Unique emission from polymer based lanthanide alloys

The incorporation of metal-ligand interactions into macromolecules imparts them with unique and potentially useful properties. We report novel macromolecules prepared via ATRP that contain activated esters for subsequent incorporation of terpyridine. The addition of lanthanide ions (Eu3+ and Tb3+) gave metal functionalized polymers that exhibited excellent emission of either pink (Eu3+) or green (Tb3+) light. A unique yellow luminescence was generated when these two different metal ions were incorporated into the same molecular backbone at a 1:1 ratio, producing an alloy. Upon heating above 50 degrees C, selective thermochromism, from yellow to orange/pink, was observed.     

Polypeptide helices in hybrid peptide sequences

A new class of polypeptide helices in hybrid sequences containing alpha-, beta-, and gamma-residues is described. The molecular conformations in crystals determined for the synthetic peptides Boc-Leu-Phe-Val-Aib-betaPhe-Leu-Phe-Val-OMe 1 (betaPhe: (S)-beta3-homophenylalanine) and Boc-Aib-Gpn-Aib-Gpn-OMe 2(Gpn: 1-(aminomethyl)cyclohexaneacetic acid) reveal expanded helical turns in the hybrid sequences (alpha alphabeta)n and (alphagamma)n. In 1, a repetitive helical structure composed of C14 hydrogen-bonded units is observed, whereas 2 provides an example of a repetitive C12 hydrogen-bonded structure. Using experimentally determined backbone torsion angles for the hydrogen-bonded units formed by hybrid sequences, we have generated energetically favorable hybrid helices. Conformational parameters are provided for C11, C12, C13, C14, and C15 helices in hybrid sequences.     

Determination of lipoic acid in rat plasma by LC-MS/MS with electrospray ionization: assay development, validation and application to a pharamcokinetic study

A simple, sensitive and specific LC-MS/MS method for the determination of lipoic acid was developed and validated over the linearity range 5-1000 ng/mL (r2 > 0.99) with 200 microL rat plasma using rosigliatzone as an internal standard (IS). The assay procedure involved a simple one-step liquid-liquid extraction of lipoic acid and IS from plasma into ethyl acetate. The organic layer was separated and evaporated under a gentle stream of nitrogen at 40 degrees C. The residue was reconstituted in the mobile phase and injected onto a Hichrom RPB column (4.6 x 250 mm, 5 microm). Separation of lipoic acid and IS was achieved with a mobile phase consisting of 0.05 M formic acid:acetonitrile (40:60, v/v) at a flow rate of 1.0 mL/min. The API-3000 LC-MS/MS was operated under the multiple reaction monitoring mode (MRM) using the electrospray ionization technique. Positive and negative ion acquisition within the same chromatographic run was used in the present method. For lipoic acid a pseudo-molecular ion transition pair was acquired in negative polarity, whereas for IS the transition pair was acquired in positive polarity. Quantitation was determined for both analyte and IS in MRM scan mode. Absolute recovery of lipoic acid and IS was >70 and 97%, respectively. The lower limit of quantification (LLOQ) of lipoic acid was 5.0 ng/mL. The inter- and intra-day precision in the measurement of quality control (QC) samples 5, 15, 400 and 800 ng/mL were in the range 2.18-5.99% relative standard deviation (RSD) and 0.93-13.77% RSD, respectively. Accuracy in the measurement of QC samples was in the range 87.40-114.40% of the nominal values. Analyte and IS were stable in the battery of stability studies, viz. bench-top, auto-sampler and freeze-thaw cycles. Stability of lipoic acid was established for 1 month at -80 degrees C. The application of the assay to a pharmacokinetic study in rats confirmed the utility of the assay.     

A Note on Tortrat Groups

A locally compact group G is called a Tortrat group if for any probability measure on G which is not idempotent, the closure of {gg ^–1 | gG} does not contain any idempotent measure. We show that a connected Lie group G is a Tortrat group if and only if for all gG all eigenvalues of Ad g are of absolute value 1. Together with well-known results this also implies that a connected locally compact group is a Tortrat group if and only if it is of polynomial growth.     

Effect of Microwave and Conventional Modes of Heating on Sintering Behavior,Microstructural Evolution and Mechanical Properties of Al-Cu-Mn Alloys

In this research, we intended to examine the effect of heating mode on the densification, microstructure, mechanical properties, and corrosion resistance of sintered aluminum alloys. The compacts were sintered in conventional (radiation-heated) and microwave (2.45 GHz, multimode) sintering furnaces followed by aging. Detailed analysis of the final sintered aluminum alloys was done using optical and scanning electron microscopes. The observations revealed that the microwave sintered sample has a relatively finer microstructure compared to its conventionally sintered counterparts. The experimental results also show that microwave sintered alloy has the best mechanical properties over conventionally sintered compacts. Similarly, the microwave sintered samples showed better corrosion resistance than conventionally sintered ones.     

Boundary integral method for Stokes flow past a porous body

In this paper we obtain an indirect boundary integral method in order to prove existence and uniqueness of the classical solution to a boundary value problem for the Stokes–Brinkman-coupled system, which describes an unbounded Stokes flow past a porous body in terms of Brinkman's model. Therefore, one assumes that the flow inside the body is governed by the continuity and Brinkman equations. Some asymptotic results in both cases of large and, respectively, of low permeability are also obtained. Copyright © 2007 John Wiley & Sons, Ltd.     

Influence of nucleation on the flow boiling heat transfer coefficient of a refrigerant mixture under varied heat flux conditions

The influence of nucleation on the flow boiling heat transfer coefficient of R-134a/R-290/R-600a refrigerant mixture is experimentally studied in a smooth horizontal tube of 12.7 mm diameter. The heat transfer coefficients are experimentally measured for stratified flow patterns under a varied heat flux condition; a condition found in the evaporator of refrigerators and deep freezers. The experiments are conducted in a counter-current heat exchanger test section. By regulating the flow rate and inlet temperature of acetone, which is the heating fluid flowing in the outer tube, a varied heat flux is provided to the refrigerant flowing in the inner tube. The refrigerant mass flow rate is fixed between 3 and 5 g s⁻¹ and its inlet temperature between −8.59 and 5.33°C, which corresponds to a pressure of 3.2 to 5 bar. The significance of nucleate boiling prevailing in the above-mentioned evaporators is highlighted. The experimental heat transfer coefficients are also compared with well known heat transfer correlations.     

Synthesis of Novel Alkyl Amide Functionalized Trifluoromethyl Substituted Furo/thieno Pyridine Derivatives: Their Anticancer Activity and CoMFA and CoMSIA Studies

A series of novel alkyl amide functionalized trifluoromethyl substituted furo/thieno pyridine derivatives 4a–h , 5a–d , and 6a–h were prepared starting from 2‐oxo/thioxo‐6‐phenyl/thien‐2‐yl‐4‐(trifluoromethyl)‐1,2‐dihydropyridine‐3‐carbonitrile 1 on reaction with bromoethylacetate followed by reaction with different primary aliphatic amines, cyclic secondary amines, or l ‐amino acids under different set of conditions. All the synthesized compounds 4a–h , 5a–d , and 6a–h were screened for anticancer activity against four cancer cell lines such as HeLa—cervical cancer (CCL‐2), COLO205—colon cancer (CCL‐222), HepG2—liver cancer (HB‐8065), and MCF7—breast cancer (HTB‐22). Compounds 4g and 4h are found to have promising anticancer activity at micromolar concentration. CoMFA and CoMSIA methods were applied to derive 3D‐QSAR models for alkyl amide tagged furo/thieno pyridine derivatives as potential anticancer inhibitors. 3D‐QSAR models provided a strong basis for future rational design of more active and selective HeLa, COLO205, HepG2, and MCF‐7 cell line inhibitors.