9,320 research outputs found
Selective data segment monitoring system
High speed data monitoring apparatus is described for displaying the bit pattern of a selected portion of a block of transmitted data comprising a shift register for receiving the transmitted data and for temporarily containing the consecutive data bits. A programmable sync detector for monitoring the contents of the shift register and for generating a sync signal when the shift register contains a predetermined sync code is included. A counter is described for counting the data bits input to the shift register after the sync signal is generated and for generating a count complete signal when a selected number of data bits have been input to the register. A data storage device is used for storing the contents of the shift register at the time the count complete signal is generated
High-speed data word monitor
Small, portable, self-contained device provides high-speed display of bit pattern or any selected portion of transmission, can suppress filler patterns so that display is not updated, and can freeze display so that specific event may be observed in detail
Natural convection with mixed insulating and conducting boundary conditions: low and high Rayleigh numbers regimes
We investigate the stability and dynamics of natural convection in two
dimensions, subject to inhomogeneous boundary conditions. In particular, we
consider a Rayleigh-B\`enard (RB) cell, where the horizontal top boundary
contains a periodic sequence of alternating thermal insulating and conducting
patches, and we study the effects of the heterogeneous pattern on the global
heat exchange, both at low and high Rayleigh numbers. At low Rayleigh numbers,
we determine numerically the transition from a regime characterized by the
presence of small convective cells localized at the inhomogeneous boundary to
the onset of bulk convective rolls spanning the entire domain. Such a
transition is also controlled analytically in the limit when the boundary
pattern length is small compared with the cell vertical size. At higher
Rayleigh number, we use numerical simulations based on a lattice Boltzmann
method to assess the impact of boundary inhomogeneities on the fully turbulent
regime up to
Patterned Irradiation of YBa_2Cu_3O_(7-x) Thin Films
We present a new experiment on YBa_2Cu_3O_{7-x} (YBCO) thin films using
spatially resolved heavy ion irradiation. Structures consisting of a periodic
array of strong and weak pinning channels were created with the help of metal
masks. The channels formed an angle of +/-45 Deg with respect to the symmetry
axis of the photolithographically patterned structures. Investigations of the
anisotropic transport properties of these structures were performed. We found
striking resemblance to guided vortex motion as it was observed in YBCO single
crystals containing an array of unidirected twin boundaries. The use of two
additional test bridges allowed to determine in parallel the resistivities of
the irradiated and unirradiated parts as well as the respective current-voltage
characteristics. These measurements provided the input parameters for a
numerical simulation of the potential distribution of the Hall patterning. In
contrast to the unidirected twin boundaries in our experiment both strong and
weak pinning regions are spatially extended. The interfaces between
unirradiated and irradiated regions therefore form a Bose-glass contact. The
experimentally observed magnetic field dependence of the transverse voltage
vanishes faster than expected from the numerical simulation and we interpret
this as a hydrodynamical interaction between a Bose-glass phase and a vortex
liquid.Comment: 7 pages, 8 Eps figures included. Submitted to PR
Thermo-elasticity for anisotropic media in higher dimensions
In this note we develop tools to study the Cauchy problem for the system of
thermo-elasticity in higher dimensions. The theory is developed for general
homogeneous anisotropic media under non-degeneracy conditions.
For degenerate cases a method of treatment is sketched and for the cases of
cubic media and hexagonal media detailed studies are provided.Comment: 33 pages, 5 figure
Ecological Observations on Predatory Coccinellidae (Coleoptera) in Southwestern Michigan
Ecological observations on habitat utilization by thirteen species of predatory Coccinellidae were made at a southern Michigan site during 1989 and 1990. Most of species were common during both years and used both agricul- tural and uncultivated habitats. Coccinella septempunctata and Coleomegilla maculata, were the most abundant in agricultural crops (alfalfa, maize, soy- bean and triticale), whereas Adalia bipunctata and Cycloneda munda, were the most abundant in deciduous and bushy habitats
Single-channel measurements of an N-acetylneuraminic acid-inducible outer membrane channel in Escherichia coli
NanC is an Escherichia coli outer membrane protein involved in sialic acid (Neu5Ac, i.e., N-acetylneuraminic acid) uptake. Expression of the NanC gene is induced and controlled by Neu5Ac. The transport mechanism of Neu5Ac is not known. The structure of NanC was recently solved (PDB code: 2WJQ) and includes a unique arrangement of positively charged (basic) side chains consistent with a role in acidic sugar transport. However, initial functional measurements of NanC failed to find its role in the transport of sialic acids, perhaps because of the ionic conditions used in the experiments. We show here that the ionic conditions generally preferred for measuring the function of outer-membrane porins are not appropriate for NanC. Single channels of NanC at pH 7.0 have: (1) conductance 100 pS to 800 pS in 100 mM: KCl to 3 M: KCl), (2) anion over cation selectivity (V (reversal) = +16 mV in 250 mM: KCl || 1 M: KCl), and (3) two forms of voltage-dependent gating (channel closures above ±200 mV). Single-channel conductance decreases by 50% when HEPES concentration is increased from 100 ?M: to 100 mM: in 250 mM: KCl at pH 7.4, consistent with the two HEPES binding sites observed in the crystal structure. Studying alternative buffers, we find that phosphate interferes with the channel conductance. Single-channel conductance decreases by 19% when phosphate concentration is increased from 0 mM: to 5 mM: in 250 mM: KCl at pH 8.0. Surprisingly, TRIS in the baths reacts with Ag|AgCl electrodes, producing artifacts even when the electrodes are on the far side of agar-KCl bridges. A suitable baseline solution for NanC is 250 mM: KCl adjusted to pH 7.0 without buffer
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