Search Results (154)

To address the increasing demand for computational and communication resources, modern networked systems often rely on heterogeneous servers, including those requiring setup times, such as virtual machines or servers, and others that are always active. In this paper, we model and analyze the performance of such hybrid systems using a level-dependent quasi-birth-and-death (LDQBD) process. Building upon an existing queueing model, we extend the analysis by considering scalable approximation methods. Since matrix analytic methods become computationally expensive in large-scale settings, we propose a stochastic bounding approach that derives upper and lower bounds for the stationary distribution, thereby significantly reducing computational cost. This approach further provides bounds on the performance metrics of the hybrid system. Full article

This study applies stochastic discrete event modeling to demonstrate that reducing wait times for specialized outpatient clinics in the Costa Rican public healthcare system is possible. The classification process identified four medical specialties with the longest wait times. It includes the creation of a separate queuing theory model for each specialty. The birth and death model allowed for estimating the number of arrivals and consultations in the simulation. Validation was performed by comparing the model’s input and output data with real-world statistical reports. An analysis of medical specialists revealed that approximately 22% of patients referred to secondary care did not require specialized medical consultation. Through simulation and the use of stochastic input data, patient waiting times decreased. In an optimistic scenario, waiting times decreased steadily across all specialties over 24 months. Ophthalmology and orthopedics reduced their waiting times to less than 300 days. Otorhinolaryngology decreased from 370 to 250 days, and urology showed the most significant improvement, decreasing from 350 to 100 days in the first year and remaining stable. This evidence transforms the traditional paradigm of increasing capacity as the only solution to the waiting list problem and positions improving the referral process as an alternative. To achieve these results, the study highlights the importance of implementing improved triage protocols in primary care, integrating decision-support tools for general practitioners using machine learning, for example, to reduce unnecessary referrals. Training programs and feedback mechanisms could also align referral practices with specialty criteria. While these strategies were not implemented in this study, the simulation results provide a solid basis for their design and future evaluation. Full article

Neonatal calves possess an immature and naïve immune system and are reliant on the intake of maternal colostrum for the passive transfer of immunoglobulins. Maternal antibodies delivered to the calf via colostrum, are crucial to prevent calfhood diseases and death. Failure of transfer of passive immunity (FTPI) is a condition in which calves do not acquire enough maternal antibodies, mostly in the form of IgG, due to inadequate colostrum quality or delayed colostrum feeding. The diagnosis and risk factors for FTPI have been widely studied in dairy cattle; however, in beef calves, the research interest in the topic is relatively recent, and the most adequate diagnostic and preventative methods are still in development, making it difficult to define recommendations for the assessment and prevention of FTPI in cow–calf operations. The objective of this scoping review is to identify the published literature on best practices for colostrum management and transfer of passive immunity (TPI) in neonatal beef calves. The literature was searched using three electronic databases (CAB Direct, Scopus, and PubMed) for publications from 2003 to 2025. The search process was performed during the period from May to July 2023, and was repeated in January 2025. All screening processes were performed using Covidence systematic review software (Veritas Health Innovation, Melbourne, Australia). A total of 800 studies were initially identified through database searches. After removing duplicates, 346 studies were screened based on their titles and abstracts, leading to the exclusion of 260 studies. The remaining 86 studies underwent full-text screening, and 58 studies were considered eligible for data extraction. Hand-searching the references from published review papers on the subject yielded an additional five studies, bringing the total to 63 included articles. The prevalence of FTPI has been estimated to be between 5.8% and 34.5% in beef calves. Factors studied related to colostrum management include quality and quantity of colostrum intake, the timing and method of colostrum feeding, and the microbial content of the colostrum. Studies on risk factors related to the calf include the topics calf sex, twin status, calf vigor, weight, month of birth, cortisol and epinephrine concentrations, and the administration of nonsteroidal anti-inflammatory drugs to calves after difficult calving. The dam-related risk factors studied include dam body condition score and udder conformation, breed, parity, genetics, prepartum vaccinations and nutrition, calving area and difficulty, and the administration of nonsteroidal anti-inflammatory drugs at C-section. Most importantly for beef systems, calves with low vigor and a weak suckling reflex are at high risk for FTPI; therefore, these calves should be given extra attention to ensure an adequate consumption of colostrum. While serum IgG levels of < 8 g/L or < 10 g/L have been suggested as cutoffs for the diagnosis of FTPI, 16 g/L and 24 g/L have emerged as cutoffs for adequate and optimal serum IgG levels in beef calves. Several field-ready diagnostics have been compared in various studies to the reference standards for measuring indicators of TPI in beef calves, where results often differ between models or manufacturers. Therefore, care must be taken when interpreting these results. Full article

Consanguinity is the marriage of two related persons. This type of marriage is one of the main pillars when it comes to recessive hereditary diseases, birth defects, infertility, miscarriages, abortion, and infant deaths. Intermarriage continues to be a common practice in various communities in North Africa, the Middle East, and West and South Asia, as well as among migrants from Europe and North America, even though in more and more countries it has become illegal. Even if security and stability are some of the motivations for consanguineous marriage, studies show that women often suffer physical and verbal abuse from their husbands. However, because of the blood bond, tolerance for these habits is much higher. In addition, it seems that the divorce rate is much lower because separation would affect the entire state of the family. The choice of partner is significantly influenced by variables such as limited access to education and financial resources. Illiterate people coming from poor rural areas are much more likely to choose consanguineous marriage to maintain wealth in the family. The lack of medical knowledge about the negative effects of consanguinity leads to an increased rate of abortions, infant deaths, and births of children with congenital birth defects. Today, because of the process of urbanization and increased levels of knowledge, the younger generation is becoming increasingly less receptive to this particular form of marriage. In addition, as education has become more accessible to women, they have become more independent and eager to fulfill their own goals and not the wishes of the family. In conclusion, contrary to the many apparent advantages of consanguineous marriage, partners should put genetic risks first, as medical problems bring with them increased costs in the medical system and also within the family, leading to even lower economic status and consequently perpetuation of this type of marriage. Full article

An $MAP/PH/N$-type queuing system functioning within a finite-state Markovian random environment is studied. The random environment’s state impacts the number of available servers, the underlying processes of customer arrivals and service, and the impatience rate of customers. The impact on the state space of the underlying processes of customer arrivals and of the more general, as compared to exponential, service time distribution defines the novelty of the model. The behavior of the system is described by a multidimensional Markov chain that belongs to the classes of the level-independent quasi-birth-and-death processes or asymptotically quasi-Toeplitz Markov chains, depending on whether or not the customers are absolutely patient in all states of the random environment or are impatient in at least one state of the random environment. Using the tools of the corresponding processes or chains, a stationary analysis of the system is implemented. In particular, it is shown that the system is always ergodic if customers are impatient in at least one state of the random environment. Expressions for the computation of the basic performance measures of the system are presented. Examples of their computation for the system with three states of the random environment are presented as 3-D surfaces. The results can be useful for the analysis of a variety of real-world systems with parameters that may randomly change during system operation. In particular, they can be used for optimally matching the number of active servers and the bandwidth used by the transmission channels to the current rate of arrivals, and vice versa. Full article

Markov chain perturbation theory is a rapidly developing subfield of the theory of stochastic processes. This review outlines emerging applications of this theory in the analysis of stochastic models of chemical reactions, with a particular focus on biochemistry and molecular biology. We begin by discussing the general problem of approximate modeling in stochastic chemical kinetics. We then briefly review some essential mathematical results pertaining to perturbation bounds for continuous-time Markov chains, emphasizing the relationship between robustness under perturbations and the rate of exponential convergence to the stationary distribution. We illustrate the use of these results to analyze stochastic models of biochemical reactions by providing concrete examples. Particular attention is given to fundamental problems related to approximation accuracy in model reduction. These include the partial thermodynamic limit, the irreversible-reaction limit, parametric uncertainty analysis, and model reduction for linear reaction networks. We conclude by discussing generalizations and future developments of these methodologies, such as the need for time-inhomogeneous Markov models. Full article

Many existing structures require retrofitting and reinforcement due to aging and damage. The stability of the retrofitted structure is key to the retrofitting scheme, while construction safety during the retrofitting process is another crucial consideration. This study proposed an evaluation method for assessing the stability and construction process of steel structure retrofitting projects based on an ANSYS finite element analysis. By establishing a nonlinear finite element model of a retrofitted gymnasium roof truss structure, the overall stability of the system was systematically verified. The dynamic simulation of demolition and retrofitting procedures was conducted using the birth-and-death element technique, and a comprehensive safety assessment framework covering the entire construction process was developed. The case analysis demonstrated that this method can simulate the redistribution of internal forces during component demolition and identify potential risks. The effectiveness of the retrofitting strategy was evaluated by comparing the nonlinear stability coefficients of the structure before and after retrofitting, indicating improved performance within the scope of the finite element model. The research results demonstrated the feasibility of incorporating modeling, simulation, and assessment in retrofitting projects and provided a reference for similar retrofitting projects. Full article

This paper deals with queueing models, in which the number of customers is described by a (inhomogeneous, in general) birth–death process. Depending on the choice of the type of intensities for the arrival and service of customers, the system can either have impatience (in which, as the queue length increases, the intensities of arrival decrease and the intensities of service increases) or attraction (in which, on the contrary, as the queue length increases, the intensities of the arrival of customers increase and service intensities decrease). In this article, various types of such models are considered, and their transient and limiting characteristics are computed. Furthermore, the rate of convergence and related bounds are also dealt with. Several numerical examples illustrate the proposed procedures. Full article

Insulin-degrading enzyme is a zinc metalloprotease that degrades low-molecular-weight substrates, including insulin. Ubiquitous expression, high evolutionary conservation, upregulation of Ide in stress situations, and literature findings suggest a broader function of Ide in cell physiology and protein homeostasis that remains to be elucidated. We used proteomics and transcriptomics approaches to search for leads related to a broader role of Ide in protein homeostasis. We combined an analysis of the proteome and single-cell transcriptome of Ide^+/+ and Ide^−/− pancreatic islet cells with an examination of the interactome of human cytosolic Ide using proximity biotinylation. We observe an upregulation of pathways related to RNA processing, translation and splicing in Ide^+/+ relative to Ide^−/− islet cells. Corroborating these results and providing a potential mechanistic explanation, proximity biotinylation reveals interaction of Ide with several subunits of CCR4-NOT, a key mRNA deadenylase regulating gene expression “from birth to death”. We propose a speculative model in which human and murine Ide cooperate with CCR4-NOT to control protein expression in proteotoxic and metabolic stress situations through cooperation between their deadenylase and protease functions. Full article

One of the methods for studying the solvability of infinite systems of integral or differential equations is the application of various fixed-point theorems to operators acting in appropriate functional Banach spaces. This method is fairly well developed, frequently used, and effective in many situations. However, there are cases in which certain infinite systems of differential equations arise—linked to the modeling of significant real-world phenomena—where this method, based on situating considerations within Banach spaces, fails and cannot be applied. In this paper, we propose a slightly different approach, which involves conducting the analysis within appropriate functional Fréchet spaces. We discuss the fundamental properties of these spaces and formulate compactness criteria. The main result of this paper is a positive answer, using the proposed method, to an open problem concerning the modeling of a stochastic birth-and-death process, as formulated in one of the cited publications. The most important conclusion is that the presented computational technique, based on functional Fréchet spaces, can be regarded as a more effective alternative to methods based on Banach spaces. Full article

Background/Objectives: Early predictive assessments for CP are recommended for infants with medical risk factors after birth. For parents of children with CP, receiving an early diagnosis is important. But most children with risk factors who have not yet developed CP are labeled “high-risk infants” and repeatedly assessed for abnormal signs. We aim to investigate the experience of parents of high-risk infants and describe the meaning that “early predictive assessments for CP” has for them before they know whether their children have CP. Methods: This was a qualitative study conducted using a phenomenological, reflective lifeworld approach. Fourteen individual in-depth interviews were conducted with parents who received different GMA results to learn about their experiences involving early predictive assessments. The interviews were analyzed for meaning. Results: Early predictive assessments take place over time while parents process the traumatic experience of becoming parents to an infant at risk. “Early predictive assessment” is perceived as any examination or assessment intended to unveil signs of illness or disability. The child’s future well-being and fulfillment, and the demands of parenthood, are at stake. Essential meaning structures are (1) on a spectrum from death to insignificancies, (2) living with uncertainty of what the parental role will entail, and (3) seeing one’s own child through the eyes of strangers, just in case. Conclusions: For months following the birth of a high-risk child, parents experience uncertainty and worrying, affecting the parent–infant relationship. Predictive assessments reduce their sense of alarm when the GMA result indicates a low risk of CP. But when the GMA result is uncertain, the burden of uncertainty is amplified and prolonged. Full article

Fused deposition modeling (FDM), as one of the most widespread and cost-effective additive manufacturing (AM) technologies, faces ongoing challenges in improving the dimensional accuracy and mechanical properties of complex shapes. The repeated heating and cooling of thermoplastic filaments make the FDM parts prone to accumulating warping deformation, which is difficult to predict due to the specificity of material deposition toolpaths. In this study, a path-based discrete modeling and process simulation method was developed for the FDM process. Based on process parameters and material deposition toolpaths, the finite element (FE) model was reconstructed using the discrete modeling method. Then, the birth–death element method (BDEM) was employed to simulate the FDM process and solve the thermo-mechanical coupling field in ANSYS 2022 R1. The corresponding computing programs were compiled in C++. The effectiveness of the proposed method was verified by three numerical examples using ABS material. According to the results, the simulated deformations show strong agreement with the deformations of real FDM parts. The findings of this study are applicable to other mainstream AM processes and are unrestricted by any complex geometries. Full article

The area along the Missouri River west of St. Louis, Missouri was a major locus of immigration from Germany between 1850 and 1860, in part due to a publication by Gottfried Duden that received wide attention in Germany. While a fair amount has been written about the lives of immigrants in Missouri, most has focused on the experiences of men. The lives of women are largely restricted to recordings of marriage, births and death. Lacking is context on what occurred between these life events. Using a variety of public and private sources, we describe the lives of five sisters from the first generation of women born in Franklin County, Missouri, bordered on its northern edge by the Missouri River. The process sheds light on the lives of immigrant women from Germany in Franklin County. Our sources allow us to shed light on the sisters’ day-to-day life experiences over time, thus better capturing the challenges that they faced and the grace and strength that they displayed in facing them. Although their childhoods were homogeneous, their adult paths diverged from one another markedly. We conclude with a discussion of the factors that might have been responsible for their divergence of experience. Full article

Background/Objectives: The objective of this research was to analyze the experiences and factors associated with perinatal grief in mothers in the urban context of Santa Cruz de la Sierra, Bolivia. Methods: The sample consisted of seven mothers who experienced a loss during pregnancy up to the second month after the baby’s birth, occurring between 2015 and 2020 in the city of Santa Cruz de la Sierra. The mean age of the mothers was 34.86 years (SD = 3.13), and they belonged to middle or upper-middle socioeconomic levels. Data were collected through semi-structured interviews and analyzed using descriptive qualitative analysis. Results: The identified characteristics of perinatal grief were sadness, anger, guilt, emotional numbness, social isolation, and anxiety. Factors contributing to grief processing included support from the partner and family, when they accommodated and respected the mother’s needs. Factors hindering the grieving process included social and cultural environments that often silence and minimize the loss, a history of previous losses, the desire to be pregnant, and the mother’s life expectations and projects focused on motherhood. Conclusions: In conclusion, this research suggests that perinatal losses in the Bolivian context may be influenced by factors such as knowledge of the cause of death, previous loss experiences, and their emotional effects. The limitations of the study include the lack of diversity in participants’ educational and socioeconomic backgrounds and the restriction of the sample to an urban area in Bolivia. Emotional interventions to support these bereaved mothers in those complex moments should be integrated in the Bolivian healthcare system. Full article

Oropouche fever is caused by the Oropouche virus (OROV; Bunyaviridae, Orthobunyavirus), one of the most frequent arboviruses that infect humans in the Brazilian Amazon. This year, an OROV outbreak was identified in Brazil, and its vertical transmission was reported, which was associated with fetal death and microcephaly. We describe the clinical manifestations identified in three cases of congenital OROV infection with confirmed serology (OROV-IgM) in the mother-newborn binomial. One of the newborns died, and post-mortem molecular analysis using real-time RT-qPCR identified the OROV genome in several tissues. All three newborns were born in the Amazon region in Brazil, and the mothers reported fever, rash, headache, myalgia, and/or retro-orbital pain during pregnancy. The newborns presented with severe microcephaly secondary to brain damage and arthrogryposis, suggestive of an embryo/fetal disruptive process at birth. Brain and spinal images identified overlapping sutures, cerebral atrophy, brain cysts, thinning of the spinal cord, corpus callosum, and posterior fossa abnormalities. Fundoscopic findings included macular chorioretinal scars, focal pigment mottling, and vascular attenuation. The clinical presentation of vertical OROV infection resembled congenital Zika syndrome to some extent but presents some distinctive features on brain imaging and in several aspects of its neurological presentation. A recognizable syndrome with severe brain damage, neurological alterations, arthrogryposis, and fundoscopic abnormalities can be associated with in utero OROV infection. Full article