We study the structure and stability of closed-ring carbon nanotubes using a theoretical model based on the Brenner-Tersoff potential. Many metastable structures can be produced. We focus on two methods of generating such structures. In the first, a ring is formed by geometric folding and is then relaxed into minimum energy using a minimizing algorithm. Short tubes do not stay closed. Yet tubes longer than 18 nm are kinetically stable. The other method starts from a straight carbon nanotube and folds it adiabatically into a closed-ring structure. The two methods give strikingly different structures. The structures of the second method are more stable and exhibit two buckles, independent of the nanotube length. This result is in strict contradiction to an elastic shell model. We analyze the results for the failure of the elastic model.
Ariel Shisha-Halevy. 2003. “Celtic Syntax, Egyptian-Coptic Syntax.” In Das Alte Ägypten und seine Nachbarn: Festschrift Helmut Satzinger, Pp. 245–302. Krems: Österreichisches Literaturforum. Abstract
H. J. Polotsky’s “Syntaxe amharique et syntaxe turque” (1960a), the Master’s only article in a properly speaking General Linguistics (typological-comparative) genre, the paper opening Polotsky’s Collected Papers (Jerusalem: the Magnes Press, 1971), has drawn little attention outside the small circle of the Jerusalem School and its adherents, perhaps because of an hermetic quality of style, as well as the exclusive Ethiopistic forum of publication. And yet, it is a wonderful fruit of Polotsky’s annus mirabilis, an insightful and sensitive exposé of an instance of the non-geographical, cross-genealogical Sprachbund and what may be called the historical-connection-indifferent typological rapprochement As is generally realized today, the Sprachbund phenomenon is varied and complex, reflecting the variety of languages-in-contact scenarios and their historical configuration. The relatively rare non-adjacent or non-geographical Sprachbund is less well understood and falls between the stools of typological and genetic comparison, and goes, to mix metaphors, against the grain of conventional comparativist temperament.
The “Eurafrican” (so Wagner in Transactions of the Philological Society 1969) hypothesis, first outlined in modern times at least as early as 1990 by John Morris-Jones, has been for most of the last century associated almost exclusively with the names of Julius Pokorny and his disciple, Heinrich Wagner. I believe it now deserves detailed objective re-appreciation, in view of the considerable expansion in our knowledge of Celtic and the advance in the unveiling of the languages commonly known as Afro-Asiatic or Hamito-Semitic, and especially of Egyptian and Coptic. Although it is generally not clear which languages are invoked on the Afro-Asiatic side — “Semitic” (which languages?) “Egyptian” (which phase or phases in its near four millennia of evolution?), Arabic, North-West Semitic, Accadian, Berber — a vagueness contributive to the scepticism with which the theory is still regarded (not that there is a generally accepted idea about hierarchies and chronologies inside the Celtic branch of Indo-European); nor is there any real confidence about either the chronological parameters, or the hierarchical structuring of syntactical and non-syntactical comparata of the comparison.
Ceramide, the basic structural unit of sphingolipids, controls the balance between cell growth and death by inducing apoptosis. We have previously shown that accumulation of ceramide, triggered by hydrogen peroxide (H(2)O(2)) or by short-chain ceramide analogs, induces apoptosis of lung epithelial cells. Here we elucidate the link between caspase-3 activation, at the execution phase, and ceramide accumulation, at the commitment phase of apoptosis in A549 human lung adenocarcinoma cells. The induction of ceramide accumulation by various triggers of ceramide generation, such as H(2)O(2), C(6)-ceramide, or UDP-glucose-ceramide glucosyltransferase inhibitor dl-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol, triggered the activation of caspase-3. This ceramide elevation also induced the cleavage of the death substrate poly(ADP-ribose) polymerase and was followed by apoptotic cell death. Ceramide-mediated apoptosis was blocked by a general caspase inhibitor, Boc-d-fluoromethylketone, and by overexpression of the antiapoptotic protein Bcl-2. Notably, overexpression of Bcl-2 reduced the basal cellular levels of ceramide and prevented the induction of ceramide generation by C(6)-ceramide, which implies ceramide generation as a possible target for the antiapoptotic effects of Bcl-2.
We performed a prospective, randomized, open-label equivalence study comparing the use of naproxen to aspirin in 33 patients with rheumatic fever. The mean time until resolution of arthritis was 2.9±2.9 days in both groups. Liver enzyme elevations were more frequent in the aspirin group (P=.002). We conclude that naproxen is as effective, is easier to use, and is safer than aspirin in the treatment of the arthritis of rheumatic fever.
Emission spectra of mixed rare gas clusters, heated by impact with a hard surface at hypersonic velocities, are shown to extend into the near-IR and visible regimes. The emission is due to the transient dipole that arises during the collision of dissimilar atoms. The simulations are for a cluster that remains in the electronic ground state throughout the collision and use classical dynamics to determine the positions of the atoms vs time. The spectrum is computed as the Fourier transform of the (quantum mechanical) time rate of change of the dipole of the cluster. The time dependence of the dipole velocity is obtained by replacing the positions of the atoms by the computed classical functions of time. Taking the Fourier transform of the dipole velocity rather than of the dipole itself introduces a quantal correction with the result that the computed spectrum satisfies the oscillator sum rule. Binary collisions make the major contribution to the spectrum and there are hardly any caging effects. The spectral density of emitted photons is found to be thermal with a temperature that scales linearly with the impact velocity. Using the oscillator sum rules, this temperature is related to the deformation energy of the electronic charge cloud of the cluster. The hot cluster shatters and the fragments are in translational thermal equilibrium with a mean energy that scales linearly with the energy of impact. The temperature of the emitted light is, therefore, significantly lower than the translational temperature.
To model the possible formation of coupled spatial corrugations and charge density modulations in lamellar DNA-lipid complexes, we use a free energy functional which includes the electrostatic, lipid mixing, and elastic degrees of freedom in a self-consistent manner. We find that the balance of forces favors membrane corrugations that are expected to be stable with respect to thermal membrane undulations for a certain range of lipid (charged and uncharged) composition. This may lead to locking between DNA strands in adjacent galleries of the complex. Furthermore, the possibility of membrane corrugations renders the lamellar complex more stable with respect to another, hexagonal, DNA-lipid phase.
HArF and HKrF are chemically bound rare-gas compounds that have been produced by photolysis of HF and subsequent thermal annealing in the respective rare-gas matrices. In this paper we present a computational study of the delayed, thermally induced formation of these molecules in the matrix. Using realistic potentials for the molecular and guest-host interactions, the potential energy along the minimum energy paths for formation is evaluated, and thermal transition rates are computed using a Monte Carlo transition state method. A closely packed, dissociated configuration of the molecular fragments is found to play an important role, both as the possible trapping site of the photolyzed fragments, and as an intermediate structure for diffusion-controlled formation. The computed threshold temperatures of formation for the HArF and HKrF molecules at different matrix sites are in good agreement with experimental findings and with previous site assignments for these molecules. (C) 2003 American Institute of Physics.
Diagnostic beads are disclosed for the detection of occult blood in animal excreta, esp. for use in a cat litter. The beads comprise a particulate material and a detection compn. attached to the particulate material. The detection compn. comprises a chromogen, a peroxide, an enhancer, a stabilizer, and a binder, the chromogen being selected to react with occult blood in the animal excreta so as to produce a visible and immediate color change when excreta contg. blood comes into contact with the diagnostic beads. [on SciFinder(R)]
