A general copper powder-catalyzed Ullmann-type reaction of 3-halo-4(1H)-quinolones with various nitrogen-containing nucleophiles

3-(N-Substituted) 4(1H)-quinolinones were synthesized using the copper-catalyzed Ullmann C-N bond forming strategy in moderate to quantitative yields. Starting from 3-halo-4(1H)-quinolones, various nucleophiles including amides, lactams, sulfonamides and NH-containing azoles have been used successfully. In all cases, the reactions take place rapidly in toluene and proceed by using copper powder as a catalyst, DMEDA as a ligand and K(2)CO(3) as a base. In addition, other related heterocycles such as 3-bromoquinolin-2(1H)-ones, 3-bromocoumarin, and 3,5-dibromo-2-pyridone show good to very high reactivity with various nucleophiles under our Cu/DMEDA catalyst system.     

Analytical modeling of bidirectional multi‐channel IEEE 802.11 MAC protocols

This paper presents an analytical approach to model the bi‐directional multi‐channel IEEE 802.11 MAC protocols (Bi‐MCMAC) for ad hoc networks. Extensive simulation work has been done for the performance evaluation of IEEE 802.11 MAC protocols. Since simulation has several limitations, this work is primarily based on the analytical approach. The objective of this paper is to show analytically the performance advantages of Bi‐MCMAC protocol over the classical IEEE 802.11 MAC protocol. The distributed coordination function (DCF) mode of medium access control (MAC) is considered in the modeling. Two different channel scheduling strategies, namely, random channel selection and fastest channel first selection strategy are also presented in the presence of multiple channels with different transmission rates. M/G/1 queue is used to model the protocols, and stochastic reward nets (SRNs) are employed as a modeling technique as it readily captures the synchronization between events in the DCF mode of access. The average system throughput, mean delay, and server utilization of each MAC protocol are evaluated using the SRN formalism. We also validate our analytical model by comparison with simulation results. The results obtained through the analytical modeling approach illustrate the performance advantages of Bi‐MCMAC protocols with the fastest channel first scheduling strategy over the classical IEEE 802.11 protocol for TCP traffic in wireless ad hoc networks. Copyright © 2010 John Wiley & Sons, Ltd.     

Anisotropy of Charge Transport in a Uniaxially Aligned and Chain‐Extended,High‐Mobility,Conjugated Polymer Semiconductor

Charge transport in the ribbon phase of poly(2,5‐bis(3‐alkylthiophen‐2‐yl)thieno[3,2‐b]thiophene) (PBTTT)—one of the most highly ordered, chain‐extended crystalline microstructures available in a conjugated polymer semiconductor—is studied. Ribbon‐phase PBTTT has previously been found not to exhibit high carrier mobilities, but it is shown here that field‐effect mobilities depend strongly on the device architecture and active interface. When devices are constructed such that the ribbon‐phase films are in contact with either a polymer gate dielectric or an SiO₂ gate dielectric modified by a hydrophobic, self‐assembled monolayer, high mobilities of up to 0.4 cm² V^?1 s^?1 can be achieved, which is comparable to those observed previously in terrace‐phase PBTTT. In uniaxially aligned, zone‐cast films of ribbon‐phase PBTTT the mobility anisotropy is measured for transport both parallel and perpendicular to the polymer chain direction. The mobility anisotropy is relatively small, with the mobility along the polymer chain direction being higher by a factor of 3–5, consistent with the grain size encountered in the two transport directions.     

Triple helical recognition of pyrimidine inversions in polypurine tracts of RNA by nucleobase-modified PNA

Peptide nucleic acids containing 2-pyrimidinone (P) and 3-oxo-2,3-dihydropyridazine (E) heterocycles recognized C-G and U-A inversions in a polypurine tract of double helical RNA with high affinity and sequence selectivity at pH 6.25. E-modified PNA bound strongly to bacterial A-site RNA, while no binding was observed to the human A-site RNA.     

Development of a novel reporter gene vector for cell based angiogenic studies

Angiogenesis is a promising area of research that targets key therapeutic areas like cancer; wound healing, inflammatory diseases, etc. There is an increasing demand for screening of potential angiogenic and anti-angiogenic agents using sensitive, robust cell-based assays. We have developed a reporter vector containing cis-acting elements that respond to growth factors/angiogenic ligands for use in a cell-based luciferase reporter assay. We performed transient transfection of our reporter gene vector in MCF-7 cells to establish its application for screening of potential pro/anti-angiogenic agents. Reporter gene transactivation studies with different concentrations of fetal bovine serum clearly indicated that the vector is functionally responsive to the angiogenic signals mediated by serum growth factors. We also used endostatin to inhibit transactivation and prove responsiveness to the anti-angiogenic agent. This vector is a promising tool for studying angiogenesis using cell-based reporter gene assays.     

A microfluidic device for self-synchronised production of droplets

The primary requirement for a mixing operation in droplet-based microfluidic devices is an accurate pairing of droplets of reaction fluids over an extended period of time. In this paper, a novel device for self-synchronous production of droplets has been demonstrated. The device uses a change in impedance across a pair of electrodes introduced due to the passage of a pre-formed droplet to generate a second droplet at a second pair of electrodes. The device was characterised using image analysis. Droplets with a volume of ~23.5 ± 3.1 nl (i.e.~93% of the volume of pre-formed droplets) were produced on applying a voltage of 500 V. The synchronisation efficiency of the device was 83%. As the device enables self-synchronised production of droplets, it has a potential to increase the reliability and robustness of mixing operations in droplet-based microfluidic devices.     

Nanosized drug formulations under microfluidic continuous flow

We present a simple method involving a rotating tube processor to fabricate ultrafine crystalline drug nanoparticles under microfluidic continuous flow with precise control over particle size, with significantly enhanced dissolution of the drug.     

Composition of a monoterpenoid-rich essential oil from the rhizome of Zingiber officinale from north western Himalayas

The chemical composition of the essential oil from the rhizome of ginger (Zingiber officinale Roscoe), collected from Nahan, Himachal Pradesh, India, was determined by gas chromatography and GC-MS. Fifty-one compounds, representing 95.1% of the oil, were identified. The oil was characterized by relatively large amounts of the monoterpenoids 1,8-cineole (10.9%), linalool (4.8%), borneol (5.6%), alpha-terpineol (3.6%), neral (8.1%), geraniol (14.5%), geranial (9.5%), trans-dimethoxy citral (5.0%) and geranyl acetate (6.3%). Five compounds, namely trans-linalool oxide, trans-linalool oxide acetate, (Z)-dimethoxycitral, (E)-dimethoxy citral and epi-zingiberenol are reported for the first time in oil of ginger.     

Antimicrobial investigation of Linum usitatissimum for the treatment of acne

Light petroleum, dichloromethane and methanolic extracts of Linum usitatissimum were investigated using GC/MS. The main components of three sequential extracts were methyl linolenate (11.9-33.9%) and methyl linoleate (3.4-9.1%). Components possessing antimicrobial activity against acne causing bacteria, namely alpha-linolenic acid (7.0 -7.1%), alpha-terpinene (1.7-3.1%), terpinen-4-ol (1.3-4.6%), 4-cymene (1.6-7.1%) and alpha-pinene (1.1%), were found in varying amounts. Antimicrobial screening indicated that the light petroleum extract was more active against aerobic and anaerobic test strains with a MIC value of 1.25 mg/mL and a MBC of 2.5 mg/mL against S. aureus and P. acnes. A MIC of 2.5 mg/mL was observed against S. epidermidis.     

Elastic interaction of interfacial spherical-cap cracks in hollow particle filled composites

This work analyzes the elastic interaction between two spherical-cap cracks present along the outer surface of a hollow particle embedded in a dissimilar medium under remote uniaxial tensile loading. A semi-analytical approach based on an enriched Galerkin method is adopted to determine stress and deformation fields as functions of particle wall thickness and cracks’ configuration. The present analysis is limited to multiple interfacial spherical-cap cracks; that is, crack propagation is restrained to the particle-matrix interface and possibility of crack kinking in the matrix is not considered. Interfacial crack growth characteristics, conditions for stable crack propagation, equal crack growth, and shielding are established through energy release rate analysis. The study is relevant to the analysis of tensile and flexural failure of syntactic foams used in marine and aerospace applications. Results specialized to glass-vinyl ester syntactic foams demonstrate that particle wall thickness can be used to control crack stability and growth characteristics as well as tailoring the magnitude of the shielding phenomenon. Predictions are compared to finite element findings for validation and to results for penny-shaped cracks to elucidate the role of crack curvature.