Vertical Uniformity Research Articles

Absorption Spectral Study of Mixed Chiral Amino Acid Porphyrin Langmuir-Blodgett Films

Absorption spectra were performed on Langmuir-Blodgett films of a new chiral amino acid porphyrin (Py) and its mixture with stearic acid (SA). Vertical uniformity of the LB films has been demonstrated by the linear relationship between the absorbance and the layer number of films. J-Aggregates were present when the film was transferred at various surface pressures and at different molar ratios of Py and SA. However, no aggregation was present for the molecules in the adjacent monolayers. the observed optical absorption spectra of mixed films were markedly dependent on the combination of Py. When the molar ratio of Py was increased from 0.05 to 0.75, the absorption peaks of Soret and Q bands bathochromically shifted ca. 5.5 and 2.2 nm. When the deposited pressure was increased from 5 to 35 mN/m, the absorption peaks of Soret and Q bands bathochromically shifted ca. 3.7, 3.2 nm and 3.5, 2.2 nm for pure Py and 1:3 Py-SA mixed LB films, respectively. on a hydrophobic substrate, the LB films showed a red shift of ca. 4.5 nm for Soret band compared with that on the hydrophilic substrate owing to their different environments.

Model analysis of the influence of gas diffusivity in soil on CO and H2 uptake

CO and H2 uptake by soil was studied as a diffusion process. A diffusion model was used to determine how the surface fluxes (net deposition velocities) were controlled by in-situ microbial uptake rates and soil gas diffusivity calculated from the 3-phase system (solid, liquid, gas) in the soil. Analytical solutions of the diffusion model assuming vertical uniformity of soil properties showed that physical properties such as air-filled porosity and soil gas diffusivity were more important in the uptake process than in the emission process. To incorporate the distribution of in-situ microbial uptake, we used a 2-layer model incorporating “a microbiologically inactive layer and an active layer” as suggested from experimental results. By numerical simulation using the 2-layer model, we estimated the effect of several factors on deposition velocities. The variations in soil gas diffusivity due to physical properties, i.e., soil moisture and air-filled porosity, as well as to the depth of the inactive layer and in-situ microbial uptake, were found to be important in controlling deposition velocities. This result shows that the diffusion process in soil is critically important for CO and H2 uptake by soil, at least in soils with higher in-situ uptake rates and/or with large variation in soil moisture. Similar uptake rates and the difference in deposition velocity between CO and H2 may be attributable to differences in CO and H2 molecular diffusivity. The inactive layer is resistant to diffusion and creates uptake limits in CO and H2 by soil. The coupling of high temperature and a thick inactive layer, common in arid soils, markedly lowers net CO deposition velocity. The temperature for maximum uptake of CO changes with depth of the inactive layer.

Green and Ampt infiltration into soils of variable pore size with depth

Most expressions for infiltration rely upon the assumption of vertical uniformity in soil texture and hydraulic properties. We present an extension of the results of Beven [1982, 1984] for infiltration and lateral flow in soils with decreasing permeability with depth. Unlike Beven, we base the derivations upon joint changes in soil properties based on an overall change in characteristic pore size via Miller scaling. A set of very simple expressions for the time rate of infiltration are obtained using a Green and Ampt approach for soils with permeability that decreases with depth following linear, power law, and exponential relationships.

Influence of several compounds on the fluorescence of rare earth complexes Eu(TTA) 3Phen and Sm(TTA) 3Phen in LB films

Five different compounds, included here arachidic acid (AA), tri-n-octyl phosphine oxide (TOPO), a kind of long chain Schiff base (SB), 5,10,15,20-tetra-4-oxy (2-stearic acid) phenyl porphyrin (TPP(−COOH)), and a long chain ferrocene derivative (Fc), were introduced into Langmuir—Blodgett (LB) films containing luminous rare earth complex Eu(TTA) 3Phen or Sm(TTA) 3Phen alternating with arachidic acid (AA). The subphase used was a composite subphase: an aqueous solution saturated with 1,10-phenanthroline, 2-thenoyltrifluoroacetone, and the complex Eu(TTA) 3Phen or Sm(TTA) 3Phen. Low angle X-ray diffraction results show that all the LB films have a periodic layer structure. Vertical uniformity of these LB films has been demonstrated by UV—Vis and fluorescence emission spectra. Both absorbance and relative fluorescence intensity increase linearly with the number of LB layers. The results of fluorescence spectra also indicate that, TOPO and SB have a fluorescence enhancement effect on the complexes, while TPP(−COOH) and Fc have a strong fluorescence quenching effect. AA does not influence the fluorescence of the complexes.

Fabrication and fluorescence characterization of the LB films of luminous rare earth complexes Eu(TTA) 3Phen and Sm(TTA) 3Phen

High quality and intensely fluorescent Langmuir-Blodgett (LB) films of Eu(TTA) 3Phen/AA (in molar ratio 1:1) (AA, arachidic acid) and Sm(TTA) 3Phen/AA (1:1) were fabricated successfully by using the composite subphase that, here, denotes the aqueous solution saturated with Phen (1,10-phenanthroline), TTA ( α-thenoyltrifluoroacetone) and Eu(TTA) 3Phen or Sm(TTA) 3Phen. FTIR results indicate that hydrogen bonds form between -CF 3 of the title complexes and -COOH of AA in these LB films. Low-angle X-ray diffraction results show that these LB films all have a periodic layer structure. The vertical uniformity of these LB films has been demonstrated by UV-Vis spectra and fluorescence emission spectra. Both absorbance and relative fluorescence intensity increase linearly with the number of LB layers. The two LB films can give off strong fluorescence, even though only one layer of LB film gives off strong fluorescence on ultraviolet irradiation. Strong fluorescence emission can be detected from this LB film by using a fluorescence spectrophotometer. Bright fluorescence spots can also be observed within the view field of a fluorescence microscope. However, when comparing one with the other, the fluorescence intensity of Eu(TTA) 3Phen LB films is stronger than that of Sm(TTA) 3Phen LB films. The intensity of the former is nearly 25 times the intensity of the latter.

Tornado-like Vortexgenesis in a Simplified Numerical Model

A novel approach to the modeling of tornado-like vortexgenesis has been developed and is used to articulate the sequence of events that leads to tornadogenesis. The “pseudostorm” is an idealized thunderstorm representation and emulates the storm-relative flow, into an updraft, of the horizontal streamwise vorticity that is baroclinically generated in cold air outflow. By not explicitly simulating the morphology of a tornadic thunderstorm, but instead concentrating on the development of low-level rotation and tornado-scale vortices, the authors are able to transcend many of the experimental limitations encountered by cloud modelers. Intense, near-ground, cyclonic vortices, which are classified herein as “tornado like,” evolve solely from horizontal streamwise vorticity due to buoyancy gradients and friction, if present, at the lower boundary. Regardless of the lower boundary condition, none of the vortices exceed the thermodynamic speed limit based on the vertically integrated buoyancy (or convective available potential energy). Sensitivity experiments reveal that the tornado-like pseudostorm vortices develop only when certain updraft propagation rates (and thus storm-relative flow strengths), downdraft intensifies, and fluid viscosities are well matched. The simplicity of the pseudostorm allows one to look closely at the actual genesis of a vortex. In particular, it is found that the such genesis is not “triggered,” but is instead the outcome of a continuous (albeit rapid) process of amplification of vertical vorticity generated initially through tilting. Also, vertical vorticity intensification proceeds with a large degree of vertical uniformity, obviating the need for a mechanism like the “dynamic pipe effect” to advance the incipient tornado-like vortex toward the ground.

Vertical three-terminal structures in semiconductor heterostructure quantum wells using a novel sidewall gating technique

We present the application of a self-aligned sidewall gating technique in the fabrication of gated resonant tunneling devices with active mesa areas in the sub-micron regime. This technique should prove useful for the fabrication of variable area, vertical quasi one- and two-dimensional structures. We present current-voltage curves of gated devices at room temperature and liquid nitrogen temperatures for conduction in both directions through the double barrier structure. An analysis demonstrating the vertical uniformity of the gate field around the double barrier structure, a discussion on the possible extension of the technique to low-dimensional structures and the limits of application are presented.

Langmuir-Blodgett Film and Second Harmonic Generation of a Europium Hemicyanine Complex, Me2NC6H4CH:CHC5H4NC16H33+Eu(NTA)4-

An amphiphilic lanthanide complex, (E)-N-hexadecyl-4-[2-(4-(dimethylamino)phenyl)ethenyllpyridinium tetrakis(8-naphthany1trifluoroacetone)europium (abbreviated as H1sEu(NTA)d), was synthesized and characterized. The film formation property is good and ita vertical uniformity has been demonstrated by UV-vis spectra. The second-order molecular hyperpolarizability 8 has been evaluated to be (6-9) X 10-28 esu, which is about 1.5 times bigger than that of the iodide anion substituted complex.

Performance of a wide-field flux delivery system for synchrotron x-ray lithography

An x-ray flux delivery system consisting of a compact storage ring and dedicated beamlines is now in routine use in the IBM Advanced Lithography Facility in East Fishkill, New York. The beamlines have been designed for use with a stepper that scans the mask and wafer vertically through a stationary beam. The performance of the system from a lithographic standpoint is reported. The measured size and stability of the synchrotron x-ray source will be presented, and the design and performance of the beamlines will be discussed. The beamlines have been designed to provide high intensity, uniform illumination over a wide field. The overall performance of the system has been evaluated by measuring the flux at the mask plane in the stepper. A horizontal uniformity of better than ±2% over a field more than 50 mm wide has been achieved; the vertical uniformity is limited by the uniformity of the stepper scanning mechanism. The delivered mask-incident flux per milliampere of stored beam current has been found to be 1.5 mW/(mA cm), approximately four times greater than obtained with a simple planar mirror. A 100 mJ/cm2 resist with a mask transmission of 50% therefore requires a less than 2 s exposure (plus overscan overhead) for a 2.5 cm high field at a typical stored current of 200 mA, independent of the field width (up to the maximum of more than 50 mm). In addition, the source has proved itself to be highly reliable, with beam available for 99% of the scheduled time over the most recent seven month period.

Spatial and Vertical Trends in Sediment-Phase Contaminants in the Upper Estuary of the St. Lawrence River

The concentration of selected contaminant trace metals and organic contaminants, namely polycyclic aromatic hydrocarbons (PAHs), normal-alkanes, total polychlorinated biphenyls (PCBs), and other organochlorines, was studied in cores from shallow-water fine-grain sediments from both sides of the maximum turbidity zone (MTZ) in the upper estuary of the St. Lawrence. Average trace metal concentrations in the cores were generally lower in downstream sediments, except for Hg and Pb. Hg levels in the cores were very high, exceeding 0.7 μg g−1 in core C168 (south shore) and 0.19 μg g−1 in core LE (north shore). Trace metal concentrations in all the cores were highly variable with depth, but after normalization with reference to iron, the trend was remarkably uniform, thus confirming an important inverse relationship with grain size. A similar lack of a well-defined trend was noted in the profiles of the organic components in the modern sediments. Average PAH values for modern sediments at core sites C168 and LO were 1.05 μg g−1 and 0.44 μg g−1, respectively (i.e., less than or equal to those in Lake Ontario and upstream in the river). PCB values far exceeded those in upstream sediments (average: 347 ng g−1 in core LE and 158 ng g−1 in C168), but were less than in Lake Ontario. Concentrations of chlordane, heachlorobenzene, and mirex were relatively low and uniform in the modern sections of the cores. The vertical uniformity of both the contaminant profiles and those for Cs-137 (C168) suggests that the sediments are relatively young (i.e., definitely less than 35 yr at C168, and probably even less at LE and LO). Therefore no long-term or historical trend is evident.

High-reflectance GaInP/GaAs distributed Bragg reflector

A high-reflectance GaInP/GaAs distributed Bragg reflector (DBR) was grown by chemical beam epitaxy (CBE). The mirror consists of 40 pairs of alternating layers and was designed for a centre wavelength of 980 nm, resulting in a total thickness of 5.8 μm. Highly stable growth conditions led to a maximum reflectance of 0.99 and to a variation in the centre wavelength of only 5 nm over the 2″ (50.8 mm) wafer. Transmission electron microscopy and X-ray diffraction measurements confirmed the vertical uniformity and the crystallographic quality of the sample.

Influence of nonuniform charge distribution in In 0.53Ga 0.47As on the interpretation of dopant incorporation

The electrical properties of In 0.53Ga 0.47As grown on full two-inch InP wafers have been studied. Special emphasis was placed on investigations of the vertical and lateral uniformity of the material quality. Using the Mobility Spectrum Technique, a way of unambiguously analyzing Hall effect data from samples with multiple conduction paths, a conducting substrate-epi interface layer was found in some In 0.53G 0.47As films. Despite the presence of the interface layer, good, vertically uniform mobilities in n-doped samples were still measured in the film. A large-scale lateral nonuniformity in the sheet resistance was associated with variations in the interface layer. A 1.5 μm thick undoped In 0.52Ga 0.47As layer with an In 0.52Al 0.48As buffer layer exhibited a 77K mobility of 65,100 cm 2/V⋯s with no sign of interface conduction. Some lateral nonuniformity in the sheet resistance similar to the doped sample was still observed, indicating that the substrate surface quality still affects the film quality to some degree. However, the lateral variations in films with AlInAs buffers are much smaller and are not expected to affect, e.g., modulation-doped structures.

A field study of photochemical smog formation under stagnant meteorological conditions

Photochemical air pollution episodes during 15–20 July 1981, covering the Tokyo Metropolitan Area under the stagnant meteorological conditions, were analyzed. Three-dimensional (3-D) pollutant and meteorological observations showed that polluted air masses followed sea and land breeze circulation patterns. Aged secondary pollutants were detected aloft from midnight until early morning. These pollutants subsequently entrained into the daytime mixed layer and affected O 3 formation. To understand this stagnating system, a simple trajectory model was used. Simulated results showed good qualitative agreement with observations, but the model overestimated the surface concentration and underestimated the aircraft observations. This was mainly caused by the assumption of vertical uniformity within the model.

Electrically active multilayer n-GaAs–p-AlGaAs quarter wave mirrors grown by molecular beam epitaxy

A novel optoelectronic structure is presented, based on an optical interference filter with a stack of quarter-wave p–n heterojunctions in the GaAs–AlGaAs III–V semiconductor system. In a 40 layer structure with a peak reflectivity at 1.3 μm, good vertical period uniformity and crystalline quality was confirmed by optical reflectance peak widths, transmission electron microscope cross sections, and double crystal rocking curves. The structure is electro-optically active near the GaAs band gap and optically passive at longer wavelengths. Electrical bistability was observed. The potential device applications include electrically tunable optical filters for optoelectronic switching, modulation, and selective wavelength detection.

Phototherapy units: Comparison of fluorescent ultraviolet B and ultraviolet A units with a high-pressure mercury system

Comparison in ultraviolet (UV) dosimetry is reported for three different phototherapy machines. Two of the machines used UV-emitting fluorescent tubes in a standard upright cabinet formation. One of these machines was equipped with predominately UVB-emitting fluorescent tubes and the other with predominately UVA-emitting tubes. The third machine consisted of a series of vertically mounted high-pressure mercury halide lamps equipped with two different filters for selection of wavelengths between 295 and 400 nm or 320 and 400 nm. The horizontal UV output of the mercury halide and UVB fluorescent units was reduced between the UV-emitting areas, and it is advised that patients rotate when using these units. It was determined that the vertical uniformity and intensity of UV emission was superior in the mercury halide unit compared with the fluorescent tubed units.

Evaluation of a Modified Air Carrier Sprayer in Sugarcane

ABSTRACT AN air carrier sprayer was modified to allow spraying over the top of mature sugarcane. The sprayer was evaluated with three different nozzle systems, two fan heights, and two liquid carriers. Three replications were made. Distribution uniformity was inadequate with all combinations of variables tested. There were no statistical differences in vertical uniformity, lateral uniformity, or mean droplet stain diameter for the variables tested.

Laminar free-convective heat transfer in vertical Uniform Heat Flux ducts. Numerical solutions with constant/variable fluid properties.

A numerical analysis is made of laminar free convection in vertical ducts with Uniform Heat Flux, in consideration of temperature-dependence of fluid thermophysical properties. The local Nusselt number of Constant Property Solutions can be wall correlated with the dimensionless parameters derived by the authors, regardless of the exit Rayleigh number, Prandtl number, and circular tube or parallel plates. The CPS of free-convective heat transfer is close to that of forced convective heat transfer in UHF-dusts. The local Nusselt number of Variable Property Solutions can be well correlated by the usual correction method used for forced convective heat transfer in duct. The difference in the heat transfer characteristics of UHF-ducts between CPS and VPS in not so large as those of Uniform Wall Temperature ducts.

Measured distribution of water turbidity in Gulf St Vincent

Large- and small-scale surveys of the horizontal and vertical distributions of turbidity in the waters of Gulf St Vincent in South Australia have been made under conditions of light winds and smooth to slight seas. The turbidity was characterized by the beam attenuation coefficient at a wavelength of 530 nm, which was determined from measurements made with a transmissometer operated from a boat. The results were evaluated with reference to independent measurements of water density distributions and circulation patterns in the Gulf. The measured values of the beam attenuation coefficient lay between 0.12 and 2.0 m-1, although most lay between 0.2 and 0.7 m-1. Both horizontal stratification and vertical uniformity of turbidity were observed and explanations for these two conditions are offered. The relative importance of several influences on water turbidity are assessed; the most important in Gulf St Vincent appear to be the type of bottom sediment, wave action on the sediment, and water currents.

Comparison of cw laser-annealed and electron-beam annealed Si

Si samples implanted with As+ have been annealed with a modified commercial scanning electron microscope and with a scanning cw Ar+ laser. A comparison of these two techniques is presented, using electron-beam-induced current as a probe of minority-carrier effects. With a minimum of parameter optimization, it is found that electron-beam annealing is usually superior to laser annealing with respect to both lateral and vertical uniformity.

Axisymmetric Plume Flow in a Vertical Uniform Free Stream

Axisymmetric Plume Flow in a Vertical Uniform Free Stream