Conduction electrons localized by charged magneto-acceptors A2−^{2-} in GaAs/GaAlAs quantum wells

A variational theory is presented of A$^{1-}$ and A$^{2-}$ centers, i.e. of a negative acceptor ion localizing one and two conduction electrons, respectively, in a GaAs/GaAlAs quantum well in the presence of a magnetic field parallel to the growth direction. A combined effect of the well and magnetic field confines conduction electrons to the proximity of the ion, resulting in discrete repulsive energies above the corresponding Landau levels. The theory is motivated by our experimental magneto-transport results which indicate that, in a heterostructure doped in the GaAs well with Be acceptors, one observes a boil-off effect in which the conduction electrons in the crossed-field configuration are pushed by the Hall electric field from the delocalized Landau states to the localized acceptor states and cease to conduct. A detailed analysis of the transport data shows that, at high magnetic fields, there are almost no conducting electrons left in the sample. It is concluded that one negative acceptor ion localizes up to four conduction electrons.Comment: 8 pages, 5 figure

Fatores associados ao consumo alimentar de crianças de 6 a 12 meses acompanhadas na atenção básica de Porto Alegre em 2018

Introdução: A alimentação complementar é recomendada a partir dos 6 meses e é fundamental para a promoção da saúde, o desenvolvimento físico e intelectual e a redução do risco dos transtornos causados pelas deficiências nutricionais comuns na infância, além de prevenir doenças crônicas não transmissíveis ao longo da vida adulta. A análise do consumo alimentar e de seus determinantes é fundamental para o monitoramento e planejamento de ações e de políticas públicas para a promoção da alimentação saudável na infância. Objetivo: Investigar os fatores associados ao consumo alimentar de crianças de 6 a 12 meses acompanhadas na atenção básica de Porto Alegre/RS em 2018. Metodologia: Estudo transversal com dados secundários da Estratégia e-SUS Atenção Básica. Foram incluídas crianças com o questionário de marcadores de consumo alimentar preenchido em 2018. Os desfechos foram: 1) diversidade alimentar mínima (DAM), que incluía ter consumido pelo menos um alimento de seis grupos no dia anterior ao inquérito; 2) consumo de ultraprocessados (UP); e, 3) alimentação não saudável (NS), definida como não atingir DAM e apresentar UP. Para testar a associação entre as variáveis independentes e os desfechos utilizou-se o teste qui-quadrado de Pearson. As variáveis que indicaram um nível de significância de até 20% no teste foram incluídas na análise multivariada, realizada por meio de Regressão de Poisson com variância robusta, considerando nível de significância de 5% (p<0,05). Os dados foram processados e analisados no software SPSS versão 25.0. O projeto foi aprovado pelo Comitê de Ética em Pesquisa da Prefeitura Municipal de Porto Alegre (CAAE nº 33783420.00000.5338). Resultados: A amostra foi composta por 906 crianças provenientes de 50,8% (n=65) das unidades de saúde elegíveis do município. As prevalências dos padrões DAM, UP e NS foram 54,1%, 31,2% e 14,1%, respectivamente. Em relação as características da amostra, 50,8% das crianças eram do sexo feminino; entre as mães, 67% eram brancas, 62% apresentavam até 8 anos de escolaridade, e 70,3% situavam-se na faixa de 20 a 34 anos. A maioria das crianças nasceu de parto vaginal (63,3%), a termo (89,4%) e com peso adequado (85,9%). A idade da criança foi associada significativamente aos desfechos DAM e UP, sendo que quanto mais velha a criança, maior a prevalência de ambos. No padrão UP, maior prevalência também foi associada ao sexo masculino. O padrão NS não apresentou associação significativa com as variáveis testadas. Considerações finais: A alimentação complementar em Porto Alegre/RS está aquém do preconizado e conforme aumenta a idade das crianças, apesar de ocorrer um aumento na diversidade alimentar, também há incremento no consumo de alimentos não recomendados. Políticas de promoção da alimentação saudável infantil devem ser fortalecidas no município para melhorar este cenário.Introduction: Complementary feeding is recommended from 6 months onwards and is essential for promoting health, physical and intellectual development and reducing the risk of disorders caused by nutritional deficiencies common in childhood, in addition to preventing chronic non-communicable diseases throughout of adult life. The analysis of food consumption and its determinants is essential for monitoring and planning actions and public policies to promote healthy eating in childhood. Objective: To investigate the factors associated with the food consumption of children aged 6 to 12 months followed up in primary care in Porto Alegre/RS in 2018. Methods: Cross-sectional study with secondary data from the e-SUS Primary Care Strategy. Children with a food consumption questionnaire completed in 2018 were included. Outcomes were: 1) minimal dietary diversity (MDD), which included having consumed at least one food from six groups on the day before the survey; 2) consumption of ultra-processed products (UP); and, 3) unhealthy diet (NS), defined as not reaching BMD and having PU. To test the association between independent variables and outcomes, Pearson's chi-square test was used. Variables that indicated a significance level of up to 20% in the test were included in the multivariate analysis, performed using Poisson regression with robust variance, considering a significance level of 5% (p<0.05). Data were processed and analyzed using SPSS software version 25.0. The project was approved by the Research Ethics Committee of Porto Alegre (CAAE nº 33783420.00000.5338). Results: The sample consisted of 906 children from 50.8% (n=65) of eligible health units in the municipality. The prevalences of MDD, UP and NS patterns were 54.1%, 31.2% and 14.1%, respectively. Regarding the characteristics of the sample, 50.8% of the children were female; among mothers, 67% were white, 62% had up to 8 years of schooling, and 70.3% were between 20 and 34 years old. Most children were born vaginally (63.3%), at term (89.4%) and with adequate weight (85.9%). Child age was significantly associated with MDD and UP outcomes, and the older the child, the greater the prevalence of both. In the UP pattern, higher prevalence was also associated with males. The NS pattern showed no significant association with the variables tested. Conclusion: Complementary feeding in Porto Alegre/RS is below what is recommended and as children age, despite an increase in food diversity, there is also an increase in the consumption of non-recommended foods. Policies to promote healthy infant nutrition should be strengthened in the municipality to improve this scenario

Straddle com opções : análise de desempenho da estratégia quando aplicada em eventos de divulgação de balanços

No mercado financeiro, denomina-se straddle uma estratégia combinada de compra de opções que pode ser aplicada com sucesso quando se espera o aumento de volatilidade do ativo subjacente. A hipótese a ser avaliada neste trabalho é de que os eventos trimestrais de divulgação de balanço sejam capazes de gerar condições favoráveis ao emprego desta estratégia. Tendo os balanços data agendada para divulgação, o investidor poderia se posicionar oportunamente em um straddle no objetivo de obter ganho financeiro com a venda após o balanço. Para avaliar esta estratégia, dados históricos de preços das ações e opções das empresas Petrobrás e Vale do Rio Doce foram coletados para análise, compreendendo os anos de 2010 a 2023, inclusive. Da mesma forma, foram levantadas as datas nas quais os balanços trimestrais destas empresas foram divulgados, em um total de 104 eventos neste período. Simulações de compra e venda de straddle foram feitas, posicionando a compra em data imediatamente anterior à da divulgação de cada balanço, e fazendo a venda na data imediatamente posterior. Esta estratégia de curtíssimo prazo tem por objetivo capturar exclusivamente o efeito do evento de balanço sobre os preços dos ativos, minimizando a contaminação com outras notícias ou eventos. Os straddle foram simulados com opções ATM, como forma de delinear uma estratégia a ser replicada, além de contar com a maior liquidez das opções assim classificadas. A sequência de simulações foi avaliada como se fosse a cota de uma carteira de investimentos e comparada ao desempenho da carteira teórica do Índice Bovespa, como referência. O resultado da aplicação sucessiva de straddles na condição estabelecida não superou o benchmark: apenas 37 dos 104 eventos avaliados apresentaram ganho financeiro, e a carteira simulada resultou perda acumulada de 98,79%, num mesmo período no qual o Índice Bovespa apresentou valorização de 48,54%. Destes resultados, conclui-se que a aplicação da estratégia de straddle em eventos de divulgação de balanço não teve êxito, dado que tais eventos, na maioria das vezes, não foram chave para gerar volatilidade suficiente para produzir straddles vencedores.In financial markets, straddle is the name given to a strategy for option purchasing which can be successfully applied when an increase in volatility is expected for the underlying asset. The hypothesis to be tested is that the quarterly balance sheet disclosure events are capable of generating favorable conditions for the use of this strategy. Since the balance sheet disclosure events are scheduled in advance, the investor could opportunistically buy a straddle aiming financial gains when selling it in the day after the event. To evaluate this strategy, historical data for stock and option prices of Petrobras and Vale do Rio Doce companies were collected for analysis, covering the years 2010 to 2023, inclusive. Likewise, it was done a survey about the dates at which the quarterly balance sheets of these companies were disclosed, comprehending a total of 104 events in this period. Straddle purchase and sale simulations were carried out, positioning the purchase at a date immediately prior to the release of each balance sheet, while making the sale at the immediately subsequent date. This very short-term strategy aims to capture the effect of the balance sheet event on asset prices, minimizing contamination with other news or events. The straddles were simulated with ATM options, as a way of outlining a strategy to be replicated, followed by the fact that ATM options are more liquid. The sequence of all simulation results was evaluated as if it were the quota of an investment portfolio and compared to the performance of the theoretical portfolio of the Bovespa Index as a benchmark. The result of the successive application of straddles in the established condition was catastrophic: only 37 of the 104 events evaluated showed financial gain, and the simulated portfolio resulted in an accumulated loss of 98.79%, in the same period at which the Bovespa Index appreciated by 48.54 %. From these results, it can be concluded that the application of the straddle strategy in balance sheet disclosure events was unsuccessful, given that such events, most of the time, were not decisive to generate enough volatility as to produce winning straddles

Respuestas de Anastrepha fraterculus (Diptera: Tephritidae) a plaguicidas utilizados en la producción orgánica de frutas

The South American fruit fly, Anastrepha fraterculus (Diptera: Tephritidae), is an economically important pest of fruit production in Southern Brazil. In organically managed orchards the species has traditionally been controlled with oils, plant extracts, and solutions such as pyroligneous extract and lime sulfur. The objectives of this study were to examine the possible deterrent effect of pesticides with the highest electroantennographic bioactivity on fruit flies and to assess their effects on the viability of pupae in treated fruits. Antennae were exposed to pyroligneous extract (BioPirol7M®, 0.4%), lime sulfur solution (SulFertilizantes, 1%), neem (Organic Neem®, 0.5%), and rotenone (Rotenat®, 0.6%), taking into account fly sex, age and reproductive status. Pupal viability was assessed for larvae reared in papaya (Carica papaya var. Calyman) and guava (Psidium guajava var. Paluma) fruits treated with the pesticides that generated the strongest electrophysiological responses. The bioactivity of A. fraterculus antennae was highest when stimulated with pyroligneous extract and lime sulfur solution, for young and mated flies. Neither substance inhibited oviposition and larval development in treated fruits, a result that has important implications for A. fraterculus management in organic systemsLa mosca sudamericana, Anastrepha fraterculus (Diptera: Tephritidae), es una plaga de importancia económica en la producción de frutas en el sur de Brasil. En huertos bajo manejo orgánico la especie se controla tradicionalmente con aceites, extractos vegetales y soluciones como el extracto piroleñoso y sulfuro de cal. Los objetivos de este estudio fueron evaluar el posible efecto disuasivo de los plaguicidas que presentan la más alta bioactividad electroantenográficas en moscas de la fruta y evaluar sus efectos sobre la viabilidad de las pupas en frutas tratadas. Las antenas fueron expuestas al extracto piroleñoso (BioPirol 7M®, 0,4%), solución de sulfuro de cal (SulFertilizantes, 1%), Nim (Organic Neem®; 0,5%) y rotenona (Rotenat®, 0,6%), teniendo en cuenta el sexo de la mosca, la edad y el estado reproductivo. La viabilidad de las pupas fue evaluada en larvas criadas en frutas de papaya (Carica papaya var. Calyman) y guayaba (Psidium guajava var. Paluma) tratadas con los plaguicidas que generaron las respuestas electrofisiológicas más fuertes. La bioactividad de las antenas de A. fraterculus fue mayor cuando fueron estimuladas con extracto piroleñoso y la solución de sulfuro de cal, para moscas jóvenes y apareadas. Ninguna de estas sustancias inhibió la oviposición y el desarrollo de las larvas en los frutos tratados, un resultado que tiene implicaciones importantes en el manejo de A. fraterculus en sistemas orgánico

Electrophysiologic and behavioral responses mediated by volatiles involved in the repellency of Apis mellifera (Lepeletier) (Hymenoptera: Apidae)

Repellent volatiles to insects might be an important tool for management of bees in areas which the presence of these organisms is not required. This study aimed to evaluate the electroantennal and behavioral responses of Africanized honeybees (workers), Apis mellifera (Lepeletier) (Hymenoptera Apidae), at different ages, to benzaldehyde (BA) and methyl anthranilate (MA) and to evaluate the potential repellency of these compounds under field conditions. Laboratory tests were conducted to study electroantennographic responses (mV) and chemotactic behavior of worker bees aged 1-5 (young) and 20-30 (old) days in four choice olfactometer. Electrophysiological responses to each compound did not differ between young and old workers. Bees antennae (young) triggered significantly greater responses to BA, in the older ones, a higher response was observed to MA, both compared to control (ethanol). The threshold response to BA and MA was achieved at 10 mg/mL, both compounds repelled bees at the same dose in olfactometer. Treatments with BA and MA, in field conditions, were less visited by scouter honey bees than those without these compounds (control)

Optimización de la gestión de cargas de una empresa de transporte carretero

Proyecto Integrador (II)--FCEFN-UNC, 2017Centra la realización de un estudio de mercado acerca del transporte carretero de cargas, en la ruta de cabotaje Buenos Aires-Mendoza, con el fin de proveer una propuesta de plan de comercialización a Transporte Multimodal Internacional S.A. Tal hecho se justifica en la aspiración de sus propietarios de insertarse en dicho tramo y mejorar así el rendimiento económico actual de la misma

Nanofibers as a Vehicle for the Synthetic Attactant TRIMEDLURE to be Used for Ceratitis capitata Wied: (Diptera, Tethritidae) Capture

 The Mediterranean fruit fly (medfly), Ceratitis capitata (Wied.) is considered a serious pest of citrus fruits in the southeast of Brazil because of the direct economic impact they have on fruit production and quarantine restrictions for fruit exports. Monitoring and detection of the medfly, using food bait and synthetic attractants, is a key step towards signalling the need for management and control. The aim of this study has been to verify the attractiveness of innovative nanofiber formulations with Trimedlure (TML) for the male of C. capitata in laboratory and field cage tests.Material and Methods: The nanofibers were produced by solution or emulsion electrospinning, containing TML and polymers, such as polycaprolactone, PEG-polycaprolactone, ethyl cellulose and polyvinyl acetate-PVP.Results: At the laboratory the electrophysiological responses were accessed by the eletroanntenogram technique and in the field by the cage test. The bioactivity of C. capitata antennae was highest when stimulated with all TML nanofiber treatments rather than their controls. There were no differences among the TML nanofiber treatments. In the field cages the same number of medflies were found on the adhesive traps baited with one of each of the TML nanofibers