Molecular statics simulations of buckling and yielding of gold nanowires deformed in axial compression

We use molecular statics simulations with the embedded atom method potential to delineate yielding (material instability) and buckling (structural instability) in gold nanowires deformed axially in compression. It is found that both local (stacking faults) and global instabilities occur when the gold nanowire yields but only global instabilities occur when the nanowire buckles. Furthermore strong surface effects reorient the lattice structure which significantly increases Young’s modulus in the axial direction and cause a nanowire of relatively small slenderness ratio (e.g., 14) to buckle. Upon complete unloading of the nanowires, the average axial stress and the total potential energy revert to their values in the reference configuration for the nanowires that buckled but not for the one that yielded.     

Body weight changes in lactating purebred and crossbred dairy cattle.

Body weights of 396 first and 205 second lactation cows in the first, second, third, and fourth generations of the dairy cattle crossbreeding project at the Illinois Agricultural Experiment Station were studied. Body weights were taken regularly on each animal during the first 9 mo of each lactation with the first weight being taken 3 to 4 days after parturition and subsequent weights at intervals of 30 days thereafter. Among least-squares means there was a decrease in body weight during the first 1 or 2 mo of lactation and a steady increase thereafter in all breed groups for both first and second lactations. There were differences between cows as well as between months for all breed groups in each generation for both lactations. Sums of squares for months were partitioned into linear, quadratic, and cubic components. A third degree polynomial was fitted for each breed group within each generation and separately for each lactation showing the changes in body weights.     

Steady state penetration of thermoviscoplastic targets

Steady state thermomechanical deformations of a target hit by a rigid cylindrical penetrator with an ellipsoidal nose are studied. The material of the target is assumed to be thermally softening but strain and strain-rate hardening. Results computed and presented graphically include the pressure distribution on the nose of the penetrator, dependence of the axial resisting force upon the speed of the penetrator, and the variation of field quantities such as the temperature and strain-rate in the target. Computed results show that the ratio of the major to minor axes of the ellipsoidal nose has a significant effect on the deformations of the target particles in the vicinity of the penetrator nose.     

Effect of frictional force and nose shape on axisymmetric deformations of a thick thermoviscoplastic target

Summary We study thermomechanical deformations of a thermally softening viscoplastic thick target impacted at normal incidence by a cylindrical rod made of a material considerably harder than the target material. Thus we regard the penetrator to be rigid and analyze the effect of the penetrator nose shape and the frictional force at the target/penetrator interface on target's deformations. In the postulated expression for the frictional force, the coefficient of friction, defined as the ratio of the tangential force at a point to the normal force there, is a function of the relative speed of sliding between the two bodies. The computed depth of penetration is found to match very well with that observed in experiments by Forrestal et al. For each nose shape studied, the consideration of frictional forces reduces significantly the computed penetration depth. For the same kinetic energy of the penetrator, the penetrator with a sharp nose gives higher values of the penetration depth as compared to that obtained with a blunt nose.     

Effect of electromechanical coupling on static deformations and natural frequencies

A two-way coupled electromechanical theory is used to study static deformations and free vibrations of a laminated hybrid rectangular plate comprised of either piezoceramic (PZT) layers or patches embedded at arbitrary locations in graphite/epoxy layers. A first-order shear deformation theory is used to develop equations for the plate which are solved by the finite-element method (FEM) using eight-node isoparametric elements. Static deflections and natural frequencies computed with open-circuited PZT layers are found to differ significantly from those of grounded PZT layers.     

Effect of non-uniform inlet velocity profile in the entrance region of a Bingham plastic flow Between parallel plates

In many practical situations the velocity profiles at the channel inlet are asymmetric and give rise to asymmetric developing velocity profiles. This may occur, for example, in the flow near the mouths of pipes in certain types of heat exchangers in which usually the velocity profile has a velocity gradient in the direction normal to the flow. A numerical analysis is carried out to describe the effects of asymmetric velocity profile at the channel inlet on the flow characteristics of a Bingham plastic between parallel plates. Considering the inlet velocity to include a constant transverse velocity gradient with respect to the channel centerline, the pressure drop, the velocity distribution and heat transfer variations along the channel are determined. It has been found that a significant asymmetry occurring near the entrance region is gradually reduced as the flow develops and a completely symmetrical profile is attained in the fully developed flow regime.     

9-azidoacridine, a new photoaffinity label for nucleotide- and aromatic-binding sites in proteins

The effect of the photolytic reagent 9-azidoacridine, optionally 3H-labelled, was studied both kinetically and structurally on nine different enzymes, namely alpha-chymotrypsin, lactate dehydrogenase, glyceraldehyde 3-phosphate dehydrogenase, alcohol dehydrogenase, alanine dehydrogenase, D-amino acid oxidase, ribonuclease A, alkaline phosphatase and alpha-amylase. Dark inhibition was observed in several cases. The concentration of the inhibitor ranged from 0.2 microM to 0.67 microM and demonstrated competitive kinetics with nucleotide cofactors when present. All concentrations of inhibitor showed increased inhibition on photolysis. Examination of the oligopeptides from hydrolysis of the covalently 3H-labelled derivative in conjunction with known amino acid sequence and tertiary structure established that the primary site of interaction in those cases for which the tertiary structure was available involved the active-site region. The above results in conjunction with those obtained with the structural analogues 9-aminoacridine and 9-amino-1,2,3,4-tetrahydroacridine established that this reagent acts as a molecular probe of aromatic- and, in particular, nucleotide-binding sites. This reagent provides a further additional method for studying the nucleotide cofactor domain.     

Evacuation infrastructure for new generating station: Options available in Indian context

Facing a deficit of 9% in power generation, India needs to harness all forms of generation including renewable energy (RE) which presently contributes less than 8% to total generation capacity. To increase the same, concerns of RE developers are being addressed by the government and regulatory bodies. One such concern is availability of transmission grid for evacuation of power. Transmission lines required for power evacuation from RE generators are typically not included in their network plan by the transmission utility. Considering the financial health and underperformance of these utilities, even if the required transmission lines are included in the network plan, RE developers are uncertain and unsure of the timely execution of the plan. Ministry of Power has earlier notified guidelines [Government of India, Ministry of Power, 2006a. Resolution on tariff based competitive-bidding guidelines for transmission service; Government of India, Ministry of Power, 2006b. Resolution on guidelines for encouraging competition in development of transmission projects] for enabling private sector participation in transmission to enable the private developers to build the required evacuation infrastructure. This paper evaluates the options available as per the legislative and regulatory framework in India through which the evacuation infrastructure for the RE projects can be built by the transmission utility or the potential investors. The key concept of “dedicated transmission line”, which has been a keenly debated and often a misunderstood issue, is also discussed in great detail.