15,636 research outputs found
Antiglycation activity and HT-29 cellular uptake of aloe-emodin, aloin, and aloe arborescens leaf extracts
Aloe arborescens is a relevant species largely used in traditional medicine of several countries. In particular, the decoction of leaves is prepared for various medicinal purposes including antidiabetic care. The aim of this research was the study of the antiglycation activity of two A. arborescens leaf extracts and isolated compounds: aloin and aloe-emodin. These phytoconstituents were quantitatively assessed in methanolic and hydroalcoholic extracts using high performance liquid chromatography (HPLC) analysis. In addition, the total phenolic and flavonoid contents were detected. In order to study their potential use in diabetic conditions, the antiglycation and antiradical properties of the two extracts and aloin and aloe-emodin were investigated by means of bovine serum albumin (BSA) and 1,1-diphenyl-2-picryl-hydrazil (DPPH) assays; further, their cytotoxicity in HT-29 human colon adenocarcinoma cells was evaluated by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay. Furthermore, the ability of aloin and aloe-emodin to permeate the cellular membranes of HT-29 cells was determined in order to estimate their potential in vivo absorption. This assessment indicated that aloe-emodin can substantially pass through cell membranes (~20%), whereas aloin did not permeate into HT-29 cells. Overall, the data show that both the methanolic and the hydroalcoholic A. arborescens extracts determine significant inhibition of glycation and free-radical persistence, without any cytotoxic activity. The data also show that the antiglycation and the antiradical activities of aloin and aloe-emodin are lower than those of the two extracts. In relation to the permeability study, only aloe-emodin is able to cross HT-29 cellular membranes, showing the attitude to pass through the intestinal layer. Overall, the present data surely support the traditional use of A. arborescens leaf extracts against hyperglycemic conditions, while aloin and aloe-emodin as potential drugs need further study
Sensitivity below the standard quantum limit in gravitational wave detectors with Michelson-Fabry-Perot readout
We calculate the quantum noise limited displacement sensitivity of a
Michelson-Fabry-Perot (MFP) with detuned cavities, followed by phase-sensitive
homodyne detection. We show that the standard quantum limit can be surpassed
even with resonant cavities and without any signal-recycling mirror nor
additional cavities. Indeed, thanks to the homodyne detection, the output field
quadrature can be chosen in such a way to cancel the effect of input amplitude
fluctuations, i.e., eliminating the force noise. With detuned cavities, the
modified opto-mechanical susceptivity allows to reach unlimited sensitivity for
large enough (yet finite) optical power. Our expressions include mirror losses
and cavity delay effect, for a realistic comparison with experiments. Our study
is particularly devoted to gravitational wave detectors and we consider both an
interferometer with free-falling mirrors, and a MFP as readout for a massive
detector. In the latter case, the sensitivity curve of the recently conceived
'DUAL' detector, based on two acoustic modes, is obtained
Corporate Hierarchies and the Size of Nations: Theory and Evidence
Corporate organization varies within a country and across countries with country size. The paper starts by establishing some facts about corporate organization based on unique data of 660 Austrian and German corporations. The larger country (Germany) has larger firms with flatter more decentral corporate hierarchies compared to the smaller country (Austria). Firms in the larger country change their organization less fast than firms in the smaller country. Over time firms have been introducing less hierarchical organizations by delegating power to lower levels of the corporation. We develop a theory which explains these facts and which links these features to the trade environment that countries and firms face. We introduce firms with internal hierarchies in a Krugman (1980) model of trade. We show that international trade and the toughness of competition in international markets induce a power struggle in firms which eventually leads to decentralized corporate hierarchies. We offer econometric evidence which is consistent with the models predictions
Power in the Multinational Corporation in Industry Equilibrium
Recent theories of the multinational corporation introduce the property rights model of the firm and examine whether to integrate our outsource firm activities locally or to a foreign country. This paper focus instead on the internal organization of the multinational corporation by examining the power allocation between headquarters and subsidiaries. We provide a framework to analyse the interaction between the decision to serve the local market by exporting or FDI, market acces and the optimal mode of organization of the multinational corporation. We find that subsidiary managers are given most autonomy in their decision how to run the firm at intermediate levels of local competition. We then provide comparative statics for changes in fixed FDI entry costs and trade costs, information technology, the number of local competitors, and in the size of the local market
Tilted excitation implies odd periodic resonances
This work was supported by the Brazilian agencies FAPESP and CNPq. MSB also acknowledges the Engineering and Physical Sciences Research Council grant Ref. EP/I032606/1. GID thanks Felipe A. C. Pereira for fruitful discussions.Peer reviewedPostprin
Measurement of Kallikrein Activity in Urine of Rats and Man Using a Chromogenic Tripeptide Substrate. Validation of the Amidolytic Assay by Means of a Bradykinin Radioimmunoassay
Peer Reviewe
Interplay between the magnetic anisotropy contributions of Cobalt nanowires
We report on the magnetic properties and the crystallographic structure of
the cobalt nanowire arrays as a function of their nanoscale dimensions. X-ray
diffraction measurements show the appearance of an in-plane HCP-Co phase for
nanowires with 50 nm diameter, suggesting a partial reorientation of the
magnetocrystalline anisotropy axis along the membrane plane with increasing
pore diameter. No significant changes in the magnetic behavior of the nanowire
system are observed with decreasing temperature, indicating that the effective
magnetoelastic anisotropy does not play a dominant role in the remagnetization
processes of individual nanowires. An enhancement of the total magnetic
anisotropy is found at room temperature with a decreasing nanowire
diameter-to-length ratio (d/L), a result that is quantitatively analyzed on the
basis of a simplified shape anisotropy model.Comment: 8 pages, 4 figure
Dynamical two-mode squeezing of thermal fluctuations in a cavity opto-mechanical system
We report the experimental observation of two-mode squeezing in the
oscillation quadratures of a thermal micro-oscillator. This effect is obtained
by parametric modulation of the optical spring in a cavity opto-mechanical
system. In addition to stationary variance measurements, we describe the
dynamic behavior in the regime of pulsed parametric excitation, showing
enhanced squeezing effect surpassing the stationary 3dB limit. While the
present experiment is in the classical regime, our technique can be exploited
to produce entangled, macroscopic quantum opto-mechanical modes
Enhanced van der Waals interaction at interfaces
Using a recently obtained (general) formula for the interaction energy
between an excited and a ground-state atom (Sherkunov Y 2007 Phys. Rev. A 75
012705), we consider the interaction energy between two such atoms near the
interface between two media. We demonstrate that under the circumstances of the
resonant coupling of the excited atom to the surface polariton mode of a
vacuum-medium system the nonretarded atom*-atom interaction energy can be
enhanced by (several) orders of magnitude in comparison with the van der Waals
interaction energy of the two isolated atoms.Comment: 8 pages, 5 figures, local-field corrections included and improved
presentatio
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