Showing 231 - 240 of 2040 Items
Homozygosity at the MTL locus in clinical strains of Candida albicans: Karyotypic rearrangments and tetraploid formation
Date: 2004-06-01
Creator: Melanie Legrand
Paul Lephart
Anja Forche
Frank Michael C. Mueller
T., Walsh
P. T. Magee
Beatrice B. Magee
Access: Open access
- One hundred and twenty Candida albicans clinical isolates from the late 1980s and early 1990s were examined for homosygosity at the MTL locus. Of these, 108 were heterozygous (MTLa/MTLα), whereas seven were MTLa and five were MTLα. Five of the homozygous isolates were able to switch to the opaque cell morphology, while opaque cells were not detectable among the remaining seven. Nevertheless, all but one of the isolates homozygous at the MTL locus were shown to mate and to yield cells containing markers from both parents; the non-mater was found to have a frameshift in the MTLα1 gene. In contrast to Saccharomyces cerevisiae, C. albicans homozygotes with no active MTL allele failed to mate rather than mating as a cells. There was no correlation between homoxygosity and fluconazole resistance, mating and fluconazole resistance or switching and fluconazole resistance, in part because most of the strains were isolated before the widespread use of this antifungal agent, and only three were in fact drug resistant Ten of the 12 homozygotes had rearranged karyotypes involving one or more homologue of chromosomes 4, 5, 6 and 7. We suggest that karyotypic rearrangement, drug resistance and homozygosity come about as the result of induction of hyperrecombination during the infection process; hence, they tend to occur together, but each is the independent result of the same event. Furthermore, as clinical strains can mate and form tetraploids, mating and marker exchange are likely to be a significant part of the life cycle of C. albicans in vivo.
All-loop group-theory constraints for color-ordered SU(N) gauge-theory amplitudes
Date: 2012-01-16
Creator: Stephen G. Naculich
Access: Open access
- We derive constraints on the color-ordered amplitudes of the L-loop four-point function in SU(N) gauge theories that arise solely from the structure of the gauge group. These constraints generalize well-known group theory relations, such as U(1) decoupling identities, to all loop orders. © 2011 Elsevier B.V.
Sutural loosening and skeletal flexibility during growth: Determination of drop-like shapes in sea urchins
Date: 2002-02-07
Creator: Amy S. Johnson
Olaf Ellers
Jim Lemire
Melissa Minor
Holly A., Leddy
Access: Open access
- The shape of sea urchins may be determined mechanically by patterns of force analogous to those that determine the shape of a water droplet. This mechanical analogy implies skeletal flexibility at the time of growth. Although comprised of many rigid calcite plates, sutural collagenous ligaments could confer such flexibility if the sutures between plates loosened and acted as joints at the time of growth. We present experimental evidence of such flexibility associated with weight gain and growth. Over 13-, 4-, and 2-week periods, fed urchins (Strongylocentrotus droebachiensis) gained weight and developed looser sutures than unfed urchins that maintained or lost weight. Further, skeletons of fed urchins force-relaxed more than did those of unfed urchins and urchins with loose sutures force-relaxed more than those with tight sutures. Urchins (Strongylocentrotus franciscanus) fed for two and a half weeks, gained weight, also had looser skeletons and deposited calcite at sutural margins, whereas unfed ones did not. In field populations of S. droebachiensis the percentage having loose sutures varied with urchin diameter and reflected their size-specific growth rate. The association between feeding, weight gain, calcite deposition, force relaxation and sutural looseness supports the hypothesis that urchins deform flexibly while growing, thus determining their drop-like shapes.
Learning the futility of the thought suppression enterprise in normal experience and in obsessive compulsive disorder
Date: 2010-01-01
Creator: Sadia Najmi
Hannah Reese
Sabine Wilhelm
Jeanne Fama
Celeste, Beck
Daniel M. Wegner
Access: Open access
- Background: The belief that we can control our thoughts is not inevitably adaptive, particularly when it fuels mental control activities that have ironic unintended consequences. The conviction that the mind can and should be controlled can prompt people to suppress unwanted thoughts, and so can set the stage for the intrusive return of those very thoughts. An important question is whether or not these beliefs about the control of thoughts can be reduced experimentally. One possibility is that behavioral experiments aimed at revealing the ironic return of suppressed thoughts might create a lesson that could reduce unrealistic beliefs about the control of thoughts. Aims: The present research assessed the influence of the thought suppression demonstration on beliefs about the control of thoughts in a non-clinical sample, and among individuals with obsessive-compulsive disorder (OCD). Method: In Study 1, we assessed the effect of the thought suppression demonstration on beliefs about the control of thoughts among low and high obsessive individuals in the non-clinical population (N = 62). In Study 2, we conducted a similar study with individuals with OCD (N = 29). Results: Results suggest that high obsessive individuals in the non-clinical population are able to learn the futility of suppression through the thought suppression demonstration and to alter their faulty beliefs about the control of thoughts; however, for individuals with OCD, the demonstration may be insufficient for altering underlying beliefs. Conclusions: For individuals with OCD, the connection between suppressing a neutral thought in the suppression demonstration and suppressing a personally relevant obsession may need to be stated explicitly in order to affect their obsessive beliefs. © British Association for Behavioural and Cognitive Psychotherapies 2009.
Individual differences in EEG correlates of recognition memory due to DAT polymorphisms
Date: 2017-12-01
Creator: Paolo Medrano
Erika Nyhus
Andrew Smolen
Tim Curran
Robert S., Ross
Access: Open access
- Introduction: Although previous research suggests that genetic variation in dopaminergic genes may affect recognition memory, the role dopamine transporter expression may have on the behavioral and EEG correlates of recognition memory has not been well established. Objectives: The study aims to reveal how individual differences in dopaminergic functioning due to genetic variations in the dopamine transporter gene influences behavioral and EEG correlates of recognition memory. Methods: Fifty-eight participants performed an item recognition task. Participants were asked to retrieve 200 previously presented words while brain activity was recorded with EEG. Regions of interest were established in scalp locations associated with recognition memory. Mean ERP amplitudes and event-related spectral perturbations when correctly remembering old items (hits) and recognizing new items (correct rejections) were compared as a function of dopamine transporter group. Results: Participants in the dopamine transporter group that codes for increased dopamine transporter expression (10/10 homozygotes) display slower reaction times compared to participants in the dopamine transporter group associated with the expression of fewer dopamine transporters (9R-carriers). 10/10 homozygotes further displayed differences in ERP and oscillatory activity compared to 9R-carriers. 10/10 homozygotes fail to display the left parietal old/new effect, an ERP signature of recognition memory associated with the amount of information retrieved. 10/10 homozygotes also displayed greater decreases of alpha and beta oscillatory activity during item memory retrieval compared to 9R-carriers. Conclusion: Compared to 9R-carriers, 10/10 homozygotes display slower hit and correct rejection reaction times, an absence of the left parietal old/new effect, and greater decreases in alpha and beta oscillatory activity during recognition memory. These results suggest that dopamine transporter polymorphisms influence recognition memory.
Incorporating an ERP project into undergraduate instruction
Date: 2016-01-01
Creator: Erika Nyhus
Nancy Curtis
Access: Open access
- Electroencephalogram (EEG) is a relatively non-invasive, simple technique, and recent advances in open source analysis tools make it feasible to implement EEG as a component in undergraduate neuroscience curriculum. We have successfully led students to design novel experiments, record EEG data, and analyze event-related potentials (ERPs) during a one-semester laboratory course for undergraduates in cognitive neuroscience. First, students learned how to set up an EEG recording and completed an analysis tutorial. Students then learned how to set up a novel EEG experiment; briefly, they formed groups of four and designed an EEG experiment on a topic of their choice. Over the course of two weeks students collected behavioral and EEG data. Each group then analyzed their behavioral and ERP data and presented their results both as a presentation and as a final paper. Upon completion of the group project students reported a deeper understanding of cognitive neuroscience methods and a greater appreciation for the strengths and weaknesses of the EEG technique. Although recent advances in open source software made this project possible, it also required access to EEG recording equipment and proprietary software. Future efforts should be directed at making publicly available datasets to learn ERP analysis techniques and making publicly available EEG recording and analysis software to increase the accessibility of hands-on research experience in undergraduate cognitive neuroscience laboratory courses. Copyright
Correction of profiles of in-situ chlorophyll fluorometry for the contribution of fluorescence originating from non-algal matter
Date: 2017-01-01
Creator: Xiaogang Xing
Hervé Claustre
Emmanuel Boss
Collin Roesler
Emanuele, Organelli
Antoine Poteau
Marie Barbieux
Fabrizio D’Ortenzio
Access: Open access
- In situ chlorophyll fluorometers have been widely employed for more than half a century, and to date, it still remains the most used instrument to estimate chlorophyll-a concentration in the field, especially for measurements onboard autonomous observation platforms, e.g., Bio-Argo floats and gliders. However, in deep waters (> 300 m) of some specific regions, e.g., subtropical gyres and the Black Sea, the chlorophyll fluorescence profiles frequently reveal "deep sea red fluorescence" features. In line with previous studies and through the analysis of a large data set (cruise transect in the South East Pacific and data acquired by 82 Bio- Argo floats), we show that the fluorescence signal measured by a humic-like DOM fluorometer is highly correlated to the "deep sea red fluorescence." Both fluorescence signals are indeed linearly related in deep waters. To remove the contribution of non-algal organic matter from chlorophyll fluorescence profiles, we introduce a new correction. Rather that removing a constant value (generally the deepest chlorophyll a fluorescence value from the profile, i.e., so-called "deep-offset correction"), we propose a correction method which relies on DOM fluorometry and on its variation with depth. This new method is validated with chlorophyll concentration extracted from water samples and further applied on the Bio-Argo float data set. More generally, we discuss the potential of the proposed method to become a standard and routine procedure in quality-control and correction of chlorophyll a fluorescence originating from Bio-Argo network.
Using the very short form of the children’s behavior questionnaire for spanish-speaking populations in low-and middle-income countries: A psychometric analysis of dichotomized variables
Date: 2021-02-01
Creator: Elsa Lucia Escalante-Barrios
Sonia Mariel Suarez-Enciso
Samuel P. Putnam
Helen Raikes
Sergi, Fàbregues
Access: Open access
- While the psychometric properties of the Spanish version of the Very Short Form of the Children’s Behavior Questionnaire (CBQ-VSF) have been assessed in the US and Europe in samples composed of middle-and high-income parents with high levels of education, no studies have tested the instrument in low-income Spanish-speaking populations living in low-and middleincome countries. To fill this gap, our cross-sectional study assessed the psychometric properties of the Spanish version of the CBQ-VSF version in a sample of 315 low-income and low-educated parents with preschool children living in the Caribbean Region of Colombia. While our findings revealed problems that were similar to those identified in previous assessments of the CBQ-VSF Spanish version, they also showed unique problems related to the sociodemographic characteristics of our sample, containing many individuals with a low income and low educational level. Most of the participants gave extreme responses, resulting in a notable kurtosis and skewness of the data. This article describes how we addressed these problems by dichotomizing the variables into binary categories. Additionally, it demonstrates that merely translating the CBQ-VSF is insufficient to be able to capture many of the underlying latent constructs associated with low-income and low-educated Latino/Hispanic populations.
Knuth relations for the hyperoctahedral groups
Date: 2009-06-01
Creator: Thomas Pietraho
Access: Open access
- C. Bonnafé, M. Geck, L. Iancu, and T. Lam have conjectured a description of Kazhdan-Lusztig cells in unequal parameter Hecke algebras of type B which is based on domino tableaux of arbitrary rank. In the integer case, this generalizes the work of D. Garfinkle. We adapt her methods and construct a family of operators which generate the equivalence classes on pairs of arbitrary rank domino tableaux described in the above conjecture. © 2008 Springer Science+Business Media, LLC.
Equivalence classes in the Weyl groups of type Bn
Date: 2008-04-01
Creator: Thomas Pietraho
Access: Open access
- We consider two families of equivalence classes in the Weyl groups of type B n which are suggested by the study of left cells in unequal parameter Iwahori-Hecke algebras. Both families are indexed by a non-negative integer r. It has been shown that the first family coincides with left cells corresponding to the equal parameter Iwahori-Hecke algebra when r=0; the equivalence classes in the second family agree with left cells corresponding to a special class of choices of unequal parameters when r is sufficiently large. Our main result shows that the two families of equivalence classes coincide, suggesting the structure of left cells for remaining choices of the Iwahori-Hecke algebra parameters. © 2007 Springer Science+Business Media, LLC.