When smoothening makes it rough: unhindered step-edge diffusion and the meandering instability on metal surfaces

The precise microscopic origin of step meandering is not known in many real situations. A detailed study of this instability has been made for copper, and none of the microscopic mechanisms proposed until now is able to describe all of the observed characteristic features of the instability, in particular, its dependence on the crystallographic orientations of steps. We propose a novel scenario, and using kinetic Monte Carlo simulations we show that essentially all features of step meandering of copper can be explained, if atoms diffuse along step edges and freely turn around the kinks they encounter along the ledge. Then, in a rather counterintuitive way, step meandering appears due to the very mechanism--step-edge diffusion--that may be expected to oppose it.     

Some observations on the performance of balloons from the rate of rotation of the fan in the F-Type radiosonde

If the rate of ascent of the balloon is constant, the rate of rotation of the fan in the F-Type radiosonde should decrease with height, due to the decrease in the density of the air. It was observed from the radiosonde ascents of Minicoy that the rate of rotation of the fan remained almost unchanged up to even 100 mb. It is shown that this is due to the increase in the rate of ascent of the balloon by about 2% of the value near the ground per km. ascent. Positive evidence of turbulence in the stratosphere is provided by the large fluctuations in the rate of rotation of the fan. It is also observed that the balloon whose fabric at the 50 mb. level is about 0·014 mm. thick bursts due to the turbulence.     

Group algebras of Lie nilpotency index 12 and 13

Let G be a group and let K be a field of characteristic p>0. Lie nilpotent group algebras of strong Lie nilpotency index up to 11 have already been classified. In this paper, our aim is to classify the group algebras KG which are strongly Lie nilpotent of index 12 or 13.     

Performance of slotted pores in particle manufacture using rotating membrane emulsification

This paper addresses the use of different slotted pores in rotating membrane emulsification technology.Pores of square and rectangular shapes were studied to understand the effect of aspect ratio (1-3.5) and their orientation on oil droplet formation.Increasing the membrane rotation speed decreased the droplet size,and the oil droplets produced were more uniform using slotted pores as compared to circular geometry.At a given rotation speed,the droplet size was mainly determined by the pore size and the fluid velocity of oil through the pore (pore fluid velocity).The ratio of droplet diameter to the equivalent diameter of the slotted pore increased with the pore fluid velocity.At a given pore fluid velocity and rotation speed,pore orientation significantly influences the droplet formation rate: horizontally disposed pores (with their longer side perpendicular to the membrane axis) generate droplets at double the rate of vertically disposed pores.This work indicates practical benefits in the use of slotted membranes over conventional methods.     

Nano-network with dual temperature and pH responsiveness based on copolymers of 2-hydroxyethyl methacrylate with 3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]-undecane

Abstract  

This study refers to the synthesis of a nano-network with dual temperature and pH responsiveness based on the 2-hydroxyethyl methacrylate (HEMA) copolymers with a comonomer with spiroacetal moiety and crosslinking capacity, namely 3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]-undecane (U). The copolymers were synthesized by radical emulsion polymerization, using 4,4′-azobis(cyanopentanoic acid) as initiator, in the presence of sodium lauryl sulfate as tensioactive agent and poly(vinyl alcohol) as protective colloid. Three copolymer variants were taken into study resulted from the different ratio between the comonomers (HEMA/U), which was about 98/2, 95/5, and 90/10, respectively. The copolymers were characterized by FTIR and thermal analysis. The copolymers sensitivity was evidenced by studying the evolution of the hydrodynamic radius and zeta potential of the polymeric particles as a function of pH. Thus, the particles size increases with the comonomer amount, from 193 nm in case of the homopolymer up to 253 nm for the copolymer with maximum content of the comonomer (10%). The increase of the particle hydrodynamic radius with the growth of temperature was also put into evidence.     

Optimal ordering policy for stock-dependent demand under progressive payment scheme

In this article, a mathematical model is developed to formulate optimal ordering policies for retailer when demand is partially constant and partially dependent on the stock, and the supplier offers progressive credit periods to settle the account. The notion of progressive credit period is as follows:     

Synthetic Polyphosphonates,Polyphosphates, and Phosphonocarboxylates as Allosteric Effectors of Hemoglobin

Abstract

Synthetic phosphonocarboxylates, diphosphonates, polyphosphates, and some triphosphonic acids were studied as effectors in the binding of dioxygen to human hemoglobin. Ethane-1,2-diphosphonic acid, and triphosphate anion were strong effectors.     

Superconductivity at 15 K in NdFe0.9Rh0.1AsO without F-doping

We present results of transport and magnetic properties measurements performed on polycrystalline NdFe_0.9Rh_0.1AsO. Despite the large size difference between Fe and Rh elements, this compound undergoes a superconducting transition with T_c ～ 15 K. We have compared the transport properties of this Rh-doped oxypnictide with that of optimally doped NdFeAsO_0.88F_0.12. Contrary to this latter compound, a strong upturn of the normal-state resistivity occurs above T_c, and no peak of the thermopower has been observed.