Combinatorial Assortment Optimization

Assortment optimization refers to the problem of designing a slate of products to offer potential customers, such as stocking the shelves in a convenience store. The price of each product is fixed in advance, and a probabilistic choice function describes which product a customer will choose from any given subset. We introduce the combinatorial assortment problem, where each customer may select a bundle of products. We consider a model of consumer choice where the relative value of different bundles is described by a valuation function, while individual customers may differ in their absolute willingness to pay, and study the complexity of the resulting optimization problem. We show that any sub-polynomial approximation to the problem requires exponentially many demand queries when the valuation function is XOS, and that no FPTAS exists even for succinctly-representable submodular valuations. On the positive side, we show how to obtain constant approximations under a "well-priced" condition, where each product's price is sufficiently high. We also provide an exact algorithm for $k$-additive valuations, and show how to extend our results to a learning setting where the seller must infer the customers' preferences from their purchasing behavior

Atropelamentos e novos registros para tatu-canastra (Priodontes maximus) no centro-oeste do Brasil

Despite the widespread distribution of the giant armadillo Priodontes maximus, this species isfound at low densities, often in disrupted populations. Here we report 12 new records, including five incidentsof roadkill of P. maximus in different points of the Cerrado and one in an Atlantic Forest fragment in centralwesternBrazil. In addition to the relevant records, we discuss the negative effects of roadkills, which is a seriousissue for the conservation and maintenance of local populations of giant armadillo.Atropelamentos e novos registros para tatu-canastra (Priodontes maximus) no centro-oeste do Brasil. Apesar da ampla distribuição do tatu-canastra Priodontes maximus, esta espécie apresenta baixas densidades em populações não conectadas. Aqui, relatamos 12 novos registros, incluindo cinco atropelamentos rodoviários de P. maximus em diferentes pontos de Cerrado e um em fragmento de Floresta Atlântica no centro-oeste do Brasil. Além dos registros relevantes, discutimos o efeito negativo da perda de espécimes por atropelamentos em estradas, o qual é um problema sério para a conservação e manutenção de populações locais de tatu-canastra.Fil: Hannibal, Wellington. Universidade Federal de Goiás; BrasilFil: Leme Da Cunha, Nicolay. Universidade Federal do Mato Grosso do Sul; Brasil. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Dalponti, Guilherme. Universidade Federal do Mato Grosso do Sul; BrasilFil: Oliveira, Seixas R.. Instituto Federal Goiano; BrasilFil: Pereira, Katia R. F.. Universidade Anhaguera; Brasi

Irrigation Scheduling to Promote Corn Productivity in Central Alabama

Agriculture is the largest consumer of water in the United States. Results from previous studies have shown thatit is possible to substantially reduce irrigation amounts and maintain corn yield. The objectives of this study wereto evaluate the advantages and disadvantages of two irrigation scheduling methods for corn production inAlabama. Two irrigation scheduling methods evaluated were: a) Checkbook, which is one of the conventionalmethods used by farmers that is based on the soil water balance estimated using water lost by evapotranspirationand its replacement through rainfall or irrigation, and b) Sensor-based, which was based on soil matric potentialvalues recorded by soil moisture tension sensors installed in the field. The experimental field was divided intotwo irrigation management zones (zone A and zone B) based on soil properties of each field. During the 2014season in zone A, significant grain yield differences were observed between the two irrigation methods. TheCheckbook plots exhibited greater yield than Sensor-based plots: 10181 kg ha-1 and 9696 kg ha-1, respectively.The greater yield on the Checkbook plots could be associated with higher irrigation rate applied, 148 mm more,compared with the Sensor-based plots. In zone B, there were no significant yield differences between bothirrigation methods; however, Sensor-based plots out yielded Checkbook plots, with 9673 kg ha-1 and 9584 kgha-1, respectively. Even though the irrigation amount applied in Checkbook located in zone B was higher, 102mm more, there were no significant yield differences. Therefore, it suggests that the Sensor-based method waspromissory irrigation scheduling strategy under the conditions of zone B. In 2015, there were no significant grainyield differences between zone A and zone B when the data from the Checkbook plots were analyzed. However,the Sensor-based treatment produced a statistically significant difference of grain yield of 13597 kg ha-1 in zoneA and 11659 kg ha-1 in zone B, also both zones received the same amount of irrigation. Overall results of bothgrowing seasons indicated that the use of the Sensor-based irrigation scheduling treatment resulted in similarvalues of total profit per hectare when compared to Checkbook method. The Sensor-based method seems apromising strategy that could result in water and financial savings, but more research is required.Fil: Da Cunha Leme Filho, Jose F.. Virginia Polytechnic Institute; Estados UnidosFil: Ortiz, Brenda V.. Auburn University.; Estados UnidosFil: Damianidis, Damianos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Santa Fe. Estación Experimental Agropecuaria Oliveros; ArgentinaFil: Balkcom, Kipling S.. Usda-soil Dynamics Research; Estados UnidosFil: Dougherty, Mark. Auburn University.; Estados UnidosFil: Poschel, Thorsten. Auburn University.; Estados Unido

Monensin and functional oil addition in feed behavior and methane emission of Nellore bulls fed low-fiber diets.

In order to minimize unwanted effects of high levels of grains in feedlot diet, antibiotic feed additives are used, but its security is challenged and the discovery of alternative natural substances becomes necessary. The aim of the study was to evaluate the effect of increasing levels of the forage neutral detergent fiber (NDFf) and additives in feeding behavior and enteric methane emissions. Seventy Nellore bulls, (408 ± 14.17 kg initial LW), were distributed in a factorial arrangement 2 x 3 + 1, where two additives (500 mg kg-1 DM, of a blend of castor oil and cashew nut shell liquid, Essential Oligo Basics, Brazil, or 30 mg kg-1 DM of monensin), three levels of NDFf (6, 9 and 15% in DM), and control group, without additive. The diet was composed by Brachiaria hay, ground corn, citrus pulp, soybean meal and mineral salt. The experiment lasted 105d, the enteric methane emission was estimated by indicator gas SF6 methodology, in two collections for five straight days, the intake behavior was performed through rumination sensors (Heatime® HR), evaluated in five animal per treatment. Data were analyzed using the SAS´s MIXED, 5% significance evaluated by contrasts. The monensina increased (P<0.05) the dry matter intake (DMI), final live weight (FLW), and methane emission compared to oil treatment, the averages 8.29 ± 0.06 kg d-1, 518.73 ± 5.7 kg and 183.22 ± 4.6 g d-1 for monensin and 7.48 ± 0.04 kg d-1; 489.8 ± 8.9 kg and 161.33 ± 4.83 g d-1 for functional oil. Regarding the NDFf levels, the DMI was higher for 15% of NDFf compared to other levels (P = 0.0156), the averages were respectively 8.69 ± 0.03, 7.10 ± 0.04 and 7.99 ± 0.05 kg d-1. The methane emission increased (P = 0.0006) as the NDFf level was increased (139.03 ± 4.97; 165.51 ± 3.4 and 213.72 ± 4.64 g d-1 for the 6 and 9% levels, respectively), with no changes when methane was analyzed by kg of DMI (P = 0.1308). There was an effect on NDFf levels on rumination time (P = 0.0106) with 23.25 ± 0.62; 21.30 ± 0.30 and 26.94 ± 0.43 kg of DM d-1 for 6, 9 e 15% levels, respectively. As well the monensina increased (P = 0.0030) the rumination time compared to the functional oil (25.56 ± 0.38 and 23.98 ± 0.49 kg of DM d-1 respectively). The diet with 15% of NDFf and the monensin were more effective in DMI, FLW and rumination, the functional oil contributed to the reduction of enteric methane emission

Variable positive end-expiratory pressure can maintain oxygenation in experimental acute respiratory distress syndrome induced by oleic acid in dogs

The use of positive end-expiratory pressure (PEEP) or lung recruitment maneuvers (RM) to improve oxygenation in acute respiratory distress syndrome (ARDS) is used but it may reduce cardiac output (CO). Intermittent PEEP may avoid these complications. Our objective was to determine if variable PEEP compared with constant PEEP is capable of maintaining arterial oxygenation and minimizing hemodynamic alterations with or without RM. Eighteen dogs with ARDS induced by oleic acid were randomized into three equal groups: group 1, low variable PEEP; group 2, high variable PEEP, and group 3, RM + high variable PEEP. All groups were submitted to constant PEEP, followed by variable PEEP (PEEP was increased from 5 to 10 cmH2O in group 1, and from 5 to 18 cmH2O in the other two groups). PaO2 was higher in group 3 (356.2 ± 65.4 mmHg) than in group 1 (92.7 ± 29.7 mmHg) and group 2 (228.5 ± 72.4 mmHg), P 0.05. Variable PEEP is able to maintain PaO2 when performed in combination with RM in dogs with ARDS. After RM, CO was reduced and there was no relevant difference between the variable and constant PEEP periods.Universidade Federal de São Paulo (UNIFESP) Escola Paulista de Medicina Departamento de MedicinaCentro Universitário São CamiloUniversidade de São Paulo Faculdade de Medicina Laboratório de Investigação Médica (LIM 12)UNIFESP, EPM, Depto. de MedicinaSciEL

Correlations of visual scores and ultrasound carcass traits with economically relevant traits in Nellore cattle.

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