Block copolymer modified novolac epoxy resin

The phase behavior of uncured and cured mixtures containing stoichiometric amounts of Epon164 novolac epoxy resin and 4,4′‐methylenedianiline combined with a nearly symmetric poly(methyl acrylate‐co‐glycidyl methacrylate‐b‐polyisoprene) diblock copolymer was investigated with small‐angle X‐ray scattering and transmission electron microscopy. A series of morphologies were documented as a function of the copolymer concentration, which ranged from pure diblock to 2.5 wt % in the thermoset resin. Ordered lamellae bordered a wide multiphase region followed by disordered wormlike micelles that transformed continuously into vesicles at the lowest compositions. The thermal curing of this pentafunctional epoxy system to complete conversion had little impact on the phase behavior of the mixtures, and this was consistent with previous experiments with difunctional epoxy and the same hardening agent. However, changing the epoxy component led to gross changes in the phase behavior that were interpreted with the concept of a wet‐to‐dry brush transition. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1994–2003, 2003     

Dynamics and Correlates of Microscopic Changes in Affect

How are momentary microscopic assessments of behavioral dynamics related to traditional macroscopic, static measures? The present study used the computerized “mouse paradigm” to assess near-instantaneous changes in affect over a short time. Dynamic indices were computed from approximately 1400 measurements from the last 2.5 minutes of a 3-minute assessment. Subjects monitored and reported emotional states by moving a cursor along a dimension from “Sadder” to “Happier.” They also completed self-report measures: Scales 2 (Depression) and 9 (Mania) of the MMPI-2, the Positive and Negative Affect Scale, and the Wisconsin scales of Physical Anhedonia and Hypomanic traits. The instantaneous data yielded a summary measure of mean affect, as well as indices of variability. Complexity indices were derived and examined. Mean affect ratings correlated in expected directions with the paper and pencil measures. There was evidence for low-dimensional chaos in short-term affect dynamics. As hypothesized, greater complexity was associated with Pleasant Affect and Hypomania but was negatively correlated with Anhedonia.     

Conjugation of arginine–glycine–aspartic acid peptides to thermoreversible N‐isopropylacrylamide polymers

Thermoreversible polymeric biomaterials are finding increased acceptance in tissue engineering applications. One drawback of the polymers is their synthetic nature, which does not allow direct interaction of mammalian cells with the polymers. This limitation may be alleviated by grafting arginine–glycine–aspartic acid (RGD) containing peptides onto the polymer backbone to facilitate interactions with cell‐surface integrins. Toward this goal, N‐isopropylacrylamide (NiPAM)‐based thermoreversible polymers containing amine‐reactive N‐acryloxysuccinimide (NASI) groups were synthesized. Conjugation of RGD‐containing peptides to polymers was demonstrated with ¹H NMR spectroscopy and reverse‐phase high‐pressure liquid chromatography. The conjugation reaction was optimal at 4 °C and pH of 8.0, and increased with the increasing NASI content of polymers. With a peptide grafting ratio of 0.25 mol %, there was no significant change in the lower critical solution temperature of the polymers. Finally, the NASI‐containing polymers, cast as films, on tissue culture polystyrene, were shown to conjugate to RGD‐containing peptides and support C2C12 cell attachment. We conclude that NASI‐containing thermoreversible polymers are amenable for grafting biomimetic peptides to impart cell adhesiveness to the polymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3989–4000, 2003     

Generalizing the Quinn–Wójs theorem on distinct multiplets of composite Fermions

The combinatorial tool of generating functions for restricted partitions is used to generalize a quantum physics theorem relating distinct multiplets of different angular momenta in the composite Fermion model of the fractional quantum Hall effect. Specifically, if g_ℓ(N,M) denotes the number of distinct multiplets of angular momentum ℓ and total angular momentum M, we prove that

where the sum is taken over all positive divisors of N and L(k)=kℓ-kN/2+3k/2-N+N/(2k)-1/2. The original Quinn–Wójs theorem results when k=1 and it appears that this generalization will be useful in further investigations of nuclear shells modeling elementary particle interactions when the particles are clustered together.     

Free energies of solvation in the context of protein folding: Implications for implicit and explicit solvent models

Implicit solvent models for biomolecular simulations have been developed to use in place of more expensive explicit models; however, these models make many assumptions and approximations that are likely to affect accuracy. Here, the changes in free energies of solvation upon folding of several fast folding proteins are calculated from previously run μs–ms simulations with a number of implicit solvent models and compared to the values needed to be consistent with the explicit solvent model used in the simulations. In the majority of cases, there is a significant and substantial difference between the values calculated from the two approaches that is robust to the details of the calculations. These differences could only be remedied by selecting values for the model parameters—the internal dielectric constant for the polar term and the surface tension coefficient for the nonpolar term—that were system‐specific or physically unrealistic. We discuss the potential implications of our findings for both implicit and explicit solvent simulations. © 2015 Wiley Periodicals, Inc.     

A review of indirect searches for particle dark matter

The indirect detection of dark matter annihilation and decay using observations of photons, charged cosmic rays and neutrinos offers a promising means of identifying the particle nature of this elusive component of the universe. The last decade has seen substantial advances in observational data-sets, complemented by new insights from numerical simulations, which together have enabled for the first time strong constraints on dark matter particle models, and have revealed several intriguing hints of possible signals. This review provides an introduction to indirect detection methods and an overview of recent results in the field.     

Capillary zone electrophoresis (CZE) coupled to time-of-flight mass spectrometry (TOF-MS) applied to the analysis of illicit and controlled drugs in blood

A new method for the determination of illicit and abused drugs in blood by capillary zone electrophoresis-electrospray ionization-time-of-flight mass spectrometry is proposed, in view of its application in clinical and forensic toxicology. The analytes (methamphetamine, methylenedioxyamphetamine, methylenedioxyethylamphetamine, methylenedioxymethamphetamine, methadone, cocaine, morphine, codeine, 6-acethylmorphine, benzoylecgonine) were separated with capillary zone electrophoresis by applying 15 kV within 25 min, in an uncoated fused-silica capillary (75 microm x 100 cm) using a 25 mM ammonium formate electrolyte solution (pH 9.5). The capillary electropherograph was coupled to time-of-flight mass spectrometry through an orthogonal electrospray ionization source, with a coaxial sheath liquid interface. The sheath liquid was composed of isopropanol-water (1:1 v/v) containing 0.5% formic acid delivered at 4 microL/min. Forensic drugs were identified by exact mass determination (mass accuracy typically < or =5 ppm) and by matching of the isotopic pattern. Under optimized conditions, linearity was assessed in the range 10-2000 ng/mL, with correlation coefficients between 0.9744 and 0.9982 for all the analytes. LODs were in the range of 2-10 ng/mL (S/N > or =3) and LOQs of 10-30 ng/mL. The CVs (tested at 40 and 800 ng/mL in biological matrix) were below 2.97% for migration times and below 14.61% for peak area ratios (analyte/internal standard). Blood samples were extracted by using a liquid-liquid extraction procedure and injected under field-amplified sample stacking conditions. The method was successfully applied to real cases.     

Fasting status as a consideration for human serum collection and preparation prior to depletion and analysis

The use of comparative serum proteomic analysis has the potential to reveal protein expression changes present at different stages of disease progression. Depletion strategies allow for the enrichment of low-abundance proteins, which are more likely to be clinically significant biomarkers. We have observed that patient serum samples filtered through 0.22 microm cellulose acetate spin filters prior to depletion showed a variable level of retention of patient material on the upper part of the filter. This could potentially be related to the fasting status of the patient as a reduction in the lipid content of samples through the incorporation of a centrifugation step prior to filtration was found to reduce this effect. In order to determine if proteins were being selectively retained during filtration, a 2-D difference gel electrophoresis (2-D DIGE) experiment was performed. This demonstrated no significant selective retention of protein within crude serum samples. However, as this analysis was carried out on crude serum, it must be emphasised that protein loss could be manifest in the low-abundance proteins which would be masked in our analysis. Depletion of the retentate was not possible due to technical limitations, however based on our results a centrifugation step might act as an alternative to filtration in serum processing prior to depletion.     

Aqueous Ammonia Soaking of Switchgrass Followed by Simultaneous Saccharification and Fermentation

Simultaneous saccharification and fermentation (SSF) of switchgrass was performed following aqueous ammonia pretreatment. Switchgrass was soaked in aqueous ammonium hydroxide (30%) with different liquid–solid ratios (5 and 10 ml/g) for either 5 or 10 days. The pretreatment was carried out at atmospheric conditions without agitation. A 40–50% delignification (Klason lignin basis) was achieved, whereas cellulose content remained unchanged and hemicellulose content decreased by approximately 50%. The Sacccharomyces cerevisiae (D₅A)-mediated SSF of ammonia-treated switchgrass was investigated at two glucan loadings (3 and 6%) and three enzyme loadings (26, 38.5, and 77 FPU/g cellulose), using Spezyme CP. The percentage of maximum theoretical ethanol yield achieved was 72. Liquid–solid ratio and steeping time affected lignin removal slightly, but did not cause a significant change in overall ethanol conversion yields at sufficiently high enzyme loadings. These results suggest that ammonia steeping may be an effective method of pretreatment for lignocellulosic feedstocks.