bluuebunny/crossref_metadata_2025 huggingface dataset:
The front speed of intrusions into a continuously stratified medium
Authors: BOLSTER DIOGO , HANG ALICE , LINDEN P. F.
Published: December 2007

This paper examines intrusive Boussinesq gravity currents, propagating into a continuously stratified fluid. We develop a model, based on energy arguments, to predict the front speed of such an intrusive gravity current from a lock release. We find that the depth at which the intrusion occurs, which corresponds to the level of neutral buoyancy (i.e. the depth where the intrusion density equals the stratified fluid density), affects the front speed. The maximum speeds occur when the intrusion travels along the top and bottom boundaries and the minimum speed occurs at mid-depth. Experiments and numerical simulations were conducted to compare to the theoretically predicted values, and good agreement was found.
Vertical scale selection in inertial instability
Authors: KLOOSTERZIEL R. C. , CARNEVALE G. F.
Published: December 2007

The linear instability of a barotropic flow with uniform horizontal shear in a stratified rotating fluid is investigated with respect to perturbations invariant in the alongflow direction. The flow can be inertially unstable if there is sufficiently strong anticyclonic shear, but only for sufficiently high Reynolds numbers Re. We determine the critical Reynolds numbers required for amplification of the instability as a function of Prandtl number, strength of the stratification and magnitude of the shear. The vertical scales at the onset of the instability are calculated. For Prandtl number P < 1.44 instability always sets in through stationary overturning motions, for P > 1.44 it may also commence through overstable (oscillatory) motions. For Re exceeding the critical value, we determine the vertical scale of the most rapidly amplifying modes and the corresponding growth rates and how they vary with Re, P, the shear and the strength of stratification.
Influence of wind on extreme wave events: experimental and numerical approaches
Authors: KHARIF C. , GIOVANANGELI J.-P. , TOUBOUL J. , GRARE L. , PELINOVSKY E.
Published: December 2007

The influence of wind on extreme wave events in deep water is investigated experimentally and numerically. A series of experiments conducted in the Large Air–Sea Interactions Facility (LASIF-Marseille, France) shows that wind blowing over a short wave group due to the dispersive focusing of a longer frequency-modulated wavetrain (chirped wave packet) may increase the time duration of the extreme wave event by delaying the defocusing stage. A detailed analysis of the experimental results suggests that extreme wave events may be sustained longer by the air flow separation occurring on the leeward side of the steep crests. Furthermore it is found that the frequency downshifting observed during the formation of the extreme wave event is more important when the wind velocity is larger. These experiments have pointed out that the transfer of momentum and energy is strongly increased during extreme wave events.

Two series of numerical simulations have been performed using a pressure distribution over the steep crests given by the Jeffreys sheltering theory. The first series corresponding to the dispersive focusing confirms the experimental results. The second series which corresponds to extreme wave events due to modulational instability, shows that wind sustains steep waves which then evolve into breaking waves. Furthermore, it was shown numerically that during extreme wave events the wind-driven current could play a significant role in their persistence.
Coherent structures in direct numerical simulation of turbulent boundary layers at Mach 3
Authors: RINGUETTE MATTHEW J. , WU MINWEI , MARTÍN M. PINO
Published: December 2007

We demonstrate that data from direct numerical simulation of turbulent boundary layers at Mach 3 exhibit the same large-scale coherent structures that are found in supersonic and subsonic experiments, namely elongated, low-speed features in the logarithmic region and hairpin vortex packets. Contour plots of the streamwise mass flux show very long low-momentum structures in the logarithmic layer. These low-momentum features carry about one-third of the turbulent kinetic energy. Using Taylor's hypothesis, we find that these structures prevail and meander for very long streamwise distances. Structure lengths on the order of 100 boundary layer thicknesses are observed. Length scales obtained from correlations of the streamwise mass flux severely underpredict the extent of these structures, most likely because of their significant meandering in the spanwise direction. A hairpin-packet-finding algorithm is employed to determine the average packet properties, and we find that the Mach 3 packets are similar to those observed at subsonic conditions. A connection between the wall shear stress and hairpin packets is observed. Visualization of the instantaneous turbulence structure shows that groups of hairpin packets are frequently located above the long low-momentum structures. This finding is consistent with the very large-scale motion model of Kim & Adrian (1999).
Interactions of a stationary finite-sized particle with wall turbulence
Authors: ZENG LANYING , BALACHANDAR S. , FISCHER PAUL , NAJJAR FADY
Published: December 2007

Reliable information on forces on a finite-sized particle in a turbulent boundary layer is lacking, so workers continue to use standard drag and lift correlations developed for a laminar flow to predict drag and lift forces. Here we consider direct numerical simulations of a turbulent channel flow over an isolated particle of finite size. The size of the particle and its location within the turbulent channel are systematically varied. All relevant length and time scales of turbulence, attached boundary layers on the particle, and particle wake are faithfully resolved, and thus we consider fully resolved direct numerical simulations. The results from the direct numerical simulation are compared with corresponding predictions based on the standard drag relation with and without the inclusion of added-mass and shear-induced lift forces. The influence of turbulent structures, such as streaks, quasi-streamwise vortices and hairpin packets, on particle force is explored. The effect of vortex shedding is also observed to be important for larger particles, whoseReexceeds a threshold.
Buoyancy-driven flow between two rooms coupled by two openings at different levels
Authors: THOMAS L. P. , MARINO B. M. , TOVAR R. , LINDEN P. F.
Published: December 2007

The stack-driven flow between two interconnected rooms produced by a single heat source is studied. In particular, the features of the transient flow for different positions and areas of two openings in the shared vertical wall are analysed. An analytical model provides the time evolution of the stratified flows in rooms of any size. The concept of an equivalent layer representing a non-uniform density profile, which is useful in other contexts, is included in the theoretical approach and provides physical insight and aids the mathematical solution of the problem. New salt-bath experiments are performed to simulate the thermal forcing between the rooms, to validate the model and to analyse the mixing generated and the effects of a source of volume in the configuration studied.
Influence of wing kinematics on aerodynamic performance in hovering insect flight
Authors: BOS FRANK M. , LENTINK D. , VAN OUDHEUSDEN B. W. , BIJL H.
Published: December 2007

The influence of different wing kinematic models on the aerodynamic performance of a hovering insect is investigated by means of two-dimensional time-dependent Navier–Stokes simulations. For this, simplified models are compared with averaged representations of the hovering fruit fly wing kinematics. With increasing complexity, a harmonic model, a Robofly model and two more-realistic fruit fly models are considered, all dynamically scaled atRe= 110. To facilitate the comparison, the parameters of the models were selected such that their mean quasi-steady lift coefficients were matched. Details of the vortex dynamics, as well as the resulting lift and drag forces, were studied.

The simulation results reveal that the fruit fly wing kinematics result in forces that differ significantly from those resulting from the simplified wing kinematic models. In addition, light is shed on the effect of different characteristic features of the insect wing motion. The angle of attack variation used by fruit flies increases aerodynamic performance, whereas the deviation is probably used for levelling the forces over the cycle.
The alpha-effect in rotating convection: size matters
Authors: HUGHES DAVID W. , CATTANEO FAUSTO
Published: December 2007

The results of numerical simulations of convection in a rotating layer are used to compute the α-effect of mean-field electrodynamics. The computations are carried out for different system sizes. It is found that the outcomes can depend critically on the system size, and that physically meaningful results can only be obtained if the system size is large compared with the typical eddy size.
In vitro inhibition of soredial growth in the epiphytic lichen Physcia tenella (Ascomycetes: Lecanorales) by a variety of bark phenols
Authors: KOOPMANN Ricarda , STEVENS Henning , FRANZEN-REUTER Isabelle , FRAHM Jan-Peter , GROTE Manfred
Published: December 2007

The in-vitro growth rate of soredia from the epiphytic lichen species Physcia tenella was tested at different concentrations of phenols added in an in vitro experiment designed to evaluate the allelopathic effects of bark derived substances in stem flow. The conditions used were designed to resemble those found on bark of Populus×canadensis, as this tree species has been widely used for lichen mapping studies in Germany. Bark phenolic glycosides, flavonoids and tannins undergo hydrolytic decomposition in stem flow, resulting in a variety of monomeric phenolic acids, aldehydes and alcohols. Eleven phenolic substances of different biosynthetic origin in the concentration range between 10−6 M and 10−3 M in the culture medium were tested. IC50 values were calculated for each substance. Inhibition was highest for catechol, substituted phenolic glycosides, benzoic and ellagic acids, moderate for flavonoids, gallic acid, salicylic alcohol, salicylic aldehyde and low for salicylic acid. The tests show that bark phenols in natural concentrations inhibit soredial growth of the test species Physcia tenella and therefore have an influence on the growth of lichens on trees.
Seasonal variations of Fo, Fm, and Fv/Fm in an epiphytic population of the lichen Punctelia subrudecta (Nyl.) Krog
Authors: BARUFFO Laurence , TRETIACH Mauro
Published: December 2007

Chlorophyll a fluorescence was measured every three months from December 2003 to December 2004 in ten, randomly selected thalli of the epiphytic lichen Punctelia subrudecta (Nyl.) Krog occurring in a deciduous, thermophilous downy oak wood in southern Tuscany (central Italy). In situ measurements were carried out with a photosynthesis yield analyser Mini-PAM (Walz, Effeltrich, Germany) on the same measuring points of 30-minute dark-adapted, fully hydrated thalli. The results show a remarkable seasonal change in Fo, Fm, and Fv/Fm, probably caused by a long-term physiological-structural adaptation of the photobiont to the gradual modification of the climatic conditions of each measurement period and the light regime of the understorey. However, P. subrudecta is also sensitive to rapid changes in microclimatic conditions as the PSII functionality is affected by the light regime of the days preceding the field measurements. Some critical observations on the statistical analysis of chlorophyll a fluorescence parameters are also made.
The lichen genus Ramalina on the Galapagos
Authors: APTROOT A. , BUNGARTZ F.
Published: December 2007

Ramalina species are among the most abundant lichens on the Galapagos Isles. A total of fifteen species have been distinguished, four of which are described as new here: Ramalina darwiniana, R. fragilis, R. furcellangulida and R. polyforma. These new species are considered to be endemic to the Galapagos whereas previous reports refer to relatively common, more widely distributed species. Several other species are reported here for the first time from the Galapagos.
Two new lichenicolous fungi: an Opegrapha and a Plectocarpon species (Ascomycota: Roccellaceae) from Chile
Authors: ETAYO J.
Published: December 2007

Opegrapha invadens Etayo on Pannaria farinosa and Plectocarpon usneaustralis Etayo on corticolous Usnea sp. are described as new from southern Chile.
A new species of Loxospora (lichenized Ascomycota: Sarrameanaceae) from Australia
Authors: LUMBSCH H. Thorsten , ARCHER Alan W. , ELIX John A.
Published: December 2007

Loxospora lecanoriformis Lumbsch, A. W. Archer & Elix is described from deeply shaded trunks of Doryphora sassafras Endl. in temperate rainforest in north-eastern New South Wales. This species is characterized by large, lecanorine apothecia, mostly unbranched paraphyses, non-amyloid asci and large, thin-walled, simple, ellipsoid ascospores. Molecular data has established that this taxon is related to Loxospora ochrophaea (Tuck.) R. C. Harris.
X-ray solution scattering (SAXS) combined with crystallography and computation: defining accurate macromolecular structures, conformations and assemblies in solution
Authors: Putnam Christopher D. , Hammel Michal , Hura Greg L. , Tainer John A.
Published: December 2007

Crystallography supplies unparalleled detail on structural information critical for mechanistic analyses; however, it is restricted to describing low energy conformations of macromolecules within crystal lattices. Small angle X-ray scattering (SAXS) offers complementary information about macromolecular folding, unfolding, aggregation, extended conformations, flexibly linked domains, shape, conformation, and assembly state in solution, albeit at the lower resolution range of about 50 Å to 10 Å resolution, but without the size limitations inherent in NMR and electron microscopy studies. Together these techniques can allow multi-scale modeling to create complete and accurate images of macromolecules for modeling allosteric mechanisms, supramolecular complexes, and dynamic molecular machines acting in diverse processes ranging from eukaryotic DNA replication, recombination and repair to microbial membrane secretion and assembly systems. This review addresses both theoretical and practical concepts, concerns and considerations for using these techniques in conjunction with computational methods to productively combine solution scattering data with high-resolution structures. Detailed aspects of SAXS experimental results are considered with a focus on data interpretation tools suitable to model protein and nucleic acid macromolecular structures, including membrane protein, RNA, DNA, and protein–nucleic acid complexes. The methods discussed provide the basis to examine molecular interactions in solution and to study macromolecular flexibility and conformational changes that have become increasingly relevant for accurate understanding, simulation, and prediction of mechanisms in structural cell biology and nanotechnology.
Singularity-free trajectory planning of platform-type parallel manipulators for minimum actuating effort and reactions
Authors: Chen Chun-Ta , Chi Hua-Wei
Published: December 2007

Due to the existence of singular configurations within the workspace for a platform- type parallel manipulator (PPM), the actuating force demands increase drastically as the PPM approaches or crosses singular points. Therefore, in this report, a numerical technique is presented to plan a singularity-free trajectory of the PPM for minimum actuating effort and reactions. By using the parametric trajectory representation, the singularity-free trajectory planning problem can be cast to the determination of undetermined control points, after which a particle swarm optimization algorithm is employed to find the optimal control points. This algorithm ensures that the obtained trajectories can avoid singular points within the workspace and that the PPM has the minimum actuating effort and reactions. Simulations and discussions are presented to demonstrate the effectiveness of the algorithm.
Executive functioning in preschool children born very preterm: Relationship with early white matter pathology
Authors: EDGIN JAMIE O. , INDER TERRIE E. , ANDERSON PETER J. , HOOD KELLY M. , CLARK CARON A.C. , WOODWARD LIANNE J.
Published: December 2007

Despite evidence for executive dysfunction in school-aged preterm children, less is known about the early development of these difficulties or their underlying neuropathology. This study used prospective longitudinal data from a regional cohort of 88 very preterm and 98 full-term comparison children to examine the executive functioning (EF) of preschool children born very preterm. The relationship between the severity of neonatal cerebral white matter (WM) abnormalities on magnetic resonance imaging (MRI) at term equivalent and children's EF at ages two and four years (corrected age) was examined. At age four, very preterm children with WM abnormalities performed less well than full-term children on the Detour Reaching Box, a measure of behavioral inhibition and cognitive flexibility, even after controlling for child IQ, SES, and medical background. Examination of patterns of EF performance between the ages of 2 and 4 years showed that the performance of all groups improved with age. However, very preterm children with mild and moderate-severe WM abnormalities were characterized by higher rates of consistent performance impairments. These findings support the presence of early and persistent executive difficulties in preschool children born very preterm, and highlight the importance of white matter pathology in the development of executive impairments. (JINS, 2008,14, 90–101.)
Depressive rumination reduces specificity of autobiographical memory recall in acquired brain injury
Authors: BESSELL A.L. , WATKINS E.R. , WILLIAMS W.H.
Published: December 2007

Individuals with acquired brain injuries (ABI) often experience depression following injury, with estimated rates between 20 and 40% within the first year and up to 50% thereafter (Fleminger et al., 2003). Previous studies with non–brain-injured individuals have identified that rumination is prevalent in both the development and maintenance of depression. The study aimed to explore how depressive rumination may contribute to overgeneral memory recall in ABI patients, by assessing the effects of manipulating ruminative self-focus on autobiographical memory performance across levels of brain injury. Fifty-eight ABI individuals with mild (28) to moderate/severe (30) cognitive impairments were assessed on measures of mood, rumination and autobiographical memory. They were then randomly assigned into matched groups for an intervention (a distraction) or a rumination task. Following intervention, they were re-assessed for autobiographical recall and rumination. Findings indicate that ruminative self-focus reduced specificity of autobiographical memory in individuals with ABI, suggesting that depressive rumination plays a role in the reduced access to autobiographical memories. Higher baseline levels of depression and rumination were also associated with less specificity in recall. These findings indicate the value of identifying and treating depression among this population. (JINS, 2008,14, 63–70.)
Inconsistency of performance on neglect subtype tests following acute right hemisphere stroke
Authors: HAMILTON R.H. , COSLETT H.B. , BUXBAUM L.J. , WHYTE J. , FERRARO M.K.
Published: December 2007

Hemispatial neglect has been conceptualized as having dissociable and potentially clinically relevant subtypes. However, the question of whether patient performance on neglect subtype measures is consistent over time remains largely unanswered. We examined changes in performance over time on measures of motor, perceptual, and personal neglect in 21 patients with neglect from acute right hemisphere stroke. Patients were assessed on three occasions, separated by at least one week, using a lateralized target test, lateralized response test, and modified fluff test. Across three testing timepoints, 18 (85.7%) patients changed subtype performance patterns at least once. In 13 (61.9%) of these patients, inconsistency between timepoints was not adequately accounted for by recovery. On initial testing, seven, patients (33.3%) demonstrated more than one neglect subtype symptom; by the third testing timepoint none of the patients demonstrated multiple symptoms. In the setting of acute stroke, performance on three measures of neglect symptoms is inconsistent across time. However, the distribution of neglect subtype symptoms appears to become more discrete over time. These findings complicate our understanding of the pathophysiology and potential prognostic value of neglect subtypes, and suggest that treatment decisions based on subtype performance assessed at a single timepoint, may be of limited utility. (JINS, 2008,14, 23–32.)
Verbal (animal) fluency scores in age/grade appropriate minority children from low socioeconomic backgrounds
Authors: PRIGATANO GEORGE P. , GRAY JENNIFER A. , LOMAY VICKY T.
Published: December 2007

Two hundred-thirteen children in grades 1 through 8 were asked to rapidly generate as many names of animals as they could in 60 seconds. These children were age appropriate for their grade level in school, did not receive any form of special education services, and as a group showed (estimated) average intellectual ability. They were primarily from minority (particularly Hispanic) backgrounds and came from families with low socioeconomic status. Normative data are presented. Hierarchical multiple regression analysis revealed that the age range/grade level score accounted for 21.5% of the variability in fluency scores and the Vocabulary level of the child accounted for an additional 5.7%. Level of performance on this animal fluency task was not lower than what has been reported in primarily white children from middle socioeconomic backgrounds. (JINS, 2008, 14, 143–147.)
Intact emotion facilitation for nonsocial stimuli in autism: Is amygdala impairment in autism specific for social information?
Authors: SOUTH MIKLE , OZONOFF SALLY , SUCHY YANA , KESNER RAYMOND P. , McMAHON WILLIAM M. , LAINHART JANET E.
Published: December 2007

Atypical amygdala development may play a key role in the emergence of social disability and other symptoms of autism (Baron-Cohen et al., 2000; Schultz, 2005). The mechanisms by which this may occur have received little attention, however, and most support from behavioral and imaging studies has been concerned with socially relevant stimuli such as faces. Given the complexity of amygdala function and its known role in many other emotional tasks, we examined whether individuals with autism would demonstrate impaired performance on several tasks that have been shown to require activation of the amygdala but that do not have any explicit social meaning. Relative to a typical comparison group matched for age and IQ, our sample of 37 adolescents and adults with autism (mean age = 19.7 years) demonstrated equivalent facilitation for perception and learning of emotionally relevant stimuli. On each of four tasks, there were significant main effects of emotion condition on performance for both groups. Future research regarding atypical amygdala function and emotion processing in autism should consider whether the response to nonsocial emotion factors (including negative valence or high arousal) may be intact, despite difficulties in responding to socially relevant stimuli. (JINS, 2008,14, 42–54.)
A comparison of letter and digit processing in letter-by-letter reading
Authors: INGLES JANET L. , ESKES GAIL A.
Published: December 2007

The extent to which letter-by-letter reading results from a specific orthographic deficit, as compared with a nonspecific disturbance in basic visuoperceptual mechanisms, is unclear. The current study directly compared processing of letters and digits in a letter-by-letter reader, G.M., using a rapid serial visual presentation (RSVP) task and a speeded matching task. Comparisons were made to a group of six brain-damaged individuals without reading deficits. In the RSVP task, G.M. had increased difficulty reporting the target identities when they were letters, as compared with digits. Although this general pattern was also evident in the control group, the magnitude of the letter–digit accuracy difference was greater in G.M. Similarly, in the matching task, G.M. was slower to match letters than digits, relative to the control group, although his response times to both item types were increased. These data suggest that letter-by-letter reading, at least in this case, results from a visuoperceptual encoding deficit that particularly affects letters, but also extends to processing of digits to a lesser extent. Results are consistent with the notion that a left occipitotemporal area is specialized for letter processing with greater bilaterality in the visual processing of digits. (JINS, 2008,14, 164–173.)
Long-term compensatory treatment of organizational deficits in a patient with bilateral frontal lobe damage
Authors: FISH JESSICA , MANLY TOM , WILSON BARBARA A.
Published: December 2007

Evans et al. (1998) described compensatory strategy use in R.P., a patient with executive dysfunction following bilateral frontal lobe damage who had difficulty acting upon her intentions. A pager was used to remind R.P. of regularly scheduled activities, along with a checklist that aimed to moderate a perseverative routine. Although successful, 10 years after the original intervention, the strategies were no longer used, and considerable everyday problems were evident. In the current study, we conducted a follow-up assessment to examine potential reasons for this deterioration. No change in neuropsychological functioning was evident. Whereas the previous study introduced the two strategies together, and examined effects upon separate goals, in the current study we reintroduced the two strategies separately, and examined effects on three common goals. In addition to prompting specific activities, we aimed to support completion of more general goals (those that could be enacted within a wider window of time). The paging intervention had a dramatic effect on all three measured behaviors, at a much more consistent level than the checklist. We suggest that, in addition to direct reminders, the pager can cue a process of goal monitoring that bridges the gap between intention and action. (JINS, 2008,14, 154–163.)
Vertical scanning biases and their possible influence on reading direction: Celtic wisdom or folly?
Authors: AMENGUAL ALEJANDRA M. , DRAGO VALERIA , FOSTER PAUL S. , LEIGUARDA RAMON C. , HEILMAN KENNETH M.
Published: December 2007

The reason people read from top to bottom is unknown, but could be related to brain-mediated directional biases or environmental factors. To learn if there is a brain-mediated directional bias responsible for top–down reading direction, we evaluated the directional scanning in the vertical dimension by using directional letter and face cancellation tasks. Twenty participants were instructed to cancel either target letters or faces using either an up–down or down–up direction, with the stimuli located in left, right, and center hemispace. The results indicated significant differences in completion time between the search direction (up vs. down) and spatial position for the letter cancellation task, with a faster completion time for the bottom–up scan in right space and top–down in left space. Because the left hemisphere primarily attends to contralateral right hemispace our results suggest that, when attending to letter stimuli, the left hemisphere is biased to scan in a proximal to distal (upward) direction. Although the reasons why this is reversed in left hemispace and why we did not see directional biases in the face condition remains unclear, these results do suggest that the direction in which we learn to read is inconsistent with the brain's intrinsic directional bias. (JINS, 2008, 14, 102–109.)
Differences in executive functioning in children with heavy prenatal alcohol exposure or attention-deficit/hyperactivity disorder
Authors: VAURIO LINNEA , RILEY EDWARD P. , MATTSON SARAH N.
Published: December 2007

Children with either fetal alcohol spectrum disorder (FASD) or attention-deficit/hyperactivity disorder (ADHD) display deficits in attention and executive function (EF) and differential diagnosis of these two clinical groups may be difficult, especially when information about prenatal alcohol exposure is unavailable. The current study compared EF performance of three groups: children with heavy prenatal alcohol exposure (ALC); nonexposed children with attention-deficit/hyperactivity disorder (ADHD); and typically developing controls (CON). Both clinical groups met diagnostic criteria for ADHD. The EF tasks used were the Wisconsin Card Sorting Test (WCST), the Controlled Oral Word Association Test (COWAT), and the Trail Making Test (TMT). Results indicated different patterns of deficit; both clinical groups displayed deficits on the WCST and a relative weakness on letterversuscategory fluency. Only the ALC group displayed overall deficits on letter fluency and a relative weakness on TMT-BversusTMT-A. In addition, WCST performance was significantly lower than expected based on IQ in the ADHD group and significantly higher than expected in the ALC group. These results, which indicate that, although EF deficits occurred in both clinical groups, the degree and pattern of deficit differed between the ALC and ADHD groups, may improve differential diagnosis. (JINS, 2008,14, 119–129.)
Neuropsychological strategies for detecting early dementia
Authors: GROBER ELLEN , HALL CHARLES , MCGINN MARYANNE , NICHOLLS TONI , STANFORD STEPHANIE , EHRLICH AMY , JACOBS LAURIE G. , KENNEDY GARY , SANDERS AMY , LIPTON RICHARD B.
Published: December 2007

As new and more effective treatments for Alzheimer's disease (AD) emerge, the development of efficient screening strategies in educationally and racially diverse primary care settings has increased in importance. A set of candidate screening tests and an independent diagnostic assessment were administered to a sample of 318 patients treated at a geriatric primary care center. Fifty-six subjects met criteria for dementia. Exploratory analysis led to the development of three two-stage screening strategies that differed in the composition of the first stage or Rapid Dementia Screen, which is applied to all patients over the age of 65. The second stage, applied to those patients who screen positively for dementia, is accomplished with the Free and Cued Selective Reminding Test to detect memory impairment. Using clinical diagnosis as a gold standard, the strategies had high sensitivity and specificity for identifying dementia and performed better for identifying AD than non-AD dementias. Sensitivity and specificity did not differ by race or education. The strategies provide an efficient approach to screening for early dementia. (JINS, 2008,14, 130–142.)
Semantic memory as assessed by the Pyramids and Palm Trees Test: The impact of sociodemographic factors in a Spanish-speaking population
Authors: GUDAYOL-FERRÉ ESTEVE , LARA JOSÉ PABLO , HERRERA-GUZMAN IXCHEL , BÖHM PETER , RODÉS ELISENDA , ANSALDO ANA INÉS , PEÑA-CASANOVA JORDI
Published: December 2007

The objective of this study is to obtain preliminary normative data on the performance the Pyramids and Palm Trees Test (PPT) for a Spanish-speaking population. The effects of age, gender, and educational level on the PPT test were also analyzed. A total of 234 healthy participants, with a broad range of age (18–80 years) and education (1–20 years) performed the three-picture version of the PPT. The mean performance was 51.1 out of 52 possible points (SD= 1.3). PPT performance did not vary with age or gender. However, subjects with less than 6 years of formal education scored significantly lower than those with more than 6 years of education though this effect was confounded with age because the group with lower education was also older. Given the ceiling effects of the PPT, further investigation is needed to determine if the visual PPT is sensitive to mild semantic memory impairment. (JINS, 2008,14, 148–151.)
Neuropsychology and clinical neuroscience of persistent post-concussive syndrome
Authors: BIGLER ERIN D.
Published: December 2007

On the mild end of the acquired brain injury spectrum, the terms concussion and mild traumatic brain injury (mTBI) have been used interchangeably, where persistent post-concussive syndrome (PPCS) has been a label given when symptoms persist for more than three months post-concussion. Whereas a brief history of concussion research is overviewed, the focus of this review is on the current status of PPCS as a clinical entity from the perspective of recent advances in the biomechanical modeling of concussion in human and animal studies, particularly directed at a better understanding of the neuropathology associated with concussion. These studies implicate common regions of injury, including the upper brainstem, base of the frontal lobe, hypothalamic-pituitary axis, medial temporal lobe, fornix, and corpus callosum. Limitations of current neuropsychological techniques for the clinical assessment of memory and executive function are explored and recommendations for improved research designs offered, that may enhance the study of long-term neuropsychological sequelae of concussion. (JINS, 2008,14, 1–22.)
Our Brain as Stone Age Computer
Authors: Greiffenstein Manfred F.
Published: December 2007

Evolutionary Cognitive Neuroscience. 2007. Steven M. Platek, Julian P. Keenan, & Todd K. Shackelford (Eds.). Cambridge, MA: MIT Press, 616 pp., $65.00 (HB)

Clinical neuropsychologists are most interested in the ‘what’ of brain function. Neuropsychological assessment requires only a working knowledge of functional localization and the tests best suited to capture that specialization. The ‘why’ of cortical specialization is not necessary for good clinical work. The edited volume Evolutionary Cognitive Neuroscience is entirely devoted to the ‘how’ and ‘why’ of brain specialization based on the fact (not ‘theory’) of natural selection. Editors Steven Platek, Julian Keenan, and Todd Shackelford are well qualified to organize and write this book; they devoted their careers to understanding neuropsychological functions as evolved mechanisms designed to solve recurrent survival and reproduction problems of our evolutionary past. In this view, our brains are Stone Age computers.
Diversity of cutaneous bacteria with antifungal activity isolated from female four-toed salamanders
Authors: Lauer Antje , Simon Mary Alice , Banning Jenifer L , Lam Brianna A , Harris Reid N
Published: December 2007

Among the microbiota of amphibian skin are bacteria that produce antifungal compounds. We isolated cutaneous bacteria from the skins of three populations of the nest-attending plethodontid salamander Hemidactylium scutatum and subsequently tested the bacterial isolates against two different fungi (related to Mariannaea elegans and Rhizomucor variabilis) that were obtained from dead salamander eggs. The culturable antifungal bacteria were phylogenetically characterized based on 16S rRNA phylogeny, and belonged to four phyla, comprising 14 bacterial families, 16 genera and 48 species. We found that about half of the antifungal bacterial genera and families were shared with a related salamander species, but there was virtually no overlap at the species level. The proportion of culturable antifungal bacterial taxa shared between two large populations of H. scutatum was the same as the proportion of taxa shared between H. scutatum and Plethodon cinereus, suggesting that populations within a species have unique antifungal bacterial species. Approximately 30% of individuals from both salamander species carried anti-M. elegans cutaneous bacteria and almost 90% of P. cinereus and 100% of H. scutatum salamanders carried anti-R. variabilis cutaneous bacteria. A culture independent method (PCR/DGGE) revealed a shared resident bacterial community of about 25% of the entire resident bacterial community within and among populations of H. scutatum. Thus, the culturable antifungal microbiota was far more variable on salamander skins than was the bacterial microbiota detected by PCR/DGGE. The resident cutaneous antifungal bacteria may play an important role in amphibians' innate defense against pathogens, including the lethal chytrid fungus Batrachochytrium dendrobatidis.
Thermodynamic constraints on methanogenic crude oil biodegradation
Authors: Dolfing Jan , Larter Stephen R , Head Ian M
Published: December 2007

Methanogenic degradation of crude oil hydrocarbons is an important process in subsurface petroleum reservoirs and anoxic environments contaminated with petroleum. There are several possible routes whereby hydrocarbons may be converted to methane: (i) complete oxidation of alkanes to H2 and CO2, linked to methanogenesis from CO2 reduction; (ii) oxidation of alkanes to acetate and H2, linked to acetoclastic methanogenesis and CO2 reduction; (iii) oxidation of alkanes to acetate and H2, linked to syntrophic acetate oxidation and methanogenesis from CO2 reduction; (iv) oxidation of alkanes to acetate alone, linked to acetoclastic methanogenesis and (v) oxidation of alkanes to acetate alone, linked to syntrophic acetate oxidation and methanogenesis from CO2 reduction. We have developed the concept of a ‘window of opportunity’ to evaluate the range of conditions under which each route is thermodynamically feasible. On this basis the largest window of opportunity is presented by the oxidation of alkanes to acetate alone, linked to acetoclastic methanogenesis. This contradicts field-based evidence that indicates that in petroleum rich environments acetoclastic methanogenesis is inhibited and that methanogenic CO2 reduction is the predominant methanogenic process. Our analysis demonstrates that under those biological constraints oxidation of alkanes to acetate and H2, linked to syntrophic acetate oxidation and methanogenesis from CO2 reduction offers a greater window of opportunity than complete oxidation of alkanes to H2 and CO2 linked to methanogenic CO2 reduction, and hence is the process most likely to occur.
The Drosophila NURF remodelling and the ATAC histone acetylase complexes functionally interact and are required for global chromosome organization
Authors: Carré Clément , Ciurciu Anita , Komonyi Orbán , Jacquier Caroline , Fagegaltier Delphine , Pidoux Josette , Tricoire Hervé , Tora Laszlo , Boros Imre M , Antoniewski Christophe
Published: December 2007

Drosophila Gcn5 is the catalytic subunit of the SAGA and ATAC histone acetylase complexes. Here, we show that mutations in Gcn5 and the ATAC component Ada2a induce a decondensation of the male X chromosome, similar to that induced by mutations in the Iswi and Nurf301 subunits of the NURF nucleosome remodelling complex. Genetic studies as well as transcript profiling analysis indicate that ATAC and NURF regulate overlapping sets of target genes during development. In addition, we find that Ada2a chromosome binding and histone H4‐Lys12 acetylation are compromised in Iswi and Nurf301 mutants. Our results strongly suggest that NURF is required for ATAC to access the chromatin and to regulate global chromosome organization.
Temperature, pressure, and isotope effects on the structure and properties of liquid water: A lattice approach
Authors: Hakem Ilhem F. , Boussaid Abdelhak , Benchouk-Taleb Hafida , Bockstaller Michael R.
Published: December 2007

We present a lattice model to describe the effect of isotopic replacement, temperature, and pressure changes on the formation of hydrogen bonds in liquid water. The approach builds upon a previously established generalized lattice theory for hydrogen bonded liquids [B. A. Veytsman, J. Phys. Chem. 94, 8499 (1990)], accounts for the binding order of 1∕2 in water-water association complexes, and introduces the pressure dependence of the degree of hydrogen bonding (that arises due to differences between the molar volumes of bonded and free water) by considering the number of effective binding sites to be a function of pressure. The predictions are validated using experimental data on the temperature and pressure dependence of the static dielectric constant of liquid water. The model is found to correctly reproduce the experimentally observed decrease of the dielectric constant with increasing temperature without any adjustable parameters and by assuming values for the enthalpy and entropy of hydrogen bond formation as they are determined from the respective experiments. The pressure dependence of the dielectric constant of water is quantitatively predicted up to pressures of 2kbars and exhibits qualitative agreement at higher pressures. Furthermore, the model suggests a—temperature dependent—decrease of hydrogen bond formation at high pressures. The sensitive dependence of the structure of water on temperature and pressure that is described by the model rationalizes the different solubilization characteristics that have been observed in aqueous systems upon change of temperature and pressure conditions. The simplicity of the presented lattice model might render the approach attractive for designing optimized processing conditions in water-based solutions or the simulation of more complex multicomponent systems.
Transient diffusion in a tube with dead ends
Authors: Dagdug Leonardo , Berezhkovskii Alexander M. , Makhnovskii Yurii A. , Zitserman Vladimir Yu.
Published: December 2007

A particle diffusing in a tube with dead ends, from time to time enters a dead end, spends some time in the dead end, and then comes back to the tube. As a result, the particle spends in the tube only a part of the entire observation time that leads to slowdown of its diffusion along the tube. We study the transient diffusion in a tube with periodic identical dead ends formed by cavities of volume Vcav connected to the tube by cylindrical channels of length L and radius a, which is assumed to be much smaller than the tube radius R and the distance l between neighboring dead ends. Assuming that the particle initial position is uniformly distributed over the tube, we analyze the monotonic decrease of the particle diffusion coefficient D(t) from its initial value D(0)=D, which characterizes diffusion in the tube without dead ends, to its asymptotic long-time value D(∞)=Deff<D. We derive an expression for the Laplace transform of D(t), denoted by D̂(s), where s is the Laplace parameter. Although the expression is too complicated to be inverted analytically, we use it to find the relaxation time of the process as a function of the geometric parameters of the system mentioned above. To check the accuracy of our results, we ran Brownian dynamics simulations and found the mean squared displacement of the particle as a function of time by averaging over 5×104 realizations of the particle trajectory. The time-dependent mean squared displacement found in simulations is compared with that obtained by numerically inverting the Laplace transform of the mean squared displacement predicted by the theory, which is given by 2D̂(s)∕s. Comparison shows excellent agreement between the two time dependences that support the approximations used when developing the theory.
High-resolution slice imaging of quantum state-to-state photodissociation of methyl bromide
Authors: Lipciuc M. Laura , Janssen Maurice H. M.
Published: December 2007

The photodissociation of rotationally state-selected methyl bromide is studied in the wavelength region between 213 and 235nm using slice imaging. A hexapole state selector is used to focus a single (JK=11) rotational quantum state of the parent molecule, and a high speed slice imaging detector measures directly the three-dimensional recoil distribution of the methyl fragment. Experiments were performed on both normal (CH3Br) and deuterated (CD3Br) parent molecules. The velocity distribution of the methyl fragment shows a rich structure, especially for the CD3 photofragment, assigned to the formation of vibrationally excited methyl fragments in the ν1 and ν4 vibrational modes. The CH3 fragment formed with ground state Br(P3∕22) is observed to be rotationally more excited, by some 230–340cm−1, compared to the methyl fragment formed with spin-orbit excited Br(P1∕22). Branching ratios and angular distributions are obtained for various methyl product states and they are observed to vary with photodissociation energy. The nonadiabatic transition probability for the Q0+3→Q11 transition is calculated from the images and differences between the isotopes are observed. Comparison with previous non-state-selected experiments indicates an enhanced nonadiabatic transition probability for state-selected K=1 methyl bromide parent molecules. From the state-to-state photodissociation experiments the dissociationenergy for both isotopes was determined, D0(CH3Br)=23400±133cm−1 and D0(CD3Br)=23827±94cm−1.
Improved device performance of InAs∕GaAs quantum dot solar cells with GaP strain compensation layers
Authors: Laghumavarapu R. B. , El-Emawy M. , Nuntawong N. , Moscho A. , Lester L. F. , Huffaker D. L.
Published: December 2007

We report optical, electrical, and spectral response characteristics of three-stack InAs∕GaAs quantum dot solar cells with and without GaP strain compensation (SC) layers. The short circuit current density, open circuit voltage, and external quantum efficiency of these cells under air mass 1.5G at 290mW∕cm2 illumination are presented and compared with a GaAs control cell. The cells with SC layers show superior device quality, confirmed by I-V and spectral response measurements. The quantum dot solar cells show an extended photoresponse compared to the GaAs control cell. The effect of the SC layer thickness on device performance is also presented.
Ultralow noise midwave infrared InAs–GaSb strain layer superlattice avalanche photodiode
Authors: Mallick Shubhrangshu , Banerjee Koushik , Ghosh Siddhartha , Plis Elena , Rodriguez Jean Baptiste , Krishna Sanjay , Grein Christoph
Published: December 2007

Eye-safe midwavelength infrared InAs–GaSb strain layer superlattice p+-n−-n homojunction avalanche photodiodes (APDs) grown by solid source molecular beam epitaxy were fabricated and characterized. Maximum multiplication gain of 1800 was measured at −20V at 77K. Excess noise factors between 0.8 and 1.2 were measured up to gain of 300. Gain of 200 was measured at 120K. Exponential nature of the gain as a function of reverse bias along with low excess noise factor at higher gain confirms single carrier electron-only impact ionization in the avalanche regime. Decrease in the multiplication gain at higher temperatures correlates with standard APD characteristics.
Schottky barrier height tuning of silicide on Si1−xCx
Authors: Sinha Mantavya , Chor Eng Fong , Tan Chung Foong
Published: December 2007

We have demonstrated the tuning of Schottky barrier height (SBH) of nickel silicide on silicon-carbon (Si1−xCx) by varying the carbon mole fraction, x. The SBH (for electron conduction) has been found to decrease with carbon concentration at a rate of ∼6.6meV/ (0.1% carbon). We have achieved ∼27meV drop in SBH with 0.4% carbon incorporation in Si1−xCx and shown that 1.3% carbon could lead to more than 85meV improvement. Furthermore, our results show an avenue to reduce the SBH of rare earth silicide contacts in n-channel Schottky transistors by fabricating them on Si1−xCx.