2,613 research outputs found
Patterns of muscle activity underlying object-specific grasp by the macaque monkey
No full textDuring object grasp, a coordinated activation of distal muscles is required to shape the hand in relation to the physical properties of the object. Despite the fundamental importance of the grasping action, little is known of the muscular activation patterns that allow objects of different sizes and shapes to be grasped. In a study of two adult macaque monkeys, we investigated whether we could distinguish between EMG activation patterns associated with grasp of 12 differently shaped objects, chosen to evoke a wide range of grasping postures. Each object was mounted on a horizontal shuttle held by a weak spring ( load force 1 - 2 N). Objects were located in separate sectors of a "carousel," and inter-trial rotation of the carousel allowed sequential presentation of the objects in pseudorandom order. EMG activity from 10 to 12 digit, hand, and arm muscles was recorded using chronically implanted electrodes. We show that the grasp of different objects was characterized by complex but distinctive patterns of EMG activation. Cluster analysis shows that these object-related EMG patterns were specific and consistent enough to identify the object unequivocally from the EMG recordings alone. EMG-based object identification required a minimum of six EMGs from simultaneously recorded muscles. EMG patterns were consistent across recording sessions in a given monkey but showed some differences between animals. These results identify the specific patterns of activity required to achieve distinct hand postures for grasping, and they open the way to our understanding of how these patterns are generated by the central motor network
Spring 2021 HIP with a virtual literature review experience with an RN-BSN Student
No full textRegistered Nurse-Bachelor of Science in Nursing (RN-BSN) students have been caring for critically ill COVID-19 patients for over a year, while remaining dedicated to advancing their education. Nurse burnout has increased with the COVID-19 stressors adding to the critical nursing shortages throughout the nation (Kelly et al., 2021). Caring mentorship supports the RN-BSN student needs as a working nurse enduring pandemic stressors
A cortico-cortical mechanism mediating object-driven grasp in humans.
No full textHumans and other primates demonstrate an exquisite ability to precisely shape their hand when reaching out to grasp an object. Here we used a recently developed transcranial magnetic stimulation paradigm to examine how information about an object's geometric properties is transformed into specific motor programs. Pairs of transcranial magnetic stimulation pulses were delivered at precise intervals to detect changes in the excitability of cortico-cortical inputs to motor cortex when subjects prepared to grasp different objects. We show that at least 600 ms before movement, there is an enhancement in the excitability of these inputs to the corticospinal neurons projecting from motor cortex to the specific muscles that will be used for the grasp. These changes were object-and muscle-specific, and the degree of modulation in the inputs was correlated with the pattern of muscular activity used later by individual subjects to grasp the objects. In a number of control experiments, we demonstrated that no change in excitability was observed during object presentation alone, under conditions in which subjects imagined grasping the object, or before movements involving the same muscles but without an object. This finding demonstrates a cortico-cortical mechanism subserving the transformation from the geometrical properties of an object to the outputs from motor cortex before grasp that is specific for object-driven movements
How-to guides for first time staff RN researchers, from staff RN researcher, published author
No full textAdvice and tips from a first time bedside staff RN researcher/ published author to potential staff RN researchers/ authors on how to start, fund, form teams, gather and analyze data, submit completed research project for conferences and publication
Excitability of human motor cortex inputs prior to grasp
No full textTranscranial magnetic stimulation (TMS) was used to investigate corticospinal excitability during the preparation period preceding visually guided self-paced grasping. Previously we have shown that while subjects prepare to grasp a visible object, paired-pulse TMS at a specific interval facilitates motor-evoked potentials (MEPs) in hand muscles in a manner that varies with the role of the muscle in shaping the hand for the upcoming grasp. This anticipatory modulation may reflect transmission of inputs to human primary motor cortex (M1) for visuomotor guidance of hand shape. Conversely, single-pulse TMS is known to suppress MEPs during movement preparation. Here we investigate the time course of single- and paired-pulse MEP modulation. TMS was delivered over M1, at different time intervals after visual presentation of either a handle or a disc to healthy subjects. Participants were instructed to view the object, and later to grasp it when given a cue. During grasp there was a specific pattern of hand muscle activity according to the object grasped. MEPs were evoked in these muscles by TMS delivered prior to grasp. Paired-pulse MEPs were facilitated, whilst single-pulse MEPs were suppressed. The pattern of facilitation matched the object-specific pattern of muscle activity for TMS pulses delivered 150 ms or more after object presentation. However, this effect was not present when TMS was delivered immediately after object presentation, or if the delivery of TMS was given separately from the cue to perform the grasp action. These results suggest that object-related information for preparation of appropriate hand shapes reaches M1 only immediately preceding execution of the grasp
Preclinical evaluation of lime juice as a topical microbicide candidate
No full textBackground: The continued growth of the global HIV epidemic highlights the urgent need to develop novel prevention strategies to reduce HIV transmission. The development of topical microbicides is likely to take a number of years before such a product would be widely available.
This has resulted in a call for the rapid introduction of simpler vaginal intervention strategies in the interim period. One suggested practice would be vaginal douching with natural products including lime or lemon juice. Here we present a comprehensive preclinical evaluation of lime juice (LiJ) as a potential intervention strategy against HIV.
Results: Pre-treatment of HIV with LiJ demonstrated direct virucidal activity, with 10% juice inactivating the virus within 5 minutes. However, this activity was significantly reduced in the presence of seminal plasma, where inactivation required maintaining a 1:1 mixture of neat LiJ and seminal plasma for more than 5 minutes. Additionally, LiJ demonstrated both time and dosedependent
toxicity towards cervicovaginal epithelium, where exposure to 50% juice caused 75–90% toxicity within 5 minutes increasing to 95% by 30 minutes. Cervicovaginal epithelial cell monolayers were more susceptible to the effects of LiJ with 8.8% juice causing 50% toxicity after 5
minutes. Reconstructed stratified cervicovaginal epithelium appeared more resilient to LiJ toxicity with 30 minutes exposure to 50% LiJ having little effect on viability. However viability was reduced by 75% and 90% following 60 and 120 minutes exposure. Furthermore, repeat application (several times daily) of 25% LiJ caused 80–90% reduction in viability.
Conclusion: These data demonstrate that the virucidal activity of LiJ is severely compromised in the presence of seminal plasma. Potentially, to be effective against HIV in vivo, women would need to apply a volume of neat LiJ equal to that of an ejaculate, and maintain this ratio vaginally for 5–30 minutes after ejaculation. Data presented here suggest that this would have significant adverse
effects on the genital mucosa. These data raise serious questions about the plausibility and safety of such a prevention approach
Bolfuncties in Rn: Spherical harmonics in Rn
No full textIn de wiskunde hebben we bij het modelleren van fysische problemen vaak te maken met randwaardeproblemen. Voor een randwaardeprobleem met een cirkel als rand en een L2- functie als randvoorwaarde, kan deze randvoorwaarde beschreven worden door een Fourierreeks. Hierdoor kan zo'n randwaardeprobleem makkelijker opgelost worden. In dit werk wordt het uitdrukken van functies in Fourierreeksen in R2 uitgebreid naar Rn door bolfuncties in Rn te gebruiken. Eerst wordt er een introductie gegeven in bolfuncties in R2 en er wordt een aantal nuttige eigenschappen van deze functies besproken. Vervolgens worden enkele handigheden voor het werken in Rn genoemd en komen de kwadratisch integreerbare functies aan bod. Tot slot zien we dat de eigenschappen van de bolfuncties in R2 nog steeds gelden in Rn en dat elke kwadratisch integreerbare functie op de eenheidssfeer te schrijven is als lineaire combinatie van bolfuncties.Electrical Engineering, Mathematics and Computer ScienceDelft Institute of Applied Mathematic
Approximation and interpolation by large entire cross-sections of second category sets in Rn+1
No full textIn [M.R. Burke, Large entire cross-sections of second category sets in Rn+1Rn+1, Topology Appl. 154 (2007) 215–240], a model was constructed in which for any everywhere second category set A⊆Rn+1A⊆Rn+1 there is an entire function f:Rn→Rf:Rn→R which cuts a large section through A in the sense that {x∈Rn:(x,f(x))∈A}{x∈Rn:(x,f(x))∈A} is everywhere second category in RnRn. Moreover, the function f can be taken so that its derivatives uniformly approximate those of a given CNCN function g in the sense of a theorem of Hoischen. In the theory of the approximation of CNCN functions by entire functions, it is often possible to insist that the entire function interpolates the restriction of the CNCN function to a closed discrete set. In the present paper, we show how to incorporate a closed discrete interpolation set into the above mentioned theorem. When the set being sectioned is sufficiently definable, an absoluteness argument yields a strengthening of the Hoischen theorem in ZFC. We get in particular the following: Suppose g:Rn→Rg:Rn→R is a CNCN function, ε:Rn→Rε:Rn→R is a positive continuous function, T⊆RnT⊆Rn is a closed discrete set, and G⊆Rn+1G⊆Rn+1 is a dense GδGδ set. Let A⊆RnA⊆Rn be a countable dense set disjoint from T and for each x∈Ax∈A, let Bx⊆RBx⊆R be a countable dense set. Then there is a function f:Rn→Rf:Rn→R which is the restriction of an entire function Cn→CCn→C such that the following properties hold. (a) For all multi-indices α of order at most N and all x∈Rnx∈Rn, |(Dαf)(x)−(Dαg)(x)|<ε(x)|(Dαf)(x)−(Dαg)(x)|<ε(x), and moreover (Dαf)(x)=(Dαg)(x)(Dαf)(x)=(Dαg)(x) when x∈Tx∈T. (b) For each x∈Ax∈A, f(x)∈Bxf(x)∈Bx. (c) {x∈Rn:(x,f(x))∈G}{x∈Rn:(x,f(x))∈G} is a dense GδGδ set in RnRn
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