Energy of Liposome Patch Adhesion to the Pipet Glass Determined by Confocal Fluorescence Microscopy.

The formation of the gigaseal in the patch clamp technique is dependent on the adhesion between the cell or liposome membrane and the glass pipet. The adhesion results in a capillary force causing creep of the patch membrane up the pipet. The membrane can be immobilized by counteracting the capillary force by positive pressure applied to the patch pipet. We use this phenomenon to develop a method for static measurement of the adhesion free energy of the lipid bilayer to the glass. Confocal fluorescent microscopy is used to track the bilayer creep inside the pipet and measure the immobilization pressure at various salt concentrations and pH. The adhesion energy is simply related to this pressure. For the studied phospholipid bilayers, its values were in the 0.3-0.7 mJ/m2 range, increased with salt concentration, and had a maximum as a function of pH. This method offers a way to measure bilayer-glass adhesion energy in patch clamp experiments that is more precise than dynamic methods

Statistical study on propagation characteristics of Omega signals (VLF) in magnetosphere detected by the Akebono satellite

This paper shows a statistical analysis of 10.2 kHz Omega broadcasts of an artificial signal broadcast from ground stations, propagated in the plasmasphere, and detected using an automatic detection method we developed. We study the propagation patterns of the Omega signals to understand the propagation characteristics that are strongly affected by plasmaspheric electron density and the ambient magnetic field. We show the unique propagation patterns of the Omega 10.2 kHz signal when it was broadcast from two high-middle-latitude stations. We use about eight years of data captured by the Poynting flux analyzer subsystem on board the Akebono satellite from October 1989 to September 1997. We demonstrate that the signals broadcast from almost the same latitude (in geomagnetic coordinates) propagated differently depending on the geographic latitude. We also study propagation characteristics as a function of local time, season, and solar activity. The Omega signal tended to propagate farther on the nightside than on the dayside and was more widely distributed during winter than during summer. When solar activity was at maximum, the Omega signal propagated at a lower intensity level. In contrast, when solar activity was at minimum, the Omega signal propagated at a higher intensity and farther from the transmitter station.Comment: 14 pages, 12 figure

Video semantic content analysis framework based on ontology combined MPEG-7

The rapid increase in the available amount of video data is creating a growing demand for efficient methods for understanding and managing it at the semantic level. New multimedia standard, MPEG-7, provides the rich functionalities to enable the generation of audiovisual descriptions and is expressed solely in XML Schema which provides little support for expressing semantic knowledge. In this paper, a video semantic content analysis framework based on ontology combined MPEG-7 is presented. Domain ontology is used to define high level semantic concepts and their relations in the context of the examined domain. MPEG-7 metadata terms of audiovisual descriptions and video content analysis algorithms are expressed in this ontology to enrich video semantic analysis. OWL is used for the ontology description. Rules in Description Logic are defined to describe how low-level features and algorithms for video analysis should be applied according to different perception content. Temporal Description Logic is used to describe the semantic events, and a reasoning algorithm is proposed for events detection. The proposed framework is demonstrated in sports video domain and shows promising results

Detection of a Fully-resolved Compton Shoulder of the Iron K-alpha Line in the Chandra X-ray Spectrum of GX 301-2

We report the detection of a fully-resolved, Compton-scattered emission line in the X-ray spectrum of the massive binary GX 301-2 obtained with the High Energy Transmission Grating Spectrometer onboard the Chandra X-ray Observatory. The iron K-alpha fluorescence line complex observed in this system consists of an intense narrow component centered at an energy of E = 6.40 keV and a redward shoulder that extends down to ~6.24 keV, which corresponds to an energy shift of a Compton back-scattered iron K-alpha photon. From detailed Monte Carlo simulations and comparisons with the observed spectra, we are able to directly constrain the physical properties of the scattering medium, including the electron temperature and column density, as well as an estimate for the metal abundance.Comment: 13 pages, 4 figures, 1 table, accepted for publication in ApJ Lette

A unique biosynthetic pathway for gangliosides exists in Xenopus laevis oocytes

AbstractIt was previously reported that monosialosylgangliopentaosyl ceramide (Ga1NAc-GM1b) was a major ganglioside in Xenopus laevis oocytes. Here we determined biosynthetic pathways for the ganglioside by detailed measurements of glycosyltransferase activities. CMP-NeuAc:asialo-GM1 α2–3 sialyltransferase (α2–3 ST) and UDP-Ga1NAc:GM1b β1–4 N-acetylgalactosaminyltransferase (β1–4 Ga1NAcT) exhibited much higher activity than CMP-NeuAc:Ga1NAc-GA1 α2–3 ST and UDP-Ga1NAc:asialo-GM1 β1–4 Ga1NAcT, respectively. These observations indicated the existence of a unique biosynthetic pathway in the oocytes as follows; asialo-GM1 → GM1b → Ga1NAc-GM1b

Inactivation of the Rcan2 Gene in Mice Ameliorates the Age- and Diet-Induced Obesity by Causing a Reduction in Food Intake

Obesity is a serious international health problem that increases the risk of several diet-related chronic diseases. The genetic factors predisposing to obesity are little understood. Rcan2 was originally identified as a thyroid hormone-responsive gene. In the mouse, two splicing variants that harbor distinct tissue-specific expression patterns have been identified: Rcan2-3 is expressed predominately in the brain, whereas Rcan2-1 is expressed in the brain and other tissues such as the heart and skeletal muscle. Here, we show that Rcan2 plays an important role in the development of age- and diet-induced obesity. We found that although the loss of Rcan2 function in mice slowed growth in the first few weeks after birth, it also significantly ameliorated age- and diet-induced obesity in the mice by causing a reduction in food intake rather than increased energy expenditure. Rcan2 expression was most prominent in the ventromedial, dorsomedial and paraventricular hypothalamic nuclei governing energy balance. Fasting and refeeding experiment showed that only Rcan2-3 mRNA expression is up-regulated in the hypothalamus by fasting, and loss of Rcan2 significantly attenuates the hyperphagic response to starvation. Using double-mutant (Lepob/ob Rcan2−/−) mice, we were also able to demonstrate that Rcan2 and leptin regulate body weight through different pathways. Our findings indicate that there may be an Rcan2-dependent mechanism which regulates food intake and promotes weight gain through a leptin-independent pathway. This study provides novel information on the control of body weight in mice and should improve our understanding of the mechanisms of obesity in humans

Dephasing by a Continuous-Time Random Walk Process

Stochastic treatments of magnetic resonance spectroscopy and optical spectroscopy require evaluations of functions like , where t is time, Q(s) is the value of a stochastic process at time s, and the angular brackets denote ensemble averaging. This paper gives an exact evaluation of these functions for the case where Q is a continuous-time random walk process. The continuous time random walk describes an environment that undergoes slow, step-like changes in time. It also has a well-defined Gaussian limit, and so allows for non-Gaussian and Gaussian stochastic dynamics to be studied within a single framework. We apply the results to extract qubit-lattice interaction parameters from dephasing data of P-doped Si semiconductors (data collected elsewhere), and to calculate the two-dimensional spectrum of a three level harmonic oscillator undergoing random frequency modulations.Comment: 25 pages, 4 figure

Spin fluctuations in CuGeO3_3 probed by light scattering

We have measured temperature dependence of low-frequency Raman spectra in CuGeO$_3$, and have observed the quasi-elastic scattering in the $(c,c)$ polarization above the spin-Peierls transition temperature. We attribute it to the fluctuations of energy density in the spin system. The magnetic specific heat and an inverse of the magnetic correlation length can be derived from the quasi-elastic scattering. The inverse of the magnetic correlation length is proportional to $(T-T_{SP})^{1/2}$ at high temperatures. We compare the specific heat with a competing-$J$ model. This model cannot explain quantitatively both the specific heat and the magnetic susceptibility with the same parameters. The origin of this discrepancy is discussed.Comment: 17 pages, REVTeX, 5 Postscript figures; in press in PR