On the Gittins index in the M/G/1 queue

For an M/G/1 queue with the objective of minimizing the mean number of jobs in the system, the Gittins index rule is known to be optimal among the set of non-anticipating policies. We develop properties of the Gittins index. For a single-class queue it is known that when the service time distribution is of type Decreasing Hazard Rate (New Better than Used in Expectation), the Foreground-Background (First-Come-First-Served) discipline is optimal. By utilizing the Gittins index approach, we show that in fact, Foreground-Background and First-Come-First-Served are optimal if and only if the service time distribution is of type Decreasing Hazard Rate and New Better than Used in Expectation, respectively. For the multi-class case, where jobs of different classes have different service distributions, we obtain new results that characterize the optimal policy under various assumptions on the service time distributions. We also investigate distributions whose hazard rate and mean residual lifetime are not monotonic. © Springer Science+Business Media, LLC 2009

Canopy uptake dominates nighttime carbonyl sulfide fluxes in a boreal forest

Nighttime vegetative uptake of carbonyl sulfide (COS) can exist due to the incomplete closure of stomata and the light independence of the enzyme carbonic anhydrase, which complicates the use of COS as a tracer for gross primary productivity (GPP). In this study we derived nighttime COS fluxes in a boreal forest (the SMEAR II station in Hyytiälä, Finland; 61°51′ N, 24°17′ E; 181 m a.s.l.) from June to November 2015 using two different methods: eddy-covariance (EC) measurements (FCOS-EC) and the radon-tracer method (FCOS-Rn). The total nighttime COS fluxes averaged over the whole measurement period were −6.8 ± 2.2 and −7.9 ± 3.8 pmol m−2 s−1 for FCOS-Rn and FCOS-EC, respectively, which is 33–38 % of the average daytime fluxes and 21 % of the total daily COS uptake. The correlation of 222Rn (of which the source is the soil) with COS (average R2  =  0.58) was lower than with CO2 (0.70), suggesting that the main sink of COS is not located at the ground. These observations are supported by soil chamber measurements that show that soil contributes to only 34–40 % of the total nighttime COS uptake. We found a decrease in COS uptake with decreasing nighttime stomatal conductance and increasing vapor-pressure deficit and air temperature, driven by stomatal closure in response to a warm and dry period in August. We also discuss the effect that canopy layer mixing can have on the radon-tracer method and the sensitivity of (FCOS-EC) to atmospheric turbulence. Our results suggest that the nighttime uptake of COS is mainly driven by the tree foliage and is significant in a boreal forest, such that it needs to be taken into account when using COS as a tracer for GPP

Characterization of air ions in boreal forest air during BIOFOR III campaign

International audienceThe behavior of the concentration of positive small (or cluster) air ions and naturally charged nanometer aerosol particles (aerosol ions) has been studied on the basis of measurements carried out in a boreal forest at the Hyytiälä SMEAR station, Finland, during the BIOFOR III campaign in spring 1999. Statistical characteristics of the concentrations of cluster ions, two classes of aerosol ions of the sizes of 2.5?8 nm and 8?ca 20 nm and the quantities that determine the balance of small ions in the atmosphere have been given for the nucleation event days and non-event days. The dependence of small ion concentration on the ion loss (sink) due to aerosol particles was investigated applying a model of bipolar diffusion charging of particles by small ions. The small ion concentration and the ion sink were closely correlated (correlation coefficient 87%) when the fog events and the hours of high relative humidity (above 97%), as well as nocturnal calms and weak wind (wind speed-1 had been excluded. In the case of nucleation burst events, variations in the concentration of small positive ions were in accordance with the changes caused by the ion sink due to aerosols; no clear indication of positive ion depletion by ion-induced nucleation was found. The estimated average ionization rate of air at the Hyytiälä station in early spring, when the ground was partly covered with snow, was about 4.8 ion pairs cm-3 s-1. The study of the charging state of nanometer aerosol particles (2.5?8 nm) revealed a strong correlation (correlation coefficient 88%) between the concentrations of particles and their charged fraction (positive air ions) during nucleation bursts. The estimated charged fraction of particles, which varied from 3% to 6% considering various nucleation event days, confirms that these particles are almost quasi-steady state charged. Also the particles and air ions in the size range of 8?ca 20 nm showed a good qualitative consistency; the correlation coefficient was 92%

Characterization of positive air ions in boreal forest air at the Hyytiälä SMEAR station

International audienceThe behavior of the concentration of positive small (or cluster) air ions and naturally charged nanometer aerosol particles (aerosol ions) has been studied on the basis of measurements carried out in a boreal forest at the Hyytiälä SMEAR station, Finland, during the BIOFOR III campaign in spring 1999. Statistical characteristics of the concentrations of cluster ions, two classes of aerosol ions of the sizes of 2.5?8 nm and 8?ca. 20 nm and the quantities that determine the balance of small ions in the atmosphere have been given for the nucleation event days and non-event days. The dependence of small ion concentration on the ion loss (sink) due to aerosol particles was investigated applying a model of bipolar diffusion charging of particles by small ions. The small ion concentration and the ion sink were closely correlated (correlation coefficient ?87%) when the fog events and the hours of high relative humidity (above 95%), as well as nocturnal calms and weak wind (wind speed ?1) had been excluded. However, an extra ion loss term presumably due to small ion deposition on coniferous forest with a magnitude equal to the average ion loss to pre-existing particles is needed to explain the observations. Also the hygroscopic growth correction of measured aerosol particle size distributions was found to be necessary for proper estimation of the ion sink. In the case of nucleation burst events, variations in the concentration of small positive ions were in accordance with the changes caused by the ion sink due to aerosols; no clear indication of positive ion depletion by ion-induced nucleation was found. The estimated average ionization rate of the air at the Hyytiälä station in early spring, when the ground was partly covered with snow, was about 6 ion pairs cm?3 s?1. The study of the charging state of nanometer aerosol particles (2.5?8 nm) revealed a strong correlation (correlation coefficient 88%) between the concentrations of particles and positively charged particles (positive air ions) during nucleation bursts. The estimated charged fraction of particles, which varied from 3% to 6% considering various nucleation event days, confirms that these particles are almost quasi-steady state charged. Also the particles and air ions in the size range of 8?ca. 20 nm showed a good qualitative consistency; the correlation coefficient was 92%

TransCom N2O model inter-comparison - Part 2:Atmospheric inversion estimates of N2O emissions

This study examines N2O emission estimates from five different atmospheric inversion frameworks based on chemistry transport models (CTMs). The five frameworks differ in the choice of CTM, meteorological data, prior uncertainties and inversion method but use the same prior emissions and observation data set. The posterior modelled atmospheric N2O mole fractions are compared to observations to assess the performance of the inversions and to help diagnose problems in the modelled transport. Additionally, the mean emissions for 2006 to 2008 are compared in terms of the spatial distribution and seasonality. Overall, there is a good agreement among the inversions for the mean global total emission, which ranges from 16.1 to 18.7 TgN yr(-1) and is consistent with previous estimates. Ocean emissions represent between 31 and 38% of the global total compared to widely varying previous estimates of 24 to 38%. Emissions from the northern mid- to high latitudes are likely to be more important, with a consistent shift in emissions from the tropics and subtropics to the mid- to high latitudes in the Northern Hemisphere; the emission ratio for 0-30A degrees N to 30-90A degrees N ranges from 1.5 to 1.9 compared with 2.9 to 3.0 in previous estimates. The largest discrepancies across inversions are seen for the regions of South and East Asia and for tropical and South America owing to the poor observational constraint for these areas and to considerable differences in the modelled transport, especially inter-hemispheric exchange rates and tropical convective mixing. Estimates of the seasonal cycle in N2O emissions are also sensitive to errors in modelled stratosphere-to-troposphere transport in the tropics and southern extratropics. Overall, the results show a convergence in the global and regional emissions compared to previous independent studies

DSP p.(Thr2104Glnfs*12) variant presents variably with early onset severe arrhythmias and left ventricular cardiomyopathy

Background Dilated cardiomyopathy (DCM) is a condition characterized by dilatation and systolic dysfunction of the left ventricle in the absence of severe coronary artery disease or abnormal loading conditions. Mutations in the titin (TTN) and lamin A/C (LMNA) genes are the two most significant contributors in familial DCM. Previously mutations in the desmoplakin (DSP) gene have been associated with arrhythmogenic right ventricular cardiomyopathy (ARVC) and more recently with DCM. Methods We describe the cardiac phenotype related to a DSP mutation which was identified in ten unrelated Finnish index patients using next-generation sequencing. Sanger sequencing was used to verify the presence of this DSP variant in the probands' relatives. Medical records were obtained, and clinical evaluation was performed. Results We identified DSP c.6310delA, p.(Thr2104Glnfs*12) variant in 17 individuals of which 11 (65%) fulfilled the DCM diagnostic criteria. This pathogenic variant presented with left ventricular dilatation, dysfunction and major ventricular arrhythmias. Two patients showed late gadolinium enhancement (LGE) and myocardial edema on cardiac magnetic resonance imaging (MRI) that may suggest inflammatory process at myocardium. Conclusions The patients diagnosed with DCM showed an arrhythmogenic phenotype as well as SCD at young age supporting the recently proposed concept of arrhythmogenic cardiomyopathy. This study also demonstrates relatively low penetrance of truncating DSP variant in the probands' family members by the age of 40. Further studies are needed to elucidate the possible relations between myocardial inflammation and pathogenic DSP variants.Peer reviewe

Prevalence of Musculoskeletal Pain and Analgesic Treatment Among Community-Dwelling Older Adults : Changes from 1999 to 2019

Background Pain is undertreated in older populations. At the same time, increased use of opioids is of concern in the Western world. Aims We sought to analyze temporal trends in musculoskeletal pain and prescribed analgesic treatment among community-dwelling people aged 75-95 years using cross-sectional cohort data spanning 20 years. Methods The Helsinki Aging Study recruited random samples of people aged 75, 80, 85, 90, and 95 years in 1999, 2009, and 2019. In total, 5707 community-dwelling persons participated in the study. The participants reported their medical diagnoses, regular prescription medications, and the presence of back pain or joint pain within the last 2 weeks (never, sometimes, or daily). We compared analgesic use among participants reporting and not reporting musculoskeletal pain in 1999, 2009, and 2019. Results Of the participants, 57-61% reported intermittent or daily musculoskeletal pain. The percentage receiving a prescribed daily analgesic increased from 9% in 1999 to 16% in 2019. The use of non-steroidal anti-inflammatory drugs (NSAIDs) decreased from 1999 to 2019, while the use of paracetamol increased from 2 to 11%. Opioids were taken by 2% in 1999 and 3% in 2019. Of those reporting daily musculoskeletal pain, 20%, 35%, and 32% received regular pain medication in 1999, 2009, and 2019, respectively. Conclusions Pain remains undertreated in the community-dwelling older population, although the use of regular prescribed analgesics increased between 1999 and 2019. The use of NSAIDs has decreased, while the use of paracetamol has increased. Daily opioid use has remained modest.Peer reviewe

Prevalence of Musculoskeletal Pain and Analgesic Treatment Among Community-Dwelling Older Adults : Changes from 1999 to 2019

Background Pain is undertreated in older populations. At the same time, increased use of opioids is of concern in the Western world. Aims We sought to analyze temporal trends in musculoskeletal pain and prescribed analgesic treatment among community-dwelling people aged 75-95 years using cross-sectional cohort data spanning 20 years. Methods The Helsinki Aging Study recruited random samples of people aged 75, 80, 85, 90, and 95 years in 1999, 2009, and 2019. In total, 5707 community-dwelling persons participated in the study. The participants reported their medical diagnoses, regular prescription medications, and the presence of back pain or joint pain within the last 2 weeks (never, sometimes, or daily). We compared analgesic use among participants reporting and not reporting musculoskeletal pain in 1999, 2009, and 2019. Results Of the participants, 57-61% reported intermittent or daily musculoskeletal pain. The percentage receiving a prescribed daily analgesic increased from 9% in 1999 to 16% in 2019. The use of non-steroidal anti-inflammatory drugs (NSAIDs) decreased from 1999 to 2019, while the use of paracetamol increased from 2 to 11%. Opioids were taken by 2% in 1999 and 3% in 2019. Of those reporting daily musculoskeletal pain, 20%, 35%, and 32% received regular pain medication in 1999, 2009, and 2019, respectively. Conclusions Pain remains undertreated in the community-dwelling older population, although the use of regular prescribed analgesics increased between 1999 and 2019. The use of NSAIDs has decreased, while the use of paracetamol has increased. Daily opioid use has remained modest.Peer reviewe

A Multi-Transistion CO Study of the "Antennae" Galaxies NGC4038/9

For the Antennae interacting galaxy pair, we have obtained high quality, fully sampled $^{12}$CO J=1-0, 2-1 and 3-2 maps of the regions surrounding the nuclei and the area of overlap between the two galaxies, with an angular resolution of 15" or 1.5 kpc. The $^{12}$CO J=1-0, 2-1, 3-2 emission all peak in the overlap region, which contains ~ 4 x 10^9 solar mass of molecular gas mass if the conventional X factor is used. Line emission at $^{13}$CO J=2-1 and 3-2 is detected at selected points in the two nuclei and the overlap region. Both the ^{12}CO/^{13}CO J=2-1 and 3-2 integrated intensity ratios are remarkably high in the overlap region. This is the first published case in which such high $^{12}$CO/$^{13}$CO J=2-1 and 3-2 ratios are found outside a galactic nucleus. Detailed LVG modeling indicates that the $^{12}$CO and ^{13}CO emission originate in different spatial components. Assuming a CO-to-H2 abundance ratio of $10^{-4}$, the X factor given by the LVG model is an order of magnitude lower than the conventional value for molecular clouds in the Milky Way. Accordingly, we suggest the possibility that the strong CO emission in the overlap region of the Antennae galaxies is associated with increased radiative efficiency, possibly caused by a large velocity dispersion within the individual molecular clouds. A comparison of the CO J=3-2 emission with the SCUBA 850 um continuum in the Antennae galaxies shows that the CO line emission contributes globally 46% of the 850 um continuum flux and that the ratio of $^{12}$CO J=3-2 to SCUBA 850 um flux varies by a factor of two across the system.Comment: Accepted by ApJ on Jan 2. 2003, and is also available on ApJ preprint site. To download the figures and tables, choose the format "other", then click on the "Download source" at the bottom of the format selector page. Some figures are in png or jpg format to save spac