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Notes: Flows under the influences of environmental rotation and stable density stratification often exhibit an approximate force balance and a consequently slow rate of evolution at large Reynolds number. Such flows are typically anisotropic in their velocity field. This regime is relevant to large-scale motions in the Earth's atmosphere and ocean, as well as many other planetary and astrophysical systems. The Balance Equations are usually an accurate approximate model for this regime. However, they have solvability limits associated with a change of type in their time-integration operator. In this paper we derive these limiting conditions for the conservative Balance Equations in isentropic coordinates, show that the least familiar of these conditions coincides with loss of convexity of the streamfunction for horizontal velocity in the inertial reference frame, and identify these conditions with the general conditions for symmetric loss of stability for circular and parallel flows as well as for the three-dimensional loss of stability for elliptical flows. We then conjecture that the identified limits of balance coincide generally with the boundary between the distinctive nonlinear dynamical behaviors (i.e., their turbulent cascade and dissipation rates) associated with the large- and small-scale regimes in geophysical and astrophysical flows. © 1998 American Institute of Physics.

Notes: Large-scale flows in the atmosphere and ocean are usually in a state of approximate momentum balance, the simplest form of which is geostrophy. Furthermore, balanced models have often been shown to be quite accurate in this regime, with the quasigeostrophic equations the simplest such model and the balance equations a more accurate one, even though such models exclude the rapidly oscillatory, unbalanced dynamics of acoustic, gravitational, and inertial oscillations. However, this behavior is not universal, and here we investigate the fluid dynamics on one of the margins of this regime. We solve for linearized, inviscid fluctuations about a horizontal shear flow with spatially uniform vorticity and strain rate in a rotating, stratified, incompressible fluid, without making any balanced approximations. In both parallel and elliptical shear flows, we find that a significant increase occurs in the growth of unbalanced fluctuations near the violation of a necessary condition for the time integrability of the balance equations. This condition is that the absolute vertical vorticity everywhere exceeds the modulus of the horizontal strain rate. Thus, we seemingly have found a new boundary to the regime of large-scale dynamics, with its approximate gradient-wind balance, anisotropic velocity field, and mostly "slow-manifold" evolutionary behavior. © 1998 American Institute of Physics.

Notes: The purpose of this study was to determine whether oral immunization of ferret kits with a whole-cell sonicate of Helicobacter mustelae lysate (Hml) and the adjuvant muramyl dipeptide (MDP) would reduce the incidence of natural colonization with H. mustelae and the extent of Helicobacter-associated gastritis by enhancing the host mucosal immune response.〈section xml:id="abs1-2"〉〈title type="main"〉Materials and Methods.Between the ages of 4 and 11 weeks, 44 ferret kits were gavaged with Hml and various doses of MDP. The extent of gastritis and duodenitis and the immune response to H. mustelae were evaluated.〈section xml:id="abs1-3"〉〈title type="main"〉Results.All kits became colonized naturally with H. mustelae and the majority developed mild to severe gastritis and duodenitis. Kits that received Hml with MDP developed significantly greater inflammation of the gastric antrum and duodenum, as compared to kits vaccinated with Hml alone. Vaccination with Hml and 50 μg of MDP was associated with severe lesions in the proximal duodenum characterized by accumulation of mononuclear inflammatory cells, mucosal erosion, and ulceration. Although serum antibody specific for H. mustelae in 4-week-old kits was approximately 50% of adult levels, a finding attributable to passively acquired maternal antibody, both systemic and mucosal antibody levels became depressed over time despite oral vaccination. The humoral immune response was sufficiently low to prevent detection of any significant dose effect of MDP on antibody levels among experimental groups.〈section xml:id="abs1-4"〉〈title type="main"〉Conclusions.Oral vaccination of young ferrets with Hml and 50 μg MDP increased the risk of Helicobacter-associated mucosal ulceration in the proximal duodenum, which was associated with low humoral (but significant cell-mediated) immune responses to H. mustelae. In retrospect, the frequency of vaccination may have suppressed the systemic humoral immune response, thereby promoting mucosal damage by H. mustelae. The 50-μg dose of MDP enhanced the cell-mediated immune response, which indirectly contributed to development of severe lesions. The increased frequency of mucosal damage associated with this vaccination regimen enhances the value of the ferret model for studying duodenal ulceration secondary to Helicobacter infection.

Notes: The growth morphology of large YBa2Cu3O7−δ grains during peritectic solidification has been reported to be responsible for the generation of processing defects, such as platelets, and an inhomogeneous distribution of 211 particles, both of which influence significantly the superconducting properties of the fully processed material. The present study demonstrates both experimentally and theoretically the formation of local dendrites at macroscopically planar YBa2Cu3O7−δ growth fronts which propagate along different crystallographic directions and identifies these as key growth features of the peritectic solidification process.

Notes: Abstract: Comparisons of the activity of the G protein-mediated phosphoinositide signal transduction system and of G protein levels were made in two regions of frontal cortex from eight schizophrenic, alcohol-dependent, and control subjects. G protein-mediated phosphoinositide hydrolysis was measured by stimulating cortical membranes incubated with [3H]phosphatidylinositol with 0.3–10 µM guanosine 5′-O-(3-thio)triphosphate (GTPγS). In frontal cortex areas 8/9, GTPγS-induced phosphoinositide hydrolysis was 50% greater in schizophrenic than control or alcohol-dependent subjects, whereas there were no differences among these groups of subjects in the response to GTPγS in frontal cortex area 10. Agonists for dopaminergic, cholinergic, purinergic, serotonergic, histaminergic, and glutamatergic receptors coupled to the phosphoinositide signaling system increased [3H]phosphatidylinositol hydrolysis in a GTPγS-dependent manner. Responses to most agonists were similar in all three subject groups in both cortical regions, with the largest difference being a 40% greater response to dopaminergic receptor stimulation in frontal cortex 8/9 from schizophrenic subjects. Measurements of the levels of phospholipase C-β, and of α-subunits of Gq, Go, Gi1, Gi2, and Gs, made by immunoblot analyses revealed no differences among the groups of subjects except for increased Gαo in schizophrenic subjects and increased Gαo and Gαi1 in alcohol-dependent subjects. These results demonstrate that schizophrenia is associated with increased activity of the phosphoinositide signal transduction system and increased levels of Gαo, whereas the phosphoinositide system was unaltered in alcohol dependence, but Gαo and Gαi1 were increased.

Notes: This work develops two techniques for optically probing the spatial profile of microwave frequency superconducting currents. As an application, we measured the effects of high microwave powers on the spatial distribution of current on coplanar superconducting transmission lines fabricated using YBa2Cu3O7−δ and Tl2Ba2CaCu2O8. For both techniques, a focused light-spot served as the spatial probe whose effect was measured through the change in transmitted microwave power. For resonant geometries, the change was due to the kinetic-inductance bolometric effect; for nonresonant geometries, the change was due to the resistive-transition bolometric effect. Kinetic-inductance photoresponse measurements were acquired by setting the microwave frequency on the shoulder of a resonance and measuring the change in the microwave power transmitted through the device that occurred when the absorption of light shifted the frequency of the resonance. These kinetic-inductance measurements were performed as a function of microwave power on a YBa2Cu3O7−δ coplanar device at 74 K and on a Tl2Ba2CaCu2O8 coplanar device at 80 K. Because the photoresponse in this technique is proportional to the square of the local current density underneath the light spot (as opposed to directly proportional), this technique is sensitive to current redistribution on length scales much smaller than the ∼6 μm spatial resolution of our measurements. Extrinsic (defect and grain boundary associated) and intrinsic photoresponses were measured. Both coplanar samples showed no change in the intrinsic spatial distribution of the current as the microwave power was varied. At all temperatures the Tl2Ba2CaCu2O8 sample exhibited substantial extrinsic spatial variations on a distance scale equal to the film's ∼5 μm grain size; these spatial variations became more dramatic as the temperature T approached the critical temperature Tc. The spatial variations for the finer-grained YBa2Cu3O7 sample were much less pronounced. Behavior consistent with Tc being several degrees lower at the film edges was observed as T approached Tc; the edge-current photoresponse started to narrow, increase faster than linearly with light power, and move away from the film edges toward the center of the strip; lowering the light power lessened these effects. Resistive-bolometric photoresponse measurements performed at temperatures within the resistive transition exhibited the same light power effects near Tc. The kinetic-inductance photoresponse can also be used as a probe of the local quality of unpatterned superconducting films; for this usage an unpatterned film serves as one wall of a resonant cavity and a focused light beam is scanned through the transparent substrate onto the underside of the superconducting film while monitoring the shift in the cavity resonance. © 1998 American Institute of Physics.

Notes: Superconductors can in theory be used to detect rotation by Josephson interference or by detection of the London field, a magnetic induction that fills the interior of any rotating bulk superconductor. One might hope to use these properties of superconductors to build a practical inertial guidance gyroscope. A problem arises from the necessity of surrounding the device with superconducting magnetic shielding: the London field generated by a co-rotating shield eliminates the response of the superconducting device within the shield. The present article demonstrates this point more rigorously than has been done before, discussing solutions of Ampère's law for rotating and nonrotating superconductors and paying careful attention to boundary conditions. Beginning with a supercurrent density derivable from either the Ginzburg-Landau or the London theory of superconductivity, the article shows: 1) that a superconducting device cannot distinguish between rotation and an applied magnetic field: 2) that a superconducting device surrounded by a co-rotating superconducting shield cannot detect rotation. The term "superconducting gyroscope" in this article refers only to a device whose working principle is the response of the superconductor itself to rotation, not to any device in which superconducting electronic components are used to detect some other effect. © 1997 American Institute of Physics.

Notes: We have constructed an ultrahigh vacuum scanning tunneling microscope (STM) for operation in the temperature range 20–300 K. The design consists of a vibration isolated sample holder mounted on a continuous flow cryostat. By rotation and linear motion of the cryostat, the sample can be positioned in front of various surface preparation and analysis instruments contained in a single vacuum chamber. A lightweight beetle-type STM head is lowered from the top onto the sample by a linear manipulator. To minimize helium convection in the cryostat, the entire vacuum system, including a liquid helium storage Dewar, can be tilted by a few degrees perpendicular to the cryostat axis, which improves the operation. The performance of the instrument is demonstrated by atomically resolved images of the Pd(111) surface and adsorbed CO molecules. © 1997 American Institute of Physics.