Federal University of Roraima

About: Federal University of Roraima is a based out in . It is known for research contribution in the topics: Population & Thermogravimetry. The organization has 981 authors who have published 1218 publications receiving 7849 citations. The organization is also known as: Federal University of Roraima.

Graphene to Graphane: A Theoretical Study

Abstract: Graphane is a two-dimensional system consisting of a single layer of fully saturated (sp$^3$ hybridization) carbon atoms. In an ideal graphane structure C-H bonds exhibit an alternating pattern (up and down with relation to the plane defined by the carbon atoms). In this work we have investigated using \textit{ab initio} and reactive molecular dynamics simulations the role of H frustration (breaking the H atoms up and down alternating pattern) in graphane-like structures. Our results show that significant percentage of uncorrelated H frustrated domains are formed in the early stages of the hydrogenation process leading to membrane shrinkage and extensive membrane corrugations. These results also suggest that large domains of perfect graphane-like structures are unlikely to be formed, H frustrated domains are always present.

Indigenous protagonism in the context of food insecurity in times of Covid-19

Abstract: In Brazil, indigenous peoples present a complex reality characterized by a marked social vulnerability that is manifested in health and nutritional indicators. In this scenario, poor sanitary conditions prevail, with a high burden of chronic noncommunicable diseases; infectious/parasitic diseases; and nutritional disorders, including malnutrition and anemia. This situation is reflected in numerous aspects of food insecurity, placing this population in a position of particular vulnerability to the coronavirus disease 2019 pandemic and its effects. The objective of our study was to present a set of preliminary reflections on food insecurity and indigenous protagonism in times of Covid-19. The pandemic has deepened the inequalities that affect the indigenous peoples, with a direct impact on food security conditions. Amid the effects of the pandemic, indigenous protagonism has played a fundamental role in guaranteeing these peoples’ rights and access to food, denouncing the absent and slow official responses as acts of institutional violence, which will have serious and lasting effects on the lives of indigenous peoples.

Comportamento ingestivo de cordeiros alimentados com dietas contendo feno de amoreira

Abstract: The experiment was conducted to evaluate the feeding behavior of lambs fed with diets containing 0, 12.5 and 25.0% of mulberry hay as a substitute for the concentrate. Twenty four Ile de France lambs, non castrated, with 25 kg of body weight and four months old, confined, in a completely randomized design, were used. The feeding daily time (242.01 minutes), rumination (435.48 minutes) and leisure (762.50 minutes), the numbers of cakes ruminated per day (658.36) and the time spent per cake (40.03 sec) were not affected (P>0.05) by different levels of hay in mulberry concentrate. The dry matter voluntary intake (1.258 kg/day) and neutral detergent fiber intake (0.302 kg/day), as well as the efficiency of dry matter intake and rumination (316.24 and 173.54 g/h, respectively) and efficiency of neutral detergent fiber intake and rumination (75.89 and 41.68 g/h, respectively) were similar in all treatments. The ruminating chew expressed in hour/day (11.29) and the number of chews expressed per cake (72.65) and per day (47.638.06), as well as the number and the feeding time (22.02 meals and 11.23 min/meal), rumination (25.95 ruminations and 17.29 min/rumination) and idle (41.81 idle and 18.30 min/idle time), were also not affected (P>0.05). The inclusion of mulberry hay did not change the rumination expressed in g of DM and NDF/cake (1.91 and 0.46, respectively) and min/kg of DM and NDF (361.51 and 1.505.78, respectively), as well as the total chew expressed in min/kg of DM and NDF (563.70 and 2.347.19, respectively). The use of mulberry hay partially replacing the concentrated, does not change the feeding behavior of feedlot lambs.

Five new species of Camelobaetidius Demoulin, 1966 (Ephemeroptera: Baetidae), and redescription of Camelobaetidius mexicanus (Traver & Edmunds, 1968).

Abstract: The genus Camelobaetidius Demoulin, 1966 has 38 species distributed throughout the Neotropical Region, being one of the most studied genera of the family Baetidae. Based on material from Brazil, the aim of the present paper is to describe five new species of Camelobaetidius with the terminal filament as long as cerci, and to redescribe the nymph of C. mexicanus (Traver & Edmunds, 1968) based on a paratype from Mexico.

Pseudocercospora fuligena causing leaf mold of tomato in Roraima, Brazil

Abstract: The cercospora leaf mold on tomato is an uncommon disease in Brazil. However, its occurrence is reported by Crous & Braun (Mycosphaerella and its anamorphs: 1. Names published in Cercospora and Passalora. 200�) and in important databases as EPPO and CABI Crop Protection Compendium. In September 2005, in Roraima, Brazil, tomato (Lycopersicon esculentum L.) plants cv. Santa Clara growing in protected cultivation conditions presented a severe foliar blight. Symptoms initially appeared as foliar spots, yellow on the adaxial leaflets surface (Figure 1A), corresponding to a dark gray fuliginous growth on the abaxial surface (Figure 1B), evolving to irregular necrotic spots. As the disease developed, leaf spots coalesced. Characteristics of the associated fungi were fascicles amphigenous, predominantly hypophyllous, effuse, stromata absent or substomatal. Conidiophores pale olivaceous to olivaceous brown, �-16 per fascicle, 20-�� x �.5-5.0 μm, 1-2 septate, conidiogenous loci inconspicuous (Figure 1C). Conidia obclavate to cylindric-obclavate, rounded to obtuse at the apex, olivaceous to subhyaline, obconic to rounded at the base, 2�-110 x 2.5-5.0 μm and �-10 septate, hila unthickened, not darkened (Figure 1D). To perform the Koch s postulates the fungi was isolated in Potato Dextrose Agar and cultivated in Potato Dextrose broth at 28 oC in rotary shaker. After 20 days, the culture was centrifuged, dispensing the culture media. Mycelium was resuspended in sterilized tap water and triturated. Thirty-days old plants of tomato hybrid Debora Plus were sprayed with the mycelium suspension (1.6 x 105 mycelium fragments per mL), kept in humid chamber for 24 h and then transferred to greenhouse conditions. As control, plants were sprayed with tap water. For each treatment, 20 plants were utilized. After nine days, first symptoms were observed only in plants sprayed with the mycelium suspension (Figure 1E), evolving to an intense foliar blight. The pathogen was successfully re-isolated. These features permit the identification of Pseudocercospora fuligena (Roldan) Deighton (basionym Cercospora fuligena) as causal agent of cercospora leaf mold on tomato (Chupp, A monograph of the fungus genus Cercospora. 1�54; Guo & Hsieh, The genus Pseudocercospora in China. 1��5). This is the first report of P. fuligena on tomato in Roraima state, Brazil. The symptoms of the disease are easily confused with Cladosporium leaf mold.