A Reinforcement Learning Approach for the Multichannel Rendezvous Problem

In this paper, we consider the multichannel rendezvous problem in cognitive radio networks (CRNs) where the probability that two users hopping on the same channel have a successful rendezvous is a function of channel states. The channel states are modelled by two-state Markov chains that have a good state and a bad state. These channel states are not observable by the users. For such a multichannel rendezvous problem, we are interested in finding the optimal policy to minimize the expected time-to-rendezvous (ETTR) among the class of {\em dynamic blind rendezvous policies}, i.e., at the $t^{th}$ time slot each user selects channel $i$ independently with probability $p_i(t)$, $i=1,2, \ldots, N$. By formulating such a multichannel rendezvous problem as an adversarial bandit problem, we propose using a reinforcement learning approach to learn the channel selection probabilities $p_i(t)$, $i=1,2, \ldots, N$. Our experimental results show that the reinforcement learning approach is very effective and yields comparable ETTRs when comparing to various approximation policies in the literature.Comment: 5 pages, 9 figures. arXiv admin note: text overlap with arXiv:1906.1042

Increasing high-sensitive C-reactive protein level predicts peritonitis risk in chronic peritoneal dialysis patients

Abstract Background The aim of this study was to evaluate whether a high baseline level of high-sensitivity C-reactive protein (hs-CRP) or changes in the level predicts the risk of peritonitis in patients on continuous ambulatory peritoneal dialysis (CAPD). Methods A prospective, cross-sectional, case–control study was conducted in a single hospital-based PD unit. A total of 327 patients were included in the study. Serum hs-CRP was measured annually for 2 years. Patients were divided into 4 groups according to the changes in annual hs-CRP levels (at baseline and at 1 year intervals): group 1 (from &lt;5 mg/L to &lt;5 mg/L, n = 171), group 2 (from &lt;5 mg/L to ≥5 mg/L, n = 45), group 3 (from ≥5 mg/L to &lt;5 mg/L, n = 45), and group 4 (from ≥5 mg/L to ≥5 mg/L, n = 80). Demographics, biochemistry results, PD adequacy indices, and peritonitis risk were compared between the groups. Results The initial serum albumin level was similar in the 4 groups (p = 0.12). There was a negative linear correlation between the serial albumin change (∆alb) and serial hs-CRP change (∆hs-CRP; r = −0.154, p = 0.005). The hazard ratio (HR) for peritonitis was significantly higher in group 2 (HR = 1, reference) than in group 4 (HR = 0.401, 95% CI 0.209 − 0.769). Group 2 had a greater serum albumin decline rate (∆alb: –3% ± 9%) and hs-CRP elevation rate (∆hs-CRP: 835% ± 1232%) compared to those for the other groups. Conclusions A progressive increase in the hs-CRP level was associated with a corresponding decline in the serum albumin level. Progressive rather than persistently high levels of serum hs-CRP predicted peritonitis risk in CAPD patients. </jats:sec

Non-leisure time physical activity is an independent predictor of longevity for a Taiwanese elderly population: an eight-year follow-up study

<p>Abstract</p> <p>Background</p> <p>The aim of this study is to determine the relationship between leisure time physical activity (LTPA) and non-leisure time physical activity (NLTPA) on mortality among the elderly in Taiwan.</p> <p>Methods</p> <p>This is a prospective observational cohort study. We analyzed the mortality data from a cohort of 876 non-institutionalized community-dwelling men and women aged 65 years or over, who were recruited by stratified clustering random sampling from Tainan city and participated in the 1996 Elderly Medication Survey. Information about activities and other variables were collected by structured interviews at baseline in the participants' home. The Cox proportional hazards model and crude death rate were applied to estimate mortality risk.</p> <p>Results</p> <p>Among the 876 participants, 312 died during the follow-up period (1996-2004). In the unadjusted Cox regression model, subjects aged over 75, having difficulty in carrying out activities of daily living (ADLs), a BMI less than 18.5, a history of diabetes mellitus or stroke, without LTPA or being inactive in NLTPA, were found to have a higher risk of eight-year mortality. With the adjustment for age, gender, education level, habitual smoking and drinking, living status, BMI and medical history, the mortality was found to be higher among the sedentary subjects, either defined by lack of LTPA or NLTPA, with the hazard ratio of 1.27 (95% confidence interval [CI] = 0.97-1.66) and 1.45 (95% CI = 1.07-1.97), respectively. Furthermore, when both LTPA and NLTPA were put into the model simultaneously, NLTPA (HR = 1.40; 95% CI = 1.03-1.91) but not LTPA (HR = 1.21, 95% CI = 0.92-1.59) significantly predicted mortality during eight-year follow-up. In addition, subjects who were actively engaged in NLTPA had a lower mortality risk especially in subjects without performing LTPA.</p> <p>Conclusions</p> <p>NLTPA is an independent predictor of longevity among older people in Taiwan. A physically active lifestyle, especially engaged in NLTPA, is associated with lower mortality risk in the elderly population. We thus suggest that encouraging older people to keep on engaging in customary NLTPA is good for their health.</p

Discriminating Glucose Tolerance Status by Regions of Interest of Dual-Energy X-Ray Absorptiometry: Clinical Implications of Body Fat Distribution

WSTĘP. Zbadanie, czy ocena rozmieszczenia tkanki tłuszczowej w organizmie metodą absorpcjometrii promieniowania rentgenowskiego o podwójnej energii (DEXA, dual energy X-ray absorptiometry) może być pomocny w ocenie stanu tolerancji glukozy. MATERIAŁ I METODY. U 1015 badanych mieszkańców Chin (559 mężczyzn i 456 kobiet) zastosowano doustny test obciążenia glukozą (75,0 g). Na podstawie jego wyników wyodrębniono osoby o prawidłowej (NGT, normal glucose tolerance) i upośledzonej (IGT, impaired glucose tolerance) tolerancji glukozy oraz osoby, u których rozpoznano cukrzycę (DM, diabetes mellitus). Mierzono wysokość ciśnienia tętniczego i oceniano profil lipidowy. Na podstawie stosunku obwodu talii do bioder (WHR, waist-to-hip ratio) i wyników DEXA oceniano rozmieszczenie tkanki tłuszczowej u osób w poszczególnych grupach. WYNIKI. Rozmieszczenie tkanki tłuszczowej, wyrażone poprzez WHR oraz wskaźnik centralizacji, wykazało znamienną częściową korelację ze stężeniem hemoglobiny glikowanej, wysokością ciśnienia tętniczego i profilem lipidowym u wszystkich badanych. Po skorygowaniu wyników wobec wieku i wskaźnika masy ciała (BMI, body mass index), stwierdzono znamienne różnice częstości wszystkich sercowo-naczyniowych czynników ryzyka w poszczególnych grupach, z wyjątkiem stężenia cholesterolu całkowitego. W grupie DM odnotowano znamiennie wyż-sze wartości WHR i wskaźnika centralizacji przy niższej procentowo zawartości tkanki tłuszczowej w udach. Ponadto, pacjentów z grupy IGT charakteryzował wyższy wskaźnik centralizacji niż osoby z grupy NGT. Nie stwierdzono jednakże znamiennych różnic masy tkanek beztłuszczowych w porównywanych grupach. Po dokonaniu wieloczynnikowej analizy logistycznej regresji wskaźnik centralizacji pozostał istotnym czynnikiem umożliwiającym ocenę tolerancji glukozy, niezależnie od procentowej zawartości tkanki tłuszczowej w organizmie. WNIOSKI. Otyłość centralna wykazuje znamienną korelację z sercowo-naczyniowymi czynnikami ryzyka w grupach osób o różnej tolerancji glukozy. Indeks centralizacji, oceniany metodą DEXA, wydaje się lepszym wskaźnikiem upośledzenia tolerancji glukozy niż WHR, otyłość brzuszna czy uogólniona otyłość (wyrażone odpowiednio jako odsetek zawartości tłuszczu całkowitego lub BMI) w dużej grupie badanych Chińczyków.OBJECTIVE. To determine whether measuring body fat distribution by dual-energy X-ray a bsor ptio metry (DEXA) can be used to discriminate glucose tolerance status. RESEARCH DESIGN AND METHODS. Using a 75-g oral glucose tolerance test, a total of 1,015 Chinese subjects (559 men and 456 women) were categorized as having normal glucose tolerance (NGT), impaired glucose tolerance (IGT), or diabetes. Blood pre ssure and lipid profiles of these subjects were measured. Waist-to-hip ratio (WHR) and DEXA were used to evaluate the varying patterns of body fat distribution among the gro ups. RESULTS. Body fat distribution, as reflected by WHR and the centrality index, showed significant partial correlation coefficients with glycosylated hemoglobin, blood pressure, and lipid profiles in all subjects. After adjusting for age and BMI, there were significant differences among the three glycemic groups for all the cardiovascular risk factors except for total cholesterol level. The diabetic group had a significantly higher WHR and centrality index, but lower femoral fat percentage than the NGT and IGT groups. The diabetic group also showed higher abdominal fat percentage than the NGT group. More over, the IGT group had a higher centrality index than the NGT group. However, no significant differences were found in the percentage of lean tissue mass among the three groups. Using multiple stepwise logistic regression models, the centrality index remained a significant factor for discriminating different glucose tolerance status independent of the percentage total body fat. CONCLUSIONS. Central obesity has shown significant correlation with cardio vascular risk factors among the three different glycemic groups. Centrality index measured by DEXA appears to be the better predictor of glucose intolerance, compared with WHR, abdominal fat, and general obesity (reflected by percentage total body fat or BMI) in a large cohort of the Chinese population

Realization of Polarization Control in High-Order Harmonic Generation

The nature of high-order harmonic generation process limits the harmonics emission to linear polarization. In this paper, we review the recent progress to generate elliptically or circularly polarized high-harmonic EUV pulses. We further demonstrate how complete control of polarization state of isolated high-harmonic pulse can be realized today by noncollinear focusing of two driving pulses with identical ellipticity but counter-rotating helicity. This paper opens a path towards the study of the fastest dynamics--down to attosecond time scales--in circular dichroism of magnetic materials, chiral molecules, and electronic spin motion.Taiwan Ministry of Science and Technology; Academia Sinica; Junta de Castilla y León; Ministerio de Economía y Competitividad; Leonardo Grant for Researchers and Cultural Creators, BBVA Foundation; Ministerio de Ciencia, Innovación y Universidades for a Ramón y Cajal; European Social Fund; Ministerio de Educación, Cultura y Deporte

Acute respiratory distress syndrome and acute myocarditis developed in a previously healthy adult with influenza B

BACKGROUND: Influenza B virus infection is generally considered to be mild and is rarely associated pulmonary cardiovascular involvement in adults. However fatal complications may occur. CASE PRESENTATION: A 43-year-old previously healthy Taiwanese male came to our emergency department due to high fever, chills, general malaise and myalgia for about 4 days. An influenza rapid test from a throat swab was negative. Chest radiography showed mild left lung infiltration and levofloxacin was prescribed. However, progressive shortness of breath and respiratory failure developed 48 h later after hospitalization. Emergent intubation was performed and he was transferred to the intensive care unit where oseltamivir (Tamiflu, Roche) 75 mg orally twice daily was given immediately. In the intensive care unit, cardiac catheterization revealed normal coronary arteries. However, a markedly elevated cardiac enzyme level (Troponin I level was up to 71.01 ng/ml), a positive cardiac magnetic resonance imaging findings and no coronary artery stenosis led to the diagnosis of acute myocarditis. Subsequent real-time polymerase chain reaction of endotracheal aspirates was positive for influenza B. His condition gradually improved and he was successfully weaned from the ventilator on day 22. He was discharged without prominent complications on day 35. CONCLUSION: Influenza B infection is not always a mild disease. Early detection, early administration of antiviral agents, appropriate antibiotics and best supportive care, is still the gold standard for patients such as the one reported

Continuum-based models and concepts for the transport of nanoparticles in saturated porous media: A state-of-the-science review

Environmental applications of nanoparticles (NP) increasingly result in widespread NP distribution within porous media where they are subject to various concurrent transport mechanisms including irreversible deposition, attachment/detachment (equilibrium or kinetic), agglomeration, physical straining, site-blocking, ripening, and size exclusion. Fundamental research in NP transport is typically conducted at small scale, and theoretical mechanistic modeling of particle transport in porous media faces challenges when considering the simultaneous effects of transport mechanisms. Continuum modeling approaches, in contrast, are scalable across various scales ranging from column experiments to aquifer. They have also been able to successfully describe the simultaneous occurrence of various transport mechanisms of NP in porous media such as blocking/straining or agglomeration/deposition/detachment. However, the diversity of model equations developed by different authors and the lack of effective approaches for their validation present obstacles to the successful robust application of these models for describing or predicting NP transport phenomena. This review aims to describe consistently all the important NP transport mechanisms along with their representative mathematical continuum models as found in the current scientific literature. Detailed characterizations of each transport phenomenon in regards to their manifestation in the column experiment outcomes, i.e., breakthrough curve (BTC) and residual concentration profile (RCP), are presented to facilitate future interpretations of BTCs and RCPs. The review highlights two NP transport mechanisms, agglomeration and size exclusion, which are potentially of great importance in controlling the fate and transport of NP in the subsurface media yet have been widely neglected in many existing modeling studies. A critical limitation of the continuum modeling approach is the number of parameters used upon application to larger scales and when a series of transport mechanisms are involved. We investigate the use of simplifying assumptions, such as the equilibrium assumption, in modeling the attachment/detachment mechanisms within a continuum modelling framework. While acknowledging criticisms about the use of this assumption for NP deposition on a mechanistic (process) basis, we found that its use as a description of dynamic deposition behavior in a continuum model yields broadly similar results to those arising from a kinetic model. Furthermore, we show that in two dimensional (2-D) continuum models the modeling efficiency based on the Akaike information criterion (AIC) is enhanced for equilibrium vs kinetic with no significant reduction in model performance. This is because fewer parameters are needed for the equilibrium model compared to the kinetic model. Two major transport regimes are identified in the transport of NP within porous media. The first regime is characterized by higher particle-surface attachment affinity than particle-particle attachment affinity, and operative transport mechanisms of physicochemical filtration, blocking, and physical retention. The second regime is characterized by the domination of particle-particle attachment tendency over particle-surface affinity. In this regime although physicochemical filtration as well as straining may still be operative, ripening is predominant together with agglomeration and further subsequent retention. In both regimes careful assessment of NP fate and transport is necessary since certain combinations of concurrent transport phenomena leading to large migration distances are possible in either case