212 research outputs found
Distribution of HLA-DPB1, -DQB1 -DQA1 alleles among Sardinian celiac patients.
The Sardinian population in many aspects differs from other Caucasoid populations, particularly for its degree of homogeneity. For this reason we have studied 50 adult Sardinian patients with celiac disease (CD) and 50 control healthy Sardinian individuals by RFLP analysis and by extensive oligotyping for 17 HLA-DPB 1, 8-DQB I and 9-DQA 1 alleles, and established their -DPB I alleles and -DQB I -DQA I genotypes. The heterodimer HLA-DQB 1 *0201/-DQA 1 *0501, present in 96% of our patients, is strongly associated with CD susceptibility, confirming published reports. On the other hand we found in 11 of 50 probands (22%) the presence of the allele -DQB 1 *05021 DQA1*0102. This genotype is extremely rare in other Caucasian populations and appears to confer limited protection in CD Sardinian patients
Primitive filtrations of the modules of invariant logarithmic forms of Coxeter arrangements
We define {\bf primitive derivations} for Coxeter arrangements which may not
be irreducible. Using those derivations, we introduce the {\bf primitive
filtrations} of the module of invariant logarithmic differential forms for an
arbitrary Coxeter arrangement with an arbitrary multiplicity. In particular,
when the Coxeter arrangement is irreducible with a constant multiplicity, the
primitive filtration has already been studied, which generalizes the Hodge
filtration introduced by K. Saito
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Automotive timing belt life laws and a user design guide
The paper presents a computer-based guide of the effect of layout and loading (tension and
torque) on the timing belt life and uses it to show the sensitivity of life to changed conditions in an
automotive camshaft drive. The predictions are in line with experience. The guide requires belt property
information, such as the tooth and tension member stiffness, the friction coefficient between the belt lands
and pulleys and the pitch difference from the pulley, in order to calculate the tooth deflections caused by
the belt loadings on the various pulleys in the layout. It also requires information on how the belt life
depends on the tooth deflections. Experimental data are presented on the life±deflection relations of a
commercial automotive timing belt tested between 100 and 140 8C, although the bulk of the data has been
obtained at 120 8C. Four different life laws have been found, depending on whether the failure-initiating
deflection occurred on a driver or a driven pulley, and whether at entry to or exit from the pulley.
Theoretical analysis of the tooth loading in the partial meshing state shows that, in three cases out of the
four, the different life±deflection laws transform to a single relation between the life and the tooth root
strain. The exception is failure caused by driven entry conditions; work is continuing to understand better
the causes of failure in this circumstanc
Did the Hilda collisional family form during the late heavy bombardment?
We model the long-term evolution of the Hilda collisional family located in
the 3/2 mean-motion resonance with Jupiter. Its eccentricity distribution
evolves mostly due to the Yarkovsky/YORP effect and assuming that: (i) impact
disruption was isotropic, and (ii) albedo distribution of small asteroids is
the same as for large ones, we can estimate the age of the Hilda family to be
. We also calculate collisional activity in the J3/2
region. Our results indicate that current collisional rates are very low for a
200\,km parent body such that the number of expected events over Gyrs is much
smaller than one.
The large age and the low probability of the collisional disruption lead us
to the conclusion that the Hilda family might have been created during the Late
Heavy Bombardment when the collisions were much more frequent. The Hilda family
may thus serve as a test of orbital behavior of planets during the LHB. We
tested the influence of the giant-planet migration on the distribution of the
family members. The scenarios that are consistent with the observed Hilda
family are those with fast migration time scales to
, because longer time scales produce a family that is depleted
and too much spread in eccentricity. Moreover, there is an indication that
Jupiter and Saturn were no longer in a compact configuration (with period ratio
) at the time when the Hilda family was created
Electronic and Vibrational Properties of PbI 2 : From Bulk to Monolayer
Using first-principles calculations, we study the dependence of the
electronic and vibrational properties of multi-layered PbI 2 crystals on the
number of layers and focus on the electronic-band structure and the Raman
spectrum. Electronic-band structure calculations reveal that the direct or
indirect semiconducting behavior of PbI 2 is strongly influenced by the number
of layers. We find that at 3L-thickness there is a direct-to-indirect band gap
transition (from bulk-to-monolayer). It is shown that in the Raman spectrum two
prominent peaks, A 1g and E g , exhibit phonon hardening with increasing number
of layers due to the inter-layer van der Waals interaction. Moreover, the Raman
activity of the A 1g mode significantly increases with increasing number of
layers due to the enhanced out-of-plane dielectric constant in the few-layer
case. We further characterize rigid-layer vibrations of low-frequency
inter-layer shear (C) and breathing (LB) modes in few-layer PbI 2 . A reduced
mono-atomic (linear) chain model (LCM) provides a fairly accurate picture of
the number of layers dependence of the low-frequency modes and it is shown also
to be a powerful tool to study the inter-layer coupling strength in layered PbI
2 .Comment: To appear in Phys. Rev.
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