A ray model for hard parallel noise barriers in high-rise cities

A ray model is developed and validated for prediction of the insertion loss of hard parallel noise barriers placed in an urban environment either in front of a row of tall buildings or in a street canyon. The model is based on the theory of geometrical acoustics for sound diffraction at the edge of a barrier and multiple reflections by the ground, barrier and fa?ade surfaces. It is crucial to include the diffraction and multiple reflection effects in the ray model as they play important roles in determining the overall sound pressure levels for receivers located between the fa?ade and the near-side barrier. Comparisons of the ray model with a wave-based boundary element formulation show reasonably good agreement over a broad frequency range. Results of scale model experimental studies are also presented. It is demonstrated that the ray model agrees tolerably well with the scale model experimental data.     

Magnetoresistance anisotropy of a one-dimensional superconducting niobium strip

We investigated confinement effects on the resistive anisotropy of a superconducting niobium strip with a rectangular cross section. When its transverse dimensions are comparable to the superconducting coherence length, the angle dependent magnetoresistances at a fixed temperature can be scaled as R(theta,H) = R(H/Hctheta) where Hctheta =Hc0(cos2theta + gamma(-2)sin2theta)(-1/2) is the angular dependent critical field, gamma is the width to thickness ratio, and Hc0 is the critical field in the thickness direction at theta=0 degrees . The results can be understood in terms of the anisotropic diamagnetic energy for a given field in a one-dimensional superconductor.     

Reverse Thinking of the Aggregation-Induced Emission Principle: Amplifying Molecular Motions to Boost Photothermal Efficiency of Nanofibers**

Using reverse thinking of the aggregation-induced emission (AIE) principle, we demonstrate an ingenious and universal protocol for amplifying molecular motions to boost photothermal efficiency of fibers. Core–shell nanofibers having the olive oil solution of AIE-active molecules as the core surrounded by PVDF-HFP shell were constructed by coaxial electrospinning. The molecularly dissolved state of AIE-active molecules allows them to freely rotate and/or vibrate in nanofibers upon photoexcitation and thus significantly elevates the proportion of non-radiative energy dissipation, affording impressive heat-generating efficiency. Photothermal evaluation shows that the core–shell nanofibers with excellent durability can reach up to 22.36 % of photothermal conversion efficiency, which is 26-fold as the non-core–shell counterpart. Such a core–shell fiber can be used for photothermal textiles and solar steam generation induced by natural sunlight with green and carbon-zero emission.     

In Situ Monitoring of RAFT Polymerization by Tetraphenylethylene‐Containing Agents with Aggregation‐Induced Emission Characteristics

A facile and efficient approach is demonstrated to visualize the polymerization in situ. A group of tetraphenylethylene (TPE)‐containing dithiocarbamates were synthesized and screened as agents for reversible addition fragmentation chain transfer (RAFT) polymerizations. The spatial‐temporal control characteristics of photochemistry enabled the RAFT polymerizations to be ON and OFF on demand under alternating visible light irradiation. The emission of TPE is sensitive to the local viscosity change owing to its aggregation‐induced emission characteristic. Quantitative information could be easily acquired by the naked eye without destroying the reaction system. Furthermore, the versatility of such a technique was well demonstrated by 12 different polymerization systems. The present approach thus demonstrated a powerful platform for understanding the controlled living radical polymerization process.     

Analysis of trifluoroacetic acid and other short-chain perfluorinated acids (C2-C4) in precipitation by liquid chromatography-tandem mass spectrometry: comparison to patterns of long-chain perfluorinated acids (C5-C18)

This paper provides analytical chemical information on selected new molecular entities (NMEs) which are drugs that have recently been approved by the FDA. These are the antiretroviral drugs, atazanavir, indinavir and emtricitabine, the antibacterial gemifloxacin, rosuvastatine which is a cholesterol-lowing drug, the anti-cancer drug gefitinib and aprepitant for neurological disorders. Electrospray ionisation-quadrupole ion trap mass spectrometry (ESI-MSⁿ) was employed to generate tandem mass spectrometric (MS²) data of the drugs studied and structural assignments of product ions were supported by quadrupole time-of-flight mass spectrometry (QToF-MS/MS). These fragmentation studies were then utilised in the development and validation of a specific and sensitive liquid chromatographic method (LC–ESI-MS²) to identify and determine these drugs at therapeutic concentration levels in serum after a single protein precipitation procedure with acetonitrile. In addition, this method was compared to the application of gas liquid chromatography-flame ionisation detection (GLC-FID) and differential pulse polarography (DPP) for the analysis of these NMEs in serum.     

Solid Phase Extraction – Voltammetric Coupled Detection of Caffeine in Acetonitrile

Caffeine (CAF) in aqueous solutions was extracted into acetonitrile (MeCN) using solid phase extraction (SPE). The voltammetric detection of CAF in MeCN was performed in a microcentrifuge tube after SPE in order to minimise the required amount of MeCN and reagents used during the analysis. The voltammetric determination of CAF from a range of beverages extracted into MeCN was in good agreement with the results obtained from HPLC measurements on the same samples. The SPE‐coupled voltammetric method gave more accurate results than those obtained via the direct voltammetric detection of CAF in real beverage samples.     

A circular ferrofluid driven microchip for rapid polymerase chain reaction

In the past few years, much attention has been paid to the development of miniaturized polymerase chain reaction (PCR) devices. After a continuous flow (CF) PCR chip was introduced, several CFPCR systems employing various pumping mechanisms were reported. However, the use of pumps increases cost and imposes a high requirement on microchip bonding integrity due to the application of high pressure. Other significant limitations of CFPCR devices include the large footprint of the microchip and the fixed cycle number which is dictated by the channel layout. In this paper, we present a novel circular close-loop ferrofluid driven microchip for rapid PCR. A small ferrofluid plug, containing sub-domain magnetic particles in a liquid carrier, is driven by an external magnet along the circular microchannel, which in turn propels the PCR mixture through three temperature zones. Amplification of a 500 bp lambda DNA fragment has been demonstrated on the polymethyl methacrylate (PMMA) PCR microchip fabricated by CO(2) laser ablation and bonded by a low pressure, high temperature technique. Successful PCR was achieved in less than 4 min. Effects of cycle number and cycle time on PCR products were investigated. Using a magnet as the actuator eliminates the need for expensive pumps and provides advantages of low cost, small power consumption, low requirement on bonding strength and flexible number of PCR cycles. Furthermore, the microchip has a much simpler design and smaller footprint compared to the rectangular serpentine CFPCR devices. To demonstrate its application in forensics, a 16-loci short tandem repeat (STR) sample was successfully amplified using the PCR microchip.     

A theoretical investigation of P-hydroxyphenacyl caged phototrigger compounds: how water induces the photodeprotection and subsequent rearrangement reactions

Complete active-space self-consistent field (CASSCF) calculations with a (14,11) active space and density functional theory calculations followed by Car-Parrinello molecular dynamic simulations are reported for the p-hydroxyphenacyl acetate, diethyl phosphate, and diphenyl phosphate phototrigger compounds. These calculations considered the explicit hydrogen bonding of water molecules to the phototrigger compound and help reveal the role of water in promoting the photodeprotection and subsequent rearrangement reactions for the p-hydroxyphenacyl caged phototrigger compounds experimentally observed in the presence of appreciable amounts of water but not observed in neat nonproton solvents like acetonitrile. The 267 nm excitation of the phototrigger compounds leads to an instantaneous population of the S3(1pipi*) state Franck-Condon region, which is followed by an internal conversion deactivation route to the S1(1npi*) state via a 1pipi*/1npi* vibronic coupling. The shorter lifetime of the S1(1npi*) state (approximately 1 ps) starting from the FC geometry is terminated by a fast intersystem crossing at a 3pipi*/3npi* intersection with a structure of mixed pipi*/npi* excitation in the triplet state. The deprotection reaction is triggered by a proton (or hydrogen atom) transfer assisted by water bridges and emanates from this pipi*/npi* triplet state intersection. With the departure of the leaving group, the reaction evolves into a water-mediated post-deprotection phase where the spin inversion of pQM (X, 3A) leads to a spiroketone in the ground state by a cyclization process that is followed by an attack of water to produce a 1,1'-di-hydroxyl-spiroketone. Finally, the H atom of the hydroxyl in 1,1'-di-hydroxyl-spiroketon transfers back to the p-O atom aided by water molecules to generate the p-hydroxyphenyl-acetic acid final rearrangement product.     

Cell adhesion properties on photochemically functionalized diamond

The biocompatibility of diamond was investigated with a view toward correlating surface chemistry and topography with cellular adhesion and growth. The adhesion properties of normal human dermal fibroblast (NHDF) cells on microcrystalline and ultrananocrystalline diamond (UNCD) surfaces were measured using atomic force microscopy. Cell adhesion forces increased by several times on the hydrogenated diamond surfaces after UV irradiation of the surfaces in air or after functionalization with undecylenic acid. A direct correlation between initial cell adhesion forces and the subsequent cell growth was observed. Cell adhesion forces were observed to be strongest on UV-treated UNCD, and cell growth experiments showed that UNCD was intrinsically more biocompatible than microcrystalline diamond surfaces. The surface carboxylic acid groups on the functionalized diamond surface provide tethering sites for laminin to support the growth of neuron cells. Finally, using capillary injection, a surface gradient of polyethylene glycol could be assembled on top of the diamond surface for the construction of a cell gradient.