University of Houston

About: University of Houston is a education organization based out in Houston, Texas, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 23074 authors who have published 53903 publications receiving 1641968 citations.

Marketing in Computer-Mediated Environments: Research Synthesis and New Directions

Abstract: Although an extensive body of research has emerged on marketing in computer-mediated environments (CMEs), the literature remains fragmented. As a result, insights and findings have accumulated without an overarching framework that provides structure and guidance to the rapidly-growing literature. We believe this is detrimental to long-term knowledge development in this area. To address this issue, we organize and synthesize findings from the literature using a framework structured around four key interactions in CMEs: consumer-firm interactions, firm-consumer interactions, consumer-consumer interactions, and firm-firm interactions. The proposed framework serves a valuable organizational function and helps identify a broad spectrum of gaps in the literature to advance the next generation of knowledge development.

Retinal Origins of the Primate Multifocal ERG: Implications for the Human Response

Abstract: Purpose To better understand the cellular contributions to the human multifocal ERG (mfERG), rhesus monkey and human mfERGs were recorded using the same stimulus conditions. The monkey mfERGs were recorded before and after injections of pharmacologic agents known to selectively block activity of particular cells and circuits in the retina. Methods Photopic mfERGs were recorded with Dawson-Trick-Litzkow (DTL) fiber electrodes from 16 eyes of 10 anesthetized adult rhesus monkeys (Macaca mulatta) and from 4 normal humans. The display consisted of 103 equal-sized hexagons within 17 degrees of the fovea. Monkey mfERGs were obtained before and after inner retinal responses were suppressed with intravitreal injections of tetrodotoxin (TTX), TTX+N-methyl-D-aspartic acid (NMDA), TTX+NMDA with the gamma-aminobutyric acid (GABA(A&C)) antagonist picrotoxin (PTX), or the inhibitory amino acid GABA and after L-2 amino-4-phosphonobutyric acid (APB) to block signal transmission to ON-bipolar cells. Finally, a combination of APB and cis-2,3 piperidine dicarboxylic acid (PDA) was used to isolate the contributions from the cone photoreceptors. Results TTX, which blocks sodium-based action potentials, removes a large contribution from the monkey's mfERG, but it does not remove all inner retinal influences. After administration of TTX, the mfERG is further modified by the addition of NMDA. TTX+NMDA, TTX+NMDA+PTX, or GABA alone have similar effects, suggesting that, at the concentrations used, they are largely removing the inner retinal contributions. After removing the inner retinal influences, the monkey's mfERG is mainly composed of ON- and OFF-bipolar contributions, as revealed after APB and PDA were injected. The leading edge of the first negative potential (N1) is largely shaped by the initial hyperpolarization of the OFF-bipolar cells. The photoreceptors also contribute to the leading edge of N1, but this contribution is small, except in the central 6 degrees. The depolarization of the ON-bipolars and the recovery of the OFF-bipolars contribute to the leading edge of the major positive component (P1), with the recovery of the ON-bipolars being the dominant influence on the trailing edge. The waveform of the human mfERG most closely resembles the rhesus monkey's mfERG after administration of TTX. Conclusions The monkey's mfERG is shaped by large contributions from ON- and OFF-bipolar cells, combined with both spiking and nonspiking inner retinal contributions, and a small contribution from the photoreceptors. In comparison, the human mfERG resembles the monkey's mfERG after reduction of inner retinal contributions. Based on the pharmacologic dissection of the monkey's mfERG, a model of the waveform of the human mfERG is proposed. This model suggests that the waveform can be understood as a combination of overlapping ON- and OFF-bipolar cell contributions combined with smaller contributions from inner retina and photoreceptors.

Toxicity of a polymer–graphene oxide composite against bacterial planktonic cells, biofilms, and mammalian cells

Abstract: It is critical to develop highly effective antimicrobial agents that are not harmful to humans and do not present adverse effects on the environment. Although antimicrobial studies of graphene-based nanomaterials are still quite limited, some researchers have paid particular attention to such nanocomposites as promising candidates for the next generation of antimicrobial agents. The polyvinyl-N-carbazole (PVK)–graphene oxide (GO) nanocomposite (PVK–GO), which contains only 3 wt% of GO well-dispersed in a 97 wt% PVK matrix, presents excellent antibacterial properties without significant cytotoxicity to mammalian cells. The high polymer content in this nanocomposite makes future large-scale material manufacturing possible in a high-yield process of adiabatic bulk polymerization. In this study, the toxicity of PVK–GO was assessed with planktonic microbial cells, biofilms, and NIH 3T3 fibroblast cells. The antibacterial effects were evaluated against two Gram-negative bacteria: Escherichia coli and Cupriavidus metallidurans; and two Gram-positive bacteria: Bacillus subtilis and Rhodococcus opacus. The results show that the PVK–GO nanocomposite presents higher antimicrobial effects than the pristine GO. The effectiveness of the PVK–GO in solution was demonstrated as the nanocomposite “encapsulated” the bacterial cells, which led to reduced microbial metabolic activity and cell death. The fact that the PVK–GO did not present significant cytotoxicity to fibroblast cells offers a great opportunity for potential applications in important biomedical and industrial fields.

Continuous mobile authentication using touchscreen gestures

Abstract: Securing the sensitive data stored and accessed from mobile devices makes user authentication a problem of paramount importance. The tension between security and usability renders however the task of user authentication on mobile devices a challenging task. This paper introduces FAST (Fingergestures Authentication System using Touchscreen), a novel touchscreen based authentication approach on mobile devices. Besides extracting touch data from touchscreen equipped smartphones, FAST complements and validates this data using a digital sensor glove that we have built using off-the-shelf components. FAST leverages state-of-the-art classification algorithms to provide transparent and continuous mobile system protection. A notable feature is FAST 's continuous, user transparent post-login authentication. We use touch data collected from 40 users to show that FAST achieves a False Accept Rate (FAR) of 4.66% and False Reject Rate of 0.13% for the continuous post-login user authentication. The low FAR and FRR values indicate that FAST provides excellent post-login access security, without disturbing the honest mobile users.

The effects of theoretically different instruction and student characteristics on the skills of struggling readers

Abstract: This study investigated the effectiveness of combining enhanced classroom instruction and intense supplemental intervention for struggling readers in first grade Further, it compared two supplemental interventions derived from distinct theoretical orientations, examining them in terms of effects on academic outcomes and whether children's characteristics were differentially related to an instructional intervention One intervention (Proactive Reading) was aligned with behavioral theory and was derived from the model of Direct Instruction The other intervention (Responsive Reading) was aligned with a cognitive theory and was derived from a cognitive-apprenticeship model These interventions were provided to small groups of first-grade students at risk for reading difficulties Students were assessed on various reading and reading-related measures associated with success in beginning reading Results indicated that (a) first-grade students who were at risk for reading failure and who received supplemental instruction in the Responsive or Proactive interventions scored higher on measures of reading and reading-related skills than students who received only enhanced classroom instruction, (b) enhanced classroom instruction appeared to promote high levels of reading growth for many children at risk for reading failure, (c) the two interventions were essentially equally effective even though they reflected different theoretical perspectives, and (d) children's characteristics did not differentially predict the effectiveness of an intervention Este estudio investigo la eficacia de combinar una ensenanza intensiva en el aula y una intervencion suplementaria exhaustiva para los lectores de primer grado con dificultades Adicionalmente se compararon dos intervenciones suplementarias derivadas de orientaciones teoricas diferentes y se las examino en terminos de sus efectos sobre los resultados academicos y de sus relaciones con las caracteristicas de los ninos Una intervencion (Lectura Proactiva) pertenecia al marco de la teoria de la conducta y derivaba del modelo de Instruccion Directa La otra intervencion (Lectura Receptiva) estaba relacionada con una teoria cognitiva y derivaba de un modelo cognitivo de aprendizaje Las intervenciones se realizaron con pequenos grupos de estudiantes en riesgo de fracaso en lectura que asistian a primer grado Se evaluo a los estudiantes en varias medidas de lectura y habilidades relacionadas que se asocian al exito en lectura inicial Los resultados indicaron que: a) los estudiantes de primer grado en riesgo de fracaso en lectura que recibieron intervencion suplementaria, tanto Receptiva como Proactiva, tuvieron mejores calificaciones en medidas de lectura y habilidades relacionadas que los estudiantes que solo recibieron ensenanza intensiva en el aula, b) la ensenanza intensiva en el aula parecio promover altos niveles de desarrollo lector en muchos ninos en riesgo de fracaso, c) los dos tipos de intervencion fueron igualmente eficaces aunque reflejaran perspectivas teoricas diferentes y d) las caracteristicas de los ninos no predijeron en forma diferencial la eficacia de una in-Unterschiedsmerkmae in der Wirksamkeit einer Intervention voraussagen Diese Studie untersuchte die Effektivitat im Kombinieren von verstarktem Klassenraumunterricht und intensiver, suppletorischer Intervention bei sich abmuhenden Schulern in der ersten Klasse Ferner verglich sie zwei suppletorische Interventionen, abgeleitet aus deutlich theoretischen Gesichtspunkten durch Untersuchen von Effekten aufgrund akademischer Auswirkungen und ob die Charakteristiken der Kinder sich abweichend zu einem unterrichteten Anweisungseingriff verhielten Eine Intervention (pro-aktives Lesen) wurde einer Verhaltenstheorie angeglichen und von dem Modell des Direktunterrichts abgeleitet Die andere Intervention (responsives Lesen) wurde einer kognitiven Theorie angeglichen und von einem kognitiven Lehrmodell abgeleitet Diese Interventionen wurden kleinen Gruppen von Schulern mit Risiken zu Leseschwierigkeiten in der ersten Klasse vermittelt Die Schuler wurden auf verschiedene Lese- und lesebezogenen Masnahmen gepruft, die mit dem Erfolg beim Lesen fur Anfanger verknupft waren Die Ergebnisse haben gezeigt, dass (a) Schuler der ersten Klasse, bei denen die Gefahr des Leseversagens bestand und die suppletorische Lehranweisungen mittels responsiver oder proaktiver Eingriffe erhielten, hohere Leistungen in der Lesebewertung und bei den lesebezogenen Leistungen erzielten, als jene Schuler die lediglich einen verstarkten Klassenraumunterricht erhielten, (b) verstarkter Unterricht im Klassenraum schien im hohen Grade die Lesesteigerung fur viele Kinder mit Risiken zum Leseversagen zu fordern, (c) die beiden Interventionen waren im wesentlichen gleichermasen wirksam, obwohl sie unterschiedliche theoretische Perspektiven reflektierten, und (d) aus den Charakteristiken der Kinder liesen sich keine Schlusse uber tervencion Cette etude a examine l'efficacite de la combinaison d'un enseignement renforce en classe avec une intervention supplementaire intense sur des lecteurs de premiere annee en difficulte Plus precisement, elle a compare deux interventions supplementaires provenant d'orientations theoriques distinctes, en les examinant en termes d'effets sur les resultats academiques et en fonction des caracteristiques des enfants selon le type d'intervention Une intervention (Lecture proactive) correspondait a une position behavioriste et etait issue du modele de l'enseignement direct L'autre intervention (Lecture repondante) correspondait a une theorie cognitiviste et etait issue d'un modele d'apprentissage cognitif Ces interventions ont ete effectuees aupres de petits groupes d'elives de premiere annee presentant des risques de difficultes en lecture On a opere differentes mesures de la lecture ou de mesures associees avec la reussite en lecture en debut d'apprentissage Les resultats ont montre que, a) les eleves de premiere annee qui etaient en risque d'echec en lecture et qui ont recu un enseignement supplementaire sous forme d'intervention en Lecture proactive ou en Lecture repondante ont obtenu de meilleurs resultats que ceux qui ont recu seulement un enseignement renforce en classe, b) un enseignement renforce en classe permet d'atteindre un plus haut niveau de developpement en lecture pour beaucoup d'enfants presentant un risque d'echec en lecture, c) les deux interventions ont ete pour l'essentiel aussi efficaces l'une que l'autre, quoique refletant des perspectives theoriques differentes, et d) les caracteristiques des enfants ne permettent pas de predire de maniere differenciee l'efficacite de telle ou telle intervention