2,349 research outputs found
The Role of Haptic Expectations in Reaching to Grasp: From Pantomime to Natural Grasps and Back Again
© Copyright © 2020 Whitwell, Katz, Goodale and Enns. When we reach to pick up an object, our actions are effortlessly informed by the objectâs spatial information, the position of our limbs, stored knowledge of the objectâs material properties, and what we want to do with the object. A substantial body of evidence suggests that grasps are under the control of âautomatic, unconsciousâ sensorimotor modules housed in the âdorsal streamâ of the posterior parietal cortex. Visual online feedback has a strong effect on the handâs in-flight grasp aperture. Previous work of ours exploited this effect to show that grasps are refractory to cued expectations for visual feedback. Nonetheless, when we reach out to pretend to grasp an object (pantomime grasp), our actions are performed with greater cognitive effort and they engage structures outside of the dorsal stream, including the ventral stream. Here we ask whether our previous finding would extend to cued expectations for haptic feedback. Our method involved a mirror apparatus that allowed participants to see a âvirtualâ target cylinder as a reflection in the mirror at the start of all trials. On âhaptic feedbackâ trials, participants reached behind the mirror to grasp a size-matched cylinder, spatially coincident with the virtual one. On âno-haptic feedbackâ trials, participants reached behind the mirror and grasped into âthin airâ because no cylinder was present. To manipulate haptic expectation, we organized the haptic conditions into blocked, alternating, and randomized schedules with and without verbal cues about the availability of haptic feedback. Replicating earlier work, we found the strongest haptic effects with the blocked schedules and the weakest effects in the randomized uncued schedule. Crucially, the haptic effects in the cued randomized schedule was intermediate. An analysis of the influence of the upcoming and immediately preceding haptic feedback condition in the cued and uncued random schedules showed that cuing the upcoming haptic condition shifted the haptic influence on grip aperture from the immediately preceding trial to the upcoming trial. These findings indicate that, unlike cues to the availability of visual feedback, participants take advantage of cues to the availability of haptic feedback, flexibly engaging pantomime, and natural modes of grasping to optimize the movement
Radiation risk predictions for Space Station Freedom orbits
Risk assessment calculations are presented for the preliminary proposed solar minimum and solar maximum orbits for Space Station Freedom (SSF). Integral linear energy transfer (LET) fluence spectra are calculated for the trapped proton and GCR environments. Organ dose calculations are discussed using the computerized anatomical man model. The cellular track model of Katz is applied to calculate cell survival, transformation, and mutation rates for various aluminum shields. Comparisons between relative biological effectiveness (RBE) and quality factor (QF) values for SSF orbits are made
Bose-Fermi mixtures in 1D optical superlattices
The zero temperature phase diagram of binary boson-fermion mixtures in
two-colour superlattices is investigated. The eigenvalue problem associated
with the Bose-Fermi-Hubbard Hamiltonian is solved using an exact numerical
diagonalization technique, supplemented by an adaptive basis truncation scheme.
The physically motivated basis truncation allows to access larger systems in a
fully controlled and very flexible framework. Several experimentally relevant
observables, such as the matter-wave interference pattern and the
condensatefraction, are investigated in order to explore the rich phase
diagram. At symmetric half filling a phase similar to the Mott-insulating phase
in a commensurate purely bosonic system is identified and an analogy to recent
experiments is pointed out. Furthermore a phase of complete localization of the
bosonic species generated by the repulsive boson-fermion interaction is
identified. These localized condensates are of a different nature than the
genuine Bose-Einstein condensates in optical lattices.Comment: 18 pages, 9 figure
Does comorbidity increase the risk of mortality among children under 3â years of age?
Objectives Diarrhoea and pneumonia remain leading causes of morbidity and mortality in children under 5â
years of age. Little data is available to quantify the burden of comorbidity and the relationship between comorbid diarrhoea and pneumonia infections and mortality. We sought to quantify the relationship between comorbidity and risk of mortality among young children in two community-based studies conducted among South Asian children. Design Secondary data analysis of two cohort studies. Participants We identified two cohort studies of children under 3â
years of age with prospective morbidity at least once every 2â
weeks and ongoing mortality surveillance. Outcome measures We calculated the mortality risk for diarrhoea and acute lower respiratory infection (ALRI) episodes and further quantified the risk of mortality when both diseases occur at the same time using a semiparametric additive model. Results Among Nepali children, the estimated additional risk of mortality for comorbid diarrhoea and ALRI was 0.0014 (â0.0033, 0.0060). Among South Indian children, the estimated additional risk of mortality for comorbid diarrhoea and ALRI was 0.0032 (â0.0098, 0.0162). This risk is in addition to the single infection risk of mortality observed among these children. Conclusions We observed an additional risk of mortality in children who experienced simultaneous diarrhoea and ALRI episodes though the CI was wide indicating low statistical support. Additional studies with adequate power to detect the increased risk of comorbidity on mortality are needed to improve confidence around the effect size estimate
Massless D-Branes on Calabi-Yau Threefolds and Monodromy
We analyze the link between the occurrence of massless B-type D-branes for
specific values of moduli and monodromy around such points in the moduli space.
This allows us to propose a classification of all massless B-type D-branes at
any point in the moduli space of Calabi-Yau's. This classification then
justifies a previous conjecture due to Horja for the general form of monodromy.
Our analysis is based on using monodromies around points in moduli space where
a single D-brane becomes massless to generate monodromies around points where
an infinite number become massless. We discuss the various possibilities within
the classification.Comment: 29 pages, LaTeX2e, 3 figures, author order fixe
Diarrhea as a risk factor for acute lower respiratory tract infections among young children in low income settings
Diarrhea and acute lower respiratory tract infections (ALRI) are leading causes of morbidity and mortality among children
under 5 years of age. We sought to quantify the correlation of diarrhea and respiratory infections within an individual child and to determine if infection with one illness increases the risk of infection with the other during the same time period
Bubble rise in a packed bed saturated with liquids
Experimental data were determined for drag coefficients on fluid bubbles rising in a saturated packed bed and in clear liquids. Air and benzene were used to form bubbles in glycerine solution, water, and normal heptane. One-inch diameter glass spheres in hexagonal, random, and cubic packings constituted the bed. The range in Reynolds number was from 0.1 to 1,000. It was found that the drag coefficients in the hexagonal and random arrays were from two to three times those in clear liquids, while the drag on bubbles rising in cubic packings was the same as that for clear liquids. The method of correlation involved the use of the minor diameter in the drag coefficient and the major diameter in the Reynolds number. This innovation improved the correlation for bubble rise in clear liquids.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37322/1/690080128_ftp.pd
Thermodynamics and collapse of self-gravitating Brownian particles in D dimensions
We address the thermodynamics (equilibrium density profiles, phase diagram,
instability analysis...) and the collapse of a self-gravitating gas of Brownian
particles in D dimensions, in both canonical and microcanonical ensembles. In
the canonical ensemble, we derive the analytic form of the density scaling
profile which decays as f(x)=x^{-\alpha}, with alpha=2. In the microcanonical
ensemble, we show that f decays as f(x)=x^{-\alpha_{max}}, where \alpha_{max}
is a non-trivial exponent. We derive exact expansions for alpha_{max} and f in
the limit of large D. Finally, we solve the problem in D=2, which displays
rather rich and peculiar features
Opioid receptor subtype-specific cross-tolerance to the effects of morphine on schedule-controlled behavior in mice
Key-press responding of mice was maintained under a fixed-ratio (FR) 30-response schedule of food presentation. Successive 3-min periods during which the experimental chamber was illuminated and the schedule was in effect were preceded by 10-min time-out (TO) periods during which all lights were out and responses had no scheduled consequences. Intraperitoneal (IP) injections of saline or of cumulative doses of drugs were given at the start of each TO period. Successive saline injections had little or no effect on response rates, whereas the ÎŒ-opioid agonists morphine (0.1â10.0 mg/kg) and levorphanol (0.1â3.0 mg/kg), the Îș-opioid agonist ethylketazocine (0.03â3.0 mg/kg), the mixed ÎŒ-/ÎŽ-opioid agonist metkephamid (0.1â10.0 mg/kg), and the nonopioid dissociative anesthetic ketamine (1.0â100.0 mg/kg) generally produced dose-related decreases in response rates. Following chronic administration of morphine (100.0 mg/kg/6 h), tolerance developed to the effects of morphine on rates of responding. In addition, a comparable degree of cross-tolerance developed to the effects of levorphanol and metkephamid. On the other hand, there was no evidence of cross-tolerance to the effects of ethylketazocine or ketamine. These results are consistent with the evidence suggesting that different opioid agonists exert their behavioral effects through distinct classes of opioid receptors.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46448/1/213_2004_Article_BF00177563.pd
Ongoing Mental Health Concerns in Post-3/11 Japan
Background: The triple disaster that struck the Tohoku region on March 11, 2011, has had massive psychiatric, social, and physical effects on the people of Japan. A staggering loss of life and property, as well as an ongoing nuclear disaster, has dramatically affected the ability of the country to recover. Objective: In an effort to better understand the current social, health, and mental health needs of the region affected by the disaster and to share lessons from 9/11, a group of 9/11 survivors and doctors from the Icahn School of Medicine at Mount Sinai traveled to sites throughout the Fukushima, Miyagi, and Iwate prefectures. Methods: A qualitative analysis was performed on transcripts of the cultural and medical exchanges, which occurred on this trip to identify relevant themes about the problems confronting the recovery effort almost 3 years after the disaster. Findings: Significant themes that emerged included a crippling radiation anxiety, a considerable stigma toward addressing mental health care, and a shortage of mental health care throughout the region, as well as ongoing psychiatric symptoms such as insomnia, anxiety, and alcohol misuse. Conclusions: These issues continue to complicate the recovery effort but suggest avenues for future interventions
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