Thermal decomposition of Co-Al layered double hydroxide: Identification of precursor to oxide with spinel structure

The layered double hydroxide (LDH) of Co with Al decomposes to yield an oxide residue with the spinel structure below 250°C. The decomposition reaction is preceded by the formation of an intermediate hydroxide in which the metal hydroxide layers are regularly stacked about the c-crystallographic axis, but the layers themselves are aperiodic. Aperiodicity is modeled by locating randomly chosen Co²⁺ ions in tetrahedral sites in the interlayer region. This phase is characterized by a single strong basal reflection in its powder diffraction pattern. All other reflections are extinguished on account of (i) turbostratic disorder which destroys all hkl reflections and (ii) layer aperiodicity, which destroys all two dimensional hk reflections. Given its topochemical relationship with the spinel structure, such an intermediate is a necessary precursor to spinel formation.     

Ultrasonic study on binary liquid mixtures of propiophenone with anilines and alkyl substituted anilines at T=303.15 to 318.15 K

Densities ‘ρ’, ultrasonic speeds of sound ‘u’ of binary mixtures of propiophenone (PPH) with aniline, N-Methylaniline, N,N-dimethylaniline and N,N-diethylaniline were measured over the entire composition range from 303.15 K to 318.15 K and at atmospheric pressure 0.1 MPa. Experimental data of ultrasonic sound were compared and discussed with the computed values of ‘u’ from various velocity theories like Nomoto’s relation (U_NOM), impedance relation (U_IMP), Van Dael and Vangeel’s ideal mix relation (U_VDV), Rao’s specific velocity relation (U_RAO), Junjie’s theory (U_JUN) and Jouyban-Acree’s (U_JOE) relation for the above binary mixtures over the entire mole fraction range at the studied temperatures. The results are satisfactory and are in agreement between the theoretical and the experimental values. Further, the molecular interaction parameter (α), average percentage error and Chi-square test values were computed by using the values of experimental and theoretical ultrasonic velocities. The Δu values were correlated with Redlich-Kister polynomial equation to compute the coefficients and the standard deviations of the binary mixtures. The results were analyzed in terms of intermolecular interactions.     

NMR structure of the extended Myb cognate sequence and modeling studies on specific DNA-Myb complexes

The recognition sequence of the Myb protein has been recently described to be pyAACKGHH (where py = T/C, K = G/T, and H = A/C/T), modifying the earlier identification as pyAACKG [Ording, E., et al. (1994) Eur. J. Biochem. 222, 113-120]. We had earlier determined the solution structure of the minimal cognate sequence TAACGG, choosing py = T and K = G, embeded in a 12-mer DNA duplex by NMR and related computational techniques [Radha, P. K., et al. (1995) Biochemistry 34, 5913-5912]. To understand the structural significance of the above modification and the role of the variability in the recognition sequence, we have investigated here the solution structure of a different DNA segment, d-ACAACTGCAGTTGT, which contains the extended Myb cognate site, CAACTGCA. The three-dimensional structure of the 14-mer duplex has been determined from NMR data by relaxation matrix and restrained molecular dynamics calculations. The structure of the above cognate sequence in the 14-mer duplex has been compared with that of the cognate sequence, TAACGG, in the 12-mer duplex and also with that in the NMR structure of the Myb DNA binding domain (R2R3)-DNA complex determined by Ogata et al. recently [Ogata, K., et al. (1994) Cell 79, 639-648]. The comparison highlighted differences in several structural parameters for the cognate sites in the DNA segments. Modeling studies by taking out the protein from the complex and presenting it with 12-mer and 14-mer DNA structures indicated that the protein induces structural alterations to drive the cognate site to a reasonably conserved structure. The extent of similarity of the derived structures was, however, dependent on the base sequences. Base changes in the minimal cognate sequence in the 12-mer-protein complex and in the 14-mer-protein complex so as to match the sequence of Ogata et al. produced a more conserved structure of the complex. A reverse exercise, in which the Ogata DNA in the complex was mutated to match the 12-mer and 14-mer minimal cognate sequences, complemented the above observations of the subtle sequence dependence of the structure in the complex. On the other hand, base changes in the extension did not influence the DNA-protein complex structure significantly. We also observed that the structural changes in the protein were very minor when different DNA sequences or different DNA structures were presented to it. These observations would be of interest from the point of view of DNA-Myb recognition.     

Resource management and task partitioning and scheduling on a run-time reconfigurable embedded system

There are many design challenges in the hardware-software co-design approach for performance improvement of data-intensive streaming applications with a general-purpose microprocessor and a hardware accelerator. These design challenges are mainly to prevent hardware area fragmentation to increase resource utilization, to reduce hardware reconfiguration cost and to partition and schedule the tasks between the microprocessor and the hardware accelerator efficiently for performance improvement and power savings of the applications.In this paper a modular and block based hardware configuration architecture named memory-aware run-time reconfigurable embedded system (MARTRES) is proposed for efficient resource management and performance improvement of streaming applications. Subsequently we design a task placement algorithm named hierarchical best fit ascending (HBFA) algorithm to prove that MARTRES configuration architecture is very efficient in increased resource utilization and flexible in task mapping and power savings. The time complexity of HBFA algorithm is reduced to O(n) compared to traditional Best Fit (BF) algorithm’s time complexity of O(n²), when the quality of the placement solution by HBFA is better than that of BF algorithm. Finally we design an efficient task partitioning and scheduling algorithm named balanced partitioned and placement-aware partitioning and scheduling algorithm (BPASA). In BPASA we exploit the temporal parallelism in streaming applications to reduce reconfiguration cost of the hardware, while keeping in mind the required throughput of the output data. We balance the exploitation of spatial parallelism and temporal parallelism in streaming applications by considering the reconfiguration cost vs. the data transfer cost. The scheduler refers to the HBFA placement algorithm to check whether contiguous area on FPGA is available before scheduling the task for HW or for SW.     

Defect models in silver halides

Silver halide crystals AgCl and AgBr exhibit all the three types of intrinsic point defects, namely, cationic Frenkel disorder, Schottky disorder and the bound vacancy pair disorder. The ionic conductivity anomaly at high temperatures, the unusual behaviour in respect of self- and impurity diffusion and the contrasting features in the anion self-diffusion between AgCl and AgBr do not all satisfactorily fit into the prevailing models of ionic transport. We review these features critically. We also discuss the potential and polarization models used in the theoretical evaluation of the enthalpies of formation of the intrinsic defects in these crystals. Results of our recent investigations on these questions will be presented to highlight their implications to the defect physics of these materials.     

Hybrid Erasure-Error Protocols for Wireless Video

Many recently proposed cross-layer protocols for wireless video, have advocated the relay of corrupted packet to higher layers. Such protocols lead to both errors and erasures at the compressed video application layer. We generically refer to such schemes as hybrid erasure-error protocols (HEEPs). In this paper, we analyze the utility of HEEPs for efficient transmission of video over wireless channels. In order to maintain the generic nature of the deductions in this paper, we base our analysis on two (rather abstract) communication schemes for wireless video: hybrid error-erasure cross-layer design (CLD) and hybrid error-erasure cross-layer design with side-information (CLDS). We make a comparative analysis of the channel capacities of these schemes over single and multi-hop wireless channels to identify the conditions under which the HEEPs can provide improved performance over conventional (CON) protocols. In addition, we employ Reed Solomon (RS) and low-density parity check (LDPC)-code-based forward-error correction (FEC) schemes to illustrate that the improvement in capacity can easily enable an FEC scheme employed in conjunction with a HEEP to provide improved throughput. Finally we compare the performance of CON, CLD, and CLDS in terms of video quality using the H.264 video standard. The simulation results show a significant advantage for the HEEPs     

Maximum-Likelihood Header Estimation: A Cross-Layer Methodology for Wireless Multimedia

We propose a novel cross-layer header estimation methodology that can be used by UDP-based wireless multimedia applications to estimate corrupted packet headers, thereby realizing significant throughput improvements. The proposed methodology requires only minor modifications to the protocol stack at the receiver while no modifications are needed to senders or intermediate nodes. We formulate header estimation as a problem of maximum-likelihood estimation of known parameters in noise. We derive likelihood functions for two wireless channel models, namely Markov and multifractal wavelet models. Our trace-driven video simulations at 2, 5.5 and 11 Mbps data rates of an 802.11b LAN demonstrate that significant improvements over normal UDP and UDP Lite can be achieved by employing header estimation with UDP.     

Fuzzy-Based Cluster Head Amendment (FCHA) Approach to Prolong the Lifetime of Sensor Networks

Wireless Personal Communications - Wireless sensor networks (WSN) consist of large number of sensor nodes that work collaboratively. Sensors segregate groups with similar traits and get arranged in...     

One-pot size and shape controlled synthesis of DMSO capped iron oxide nanoparticles

We report here the capping of iron oxide nanoparticles with dimethyl sulfoxide (DMSO) to make chloroform soluble iron oxide nanoparticles. Size and shape of the capped iron oxide nanoparticles are well controlled by simply varying the reaction parameters. The synthesized nanocrystallites were characterized by thermal analysis (TG-DTA), powder X-ray diffraction (XRD), transmission electron microscopy (TEM) for evaluating phase, structure and morphology. ¹H NMR spectra of the synthesized samples confirm DMSO, and the capping of DMSO on the ferrite samples. Shift of the S=O stretching frequency in Fourier transformed infra-red (FTIR) spectra indicates that the bonding between DMSO and ferrite is through an oxygen moiety. The magnetic measurements of all the synthesized samples were investigated with a SQUID magnetometer which shows that the magnetic properties are strongly dependent on the size as well as shape of the iron oxide.     

Majority and minority intrinsic defects in lithium and sodium halides

We present new findings on the enthalpies of formation of vacancies and interstitial ion defects on either sublattice in the alkali halide crystals MX (X=F, Cl, Br and M=Li, Na) using the MPPI model. The model uses a minimum fit to crystal properties and is fully consistent with the dielectric response. The role of the non-Coulombic short range forcesvis-a-vis polarization fields in the stabilization of the defect formation process is examined and discussed in detail. It is shown that it is important to treat the electrostatic polarization caused by the point defect carefully and variation in potential modelling has a comparatively minor effect on the calculations of enthalpies of formation.