Scarring of Florida’s seagrasses: assessment and management options

Management programs that address scarring of seagrasses should be based on an approach that involves (1) education, (2) channel marking, (3) increased enforcement, and (4) limited-motoring zones. Aerial monitoring and photography of the managed area are essential in evaluating the effectiveness of a program. Management programs that use this multifaceted approach have been instituted by a few local governments and at several state parks. Initial results of the programs indicate that in some areas seagrass scarring has been reduced but that in other areas emphasis may need to be increased on one or more of the components of the four-point approach. A statewide management plan is needed to address the most egregious scarring over large areas that may be difficult to regulate at the local-government level

S-4B orbital workshop attitude control system study

Saturn S-4B orbital workshop attitude control system analysi

Bats of Kansas

In memory of Curtis J. Schmidt (1977-2022) Invariably, our most feared neighbors on planet earth are the animals that we know the least about. Almost as frequently, when people are exposed to these animals, the fear turns quickly to fascination. Unfortunately, many of these animals are accessible only to the professional scientist. Though science has made great strides in understanding the basic biology and behaviors of many of our least-known animals, this information is generally kept locked away from the general public by the dry, technical language of science. In this publication, it is our hope to open your eyes to the world of perhaps the last great, misunderstood group of animals-the bats. Further, it is our hope, by dispensing (as much as possible) with technical language, to bring across the intense fascination that we share for these animals and to infect you with that same fascination. In order to accomplish our task we have prepared the book in five sections. Because our main goal is to open your eyes to the fascinating world of bats, we have designed the first section to answer the most often asked questions about bats. The second provides a key to the bats of Kansas so that you can identify any bat you discover. In the third section we introduce you to the sixteen species that are known to occur in Kansas. As is the case for human neighbors, there may be bats in Kansas that we haven\u27t met yet. The fourth section describes these species of possible occurrence and tells you where to look for them. Unfortunately, we have only a limited amount of space, so the fifth section tells you how to find additional information

A facility for high resolution spectroscopy: Laboratory and ground based observations in support of upper atmospheric research

This research task consists of operating a facility for making spectroscopic observations in support of upper atmospheric research. The facility responds to the needs and interests of the visiting investigators. Therefore, the research objectives are not predetermined except in broad outline. The emphasis is on studies that take advantage of the particular strengths of the Fourier Transform Spectrometer on Kitt Peak: high spectral resolution combined with wide spectral range and low noise

Effect of Wavefunction Renormalisation in N-Flavour Qed3 at Finite Temperature

A recent study of dynamical chiral symmetry breaking in N-flavour QED$_3$ at finite temperature is extended to include the effect of fermion wavefunction renormalisation in the Schwinger-Dyson equations. The simple ``zero-frequency'' truncation previously used is found to lead to unphysical results, especially as $T \to 0$. A modified set of equations is proposed, whose solutions behave in a way which is qualitatively similar to the $T=0$ solutions of Pennington et al. [5-8] who have made extensive studies of the effect of wavefunction renormalisation in this context, and who concluded that there was no critical $N_c$ (at T=0) above which chiral symmetry was restored. In contrast, we find that our modified equations predict a critical $N_c$ at $T \not= 0$, and an $N-T$ phase diagram very similar to the earlier study neglecting wavefunction renormalisation. The reason for the difference is traced to the different infrared behaviour of the vacuum polarisation at $T=0$ and at $T \not= 0$.Comment: 17 pages + 13 figures (available upon request), Oxford preprint OUTP-93-30P, IFUNAM preprint FT94-39, LaTe

The Search for Intergalactic Hydrogen Clouds in Voids

I present the results of a search for intergalactic hydrogen clouds in voids. Clouds are detected by their HI LyA absorption lines in the HST spectra of low-redshift AGN. The parameter with which the environments of clouds are characterized is the tidal field, which places a lower limit on the cloud mass-density which is dynamically stable against disruption. Galaxy redshift catalogs are used to sum the tidal fields along the lines of sight, sorting clouds according to tidal field upper, or lower limits. The analytical methodology employed is designed to detect gas clouds whose expansion following reionization is restrained by dark matter perturbations. End-products are the cloud equivalent width distribution functions (EWDF) of catalogs formed by sorting clouds according to various tidal field upper, or lower limits. Cumulative EWDFs are steep in voids (S ~ -1.5 \pm 0.2), but flatter in high tidal field zones (S ~ -0.5 \pm 0.1). Most probable cloud Doppler parameters are ~30 km/s in voids and ~60 km/s in proximity to galaxies. In voids, the cumulative line density at low EW (~ 15 mA) is ~ 500 per unit redshift. The void filling factor is found to be 0.87 <= f_v <= 0.94. The void EWDF is remarkably uniform over this volume, with a possible tendency for more massive clouds to be in void centers. The size and nature of the void cloud population suggested by this study is completely unanticipated by the results of published 3-D simulations, which predict that most clouds are in filamentary structures around galaxy concentrations, and that very few observable absorbers would lie in voids. Strategies for modeling this population are briefly discussed.Comment: 21 pages, 19 figures, apjemulate style, to appear in ApJ vol. 57

A high-resolution gamma-ray and hard X-ray spectrometer for solar flare observations in Max 1991

A long duration balloon flight instrument for Max 1991 designed to study the acceleration of greater than 10 MeV ions and greater than 15 keV electrons in solar flares through high resolution spectroscopy of the gamma ray lines and hard X-ray and gamma ray continuum is described. The instrument, HIREGS, consists of an array of high-purity, n-type coaxial germanium detectors (HPGe) cooled to less than 90 K and surrounded by a bismuth germanate (BGO) anticoincidence shield. It will cover the energy range 15 keV to 20 MeV with keV spectral resolution, sufficient for accurate measurement of all parameters of the expected gamma ray lines with the exception of the neutron capture deuterium line. Electrical segmentation of the HPGe detector into a thin front segment and a thick rear segment, together with pulse-shape discrimination, provides optimal dynamic range and signal-to-background characteristics for flare measurements. Neutrons and gamma rays up to approximately 0.1 to 1 GeV can be detected and identified with the combination of the HPGe detectors and rear BGO shield. The HIREGS is planned for long duration balloon flights (LDBF) for solar flare studies during Max 1991. The two exploratory LDBFs carried out at mid-latitudes in 1987 to 1988 are described, and the LDBFs in Antarctica, which could in principle provide 24 hour/day solar coverage and very long flight durations (20 to 30 days) because of minimal ballast requirements are discussed

Absolute Frequency Measurements of the Hg^+ and Ca Optical Clock Transitions with a Femtosecond Laser

The frequency comb created by a femtosecond mode-locked laser and a microstructured fiber is used to phase coherently measure the frequencies of both the Hg^+ and Ca optical standards with respect to the SI second as realized at NIST. We find the transition frequencies to be f_Hg=1 064 721 609 899 143(10) Hz and f_Ca=455 986 240 494 158(26) Hz, respectively. In addition to the unprecedented precision demonstrated here, this work is the precursor to all-optical atomic clocks based on the Hg^+ and Ca standards. Furthermore, when combined with previous measurements, we find no time variations of these atomic frequencies within the uncertainties of |(df_Ca/dt)/f_Ca| < 8 x 10^{-14} yr^{-1}, and |(df_Hg/dt)/f_Hg|< 30 x 10^{-14} yr^{-1}.Comment: 6 pages, including 4 figures. RevTex 4. Submitted to Phys. Rev. Let

Direct Observation of Hyperfine Quenching of the (2)3p0 Level in Helium-Like Nickel

Journals published by the American Physical Society can be found at http://publish.aps.org/We report a clear demonstration of the effect of hyperfine quenching of a forbidden transition by direct comparison of the lifetimes of the 2 3P0 level in the heliumlike isotopes Ni-61(26+) and Ni-58(26+). We find the quenched lifetime of the 2 3P0 level in Ni-61(26+) to be 470(50) ps. From this we deduce the 2 3P0-2 3P1 energy splitting to be 2.33(15) eV. We also report a measurement of the lifetime of the 2 3P2 level in Ni-58(26+), which is found to be 70(3) ps

Quenched Narrow-Line Laser Cooling of 40Ca to Near the Photon Recoil Limit

We present a cooling method that should be generally applicable to atoms with narrow optical transitions. This technique uses velocity-selective pulses to drive atoms towards a zero-velocity dark state and then quenches the excited state to increase the cooling rate. We demonstrate this technique of quenched narrow-line cooling by reducing the 1-D temperature of a sample of neutral 40Ca atoms. We velocity select and cool with the 1S0(4s2) to 3P1(4s4p) 657 nm intercombination line and quench with the 3P1(4s4p) to 1S0(4s5s) intercombination line at 553 nm, which increases the cooling rate eight-fold. Limited only by available quenching laser power, we have transferred 18 % of the atoms from our initial 2 mK velocity distribution and achieved temperatures as low as 4 microK, corresponding to a vrms of 2.8 cm/s or 2 recoils at 657 nm. This cooling technique, which is closely related to Raman cooling, can be extended to three dimensions.Comment: 5 pages, 4 figures; Submitted to PRA Rapid Communication