High resolution solid state NMR in paramagnetic metal-organic frameworks

We study the metal-organic framework (MOF) ZIF-67 with ¹H and ¹³C nuclear magnetic resonance (NMR). In addition to the usual orbital chemical shifts, we observe spinning sideband manifolds in the NMR spectrum due to hyperfine interactions of the paramagnetic cobalt with ¹H and ¹³C. Both orbital and paramagnetic chemical shifts are in good agreement with values calculated from first principles, allowing high-confidence assignment of the observed peaks to specific sites within the MOF. Our measured resonance shifts, line shapes, and spin lattice relaxation rates are also consistent with calculated values. We show that molecules in the pores of the MOF can exhibit high-resolution NMR spectra with fast spin lattice relaxation rates due to dipole-dipole couplings to the Co²⁺ nodes in the ZIF-67 lattice, showcasing NMR spectroscopy as a powerful tool for identification and characterization of "guests" that may be hosted by the MOF in electrochemical and catalytic applications.

Glenohumeral stabilizing roles of the scapulohumeral muscles: Implications of muscle geometry

Dynamic stability provided by muscles is integral for function and integrity of the glenohumeral joint. Although the high degree of inter-individual variation that exists in musculoskeletal geometry is associated with shoulder injuries, there is limited research associating the effects of muscle geometry on the potential stabilizing capacities of shoulder muscles. The purpose of this investigation was to evaluate the stabilizing functions of the scapulohumeral muscles using computational modeling and to quantify the sensitivity of muscle stabilizing roles to changes in muscle geometry. Muscle stability ratios in the superior/inferior and anterior/posterior directions were computed as the ratio between the muscle's shear components relative to compression throughout arm elevation in the scapular plane. Muscle attachment locations on the clavicle, scapula, and humerus were iteratively adjusted using Monte Carlo simulations. Consistent with previous experimental studies, the rotator cuff muscles were identified as the primary stabilizers of the glenohumeral joint; whereas the deltoids and coracobrachialis have a strong potential for superiorly translating the humerus at low elevation angles. Variations in the stability ratios due to altered muscle geometry were muscle- and angle-specific. In general, the highest variation was observed for the subscapularis and deltoids (at low elevation angles), while the remaining rotator cuff muscles largely maintained their capacity to provide compressive stabilizing forces at the glenohumeral joint. Changes in muscle stability ratios may affect dynamic stability of the humerus that could differentially predispose individuals to greater risk for injury.

Iterative Spatial Updating During Forward Linear Walking Revealed Using a Continuous Pointing Task

The continuous pointing task uses target-directed pointing responses to determine how perceived distance traveled is estimated during forward linear walking movements. To more precisely examine the regulation of this online process, the current study measured upper extremity joint angles and step-cycle kinematics in full vision and no-vision continuous pointing movements. Results show perceptual under-estimation of traveled distance in no-vision trials compared to full vision trials. Additionally, parsing of the shoulder plane of elevation trajectories revealed discontinuities that reflected this perceptual under-estimation and that were most frequently coupled with the early portion of the right foot swing phase of the step-cycle. This suggests that spatial updating may be composed of discrete iterations that are associated with gait parameters.

Examining the effect of state anxiety on compensatory and strategic adjustments in the planning of goal-directed aiming

The anxiety-perceptual-motor performance relationship may be enriched by investigations involving discrete manual responses due to the definitive demarcation of planning and control processes, which comprise the early and late portions of movement, respectively. To further examine the explanatory power of self-focus and distraction theories, we explored the potential of anxiety causing changes to movement planning that accommodate for anticipated negative effects in online control. As a result, we posed two hypotheses where anxiety causes performers to initially undershoot the target and enable more time to use visual feedback ("play-it-safe"), or fire a ballistic reach to cover a greater distance without later undertaking online control ("go-for-it"). Participants were tasked with an upper-limb movement to a single target under counter-balanced instructions to execute fast and accurate responses (low/normal anxiety) with non-contingent negative performance feedback (high anxiety). The results indicated that the previously identified negative impact of anxiety in online control was replicated. While anxiety caused a longer displacement to reach peak velocity and greater tendency to overshoot the target, there appeared to be no shift in the attempts to utilise online visual feedback. Thus, the tendency to initially overshoot may manifest from an inefficient auxiliary procedure that manages to uphold overall movement time and response accuracy.

The influence of intrapersonal sensorimotor experiences on the corticospinal responses during action-observation

The coupling of perception and action has been strongly indicated by evidence that the observation of an action primes a response in the observer. It has been proposed that these primed responses may be inhibited when the observer is able to more closely distinguish between self- and other-generated actions - the greater the distinction, then the greater the inhibition of the primed response. This self-other distinction is shown to be enhanced following a period of visual feedback of self-generated action. The present study was designed to examine how sensorimotor experiences pertaining to self-generated action affect primed responses from observed actions. Single-pulse transcranial magnetic stimulation was used to investigate corticospinal activity elicited during the observation of index- and little-finger actions before and after training (self-generated action). For sensorimotor training, participants executed finger movements with or without visual feedback of their own movement. Results showed that the increases in muscle-specific corticospinal activity elicited from action-observation persisted after training without visual feedback, but did not emerge following training with visual feedback. This inhibition in corticospinal activity during action-observation following training with vision could have resulted from the refining of internal models of self-generated action, which then led to a greater distinction between "self" and "other" actions.

Object-Tool-Actor Interaction: Object Information Drives Intended Action

Tool use is typically explored via actor-tool interactions. However, the target-object (that which is being acted on) may influence perceived action possibilities and thereby guide action. Three different tool-target-object pairings were tested (Experiment 1). The hammering action demonstrated the greatest sensitivity and therefore subsequently used to further investigate target-object pairings. The hammer was removed as an option and instructions were provided using pictorial (Experiment 2), written (Experiment 3), and both pictorial and written formats (Experiment 4). The designed tool is chosen when available (Experiment 1) and when removed as a choice (i.e., the hammer), participants perform the same action associated with the designed tool (i.e., hammering) regardless of instruction method (Experiments 2, 3, and 4).

Extending Energy Optimization in Goal-Directed Aiming from Movement Kinematics to Joint Angles

Energy optimization in goal-directed aiming has been demonstrated as an undershoot bias in primary movement endpoint locations, especially in conditions where corrections to target overshoots must be made against gravity. Two-component models of upper limb movement have not yet considered how joint angles are organized to deal with the energy constraints associated with moving the upper limb in goal-directed aiming tasks. To address this limitation, participants performed aiming movements to targets in the up and down directions with the index finger and two types of rod extensions attached to the index finger. The rod extensions were expected to invoke different energy optimizing strategies in the up and down directions by allowing the distal joints the opportunity to contribute to end effector displacement. Primary movements undershot the farthest target to a greater extent in the downward direction compared to the upward direction, showing that movement kinematics optimize energy expenditure in consideration of the effects of gravity. As rod length increased, shoulder elevation was optimized in movements to the far-up target and elbow flexion was optimally minimized in movements to the far-down target. The results suggest energy optimization in the control of joint angles independent of the force of gravity.

The Impact of Strategic Trajectory Optimization on Illusory Target Biases During Goal-Directed Aiming

During rapid aiming, movements are planned and executed to avoid worst-case outcomes that require time and energy to correct. As such, downward movements initially undershoot the target to avoid corrections against gravity. Illusory target context can also impact aiming bias. Here, the authors sought to determine how strategic biases mediate illusory biases. Participants aimed to Müller-Lyer figures in different directions (forward, backward, up, down). Downward biases emerged late in the movement and illusory biases emerged from peak velocity. The illusory effects were greater for downward movements at terminal endpoint. These results indicate that strategic biases interact with the limb-target control processes associated with illusory biases. Thus, multiple control processes during rapid aiming may combine and later affect endpoint accuracy (D. Elliott et al., 2010 ).

African-American Grandmothers as Health Educators in the Family

More than 18,000 adolescents die each year in the United States from bicycle, motorcycle, car, and truck accidents. This study sought to understand the role of African-American grandmothers as prevention-oriented health educators in the family. Full Model Fitted Regression Analyses were conducted on a sample of African-American grandmothers ( N = 105) with 10- to 19-year-old grandchildren. Findings suggest that grandmothers who adopt a proactive, teaching role with their grandchildren are more committed to doing so, confident about doing so, and in a context to do so. In particular, grandmothers who co-reside with their grandchildren are more likely to teach them about how to prevent transportation accidents than those who do not co-reside. These findings could contribute to innovations in existing grandparent education curricula.

Surprising stability of neutral interstitial hydrogen in diamond and cubic BN

In virtually all semiconductors and insulators, hydrogen interstitials ([Formula: see text]) act as negative-U centers, implying that hydrogen is never stable in the neutral charge state. Using hybrid density functional calculations, we find a different behavior for [Formula: see text] in diamond and cubic BN. In diamond, [Formula: see text] is a very strong positive-U center, and the [Formula: see text] charge state is stable over a Fermi-level range of more than 2 eV. In cubic BN, a III-V compound similar to diamond, we also find positive-U behavior, though over a much smaller Fermi-level range. These results highlight the unique behavior of [Formula: see text] in these covalent wide-band-gap semiconductors.

Common vs. independent limb control in sequential vertical aiming: The cost of potential errors during extensions and reversals

The following study explored movement kinematics in two-component aiming contexts that were intended to modulate the potential cost of overshoot or undershoot errors in up and down directions by having participants perform a second extension movement (Experiment 1) or a reversal movement (Experiment 2). For both experiments, the initial movement toward a downward target took longer, and had lower peak acceleration and peak velocity than upward movements. These movement characteristics may reflect a feedback-based control strategy designed to prevent energy-consuming limb modifications against gravitational forces. The between-component correlations of displacement at kinematic landmarks (i.e., trial-by-trial correlation between the first and second components) increased as both components unfolded. However, the between-component correlations of extensions were primarily negative, while reversals were positive. Thus, movement extensions appear to be influenced by the use of continuous on-line sensory feedback to update limb position at the second component based on the position attained in the first component. In contrast, reversals seem to be driven by pre-planned feedforward procedures where the position of the first component is directly replicated in the second component. Finally, the between-component correlations for the magnitude of kinematic landmarks showed that aiming up generated stronger positive correlations during extensions, and weaker positive correlations toward the end of the first component during reversals. These latter results suggest the cost of potential errors associated with the upcoming second component directly influence the inter-dependence between components. Therefore, the cost of potential errors is not only pertinent to one-component discrete contexts, but also two-component sequence aims. Together, these findings point to an optimized movement strategy designed to minimize the cost of errors, which is specific to the two-component context.

The use of action phrases in individuals with Autism Spectrum Disorder

Previous research has shown that individuals with Autism Spectrum Disorder (ASD) may be able to perceive the intentions of another individual through tool use (e.g., Aldridge et al., 2000; Gonzalez et al., 2013). However, it is not well understood how individuals with ASD respond to an indirect connection between an extrapolated action and the required object. To address this question, we employed action phrases that indirectly provided the contextual information about which object to use. Individuals with ASD, and sex and age matched typically developing peers, were asked to pick which object would be needed to complete the task described in a sentence displayed on a computer screen. Although individuals with ASD exhibited slower response times overall, their accuracy scores were comparable to typically developing individuals. The longer response times support the notion that individuals with ASD may have a harder time disengaging their initial perceived use for the object before considering other inherent action possibilities afforded by the object.

Outcomes of intravenous tissue plasminogen activator for acute ischaemic stroke in HIV-infected adults

BACKGROUND AND PURPOSE

To our knowledge there are no studies reporting the use and short-term outcomes of intravenous tissue plasminogen activator (IV-TPA) for the treatment of acute ischaemic stroke (AIS) in people living with HIV.

METHODS

The US Nationwide Inpatient Sample (NIS) (2006-2010) was searched for HIV-infected AIS patients treated with IV-TPA.

RESULTS

In the NIS, 2.2% (62/2877) of HIV-infected AIS cases were thrombolyzed with IV-TPA (median age 52 years, range 27-78, 32% female, 22% Caucasian) vs. 2.1% (19 335/937 896) of HIV-uninfected cases (median age 72 years, range 17-102 years, 50% female, 74% Caucasian; P = 0.77). There were more deaths in HIV-infected versus uninfected patients with stroke (220/2877, 7.6% vs. 49 089/937 547, 5.2%, P < 0.001) but no difference in the proportion of deaths amongst IV-TPA-treated patients. The age- and sex-adjusted odds ratio for death following IV-TPA administration in HIV-infected versus uninfected patients was 2.26 (95% CI 1.12, 4.58), but the interaction on mortality between HIV and IV-TPA use was not statistically significant, indicating no difference in risk of in-hospital death by HIV serostatus with IV-TPA use. A higher number of HIV-infected patients remained in hospital versus died or were discharged at both 10 and 30 days (P < 0.01 at 10 and 30 days). No difference in the proportion of intracerebral hemorrhage in the two groups was found (P = 0.362).

CONCLUSIONS

The in-hospital mortality is higher amongst HIV-infected AIS patients than HIV-uninfected patients. However, the risk of death amongst HIV-infected patients treated with IV-TPA is similar to HIV-uninfected groups.

Separating responses based on demand characteristics and phenomenological-spatial associations

Previous researchers have found that participants associate higher frequencies with locations that are higher in space and lower frequencies with lower locations, creating a phenomenological-spatial association for the frequency of auditory tones. With such an association, the frequency of an auditory tone could potentially bias movements along multiple axes. This hypothesis was tested. In four experiments, nine frequencies (250-1,250 Hz) were binaurally presented to blindfolded participants (n = 10, 12, 20, & 9; M age = 22 yr.) who indicated the perceived location of the stimuli on a measurement scale oriented in the vertical, the horizontal (Experiment 1), or depth dimension (Experiment 2). In Experiment 3, participants were asked to indicate the perceived location of the frequencies on a two-dimensional vertical board located in front of them. In Experiment 4, participants indicated the perceived location in three-dimensional space. An optoelectronic device recorded at all locations. Analyses of constant error indicated a spatial association in the vertical, horizontal, and depth dimensions when responses were restricted to only one dimension (Experiments 1 & 2). Higher frequencies were perceived to be located higher, farther to the right, and farther away from the body than lower frequencies. However, this spatial association was only exhibited in the vertical dimension when the responses were unconstrained in two dimensions (vertical and horizontal; Experiment 3) and all three dimensions (Experiment 4). Although this spatial association is a robust phenomenon, it appears that the association only biases actions when indicating perceived locations in the vertical dimension during unconstrained responses.

The gunslinger effect: why are movements made faster when responding to versus initiating an action?

The authors replicated and extended results from the gunfight paradigm (A. Welchman, J. Stanley, M. Schomers, R. Miall, & H. Bulthoff, 2010a) in which participants moved faster when reacting to the perceived initiation of an opponent compared to initiating an action themselves. In addition to replicating these movement time effects, the authors found that time to peak velocity, peak velocity, and movement-endpoint dispersions were similarly impacted. The findings are discussed in terms of a triggering mechanism involved in ballistic and internally generated movements.

Gaze-down endoscopic practise leads to better novice performance on gaze-up displays

OBJECTIVES

It is well known that precision skills are best learned when they are practised in the sensorimotor context that is present when performance is most important. However, a particular skill may vary with respect to the sensorimotor context in which it is performed. Certain sensorimotor variations can make a task more or less complex than others. Recent accounts of skill learning describe how task difficulty can be manipulated to provide optimised challenges to progress learners beyond their current level of expertise. This study tests the idea that simplified practise contexts lead novice learners to acquire skill proficiency that is more generalisable to new contexts.

METHODS

We present a learning experiment in which the performances of novices who acquired a set level of proficiency in the endoscopic pots-and-beans task through performance-based practise using a gaze-up endoscopic monitor arrangement were compared against the performances of novices who acquired an equivalent level of proficiency using a simplified gaze-down arrangement. Participants returned after 1 week for retention and transfer testing.

RESULTS

Time and accuracy analyses revealed that participants in both training groups improved significantly over the practise protocol and maintained this performance after a period of retention. However, the comparisons of the visual display transfer performances (i.e. on the gaze-up arrangement) of the gaze-down trainees against the retention performances (i.e. also on the gaze-up arrangement) of their gaze-up counterparts and vice versa revealed that gaze-down trainees made fewer errors in both performance contexts (F(1,16) = 7.97, p = 0.01 and F(1,16) = 57.05, p = 0.04, respectively).

CONCLUSIONS

These findings highlight the benefits associated with using simplified sensorimotor practise contexts for novice learners. Beginners will learn best from simplified practise because it allows them to develop good movement strategies for dealing with potential error without being overwhelmed by task complexity.

Spatial properties of perceived pitch: influence on reaching movements

We present three experiments that show a clear influence of pitch on reaching movements. The first experiment shows that when there are incompatibilities between the spatial representations of target coordinates and perceived pitches, response times are longer than when spatial representations are congruous. The second experiment shows that pitch can influence motor responses, biasing their direction. The third experiment shows that in the absence of any other spatial cues, tones are assigned spatial coordinates based on frequency. Our results suggest that pitch may indeed have inherent spatial properties, and that these properties may affect movement planning and execution.

Attentional and Motor Response Priming in a Bimanual Task

This study examined the performance of the upper limbs during responses to previously cued and un-cued locations. Participants made unimanual and bimanual responses under homologous and non-homologous muscular control, within a cuetarget (Experiment 1; n = 10), and a target-target (Experiment 2; n = 10) aiming protocol. The inhibition of return (IOR) to a target location was expected to increase with (a) an increase in the organization of the movement response required, and (b) the decrease in the muscular coupling under which the bimanual movement was performed. IOR was observed in both experiments when participants completed their movements in either the unimanual or homologous conditions, but not in the non-homologous condition. In addition, reaction times were significantly shorter when a movement preceded the response than when no manual response was made to the initial visual cue. The results indicate that common processing delays in response to exogenously cued targets are dependent on the muscular control of those responses. Thus, this study provides evidence that IOR is moderated by the muscular control under which the bimanual movement was performed indicating an influential involvement of the motor system in both the movement planning and movement response to multiple target stimuli.

The effect of the Müller-Lyer illusion on the planning and control of manual aiming movements

Two experiments used Müller-Lyer stimuli to test the predictions of the planning-control model (S. Glover, 2002) for aiming movements. In Experiment 1, participants aimed to stimuli that either remained the same or changed upon movement initiation. Experiment 2 was identical except that the duration of visual feedback for online control was manipulated. The authors found that the figures visible during movement planning and online control had additive effects on endpoint bias, even when participants had ample time to use visual feedback to modify their movements (Experiment 2). These findings are problematic not only for the planning-control model but also for A. D. Milner and M. A. Goodale's (1995) two visual system explanation of illusory bias. Although our results are consistent with the idea that a single representation is used for perception, movement planning, and online control (e.g., V. H. Franz, 2001), other work from our laboratory and elsewhere suggests that the manner in which space is coded depends on constraints associated with the specific task, such as the visual cues available to the performer.

Does Joe influence Fred's action?

Inhibition of return (IOR) refers to the slowing of responses to a target that appears in the same location as a previous event. Many researchers have speculated that IOR arises from inhibitory neural processes that have developed through evolution to facilitate efficient search patterns by biasing the action and/or attention of an individual towards novel locations. Throughout evolution, however, humans conducted searches as individuals as well as members of a group. In this context, we sought to determine if IOR could also be observed in the behavior of one individual after the observation of another's behavior. Consistent with our reasoning, there was no difference in the magnitude of the IOR effect found when participants followed their own response or the response of their partner. These results are discussed in the context of action-based attention and possible underlying neural mechanisms.

A novel model of bacterially-induced acute anterior uveitis in rats and the lack of effect from HLA-B27 expression

BACKGROUND

Humans with the major histocompatibility antigen B27 (HLA-B27) are especially at risk for developing rheumatic disorders such as ankylosing spondylitis and Reiter's syndrome. Acute anterior uveitis (AAU) often occurs in association with these diseases or in HLA B27 positive individuals without joint disease.

METHODS

We induced acute anterior uveitis in Lewis rats by a standard model, the intraperitoneal injection of 200 micrograms of Escherichia coli endotoxin. We also developed a novel model of uveitis secondary to gram-negative infection.

RESULTS

Transgenic rats that expressed a low copy number of the B27 gene did not differ statistically from litter mate controls in the intensity of anterior uveitis as judged by histology, enumeration of cells in aqueous humor, protein in aqueous humor, or slit lamp examination. The majority of rats exposed to live Salmonella enteritidis or Yersinia enterocolitica 0:3 using either an oral or intravenous route of infection developed anterior uveitis. In contrast to the disease induced by endotoxin that is most intense 24 hours after the endotoxin challenge, uveitis induced by live bacteria usually began 7 to 9 days after exposure to bacterial products, was more often unilateral, persisted for as long as 3 weeks, and was sometimes recurrent. The expression of HLA-B27 did not appear to influence the incidence or severity of uveitis in B27+ low copy heterozygous animals.

CONCLUSION

This rat model of AAU should facilitate evaluation of bacterial antigenic component(s) involved in the pathogenesis of live gram-negative bacteria induced AAU.

Uveitis associated with inflammatory bowel disease compared with uveitis associated with spondyloarthropathy

BACKGROUND

Inflammatory bowel disease (IBD) and spondyloarthropathy (SA) such as Reiter syndrome may be characterized by diarrhea, arthritis, stomatitis, and uveitis.

OBJECTIVE

To determine if the characteristics of the eye disease could help distinguish these 2 diagnoses.

DESIGN

Seventeen patients with uveitis and IBD referred to a university clinic were compared retrospectively with 89 patients with uveitis and SA referred to the same clinic.

RESULTS

Twelve (80%) of the 15 patients with evaluable IBD had Crohn disease. In marked contrast to patients with SA, patients with IBD were usually female (82%). Whereas uveitis with SA was predominantly anterior, unilateral, sudden in onset, and limited in duration, patients with IBD frequently had uveitis that was bilateral, posterior, insidious in onset, and/or chronic in duration. Results for 89% of the patients with SA who underwent HLA-B27 typing were positive, compared with only 46% of such patients with IBD. Episcleritis, scleritis, and glaucoma were more common among patients with IBD. Arthritis did not easily distinguish the 2 groups, as 13 (76%) of the patients with IBD had a history of joint disease. In 10 (59%) of the patients with IBD, the diagnosis of uveitis preceded that of IBD.

CONCLUSION

The hallmarks of uveitis can often distinguish SA and IBD.

A therapeutic work program for head-injured adults

The Therapeutic Work Program operates in an ambulatory care setting and aids in assessing and developing prevocational skills in adults with head injuries. The program has eight phases, including initial evaluation, individual and group treatment, and prevocational assessment and treatment. We conducted a phone survey to evaluate the program's effectiveness and found that 79% of the 29 respondents participated in occupational activities (i.e., they were competitive or volunteer employees, homemakers, or students), a greater percentage than reported by other prevocational programs for patients with head injuries.