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Possible Variations (possible + variation)
Selected AbstractsEvidence for a hallucinogen dependence syndrome developing soon after onset of hallucinogen use during adolescenceINTERNATIONAL JOURNAL OF METHODS IN PSYCHIATRIC RESEARCH, Issue 3 2006A.L. Stone Abstract This study uses latent class methods and multiple regression to shed light on hypothesized hallucinogen dependence syndromes experienced by young people who have recently initiated hallucinogen use. It explores possible variation in risk. The study sample, identified within public-use data files of the 1999 National Household Survey on Drug Abuse (NHSDA), consists of 1186 recent-onset hallucinogen users, defined as having initiated hallucinogen use within 24 months of assessment (median elapsed time since onset of use ,12 to 13 months). The recent-onset users in this sample were age 12 to 21 at the time of assessment and were between the ages of 10 and 21 at the time of their first hallucinogen use. The NHSDA included items to assess seven clinical features often associated with hallucinogen dependence, which were used in latent class modelling. Latent class analysis, in conjunction with prior theory, supports a three-class solution, with 2% of recent-onset users in a class that resembles a hallucinogen dependence syndrome, whereas 88% expressed few or no clinical features of dependence. The remaining 10% may reflect users who are at risk for dependence or in an early stage of dependence. Results from latent class regressions indicate that susceptibility to rapid transition from first hallucinogen use to onset of this hallucinogen dependence syndrome might be influenced by hallucinogenic compounds taken (for example, estimated relative risk, RR = 2.4, 95% CI = 1.6, 7.6 for users of MDMA versus users of LSD). Excess risk of rapid transition did not appear to depend upon age, sex, or race/ethnicity. Copyright © 2006 John Wiley & Sons, Ltd. [source] On the calculation of the concentration dependence of drug binding to plasma proteins with multiple binding sites of different affinities: Determination of the possible variation of the unbound drug fraction and calculation of the number of binding sites of the proteinJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 2 2007Leonid M. Berezhkovskiy Abstract The measurement of the unbound drug fraction in plasma is routinely performed at drug concentrations much less than that of plasma proteins. Commonly, the protein has several binding sites of different affinities. The obtained value of the unbound drug fraction does not yield the affinity of each binding site separately. For drug binding to a single type of protein, it is shown that the assumption that all binding sites of the protein have the same affinity yields the slowest possible concentration increase of the unbound drug fraction, while the assumption that a drug binds to a single binding site yields the highest possible value of the unbound fraction for a given drug concentration. The conditions to be imposed on the affinities of binding sites, to provide the fastest and the slowest possible concentration increase of the unbound drug fraction are also obtained for the case of drug binding to several types of plasma proteins. The suggested approach is applied to the determination of the number of binding sites of the protein from the measured values of the unbound drug fraction at different drug concentrations. ©2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96:249,257, 2007 [source] Extreme-ultraviolet laser metrology of O i transitionsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY: LETTERS (ELECTRONIC), Issue 1 2008T. I. Ivanov ABSTRACT Some 16 transitions in atomic oxygen originating from its 3P ground state were measured using a tunable narrow-band extreme-ultraviolet laser source, with an unprecedented accuracy of ,,/,= 8 × 10,8. The results are relevant for comparisons with spectral absorption features observed in the line of sight of quasars, in order to test a possible variation of the fine-structure constant , on a cosmological time-scale. [source] An oscillatory interference model of grid cell firingHIPPOCAMPUS, Issue 9 2007Neil Burgess Abstract We expand upon our proposal that the oscillatory interference mechanism proposed for the phase precession effect in place cells underlies the grid-like firing pattern of dorsomedial entorhinal grid cells (O'Keefe and Burgess (2005) Hippocampus 15:853,866). The original one-dimensional interference model is generalized to an appropriate two-dimensional mechanism. Specifically, dendritic subunits of layer II medial entorhinal stellate cells provide multiple linear interference patterns along different directions, with their product determining the firing of the cell. Connection of appropriate speed- and direction- dependent inputs onto dendritic subunits could result from an unsupervised learning rule which maximizes postsynaptic firing (e.g. competitive learning). These inputs cause the intrinsic oscillation of subunit membrane potential to increase above theta frequency by an amount proportional to the animal's speed of running in the "preferred" direction. The phase difference between this oscillation and a somatic input at theta-frequency essentially integrates velocity so that the interference of the two oscillations reflects distance traveled in the preferred direction. The overall grid pattern is maintained in environmental location by phase reset of the grid cell by place cells receiving sensory input from the environment, and environmental boundaries in particular. We also outline possible variations on the basic model, including the generation of grid-like firing via the interaction of multiple cells rather than via multiple dendritic subunits. Predictions of the interference model are given for the frequency composition of EEG power spectra and temporal autocorrelograms of grid cell firing as functions of the speed and direction of running and the novelty of the environment. © 2007 Wiley-Liss, Inc. [source] A domain decomposition technique for finite element based parametric sweep and tolerance analyses of microwave passive devicesINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 3 2009Giacomo Guarnieri Abstract A domain decomposition approach is here applied to the finite element solution of a multiport waveguide passive device. The approach allows separating the problem in multiple, coupled subproblems which can be solved individually. By appropriately defining one of these subdomains as containing all the possible variations to be studied it is hence possible to restrict the tolerance analysis to this latter, smaller domain. Numerical results showing the gain in computing time are presented. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009. [source] HCV genotypes in Sicily: Is there any evidence of a shift?JOURNAL OF MEDICAL VIROLOGY, Issue 6 2009Paola Pizzillo Abstract The distribution of HCV strains in any area is characterized by a relative prevalence of one genotype, and a number of less prevalent types. In some Western countries a change from the prevalent HCV genotype 1 to genotypes 3 and 4 has been reported in the last decade. In order to assess possible variations of the distribution of HCV genotypes in Sicily, a southern region of Italy, a hospital-based cohort, collected prospectively, of 3,209 subjects with chronic HCV infection was surveyed, comparing the distribution of HCV genotypes during two consecutive periods, from 1997 to 2002 and from 2003 to 2007, according to age and gender. The results show that genotype 1b, which has been historically the most prevalent in Sicily, is still predominant, followed more distantly by genotypes 2 and 3a. However, a cohort effect for these genotypes was seen when comparing the two time periods. Genotype 1b decreased slowly over the last decade, due to the death of the people infected, leading to a proportional increase of the other genotypes. No evidence was found in support of a major increase in the prevalence of other genotypes, such as genotype 4, in relation to migration patterns. J. Med. Virol. 81:1040,1046, 2009. © 2009 Wiley-Liss, Inc. [source] The role of mass spectrometry to study the Oklo,Bangombé natural reactors,MASS SPECTROMETRY REVIEWS, Issue 5 2007J.R. De Laeter Abstract The discovery of the existence of chain reactions at the Oklo natural reactors in Gabon, Central Africa in 1972 was a triumph for the accuracy of mass spectrometric measurements, in that a 0.5% anomaly in the 235U/238U ratio of certain U ore samples indicated a depletion in 235U. Mass spectrometric techniques thereafter played a dominant role in determining the nuclear parameters of the reactor zones themselves, and in deciphering the geochemical characteristics of various elements in the U-rich ore and in the surrounding rock strata. The variations in the isotopic composition of a large number of elements, caused by a combination of nuclear fission, neutron capture and radioactive decay, provide a powerful tool for investigating this unique geological environment. Mass spectrometry can be used to measure the present-day elemental and isotopic abundances of numerous elements, so as to decipher the past history of the reactors and examine the retentivity/mobility of these elements. Many of the fission products have a radioactive decay history that have been used to date the age and duration of the reactor zones, and to provide insight into their nuclear and geochemical behavior as a function of time. The Oklo fission reactors and their near neighbor at Bangombé, some 30 km to the south-east of Oklo, are unique in that not only did they become critical some 2,×,109 years ago, but also the deposits have been preserved over this period of geological time. The long-term geochemical behavior of actinides and fission products have been extensively studied by a variety of mass spectrometric techniques over the past 30 years to provide us with significant information on the mobility/retentivity of this material in a natural geological repository. The Oklo,Bangombé natural reactors are therefore geological analogs that can be evaluated in terms of possible radioactive waste containment sites. As more reactor zones were discovered, it was realized that they could be classified into two groups according to their burial depth in the Oklo mine-site. Reactor Zones 10, 13, and 16 were buried more deeply, and were therefore less weathered than the other zones. The less-weathered zones are of great importance in mobility/retentivity studies and therefore to the question of radioactive waste containment. Isotopic studies of these natural reactors are also of value in physics to examine possible variations in fundamental constants over the past 2 billion years. © 2007 Wiley Periodicals, Inc., Mass Spec Rev 26:683,712, 2007 [source] Possible evidence for a variable fine-structure constant from QSO absorption lines: systematic errorsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2001M.T. Murphy Comparison of quasar (QSO) absorption spectra with laboratory spectra allows us to probe possible variations in the fundamental constants over cosmological time-scales. In a companion paper we present an analysis of Keck/HIRES spectra and report possible evidence suggesting that the fine-structure constant, ,, may have been smaller in the past: over the redshift range . In this paper we describe a comprehensive investigation into possible systematic effects. Most of these do not significantly influence our results. When we correct for those which do produce a significant systematic effect in the data, the deviation of from zero becomes more significant. We are led increasingly to the interpretation that , was slightly smaller in the past. [source] Electrospray ionization tandem mass spectrometry fragmentation of protonated flavone and flavonol aglycones: a re-examinationRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 2 2009Gonçalo C. Justino Flavonoids are important phytochemicals which have been intensively studied in the last decades in view of their antioxidant activity, which is of particular importance in the case of flavones and flavonols, that differ in a single 3-OH group. Mass spectrometry has been used to elucidate the structures of many types of flavonoids and their metabolites. The work we present here is focused on the electrospray ionization tandem mass spectrometry (ESI-MS/MS) analysis of flavone and flavonols aglycones. Their fragmentation mechanisms in the positive ion mode are described and compared with previously reported mechanisms. We analyzed flavonoid derivatives produced by reaction of the flavonoids with chemically synthesized hypohalous acids (HOCl, HOBr and HOI) and peroxynitrite, reactive species involved in the inflammatory response. All the proposed pathways have been analyzed using computational chemistry methods in order to seek for possible variations and establish the most plausible ones. We observed that the losses of one and two CO molecules can be useful in terms of antioxidant activity prediction. Losses of one and two C2H2O groups are also informative in terms of structure and activity predictions. The retro-Diels-Alder fragmentations, and subsequent neutral losses, were reviewed and, according to our calculations, the most plausible structures for the product ions were established. These fingerprints will be of great value for differentiating flavonoids from other compounds in complex biological mixtures and for a thorough structural identification of flavonoid aglycones and their invivo metabolites. Copyright © 2008 John Wiley & Sons, Ltd. [source] Modelling growth and body composition in fish nutrition: where have we been and where are we going?AQUACULTURE RESEARCH, Issue 2 2010André Dumas Abstract Mathematical models in fish nutrition have proven indispensable in estimating growth and feed requirements. Nowadays, reducing the environmental footprint and improving product quality of fish culture operations are of increasing interest. This review starts by examining simple models applied to describe/predict fish growth profiles and progresses towards more comprehensive concepts based on bioenergetics and nutrient metabolism. Simple growth models often lack biological interpretation and overlook fundamental properties of fish (e.g. ectothermy, indeterminate growth). In addition, these models disregard possible variations in growth trajectory across life stages. Bioenergetic models have served to predict not only fish growth but also feed requirements and waste outputs from fish culture operations. However, bioenergetics is a concept based on energy-yielding equivalence of chemicals and has significant limitations. Nutrient-based models have been introduced into the fish nutrition literature over the last two decades and stand as a more biologically sound alternative to bioenergetic models. More mechanistic models are required to expand current understanding about growth targets and nutrient utilization for biomass gain. Finally, existing models need to be adapted further to address effectively concerns regarding sustainability, product quality and body traits. [source] Prenatal diagnosis, pregnancy terminations and prevalence of Down syndrome in Atlanta,BIRTH DEFECTS RESEARCH, Issue 9 2004Csaba Siffel Abstract BACKGROUND The impact of prenatal diagnosis on the live birth prevalence of Down syndrome (trisomy 21) has been described. This study examines the prevalence of Down syndrome before (1990,1993) and after inclusion of prenatally diagnosed cases (1994,1999) in a population-based registry of birth defects in metropolitan Atlanta. METHODS We identified infants and spontaneous fetal deaths with Down syndrome (n = 387), and pregnancies electively terminated after a prenatal diagnosis of Down syndrome (n = 139) from 1990 to 1999 among residents of metropolitan Atlanta from a population-based registry of birth defects, the Metropolitan Atlanta Congenital Defects Program (MACDP). Only diagnoses of full trisomy 21 were included. Denominator information on live births was derived from State of Georgia birth certificate data. We compared the prevalence of Down syndrome by calendar period (1990,1993, 1994,1999), maternal age (<35 years, 35+ years), and race/ethnicity (White, Black, other), using chi-square and Fisher's exact tests. RESULTS During the period when case ascertainment was based only on hospitals (1990,1993), the prevalence of Down syndrome was 8.4 per 10,000 live births when pregnancy terminations were excluded and 8.8 per 10,000 when terminations were included. When case ascertainment also included perinatal offices (1994,1999), the prevalence of Down syndrome was 10.1 per 10,000 when terminations were excluded and 15.3 when terminations were included. During 1990,1993, the prevalence of Down syndrome was 24.7 per 10,000 among offspring to women 35+ years of age compared to 6.8 per 10,000 among offspring to women <35 years of age (rate ratio [RR] = 3.65, 95% confidence interval [CI] = 2.53,5.28). During 1994,1999, the prevalence of Down syndrome was 55.3 per 10,000 among offspring to women 35+ years compared to 8.5 per 10,000 among offspring to women <35 years (RR = 6.55, 95% CI = 5.36,7.99). There was no statistically significant variation in the prevalence of Down syndrome by race/ethnicity within maternal age and period of birth strata. During 1994,1999, the proportion of cases that were electively terminated was greater for women 35+ years compared to women <35 years (RR = 5.10, 95% CI = 3.14,8.28), and lower for Blacks compared to Whites among women 35+ years of age (RR = 0.33, 95% CI = 0.16,0.66). CONCLUSIONS In recent years, perinatal offices have become an important source of cases of Down syndrome for MACDP, contributing at least 34% of cases among pregnancies in women 35+ years of age. Variation in the prevalence of Down syndrome by race/ethnicity, before or after inclusion of cases ascertained from perinatal offices, was not statistically significant. Among Down syndrome pregnancies in mothers 35+ years we found a lower proportion of elective termination among Black women compared to White women. We suggest that future reports on the prevalence of Down syndrome by race/ethnicity take into account possible variations in the frequency of prenatal diagnosis or elective termination by race/ethnicity. Birth Defects Research (Part A) 70565,571, 2004. Published 2004 Wiley-Liss, Inc. [source] Anatomical variations of the plantaris muscle and a potential role in patellofemoral pain syndromeCLINICAL ANATOMY, Issue 2 2008A. Jay Freeman Abstract The plantaris muscle has been given little attention in the reviewed literature. It is most commonly mentioned only when absent from a specimen. This study aimed to document the anatomy of the plantaris muscle and to discuss the clinical significance of the observations. Cadaveric knees (n = 46) were dissected to identify the possible variations of the plantaris muscle. The muscle conformed with standard descriptions (n = 26; 56.52%), was present but varied from previous descriptions (n = 14; 30.44%), or was absent (n = 6; 13.04%). The variations consisted of distinct interdigitations with the lateral head of the gastrocnemius muscle (n = 9; 19.57%) and a strong fibrous extension of the plantaris muscle to the patella (n = 5; 10.87%). The presence of interdigitations strengthen the argument that the plantaris muscle supplement the activity of the lateral head of the gastrocnemius muscle whereas the patellar extension suggests an involvement with patellofemoral dynamics and may play a role in the various presentations of patellofemoral pain syndrome. Greater understanding of the relationship between these and other posterior knee structures will facilitate more precise interpretation and treatment of knee injuries. Clin. Anat. 21:178,181, 2008. © 2008 Wiley-Liss, Inc. [source] Vulnerability factors in OCD symptoms: cross-cultural comparisons between Turkish and Canadian samplesCLINICAL PSYCHOLOGY AND PSYCHOTHERAPY (AN INTERNATIONAL JOURNAL OF THEORY & PRACTICE), Issue 2 2010Orçun Yorulmaz Abstract Recent findings have suggested some potential psychological vulnerability factors for development of obsessive-compulsive (OC) symptoms, including cognitive factors of appraisal and thought control, religiosity, self-esteem and personality characteristics such as neuroticism. Studies demonstrating these associations usually come from Western cultures, but there may be cultural differences relevant to these vulnerability factors and OC symptoms. The present study examined the relationship between putative vulnerability factors and OC symptoms by comparing non-clinical samples from Turkey and Canada, two countries with quite different cultural characteristics. The findings revealed some common correlates such as neuroticism and certain types of metacognition, including appraisals of responsibility/threat estimation and perfectionism/need for certainty, as well as thought,action fusion. However, culture-specific factors were also indicated in the type of thought control participants used. For OC disorder symptoms, Turkish participants were more likely to utilize worry and thought suppression, while Canadian participants tended to use self-punishment more frequently. The association with common factors supports the cross-cultural validity of some factors, whereas unique factors suggest cultural features that may be operative in cognitive processes relevant to OC symptoms.,Copyright © 2009 John Wiley & Sons, Ltd. Key Practitioner Message: , Despite cross-cultural validity in the cognitive accounts for OCD, there are some evidences implying the impact of cultural characteristics on some cognitive factors across different cultures. Thus, it is important for clinicians who work with people from different cultural backgrounds to be vigilant for possible variations in the cognitive processes during psychotherapy and psychological assessment. [source] | ||||||||||||||||