Staffing to Maximize Profit for Call Centers with Impatient and Repeat-Calling Customers

Motivated by call center practice, we study the optimal staffing of many-server queues with impatient and repeat-calling customers. A call center is modeled as an M/M/s+M queue, which is developed to a behavioral queuing model in which customers come and go based on their satisfaction with waiting time. We explicitly take into account customer repeat behavior, which implies that satisfied customers might return and have an impact on the arrival rate. Optimality is defined as the number of agents that maximize revenues net of staffing costs, and we account for the characteristic that revenues are a direct function of staffing. Finally, we use numerical experiments to make certain comparisons with traditional models that do not consider customer repeat behavior. Furthermore, we indicate how managers might allocate staffing optimally with various customer behavior mechanisms

Recent advances in the epithelial barrier theory

The epithelial barrier theory links the recent rise in chronic non-communicable diseases, notably autoimmune and allergic disorders, to environmental agents disrupting the epithelial barrier. Global pollution and environmental toxic agent exposure have worsened over six decades because of uncontrolled growth, modernisation, and industrialisation, affecting human health. Introducing new chemicals without any reasonable control of their health effects through these years has led to documented adverse effects, especially on the skin and mucosal epithelial barriers. These substances, such as particulate matter, detergents, surfactants, food emulsifiers, micro- and nano-plastics, diesel exhaust, cigarette smoke and ozone, have been shown to compromise the epithelial barrier integrity. This disruption is linked to the opening of the tight junction barriers, inflammation, cell death, oxidative stress and metabolic regulation. Consideration must be given to the interplay of toxic substances, underlying inflammatory diseases, and medications, especially in affected tissues. This review article discusses the detrimental effect of environmental barrier-damaging compounds on human health and involves cellular and molecular mechanisms

Epithelial barrier hypothesis and the development of allergic and autoimmune diseases

The “epithelial barrier hypothesis” proposes that genetic predisposition to epithelial barrier damage, exposure to various epithelial barrier–damaging agents and chronic periepithelial inflammation are responsible for the development of allergic and autoimmune diseases. Particularly, the introduction of more than 200,000 new chemicals to our daily lives since the 1960s has played a major role in the pandemic increase of these diseases. The epithelial barrier constitutes the first line of physical, chemical, and immunological defence against external factors. A leaky epithelial barrier initiates the translocation of the microbiome from the surface of affected tissues to interepithelial and even deeper subepithelial areas. In tissues with a defective epithelial barrier, colonization of opportunistic pathogens, decreased microbiota biodiversity, local inflammation, and impaired regeneration and remodelling takes place. A dysregulated immune response against commensals and opportunistic pathogens starts. Migration of inflammatory cells to other tissues and their contribution to tissue injury and inflammation in the affected tissues are key events in the development and exacerbation of many chronic inflammatory diseases. Understanding the underlying factors that affect the integrity of epithelial barriers is essential to find preventive measures or effective treatments to restore its function. The aim of this review is to assess the origins of allergic and autoimmune diseases within the framework of the epithelial barrier hypothesis

Household laundry detergents disrupt barrier integrity and induce inflammation in mouse and human skin

BackgroundEpithelial barrier impairment is associated with many skin and mucosal inflammatory disorders. Laundry detergents have been demonstrated to affect epithelial barrier function in vitro using air–liquid interface cultures of human epithelial cells.MethodsBack skin of C57BL/6 mice was treated with two household laundry detergents at several dilutions. Barrier function was assessed by electric impedance spectroscopy (EIS) and transepidermal water loss (TEWL) measurements after the 4 h of treatments with detergents. RNA sequencing (RNA‐seq) and targeted multiplex proteomics analyses in skin biopsy samples were performed. The 6‐h treatment effect of laundry detergent and sodium dodecyl sulfate (SDS) was investigated on ex vivo human skin.ResultsDetergent‐treated skin showed a significant EIS reduction and TEWL increase compared to untreated skin, with a relatively higher sensitivity and dose–response in EIS. The RNA‐seq showed the reduction of the expression of several genes essential for skin barrier integrity, such as tight junctions and adherens junction proteins. In contrast, keratinization, lipid metabolic processes, and epidermal cell differentiation were upregulated. Proteomics analysis showed that the detergents treatment generally downregulated cell adhesion‐related proteins, such as epithelial cell adhesion molecule and contactin‐1, and upregulated proinflammatory proteins, such as interleukin 6 and interleukin 1 beta. Both detergent and SDS led to a significant decrease in EIS values in the ex vivo human skin model.ConclusionThe present study demonstrated that laundry detergents and its main component, SDS impaired the epidermal barrier in vivo and ex vivo human skin. Daily detergent exposure may cause skin barrier disruption and may contribute to the development of atopic diseases

Disrupted epithelial permeability as a predictor of severe COVID-19 development

BackgroundAn impaired epithelial barrier integrity in the gastrointestinal tract is important to the pathogenesis of many inflammatory diseases. Accordingly, we assessed the potential of biomarkers of epithelial barrier dysfunction as predictive of severe COVID‐19.MethodsLevels of bacterial DNA and zonulin family peptides (ZFP) as markers of bacterial translocation and intestinal permeability and a total of 180 immune and inflammatory proteins were analyzed from the sera of 328 COVID‐19 patients and 49 healthy controls.ResultsSignificantly high levels of circulating bacterial DNA were detected in severe COVID‐19 cases. In mild COVID‐19 cases, serum bacterial DNA levels were significantly lower than in healthy controls suggesting epithelial barrier tightness as a predictor of a mild disease course. COVID‐19 patients were characterized by significantly elevated levels of circulating ZFP. We identified 36 proteins as potential early biomarkers of COVID‐19, and six of them (AREG, AXIN1, CLEC4C, CXCL10, CXCL11, and TRANCE) correlated strongly with bacterial translocation and can be used to predict and discriminate severe cases from healthy controls and mild cases (area under the curve (AUC): 1 and 0.88, respectively). Proteomic analysis of the serum of 21 patients with moderate disease at admission which progressed to severe disease revealed 10 proteins associated with disease progression and mortality (AUC: 0.88), including CLEC7A, EIF4EBP1, TRANCE, CXCL10, HGF, KRT19, LAMP3, CKAP4, CXADR, and ITGB6.ConclusionOur results demonstrate that biomarkers of intact or defective epithelial barriers are associated with disease severity and can provide early information on the prediction at the time of hospital admission

The epithelial barrier: The gateway to allergic, autoimmune, and metabolic diseases and chronic neuropsychiatric conditions

Since the 1960 s, our health has been compromised by exposure to over 350,000 newly introduced toxic substances, contributing to the current pandemic in allergic, autoimmune and metabolic diseases. The "Epithelial Barrier Theory" postulates that these diseases are exacerbated by persistent periepithelial inflammation (epithelitis) triggered by exposure to a wide range of epithelial barrier-damaging substances as well as genetic susceptibility. The epithelial barrier serves as the body's primary physical, chemical, and immunological barrier against external stimuli. A leaky epithelial barrier facilitates the translocation of the microbiome from the surface of the afflicted tissues to interepithelial and even deeper subepithelial locations. In turn, opportunistic bacterial colonization, microbiota dysbiosis, local inflammation and impaired tissue regeneration and remodelling follow. Migration of inflammatory cells to susceptible tissues contributes to damage and inflammation, initiating and aggravating many chronic inflammatory diseases. The objective of this review is to highlight and evaluate recent studies on epithelial physiology and its role in the pathogenesis of chronic diseases in light of the epithelial barrier theory

The complete chloroplast genome of Scurrula chingii (W.C. Cheng) H.S. Kiu (Loranthaceae), a hemiparasitic shrub

Scurrula chingii (W.C. Cheng) H.S. Kiu is a stem hemiparasite of the genus Scurrula in the family Loranthaceae distributed in southwest China and northern Vietnam. Here, we report and characterize the complete plastid genome sequence of S. chingii to provide genomic resources useful for the phylogenetic studies of Santalales. The plastome of S. chingii is 122,764 bp in length, consisted of a large single-copy region (70,726 bp), a small single-copy region (6,091 bp), and a pair of inverted repeat regions (22,974 bp). The GC content of the whole plastome is 37.2%. It contains 109 genes, including 69 CDS (protein-coding genes), eight rRNAs, and 32 tRNAs. The alignment of 14 species complete chloroplast genomes of Loranthaceae was implemented and a phylogenetic tree was constructed using maximum-likelihood (ML) method, which revealed that S. chingii clustered with Scurrula parasitica and Taxillus thibetensis as a monophyletic group

Staffing to Maximize Profit for Call Centers with Impatient and Repeat-Calling Customers

Motivated by call center practice, we study the optimal staffing of many-server queues with impatient and repeat-calling customers. A call center is modeled as an M/M/s+M queue, which is developed to a behavioral queuing model in which customers come and go based on their satisfaction with waiting time. We explicitly take into account customer repeat behavior, which implies that satisfied customers might return and have an impact on the arrival rate. Optimality is defined as the number of agents that maximize revenues net of staffing costs, and we account for the characteristic that revenues are a direct function of staffing. Finally, we use numerical experiments to make certain comparisons with traditional models that do not consider customer repeat behavior. Furthermore, we indicate how managers might allocate staffing optimally with various customer behavior mechanisms