Researching “Intellectual Radicals” in the West

The present case study is an account of the research method used in my previous article “Intellectual Radicals Challenging the State: The Case of Hizb ut-Tahrir in the West.” In the case study, I document the research process and, in particular, the process of choosing a research method by navigating the opportunities, obstacles, and challenges faced by the researcher studying a sensitive population, in this case members of an Islamist group. This case study explores all the relevant steps in developing a research project, starting with preliminary research and research design, exploring the method in action and the practicalities and lessons learnt during the research process. This case study concludes by identifying the following five core elements for developing and carrying out a good research project: choosing a pertinent research topic, choosing a suitable research method, planning the fieldwork, data analysis, and the researcher’s flexibility. These five core elements constituted the basis of my research on Hizb ut-Tahrir and why the group is committed to a continuous vocal challenge against Western states. They also helped me overcome a number of challenges (both in the field and during the research planning) by providing an effective equilibrium between flexibility and rigor

Faint progenitors of luminous z ∼ 6 quasars: Why do not we see them?

Observational searches for faint active nuclei at z > 6 have been extremely elusive, with a few candidates whose high-z nature is still to be confirmed. Interpreting this lack of detections is crucial to improve our understanding of high-z supermassive black holes (SMBHs) formation and growth. In this work, we present a model for the emission of accreting black holes (BHs) in the X-ray band, taking into account super-Eddington accretion, which can be very common in gas-rich systems at high-z. We compute the spectral energy distribution for a sample of active galaxies simulated in a cosmological context, which represent the progenitors of a z ˜ 6 SMBH with MBH ˜ 109 M⊙. We find an average Compton-thick fraction of ˜45 per cent and large typical column densities (NH ≳ 1023 cm2). However, faint progenitors are still luminous enough to be detected in the X-ray band of current surveys. Even accounting for a maximum obscuration effect, the number of detectable BHs is reduced at most by a factor of 2. In our simulated sample, observations of faint quasars are mainly limited by their very low active fraction (fact ˜ 1 per cent), which is the result of short, supercritical growth episodes. We suggest that to detect high-z SMBHs progenitors, large area surveys with shallower sensitivities, such as COSMOS Legacy and XMM-LSS+XXL, are to be preferred with respect to deep surveys probing smaller fields, such as Chandra Deep Field South

IR emission from circumstellar envelopes of C-rich stars

The reliability of a theoretical model that solves the radiative transfer equation in dust clouds surrounding a central star is checked. In particular, it is found that both classical scattering by dust and the back-heating effects are negligible in the radiative transfer when envelopes similar to IRC+10216 are taken into consideration. In addition, new fits of IRC+10216 spectra are presented which were obtained, when the source is in different luminosity phases, under the assumption that amorphous carbon grains are in the circumstellar envelope. The same model is currently used to simulate the emission from carbon-rich sources showing the silicon carbide feature at 11.3 microns

O uso da argumentação na montagem de um modelo

Trabalhos recentes na área de Ensino de ciência têm tratado a argumentação como parte imprescindível das aulas de ciência, pois argumentar seria uma das características da ciência. A forma de análise recorrente em tais trabalhos é o padrão criado por Toulmin, que permite uma divisão do argumento e a identificação de seus elementos constituintes. Foi analisada uma seqüência didática com as turmas de 3º ano da escola de Aplicação da Universidade de São Paulo que culminou na montagem de um modelo de DNA. Tal montagem foi feita em grupos e as discussões ocorridas durante a tarefa foram gravadas e transcritas. A análise dos discursos mostrou argumentos simples compostos basicamente por dados e conclusão. A atividade se mostra diferente da ciência já que não são defendidos pontos de vista sobre uma questão aberta, mas sim opiniões sobre algo já estabelecido

Experimental evidence for amorphous carbon grains in comets

Amorphous carbon grains similar to those produced in the laboratory, but with a higher hydrogen content, appear to be good candidates to simulate both the IR continuum emission and the 3.4 micron band measured for P/Halley. The comparison of the cometary features with those detected in the laboratory for carbon grains characterized by various sp(exp 2)/sp(exp 3) ratios seems to indicate that a prevalent diamond-like (sp(exp 3)) structure should be present in cometary particles. These kinds of solid particles seem also suitable to explain the daily and monthly variations of the 3.4 micron band intensity, relative to the continuum, and, at the same time,- to fulfill the abundance constraints. The same grains appear to be able to reproduce the absorption bands detected in the IR galactic source IRS 7. This result may be considered as a first experimental evidence of a relation existing between interstellar dust and cometary materials

Raman properties of various carbonaceous materials and their astrophysical implications

It is well known that a large number of celestial objects exhibit, in the range 3 to 12 micron, a family of emission features called unidentified infrared bands (UIR). They usually appear together and are associated with UV sources. Recently various authors have suggested that these features could be attributed to solid carbonaceous materials. Following this interest, a systematic analysis was performed of various types of amorphous carbon grains and polycyclic aromatic hydrocarbons (PAH), produced in lab. Updating results of Raman measurements performed on several carbonaceous materials, chosen according to their astrophysical interest, are presented. The measurements were made by means of a Jobin-Yvon monochromator HG2S and standard DC electronic. The line at 5145 A of an Ar+ laser was used as excitation source