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Granular flows occur in a wide range of situations of practical interest to industry, in our natural environment and in our everyday lives. This paper focuses on granular flow in the so-called inertial regime, when the rheology is independent of the very large particle stiffness. Such flows have been modelled with the
-rheology, which postulates that the bulk friction coefficient
(i.e. the ratio of the shear stress to the pressure) and the solids volume fraction
are functions of the inertial number
only. Although the
-rheology has been validated in steady state against both experiments and discrete particle simulations in several different geometries, it has recently been shown that this theory is mathematically ill-posed in time-dependent problems. As a direct result, computations using this rheology may blow up exponentially, with a growth rate that tends to infinity as the discretization length tends to zero, as explicitly demonstrated in this paper for the first time. Such catastrophic instability due to ill-posedness is a common issue when developing new mathematical models and implies that either some important physics is missing or the model has not been properly formulated. In this paper an alternative to the
-rheology that does not suffer from such defects is proposed. In the framework of compressible
-dependent rheology (CIDR), new constitutive laws for the inertial regime are introduced; these match the well-established
relations in the steady-state limit and at the same time are well-posed for all deformations and all packing densities. Time-dependent numerical solutions of the resultant equations are performed to demonstrate that the new inertial CIDR model leads to numerical convergence towards physically realistic solutions that are supported by discrete element method simulations.
Data were records of daily food intake and milk production, periodic measures of milk composition and all health and reproductive information from 140 multiparous Holstein cows involved in various experiments at the Agriculture Canada dairy research station in Lennoxville, Quebec. Energy concentrations of the total mixed rations were also available. Daily energy balance was calculated by multiplying the food intake by the concentration of energy in the diet and then subtracting from this quantity the expected (National Research Council) amount of energy required for maintenance (based on parity and body weight) and for milk production (based on yield and concentrations of fat, protein and lactose). Four energy balance traits were defined: (1) average daily energy balance within the first 10 to 100 days of lactation, (2) minimum daily energy balance, (3) days in negative energy balance and (4) total energy deficit during the period of negative energy balance. Health traits were the numbers of incidences of each of the following: (1) all udder problems, (2) mastitis, (3) all locomotive problems, (4) laminitis, (5) digestive problems and (6) reproductive problems. Reproductive traits were the number of days to first observed oestrous and number of inseminations. Phenotypic relationships between energy balance and health were investigated by regressing the energy balance traits on each health trait. Parity and treatment (according to the research trial that the cow was involved with) were also included in the model. Genetic parameters were estimated with restricted maximum likelihood and a model that included effects of parity, treatment and animal. Phenotypically, several significant (P<0.10) relationships between energy balance and health were observed. Cows with longer periods of negative energy balance had increased digestive problems. Cows with greater total energy deficit had more digestive problems and laminitis. Estimates of heritabilities for energy intake and milk energy were 0.42 and 0.12, respectively but estimates of heritability for all energy balance traits were zero. The low estimates for these traits may have been due to (1) low true additive genetic variance, (2) small amount of data, or (3) relatively few genetic ties among cows.
Some aspect of a semi-empirical model of galaxy formation is presented. In this model, galaxy formation proceeds through a series of rapid non-merging collisions with surrounding objects. For a given galaxy, a collision at an epoch z is characterized in terms of the fractional rate of change of binding energy induced by the tidal field . The total rate of change of binding energy during the lifetime of the galaxy is computed in an Einstein-de Sitter universe, assuming that collisions continuously occur from birth up to the present day against a set of background galaxies with various masses. Rules for the formation of morphological types are then derived along the following (phenomenological) line: substantial or efficient collisions – characterized by a high rate of energy exchange – drive the formation of elliptical galaxies, whereas little or inefficient collisions lead to the formation of disks. These rules are coupled to the Press & Schechter mass function for a Cold Dark Matter spectrum normalized to the present distribution of X-ray clusters, allowing one to predict the evolution, for each morphological type, of number densities as a function of redshift. The model reproduces the observed present-day morphology-density relation  and predicts the formation redshift of field ellipticals to be z ≥ 2, while spirals form at z ≤ 1.5. Predictions are made for the redshift evolution of morphological populations in the field as well as in clusters (see  for more details).
In light of the successes of the Navier–Stokes equations in the study of fluid flows, similar continuum treatment of granular materials is a long-standing ambition. This is due to their wide-ranging applications in the pharmaceutical and engineering industries as well as to geophysical phenomena such as avalanches and landslides. Historically this has been attempted through modification of the dissipation terms in the momentum balance equations, effectively introducing pressure and strain-rate dependence into the viscosity. Originally, a popular model for this granular viscosity, the Coulomb rheology, proposed rate-independent plastic behaviour scaled by a constant friction coefficient
. Unfortunately, the resultant equations are always ill-posed. Mathematically ill-posed problems suffer from unbounded growth of short-wavelength perturbations, which necessarily leads to grid-dependent numerical results that do not converge as the spatial resolution is enhanced. This is unrealistic as all physical systems are subject to noise and do not blow up catastrophically. It is therefore vital to seek well-posed equations to make realistic predictions. The recent
-rheology is a major step forward, which allows granular flows in chutes and shear cells to be predicted. This is achieved by introducing a dependence on the non-dimensional inertial number
in the friction coefficient
. In this paper it is shown that the
-rheology is well-posed for intermediate values of
, but that it is ill-posed for both high and low inertial numbers. This result is not obvious from casual inspection of the equations, and suggests that additional physics, such as enduring force chains and binary collisions, becomes important in these limits. The theoretical results are validated numerically using two implicit schemes for non-Newtonian flows. In particular, it is shown explicitly that at a given resolution a standard numerical scheme used to compute steady-uniform Bagnold flow is stable in the well-posed region of parameter space, but is unstable to small perturbations, which grow exponentially quickly, in the ill-posed domain.
Intestinal health is important for maximising the health, welfare, and performance of poultry. In addition, intestinal health issues in poultry can have devastating financial impacts for producers, and food safety concerns for consumers. Until recently, intestinal health issues were seen as a handful of known infectious agents leading to a set of severe and identifiable named diseases. There is however an emerging area which depicts intestinal health as a more complex and multifaceted system than previously known. Recent progress in technology suitable for microbial community analysis has evolved our understanding of the chicken intestinal microbiome. It is now understood that shifts in the composition of microbial communities can occur. These shifts can result in a series of implications, including: disease, welfare, environmental, and food safety concerns. Minor shifts in intestinal microbial balance can result in a wide continuum of disease presentations ranging from severe to mild clinical, subclinical or asymptotic. Differential diagnosis of poultry intestinal health issues may be challenging and is important for applying appropriate treatment options. This review discusses new and emerging topics in broiler chicken intestinal health, with a focus on microbial composition, newly discovered microbial shifts in classical poultry diseases, range in severity of enteric diseases, newly identified organisms in normal intestinal flora, implications of shifts in intestinal microbial communities and diagnosis of emerging intestinal health issues in poultry.
Health traits are of paramount importance for economic dairy production. Improvement in liability to diseases has been made with better management practices, but genetic aspects of health traits have received less attention. Dairy producers in Canada have been recording eight health traits (mastitis (MAST), lameness (LAME), cystic ovarian disease (COD), left displaced abomasum (LDA), ketosis (KET), metritis (MET), milk fever (MF) and retained placenta (RP)) since April 2007. Genetic analyses of these traits were carried out in this study for the Holstein breed. Edits on herd distributions of recorded diseases were applied to the data to ensure a sufficient quality of recording. Traits were analysed either individually (MAST, LAME, COD) or were grouped according to biological similarities (LDA and KET, and MET, MF and RP) and analysed with multiple-trait models. Data included 46 104 cases of any of the above diseases. Incidence ranged from 2.3% for MF to 9.7% for MAST. MET and KET also had an incidence below 4.0%. Variance components were estimated using four different sire threshold models. The differences between models resulted from the inclusion of days at risk (DAR) and a cow effect, in addition to herd, parity and sire effects. Models were compared using mean squared error statistic. Mean squared error favoured, in general, the sire and cow within sire model with regression on DAR included. Heritabilities on the liability scale were between 0.02 (MET) and 0.21 (LDA). There was a moderate, positive genetic correlation between LDA and KET (0.58), and between MET and RP (0.79).
The relative stabilities of the copper/zinc solid solutions of hydroxyl sulphates, carbonates, nitrates, chlorides and bromides were studied by attempting their preparation using a variety of methods. All of the naturally occurring solid solutions except rosasite were obtained as single phases. Rosasite crystallized in a mixture with malachite and calcium carbonate during a room temperature preparation from calcium carbonate, copper nitrate and zinc nitrate. The solid solution with the antlerite stoichiometry [endmember Cu3SO4(OH)4] as well as the nitrates were not produced by the methods employed. All of the natural polymorphs of Cu2(OH)3Cl were obtained and a new method for the preparation of botallackite is reported. Botallackite was found to be stable in solution for over a year, contrary to previous reports. A bromine-bearing analogue of botallackite was prepared. Compounds were characterized by X-ray diffractometry, which was used to determine the unit-cell parameters, and by atomic absorption spectroscopy. The relative instability of solid solutions with certain stoichiometries is discussed in terms of the Jahn-Teller effect and relative solubilities.
As traditional poly-silicon gated MOSFET devices scale, the additional series capacitance due to poly-silicon depletion becomes an increasingly large fraction of the total gate capacitance, excessive boron penetration causes threshold voltage shifts, and the gate resistance is elevated. To solve these problems and continue aggressive device scaling we are studying metal electrodes with suitable work-functions and sufficient physical and electrical stability. Our studies of metal gates on HfO2 indicate that excessive inter-diffusion, inadequate phase stability, and interfacial reactions are mechanisms of failure at source drain activation temperatures that must be considered during the electrode selection process. Understanding the physical properties of the metal gate – HfO2 interface is critical to understanding the electrical behavior of MOS devices. Of particular interest is Fermi level pinning, a phenomenon that occurs at metal – dielectric interfaces which causes undesirable shifts in the effective metal work function. The magnitude of Fermi level pinning on HfO2 electrodes is studied with Pt and LaB6 electrodes. In addition, the intrinsic and extrinsic contributions to Fermi level pinning of platinum electrodes on HfO2 gate dielectrics are investigated by examining the impact of oxygen and forming gas anneals on the work function of platinum-HfO2-silicon capacitors. The presence of interfacial oxygen vacancies or Pt-Hf bonds is believed to be responsible for a degree of pinning that is stronger than predicted from the MIGS model alone. Interface chemistry and defects influence the effective metal work function.
Against a backdrop of the latest ITRS predictions for CMOS junctions, we compare methods for dopant introduction and activation, methods for making contact to these regions, and methods for measurement of material and device properties. As activation without diffusion (sub-melt laser, capacitor discharge flash, or solid phase epitaxy) becomes more feasible, the burden on Xj, Rsh and abruptness falls on the implanters, and the process margin appears slim, opening the door for other methods of doping. For contact resistance, a major component of transistor parasitics, we find that either a move to a different substrate, or from a single midgap silicide to two band-edge metals/silicides can be quite beneficial. Through the use of simple test structures, we describe a means of extracting each component of the parasitic resistance, facilitating development of materials for CMOS junctions.
As the MOSFET gate lengths are scaled down to 50 nm or below, the expected increase in gate leakage will be countered by the use of a high dielectric constant (high K) material. The series capacitance from polysilicon gate electrode depletion significantly reduces the gate capacitance as the dielectric thickness is scaled down to 10 Å equivalent oxide thickness (EOT) or below. Metal gates promise to solve this problem and address other problems like boron penetration and enhanced gate resistance that will have increased focus as the polysilicon gate thickness is reduced. Extensive simulations have shown that the optimal gate work-functions for the sub-50 nm channel lengths should be 0.2 eV below (above) the conduction (valence) band edge of silicon for n-MOSFETs (p-MOSFETs). This study summarizes the evaluations of TiN, TaSiN, WN, TaN, TaSi, Ir and IrO2 as candidate metals for dual-metal gate CMOS using HfO2 as the gate dielectric. The gate work-function was determined by fabricating MOS capacitors with varying dielectric thicknesses and different post-gate anneals. The metal-dielectric compatibility and thermal stability was studied by annealing the stacks at different temperatures. The gate stacks were characterized using TEM, SIMS and X-ray diffraction. Based on workfunctions and thermal stability, TaSiN and TaN show most promise as metal electrodes for HfO2 n-MOSFETs.
Syntheses for the three members of the copper hydroxyl nitrate family – the polymorphs rouaite and gerhardtite, and likasite – are presented along with powder diffraction data and unit-cell parameters. The solubilities, determined in 0.05 M KNO3 solution after equilibration at 25°C for 10 days were used to calculate activity-based solubility product constants. The Gibbs energies of formation, obtained from the solubility products, are –653.2±0.7 kJ/mol, –655.1±1.2 kJ/mol and –1506.4±1.1 kJ/mol, for rouaite, gerhardtite, and likasite (Cu3NO3(OH)5·2H2O), respectively. The values for the polymorphs rouaite and gerhardtite validate the observations of Oswald that gerhardtite is the most stable polymorph at room temperature and that the preparation of predominantly rouaite in syntheses carried out at room temperature must be due to the metastability and low rate of conversion to the more stable gerhardtite.
The literature contains considerable disagreements on the relative stabilities of the members of the copper hydroxyl sulphate family. Titration of copper sulphate with sodium hydroxide is claimed by some to produce only brochantite, while other reports indicate that antlerite and a dihydrate of antlerite are produced in the titration. Most stability field diagrams show that antlerite is the more stable stoichiomer at pH 4 and sulphate activity of 0.05–1. We have reexamined this stoichiometric family by titration of aqueous copper sulphate with sodiumhydroxide and sodium carbonate, reverse titration of sodiumhydroxide with copper sulphate and simultaneous addition of copper sulphate and sodium hydroxide at a variety of mole ratios, concentrations, temperatures and reaction times. We have also explored the reaction of copper hydroxide with copper sulphate and the reaction of weak bases, such as sodiumacetate, sodiumcarbonate and urea, with copper sulphate. Our work indicates that: (1) antlerite is not formed in reactions of 0.05 to 1.2 M CuSO4 with 0.05–1.0 M NaOH or Na2CO3 at room temperature; (2) antlerite is formed in the addition of small concentrations of base (≤0.01 M) to 1 M CuSO4 at 80°C, but not at roomtem perature or with 0.01 M CuSO4 at 80°C; (3) the formation of Cu5(SO4)2(OH)6·4H2O occurs at large Cu2+ to base mole ratios; (4) the compound described in the literature as antlerite dihydrate is actually Cu5(SO4)2(OH)6.4H2O; (5) at mole ratios of Cu2+ to OH– ranging from 2:1 to 1:2 the predominant product is brochantite; and (6) brochantite and Cu5(SO4)2(OH)6.4H2O are converted to antlerite in the presence of 1 M CuSO4 (the latter requires temperatures of 80°C or greater).
The Ksp (ion activity product) values of antlerite and brochantite were determined to be 2.53 (0.01)⨯10−48 and 1.01 (0.01)⨯10−69, respectively, using atomic absorption spectroscopy and Visual MINTEQ after equilibration in solutions of varying ionic strength and pH for six days. These values are in good agreement with those from the literature. However, after 6 months, antlerite in contact with solution is partially converted to brochantite and hence is metastable with a relatively low conversion rate. The Ksp value for antlerite must therefore be considered approximate. The relative stabilities of the copper hydroxyl sulphates are rationalized using appropriate equations and Gibbs energy calculations. A Gibbs free energy of formation for Cu5(SO4)2(OH)6.4H2O of –3442 kJ/mol was obtained from the simple salt approximation.
Silicon technology has become a good alternative to copper for the elaboration of efficient cooling
devices required in power electronics domain. Owing to its high degree of miniaturization, it is
expected to provide suitable microchannels and other inlets holes that were not achievable by
copper micromachining. Besides, the use of silicon technology provides a variety of bare materials
(silicon dioxide, silicon nitride, silicide, etc.) which may be either insulator or conductive, with a good or bad thermal conductivity. This large choice makes it possible to built up rather complex multilayer devices with mechanical properties good enough in comparison with hybrid copper
technology heat sinks. Nevertheless, the use of silicon technology, where the microchannel width
may reach few tens of microns, raises fundamental features concerning the fluid displacement
within such small sections. More precisely, fundamental fluid mechanics studies have to be
conducted out in order to get an accurate description of the fluid boundary layers and to provide
basic data on the exchange mechanisms occurring at these surfaces.
In this paper, we review the operation principles of both single- and double-phase heat exchange
devices elaborated in silicon technology. Forced-convection heat sinks as well as integrated micro
heat pipes are analyzed. An analytical approach is adopted to evaluate their total thermal
resistances as a function of several geometrical parameters. Numerical simulations are then used in
order to assess the accuracy of the analytical approach and to evaluate the impact of the fluidic
aspects on the whole performance. The optimum devices are then conceived thanks to an
appropriate optimization procedure taken into account the several experimental constraints.
Reference values of similar copper devices are reminded and the advantages of the silicon
integrated approach are highlighted.
Membrane phospholipid abnormalities in people with schizophrenia, measured with 31P magnetic resonance spectroscopy (31P-MRS), have been previously reported in brain regions involved in this disorder.
In this 4.0 Tesla 31P-MRS study of people with schizophrenia, membrane phospholipid metabolism was examined in brain regions previously inaccessible due to their small volumes.
Three-dimensional chemical-shift imaging (3D–CSI) examined 15 cc volumes in 12 brain regions in 11 people with chronic schizophrenia and 11 healthy control volunteers.
Glycerophosphoethanolamine was decreased in the anterior cingulate, right prefrontal cortex and left thalamus, but increased in the left hippocampus and cerebellum in those with schizophrenia. Phosphoethanolamine and glycerophosphocholine were decreased in the right prefrontal region and phosphocholine was decreased in the anterior cingulate. No significant difference in membrane phospholipid levels existed between groups in the parieto-occipital and posterior cingulate regions.
Altered membrane phospholipid metabolism was demonstrated in all regions implicated in schizophrenia.
Phase pure YBa2Cu3O7 high transition temperature superconductor powders were synthesized by a new precursor route. This new synthesis procedure is easy, leads to an atomic mixture of the relevant constituents, and is readily adaptable to many other systems or to the doping of existing systems. A gel of yttrium, barium, and copper salts was prepared using organic gelling agents. The gel was then dried and ground, leaving the xerogel precursor. These xerogels are perfectly stable even under high humidity atmospheric conditions and show an amorphous structure when characterized by x-ray diffraction, which is consistent with the existence of an atomic mixture of the three relevant metal salts. The organic gelling agent was selected after optimization studies focused on such issues as ash residue after calcination, solubility, and chemical interference with the metal salts. From a great variety of these gelling agents (agar, xanthan gum, gelatin, alginates, and others), gelatin was chosen as the ideal gelling agent for this specific application. The final product characterization shows very unexpected results. The crystalline phase purity of the YBa2Cu3O7 superconducting phase was about 99%, with no traces of barium carbonate, as expected from pseudo-organic precursors (xerogels). The product shows superconducting properties even before oxygen anneal (Tc ≍ 70 K), and after oxygen annealing of the powders the transition temperature was found to be 91 K, showing a linear behavior of the resistivity versus temperature before the drop at Tc, extrapolating to zero at 0 K. The particle size of these powders is smaller than 1 μm, as shown by SEM.
In this paper we consider the equilibrium configurations of a homogeneous, incompressible, isotropic elastic body subjected to a uniform dead load surface traction of magnitude T whose direction is normal to the surface of the body in the reference configuration, and to no other forces. We concentrate on homogeneous equilibrium solutions, that is those for which the deformation gradient F is constant, and we study their bifurcations and stability (with respect to an appropriate static criterion) as T varies. Since it turns out that the equations for homogeneous equilibrium solutions, and the stability properties that we consider of these solutions, are independent of the shape of the body in the reference configuration, we can suppose if desired that this shape is a cube. (See Fig. 1.1.)
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