Cohomology in superstring field theory and properties of D-branes

The paper presents recent achievements and open questions in string field theory that are related to the cohomology of BRST operators. We sketch the construction of a nonpolynomial action based on cubic theory that uses the triviality of the BRST operator in the so-called large algebra. We also construct special solutions of equations of motion in superstring field theory and study the cohomology of a modified BRST operator near these solutions.     

Elasticity of a magnetic fluid in a strong magnetic field

Complex measurements of the following elastic-magnetic parameters of a magnetic fluid suspended by magnetic levitation within a horizontal tube in a strong magnetic field were performed: the oscillation frequency and decay coefficient; the static, ponderomotive, and dynamic elasticity coefficients; the fluid displacement under hydrostatic pressure; magnetization curve; and the magnetic field strength and gradient. Calculations based on a model of ponderomotive elasticity with correction for the resistance of a viscous fluid in motion and on the fluid column displacement for two magnetic fluid samples agree well with the experimental magnetization curve. The discussed technique holds promise for research into magnetophoresis and nanoparticle aggregation in magnetic colloids.     

Catalysis of black holes/wormholes formation in high energy collisions

The current paradigm suggests that BH/WH formation in particles collisions will happen when a center-mass energy of colliding particles is sufficiently above the Planck scale (the transplanckian region). We confirm the classical geometrical cross section of the BH production reconsidering the process of two transplanckian particles collision in the rest frame of one of incident particles. This consideration permits to use the standard Thorne’s hoop conjecture for a matter compressed into a region to prove a variant of the conjecture dealing with a total amount of compressed energy in the case of colliding particles. We briefly mention that the process of BH formation is catalyzed by the negative cosmological constant and by a particular scalar matter, namely dilaton, while it is relaxed by the positive cosmological constant and at a critical value just turns off.     

Magnetocaloric effect and the heat capacity of ferrimagnetic nanosystems in magnetic fluids

The specific heat capacity of a magnetite-based magnetic fluid and changes in the magnetic part of the molar heat capacity of its magnetic phase in magnetic fields of 0–0.7 T were determined calorimetrically over the temperature range 288–353 K. The temperature dependence of changes in the magnetic part of entropy in an applied magnetic field was calculated. It was found that the field dependence of heat capacity had a maximum in fields of 0.3–0.4 T, and the temperature dependences of changes in the magnetic part of heat capacity ΔC _p (H) and entropy ΔS _m(H) had maxima at the magnetic phase transition temperature.     

Hybrid Split Hopkinson Pressure Bar to Identify Impulse-dependent Wave Characteristics of Viscoelastic Phononic Crystals

Experimental Mechanics - There has recently been a rising interest in the nonlinear wave transmission behavior of phononic crystals. However, experimental studies focusing on the nonlinear wave...     

Building cost effective lower layer VPNs: The ILEC/CLEC dilemma

Layer 2 and layer 1 Virtual Private Network (VPN) services; ranging from simple leased lines to extending private LANs across public networks, are commonplace today. With the continuously growing economic difficulties, capital meltdown, and telecommunication business turmoil, delivering those VPN services at the lowest cost or with the maximum revenue margin, while committing to Service Level Agreements (SLA), has become essential. We show that whether we tackle the optimal VPN design problem from an Incumbent Local Exchange Carrier (ILEC) standpoint or from a Competitive Local Exchange Carrier (CLEC) standpoint, we obtain contradictory rules. We show that by building Edge Disjoint VPN trees and spreading the traffic all over the network, the ILEC can achieve maximum throughput and enhanced network performance; while by concentrating all the VPN traffic over a single tree, the CLEC can minimize the cost of leased bandwidth. We then propose two simple algorithms that can help carriers and service providers leverage their networks and increase their revenue margins while meeting SLA requirements. Copyright © 2010 John Wiley & Sons, Ltd.     

General Solvothermal Synthesis Method for Complete Solubility Range Bimetallic and High‐Entropy Alloy Nanocatalysts

Nanoalloys (NAs) have extraordinary catalytic properties, but metals are often immiscible giving compositional limits on catalytic design. It is generally believed that solution‐based chemical synthesis is inadequate for obtaining NAs, and often exotic shock synthesis or severe decomposition or reduction reactions are required. However, such methods only work on the laboratory scale making real‐world applications difficult. Here, a general solvothermal method is reported to obtain phase‐pure bimetallic and high‐entropy nano‐alloys across the entire composition range. Tuning of solvent chemistry and precursors leads to six different bimetallic NAs: Pd_xRu_1‐x, Pt_xRu_1‐x, Ir_xRu_1‐x, Rh_xRu_1‐x, Ir_1‐xPt_x, and Rh_1‐xPt_x, without immiscibility regions. All samples have face‐centered‐cubic crystal structures, which have not previously been observed for the ruthenium‐based systems. Additionally, quaternary and quinary systems are produced, demonstrating the ability to obtain medium‐ and high‐entropy NAs. The method described herein provides a simple, general production method of previously unknown solid solutions throughout their entire composition range potentially allowing for detailed tuning of nanocatalyst properties.