Semiconductor saturable absorbers for ultrafast THz signals

We demonstrate saturable absorber behavior of n-type semiconductors GaAs, GaP and Ge in THz frequency range at room temperature using nonlinear THz spectroscopy. The saturation mechanism is based on a decrease in electron conductivity of semiconductors at high electron momentum states, due to conduction band nonparabolicity and scattering into satellite valleys in strong THz fields. Saturable absorber parameters, such as linear and non-saturable transmission, and saturation fluence, are extracted by fits to a classic saturable absorber model. Further, we observe THz pulse shortening, and an increase of the group refractive index of the samples at higher THz pulse peak fields.Comment: Submitted to Appl. Phys. Lett

Grande potencial.

Embora ainda pouco conhecido, o mirtilo é uma fruta muito apreciada no exterior, com crescimento de consumo de cerca de 20% ao ano. No Brasil, representa uma oportunidade de diversificação devido a seu elevado valor agregado.Número especial. Contém orientações gerais de como produzir mirtilo

Automatic segmentation of centromeres, foci and delineation of chromosomes

The observation of chromosomes has been crucial for our understanding of their structure, function, organization, and evolution of genes and genomes as well as morphological changes during mitotic and meiotic divisions. In this work, we present an automatic algorithm for the segmentation of centromeres and foci of DNA processing proteins, as well as the delineation of convoluted chromosomes. The algorithm is fully automatic and does not require tuning of parameters. Statistical measurements of numbers, areas distance and lengths are provided by the algorithm. The work is preliminary as this algorithm has not been tested on a large database nor used to differentiate between populations, however, it is considered that given it is fully automatic and fast it should be a useful tool for the analysis of chromosomes

Evaluating stroke patients' awareness of risk factors and readiness to change stroke risk-related behaviors in a randomized controlled trial

To identify the effects of a brief educational intervention on stroke patients' recall and recognition of risk factors and performance of and stage of change for stroke risk-related behaviors.Sixty-six patients with stroke participated in a multisite randomized controlled trial. The intervention group (n = 35) received a brief education intervention (tailored written stroke information, verbal reinforcement of information for 3 months after discharge, and provision of a telephone number). The control group (n = 31) received usual care. Unprompted recall (personal and general), prompted recognition of risk factors (0-13), and performance of (0-10) and stage of change for up to 7 stroke risk-related behaviors were assessed before and 3 months after discharge.No significant between-group differences were found. For all participants over time, there were significant improvements for personal (mean difference [MD], 0.3; 95% CI, 0.004-0.69; P = .05) and general (MD, 0.6; 95% CI, 0.09-1.16; P = .02) risk factor recall; performance of stroke risk-related behaviors (MD, 0.8; 95% CI, 0.28-1.26; P < .01); and progression from a nonaction to an action stage of change for 4 of 7 behaviors over time. There was a significant decline in total risk factor recognition scores (MD, -0.8; 95% CI, 0.39-1.13; P < .01).Stroke patients' unprompted recall of risk factors and performance of risk-related behaviors improved over time; readiness to change risk-related behaviors progressed for some behaviors. A brief educational intervention did not improve risk factor awareness or behavior change more than usual care

Testrun results from prototype fiber detectors for high rate particle tracking

A fiber detector concept has been realized allowing to registrate particles within less than 100 nsec with a space point precision of about 0.1 mm at low occupancy. Three full size prototypes have been build by different producers and tested at a 3 GeV electron beam at DESY. After 3 m of light guides 8-10 photoelectrons were registrated by multichannel photomultipliers providing an efficiency of more than 99%. Using all available data a resolution of 0.086 mm was measured.Comment: 18 pages, 17 figure