2,499 research outputs found
Quantum vortex tunneling in thin films
Cuprate films offer a unique opportunity to observe vortex tunneling effects,
due to their unusually low superfluid density and short coherence length. Here,
we measure the magnetoresistance (\textit{MR}) due to vortex motion of a long
meander line of a superconducting film made of underdoped
. At low temperatures (\textit{T}), the \textit{MR}
shows a significant deviation from Arrhenius activation. The data is consistent
with two dimensional Variable Range Hopping (VRH) of single vortices, i.e.
. The VRH temperature scale depends on the
vortex tunneling rates between pinning sites. We discuss its magnitude with
respect to estimated parameters of the meander thin film.Comment: 5 figure
Semi-optimal Practicable Algorithmic Cooling
Algorithmic Cooling (AC) of spins applies entropy manipulation algorithms in
open spin-systems in order to cool spins far beyond Shannon's entropy bound. AC
of nuclear spins was demonstrated experimentally, and may contribute to nuclear
magnetic resonance (NMR) spectroscopy. Several cooling algorithms were
suggested in recent years, including practicable algorithmic cooling (PAC) and
exhaustive AC. Practicable algorithms have simple implementations, yet their
level of cooling is far from optimal; Exhaustive algorithms, on the other hand,
cool much better, and some even reach (asymptotically) an optimal level of
cooling, but they are not practicable. We introduce here semi-optimal
practicable AC (SOPAC), wherein few cycles (typically 2-6) are performed at
each recursive level. Two classes of SOPAC algorithms are proposed and
analyzed. Both attain cooling levels significantly better than PAC, and are
much more efficient than the exhaustive algorithms. The new algorithms are
shown to bridge the gap between PAC and exhaustive AC. In addition, we
calculated the number of spins required by SOPAC in order to purify qubits for
quantum computation. As few as 12 and 7 spins are required (in an ideal
scenario) to yield a mildly pure spin (60% polarized) from initial
polarizations of 1% and 10%, respectively. In the latter case, about five more
spins are sufficient to produce a highly pure spin (99.99% polarized), which
could be relevant for fault-tolerant quantum computing.Comment: 13 pages, 5 figure
Design approaches in technology enhanced learning
Design is a critical to the successful development of any interactive learning environment (ILE). Moreover, in technology enhanced learning (TEL), the design process requires input from many diverse areas of expertise. As such, anyone undertaking tool development is required to directly address the design challenge from multiple perspectives. We provide a motivation and rationale for design approaches for learning technologies that draws upon Simon's seminal proposition of Design Science (Simon, 1969). We then review the application of Design Experiments (Brown, 1992) and Design Patterns (Alexander et al., 1977) and argue that a patterns approach has the potential to address many of the critical challenges faced by learning technologists
Steady-State Analysis of Load Balancing with Coxian- Distributed Service Times
This paper studies load balancing for many-server ( servers) systems. Each
server has a buffer of size and can have at most one job in service and
jobs in the buffer. The service time of a job follows the Coxian-2
distribution. We focus on steady-state performance of load balancing policies
in the heavy traffic regime such that the normalized load of system is for We identify a set of policies that
achieve asymptotic zero waiting. The set of policies include several classical
policies such as join-the-shortest-queue (JSQ), join-the-idle-queue (JIQ),
idle-one-first (I1F) and power-of--choices (Po) with . The proof of the main result is based on Stein's method and state space
collapse. A key technical contribution of this paper is the iterative state
space collapse approach that leads to a simple generator approximation when
applying Stein's method
Learning design studio: educational practice as design inquiry of learning
Recently we are urged to transform education into an evidence based profession, and promote scientific standards or practice. These calls are not new – they seem to emerge every few years. We do not argue with their goal, but we contend that the suitable frame of reference is the paradigm of design science, rather than the common metaphor of medical research. This paper proposes Design Inquiry of Learning as a projection of educational design science into a professional domain, and offers the Learning Design Studio as a pedagogical manifestation of this approach. The learning design studio is a collaborative, blended, project based framework for training educators in effective and evidence-based use of educational technology. We present its theoretical underpinnings, note its fundamental principles and structures, and review three independent cases where it has been trialed. The results show that this model is effective in developing learners’ theoretical knowledge as well as their practical skills, and allows them to link the two. However, it requires a considerable commitment of both learners and tutors, and may not be applicable in more casual settings
Enhanced biomechanical closed kinetic chain therapy intervention in the rehabilitation of patients after total Hip Arthroplasty
Prospective Evaluation of the Ultrasound Signs Proposed for the Description of Uterine Niche in Nonpregnant Women
OBJECTIVES: To evaluate the new ultrasound-based signs for the diagnosis of post-cesarean section uterine niche in nonpregnant women. METHODS: We investigated prospectively a cohort of 160 consecutive women with one previous term cesarean delivery (CD) between December 2019 and 2020. All women were separated into two subgroups according to different stages of labor at the time of their CD: subgroup A (n = 109; 68.1%) for elective CD and CD performed in latent labor at a cervical dilatation (≤4 cm) and subgroup B (n = 51; 31.9%); for CD performed during the active stage of labor (>4 cm). RESULTS: Overall, the incidence of a uterine niche was significantly (P 3 mm in subgroup A than in subgroup B and a significant negative relationship was found between the RMT and the cervical dilatation at CD (r = -0.22; P = .008). CONCLUSIONS: Sonographic cesarean section scar assessment indicates that the type of CD and the stage of labor at which the hysterotomy is performed have an impact on the location of the scar and the scarification process including the niche formation and RMT
N-Acylethanolamine Acid Amidase (NAAA): Structure, Function, and Inhibition
N-Acylethanolamine acid amidase (NAAA) is an N-terminal cysteine hydrolase primarily found in the endosomal-lysosomal compartment of innate and adaptive immune cells. NAAA catalyzes the hydrolytic deactivation of palmitoylethanolamide (PEA), a lipid-derived peroxisome proliferator-activated receptor-α (PPAR-α) agonist that exerts profound anti-inflammatory effects in animal models. Emerging evidence points to NAAA-regulated PEA signaling at PPAR-α as a critical control point for the induction and the resolution of inflammation and to NAAA itself as a target for anti-inflammatory medicines. The present Perspective discusses three key aspects of this hypothesis: the role of NAAA in controlling the signaling activity of PEA; the structural bases for NAAA function and inhibition by covalent and noncovalent agents; and finally, the potential value of NAAA-targeting drugs in the treatment of human inflammatory disorders
Confinement Effects on the Kinetics and Thermodynamics of Protein Dimerization
In the cell, protein complexes form relying on specific interactions between
their monomers. Excluded volume effects due to molecular crowding would lead to
correlations between molecules even without specific interactions. What is the
interplay of these effects in the crowded cellular environment? We study
dimerization of a model homodimer both when the mondimers are free or tethered
to each other. We consider a structured environment: Two monomers first diffuse
into a cavity of size and then fold and bind within the cavity. The folding
and binding are simulated using molecular dynamics based on a simplified
topology based model. The {\it confinement} in the cell is described by an
effective molecular concentration . A two-state coupled folding
and binding behavior is found. We show the maximal rate of dimerization
occurred at an effective molecular concentration M which is a
relevant cellular concentration. In contrast, for tethered chains the rate
keeps at a plateau when .
For both the free and tethered cases, the simulated variation of the rate of
dimerization and thermodynamic stability with effective molecular concentration
agrees well with experimental observations. In addition, a theoretical argument
for the effects of confinement on dimerization is also made
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