Microwave Spectroscophy

Contains reports on four research projects.U. S. Army Signal Corps under Contract DA36-039-sc-87376Lincoln Laboratory, Purchase Order DDL B-00337U. S. ArmyU. S. NavyU. S. Air Force under Air Force Contract AF19(604)-740

PETIs as High-Temperature Resin-Transfer-Molding Materials

Compositions of, and processes for fabricating, high-temperature composite materials from phenylethynyl-terminated imide (PETI) oligomers by resin-transfer molding (RTM) and resin infusion have been developed. Composites having a combination of excellent mechanical properties and long-term high-temperature stability have been readily fabricated. These materials are particularly useful for the fabrication of high-temperature structures for jet-engine components, structural components on highspeed aircraft, spacecraft, and missiles. Phenylethynyl-terminated amide acid oligomers that are precursors of PETI oligomers are easily made through the reaction of a mixture of aromatic diamines with aromatic dianhydrides at high stoichiometric offsets and 4-phenylethynylphthalic anhydride (PEPA) as an end-capper in a polar solvent such as N-methylpyrrolidinone (NMP). These oligomers are subsequently cyclodehydrated -- for example, by heating the solution in the presence of toluene to remove the water by azeotropic distillation to form low-molecular-weight imide oligomers. More precisely, what is obtained is a mixture of PETI oligomeric species, spanning a range of molecular weights, that exhibits a stable melt viscosity of less than approximately 60 poise (and generally less than 10 poise) at a temperature below 300 deg C. After curing of the oligomers at a temperature of 371 deg C, the resulting polymer can have a glass-transition temperature (Tg) as high as 375 C, the exact value depending on the compositions

Flight evaluation of advanced flight control systems and cockpit displays for powered-lift STOL Aircraft

A flight research program was conducted to assess the improvements, in longitudinal path control during a STOL approach and landing, that can be achieved with manual and automatic control system concepts and cockpit displays with various degrees of complexity. NASA-Ames powered-lift Augmentor Wing Research Aircraft was used in the research program. Satisfactory flying qualities were demonstrated for selected stabilization and command augmentation systems and flight director combinations. The ability of the pilot to perform precise landings at low touchdown sink rates with a gentle flare maneuver was also achieved. The path-control improvement is considered to be applicable to other powered-lift aircraft configurations

Evidence for a diffusion-controlled mechanism for fluorescence blinking of colloidal quantum dots

Fluorescence blinking in nanocrystal quantum dots is known to exhibit power-law dynamics, and several different mechanisms have been proposed to explain this behavior. We have extended the measurement of quantum-dot blinking by characterizing fluctuations in the fluorescence of single dots over time scales from microseconds to seconds. The power spectral density of these fluctuations indicates a change in the power-law statistics that occurs at a time scale of several milliseconds, providing an important constraint on possible mechanisms for the blinking. In particular, the observations are consistent with the predictions of models wherein blinking is controlled by diffusion of the energies of electron or hole trap states

Patient-maintained sedation for oral surgery using a target-controlled infusion of propofol - a pilot study

OBJECTIVE: To assess the safety and efficacy of a new patient-maintained propofol system for conscious sedation in dentistry. DESIGN: Prospective clinical trial SETTING: Department of Sedation, Glasgow Dental Hospital and School, 2001 SUBJECTS AND METHODS: Patients scheduled for oral surgery with conscious sedation. Exclusions included ASA IV -V, inability to use the handset, opioid use and severe respiratory disease. INTERVENTIONS: Patients were given intravenous propofol to a level of 1.0 microg/ml (reducing from 1.5 microg/ml) using a target controlled infusion system, they then controlled their sedation level by double-clicking a handset which on each activation increased the propofol concentration by 0.2 microg/ml. MAIN OUTCOME MEASURES: Oxygen saturation, patient satisfaction, and surgeon satisfaction. RESULTS: Twenty patients were recruited, 16 female and four male. Nineteen patients completed sedation and treatment successfully. Mean lowest oxygen saturation was 94%. No patients were over-sedated. All patients successfully used the system to maintain a level of sedation adequate for their comfort. Patient and surgeon satisfaction were consistently high. CONCLUSIONS: Initial experience with this novel system has confirmed safety, patient satisfaction and surgeon satisfaction

Structure-based Design of Broadly Neutralizing HCV Antibody and Vaccine

Hepatitis C virus (HCV) chronically infects nearly 200 million people worldwide. Antibodies have the potential to prevent establishment of chronic HCV infection in individuals exposed to the virus. Several broadly neutralizing monoclonal antibodies capable of binding HCV surface glycoproteins have been identified, including HCV1 identified by MassBiologics at UMMS, which targets a highly conserved linear epitope. We utilized the recently solved structure of the HCV1-bound epitope to identify regions of the antibody that could be modified to potentially improve binding to a mutation (N415K) which facilitates escape from neutralization. Based on systematic in silico mutagenesis of HCV1 residues in the Rosetta protein modeling program, a number of single or double antibody mutants were selected for in vitro evaluation. The mutated antibodies were synthesized and their ability to neutralize HCV pseudoviruses expressing either wild-type epitope sequence or the N415K variant was evaluated. Antibodies with mutations on the heavy chain, R65Q and V50L, demonstrated improved neutralizing activity against the N415K escape mutant without impacting their ability to neutralize wild type virus. We also sought to design a novel HCV vaccine that could focus the response to a small conserved neutralizing epitope of the virus defined by HCV1. The HCV1 epitope structure was used to search a large dataset of known protein structures from the Protein Data Bank, resulting in designs of scaffolds that were predicted to stably accommodate the epitope. These epitope-presenting scaffold proteins have been made and will be screened in animal studies to determine their potential as vaccine candidates for HCV prevention

Presence of Atrazine in Water in a Recharge Area of Guarany Aquifer in Brazil

The region of Ribeirao Preto City located in Sao Paulo State, southeastern Brazil, is an important sugarcane, soybean and corn producing area. This region is also an important recharge area for groundwater of the Guarany aquifer, a water supply source of the city and region. The cultivation of grain and sugar cane in thes area demands the frequent use of the herbicide atrazine (2-chloro-4- (ethylamino)-6-(isopropylamino)-S-triazine). This research was conducted to characterize the potential contamination of groundwater with atrazine. Surface water samples were collected in the Espraiado stream in a selected watershed on the area, during the years of 1995-1998. Groundwater was also collected in wells located at the edge of the watershed during the years of 1999 to 2002. The water samples were analyzed by HPLC (High Performance Liquid Chromatography) procedure followed by GC-MS form confirmation. To predict the atrazine leaching in the area, the CMLS-94 (Chemical Movement Layered Soil) simulation model was also used. Only four atrazine detections in surface water were found, however, none of them were confirmed with GC-MS. No atrazine was detected in groundwater samples. The results obtained by the CMLS-94 simulations predicted that atrazine, after four years from the application date, would not have reached the depth of the confined aquifer (40m)

IRAC Observations of M81

IRAC images of M81 show three distinct morphological constituents: a smooth distribution of evolved stars with bulge, disk, and spiral arm components; a clumpy distribution of dust emission tracing the spiral arms; and a pointlike nuclear source. The bulge stellar colors are consistent with M-type giants, and the disk colors are consistent with a slightly younger population. The dust emission generally follows the blue and ultraviolet emission, but there are large areas that have dust emission without ultraviolet and smaller areas with ultraviolet but little dust emission. The former are presumably caused by extinction, and the latter may be due to cavities in the gas and dust created by supernova explosions. The nucleus appears fainter at 8 um than expected from ground-based 10 um observations made four years ago.Comment: ApJS in press (Spitzer special issue); 15 pages, 3 figures. Changes: unused references removed, numbers and labels in Table 1 change

Survivin as a therapeutic target in Sonic hedgehog-driven medulloblastoma.

Medulloblastoma (MB) is a highly malignant brain tumor that occurs primarily in children. Although surgery, radiation and high-dose chemotherapy have led to increased survival, many MB patients still die from their disease, and patients who survive suffer severe long-term side effects as a consequence of treatment. Thus, more effective and less toxic therapies for MB are critically important. Development of such therapies depends in part on identification of genes that are necessary for growth and survival of tumor cells. Survivin is an inhibitor of apoptosis protein that regulates cell cycle progression and resistance to apoptosis, is frequently expressed in human MB and when expressed at high levels predicts poor clinical outcome. Therefore, we hypothesized that Survivin may have a critical role in growth and survival of MB cells and that targeting it may enhance MB therapy. Here we show that Survivin is overexpressed in tumors from patched (Ptch) mutant mice, a model of Sonic hedgehog (SHH)-driven MB. Genetic deletion of survivin in Ptch mutant tumor cells significantly inhibits proliferation and causes cell cycle arrest. Treatment with small-molecule antagonists of Survivin impairs proliferation and survival of both murine and human MB cells. Finally, Survivin antagonists impede growth of MB cells in vivo. These studies highlight the importance of Survivin in SHH-driven MB, and suggest that it may represent a novel therapeutic target in patients with this disease

Redshift-distance Survey of Early-type Galaxies: The D_n-sigma Relation

In this paper R-band photometric and velocity dispersion measurements for a sample of 452 elliptical and S0 galaxies in 28 clusters are used to construct a template D_n-sigma relation. This template relation is constructed by combining the data from the 28 clusters, under the assumption that galaxies in different clusters have similar properties. The photometric and spectroscopic data used consist of new as well as published measurements, converted to a common system, as presented in a accompanying paper. The resulting direct relation, corrected for incompleteness bias, is log{D_n} =1.203 log{sigma} + 1.406; the zero-point has been defined by requiring distant clusters to be at rest relative to the CMB. This zero-point is consistent with the value obtained by using the distance to Virgo as determined by the Cepheid period-luminosity relation. This new D_n-sigma relation leads to a peculiar velocity of -72 (\pm 189) km/s for the Coma cluster. The scatter in the distance relation corresponds to a distance error of about 20%, comparable to the values obtained for the Fundamental Plane relation. Correlations between the scatter and residuals of the D_n-sigma relation with other parameters that characterize the cluster and/or the galaxy stellar population are also analyzed. The direct and inverse relations presented here have been used in recent studies of the peculiar velocity field mapped by the ENEAR all-sky sample.Comment: 46 pages, 20 figures, and 7 tables. To appear in AJ, vol. 123, no. 5, May 200