Asymptotics of a small liquid drop on a cone and plate rheometer

A cone and a plate rheometer is a laboratory apparatus used to measure the viscosity and other related parameters of a non-Newtonian liquid subject to an applied force. A small drop, of order millimetres, of the liquid is located between the horizontal plate and the shallow cone of the rheometer. Rotation of the cone ensues, the liquid begins to flow and the plate starts to rotate. Liquid parameters are inferred based on the difference in the applied rotational force and the resulting rotational force of the plate. To describe the flow of the drop, the initial drop configuration, before rotation commences, must be determined. The equilibrium drop profile is given by the solution to the well-known nonlinear Young-Laplace equation. We formulate asymptotic solutions for the drop profile based on the small Bond number. The modelling of the drop exhibits a rich asymptotic structure consisting of five distinct scalings which are resolved via the method matched asymptotics

Strangeness contribution to the vector and axial form factors of the nucleon

The strangeness contribution to the vector and axial form factors of the nucleon is presented for momentum transfers in the range $0.45<Q^2<1.0$ GeV$^2$. The results are obtained via a combined analysis of forward-scattering parity-violating elastic $\vec{e}p$ asymmetry data from the $G^0$ and HAPPEx experiments at Jefferson Lab, and elastic $\nu p$ and $\bar{\nu} p$ scattering data from Experiment 734 at Brookhaven National Laboratory. The parity-violating asymmetries measured in elastic $\vec{e}p$ scattering at forward angles establish a relationship between the strange vector form factors $G_E^s$ and $G_M^s$, with little sensitivity to the strange axial form factor $G_A^s$. On the other hand, elastic neutrino scattering at low $Q^2$ is dominated by the axial form factor, with still some significant sensitivity to the vector form factors as well. The combination of the two data sets allows the simultaneous extraction of $G_E^s$, $G_M^s$, and $G_A^s$ over a significant range of $Q^2$ for the very first time.Comment: 3 pages, 1 figure, will appear in AIP Conference Proceedings for PANIC 200

Guidelines for fabrication of hybrid microcircuits

Document is summary of approaches that may be taken in designing hybrid microcircuits similar to those for aerospace application

Far-infrared rotational emission by carbon monoxide

Accurate theoretical collisional excitation rates are used to determine the emissivities of CO rotational lines 10 to the 4th power/cu cm n(H2), 100 K T 2000 K, and J 50. An approximate analytic expression for the emissitivities which is valid over most of this region is obtained. Population inversions in the lower rotational levels occur for densities n(H2) approximately 10 (to the 3rd to 5th power)/cu cm and temperatures T approximately 50 K. Interstellar shocks observed edge on are a potential source of millimeter wave CO maser emission. The CO rotational cooling function suggested by Hollenbach and McKee (1979) is verified, and accurate numerical values given. Application of these results to other linear molecules should be straightforward

The shape of a small liquid drop on a cone and plate rheometer

We construct asymptotic solutions for the shape of a small liquid sessile drop in a cone and plate rheometer. The approximation is based on small Bond number or, equivalently, on a characteristic length scale which is much smaller than the capillary length. The drop has a complicated asymptotic structure, consisting of five separate scalings, which is resolved using the method of matched asymptotic expansions. We find that the presence of a substrate above (and below) the drop gives rise to qualitatively new drop configurations

Strange Quark Contribution to the Vector and Axial Form Factors of the Nucleon: Combined Analysis of G0, HAPPEx, and Brookhaven E734 Data

The strange quark contribution to the vector and axial form factors of the nucleon has been determined for momentum transfers in the range $0.45<Q^2<1.0$ GeV$^2$. The results are obtained via a combined analysis of forward-scattering, parity-violating elastic $\vec{e}p$ asymmetry data from the G0 and HAPPEx experiments at Jefferson Lab, and elastic $\nu p$ and $\bar{\nu} p$ scattering data from Experiment 734 at Brookhaven National Laboratory. The parity-violating asymmetries measured in elastic $\vec{e}p$ scattering at forward angles establish a relationship between the strange vector form factors $G_E^s$ and $G_M^s$, with little sensitivity to the strange axial form factor $G_A^s$. On the other hand, elastic neutrino scattering at low $Q^2$ is dominated by the axial form factor, with some significant sensitivity to the vector form factors as well. Combination of the two data sets allows the simultaneous extraction of $G_E^s$, $G_M^s$, and $G_A^s$ over a significant range of $Q^2$ for the very first time. The $Q^2$-dependence of the strange axial form factor suggests that the strange quark contribution to the proton spin, $\Delta s$, is negative.Comment: 21 pages, 2 figures, 6 tables, 63 references; revised to fix minor typos and to add a missing reference; to be submitted to Physical Review

The Formation of the First Stars II. Radiative Feedback Processes and Implications for the Initial Mass Function

We consider the radiative feedback processes that operate during the formation of the first stars, including the photodissociation of H_2, Ly-alpha radiation pressure, formation and expansion of an HII region, and disk photoevaporation. These processes may inhibit continued accretion once the stellar mass has reached a critical value, and we evaluate this mass separately for each process. Photodissociation of H_2 in the local dark matter minihalo occurs relatively early in the growth of the protostar, but we argue this does not affect subsequent accretion since by this time the depth of the potential is large enough for accretion to be mediated by atomic cooling. However, neighboring starless minihalos can be affected. Ionization creates an HII region in the infalling envelope above and below the accretion disk. Ly-alpha radiation pressure acting at the boundary of the HII region is effective at reversing infall from narrow polar directions when the star reaches ~20-30Msun, but cannot prevent infall from other directions. Expansion of the HII region beyond the gravitational escape radius for ionized gas occurs at masses ~50-100Msun, depending on the accretion rate and angular momentum of the inflow. However, again, accretion from the equatorial regions can continue since the neutral accretion disk has a finite thickness and shields a substantial fraction of the accretion envelope from direct ionizing flux. At higher stellar masses, ~140Msun in the fiducial case, the combination of declining accretion rates and increasing photoevaporation-driven mass loss from the disk act to effectively halt the increase in the protostellar mass. We identify this process as the mechanism that terminates the growth of Population III stars... (abridged)Comment: 31 pages, including 10 figures, accepted to Ap

Two-component model of the interaction of an interstellar cloud with surrounding hot plasma

We present a two-component gasdynamic model of an interstellar cloud embedded in a hot plasma. It is assumed that the cloud consists of atomic hydrogen gas, interstellar plasma is quasineutral. Hydrogen atoms and plasma protons interact through a charge exchange process. Magnetic felds and radiative processes are ignored in the model. The influence of heat conduction within plasma on the interaction between a cloud and plasma is studied. We consider the extreme case and assume that hot plasma electrons instantly heat the plasma in the interaction region and that plasma flow can be described as isothermal. Using the two-component model of the interaction of cold neutral cloud and hot plasma, we estimate the lifetime of interstellar clouds. We focus on the clouds typical for the cluster of local interstellar clouds embedded in the hot Local Bubble and give an estimate of the lifetime of the Local interstellar cloud where the Sun currently travels. The charge transfer between highly charged plasma ions and neutral atoms generates X-ray emission. We assume typical abundance of heavy ions for the Local Bubble plasma and estimate the X-ray emissivity due to charge exchange from the interface between cold neutral cloud and hot plasma. Our results show that charge exchange X-ray emission from the neutral-plasma interfaces can be a non-negligible fraction of the observed X-ray emission.Comment: 9 pages, 7 figure

Alcohol increases circulatory disease mortality in Russia: acute and chronic effects or misattribution of cause?

Background There is a consensus that the large fluctuations in mortality seen in Russia in the past two decades can be attributed to trends in alcohol consumption. However, the precise mechanisms linking alcohol to mortality from circulatory disease remain unclear. It has recently been argued that a substantial number of such deaths currently ascribed to cardiovascular disorders are misclassified cases of acute alcohol poisoning

Factors and issues surrounding development of one community college baccalaureate degree program

The purpose of this study is to describe the factors and issues surrounding development of one community college baccalaureate degree program, the three-year Bachelor of Manufacturing Technology at Westark College in Arkansas. This study probes three primary movements at play in the Westark baccalaureate program, which was developed to respond to industry demands. First, and most obvious, this new program proposes that the community college expand its mission to include baccalaureate programs. Second, the Westark program is based on the demonstration of student mastered competencies. Finally, the Westark baccalaureate attempts to integrate the general education requirement into the competency-based curriculum. Individually, these threads are relatively untested. Combining these components into one degree program is a relatively new concept. The intent of this inquiry was not an evaluation of the Westark Bachelor of Manufacturing Technology degree program. What the researcher hoped to accomplish was to uncover the salient factors and issues related to the development of this new program. What was gained through this process is an understanding of how one community college baccalaureate was established, including identifying important themes. Several issues have been described from the interviews and ongoing document search that should be useful for future studies of the community college baccalaureate. Furthermore, the study clearly implies that curricula supporting student master competencies is an entirely different direction of inquiry that is perhaps even more essential than the study of the community college baccalaureate. Whether or not the Westark baccalaureate will be unique to Fort Smith, Arkansas remains to be seen. Other community colleges may attempt to adopt the Westark College model. Lining up the social, economic, political, and pedagogical forces to expand the community college degree offerings to include a baccalaureate that includes integrated student master competencies could be difficult. However, Westark College has provided a model for other community colleges that may currently, or in the future, be considering a bachelor degree program