Exploiting fitness distance correlation of set covering problems

The set covering problem is an NP-hard combinatorial optimization problemthat arises in applications ranging from crew scheduling in airlines todriver scheduling in public mass transport. In this paper we analyze searchspace characteristics of a widely used set of benchmark instances throughan analysis of the fitness-distance correlation. This analysis shows thatthere exist several classes of set covering instances that have a largelydifferent behavior. For instances with high fitness distance correlation,we propose new ways of generating core problems and analyze the performanceof algorithms exploiting these core problems.

Energetic cost of digging behavior in workers of the leaf-cutting ant Atta sexdens (Fabricius)

Energetic cost of digging behavior in workers of the leaf-cutting ant Atta sexdens (Fabricius). During nest excavation, leaf-cutting ant workers undergo reduction in their body reserve, particularly carbohydrates. In order to estimate the energetic cost of digging, groups of 30 workers of the leaf-cutting ant Atta sexdens were sealed in a hermetic chamber for 24, 48 and 72 hours, with and without soil for digging, and had the CO2 concentration measured using respirometric chambers as well as volume of soil excavated (g). As expected, the worker groups that carried out soil excavation expelled more carbon dioxide than the groups that did not excavate. Therefore, a worker with body mass of 9.65 ± 1.50 mg dug in average 0.85 ± 0.27 g of soil for 24 hours, consuming ca. 0.58 ± 0.23 J. In this study, we calculate that the energetic cost of excavation per worker per day in the experimental set-up was ca. 0.58 J.

Energetic and metabolic cost of growth in Gambian infants.

The aim of the study was to measure the energy used for growth of healthy fullterm and breast-fed Gambian infants. The weight gain (WG) of 14 infants (mean age +/- SEM 17 +/- 1 d, weight 3.581 +/- 0.105 kg) was measured over a 2-week period; the energy intake (EI) from breast milk was assessed for 24 h in the middle of the study period by weighing the infant before and after each breast-feed. On the same day, sleeping energy expenditure (SEE) and respiratory quotient (RQ) were measured for 30 min on five occasions through the 24-h period. EI averaged 502 +/- 25 kJ/kg.d, and SEE 230 +/- 6 kJ/kg.d; thus, an average of 272 kJ/kg.d were available for physical activity and the energy stored for growth. The total energy spent by infants while sleeping and for periods of physical activity was calculated to be 1.7 x SEE. The mean RQ measured on five occasions averaged 0.879 +/- 0.009. SEE was correlated with WG (r = 0.747, P less than 0.005), with a slope of the regression line of 5.5 kJ/g; this value can be considered as an estimate of the energy spent for new tissue synthesis in the resting infant. The efficiency of weight gain was lower in this study (67%) than in studies conducted on fast-growing preterm infants or children recovering from malnutrition.

The cost of inappropriateness of coagulation testing [I costi dell'inappropriatezza in coagulazione]

Background. Laboratory utilization has steadily increased with a corresponding increase in overall costs; several authors have attempted to measure the impact of inappropriateness on clinical outcomes but data are insufficient. The aim of the study is to assess the cost of inappropriateness of test-ordering behaviour for second-level coagulation tests (hemorrhagic diathesisand thrombophilia). Methods. We reviewed all second-level coagulation testrequests received by our department during a six months period. Clinicians must fill out a specific order form for these kind of tests, containing all informations deemed necessary for the laboratory specialist to evaluatethe appropriateness of the request. We identified all inappropriate requests and counted the numbers and types of all coagulation tests that were not performed during the period. An analysis of the laboratory activity costs was done in order to calculate the global costof each test in our department and to estimate the savings achieved. Results. On a total of 1664 second-level coagulationtest requests, we estimated 150 as completely inappropriate. We found an overall of 295 inappropriate testswhich were not performed. This resulted in an economic saving of 20.000 euro in 6 months. Conclusions. The analysis of cost of our intervention shows the urgent need for a definite and sustained reduction in inappropriate requests of second-level coagulation tests. Even though we estimated only the economic aspect of inappropriate testing, this is also associated with the overuse of diagnostic tests which entailsthe risk of generating erroneous results with potentialnegative consequences on patients' health.

Cost-effective utilization of a private facility to perform outpatient surgery in public hospital waiting list patients.

Background: Public hospitals' long waiting lists make outpatient surgery in private facilities very attractive provided a standardized protocol is applied. The aim of this study was to assess this kind of innovative collaboration in abdominal surgery from a clinical and economical perspective. Methods: All consecutive patients operated on in an outpatient basis in a private facility by a public hospital abdominal surgeon and an assistant over a 5-year period (2004-2009) were included. Clinical assessment was carried out from patients' charts and satisfaction questionnaire, and economic assessment from the comparison between the surgeons' charges paid by the private facility and the surgeons' hospital salaries during the days devoted to surgery at the private facility. Results: Over the 5 years, 602 operative procedures were carried out during 190 operative days. All patients could be discharged the same day and only 1% of minor complications occurred. The patients' satisfaction was 98%. The balance between the surgeons' charges paid by the private facility and their hospital salary costs was positive by 25.8% for the senior surgeon and 12.6% for the assistant or, on average, 21.9% for both. Conclusion: Collaboration between an overloaded university hospital surgery department and a private surgical facility was successful, effective, safe, and cost-effective. It could be extended to other surgical specialities. Copyright (C) 2011 S. Karger AG, Basel

Governor's Task Force on Efficiencies and Cost-Effectiveness in Iowa State Government,Final Report, December 1983

A special task force was formed and worked through its various committees to uncover and investigate possible areas for cutting costs and saving money in State Government operations. A total of 81 recommendations are made in this report, with potential savings of over $32 million during the next several years.

Four 13-lipoxygenases contribute to rapid jasmonate synthesis in wounded Arabidopsis thaliana leaves: a role for lipoxygenase 6 in responses to long-distance wound signals.

Damage-inducible defenses in plants are controlled in part by jasmonates, fatty acid-derived regulators that start to accumulate within 30 s of wounding a leaf. Using liquid chromatography-tandem mass spectrometry, we sought to identify the 13-lipoxygenases (13-LOXs) that initiate wound-induced jasmonate synthesis within a 190-s timeframe in Arabidopsis thaliana in 19 single, double, triple and quadruple mutant combinations derived from the four 13-LOX genes in this plant. All four 13-LOXs were found to contribute to jasmonate synthesis in wounded leaves: among them LOX6 showed a unique behavior. The relative contribution of LOX6 to jasmonate synthesis increased with distance from a leaf tip wound, and LOX6 was the only 13-LOX necessary for the initiation of early jasmonate synthesis in leaves distal to the wounded leaf. Herbivory assays that compared Spodoptera littoralis feeding on the lox2-1 lox3B lox4A lox6A quadruple mutant and the lox2-1 lox3B lox4A triple mutant revealed a role for LOX6 in defense of the shoot apical meristem. Consistent with this, we found that LOX6 promoter activity was strong in the apical region of rosettes. The LOX6 promoter was active in and near developing xylem cells and in expression domains we term subtrichomal mounds.

Detecció de matrícules amb sistemes de baix cost

En aquest projecte s'avaluen els mètodes utilitzats per els mecanismes de detecció de matrícules, i es proposarà un algorisme de detecció de matrícules dissenyat específicament per a sistemes de baix cost com ara els ordinadors actuals. Utilitzarem eines al nostre abast, com càmeres fotogràfiques domèstiques o de mòbil per analitzar el rendiment de l'algorisme

Constraint and cost of oxidative stress on reproduction: correlative evidence in laboratory mice and review of the literature.

ABSTRACT: BACKGROUND: One central concept in evolutionary ecology is that current and residual reproductive values are negatively linked by the so-called cost of reproduction. Previous studies examining the nature of this cost suggested a possible involvement of oxidative stress resulting from the imbalance between pro- and anti-oxidant processes. Still, data remain conflictory probably because, although oxidative damage increases during reproduction, high systemic levels of oxidative stress might also constrain parental investment in reproduction. Here, we investigated variation in oxidative balance (i.e. oxidative damage and antioxidant defences) over the course of reproduction by comparing female laboratory mice rearing or not pups. RESULTS: A significant increase in oxidative damage over time was only observed in females caring for offspring, whereas antioxidant defences increased over time regardless of reproductive status. Interestingly, oxidative damage measured prior to reproduction was negatively associated with litter size at birth (constraint), whereas damage measured after reproduction was positively related to litter size at weaning (cost). CONCLUSIONS: Globally, our correlative results and the review of literature describing the links between reproduction and oxidative stress underline the importance of timing/dynamics when studying and interpreting oxidative balance in relation to reproduction. Our study highlights the duality (constraint and cost) of oxidative stress in life-history trade-offs, thus supporting the theory that oxidative stress plays a key role in life-history evolution.

Nestmate recognition in the unicolonial ant Formica paralugubris

In unicolonial populations of ants, individuals can mix freely within large networks of nests that contain many queens. It has been proposed that the absence of aggression in unicolonial populations stems from a loss of nest mate recognition, but few studies have tested this hypothesis. We investigated patterns of aggression and nest mate recognition in the unicolonial wood ant, Formica paralugubris. Little aggression occurred, even between workers from nests separated by up to 5 km. However, when aggression took place, it was directed toward non-nest mates rather than nest mates. Trophallaxis (exchange of liquid food) occurred very frequently, and surprisingly, workers performed significantly more trophallaxis with non-nest mates than with nest mates (bias 2.4:1). Hence, workers are able to discriminate nest mates from non-nest mates. Higher rates of trophallaxis between non-nest mates may serve to homogenize the colony odor or may be an appeasement mechanism. Trophallaxis rate and aggression level were not correlated with geographical distance and did not differ within and between two populations separated by several kilometers. Hence, these populations do not represent differentiated supercolonies with clear-cut behavioral boundaries. Overall, the data demonstrate that unicoloniality can evolve despite well-developed nest mate recognition. Reduced levels of aggression might have been favored by the low rate of interactions with foreign workers, high cost of erroneously rejecting nest mates, and low cost of accepting foreign workers.

Prevalence of cardiovascular risk factors in a middle-income country and estimated cost of a treatment strategy.

BACKGROUND: We assessed the prevalence of risk factors for cardiovascular disease (CVD) in a middle-income country in rapid epidemiological transition and estimated direct costs for treating all individuals at increased cardiovascular risk, i.e. following the so-called "high risk strategy". METHODS: Survey of risk factors using an age- and sex-stratified random sample of the population of Seychelles aged 25-64 in 2004. Assessment of CVD risk and treatment modalities were in line with international guidelines. Costs are expressed as USD per capita per year. RESULTS: 1255 persons took part in the survey (participation rate of 80.2%). Prevalence of main risk factors was: 39.6% for high blood pressure (> or =140/90 mmHg or treatment) of which 59% were under treatment; 24.2% for high cholesterol (> or =6.2 mmol/l); 20.8% for low HDL-cholesterol (<1.0 mmol/l); 9.3% for diabetes (fasting glucose > or =7.0 mmol/l); 17.5% for smoking; 25.1% for obesity (body mass index > or =30 kg/m2) and 22.1% for the metabolic syndrome. Overall, 43% had HBP, high cholesterol or diabetes and substantially increased CVD risk. The cost for medications needed to treat all high-risk individuals amounted to USD 45.6, i.e. 11.2 dollars for high blood pressure, 3.8 dollars for diabetes, and 30.6 dollars for dyslipidemia (using generic drugs except for hypercholesterolemia). Cost for minimal follow-up medical care and laboratory tests amounted to 22.6 dollars. CONCLUSION: High prevalence of major risk factors was found in a rapidly developing country and costs for treatment needed to reduce risk factors in all high-risk individuals exceeded resources generally available in low or middle income countries. Our findings emphasize the need for affordable cost-effective treatment strategies and the critical importance of population strategies aimed at reducing risk factors in the entire population.

Rate, type, and cost of adverse drug reactions in emergency department admissions.

Background: Adverse drug reactions (ADRs) are a threat to patients' health and quality of life, and can generate significant expenses. They are generally underreported, with different rates in different health care systems. Methods: We conducted a 6-month survey of all primary admissions to the medical emergency department of a university hospital and assessed the rate, characteristics, avoidability, and marginal costs of ADRs. Results: A total of 7% of all admissions were mainly caused by ADRs. The most frequent were gastrointestinal bleeding (22.3%) and febrile neutropenia (14.4%). Anticancer drugs were involved in 22.7% of the cases, and anticoagulants, analgesics, and non-steroidal anti-inflammatory drugs in 8% each. Physicians had prescribed 70% of these drugs. Patients were predominantly treated in intermediate care units and ordinary wards. The mean cost per case amounted to CHF 3586+/-342, or a total of CHF 821204 over the 6-month-period (1 CHF=0.56 US$=0.87 Euro). A total of 67% were considered definitely imputable to drug effects and 32% were retrospectively regarded as avoidable. Conclusions: Interventions aimed at reducing the incidence of ADRs should be directed towards both patient education and physician training. This could save hospitals admissions and money, and could be used as an indicator of prescription quality.