Dynamic Odd–Even Effect in Liquid n‐Alkanes near Their Melting Points

n‐Alkanes are the textbook examples of the odd–even effect: The difference in the periodic packing of odd‐ and even‐numbered n‐alkane solids results in odd–even variation of their melting points. However, in the liquid state, in which this packing difference is not obvious, it seems natural to assume that the odd–even effect does not exist, as supported by the monotonic dependence of the boiling points of n‐alkanes on the chain length. Herein, we report a surprising odd–even effect in the translational diffusional dynamic properties of n‐alkanes in their liquid states. To measure the dynamics of the molecules, we performed quasi‐elastic neutron scattering measurements near their melting points. We found that odd‐numbered n‐alkanes exhibit up to 30 times slower dynamics than even‐numbered n‐alkanes near their respective melting points. Our results suggest that, although n‐alkanes are the simplest hydrocarbons, their dynamic properties are extremely sensitive to the number of carbon atoms.     

Interactive simulation of aircraft noise in aural and visual virtual environments

This paper describes a novel aircraft noise simulation technique developed at RWTH Aachen University, which makes use of aircraft noise auralization and 3D visualization to make aircraft noise both heard and seen in immersive Virtual Reality (VR) environments. This technique is intended to be used to increase the residents’ acceptance of aircraft noise by presenting noise changes in a more directly relatable form, and also aid in understanding what contributes to the residents’ subjective annoyance via psychoacoustic surveys. This paper describes the technique as well as some of its initial applications. The reasoning behind the development of such a technique is that the issue of aircraft noise experienced by residents in airport vicinities is one of subjective annoyance. Any efforts at noise abatement have been conventionally presented to residents in terms of noise level reductions in conventional metrics such as A-weighted level or equivalent sound level L_eq. This conventional approach however proves insufficient in increasing aircraft noise acceptance due to two main reasons – firstly, the residents have only a rudimentary understanding of changes in decibel and secondly, the conventional metrics do not fully capture what the residents actually find annoying i.e. characteristics of aircraft noise they find least acceptable. In order to allow least resistance to air-traffic expansion, the acceptance of aircraft noise has to be increased, for which such a new approach to noise assessment is required.     

Mechanistic studies on pyridoxal phosphate synthase: the reaction pathway leading to a chromophoric intermediate

Two routes for the de novo biosynthesis of pyridoxal-5'-phosphate (PLP) have been discovered and reconstituted in vitro. The most common pathway that organisms use is dependent upon the activity of just two enzymes, known as Pdx1 (YaaD) and Pdx2 (YaaE) in bacteria. Pdx2 has been shown to have glutaminase activity and most likely channels ammonia to the active site of the PLP synthase subunit, Pdx1, where ribose-5-phosphate (R5P), glyceraldehyde-3-phosphate (G3P), and ammonia are condensed in a complex series of reactions. In this report we investigated the early steps in the mechanism of PLP formation. Under pre-steady-state conditions, a chromophoric intermediate (I320) is observed that accumulates upon addition of only two of the substrates, R5P and glutamine. The intermediate is covalently bound to the protein. We synthesized C5 monodeuterio (pro-R, pro-S) and dideuterio R5P and showed that there is a primary kinetic isotope effect on the formation of this intermediate using the pro-R but not the pro-S labeled isomer. Furthermore, it was shown that the phosphate unit of R5P is eliminated rather than hydrolyzed in route to intermediate formation and also that there is an observed C5-deuterium kinetic isotope effect on this elimination step. Interestingly, it was observed that the formation of the intermediate could be triggered in the absence of Pdx2 by the addition of high concentrations of NH4Cl to a preincubated solution of Pdx1 and R5P. The formation of I320 was also monitored using high-resolution electrospray ionization Fourier transform mass spectrometry and revealed a species of mass 34,304 Da (Pdx1 + 95 Da). These results allow us to narrow the mechanistic possibilities for the complex series of reactions involved in PLP formation.     

Detection and characterization of recombinant DNA expressing <Emphasis Type="Italic">vip3A</Emphasis>-type insecticidal gene in GMOs—standard single,multiplex and construct-specific PCR assays

Vegetative insecticidal protein (Vip), a unique class of insecticidal protein, is now part of transgenic plants for conferring resistance against lepidopteron pests. In order to address the imminent regulatory need for detection and labeling of vip3A carrying genetically modified (GM) products, we have developed a standard single PCR and a multiplex PCR assay. As far as we are aware, this is the first report on PCR-based detection of a vip3A-type gene (vip-s) in transgenic cotton and tobacco. Our assay involves amplification of a 284-bp region of the vip-s gene. This assay can possibly detect as many as 20 natural wild-type isolates bearing a vip3A-like gene and two synthetic genes of vip3A in transgenic plants. The limit of detection as established by our assay for GM trait (vip-s) is 0.1%. Spiking with nontarget DNA originating from diverse plant sources had no inhibitory effect on vip-s detection. Since autoclaving of vip-s bearing GM leaf samples showed no deterioration/interference in detection efficacy, the assay seems to be suitable for processed food products as well. The vip-s amplicon identity was reconfirmed by restriction endonuclease assay. The primer set for vip-s was equally effective in a multiplex PCR assay format (duplex, triplex and quadruplex), used in conjunction with the primer sets for the npt-II selectable marker gene, Cauliflower mosaic virus 35S promoter and nopaline synthetase terminator, enabling concurrent detection of the transgene, regulatory sequences and marker gene. Further, the entire transgene construct was amplified using the forward primer of the promoter and the reverse primer of the terminator. The resultant amplicon served as a template for nested PCR to confirm the construct integrity. The method is suitable for screening any vip3A-carrying GM plant and food. The availability of a reliable PCR assay method prior to commercial release of vip3A-based transgenic crops and food would facilitate rapid and efficient regulatory compliance. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. An application for an Indian patent (1891/DEL2006/17.08.07) comprising a substantive part of this study has been filed. ITRC communication no. 2516.     

Bimetallic Cooperativity and Hydrogen Bonding Allow Efficient Reduction of CO2

Reducing CO₂ selectively to one of the several C1 products is challenging, as the thermodynamic reduction potentials for the different n e⁻/n H⁺ reductions of CO₂ are similar and so is the reduction potential for H⁺ reduction. Recently, Halime, Aukauloo, and co-workers have taken inspiration from the active site of nickel CO dehydrogenase (Ni-CODH) to design bimetallic iron porphyrins bridged by a urea moiety. These complexes show fast and selective reduction of CO₂ to CO and the results suggest a Ni-CODH type mechanism at play where one of the two metals binds and reduces the CO₂ while the other stabilizes the reduced species by forming a bridged complex, facilitating the C−O bond cleavage.     

Model studies of azide binding to functional analogues of CcO

N3- binding to a functional model of CcO is investigated in its Fe3+, Fe3+Cu+, and Fe3+Cu2+ forms. A combination of EPR and FTIR indicates that N3- binds in a bridging mode in the bimetallic sites and signature N3- bands are identified for several forms of N3- binding to the site. The presence of the distal metal increases the binding affinity of N3-. This bridging enables antiferromagnetic interaction between the two metal centers in the Fe3+Cu2+ state, which results in an EPR-silent ground state.     

High-Performance Thin-Layer Chromatographic Analysis for the Simultaneous quantification of Gallic Acid,Vanillic Acid,Protocatechuic Acid,and Quercetin in the Methanolic Fraction of Limonia acidissima L. Fruits

JPC – Journal of Planar Chromatography – Modern TLC - A high-performance thin-layer chromatography (HPTLC) method for the simultaneous quantitative determination of gallic acid,...     

Investigations on the Phase Transformation,Optical Characteristics,and Photocatalytic Activity of Synthesized Heterostructured Nanoporous Bi2O3–TiO2

Fine‐powdered, heterostructured, nanoporous Bi₂O₃–TiO₂ (BTO) was synthesized by a green approach using ultrasonication, with the mole ratio Bi/Ti of 1:1 and calcined at different temperatures. The physical and optical properties of the mixed oxides were investigated. The phase structure, as identified by X‐ray diffraction (XRD), showed the appearance of new phases as a function of the calcination temperature. Morphological examinations indicated the formation of a nanoporous structure with a drastic change in morphology at the calcination temperature of 850°C from a globule to a rod‐shaped structure, which further got transformed to a rocky appearance at 1200°C. Doping with Bi₂O₃ led to the lowering of the bandgap of TiO₂ from 3.25 to 2.5 eV. A BTO nanocatalyst calcined at 450°C exhibited promising photocatalytic activity for the degradation of quinalphos (QP) (92%) after a time interval of 100 min under visible light and at the optimum pH 8. The kinetics of degradation of QP showed that it follows a pseudo‐first‐order path with a rate constant 0.01267 min^?1. The synthesized BTO mixed oxide showed profound improvement in photocatalytic activity in the visible region as compared to TiO₂.     

Evaluation of network parameters and drug release behavior of gum acacia-crosslinked-carbopol hydrogel wound dressings

Present article discusses the synthesis, characterization, biodegradation, network parameter and drug release of gum acacia-crosslinked-carbopol hydrogel wound dressing. Polymers have been characterized by ¹³C solid state nuclear magnetic resonance spectroscopy, elemental analysis, cryo-scanning electron microscopy, atomic force microscopy, thermogravimetric analysis, differential thermal analysis, differential thermogravimetry, and differential scanning calorimetry studies. Network parameters of hydrogel wound dressings such as polymer volume fraction in the swollen state φ, Flory–Huggins interaction parameter χ, molecular weight of the polymer chain between two neighboring cross links M_c, crosslink density ρ and the corresponding mesh size ξ have also been determined. Different in vitro release kinetic models (zero order, first order, Higuchi square root law, Korsmeyer-Peppas, and Hixson-Crowell cube root models) have been applied on the drug release profile. The release of antibiotic drug moxifloxacin from the drug loaded hydrogel matrix occurred through non-Fickian diffusion mechanism and release profile best fitted in the Korsmeyer-Peppas model. Semi-contact mode atomic force microscopic imaging showed that rough surface with root mean square roughness 82.868 nm of the polymer films.     

On two‐liquid AC electroosmotic system for thin films

Lab‐on‐chip devices employ EOF for transportation and mixing of liquids. However, when a steady (DC) electric field is applied to the liquids, there are undesirable effects such as degradation of sample, electrolysis, bubble formation, etc. due to large magnitude of electric potential required to generate the flow. These effects can be averted by using a time‐periodic or AC electric field. Transport and mixing of nonconductive liquids remain a problem even with this technique. In the present study, a two‐liquid system bounded by two rigid plates, which act as substrates, is considered. The potential distribution is derived by assuming a Boltzmann charge distribution and using the Debye–Hückel linearization. Analytical solution of this time‐periodic system shows some effects of viscosity ratio and permittivity ratio on the velocity profile. Interfacial electrostatics is also found to play a significant role in deciding velocity gradients at the interface. High frequency of the applied electric field is observed to generate an approximately static velocity profile away from the Electric Double Layer (EDL).