5,077 research outputs found
A Learning Based Approach to Control Synthesis of Markov Decision Processes for Linear Temporal Logic Specifications
We propose to synthesize a control policy for a Markov decision process (MDP)
such that the resulting traces of the MDP satisfy a linear temporal logic (LTL)
property. We construct a product MDP that incorporates a deterministic Rabin
automaton generated from the desired LTL property. The reward function of the
product MDP is defined from the acceptance condition of the Rabin automaton.
This construction allows us to apply techniques from learning theory to the
problem of synthesis for LTL specifications even when the transition
probabilities are not known a priori. We prove that our method is guaranteed to
find a controller that satisfies the LTL property with probability one if such
a policy exists, and we suggest empirically with a case study in traffic
control that our method produces reasonable control strategies even when the
LTL property cannot be satisfied with probability one
Artificial micro-swimmers in simulated natural environments
Microswimmers, such as bacteria, are known to show different behaviours depending on their local environment. They identify spatial chemical gradients to find nutrient rich areas (chemotaxis) and interact with shear flows to accumulate in high shear regions. Recently, artificial microswimmers have been developed which mimic their natural counterparts in many ways. One of the exciting topics in this field is to study these artificial motors in several natural settings like the ones bacteria interact with. In this Focus article, we summarize recent observations of artificial swimmers in chemical gradients, shear flows and other interesting natural environments simulated in the lab using microfluidics and nanotechnology
Competing Demands for Time and Self-Care Behaviors, Processes of Care, and Intermediate Outcomes Among People With Diabetes: Translating Research Into Action for Diabetes (TRIAD)
ObjectiveTo determine whether competing demands for time affect diabetes self-care behaviors, processes of care, and intermediate outcomes.Research design and methodsWe used survey and medical record data from 5,478 participants in Translating Research Into Action for Diabetes (TRIAD) and hierarchical regression models to examine the cross-sectional associations between competing demands for time and diabetes outcomes, including self-management, processes of care, and intermediate health outcomes.ResultsFifty-two percent of participants reported no competing demands, 7% reported caregiving responsibilities only, 36% reported employment responsibilities only, and 6% reported both caregiving and employment responsibilities. For both women and men, employment responsibilities (with or without caregiving responsibilities) were associated with lower rates of diabetes self-care behaviors, worse processes of care, and, in men, worse HbA(1c).ConclusionsAccommodations for competing demands for time may promote self-management and improve the processes and outcomes of care for employed adults with diabetes
Antimony thin films demonstrate programmable optical non-linearity
The use of metals of nanometer dimensions to enhance and manipulate
light-matter interactions for a range of emerging plasmonics-enabled
nanophotonic and optoelectronic applications is an interesting, yet not highly
explored area of research outside of plasmonics1,2. Even more importantly, the
concept of an active metal, i.e. a metal that can undergo an optical
non-volatile transition has not been explored. Nanostructure-based applications
would have unprecedented impact on both the existing and future of optics with
the development of active and nonlinear optical tunabilities in single
elemental metals3-5. Compared to alloys, pure metals have the material
simplicity and uniformity; however single elemental metals have not been viewed
as tunable optical materials, although they have been explored as viable
electrically switchable materials. In this paper we demonstrate for the first
time that antimony (Sb), a pure metal, is optically distinguishable between two
programmable states as nanoscale thin films. We then show that these states are
stable at room temperature, and the states correspond to the crystalline and
amorphous phases of the metal. Crucially from an application standpoint, we
demonstrate both its optoelectronic modulation capabilities as well as speed of
switching using single sub-picosecond (ps) pulses. The simplicity of depositing
a single metal portends its potential for use in applications ranging from high
speed active metamaterials to photonic neuromorphic computing, and opens up the
possibility for its use in any optoelectronic application where metallic
conductors with an actively tunable state is important
Impact of obesity on surgical outcomes following laminectomy for spinal metastases
To determine the effect of obesity (body mass index >30 kg/m(2)) on perioperative morbidity and mortality after surgical decompression of spinal metastases. Methods: The American College of Surgeons National Surgical Quality Improvement Program database is a large multicenter clinical registry that collects preoperative risk factors, intraoperative variables, and 30-day postoperative morbidity and mortality outcomes from hospitals nationwide. Current Procedural Terminology codes were used to query the database for adults who underwent decompression with laminectomy for treatment of metastatic spinal lesions between 2010 and 2014. Patients were separated into 2 cohorts based on the presence of absence of obesity. Univariate analysis and multivariate logistic regression analysis were used to analyze the effect of obesity on perioperative morbidity and mortality. Results: There was a significantly higher rate of venous thromboembolism (VTE; obese 6.6% vs nonobese 4.2%; P = .01) and pulmonary complications (obese 2.6% vs nonobese 2.2%; P = .046) in the obese group compared with the nonobese group. The nonobese group had prolonged hospitalization (obese 62.0% vs nonobese 69.0%; P = .001) and a higher incidence of blood transfusions (obese 26.8% vs nonobese 34.2%; P < .001). On multivariate analysis, obesity was found to be an independent risk factor for VTE (odds ratio = 1.75, confidence interval = 1.17-2.63, P = .007). Conclusions: Obese patients were predisposed to an elevated risk of VTE following laminectomy for spinal metastases. Early postoperative mobilization and a low threshold to evaluate for perioperative VTE are important in these patients in order to appropriately diagnose and treat these complications and minimize morbidity93254259sem informaçãosem informaçã
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