Micro parallel liquid chromatography for high-throughput compound purity analysis and early ADMET profiling

The Nanostream (Pasadena, CA) Veloce system, together with 24-column Brio cartridges, offers a novel approach to micro parallel liquid chromatography (μPLC). This system allows users to achieve unprecedented throughput for standard assays while matching the performance of conventional LC instrumentation, thus enabling routine compound purity assessment and physiochemical property profiling early in the drug discovery and development process.The Veloce system—which includes instrumentation, software, and replaceable microfluidic cartridges—incorporates pressure-driven flow to achieve chromatograms comparable to conventional high performance liquid chromatography (HPLC) instrumentation for a broad class of analytical applications while offering a dramatic increase in sample analysis capacity. The system enables parallel chromatographic separations and simultaneous, real-time UV detection. Each Nanostream Brio cartridge, made of polymeric materials, incorporates 24 columns packed with standard (C-18) stationary phase material to achieve reverse phase separations. Mixing and distribution of the mobile phase to each of the 24 columns is precisely controlled in each cartridge. The system provides an ideal platform to accelerate assessment of compound purity and physicochemical properties (i.e., log P, CHI, etc.) for a large number of compounds. In addition, the 24-fold increase in sample analysis capacity allows standard curve generation and simultaneous analysis of multiple replicates of samples in a single run.     

Adaptive-modulation schemes for minimum outage probability in wireless systems

Adaptive-modulation schemes are designed that yield the minimum outage probability for wireless systems with strict delay constraints, under the assumption of perfect causal channel state information at the transmitter and receiver. Numerical results indicate that the proposed schemes significantly outperform adaptive schemes designed to maximize the average rate.     

Change in surface chemistry of the cuticle of human hair by chemical and photochemical oxidation

This is a multifaceted study on the characterization and quantification of damage to the hair fiber surface caused by photochemical and cosmetic chemical oxidative processes. Unique techniques were used, including a microfluorometric method that had been adapted to characterize and quantify the delipidation and acidification of the human hair surface during light exposure and cosmetic chemical grooming processes such as bleaching. During photochemical and chemical oxidation, breakdown of the lipid domains (also called the F‐layer) of the outer b‐layer occurs on the exposed scale faces and cysteic acid groups are generated on the cuticle cell surface. The newly formed acid functionalities can be tagged with the cationic fluorochrome Rhodamine B, allowing not only quantification of the level of progressive acidification but also localization of the newly formed acid functionalities. On the other hand, the negative charges generated on the hair surface by oxidation can also bind low molecular weight quaternary cationic conditioning compounds such as cetyltrimethylammonium bromide. This process can be considered a relipidation by adsorption. We have shown that the entire process of delipidation/acid formation and subsequent relipidation by adsorption on the scale faces can be quantified by X‐ray photoelectron spectroscopy. Since X‐ray photoelectron spectroscopy analysis is highly sensitive and able to detect atomic species at the very surface of the hair fibers, receiving signals from an escape depth as shallow as 25 Å, it appeared ideal for the characterization of treatment‐induced changes in the hair surface. However, X‐ray photoelectron spectroscopy provides an average elemental composition of the hair surface including scale faces and scale edges. The microfluorometric technique, on the other hand, can distinguish progressive delipidation of the scale faces from changes occurring at the broken scale edges. This distinction was shown and characterized in detail by slow speed microfluorometric scanning of the hair surface. Chemical and photochemical oxidative processes at the hair surface result in certain collateral effects. Particularly changes in surface wettability and fiber friction are of significance to the cosmetic chemist because they affect the spreading and wicking of products in hair as well as the managability and the body of hair assemblies. Methods of characterizing these effects are discussed briefly.     

Growth characteristics of LPE InSb and InGaSb

Growth characteristics of InSb and In_l-xGa_xSb (x < 0.09) prepared by infinite solution epitaxy are investigated. Substrate surface contamination is found to be a controlling factor in epitaxial layer continuity and surface morphology; as the degree of contamination decreases, growth varies from discontinuous to terraced continuous to terrace-free continuous. The dependence of layer thickness on growth parameters is consistent with a diffusion-controlled process in which the Sb diffusion coefficient D is given by D = 1.1 × 10⁻³ exp[(-0.43 eV)/kT] cm² sec⁻¹. Electron microprobe analysis of the Ga distribution through epitaxial layers indicates that Ga diffuses fast enough in the solution under typical growth conditions to maintain a constant ternary composition.     

Immobilization of β-galactosidase onto polymeric supports

Poly(vinyl alcohol) cross-linked with para-formaldehyde (PVA–F) and natural polysaccharide–chitosan in bead form and salicylic acid–resorcinol–formaldehyde polymeric resin (SRF) in powder form were used for immobilization of β-galactosidase through covalent linkages. Various activation processes and conditions were optimized. Immobilized enzyme showed very good storage stability at room temperature. Durability of the enzyme was also improved on immobilization. On repeated use of enzyme immobilized on chitosan beads, no loss was observed in enzyme activity even after 10 batches. Michaelis constant K_m and maximum reaction velocity V_m were calculated for free and immobilized enzyme systems. Effect of pH and temperature on enzyme activity was estimated and energy of activation (E_a) and inactivation constant (K_i) for free and immobilized enzyme were calculated. © 1995 John Wiley & Sons, Inc.     

Comparative effects of cobalt carboxylates on the thermo‐oxidative degradation of LDPE films

This article reports the effect of three cobalt carboxylates—cobalt stearate (CoSt₃), cobalt palmitate (CoPal₃), and cobalt laurate (CoLau₃)—on the thermo‐oxidative degradation of low‐density polyethylene (LDPE) films prepared by sheeting process. The carboxylates were blended with LDPE in the concentration range of 0.05–0.2% (w/w). The degradation was monitored by techniques such as FTIR spectroscopy, change in the mechanical properties (tensile strength and elongation at break), viscometry, surface electron microscopy, melt flow index measurements, and apparent density measurements. Studies indicate that films containing these additives are highly susceptible to thermo‐oxidative degradation. Oxygen containing functionalities such as carbonyl and vinyl species are generated on the surface of polyethylene because of thermo‐oxidation, as indicated by FTIR studies. This oxidative process is accelerated in the presence of cobalt carboxylates. The degradation of LDPE was found to increase proportionally with concentration as well as with increasing chain length of the cobalt carboxylate, and follow the order CoSt₃ > CoPal₃ > CoLau₃. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3758–3765, 2007     

Thoracic duct-cutaneous fistula in a patient with cirrhosis of the liver: successful treatment with a transjugular intrahepatic portosystemic shunt

Patients with cirrhosis of the liver have increased hepatic and gastrointestinal lymph flow that may contribute to the formation of ascites and pleural effusions. Increased lymph flow, which is due to postsinusoidal portal hypertension, causes a high rate of flow through the thoracic duct. Because of the high flow rates, disrupted lymphatic vessels in patients with cirrhosis of the liver may fail to close, a situation that results in chylous ascites, pleural effusions, or chylous fistulas. Chylous fistulas deplete proteins, fluid, and lymphocytes and thus lead to volume depletion and coagulopathy. Herein we describe an unusual case in which a high-output traumatic thoracic duct-cutaneous fistula developed in a patient with cirrhosis and led to volume depletion and coagulopathy. Correction of the portal hypertension with placement of a transjugular intrahepatic portosystemic shunt led to closure of the fistula and normalization of accompanying metabolic abnormalities.     

Poly(ethyleneterephthalate) glycolysates as effective toughening agents for epoxy resin

The potential of poly(ethyleneterephthalate) glycolysates toward improving the energy absorption characteristics of cycloaliphatic epoxy resins has been explored. Microwave‐assisted glycolytic depolymerization of PET was performed in the presence of polyether diols of different molecular weights. The obtained glycolysates were blended with epoxy, and their mechanical properties were studied under both quasi‐static and dynamic conditions. Significant improvements were observed, which were found to depend both on the amount as well as nature of glycolysate. Amine functionalities were introduced at the terminal positions of glycolysates to improve the compatibility between the two phases. The amine derivatives exhibited superior performance and the Mode I fracture toughness (K_IC) of epoxy increased by ～18% in optimized compositions, which is indicative of its improved notch sensitivity. Neat epoxy specimens fractured in a brittle fashion, but all the blends exhibited ductile failure, as evidenced by surface morphological investigations. The mechanical properties of epoxy blends prepared with analogous aliphatic polyols, both before and after amine functionalization, were also studied which clearly reveal the beneficial role of aromatic groups toward improving the toughness of the base cycloaliphatic epoxy resin without compromising on the material stiffness. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39941.