Partially Ionized Plasmas in Astrophysics Ballester, José Luis; Alexeev, Igor; Collados, Manuel ...
Space science reviews,
03/2018, Letnik:
214, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Partially ionized plasmas are found across the Universe in many different astrophysical environments. They constitute an essential ingredient of the solar atmosphere, molecular clouds, planetary ...ionospheres and protoplanetary disks, among other environments, and display a richness of physical effects which are not present in fully ionized plasmas. This review provides an overview of the physics of partially ionized plasmas, including recent advances in different astrophysical areas in which partial ionization plays a fundamental role. We outline outstanding observational and theoretical questions and discuss possible directions for future progress.
ATP-dependent chromatin remodelling enzymes (remodellers) regulate DNA accessibility in eukaryotic genomes. Many remodellers reposition (slide) nucleosomes, however, how DNA is propagated around the ...histone octamer during this process is unclear. Here we examine the real-time coordination of remodeller-induced DNA movements on both sides of the nucleosome using three-colour single-molecule FRET. During sliding by Chd1 and SNF2h remodellers, DNA is shifted discontinuously, with movement of entry-side DNA preceding that of exit-side DNA. The temporal delay between these movements implies a single rate-limiting step dependent on ATP binding and transient absorption or buffering of at least one base pair. High-resolution cross-linking experiments show that sliding can be achieved by buffering as few as 3 bp between entry and exit sides of the nucleosome. We propose that DNA buffering ensures nucleosome stability during ATP-dependent remodelling, and provides a means for communication between remodellers acting on opposite sides of the nucleosome.
Background:
Outcomes after transtibial pull-out repair for posterior meniscal root tears remain underreported, and factors that may affect outcomes are unknown.
Purpose/Hypothesis:
The purpose of ...this study was to compare patient-centered outcomes after transtibial pull-out repair for posterior root tears in patients <50 and ≥50 years of age. We hypothesized that improvement in function and activity level at minimum 2-year follow-up would be similar among patients <50 years of age compared with patients ≥50 years and among patients undergoing medial versus lateral root repairs.
Study Design:
Cohort study; Level of evidence, 3.
Methods:
Inclusion criteria were patients aged 18 years or older who underwent anatomic transtibial pull-out repair of the medial or lateral posterior meniscus root by a single surgeon. All patients were identified from a data registry consisting of prospectively collected data in a consecutive series. Cohorts were analyzed by age (<50 years n = 35 vs ≥50 years n = 15) and laterality (lateral n = 15 vs medial n = 35). Patients completed a subjective questionnaire preoperatively and at minimum of 2 years postoperatively (Lysholm, Tegner, Western Ontario and McMaster Universities Osteoarthritis Index WOMAC, 12-Item Short Form Health Survey SF-12, and patient satisfaction with outcome). Failure was defined as revision meniscal root repair or partial meniscectomy.
Results:
The analysis included 50 knees in 49 patients (16 females, 33 males; mean age, 38.3 years; mean body mass index, 26.6). Of the 50 knees, 45 were available for analysis. Three of 45 (6.7%) required revision surgery. All failures were in patients <50 years old, and all failures underwent medial root repair. No significant difference in failure was found based on age (P=.541) or laterality (P = .544). For age cohorts, Lysholm and WOMAC scores demonstrated significant postoperative improvement. For laterality cohorts, all functional scores significantly improved postoperatively. No significant difference was noted in postoperative Lysholm, WOMAC, SF-12, Tegner, or patient satisfaction scores for the age cohort or the laterality cohort.
Conclusion:
Outcomes after posterior meniscal root repair significantly improved postoperatively and patient satisfaction was high, regardless of age or meniscal laterality. Patients <50 years had outcomes similar to those of patients ≥50 years, as did patients who underwent medial versus lateral root repair. Transtibial double-tunnel pull-out meniscal root repair provided improvement in function, pain, and activity level, which may aid in delayed progression of knee osteoarthritis.
Abstract We describe the Stagger code for simulations of magnetohydrodynamic (MHD) systems. This is a modular code with a variety of physics modules that will let the user run simulations of deep ...stellar atmospheres, sunspot formation, stellar chromospheres and coronae, proto-stellar disks, star formation from giant molecular clouds, and even galaxy formation. The Stagger code is efficiently and highly parallelizable, enabling such simulations with large ranges of both spatial and temporal scales. We describe the methodology of the code and present the most important of the physics modules, as well as its input and output variables. We show results of a number of standard MHD tests to enable comparison with other, similar codes. In addition, we provide an overview of tests that have been carried out against solar observations, ranging from spectral line shapes, spectral flux distribution, limb darkening, intensity and velocity distributions of granulation, to seismic power spectra and the excitation of p -modes. The Stagger code has proven to be a high-fidelity code with a large range of uses.
Transdiagnostic factors of mental disorders Krueger, Robert F.; Eaton, Nicholas R.
World psychiatry,
February 2015, 2015-Feb, 2015-02-00, 20150201, Letnik:
14, Številka:
1
Journal Article
Bioelectronics herald the rise of the cyborg Service, Robert F.
Science (American Association for the Advancement of Science),
12/2017, Letnik:
358, Številka:
6368
Journal Article
Recenzirano
Flexible plastic electronics can be wedded to brain tissue to monitor neural chatter.
Researchers are ushering in a new era in bioelectronics, developing electronics that can be integrated seamlessly ...into nervous tissue. Such devices could lead to innovative treatments in humans for everything from blindness and paralysis to brain diseases such as Parkinson's and Alzheimer's. For now, the researchers are working in animals, and they are mostly just listening to neural activity to understand the brain. But because newly designed electrodes can carry inputs as well as outputs, the day when bioelectronics will not just monitor animal behavior, but also control it, is not far off. These advances are beginning to dissolve the boundary between living organisms and the outside world.
Summary Background People with chronic tetraplegia, due to high-cervical spinal cord injury, can regain limb movements through coordinated electrical stimulation of peripheral muscles and nerves, ...known as functional electrical stimulation (FES). Users typically command FES systems through other preserved, but unrelated and limited in number, volitional movements (eg, facial muscle activity, head movements, shoulder shrugs). We report the findings of an individual with traumatic high-cervical spinal cord injury who coordinated reaching and grasping movements using his own paralysed arm and hand, reanimated through implanted FES, and commanded using his own cortical signals through an intracortical brain–computer interface (iBCI). Methods We recruited a participant into the BrainGate2 clinical trial, an ongoing study that obtains safety information regarding an intracortical neural interface device, and investigates the feasibility of people with tetraplegia controlling assistive devices using their cortical signals. Surgical procedures were performed at University Hospitals Cleveland Medical Center (Cleveland, OH, USA). Study procedures and data analyses were performed at Case Western Reserve University (Cleveland, OH, USA) and the US Department of Veterans Affairs, Louis Stokes Cleveland Veterans Affairs Medical Center (Cleveland, OH, USA). The study participant was a 53-year-old man with a spinal cord injury (cervical level 4, American Spinal Injury Association Impairment Scale category A). He received two intracortical microelectrode arrays in the hand area of his motor cortex, and 4 months and 9 months later received a total of 36 implanted percutaneous electrodes in his right upper and lower arm to electrically stimulate his hand, elbow, and shoulder muscles. The participant used a motorised mobile arm support for gravitational assistance and to provide humeral abduction and adduction under cortical control. We assessed the participant's ability to cortically command his paralysed arm to perform simple single-joint arm and hand movements and functionally meaningful multi-joint movements. We compared iBCI control of his paralysed arm with that of a virtual three-dimensional arm. This study is registered with ClinicalTrials.gov , number NCT00912041. Findings The intracortical implant occurred on Dec 1, 2014, and we are continuing to study the participant. The last session included in this report was Nov 7, 2016. The point-to-point target acquisition sessions began on Oct 8, 2015 (311 days after implant). The participant successfully cortically commanded single-joint and coordinated multi-joint arm movements for point-to-point target acquisitions (80–100% accuracy), using first a virtual arm and second his own arm animated by FES. Using his paralysed arm, the participant volitionally performed self-paced reaches to drink a mug of coffee (successfully completing 11 of 12 attempts within a single session 463 days after implant) and feed himself (717 days after implant). Interpretation To our knowledge, this is the first report of a combined implanted FES+iBCI neuroprosthesis for restoring both reaching and grasping movements to people with chronic tetraplegia due to spinal cord injury, and represents a major advance, with a clear translational path, for clinically viable neuroprostheses for restoration of reaching and grasping after paralysis. Funding National Institutes of Health, Department of Veterans Affairs.
Unlike advertising in traditional media, a mobile platform's in‐app advertising market exhibits two unique features—split structure of the mobile platform with a platform owner and an app developer ...jointly provisioning in‐app advertising, and agency pricing for app sales. We develop a two‐sided market model to analyze the role of these two unique features in determining the platform owner's optimal advertising revenue‐sharing contract. Our results reveal an interesting N‐shaped dynamic regarding the platform owner's optimal choice of her ad revenue share with respect to the overall advertisers’ valuation of in‐app ads. We identify a between‐agent subsidization strategy for the platform owner, where she finds it optimal to subsidize the developer via the advertising channel, leading to greater profits for both of them. We find that the advertising revenue‐sharing contract under agency pricing for app sales leads to a higher app price than would be offered by the integrated platform found in traditional advertising. However, the ad price is coordinated under the platform owner's optimal choice of ad revenue share when she obtains revenue from both the advertising and app sales channels, leading to an alignment of her interest with the app developer's on ad level.
Controlling the complex spatio-temporal dynamics underlying life-threatening cardiac arrhythmias such as fibrillation is extremely difficult, because of the nonlinear interaction of excitation waves ...in a heterogeneous anatomical substrate. In the absence of a better strategy, strong, globally resetting electrical shocks remain the only reliable treatment for cardiac fibrillation. Here we establish the relationship between the response of the tissue to an electric field and the spatial distribution of heterogeneities in the scale-free coronary vascular structure. We show that in response to a pulsed electric field, E, these heterogeneities serve as nucleation sites for the generation of intramural electrical waves with a source density ρ(E) and a characteristic time, τ, for tissue depolarization that obeys the power law τ ∝ E(α). These intramural wave sources permit targeting of electrical turbulence near the cores of the vortices of electrical activity that drive complex fibrillatory dynamics. We show in vitro that simultaneous and direct access to multiple vortex cores results in rapid synchronization of cardiac tissue and therefore, efficient termination of fibrillation. Using this control strategy, we demonstrate low-energy termination of fibrillation in vivo. Our results give new insights into the mechanisms and dynamics underlying the control of spatio-temporal chaos in heterogeneous excitable media and provide new research perspectives towards alternative, life-saving low-energy defibrillation techniques.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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