10,200 research outputs found
Test fixture insures high degree of accuracy in flexure tests
Modified die set improves accuracy in load application, minimizes problems of parallelism, and eliminates testing errors normally encountered during flexure tests. Test results are given for a comparison test of the old and new fixtures
Compaction of anisotropic granular materials : experiments and simulations
We present both experimental and numerical investigations of compaction in
granular materials composed of rods. As a function of the aspect ratio of the
particles, we have observed large variations of the asymptotic packing volume
fraction in vertical tubes. The relevant parameter is the ratio between the rod
length and the tube diameter . Even the compaction dynamics remains
unchanged for various particle lengths, a 3d/2d phase transition for grain
orientations is observed for . A toy model for the compaction of
needles on a lattice is also proposed. This toy model gives a complementary
view of our experimental results and leads to behaviors similar to experimental
ones.Comment: 5 pages, 10 figure
On the existence of bounded solutions for a nonlinear elliptic system
This work deals with the system , with Dirichlet boundary condition in a domain \Omega\subset\RR^n,
where is a ball if or a smooth perturbation of a ball when
.
We prove that, under appropriate conditions on the parameters
(), any non-negative solution of the system is bounded by
a constant independent of . Moreover, we prove that the conditions are
sharp in the sense that, up to some border case, the relation on the parameters
are also necessary.
The case was considered by Souplet in \cite{PS}. Our paper generalize
to the results of that paper
Experimental study of the compaction dynamics for 2D anisotropic granular materials
We present an experimental study of the compaction dynamics for
two-dimensional anisotropic granular systems. Compaction dynamics is measured
at three different scales : (i) the macroscopic scale through the packing
fraction , (ii) the mesoscopic scale through both fractions of aligned
grains and ideally ordered grains , and (iii) the
microscopic scale through both rotational and translational grain mobilities
. The effect of the grain rotations on the compaction dynamics has
been measured. At the macroscopic scale, we have observed a discontinuity in
the late stages of the compaction curve. At the mesoscopic scale, we have
observed the formation and the growth of domains made of aligned grains. From a
microscopic point of view, measurements reveal that the beginning of the
compaction process is essentially related to translational motion of the
grains. The grains rotations drive mainly the process during the latest stages
of compaction.Comment: 8pages, 11 figure
Efficient vasculature investment in tissues can be determined without global information
Cells are the fundamental building blocks of organs and tissues. Information and mass flow through cellular contacts in these structures is vital for the orchestration of organ function. Constraints imposed by packing and cell immobility limit intercellular communication, particularly as organs and organisms scale up to greater sizes. In order to transcend transport limitations, delivery systems including vascular and respiratory systems evolved to facilitate the movement of matter and information. The construction of these delivery systems has an associated cost, as vascular elements do not perform the metabolic functions of the organs they are part of. This study investigates a fundamental trade-off in vascularization in multicellular tissues: the reduction of path lengths for communication versus the cost associated with producing vasculature. Biologically realistic generative models, using multicellular templates of different dimensionalities, revealed a limited advantage to the vascularization of two-dimensional tissues. Strikingly, scale-free improvements in transport efficiency can be achieved even in the absence of global knowledge of tissue organization. A point of diminishing returns in the investment of additional vascular tissue to the increased reduction of path length in 2.5- and three-dimensional tissues was identified. Applying this theory to experimentally determined biological tissue structures, we show the possibility of a co-dependency between the method used to limit path length and the organization of cells it acts upon. These results provide insight as to why tissues are or are not vascularized in nature, the robustness of developmental generative mechanisms and the extent to which vasculature is advantageous in the support of organ function
Radial Solutions for Hamiltonian Elliptic Systems with Weights
We prove the existence of infinitely many radial solutions for elliptic
systems in Rn with power weights. A key tool for the proof will be a weighted
imbedding theorem for fractional-order Sobolev spaces, that could be of
independent interest.Comment: 13 page
In Vitro Embryo Production in Water Buffalo
In vitro embryo production (IVEP) is a promising tool with many applications in producing calves from genetically superior animals desired for propagation and in the conservation and revival of endangered species. The techniques of IVEP were adopted from cattle and refined to suit the water buffalo requirements. From the collection of ovaries from a local abattoir and the collection of oocytes by ovum pick up from live animals, gamete storage, collection techniques, handling of ovaries and oocytes to keep the viability and developmental competence, selection of oocytes to the type of culture media and in vitro culture condition, and treatment of the sperm cells for in vitro fertilization are all-important components of the process that requires careful and precise action to ensure success. Trials on intracytoplasmic injection, the use of sex-sorted sperm cells as a tool for producing sex-predetermined embryos, and the somatic cell nuclear transfer are methods that can be used to produce embryos in vitro. This paper provides the important considerations involved in the production of healthy live calves out of in vitro-produced water buffalo embryos
Anomalous resonant production of the fourth family up type quarks at the LHC
Considering the present limits on the masses of fourth family quarks from the
Tevatron experiments, the fourth family quarks are expected to have mass larger
than the top quark. Due to their expected large mass they could have different
dynamics than the quarks of three families of the Standard Model. The resonant
production of the fourth family up type quark t' has been studied via anomalous
production subprocess gq_i-->t' (where q_i=u,c) at the LHC with the center of
mass energy 10 TeV and 14 TeV. The signatures of such process are discussed
within the SM decay modes. The sensitivity to anomalous coupling
\kappa/\Lambda=0.1 TeV^(-1) can be reached at \sqrt{s}=10 TeV and L_int=100
pb^(-1).Comment: 14 pages, 13 figures, 7 table
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