The effect of the convection coefficient on the temperature amplitude in periodic heat flow

The problem to be investigated in this thesis is that of periodic heat flow in a semi-infinite solid. Periodic flow means that heat flow is a continuous function of time and repeats itself at regular intervals. A semi-infinite solid is one which is bounded by one and only one plane. This subject has received considerable attention in the field of soil temperatures, both at the surface of the earth and at various depths. The surface of the earth is subjected to temperature changes which are nearly periodic. These temperature changes take place both daily and annually. A knowledge of these fluctuations is helpful in deciding such things as the depth at which water main will be out of danger of freezing. Its importance is not limited to problems on the earth\u27s soil. The subject has also received attention in the fields of heat flow in cylinder walls. It is of interest in the field of temperature stresses where these stresses are set up by expansions and contractions of the material subjected to cyclic temperatures. Because the analytical treatment becomes very involved in the more complex problems, these problems are usually attacked from the physical measurement standpoint. This particular subject was chosen by the author because thus far all analytical treatment has been on the basis of heat flow taking place by conduction alone. It is the object of this paper to investigate the feasibility of considering the effect of both convection and conduction on the flow of heat --Introduction, page 1-2

Effects of oxidative stress on Ascidia interrupta embryogenesis

Discussion: Oxidative stress does not affect very early development, which is consistent with the be prepared hypothesis (Epel, 2003). Two possible hypotheses could explain this result. The be prepared hypothesis suggests that very early embryos have static but short-lived anti-oxidant defensive mechanism in place, such as enzymes that neutralize hydrogen peroxide..

The Uniform Soybean Tests: Northern Region 2015

United States Department of Agriculture Agricultural Research Service, West Lafayette, Indiana, Cooperating with State Agricultural Experiment Stations, Northern States

Bottom-up Photonic Crystal Lasers

The directed growth of III–V nanopillars is used to demonstrate bottom-up photonic crystal lasers. Simultaneous formation of both the photonic band gap and active gain region is achieved via catalyst-free selective-area metal–organic chemical vapor deposition on masked GaAs substrates. The nanopillars implement a GaAs/InGaAs/GaAs axial double heterostructure for accurate, arbitrary placement of gain within the cavity and lateral InGaP shells to reduce surface recombination. The lasers operate single-mode at room temperature with low threshold peak power density of ~625 W/cm^2. Cavity resonance and lasing wavelength is lithographically defined by controlling pillar pitch and diameter to vary from 960 to 989 nm. We envision this bottom-up approach to pillar-based devices as a new platform for photonic systems integration

Serum Amyloid P Component (SAP)-Like Protein From Botryllid Ascidians Provides a Clue to Amyloid Function

The HA-1 lectin isolated from Botrylloides leachii has an amino acid composition similar to that of mammalian serum amyloid protein (SAP). SAP is a universal component of mammalian amyloid deposits. Like SAP, HA-1 has a disc ultrastructure, and antibody to HA-1 binds both (a) to amyloidlike fibers deposited between rejected Botrylloides colonies and (b) to cerebral amyloid deposits in Alzheimer's disease brains. Deposition of protochordate amyloid within rejection sites and surrounding fouling organisms implies that these fibers function as barriers to allogeneic and infectious challenge. Similarly, mammalian amyloid may also function to contain inflammatory lesions and to limit the spread of certain infections. Pathological amyloidotic conditions in humans, such as Alzheimer's disease, may result from unregulated expression of this primitive encapsulation response

Evidence for a Frozen Bed, Byrd Glacier, Antarctica

Ice thickness, computed within the fjord region of Byrd Glacier on the assumptions that Byrd Glacier is in mass-balance equilibrium and that ice velocity is entirely due to basal sliding, are on average 400 m less than measured ice thicknesses along a radio-echo profile. We consider four explanations for these differences: (1) active glacier ice is separated from a zone of stagnant ice near the base of the glacier by a shear zone at depth; (2) basal melting rates are some 8 m/yr; (3) internal shear occurs with no basal sliding in much of the region above the grounding zone; or (4) internal creep and basal sliding contribute to the flow velocity in varying proportions above the grounding zone. Large gradients of surface strain rate seem to invalidate the first explanation. Computed values of basal shear stress (140 to 200 kPa) provide insufficient frictional heat to melt the ice demanded by the second explanation. Both the third and fourth explanations were examined by making simplifying assumptions that prevented a truly quantitative evaluation of their merit. Nevertheless, there is no escaping the qualitative conclusion that internal shear contributes strongly to surface velocities measured on Byrd Glacier, as is postulated in both these explanations

The Uniform Soybean Tests: Northern Region 2016

United States Department of Agriculture Agricultural Research Service, West Lafayette, Indiana, Cooperating with State Agricultural Experiment Stations, Northern States

Ascidians of South Padre Island, Texas, with a Key to Species

The ascidians of South Padre Island, Texas were surveyed in August 2004. Because the subtidal area is limited to soft sediments, the survey was restricted to marina floats and pilings, harbor buoys, boat hulls and other artificial substrates which offer suitable attachment surfaces for ascidians. Fifteen species were documented, with multiple species representing each of the three orders of ascidians. None of the species found in this survey are native, suggesting they were all introduced through boat traffic. About half the species were found in a reproductive state, however, indicating that they have established local breeding populations

Biochemical and physiological characterization of the GTP-binding protein Obg of Mycobacterium tuberculosis

<p>Abstract</p> <p>Background</p> <p>Obg is a highly conserved GTP-binding protein that has homologues in bacteria, archaea and eukaryotes. In bacteria, Obg proteins are essential for growth, and they participate in spore formation, stress adaptation, ribosome assembly and chromosomal partitioning. This study was undertaken to investigate the biochemical and physiological characteristics of Obg in <it>Mycobacterium tuberculosis</it>, which causes tuberculosis in humans.</p> <p>Results</p> <p>We overexpressed <it>M. tuberculosis </it>Obg in <it>Escherichia coli </it>and then purified the protein. This protein binds to, hydrolyzes and is phosphorylated with GTP. An anti-Obg antiserum, raised against the purified Obg, detects a 55 kDa protein in immunoblots of <it>M. tuberculosis </it>extracts. Immunoblotting also discloses that cultured <it>M. tuberculosis </it>cells contain increased amounts of Obg in the late log phase and in the stationary phase. Obg is also associated with ribosomes in <it>M</it>. <it>tuberculosis</it>, and it is distributed to all three ribosomal fractions (30 S, 50 S and 70 S). Finally, yeast two-hybrid analysis reveals that Obg interacts with the stress protein UsfX, indicating that <it>M. tuberculosis </it>Obg, like other bacterial Obgs, is a stress related protein.</p> <p>Conclusions</p> <p>Although its GTP-hydrolyzing and phosphorylating activities resemble those of other bacterial Obg homologues, <it>M. tuberculosis </it>Obg differs from them in these respects: (a) preferential association with the bacterial membrane; (b) association with all three ribosomal subunits, and (c) binding to the stress protein UsfX, rather than to RelA. Generation of mutant alleles of Obg of <it>M. tuberculosis</it>, and their characterization in vivo, may provide additional insights regarding its role in this important human pathogen.</p