Edward Segovia | Universidad Cesar Vallejo - Lima Norte (original) (raw)

Papers by Edward Segovia

Contrary to popular opinion, the use of paper in our society will not disappear any time during t... more Contrary to popular opinion, the use of paper in our society will not disappear any time during the foreseeable future. In fact, the use of paper continues to grow rather than decline. It is certainly true that as individuals, we may be printing less than we used to. And the role of paper has been transformed from the archival record of a document to a convenient and aesthetically appealing graphical user interface. The use of paper is now intimately linked to the electronic systems that capture, process, transmit, generate, and reproduce textual and graphical content. Paper can be thought of as an interface between humans and the digital world. If this interface is not secure, the entire system becomes vulnerable to attack and abuse. Although paper is read by humans in the same way that it has been for millennia, and has had the same fundamental form and composition for almost that long as well, the technologies for printing and scanning documents and capturing their content have evolved tremendously, especially during the last twenty years. This has moved the capability to generate printed documents from the hands of a select few to anyone with access to lowcost scanners, printers, and personal computers. It has greatly broadened the opportunities for abuse of trust through the generation of fallacious documents and tampering with existing documents, including the embedding of messages in these documents.

Surface Science, 2000

Processes of adsorption-desorption with glycine admitted to the TiO 2 (110) (1×2) reconstructed s... more Processes of adsorption-desorption with glycine admitted to the TiO 2 (110) (1×2) reconstructed surface have been studied using synchrotron light, energy 55 eV, and with coverages both sub to monolayer, and multilayer at room temperature. The findings are discussed in terms of processes of dissociative adsorption at the sub-monolayer stage with only minor amounts of the amino radical of the glycine molecule remaining at the surface. The Ti 3d ) peak is significantly affected in the evolution towards initial monolayer coverage. Aspects of photon induced desorption with photoelectron spectroscopy are compared with thermal treatments of the glycine-covered surface.

Surface Science, 1997

The adsorption of acetic acid on the TiO2(110) surface has been studied with PES, using synchrotr... more The adsorption of acetic acid on the TiO2(110) surface has been studied with PES, using synchrotron radiation ∼47 eV, both at the stoichiometric (1 × 1) surface and the (1 × 2)-reconstructed surface. The results indicate a similar bonding configuration for each surface, and that the saturation acetate coverage at room temperature on the (1 × 2)-reconstructed surface is approximately half that of the (1 × 1) surface. The results are interpreted in favour of the added Ti2O3-row model of the (1 × 2) reconstruction at the clean surface.

Journal of Traumatic Stress, 1996

The relationship of traumatic events to physical health was examined in a randomized community su... more The relationship of traumatic events to physical health was examined in a randomized community survey (N = 2,364) of Los Angeles residents, 16% of whom had experienced a lifetime traumatic event. This study tested hypotheses that individuals experiencing traumatic events have poorer physical health and that the negative impact of traumatic events on physical health is greater among disadvantaged sociodemographic groups. Regression analyses showed that respondents with a traumatic event history indicated poorer perceptions of their physical health, more chronic limitations in physical functioning, and more chronic medical conditions compared with respondents without such a history, while controlling for demographics, psychiatric history, and other stressful life events. The association of traumatic events with poorer physical health among vulnerable sociodemographic groups was partially supported.

Microbiology-sgm, 2008

The activity of NifA, the transcriptional activator of the nitrogen fixation (nif) gene, is tight... more The activity of NifA, the transcriptional activator of the nitrogen fixation (nif) gene, is tightly regulated in response to ammonium and oxygen. However, the mechanisms for the regulation of NifA activity are quite different among various nitrogen-fixing bacteria. Unlike the well-studied NifL-NifA regulatory systems in Klebsiella pneumoniae and Azotobacter vinelandii, in Rhodospirillum rubrum NifA is activated by a direct protein-protein interaction with the uridylylated form of GlnB, which in turn causes a conformational change in NifA. We report the identification of several substitutions in the N-terminal GAF domain of R. rubrum NifA that allow NifA to be activated in the absence of GlnB. Presumably these substitutions cause conformational changes in NifA necessary for activation, without interaction with GlnB. We also found that wild-type NifA can be activated in a GlnB-independent manner under certain growth conditions, suggesting that some other effector(s) can also activate NifA. An attempt to use Tn5 mutagenesis to obtain mutants that altered the pool of these presumptive effector(s) failed, though much rarer spontaneous mutations in nifA were detected. This suggests that the necessary alteration of the pool of effector(s) for NifA activation cannot be obtained by knockout mutations.

The enzymatic reduction of molecular nitrogen to ammonia requires high amounts of energy, and the... more The enzymatic reduction of molecular nitrogen to ammonia requires high amounts of energy, and the presence of oxygen causes the catalyzing nitrogenase complex to be irreversible inactivated. Thus nitrogen-fixing microorganisms tightly control both the synthesis and activity of nitrogenase to avoid the unnecessary consumption of energy. In the free-living diazotrophs Klebsiella pneumoniae and Azotobacter vinelandii, products of the nitrogen fixation nifLA operon regulate transcription of the other nif operons. NifA activates transcription of nif genes by the alternative form of RNA-polymerase, s 54

L'usage de la cigarette est nuisible à la santé, c'est bien connu. Le coût qui en résulte et que ... more L'usage de la cigarette est nuisible à la santé, c'est bien connu. Le coût qui en résulte et que doit assumer le système de santé financé par les fonds publics préoccupe vivement les décideurs de politiques. Nous considérons deux éléments essentiels du système de santé: les hôpitaux et les médecins. Notre étude, à la différence de celles qui l'ont précédée, adopte une approche économétrique pour évaluer ce coût, rendue possible par la disponibilité de l'Enquête sur la Santé des Adultes, menée en 1995 à Terre-Neuve. Cette enquête, qui porte sur des milliers d'individus, fournit une image de leurs caractéristiques sociodémographiques, économiques et de santé et elle est liée à l'utilisation du dossier médical des individus sur une période de sept ans. On estime que plus de 12% des recours à l'hôpital et environ 7% des visites au cabinet du médecin sont attribuables à l'usage de la cigarette. Le coût monétaire annuel que cela entraîne est considérable: de 110 à 140 dollars environ, par personne.

Behavioral Neuroscience, 2003

Sexual experience facilitates subsequent male sexual behavior; activation of the N-methyl-D-aspar... more Sexual experience facilitates subsequent male sexual behavior; activation of the N-methyl-D-aspartate (NMDA) glutamate receptor may play a role in this experience-induced enhancement. In this article, the authors report that systemic injections of MK-801, an NMDA receptor antagonist, impaired male sexual behavior in sexually naive and sexually experienced male rats. Furthermore, saline-treated rats that received 7 daily exposures to an inaccessible estrous female instead of sexual experience displayed enhancement of copulation on the following day. Injections of MK-801 before each of these exposures inhibited the experience-induced enhancement on the drug-free test on Day 8. These data suggest that stimulation of NMDA receptors enhances sexual performance immediately and mediates the experienceinduced enhancement of subsequent copulatory behavior.

Educational Gerontology, 2004

Health promoting behaviors have become increasingly important as Americans attempt to retain thei... more Health promoting behaviors have become increasingly important as Americans attempt to retain their youth and health. This study collected self-reported data from 559 participants in the Southwest United States using the Health Promoting Lifestyle Profile II to compare the health promoting behaviors of older adults (60–92 years), middle-aged adults (40–59 years), and younger adults (18–39 years). Results indicate that older

IEEE Signal Processing Magazine, 2009

Neuropsychopharmacology, 2008

Neuropsychopharmacology, the official publication of the American College of Neuropsychopharmacol... more Neuropsychopharmacology, the official publication of the American College of Neuropsychopharmacology, publishing the highest quality original research and advancing our understanding of the brain and behavior.

In Syrian hamsters, social behavior is mediated exclusively by chemosensory cues and circulating ... more In Syrian hamsters, social behavior is mediated exclusively by chemosensory cues and circulating gonadal steroid hormones. Where these two signals are processed in the brain is unknown, but the posterior bed nucleus of the stria terminalis (pBNST) has been suggested as a candidate site. Therefore, we tested male hamsters' preference for opposite-sex odors following excitotoxic lesions of the pBNST. Lesions of the pBNST (pBNST-X) eliminated male hamsters' preference for opposite-sex odors. Furthermore, pBNST-X males spent significantly less time investigating female odors than clean odors and significantly less time investigating female odors than control males did. Lesions of the pBNST did not change male hamsters' investigation of male odors. The deficits observed in pBNST-X males were not due to a failure to discriminate between odors, as pBNST-X males were able to distinguish between odors. Together, these data suggest the pBNST is critical for opposite-sex odor preference in male hamsters.

Brain Structure & Function

Cholinergic and non-cholinergic neurons in the brainstem pedunculopontine (PPT) and laterodorsal ... more Cholinergic and non-cholinergic neurons in the brainstem pedunculopontine (PPT) and laterodorsal tegmental (LDT) nuclei innervate diverse forebrain structures. The cholinergic neurons within these regions send heavy projections to thalamic nuclei and provide modulatory input as well to midbrain dopamine cells in the ventral tegmental area (VTA). Cholinergic PPT/LDT neurons are known to send collateralized projections to thalamic and non-thalamic targets, and previous studies have shown that many of the afferents to the VTA arise from neurons that also project to midline and intralaminar thalamic nuclei. However, whether cholinergic projections to the VTA and anterior thalamus (AT) are similarly collateralized is unknown. Ultrastructural work from our laboratory has demonstrated that cholinergic axon varicosities in these regions differ both morphologically and with respect to the expression and localization of the high-affinity choline transporter. We therefore hypothesized that the cholinergic innervation to these regions is provided by separate sets of PPT/LDT neurons. Dual retrograde tract-tracing from the AT and VTA indicated that only a small percentage of the total afferent population to either region showed evidence of providing collateralized input to the other target. Cholinergic and non-cholinergic cells displayed a similarly low percentage of collateralization. These results are contrasted to a control case in which retrograde labeling from the midline paratenial thalamic nucleus and the VTA resulted in higher percentages of cholinergic and non-cholinergic dual-tracer labeled cells. Our results indicate that functionally distinct limbic target regions receive primarily segregated signaling from PPT/LDT neurons.

1 Environmental change has often been put forward as a main reason for invasions by exotic plant ... more 1 Environmental change has often been put forward as a main reason for invasions by exotic plant species into natural habitats. Alternatively, or in addition, high propagule pressure has been hypothesized to be the single most important factor for biological invasions.

Social Science & Medicine, 1989

The objective of this study is to verify empirically the existence of separate dimensions in the ... more The objective of this study is to verify empirically the existence of separate dimensions in the overall concept of health status by analysing 10 variables included in a questionnaire that was applied to all adults in a simple random sample of households in St John's, Newfoundland. The response rate was 85% for a total of 3300 subjects.These data were analyzed by frequencies and by associations with sex, age and education. Nonparametric correlation, factor and cluster analyses on variables were used to verify if health status had identifiable dimensions. All these methods produced similar results showing five distinct factors. The first factor is composed of variables related to disease (disability/chronic conditions/worry about health); the second, to happiness (happiness/emotional); the third, to subjective appraisal of health (physical condition/ comparative level of energy/self-rated health status). Finally, the fourth and fifth factors were single variables; restriction of normal activities and social contacts. An interesting finding was that self-rated health status was distributed with almost equal weight in both the first and third factors.A validation of the 10 variables and the 5 factors was undertaken by studying their association with health care utilization. Two measures of utilization were used; number of physicians' visits in a year and number of hospital days in a 4-year period. Number of chronic conditions, disability and self-rated health status were associated with both measures of utilization; factor 1 was the only summary construct showing association with utilization.This paper demonstrates that self-rated health status is valid as a single measure of overal health status in this sample, being associated with both disease and subjective assessment components.

Demography, 1999

We refine the established association between education and health by distinguishing three aspect... more We refine the established association between education and health by distinguishing three aspects of a person s education (quantity, credential, and selectivity) and by examining the mechanisms through which they may correlate with health. Data are from the 1995 Aging, Status, and the Sense of Control Survey, a representative U.S. national telephone survey of 2,593 respondents aged 18 to 95, with an oversample of elderly. Results show that physical functioning and perceived health increase significantly with years of formal education and with college selectivity for those with a bachelor s or higher degree, adjusting for age, sex, race, marital status, and parental education. The credential of a college degree has no net association with physical functioning and perceived health beyond the amount attributable to the additional years of schooling. Of the three aspects of education, years of schooling has the largest effect. Most of that association appears attributable to its correlation with work and economic conditions, social psychological resources, and health lifestyle. A large portion of the net association of college selectivity with physical functioning and perceived health appears attributable to health lifestyle.

International Journal of Epidemiology, 1991

Using the population of St John's, Newfoundland, we did a constructive replication of pre... more Using the population of St John's, Newfoundland, we did a constructive replication of previous studies testing the association between health practices and health status. A telephone questionnaire was applied to all adults in a probabilistic sample of households (3300 subjects, 85% response rate). Several health practices and preventive behaviours indexes were developed and tested. An additive index of six practices (breakfast, sleeping, drinking, smoking, weight and exercise) using the Alameda County definitions, and an additive score of five practices (excluding breakfast and with revised definitions for smoking, drinking and exercise) were analysed using log-linear models; there was association between the indexes and self-assessed health status when controlling for sex, age and education, with the exception of the six-practice index in males. The association between these two indexes and several variables and constructs of health status showed that the best relationships were with self-assessed health status and with a construct including variables measuring subjective health.

Surface Science, 1999

Photon damage of multilayers of glycine adsorbed on a TiO2(110) surface at room temperature has b... more Photon damage of multilayers of glycine adsorbed on a TiO2(110) surface at room temperature has been studied with photoelectron spectroscopy of the valence band, the 2s band, and the Ti 3p level using synchrotron radiation at the Daresbury S.R.S. The UPS spectra of the multilayer (comprising about seven monolayers) show structures which can be assigned to the molecular structure of the zwitterionic form of glycine. Photon induced damage of multilayers up to θ=2 monolayers produces a first order desorption of the zwitterionic molecules with total cross section 5.4×10−16 cm2 which is similar to the ionisation cross section in the gas phase. The remaining layer is formed by C, NHx (x=1,2) and OH hydroxyl species. A significant feature is the increase of the structure at 0.8 eV pointing to the growth of Ti3+ surface species. This could be due to the formation of OH radicals on the surface or the adsorption of fragments on top of the O surface atoms involving some charge transfer to the surface.

Journal of Neural Transmission

There is evidence that deep brain stimulation (DBS) of the pedunculopontine tegmental nucleus (PP... more There is evidence that deep brain stimulation (DBS) of the pedunculopontine tegmental nucleus (PPTg) improves parkinsonian motor signs. The mechanisms that mediate these effects and the modifications that occur in the PPTg in Parkinson&amp;amp;amp;amp;amp;#39;s disease (PD) are not fully known and are the object of current debate. The aim of this paper was to critically review available data with respect to (1) the presence of PPTg neurons linked to reticulospinal projections, (2) the involvement of these neurons in modulating spinal reflexes, and (3) the participation of fibers close to or within the PPTg region in such modulation. The PPTg neurons are distributed in a large pontotegmental region, stimulation of which can evoke activity in hindlimb, shoulder and neck muscles, and potentiate motor responses evoked by stimulation of dorsal roots. This influence seems to be carried out by fast-conducting descending fibers, which likely run in the medial reticulospinal pathway. It is yet unclear which neurotransmitters are involved and on which elements of the gray matter of the spinal cord PPTg fibers synapse. The modulation of spinal cord activity which can be achieved by stimulating the PPTg region seems to be mediated not only by PPTg neurons, but also by tecto-reticular fibers which run in the pontotegmental area, and which likely are activated during PPTg-DBS. The importance of these fibers is discussed taking into account the degeneration of PPTg neurons in PD and the benefits in gait and postural control that PPTg-DBS exerts in PD. The potential usefulness of PPTg-DBS in other neurodegenerative disorders characterized by neuronal loss in the brainstem is also considered.