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An important question in turbulent Rayleigh–Bénard convection is the scaling of the Nusselt number with the Rayleigh number in the so-called ultimate state, corresponding to asymptotically high Rayleigh numbers. A related but separate question is whether the measurements support the so-called Kraichnan law, according to which the Nusselt number varies as the square root of the Rayleigh number (modulo a logarithmic factor). Although there have been claims that the Kraichnan regime has been observed in laboratory experiments with low aspect ratios, the totality of existing experimental results presents a conflicting picture in the high-Rayleigh-number regime. We analyse the experimental data to show that the claims on the ultimate state leave open an important consideration relating to non-Oberbeck–Boussinesq effects. Thus, the nature of scaling in the ultimate state of Rayleigh–Bénard convection remains open.
This study evaluated the measurement invariance of the strengths and difficulties questionnaire (SDQ) self-report among adolescents from seven different nations.
Data for 2367 adolescents, aged 13–18 years, from India, Indonesia, Nigeria, Serbia, Turkey, Bulgaria and Croatia were available for a series of factor analyses.
The five-factor model including original SDQ scales emotional symptoms, conduct problems, hyperactivity–inattention problems, peer problems and prosocial behaviour generated inadequate fit degree in all countries. A bifactor model with three factors (i.e., externalising, internalising and prosocial) and one general problem factor yielded adequate degree of fit in India, Nigeria, Turkey and Croatia. The prosocial behaviour, emotional symptoms and conduct problems factor were found to be common for all nations. However, originally proposed items loaded saliently on other factors besides the proposed ones or only some of them corresponded to proposed factors in all seven countries.
Due to the lack of a common acceptable model across all countries, namely the same numbers of factors (i.e., dimensional invariance), it was not possible to perform the metric and scalar invariance test, what indicates that the SDQ self-report models tested lack appropriate measurement invariance across adolescents from these seven nations and it needs to be revised for cross-country comparisons.
Over the past few years a major effort has been put into the exploration of potential sites for the deployment of submillimetre (submm) astronomical facilities. Amongst the most important sites are Dome C and Dome A on the Antarctic Plateau, and the Chajnantor area in Chile. In this context, we report on measurements of the sky opacity at 200 μm over a period of three years at the French-Italian station, Concordia, at Dome C, Antarctica. Based on satellite data, we present a comparison of the atmospheric transmission at 200, 350 μm between the best potential/known sites for submillimetre astronomy all around the world.
The precipitable water vapour (PWV) was extracted from satellite measurements of the Infrared Atmospheric Sounding Interferometer (IASI) on the METOP-A satellite, between 2008 and 2010. We computed the atmospheric transmission at 200 μm and 350 μm using the forward atmospheric model MOLIERE (Microwave Observation LIne Estimation and REtrieval). This method allows us to compare known sites all around the world without the calibration biases of multiple in-situ instruments, and to explore the potential of new sites.
According to the criteria of the International Headache Society (IHS), a migraine is defined as a disease with periodic occurring headache episodes, typically associated with autonomic symptoms. The release of neuropeptides explains the actual origin of pain but not how and why the attack begins so abruptly in humans. Triptans improves the typical additional symptoms like nausea or vomiting, photo- and photophobia, and improves the ability to return to work. During a migraine attack, most patients suffer from gastrointestinal symptoms. The aim of migraine prophylaxis is a reduction of frequency, severity and duration of migraine attacks and the prevention of medication overuse headache. Effective for preventive migraine therapy are the non-selective beta-blocker propranolol and the beta-1-selective beta-blocker metoprolol. Most psychological treatments used in migraine therapy are behavior therapies. Paroxysmal pain of short duration located in a region of one of the trigeminus nerves is very characteristic for the trigeminal neuralgia.
State-of-the-art tissue engineering strategies increasingly rely on the performance of bioactive hydrogels formed via cell-friendly crosslinking reactions. Enzymatic reactions possess ideal characteristics for such applications, but they are currently still underexplored in biomaterials design. Here we report the development of hybrid bioactive hydrogels formed via a posttranslational modification reaction using phosphopantetheinyl transferase (PPTase). PPTase was shown to catalyze the covalent crosslinking of CoenzymeA-functionalized poly(ethylene glycol) (PEG) multiarm macromers and recombinantly produced acyl carrier protein (ACP) dimers. Crosslinking kinetics and physicochemical properties of PPTase hydrogels were characterized. Proof-of-principle experiments demonstrate the successful covalent bio-functionalization of gels with a CoA-derivatized cell adhesion peptide. Polymerization of gels in the presence of primary mammalian cells was shown to result in no loss in cell viability compared to a well established, chemically crosslinked gel system.
Silicon is an important material not only for semiconductor applications, but also for the development of novel bioinspired and biomimicking materials and structures or drug delivery systems in the context of nanomedicine. For these applications, a thorough understanding of the fracture behavior of the material is critical. In this paper we address this issue by investigating a fundamental issue of the mechanical properties of silicon, its behavior under extreme mechanical loading. Earlier experimental work has shown that at low temperatures, silicon is a brittle material that fractures catastrophically like glass once the applied load exceeds a threshold value. At elevated temperatures, however, the behavior of silicon is ductile. This brittle-to-ductile transition (BDT) has been observed in many experimental studies of single crystals of silicon. However, the mechanisms that lead to this change in behavior remain questionable, and the atomic-scale phenomena are unknown. Here we report for the first time the direct atomistic simulation of the nucleation of dislocations from a crack tip in silicon only due to an increase of the temperature, using large-scale atomistic simulation with the first principles based ReaxFF force field. By raising the temperature in a computational experiment with otherwise identical boundary conditions, we show that the material response changes from brittle cracking to emission of a dislocation at the crack tip, representing evidence for a potential mechanisms of dislocation mediated ductility in silicon.
We present model calculations of the atmospheric transmission for
DOME C in Antarctica for frequencies up to 10 THz (30 μm) using
the forward model MOLIERE-5. Measurements of precipitable water vapor
(pwv), obtained by the SUMMIT radiometer installed at the Concordia
station during 2008 and working at a wavelength of 200 μm, are
translated into atmospheric transmission using MOLIERE. Quartiles of
transmission, calculated from 200 μm data are extrapolated to
350 μm and compared to the CCAT (Cornell-Caltech Atacama
Telescope) site in Chile. It turns out that for 25% of the time at
DOME C (CCAT), the transmission is around 20% (5%) at
200 μm. This corresponds to a pwv of 0.18 mm for DOME C. At
350 μm, for 50% of time at DOME C (CCAT) the transmission is
around 55% (25%). This corresponds to a pwv of 0.22 mm for
DOME C. These results show that DOME C is one of the best observing
sites on Earth for submm-astronomy with respect to high atmospheric
transmission over long time periods.
We present preliminary results of the measurements of sky transparency conducted at Dome C during the winter 2008. Using MOLIERE modeling, we estimate a low precipitable water vapour content above Concordia station, which is very promising for future submillimetre wave observations on the Antarctic Plateau.
2D-crystallization in combination with transmission electron microscopy (TEM) is one of the few methods for the structural analysis of membrane proteins in their native state. However, the parameters for the generation of large crystalline sheets are typically difficult to identify for a given protein. Many repetitive and time consuming screening steps by TEM are therefore necessary to find the best crystallization and preparation conditions. Although several software packages offer the possibility to control an electron microscope, none is completely adapted for a fully automated and completely integrated acquisition and analysis of 2D crystals. Here we report on the development of a fully automatic screening and on-line analysis software for the fast and automatic survey of large quantities of negatively stained EM samples for 2D crystallography.
At the 2003 Sydney IAU meeting, Marion Schmitz (Caltech, USA) took over the chair of the Commission 5 Working Group Designations, succeeding Helene Dickel. The Working Group Designations of IAU Commission 5 clarifies existing astronomical nomenclature and helps astronomers avoid potential problems when designating their sources. The most important function of WG Designations during the period 2003-2005 was overseeing the IAU REGISTRY FOR ACRONYMS (for newly discovered astronomical sources of radiation: see the website <http://cdsweb.u-strasbg.fr/cgi-bin/DicForm>) which is sponsored by the WG and operated by the Centre de Données de Strasbourg (CDS). The Clearing House, a subgroup of the WG, screens the submissions for accuracy and conformity to the IAU Recommendations for Nomenclature (<http://cdsweb.u-strasbg.fr/iau-spec.html>). From its beginning in 1997 through August 2006, there have been 132 submissions and 111 acceptances. Attempts to register asterisms, common star names, and suspected variable stars were rejected. The past three years saw 61 acronyms submitted with 50 of them being accepted. (GIRL - yes; WOMEN - no).
This business meeting was held from 16:00 to 17:30. Toshio Fukushima and George Kaplan were welcomed as the next president and vice-president, respectively. The following, in no particular order, are the summary reports from the various offices. The full versions will be made available on the Commission 4 website at <http://iau-comm4.jpl.nasa.gov/>.
The structural properties of β-phase tantalum nanocrystallites
prepared by room temperature magnetron sputter deposition on amorphous
carbon substrates are investigated at atomic resolution. For these
purposes spherical aberration-corrected high-resolution transmission
electron microscopy is applied in tandem with the numerical retrieval of
the exit-plane wavefunction as obtained from a through-focus series of
experimental micrographs. We demonstrate that recent improvements in the
resolving power of electron microscopes enable the imaging of the atomic
structure of β-tantalum with column spacings of solely 0.127 nm with
directly interpretable contrast features. For the first time ever, we
substantiate the existence of grain boundaries of 30° tilt type in
β-Ta whose formation may be well explained by atomic agglomeration
processes taking place during sputter deposition.
Between January 1994 and October 1997, we interviewed 2576 black in-patients with newly diagnosed cancer in Johannesburg and Soweto, South Africa. Blood was tested for HIV-1 and HHV-8 antibodies and the study was restricted to 2191 HIV-1 antibody-negative patients. We examined the relationship between infection with HHV-8 and sociodemographic and behavioural factors using unconditional logistic regression models. Of the 2191 HIV-1 negative patients who did not have Kaposi's sarcoma, 854 (39·1%) were positive for antibodies against the latent nuclear antigen of HHV-8 encoded by orf73 in a immunofluorescence assay. Infection with HHV-8 was independently associated with increasing age (P trend=0·02). For females, independent risk factors also included working in a paid domestic capacity (OR 1·63, 95% CI 1·09–2·44, P=0·02), defining occupational status as economically non-active unemployed (OR 1·70, 95% CI 1·06–2·72, P=0·03), having a state pension or being on a disability grant (OR 1·49, 95% CI 1·05–2·11, P=0·02), using oral contraceptives (OR 1·43, 95% CI 1·03–1·99, P=0·03) and having a delayed age at menarche (P trend=0·04). The relationship between these variables and HHV-8 antibody status requires further, prospective study.
Background and objective: To investigate the effects of barbiturates on batrachotoxin-modified sodium channels from different regions of the human heart. Single sodium channels from human atria were studied and compared with existing data from the human ventricle and from the central nervous system.
Methods: Sodium channels from preparations of human atrial muscle were incorporated into planar lipid bilayers in the presence of batrachotoxin, a sodium channel activator. The steady-state behaviour of single sodium channels was recorded in symmetrical 500 mmol NaCl before and after the addition of pentobarbital 0.34–1.34 mmol.
Results: The batrachotoxin-treated human atrial sodium channel had an average single-channel conductance of 23.8 ± 1.6 pS in symmetrical 500 mmol NaCl and a channel fractional open time of 0.83 ± 0.06. The activation mid-point potential was −98.0 ± 2.3 mV. Extracellular tetrodotoxin (a specific sodium channel blocking agent) blocked these channels with a k1/2 = 0.53 μmol at 0 mV. Pentobarbital reduced the time average conductance of single atrial sodium channels in a concentration-dependent manner (ID50 = 0.71 mmol). In the same way, the steady-state activation was shifted to more hyperpolarized potentials (−10.6 mV at 0.67 mmol pentobarbital).
Conclusions: The properties of batrachotoxin-modified sodium channels from human atrial tissue did not differ greatly from those described for ventricular sodium channels in the literature. Our data yielded no explanation for the observed functional diversity. However, cardiac sodium channels differ from those found in the central nervous system.
Background and objective: Similar doses of ketamine are employed in regional and general anaesthesia. In contrast to commonly used local anaesthetic agents, accidental systemic application of local anaesthetic doses of ketamine will not result in seizure, dysrhythmia or cardiovascular depression. However, there is some doubt about the quality of regional analgesia induced by ketamine. As human sodium channels constitute an important molecular target of local anaesthetics, the study was designed to establish concentration-dependent effects of ketamine on conductance, steady-state activation and steady-state inactivation of human neuronal sodium channels. This information — that has, so far, not been published — will help to characterize further local anaesthetic properties of ketamine.
Methods: Whole-cell patch-clamp recordings were made of sodium channels natively expressed in human neuroblastoma SH-SY5Y cells.
Results: The sodium channels activated at a threshold of −60 mV and exhibited a maximal peak current at −10 mV. The voltage of half-maximal activation was −20 mV. The Na+ currents depended on the prepulse potential. The voltage of half-maximal inactivation was —80 mV. Ketamine inhibited the sodium conductance in a concentration-dependent manner (IC50 = 1140 µmol). A concentration-dependent hyperpolarizing shift of both steady-state activation and steady-state inactivation accounted for at most 5 mV.
Conclusions: The effects of ketamine on these human ion channels occur at clinical concentrations. They are consistent with the local anaesthetic action of ketamine. Whether ketamine helps to decrease the incidence of severe side-effects during regional anaesthesia needs to be addressed in further clinical studies.