A global cloud map of the nearest known brown dwarf.

Brown dwarfs--substellar bodies more massive than planets but not massive enough to initiate the sustained hydrogen fusion that powers self-luminous stars--are born hot and slowly cool as they age. As they cool below about 2,300 kelvin, liquid or crystalline particles composed of calcium aluminates, silicates and iron condense into atmospheric 'dust', which disappears at still cooler temperatures (around 1,300 kelvin). Models to explain this dust dispersal include both an abrupt sinking of the entire cloud deck into the deep, unobservable atmosphere and breakup of the cloud into scattered patches (as seen on Jupiter and Saturn). However, hitherto observations of brown dwarfs have been limited to globally integrated measurements, which can reveal surface inhomogeneities but cannot unambiguously resolve surface features. Here we report a two-dimensional map of a brown dwarf's surface that allows identification of large-scale bright and dark features, indicative of patchy clouds. Monitoring suggests that the characteristic timescale for the evolution of global weather patterns is approximately one day.

Models of very-low-mass stars, brown dwarfs and exoplanets.

Within the next few years, GAIA and several instruments aiming to image extrasolar planets will be ready. In parallel, low-mass planets are being sought around red dwarfs, which offer more favourable conditions, for both radial velocity detection and transit studies, than solar-type stars. In this paper, the authors of a model atmosphere code that has allowed the detection of water vapour in the atmosphere of hot Jupiters review recent advances in modelling the stellar to substellar transition. The revised solar oxygen abundances and cloud model allow the photometric and spectroscopic properties of this transition to be reproduced for the first time. Also presented are highlight results of a model atmosphere grid for stars, brown dwarfs and extrasolar planets.

Compensatory postural adaptations during continuous, variable amplitude perturbations reveal generalized rather than sequence-specific learning.

We examined changes in the motor organization of postural control in response to continuous, variable amplitude oscillations evoked by a translating platform and explored whether these changes reflected implicit sequence learning. The platform underwent random amplitude (maximum +/- 15 cm) and constant frequency (0.5 Hz) oscillations. Each trial was composed of three 15-s segments containing seemingly random oscillations. Unbeknownst to participants, the middle segment was repeated in each of 42 trials on the first day of testing and in an additional seven trials completed approximately 24 h later. Kinematic data were used to determine spatial and temporal components of total body centre of mass (COM) and joint segment coordination. Results showed that with repeated trials, participants reduced their magnitude of COM displacement, shifted from a COM phase lag to a phase lead relative to platform motion and increased correlations between ankle/platform motion and hip/platform motion as they shifted from an ankle strategy to a multi-segment control strategy involving the ankle and hip. Maintenance of these changes across days provided evidence for learning. Similar improvements for the random and repeated segments, indicated that participants did not exploit the sequence of perturbations to improve balance control. Rather, the central nervous system may have been tuning into more general features of platform motion. These findings provide important insight into the generalizabilty of improved compensatory balance control with training.

Relationship between outdoor and indoor air quality in eight French schools.

UNLABELLED: In the frame of the French national research program PRIMEQUAL (inter-ministry program for better air quality in urban environments), measurements of outdoor and indoor pollution have been carried out in eight schools in La Rochelle (France) and its suburbs. The buildings were naturally ventilated by opening the windows, or mechanically ventilated, and showed various air permeabilities. Ozone, nitrogen oxides (NO and NO(2)), and airborne particle (particle counts within 15 size intervals ranging from 0.3 to 15 mum) concentrations were continuously monitored indoors and outdoors for two 2-week periods. The indoor humidity, temperature, CO(2) concentration (an indicator of occupancy), window openings and building permeability were also measured. The temporal profiles of indoor and outdoor concentrations show ozone and nitrogen oxides behave differently: NO and NO(2) indoor/outdoor concentration ratios (I/O) were found to vary in a range from 0.5 to 1, and from 0.88 to 1, respectively, but no correlation with building permeability was observed. On the contrary, I/O ratios of ozone vary in a range from 0 to 0.45 and seem to be strongly influenced by the building air-tightness: the more airtight the building envelope, the lower the ratio. Occupancy, through re-suspension of previously deposited particles and possible particle generation, strongly influences the indoor concentration level of airborne particles. However, this influence decreases with particle size, reflecting the way deposition velocities vary as a function of size. The influence of particle size on deposition and penetration across the building envelope is also discussed by analyzing the I/O ratios measured when the buildings were unoccupied, by comparing the indoor concentrations measured when the buildings were occupied and when they were not (O/U ratios), and by referring to previously published studies focussing on this topic. Except one case, I/O were found to vary in the range from 0.03 to 1.79. All O/U are greater than one and increase up to 100 with particle size. PRACTICAL IMPLICATIONS: Assessing children's total exposure requires the knowledge of outdoor and indoor air contaminant concentrations. The study presented here provides data on compared outdoor and indoor concentration levels in school buildings, as well as information on the parameters influencing the relationship between outdoor and indoor air quality. It may be used as a basis for estimating indoor concentrations from outdoor concentrations data, or as a first step in designing buildings sheltering children against atmospheric pollution.

Influence of a visuo-spatial, verbal and central executive working memory task on postural control.

In this study, participants were required to perform different working memory (WM) tasks (a verbal task, a visuo-spatial task with two levels of difficulty and a central executive task) under different challenges to postural control (sitting, shoulder width stance and tandem stance). When a WM task was added, changes in postural sway were characterized by an increase in frequency and decrease in amplitude of sway indicating a tighter control. We found no changes in postural control between the different types of WM tasks, which might support a general capacity limitation hypothesis. However, no changes were found in performance of the WM when postural stance was modified and no changes were found in postural sway, when the difficulty level of the visuo-spatial task was modified. Consequently, the results seem to indicate that the addition of a WM task, regardless of task type or task difficulty, forces the central nervous system to choose a tighter control strategy.

Nasal immunization with subunit proteosome influenza vaccines induces serum HAI, mucosal IgA and protection against influenza challenge.

The immunogenicity of a mucosally delivered subunit influenza vaccine was assessed in mice. Split influenza virus vaccine (sFlu) was formulated with proteosomes (Pr-sFlu), administered intranasally, and the induced immunity was compared with the responses elicited by sFlu alone given either intramuscularly or intranasally. Intranasal (i.n.) immunization with Pr-sFlu induced specific serum IgG and hemagglutination inhibition (HAI) titers comparable to or better than those induced by intramuscular (i.m.) sFlu, and in contrast to sFlu alone, i.n. Pr-sFlu also induced high levels of influenza-specific IgA in lung and nasal washes. Mice receiving i.n. Pr-sFlu were completely protected against live virus challenge, as were mice immunized by injection with sFlu alone. The i.n. Pr-sFlu elicited cytokine responses polarized towards a type 1 phenotype whereas those elicited by sFlu alone were of a mixed type 1/type 2 phenotype. The data strongly suggest that i.n. proteosome-formulated influenza antigens are highly effective and are excellent candidates for a non-invasive human vaccine.

What guides the selection of alternate foot placement during locomotion in humans.

Our goal was to understand the bases for selection of alternate foot placement during locomotion when the normal landing area is undesirable. In this study, a light spot of different shapes and sizes simulated an undesirable landing area. Participants were required to avoid stepping on this spot under different time constraints. Alternate chosen foot placements were categorised into one of eight choices. Results showed that selection of alternate foot placement is systematic. There is a single dominant choice for each combination of light spot and normal landing spot. The dominant choice minimises the displacement of the foot from its normal landing spot (less than half a foot length). If several response choices satisfy this criterion, three selection strategies are used to guide foot placement: placing the foot in the plane of progression, choosing to take a longer step over a shorter step and selecting a medial rather than lateral foot placement. All these alternate foot-placement choices require minimal changes to the ongoing locomotor muscle activity, pose minimal threat to dynamic stability, allow for quick initiation of change in ongoing movement and ensure that the locomotor task runs without interruption. Thus, alternate foot-placement choices are dependent not only on visual input about the location, size and shape of the undesirable surface, but also on the relationship between the characteristics of the undesirable surface and the normal landing area.

The effect of nonregulatory stimuli on the triple jump approach run.

The purpose of this experiment was to examine the approach run of the triple jump. Specifically, we examined the effect of nonregulatory stimuli (Gentile, 1972) on two different ability levels in performing the triple jump approach run. These nonregulatory constraints (situational factors such as those seen in actual competition) were employed in three jumping conditions: Control (to obtain baseline performance measures), Distance (where participants attempted to obtain as great a jump as possible), and Accuracy (participants attempted to be as accurate as possible on takeoff without sacrificing distance). The results showed that the footfall position variability for all conditions was similar to those previously reported for the long jump approach run. However, in compliance with the nonregulatory constraints, participants altered other performance parameters in executing the approach run. The situational factors created changes that revealed themselves in foot placement on the takeoff board at the end of the approach run (foot position constant error and number of fouls increased for the Distance condition) and decreased horizontal velocity at takeoff in the Accuracy condition. Changes in performance parameters were related to the context in which the skill was performed and may further reflect changes made by jumpers in the course, such as a visual-motor task in competition. We suggest that the characteristics of the approach run may not be fully revealed by the pattern of footfall variability only, as has been suggested in previous work (e.g., Lee, Lishman, & Thomson, 1982), but that the situation under which the jump is performed may have a significant effect on the performance parameters that emerge in executing this type of motor skill.

Prevalence and risk behaviours for HIV infection among inmates of a provincial prison in Quebec City.

OBJECTIVE: To assess HIV prevalence and related risk factors among inmates at the Quebec Detention Centre (QDC). DESIGN: Cross-sectional prevalence study. METHODS: Inmates incarcerated at the QDC in September 1994 were asked to participate in an anonymous survey concerning HIV infection. Volunteers answered a questionnaire and provided a saliva sample during a meeting with an interviewer. RESULTS: The overall participation rate was 95% (618 out of 651). HIV prevalence was 2% (11 out of 499) in men. All HIV-infected men were injecting drug users (IDU) with an HIV prevalence of 9% (11 out of 129) in this group. HIV prevalence was 14% (9/63) among male IDU admitting previous needle-sharing and 3% (two out of 66) among the other IDU (odds ratio, 5.3; P = 0.028). Twelve male inmates admitted injecting drugs during imprisonment, of whom 11 shared needles and three were HIV-positive. HIV prevalence in men reporting sexual intercourse with men prior to incarceration was 10% (five out of 52). Nine of the 119 women were HIV-infected (8%), seven of whom were IDU (prevalence of 16% in female IDU). One of the two non-IDU had sexual contacts with male IDU, and the other with men who had sex with men. Tattooing was not associated with HIV infection in either men or women. CONCLUSIONS: Prisoners constitute a group at high risk of HIV infection mainly because of the high proportion of them who are IDU. Imprisonment offers a good opportunity to provide education and preventive programs to this specific group that might otherwise be difficult to reach.

The composition of fluorescent pseudomonad populations associated with roots is influenced by plant and soil type.

Populations of fluorescent pseudomonads isolated from an uncultivated soil and from the roots of two plant species were previously shown to differ (P. Lemanceau, T. Corberand, L. Gardan, X. Latour, G. Laguerre, J.-M. Boeufgras, and C. Alabouvette, Appl. Environ. Microbiol. 61:1004-1012, 1995). The diversities of fluorescent pseudomonads, from two uncultivated soils and from the roots of two plant species cultivated in these two soils, were compared. The phenotypic diversity of the bacterial isolates was characterized on the basis of biochemical and physiological tests and on the basis of their ability to utilize 147 different organic compounds. The genotypic diversity of the isolates was characterized on the basis of the types of 16S genes coding for rRNA (rDNA), their repetitive extragenic palindromic patterns by PCR, and plasmid profiles. Taxonomic identification of the isolates was achieved with both biochemical and physiological tests and by comparing their 16S rDNA types to those of reference and type strains of fluorescent Pseudomonas spp. Numerical analysis of phenotypic characteristics allowed the clustering of isolates that showed high levels of similarity. This analysis indicated that both soil type and host plant had an effect on the diversity of fluorescent pseudomonads. However, of the two factors studied, the soil was clearly the dominating one. Indeed, the populations associated with the roots of each plant species varied from one soil to the other. This variation could possibly be ascribed to the differences recorded between the phenotypically diverse populations of fluorescent pseudomonads from the two uncultivated soils. The plant selection was, at least partly, plant specific. It was not related to bacterial species and biovars or to the presence of plasmid DNA. The phenotypic clustering of isolates was well correlated with genotypic characterization by repetitive extragenic palindrome-PCR fingerprinting.

Immunolocalization of freezing-tolerance-associated proteins in the cytoplasm and nucleoplasm of wheat crown tissues.

A protein family associated with the development of freezing tolerance in wheat has been identified. This protein family is Gramineae-specific and coordinately regulated by low temperature. Antibodies directed against the 50 kDa (WCS120) protein recognize at least 5 members of this family. Using these antibodies, the cellular content and location of this protein family was determined in cold-acclimated wheat seedlings. Western analyses of subcellular fractions indicated the presence of all members of the family in the cytosolic and purified nuclear fractions. These proteins accumulated to 0.9% of soluble proteins after 21 days of cold acclimation in winter wheat. This represents a cellular concentration of 1.34 microM. Immunohistochemical localization showed that these proteins are highly expressed in the vascular transition zone. No detectable expression was found in mature xylem, in the shoot apical meristem or lateral root primordia. This differential tissue expression suggests that the sensitive cells near the regions where water tends to freeze first require a higher amount of these proteins. This observation is consistent with the fact that regrowth after freezing stress is highly dependent on the viability of this region of the crown. Electron microscopy analysis using immunogold labelling showed that these proteins are present in the cytoplasm and in the nucleoplasm. They are not found in cell walls or other organelles. In vitro cryoprotective assays indicated that the WCS120 protein (PD50 of 10 micrograms ml-1 or 0.2 microM) are as effective as BSA and sucrose (at 250 mM) against freezing denaturation of lactate dehydrogenase. These results suggest that this protein family may be involved in a general mechanism of protection in the soluble fraction of the cell. Their presence in the nucleoplasm may also suggest a possible protective function of the transcriptional machinery. The high hydrophilicity, the abundance and stability of these proteins to boiling suggest that they may provide a particular micro-environment needed for cell survival in the sensitive vascular transition zone during freezing stress.

Evaluation of a semi-automated 24-hour commercial system for identification of Enterobacteriaceae and other gram-negative bacteria.

A semi-automated commercial system (ID 32 E, bioMérieux) for 24-hour identification of Enterobacteriaceae and other gram-negative fermentative and nonfermentative bacteria encountered in diagnostic microbiology was evaluated. Overall, the system correctly identified 506 (91.5%) of the 553 strains tested, 94 (17.0%) strains requiring additional tests for complete identification. Six (1.1%) strains were misidentified and 33 (6.0%) strains were not identified. Eight (1.4%) strains were not present in the database and were misidentified or not identified. The system is a suitable alternative to existing systems for the identification of Enterobacteriaceae and other gram-negative bacteria frequently encountered in clinical samples.

Simulated control of unilateral, anticipatory locomotor adjustments during obstructed gait.

Anticipatory adjustments of our locomotor patterns are necessary in order to negotiate our uneven daily environments. Recent work (McFadyen and Winter 1991) has shown the re-organization of lower limb mechanics for obstacle avoidance during level walking. The present work describes a model which sets the ground work for predicting how such re-organized motor patterns might be generated from stereotypic unobstructed patterns. Pattern-generating algorithms use an estimation of future contacts with obstacles to create weighting functions that modify joint angle trajectories towards new patterns capable of clearing the obstacle. Feedforward/feedback control is then used to generate the necessary joint torques. The results show that model parameters can be found to generate not only kinematic but also energetic patterns for obstacle clearance that mimic experimental results. The validity of the model with respect to human locomotor control is discussed.

Brain correlates of hand dominance: the association between peripheral and cerebral asymmetries revisited.

Measures reflecting central processing of somatosensory stimulation were recorded in left- and in right-handed subjects in order to evaluate differences between the two handedness groups in the vertical, rather than lateral, axis of processing. Somatosensory evoked potentials were recorded in left- and right-handers following electrical stimulation of the median nerve at the wrist. The relative vertical balance of processing was probed by comparing the amplitudes of the underlying activity in early evoked potentials, presumably originating subcortically, with later, cortically originating potentials. Central conduction time (CCT) of the sensory volleys was also recorded. The data revealed higher amplitude ratios (ARs) between subcortical and cortical potentials, as well as shorter CCTs, in left-handers. These results demonstrate that transmission differences between the handedness groups may occur early in central nervous system (CNS) conductance. The results are further discussed in light of evidence suggesting that stronger reliance on a subcortical mode of processing may underlie phenomenon of left-handedness.

Description and evaluation of the semiautomated 4-hour ATB 32E method for identification of members of the family Enterobacteriaceae.

A study was performed to compare the rapid identification system ATB 32E (API-bioMérieux SA, La Balme-les-Grottes, France) with conventional biochemical methods for identifying 414 isolates of the family Enterobacteriaceae and the genus Aeromonas, mainly of clinical origin. Overall, 395 strains (95.4%) were correctly identified, with 48 (11.6%) requiring extra tests for complete identification. Ten strains (2.4%) were not identified, and nine (2.9%) were misidentified. The ATB 32E is a suitable alternative for rapid identification of members of the family Enterobacteriaceae.

Evaluation of API Coryne in comparison with conventional methods for identifying coryneform bacteria.

A study was performed to evaluate a new manual miniaturized system, API Coryne (API-bioMérieux, Inc., La Balme les Grottes, France), in which conventional biochemical methods were used to identify 240 isolates of coryneform and related bacteria. A total of 40% of the isolates were excluded from the study because they could not be identified by conventional methods. Identifications of the 240 isolates obtained with API Coryne showed a 97.6% concordance with conventional methods (79% after 24 h of incubation, 21% after 48 h of incubation): 158 (65.8%) isolates were identified with no further testing, and extra testing was required for 76 (31.8%) isolates. In three (1.2%) cases, the organisms did not correspond to any key in the code book and could not be identified by the computer service of the manufacturer. Only three (1.2%) strains were misidentified. The system was shown to be reliable and rapid when compared with standard identification methods.

Skilled memory in expert figure skaters.

The present studies extend skilled-memory theory to a domain involving the performance of motor sequences. Skilled figure skaters were better able than their less skilled counterparts to perform short skating sequences that were choreographed, rather than randomly constructed. Expert skaters encoded sequences for performance very differently from the way in which they encoded sequences that were verbally presented for verbal recall. Tasks interpolated between sequence and recall showed no significant influence on recall accuracy, implicating long-term memory in skating memory. There was little evidence for the use of retrieval structures when skaters learned the brief sequences used throughout these studies. Finally, expert skaters were able to judge the similarity of two skating elements faster than less skilled skaters, indicating a faster access to semantic memory for experts. The data indicate that skaters show many of the same skilled-memory characteristics as have been described in other skill domains involving memorization, such as digit span and memory for dinner orders.

A noted on the relationship between task requirements and the contextual interference effect.

Typically, tasks used in past contextual interference experiments had movement, spatial pattern, or timing requirements. The possibility exists that the blocked/random manipulation of only one of these task characteristics contributes to the contextual interference effect. The purpose of the experiment reported here was to test the impact of separate movement and timing tasks on the superior learning of random trained groups. The task for all subjects in the movement condition was to release a start button and knock over a wooden barrier. There were three movement goals to be learned. Half of the subjects in this condition practiced the three movements in a blocked schedule and half practiced them in a random schedule. The subjects in the no-movement condition estimated the same three times by holding down the start button for the appropriate duration. Similarly, these subjects were divided into random and blocked practice groups. All subjects then performed a retention test. Results showed that for the movement condition, the blocked group performed with less error than the random group during acquisition. In retention, however, the random group performed with less error than the blocked group. conversely, for the no-movement condition, there were no differences between the two practice schedule groups during acquisition or during retention for any of the dependent measures. These results indicated that experimental tasks must have some type of movement requirement in order to facilitate learning through the use of random practice schedules.

The effect of handedness on spinal and supra-spinal reflex excitability.

Twenty-four subjects, 8 right-handers, 8 left-handers, and 8 familial left-handers, participated in a study aimed at understanding the relations between handedness, cerebral asymmetry, and a possible asymmetry in spinal excitability. This was accomplished by employing 3 different techniques of investigating the H reflex, measuring 3 different parameters of spinal excitability. The recovery curve height (RCH) of left-handers was significantly higher than the RCH of right-handers, and, as well, familial left-handers exhibited higher RCH than non-familial left-handers. The recovery ability was not found to be significantly more inhibited on the dominant side, as would be expected from previous work. Instead, recovery ability was associated with the fractional involvement of the motoneuron pool in the H process (H/M ratio). RCH was highly correlated with both hand preference and hand performance. The above results suggest involvement of a long-loop transcortical reflex in lateral asymmetries.

Expectancy effects: cost-benefit analysis of monaurally and dichotically presented speech.

In three experiments, cost-benefit analysis was used to determine the role of attention in the processing of auditory information. In two experiments consonant-vowel syllables were presented monaurally, while in the third the mode of presentation was dichotic. For all three experiments the ability to detect a target stimulus under conditions in which precued location information was valid or invalid was contrasted with detection in a neutral condition where no location information was provided. The results indicated that attention can be effectively deployed under monaural conditions when either a simple detection or a discriminative response is required. Similar conclusions cannot be reached when considering the effectiveness of attention under conditions of dichotic listening. These results are discussed in relation to accounts which argue that dichotic listening performance is critically dependent upon auditory disembedding and where attention is viewed as a late process involving response selection.