Optoelectronic Properties and Excitons in Hybridized Boron Nitride and Graphene Hexagonal Monolayers

We explain the nature of the electronic band gap and optical absorption spectrum of Carbon - Boron Nitride (CBN) hybridized monolayers using density functional theory (DFT), GW and Bethe-Salpeter equation calculations. The CBN optoelectronic properties result from the overall monolayer bandstructure, whose quasiparticle states are controlled by the C domain size and lie at separate energy for C and BN without significant mixing at the band edge, as confirmed by the presence of strongly bound bright exciton states localized within the C domains. The resulting absorption spectra show two marked peaks whose energy and relative intensity vary with composition in agreement with the experiment, with large compensating quasiparticle and excitonic corrections compared to DFT calculations. The band gap and the optical absorption are not regulated by the monolayer composition as customary for bulk semiconductor alloys and cannot be understood as a superposition of the properties of bulk-like C and BN domains as recent experiments suggested

Impegno in the work of silvia ballestra: A space of political engagement between realism and postmodernism

L’opera di Silvia Ballestra è emblematica della transizione dei cosiddetti scrittori ‘pulp’ dalla produzione giovanile dei primi anni Novanta, di taglio esplicitamente sperimentale, ironico ed auto-riflessivo, a generi e stili che si rifanno invece alla tradizione realista ed impegnata, quali il romanzo storico e familiare, il pamphlet politico e femminista, e il giornalismo, visti come strumenti più immediati e diretti da opporre alla reazione culturale di destra dell’era berlusconiana. La raccolta di racconti Gli orsi (1994), in particolare, mostra come per Ballestra il passaggio da un’estetica postmoderna ad una più realista sia frutto di una profonda riflessione poetica sulle possibilità degli intellettuali di intervenire sulla realtà in un momento di grande urgenza politica

The synchrotron foreground and CMB temperature-polarization cross correlation power spectrum from the first year WMAP data

We analyse the temperature-polarization cross-correlation in the Galactic synchrotron template that we have recently developed, and between the template and CMB temperature maps derived from WMAP data. Since the polarized synchrotron template itself uses WMAP data, we can estimate residual synchrotron contamination in the CMB $C_\ell^{TE}$ angular spectrum. While $C_2^{TE}$ appears to be contamined by synchrotron, no evidence for contamination is found in the multipole range which is most relevant for the fit of the cosmological optical depth.Comment: Accepted for pubblication on MNRAS Lette

Exiles/Nomads: Journeys through Language and Gender in Italian Women’s Pulp Fiction of the 1990s

Le definizioni di esilio e nomadismo elaborate da Rosi Braidotti quali metafore dell’identità postmoderna costituiscono il punto di partenza per la discussione di alcuni scrittori degli anni Novanta (Brizzi, Culicchia, Caliceti, Scarpa, Nove, Ballestra, Campo e Santacroce), la cui narrativa prende le distanze dal contesto sociale, culturale e linguistico in cui si è tradizionalmente sviluppata la narrativa italiana. I personaggi dei loro testi si sentono estranei alla propria realtà geografica e culturale, in cui sono tuttavia costretti a ricercare le radici del proprio disagio, soprattutto quando vogliono trasformarsi da esiliati in patria in soggetti nomadi, capaci cioè di identificarsi in modo positivo nella loro perenne condizione di transizione e molteplicità. I personaggi femminili, in particolare se scritti da autrici, sembrano maggiormente in grado di quelli maschili di gestire gli opposti desideri di fuga e ritorno, in virtù di una soggettività più duttile e flessibile. Al contrario, i personaggi maschili appaiono spesso inchiodati ad una concezione fissa ed immutabile della mascolinità italiana, alla quale tentano di sfuggire ma di cui continuano a subire la fatale attrazione.Ma lo volete capire che oggi il mondo è pieno digiovani ribelli che a casa non ci stanno più neanchese li ammazzano?La Gabri chiede. E dove vanno i giovani ribelli?La Natascia risponde che i giovani ribelli nonvanno in un posto preciso, ma partono all’avventuraper conoscere il mondo

The inner structure of very massive elliptical galaxies: implications for the inside-out formation mechanism of z~2 galaxies

We analyze a sample of 23 supermassive elliptical galaxies (central velocity dispersion larger than 330 km s-1), drawn from the SDSS. For each object, we estimate the dynamical mass from the light profile and central velocity dispersion, and compare it with the stellar mass derived from stellar population models. We show that these galaxies are dominated by luminous matter within the radius for which the velocity dispersion is measured. We find that the sizes and stellar masses are tightly correlated, with Re ~ M*^{1.1}$, making the mean density within the de Vaucouleurs radius a steeply declining function of M*: rho_e ~ M*^{-2.2}. These scalings are easily derived from the virial theorem if one recalls that this sample has essentially fixed (but large) sigma_0. In contrast, the mean density within 1 kpc is almost independent of M*, at a value that is in good agreement with recent studies of z ~ 2 galaxies. The fact that the mass within 1 kpc has remained approximately unchanged suggests assembly histories that were dominated by minor mergers -- but we discuss why this is not the unique way to achieve this. Moreover, the total stellar mass of the objects in our sample is typically a factor of ~ 5 larger than that in the high redshift (z ~ 2) sample, an amount which seems difficult to achieve. If our galaxies are the evolved objects of the recent high redshift studies, then we suggest that major mergers were required at z > 1.5, and that minor mergers become the dominant growth mechanism for massive galaxies at z < 1.5.Comment: 11 pages, 8 figures, accepted in MNRA

PC1643+4631A,B: The Lyman-Alpha Forest at the Edge of Coherence

This is the first measurement and detection of coherence in the intergalactic medium (IGM) at substantially high redshift (z~3.8) and on large physical scales (~2.5 h^-1 Mpc). We perform the measurement by presenting new observations from Keck LRIS of the high redshift quasar pair PC 1643+4631A, B and their Ly-alpha absorber coincidences. This experiment extends multiple sightline quasar absorber studies to higher redshift, higher opacity, larger transverse separation, and into a regime where coherence across the IGM becomes weak and difficult to detect. We fit 222 discrete Ly-alpha absorbers to sightline A and 211 to sightline B. Relative to a Monte Carlo pairing test (using symmetric, nearest neighbor matching) the data exhibit a 4sigma excess of pairs at low velocity splitting (<150 km/s), thus detecting coherence on transverse scales of ~2.5 h^-1 Mpc. We use spectra extracted from an SPH simulation to analyze symmetric pair matching, transmission distributions as a function of redshift and compute zero-lag cross-correlations to compare with the quasar pair data. The simulations agree with the data with the same strength (~4sigma) at similarly low velocity splitting above random chance pairings. In cross-correlation tests, the simulations agree when the mean flux (as a function of redshift) is assumed to follow the prescription given by Kirkman et al. (2005). While the detection of flux correlation (measured through coincident absorbers and cross-correlation amplitude) is only marginally significant, the agreement between data and simulations is encouraging for future work in which even better quality data will provide the best insight into the overarching structure of the IGM and its understanding as shown by SPH simulations.Comment: 15 pages, 11 figures; accepted for publication in Astronomical Journa

Programa de análise de qualidade de laboratórios de fertilidade (PAQLF) que usam o método Embrapa: resultados de 2001.

bitstream/CNPS/11188/1/ct1102paqlf2001.pd

Assessing composition gradients in multifilamentary superconductors by means of magnetometry methods

We present two magnetometry-based methods suitable for assessing gradients in the critical temperature and hence the composition of multifilamentary superconductors: AC magnetometry and Scanning Hall Probe Microscopy. The novelty of the former technique lies in the iterative evaluation procedure we developed, whereas the strength of the latter is the direct visualization of the temperature dependent penetration of a magnetic field into the superconductor. Using the example of a PIT Nb3Sn wire, we demonstrate the application of these techniques, and compare the respective results to each other and to EDX measurements of the Sn distribution within the sub-elements of the wire.Comment: 7 pages, 8 figures; broken hyperlinks are due to a problem with arXi

Programa de Análise de Qualidade de Laboratórios de Fertilidade (PAQLF) que usam o método Embrapa: resultados de 2002.

No ano de 2002, o desempenho dos laboratórios participantes do PAQLF foi avaliado através dos resultados analíticos de 12 amostras de terra. Os participantes analisaram obrigatoriamente P e K (Mehlich-1); pH (água); Ca, Mg e Al (KCl); H+Al (acetato de Ca ou SMP); e matéria orgânica (colorimétrico ou Walkey-Black); e facultativamente os micronutrientes B (água quente); Cu, Fe Mn e Zn (Mehlich- 1) e granulometria. Dos 92 laboratórios inscritos inicialmente, foram avaliados 64 laboratórios, dos quais 93,7% apresentaram conceitos A ou B e foram habilitados ao uso do selo de qualidade. Destes, 13 laboratórios (20,3%) obtiveram conceito A. A ordem decrescente do número total de asteriscos nas análises de rotina foi P > matéria orgânica > K > Mg > H+Al > Ca > pH > Al. Para os micronutrientes, a ordem foi Fe > Mn > Zn > Cu > B, e para granulometria, silte > argila > areia. Os coeficientes de variação dos parâmetros analisados nas 12 amostras do ano pelos participantes foram, em ordem decrescente, Al > Mg > Ca > K > H+Al > P > matéria orgânica > pH, sendo que os valores ficaram na faixa de 158 a 4%. Para os micronutrientes, a ordem foi B > Zn > Cu > Fe > Mn, com valores entre 162 a 16%. Para granulometria, foi silte > argila > areia, com valores de 43, 29, e 12%.bitstream/CNPS/11568/1/comtec_14_2003_paqlf_result_2002.pd