Drexel University

About: Drexel University is a education organization based out in Philadelphia, Pennsylvania, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 26770 authors who have published 51438 publications receiving 1949443 citations. The organization is also known as: Drexel & Drexel Institute.

Analysis of protein aggregation kinetics.

Abstract: Given a set of kinetic data, then, the preceding discussions suggest the following approach to its analysis. 1. 1. For purposes of establishing the reaction, ignore the final stages and concentrate on the initial 10–20% of the reaction at first. A globally optimized model may be based on a faulty assumption for the initial steps. Thus, although the whole data set may look reasonably well fit, the reaction could be misrepresented, and thus the fit unhelpful if accuracy at the later stages has come at the expense of the initial phase of the reaction. 2. 2. What is the time course of the initial reaction? (A) Is the reaction exponential? Exponential growth gives dramatic lag times (see Fig. 3), whereas nonexponential “lag times” have a visible signal from time 0 (i.e., Fig. 2). If the data set shows the abrupt appearance of signals after a period of quiescence, the chances are excellent that the time course is exponential. High sensitivity measurement of the signal at times during the lag phase should be used to confirm the exponential nature quantitatively. Exponential reactions mean a secondary pathway is operative. (a) A cascade ( t n ) can look similar to an exponential, but may proceed from a multistep single-path reaction. Thus the exponential needs to be ascertained with some accuracy. (b) It is possible that some or all of the lag results from a stochastic process, i.e., formation of a single nucleus being observed. This, however, is likely to be accompanied by a secondary process, as few techniques are sensitive enough to detect a single polymer at a time, and having one nucleus form many polymers is a hallmark of a secondary process. Thus, the reproducibility of the kinetics must be established to rule out stochastics. If data show wide variation, stochastic methods as described earlier may be employed. (c) Given a secondary process, one must separate the primary nucleation process from the secondary process (by stochastic means or by use of the product B 2 A , as described earlier). (B) If the reaction does not begin with an exponential, is it parabolic? If so, it falls in the general class of linear polymerizations. 3. 3. What is the concentration dependence of the reaction(s)? This will separate nucleation processes from growth, and so on. 4. 4. If the initial reaction is neither exponential nor parabolic, a reaction mechanism needs to be proposed and evaluated. Solving the resulting equations is best done by linearization, which has the best chance of giving equations whose solutions and their sensitivity to parameters are readily understood. If this proves fruitful, full numeric solutions may be useful. 5. 5. At this point, the full reaction may be considered to completion. 6. 6. The physical basis of the description (sizes of parameters and their dependencies) needs to be finally considered to ensure that the mathematical success of the description rests on tenable physical grounds.

Methods of Multivariate Analysis, 2nd Ed.

Abstract: (2004). Methods of Multivariate Analysis, 2nd Ed. Journal of Quality Technology: Vol. 36, No. 1, pp. 125-126.

Afferent regulation of locus coeruleus neurons: anatomy, physiology and pharmacology

Abstract: Tract-tracing and electrophysiology studies have revealed that major inputs to the nucleus locus coeruleus (LC) are found in two structures, the nucleus paragigantocellularis (PGi) and the perifascicular area of the nucleus prepositus hypoglossi (PrH), both located in the rostral medulla. Minor afferents to LC were found in the dorsal cap of the paraventricular hypothalamus and spinal lamina X. Recent studies have also revealed limited inputs from two areas nearby the LC, the caudal midbrain periaqueductal gray (PAG) and the ventromedial pericoerulear region. The pericoeruleus may provide a local circuit interface to LC neurons. Recent electron microscopic analyses have revealed that LC dendrites extend preferentially into the rostromedial and caudal juxtaependymal pericoerulear regions. These extracoerulear LC dendrites may receive afferents in addition to those projecting to LC proper. However, single-pulse stimulation of inputs to such dendritic regions reveals little or no effect on LC neurons. Double-labeling studies have revealed that a variety of neurotransmitters impinging on LC neurons originate in its two major afferents, PGi and PrH. The LC is innervated by PGi neurons that stain for markers of adrenalin, enkephalin or corticotropin-releasing factor. Within PrH, large proportions of LC-projecting neurons stained for GABA or met-enkephalin. Finally, in contrast to previous conclusions, the dorsal raphe does not provide the robust 5-HT innervation found in the LC. We conclude that 5-HT inputs may derive from local 5-HT neurons in the pericoerulear area. Neuropharmacology experiments revealed that the PGi provides a potent excitatory amino acid (EAA) input to the LC, acting primarily at non-NMDA receptors in the LC. Other studies indicated that this pathway mediates certain sensory responses of LC neurons. NMDA-mediated sensory responses were also revealed during local infusion of magnesium-free solutions. Finally, adrenergic inhibition of LC from PGi could also be detected in nearly every LC neuron tested when the EAA-mediated excitation is first eliminated. In contrast to PGi, the PrH potently and consistently inhibited LC neurons via a GABAergic projection acting at GABAA receptors within LC. Such PrH stimulation also potently attenuated LC sensory responses. Finally, afferents to PGi areas that also contain LC-projecting neurons were identified. Major inputs were primarily autonomic in nature, and included the caudal medullary reticular formation, the parabrachial and Kolliker-Fuse nuclei, the PAG, NTS and certain hypothalamic areas.(ABSTRACT TRUNCATED AT 400 WORDS)

Bunch: a clustering tool for the recovery and maintenance of software system structures

Abstract: Software systems are typically modified in order to extend or change their functionality, improve their performance, port them to different platforms, and so on. For developers, it is crucial to understand the structure of a system before attempting to modify it. The structure of a system, however, may not be apparent to new developers, because the design documentation is non-existent or, worse, inconsistent with the implementation. This problem could be alleviated if developers were somehow able to produce high-level system decomposition descriptions from the low-level structures present in the source code. We have developed a clustering tool called Bunch that creates a system decomposition automatically by treating clustering as an optimization problem. The paper describes the extensions made to Bunch in response to feedback we received from users. The most important extension, in terms of the quality of results and execution efficiency, is a feature that enables the integration of designer knowledge about the system structure into an otherwise fully automatic clustering process. We use a case study to show how our new features simplified the task of extracting the subsystem structure of a medium size program, while exposing an interesting design flaw in the process.

A treatment outcome study for sexually abused preschool children: initial findings

Abstract: Objective Treatment outcome for sexually abused preschool-age children and their parents was assessed, comparing the effectiveness of a cognitive-behavioral intervention to nondirective supportive treatment. Method Sixty-seven sexually abused preschool children and their parents were randomly assigned to either (1) cognitive-behavioral therapy adapted for sexually abused preschool children (CBT-SAP) or (2) nondirective supportive therapy (NST). Treatment consisted of 12 individual sessions for both the child and parent, monitored for integrity with the therapeutic model through intensive training and supervision, use of treatment manuals, and rating of audio taped sessions. Parents completed the Child Behavior Checklist, the Child Sexual Behavior Inventory, and the Weekly Behavior Report to measure a variety of emotional and behavioral symptoms. Results Within-group comparison of pretreatment and posttreatment outcome measures demonstrated that while the NST group did not change significantly with regard to symptomatology, the CBT-SAP group had highly significant symptomatic improvement on most outcome measures. Repeated-measures analyses of variance demonstrated group × time interactions on some variables as well. Clinical findings also supported the effectiveness of the CBT-SAP intervention over NST. Conclusions Findings provide strong preliminary evidence for the effectiveness of a specific cognitive-behavioral treatment model for sexually abused preschool children and their parents.