguingly, the GLP-1 degradation metabolite, GLP-1(9-36), showed similar effects. Conclusions: Besides of its anti-hyperglycemic effect, sitagliptin-enhanced GLP-1 may ameliorate diastolic dysfunction in type-II diabetes by shifting fatty acid to glucose utilization in the cardiomyocyte, and thus, improving cardiac efficiency and reducing lipolysisThis work was supported by national grants from Ministerio de Educación
y Ciencia (SAF2009-08367), Comunidad de Madrid (CCG10-UAM/BIO-5289),
and PIE13/00051 and PI14/00386 (IS. Carlos III). Merck Sharp and Dohme
(Darmstadt, Germany) provided sitagliptin and partial financial support to the
conduct of the stud
Herschel Far-IR counterparts of SDSS galaxies: Analysis of commonly used Star Formation Rate estimates
We study a hundred of galaxies from the spectroscopic Sloan Digital Sky
Survey with individual detections in the Far-Infrared Herschel PACS bands (100
or 160 m) and in the GALEX Far-UltraViolet band up to z0.4 in the
COSMOS and Lockman Hole fields. The galaxies are divided into 4 spectral and 4
morphological types. For the star forming and unclassifiable galaxies we
calculate dust extinctions from the UV slope, the H/H ratio and
the ratio. There is a tight correlation between the
dust extinction and both and metallicity. We calculate
SFR and compare it with other SFR estimates (H, UV, SDSS)
finding a very good agreement between them with smaller dispersions than
typical SFR uncertainties. We study the effect of mass and metallicity, finding
that it is only significant at high masses for SFR. For the AGN and
composite galaxies we find a tight correlation between SFR and L
(0.29), while the dispersion in the SFR - L relation is
larger (0.57). The galaxies follow the prescriptions of the
Fundamental Plane in the M-Z-SFR space.Comment: 24 pages, 23 figures, accepted for publication in MNRA
Analysis of the interaction of vinyl and carbonyl silanes with carbon nanofiber surfaces
Carbon nanofibers (CNFs) have been treated with vinyltryethoxy silane (VTS) and 3-metacryloxypropyltrimethoxy silane (MPS). CNF–silane interactions have been analyzed by means of TGA, FTIR-ATR, TEM, HRTEM, SEM and nitrogen adsorption. For similar silane concentration solutions TG analysis has shown that VTS and MPS form one and three silane monolayers, respectively. This has also been corroborated by the presence of an FTIR-ATR band at 1250 cm−1 assigned to Si–O–Si bonds of silica layers. For low silane concentrations, the vinyl group of VTS is bonded to the graphene CNF surface mainly through π–π interactions. However, MPS interacts through the carbonyl group with hydroxyl groups of graphene defect sheets existing probably in micropores. Silanol–CNF hydroxyl interactions are also expected at these silane concentrations. For high silane concentration, when the silica layer is formed, both silanes present vinyl free and carbonyl free groups, as observed by the 1370 and 1686 cm−1 FTIR-ATR bands, respectively. Nitrogen adsorption has shown that while VTS is adsorbed mainly on the defect free graphene surface, MPS is adsorbed on the micropores and, therefore on the hydroxyl defect graphene sites. These results are finally correlated with the dispersion stability of both silanes on water and styrene solutions
One pendulum to run them all
The analytical solution for the three-dimensional linear pendulum in a rotating frame of reference is obtained, including Coriolis and centrifugal accelerations, and expressed in terms of initial conditions. This result offers the possibility of treating Foucault and Bravais pendula as trajectories of the same system of equations, each of them with particular initial conditions. We compare them with the common two-dimensional approximations in textbooks. A previously unnoticed pattern in the three-dimensional Foucault pendulum attractor is presented
Rota-Baxter algebras and new combinatorial identities
The word problem for an arbitrary associative Rota-Baxter algebra is solved.
This leads to a noncommutative generalization of the classical Spitzer
identities. Links to other combinatorial aspects, particularly of interest in
physics, are indicated.Comment: 8 pages, improved versio
Physical properties of Lyman-alpha emitters at from UV-to-FIR measurements
The analysis of the physical properties of low-redshift Ly emitters
(LAEs) can provide clues in the study of their high-redshift analogues. At , LAEs are bright enough to be detected over almost the entire
electromagnetic spectrum and it is possible to carry out a more precise and
complete study than at higher redshifts. In this study, we examine the UV and
IR emission, dust attenuation, SFR and morphology of a sample of 23
GALEX-discovered star-forming (SF) LAEs at with direct UV (GALEX),
optical (ACS) and FIR (PACS and MIPS) data. Using the same UV and IR limiting
luminosities, we find that LAEs at tend to be less dusty, have
slightly higher total SFRs, have bluer UV continuum slopes, and are much
smaller than other galaxies that do not exhibit Ly emission in their
spectrum (non-LAEs). These results suggest that at Ly
photons tend to escape from small galaxies with low dust attenuation. Regarding
their morphology, LAEs belong to Irr/merger classes, unlike non-LAEs. Size and
morphology represent the most noticeable difference between LAEs and non-LAEs
at . Furthermore, the comparison of our results with those obtained
at higher redshifts indicates that either the Ly technique picks up
different kind of galaxies at different redshifts or that the physical
properties of LAEs are evolving with redshift.Comment: Accepted for publication in Ap
Untangling Neolithic and Bronze Age mitochondrial lineages in South Asia
Two key moments shaped the extant South Asian gene pool within the last 10 thousand years (ka): the Neolithic period, with the advent of agriculture and the rise of the Harappan/Indus Valley Civilisation; and Late Bronze Age events that witnessed the abrupt fall of the Harappan Civilisation and the arrival of Indo-European speakers. This study focuses on the phylogeographic patterns of mitochondrial haplogroups H2 and H13 in the Indian Subcontinent and incorporates evidence from recently released ancient genomes from Central and South Asia. It found signals of Neolithic arrivals from Iran and later movements in the Bronze Age from Central Asia that derived ultimately from the Steppe. This study shows how a detailed mtDNA phylogeographic approach, combining both modern and ancient variation, can provide evidence of population movements, even in a scenario of strong male bias such as in the case of the Bronze Age Steppe dispersals
- …