16 research outputs found
Positron lifetime measurements in chiral nematic liquid crystals
Positron lifetimes in the isotropic phases of chiral nematic liquid crystal formulations and their mixtures up to the racemic level were measured. The lifetime spectra for all liquid crystal systems were analyzed into three components. Although the individual spectra in the left- and right-handed components are identical, their racemic mixtures exhibit much larger orthopositronium lifetimes; these larger lifetimes indicate the presence of larger microvoids. This result is consistent with the reportedly higher thermodynamic stability and color play range in the racemic mixtures of chiral nematic liquid crystals
Pressure sensor using liquid crystals
A pressure sensor includes a liquid crystal positioned between transparent, electrically conductive films (18 and 20), that are biased by a voltage (V) which induces an electric field (E) that causes the liquid crystal to assume a first state of orientation. Application of pressure (P) to a flexible, transparent film (24) causes the conductive film (20) to move closer to or farther from the conductive film (18), thereby causing a change in the electric field (E'(P)) which causes the liquid crystal to assume a second state of orientation. Polarized light (P.sub.1) is directed into the liquid crystal and transmitted or reflected to an analyzer (A or 30). Changes in the state of orientation of the liquid crystal induced by applied pressure (P) result in a different light intensity being detected at the analyzer (A or 30) as a function of the applied pressure (P). In particular embodiments, the liquid crystal is present as droplets (10) in a polymer matrix (12) or in cells (14) in a polymeric or dielectric grid (16) material in the form of a layer (13) between the electrically conductive films (18 and 20). The liquid crystal fills the open wells in the polymer matrix (12) or grid (16) only partially
Istra啪ivanja 3,4-diaril-1,2,5-oksadiazola i njihovih N-oksida: Potraga za boljim COX-2 inhibitorima
A series of 3,4-diaryl-1,2,5-oxadiazoles and 3,4-diaryl-1,2,5-oxadiazole N-oxides were prepared and evaluated for COX-2 and COX-1 binding affinity in vitro and for anti-inflammatory activity by the rat paw edema method. p-Methoxy (p-OMe) substituted compounds 9, 21, 34, 41, 42 showed COX-2 enzyme inhibition higher than that showed by compounds with other substituents. 3,4-Di(4-methoxyphenyl)-1,2,5-oxadiazole N-oxide (42) showed COX-2 enzyme inhibition of 54% at 22 碌mol L-1 and COX-1 enzyme inhibition of 44% at 88 碌mol L-1 concentrations, but showed very low in vivo anti-inflammatory activity. Its deoxygenated derivative (21) showed lower COX-2 enzyme inhibition (26% at 22 碌mol L-1) and higher COX-1 enzyme inhibition (53% at 88 碌mol L-1) but marked in vivo anti-inflammatory activity (71% at 25 mg kg-1) vs. celecoxib (48% at 12.5 mg kg-1). Molecular modeling (docking) studies showed that the methoxy group is positioned in the vicinity of the COX-2 secondary pocket and it also participates in hydrogen bonding interactions in the COX-2 active site. These preliminary studies suggest that the p-methoxy (p-OMe) group in one of benzene rings may give potentially active leads in this series of oxadiazole/N-oxides.Sintetizirana je serija 3,4-diaril-1,2,5-oksadiazola i 3,4-diaril-1,2,5-oksadiazol N-oksida i ocijenjena njihova sposobnost vezivanja na COX-2 i COX-1 in vitro i protuupalno djelovanje na edem 拧ape 拧takora. Spojevi sa p-metoksi (p-OMe) supstituentom 9, 21, 34, 41, 42 bolje su inhibirali COX-2 nego ostali spojevi. 3,4-Di(4-metoksifenil)-1,2,5-oksadiazol N-oksid (42) inhibirao je COX-2 za 54% u koncentraciji od 22 碌mol L-1, a COX-1 za 44% u koncentraciji 88 碌mol L-1, ali je in vivo slabo djelovao protuupalno. Njegov deoksigenirani derivat 21 pokazao je slabiju inhibiciju COX-2 enzima (26% u koncentraciji 22 碌mol L-1) i ja膷u inhibiciju COX-1 (71% u koncentraciji 25 mg kg-1) 拧to je bolje od standarda celekoksiba (48% u koncentraciji 12,5 mg kg-1). Molekularno je modeliranje pokazalo da je metoksi skupina smje拧tena u blizini sekundarnog d啪epa na enzimu COX-2 i da utje膷e na vodikove veze interakcija na aktivnom mjestu COX-2. Ova preliminarna istra啪ivanja sugeriraju da bi se u seriji oksadiazol/N-oksida mogao na膰i predvodni spoj s p-metoksi skupinom na benzenskom prstenu
Aerothermal Instrumentation Loads To Implement Aeroassist Technology in Future Robotic and Human Missions to MARS and Other Locations Within the Solar System
The strategy of NASA to explore space objects in the vicinity of Earth and other planets of the solar system includes robotic and human missions. This strategy requires a road map for technology development that will support the robotic exploration and provide safety for the humans traveling to other celestial bodies. Aeroassist is one of the key elements of technology planning for the success of future robot and human exploration missions to other celestial bodies. Measurement of aerothermodynamic parameters such as temperature, pressure, and acceleration is of prime importance for aeroassist technology implementation and for the safety and affordability of the mission. Instrumentation and methods to measure such parameters have been reviewed in this report in view of past practices, current commercial availability of instrumentation technology, and the prospects of improvement and upgrade according to the requirements. Analysis of the usability of each identified instruments in terms of cost for efficient weight-volume ratio, power requirement, accuracy, sample rates, and other appropriate metrics such as harsh environment survivability has been reported
Aerothermal Instrumentation Loads To
The strategy of NASA to explore space objects in the vicinity of Earth and other planets of the solar system includes robotic and human missions
Surface-Pressure and Flow-Visualization Data at Mach Number of 1.60 for Three 65 deg Delta Wings Varying in Leading-Edge Radius and Camber
An experimental investigation of the effect of leading-edge radius, camber, Reynolds number, and boundary-layer state on the incipient separation of a delta wing at supersonic speeds was conducted at the Langley Unitary Plan Wind Tunnel at Mach number of 1.60 over a free-stream Reynolds number range of 1 x 106 to 5 x 106 ft-1. The three delta wing models examined had a 65 deg swept leading edge and varied in cross-sectional shape: a sharp wedge, a 20:1 ellipse, and a 20:1 ellipse with a -9.750 circular camber imposed across the span. The wings were tested with and without transition grit applied. Surface-pressure coefficient data and flow-visualization data are electronically stored on the CD-ROM. The data indicated that by rounding the wing leading edge or cambering the wing in the spanwise direction, the onset of leading-edge separation on a delta wing can be raised to a higher angle of attack than that observed on a sharp-edged delta wing. The data also showed that the onset of leading-edge separation can be raised to a higher angle of attack by forcing boundary-layer transition to occur closer to the wing leading edge by the application of grit or the increase in free-stream Reynolds number
Wings Varying in Leading-Edge Radius and
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