A Microscopic Theory of the f.c.c.-b.c.c. Interface .

We present a first-principles theory of the equilibrium b.c.c.-f.c.c. interface at coexistence using the density functional method. We assume that the interfacial region has local body-centred tetragonal (b.c.t.) symmetry and predict typical interfacial widths to be of order 2 to 3 lattice spacings with typical energies close to 0.05 J/m2. These quantities are in good agreement with laboratory measurements on coherent interfaces.

Mechanical properties of B-modified Ti-6Al-4V alloys

Minor addition of B to the Ti-6Al-4V alloy reduces the prior beta grain size by more than an order of magnitude. TiB formed in-situ in the process has been noted to decorate the grain boundaries. This microstructural modification influences the mechanical behavior of the Ti-6Al-4V alloy significantly. In this paper, an overview of our current research on tensile properties, fracture toughness as well as notched and un-notched fatigue properties of Ti-6Al-4V-xB with x varying between 0.0 to 0.55 wt.% is presented. A quantitative relationship between the microstructural length scales and the various mechanical properties have been developed. Moreover, the effect of the presence of hard and brittle TiB has also been studied.

A stereoselective synthesis of (±)-homogynolide-b

A highly stereoselective formal total synthesis of homogynolide-B via the ketoketals 4 and the ketospirolactone 3a starting from Hagemann's eater 2 is described.

Cracks emanating from pin-loaded lugs

Pin-loaded lugs were analysed in the presence of cracks emanating from circular holes. The analysis presents a unified treatment of interference, push or clearance fit pins. Both metallic (isotropic) and composite (orthotropic) plates were dealt with. The finite element model used special singular six-noded quadrilateral elements at the crack tip. The non-linear load contact behaviour at the pin-hole interface was dealt with by an inverse technique. A modified crack closure integral (MCCI) technique was used to evaluate the strain energy release rates (SERRs) and stress intensity factors (SIFs) at the crack tips. Numerical results are presented showing the non-linear variation of SIF with applied stress, and the influence of the amount of interference or clearance and the interfacial friction on SIF.

Explicit and Optimal Exact-Regenerating Codes for the Minimum-Bandwidth Point in Distributed Storage

In the distributed storage setting that we consider, data is stored across n nodes in the network such that the data can be recovered by connecting to any subset of k nodes. Additionally, one can repair a failed node by connecting to any d nodes while downloading beta units of data from each. Dimakis et al. show that the repair bandwidth d beta can be considerably reduced if each node stores slightly more than the minimum required and characterize the tradeoff between the amount of storage per node and the repair bandwidth. In the exact regeneration variation, unlike the functional regeneration, the replacement for a failed node is required to store data identical to that in the failed node. This greatly reduces the complexity of system maintenance. The main result of this paper is an explicit construction of codes for all values of the system parameters at one of the two most important and extreme points of the tradeoff - the Minimum Bandwidth Regenerating point, which performs optimal exact regeneration of any failed node. A second result is a non-existence proof showing that with one possible exception, no other point on the tradeoff can be achieved for exact regeneration.

A Flexible Class of Regenerating Codes for Distributed Storage

In the distributed storage setting introduced by Dimakis et al., B units of data are stored across n nodes in the network in such a way that the data can be recovered by connecting to any k nodes. Additionally one can repair a failed node by connecting to any d nodes while downloading at most beta units of data from each node. In this paper, we introduce a flexible framework in which the data can be recovered by connecting to any number of nodes as long as the total amount of data downloaded is at least B. Similarly, regeneration of a failed node is possible if the new node connects to the network using links whose individual capacity is bounded above by beta(max) and whose sum capacity equals or exceeds a predetermined parameter gamma. In this flexible setting, we obtain the cut-set lower bound on the repair bandwidth along with a constructive proof for the existence of codes meeting this bound for all values of the parameters. An explicit code construction is provided which is optimal in certain parameter regimes.

Generating synchronizable test sequences based on finite-statemachine with distributed ports

In the area of testing communication systems, the interfaces between systems to be tested and their testers have great impact on test generation and fault detectability. Several types of such interfaces have been standardized by the International Standardization Organization (ISO). A general distributed test architecture, containing distributed interfaces, has been presented in the literature for testing distributed systems based on the Open Distributing Processing (ODP) Basic Reference Model (BRM), which is a generalized version of ISO distributed test architecture. We study in this paper the issue of test selection with respect to such an test architecture. In particular, we consider communication systems that can be modeled by finite state machines with several distributed interfaces, called ports. A test generation method is developed for generating test sequences for such finite state machines, which is based on the idea of synchronizable test sequences. Starting from the initial effort by Sarikaya, a certain amount of work has been done for generating test sequences for finite state machines with respect to the ISO distributed test architecture, all based on the idea of modifying existing test generation methods to generate synchronizable test sequences. However, none studies the fault coverage provided by their methods. We investigate the issue of fault coverage and point out a fact that the methods given in the literature for the distributed test architecture cannot ensure the same fault coverage as the corresponding original testing methods. We also study the limitation of fault detectability in the distributed test architecture.

Evolution of Transformation Texture in a Metastable B - Titanium Alloy

Texture evolution in h. c. p. (alpha) phase derived from aging of a differently processed metastable b.c.c. (beta) titanium alloy was investigated. The study was aimed at examining (i) the effect of different b. c. c. cold rolling textures and (ii) the effect of different defect structures on the h. c. p transformation texture. The alloy metastable beta alloy Ti-10V-4.5Fe-1.5Al was rolled at room temperature by unidirectional (UDR) and multi-step cross rolling (MSCR). A piece of the as-rolled materials were subjected to aging in order to derive the h. c. p. (alpha) phase. In the other route, the as-rolled materials were recrystallized and then aged. Textures were measured using X-ray as well as Electron Back Scatter Diffraction. Rolling texture of beta phase, as characterized by the presence of a strong gamma fibre, was found stronger in M S C R compared to UDR, although they were qualitatively similar. The stronger texture of MSCR sample could be attributed to the inhomogeneous deformation taking place in the sample that might contribute to weakening of texture. Upon recrystallization in beta phase field close to beta-transus. the textures qualitatively resembled the corresponding beta deformation textures; however, they got strengthed. The aging of differently beta rolled samples resulted in the product alpha-phase with different textures. The (UDR + Aged) sample had a stronger texture than (MSCR + Aged) sample, which could be due to continuation of defect accumulation in UDR sample, thus providing more potential sites for the nucleation of alpha phase. The trend was reversed in samples recrystallized prior to aging. The (MSCR + Recrystallized + Aged) sample showed stronger texture of alpha phase than the (UDR + Recrystallized + Aged) sample. This could be attributed to extensive defect annihilation in the UDR sample on recrystallization prior to aging. The (MSCR + Aged) sample exhibited more alpha variants when compared to (MSCR + Recrystallized + Aged) sample. This has been attributed to the availability of more potential sites for nucleation of alpha phase in the former. It could be concluded that alpha transformation texture depends mainly on the defect structure of the parent phase.

Asymmetric synthesis of steroidal Tröger's base analogues. X-Ray molecular structure of methyl 3?,12?-{6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine-2,8-bisacetoxy}-5?-cholan-24-oate

Cyclization of compound 5c in trifluoroacetic acid/hexamethylenetetramine produces Tröger's base analogue 6c in 75% yield with 70% diastereoselectivity.

Design and realization of high-performance wave-pipelined 8×8 b multiplier in CMOS technology

Wave pipelining is a design technique for increasing the throughput of a digital circuit or system without introducing pipelining registers between adjacent combinational logic blocks in the circuit/system. However, this requires balancing of the delays along all the paths from the input to the output which comes the way of its implementation. Static CMOS is inherently susceptible to delay variation with input data, and hence, receives a low priority for wave pipelined digital design. On the other hand, ECL and CML, which are amenable to wave pipelining, lack the compactness and low power attributes of CMOS. In this paper we attempt to exploit wave pipelining in CMOS technology. We use a single generic building block in Normal Process Complementary Pass Transistor Logic (NPCPL), modeled after CPL, to achieve equal delay along all the propagation paths in the logic structure. An 8×8 b multiplier is designed using this logic in a 0.8 ?m technology. The carry-save multiplier architecture is modified suitably to support wave pipelining, viz., the logic depth of all the paths are made identical. The 1 mm×0.6 mm multiplier core supports a throughput of 400 MHz and dissipates a total power of 0.6 W. We develop simple enhancements to the NPCPL building blocks that allow the multiplier to sustain throughputs in excess of 600 MHz. The methodology can be extended to introduce wave pipelining in other circuits as well

Synthetic approaches to homogynolides A and B

A four step, efficient and general methodology for the conversion of a cyclic ketone into the corresponding alpha-spiro-beta-methylene-gamma-butyrolactone, the key structural feature present in tricyclic sesquiterpenes bakkanes, has been developed employing a regiospecific 5-exo dig radical cyclisation reaction as the key step. The methodology has been extended to the total synthesis of bakkanes including homogynolide-B and chiral homogynolide-A.

What makes a cell tick? The A, B and C of the matter

Nuclear lamina in an eukaryotic cell is primarily composed of the lamins A, B and C. The A type lamins are found only in differentiated cell types while the B type lamins are present both in differentiated and undifferentiated cells. Lamin B interacts with the inner nuclear membrane, In recent years there have been extensive studies on the relationship between the dynamic state of lamin B and the nuclear envelope integrity with respect to the fate of a particular cell, In this article, we have analysed the recent developments and have considered the sequence of events that might be contributing to the fate of a cell either to undergo normal cell division or uncontrolled cellular proliferation or apoptosis.

Low-temperature specific heat of antiferromagnetic EuNi5P3 and mixed-valent EuNi2P2 in magnetic fields to 7 T

he specific heats of EUNi(5)P(3), an antiferromagnet, and EuNi2P2, a mixed-valence compound, have been measured between 0.4 and 30 K in magnetic fields of, respectively, 0, 0.5, 1, 1.5, 2.5, 5, and 7 T, and 0 and 7 T. In zero field the specific heat of EuNi5P3 shows a h-like anomaly with a maximum at 8.3 K. With increasing field in the range 0-2.5 T, the maximum shifts to lower temperatures, as expected for an antiferromagnet. In higher fields the antiferromagnetic ordering is destroyed and the magnetic part of the specific heat approaches a Schottky anomaly that is consistent with expectations for the crystal-field/Zeeman levels. In low fields and for temperatures between 1.5 acid 5 K the magnetic contribution to the specific heat is proportional to the temperature, indicating a high density of excited states with an energy dependence that is very unusual for an antiferromagnet. The entropy associated with the magnetic ordering is similar to R In8, confirming that only the Eu2+-with J=7/2, S=7/2, L=0-orders below 30 R. In zero field approximately 20% of the entropy occurs above the Neel temperature, consistent. with the usual amount of short-range order observed in antiferromagnets. The hyperfine magnetic field at the Eu nuclei in EUNi(5)P(3) is 33.3 T, in good agreement with a value calculated from electron-nuclear double resonance measurements. For EuNi2P2 the specific heat is nearly field independent and shows no evidence of magnetic ordering or hyperfine fields. The coefficient of the electron contribution to the specific heat is similar to 100 mJ/mol K-2.

Enantioselective total synthesis of iso-cladospolide B, cladospolide C and cladospolide B from tartaric acid

The enantioselective synthesis of the natural products cladospolide B, cladospolide C, and iso-cladospolide B has been accomplished from tartaric acid. Key reactions in the synthetic sequence include the elaboration of a gamma-hydroxy amide derived from tartaric acid via alkene cross metathesis, Yamaguchi lactonization, and ring closing metathesis. (C) 2011 Elsevier Ltd. All rights reserved.