2,005 research outputs found
Infrared tunable laser: A concept
Apparatus in which laser wavelengths of two dyes are mixed in intracavity, nonlinear crystal provides intense source of coherent laser radiation which is tunable from visible through infrared wavelengths of electromagnetic spectrum
Infrared tunable laser
A tunable laser apparatus is reported with a first wavelength selective reflector and a second wavelength selective reflector forming one end of an optical cavity, and a third wavelength selective reflector forming the other end of an optical cavity. A first lasable dye solution develops radiation of a wavelength selected by the first reflector and a second lasable dye solution develops radiation of a wavelength selected by the second reflector and a non-linear mixing crystal disposed within the optical cavity. The selected radiation is passed through the nonlinear mixing crystal causing it to develop radiation of a third wavelength which is transmitted out of the optical cavity through the third reflector
Picosecond pulse measurement by two-photon excitation of photographic film
Technique shoots two broad light beams onto a photosensitive surface which responds nonlinearly to the intensity in the beams. The resultant signal contains a component depending on the intensity correlation function between the two light beams
Alignment apparatus using a laser having a gravitationally sensitive cavity reflector
A description is given of a device for determining a true gravitational vertical. The apparatus is composed of a vertically disposed laser with a gravitationally sensitive lower regeneration reflector. The reflector enables an output beam to be developed only when the optical axis of the laser is disposed normal to the gravitationally sensitive reflective surface. In an alternative embodiment, the devices is combined with a servo system to provide a gravitationally stabilized horizontal platform
IR pumped third-harmonic generation and sum-frequency generation in diatomic molecules
The potential efficiency of using nonlinear up-conversion techniques for the high efficiency type lasers (CO,CO2, and chemical) is assessed. Results indicate that: the small pump photon energy necessitates the use of molecular media for conversion if resonance enhancement is to be used and that molecular systems present several problems. These difficulties include: their levels are complex; their transition probabilities are often unknown; and the oscillator strengths among vibrational levels in the ground electronic state of a molecule are much smaller than those among electronic states of an atom, thus limiting the magnitude of nonlinear interactions. It is shown that this problem can be eliminated by making use of vibronic transitions which, being primarily electronic transitions have much larger matrix elements and efficient conversion can be achieved with molecular systems
Population Synthesis of Normal Radio and Gamma-ray Pulsars Using Markov Chain Monte Carlo Techniques
We present preliminary results of a pulsar population synthesis of normal
pulsars from the Galactic disk using a Markov Chain Monte Carlo method to
better understand the parameter space of the assumed model. We use the Kuiper
test, similar to the Kolmogorov-Smirnov test, to compare the cumulative
distributions of chosen observables of detected radio pulsars with those
simulated for various parameters. Our code simulates pulsars at birth using
Monte Carlo techniques and evolves them to the present assuming initial
spatial, kick velocity, magnetic field, and period distributions. Pulsars are
spun down to the present, given radio and gamma-ray emission characteristics,
filtered through ten selected radio surveys, and a {\it Fermi} all-sky
threshold map. Each chain begins with a different random seed and searches a
ten-dimensional parameter space for regions of high probability for a total of
one thousand different simulations before ending. The code investigates both
the "large world" as well as the "small world" of the parameter space. We apply
the K-means clustering algorithm to verify if the chains reveal a single or
multiple regions of significance. The outcome of the combined set of chains is
the weighted average and deviation of each of the ten parameters describing the
model. While the model reproduces reasonably well the detected distributions of
normal radio pulsars, it does not replicate the predicted detected
distribution of {\it Fermi} pulsars. The simulations do not produce sufficient
numbers of young, high- pulsars in the Galactic plane.Comment: 4 pages, 2 figures, The proceedings from the Pulsar Conference:
Electromagnetic Radiation from Pulsars and Magnetars will be published in the
Astronomical Society of the Pacific Conference Serie
Thermal tuning of organic dye lasers
Non-mechanical method for tuning liquid laser wavelengths involves electrically varying temperature of laser medium. Technique is used to investigate behavior of laser dyes, and may lead to broad, tunable, light source for spectroscopy measurements of long path absorption
Marriage For Some: Explaining The Variation In Gay Rights And Marriage Policy And Opinion Among States And Individuals
This research aims to answer a simple question: Why are some individuals, and some states, more willing to extend protections to same-sex couples than are others? Drawing from the literature, I perform a battery of quantitative tests on variables most commonly associated with gay rights and gay marriage policy development: liberalism, education, age, religiosity, authoritarianism, tolerance, urbanization, and moral traditionalism. While I find that all of these variables have a relationship with gay rights and gay marriage opinion, I argue that those associated with religiosity have the strongest pull. However, religiosity does not act alone; moral traditionalism, age, and ideology play particularly robust roles as well. In conclusion, I contend that the data show a strong likelihood for the continued liberalization of gay rights and gay marriage policy into the foreseeable future
Breeding of Cool-Season Forage Grasses for Abiotic and Biotic Stress Tolerance in the Southern United States
Abiotic stress tolerance and biotic stress resistance have long been targets for trait improvement in the field of plant breeding. To date, much of the target crop focus has been centered on commodity crops such as corn, soybean, wheat, and rice. However, little work has been conducted on improvement of these traits in forage grasses. This is due to a number of issues, particularly that most species are obligately outcrossing, the traits are governed by many genes at unknown loci, and are greatly affected by environmental variation. This creates major complications in successfully selecting and breeding populations of forage grasses tolerant to extreme high or low temperatures, as well as disease resistance. Recurrent phenotypic selection was used to select elite individuals of annual ryegrass (Lolium multiflorum Lam.) and orchardgrass (Dactylis glomerata L.) that expressed improved germination at high temperature. Selections were conducted within growth chambers at fixed temperature and light regimes (40/30 DEGREES C, 12/12 hr, light/darkness) to eliminate environmental variation. Following three cycles of selection, we observed gains (P LESSTHAN 0.001) in selection over the base population for both species. Annual ryegrass mean cumulative germination for cycle 3 peaked at 45.8%, and orchardgrass mean cumulative germination for cycle 3 peaked at 82.67%. Further selection of annual ryegrass for freezing tolerance was also conducted. Flats of unselected germplasm were grown to the three-leaf stage, then frozen for nine hours. Significant differences (P LESSTHAN 0.05) in freezing tolerance were observed between selected germplasm in both cycle 1 (0.076%) and cycle 2 (0.125%) over the unselected cycle 0 (0.025%). Finally, initial stages of resistance breeding work were conducted involving gray leaf spot (causal agent Pyricularia grisea Cke. [Sacc.]) on annual ryegrass. Isolates of the pathogen were obtained and stored for future use. It was determined that the actual pathogen species responsible was Pyricularia oryzae Cavara. Future work for annual ryegrass and orchardgrass germplasm that germinates at high temperatures will involve variety testing and cultivar release. Freezing tolerance and disease resistance work will require larger-scale screening methodology that was able to be conducted in this work to acquire sufficient population sizes for breeding
Relative Attractiveness of Sugar and Liver to Phormia regina Meigen
Behavior of insects in association with locating food, ovipositional sites, the opposite sex, as well as the discrimination of other insects, is accomplished through olfactory stimulations and other sense perceptions. Perception is an active organizing process involving conation, comparison, anticipation, and possibly purpose. If a piece of meat is placed in an accessable location, flies will, in a very short period of time, frequent it. If the same procedure is followed with sugar, more time is required before an equivalent number of flies is present. However, in both cases, extension of the mouth-part is observed; presumably for the purpose of feeding. Considering that no apparent restrictions upon the fly population are present, sense perceptions could stimulate behavior patterns to the piece of meat and sugar for such things as food value, ovipositional sites, or possibly the location of the opposite sex. The relative attractiveness of the meat and sugar as food could be ascertained with a known fly population; that is, of one species and an age group which would exclude sexually mature females
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