186 research outputs found
Altered white matter connectivity associated with visual hallucinations following occipital stroke
Introduction: Visual hallucinations that arise following vision loss stem from aberrant functional activity in visual cortices and an imbalance of activity across associated cortical and subcortical networks subsequent to visual pathway damage. We sought to determine if structural changes in white matter connectivity play a role in cases of chronic visual hallucinations associated with visual cortical damage.
Methods: We performed diffusion tensor imaging (DTI) and probabilistic fiber tractography to assess white matter connectivity in a patient suffering from continuous and disruptive phosphene (simple) visual hallucinations for more than 2 years following right occipital stroke. We compared these data to that of healthy age-matched controls.
Results: Probabilistic tractography to reconstruct white matter tracts suggests regeneration of terminal fibers of the ipsilesional optic radiations in the patient. However, arrangement of the converse reconstruction of these tracts, which were seeded from the ipsilesional visual cortex to the intrahemispheric lateral geniculate body, remained disrupted. We further observed compromised structural characteristics, and changes in diffusion (measured using diffusion tensor indices) of white matter tracts in the patient connecting the visual cortex with frontal and temporal regions, and also in interhemispheric connectivity between visual cortices.
Conclusions: Cortical remapping and the disruption of communication between visual cortices and remote regions are consistent with our previous functional magnetic resonance imaging (fMRI) data showing imbalanced functional activity of the same regions in this patient (Rafique et al, 2016, Neurology, 87, 1493–1500). Long-term adaptive and disruptive changes in white matter connectivity may account for the rare nature of cases presenting with chronic and continuous visual hallucinations.York University Librarie
Are You "Tilting at Windmills" or Undertaking a Valid Clinical Trial?
In this review, several aspects surrounding the choice of a therapeutic intervention and the conduct of clinical trials are discussed. Some of the background for why human studies have evolved to their current state is also included. Specifically, the following questions have been addressed: 1) What criteria should be used to determine whether a scientific discovery or invention is worthy of translation to human application? 2) What recent scientific advance warrants a deeper understanding of clinical trials by everyone? 3) What are the different types and phases of a clinical trial? 4) What characteristics of a human disorder should be noted, tracked, or stratified for a clinical trial and what inclusion /exclusion criteria are important to enrolling appropriate trial subjects? 5) What are the different study designs that can be used in a clinical trial program? 6) What confounding factors can alter the accurate interpretation of clinical trial outcomes? 7) What are the success rates of clinical trials and what can we learn from previous clinical trials? 8) What are the essential principles for the conduct of valid clinical trials
Optimization of Electrode Configuration in Surface-Parallel Actuated Deformable Mirrors
Thin, lightweight and low-cost deformable mirrors have been recently proposed, providing a pertinent device for wavefront error correction. We present different approaches to optimize actuator arrangement. The design is optimized according to a given correction requirement, through the number of electrodes, their shape and location. A first method focuses on the compensation of a given optical aberration (astigmatism). A second method directly optimizes the correction of a set of optical modes, taking into account the voltage limitation. We will describe the optimization techniques and give some examples of applications and design performance
Human Rickettsial Pathogen Modulates Arthropod Organic Anion Transporting Polypeptide and Tryptophan Pathway for Its Survival in Ticks
The black-legged tick Ixodes scapularis transmits the human anaplasmosis agent, Anaplasma phagocytophilum. In this study, we show that A. phagocytophilum specifically up-regulates I. scapularis organic anion transporting polypeptide, isoatp4056 and kynurenine amino transferase (kat), a gene involved in the production of tryptophan metabolite xanthurenic acid (XA), for its survival in ticks. RNAi analysis revealed that knockdown of isoatp4056 expression had no effect on A. phagocytophilum acquisition from the murine host but affected the bacterial survival in tick cells. Knockdown of the expression of kat mRNA alone or in combination with isoatp4056 mRNA significantly affected A. phagocytophilum survival and isoatp4056 expression in tick cells. Exogenous addition of XA induces isoatp4056 expression and A. phagocytophilum burden in both tick salivary glands and tick cells. Electrophoretic mobility shift assays provide further evidence that A. phagocytophilum and XA influences isoatp4056 expression. Collectively, this study provides important novel information in understanding the interplay between molecular pathways manipulated by a rickettsial pathogen to survive in its arthropod vector
Bullying at Work and Its Impact on Job Satisfaction: An Exploration of School Psychologists
Given the persistent national shortage of school psychologists, as well as their job retention concerns, likely related to burnout, it is necessary to examine any factors that negatively impact school psychologists’ job satisfaction. In this sample of 94 Pennsylvania school psychologists, the experience of being bullied at work was associated with diminished job satisfaction. Specifically, the independent variables of being bullying at work predicted 18.2% of the variance in job satisfaction in this sample, with verbal and indirect bullying the only types of bullying that contributed a significant amount of the variance. This study indicates that this issue should be closely monitored by management and addressed promptly
Fabrication Methods for Adaptive Deformable Mirrors
Previously, it was difficult to fabricate deformable mirrors made by piezoelectric actuators. This is because numerous actuators need to be precisely assembled to control the surface shape of the mirror. Two approaches have been developed. Both approaches begin by depositing a stack of piezoelectric films and electrodes over a silicon wafer substrate. In the first approach, the silicon wafer is removed initially by plasmabased reactive ion etching (RIE), and non-plasma dry etching with xenon difluoride (XeF2). In the second approach, the actuator film stack is immersed in a liquid such as deionized water. The adhesion between the actuator film stack and the substrate is relatively weak. Simply by seeping liquid between the film and the substrate, the actuator film stack is gently released from the substrate. The deformable mirror contains multiple piezoelectric membrane layers as well as multiple electrode layers (some are patterned and some are unpatterned). At the piezolectric layer, polyvinylidene fluoride (PVDF), or its co-polymer, poly(vinylidene fluoride trifluoroethylene P(VDF-TrFE) is used. The surface of the mirror is coated with a reflective coating. The actuator film stack is fabricated on silicon, or silicon on insulator (SOI) substrate, by repeatedly spin-coating the PVDF or P(VDFTrFE) solution and patterned metal (electrode) deposition. In the first approach, the actuator film stack is prepared on SOI substrate. Then, the thick silicon (typically 500-micron thick and called handle silicon) of the SOI wafer is etched by a deep reactive ion etching process tool (SF6-based plasma etching). This deep RIE stops at the middle SiO2 layer. The middle SiO2 layer is etched by either HF-based wet etching or dry plasma etch. The thin silicon layer (generally called a device layer) of SOI is removed by XeF2 dry etch. This XeF2 etch is very gentle and extremely selective, so the released mirror membrane is not damaged. It is possible to replace SOI with silicon substrate, but this will require tighter DRIE process control as well as generally longer and less efficient XeF2 etch. In the second approach, the actuator film stack is first constructed on a silicon wafer. It helps to use a polyimide intermediate layer such as Kapton because the adhesion between the polyimide and silicon is generally weak. A mirror mount ring is attached by using adhesive. Then, the assembly is partially submerged in liquid water. The water tends to seep between the actuator film stack and silicon substrate. As a result, the actuator membrane can be gently released from the silicon substrate. The actuator membrane is very flat because it is fixed to the mirror mount prior to the release. Deformable mirrors require extremely good surface optical quality. In the technology described here, the deformable mirror is fabricated on pristine substrates such as prime-grade silicon wafers. The deformable mirror is released by selectively removing the substrate. Therefore, the released deformable mirror surface replicates the optical quality of the underlying pristine substrate
Small Satellites: A Revolution in Space Science
This report describes the results of a study program sponsored by the Keck Institute
for Space Studies (KISS) at the California Institute of Technology to explore how small
satellite systems can uniquely enable new discoveries in space science. The
disciplines studied span astrophysics, heliophysics, and planetary science (including
NEOs, and other small bodies) based on remote and in-situ observations. The two
workshops and study period that comprised this program brought together space
scientists, engineers, technologists, mission designers, and program managers over 9
months. This invitation-only study program included plenary and subject matter
working groups, as well as short courses and lectures for the public. Our goal was to
conceive novel scientific observations, while identifying technical roadblocks, with the
vision of advancing a new era of unique explorations in space science achievable
using small satellite platforms from 200 kg down to the sub-kg level.
The study program participants focused on the role of small satellites to advance
space science at all levels from observational techniques through mission concept
design. Although the primary goal was to conceive mission concepts that may require
significant technology advances, a number of concepts realizable in the near-term
were also identified. In this way, one unexpected outcome of the study program
established the groundwork for the next revolution in space science, driven by small
satellites platforms, with a near-term and far-term focus.
There were a total of 35 KISS study participants across both workshops (July 16-20,
2012 and October 29-31, 2012) from 15 institutions including JPL, Caltech, JA /
PocketSpacecraft.com, MIT, UCLA, U. Texas at Austin, U. Michigan, USC, The
Planetary Society, Space Telescope Science Institute, Cornell, Cal Poly SLO, Johns
Hopkins University, NRL, and Tyvak LLC. The first workshop focused on identifying
new mission concepts while the second workshop explored the technology and
engineering challenges identified via a facilitated mission concept concurrent design
exercise. The Keck Institute limits the number of participants per workshop to at most
30 to encourage close interaction where roughly 20% involved in this study were
students.
This report is organized to communicate the outcome of the study program. It is also
meant to serve as a public document to inform the larger community of the role small
satellites can have to initiate a new program of exploration and discovery in space
science. As such, it includes recommendations that could inform programmatic
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decision making within space exploration agencies, both in the USA and
internationally, on the promise of low-cost, focused, and high impact science should a
strategic plan for small satellite space science be pursued. As such, the study
program organizers and all participants are available to respond to any aspect of this
report
Experimental Treatments for Spinal Cord Injury: What you Should Know
Experiencing a spinal cord injury (SCI) is extremely distressing, both physically and psychologically, and throws people into a complex, unfamiliar world of medical procedures, terminology, and decision making. You may have already had surgery to stabilize the spinal column and reduce the possibility of further damage. You are understandably distressed about the functions you may have lost below the level of spinal injury. You wish to recover any lost abilities as soon as possible. You, your family, or friends may have searched the Internet for treatments and cures
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