Various natural phenomena are often modeled using differential equations. However, an analytical solution of such equations is not always possible, so numerical methods must be part of the physicists’ arsenal to study their system of interest. In this work we hope to provide a pedagogical presentation for projects that need to find solutions to ordinary differential equations using numerical methods. For this, we use the fourth-order Runge-Kutta method to describe the simple pendulum with the presence of a resistive force through its phase diagrams in subcritical, critical and supercritical damping, finally we compare the numerical solutions with the analytical results. However possible physicists interest fourthorder fourth order RungeKutta Runge Kutta subcritical damping results

Diversos fenômenos naturais são frequentemente modelados usando equações diferenciais. Contudo, uma solução analítica de tais equações nem sempre é possível, de forma que métodos numéricos devem fazer parte do arsenal dos físicos para estudar seu sistema de interesse. Nesse trabalho esperamos proporcionar uma apresentação pedagógica para projetos que necessitem encontrar as soluções de equações diferenciais ordinárias por métodos numéricos. Para isso, usamos o método de Runge-Kutta de quarta ordem para descrever o pêndulo simples com a presença de uma força resistiva através dos seus diagramas de fase nos amortecimentos subcrítico, crítico e supercrítico, por fim comparamos as soluções numéricas com os resultados analíticos. Contudo possível interesse isso RungeKutta Runge Kutta subcrítico supercrítico analíticos

The hydrogen absorption and desorption of Ti53Zr27Ni20 icosahedral quasicrystal (ICQ) and Ti50Ni50 shape memory alloy (SMA) melt-spun ribbons was studied. Samples were exposed to hydrogen gas at 623 K and 4 MPa for 1000 minutes. The total capacity of hydrogen obtained for Ti53Zr27Ni20 and Ti50Ni50 was 3.2 and 2.4 wt. % respectively. The Thermal Desorption Spectrometry (TDS) of the hydrogenated alloys shows that both alloys start to desorb hydrogen around 750 K. X-ray diffraction (XRD) patterns, performed after hydrogenation, indicate a complete amorphization of the Ti53Zr27Ni20 i-phase alloy, while the Ti50Ni50 alloy remained crystalline after hydride formation.

Relata-se pela primeira vez a ocorrência de Neosilba (Diptera: Lonchaeidae) em frutos de pinhão manso (Jatropha curcas) no Município de Rio Largo, AL, Brasil. O total de 438 exemplares foi obtido de 1.000 frutos entre os meses de maio a julho de 2010. Cinco espécies foram registradas: Neosilba zadolicha McAlpine & Steyskal, 1982 Neosilba glaberrima (Wiedemann, 1830), Neosilba certa (Walker, 1850), Neosilba pendula (Bezzi) e Neosilba bella Strikis & Prado, 2008. Este é o primeiro registro de J. curcas como planta hospedeira de Neosilba no Brasil.

Neosilba spp. is firstly reported in physic nut fruits (Jatropha curcas), in Rio Largo, State of Alagoas, Brazil. A total of 438 specimens were found on 1,000 fruits between May and July 2010. Five species were recorded in the State of Alagoas: Neosilba zadolicha McAlpine & Steyskal 1982, Neosilba glaberrima (Wiedemann, 1830), Neosilba certa (Walker, 1850), Neosilba pendula (Bezzi) and Neosilba bella Strikis & Prado 2008. This is the first record of J. curcas as host plant of Neosilba in Brazil.

The histone-like protein H1 (H-NS) is an abundant structural component of the bacterial nucleoid and influences many cellular processes including recombination, transcription and transposition. Mutations in the hns gene encoding H-NS are highly pleiotropic, affecting the expression of many unrelated genes. We have studied the role of H-NS on the regulation of hemolysin gene expression in Serratia marcescens. The Escherichia coli hns mutant carrying S. marcescens hemolysin genes on a plasmid constructed by ligation of the 3.2-kb HindIII-SacI fragment of pR02 into pBluescriptIIKS, showed a high level of expression of this hemolytic factor. To determine the osmoregulation of wild-type and hns defective mutants the cells were grown to mid-logarithmic phase in LB medium with 0.06 or 0.3 M NaCl containing ampicillin and kanamycin, whereas to analyze the effect of pH on hemolysin expression, the cells were grown to late-logarithmic phase in LB medium buffered with 0.1 M Tris-HCl, pH 4.5 to 8.0. To assay growth phase-related hemolysin production, bacterial cells were grown in LB medium supplemented with ampicillin and kanamycin. The expression of S. marcescens hemolysin genes in wild-type E. coli and in an hns-defective derivative at different pH and during different growth phases indicated that, in the absence of H-NS, the expression of hemolysin did not vary with pH changes or growth phases. Furthermore, the data suggest that H-NS may play an important role in the regulation of hemolysin expression in S. marcescens and its effect may be due to changes in DNA topology influencing transcription and thus the amount of hemolysin expression. Implications for the mechanism by which H-NS influences gene expression are discussed.

The crystallization processes for the amorphous metallic alloys Fe74B17Si2Ni4Mo3 and Fe86B6Zr7Cu1 (at. %) were investigated using X-rays diffraction measurements performed in-situ during Joule-heating, with simultaneous monitoring of the electrical resistance. We determined the main structural transitions and crystalline phases formed during heating, and correlated these results to the observed resistance variations. As the annealing current is increased, the resistance shows an initial decrease due to stress relaxation, followed by a drop to a minimum value due to massive nucleation and growth of alpha-Fe nanocrystals. Further annealing causes the formation of small fractions of Fe-B, B2Zr or ZrO2, while the resistance increases due to temperature enhancement. In situ XRD measurements allowed the identification of metastable phases, as the gamma-Fe phase which occurs at high temperatures. The exothermal peaks observed in the differential scanning calorimetry (DSC) for each alloy corroborate the results. We also have performed DSC measurements with several heating rates, which allowed the determination of the Avrami exponent and crystallization activation energy for each alloy. The obtained activation energies (362 and 301 kJ/mol for Fe-B-Zr-Cu; 323 kJ/mol for Fe-B-Si-Ni-Mo) are comparable to reported values for amorphous iron alloys, while the Avrami exponent values (n = 1.0 or n = 1.2) are consistent with diffusion controlled crystallization processes with nucleation rates close to zero.