4,996 research outputs found
Passive exercise of the hind limbs after complete thoracic transection of the spinal cord promotes cortical reorganization.
Physical exercise promotes neural plasticity in the brain of healthy subjects and modulates pathophysiological neural plasticity after sensorimotor loss, but the mechanisms of this action are not fully understood. After spinal cord injury, cortical reorganization can be maximized by exercising the non-affected body or the residual functions of the affected body. However, exercise per se also produces systemic changes - such as increased cardiovascular fitness, improved circulation and neuroendocrine changes - that have a great impact on brain function and plasticity. It is therefore possible that passive exercise therapies typically applied below the level of the lesion in patients with spinal cord injury could put the brain in a more plastic state and promote cortical reorganization. To directly test this hypothesis, we applied passive hindlimb bike exercise after complete thoracic transection of the spinal cord in adult rats. Using western blot analysis, we found that the level of proteins associated with plasticity - specifically ADCY1 and BDNF - increased in the somatosensory cortex of transected animals that received passive bike exercise compared to transected animals that received sham exercise. Using electrophysiological techniques, we then verified that neurons in the deafferented hindlimb cortex increased their responsiveness to tactile stimuli delivered to the forelimb in transected animals that received passive bike exercise compared to transected animals that received sham exercise. Passive exercise below the level of the lesion, therefore, promotes cortical reorganization after spinal cord injury, uncovering a brain-body interaction that does not rely on intact sensorimotor pathways connecting the exercised body parts and the brain
Overrated gaps: Inter-speaker gaps provide limited information about the timing of turns in conversation
Corpus analyses have shown that turn-taking in conversation is much faster than laboratory studies of speech planning would predict. To explain fast turn-taking, Levinson and Torreira (2015) proposed that speakers are highly proactive: They begin to plan a response to their interlocutor's turn as soon as they have understood its gist, and launch this planned response when the turn-end is imminent. Thus, fast turn-taking is possible because speakers use the time while their partner is talking to plan their own utterance. In the present study, we asked how much time upcoming speakers actually have to plan their utterances. Following earlier psycholinguistic work, we used transcripts of spoken conversations in Dutch, German, and English. These transcripts consisted of segments, which are continuous stretches of speech by one speaker. In the psycholinguistic and phonetic literature, such segments have often been used as proxies for turns. We found that in all three corpora, large proportions of the segments comprised of only one or two words, which on our estimate does not give the next speaker enough time to fully plan a response. Further analyses showed that speakers indeed often did not respond to the immediately preceding segment of their partner, but continued an earlier segment of their own. More generally, our findings suggest that speech segments derived from transcribed corpora do not necessarily correspond to turns, and the gaps between speech segments therefore only provide limited information about the planning and timing of turns
AR function in promoting metastatic prostate cancer.
Prostate cancer (PCa) remains a leading cause of cancer-related death in the USA. While localized lesions are effectively treated through radical prostatectomy and/or radiation therapy, treatment for metastatic disease leverages the addiction of these tumors on the androgen receptor (AR) signaling axis for growth and disease progression. Though initially effective, tumors resistant to AR-directed therapeutics ultimately arise (a stage of the disease known as castration-resistant prostate cancer) and are responsible for PCa-specific mortality. Importantly, an abundance of clinical and preclinical evidence strongly implicates AR signaling cascades in the development of metastatic disease in both early and late stages, and thus a concerted effort has been made to delineate the AR-specific programs that facilitate progression to metastatic PCa. A multitude of downstream AR targets as well as critical AR cofactors have been identified which impinge upon both the AR pathway as well as associated metastatic phenotypes. This review will highlight the functional significance of these pathways to disseminated disease and define the molecular underpinnings behind these unique, AR-driven, metastatic signatures
New insights on the dense molecular gas in NGC253 as traced by HCN and HCO+
We have imaged the central ~1kpc of the circumnuclear starburst disk in the
galaxy NGC253 in the HCN(1-0), HCO+(1-0), and CO(1-0) transitions at 60pc
resolution using the Owens Valley Radio Observatory Millimeter-Wavelength Array
(OVRO). We have also obtained Atacama Pathfinder Experiment (APEX) observations
of the HCN(4-3) and the HCO+(4-3) lines of the starburst disk. We find that the
emission from the HCN(1-0) and HCO+(1-0) transitions, both indicators of dense
molecular gas, trace regions which are non-distinguishable within the
uncertainties of our observations. Even though the continuum flux varies by
more than a factor 10 across the starburst disk, the HCN/HCO+ ratio is constant
throughout the disk, and we derive an average ratio of 1.1+/-0.2. From an
excitation analysis we find that all lines from both molecules are subthermally
excited and that they are optically thick. This subthermal excitation implies
that the observed HCN/HCO+ line ratio is sensitive to the underlying chemistry.
The constant line ratio thus implies that there are no strong abundance
gradients across the starburst disk of NGC253. This finding may also explain
the variations in L'(HCN)/L'(HCO+) between different star forming galaxies both
nearby and at high redshifts.Comment: 9 pages, 12 figures, ApJ in press (volume 666 September
Methods for comparative evaluation of propulsion system designs for supersonic aircraft
The propulsion system comparative evaluation study was conducted to define a rapid, approximate method for evaluating the effects of propulsion system changes for an advanced supersonic cruise airplane, and to verify the approximate method by comparing its mission performance results with those from a more detailed analysis. A table look up computer program was developed to determine nacelle drag increments for a range of parametric nacelle shapes and sizes. Aircraft sensitivities to propulsion parameters were defined. Nacelle shapes, installed weights, and installed performance was determined for four study engines selected from the NASA supersonic cruise aircraft research (SCAR) engine studies program. Both rapid evaluation method (using sensitivities) and traditional preliminary design methods were then used to assess the four engines. The method was found to compare well with the more detailed analyses
The end-state comfort effect in 3- to 8-year-old children in two object manipulation tasks
The aim of the study was to compare 3- to 8-year-old children’s propensity to antici- pate a comfortable hand posture at the end of a grasping movement ( end-state comfort effect ) between two different object manipulation tasks, the bar-transport task, and the overturned-glass task. In the bar-transport task, participants were asked to insert a verti- cally positioned bar into a small opening of a box. In the overturned-glass task, participants were asked to put an overturned-glass right-side-up on a coaster. Half of the participants experienced action effects (lights) as a consequence of their movements (AE groups), while the other half of the participants did not (No-AE groups). While there was no differ- ence between the AE and No-AE groups, end-state comfort performance differed across age as well as between tasks. Results revealed a significant increase in end-state comfort performance in the bar-transport task from 13% in the 3-year-olds to 94% in the 8-year- olds. Interestingly, the number of children grasping the bar according to end-state comfort doubled from 3 to 4 years and from 4 to 5 years of age. In the overturned-glass task an increase in end-state comfort performance from already 63% in the 3-year-olds to 100% in the 8-year-olds was significant as well. When comparing end-state comfort performance across tasks, results showed that 3- and 4-year-old children were better at manipulating the glass as compared to manipulating the bar, most probably, because children are more familiar with manipulating glasses. Together, these results suggest that preschool years are an important period for the development of motor planning in which the familiarity with the object involved in the task plays a significant role in children’s ability to plan their movements according to end-state comfort
Fluctuation theorem for the effusion of an ideal gas
The probability distribution of the entropy production for the effusion of an
ideal gas between two compartments is calculated explicitly. The fluctuation
theorem is verified. The analytic results are in good agreement with numerical
data from hard disk molecular dynamics simulations.Comment: 11 pages, 10 figures, 2 table
MV3: A new word based stream cipher using rapid mixing and revolving buffers
MV3 is a new word based stream cipher for encrypting long streams of data. A
direct adaptation of a byte based cipher such as RC4 into a 32- or 64-bit word
version will obviously need vast amounts of memory. This scaling issue
necessitates a look for new components and principles, as well as mathematical
analysis to justify their use. Our approach, like RC4's, is based on rapidly
mixing random walks on directed graphs (that is, walks which reach a random
state quickly, from any starting point). We begin with some well understood
walks, and then introduce nonlinearity in their steps in order to improve
security and show long term statistical correlations are negligible. To
minimize the short term correlations, as well as to deter attacks using
equations involving successive outputs, we provide a method for sequencing the
outputs derived from the walk using three revolving buffers. The cipher is fast
-- it runs at a speed of less than 5 cycles per byte on a Pentium IV processor.
A word based cipher needs to output more bits per step, which exposes more
correlations for attacks. Moreover we seek simplicity of construction and
transparent analysis. To meet these requirements, we use a larger state and
claim security corresponding to only a fraction of it. Our design is for an
adequately secure word-based cipher; our very preliminary estimate puts the
security close to exhaustive search for keys of size < 256 bits.Comment: 27 pages, shortened version will appear in "Topics in Cryptology -
CT-RSA 2007
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