A comparative study of FMS tool allocation and part type selection approaches for a varying part type mix

Hankins and Rovito (1984) examined the impact of different tool policies on cutting tool inventory levels and spindle utilization for a flexible manufacturing system (FMS). This study provides a broader perspective of the impact of tool allocation approaches on flow times, tardiness, percent of orders tardy, machine utilization, and robot utilization. Part type selection procedures have been suggested for the FMS prerelease planning problem. However, very little research has specifically evaluated the part type selection procedures across different tool allocation approaches. Also, with the exception of Stecke and Kim (1988, 1991) no other known study has provided any insights on what tool allocation approaches are appropriate when processing different mixes of part types. This research is devoted to addressing those issues. Three tool allocation approaches, three production scheduling rules, and three levels of part mix are evaluated in this study through a similation model of a flexible manufacturing system. The specific impacts of the tool approaches, their interaction effects with the part type selection rules, and their effectiveness at different part type mix levels are provided through the use of a regression metamodel.     

Reasons for Missing Antiretroviral Therapy: Results from a Multi-Country Study in Tanzania,Uganda, and Zambia

Objectives

To identify the reasons patients miss taking their antiretroviral therapy (ART) and the proportion who miss their ART because of symptoms; and to explore the association between symptoms and incomplete adherence.

Methods

Secondary analysis of data collected during a cross-sectional study that examined ART adherence among adults from 18 purposefully selected sites in Tanzania, Uganda, and Zambia. We interviewed 250 systematically selected patients per facility (≥18 years) on reasons for missing ART and symptoms they had experienced (using the HIV Symptom Index). We abstracted clinical data from the patients’ medical, pharmacy, and laboratory records. Incomplete adherence was defined as having missed ART for at least 48 consecutive hours during the past 3 months.

Results

Twenty-nine percent of participants reported at least one reason for having ever missed ART (1278/4425). The most frequent reason was simply forgetting (681/1278 or 53%), followed by ART-related hunger or not having enough food (30%), and symptoms (12%). The median number of symptoms reported by participants was 4 (IQR: 2–7). Every additional symptom increased the odds of incomplete adherence by 12% (OR: 1.1, 95% CI: 1.1–1.2). Female participants and participants initiated on a regimen containing stavudine were more likely to report greater numbers of symptoms.

Conclusions

Symptoms were a common reason for missing ART, together with simply forgetting and food insecurity. A combination of ART regimens with fewer side effects, use of mobile phone text message reminders, and integration of food supplementation and livelihood programmes into HIV programmes, have the potential to decrease missed ART and hence to improve adherence and the outcomes of ART programmes.     

Sexual behaviour and contraception among unmarried adolescents and young adults in Greater Accra and Eastern regions of Ghana

A fertility survey of unmarried adolescents and young adults (953 males and 829 females) in Greater Accra and Eastern regions of Ghana revealed that a substantial proportion of the respondents were sexually experienced. Overall, 66.8% of the males and 78.4% of the females were sexually experienced. The mean ages (+/- SD) of the males and females were 15.5 +/- 2.5 and 16.2 +/- 2.0 years, respectively. Most respondents claimed to have received adequate information on reproductive health and sexually transmitted diseases (STDs), including AIDS. However, 20% and 30% of the respondents in peri-urban and rural areas, respectively, did not know that a girl could get pregnant the first time she has sexual intercourse. The incidence of pregnancy among the unmarried female respondents was relatively high (37%), and was higher in urban than in rural areas. Approximately 47% of those who had ever been pregnant reported that they had had an abortion. Levels of contraceptive awareness were high (98.2% among males and 95.5% among females) but many still engaged in unprotected sexual relations. The most commonly used methods were the condom and the pill. The main reasons given for non-use were that they did not think about contraception, were concerned about the safety of contraceptives, and partner objection. These findings point to the need for targeting of unmarried adolescents and young adults with information on reproductive health and family planning to increase their awareness of the risks of pregnancy, STDs and HIV infection.     

Caenorhabditis elegans,a pluricellular model organism to screen new genes involved in mitochondrial genome maintenance

The inheritance of functional mitochondria depends on faithful replication and transmission of mitochondrial DNA (mtDNA). A large and heterogeneous group of human disorders is associated with mitochondrial genome quantitative and qualitative anomalies. Several nuclear genes have been shown to account for these severe OXPHOS disorders. However, in several cases, the disease-causing mutations still remain unknown.Caenorhabditis elegans has been largely used for studying various biological functions because this multicellular organism has short life cycle and is easy to grow in the laboratory. Mitochondrial functions are relatively well conserved between human and C. elegans, and heteroplasmy exists in this organism as in human. C. elegans therefore represents a useful tool for studying mtDNA maintenance. Suppression by RNA interference of genes involved in mtDNA replication such as polg-1, encoding the mitochondrial DNA polymerase, results in reduced mtDNA copy number but in a normal phenotype of the F1 worms. By combining RNAi of genes involved in mtDNA maintenance and EtBr exposure, we were able to reveal a strong and specific phenotype (developmental larval arrest) associated to a severe decrease of mtDNA copy number. Moreover, we tested and validated the screen efficiency for human orthologous genes encoding mitochondrial nucleoid proteins. This allowed us to identify several genes that seem to be closely related to mtDNA maintenance in C. elegans.This work reports a first step in the further development of a large-scale screening in C. elegans that should allow to identify new genes of mtDNA maintenance whose human orthologs will obviously constitute new candidate genes for patients with quantitative or qualitative mtDNA anomalies.     

Carbohydrate utilization affects Lactobacillus delbrueckii subsp. lactis 313 cell-enveloped-associated proteinase production

The effect of different sugars (glucose, glycerol, maltose, galactose and lactose) on cell-membrane-associated proteinase production by Lactobacillus delbrueckii subsp. lactis 313 (LDL 313) was investigated. The experimental results showed that aside glycerol and galactose, all the other sugars supported high growth levels of LDL 313, with glucose displaying the maximum biomass concentration of 0.85 mg/mL dry cell weight for cells harvested at the mid-exponential phase of ??12 h after inoculation. The specific proteinase yield, a measure of the rate of proteinase production relative to cell wall biosynthesis, was used to evaluate the preferential degree of proteinase metabolism as induced by the consumption of different sugar substrates by LDL 313. It was found that maltose displayed the highest specific proteinase yield of 12.59 U/mg sugar consumed. Further, molecular differences were observed in the SDS electrophoretic profile of cell surface proteins generated for the different carbon substrates. This is a preliminary study which supports the inference that different sugars stimulate the production of different cell-surface proteins with a significant effect on cell proteinase activity.     

Tau Kinetics in Neurons and the Human Central Nervous System

1. Download high-res image (181KB)
2. Download full-size image

     

Cu(II) organizes beta-2-microglobulin oligomers but is released upon amyloid formation

beta-2-Microglobulin (beta2m) is deposited as amyloid fibrils in the bones and joints of patients undergoing long-term dialysis treatment as a result of kidney failure. Previous work has shown that biologically relevant amounts of Cu(II) can cause beta2m to be converted to amyloid fibrils under physiological conditions in vitro. In this work, dynamic light scattering, mass spectrometry, and size-exclusion chromatography are used to characterize the role that Cu plays in the formation of oligomeric intermediates that precede fibril formation. Cu(II) is found to be necessary for the stability of the dimer and an initial form of the tetramer. The initially formed tetramer then undergoes a structural change to a state that no longer binds Cu(II) before progressing to a hexameric state. Based on these results, we propose that the lag phase associated with beta2m fibril formation is partially accounted for by the structural transition of the tetramer that results in Cu(II) loss. Consistent with this observation is the determination that the mature beta2m amyloid fibrils do not contain Cu. Thus, Cu(II) appears to play a catalytic role by enabling the organization of the necessary oligomeric intermediates that precede beta2m amyloid formation.     

Empirical studies of escape behavior find mixed support for the race for life model

Escape theory has been exceptionally successful in conceptualizing and accurately predicting effects of numerous factors that affect predation risk and explaining variation in flight initiation distance (FID; predator–prey distance when escape begins). Less explored is the relative orientation of an approaching predator, prey, and its eventual refuge. The relationship between an approaching threat and its refuge can be expressed as an angle we call the “interpath angle” or “Φ,” which describes the angle between the paths of predator and prey to the prey’s refuge and thus expresses the degree to which prey must run toward an approaching predator. In general, we might expect that prey would escape at greater distances if they must flee toward a predator to reach its burrow. The “race for life” model makes formal predictions about how Φ should affect FID. We evaluated the model by studying escape decisions in yellow-bellied marmots Marmota flaviventer, a species which flees to burrows. We found support for some of the model’s predictions, yet the relationship between Φ and FID was less clear. Marmots may not assess Φ in a continuous fashion; but we found that binning angle into 4 45° bins explained a similar amount of variation as models that analyzed angle continuously. Future studies of Φ, especially those that focus on how different species perceive relative orientation, will likely enhance our understanding of its importance in flight decisions.     

Experiences with the Mass Distribution of LPG Stoves in Rural Communities of Ghana

Household air pollution (HAP) is a leading cause of morbidity and mortality worldwide. To limit HAP exposure and environmental degradation from biomass fuel use, the Government of Ghana promotes liquefied petroleum gas (LPG) use in rural Ghana via the Rural LPG program (RLP). We assessed the experiences of the RLP in 2015, 2 years after its launch. A mixed methods approach was used involving Focus Group Discussions (19) and in-depth interviews (25). In addition, a survey questionnaire was administered to elicit socio-demographic characteristics, household cooking practices and stove use patterns of 200 randomly selected respondents. At about 9 months after LPG acquisition,?<?5% of LPG beneficiaries used their stoves. Some of the reasons ascribed to the low usage of the LPG cookstoves were financial constraints, distance to LPG filling point and fear of burns. Community members appreciate the convenience of using LPG. Our results underscore a need for innovative funding mechanisms contextualized within an overall economic empowerment of rural folks to encourage sustained LPG use. It emphasizes the need for innovative accessibility interventions. This could include establishing new LPG filling stations in RLP beneficiary districts to overcome the barriers to sustained LPG use.