Disorder effects in spiral spin liquids: Long-range spin textures, Friedel-like oscillations, and spiral spin glasses

Spiral spin liquids are correlated states of matter in which a frustrated magnetic system evades order by fluctuating between a set of (nearly) degenerate spin spirals. Here, we investigate the response of spiral spin liquids to quenched disorder in a $J_1$-$J_2$ honeycomb-lattice Heisenberg model. At the single-impurity level, we identify different order-by-quenched-disorder phenomena and analyze the ensuing spin textures. In particular, we show that the latter generally display Friedel-like oscillations, which encode direct information about the spiral contour, i.e., the classical ground-state manifold. At finite defect concentrations, we perform extensive numerical simulations and characterize the resulting phases at zero temperature. As a result, we find that the competition between incompatible order-by-quenched-disorder mechanisms can lead to spiral spin glass states already at low to moderate disorder. Finally, we discuss extensions of our conclusions to nonzero temperatures and higher-dimensional systems, as well as their applications to experiments.Comment: 15+11 pages, 12+6 figure

Ovary Development and Maturation in Nezara viridula (L.) (Hemiptera: Pentatomidae)

Ovary development and maturation of Nezara viridula (L.) were evaluated by examining ovariole morphology and the alterations in the biochemical (protein synthesis related to reproduction) composition of the hemolymph. Quantitative and qualitative protein analyses were performed and ovary structural alterations for the pre-reproductive and reproductive stages were recorded. Total concentration of proteins in female hemolymph gradually increased until the end of the pre-mating stage, remaining unaltered thereafter. Proteins linked to reproduction (vitellogenins) appeared in the hemolymph 10 days after adult emergence and indicated the end of the pre-mating stage. After mating, total protein concentration in the hemolymph was lower compared to virgin females; vitellogenin levels were similar during most of the observation period. Oocyte development and maturation were gradual and age dependent. Ten-day-old females had chorionated oocytes ready for fertilization. Mating did not stimulate oocyte development in N. viridula, but the lack of mating activity appeared to have stimulated oocyte resorption in 17-day-old females.Conselho Nacional de Desenvolvimento Cientifico e Tecnológico (CNPq

External morphology of Cotesia flavipes (Hymenoptera: Braconidae) during larval development

Cotesia flavipes (Cameron, 1891) (Hymenoptera) is a gregarious endoparasitoid used in applied biological control against Diatraea saccharalis (Fabricius, 1794) (Lepidoptera). In this study, we characterize the larval external morphology and the number of instars of C. flavipes. Parasitized larvae of D. saccharalis were sampled from the 1st to the 10th day after parasitism and dissected in an anticoagulant buffer for collection of C. flavipes immatures. Immatures were processed for scanning electron microscopy. Larvae of C. flavipes were prepared in NaOH solution and slide mounted to allow for mandible size measurements. Analysis of measurements of the parasitoid larval mandible size indicated that C. flavipes has three instars. Newly hatched larvae are caudate-mandibulate, assuming a hymenopteriform shape later in their development. The anal vesicle began to expand in the first instar and, once expanded, remained unchanged up to the beginning of the third instar. At the third instar, the anal vesicle decreased in volume. Herein we report the development and possible functions of the larval external structures modified during the development of C. flavipes, as for example their role in aiding newly-eclosed larvae to avoid the host immune response and to move within the host. To summarize the morphological changes during parasitoid growth, we should mention that the modifications in the anal vesicle were correlated with the feeding activity, and the maintenance of the anal vesicle indicates that this structure remained functional, probably playing a role in nutrient absorption and host regulation. On the other hand, the mandibles of early stage larvae are probably used to assist the parasitoid larvae during eclosion.FAPES

Ovarian development and analysis of mating effects on ovary maturation of Diaphorina citri Kuwayama (Hemiptera: Psyllidae)

As many other insects with a restricted diet, the citrus psyllid Diaphorina citri Kuwayama, which vector the causing agent of the Huanglongbing, the bacteria Candidatus Liberibacter spp., is intimately associated with symbiotic microorganisms. These mutualist symbionts play a key role on their host nutritional ecology, and are vertically transmitted to the progeny. However, despite the role symbionts play on host development and reproduction, and the growing opportunities of exploitation of the association insect-symbiont to control insect vectored-pathogens, there are very few studies on the host reproductive biology and on the symbiont transovarial transmission. Therefore, we aimed at analyzing the ovary development during D. citri adulthood, and at verifying for the mating requirement as a trigger to initiate ovary development. Newly-emerged D. citri females were grouped as virgin or mated and ovary development was observed during adulthood. Newly-emerged females have immature ovaries, and ovaries remain without any mature eggs until females mate. Once female mates, the vitellogenesis synthesis and uptake are estimulated, and oocytes are quickly developed. Oocytes maturation in ovarioles is metachronic, with only one oocyte developing at a time in each oogenic cycle. Morphological observations of the reproductive system including the ovaries and spermatheca, after the first cluster of eggs is laid, indicated D. citri is polyandrous, and may require multiple mating to develop additional oogenic maturation cycles.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Análise de classes latentes: classificação de perfis na concessão de crédito

Credit granting analysis is a very studied and important branch of finance. This is because it no longer uses purely subjective criteria such as human judgment, but employs faster, more accurate and reliable statistical and computational techniques. As a primary and preliminary way to grant credit, a careful analysis of the type of client (good and bad payers is necessary. Therefore, the latent class analysis (LCA) emerges as a new proposal for the evaluation of clients’ profile subject to the granting of bank credit. In this context, this paper aims to present which variables determine the conjecture of the characteristics of good and bad payers, through LCA, as a way of helping creditor institutions in decision-making. In addition, it was also the objective of this paper to study techniques and procedures on credit risk analysis, as well as to know the database and analyze its characteristics in an exploratory manner. For that, descriptive statistics, simple and multiple logistic regressions, and stepwise regression were used, in order to pre-select the LCA variables, which were then used in the poLCA package of the R software. From the analysis of data, it was possible to perceive a distinction between two latent classes, even with only a few observed variables: the good and the bad payers. However, this work suggests future studies associated with other methodologies, such as cross-validation, discriminant analysis and cluster analysis.A análise de concessão de crédito é um ramo da área financeira muito estudado e importante. Isso porque deixou de utilizar critérios meramente subjetivos como o julgamento humano, e passou a empregar técnicas estatísticas e computacionais mais rápidas, precisas e confiáveis. E como forma principal e preliminar para conceder o crédito, é necessário uma análise criteriosa do tipo de cliente que esse mais se enquadra, tal como adimplente ou inadimplente. Diante disso, a análise de classes latentes (LCA) surge como uma nova proposta para a avaliação do perfil dos clientes sujeitos a concessão do crédito bancário. Neste contexto, este trabalho objetivou apresentar quais variáveis determinam a conjectura das características dos bons e dos maus pagadores, através da LCA, como forma de ajudar as instituições credoras na tomada de decisão. Além disso, também foi alvo deste trabalho estudar técnicas e procedimentos sobre a análise de risco de crédito, bem como conhecer o banco de dados e analisar suas características de forma exploratória. Para tanto, foram utilizadas estatísticas descritivas, regressões logística simples, múltipla e o comando stepwise do R, com intuito de fazer uma pré-seleção das variáveis do LCA que, em seguida, foram utilizadas no pacote poLCA do mesmo software. A partir da análise de dados foi possível perceber, mesmo que com poucas variáveis manifestas, uma distinção entre duas classes latentes: os bons e os maus pagadores. No entanto, a partir desse trabalho sugere-se futuros estudos associados a outras metodologias, tais como: validação cruzada, análise discriminante e análise de cluster

Tripes (Thysanoptera: Thripidae) em plantios de bananeiras Cv. Prata Anã.

Os danos causados por tripes no fruto da bananeira, puncturas de cor marrom e ásperas ao tato, são bastante significativos, pois reduzem o valor comercial do produto (1).