Analysis of protein adsorption and binding at biosensor polymer interfaces using X-ray photon spectroscopy and scanning electrochemical microscopy

We describe a method, based on X-ray photoelectron spectroscopy (XPS) measurements, to assess the extent of protein adsorption or binding on a variety of different muTAS and biosensor interfaces. Underpinning this method is the labeling of protein molecules with either iodine- or bromine-containing motifs by using protocols previously developed for radiotracer studies. Using this method, we have examined the adsorption and binding properties of a variety of modified electrodeposited polymer interfaces as well as other materials used in muTAS device fabrication. Using polymer interfaces modified with poly(propylene glycol) (PPG) chains, our results indicate that a chain of at least approximately 30 monomer units is required to inhibit nonspecific adsorption from concentrated protein solutions. The XPS methodology was also used to probe specific binding of avidins and enzyme conjugates thereof to biotinylated and mixed biotin/PPG-modified polymer interfaces. In one example, using competitive binding, it was established that the mode of binding of a peroxidase-streptavidin conjugate to a biotinylated modified polymer interface was primarily via the streptavidin moiety (as opposed to nonspecific binding via the enzyme conjugate). XPS evaluation of nonspecific and specific peroxidase-streptavidin immobilization on various functionalized polymers has guided the design and fabrication of functionalized interdigitated electrodes in a biosensing muTAS device. Subsequent characterization of this device using scanning electrochemical microscopy (SECM) corroborated the adsorption and binding previously inferred from XPS measurements on macroscale electrodes.     

Screening of biomarkers in rat urine using LC/electrospray ionization-MS and two-way data analysis

Biofluids, like urine, form very complex matrixes containing a large number of potential biomarkers, that is, changes of endogenous metabolites in response to xenobiotic exposure. This paper describes a fast and sensitive method of screening biomarkers in rat urine. Biomarkers for phospholipidosis, induced by an antidepressant drug, were studied. Urine samples from rats exposed to citalopram were analyzed using solid-phase extraction (SPE) and liquid chromatography mass spectrometry (LC/MS) analysis detecting negative ions. A fast iterative method, called Gentle, was used for the automatic curve resolution, and metabolic fingerprints were obtained. After peak alignment principal component analysis (PCA) was performed for pattern recognition, PCA loadings were studied as a means of discovering potential biomarkers. In this study a number of potential biomarkers of phospholipidosis in rats are discussed. They are reported by their retention time and base peak, as their identification is not within the scope of the study. In addition to the fact that it was possible to differentiate control samples from dosed samples, the data were very easy to interpret, and signals from xenobiotic-related substances were easily removed without affecting the endogenous compounds. The proposed method is a complement or an alternative to NMR for metabolomic applications.     

Principal Rings and their Invariant Factors

In this article we put forward a new look at the theory of principal and Invariant-Factor rings, with a view toward facilitating the formalization, automation, and archiving of results and their proofs. We take an elementary and constructive approach: standard techniques such as prime ideals and factorization of elements are avoided, and determinant constructions are minimized. Using such computationally friendly methods, the main existence and uniqueness results on invariant factors for a f.g. torsion module are derived, and several new algebraic constructions and results are found. The lattice of principal integral ideals for any commutative Bézoutian ring is explicitly constructed based on a first-order proof overlooked in the literature, together with a proof that this lattice is distributive. A Lagrange quotient theorem for finitely generated modules over any principal ring is stated for the first time. A very constructive new proof is given that a principal ring has the Hermite property, so is also an Invariant-Factor ring. A calculus that is needed in the ideal lattice, naturally yields a number of formulas valid for a function lattice.     

Microwave Initiated Self-Propagating High-Temperature Synthesis of SiC

The use of microwave energy to initiate self-propagating, high-temperature synthesis (SHS) of Si + graphite mixtures has been investigated. The results indicate that, unlike with conventional ignition techniques, green densities in excess of 80% of theoretical can be ignited and the combustion wavefront can be crudely controlled. It was found that the induction time for ignition increased with increasing green density and that a higher microwave power level was required with the denser green pellets to achieve the same ignition time. Combustion front velocity increased with green density. The degree of densification was found to decrease with increasing green density. For a given green density, the degree of densification increased with increasing microwave power. The product contained a significant proportion of ultrafine (36–72 nm diameter) SiC whiskers; despite this, final densities as high as 83.6% of theoretical could be obtained without the use of applied pressure. This compares with the 50% densities obtained via conventional ignition techniques.     

In situ column generation for a cutting-stock problem

Working with an integer bilinear programming formulation of a one-dimensional cutting-stock problem, we develop an ILP-based local-search heuristic. The ILPs holistically integrate the master and subproblem of the usual price driven pattern-generation paradigm, resulting in a unified model that generates new patterns in situ. We work harder to generate new columns, but we are guaranteed that new columns give us an integer linear-programming improvement (rather then the continuous linear-programming improvement sought by the usual price driven column generation). The method is well suited to practical restrictions such as when a limited number of cutting patterns should be employed, and our goal is to generate a profile of solutions trading off trim loss against the number of patterns utilized. We describe our implementation and results of computational experiments on instances from a chemical-fiber company.     

A randomized controlled trial of goal choice interventions for alcohol use disorders among men who have sex with men.

This study tested the efficacy of behavioral treatments for alcohol use disorders (AUD) among men who have sex with men (MSM) and who are at risk for HIV transmission. HIV-negative MSM with current AUD (N = 198) were recruited, offered treatment focused on reducing drinking and HIV risk, and followed during treatment and 12 months posttreatment. Participants (n = 89) accepted treatment and were randomized to either 4 sessions of motivational interviewing (MI) or 12 sessions of combined MI and coping skills training (MI + CBT). Other participants (n = 109) declined treatment but were followed, forming a non-help-seeking group (NHS). MI yielded significantly better drinking outcomes during the 12-week treatment period than MI + CBT, but posttreatment outcomes were equivalent. NHS participants significantly reduced their drinking as well. Service delivery and treatment research implications are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Science, Social Networks and Spillovers

Although prior empirical research has established an association between science and the widespread diffusion of knowledge, the exact mechanism(s) through which science catalyses information flow remains somewhat ambiguous. This paper investigates whether the knowledge diffusion associated with science-based innovation stems from the norm of openness and incentives for publication, or whether scientists maintain more extensive and dispersed social networks that facilitate the dissemination of tacit knowledge. Our analysis supports the first mechanism: we track the movement of knowledge with patent citations, and find that science-based innovations diffuse more rapidly and widely, even after controlling for the underlying social networks of researchers as measured using information on prior collaborations. We also find that publication and social networks act as substitutes in the diffusion of knowledge.     

Coping style use predicts posttraumatic stress and complicated grief symptom severity among college students reporting a traumatic loss.

Problem-focused coping, and active and avoidant emotional coping were examined as correlates of grief and posttraumatic stress disorder (PTSD) severity among 123 college students reporting the unexpected death of an immediate family member, romantic partner, or very close friend. The authors administered to participants, via the Internet, 5 survey instruments that measured demographic characteristics, traumatic event exposure (Stressful Life Events Screening Questionnaire; L. Goodman, C. Corcoran, K. Turner, N. Yuan, & B. L. Green, 1998), complicated grief (CG) severity (Inventory of Complicated Grief--Revised--Short Form; A. E. Latham & H. G. Prigerson, 2004; H. G. Prigerson & S. C. Jacobs, 2001), PTSD severity (PTSD Checklist; F. W. Weathers, B. T. Litz, D. S. Herman, J. A. Huska, & T. M. Keane, 1993), and coping style use (Brief COPE; C. S. Carver, 1997). Results demonstrated that CG and PTSD severity were both significantly positively correlated with problem-focused, and active and avoidant emotional coping styles. The authors used path analysis to control for time since the loss and trauma frequency and found that only avoidant emotional coping remained significant in predicting CG and PTSD severity. Results are discussed in terms of their clinical implications for treating individuals with traumatic losses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)