The Socio-Economic Value of the Shark-Diving Industry in Fiji

Based on a survey of divers, dive operators, resort managers, estimates business revenues from shark diving and related expenditures by area; tax revenues; and economic benefit to local communities

Quantum state of a free spin-1/2 particle and the inextricable dependence of spin and momentum under Lorentz transformations

We revise the Dirac equation for a free particle and investigate Lorentz transformations on spinors. We study how the spin quantization axis changes under Lorentz transformations, and evince the interplay between spin and momentum in this context.Comment: 14 pages, 3 figures, published as a Review in the IJQ

Measuring AGN Feedback with the Sunyaev-Zel'dovich Effect

One of the most important and poorly-understood issues in structure formation is the role of outflows driven by active galactic nuclei (AGN). Using large-scale cosmological simulations, we compute the impact of such outflows on the small-scale distribution of the cosmic microwave background (CMB). Like gravitationally-heated structures, AGN outflows induce CMB distortions both through thermal motions and peculiar velocities, by processes known as the thermal and kinetic Sunyaev-Zel'dovich (SZ) effects, respectively. For AGN outflows the thermal SZ effect is dominant, doubling the angular power spectrum on arcminute scales. But the most distinct imprint of AGN feedback is a substantial increase in the thermal SZ distortions around elliptical galaxies, post-starburst ellipticals, and quasars, which is linearly proportional to the outflow energy. While point source subtraction is difficult for quasars, we show that by appropriately stacking microwave measurements around early-type galaxies, the new generation of small-scale microwave telescopes will be able to directly measure AGN feedback at the level important for current theoretical models.Comment: 12 pages, 12 figures, submitted to ApJ (comments welcome

Treatment of neurocysticercosis with praziquantel

27 pacientes com neurocisticercose foram tratados com praziquantel, utilizado em doses progressivamente crescentes até alcançar 50 mg/kg/dia, por período de 21 dias, associado a dexametasona. Os doentes foram avaliados clínica e laboratorialmente durante o tratamento e, aqueles que completaram um ano de evolução, repetiram os testes imunofluorescência e ELISA neste período. Cefaléia foi o sintoma encontrado mais freqüentemente durante o tratamento, ocorrendo em 37% dos pacientes; 18,5% dos doentes apresentaram hipertensão intracraniana, um deles evoluindo para o óbito; 25,9% dos enfermos tiveram que suspender o praziquantel antes de completar o tratamento, devido ao surgimento de complicações importantes. Nos exames laboratoriais realizados no sétimo dia de tratamento, 33,3% dos pacientes apresentaram anormalidades, sendo leucocitose a mais freqüente. No período de um ano, 72,2% dos enfermos tiveram melhora do quadro clínico, enquanto os testes imunológicos tornaram-se não-reagentes no soro em 45,4% dos doentes e no LCR em 42,8%. Entretanto, nem sempre houve coincidência da melhora clínica com a apresentação dos testes imunológicos não-reagentes. No presente trabalho, não é possível afirmar que os testes imunológicos não-reagentes, assim como a melhora clínica dos pacientes, sejam conseqüentes à eficácia do tratamento com o praziquantel. Devido à grande freqüência e gravidade das complicações deste tratamento, os pacientes devem ser avaliados individualmente quanto aos riscos versus os benefícios dele.Twenty seven patients with neurocysticercosis were treated with praziquantel in progressive doses reaching 50 mg/kg/day associated with dexamethasone for 21 days. The patients were followed during and after treatment and those followed up for one year repeated their immunological tests (indirect immunofluorescence and ELISA) at this time. Headache was the most frequent symptom during the treatment, occurring on 37% of patients. During the treatment 18.5% of patients had intracranial hypertension and one died. One year after treatment 72.2% of patients who finished treatment improved. The immunological tests became negative in 45.4% of patients sera and 42.8% of cerebrospinal fluids. There was no correlation between the clinical evolution and immunological, testis. In this study it is not possible to afirm that both negative immunological tests and good clinical evolution were consequents to the efficacy of praziquantel treatment. Due to the great frequency and seriousness of this treatment complications, the patients with neurocysticercosis must be individually evaluated to know the risks and the benefits of the treatment with praziquantel

Quasars: What turns them off?

(Abridged) We explore the idea that the anti-hierarchical turn-off observed in the quasar population arises from self-regulating feedback, via an outflow mechanism. Using a detailed hydrodynamic simulation we calculate the luminosity function of quasars down to a redshift of z=1 in a large, cosmologically representative volume. Outflows are included explicitly by tracking halo mergers and driving shocks into the surrounding intergalactic medium. Our results are in excellent agreement with measurements of the spatial distribution of quasars, and we detect an intriguing excess of galaxy-quasar pairs at very short separations. We also reproduce the anti-hierarchical turnoff in the quasar luminosity function, however, the magnitude of the turn-off falls short of that observed as well as that predicted by analogous semi-analytic models. The difference can be traced to the treatment of gas heating within galaxies. The simulated galaxy cluster L_X-T relationship is close to that observed for z~1 clusters, but the simulated galaxy groups at z=1 are significantly perturbed by quasar outflows, suggesting that measurements of X-ray emission in high-redshift groups could well be a "smoking gun" for the AGN heating hypothesis.Comment: 16 pages, 11 figures, submitted to ApJ, comments welcome

Estimating small angular scale CMB anisotropy with high resolution N-body simulations: weak lensing

We estimate the impact of weak lensing by strongly nonlinear cosmological structures on the cosmic microwave background. Accurate calculation of large $\ell$ multipoles requires N-body simulations and ray-tracing schemes with both high spatial and temporal resolution. To this end we have developed a new code that combines a gravitational Adaptive Particle-Particle, Particle-Mesh (AP3M) solver with a weak lensing evaluation routine. The lensing deviations are evaluated while structure evolves during the simulation so that all evolution steps--rather than just a few outputs--are used in the lensing computations. The new code also includes a ray-tracing procedure that avoids periodicity effects in a universe that is modeled as a 3-D torus in the standard way. Results from our new simulations are compared with previous ones based on Particle-Mesh simulations. We also systematically investigate the impact of box volume, resolution, and ray-tracing directions on the variance of the computed power spectra. We find that a box size of $512 h^{-1}$ Mpc is sufficient to provide a robust estimate of the weak lensing angular power spectrum in the $\ell$-interval (2,000--7,000). For a reaslistic cosmological model the power $[\ell(\ell+1)C_{\ell}/2\pi]^{1/2}$ takes on values of a few $\mu K$ in this interval, which suggests that a future detection is feasible and may explain the excess power at high $\ell$ in the BIMA and CBI observations.Comment: 49 pages, 13 figures, accepted for publication in Ap

Relativistic entanglement in single-particle quantum states using Non-Linear entanglement witnesses

In this study, the spin-momentum correlation of one massive spin-1/2 and spin-1 particle states, which are made based on projection of a relativistic spin operator into timelike direction is investigated. It is shown that by using Non-Linear entanglement witnesses (NLEWs), the effect of Lorentz transformation would decrease both the amount and the region of entanglement.Comment: 16 pages, 2 figures; to be published in Quantum Inf Process, 10.1007/s11128-011-0289-z (2011