360 research outputs found
Investigation of the Unbalanced Magnetic Pull Damping Effect in Squirrel Cage Induction Machines
Evaluation of alpha-synuclein immunohistochemical methods for the detection of Lewy-type synucleinopathy in gastrointestinal biopsies
The observation showing that Lewy type synucleinopathy (LTS), the pathological hallmark of Parkinsonâs disease (PD), is found in the gut of almost all PD subjects led to a substantial amount of research to develop a diagnostic procedure in living patients based on endoscopically obtained gastrointestinal biopsies. However, the existing studies have provided conflicting results regarding the sensitivity and specificity of gastrointestinal biopsies for the detection of LTS. We therefore undertook a multi-center staining and blinded judging of a common set of slides from colonic biopsies to determine the optimal protocol for the detection of LTS. Four different immunohistochemical methods, developed in four separate expert laboratories, were evaluated for their sensitivity and specificity to detect enteric LTS. Test sets of formalin-fixed, paraffin-embedded sections from biopsies of 9 PD subjects and 3 controls were stained with the 4 methods and graded by 4 different observers. Four types of staining morphology (granular staining in the lamina propria, perivascular/vascular wall staining in the submucosa, lacy-granular pattern in the submucosa and epithelial cell nuclear staining) were variably observed in the slides stained by the 4 methods. Positive alpha-synuclein staining was observed by all 5 judges in most of the slides from control cases, regardless of the staining methods that were used. Moreover, none of the tested method or staining pattern had a specificity and sensitivity more than 80Â % regarding to PD. Overall, our study suggest that the tested methods are not adequate for the prediction of PD using gastrointestinal biopsies. Future studies are warranted to test new immunostaining methods
Theoretical predictions for the direct detection of neutralino dark matter in the NMSSM
We analyse the direct detection of neutralino dark matter in the framework of
the Next-to-Minimal Supersymmetric Standard Model. After performing a detailed
analysis of the parameter space, taking into account all the available
constraints from LEPII, we compute the neutralino-nucleon cross section, and
compare the results with the sensitivity of detectors. We find that sizable
values for the detection cross section, within the reach of dark matter
detectors, are attainable in this framework. For example, neutralino-proton
cross sections compatible with the sensitivity of present experiments can be
obtained due to the exchange of very light Higgses with m_{h_1^0}\lsim 70
GeV. Such Higgses have a significant singlet composition, thus escaping
detection and being in agreement with accelerator data. The lightest neutralino
in these cases exhibits a large singlino-Higgsino composition, and a mass in
the range 50\lsim m_{\tilde\chi_1^0}\lsim 100 GeV.Comment: Final version to appear in JHEP. References added. LaTeX, 53 pages,
23 figure
Postmortem examination of vascular lesions in cognitive impairment: A survey among neuropathological services
Background and Purpose - A full appreciation of the presence of cerebral vascular lesions in cognitively impaired patients can be ultimately reached at the neuropathological level. However, there are no detailed guidelines regarding what neuropathologists should look for at autopsy in cases of suspected vascular dementia or vascular cognitive impairment. We aimed at surveying the postmortem neuropathological procedures used in different centers in examining brain lesions of presumable or possible vascular origin in cognitively impaired patients. Methods - Thirteen laboratories participated in the survey by filling in a semistructured questionnaire. We reviewed sampling and histology procedures in use and the neuropathological definitions of some of these lesions. Neuropathological criteria for the definition of a vascular origin of the dementing process were also surveyed. Results - A large variability across centers was observed in the procedures used for the neuropathological examination and the histology techniques. Heterogeneity existed also in the definition of commonly found lesions (eg, white matter alterations, small vessel disease), interpretation of whether or not the lesions were reputed to be of vascular origin, and consequently in the interpretation of the cause of cognitive decline. Conclusions - The appreciation of the presence of neuropathologically verified vascular lesions in cognitively impaired cases may be heavily influenced by the laboratory tools used and also by the heterogeneity of the criteria applied in different centers. Harmonization of neuropathological procedures is badly needed in the field of vascular dementia and vascular cognitive impairment to better understand the association between various vascular lesions and clinical symptoms such as cognitive impairment
Fermion Masses and Mixing in Intersecting Branes Scenarios
We study the structure of Yukawa couplings in intersecting D6-branes wrapping
a factorizable 6-torus compact space T^6. Models with MSSM-like spectrum are
analyzed and found to fail in predicting the quark mass spectrum because of the
way in which the family structure for the left-handed, right-handed quarks and,
eventually, the Higgses is `factorized' among the different tori. In order to
circumvent this, we present a model with three supersymmetric Higgs doublets
which satisfies the anomaly cancellation condition in a more natural way than
the previous models, where quarks were not treated universally regarding their
branes assignments, or some particular branes were singled out being invariant
under orientifold projection. In our model, the family structures for the left,
right quarks, left leptons and the Higgses arise from one of the tori and can
naturally lead to universal strength Yukawa couplings which accommodate the
quark mass hierarchy and the mixing angles.Comment: 21 pages, latex, matches the Phys. Rev. D versio
Constraints on the Nucleon Strange Form Factors at Q^2 ~ 0.1 GeV^2
We report the most precise measurement to date of a parity-violating
asymmetry in elastic electron-proton scattering. The measurement was carried
out with a beam energy of 3.03 GeV and a scattering angle =6
degrees, with the result A_PV = -1.14 +/- 0.24 (stat) +/- 0.06 (syst) parts per
million. From this we extract, at Q^2 = 0.099 GeV^2, the strange form factor
combination G_E^s + 0.080 G_M^s = 0.030 +/- 0.025 (stat) +/- 0.006 (syst) +/-
0.012 (FF) where the first two errors are experimental and the last error is
due to the uncertainty in the neutron electromagnetic form factor. This result
significantly improves current knowledge of G_E^s and G_M^s at Q^2 ~0.1 GeV^2.
A consistent picture emerges when several measurements at about the same Q^2
value are combined: G_E^s is consistent with zero while G_M^s prefers positive
values though G_E^s=G_M^s=0 is compatible with the data at 95% C.L.Comment: minor wording changes for clarity, updated references, dropped one
figure to improve focu
Relating the CMSSM and SUGRA models with GUT scale and Super-GUT scale Supersymmetry Breaking
While the constrained minimal supersymmetric standard model (CMSSM) with
universal gaugino masses, m_{1/2}, scalar masses, m_0, and A-terms, A_0,
defined at some high energy scale (usually taken to be the GUT scale) is
motivated by general features of supergravity models, it does not carry all of
the constraints imposed by minimal supergravity (mSUGRA). In particular, the
CMSSM does not impose a relation between the trilinear and bilinear soft
supersymmetry breaking terms, B_0 = A_0 - m_0, nor does it impose the relation
between the soft scalar masses and the gravitino mass, m_0 = m_{3/2}. As a
consequence, tan(\beta) is computed given values of the other CMSSM input
parameters. By considering a Giudice-Masiero (GM) extension to mSUGRA, one can
introduce new parameters to the K\"ahler potential which are associated with
the Higgs sector and recover many of the standard CMSSM predictions. However,
depending on the value of A_0, one may have a gravitino or a neutralino dark
matter candidate. We also consider the consequences of imposing the
universality conditions above the GUT scale. This GM extension provides a
natural UV completion for the CMSSM.Comment: 16 pages, 11 figures; added erratum correcting several equations and
results in Sec.2, Sec.3 and 4 remain unaffected and conclusions unchange
Towards a resolution of the proton form factor problem: new electron and positron scattering data
There is a significant discrepancy between the values of the proton electric
form factor, , extracted using unpolarized and polarized electron
scattering. Calculations predict that small two-photon exchange (TPE)
contributions can significantly affect the extraction of from the
unpolarized electron-proton cross sections. We determined the TPE contribution
by measuring the ratio of positron-proton to electron-proton elastic scattering
cross sections using a simultaneous, tertiary electron-positron beam incident
on a liquid hydrogen target and detecting the scattered particles in the
Jefferson Lab CLAS detector. This novel technique allowed us to cover a wide
range in virtual photon polarization () and momentum transfer
() simultaneously, as well as to cancel luminosity-related systematic
errors. The cross section ratio increases with decreasing at . This measurement is consistent with the size of the form
factor discrepancy at GeV and with hadronic calculations
including nucleon and intermediate states, which have been shown to
resolve the discrepancy up to GeV.Comment: 6 pages, 4 figures, submitted to PR
Photoproduction of K+Kâ meson pairs on the proton
The exclusive reaction ÎłpâpK+Kâ was studied in the photon energy range 3.0â3.8ââGeV and momentum transfer range 0.6<ât<1.3ââGeV2. Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility. In this kinematic range the integrated luminosity was approximately 20ââpbâ1. The reaction was isolated by detecting the K+ and the proton in CLAS, and reconstructing the Kâ via the missing-mass technique. Moments of the dikaon decay angular distributions were extracted from the experimental data. Besides the dominant contribution of the Ï meson in the P wave, evidence for SâP interference was found. The differential production cross sections dÏ/dt for individual waves in the mass range of the Ï resonance were extracted and compared to predictions of a Regge-inspired model. This is the first time the t-dependent cross section of the S-wave contribution to the elastic K+Kâ photoproduction has been measured
Demonstration of a novel technique to measure two-photon exchange effects in elastic scattering
The discrepancy between proton electromagnetic form factors extracted using
unpolarized and polarized scattering data is believed to be a consequence of
two-photon exchange (TPE) effects. However, the calculations of TPE corrections
have significant model dependence, and there is limited direct experimental
evidence for such corrections. We present the results of a new experimental
technique for making direct comparisons, which has the potential to
make precise measurements over a broad range in and scattering angles. We
use the Jefferson Lab electron beam and the Hall B photon tagger to generate a
clean but untagged photon beam. The photon beam impinges on a converter foil to
generate a mixed beam of electrons, positrons, and photons. A chicane is used
to separate and recombine the electron and positron beams while the photon beam
is stopped by a photon blocker. This provides a combined electron and positron
beam, with energies from 0.5 to 3.2 GeV, which impinges on a liquid hydrogen
target. The large acceptance CLAS detector is used to identify and reconstruct
elastic scattering events, determining both the initial lepton energy and the
sign of the scattered lepton. The data were collected in two days with a
primary electron beam energy of only 3.3 GeV, limiting the data from this run
to smaller values of and scattering angle. Nonetheless, this measurement
yields a data sample for with statistics comparable to those of the
best previous measurements. We have shown that we can cleanly identify elastic
scattering events and correct for the difference in acceptance for electron and
positron scattering. The final ratio of positron to electron scattering:
for GeV and
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