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We consider a two-node queue modeled as a two-dimensional random walk. In particular, we consider the case that one or both queues have finite buffers. We develop an approximation scheme based on the Markov reward approach to error bounds in order to bound performance measures of such random walks. The approximation scheme is developed in terms of a perturbed random walk in which the transitions along the boundaries are different from those in the original model and the invariant measure of the perturbed random walk is of product-form. We then apply this approximation scheme to a tandem queue and some variants of this model, for the case that both buffers are finite. The modified approximation scheme and the corresponding applications for a two-node queueing system in which only one of the buffers has finite capacity have also been discussed.
We identified a pseudo-outbreak of Mycobacterium avium in an outpatient bronchoscopy clinic following an increase in clinic procedure volume. We terminated the pseudo-outbreak by increasing the frequency of automated endoscope reprocessors (AER) filter changes from quarterly to monthly. Filter changing schedules should depend on use rather than fixed time intervals.
Ice shelves play an important role in buttressing land ice from reaching the sea, thus restraining the rate of grounded ice loss. Long-period gravity-wave impacts excite vibrations in ice shelves that can expand pre-existing fractures and trigger iceberg calving. To investigate the spatial amplitude variability and propagation characteristics of these vibrations, a 34-station broadband seismic array was deployed on the Ross Ice Shelf (RIS) from November 2014 to November 2016. Two types of ice-shelf plate waves were identified with beamforming: flexural-gravity waves and extensional Lamb waves. Below 20 mHz, flexural-gravity waves dominate coherent signals across the array and propagate landward from the ice front at close to shallow-water gravity-wave speeds (~70 m s−1). In the 20–100 mHz band, extensional Lamb waves dominate and propagate at phase speeds ~3 km s−1. Flexural-gravity and extensional Lamb waves were also observed by a 5-station broadband seismic array deployed on the Pine Island Glacier (PIG) ice shelf from January 2012 to December 2013, with flexural wave energy, also detected at the PIG in the 20–100 mHz band. Considering the ubiquitous presence of storm activity in the Southern Ocean and the similar observations at both the RIS and the PIG ice shelves, it is likely that most, if not all, West Antarctic ice shelves are subjected to similar gravity-wave excitation.
One of the goals of soft robotics is the ability to interface with the human body. Traditionally, silicone materials have dominated the field of soft robotics. In order to shift to materials that are more compatible with the body, developments will have to be made into biodegradable and biocompatible soft robots. This investigation focused on developing gummy actuators which are biodegradable, edible, and tasty. Creating biodegradable and edible actuators can be both sold as an interactive candy product and also inform the design of implantable soft robotic devices. First, commercially available gelatin-based candies were recast into pneumatic actuators utilizing molds. Edible robotic devices were pneumatically actuated repeatedly (up to n=8 actuations) using a 150 psi power inflator. To improve upon the properties of actuators formed from commercially available candy, a novel gelatin-based formulation, termed the “Fordmula” was also developed and used to create functional actuators. To investigate the mechanics and functionality of the recast gummy material and the Fordmula, compression testing and biodegradation studies were performed. Mechanical compression tests showed that recast gummy materials had similar properties to commercially available candies and at low strain had similar behavior to traditional silicone materials. Degradation studies showed that actuation was possible within 15 minutes in a biologically relevant solution followed by complete dissolution of the actuator afterwards. A taste test with elementary aged children demonstrated the fun, edible, and educational appeal of the candy actuators. Edible actuator development was an entry and winning submission in the High School Division of the Soft Robotics Toolkit Design Competition hosted by Harvard University. Demonstration of edible soft robotic actuators created by middle and high school aged students shows the applicability of the Soft Robotics Toolkit for K12 STEM education.
The construction chronology of three of the earliest Dunhuang Mogao Grottoes (Caves 268, 272, and 275) has been the subject of ongoing debate for over half a century. This chronology is a crucial topic in terms of further understanding of the establishment of the Dunhuang Mogao Grottoes, early Buddhism in the Gansu corridor, and its relationship with Buddhism developed in the Central Plains. Building upon archaeological, art historical and radiocarbon (14C) dating studies, we integrate new 14C data with these previously published findings utilizing Bayesian statistical modeling to improve the chronological resolution of this issue. Thus, we determine that all three of these caves were constructed around AD 410–440, suggesting coeval rather than sequential construction.
The aim of this study was to explore perinatal and early postnatal outcomes in fetuses with prenatally diagnosed d-transposition of the great arteries and impacts of standardised prenatal consultation.
All fetuses with prenatally diagnosed d-transposition of the great arteries prospectively enrolled at South China cardiac centre from 2011 to 2015. Standardised prenatal consultation was introduced in 2013 and comprehensive measures were implemented, such as establishing fetal CHD Outpatient Consultation Service, performing standard prenatal consultation according to specifications, and establishing a multidisciplinary team with senior specialists performing in-person consultations. Continuous follow-up investigation was conducted. Perinatal and postnatal outcomes were compared before and after consultation including live birth, elective termination of pregnancy, spontaneous fetal death, stillbirths, referral for surgery, and survival.
In all, 146 fetuses were enrolled with 41 (28%) lost to follow-up. Among 105 remaining fetuses, 29 (28%) were live births and 76 (72%) were terminated. After consultation, live birth rate was higher (50 versus 33%) and termination rate was lower (50 versus 76%), although there was no statistical significance. Excluding three live births without postnatal d-transposition of the great arteries, 65% (17/26) underwent arterial switch operation within 30 days. A total of three in-hospital deaths occurred and during the 10-month follow-up period, one death was observed. In one case, the switch procedure was performed at 13 months and the infant survived. Out of eight infants without arterial switch operation, two died.
Live birth rate increased after consultation; however, termination remained high. Combining termination, patients without arterial switch operation, and operative mortality, outcomes of d-transposition of the great arteries infants can be improved. Standard consultation, multidisciplinary collaboration, and improved perinatal care are important to improve outcomes.
The shock between the colliding winds in binary systems containing two massive stars accelerates particles to relativistic energies. These energetic particles can produce observable non-thermal radiation from the radio to γ-rays. The important physical processes in such systems are very similar to those we have proposed for non-thermal emissions from single hot stars, which have shocks generated by instabilities in the radiatively driven stellar winds. This paper discusses the theory and observations of non-thermal radiation in the radio, X-ray, and γ-ray regions from both single stars and massive binaries. Similarities and differences between the two types of systems are outlined. We discuss two important physical effects that apparently have been neglected in previous theoretical work on colliding wind binaries.
A few studies have evaluated the impact of clinical trial results on practice in paediatric cardiology. The Infant Single Ventricle (ISV) Trial results published in 2010 did not support routine use of the angiotensin-converting enzyme inhibitor enalapril in infants with single-ventricle physiology. We sought to assess the influence of these findings on clinical practice.
A web-based survey was distributed via e-mail to over 2000 paediatric cardiologists, intensivists, cardiothoracic surgeons, and cardiac advance practice nurses during three distribution periods. The results were analysed using McNemar’s test for paired data and Fisher’s exact test.
The response rate was 31.5% (69% cardiologists and 65% with >10 years of experience). Among respondents familiar with trial results, 74% reported current practice consistent with trial findings versus 48% before trial publication (p<0.001); 19% used angiotensin-converting enzyme inhibitor in this population “almost always” versus 36% in the past (p<0.001), and 72% reported a change in management or improved confidence in treatment decisions involving this therapy based on the trial results. Respondents familiar with trial results (78%) were marginally more likely to practise consistent with the trial results than those unfamiliar (74 versus 67%, p=0.16). Among all respondents, 28% reported less frequent use of angiotensin-converting enzyme inhibitor over the last 3 years.
Within 5 years of publication, the majority of respondents was familiar with the Infant Single Ventricle Trial results and reported less frequent use of angiotensin-converting enzyme inhibitor in single-ventricle infants; however, 28% reported not adjusting their clinical decisions based on the trial’s findings.
To evaluate the greatest impact that sea-ice anomalies around Antarctica could have on the global atmosphere, 15 year seasonal cycle simulations are conducted with the U.S. National Center for Atmospheric Research Community Climate Model version 2.1. Sensitivity simulations are performed with the following conditions: (1) all sea ice in the Southern Hemisphere is replaced by year-round open water, but the permanent ice shelves are retained (NSIS); and (2) all sea ice in the Southern Hemisphere and the major ice shelves are removed and replaced by open water (NISH). The results are compared to a standard run (CNT) with boundary conditions set for the present climate. The comparison shows that trains of positive and negative anomalies in zonal-mean fields extend into the tropical latitudes of the Northern Hemisphere. Anomalies are largest during April-October. The additional removal of the ice shelves in NISH enhances the response, as zonally averaged anomalies are similar in pattern to those in NSIS but are roughly twice as large poleward of 50° S, and only slightly larger farther north. Anomalies in the eddy fields are found in both hemispheres. in NISH, and to a lesser degree in NSIS. these anomalies appear to be related to a delayed northern advance over China during June of the rain front associated with the summer monsoon. Consequently, precipitation is enhanced in middle and southern China and decreased in northern China. Observational analyses have also found links between Antarctic sea-ice variations and modulations of the East Asian monsoon.
Using the Healthy Eating Index-2010 (HEI-2010), the present study aimed to examine diet quality and the impact of overall diet quality and its components on central obesity among Mexican-American men and women.
Cross-sectional data from NHANES 1999–2012 were used. The HEI-2010 data, including twelve components for a total score of 100, were collected with a 24 h recall interview. Central obesity was defined as a waist circumference of ≥88 cm for women and ≥102 cm for men. Weighted logistic regressions were performed to assess associations between HEI-2010 scores and central obesity.
National Health and Nutrition Examination Survey (NHANES) 1999–2012.
A total of 6847 Mexican Americans aged ≥20 years with reliable dietary recall status and non-pregnancy status.
Higher HEI-2010 total score was associated with lower odds of central obesity in Mexican-American men (OR; 95 % CI=0·98; 0·98, 1·00). Among all Mexican Americans, one-unit higher score of total fruit and sodium (i.e. lower level of intake) was associated with 4 % (0·96; 0·93, 0·99) and 2 % (0·98; 0·96, 0·99) lower odds of central obesity, respectively. However, a higher total proteins score was associated with higher odds of central obesity (1·08; 1·00, 1·16). In gender-specific analyses, a higher whole fruit or sodium score was inversely associated with central obesity in men but not in women.
HEI-2010 scores of total fruit and sodium were inversely associated with central obesity among all Mexican Americans. However, total proteins score and central obesity was positively associated. In Mexican-American men, HEI-2010 total and whole fruit scores were inversely associated with central obesity.
The validity and reliability of the informant AD8 in primary healthcare has not been established. Therefore, the present study examined the validity and reliability of the informant AD8 in government subsidized primary healthcare centers in Singapore.
Eligible patients (≥60 years old) were recruited from primary healthcare centers and their informants received the AD8. Patient-informant dyads who agreed for further cognitive assessments received the Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), Clinical Dementia Rating (CDR), and a locally validated formal neuropsychological battery at a research center in a tertiary hospital.
1,082 informants completed AD8 assessment at two primary healthcare centers. Of these, 309 patients-informant dyads were further assessed, of whom 243 (78.6%) were CDR = 0; 22 (7.1%) were CDR = 0.5; and 44 (14.2%) were CDR≥1. The mean administration time of the informant AD8 was 2.3 ± 1.0 minutes. The informant AD8 demonstrated good internal consistency (Cronbach's α = 0.85); inter-rater reliability (Intraclass Correlation Coefficient (ICC) = 0.85); and test–retest reliability (weighted κ = 0.80). Concurrent validity, as measured by the correlation between total AD8 scores and CDR global (R = 0.65, p < 0.001), CDR sum of boxes (R = 0.60, p < 0.001), MMSE (R = −0.39, p < 0.001), MoCA (R = −0.41, p < 0.001), as well as the formal neuropsychological battery (R = −0.46, p < 0.001), was good and consistent with previous studies. Construct validity, as measured by convergent validity (R ≥ 0.4) between individual items of AD8 with CDR and neuropsychological domains was acceptable.
The informant AD8 demonstrated good concurrent and construct validity and is a reliable measure to detect cognitive dysfunction in primary healthcare.
To describe and compare the mortality associated with nosocomial pneumonia due to Pseudomonas aeruginosa (Pa-NP) according to pneumonia classification (community-onset pneumonia [COP], hospital-acquired pneumonia [(HAP], and ventilator-associated pneumonia [VAP]).
We conducted a retrospective cohort study of adults with Pa-NP. We compared mortality for Pa-NP among patients with COP, HAP, and VAP and used logistic regression to identify risk factors for hospital mortality and inappropriate initial antibiotic therapy (IIAT).
Twelve acute care hospitals in 5 countries (United States, 3; France, 2; Germany, 2; Italy, 2; and Spain, 3).
A total of 742 patients with Pa-NP.
Hospital mortality was greater for those with VAP (41.9%) and HAP (40.1%) compared with COP (24.5%) (P<.001). In multivariate analyses, independent predictors of hospital mortality differed by pneumonia classification (COP: need for mechanical ventilation and intensive care; HAP: multidrug-resistant isolate; VAP: IIAT, increasing age, increasing Charlson comorbidity score, bacteremia, and use of vasopressors). Presence of multidrug resistance was identified as an independent predictor of IIAT for patients with COP and HAP, whereas recent antibiotic administration was protective in patients with VAP.
Among patients with Pa-NP, pneumonia classification identified patients with different risks for hospital mortality. Specific risk factors for hospital mortality also differed by pneumonia classification and multidrug resistance appeared to be an important risk factor for IIAT. These findings suggest that pneumonia classification for P. aeruginosa identifies patients with different mortality risks and specific risk factors for outcome and IIAT.
Infect Control Hosp Epidemiol 2015;36(10):1190–1197
We consider the invariant measure of homogeneous random walks in the quarter-plane. In particular, we consider measures that can be expressed as a finite linear combination of geometric terms and present conditions on the structure of these linear combinations such that the resulting measure may yield an invariant measure of a random walk. We demonstrate that each geometric term must individually satisfy the balance equations in the interior of the state space and further show that the geometric terms in an invariant measure must have a pairwise-coupled structure. Finally, we show that at least one of the coefficients in the linear combination must be negative.