Use of a liquid chromatograph-ion trap mass spectrometer for end-group characterization of various polyethoxylate materials

The separation and detection properties of various ethoxylated polymers were investigated with atmospheric pressure ionization liquid chromatography/mass spectrometry (LC/MS). Interesting chromatographic elution behavior based on functionality was noted. LC/MS using in-source CID (collision-induced dissociation) and tandem mass spectrometry (MS/MS) detection was compared for end-group identification. Excellent end-group identification was achieved when the end-group molecular weight (MW) was greater than 100 Da and the average MW of the polymer was less than 400 Da by both MS/MS and in-source CID. In cases where the end-group MW was less than 100 Da, because of the low mass cut-off in a quadrapole ion trap analyzer, in-source CID produced the only characteristic end-group ions. The use of a dual scan function allowed investigation of the oligomeric distribution followed by a narrow low-mass scan using in-source CID to generate end-group information. This approach is applicable on instruments without MS/MS capability.     

Overheating in care settings: magnitude,causes, preparedness and remedies

ABSTRACT

Research in UK and elsewhere has highlighted that older people are particularly vulnerable to negative health effects of overheating. This paper examines the magnitude, causes, preparedness and remedies for addressing the risk of summertime overheating in four case study residential care and extra-care settings across the UK, spanning different building types, construction and age. An interdisciplinary approach is adopted, drawing from building science and social science methods, including temperature monitoring, building surveys, and interviews with design and management teams. The findings suggest that overheating is a current and prevalent risk in the case study schemes, yet currently little awareness or preparedness exists to implement suitable and long-term adaptation strategies (e.g., external shading). There was a perception from designers to managers, that cold represents a bigger threat to older occupants’ health than excessive heat. A lack of effective heat management was found across the case studies that included unwanted heat gains from the heating system, confusion in terms of responsibilities to manage indoor temperatures, and conflicts between window opening and occupant safety. Given that care settings should provide protection against risks from cold and hot weather, design, management and care practices need to become better focused towards this goal.     

Phosphorous limitation in an arctic river biofilm—A whole ecosystem experiment

A fourth-order arctic river was experimentally enriched with phosphate (7.7 ± 7.0 μ g 1⁻¹) to determine the effect of such a loading (equivalent to a community of 10,000 people) upon the trophically important biofilm. The effect upon a light-grown biofilm (an autotrophic/heterotrophic assemblage) and a dark-grown biofilm (predominantly heterotrophic assemblage) was determined after 28 days of colonization. Seven attributes of the biofilms were monitored, 2 autotrophic indices, chlorophyll , [¹⁴C]HCO₃ incorporation into lipids and 5 heterotrophic indices; [¹⁴C]acetate incorporation into lipids, metabolic heat output, turn-over times of microbially labile glucose and glutamate and mineralization of microbially recalcitrant ring-labelled [¹⁴C]hydroxybenzoic acid. The findings showed that the addition of phosphorus resulted in a substantial stimulation of both autotrophic and heterotrophic processes suggesting that arctic rivers of this type would be liable to cultural eutrophication.     

A comparison of time-domain solutions for the full-wave equation and the parabolic wave equation for a diagnostic ultrasound transducer

A study of numerical solutions to the linear wave equation and the parabolic wave equation is presented. Finite-difference, time-domain methods are used to calculate the acoustic field emitted from a phased diagnostic ultrasound transducer in a non-attenuating medium. Results are compared to Field II, a simulation package that has been used extensively to linearly model transducers in ultrasound. The simulation of the parabolic equation can accurately predict the lateral beamplot for large f/#s, but, it exhibits 2-3 dB errors for small f/#s. It also overestimates the depth at which the focus occurs. For the considered array, it is shown that the finite-difference solution of the wave equation is accurate for a small and large f/#. The lateral beamplots and axial intensities are in excellent agreement with the Field II simulations.     

Oblique-incidence reflectivity difference microscope for label-free high-throughput detection of biochemical reactions in a microarray format

We describe a recently developed oblique-incidence reflectivity difference (OI-RD) microscope, a form of polarization-modulated imaging ellipsometer, for label-free-high-throughput detection of biomolecular reactions on DNA and protein microarrays. We present examples of application of this technique to end-point and real-time investigations of DNA-DNA hybridization, antibody-antigen capture, and protein-small-molecule binding reactions. Compared to a conventional imaging ellipsometer based on the polarizer-compensator-sample-analyzer scheme and under the off-null condition, a polarization-modulated OI-RD microscope is inherently more sensitive by at least 1 order of magnitude to thickness changes on a solid surface. Compared with imaging surface plasmon resonance microscopes based on reflectance change on falling or rising slopes of the surface plasmon resonance, the OI-RD microscope (1) has a comparable sensitivity, (2) is applicable to conventional microscope glass slides, and (3) easily covers a field of view as large as the entire surface of a 1 in. x 3 in. (2.54 cm x 7.62 cm) microscope slide.     

Fragment-based synthesis and SAR of modified FKBP ligands: influence of different linking on binding affinity

The viability of the fragment-based approach for lead discovery depends on reliable fragment-screening methods combined with straightforward fragment-linking- or fragment-growing-chemistry. In the present study we sought a flexible synthetic approach that would allow efficient synthesis of a variety of linkers that can subsequently be tested for biological activity. We applied this approach to fragments known to bind to FKBP12 (FK506 binding protein), a peptidyl-prolyl isomerase involved in immunosuppression and neural functioning. In our set of linked FKBP ligands, ester and thioester linkages resulted in high-affinity ligands, whereas an amide linkage decreased affinity remarkably; oxime and triazole linkages were not tolerated by the target protein's binding pocket, rendering these ligands ineffective. By investigating corresponding derivatized non-linked fragments and docking studies of linked fragments, we were able to evaluate the effect of the linker region on ligand binding affinity.     

Exercise therapy for patients with psychiatric disorders: Research and clinical implications.

There is now considerable evidence that regular exercise is (a) a viable, cost-effective, but underused treatment for mild to moderate depression that compares favorably to individual psychotherapy, group psychotherapy, and cognitive therapy, and (b) a necessary ingredient in effective behavioral treatments that reduce self-reported pain in individuals with chronic pain. Preliminary evidence also suggests that regular exercise deserves further attention as (a) a singular treatment for some anxiety disorders, for individuals suffering from body image disturbance, and for the reduction of problem behavior of developmentally disabled persons, and (b) an adjunct in treatment programs for schizophrenia, conversion disorder, and alcohol dependence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tests of a Two-Photon Technique for Measuring Polarization Mode Dispersion With Subfemtosecond Precision

An investigation is made of a recently introduced quantum interferometric method capable of measuring polarization mode dispersion (PMD) on sub-femtosecond scales, without the usual interferometric stability problems associated with such small time scales. The technique makes use of the extreme temporal correlation of orthogonally polarized pairs of photons produced via type-II phase-matched spontaneous parametric down-conversion. When sent into a simple polarization interferometer these photon pairs produce a sharp interference feature seen in the coincidence rate. The PMD of a given sample is determined from the shift of that interference feature as the sample is inserted into the system. The stability and resolution of this technique is shown to be below 0.2 fs. We explore how this precision is improved by reducing the length of the down-conversion crystal and increasing the spectral band pass of the system.     

Aliphatic polyamides prepared by ester-amine polycondensation as potential drug carrier polymers

Aliphatic polyamides of interest as macromolecular drug carriers are synthesized by base-catalyzed polycondensation of aliphatic diesters with diamines. The reactions are conducted in the presence of anhydrous sodium carbonate at temperatures ranging from ambient to 65°C, initially in the undilute state. The addition of aprotic solvent at a later stage serves to maintain sufficiently low viscosity for proper homogenization. The comonomers, diethyl 3,6,9-trioxaundecanedioate and 4,7,10-trioxa-1,13-tridecanediamine, copolymerize to form polymer 1, a straight-chain polyamide devoid of specific functionality. Use of diethyl tartrate in lieu of the aforementioned diester leads to polyamide 2 possessing hydroxyl side groups. Other experiments in which diamines incorporating additional (secondary) amino groups are employed afford polyamides 3–8 containing such secondary amine functions as main-chain constituents. The water-soluble target polymers are crudely fractionated by aqueous dialysis (12000–14000 molecular mass cut-off) and collected by freeze-drying in yields of 20 to 40%. The low-yield range has been accepted in this investigation as the price to be paid for the realization of linear polyamide structures in accordance with compositional expectations, a requirement vital for the proper functioning of the polymers as drug carriers. The practicability of drug binding (conjugating) is exemplified by the coupling of ferrocene as a drug model to polyamide 5 via amide linkage. The water-soluble conjugate 5-Fc features an iron content corresponding to one ferrocene group in the repeat unit. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2143–2150, 1999