Institutional frameworks powerfully determine the goals, violence, and trajectories of identitarian movements-including secessionist movements. However, both small-N and large-N researchers disagree on the question of whether ``power-sharing'' arrangements, instead of repression, are more or less likely to mitigate threats of secessionist mobilizations by disaffected, regionally concentrated minority groups. The PS-I modeling platform was used to create a virtual country ``Beita,'' containing within it a disaffected, partially controlled, regionally concentrated minority. Drawing on constructivist identity theory to determine behaviors by individual agents in Beita, the most popular theoretical positions on this issue were tested. Data were drawn from batches of hundreds of Beita histories produced under rigorous experimental conditions. The results lend support to sophisticated interpretations of the effects of repression vs. responsive or representative types of power-sharing. Although in the short run repression works to suppress ethnopolitical mobilization, it does not effectively reduce the threat of secession. Power-sharing can be more effective, but it also tends to encourage larger minority identitarian movements.
Olfactoric imagery is abundantly employed in the Bramhall-Hobbes controversy. I survey some examples and then turn to the possible significance of this. I argue that by forcing Hobbes into the figurative exchange Bramhall scores points in terms of moving the controversy into ground that is not covered by the limited view of rationality that Hobbes is committed to according to his rhetoric (at least as Bramhall perceives it). Bramhall clearly wants to move from cool argument to a more affluent rhetorical appeal. I argue that choosing such a richer epistemology coheres with Bramhall's deeper anxieties regarding the moral method used in the Leviathan. This essay thus deviates from other form-content analysis of Hobbes, in attempting to examine his rhetoric in practice, under the pressure of controversy. My more general concern is in relating seemingly formal polemical choices to moral concerns.
Currently available murine models to evaluate mesenchymal stem cell (MSC) differentiation are based on cell injection at ectopic sites such as muscle or skin. Due to the importance of environmental factors on the differentiation capacities of stem cells in vivo, we investigated whether the peculiar synovial/cartilaginous environment may influence the lineage specificity of bone morphogenetic protein (BMP)-2-engineered MSCs. To this aim, we used the C3H10T1/2-derived C9 MSCs that express BMP-2 under control of the doxycycline (Dox)-repressible promoter, Tet-Off, and showed in vitro, using the micropellet culture system that C9 MSCs kept their potential to differentiate toward chondrocytes. Implantation of C9 cells, either into the tibialis anterior muscles or into the joints of CB17-severe combined immunodeficient bg mice led to the formation of cartilage and bone filled with bone marrow as soon as day 10. However, no differentiation was observed after injection of naive MSCs or C9 cells that were repressed to secrete BMP-2 by Dox addition. The BMP-2-induced differentiation of adult MSCs is thus independent of soluble factors present in the local environment of the synovial/cartilaginous tissues. Importantly, we demonstrated that a short-term expression of the BMP-2 growth factor is necessary and sufficient to irreversibly induce bone formation, suggesting that a stable genetic modification of MSCs is not required for stem cell-based bone/cartilage engineering.
Evapn. of liq. drops contg. nanospheres resulted in circular deposition patterns. The circularity of the patterns depended on the uniformity of the surface tension on the substrate. By employing binary suspensions, contg. two differently sized nanospheres, it was possible to modulate the fine structure of such rings. Slow evapn. on mirror-polished substrates resulted in well-ordered distributions, where larger particles self-assembled in dense hexagonal packages, forming apparently an external ring, deposited around the massive inner ring. Deposition started at the air/liq./solid-contact line. Results could inspire principles for the fabrication of optical devices and may be fruitfully used to design biomaterials with cell-selective properties. A simple model is employed to predict the radial arrangement of nanospheres in rings. Deviations from a std. order (predicted by the model) may be useful to detect biol. active nanoparticles. [on SciFinder(R)]
A modification of the semi-empirical PM3 electronic structure method is proposed. It employs a coordinate scaling procedure, such that the harmonic frequencies from the modified PM3 potentials for lower-energy conformers of glycine (conformer 1), alanine (conformers I and 11) and proline (conformer 11), fit more closely with ab initio (MP2/DZP) harmonic frequencies. The anharmonic frequencies are then calculated using the modified PM3 surfaces with the Vibrational Self-Consistent Field (VSCF) and Correlation-Corrected VSCF (CC-VSCF) methods. The computed anharmonic frequencies are in very good accord with spectroscopic experiments for the three amino acids. The results are much superior to those obtained from standard (unscaled) PM3 potentials, indicating that the modified PM3 potentials may be used as high quality potentials for biological molecules, at least in the configuration ranges pertinent to vibrational spectroscopy. The scaling parameters computed for the lowest energy conformers listed above were tested for transferability: they were used in computing the anharmonic spectra of two other conformers (glycine 11 and proline 1). The good agreement of the resulting frequencies with observed frequencies, indicates the transferability of the scaling parameters. It is concluded from this study that the improved PM3 potentials offer accurate and computationally efficient force fields for vibrational spectroscopy calculations of biological molecules. Possible additional applications of the new potentials are discussed.
We have been able to determine the density of states map in the band gap of a semiconductor by the measurement of the phototransport properties of its majority and minority carriers. In particular we found that the carrier recombination in single-phase hydrogenated microcrystalline silicon ($μ$c-Si:H) is significantly different from the one in hydrogenated amorphous silicon (a-Si:H) and that it is controlled only by its two band tails. Th e comparison of the observed temperature dependence of the phototransport properties of this material with model simulations further suggests that, while the conduction-band tail has an exponential distribution of states, the valence-band-tail states have a Gaussian-like distribution. This, in turn, meets the challenge of the determination of the analytical shape of the density of states distribution from experimental data. Our experimental procedure implies then that this distribution is associated with the route through which the transport and phototransport take place and thus we conclude that both the recombination and transport in undoped single-phase $μ$c-Si:H take place in the disordered layer that wraps the crystallites. We further conclude that, from the transport and phototransport points of view, the single-phase $μ$c-Si:H is, in general, different from both polycrystalline silicon and a-Si:H. The polycrystalline-silicon-like behavior, when found, appears to be an asymptotic case in which the crystallites are large enough, while the a-Si:H behavior prevails only when there is a significant content of its phase within the system.
We present a simple statistical thermodynamic model for budding of viral nucleocapsids at the cell membrane. The membrane is modeled as a flexible lipid bilayer embedding linker (spike) proteins, which serve to anchor and thus wrap the membrane around the viral capsids. The free energy of a single bud is expressed as a sum of the bending energy of its membrane coat, the spike-mediated capsid-membrane adhesion energy, and the line energy associated with the bud's rim, all depending on the extent of wrapping (i.e., bud size), and density of spikes in the curved membrane. This self-energy is incorporated into a simple free energy functional for the many-bud system, allowing for different spike densities, and hence entropy, in the curved (budding) and planar membrane regions, as well as for the configurational entropy of the polydisperse bud population. The equilibrium spike densities in the coexisting, curved and planar, membrane regions are calculated as a function of the membrane bending energy and the spike-mediated adhesion energy, for different spike and nucleocapsid concentrations in the membrane plane, as well as for several values of the bud's rim energy. We show that complete budding (full wrapping of nucleocapsids) can only take place if the adhesion energy exceeds a certain, critical, bending free energy. Whenever budding takes place, the spike density in the mature virions is saturated, i.e., all spike adhesion sites are occupied. The rim energy plays an important role in determining the size distribution of buds. The fraction of fully wrapped buds increases as this energy increases, resulting eventually in an all-or-nothing mechanism, whereby nucleocapsids at the plasma membrane are either fully enveloped or completely naked (just touching the membrane). We also find that at low concentrations all capsids arriving at the membrane get tightly and fully enveloped. Beyond a certain concentration, corresponding approximately to a stoichiometric spike/capsid ratio, newly arriving capsids cannot be fully wrapped; i.e., the budding yield decreases.
Adult stem cells reside in adult tissues and serve as the source for their specialized cells. In response to specific factors and signals, adult stem cells can differentiate and give rise to functional tissue specialized cells. Adult mesenchymal stem cells (MSCs) have the potential to differentiate into various mesenchymal lineages such as muscle, bone, cartilage, fat, tendon and ligaments. Adult MSCs can be relatively easily isolated from different tissues such as bone marrow, fat and muscle. Adult MSCs are also easy to manipulate and expand in vitro. It is these properties of adult MSCs that have made them the focus of cell-mediated gene therapy for skeletal tissue regeneration. Adult MSCs engineered to express various factors not only deliver them in vivo, but also respond to these factors and differentiate into skeletal specialized cells. This allows them to actively participate in the tissue regeneration process. In this review, we examine the recent achievements and developments in stem-cell-based gene therapy approaches and their applications to bone, cartilage, tendon and ligament tissues that are the current focus of orthopedic medicine.
A mathematical, three-dimensional, anatomically accurate model of the canine knee was created to determine the forces in the knee ligaments and the kneejoint reaction forces during the stance phase of a slow walk. This quasi-static model considered both the tibio-femoral and patello-femoral articulations. The geometric and morphometric data of the hind limb were obtained from cadaver data. Muscle forces acting on the femur and the hip joint reaction force were determined by numerical optimization. Ligaments were modeled as non-linear-springs. Ligament material properties were obtained from the literature pertaining to the human knee. The model consists of -28 non-linear algebraic equations describing equilibrium of the femur and the patella, and geometric constraints. This system of equations was solved by a non-linear least-squares method. Results are presented for a knee with an intact cranial cruciate ligament (CCL) and for a knee with a ruptured CCL. Forces predicted to occur in the CCL by analysis of the model were found to be very similar to reported results of CCL forces measured in vivo in goats. (C) 2004 Elsevier Ltd. All rights reserved.
Objective-To report partial esophagectomy (PE) as a treatment for esophageal sarcoma in dogs.
Study Design-Retrospective study (2000-2002).
Animals-Six dogs with caudal thoracic esophageal tumors.
Methods-Medical records of 6 dogs that had surgical removal of esophageal tumors were reviewed. Signalment, medical history, physical examination results, complete blood count, surgical procedure, tumor classification, postoperative treatment, and complications were retrieved.
Results-Esophageal masses were approached by thoracotomy and esophagotomy on the side opposite the mass, removed with I cm margins by full thickness excision, and the defects closed with a single layer of interrupted sutures. All dogs recovered rapidly without major complications. Tumors were fibrosarcoma (3 dogs), undifferentiated sarcoma (1), and osteosarcoma (2). Five dogs were administered doxorubicin chemotherapy after surgery. Good quality of life was observed postoperatively in 5 dogs until deterioration necessitated euthanasia; survival ranged from 2-16 months. The remaining dog was alive, 20 months after surgery.
Conclusions-Partial esophagectomy and closure using I suture layer, was an effective, simple, and safe technique for removal of sarcomas of the distal thoracic esophagus.
Clinical Relevance Removal of esophageal masses by partial esophagectomy can be used reliably as a method of esophageal surgery. (C) Copyright 2004 by The American College of Veterinary Surgeons.
A wide variety of surgical techniques to stabilize the coxo-femoral joint have been described in the veterinary literature. In this paper twenty small animals (19 dogs and 1 cat) were treated successfully with open reduction and an extra-capsular suture taken between the greater trochanter of the femur and the origin of the rectus femoris muscle. The technique is simple, quick and safe, and avoids many of the potential complications associated with other methods.
The object of this study was to examine the effect of high intensity, short duration pulsed electromagnetic fields (PEMF) on the healing of full thickness skin wounds in rats. Full thickness skin wounds were surgically created in two groups of Sprague-Dawley male rats. The rats were randomly divided into two groups, each containing 20 rats. Animals in the treatment group received treatments with the PEMF device on day 0, 3, 7, 9, 12, 14, 17, and 22, while the rats in the control group were subjected to the same procedure, but with the PEMF device not activated. Photographs of the surgically created wounds were obtained on day 0, 3, 7, 9, 12, 14, 17, and 22. Wound contraction (WC), wound epithelialization (WE), non-healed wound, and contraction-epithelialization (CE) ratio were calculated for each wound. No significant difference was found between the two groups for the parameters of WC, WE, non-healed wound, and CE ratio. A significant group x time interaction was found for WE and CE ratio. This type of PEMF did not have a significantly beneficial effect on wound healing. Wounds in the PEMF treated group were relatively less contracted and showed a compensatory increase in epithelialization in the early stages of wound repair. (C) 2004 Wiley-Liss, Inc.
