37,416 research outputs found
The ALEPH Search for the Standard Model Higgs Boson
A search has been performed for the Standard Model Higgs boson in the data
collected with the ALEPH detector in 2000. An excess of 3 sigma above the
background expectation is found. The observed excess is consistent with the
production of the Higgs boson with a mass close to 114 GeV/c2.Comment: 5 pages, 5 figure
Temperature effects on material characteristics
Some of the physical properties of the main elements of interest in
high temperature technology are reviewed. Some general trends emerge
when these properties are viewed as a function of melting point, but there
are a few notable exceptions. Titanium, zirconium, niobium and tantalum
all have disappointingly low moduli; chromium is excellent in many ways,
but has a limited ductility at lower temperatures; molybdenum oxidises
catastrophically above about 700° C, and niobium suffers from severe
oxygen embrittlement. Beryllium and carbon (in the graphitic form) both
stand out as exceptional materials, both have very low densities, beryllium
a very high modulus but an unfortunately low ductility, while graphite has
a relatively low strength at the lower temperatures, although at temperatures
of 2000° C and above it emerges as a quite exceptional (and probably as the
ultimate) high temperature material. Some of the fundamental factors
involved in high temperature material development are examined, in the
light, particularly, of past progress with the nickel alloys. If a similar
progress can be achieved with other base elements then a considerable
margin still remains to be exploited. Protection from oxidation at high
temperatures is evidently a factor of major concern, not only with metals,
but with graphite also. Successful coatings are therefore of high importance and the questions they raise, such as bonding, differential thermal expansion,
and so on, represent aspects of an even wider class covered by the term
âcomposite structures". Such structures appear to offer the only serious
solution to many high temperature requirements, and their design,
construction and utilization has created a whole series of new exercises
in materials assessment. Matters have become so complex, that a very
radical and fundamental reassessment is required if we are to change, in
any very significant way, the wasteful and ad hoc methods which characterise
so much of present-day materials engineering
Preliminary Test of Prescribed Burning for Control of Maple Leaf Cutter (Lepidoptera: Incurvariidae)
Leaf litter burning in the spring resulted in 87.5% mortality of maple leaf cutter pupae, Paraclemensia acerifoliella (Fitch). No apparent damage was observed on sugar maple or beech trees within the burn area
PSD-95 Is Associated with the Postsynaptic Density and Not with the Presynaptic Membrane at Forebrain Synapses
PSD-95, a prominent protein component of the postsynaptic density (PSD) fraction from rat forebrain, has been localized by light microscopy to dendrites of hippocampal neurons (Cho et al., 1992) and to the presynaptic plexus of cerebellar basket cells (Kistner et al., 1993). Here we extend these studies to show that an affinity-purified antibody to PSD-95 labels the dendrites of most neurons in the forebrain and of a subset of neurons in the cerebellum. To confirm that PSD-95 is associated with the PSD at forebrain synapses and to clarify whether it is also associated with the presynaptic membrane, we employed immunogold electron microscopy of forebrain synaptosomes. Gold-labeled antibodies to PSD-95 labeled postsynaptic densities in both intact and lysed forebrain synaptosomes but did not label presynaptic terminals or the presynaptic membrane. The asymmetric distribution of PSD-95 at synapses contrasts with that of its homologs, disks-large and ZO-1, which are arranged symmetrically at septate and tight junctions, respectively
High power coupled CO2 waveguide laser array
A hollow-bore ridge waveguide technique for phase locking arrays of coupled CO2 rf excited waveguide lasers was demonstrated. Stable phase-locked operation of two- and three-channel arrays has been demonstrated at the 50 W output level. Preliminary experiments with a five-element array generated an output power of 95 W but phase-locked operation was not conclusively demonstrated
Some remarks on the isoperimetric problem for the higher eigenvalues of the Robin and Wentzell Laplacians
We consider the problem of minimising the th eigenvalue, , of
the (-)Laplacian with Robin boundary conditions with respect to all domains
in of given volume . When , we prove that the second
eigenvalue of the -Laplacian is minimised by the domain consisting of the
disjoint union of two balls of equal volume, and that this is the unique domain
with this property. For and , we prove that in many cases a
minimiser cannot be independent of the value of the constant in the
boundary condition, or equivalently of the volume . We obtain similar
results for the Laplacian with generalised Wentzell boundary conditions .Comment: 16 page
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