Persistence of conidia of Entomophthora muscae in relation to age, temperature, and humidity

In this paper, the effect of age, humidity, and temperature on the conidial survival of Entomophthora muscae was evaluated. E. muscae was obtained from Musca domestica in a dairy in Itatiba (São Paulo, Brazil) and maintained in the laboratory by continuous passage through flies. Furthermore, the ability of conidia to infect flies at three temperatures (17, 21, and 27 degrees C), four ages of conidia (12, 72, 96, and 154 hours) and two humidities (100 and 60% RH) was evaluated. The temperature of 21 degrees C was the most favorable for the infection of house flies. Humidity was a cause of variation at 27 degrees C when the conidia were up to 12 hours old, but had no effect at lower temperatures. Conidia held at 100% RH and aged 72 hours caused no infection at 17 degrees C, but were infective at 21 degrees C. In the present study, conidia retained viability much longer than previously observed. Finally, the effect of humidity, temperature, and conidial age is discussed.

Small angle X-ray scattering study of surface modified tin oxide nanoparticles prepared by sol-gel route

The surface properties of SnO2 nanoparticles were modified by grafting ionic (Tiron (R). (OH)(2)C6H2(SO3Na)(2)(H2O)-H-.) or non-ionic (Catechol (R). C6H4-1,2-(OH)(2)) capping Molecules during aqueous sol-gel processing to improve the redispersibility of powdered xerogel. The effect of the amount of grafted organic molecules on the redispersibility of powders in aqueous solution at several basic pH values was Studied. The nanostructural features of the colloidal suspensions were analyzed by small angle X-ray scattering (SAXS) measurements. Irrespective of the nature and amount of grafted molecules, complete redispersion was obtained in aqueous solution at pH = 13. The redispersion at pH = 11 results in a mixture of dispersed primary particles and aggregates. The proportion of well dispersed nanoparticles and aggregates (and their average size) can be tuned by the quantity of grafted ionic molecules.

Inhibiting effect of citric acid on the pitting corrosion of tin

Potentiostatic and potentiodynamic studies were carried out to establish the inhibiting effects of citric acid on the pitting corrosion of tin. The critical potential (E-crit), which leads to pitting or general corrosion, was determined in sodium perchlorate solution in the pH range 1.0 to 4.0. Pit nucleation and growth, at pH 4.0, can be described by instantaneous nucleation followed by progressive nucleation. The results show that the minimum acid concentration needed to inhibit pitting of tin is 10(-2) M. Pitting occurrence by direct interaction between metal and perchlorate anions was observed.

Boron translocation in coffee trees

Boron deficiency in coffee trees ( Coffea arabica) is widespread, however, responses to B fertilizer have been erratic, depending on the year, method, and time of application. A better understanding of B uptake, distribution, and remobilization within the plant is important in developing a rational fertilization program. Field and greenhouse experiments were conducted to study B distribution and remobilization in coffee trees. Boron was provided either in the nutrient solution or sprayed on the leaves of trees grown under adequate or transient B deficiency. There was clear evidence for B translocation via symplast ( remobilization) to coffee grains, even in well-nourished plants. When 10 B was present in the nutrient solution during most part of fruit filling, from 33 to 40% of the B found in coffee fruits was absorbed during this period, depending on the timing and duration of the B deficiency treatment. In the field, when B was sprayed once on the leaves, around 4% of the fruit B was derived from the foliar fertilizer. Boron remobilization within coffee trees is limited in well nourished plants, but it can be significant during periods of temporary B deficiency in plants otherwise well nourished with B. The implications of these findings for B fertilization practice, are discussed.

Thermal behavior of the maleic anhydride modified poly(3-hydroxybutyrate)

Poly(3-hydroxybutyrate), PHB has been structurally modified through reaction with maleic anhydride, MA. Transesterification reaction was carried out fixing the PHB and MA and besides time and temperature the concentration of the triethylamine (used as catalyst) was changed. Glass transition, melting and crystallization temperature obtained from DSC curves and thermal degradation temperatures obtained from TG traces were used to evaluate the influence of the reaction conditions on the modification of PHB according to factorial design. on the base of the results the optimum conditions are to perform the PHB modification reaction with MA reaction at 110 degrees C for 1 h with 5% v/v triethylamine.

Purification and characterization of polygalacturonase produced by thermophilic Thermoascus aurantiacus CBMAI-756 in submerged fermentation

An extracellular polygalacturonase was isolated from 5-day culture filtrates of Thermoascus aurantiacus CBMAI-756 and purified by gel filtration and ion-exchange chromatography. The enzyme was maximally active at pH 5.5 and 60-65 degrees C. The apparent K (m) with citrus pectin was 1.46 mg/ml and the V (max) was 2433.3 mu mol/min/mg. The apparent molecular weight of the enzyme was 30 kDa. The enzyme was 100% stable at 50 degrees C for 1 h and showed a half-life of 10 min at 60 degrees C. Polygalacturonase was stable at pH 5.0-5.5 and maintained 33% of initial activity at pH 9.0. Metal ions, such as Zn+2, Mn+2, and Hg+2, inhibited 50, 75 and 100% of enzyme activity. The purified polygalacturonase was shown to be an endo/exo-enzyme, releasing mono, di and tri-galacturonic acids within 10 min of hydrolysis.

Analysing the new Saturnian rings, R/2004 S1 and R/2004 S2

The Cassini-Huygens arrival into the Saturnian system brought a large amount of data about the satellites and rings. Two diffuse rings were found in the region between the A ring and Prometheus. R/2004 S1 is coorbital to Atlas and R/2004 S2 is close to Prometheus. In this work we analysed the closest approach between Prometheus and both rings. As a result we found that the satellite removes particles from R/2004 S2 ring. Long-term numerical simulations showed that some particles can cross the F ring region . The well known region of the F ring, where small satellites are present and particles are being taking from the ring, gains a new insight with the presence of particles from R/2004 S2 ring. The computation of the Lyapunov Characteristic Exponent reveled that the R/2004 S2 ring lies in a chaotic region while R/2004 S1 ring and Atlas are in a stable region. Atlas is responsible for the formation of three regimes in the R/2004 S1 ring, as expected for a satellite embedded in a ring.

Solid state reactions in the platinum-mercury system

Thermogravimetry, Differential Scanning Calorimetry and other analytical techniques (Energy Dispersive X-ray Analysis; Scanning Electron Microscopy; Mapping Surface; X-ray Diffraction; Inductively Coupled Plasma Atomic Emission Spectroscopy and Cold Vapor Generation Atomic Absorption Spectroscopy) have been used to study the reaction of mercury with platinum foils. The results suggest that, when heated, the electrodeposited Hg film reacts with Pt to form intermetallic compounds each having a different stability, indicated by at least three mass loss steps. Intermetallic compounds such as PtHg4, PtHg and PtHg2 were characterized by XRD. These intermetallic compounds were the main products formed on the surface of the samples after partial removal of bulk mercury via thermal desorption. The Pt(Hg) solid solution formation caused great surface instability, attributed to the atomic size factor between Hg and Pt, facilitating the acid solution's attack to the surface.

Oriented growth of Bi3.25La0.75Ti3O12 thin films on RuO2/SiO2/Si substrates by using the polymeric precursor method: Structural, microstructural and electrical properties

c-axis oriented Bi3.25La0.75Ti3O12 (BLT) thin films were grown on a RuO2 top electrode deposited on a (100) SiO2/Si substrate by the polymeric precursor method. X-ray diffraction and atomic force microscope investigations indicate that the films exhibit a dense, well crystallized microstructure having random orientations with a rather smooth surface morphology. The electrical properties of preferred oriented Bi3.25La0.75Ti3O12 (BLT) thin films deposited on RuO2 bottom electrode leaded to a large remnant polarization (P-r ) of 17.2 mu C/cm(2) and (V-c ) of 1.8 V, fatigue free characteristics up to 10(10) switching cycles and a current density of 2.2 mu A/cm(2) at 5 V. We found that the polarization loss is insignificant with nine write/read voltages at a waiting time of 10,000 s. Independently of the applied electric field the retained switchable polarization approached a nearly steady-state value after a retention time of 10 s.

Modified Chebyshev algorithm: some applications

Two applications of the modified Chebyshev algorithm are considered. The first application deals with the generation of orthogonal polynomials associated with a weight function having singularities on or near the end points of the interval of orthogonality. The other application involves the generation of real Szego polynomials.

Synthesis, characterization and thermal behaviour of solid-state compounds of yttrium and lanthanide benzoates

Solid-state Ln(Bz)(3)center dot H(2)O compounds where Ln stands for trivalent yttrium or lanthanides and Bz is benzoate have been synthesized. Simultaneous thermogravimetry-differential thermal analysis (TG-DTA), X-ray powder diffractometry, infrared spectroscopy and chemical analysis were used to characterize and to study the thermal behaviour of these compounds. The results led to information about the composition, dehydration, thermal stability and thermal decomposition of the isolated compounds.

A COMPARATIVE-STUDY OF 4 DIFFERENT STAINING METHODS FOR ESTIMATION OF LIVE YEAST FORM CELLS OF PARACOCCIDIOIDES-BRASILIENSIS

A comparative study of four different staining methods for estimation of live yeast form cells of Paracoccidioides brasiliensis was carried out. The staining methods used were fluorescent staining, vital dye exclusion tests with erythrosin B and by Janus green and lactophenol cotton blue staining. Colony forming units (cfu) of the yeast form of eight P. brasiliensis isolates on brain heart infusion agar (BHIA) supplemented with 4% horse serum plus 5% P. brasiliensis cell extract (BHIA + HS + EXT) were examined for reliability of staining in determining the number of live fungal units in eight different isolates. Cfu on BHIA + HS + EXT plates showed an excellent plating efficiency over 96% in all isolates tested. The percentage of the live cells indicated by fluorescent staining (FL) or vital dye exclusion test with erythrosin B (EB) or Janus green (JG-1) was lower than that of cfu. By contrast, the percentage due to modified dye exclusion test with Janus green (JG-2) and that due to lactophenol cotton blue staining (LPCB) showed a close correration to that of cfu. Our results indicate that the modified dye exclusion test with Janus green and lactophenol cotton blue staining are useful for estimating cell viability of yeast form cells of P. brasiliensis.