6,631 research outputs found
A practical approach to cosmological perturbations in modified gravity
The next generation of large scale surveys will not only measure cosmological
parameters within the framework of General Relativity, but will also allow for
precision tests of the framework itself. At the order of linear perturbations,
departures from the growth in the LCDM model can be quantified in terms of two
functions of time and Fourier number k. We argue that in local theories of
gravity, in the quasi-static approximation, these functions must be ratios of
polynomials in k, with the numerator of one function being equal to the
denominator of the other. Moreover, the polynomials are even and of second
degree in practically all viable models considered today. This means that,
without significant loss of generality, one can use data to constraint only
five functions of a single variable, instead of two functions of two variables.
Furthermore, since the five functions are expected to be slowly varying, one
can fit them to data in a non-parametric way with the aid of an explicit
smoothness prior. We discuss practical application of this parametrization to
forecasts and fits.Comment: 9 pages, v2: matching the published versio
Quasi-Freestanding Multilayer Graphene Films on the Carbon Face of SiC
The electronic band structure of as-grown and doped graphene grown on the
carbon face of SiC is studied by high-resolution angle-resolved photoemission
spectroscopy, where we observe both rotations between adjacent layers and
AB-stacking. The band structure of quasi-freestanding AB- bilayers is directly
compared with bilayer graphene grown on the Si-face of SiC to study the impact
of the substrate on the electronic properties of epitaxial graphene. Our
results show that the C-face films are nearly freestanding from an electronic
point of view, due to the rotations between graphene layers.Comment: http://link.aps.org/doi/10.1103/PhysRevB.81.24141
Early handling and repeated cross-fostering have opposite effect on mouse emotionality
Early life events have a crucial role in programming the individual phenotype and exposure to traumatic experiences during infancy can increase later risk for a variety of neuropsychiatric conditions, including mood and anxiety disorders. Animal models of postnatal stress have been developed in rodents to explore molecular mechanisms responsible for the observed short and long lasting neurobiological effects of such manipulations. The main aim of this study was to compare the behavioral and hormonal phenotype of young and adult animals exposed to different postnatal treatments. Outbred mice were exposed to (i) the classical Handling protocol (H: 15 min-day of separation from the mother from day 1 to 14 of life) or to (ii) a Repeated Cross-Fostering protocol (RCF: adoption of litters from day 1 to 4 of life by different dams). Handled mice received more maternal care in infancy and showed the already described reduced emotionality at adulthood. Repeated cross fostered animals did not differ for maternal care received, but showed enhanced sensitivity to separation from the mother in infancy and altered respiratory response to 6% CO2 in breathing air in comparison with controls. Abnormal respiratory responses to hypercapnia are commonly found among humans with panic disorders (PD), and point to RCF-induced instability of the early environment as a valid developmental model for PD. The comparisons between short-and long-term effects of postnatal handling vs. RCF indicate that different types of early adversities are associated with different behavioral profiles, and evoke psychopathologies that can be distinguished according to the neurobiological systems disrupted by early-life manipulation
Relevance of lactate level detection in migrane and fibromyalgia
The aim of this study was to determine the blood lactate levels in healthy and pathological subjects, particularly with migraine and fibromyalgia. Moreover we investigated the possible correlation between lactate concentration, postural stability and balance disorders; the composition of the groups were: migraine (n = 25; age 49.7 +/- 12.5), fibromyalgia (n = 10; age 43.7 +/- 21.2), control group (n = 16 age 28.52 +/- 2.4). The results showed that patients with fibromyalgia (FG) had higher lactate levels compared to migraine (MG) and control group (CG) (mean +/- sd: FG = 1.78 +/- 0.9 mmol/L; MG = 1.45 +/- 1 mmol/L; CG = 0,85 +/- 0,07 mmol/L). The same situation was highlighted about the sway path length with eyes closed (FG = 518 +/- 195 mm; MG = 465 +/- 165 mm; CG = 405 +/- 94,72 mm) and with eyes open (FG = 430 +/- 220 mm; MG = 411 +/- 143 mm; CG = 389 +/- 107 mm). This can be explained by the fact that energy-intensive postural strategies must be used to optimize both static and dynamic coordination, in particular with repeated contractions of tonic oxidative muscle cells responsible for postural control
Substitution of antibodies and receptors with molecularly imprinted polymers in enzyme-linked and fluorescent assays
A new technique for coating microtitre plates with molecularly imprinted
polymers (MIP), specific for low-molecular weight analytes (epinephrine,
atrazine) and proteins is presented. Oxidative polymerization was performed in
the presence of template; monomers: 3-aminophenylboronic acid, 3-
thiopheneboronic acid and aniline were polymerized in water and the polymers
were grafted onto the polystyrene surface of the microplates. It was found that
this process results in the creation of synthetic materials with antibody-like
binding properties. It was shown that the MIP-coated microplates are
particularly useful for assay development. The high stability of the polymers
and good reproducibility of the measurements make MIP coating an attractive
alternative to conventional antibodies or receptors used in ELISA
Many-body interactions in quasi-freestanding graphene
The Landau-Fermi liquid picture for quasiparticles assumes that charge
carriers are dressed by many-body interactions, forming one of the fundamental
theories of solids. Whether this picture still holds for a semimetal like
graphene at the neutrality point, i.e., when the chemical potential coincides
with the Dirac point energy, is one of the long-standing puzzles in this field.
Here we present such a study in quasi-freestanding graphene by using
high-resolution angle-resolved photoemission spectroscopy. We see the
electron-electron and electron-phonon interactions go through substantial
changes when the semimetallic regime is approached, including renormalizations
due to strong electron-electron interactions with similarities to marginal
Fermi liquid behavior. These findings set a new benchmark in our understanding
of many-body physics in graphene and a variety of novel materials with Dirac
fermions.Comment: PNAS 2011 ; published ahead of print June 27, 201
Cancer patients requiring interruption of long-term warfarin because of surgery or chemotherapy induced thrombocytopenia: the use of fixed sub-therapeutic doses of low-molecular weight heparin.
No data are available regarding the management of cancer patients requiring interruption of long-term vitamin-K antagonist (VKA) therapy. For this purpose, we tested the efficacy and safety of fixed doses of low-molecular weight heparin (LMWH) in substitution of VKA because of invasive procedures or chemotherapy-induced thrombocytopenia. In cancer patients on VKA, therapy was discontinued 5 ± 1 days before surgery or chemotherapy. Heparin was given at prophylactic dosage in patients at low risk and at fixed subtherapeutic doses (3,800 or 4,000 UI anti-FXa, b.i.d.) in those at high-risk for thrombosis. LMWH was reinitiated 12 hr after surgery and VKA the day after. In patients receiving chemotherapy, LMWH was reinitiated 12/24 hr after obtaining a stable platelet count ≥ 30,000 mmc(3) and VKA after a stable platelet count ≥ 50,000 mmc(3) . Thromboembolism and major bleeding events were recorded from the time of VKA suspension to 30 ± 2 days postprocedure or until the next chemotherapy. Overall, 156 patients (56.4% at low risk and 43.5% at high risk for thrombosis) were enrolled; 34.6% underwent major surgery, 40.4% nonmajor surgery, and 25% chemotherapy. Thrombotic events occurred in five patients [3.2%, 95% confidence interval (CI): 1.41-7.27], four belonging to the high-risk and one to the low-risk group. Major bleeding occurred in five patients (3.2%, 95 CI: 1.41-7.27), all belonging to the high-risk group (three during major surgery and two during chemotherapy). In conclusion, LMWH given at fixed subtherapeutic is a feasible and relatively safe approach for bridging therapy in cancer patients on long-term VK
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