Contagion and regulation in endogenous bank networks

We develop a simple model of endogenous bank networks to study financial contagion and how leverage regulation may affect it. Banks maximize expected profit by choosing the optimal allocation of resources between three different classes of assets. An interbank network arise as result of loans between banks, creating a direct channel of contagion in the financial system. Contagion may occur when the realized return of the risky asset is sufficiently low to make a bank insolvent, subsequently triggering a cascade effect that propagates through default in interbank loans. Contrary to what would be expected, our results show that despite forcing banks to deleverage, increasing minimum capital requirements may lead to a system with higher aggregate levels of default.

Entry and externality : hydroelectric generators in Brazil

This work analyzes the entry problem in the hydroelectric generation industry. The operation of a generator upstream regularizes the river flow for generators located downstream on the same river, increasing the production capacity of the latter. This positive externality increases the attractiveness of the locations downstream whenever a generator decides to enter upstream. Therefore, the entry decision of a generator in a given location may affect all entry decisions in potential locations for plants downstream. I first model the problem of generators located in cascade on the same river to show the positive effect of the externality. Next, I develop a method to estimate an entry model specific to the hydro generation industry which takes into account the externality of the entry decisions. Finally, I use a data set on investment decisions of Brazilian hydro-generators to estimate the model. The results show a positive incentive to locate downstream from existing plants and from locations where entry is likely to occur. An interesting by-product of the analysis is that the year effects’ estimates show an increase one year before the energy crisis of 2001, providing evidence that the market anticipated the crisis. It contradicts the governmental version that the crisis was due to an unexpected drought.

Homogalactanas sulfatadas da alga Codium isthmocladum com atividade anticoagulante

Since the first description of sulfated polysaccharides from seaweeds, the biological activities of these compounds have been evaluated under different aspects and experimental procedures. Among the broad biological activities presented by seaweed polysaccharides, anticoagulant action appears as a promising function. In this present study we have obtained sulfated polysaccharides from the green seaweed Codium isthmocladium by proteolytic digestion, followed by separation into five fractions (0.3, 0.5, 0.7, 0.9 and 1.2) by sequential acetone precipitation. The chemical analyses have demonstrated that all fractions are composed mainly by sulfated polysaccharides. The anticoagulant activity of these fractions was determined by activated partial thromboplastin time (aPTT) and prothrombin time test (PT) using citrate normal human plasma. None fraction has shown anticoagulant activity by PT test. Furthermore, all of them have shown anticoagulant activity by aPTT test. These results indicated that the molecular targets of these sulfated polysaccharides are mainly in the intrinsic via of the coagulation cascade. Agarose gel electrophoresis in 1,3-diaminopropane acetate buffer, pH 9.0, stained with 0.1% toluidine blue showed the presence of two or three bands in several fractions while the fraction 0.9 showed a single spot. By anion exchange chromatography, the acid polysaccharides from the 0.9 acetone fraction were separated into two new fractions eluted respectively with 2.0 and 3.0 M NaCl. These compounds showed a molecular weight of 6.4 and 7.4 kDa respectively. Chemical analyses and infrared spectroscopy showed that Gal 1 and Gal 2 are sulfated homogalactans and differ one from the other in degree and localization of sulfate groups. aPPT test demonstrated that fractions 2,0 and 3,0M (Gal1 and Gal 2, respectively) have anticoagulant activity. This is the first time that anticoagulant sulfated homogalatans have been isolated from green algae. To prolong the coagulation time to double the baseline value in the aPTT, the required amount of sulfated galactan 1 (6,3mg) was similar to low molecular heparin Clexane®, whereas only 0,7mg of sulfated galactan 2 was needed to obtain the same effect. Sulfated galactan 2 in high doses (250mg) induces platelet aggregation. These results suggest that these galactans from C. isthmocladum have a potential application as an anticoagulant drug

Caracterização físico-química e ações farmacológicas hepatoprotetora, antiinflamatória, pró-angiogênica, antioxidante e anticoagulante da fração rica em fucana 0,8FRF 0,8 da alga marrom Lobophora variegata

This study examines the physical and chemical composition and the pharmacological effects of brown seaweed FRF 0.8 Lobophora variegata. Fractionation of the crude extract was done with the concentration of 0.8 volumes of acetone, obtaining the FRF 0.8. The physicochemical characterization showed that it was a fucana sulfated. Anti-inflammatory activity was assessed by paw edema model by the high rates of inhibition of the edema and the best results were in the fourth hour after induction (100 ± 1.4% at the dose of 75 mg / kg) and by the strong inhibitory activity of the enzyme myeloperoxidase (91.45% at the dose of 25 mg / kg). The hepataproteção was demonstrated by measurements of enzymatic and metabolic parameters indicative of liver damage, such as bilirubin (reduction in 68.81%, 70.68% and 68.21% for bilirubin total, direct and indirect, respectively at a dose of 75 mg / kg), ALT, AST and γ-GT (decrease of 76.93%, 44.58% and 50% respectively at a dose of 75 mg / kg) by analysis of histological slides of liver tissue, confirming that hepatoprotective effect the polymers of carbohydrates, showing a reduction in tissue damage caused by CCl4 and the inhibition of the enzyme complex of cytochrome P 450 (increasing sleep time in 54.6% and reducing the latency time in 71.43%). The effectiveness of the FRF 0.8 angiogenesis was examined in chorioallantoic membrane (CAM) of fertilized eggs, with the density of capillaries evaluated and scored, showing an effect proangigênico at all concentrations tested FRF (10 mg- 1000 mg). The FRF showed antioxidant activity on free radicals (by inhibiting Superoxide Radical in 55.62 ± 2.10%, Lipid Peroxidation in 100.15 ± 0.01%, Hydroxyl Radical in 41.84 ± 0.001% and 71.47 Peroxide in ± 2.69% at concentration of 0.62 mg / mL). The anticoagulant activity was observed with prolongation of activated partial thromboplastin time (aPTT) at 50 mg (> 240 s), showing that its action occurs in the intrinsic pathway of the coagulation cascade. Thus, our results indicate that these sulfated polysaccharides are an important pharmacological target

Transcription of the Hsp30, Hsp70, and Hsp90 heat shock protein genes is modulated by the PalA protein in response to acid pH-sensing in the fungus Aspergillus nidulans

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Extração, caracterização e atividades biológicas de proteínas da espécie cnidoscolus urens (L.) Arthur

The extraction, chemical and structural characterization of a wide variety of compounds derived from plants has been a major source of bioactive molecules. Several proteases have been isolated in the plant kingdom, with numerous pharmacological and biotechnological applications. Among the proteases isolated from plants, are the fibrinogenolytic, with relevant application in the treatment of disorders in the coagulation cascade, in addition to potential use as a tool in clinical laboratories. In this study, in addition to evaluating the effects of the protein extract of Cnidoscolus urens (L.) Arthur (Euphorbiaceae) in the coagulation cascade also investigates the presence of antimicrobial activity and characterizes the proteolytic activity detected in this extract, aiming to determine their potential pharmacological and biotechnological application. In this way, crude protein extracts obtained from the leaves of C. urens in Tris-HCl 0.05M, NaCl 0.15M, pH 7.5, were precipitated in different concentrations of acetone, and assessed for the presence of proteolytic activity in azocaseína and fibrinogen. The most active fraction (F1.0) in these tests was chosen for assessment of biological activity and biochemical characterization. The Aα chain and Bβ of fibrinogen were completely cleaved at a concentration of 0.18 μg/μL of protein fraction in 4 minutes. Fibrinogenolytic activity presented total inhibition in the presence of E-64 and partial in the presence of EDTA. The fraction demonstrated coagulant activity in plasm and reduced the APTT, demonstrating acting on the factors coagulation of the intrinsic pathway and common, not exerting effects on the PT. Fibrinolytic activity on plasma clot was detected only in SDS-PAGE in high concentrations of fraction, and there were no defibrinating. Although several proteases isolated from plants and venomous animals are classically toxic, the fraction F1.0 of C. urens not expressed hemorrhagic nor hemolytic activities. Fraction F1.0 also showed no antimicrobial activity. In proteolytic activity on the azocasein, the optimal pH was 5.0 and optimum temperature of 60ºC. The enzyme activity has been shown to be sensitive to the presence of salts tested, with inhibition for all compounds. The surfactant triton did not influence the enzyme activity, but the tween-20 and SDS inhibited the activity. In the presence of reducing agents increase in enzyme activity occurred, a typical feature of enzymes belonging to the class of cysteine proteases. Several bands with proteolytic activity were detected in zymogram, in the region of high-molecular-weight, which were inhibited by E-64. In this study, we found that C. urens presents in its constitution cysteine proteases with fibrinogenolytic and procoagulant activity, which may be isolated, with potential application in treatment of bleeding disorders, thrombolytic and clinical laboratory

Ceratomicose em equinos

O cavalo, dado o seu meio ambiente, está sujeito a afecções frequentes da córnea e da conjuntiva, tecidos oculares bastante expostos a bactérias e fungos, principalmente Aspergillus spp. e Fusarium spp. As ceratites ulcerativas bacterianas e fúngicas, bem como as ceratites fúngicas não ulcerativas, caracterizadas principalmente pelo abscesso estromal, são frequentes nessa espécie. Ocorrida a lesão inicial, perpetua-se um ciclo vicioso, com liberação de citocinas inflamatórias, que desencadeiam uma rápida e severa infiltração corneal por células polimorfonucleares. A córnea torna-se sujeita à destruição por enzimas proteolíticas liberadas pelos micro-organismos e por células inflamatórias, capazes de desencadear a dissolução estromal e a perfuração do bulbo ocular. O tratamento clínico para a resolução da doença corneal e o controle da uveíte reflexa deve ser agressivo e associado, muitas das vezes, à terapia cirúrgica. Este artigo discorre sobre a fisiopatologia e o tratamento da ceratomicose em equinos.

Efeitos de peixes zooplanctívoros e onívoros sobre a resposta de comunidades planctônicas à fertilização por nutrientes

The food chain theory predict that presence of omnivory prevent the trophic cascade and could be a strong stabilizing factor over resource and consumer community dynamics, and that the nutrient enrichment destabilize populations dynamics. Most of the freshwater tropical reservoirs are eutrophic, and strategies that seek improve the water quality through the control of phytoplankton biomass and nutrient input, become essential for the improvement and preservation of water quality. The aim of this study was test the zooplanktivory (when larvae) and omnivory (when young and adult) effects of Nile Tilapia over the structure and dynamics of plankton communities, in addition or absence of nutrients enrichment. For this, one field experiment was performed with a factorial design 2x3 resulting in six treatments: control, without fish and nutrient (C); with omnivorous fish (O); with zooplanktivorous fish (Z); without fish and with enrichment of nutrients (NP); with omnivorous fish and nutrients (ONP); and, with zooplanktivorous fish and nutrients (ZNP). The two planktivory types reduced the zooplankton biomass and increased the phytoplankton biomass, but the omnivory of filter-feeding fish attenuated the trophic cascade magnitude. The fertilization by nutrients increases the nutrient concentrations in water and the phytoplankton biomass, but the effect on zooplankton is dependent of the trophic structure. In a general way, the effects of the fish and nutrient addition were addictive, but significant interactions among those factors were observed in the answer of some zooplankton groups. The effects of omnivorous fish over the temporal variability of phytoplankton and zooplankton biomass were very variable, the increase or reduce in variability of the plankton depending of the level of nutrients and of the analyzed variable. With base in this study, we conclude that the planktivory type exercised by the fish and the concentrations of nutrients in the water affects the force of pelagic trophic cascades and probably the success of biomanipulation programs for the handling of water quality in lakes and tropical reservoirs

O elo microbiano como alimento alternativo para o zooplâncton em reservatórios dominados por cianobactérias

Protozoa may be an important alternative food source for Calanoida copepods in these environments. Aiming to quantify the feeding preferences of N. cearensis by ciliates in the presence of cyanobacteria, in vitro experiments were conducted, using mixed cultures in different concentrations of total food for copepod. Two ciliates species (Paramecium sp. and Cyclidium sp.) and a cyanobacteria toxic strain (Microcystis aeruginosa) were offered as food. Previous experiments were done to identify the copepod s maximum ingestion rate through the use of a type II functional response model when each prey is offered separately. High maximum ingestion rate were found when those protists were offered as prey. N. cearensis showed significant preference for protozoal prey over the cyanobacterium tested both in low (corresponding 95.15% of the diet) and in high food concentration treatments (about 91.56% of the diet), preferring the bigger ciliate in lower concentrations (67.52% of the diet). The meaningful involvement of heterotrophic organisms in the zooplankton diet emphasis the microbial loop participation in the energy transition from copepods to higher trophic levels. This data contributes to understand the stability of existing trophic interactions in reservoirs subjected to eutrophication and assists trophic cascade studies in these environments

Análise de onda completa de superfície seletiva em freqüência do tipo anteparo duplo

This work presents a theoretical analysis and numerical and experimental results of the scattering characteristics of frequency selective surfaces, using elements of type patch perfectly conductor. The structures are composed of two frequency selective surfaces on isotropic dielectric substrates cascaded, separated by a layer of air. The analysis is performed using the method of equivalent transmission line in combination with the Galerkin method, to determine the transmission and reflection characteristics of the structures analyzed. Specifically, the analysis uses the impedance method, which models the structure by an equivalent circuit, and applies the theory of transmission lines to determine the dyadic Green's function for the cascade structure. This function relates the incident field and surface current densities. These fields are determined algebraically by means of potential incidents and the imposition of the continuity of the fields in the dielectric interfaces. The Galerkin method is applied to the numerical determination of the unknown weight coefficients and hence the unknown densities of surface currents, which are expanded in terms of known basis functions multiplied by these weight coefficients. From the determination of these functions, it becomes possible to obtain numerical scattered fields at the top and bottom of the structures and characteristics of transmission and reflection of these structures. At work, we present numerical and experimental results for the characteristics of transmission and reflection. Comparisons were made with other results presented in literature, and it was observed a good agreement in the cases presented suggestions continuity of the work are presented

Estudo e implementação em plantas físicas de um controlador preditivo generalizado com restrições

This work shows a study about the Generalized Predictive Controllers with Restrictions and their implementation in physical plants. Three types of restrictions will be discussed: restrictions in the variation rate of the signal control, restrictions in the amplitude of the signal control and restrictions in the amplitude of the Out signal (plant response). At the predictive control, the control law is obtained by the minimization of an objective function. To consider the restrictions, this minimization of the objective function is done by the use of a method to solve optimizing problems with restrictions. The chosen method was the Rosen Algorithm (based on the Gradient-projection). The physical plants in this study are two didactical systems of water level control. The first order one (a simple tank) and another of second order, which is formed by two tanks connected in cascade. The codes are implemented in C++ language and the communication with the system to be done through using a data acquisition panel offered by the system producer

Estudo da hidrodinâmica de um novo separador líquido-líquido: aplicação ao sistema óleo-bruto/água produzida

This work aims to use a different hydrodynamic condition applied to a new design of mixer-settler on treating wastewater produced by petroleum industry, called MDIF (Misturador-Decantador à Inversão de Fases/ Mixer-Settler based on Phase Inversion MSPI). The use of this different hydrodynamic behaviour is possible due to vertical disposition of the device and the principle of Phase Inversion that controls the MDIF, providing the generation (creation) of a cascade of drops, into an organic layer, that works as micro-decanters, thus making possible the formation of a bed of non-coalesced drops, called Bed Formation . The use of this new hydrodynamics condition allows to increase the residence time of the oil carrier drops, into an organic layer, and the device can treat a greater volume of wastewater. In view of to get this condition it is necessary to operate at high throughput (58,6 m3.m-2.h-1). By results, the condition of Bed Formation is the best one to be used when MSPI operates with throughput up to 58,6 m3.m-2.h-1. The results using the condition of Bed Formation show that increasing the height of the bed of non-coalesced drops and/or decreasing the volumetric ratio (O/A) an increase of the separation efficiency is detected

Pkc1 acts through Zds1 and Gic1 to suppress growth and cell polarity defects of a yeast eIF5A mutant

eIF5A is a highly conserved putative eukaryotic translation initiation factor that has been implicated in translation initiation, nucleocytoplasmic transport, mRNA decay, and cell proliferation, but with no precise function assigned so far. We have previously shown that high-copy PKCI suppresses the phenotype of tif51A-1, a temperature-sensitive mutant of eIF5A in S. cerevisiae. Here, in an attempt to further understand how Pkc1 functionally interacts with eIF-5A, it was determined that PKCI suppression of tif51A-1 is independent of the cell integrity MAP kinase cascade. Furthermore, two new suppressor genes, ZDS1 and GIC1, were identified. We demonstrated that ZDS1 and ZDS2 are necessary for PKC1, but not for GIC1 suppression. Moreover, high-copy GIC1 also suppresses the growth defect of a PKCI mutant (stt1), suggesting the existence of a Pkc1-Zds1-Gic1 pathway. Consistent with the function of Gic1 in actin organization, the tif51A-1 strain shows an actin polarity defect that is partially recovered by overexpression of Pkc1 and Zds1 as well as Gic1. Additionally, PCL1 and BNI1, important regulators of yeast cell polarity, also suppress tif51A-1 temperature sensitiviiy Taken together, these data strongly Support the correlated involvement of Pkc1 and eIF5A in establishing actin polarity, which is essential for bud formation and G1/S transition in S. cerevisiae.

Representação de linhas de transmissão por meio de variáveis de estado levando em consideração o efeito da freqüência sobre os parâmetros longitudinais

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Heterodyne Interferometry Applied to the Characterization of Acousto-Electro-Optic Light Modulators

When the electro-optic and acousto-optic effects are combined into a single device, the resulting acousto-electro-optic (AEO) modulator shows improved flexibility to overcome some limitations of the individual modulators or their cascade combinations. By using optical interferometry, it is possible to investigate the AEO modulator behavior as a function of this applied voltage. By this way, a lithium niobate AEO modulator is positioned in one of the arms of a Mach-Zehnder interferometer and operates at 62 MHz frequency, which constitutes the intermediate frequency of the heterodyne interferometer. Operating the AEO modulator in the acousto-optic small diffraction efficiency regime, the photodetected signal amplitude and phase are analyzed, and the induced phase shift, transmission curve and linearity response are obtained. The experimental results show good agreement with that expected from the coupled-mode theory. The possibility of linear control of the optical phase shift by the external voltage, from 0 to 2 p radians, is demonstrated.