Intense rainstorms cause debris flows on escarpments in hyperarid environments. In contrast with more temperate environments, there have been no direct observations on rainfall intensities and durations required for initiating debris flows in hyperarid environments. Here, we report rainfall volume and intensities, acquired by gauge and radar measurements, for two successive storms along the hyperarid (\textless50 mm/yr) western escarpment of the Dead Sea basin. These rainfall data were analyzed in conjunction with detailed mapping of debris flows that occurred during these storms to determine values of rainfall intensity and duration required to generate debris flows on the Dead Sea western escarpment. The first of the two analyzed storms occurred on 2 November 1995. During this storm, two convective cells rained sequentially within a 5 It period at the lower reaches of the Nahal David and the Nahal 'Arugot that dissects the western escarpment of the Dead Sea, Israel. This storm triggered debris flows in 38 small (\textless3 km(2)) and high-gradient drainage basins along the escarpment. Total rainfall volume and spatial distribution were determined by 10 cumulative rain gauges that were also used to calibrate rainfall-intensity distributions from radar data. For this storm, region, and landscape, rainfall intensities exceeding 30 mm/h for a duration of I h were required to initiate debris flows. A second storm in the same area on 1718 October 1997 allowed the evaluation of the results determined from the 1995 storm. In this second, more regional storm, maximum rainfall intensities were 19-27 mm/h for a duration of 45 min. These values, lower than the 30 mm/h minimal threshold defined in the previous storm, are consistent with the occurrence of only three debris flows. The small number of debris flows resulted from the concentration of the highest intensities of rainfall on the desert plateau and not directly on top of the canyon walls. Most first- to third-order basins draining the Dead Sea escarpment contain evidence of zero to three late Holocene (\textless3000 yr) debris flows. From analysis of the two storms, we propose that most of these debris flows were triggered by storms similar to the 2 November 1995 event in which localized convective cells had rainfall intensities of \textgreater30 mm/h and durations of at least 1 h. The small number of debris flows that has occurred during the late Holocene indicates that such events are rare at the scale of individual drainage basins.
Examines the Philonic midrash on the biblical construction of femininity in the figure of biblical character Sarah. Key issues concerning the nature and status of women in the Bible being raised by the story of Sarah; Interpretation of the relationship of Sarah with God; Allegorical exegesis of Sarah.
F Remacle, I WILLNER, and RD LEVINE. 2004. “Nanowiring by molecules.” JOURNAL OF PHYSICAL CHEMISTRY B, 108, Pp. 18129-18134. Abstract
Microelectronic sensors require the nanowiring of a selectively active site to an electrode. Different molecules can be used as the bridge that establishes the electrical communication. We report computational results for the current carried by molecules tethered between two gold clusters as a function of the overvoltage. The computations include the effect of the voltage at the ab initio level. The trends are consistent with the currents as measured by electrochemical means and suggest that the rate of charge migration can reach far higher values than measured given somewhat higher applied bias or the application of a gate voltage. The role of polarization of the molecular charge density by the applied voltage can be quite significant with definite propensity for the orientation of the molecular charge density with respect to the field. Conduction spectroscopy is therefore analogous to optical spectroscopy in strong laser fields where the field is not a weak probe but C dresses the system and can be used to control it.
We report on culturing of Aplysia neurons on porous silicon substrates. Good adhesion of the neurons to the porous silicon substrate and a formation of neuron-semiconductor contact have been accomplished. Cultured neurons survived for at least one week on porous silicon showing normal passive membrane properties and generation of action potentials. We have investigated the possibility of using the photoluminescence from porous silicon for transducing neuronal activity into photonic signals. We found that photoluminescence quenching occurs for cathodic current polarization using aqueous salt-based liquid solution contact. The quenching process is due to diffusion of electrons into the porous silicon, giving rise to Auger nonradiative recombination in the siliconnanocrystallites. The decay time of the photoluminescence was found to be relatively slow due to diffusive nature of the process.
Protein modification by ubiquitin has emerged as an important cellular regulatory mechanism. Recent studies illustrate the surprising ways in which polyubiquitin chains are manipulated in the regulation of NF-kappaB signaling.
A major limitation to clinical stem cell-mediated gene therapy protocols is the low levels of engraftment by transduced progenitors. We report that CXCR4 overexpression on human CD34+ progenitors using a lentiviral gene transfer technique helped navigate these cells to the murine bone marrow and spleen in response to stromal-derived factor 1 (SDF-1) signaling. Cells overexpressing CXCR4 exhibited significant increases in SDF-1-mediated chemotaxis and actin polymerization compared with control cells. A major advantage of CXCR4 overexpression was demonstrated by the ability of transduced CD34+ cells to respond to lower, physiologic levels of SDF-1 when compared to control cells, leading to improved SDF-1-induced migration and proliferation/survival, and finally resulting in significantly higher levels of in vivo repopulation of nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice including primitive CD34+/CD38(-/low) cells. Importantly, no cellular transformation was observed following transduction with the CXCR4 vector. Unexpectedly, we documented lack of receptor internalization in response to high levels of SDF-1, which can also contribute to increased migration and proliferation by the transduced CD34+ cells. Our results suggest CXCR4 overexpression for improved definitive human stem cell motility, retention, and multilineage repopulation, which could be beneficial for in vivo navigation and expansion of hematopoietic progenitors.
The purpose of this study was to develop a reliable and repeatable radiographic protocol for the measurement of joint angles in the standing dog, and to use this protocol to determine all standing joint angles for dogs over a wide range of body weights. The radiographic technique and the method of joint angle measurements were found to be highly repeatable, suggesting that the technique is reliable. Most joint angles did not vary between dogs of different weights. In those few instances where significant differences (p<0.05) were found, certain trends were followed and represent differences in conformation. This paper presents a complete description of the angles defining the position of the joints in a standing dog. This information is important for biomechanical studies, for clinical assessment of dogs, and for the design of surgical procedures such as arthrodesis.
The clinical use of stainless steel wire in veterinary orthopaedics is common, and occurs in diverse situations. One of the most common uses of stainless steel wire is the fabello-tibial suture to stabilize the cranial cruciate deficient knee (10). Numerous reports have appeared in the literature, describing biomechanical aspects of the use of stainless steel wire. The purpose of the study presented herein was to compare the strength and performance of two methods used to fasten loops of stainless steel wire: the traditional twist-knot method and the crimp-clamp method. Both loop-fastening methods were evaluated with two diameters of wire (1.0 mm and 1.2 mm). Both static and dynamic (cyclical) testing procedures were performed. Using a materials testing machine maximum tensile strength (load to failure), loop elongation, mode of loop failure and location of loop failure were recorded. The results of the study demonstrate that loops fastened with the crimp clamp method resulted in higher load to failure than the traditional twist knot method.
Bilateral external fixator frames ore frequently preferred over unilateral frames due to their superior rigidity. The objective of this study was to compare the biomechanical features of bilateral external fixators with those of unilateral external fixators that are combined with an intra-medullary pin. Three-dimensional, solid models were created of several unilateral and bilateral external fixator frames. The callus in the fracture gap was also modeled. Biomechanical analyses of all constructs were performed by the finite element method. This modeling approach allows the determination of stresses, displacements, and strains in the components of the various constructs, and thus the calculation of their relative stiffness. In addition, local shear strain values in the fracture gap, currently thought to be one of the deciding factors in the process of bone healing, can also be determined. The concept of equivalent stiffness modulus, which represents a weighed average stiffness of a construct to various loads, was defined. Using this concept, it was shown that when the intramedullary pin is well seated in the epiphyseal bone, the various unilateral frames have an equivalent stiffness modulus that is similar or even greater than that of bilateral frames with a similar arrangement of transcortical pins.
