Constellation Shaping for WDM systems using 256QAM/1024QAM with Probabilistic Optimization

In this paper, probabilistic shaping is numerically and experimentally investigated for increasing the transmission reach of wavelength division multiplexed (WDM) optical communication system employing quadrature amplitude modulation (QAM). An optimized probability mass function (PMF) of the QAM symbols is first found from a modified Blahut-Arimoto algorithm for the optical channel. A turbo coded bit interleaved coded modulation system is then applied, which relies on many-to-one labeling to achieve the desired PMF, thereby achieving shaping gain. Pilot symbols at rate at most 2% are used for synchronization and equalization, making it possible to receive input constellations as large as 1024QAM. The system is evaluated experimentally on a 10 GBaud, 5 channels WDM setup. The maximum system reach is increased w.r.t. standard 1024QAM by 20% at input data rate of 4.65 bits/symbol and up to 75% at 5.46 bits/symbol. It is shown that rate adaptation does not require changing of the modulation format. The performance of the proposed 1024QAM shaped system is validated on all 5 channels of the WDM signal for selected distances and rates. Finally, it was shown via EXIT charts and BER analysis that iterative demapping, while generally beneficial to the system, is not a requirement for achieving the shaping gain.Comment: 10 pages, 12 figures, Journal of Lightwave Technology, 201

Conformal Symmetry for General Black Holes

We show that the warp factor of a generic asymptotically flat black hole in five dimensions can be adjusted such that a conformal symmetry emerges. The construction preserves all near horizon properties of the black holes, such as the thermodynamic potentials and the entropy. We interpret the geometry with modified asymptotic behavior as the "bare" black hole, with the ambient flat space removed. Our warp factor subtraction generalizes hidden conformal symmetry and applies whether or not rotation is significant. We also find a relation to standard AdS/CFT correspondence by embedding the black holes in six dimensions. The asymptotic conformal symmetry guarantees a dual CFT description of the general rotating black holes.Comment: 26 page

The Globular Cluster System of NGC4374

We study the globular cluster system (GCS) of the giant elliptical NGC4374 (M84) in the Virgo cluster using B and R photometry. The colour distribution is bimodal with peaks at B-R=1.11 and B-R=1.36, fitting well to those found in other early-type galaxies. The radial profile of the cluster number density is flatter than the galaxy light. Using the luminosity function we derive a distance modulus of $\mu=31.61\pm0.2$, which within the uncertainty agrees with the distance from surface brightness fluctuations. Blue and red clusters show similar radial concentrations and azimuthal distributions. The total number of clusters is $N=1775\pm150$, which together with our distance modulus leads to a specific frequency of $S_{N}=1.6\pm0.3$. This value is surprisingly low for a giant elliptical, but resembles the case of merger remnants like NGC1316, where the low specific frequency is probably caused by the luminosity contribution of an intermediate-age population. A further common property is the high rate of type Ia supernovae which also may indicate the existence of a younger population. However, unlike in the case of NGC1316, one cannot find any further evidence that NGC4374 indeed hosts younger populations. The low specific frequency would also fit to a S0 galaxy seen face-on.Comment: Accepted for publication in Astronomy & Astrophysics. 11 page

Spectroscopy of globular clusters in the low-luminosity spiral galaxy NGC 45

CONTEXT: Extragalactic globular clusters have been studied in elliptical galaxies and in a few luminous spiral galaxies, but little is known about globular clusters in low-luminosity spirals. AIMS: Past observations with the ACS have shown that NGC 45 hosts a large population of globular clusters (19), as well as several young star clusters. In this work we aim to confirm the bona fide globular cluster status for 8 of 19 globular cluster candidates and to derive metallicities, ages, and velocities. METHODS: VLT/FORS2 multislit spectroscopy in combination with the Lick/IDS system was used to derive velocities and to constrain metallicities and [alpha/Fe] element ratio of the globular clusters. RESULTS: We confirm the 8 globular clusters as bona fide globular clusters. Their velocities indicate halo or bulge-like kinematics, with little or no overall rotation. From absorption indices such as H_beta, H_gamma, and H_delta and the combined [MgFe]' index, we found that the globular clusters are metal-poor [Z/H]<=-0.33 dex and [alpha/Fe]<=0.0 element ratio. These results argue in favor of a population of globular clusters formed during the assembling of the galaxy.Comment: Accepted for publication in Astronomy and Astrophysics. 10 pages, 6 figures. Table 6 and Fig. 6 will only be published in the electronic edition of the A&A journa

Properties of Intra-group Stars and Galaxies in Galaxy Groups: "Normal" versus "Fossil" Groups

Cosmological LCDM simulations of 12 M_vir~10^14 Msun galaxy groups have been performed, invoking star formation, chemical evolution with non-instantaneous recycling, metallicity dependent radiative cooling, strong star-burst driven galactic super-winds and effects of a meta-galactic UV field. At z=0, intra-group light (IGL) fractions are found to be 12-45%. Low values refer to groups with only a small difference between the R-band magnitudes of the first and second ranked group galaxy, large are typical of "fossil" groups (FGs). The IG stars in the 4 FGs are 0.3-0.5 Gyr older than in the 8 nonFGs. For the IGL, B-R=~1.4, in good agreement with observations. For FGs/nonFGs the iron abundance of the IG stars is slightly sub-solar in the central parts (r~100 kpc) decreasing to about 40% solar at about 0.5 r_vir The IG stars are alpha-element enhanced with [O/Fe] increasing with r, and an overall [O/Fe]~0.45, indicating predominant SNII enrichment. The velocity distributions of the IG stars and group galaxies are, at r>~30 kpc, significantly more radially anisotropic for FGs than for nonFGs. So a characteristic of FG formation, apart from formation time (D'Onghia et al.), may be the "initial" velocity distribution of the group galaxies. For FGs one can dynamically infer the (dark matter dominated) mass distribution of the groups all the way to r_vir, from the kinematics of the IG stars or group galaxies. For the nonFGs this method overestimates the group mass at r>~200 kpc, by up to a factor of two at r_vir. This is interpreted as FGs being, in general, more relaxed than nonFGs. Finally, FGs of the above M_vir should host ~500 planetary nebulae at projected distances between 100 and 1000 kpc from the first ranked galaxy. All results appear consistent with the FG formation scenario of D'Onghia et al.Comment: 12 pages, 15 figures, Accepted for MNRAS, Printing in colour recommende

Análise do comportamento de um navio utilizando a teoria das faixas

Dissertação para obtenção do Grau de Mestre em Engenharia MecânicaA teoria das faixas (Strip Theory) é uma teoria muito usada no estudo do comportamento de navios (Rawson, 2001). Segundo esta teoria o navio é considerado um corpo rígido, dividido em várias faixas ou ‘Strips’. O movimento do seu centro de massa é obtido resolvendo as equações de equilíbrio dinâmico, considerando todas as forças, incluindo as hidrodinâmicas actuando sobre cada uma dessas faixas de forma independente e obtendo a sua resultante (Salvesen and Faltinsen,1970). O objectivo desta dissertação é o desenvolvimento de um programa utilizando a plataforma MATLAB que aplique a teoria das faixas de modo a determinar os operadores de amplitude de resposta (RAO’s) para os movimentos de Heave e Pitch quando sujeito à acção de ondas regulares. A validação dos resultados obtidos no programa desenvolvido é efectuada por comparação com resultados experimentais obtidos para um modelo de barcaça sujeita às mesmas solicitações exteriores

The when and how of male circumcision and the risk of HIV: a retrospective crosssectional analysis of two HIV surveys from Guinea-Bissau

Introduction: Male circumcision (MC) reduces the risk of HIV, and this risk reduction may be modified by socio-cultural factors such as the timing and method (medical and traditional) of circumcision. Understanding regional variations in circumcision practices and their relationship to HIV is crucial and can increase insight into the HIV epidemic in Africa. Methods: We used data from two retrospective HIV surveys conducted in Guinea- Bissau from 1993 to 1996 (1996 cohort) and from 2004 to 2007 (2006 cohort). Multivariate logistical models were used to investigate the relationships between HIV risk and circumcision status, timing, method of circumcision, and socio-demographic factors. Results: MC was protective against HIV infection in both cohorts, with adjusted odds ratios (AORs) of 0.28 (95% CI 0.12-0.66) and 0.30 (95% CI 0.09-0.93), respectively. We observed that post-pubertal (≥13 years) circumcision provided the highest level of HIV risk reduction in both cohorts compared to non-circumcised. However, the difference between pre-pubertal (≤12 years) and post-pubertal (≥13 years) circumcision was not significant in the multivariate analysis. Seventy-six percent (678/888) of circumcised males in the 2006 cohort were circumcised traditionally, and 7.7% of those males were HIV-infected compared to 1.9% of males circumcised medically, with AOR of 2.7 (95% CI 0.91-8.12). Conclusion: MC is highly prevalent in Guinea-Bissau, but ethnic variations in method and timing may affect its protection against HIV. Our findings suggest that sexual risk behaviour and traditional circumcision may increases HIV risk. The relationship between circumcision age, sexual behaviour and HIV status remains unclear and warrants further research.Pan African Medical Journal 2016; 2

The ACS Fornax Cluster Survey VII. Half-Light Radii of Globular Clusters in Early-Type Galaxies

We measure the half-light radii of globular clusters (GCs) in 43 galaxies from the ACS Fornax Cluster Survey (ACSFCS). We use these data to extend previous work in which the environmental dependencies of the half-light radii of GCs in early type galaxies in the ACS Virgo Cluster Survey (ACSVCS) were studied, and a corrected mean half-light radius (corrected for the observed environmental trends) was suggested as a reliable distance indicator. This work both increases the sample size for the study of the environmental dependencies, and adds leverage to the study of the corrected half-light radius as a possible distance indicator (since Fornax lies at a larger distance than the Virgo cluster). We study the environmental dependencies of the size of GCs using both a Principal Component Analysis as well as 2D scaling relations. We largely confirm the environmental dependencies shown in Jordan et al. (2005), but find evidence that there is a residual correlation in the mean half-light radius of GC systems with galaxy magnitude, and subtle differences in the other correlations - so there may not be a universal correction for the half-light radii of lower luminosity galaxy GC systems. The main factor determining the size of a GC in an early type galaxy is the GC color. Red GCs have = 2.8+/-0.3 pc, while blue GCs have = 3.4+/-0.3 pc. We show that for bright early-type galaxies (M_B < -19 mag), the uncorrected mean half-light radius of the GC system is by itself an excellent distance indicator (with error ~11%), having the potential to reach cosmologically interesting distances in the era of high angular resolution adaptive optics on large optical telescopes.Comment: ApJ in press, 19 pages, 16 figures

Produção brasileira de bovinos de corte : A carne é forte : revisão

Trabalho de Conclusão de Curso (graduação)—Universidade de Brasília, Faculdade de Agronomia e Medicina Veterinária, 2017.Os sistemas de produção de carne de corte bovina têm buscado novas tecnologias para aperfeiçoar a obtenção de um produto com melhor qualidade para o consumidor, em menor tempo e de forma aprimorada economicamente que se torne viável. O Brasil sendo um dos maiores produtores e exportadores de carne bovina aderiu às novas tecnologias, com a visão de crescimento da produtividade e lucratividade da produção, pensando também nas boas práticas de manejo e no bem estar dos animais de produção. Quando se fala de qualidade de alimentos não podemos deixar de falar das certificações e da rastreabilidade do produto, bem como da boa condição sanitária do mesmo, livre de doenças como, por exemplo, a febre aftosa. Apesar da operação “Carne Fraca”, que trouxe a tona problemas de corrupção e irregularidades em alguns frigoríficos brasileiros, o Brasil continua sendo um país referência em produção e exportação de carne bovina, devido à credibilidade conquistada por comercializar produtos de qualidade para vários mercados emergentes e de alto grau de exigência quanto à qualidade do produto. Diante disso, objetivou-se com o presente trabalho realizar uma revisão de literatura sobre os pontos positivos da produção de carne bovina brasileira, destacando os problemas ocorridos com a “Operação a Carne é Fraca”.Bovine meat production systems have been looking for new technologies to im- prove the quality of the product for the consumer in a shorter time and in an economi- cally improved way that becomes viable. Brazil being one of the largest producers and exporters of beef adhered to the new technologies, with the vision of increasing produc- tivity and profitability of production, also thinking about good management practices and the welfare of production animals. When talking about food quality, we must speak about the certifications and the traceability of the product, as well as the good health condition of the product, free of diseases such as foot and mouth disease. Despite the "Weak Meat" operation, which has brought about problems of corruption and irregulari- ties in some Brazilian slaughterhouses, Brazil continues to be a reference country in the production and export of beef, due to the credibility gained by marketing quality prod- ucts to several emerging markets and of high degree of exigency as to the quality of the product. Therefore, the objective of this work was to review the literature on the posi- tive aspects of Brazilian beef production, highlighting the problems that occurred with the "Operation Meat is Weak"