A general theory on spectral properties of state-homogeneous finite-state quasi-birth-death process

Cataloged from PDF version of article.In this paper a spectral theory pertaining to Quasi-Birth±Death Processes (QBDs) is presented. The QBD, which is a generalization of the birth±death process, is a powerful tool that can be utilized in modeling many stochastic phenomena. Our theory is based on the application of a matrix polynomial method to obtain the steady-state probabilities in state-homogeneous ®nite-state QBDs. The method is based on ®nding the eigenvalue±eigenvector pairs that solve a matrix polynomial equation. Since the computational e ort in the solution procedure is independent of the cardinality of the counting set, it has an immediate advantage over other solution procedures. We present and prove di erent properties relating the quantities that arise in the solution procedure. By also compiling and formalizing the previously known properties, we present a formal uni®ed theory on the spectral properties of QBDs, which furnishes a formal framework to embody much of the previous work. This framework carries the prospect of furthering our understanding of the behavior the modeled systems manifest. Ó 2001 Elsevier Science B.V. All rights reserved

Thermal and Carbon Dioxide Inactivation of Alkaline Phosphatase in Buffer and Milk

The effects of temperature and CO2 treatment on the inactivation of alkaline phosphatase (ALP) were studied. The thermal stability of ALP was found to be significantly (P< 0.05) different in glycine/NaOH buffer, pasteurized milk and raw milk. ALP was completely inactivated in the buffer at 60, 70 and 80 °C but approximately 12 % of activity was present at 50 °C after 55 min of treatment. The time required for complete inactivation of the enzyme in the buffer was reduced from 50 to 4 min as temperature increased from 60 to 80 °C. Complete inactivation of the enzyme in pasteurized milk was achieved at 70 and 80 °C but 28 and 15 % of ALP activity was still present at 50 and 60 °C after 120 min of treatment. Inactivation time for raw milk was reduced nearly 18-fold by increasing temperature from 50 to 70 °C. ALP in the buffer exposed to CO2 (under atmospheric pressure) treatment at different temperatures showed a decrease in enzyme activity. Inactivation was found to be higher as the temperature increased from 20 to 50 °C. At the end of a 30-min treatment, residual ALP activity was found to be 84 and 19 % at 20 and 50 °C, respectively. Faster drop in pH and enzyme activity occurred within 5 min. The change in pH and enzyme activity dependant on CO2 treatment was not observed in raw milk mainly due to strong buffering capacity of milk

Models of production lines as quasi-birth-death processes

The aim of this work is to illustrate the suitability of quasi-birth-death processes (QBDs) for stochastic modelling of production lines. With this end in mind, first, an introduction to QBDs is made, so that the reader who may not be acquainted with this aspect of stochastic modelling may be introduced to the basics of the topic. Then, a formal definition of QBD is given and the QBDs are contrasted with the traditional birth-death processes. Later, examples of QBD models pertaining to production lines are presented. The rational of this exposition is to show how QBDs present themselves within the context of production lines and to show the kind of work that needs to be performed to fully specify the corresponding QBD. By compiling the aforementioned models, the strength of QBDs in modelling production lines is demonstrated. © 2002 Elsevier Science Ltd. All rights reserved

Determination of the oxidative stability and shelf life of anchovy (Engraulis engrasicholus 1., 1758) fish burgers supplemented with garlic peel extract during cold storage

The effect of garlic peel extract (GPE) on the quality of anchovy (Engraulis engrasicholus L., 1758) burgers during cold storage was investigated. GPE was able to prevent lipid oxidation compared to control, since the scores of PV, TBARS and pH of the burgers supplemented with GPE showed lower values. The lowest TVC and PBC values were observed in the burgers treated with GPE, especially in the burgers treated %4 GPE. Sensory results showed that the use of 2% and 4% garlic peel extract extended the shelf life of anchovy burgers for 3 days

Psychotic Experiences and Risk of Suicidal Thoughts and Behaviors:A Systematic Review and Meta-Analysis of Longitudinal Population Studies

BACKGROUND AND HYPOTHESIS: Since a prior systematic review and meta-analysis reported an association between psychotic experiences (PEs) and suicidal thoughts and behaviors, a large number of new studies have been published on the topic, including several novel studies on the association between PEs and transition from suicidal ideation to attempt.STUDY DESIGN: Two authors independently searched PubMed, Embase, CINAHL, and PsycINFO databases from inception until July 2023, conducted data extraction, and assessed study quality using the Newcastle-Ottawa Quality Assessment Scale. Random-effects models were used to calculate pooled odds ratios (ORs) for the association of PEs and subsequent suicide ideation, suicide attempts, suicide death, and transition from suicidal ideation to attempt, first for the total population, and second stratified by age group. Secondary analyses assessed the mediating role of co-occurring psychopathology.STUDY RESULTS: Twenty studies from 18 different samples (n = 81,861) were identified. Individuals who reported PEs had increased odds of subsequent suicidal ideation (k = 12, OR = 1.90, 95% CI = 1.65-2.19), suicide attempt (k = 13, OR = 2.95, 95% CI = 2.21-3.94), transition from suicidal ideation to suicide attempt (k = 3, OR = 2.83, 95% CI = 1.60-4.99), and suicide death (k = 1, OR = 4.39, 95% CI = 1.63-11.80). This heightened risk was stable across childhood, adolescence, and adulthood. PEs predicted suicide attempts over and above co-occurring psychopathology (k = 8, OR = 2.85, 95% CI = 2.06-3.95).CONCLUSIONS: Individuals reporting PEs are at increased risk of all types of suicidal thoughts and behaviors. In addition, PEs are particularly important risk markers for future suicidal behaviors, including in individuals already reporting suicidal ideation. This risk is in excess of what is explained by co-occurring psychopathology.</p

Variance reduction techniques: Experimental comparison and analysis for single systems

We provide a thorough analysis of the effectiveness of different Variance Reduction Techniques (VRTs). We consider both stand-alone and combined applications of two input techniques, Antithetic Variates (AV) and Latin Hypercube Sampling (LHS), and two output techniques, Control Variates (CV) and Poststratified Sampling (PS). Previous research in the area mainly focuses on asymptotic variance reduction. In this experimental study, we measure the performance of VRTs under finite simulation run lengths and analyze their effects. Our findings show that the asymptotic variance reduction results do not readily apply to finite-length simulations. We consider three different types of systems (M/M/1, serial production line and (s, S) inventory control systems) and compare the VRTs under various experimental conditions. We observe that a variance reduction cannot be guaranteed for every instance a VRT is applied. Our results also indicate that the output VRTs (CV, PS) are better than input VRTs (AV, LHS) on the average for the single systems considered in this study. More interestingly, the less-sophisticated techniques (AV, CV) often perform better than the relatively more-complex techniques (LHS, PS). A comprehensive bibliography is also provided

Assessıng the predıctıve accuracy of blood-based bıomarkers ın neonatal outcomes for pregestatıonal dıabetes mellıtus

Abstract Objective: This retrospective study aimed to investigate blood-based immune-inflammatory biomarkers (IIBs) in predicting neonatal outcomes in pregnancies with pregestational diabetes mellitus (PGDM).PIV[(neutrophil×platelet×monocyte)/lymphocyte)], SII (neutrophil×platelet/lymphocyte), and NLR neutrophil/lymphocyte) values were evaluated in all three trimesters, and their correlation with neonatal outcomes was examined. Methods: We included 82 cases of PGDM pregnancies delivered after 32 weeks. Maternal age, gravidity, parity, types of diabetes, and route of delivery were noted. For neonatal outcomes, we recorded gestational age at birth, birth weight percentile, existence of fetal growth restriction, LGA, neonatal intensive care unit (NICU) requirement, Apgar Score <7 at 1, 5, or 10 minutes, need for positive pressure ventilation (PPV), need for mechanical ventilation, hypoglycaemia, hyperbilirubinemia and the need for phototherapy. PIV, SII and NLR values were calculated in each trimester and their association with adverse neonatal outcomes was analyzed. Results: We could not detect any consistent and significant correlation between SII and PIV values and adverse neonatal outcomes for each trimester. There was a correlation between 3rd trimester NLR and adverse neonatal outcomes, including APGAR <7, the requirement for PPV and mechanical ventilation (p=0.056, 0.013 and 0.060, respectively). Conclusion: While SII and PIV values did not consistently correlate with adverse neonatal outcomes throughout each trimester in PGDM pregnancies, 3rd-trimester NLR showed a notable association with the requirement for PPV with statistical significance and with Apgar Score <7 and the requirement for mechanical ventilation without statistical significance. NLR in the third trimester may hold potential as a predictive marker for specific adverse neonatal outcomes in PGDM pregnancies, warranting further investigation

A dynamic rationing policy for continuous-review inventory systems

Cataloged from PDF version of article.Stock rationing is an inventory policy that allows differential treatment of customer classes without using separate inventories. In this paper, we propose a dynamic rationing policy for continuous-review inventory systems, which utilizes the information on the status of the outstanding replenishment orders. For both backordering and lost sales environments, we conduct simulation studies to compare the performance of the dynamic policy with the static critical level and the common stock policies and quantify the gain obtained. We propose two new bounds on the optimum dynamic rationing policy that enables us to tell how much of the potential gain the proposed dynamic policy realizes. We discuss the conditions under which stock rationing – both dynamic and static – is beneficial and assess the value of the dynamic policy. 2009 Elsevier B.V. All rights reserved