6,456 research outputs found
FREE-FLIGHT MEASUREMENTS OF STATIC AND DYNAMIC STABILITY OF MODELS OF THE PROJECT MERCURY RE-ENTRY CAPSULE AT MACH NUMBERS 3 AND 9.5
Static & dynamic stability of mercury reentry capsule scale models at mach 3 & 9.
Sea surface and remotely sensed temperatures off Cape Mendocino, California
During September 3 to 5, 1979, a multisensor oceanographic experiment was conducted off Cape Mendocino, California. The purpose of this experiment was to validate the use of remote sensing techniques over an area along the U.S. west coast where coasted upwelling is known to be intense. Remotely sensed mutlispectral data, including thermal infrared imagery, were collected above an upwelling feature off Cape Mendocino. Data were acquired from the TIRNOS-N and NOAA-6 polar orbiting satellites, the NASA Ames Research Center's high altitude U-2 aircraft, and a U.S. Coast Guard C-130 aircraft. Supporting surface truth data over the same feature were collected aboard the National Oceanic and Atmospheric Administration (NOAA) ship, OCEANOGRAPHER. Atmospheric soundings were also taken aboard the ship. The results indicate that shipboard measurements of sea surface temperatures can be reproduction within 1 C or better through remote observation of absolute infrared radiance values (whether measured aboard the NOAA polar orbiting satellite, the U-2 aircraft, or the Coast Guard aircraft) by using appropriate atmospheric corrections. Also, the patterns of sea surface temperature which were derived independently from the various remote platforms provide a consistent interpretation of the surface temperature field
Achieving spatially precise diagnosis and therapy in the mammalian gut using synthetic microbial gene circuits
The mammalian gut and its microbiome form a temporally dynamic and spatially heterogeneous environment. The inaccessibility of the gut and the spatially restricted nature of many gut diseases translate into difficulties in diagnosis and therapy for which novel tools are needed. Engineered bacterial whole-cell biosensors and therapeutics have shown early promise at addressing these challenges. Natural and engineered sensing systems can be repurposed in synthetic genetic circuits to detect spatially specific biomarkers during health and disease. Heat, light, and magnetic signals can also activate gene circuit function with externally directed spatial precision. The resulting engineered bacteria can report on conditions in situ within the complex gut environment or produce biotherapeutics that specifically target host or microbiome activity. Here, we review the current approaches to engineering spatial precision for in vivo bacterial diagnostics and therapeutics using synthetic circuits, and the challenges and opportunities this technology presents
Spectral Type and Radial Velocity Variations in Three SRC Variables
SRC variables are M supergiants, precursors to Type II supernovae, that vary
in brightness with moderately regular periods of order 100-1000 days. Although
identified as pulsating stars that obey their own period-luminosity relation,
few have been examined in enough detail to follow the temperature and spectral
changes that they undergo during their long cycles. The present study examines
such changes for several SRC variables revealed by CCD spectra obtained at the
Dominion Astrophysical Observatory (DAO) during 2005-2009, as well as by
archival spectra from the DAO (and elsewhere) for some stars from the 1960s to
1980s, and Cambridge radial velocity spectrometer measures for Betelgeuse.
Described here is our classification procedure and information on the spectral
type and radial velocity changes in three of the stars. The results provide
insights into the pulsation mechanism in M supergiants.Comment: To appear in the Odessa Variable Stars 2010 conference proceedings
(see http://uavso.org.ua/?page=vs2010), edited by I. Andronov and V. Kovtyuk
Towards the production of radiotherapy treatment shells on 3D printers using data derived from DICOM CT and MRI: preclinical feasibility studies
Background: Immobilisation for patients undergoing brain or head and neck radiotherapy is achieved using perspex or thermoplastic devices that require direct moulding to patient anatomy. The mould room visit can be distressing for patients and the shells do not always fit perfectly. In addition the mould room process can be time consuming. With recent developments in three-dimensional (3D) printing technologies comes the potential to generate a treatment shell directly from a computer model of a patient. Typically, a patient requiring radiotherapy treatment will have had a computed tomography (CT) scan and if a computer model of a shell could be obtained directly from the CT data it would reduce patient distress, reduce visits, obtain a close fitting shell and possibly enable the patient to start their radiotherapy treatment more quickly. Purpose: This paper focuses on the first stage of generating the front part of the shell and investigates the dosimetric properties of the materials to show the feasibility of 3D printer materials for the production of a radiotherapy treatment shell. Materials and methods: Computer algorithms are used to segment the surface of the patientās head from CT and MRI datasets. After segmentation approaches are used to construct a 3D model suitable for printing on a 3D printer. To ensure that 3D printing is feasible the properties of a set of 3D printing materials are tested. Conclusions: The majority of the possible candidate 3D printing materials tested result in very similar attenuation of a therapeutic radiotherapy beam as the Orfit soft-drape masks currently in use in many UK radiotherapy centres. The costs involved in 3D printing are reducing and the applications to medicine are becoming more widely adopted. In this paper we show that 3D printing of bespoke radiotherapy masks is feasible and warrants further investigation
Superconductivity and Cobalt Oxidation State in Metastable Na(x)CoO(2-delta)*yH2O (x ~ 1/3; y ~ 4x)
We report the synthesis and superconducting properties of a metastable form
of the known superconductor NaxCoO2*yH2O (x ~ 1/3, y ~ 4x). Instead of using
the conventional bromine-acetonitrile mixture for sodium deintercalation, we
use an aqueous bromine solution. Using this method, we oxidize the sample to a
point that the sodium cobaltate becomes unstable, leading to formation of other
products if not controlled. This compound has the same structure as the
reported superconductor, yet it exhibits a systematic variation of the
superconducting transition temperature (Tc) as a function of time. Immediately
after synthesis, this compound is not a superconductor, even though it contains
appropriate amounts of sodium and water. The samples become superconducting
with low Tc values after ~ 90 h. Tc continually increases until it reaches a
maximum value (4.5 K) after about 260 h. Then Tc drops drastically, becoming
non-superconducting approximately 100 h later. Corresponding time-dependent
neutron powder diffraction data shows that the changes in superconductivity
exhibited by the metastable cobaltate correspond to slow formation of oxygen
vacancies in the CoO2 layers. In effect, the formation of these defects
continually reduces the cobalt oxidation state causing the sample to evolve
through its superconducting life cycle. Thus, the dome-shaped superconducting
phase diagram is mapped as a function of cobalt oxidation state using a single
sample. The width of this dome based on the formal oxidation state of cobalt is
very narrow - approximately 0.1 valence units wide. Interestingly, the maximum
Tc in NaxCoO2*yH2O occurs when the cobalt oxidation state is near 3.5. Thus, we
speculate that the maximum Tc occurs near the charge ordered insulating state
that correlates with the average cobalt oxidation state of 3.5.Comment: 22 pages, 9 figures, 1 tabl
On the validation of rainfall retrieval algorithms for satellite microwave data
The Algorithm Intercomparison Project utilises rainfall estimates derived from radar data to validate the algorithms developed for rainfall retrievals from satellite microwave data. Since seven minutes are needed in order to have a complete radar scan, while the acquisition of the corresponding satellite microwave image needs only a few seconds, the same pixel can be sensed by radar as much as
seven minutes later. Within this time delay the raining cells can be displaced and the consequent mismatch can cause a decrease in the correlation coefficient of the
comparison. A method to reveal this time-lag effect is presented and a possible approach to take it into account in the validation process for future missions is suggested
On the validation of rainfall retrieval algorithms for satellite microwave data
The Algorithm Intercomparison Project utilises rainfall estimates derived from radar data to validate the algorithms developed for rainfall retrievals from satellite microwave data. Since seven minutes are needed in order to have a complete radar scan, while the acquisition of the corresponding satellite microwave image needs only a few seconds, the same pixel can be sensed by radar as much as
seven minutes later. Within this time delay the raining cells can be displaced and the consequent mismatch can cause a decrease in the correlation coefficient of the
comparison. A method to reveal this time-lag effect is presented and a possible approach to take it into account in the validation process for future missions is suggested
A generalized quantum microcanonical ensemble
We discuss a generalized quantum microcanonical ensemble. It describes
isolated systems that are not necessarily in an eigenstate of the Hamilton
operator. Statistical averages are obtained by a combination of a time average
and a maximum entropy argument to resolve the lack of knowledge about initial
conditions. As a result, statistical averages of linear observables coincide
with values obtained in the canonical ensemble. Non-canonical averages can be
obtained by taking into account conserved quantities which are non-linear
functions of the microstate.Comment: improved version, new titl
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