Instrumented drop-weight test results for normalised and tempered 9Cr1Mo steel

From instrumented drop-weight tests, the nil ductility transition temperature (T_NDT), and a conservative estimate of dynamic fracture toughness (K_Id), at T_NDT for normalised and tempered 9Cr---1Mo steel, are determined to be −25°C and 70 MPa√m, respectively. The latter value agrees well with that determined from pre-cracked Charpy tests. The K_Id/σ_Yd (σ_Yd is the dynamic yield stress) ratio at T_NDT is estimated to be 0·076 √m, in agreement with previous estimates. The uncertainties in crack profile measurement and effect of microstructural variation in the heat affected zone on fracture loads are also discussed.     

Ductile-brittle transition temperatures and dynamic fracture toughness of 9Cr-1Mo steel

The ductile-brittle transition temperature (DBTT) of 9Cr-1Mo steel was characterized by an RT _NDT-based K _IR curve approach and a reference temperature (T ₀)-based master curve (MC) approach. The MC was developed at a dynamic loading condition (loading rate of 5.12 m/s), using precracked Charpy V-notch (PCVN) specimens, and the reference temperature was termed T ₀ ^dy . The RT _NDT and T ₀ ^dy were determined to be −25 °C and −52 °C, respectively. The T ₀ ^dy was also estimated from instrumented CVN tests, using a modified Schindler procedure to evaluate K _Jd ; the result shows close agreement with that obtained from the PCVN tests. The ASME K _IR -curve approach proves to be too conservative compared to the obtained trend of the fracture toughness with temperature. The cleavage fracture stress, σ* _f , estimated from the critical length, l*, shows good agreement with that estimated from the load-temperature diagram (2400 to 2450 MPa), which was constructed from the CVN test results. The crack initiation mechanism has been identified as decohesion of the particle-matrix interface, rather than as the fracture of the particles.     

Design of a leucine zipper coiled coil stabilized 1.4 kcal mol-1 by phosphorylation of a serine in the e position

Using a dimeric bZIP protein, we have designed a leucine zipper that becomes more stable after a serine in the e position is phosphorylated by protein kinase A (delta delta GP = -1.4 kcal mol-1 dimer-1 or -0.7 kcal mol-1 residue-1). Mutagenesis studies indicate that three arginines form a network of inter-helical (i,i' + 5; i, i' + 2) and intra-helical (i, i + 4) attractive interactions with the phosphorylated serine. When the arginines are replaced with lysines, the stabilizing effect of serine phosphorylation is reduced (delta delta GP = -0.5 kcal mol-1 dimer-1). The hydrophobic interface of the leucine zipper needs a glycine in the d position to obtain an increase in stability after phosphorylation. The phosphorylated protein binds DNA with a 15-fold higher affinity. Using a transient transfection assay, we document a PKA dependent four-fold activation of a reporter gene. Phosphorylation of a threonine in the same e position decreases the stability by delta delta GP = +1.2 kcal mol-1 dimer-1. We present circular dichroism (CD) thermal denaturations of 15 bZIP proteins before and after phosphorylation. These data provide insights into the structural determinants that result in stabilization of a coiled coil by phosphorylation.     

Synthesis of beaded and entwined carbon nanofibers in Ni:Al alloy catalyst

This paper reports two new types of carbon nanofibers synthesis by thermal decomposition of n-hexane in presence of Ni-Al alloy in hydrogen atmosphere at 1100 degrees C. One type is "beaded fibers" in which spherical carbon beads (approximately 1 microm) are regularly grown from outer surface of fibers (approximately 0.3 microm). The other new microstructure is "entwined fibers" in which multiple nanofibers of diameter approximately 100 nm grow self-entwined like a braid of hair. Both bead-fiber bonding (in beaded fibers) and fiber-fiber interaction (in entwined fibers) are strong to be detached/unfolded by 30-min ultrasonication.     

An attack invariant scheme for content-based video copy detection

Due to the advancement in the field of multimedia technology and communication, it has become easier to access, store, and edit video data. Easy manipulation of video data and its rapid distribution have made content-based video copy detection (CBVCD) an active area of research. In a CBVCD system, reference video sequence and query sequence are compared to detect whether the query video sequence is a copy of reference video sequence. Thus, the generation of fingerprint of a video sequence and sequence matching technique are the core tasks of such system. In order to evade such detection process, a copied version may undergo different kinds of transformations like photometric and post-production attack. So the detection system must be robust enough against such attacks. In this work, fingerprint is generated from the sub-bands of wavelet decomposed intensity image and localized intensity gradient histograms of low sub-band. The fingerprint thus obtained reflects considerable discriminating capability and robustness against the attacks. Furthermore, to cope up with the attacks, we have adopted simple pre-processing technique, which enhances the robustness of the system further. A robust sequence matching technique based on multivariate Wald–Wolfowitz test is proposed here. An experiment has been carried out with a database consisting of distinct 642 shots and 1,485 query sequences representing different attacks. Proposed methodology achieves high copy detection rate (99.39 %) and very low false alarm rate (0.14 %) and performs better than other spatio-temporal measure based systems.     

Enhancement of the transport and dielectric properties of graphite oxide nanoplatelets‐polyvinyl alcohol composite showing low percolation threshold

Graphite oxide nanoplatelets (GOnP) were prepared using standard method and used to make GOnP‐polyvinyl alcohol (PVA) composites by using solution cast technique. Significant enhancement of electrical conductivity and dielectric permittivity of the GOnP/PVA composites are observed at low GOnP concentration (f_GOnP = f_c∼0.41 vol%) which is the percolation threshold value estimated from the concentration dependent transport and dielectric data. Nearly 300 times increase in dielectric permittivity (compared with that of PVA) is observed in the GOnP/PVA composite around f_c. We notice interesting metal‐insulator like transition (a sudden increase in resistivity) from the temperature dependent resistivity data in the pure GOnP sample around T_MI ∼ 275 K which is shifted to 300 K in the GOnP/PVA composite for f_c = 0.41 vol%, indicating drastic change of sp³/sp² ratio around respective T_MI. The present graphite‐based composite material might be processed for different applications. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Biohydrogen production from Enterobacter cloacae IIT-BT 08 using distillery effluent

Distillery effluent poses severe environmental pollution problem mainly due to its high organic content. During alcohol fermentation, most of the essential macro- and micro-nutrients get utilized. Therefore, supplementation of these nutrients becomes imperative for the improvement of biohydrogen production. In the present study, starch based distillery effluent was used for dark fermentative hydrogen production using Enterobacter cloacae IIT-BT 08. Hence, this study was undertaken to evaluate the effect of supplementation of yeast extract, malt extract, Fe⁺⁺, Cu⁺⁺ and Mg⁺⁺ on biohydrogen production. The interaction among supplements and their mutual effect on the hydrogen production was studied using five factor–five level central composite design). Optimum hydrogen yield of 7.4 mol H₂/kg COD_reduced was predicted by the model, which showed an excellent correlation with experimental hydrogen yield of 7.38 ± 0.24 mol H₂/kg COD_reduced. An average hydrogen production rate of 80 mL/L h was achieved after supplementation, having 2.2 times higher hydrogen yield as compared to non-supplemented distillery effluent.     

Photofermentative molecular biohydrogen production by purple-non-sulfur (PNS) bacteria in various modes: The present progress and future perspective

Hydrogen is green fuel for the future, mainly due to its recyclability. Biohydrogen production processes are less energy intensive and environmental friendly in compared to chemical processes. Fermentative biohydrogen production can be broadly classified as: dark and photo fermentation. Two enzymes, nitrogenase and hydrogenase play important role in biohydrogen production. Purple Non-Sulfur bacteria (PNS) are mainly used in photofermentative hydrogen production through which the overall yield can be improved manifolds. The scope and objective of this review paper is to investigate the performance of various light driven photofermentative hydrogen production by PNS bacteria along with several developmental works related to batch, repeated batch, feed batch and continuous operation. However the study of Photobiological process by microalgae or cyanobacteria is outside the scope of this review. Optimization of suitable process parameters such as carbon and nitrogen ratio, illumination intensity, bioreactor configuration, immobilization of active cells in specific continuous mode and inoculum age may lead to higher yield of hydrogen generation.     

Effect of fuel characteristics on synthesis of calcium hydroxyapatite by solution combustion route

The effect of fuel characteristics on the processing of nano sized calcium hydroxyapatite (HA) fine powders by the solution combustion technique is reported. Urea, glycine and glucose were used as fuels in this study. By using different combinations of urea and glycine fuels and occasional addition of small amounts of highly water-soluble glucose, the flame temperature (T _f) of the process as well as product characteristics could be controlled easily. The powders obtained by this modified solution combustion technique were characterized by XRD, FTIR spectroscopy, SEM, FESEM-EDX, particle size analyser (PSD) and specific surface area (SSA) measurements. The particle size of phase pure HA powder was found to be <20 nm in this investigation. The effects of glucose addition with stoichiometric (μ = 1) and fuel excess (μ > 1) urea and glycine precursor batches were investigated separately.