QFT in the flat chart of de Sitter space

We study the correlators for interacting quantum field theory in the flat chart of de Sitter space at all orders in perturbation. The correlators are calculated in the in-in formalism which are often applied to the calculations in the cosmological perturbation. It is shown that these correlators are de Sitter invariant. They are compared with the correlators calculated based on the Euclidean field theory. We then find that these two correlators are identical. This correspondence has been already shown graph by graph but we give an alternative proof of it by direct calculation.Comment: 24 pages, 7 figures. References added with some minor corrections. To appear in Phys. Rev.

Nonlinear photonics with applications in lightwave communications

This doctoral dissertation investigates the use of nonlinear photonics in targeted Lightwave communication applications. Different highly nonlinear optical materials have been considered for the investigation of Lightwave communications data carriers, with a focus on the optical carrier pulsewidth. A state-of-the-art novel method has been developed to measure pico-second optical carrier pulses using highly nonlinear optical fiber. This method is based on the nonlinear optical loop mirror (NOLM), with consideration focused on the third order nonlinearity. Silicon is considered to be one of the most attractive materials for photonics integrated circuit technology (PIC) due to its compatibility with complementary metal oxide semiconductor (CMOS). As such, the method has been applied to the SOI platform Mach-Zehnder interferometer (MZI), also by considering the third order nonlinearity. In the NOLM approach, the picosecond optical data carrier pulsewidth is measured by using an optical power meter. Simulations for both the self-phase and cross-phase modulation schemes are carried out, and as expected, the cross phase modulation gives an increment in the sensitivity twice that of the self-phase modulation. Due to very high repetition rates of the order 10 GHz, the effect of counter propagating non-linear interactions in the NOLM are also considered in the theoretical evaluation. In the experimental validation, the pulses from an active fiber mode-locked laser at a repetition rate of 10 GHz were incrementally temporally dispersed using an SMF-28 fiber. The optical data carrier pulses over a range of 2-10 ps were successfully measured with a resolution of 0.25 ps. By extrapolating the theoretical evaluation and by selecting different physical parameters for the setup, the method was found to exhibit an extended range of 0.25 to 40 ps.;The concept described above is then extended to the investigation of nonlinear SOI devices using an MZI, thus miniaturizing the setup. In this investigation, the silicon waveguide has been simulated for self-phase and cross-phase modulation by solving the nonlinear Schrodinger equations using the split step method. Silicon has strong two photon absorption at telecommunication wavelengths, i.e. 1550 nm, and therefore all nonlinear losses (i.e. TPA and free carriers generated through TPA) are included in the split step simulations. The results obtained show that the on-chip nonlinear MZI (based on the SOI platform) can also be used for the measurement of optical data carrier pulse-widths of up to 10 ps. In the last part of this doctoral dissertation, a novel design for a temperature insensitive MZI is presented. Temperature dependence is one of the main challenges in the design of the SOI platform due to the large thermo-optic coefficient of its core material. A change in temperature can cause the device properties to deviate significantly, and can also alter the nonlinear properties of the device. Therefore, a design of an all-passive athermal MZI device based on the SOI platform has been developed and investigated. The MZI's temperature compensation is achieved by optimizing the relative length of the wire and subwavelength grating arms, and by tailoring the thermal response of the subwavelength structure. The simulation results of the athermal MZI design indicated that an overall temperature sensitivity of 7.5 pm/K could be achieved over a 100 nm spectral range near the 1550 nm region.This doctoral dissertation investigates the use of nonlinear photonics in targeted Lightwave communication applications. Different highly nonlinear optical materials have been considered for the investigation of Lightwave communications data carriers, with a focus on the optical carrier pulsewidth. A state-of-the-art novel method has been developed to measure pico-second optical carrier pulses using highly nonlinear optical fiber. This method is based on the nonlinear optical loop mirror (NOLM), with consideration focused on the third order nonlinearity. Silicon is considered to be one of the most attractive materials for photonics integrated circuit technology (PIC) due to its compatibility with complementary metal oxide semiconductor (CMOS). As such, the method has been applied to the SOI platform Mach-Zehnder interferometer (MZI), also by considering the third order nonlinearity. In the NOLM approach, the picosecond optical data carrier pulsewidth is measured by using an optical power meter. Simulations for both the self-phase and cross-phase modulation schemes are carried out, and as expected, the cross phase modulation gives an increment in the sensitivity twice that of the self-phase modulation. Due to very high repetition rates of the order 10 GHz, the effect of counter propagating non-linear interactions in the NOLM are also considered in the theoretical evaluation. In the experimental validation, the pulses from an active fiber mode-locked laser at a repetition rate of 10 GHz were incrementally temporally dispersed using an SMF-28 fiber. The optical data carrier pulses over a range of 2-10 ps were successfully measured with a resolution of 0.25 ps. By extrapolating the theoretical evaluation and by selecting different physical parameters for the setup, the method was found to exhibit an extended range of 0.25 to 40 ps.;The concept described above is then extended to the investigation of nonlinear SOI devices using an MZI, thus miniaturizing the setup. In this investigation, the silicon waveguide has been simulated for self-phase and cross-phase modulation by solving the nonlinear Schrodinger equations using the split step method. Silicon has strong two photon absorption at telecommunication wavelengths, i.e. 1550 nm, and therefore all nonlinear losses (i.e. TPA and free carriers generated through TPA) are included in the split step simulations. The results obtained show that the on-chip nonlinear MZI (based on the SOI platform) can also be used for the measurement of optical data carrier pulse-widths of up to 10 ps. In the last part of this doctoral dissertation, a novel design for a temperature insensitive MZI is presented. Temperature dependence is one of the main challenges in the design of the SOI platform due to the large thermo-optic coefficient of its core material. A change in temperature can cause the device properties to deviate significantly, and can also alter the nonlinear properties of the device. Therefore, a design of an all-passive athermal MZI device based on the SOI platform has been developed and investigated. The MZI's temperature compensation is achieved by optimizing the relative length of the wire and subwavelength grating arms, and by tailoring the thermal response of the subwavelength structure. The simulation results of the athermal MZI design indicated that an overall temperature sensitivity of 7.5 pm/K could be achieved over a 100 nm spectral range near the 1550 nm region

Effect of Sugarcane Pressmud Biocompost on Dry Matter Yield and Nutrient Uptake in Maize

An experiment was conducted to determine the nutrient contents and manurial value of  biocompost, collected from Matiari Sugar Mill, Matiari and analyzed for macro nutrients N, P and K. The biocompost was evaluated in a pot experiment on maize crop  with eight treatments in factorial combinations of two rates of biocompost (0 and 10 tons ha-1) and four fertilizer treatments (0-0-0, 150-0-0, 150-75-0 and 150-75-60 kg ha-1 N, P and K) . The treatments were replicated three times in a randomized complete block design and maize was grown for 7 weeks. The soil was a clay loam (31% clay) with EC 0.35 dSm-1, pH 7.87, low in organic matter (0.80%) and Olsen P (7.0 mg kg-1) and high in NH4OAC-K (320 mg kg-1). The nutrient contents of biocompost were 1.8% N, 1.83% P and 0.9% K. Results revealed that there were pronounced positive effects of addition of biocompost, as well as N on plant height and dry weights of maize. Plant analysis data showed that the effect biocompost and mineral fertilizers was non-significant with respect to N, P and K contents. Soil analytical data showed that the EC values of post harvest samples increased with the application of biocompost while pH was not affected. Soil organic matter, Olsen P and NH4OAC-K increased significantly with the application of biocompost. Fertilizer application also increased Olsen P and NH4OAC-K contents in soil. The results of this study showed that biocompost can be used along with mineral fertilizers to increase maize growth and dry matter yield. Keywords: Maize, Dry matter yield, Pressmud Biocompost

ESTRATÉGIAS DE SOBREVIVÊNCIA DO GOVERNO MUGABE

O principal objetivo deste artigo é explicitar como vem sendo sustentado o regime de Robert Mugabe no Zimbábue, frente à situação calamitosa em que se encontra o país, conferindo destaque para o papel do ambiente internacional nas estratégias de sobrevivência do Governo. Desprovido de muitos recursos materiais de poder, Mugabe desenvolve em sua política exterior uma identidade e um discurso que lhe garantem apoio de parceiros internacionais, principalmente regionais, e fundamentam certa legitimidade interna, contribuindo assim, para que ele se mantenha no controle do Estado

Nonlinear effects in silicon waveguides

In this work, we modelled the nonlinear effects in silicon waveguides which are crucial for many applications, including all-optical signal processing, switching, wavelength conversion. I have developed the model for ultrafast all-optical switching using split-step Fourier method and calculated the nonlinear phase shift due to the Kerr effect and including the nonlinear losses (i.e. two-photon absorption, free carrier absorption and free carrier index)

Bazedoxifene, a selective estrogen receptor modulator, reduces cerebral aneurysm rupture in Ovariectomized rats.

BackgroundEstrogen deficiency is thought to be responsible for the higher frequency of aneurysmal subarachnoid hemorrhage in post- than premenopausal women. Estrogen replacement therapy appears to reduce this risk but is associated with significant side effects. We tested our hypothesis that bazedoxifene, a clinically used selective estrogen receptor (ER) modulator with fewer estrogenic side effects, reduces cerebral aneurysm rupture in a new model of ovariectomized rats.MethodsTen-week-old female Sprague-Dawley rats were subjected to ovariectomy, hemodynamic changes, and hypertension to induce aneurysms (ovariectomized aneurysm rats) and treated with vehicle or with 0.3 or 1.0 mg/kg/day bazedoxifene. They were compared with sham-ovariectomized rats subjected to hypertension and hemodynamic changes (HT rats). The vasoprotective effects of bazedoxifene and the mechanisms underlying its efficacy were analyzed.ResultsDuring 12 weeks of observation, the incidence of aneurysm rupture was 52% in ovariectomized rats. With no effect on the blood pressure, treatment with 0.3 or 1.0 mg/kg/day bazedoxifene lowered this rate to 11 and 17%, almost the same as in HT rats (17%). In ovariectomized rats, the mRNA level of ERα, ERβ, and the tissue inhibitor of metalloproteinase-2 was downregulated in the cerebral artery prone to rupture at 5 weeks after aneurysm induction; the mRNA level of interleukin-1β and the matrix metalloproteinase-9 was upregulated. In HT rats, bazedoxifene restored the mRNA level of ERα and ERβ and decreased the level of interleukin-1β and matrix metalloproteinase-9. These findings suggest that bazedoxifene was protective against aneurysmal rupture by alleviating the vascular inflammation and degradation exacerbated by the decrease in ERα and ERβ.ConclusionsOur observation that bazedoxifene decreased the incidence of aneurysmal rupture in ovariectomized rats warrants further studies to validate this response in humans

Hyperhomocysteinemia induced by excessive methionine intake promotes rupture of cerebral aneurysms in ovariectomized rats.

BackgroundHyperhomocysteinemia (HHcy) is associated with inflammation and a rise in the expression of matrix metalloproteinase-9 (MMP-9) in the vascular wall. However, the role of HHcy in the growth and rupture of cerebral aneurysms remains unclear.MethodsThirteen-week-old female Sprague-Dawley rats were subject to bilateral ovariectomy and ligation of the right common carotid artery and fed an 8 % high-salt diet to induce cerebral aneurysms. Two weeks later, they underwent ligation of the bilateral posterior renal arteries. They were divided into two groups and methionine (MET) was or was not added to their drinking water. In another set of experiments, the role of folic acid (FA) against cerebral aneurysms was assessed.ResultsDuring a 12-week observation period, subarachnoid hemorrhage due to aneurysm rupture was observed at the anterior communicating artery (AcomA) or the posterior half of the circle of Willis. HHcy induced by excessive MET intake significantly increased the incidence of ruptured aneurysms at 6-8 weeks. At the AcomA of rats treated with MET, we observed the promotion of aneurysmal growth and infiltration by M1 macrophages. Furthermore, the mRNA level of MMP-9, the ratio of MMP-9 to the tissue inhibitor of metalloproteinase-2, and the level of interleukin-6 were higher in these rats. Treatment with FA abolished the effect of MET, suggesting that the inflammatory response and vascular degradation at the AcomA is attributable to HHcy due to excessive MET intake.ConclusionsWe first demonstrate that in hypertensive ovariectomized rats, HHcy induced by excessive MET intake may be associated with the propensity of the aneurysm wall to rupture

A importância do estudo das Relações Internacionais africanas para o campo das Relações Internacionais.

A partir de um estudo sobre o papel das Relações Internacionais na manutenção do regime de Robert Mugabe no Zimbábue, foi analisado o papel tradicionalmente designado a Estados pequenos e fracos nas Teorias de Relações Internacionais. Foram examinados criticamente os paradigmas clássicos e seus conceitos, buscando explicações satisfatórias para as questões que emergem no estudo das Relações Internacionais africanas. Percebe-se que, indo além dos tradicionais focos de estudo, como as grandes potências, e trazendo a África para o centro dos debates teóricos como fonte de explicações aplicáveis aos fenômenos do meio internacional, é possível repensar as Relações Internacionais de modo mais inclusivo e democrático. Assim podem ser reavaliadas as lentes teóricas que fundamentam o olhar sobre os fenômenos internacionais, contribuindo para o desenvolvimento do campo de estudos

Imagens e narrativas da África: desmistificando as teorias de Relações Internacionais

The article intends to question the images and narratives we know about Africa and question certain myths we believe in about the continent in the field of International Relations. A brief mapping of the space that the continent occupies in the theories of International Relations is developed and the adequacy of this situation that confronts us, of incomplete and biased narratives that privilege an Eurocentric perspective, is questioned. Finally, the article ends with a proposal for theoretical and epistemological pluralism.Procura-se questionar as imagens que temos e as narrativas que conhecemos acerca da África e, a partir disso, questionar alguns mitos que construímos acerca do continente no campo das Relações Internacionais. É feito um breve levantamento acerca do espaço que o continente tem nas teorias de Relações Internacionais e um questionamento acerca da adequação do panorama com que nos confrontamos, de narrativas incompletas e enviesadas privilegiando um olhar eurocêntrico. Finaliza-se com uma proposta de pluralismo teórico e epistemológico