Search

The Multi-angle Imaging SpectroRadiometer (MISR) was launched in 1999 as part of NASA’s Terra satellite suite of instruments. Still operational, it makes use of observations from multiple view angles to retrieve aerosol abundance and particle properties. The Multi-Angle Imager for Aerosols (MAIA) instrument improves on this heritage by incorporating polarimetry and an expanded spectral range. Combining these data with surface measurements, the relationship between pollution and human health will be explored. MAIA has just completed camera testing, building on the experience from MISR. Spectral calibration now makes use of a double subtractive monochromator, built with the intent to allow the exit slit output to be uniform in spectral content. For radiometric testing, hardware upgrades have included adding UV lamps to the 1.65 cm (65") integrating sphere, use of a NIST-traceable sphere to establish absolute radiances, and the addition of a UV transfer spectrometer to support characterization of the sphere output from 300 to 2500 nm. During camera build, Newton’s rings were observed in the detector Quantum Efficiency (QE) measurements. This is due to etaloning within the detector itself. Etaloning was also evident in the spectral and radiometric characterizations performed on the completed camera. Spectral metrics, including center wavelength and width, are presented here using a moment’s analysis. This better represents the band properties, particularly in bands where fringing is observed, as compared to a full-width at halfmaximum determination. The MAIA camera has been carefully characterized, and meets its spectral and radiometric requirements.

We examine inorganic chlorine (Cly) partitioning in the summer lower stratosphere using in situ ER-2 aircraft observations made during the Photochemistry of Ozone Loss in the Arctic Region in Summer (POLARIS) campaign. New steady state and numerical models estimate [ClONO2]/[HCl] using currently accepted photochemistry. These models are tightly constrained by observations with OH (parameterized as a function of solar zenith angle) substituting for modeled HO2 chemistry. We find that inorganic chlorine photochemistry alone overestimates observed [ClONO2]/[HCl] by approximately 55-60% at mid and high latitudes. On the basis of POLARIS studies of the inorganic chlorine budget, [ClO]/[ClONO2], and an intercomparison with balloon observations, the most direct explanation for the model-measurement discrepancy in Cly partitioning is an error in the reactions, rate constants, and measured species concentrations linking HCl and ClO (simulated [ClO]/[HCl] too high) in combination with a possible systematic error in the ER-2 ClONO2 measurement (too low). The high precision of our simulation (+/-15% 1-sigma for [ClONO2]/[HCl], which is compared with observations) increases confidence in the observations, photolysis calculations, and laboratory rate constants. These results, along with other findings, should lead to improvements in both the accuracy and precision of stratospheric photochemical models.

Nitrous oxide (N 2 O) and methane (CH 4 ) were measured in the upper troposphere and lower stratosphere by multiple instruments aboard the NASA ER-2 aircraft during the 1995-1996 Stratospheric Tracers of Atmospheric Transport (STRAT) and 1997 Photochemistry of Ozone Loss in the Arctic Region in Summer (POLARIS) campaigns. Differences between coincidental, in situ measurements are examined to evaluate the agreement and variability in the agreement between these instruments during each flight. Mean N 2 O measurement differences for each flight were much smaller than limits calculated from quoted values of N 2 O measurement accuracy and for all but two flights were ≤8.7 ppb (3.5%). Mean CH 4 measurement differences for flights were similarly much smaller than calculated limits and for all but three flights were ≤65 ppb (4.4%). Typical agreement between instruments during flights averaged 6.2 ppb (2.5%) for N 2 O and 43 ppb (2.9%) for CH 4 . In contrast, for about half of the flights, the variability of N 2 O and CH 4 measurement differences exceeded limits calculated from quoted values of measurement precision. The typical measurement difference variability (1σ) during a flight averaged ±8.0 ppb (3.2%) for N 2 O and ±43 ppb (2.9%) for CH 4 . For some flights, large differences or variations in differences are attributable to the poor measurement accuracy or precision of one instrument. It is demonstrated that small offsets between the computer clocks of these instruments can result in significant differences between their coincidental N 2 O and CH 4 data, especially when there is high spatial variability in tracer abundance along a flight track.

Randomly branched bisphenol A polycarbonates (PCs) were prepared by interfacial polymerization methods to explore the limits of gel-free compositions available by the adjustment of various composition and process variables. A molecular weight distribution (MWD) model was devised to predict the MWD, G, and weight-average molecular weight per arm (M w /arm) values based on the composition variables. The amounts of the monomer, branching agent, and chain terminator must be adjusted such that the weight-average functionality of the phenolic monomers (F OH ) was less than 2 to preclude gel formation in both the long- and short-chain branched (SCB) PCs. Several series of SCB and long-chain branched PCs were prepared, and those lacking gels showed molecular weights measured by gel permeation chromatography-UV and gel permeation chromatography-LS consistent with model calculations. In SCB PCs, the minimum M,Jarm that could be realized without gel formation depended on both composition (molecular weight, terminator type) and process (terminator addition point, coupling catalyst) variables. The minimum M w /arm achieved in the low molecular weight series studied ranged from ∼3300 to ∼1000. The use of long chain alkyl phenol terminators gave branched PCs with lower glass-transition temperatures but a higher gel-free minimum M w /arm. SCB PCs where M w /arm was less than ∼M c spontaneously cracked after compression molding, a result attributed to their lack of polymer chain entanglements.

We use the correlation between CH(sub 4) and N(sub 2)O as measured during the POLARIS campaign in spring 1997 to estimate the degree of mixing between descended air masses from the vortex and air masses from mid-latitudes.

Observations made in the 1994 Antarctic vortex show that Cl y recovered completely into HCl following conversion of Cl y reservoir species to active radicals, and NO x constituted a 4-5 times higher fraction of NO y inside the vortex than outside. Measurements made in October and November from the Airborne Southern Hemisphere Ozone Expedition/Measurements of the Atmospheric Effects of Stratospheric Aircraft (ASHOE/MAESA) ER-2 aircraft mission, the third Atmospheric Laboratory for Applications and Science (ATLAS-3) space shuttle mission, and the Upper Atmosphere Research Satellite (UARS) demonstrate that this unusual partitioning of Cl y and NO y was maintained for at least 4 weeks in the springtime vortex. In response to severe ozone loss, abundances of HCl and NO x remained high despite temperatures low enough to reactivate Cl y and convert NO x to HNO 3 via heterogeneous processes. Thus, under severely ozone depleted conditions, high HCl and NO x abundances in the vortex are maintained until the vortex breaks up or an influx of ozone-rich extravortex air is entrained into the vortex. These observations suggest that the flux of extravortex air entering the core of the lower stratospheric vortex was small or negligible above ∼400 K during late spring, despite weakening of the vortex during this time period. Results of a photochemical model constrained by the measurements suggest that extravortex air entrained into the vortex during October and early November made up less than 5% of the vortex core air at 409 K. The model results also show that heterogeneous chemistry has little effect on the Cl y and NO y partitioning once high abundances of HCl have been attained under ozone depleted conditions, even when aerosol loading is high.

A suite of compounds with a wide range of photochemical lifetimes (3 months to several decades) was measured in the tropical and midlatitude upper troposphere and lower stratosphere during the Stratospheric Tracers of Atmospheric Transport (STRAT) experiment (fall 1995 and winter, summer, and fall 1996) and the Photochemistry of Ozone Loss in the Arctic Region in Summer (POLARIS) deployment in late summer 1997. These species include various chlorofluorocarbons, hydrocarbons, halocarbons, and halons measured in whole air samples and CO measured in situ by tunable diode laser spectroscopy. Mixing ratio profiles of long-lived species in the tropical lower stratosphere are examined using a one-dimensional (1-D) photochemical model that includes entrainment from the extratropical stratosphere and is constrained by measured concentrations of OH. Profiles of tracers found using the 1-D model agree well with all the observed tropical profiles for an entrainment time scale of 8.5 -4 +6 months, independent of altitude between potential temperatures of 370 and 500 K. The tropical profile of CO is used to show that the annually averaged ascent rate profile, on the basis of a set of radiative heating calculations, is accurate to approximately ±44%, a smaller uncertainty than found by considering the uncertainties in the radiative model and its inputs. Tropical profiles of ethane and C 2 Cl 4 reveal that the concentration of Cl is higher than expected on the basis of photochemical model simulations using standard gas phase kinetics and established relationships between total inorganic chlorine and CFC-11. Our observations suggest that short-lived organic chlorinated compounds and HCI carried across the tropical tropopause may provide an important source of inorganic chlorine to the tropical lower stratosphere that has been largely unappreciated in previous studies. The entrainment timescale found here is considerably less than the value found by a similar study that focused on observations obtained in the lower stratosphere during 1994. Several possible explanations for this difference are discussed.

(Meth)acrylate terminated bisphenol A polycarbonates [(M)AC PCs] were prepared under interfacial conditions by reaction of (meth)acryloyl chloride with bisphenol A (BA) followed by phosgenation. Addition of (M)ACl to an interfacial mixture of BA containing a catalytic amount of triethylamine followed by phosgenation gave linear polymers with good control of molecular weight. Thermal crosslinking of MAC PCs was generally achieved only in the presence of dicumyl peroxide. Between 75 and 98% gel was obtained by using 2 wt % initiator and heating for 30 min each at 150 and 200°C. All of the AC PCs crosslinked without added initiator to form 92–100% gel by heating for 30 min at 250°C. Coatings of high crosslink density (M)AC PCs on linear BA PC plaques were prepared by a combination of solvent casting, compression molding, and (optionally) oven curing. Moderate to high crosslink density (M)AC PC coatings showed relatively high pencil hardness values and good abrasion resistance. In weathering studies, both MAC and AC PC-coated plaques showed low YI increases, but the MAC PC coating developed higher haze due to microcracking. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 663–675, 1999

In situ measurements of CO were made in the upper troposphere and lower stratosphere (7–21 km altitude) with the Jet Propulsion Laboratory (JPL) Aircraft Laser Infrared Absorption Spectrometer (ALIAS) on 58 flights of the NASA ER-2 aircraft from October 1995 through September 1997, between 90°N and 3°S latitude. Measured upper tropospheric CO was variable and typically ranged between 55 and 115 ppb, except for higher values over Alaska during summer 1997. Tropical stratospheric CO ranged from 58 ± 5 ppb at the tropopause to 12 ± 2 ppb above 20 km, having similar profiles in all seasons of the year. The tropical profile is reproduced by a simple Lagrangian box model of tropical ascent using measured CH4 and OH concentrations, Cl and O(^1D) concentrations from a photochemical model, and diabatic heating rates from a radiative heating model. From measured CO, quasi-horizontal mixing between the tropical and mid-latitude lower stratosphere is inferred to be rapid in the region between 400 K and 450 K potential temperature (altitudes less than 20 km).

Methane (CH4), molecular hydrogen (H2), and water vapor (H2O) were measured concurrently on board the NASA ER-2 aircraft during the 1995–1996 Stratospheric Tracers of Atmospheric Transport (STRAT) and 1997 Photochemistry of Ozone Loss in the Arctic Region in Summer (POLARIS) campaigns. Correlations between these three main hydrogen reservoirs in the northern extratropical lower stratosphere are examined to evaluate H2O production from CH4 and H2 oxidation. The expected ratio of stratospheric H2O production (PH2O)to CH4 destruction (LCH4) = −1.973±0.003 is calculated from an evaluation of CH4 and H2 oxidation reactions and the relationship between H2 and CH4 mixing ratios measured during STRAT. Correlations between H2O and CH4 were tight and linear only for air masses with mean ages ≥3.8 years, restricting this analysis predominantly to latitudes between 40° and 90°N and potential temperatures between 470 and 540 K. The mean observed ΔH2O/CH4 (−2.15±0.18) is in statistical agreement with the expected PH2O/LCH4. The annual mean stratospheric entry mixing ratio for H2O calculated from this slope is 4.0 ± 0.3 ppm. The quantity H2O + 2·CH4 is quasi-conserved at 7.4 ± 0.5 ppm in older air masses in the northern extratropical lower stratosphere. Significant departure of H2O + 2·CH4 from the mean value is a sensitive indicator of processes which influence H2O without affecting CH4, such as dehydration in a polar vortex or near the tropical tropopause. No significant trend is observed in ER-2 aircraft data for H2O + 2·CH4 in the lower stratosphere from 1993 through 1997.

Recent studies using NO, NOy, OH and HO2 (HOx) observations have postulated acetone and convection of peroxides as significant sources of HOx in the upper troposphere (UT). This work focuses on the effect these additional HOx sources have on the modeled NOy partitioning and comparisons of the modeled NOx/NOy ratio to observations. The measured NOx/NOy ratio is usually much higher than predicted regardless of the presence of acetone in the model. The exception occurs for air parcels having low NOy and O3 values. For these air parcels the measured NOx/NOy ratio is much lower than the calculated ratio unless acetone is included in the model. In all cases acetone increases the fraction of NOy that is peroxy acetyl nitrate (PAN) from typical values of much less than 0.1 to values as high as 0.35. Including acetone also reduces the scatter in a comparison between modeled and observed NOx/NOy ratios.

Long chain branched bisphenol A polycarbonates (BA PC's) were prepared by use of a combination of thermally reactive 4-hydroxybenzocyclobutene (BCB-OH) and the nonreactive p-tert-butylphenol (PTBP) chain terminators. These two monophenols react under interfacial conditions at similar rates to provide a statistical distribution of coterminated PC's having molecular weights controlled by the total amount of coterminators. Heating these materials to 300 °C causes branching and/or cross-linking depending on the value of X BCB , thereby separating the polycondensation and branching processes and allowing greater degrees of branching than possible by random branching during polycondensation. At X BCB ∼2M e are relatively tough and flexible, while those having lower M n 'S, regardless of M w , are relatively brittle. The melt viscosities of branched BCB-OH/PTBP PC's are very high at low shear rates, as expected from their high M w 'S, but decrease dramatically with increasing shear rates to values approaching those of conventional linear and randomly branched PC's. Such high zero-shear viscosity, which is indicative of high melt strength, and large shear sensitivity suggests that these new materials could display significant improvements in melt processing by techniques such as blow molding, thermoforming, injection molding, and extrusion.

Simultaneous in situ measurements of N_2O and CH_4 were made with a tunable diode laser spectrometer (ALIAS II) aboard the Observations from the Middle Stratosphere (OMS) balloon platform from New Mexico, Alaska, and Brazil during 1996 and 1997. We find different compact relationships of CH_4 with N_2O in the tropics and extra-tropics because mixing is slow between these regions. Transport into the extra-tropics from the tropics or the polar vortex leads to deviations from the normal compact relationship. We use measured N_2O and CH_4 and a simple model to quantify entrainment of mid-latitude stratospheric air into the tropics. The entrainment time scale is estimated to be 16 (+17, −8) months for altitudes between 20 and 28 km. The fraction of tropical air entrained from the extra-tropical stratosphere is 50% (+18%, −30%) at 20 km, increasing to 78% (+11%, −19%) at 28 km.

In situ measurements of hydrochloric acid (HCI) concentrations in the lower stratosphere from 1991 to 1996 reveal that its abundance relative to that of total inorganic chlorine (CIy) has evolved upwards from HCI/CIy=40% in late 1991 to 70% in 1996.

We compared the performance characteristics of a commercial dilute Russell's viper venom (DRVV)-based APC resistance assay (Gradipore PC Impedance Test) to a routinely utilized commercial APTT based assay (Coatest APC Resistance Assay). The DRVV based assay offers improved sensitivity and specificity for the factor V Leiden mutation. However, the routine use of both assays provides optimum reliability for diagnosis of genetic APC resistance. Our results suggest that when both tests are either positive or negative, DNA analysis is unnecessary. Interference by lupus anticoagulants is dramatically minimized by the phospholipid rich DRVV reagent used in the assay and it is insensitive to high factor VIII activity. Additionally, discrepant functional assay results allow identification of patients who may have an acquired APC resistant phenotype.

Simultaneous in situ measurements of HCl and ClO have been made for the first time in the southern hemisphere, allowing a systematic study of the processes governing chlorine activation between 15 and 20 km in the 1994 Antarctic winter. Data for several other gases (O_3, NO, NO_y, OH, HO_2, N_(2)O, CH_4, CO, H_(2)O, CFCs), particulates, and meteorological parameters were collected from the ER-2 aircraft out of New Zealand as part of the 1994 Airborne Southern Hemisphere Ozone Experiment/Measurements of Atmospheric Effects of Stratospheric Aircraft (ASHOE/MAESA) campaign. Observations from the ER-2 in the fall (April–May), prior to polar night, show that chlorine activation begins with 60–75% of inorganic chlorine as HCl. By midwinter (July–August), near-total removal of HCl is observed. The wintertime loss of HCl in air recently exposed to extreme temperatures is found to be correlated with high levels of reactive chlorine (ClO and its dimer, Cl_(2)O_2) in the linear fashion expected from the stoichiometry of the heterogeneous reaction of hydrochloric acid with chlorine nitrate on polar stratospheric clouds (PSCs): HCl + ClONO_2 → Cl_2 + HNO_3. To constrain the role of different heterogeneous reactions and PSC types, we have used a photochemical trajectory model which includes heterogeneous sulfate and PSC chemistry. Model calculations of the evolution of reactive gases are compared with the in situ observations. In addition, simultaneous measurements of OH and HO_2 are used as a diagnostic for the occurrence of the heterogeneous reaction HOCl + HCl → Cl_2 + H_(2)O, which contributes to suppressed levels of HO_x inside the vortex. It is shown that the amount of chlorine activation is not strongly dependent on the composition of PSCs. However, HO_x levels exhibit different signatures depending on the type of heterogeneous surfaces that affected chlorine activation. Furthermore, this analysis implies that in the edge region of the Antarctic vortex, the observed near-total removal of HCl can result from latitudinal excursions of air parcels in and out of sunlight during the winter, which photochemically resupply HOCl and ClONO_2 as oxidation partners for HCl.

Phenylmaleimide (PMI)- and phenylnadimide (PNI)-terminated bisphenol A polycarbonates (PCs) were prepared by solution or interfacial phosgenation processes, and their thermal crosslinking, both with and without a free radical initiator, and the thermal stability of the resultant network polymers were investigated. m-PMI PCs were prepared by interfacial phosgenation of bisphenol A and m-hydroxyphenylmaleimide, but p-hydroxyphenylmaleimide caused rapid phosgene hydrolysis under interfacial conditions and PCs from it could only be made by solution phosgenation. The degree of crosslinking of PMI PCs, as measured by their gel fraction, heated in the absence of a free radical initiator was generally higher at 250°C than at 300°C and increased with the concentration of PMI end groups. m- and p-PMI PCs form thermosets having nearly complete gel fractions by radical initiated curing at 150-200°C. The gel fraction of these thermosets decreases with exposure to higher temperatures (300°C). This behavior is attributed to BA PC chain degradation induced by nitrogen-containing maleimide reaction products. p-PNI PC was prepared by solution phosgenation and the thermal reaction of it in the presence of the initiator produced only a small increase in molecular weight.

Periodic growth and decay of linearly unstable plasmon modes are predicted by numerical solution of the one-dimensional collisionless quantum Boltzmann equation. The nonlinear mode stabilization is accompanied by the generation of higher harmonics. The results are analyzed using quantum generalized quasilinear theory.

Intraband pair excitation and plasmon spectra of nonequilibrium plasmas are analyzed using the dynamic dielectric function in the random-phase approximation. Nonequilibrium conditions are identified for which the Landau damping of acoustic plasmons vanishes. This acoustic-plasmon undamping is discussed for two-component plasmas and for one-component plasmas with a double-peaked distribution in momentum space.

Strong enhancement of acoustic plasmons in optically excited nonequilibrium electron-hole plasmas in bulk semiconductors is shown to cause ultrashort (\ensuremath{\sim}10 fs) dephasing times and very high carrier-carrier scattering rates.

A theoretical basis is presented for the design of dosage forms containing a drug which is initially distributed throughout a noneroding diffusional matrix in a nonuniform manner, for the purpose of achieving zero-order release. Modeling of these dosage forms is based on Higuchi's square root of time diffusional model. Derivations of theoretical drug release profiles for both flat slab and spherical geometry are included. Pellets were prepared utilizing this nonuniform distribution concept using fluid bed suspension layering technology. A gradient pumping system used in conjunction with a specially fabricated miniature fluid bed apparatus was utilized to prepare pellets containing drug nonuniformly dispersed. Actual drug release profiles were obtained for pellets containing drug distributed in the traditional uniform manner and the nonuniform manner described above. Nonuniform distribution of drug in a noneroding diffusional matrix, in theory and practice, is shown to linearize dissolution profiles.

Cumulative step length adaptation is a mutation strength control mechanism commonly employed with evolution strategies. When using weighted recombination with negative weights it can be observed to be prone to failure, often leading to divergent behaviour in low-dimensional search spaces. This paper traces the reasons for this breakdown of step length control. It then proposes a novel variant of the algorithm that reliably results in convergent behaviour for the test functions considered. The influence of the dimensionality as well as of the degree of ill-conditioning on optimisation performance are evaluated in computer experiments. Implications for the use of weighted recombination with negative weights are discussed.

[1] Four nitrous oxide (N2O) instruments were part of the NASA ER-2 aircraft payload during the 2000 SAGE-III Ozone Loss and Validation Experiment (SOLVE). Coincident data from the three in situ instruments and a whole air sampler are compared. Agreement between these instruments was typically good; however, there are several types of important differences between the data sets. These differences prompted a collaborative effort to combine data from the three in situ instruments, using an objective method, to produce a self-consistent, high-resolution, unified N2O data set for each SOLVE flight. The construction method developed by the four N2O instrument teams is described in detail. An important step in this method is the evaluation and reduction of bias in each of the in situ data sets before they are combined. The quality of unified N2O data is examined through its agreement with high-accuracy and high-precision N2O data from whole air samples collected from the ER-2 during SOLVE flights. Typical agreement between these two data sets is 2.9 ppb (1.5%), better than the typical agreement between any pair of N2O instruments.

During Arctic winters with a cold, stable stratospheric circulation, reactions on the surface of polar stratospheric clouds (PSCs) lead to elevated abundances of chlorine monoxide (ClO) that, in the presence of sunlight, destroy ozone. Here we show that PSCs were more widespread during the 1999/2000 Arctic winter than for any other Arctic winter in the past two decades. We have used three fundamentally different approaches to derive the degree of chemical ozone loss from ozonesonde, balloon, aircraft, and satellite instruments. We show that the ozone losses derived from these different instruments and approaches agree very well, resulting in a high level of confidence in the results. Chemical processes led to a 70% reduction of ozone for a region similar to1 km thick of the lower stratosphere, the largest degree of local loss ever reported for the Arctic. The Match analysis of ozonesonde data shows that the accumulated chemical loss of ozone inside the Arctic vortex totaled 117 +/- 14 Dobson units (DU) by the end of winter. This loss, combined with dynamical redistribution of air parcels, resulted in a 88 +/- 13 DU reduction in total column ozone compared to the amount that would have been present in the absence of any chemical loss. The chemical loss of ozone throughout the winter was nearly balanced by dynamical resupply of ozone to the vortex, resulting in a relatively constant value of total ozone of 340 +/- 50 DU between early January and late March. This observation of nearly constant total ozone in the Arctic vortex is in contrast to the increase of total column ozone between January and March that is observed during most years.

Public concern with societal violence is intensified when persons who have been found not guilty by reason of insanity (NGRI) of having committed a homicide or serious assault are returned to the community. Successful management of such acquittees in the community requires a sophisticated understanding of the person and the illness within the larger context of the violent incident, the family, the community, and the culture. In this article, we present an analysis of psychotic violence within a family context. A qualitative study of 64 subjects who were found NGRI of killing or seriously injuring a family member resulted in four prototypes of intrafamilial homicide/assault: Till Death Us Do Part; Overwhelming Burden, Elimination of the Limit Setter; and Family-Focused Delusional Killing. The prototypes are presented as a model for developing management strategies both for future risk assessment and for successful transition of the insanity acquittee into the community.

Pseudohypoparathyroidism type Ia (PHP type Ia) is associated with several endocrinopathies. We describe two siblings with PHP type Ia, hypothyroidism and growth hormone deficiency (GHD). To our knowledge, these patients are the first to have PHP type Ia and GHD. The defect which is most likely responsible for the three endocrinopathies is a deficiency of the stimulatory guanine nucleotide-binding regulatory protein, Gs.

Pseudohypoparathyroidism type Ia (PHP type Ia) is associated with several endocrinopathies. We describe two siblings with PHP type Ia, hypothyroidism and growth hormone deficiency (GHD). To our knowledge, these patients are the first to have PHP type Ia and GHD. The defect which is most likely responsible for the three endocrinopathies is a deficiency of the stimulatory guanine nucleotide-binding regulatory protein, Gs.

An analysis of collective longitudinal electrostatic plasma excitations in quasi-one-dimensional degenerate plasmas is presented using the dielectric function in the random phase approximation. Analytical continuation of the dielectric function into the lower energy half plane allows us to compute the complete spectrum of the collective excitations, including frequencies and damping or growth rates. In contrast to two- and three-dimensional plasmas, a multicomponent quasi-one-dimensional system at zero temperature is found to exhibit one undamped plasmon mode for each component. The conditions for the occurrence of unstable modes are investigated and the influence of temperature and collisions on the results is discussed.

A coupled set of equations for carrier distributions and stimulated emission in a semiconductor laser is presented, based on a nonequilibrium Green's-function formulation. Carrier momentum-dependent dephasing caused by carrier-carrier scattering and frequency-dependent optical gain are shown to govern the interplay between carrier relaxation and stimulated recombination. Ignoring the interband Coulomb interaction, the coupled system of equations for the carrier distribution functions and the optical gain is solved self-consistently for a single-mode short-cavity semiconductor laser under steady-state operation conditions. Numerical results show spectral and kinetic hole burning as well as nonlinear gain saturation.

A quantitative analysis of carrier-carrier scattering and optical dephasing in semiconductors is presented and results are given for quasiequilibrium situations and for the relaxation of a kinetic hole in a quasithermal carrier distribution. The calculations involve direct numerical integration of the Boltzmann equation for carrier-carrier scattering in the Born approximation. The screening of the Coulomb interaction is treated consistently in the fully dynamical random-phase approximation. Carrier relaxation rates are extracted from the Boltzmann-equation solution and a quantitative test of the relaxation-time approximation for situations near thermal quasiequilibrium is performed. The parametric dependence of carrier-collision rates and dephasing on plasma density, temperature, and electron and hole masses is discussed and analyzed in terms of phase-space blocking and screening.

Millimeter waves have been generated by driving HBTs with both mode locked and cw semiconductor lasers. The mode locked diode lasers incorporated a saturable absorber section and produced

A theoretical basis is presented for the design of dosage forms containing a drug which is initially distributed throughout a noneroding diffusional matrix in a nonuniform manner, for the purpose of achieving zero-order release. Modeling of these dosage forms is based on Higuchi's square root of time diffusional model. Derivations of theoretical drug release profiles for both flat slab and spherical geometry are included. Pellets were prepared utilizing this nonuniform distribution concept using fluid bed suspension layering technology. A gradient pumping system used in conjunction with a specially fabricated miniature fluid bed apparatus was utilized to prepare pellets containing drug nonuniformly dispersed. Actual drug release profiles were obtained for pellets containing drug distributed in the traditional uniform manner and the nonuniform manner described above. Nonuniform distribution of drug in a noneroding diffusional matrix, in theory and practice, is shown to linearize dissolution profiles.

The Airborne Laser Infrared Absorption Spectrometer II (ALIAS-II) is a lightweight, high-resolution (0.0003-cm(-1)), scanning, mid-infrared absorption spectrometer based on cooled (80 K) lead-salt tunable diode laser sources. It is designed to make in situ measurements in the lower and middle stratosphere on either a balloon platform or high-altitude remotely piloted aircraft. Chemical species that can be measured precisely include long-lived tracers N(2)O and CH(4), the shorter-lived tracer CO, and chemically active species HCl and NO(2). Advances in electronic instrumentation developed for ALIAS-I, with the experience of more than 250 flights on board NASA's ER-2 aircraft, have been implemented in ALIAS-II. The two-channel spectrometer features an open cradle, multipass absorption cell to ensure minimal contamination from inlet and surfaces. Time resolution of the instrument isor=3 s, allowing rapid in situ measurements with excellent spatial resolution. ALIAS-II has completed successful balloon flights from New Mexico, Alaska, and Brazil providing CH(4) and N(2)O vertical profiles in the tropics, mid-latitudes, and high northern latitudes up to altitudes of 32 km.

Measurements of HCl and CH4 taken by the aircraft laser infrared absorption spectrometer (ALIAS) on the ER-2 high-altitude research aircraft during the Southern Hemisphere winter of 1994 have been used to examine the abundance of HCl as a fraction of total inorganic chlorine. The fractional abundance of HCl shows a threshold behaviour as a function of temperature history; on a 10 day timescale, the abundance dropped sharply in those air parcels experiencing a temperature < 195 K, but little or no change was seen in parcels which stayed warmer than this temperature. The behaviour mirrors well the temperature behaviour calculated for the transformation of HCl into reactive forms (Cl2, HOCl) from laboratory studies of sulfate aerosols and polar stratospheric clouds. During the course of the winter, the fractional abundance of HCl outside the vortex decreased from its values in late May by about a third, while inside it dropped to near zero by early August. Some recovery was evident in October. Examples of the peel-off of low-HCl air equatorward of the wind maximum were evident in early June. Meteorological trajectories are used to show, in a case study of a flight in early August, that air parcels which experienced temperatures of < 195 K, and as a result had low fractional HCl abundances, did so largely poleward of the maximum in the polar night jet stream. Encountering temperatures of < 195 K during the previous 10 days was a necessary and sufficient condition for the transformation of HCl into reactive forms by heterogeneous reactions. The trajectories further showed that air arriving from sub-tropical latitudes had higher fractional HCl abundances than the air in the middle latitudes, and much higher fractions than the air at high latitudes. The resulting picture is one in which the fractional abundance of HCl in air at mid latitudes was the result of mixing of air from sub-tropical latitudes with air mainly from polward of the jet stream core which has experienced temperatures < 195 K. The sensitivity of the fractional abundance of HCl to the assumption that no HCl enters the stratosphere via the tropical tropopause is examined in the light of an observed profile near the equator with a volume fraction of 0.4 ppb HCl, zero ClO and tropospheric mixing ratios of CFCs at the tropical tropopause.

Amylose and lysophospholipid contents, swelling factor, and dimensions of large A-type and small B-type granules were measured in 21 waxy, normal and high-amylose starches. Amylose and lipid contents were highly correlated, and both were inversely related to swelling factor. Susceptibility of the starch granules to amyloglucosidase was a function of specific surface area, and was not affected by amylose or lipid content. Environmental (climatic and edaphic) effects seen in 16 samples of Triumph barley starch were generally small (coeff. variation < 10%) and not related to weather statistics, except for lysophospholipid content which was positively correlated with accumulated temperature and solar radiation during the grain-filling period and inversely related to swelling factor. Anderung der Zusammensetzung und der physikalischen Eigenschaften von Gerstenstarken. Der Gehalt an Amylose und an Lysophospholipiden, der Quellfaktor und die Abmessungen der grosen A-Typ- und der kleinen B-Typ-Korner wurden in 21 wachsigen, normalen und hochamylosehaltigen Starken ermittelt. Der Amylose- und der Lipidgehalt standen zueinander in Beziehung und verhielten sich umgekehrt proportional zum Quellfaktor. Die Empfindlichkeit der Starkekorner gegenuber Amyloglucosidase war eine Funktion der spezifischen Oberflache und wurde vom Amylose- oder Lipidgehalt nicht beeinflust. Umwelt-klimatische Einflusse, die bei 16 Proben Triumph-Gerstenstarke beobachtet wurden, waren im allgemeinen gering (Variations-Koeffizient < 10%) und standen nicht in Beziehung zu Wetterstatistiken, mit Ausnahme des Gehaltes an Lysophospholipiden, der wahrend der Zeit der Kornfullung der aufgespeicherten Temperatur und der Sonneneinstrahlung proportional und dem Quellfaktor umgekehrt proportional war.

A method for the fabrication of a completely integrated solid-state electrochemical sensor which combines a minature liquid junction reference electrode with a CMOS ISFET is presented. The reference electrode is fabricated by preferentially etching silicon to form a porous silicon frit. The CMOS process provides electrical encapsulation of the ISFET. The performance of the reference electrode and CMOS ISFET as an integrated sensor is demonstrated.

n/a

(1964). Respiratory Metabolism of Fat and Lean Channel Catfish. The Progressive Fish-Culturist: Vol. 26, No. 1, pp. 16-20.