Count Variables Research Articles

A Counting Process with Generalized Exponential Inter-Arrival Times

This paper introduces a new counting process which is based on Generalized Exponentially distributed inter-arrival times. The advantage of this new count model over the existing Poisson count model is that the hazard function of the inter arrival time distribution is non-constant, so that the distribution is duration dependent and hence, is able to model both under dispersed and over dispersed count data, as opposed to the exponentially distributed inter arrival time of the Poisson count model, which is not duration dependent and the corresponding count model is able to model only equidispersed data. Further, some properties of this model are explored. Simulation from this new model is performed to study the behavior of count probabilities, mean and variance of the model for different values of the parameter. Use of the proposed model is illustrated with the help of real life data sets on arrival times of patients at a clinic and on arrival times of customers at a departmental store.

Reliability of StepWatch Activity Monitor to Measure Locomotor Activity in Youth With Lower Limb Salvage.

The study purpose was to determine the minimum number of monitoring days necessary to reliably capture walking among individuals with lower limb salvage. Nineteen participants with lower limb salvage wore an ankle-mounted motion sensor over a 7-day period to obtain step counts. Generalizability theory was used to examine the variance components in step counts (G study) and to determine the appropriate length of activity monitoring using various combinations of days (D study). Mean step counts were higher on weekends than on weekdays. Fifty percent of the total variance in step counts was accounted for by interindividual variability in walking (D study). Eighty percent was reached individually with 4 weekdays, 2 weekend days, or 3 week days + weekend days. The study provides data for an appropriate monitoring method to track walking outcomes of rehabilitation for individuals with lower limb salvage.

Abstract 4272: A novel approach to differentiation of somatic vs. germline variants in liquid biopsies using a betabinomial model

Abstract Background: A recent large study found that over 2% of advanced cancer patients have unidentified germline alterations found incidentally during next-generation sequencing (NGS) for targetable somatic alterations. However, tissue-based NGS cannot definitively distinguish germline from somatic mutations without comparison to normal tissue. Because somatic variants typically occur in plasma at allele fractions 1-2 orders of magnitude lower than germline, liquid biopsy often enables differentiation of incidental germline mutations. Not uncommonly, high tumor burden or allelic imbalance from copy number variation or loss of heterozygosity complicates simplistic differentiation based on assumption of germline 50% allele frequency. We developed a novel statistical method for discriminating between somatic and germline variants in deep sequencing data, and applied to data generated from the Guardant 360 targeted cfDNA assay. Our model dynamically incorporates prior knowledge of germline SNP variants and observed allele frequencies within a sample, and gains power in larger panels like the GuardantOmni 500-gene assay. Methods: Our method uses common heterozygous SNPs to model local germline allele count behavior, and calls variants somatic if they deviate significantly from the observed germline mutant allele fraction (MAF). A betabinomial model is well suited to this problem, because it models both the mean and variance of mutant allele counts at common SNPs. This is important since simpler methods like fixed MAF cutoffs or Poisson models may not represent the variance in molecule counts appropriately. Results: We evaluated our method against variants from 361 clinical samples that were manually annotated by reviewers with expertise in cancer genomics. Of the 11,679 heterozygous variants considered in these samples, 7,221 (62%) had two or more common SNPs in the same gene, so that a local germline heterozygous MAF could be estimated and the betabinomial model could be applied. Using the manual annotation as ground truth, we created ROC curves for a classifier based on the betabinomial model with varying p-value cutoffs, as well as a classifier based on MAF cutoffs. The AUC for the betabinomial model was 0.996, as compared with an AUC of 0.985 for MAF cutoffs. The ROC curve allowed us to choose a betabinomial p-value cutoff that maintained a similar level of specificity as a 15% MAF cutoff (99.2% for MAF cutoff, 99% for betabinomial), but with significantly increased sensitivity (89% for MAF cutoff, 97% for betabinomial). Conclusions: We have developed a novel method for differentiation of somatic versus germline variants in a single plasma sample. Identifying incidental germline alterations in advanced cancer patients may identify new opportunities to apply targeted therapy such as PARP inhibitors for BRCA1/2, and may also serve to alert physicians and their patients to familial risk. Citation Format: Tracy Nance, Elena Helman, Carlo Artieri, Jennifer Yen, Thomas P. Slavin, Darya Chudova, Richard B. Lanman, AmirAli Talasaz. A novel approach to differentiation of somatic vs. germline variants in liquid biopsies using a betabinomial model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4272.

A Genomic Region Containing REC8 and RNF212B Is Associated with Individual Recombination Rate Variation in a Wild Population of Red Deer (Cervus elaphus).

Recombination is a fundamental feature of sexual reproduction, ensuring proper disjunction, preventing mutation accumulation and generating new allelic combinations upon which selection can act. However it is also mutagenic, and breaks up favorable allelic combinations previously built up by selection. Identifying the genetic drivers of recombination rate variation is a key step in understanding the causes and consequences of this variation, how loci associated with recombination are evolving and how they affect the potential of a population to respond to selection. However, to date, few studies have examined the genetic architecture of recombination rate variation in natural populations. Here, we use pedigree data from ∼ 2,600 individuals genotyped at ∼ 38,000 SNPs to investigate the genetic architecture of individual autosomal recombination rate in a wild population of red deer (Cervus elaphus). Female red deer exhibited a higher mean and phenotypic variance in autosomal crossover counts (ACC). Animal models fitting genomic relatedness matrices showed that ACC was heritable in females ( = 0.12) but not in males. A regional heritability mapping approach showed that almost all heritable variation in female ACC was explained by a genomic region on deer linkage group 12 containing the candidate loci REC8 and RNF212B, with an additional region on linkage group 32 containing TOP2B approaching genome-wide significance. The REC8/RNF212B region and its paralogue RNF212 have been associated with recombination in cattle, mice, humans and sheep. Our findings suggest that mammalian recombination rates have a relatively conserved genetic architecture in both domesticated and wild systems, and provide a foundation for understanding the association between recombination loci and individual fitness within this population.

Efficacy evaluation of preoperative intensity-modulated radiotherapy combined with concurrent chemotherapy in patients with locally advanced rectal cancer

Objective To evaluate the efficacy and adverse reactions of preoperative intensity-modulated radiotherapy (IMRT) combined with mFOLFOX6 chemotherapy regimen for locally advanced rectal cancer (LARC). Methods A total of 86 patients with LARC who received preoperative IMRT combined with chemotherapy in Shanxi Provincial Cancer Hospital from June 2010 to December 2012 were enrolled. The patients were randomly divided into 2 groups according to the random number table method. Forty-six patients were treated with mFOLFOX6 regimen (mFOLFOX6 group) and 40 patients were treated with fluorouracil (5-Fu) single drug injection (5-Fu group). The total dose of IMRT target region was 45-54 Gy, 25 times in total. Short-term efficacy, adverse reactions, survival and metastasis were evaluated respectively. χ2 test or Fisher test were used to compare the count variable. Kaplan-Meier method was used to calculate the survival rates and Log-rank was used to detect. Results The total follow-up rate was 97.67% (84/86). There were no statistical differences in the rate of resection (93.5% vs. 80.0%), pathological complete remission (pCR) rate (6.5% vs. 0) and 3-year overall survival (OS) rate (87.0% vs. 70.0%) in the mFOLFOX6 group and 5-Fu group respectively (all P > 0.05). Down-staging rate, 3-year disease free survival (DFS) rate and distant metastasis free survival (DMFS) rate in the mFOLFOX6 group were significantly higher than those in 5-Fu group (58.7% vs. 32.5%, 79.1% vs. 50.0%, 89.1% vs. 72.5%, all P < 0.05). Conclusions Preoperative IMRT combined with mFOLFOX6 regimen can decrease the preoperative staging of LARC patients, improve 3-year DFS rate and DMFS rate. The adverse reactions may increase, but it is tolerant. Key words: Rectal neoplasms; Radiotherapy, intensity-modulated; Drug therapy, combination

Participation vs. Effectiveness of Paid Endorsers in Social Advertising Campaigns: A Field Experiment

We investigate the participation and effectiveness of paid endorsers in viral-for-hire social advertising. Specifically, we investigate (i) how the financial incentive affects endorsers’ participation and effectiveness in paid endorsement campaigns, (ii) what types of endorsers are most effective in generating online engagements (likes, comments, and retweets), and (iii) whether that varies across types of engagements that require different levels of efforts from followers. We conduct a field experiment with an invitation design in which we manipulate both incentives and a soft eligibility requirement to participate in the campaign. The latter provides a strong and valid instrument to separate participation from outcomes effects. Since likes, comments, and retweets are count variables, and since potential endorsers can self-select to participate in multiple campaigns, we use a Poisson lognormal model with sample selection and correlated random effects to analyze variations in participation and effectiveness. There are three main findings. (1) Payments higher than the average reward a potential endorser received in the past do not increase participation, whereas lower payments decrease participation. Neither gains nor losses affect performance. (2) Potential endorsers who are more likely to participate tend to be less effective. (3) Which characteristics are associated with effectiveness depends on whether success is measured in likes, comments, or retweets. These findings provide new insights on how marketers can improve social advertising campaigns by better targeting and incenting potential endorsers.​

Trip and parking generation rates for different housing types: Effects of compact development

Guidelines for trip and parking generation in the United States come mainly from the Institute of Transportation Engineers (ITE). However, their trip and parking manuals focus on suburban locations with limited transit and pedestrian access. This study aims to determine how many fewer vehicle trips are generated and how much less parking demand is generated, by different housing types (single-family attached, single-family detached, and apartment and condo) and in different settings (from low density suburban environments to compact, mixed-use urban environments). Using household travel survey data from 30 diverse regions of the United States, we estimate a multilevel negative binomial model of vehicle trip generation and a multilevel Poisson model of vehicle ownership, vehicle trip generation and vehicle ownership being logically modelled as count variables. The models have the expected signs on their coefficients and have respectable explanatory power. Vehicle trip generation and vehicle ownership (and hence parking demand) decrease with the compactness of neighbourhood development, measured with a principal component that depends on activity density, land use diversity, percentage of four-way intersections, transit stop density and employment accessibility (after controlling for sociodemographic variables). The models capture the phenomena of ‘trip degeneration’ and ‘car shedding’ as development patterns become more compact. Reducing the number of required parking spaces, and vehicle trips for which mitigation is required, creates the potential for significant savings when developing urban projects. Guidelines are provided for using study results in transportation planning.

Acoustical Enrichment during Early Development Improves Response Reliability in the Adult Auditory Cortex of the Rat.

It is well known that auditory experience during early development shapes response properties of auditory cortex (AC) neurons, influencing, for example, tonotopical arrangement, response thresholds and strength, or frequency selectivity. Here, we show that rearing rat pups in a complex acoustically enriched environment leads to an increased reliability of responses of AC neurons, affecting both the rate and the temporal codes. For a repetitive stimulus, the neurons exhibit a lower spike count variance, indicating a more stable rate coding. At the level of individual spikes, the discharge patterns of individual neurons show a higher degree of similarity across stimulus repetitions. Furthermore, the neurons follow more precisely the temporal course of the stimulus, as manifested by improved phase-locking to temporally modulated sounds. The changes are persistent and present up to adulthood. The results document that besides basic alterations of receptive fields presented in our previous study, the acoustic environment during the critical period of postnatal development also leads to a decreased stochasticity and a higher reproducibility of neuronal spiking patterns.

A Joint Model for Exponential Survival Data and Poisson Count Data

This research is motivated by the correlated outcomes of survival times and counts particularly in medical data. Analysis on individual patient data consisting of recurrent events of disease progression and survival times/death times give better results when a bivariate model/joint model of ‘survival’ and ‘count’ is used rather than fitting separate univariate models. For this purpose, a joint model for a proportional hazard survival response and a Poisson count responses is presented. The methodological aspects of the proposed model is outlined including parameter estimation. The proposed model was examined on a large scale simulation study and superior performance was demonstrated over the separate univariate models. The model was further showcased on an actual clinical trial data and found out to be capable of capturing the correlation between the survival and count variables found in the data.

T126. PSYCHOTIC EXPERIENCES AND COMMON MENTAL DISORDERS IN CHILDHOOD AND ADOLESCENCE: BIDIRECTIONAL AND TRANSDIAGNOSTIC ASSOCIATIONS IN A LONGITUDINAL COMMUNITY-BASED STUDY

BackgroundThe prevalence of Psychotic Experiences (PE) in the general population is approximately 7%. Several studies report on the association of PE with non-psychotic mental disorders and dimensional psychopathology. However, few have addressed this relationship during adolescence using longitudinal data. Here, we aim to explore bidirectional associations of PE and common mental disorder in youth in a 3-year follow-up community-based study. We hypothesized that there is a link between PE and depression, corroborating findings from adult studies, and that mental disorders comorbidity significantly correlates to PE, showing a nonspecific effect of PE as a risk for a broad “psychiatric load/liability”.MethodsWe analyzed data from the Brazilian High Risk Cohort (HRC), a large multi-site school-based study. At baseline, we evaluated 2,244 subjects (6–12 years old) using the Community Assessment of Psychotic Experiences (CAPE) and an adapted version of the Comprehensive Assessment of At-risk Mental States (CAARMS) by self-report and clinician ratings, respectively. Mental disorders in youth were assessed by the Development and Well-Being Assessment (DAWBA). We grouped mental disorders into 4 DSM-based categories: any depressive disorder, any anxiety disorder, any Attention Deficit Hyperactivity Disorder (ADHD), and any Oppositional Defiant Disorder or Conduct Disorder (ODD/CD). Subjects were reassessed after 3 years, with a retention rate of 75%. We used regression analyses to explore predictors of PE and mental disorders at follow-up. Finally, we investigated the bidirectional effect of PE as a nonspecific psychiatric “load/liability” by creating count variables for the number of comorbid psychiatric disorders for each participant. Poisson regression models tested the effect of PE (as a predictor) in the count variable (the outcome) controlling for potential confounders.ResultsWe found bidirectional associations between PE and mental disorders in youth. Baseline PE increased the risk of any depressive disorder at follow-up, and baseline ADHD was associated with PE at 3-year follow-up. Comorbidity analyses showed significant relationships in both directions, with an increased risk of PE according to the number of comorbid psychiatric disorders.DiscussionWe showed that subthreshold psychotic symptoms predict subsequent depressive disorder, and nonspecifically relate to psychiatric comorbidity. These findings are concordant with the notion that psychotic experiences are part of the same psychiatric vulnerability conferred to common mental disorders, such as depression and ADHD.Our results may inform future research on testing subclinical psychotic symptoms to further our understating on identifying high-risk groups for early intervention.

Evaluation of neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) in critical care patients with synthetic cannabinoid (bonzai) intoxication

ObjectiveSynthetic cannabinoid drug abuse has been dramatically increasing among young individuals in many countries. There have been reports of serious side effects with SC abuse in these patients. Previous researches have exhibited that neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) are associated with mortality and morbidity in many chronic diseases. The aim of this study was to evaluate PLR and NLR in critical care patients with synthetic cannabinoid (bonzai) intoxication. Materials and methodsOne hundred and seven synthetic cannabinoid intoxication patients requiring intensive care and 40 healthy controls were included in the study. Patients characteristics and the complete blood count (CBC) variables, including white blood cell (WBC), hemoglobin (Hb), platelet count, NLR, PLR as well as AST, ALT, albumin total bilirubin, and other routine biochemical parameters were tested. Data analyses were conducted with SPSS-15 software (SPSS Inc., Chicago, Illinois, USA). Statistical significance was set at a p-value of <0.05. ResultsAll participants were male, and the mean age of the patients was 21.74 ± 1.57 and healthy controls was 22.62 ± 2.9 years (p > 0.05). All the routine laboratory tests and inflammatory markers (Erythrocyte sedimentation rate and C-reactive protein) were similar between groups. As complete blood cell count; mean WBC values were 9.43 ± 3.27 × 103/mm3 vs 7.05 ± 2.12 × 103/mm3 (p < 0.001), mean platelet counts were 237.33 ± 60 × 103/mm3 vs 263.90 ± 65.98 × 103/mm3 (p = 0.022), NLR counts were 3.17 ± 1.95 vs 2.32 ± 1.27 (p = 0.003) and PLR values were 114.43 ± 36.39 vs 133.94 ± 45.27 (p = 0.008), in patients and controls, respectively. Cardiac side effects were observed among 36 patients but nobody was died. ConclusionOur results exhibited a significant increase of NLR values and decrease of PLR counts among critical care patients with synthetic cannabinoid (bonzai) intoxication. After at least 24 h of intensive care stay without side effects, the patients might transfer out to inpatient clinic for ongoing follow up period and psychiatric consultation.

Trends in Cigarette Advertising, Price-Reducing Promotions, and Policy Compliance in New York State Licensed Tobacco Retailers, 2004 to 2015.

To describe the presence of licensed tobacco retailers (LTRs), cigarette advertisements, price-reducing promotions, and compliance with tobacco control policies in New York State from 2004 to 2015 and to discuss implications and lessons learned from 11 years of experience conducting LTR surveys. Annual surveys of tobacco advertising from cross-sectional, stratified random samples of LTRs in New York State from 2004 to 2015 were conducted by professional data collectors. Data for 2013 were unavailable as the survey was not fielded in that year. New York State. Licensed tobacco retailers, which are stores licensed to sell tobacco in the state of New York. Between 3.6% (n = 800) and 19.7% (n = 3945) of all LTRs were sampled annually. The presence and number of cigarette advertisements and the presence of price-reducing promotions, required age-of-sale signage, and self-service tobacco displays were documented. We tested for significant differences between 2014 and 2015 and significant trends overall and by outlet type. We used logistic regression for binary outcomes and Poisson regression for count variables. The number of LTRs in New York State decreased 22.9% from 2004 (n = 25 740) to 2015 (n = 19 855). The prevalence and number of cigarette advertisements and the prevalence of cigarette price-reducing promotions decreased significantly over time. Compliance with posting required age-of-sale signs increased significantly from 2004 to 2015 and from 2014 to 2015. Compliance with the ban on self-service tobacco displays was consistently near 100%. The tobacco retail environment in New York State improved substantially from 2004 to 2015. The implications of these findings for youth and adult smoking and the associated social costs are unknown; however, decreases in pro-tobacco marketing, decreases in the number of LTRs, and improvements in compliance are likely to have positive impacts on youth and adult smoking outcomes, such as reduced initiation and increased cessation, given previous research findings.

Factors associated with life jacket use among cabin sailboat and day sailor boaters in the United States

IntroductionIn 2015, drowning accounted for 68% of the 626 recreational boating related deaths in the United States. Although life jackets are estimated to prevent between 50% to 80% of boating deaths, approximately 83% of sailboat-related drowning victims were reported to not be wearing life jackets. Life jacket use among adult boaters has remained consistently low across most boat types and may vary by boater, boating, and environmental conditions. Although many risky environmental and boating factors may be associated with a higher risk of boating death, drowning occurs in all situations and it is useful to understand adult life jacket wearing behaviors in differing boating situations. MethodsThis study uses observational survey data from 61318 adult sailors collected during the summer months of 1999 – 2017 from 124 selected study sites across 30 states in the US. Life jacket use was compared for day sailors and cabin sailboats by multiple boating, boater, and environmental conditions using Chi-square tests for equality of proportions. Results of these tests led to a choice of 3 informative and scientifically compelling variables to summarize variation in life jacket use for each sailboat type. Odds ratios were calculated comparing life jacket use from each boating situation to the lowest risk situation as determined by the 3 selected variables. These variables were represented in a tree diagram, detailing the additive impact of each factor. Following these analyses, all boating conditions were categorized to be risky or non-risky and a count variable was created for each observation based on the number of risks present. Cochran-Armitage trend tests were conducted to test for linearity in life jacket use for both boat types. ResultsThe overall life jacket wear rate was higher among adults in day sailor sailboats (51.6%) compared to cabin sailboats (13.8%) and in all measured demographic, boating, and environmental circumstances. Comparing high-risk cabin sailboat conditions of low water temperatures, small boat size, and high wind speed to the lowest-risk situation accounted for a 23.3% range in life jacket wear rate (OR=4.7). Comparing high-risk day sailor sailboat conditions of small boat size, one boater on board, and choppy/rough wave height to the lowest-risk situation accounted for a 39.3% range in life jacket wear rate (OR=5.9). For both boat types, the number of risks present and life jacket wear rate exhibited a statistically significant positive linear relationship at p<0.0001. ConclusionStudy results suggest that boaters are aware of the connection between life jacket use and drowning prevention and are more likely to wear life jackets when boating in conditions perceived to be risky. Practical applicationsBoating safety promotion efforts should recommend adult life jacket use in all boating situations, as seemingly non-risky conditions may still result in drownings.

Shifts in Leukocyte Counts Drive the Differential Expression of Transcriptional Stroke Biomarkers in Whole Blood.

Our group recently identified a panel of ten genes whose RNA expression levels in whole blood have utility for detection of stroke. The purpose of this study was to determine the mechanisms by which these genes become differentially expressed during stroke pathology. First, we assessed the transcriptional distribution of the ten genes across the peripheral immune system by measuring their expression levels on isolated neutrophils, monocytes, B-lymphocytes, CD-4+ T-lymphocytes, CD-8+ T-lymphocytes, and NK-cells generated from the blood of healthy donors (n = 3). Then, we examined the relationship between the whole-blood expression levels of the ten genes and white blood cell counts in a cohort of acute ischemic stroke patients (n = 36) and acute stroke mimics (n = 15) recruited at emergency department admission. All ten genes displayed strong patterns of lineage-specific expression in our analysis of isolated leukocytes, and their whole-blood expression levels were correlated with white blood cell differential across the total patient population, suggesting that many of them are likely differentially expressed in whole blood during stroke as an artifact of stroke-induced shifts in leukocyte counts. Specifically, factor analysis inferred that over 50% of the collective variance in their whole-blood expression levels across the patient population was driven by underlying variance in white blood cell counts alone. However, the cumulative expression levels of the ten genes displayed a superior ability to discriminate between stroke patients and stroke mimics relative to white blood cell differential, suggesting that additional less prominent factors influence their expression levels which add to their diagnostic utility. These findings not only provide insight regarding this particular panel of ten genes, but also into the results of prior stroke transcriptomics studies performed in whole blood.

Self-Reported Functional Mobility, Balance Confidence, and Prosthetic Use Are Associated With Daily Step Counts Among Individuals With a Unilateral Transtibial Amputation.

Adults postamputation are not meeting physical activity recommendations. Physical activity is an important consideration in prosthetic prescription. The objective of this study was to determine if functional mobility, balance confidence, and prosthetic use are associated with physical activity among adults with a lower-limb amputation. This study recruited patients aged 18-85 years with unilateral transtibial amputations. The Cumulative Illness Rating Scale was used to determine comorbidity burden. Participants completed the Prosthetic Evaluation Questionnaire-Mobility Section, Activities-specific Balance Confidence Scale, and Houghton Scale of Prosthetic Use and wore a StepWatch monitor for 7 days to obtain daily step counts. Linear regression was used to evaluate relationships between each self-report measure and step counts after controlling for covariates, that is, sex, age, time since initial amputation, and comorbidity burden. Forty-seven participants had ≥5 days of step data and were included in this analysis. The Prosthetic Evaluation Questionnaire-Mobility Section [mean (SD): 35.0 (9.6) points] and Activities-specific Balance Confidence Scale [79.2% (15.9%)] each explained 13% of the variance in step count [5491 (4043) steps], whereas the Houghton Scale of Prosthetic Use [10.3 (1.2) points] explained 10% of the variance. Self-reported functional mobility, balance confidence, and prosthetic use predict short-term average daily step counts as determined from research-grade accelerometers.

The use of historical platelet counts from blood donors to program apheresis platelet donation: An Australian perspective

BackgroundFor Australian apheresis platelet donations, in-centre haematology analysers provided the platelet count used to program the platelet collection machines. When the haematology analysers were not functional, historical platelet counts from previous donations were used. This study aimed to confirm that the routine use of historical platelet counts for programming apheresis collection machines would maintain platelet yields within the donated units and that haematology analysers could be removed. Study designA staggered implementation for the routine use of mean historical platelet counts to program apheresis platelet collection machines was conducted. The donors’ full blood counts following donation were tested centrally for comparison to the historical mean. The component yields when using on-the-day platelet counts to program platelet collection were compared with those collected using historical platelet counts. For historical platelet counts to be deemed successful, the target was for 90% of the mean historical donor platelet counts to have less than 20% variance from the on-the-day platelet count. ResultsOver 96% of the mean historical platelet counts were within 20% variance of the platelet count on the day of donation. The component yield (platelet count x109 cell/unit) before analyser removal was 273.3 ± 32.0 (n = 2639) and post-removal was 282.8 ± 38.8 (n = 2689). ConclusionThe removal of haematology analysers from donor centres and replacement with mean historical platelet counts was successful in maintaining platelet yields. Replacement of the haematology analysers with historical platelet counts simplified regulatory compliance, reduced staff workload and costs associated with analyser registration.

How Much Does Movement and Location Encoding Impact Prefrontal Cortex Activity? An Algorithmic Decoding Approach in Freely Moving Rats.

Specialized brain structures encode spatial locations and movements, yet there is growing evidence that this information is also represented in the rodent medial prefrontal cortex (mPFC). Disambiguating such information from the encoding of other types of task-relevant information has proven challenging. To determine the extent to which movement and location information is relevant to mPFC neurons, tetrodes were used to record neuronal activity while limb positions, poses (i.e., recurring constellations of limb positions), velocity, and spatial locations were simultaneously recorded with two cameras every 200 ms as rats freely roamed in an experimental enclosure. Regression analyses using generalized linear models revealed that more than half of the individual mPFC neurons were significantly responsive to at least one of the factors, and many were responsive to more than one. On the other hand, each factor accounted for only a very small portion of the total spike count variance of any given neuron (<20% and typically <1%). Machine learning methods were used to analyze ensemble activity and revealed that ensembles were usually superior to the sum of the best neurons in encoding movements and spatial locations. Because movement and location encoding by individual neurons was so weak, it may not be such a concern for single-neuron analyses. Yet because these weak signals were so widely distributed across the population, this information was strongly represented at the ensemble level and should be considered in population analyses.

Dethroning the Fano Factor: A Flexible, Model-Based Approach to Partitioning Neural Variability.

Neurons in many brain areas exhibit high trial-to-trial variability, with spike counts that are overdispersed relative to a Poisson distribution. Recent work(Goris, Movshon, & Simoncelli, 2014 ) has proposed to explain this variability in terms of a multiplicative interaction between a stochastic gain variable and a stimulus-dependent Poisson firing rate, which produces quadratic relationships between spike count mean and variance. Here we examine this quadratic assumption and propose a more flexible family of models that can account for a more diverse set of mean-variance relationships. Our model contains additive gaussian noise that is transformed nonlinearly to produce a Poisson spike rate. Different choices of the nonlinear function can give rise to qualitatively different mean-variance relationships, ranging from sublinear to linear to quadratic. Intriguingly, a rectified squaring nonlinearity produces a linear mean-variance function, corresponding to responses with a constant Fano factor. We describe a computationally efficient method for fitting this model to data and demonstrate that a majority of neurons in a V1 population are better described by a model with a nonquadratic relationship between mean and variance. Finally, we demonstrate a practical use of our model via an application to Bayesian adaptive stimulus selection in closed-loop neurophysiology experiments, which shows that accounting for overdispersion can lead to dramatic improvements in adaptive tuning curve estimation.

The impact of preapheresis white blood cell count on autologous peripheral blood stem cell collection efficiency and HSC infusion side effect rate.

Autologous peripheral blood hematopoietic stem cell (PBSC) collection efficiency (CE) is reportedly affected by the patient's blood properties; however, studies to identify factors correlated with CE have shown inconsistent results. Additionally, variables such as stem cell graft granulocyte content and patient age, sex, and underlying disease, may be associated with hematopietic stem cell (HSC) infusion-related adverse reactions. In this study, we evaluated the correlation of preleukapheresis PB granulocyte count and PBSC harvest variables with CD34+ collection yield and efficiency, and thawed HSC infusion side effect occurrence. We evaluated data from 361 patients who had undergone autologous PBSC transplant. Large volume leukapheresis was the method for PBSC collection. Complete Blood Count and CD34+ cell enumeration were performed in the preapheresis PB and the apheresis product sample. The PBSC grafts were submitted to non-controlled rate freezing after addition of 5% DMSO plus 6% hidroxyethylstarch as a cryoprotectant solution. The cryopreserved graft was thawed in a 37°C water bath and then infused without further manipulation. The CD34+ yield was associated with preapheresis PB CD34+ count and immature granulocyte count. The PBSC CE was negatively correlated with preapheresis white blood cell (WBC), immature granulocyte and granulocyte count. The leukapheresis product total nucleated cell (TNC) and granulocyte content was correlated with the thawed graft infusion side effect occurrence. This study has shown that preapheresis PB WBC and granulocyte counts were associated with leukapheresis CE. Additionally, the leukapheresis product TNC and granulocyte content was correlated with thawed graft infusion side effect occurrence.

The impacts of built environment characteristics of rail station areas on household travel behavior

Transit-oriented development (TOD) has gained popularity worldwide as a sustainable form of urbanism by concentrating developments near a transit station so as to minimize auto-dependency and maximize ridership. Existing TOD studies, however, have limits in terms of small sample size and aggregate-level analysis. This study examines various travel outcomes – VMT, auto trips, transit trips, and walk trips – in rail-based station areas in eight U.S. metropolitan areas in order to understand the role of neighborhood built environment characteristics. Two-stage hurdle models handle excess zero values in trip count variables and multi-level models deal with three-level data structure – household within station areas within regions. The final models show that automobile use is associated with land-use diversity and street network design of a station area; transit use is strongly related to transit availability and land-use diversity; and walking is related to transit availability, land-use diversity, and street network design. The weakest influence among station-area environment factors is density. In sum, a TOD, a station area having a dense, mixed-use, walkable, and transit-friendly environment, motivates residents to walk more and take transit more while driving less.