1,214 research outputs found
The application of active controls technology to a generic hypersonic aircraft configuration
Analytical methods are described for the prediction of aerothermoelastic stability of hypersonic aircraft including active control systems. Thermal loads due to aerodynamic heating were applied to the finite element model of the aircraft structure and the thermal effects on flutter were determined. An iterative static aeroelastic trim analysis procedure was developed including thermal effects. And active control technology was assessed for flutter suppression, ride quality improvement, and gust load alleviation to overcome any potential adverse aeroelastic stability or response problems due to aerodynamic heating. A generic hypersonic aircraft configuration was selected which incorporates wing flaps, ailerons, and all moveable fins to be used for active control purposes. The active control system would use onboard sensors in a feedback loop through the aircraft flight control computers to move the surfaces for improved structural dynamic response as the aircraft encounters atmospheric turbulence
Atmospheric bromoform at Mace Head, Ireland: Evidence for a peatland source
International audienceIn situ atmospheric observations of bromoform (CHBr3) made over a 2.5 year period at Mace Head, Ireland from May 2001?December 2003, including during the NAMBLEX (North Atlantic Marine Boundary Layer Experiment) campaign, show broad maxima from spring until autumn and winter minima, with mixing ratios of 5.3+1.0 pptv (mid March?mid October) and 1.8+0.8 pptv (December?February). This indicates that, unlike CHCl3, which has a summer minimum and winter maximum at Mace Head, local biological sources of CHBr3 have a greater influence on the atmospheric data than photochemical decay during long-range transport. The emission sources are predominantly macroalgal, but we find evidence for a small terrestrial flux from peatland ecosystems, which so far has not been accounted for in the CHBr3 budget. Sharp increases in CHCl3 and CHBr3 concentrations and decreases in O3 concentrations occurred at night when the wind direction switched from an ocean- to a land-based sector (land breeze) and the wind speed dropped to below 5 ms?1. These observations infer a shallow atmospheric boundary layer with increased O3 deposition and concentration of local emissions of both CHCl3 and CHBr3. The ratio of ?CHCl3/?CHBr3 varied strongly according to the prevailing wind direction; from 0.6+0.1 in south-easterly (100?170°) air to 1.9+0.8 in north-easterly (40?70°) air. Of these land-sectors, the south-easterly air masses are likely to be strongly influenced by macroalgal beds along the coast and the emission ratios probably reflect those from seaweeds in addition to land sources. The north-easterly airmasses however have a fetch predominantly over land, which locally is comprised of coastal peatland ecosystems (peat bogs and coastal conifer plantations), previously identified as being strong sources of atmospheric CHCl3 under these conditions. Although we cannot entirely rule out other local land or coastal sources, our observations also suggest peatland ecosystem emissions of CHBr3. We use correlations between CHCl3 and CHBr3 during the land breeze events in conjunction with previous estimates of local wetland CHCl3 release to tentatively deduce a global wetland CHBr3 source of 26.9 (0.5?1247) Gg yr?1, which is approximately 10% of the total global source
Atmospheric bromoform at Mace Head, Ireland: seasonality and evidence for a peatland source
In situ atmospheric observations of bromoform (CHBr<sub>3</sub>) made over a 2.5 year period at Mace Head, Ireland from May 2001- Dec 2003, including during the NAMBLEX (North Atlantic Marine Boundary Layer Experiment) campaign, show broad maxima from spring until autumn and winter minima, with mixing ratios of 5.3+1.0 pptv (mid March - mid October) and 1.8+0.8 pptv (December-February). This indicates that, unlike CHCl<sub>3</sub>, which has a summer minimum and winter maximum at Mace Head, local biological sources of CHBr<sub>3</sub> have a greater influence on the atmospheric data than photochemical decay during long-range transport. The emission sources are predominantly macroalgal, but we find evidence for a small terrestrial flux from peatland ecosystems, which so far has not been accounted for in the CHBr<sub>3</sub> budget. Sharp increases in CHCl<sub>3</sub> and CHBr<sub>3</sub> concentrations and decreases in O<sub>3</sub> concentrations occurred at night when the wind direction switched from an ocean- to a land-based sector (land breeze) and the wind speed dropped to below 5 ms<sup>-1</sup>. These observations infer a shallow atmospheric boundary layer with increased O<sub>3</sub> deposition and concentration of local emissions of both CHCl<sub>3</sub> and CHBr<sub>3</sub>. The ratio of ΔCHCl<sub>3</sub>/ΔCHBr<sub>3</sub> varied strongly according to the prevailing wind direction; from 0.60+0.15 in south-easterly (100-170° and northerly (340-20°) air to 2.5+0.4 in north-easterly (40-70°) air. Of these land-sectors, the south-easterly air masses are likely to be strongly influenced by macroalgal beds along the coast and the emission ratios probably reflect those from seaweeds in addition to land sources. The north-easterly airmasses however had an immediate fetch inland, which locally is comprised of coastal peatland ecosystems (peat bogs and coastal conifer plantations), previously identified as being strong sources of atmospheric CHCl<sub>3</sub> under these conditions. Although we cannot entirely rule out other local land or coastal sources, our observations also suggest peatland ecosystem emissions of CHBr<sub>3</sub>. We use correlations between CHCl<sub>3</sub> and CHBr<sub>3</sub> during the north-easterly land breeze events in conjunction with previous estimates of local wetland CHCl<sub>3</sub> release to tentatively deduce a global wetland CHBr<sub>3</sub> source of 20.4(0.4-948) Gg yr<sup>-1</sup>, which is approximately 7% of the total global source
Polyvalent diazonium polymers provide efficient protection of oncolytic adenovirus Enadenotucirev from neutralising antibodies while maintaining biological activity in vitro and in vivo
Oncolytic viruses offer many advantages for cancer therapy when administered directly to confined solid tumors. However, the systemic delivery of these viruses is problematic due to host immune response, undesired interactions with blood components and inherent targeting to the liver. Efficacy of systemically administered viruses has been improved by masking viral surface proteins with polymeric materials, through modulation of viral pharmacokinetic profile and accumulation in tumors in vivo. Here we describe a new class of polyvalent reactive based upon poly(N-(2-hydroxypropyl)methacrylamide) (polyHPMA) with diazonium reactive groups and their application in the modification of the chimeric oncolytic virus Enadenotucirev (EnAd). A series of six reactive copolymers with different chain lengths and density of reactive groups was synthesised and used to coat EnAd. Polymer coating was found to be extremely efficient with concentrations as low as 1 mg/mL resulting in complete (>99%) ablation of neutralising antibody binding. Coating efficiency was found to be dependent on both chain length and reactive group density. Coated viruses were found to have reduced transfection activity both in vitro and in vivo with greater protection against neutralising antibodies resulting in lower transgene production. However, in the presence of neutralising antibodies some in vivo transgene expression was maintained for coated virus compared to the uncoated control. Reduction in transgene expression was found to not be solely due to reduced cellular uptake but due to reducing unpackaging of the virus within the cells and reducing replication indicating that polymer coating does not cause permanent inactivation of the virus. These data suggest that virus activity may be modulated by appropriate design of coating polymers while retaining protection against neutralising antibodies
Compressibility of and (M = Rh, Ir and Co) Compounds
The lattice parameters of the tetragonal compounds CeIn and
CeIn(Rh, Ir and Co) have been studied as a function of
pressure up to 15 GPa using a diamond anvil cell under both hydrostatic and
quasihydrostatic conditions at room temperature. The addition of In
layers to the parent CeIn compound is found to stiffen the lattice as the
2-layer systems (average of bulk modulus values is 70.4 GPa) have a
larger than CeIn (67 GPa), while the 1-layer systems with the are
even stiffer (average of is 81.4 GPa). Estimating the hybridization
using parameters from tight binding calculations shows that the dominant
hybridization is in nature between the Ce and In atoms. The values of
at the pressure where the superconducting transition temperature
reaches a maximum is the same for all CeIn compounds. By
plotting the maximum values of the superconducting transition temperature
versus for the studied compounds and Pu-based superconductors, we
find a universal versus behavior when these quantities are
normalized appropriately. These results are consistent with magnetically
mediated superconductivity.Comment: Updated version resubmitted to Phys. Rev.
Photoelectric Emission from Interstellar Dust: Grain Charging and Gas Heating
We model the photoelectric emission from and charging of interstellar dust
and obtain photoelectric gas heating efficiencies as a function of grain size
and the relevant ambient conditions. Using realistic grain size distributions,
we evaluate the net gas heating rate for various interstellar environments, and
find less heating for dense regions characterized by R_V=5.5 than for diffuse
regions with R_V=3.1. We provide fitting functions which reproduce our
numerical results for photoelectric heating and recombination cooling for a
wide range of interstellar conditions. In a separate paper we will examine the
implications of these results for the thermal structure of the interstellar
medium. Finally, we investigate the potential importance of photoelectric
heating in H II regions, including the warm ionized medium. We find that
photoelectric heating could be comparable to or exceed heating due to
photoionization of H for high ratios of the radiation intensity to the gas
density. We also find that photoelectric heating by dust can account for the
observed variation of temperature with distance from the galactic midplane in
the warm ionized medium.Comment: 50 pages, including 18 figures; corrected title and abstract field
New apparatus for DTA at 2000 bar: thermodynamic studies on Au, Ag, Al and HTSC oxides
A new DTA (Differential Thermal Analysis) device was designed and installed
in a Hot Isostatic Pressure (HIP) furnace in order to perform high-pressure
thermodynamic investigations up to 2 kbar and 1200C. Thermal analysis can be
carried out in inert or oxidising atmosphere up to p(O2) = 400 bar. The
calibration of the DTA apparatus under pressure was successfully performed
using the melting temperature (Tm) of pure metals (Au, Ag and Al) as standard
calibration references. The thermal properties of these metals have been
studied under pressure. The values of DV (volume variation between liquid and
solid at Tm), ROsm (density of the solid at Tm) and ALPHAm (linear thermal
expansion coefficient at Tm) have been extracted. A very good agreement was
found with the existing literature and new data were added. This HP-DTA
apparatus is very useful for studying the thermodynamics of those systems where
one or more volatile elements are present, such as high TC superconducting
oxides. DTA measurements have been performed on Bi,Pb(2223) tapes up to 2 kbar
under reduced oxygen partial pressure (p(O2) = 0.07 bar). The reaction leading
to the formation of the 2223 phase was found to occur at higher temperatures
when applying pressure: the reaction DTA peak shifted by 49C at 2 kbar compared
to the reaction at 1 bar. This temperature shift is due to the higher stability
of the Pb-rich precursor phases under pressure, as the high isostatic pressure
prevents Pb from evaporating.Comment: 6 figures, 3 tables, Thermodynamics, Thermal property, Bi-2223,
fundamental valu
Magnetic Field and Pressure Phase Diagrams of Uranium Heavy-Fermion Compound UZn
We have performed magnetization measurements at high magnetic fields of up to
53 T on single crystals of a uranium heavy-fermion compound UZn
grown by the Bridgman method. In the antiferromagnetic state below the N\'{e}el
temperature = 9.7 K, a metamagnetic transition is found at
32 T for the field along the [110] direction (-axis). The
magnetic phase diagram for the field along the [110] direction is
given. The magnetization curve shows a nonlinear increase at 35
T in the paramagnetic state above up to a characteristic
temperature where the magnetic susceptibility or
electrical resistivity shows a maximum value. This metamagnetic behavior of the
magnetization at is discussed in comparison with the metamagnetic
magnetism of the heavy-fermion superconductors UPt, URuSi, and
UPdAl. We have also carried out high-pressure resistivity measurement
on UZn using a diamond anvil cell up to 8.7 GPa. Noble gas argon was
used as a pressure-transmitting medium to ensure a good hydrostatic
environment. The N\'{e}el temperature is almost
pressure-independent up to 4.7 GPa and starts to increase in the
higher-pressure region. The pressure dependences of the coefficient of the
term in the electrical resistivity , the antiferromagnetic gap
, and the characteristic temperature are
discussed. It is found that the effect of pressure on the electronic states in
UZn is weak compared with those in the other heavy fermion
compounds
Greenhouse gas measurements from a UK network of tall towers: technical description and first results
A network of three tall tower measurement stations was set up in 2012 across the United Kingdom to expand measurements made at the long-term background northern hemispheric site, Mace Head, Ireland. Reliable and precise in situ greenhouse gas (GHG) analysis systems were developed and deployed at three sites in the UK with automated instrumentation measuring a suite of GHGs. The UK Deriving Emissions linked to Climate Change (UK DECC) network uses tall (165–230 m) open-lattice telecommunications towers, which provide a convenient platform for boundary layer trace gas sampling. In this paper we describe the automated measurement system and first results from the UK DECC network for CO2, CH4, N2O, SF6, CO and H2. CO2 and CH4 are measured at all of the UK DECC sites by cavity ring-down spectroscopy (CRDS) with multiple inlet heights at two of the three tall tower sites to assess for boundary layer stratification. The short-term precisions (1σ on 1 min means) of CRDS measurements at background mole fractions for January 2012 to September 2015 is < 0.05 µmol mol−1 for CO2 and < 0.3 nmol mol−1 for CH4. Repeatability of standard injections (1σ) is < 0.03 µmol mol−1 for CO2 and < 0.3 nmol mol−1 for CH4 for the same time period. N2O and SF6 are measured at three of the sites, and CO and H2 measurements are made at two of the sites, from a single inlet height using gas chromatography (GC) with an electron capture detector (ECD), flame ionisation detector (FID) or reduction gas analyser (RGA). Repeatability of individual injections (1σ) on GC and RGA instruments between January 2012 and September 2015 for CH4, N2O, SF6, CO and H2 measurements were < 2.8 nmol mol−1, < 0.4 nmol mol−1, < 0.07 pmol mol−1, < 2 nmol mol−1 and < 3 nmol mol−1, respectively. Instrumentation in the network is fully automated and includes sensors for measuring a variety of instrumental parameters such as flow, pressures, and sampling temperatures. Automated alerts are generated and emailed to site operators when instrumental parameters are not within defined set ranges. Automated instrument shutdowns occur for critical errors such as carrier gas flow rate deviations. Results from the network give good spatial and temporal coverage of atmospheric mixing ratios within the UK since early 2012. Results also show that all measured GHGs are increasing in mole fraction over the selected reporting period and, except for SF6, exhibit a seasonal trend. CO2 and CH4 also show strong diurnal cycles, with night-time maxima and daytime minima in mole fractions
Using honey to heal diabetic foot ulcers
Diabetic ulcers seem to be arrested in the inflammatory/proliferative stage of the healing process, allowing infection and inflammation to preclude healing. Antibiotic-resistant bacteria have become a major cause of infections, including diabetic foot infections. It is proposed here that the modern developments of an ancient and traditional treatment for wounds, dressing them with honey, provide the solution to the problem of getting diabetic ulcers to move on from the arrested state of healing. Honeys selected to have a high level of antibacterial activity have been shown to be very effective against antibiotic-resistant strains of bacteria in laboratory and clinical studies. The potent anti-inflammatory action of honey is also likely to play an important part in overcoming the impediment to healing that inflammation causes in diabetic ulcers, as is the antioxidant activity of honey. The action of honey in promotion of tissue regeneration through stimulation of angiogenesis and the growth of fibroblasts and epithelial cells, and its insulin-mimetic effect, would also be of benefit in stimulating the healing of diabetic ulcers. The availability of honey-impregnated dressings which conveniently hold honey in place on ulcers has provided a means of rapidly debriding ulcers and removing the bacterial burden so that good healing rates can be achieved with neuropathic ulcers. With ischemic ulcers, where healing cannot occur because of lack of tissue viability, these honey dressings keep the ulcers clean and prevent infection occurring
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