In vitro culture of Annona emarginata: a rootstock for commercial annonaceae species

Annona emarginata is a native fruit tree in the Brazilian Cerrado which, unlike the commercial species, does not present a high fruit quality. On the other hand, it stands out based on its rootstock value. However, there are some problems that hinder the largescale production of Annona emarginata seedlings for use as a rootstock. In order to overcome these difficulties, micropropagation has become a viable alternative for the rapid and efficient propagation of Annona spp, but Annona emarginata micropropagation has not yet been reported. Therefore, the aim of this study was to initiate Annona emarginata in vitro growth. For axillary shoot proliferation, in vitro nodal segments of 0.5 cm were transferred to MS or WPM supplemented with BA at different concentrations. Nodal segments were also cultured on WPM medium with ranging concentrations of different plant growth regulators, aiming for either shoot elongation or rooting. The results showed that the use of 1 µM BA in WPM medium is recommended for in vitro multiplication of Annona emarginata. This is based on the low adventitious shoot formation, combined with a higher number of buds and leaves. The use of GA3 at any concentration tested induced the formation of malformed plants. Root formation could not be stimulated, regardless the duration of auxin treatment

Distributed Approximation of Minimum Routing Cost Trees

We study the NP-hard problem of approximating a Minimum Routing Cost Spanning Tree in the message passing model with limited bandwidth (CONGEST model). In this problem one tries to find a spanning tree of a graph $G$ over $n$ nodes that minimizes the sum of distances between all pairs of nodes. In the considered model every node can transmit a different (but short) message to each of its neighbors in each synchronous round. We provide a randomized $(2+\epsilon)$-approximation with runtime $O(D+\frac{\log n}{\epsilon})$ for unweighted graphs. Here, $D$ is the diameter of $G$. This improves over both, the (expected) approximation factor $O(\log n)$ and the runtime $O(D\log^2 n)$ of the best previously known algorithm. Due to stating our results in a very general way, we also derive an (optimal) runtime of $O(D)$ when considering $O(\log n)$-approximations as done by the best previously known algorithm. In addition we derive a deterministic $2$-approximation

Measurement-induced nonlinearity in linear optics

Published versio

Current and Future Prospects of Nitro-compounds as Drugs for Trypanosomiasis and Leishmaniasis

Interest in nitroheterocyclic drugs for the treatment of infectious diseases has undergone a resurgence in recent years. Here we review the current status of monocyclic and bicyclic nitroheterocyclic compounds as existing or potential new treatments for visceral leishmaniasis, Chagas' disease and human African trypanosomiasis. Both monocyclic (nifurtimox, benznidazole and fexinidazole) and bicyclic (pretomanid (PA-824) and delamanid (OPC-67683)) nitro-compounds are prodrugs, requiring enzymatic activation to exert their parasite toxicity. Current understanding of the nitroreductases involved in activation and possible mechanisms by which parasites develop resistance is discussed along with a description of the pharmacokinetic / pharmacodynamic behaviour and chemical structure-activity relationships of drugs and experimental compounds.</p

Willingness to pay for quality traits and implications for sweetpotato variety breeding: case of Mozambique

Despite decades of research and dissemination of improved sweetpotato varieties, uptake at scale remains low and envisaged development goals of food security and livelihoods remain elusive. This is despite demonstrated impacts of such technologies in combating food and nutrition insecurity, amidst global challenges like climate change. Growing evidence show that end-user acceptance of improved varieties is critical in the widespread adoption of such varieties, and inclusion of the heterogenous preferences of diverse sets of end-users in the variety development process is therefore critical. With global changes in weather and consumption patterns, end-users are now demanding varieties that are more suitable to their unique consumption needs, production environments, new market demands and have desired processing characteristics. Such dynamics in demand have necessitated rethinking of breeding programs from the traditional focus on agronomic gains such as increase in yields and yield protection, to consideration of more nuanced quality-related traits that appeal to targeted populations. Against this background, this study sets out to explore the decision-making behavior of Mozambican sweetpotato producers in variety selection, and the implicit value placed on different sweetpotato traits, including the often ignored but crucial quality traits. The aim of the study is to identify the economic valuation of such traits and how they are traded off in variety selection decisions, to allow for prioritization in breeding efforts. To achieve this, an exploratory sequential design in a predominantly quantitative mixed-method design was adopted for the study. First, based on the insights from a gender disaggregated qualitative assessment among sweetpotato growers and consumers and in consultation with breeding experts from Mozambique, the most preferred sweetpotato variety traits in the regions of study were established. These traits were then utilized in the design of a choice experiment, implemented among 860 sweetpotato producers spread across four sweetpotato growing regions in the country. Finally, a generalized multinomial logit model was used to estimate implicit economic valuation of each of the considered trait, as well as heterogenous valuation of such traits across gender, education and age of respondent groups. Results from the study show that producers have a high preference for quality-related traits, with preference for Vitamin A being higher than that for drought tolerance, while dry matter content is valued about the same as drought tolerance. While scoring significantly lower than Vitamin A, drought tolerance and dry matter content, other quality-related traits like root size and sweet taste also have significant positive values implying their importance in informing sweetpotato variety choice. In terms of gender heterogeneity, flesh color is highly valued among the women sub-sample. The study identifies Vitamin A, dry matter content, sweet taste, and medium to big root size, as the key preferred quality traits in Mozambique, in that order. The results imply that these quality traits should be pursued as a suite in breeding objectives, in combination with essential agronomic traits such as high yields and drought tolerance, for higher acceptance and demand of improved sweetpotato varieties across the country

Recovery of soil physical properties by green manure, liming, gypsum and pasture and spontaneous native species¹

Inadequate usage can degrade natural resources, particularly soils. More attention has been paid to practices aiming at the recovery of degraded soils in the last years, e.g, the use of organic fertilizers, liming and introduction of species adapted to adverse conditions. The purpose of this study was therefore to investigate the recovery of physical properties of a Red Latosol (Oxisol) degraded by the construction of a hydroelectric power station. In the study area, a soil layer about 8m thick had been withdrawn by heavy machines leading not only to soil compaction, but resulting in high-degree degradation. The experiment was arranged in a completely randomized design with nine treatments and four replications. The treatments consisted of: 1- soil mobilization by tilling (to ensure the effect of mechanical mobilization in all treatments) without planting, but growth of spontaneous vegetation; 2- Black velvet bean (Stizolobium aterrimum Piper & Tracy); 3- Pigeonpea (Cajanus cajan (L.) DC); 4- Liming + black velvet bean; 5-Liming + pigeonpea until 1994, when replaced by jack bean (Canavalia ensiformis); 6- Liming + gypsum + black velvet bean; 7- Liming + gypsum + pigeonpea until 1994, when replaced by jack bean; and two controls as reference: 8- Native Cerrado vegetation and 9- bare soil (no tilling and no planting), left under natural conditions and in this situation, without spontaneous vegetation. In treatments 1 through 7, the soil was tilled. Treatments were installed in 1992 and left unmanaged for seven years, until brachiaria (Brachiaria decumbens) was planted in all plots in 1999. Seventeen years after implantation, the properties soil macroporosity, microporosity, total porosity, bulk density and aggregate stability were assessed in the previously described treatments in the soil layers 0.00-0.10; 0.10-0.20 and 0.20-0.40 m, and soil Penetration Resistance and soil moisture in 0.00-0.15 and 0.15-0.30 m. The plants were evaluated for: brachiaria dry matter and spontaneous growth of native tree species in the plots as of 2006. Results were analyzed by variance analysis and Tukey´s test at 5 % for mean comparison. In all treatments, except for the bare soil (no recovery measures), ongoing recovery of the degraded soil physical properties was observed. Macroporosity, soil bulk density and total porosity were good soil quality indicators. The occurrence of spontaneous native species indicated the soil recovery process. The best adapted species was Machaerium acutifolium Vogel, with the largest number of plants and most advanced development; the dry matter production of B. decumbens in recovering soil was similar to normal conditions, evidencing soil recovery

Viabilidade econômica e de risco da produção de tomate no município de Cambuci/RJ, Brasil

A tomaticultura possui grande importância econômica e social para muitos municípios produtores e para todos os demais municípios participantes do mercado consumidor. O tomate sofre elevadas variações de preços no mercado. Tal característica expõe produtores a riscos e incertezas de preços. Nesse sentido, questiona-se o que, quanto, como, e para quem produzir? Objetivou-se analisar a viabilidade econômica da produção de tomate de mesa no município de Cambuci/RJ. Para obter os indicadores de viabilidade econômica, foram estimados o Valor Presente Líquido (VPL), a Taxa Interna de Retorno (TIR). Para determinar as incertezas do empreendimento, foi realizada a análise de sensibilidade. O risco envolvido na tomaticultura deste município foi avaliado por meio da Simulação de Monte Carlo. Os resultados mostraram indicadores econômicos satisfatórios para o período analisado. A análise de sensibilidade revelou que o preço de venda do tomate foi a variável com maior efeito sobre os resultados econômicos da atividade, seguido pelo custo da mão de obra. A simulação de Monte Carlo demonstrou que é baixa a probabilidade dos produtores de tomate obterem VPL negativo. Assim, conclui-se que o cultivo de tomate em Cambuci/RJ apresenta-se como alternativa viável para seus produtores, entretanto, variações pessimistas de preços podem inviabilizar esta atividad

Efeito do extrato aquoso de cabelo de milho (Zea mays L.) sobre a excreção renal de água e eletrólitos e pressão arterial em ratos Wistar anestesiados

O milho (Zea mays L.) possui nos estigmas (cabelo de milho) substâncias que o tornam diurético, podendo ser importante no controle da hipertensão. No presente estudo, foi investigado o efeito do extrato aquoso (EA) do cabelo de milho sobre o fluxo renal de água (V) e eletrólitos e a pressão arterial (PA) em ratos Wistar anestesiados. Foram realizados 3 grupos: I) Controle - administração intragástrica (AI) de 1mL de água destilada; II) AI de 1 mL de EA de cabelo de milho a 20% e III) AI de 1 mL de solução contendo furosemida. Canulou-se a artéria carótida esquerda para mensuração da PA, de 10 em 10 minutos, e a bexiga urinária, para mensuração de V de 30 em 30 minutos e da carga excretada dos íons sódio (Qe (Na+)) e potássio (Qe (K+)). Protocolo experimental: quatro períodos de 30 minutos cada: basal (avaliação dos parâmetros basais) e experimentais (Ex) 1, 2 e 3 (30, 60 e 90 minutos após a AI, respectivamente). O Grupo I não apresentou alterações significativas entre os períodos nos parâmetros analisados (p>0,05). O Grupo II apresentou aumento significativo (pThe corn (Z. mays) has in its stigmas (corn silks) substances that make it diuretic, which may be important in hypertension control. In this study, the effect of aqueous extract (AE) of corn silks on the renal flow of water (V) and electrolytes and arterial pressure (AP) was investigated in anesthetized Wistar rats. Three groups were tested: I) Control - intragastric administration (IA) of 1mL of distilled water, II) IA of 1 mL of AE of corn silks at 20% and III) IA of 1 mL of a solution containing furosemide. Cannulation was performed in the left carotid artery to measure AP, at every 10 minutes, and in the urinary bladder to measure V, at every 30 minutes, and the excreted load of ions sodium (Qe (Na+)) and potassium (Qe (K+)). Experimental protocol: four periods of 30 minutes each: basal (evaluation of basal parameters) and experimental (Ex) 1, 2 and 3 (30, 60 and 90 minutes after IA, respectively). Group I had no significant differences between periods for the analyzed parameters (p>0.05). Group II presented a significant increase (p<0.05) in V, Qe (Na+) and Qe (K+) in periods Ex2 and Ex3, with significant reduction in AP (p<0.05) in Ex2 and Ex3. As expected, Group III had a significant increase in V in periods Ex2 (p<0.05) and Ex3 (p<0.001), an increase in Qe (Na+) in Ex1 (p<0.05), Ex2 (p<0.001) and Ex3 (p<0.001) and an increase in Qe (K+) in Ex2 (p<0.05) and Ex3 (p<0.001), with an important reduction in AP (p<0.05) in Ex2 and Ex3. These data show that AE of corn silks has a diuretic effect but does not act as a loop diuretic since it did not lead to potassium loss or marked sodium loss, compared to furosemide