551,237 research outputs found
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Dynamic error characteristics of touch trigger probes used with coordinate measuring machines
This paper discusses the dynamic error characteristics of touch trigger probes used with coordinate measuring machines. During the investigation, a number of important parameters have been identified, including measurement speed, probe longitude, approach distance, probe latitude, stylus length/stylus tip diameter, probe orientation, operating mode (scanning and nonscanning), scan pitch, preload spring force (gauging force), probe type, and the surface approach angle. This paper presents the detailed experimental design and the results obtained from the systematic experiments. These results have led to some useful recommendations for the reduction of the probe dynamic errors. Some of these recommendations included the selection of the optimum measurement speed, the setting of the preload spring force, and the choice of the probe type
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Analysis of thermal-probe measurements using an iterative method to give sample conductivity and diffusivity data
The application of Microsoft Excel Solver routines to analyze data from a thermal probe placed in a number of samples is described. The successful application of the Solver routine to the thermal probe temperature time data requires the selection of an appropriate time interval. The various critical times are discussed and a method is proposed for selecting the appropriate Solver routine and the time interval over which the experimental data must be analyzed. Values of the sample thermal conductivity, the thermal diffusivity and the probe to sample conductance are reported for a stainless steel probe in unused mineral oil, and paraffin wax and for a copper probe in Magna904 and PTFE. The results for a commercial probe in agar agree with accepted data for water and the results for a clay-straw mixture demonstrates the method applied to a good insulator
Separable mechanisms underlying global feature-based attention
Feature-based attention is known to operate in a spatially global manner, in that the selection of attended features is not bound to the spatial focus of attention. Here we used electromagnetic recordings in human observers to characterize the spatiotemporal signature of such global selection of an orientation feature. Observers performed a simple orientation-discrimination task while ignoring task-irrelevant orientation probes outside the focus of attention. We observed that global feature-based selection, indexed by the brain response to unattended orientation probes, is composed of separable functional components. One such component reflects global selection based on the similarity of the probe with task-relevant orientation values ("template matching"), which is followed by a component reflecting selection based on the similarity of the probe with the orientation value under discrimination in the focus of attention ("discrimination matching"). Importantly, template matching occurs at similar to 150 ms after stimulus onset, similar to 80 ms before the onset of discrimination matching. Moreover, source activity underlying template matching and discrimination matching was found to originate from ventral extrastriate cortex, with the former being generated in more anterolateral and the latter in more posteromedial parts, suggesting template matching to occur in visual cortex higher up in the visual processing hierarchy than discrimination matching. We take these observations to indicate that the population-level signature of global feature-based selection reflects a sequence of hierarchically ordered operations in extrastriate visual cortex, in which the selection based on task relevance has temporal priority over the selection based on the sensory similarity between input representations
Dynamics of broken symmetry nodal and anti-nodal excitations in Bi_{2} Sr_{2} CaCu_{2} O_{8+\delta} probed by polarized femtosecond spectroscopy
The dynamics of excitations with different symmetry is investigated in the
superconducting (SC) and normal state of the high-temperature superconductor
BiSrCaCuO (Bi2212) using optical pump-probe (Pp)
experiments with different light polarizations at different doping levels. The
observation of distinct selection rules for SC excitations, present in A and B symmetries, and for the PG excitations, present in
A and B symmetries, by the probe and absence of any
dependence on the pump beam polarization leads to the unequivocal conclusion of
the existence of a spontaneous spatial symmetry breaking in the pseudogap (PG)
state
Searches for weakly produced SUSY at LHC
A summary of the different searches for weakly produced SUSY by both CMS and
ATLAS is presented here. A review on the methodology of these searches,
including event selection, background suppression and estimation methods, etc
is covered. Other searches at the LHC already probe squarks and gluino masses
up to 1.4 TeV, such scenario, may favour electroweak production of charginos
and neutralinos, that will produce many-lepton final states accompanied by
E and very little hadronic activity. Latest searches
include Higgs boson in the decay and exploits VBF associated production to
probe scenarios with very small mass splittings.Comment: 4 pages, 7 figures, conference proceeding
Testing the Rule with Exclusive Semi-Leptonic Kaon Decays
We consider the possibility of violations of the selection rule at an appreciable level in {\it exclusive} semi-leptonic decays of
Kaons. At -Factories, intense Kaon beams will be available and will probe
among others, the semi-leptonic decays and in addition
to and could provide novel testing grounds for the
rule. In particular, the branching ratio of is non-negligible
and could be used to probe new phenomena associated with the violation of this
selection rule. Furthermore, we modify certain di-lepton event rate ratios and
asymmetries and time asymmetries that have been constructed by Dass and Sarma
for di-lepton events from Beon decays to test the at the
, to the Kaon system at the . We find that the large
width of the relative to that of plays an important role in
enhancing some of the time asymmetries.Comment: 10 pages, Plain Latex, To be run twice
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Optimising the analysis of transcript data using high density oligonucleotide arrays and genomic DNA-based probe selection
Background: Affymetrix GeneChip arrays are widely used for transcriptomic studies in a diverse range of species. Each gene is represented on a GeneChip array by a probe-set, consisting of up to 16 probe-pairs. Signal intensities across probe-pairs within a probe-set vary in part due to different physical hybridisation characteristics of individual probes with their target labelled transcripts. We
have previously developed a technique to study the transcriptomes of heterologous species based
on hybridising genomic DNA (gDNA) to a GeneChip array designed for a different species, and subsequently using only those probes with good homology.
Results: Here we have investigated the effects of hybridising homologous species gDNA to study the transcriptomes of species for which the arrays have been designed. Genomic DNA from Arabidopsis thaliana and rice (Oryza sativa) were hybridised to the Affymetrix Arabidopsis ATH1 and Rice Genome GeneChip arrays respectively. Probe selection based on gDNA hybridisation
intensity increased the number of genes identified as significantly differentially expressed in two
published studies of Arabidopsis development, and optimised the analysis of technical replicates obtained from pooled samples of RNA from rice.
Conclusion: This mixed physical and bioinformatics approach can be used to optimise estimates of gene expression when using GeneChip arrays
Science aspects of a 1980 flyby of Comet Encke with a Pioneer spacecraft
Results are presented of an investigation of the feasibility of a 1980 flyby of Comet Encke using a Pioneer class spacecraft. Specific areas studied include: science objectives and rationale; science observables; effects of encounter velocity; science encounter and targeting requirements; selection and description of science instruments; definition of a candidate science payload; engineering characteristics of suggested payload; value of a separable probe; science instruments for a separable probe; science payload integration problems; and science operations profile
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