5,015 research outputs found
Maxometers (peak wind speed anemometers)
An instrument for measuring peak wind speeds under severe environmental conditions is described, comprising an elongated cylinder housed in an outer casing. The cylinder contains a piston attached to a longitudinally movable guided rod having a pressure disk mounted on one projecting end. Wind pressure against the pressure disk depresses the movable rod. When the wind reaches its maximum speed, the rod is locked by a ball clutch mechanism in the position of maximum inward movement. Thereafter maximum wind speed or pressure readings may be taken from calibrated indexing means
Arm cavity resonant sideband control for laser interferometric gravitational wave detectors
We present a new optical control scheme for a laser interferometric gravitational wave detector that has a high degree of tolerance to interferometer spatial distortions and noise on the input light. The scheme involves resonating the rf sidebands in an interferometer arm cavity
Model of Thermal Wavefront Distortion in Interferometric Gravitational-Wave Detectors I: Thermal Focusing
We develop a steady-state analytical and numerical model of the optical
response of power-recycled Fabry-Perot Michelson laser gravitational-wave
detectors to thermal focusing in optical substrates. We assume that the thermal
distortions are small enough that we can represent the unperturbed intracavity
field anywhere in the detector as a linear combination of basis functions
related to the eigenmodes of one of the Fabry-Perot arm cavities, and we take
great care to preserve numerically the nearly ideal longitudinal phase
resonance conditions that would otherwise be provided by an external
servo-locking control system. We have included the effects of nonlinear thermal
focusing due to power absorption in both the substrates and coatings of the
mirrors and beamsplitter, the effects of a finite mismatch between the
curvatures of the laser wavefront and the mirror surface, and the diffraction
by the mirror aperture at each instance of reflection and transmission. We
demonstrate a detailed numerical example of this model using the MATLAB program
Melody for the initial LIGO detector in the Hermite-Gauss basis, and compare
the resulting computations of intracavity fields in two special cases with
those of a fast Fourier transform field propagation model. Additional
systematic perturbations (e.g., mirror tilt, thermoelastic surface
deformations, and other optical imperfections) can be included easily by
incorporating the appropriate operators into the transfer matrices describing
reflection and transmission for the mirrors and beamsplitter.Comment: 24 pages, 22 figures. Submitted to JOSA
High expansion coefficient glasses can be sealed to common metals
New series of high expansion coefficient glasses can be sealed by fusion onto hot surfaces of metals and alloys. Glasses have relatively low working temperatures, good chemical durability, and can be used in electrical insulators and feedthroughs to fluid or vacuum systems
Coral community structure and recruitment in seagrass meadows
Coral communities are increasingly found to populate non-reef habitats prone to high environmental variability. Such sites include seagrass meadows, which are generally not considered optimal habitats for corals as a result of limited suitable substrate for settlement and substantial diel and seasonal fluctuations in physicochemical conditions relative to neighboring reefs. Interest in understanding the ability of corals to persist in non-reef habitats has grown, however little baseline data exists on community structure and recruitment of scleractinian corals in seagrass meadows. To determine how corals populate seagrass meadows, we surveyed the established and recruited coral community over 25 months within seagrass meadows at Little Cayman, Cayman Islands. Simultaneous surveys of established and recruited coral communities at neighboring back-reef sites were conducted for comparison. To fully understand the amount of environmental variability to which corals in each habitat were exposed, we conducted complementary surveys of physicochemical conditions in both seagrass meadows and back-reefs. Despite overall higher variability in physicochemical conditions, particularly pH, compared to the back-reef, 14 coral taxa were capable of inhabiting seagrass meadows, and multiple coral families were also found to recruit to these sites. However, coral cover and species diversity, richness, and evenness were lower at sites within seagrass meadows compared to back-reef sites. Although questions remain regarding the processes governing recruitment, these results provide evidence that seagrass beds can serve as functional habitats for corals despite high levels of environmental variability and suboptimal conditions compared to neighboring reefs
Study of arc-jet propulsion devices Final report, 20 Nov. 1964 - 19 Dec. 1965
Energy transfer mechanisms in radiation, water, and regeneratively cooled, and MPD arc jet propulsion device
Follow-up of bone lesions in an experimental multiple myeloma mouse model: description of an in vivo technique using radiography dedicated for mammography.
The evolution of bone lesions in transplantable C57BL/KaLwRjj 5T mouse myeloma (MM) has been followed in vivo. Mice were anaesthetised and a radiograph of the pelvis and hind legs was performed by a radiograph dedicated for mammography. This is the first description of an in vivo technique under experimental conditions whereby the development of bone lesions owing to the MM growth was demonstrated
Efficacy of Online Training for Improving Camp Staff Competency
Preparing competent staff is a critical issue within the camp community. This quasi-experimental study examined the effectiveness of an online course for improving staff competency in camp healthcare practices among college-aged camp staff and a comparison group (N = 55). We hypothesized that working in camp would increase competency test scores due to opportunities for staff to experientially apply knowledge learned online. Hierarchical linear modeling was used to analyse the cross-level effects of a between-individuals factor (assignment to experimental or comparison group) and within-individual effects of time (pre-test, post-test #1, and post-test #2) on online course test scores. At post-test #2, the difference in average test scores between groups was ~30 points, with the treatment group scoring lower on average than the comparison group. Factors that may have influenced these findings are explored, including fatigue and the limited durability of online learning. Recommendations for research and practice are discussed
The toxicity and intraspecific variability of Alexandrium andersonii Balech
The toxicity of Alexandrium andersonii Balech is unclear and its intraspecific variability has yet to be
studied. To address these gaps in our knowledge, in the present work five strains of A. andersonii from
four different localities were characterized. The results showed that despite genetic homogeneity in the
5.8-ITS (internal transcribed spacer) and large subunit (LSU) regions and similar growth rates, strains
originating from different locations varied with respect to cell size, the ratios of certain pigments, and
their growth patterns. Cultures of the strains grown at 20 8C were analyzed for toxicity using four
different methodologies. The two officially established methods, mouse bioassay and high-performance
liquid chromatography with fluorescence detection (HPLC-FLD) and post-column reaction analysis of
PSP toxins, failed to show the toxicity of any strain. Strains grown at 14 8C were also negative for PSP
toxins by HPLC-FLD. However, strains grown at 20 8C exhibited both a response characteristic of the
presence of toxin-inhibiting voltage-gated sodium channels, as demonstrated in a neuroblastoma neuro-
2a cell-based assay, as well as hemolytic activity in a sheep red blood cell assay
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