At times, a pronounced trough of low barometric pressure extends from equatorial Africa northward, over the Red Sea and the eastern Mediterranean countries, i.e., the Red Sea Trough. The associated weather is usually hot and dry, and consequently the atmosphere becomes conditionally unstable. In cases in which additional moisture is supplied and dynamic conditions become supportive, as the case analyzed here, intense thunderstorms occur, with extreme rain rates, hail and floods. The storm herein analyzed caused extensive damage both in casualties and property and evolved in two main consecutive phases: In the first a Mesoscale Convective System that moved from Sinai northward over Israel dominated, and in the second deep convection was organized mainly along a cold front. Data analysis indicates several synoptic-scale factors that had a supportive effect on the storm formation and intensification: Conditional instability established by the Red Sea trough, mid-level moisture transport from Northern Africa, and upper-level divergence imparted by both polar and subtropical jet streams over the Middle-East. Mesoscale features were further investigated by means of a hydro-meteorological observational analysis with high spatio-temporal resolution using raingauge and radar data, and satellite imagery. It is shown that local factors, particularly topographic effects, play a major role in the evolution, intensity and spatial organization of the convective activity. Our findings support results of a numerical study of another autumn rainstorm associated with the Red Sea trough. In the present case we identify an additional contributing factor, i.e., a mid-latitude upper-level trough that further intensified the storm as it was approaching the Middle-East.
At times, a pronounced trough of low barometric pressure extends from equatorial Africa northward, over the Red Sea and the eastern Mediterranean countries, i.e., the Red Sea Trough. The associated weather is usually hot and dry, and consequently the atmosphere becomes conditionally unstable. In cases in which additional moisture is supplied and dynamic conditions become supportive, as the case analyzed here, intense thunderstorms occur, with extreme rain rates, hail and floods. The storm herein analyzed caused extensive damage both in casualties and property and evolved in two main consecutive phases: In the first a Mesoscale Convective System that moved from Sinai northward over Israel dominated, and in the second deep convection was organized mainly along a cold front. Data analysis indicates several synoptic-scale factors that had a supportive effect on the storm formation and intensification: Conditional instability established by the Red Sea trough, mid-level moisture transport from Northern Africa, and upper-level divergence imparted by both polar and subtropical jet streams over the Middle-East. Mesoscale features were further investigated by means of a hydro-meteorological observational analysis with high spatio-temporal resolution using raingauge and radar data, and satellite imagery. It is shown that local factors, particularly topographic effects, play a major role in the evolution, intensity and spatial organization of the convective activity. Our findings support results of a numerical study of another autumn rainstorm associated with the Red Sea trough. In the present case we identify an additional contributing factor, i.e., a mid-latitude upper-level trough that further intensified the storm as it was approaching the Middle-East.
The vibrational self-consistent field method is used to analyze the inhomogeneous spectral distribution of transitions caused by vacancies and thermally populated phonons, specializing to molecular iodine isolated in an Ar matrix. At experimentally relevant temperatures, for a vacancy concentration of 1.4%, both defect-induced and phonon-induced spectral shifts contribute to the spectral distribution. Both contributions scale linearly with vibrational overtone number. The predicted widths are consistent with reported resonant Raman spectra. In time-resolved coherent anti-Stokes Raman scattering (TRCARS) measurements, spectral indistinguishability implies that all members of the inhomogeneous ensemble contribute coherently to the detectable homodyne signal. The connection between spectral distribution and the observable in TRCARS is derived. The predicted polarization beats and free induction decay due to the inhomogeneous ensemble are in qualitative agreement with experiments. (C) 2001 American Institute of Physics.
Objective-To obtain theanatomic and morphometric data required for biomechanical analysis ofthehindlimb in dogs.
Animals-A healthy adult mixed-breed 23-kg male dog.
Procedure-Following euthanasia ofthe dog, all muscles ofthe right hind limb were identified and meticulously removed. Physiologic cross-sectional areas (PCSA) and architectural indices (Al) were calculated. The coordinates for the origin and insertion of each muscle were determined, using orthogonal right-handed coordinate systems embedded in the pelvis, femur, and tibia.
Results-PCSA and Al were calculated for 29 muscles, and coordinates for the origins and insertions ofthese muscles were determined.
Conclusions-Results provide themorphometric and anatomic data necessary for S-dimensional biomechanical studies ofthehind limb in dogs.
This study uses the Agent-Based Identity Repertoire model to investigate the ability of populations to adapt and learn in an unpredictable environment. The authors' findings highlight the trade-off between adaptation and diversity in the pursuit of performance but also show that this trade-off is far from straightforward Increasing sophistication improves the ability to adapt but reduces diversity, imposing high costs down the line. However, high levels of sophistication also produce small, stable homogeneous clusters of agents, which slow down declines in diversity. Innovative or entrepreneurial agents reacting more rapidly to environmental signals increase the prevalence of such clusters, helping diversity but hampering adaptability. The authors also show that more predictable environments facilitate successful adaptation, especially for populations of intermediate sophistication. Finally, the authors conclude that the trade-off between adaptation and diversity is such that in the present model, long-term learning is difficult to achieve.
Superexchange is a longer-range electron-transfer mediated by a nonresonant bridge between the donating and accepting states. We discuss a coupled set of donor/acceptor levels that are not resonant, with special reference to coupling of intermediate strengths. Examples of such systems are peptide cations or arrays of quantum dots. If the coupling is strong enough to overcome the gaps, charge can migrate. If the coupling is too weak, the charge remains localized. In the intermediate case, the charge is shown to be localized over a finite, connected, subset of sites. Degenerate perturbation theory provides a suitable zero-order basis for this intermediate regime. In a time dependent language, in the domain-localized regime, the charge migrates over a limited range of states. Also discussed is an effect of electron correlation, the so-called Coulomb blockade, on charge localization with computational examples. The experimental probing of the domain-localized regime is considered. Probes of the energy dependence of the local density of states such as scanning tunneling microscopy (STM) of arrays of quantum dots and photoelectron spectroscopy (PES) of chromophore bearing molecules are suggested.
Finite state logic machines can be realized by pump-probe spectroscopic experiments on an isolated molecule. The most elaborate setup, a Turing machine, can be programmed to carry out a specific computation. We argue that a molecule can be similarly programmed, and provide examples using two photon spectroscopies. The states of the molecule serve as the possible states of the head of the Turing machine and the physics of the problem determines the possible instructions of the program. The tape is written in an alphabet that allows the listing of the different pump and probe signals that are applied in a given experiment. Different experiments using the same set of molecular levels correspond to different tapes that can be read and processed by the same head and program. The analogy to a Turing machine is not a mechanical one and is not completely molecular because the tape is not part of the molecular,machine. We therefore also discuss molecular finite state machines, such as sequential devices, for which the tape is not part of the machine. Nonmolecular tapes allow for quite long input sequences with a rich alphabet (at the level of 7 bits) and laser pulse:shaping experiments provide concrete examples. Single molecule spectroscopies show that a single molecule can be repeatedly cycled through a logical operation. (C) 2001 American Institute of Physics.
The number and complexity of genes encoding nuclear lamina proteins has increased during metazoan evolution. Emerging evidence reveals that transcriptional repressors such as the retinoblastoma protein, and apoptotic regulators such as CED-4, have functional and dynamic interactions with the lamina. The discovery that mutations in nuclear lamina proteins cause heritable tissue-specific diseases, including Emery-Dreifuss muscular dystrophy, is prompting a fresh look at the nuclear lamina to devise models that can account for its diverse functions and dynamics, and to understand its enigmatic structure.
Anharmonic vibrational frequencies and intensities are calculated for 1:1 and 2:2 (HCl)(n)(NH(3))(n) and (HCl)(n-)(H(2)O)(n) complexes, employing the correlation-corrected vibrational self-consistent field method with ab initio potential surfaces at the MP2/TZP computational level. In this method, the anharmonic coupling between all vibrational modes is included, which is found to be important for the systems studied. For the 4:4 (HCL)(n)- (H(2)O)(n) complex, the vibrational spectra are calculated at the harmonic level, and anharmonic effects are estimated. Just as the (HCl)(n)(NH(3))(n) Structure switches from hydrogen-bonded to ionic for n = 2, the (HCl)(n)-(H(2)O)(n) switches to ionic structure for n = 4. For (HCl)(2)(H(2)O)2, the lowest energy structure corresponds to the hydrogen-bonded form. However, configurations of the ionic form are separated from this minimum by a barrier of less than an O-H stretching quantum. This suggests the possibility of experiments on ionization dynamics using infrared excitation of the hydrogen-bonded form. The strong cooperative effects on the hydrogen bonding, and concomitant transition to ionic bonding, makes an accurate estimate of the large anharmonicity crucial for understanding the infrared spectra of these systems. The anharmonicity is typically of the order of several hundred wavenumbers for the proton stretching motions involved in hydrogen or ionic bonding, and can also be quite large for the intramolecular modes. In addition, the large cooperative effects in the 2:2 and higher order (HCl)(n)(H(2)O)(n) Complexes may have interesting implications for solvation of hydrogen halides at ice surfaces.
Gbx2 homeobox genes are important for formation and function of the midbrain/hindbrain boundary, namely the isthmic organizer. Two Gbx2 genes were identified in Xenopus laevis, differing in 13 amino acids, including a change in the homeodomain. Xgbx2a is activated earlier during gastrulation and reaches higher levels of expression while Xgbx2b is expressed later, at lower levels and has an additional domain in the ventral blood islands. Their overexpression results in microcephalic embryos with shortened axes and defects in brain and notochord formation. Both genes encode functionally homologous proteins, which differ primarily in their temporal and spatial expression patterns.
