Comparison of three techniques used to measure diffusive gas exchange from sheltered aquatic surfaces

Three approaches commonly used to quantify diffusive gas exchange across aquatic surfaces were compared in a densely treed, low-wind environment Diffusive surface fluxes of carbon dioxide (CO2) and methane (CH4) from a small boreal reservoir were estimated using (i) surface water concentrations, the thin boundary layer (TBL) equation, and gas transfer velocities (k) calculated using sulfur hexafluoride (SF6); (ii) surface water concentrations, the TBL equation, and k estimated from wind speed; and (iii) static floating chambers (FCs). Comparisons were made during three different approximately 10-day intervals (August 2000, June and September 2001). CO2 and CH4 fluxes estimated from SF6-derived k were on average 1-3 times greater than those determined from wind-estimated k Overall agreement between FC CO2 and CH4 flux estimates and those based on SF6 and wind speed derived kvalues was much weaker, with FC CO2 and CH4 flux estimates ranging from -9 to 23 times those based on SF6 and wind-estimated k values. Chamber deployment likely enhanced gas transfer through disturbance of the surface boundary layer, and results of this study suggest that caution must be exercised concerning the use of FCs on very still water surfaces. Furthermore, findings of this study contradict the common belief that use of wind speed to approximate k is inappropriate for small bodies of water characterized by low winds and surface obstructions.     

Gas scattering effects and microstructural evaluation of electron beam evaporated titanium coatings in neon and argon at different gas pressures

Titanium coatings were deposited on stainless steel and glass substrates by electron beam evaporation in vacuum (4×10⁻⁴ Pa) and at different neon and argon gas pressures (from 0.33 to 2.00 Pa). The effect of background gas pressure and type on film microstructure was evaluated by scanning electron microscopy (SEM). Since it was not feasible to maintain a constant evaporation rate for all runs, the ‘deposition efficacy’, a parameter defined as the ratio between coating thickness and mass of material evaporated, was statistically modelled using non-linear regression analysis to determine the effects of gas scattering. The results revealed that neon and argon promote similar scattering of the titanium vapour and this may point to a lower likelihood of gas-phase metal cluster formation in neon. The coating microstructure was found to change from a tapered grain structure, obtained under vacuum conditions, to a faceted one at low gas pressure (0.33 Pa), becoming more porous as gas pressure increased. For a given gas pressure, no significant differences could be observed in coating microstructure between the use of argon or neon. These findings may be significant when considering the use of neon as an alternative gas to argon, for improving reactive gas ionisation (through Penning mechanisms) in Plasma-Assisted Physical Vapour Deposition.     

The effect of cell phone type on drivers subjective workload during concurrent driving and conversing

The effect of three types of cell phones (hand held, hands free with an external speaker and personal hands free) on total subjective workload (including its constituent components; mental demand, physical demand, temporal demand, performance, effort and frustration) and intelligibility was measured using the NASA-task load index (TLX) and the modified rhyme test (MRT), respectively in 13 experienced drivers (nine male, four female, age range 28-65 years), whilst driving on a rural highway. The drivers rated all components of workload for each type of cell phone to be significantly higher than for a control condition in which no cell phone was used. The mean (standard deviation) total workload was lowest for the personal hands free cell phone (7.1(3.65)) and highest for the hands free speaker phone (10.8 (3.63)) (P<0.001). The mean (standard deviation) intelligibility score was highest for the personal hands free cell phone (74.1 (7.9)) and lowest for the hands free speaker phone (55.0 (10.4)) (P<0.001). Frustration was significantly correlated with total workload (0.60, P<0.001) and intelligibility was significantly correlated with frustration (-0.35, P<0.05). Physical demand was not a high contributor to total workload. It is concluded that a personal hands free cell phone would interfere least with the cognitive demands of driving.     

Changes in deposition of phytoplankton constituents in a Ca2+ polluted lake

Systematic reductions in the deposition rate of organic C, N, P, and chlorophyll (Chl) are documented for Ca2+ polluted, culturally eutrophic, Onondaga Lake, NY, based on analyses of weekly sediment trap collections over the May-October interval for 10 years of the 1980-1992 period. Inputs of both nutrient-rich domestic waste and industrial salt waste (including Ca2+) decreased over this period. Constituent ratios of the collected sediment indicate phytoplankton biomass was the dominant source of the deposited organic C, N, and Chl. Substantial decreases in downward fluxes of these constituents occurred starting in 1987: 37, 42, 25, and 54%, on average, for organic C, N, P, and Chl, respectively. These reductions were driven primarily by the decreases in the lake's salinity and Ca2+ concentration, that resulted from the closure of a soda ash manufacturing facility (1986), rather than decreases in water column P concentrations from reductions in domestic waste loading. Three different mechanisms for the decreased deposition, related to the reductions in salinity and Ca2+ concentration, are considered: (i) decrease in coating of phytoplankton with CaCO3 precipitate, (ii) increased grazing of phytoplankton by large cladocerans, and (iii) decreases in coagulation of phytoplankton. The greater loss of phytoplankton biomass through deposition, driven by salt waste inputs from the industry, exacerbated the lake's problem of high primary production. This response is consistent with ecological theory for nutrient saturated phytoplankton growth but has not previously been demonstrated on a whole-lake basis.     

2D vs. 3D Deformable Face Models: Representational Power,Construction, and Real-Time Fitting

Model-based face analysis is a general paradigm with applications that include face recognition, expression recognition, lip-reading, head pose estimation, and gaze estimation. A face model is first constructed from a collection of training data, either 2D images or 3D range scans. The face model is then fit to the input image(s) and the model parameters used in whatever the application is. Most existing face models can be classified as either 2D (e.g. Active Appearance Models) or 3D (e.g. Morphable Models). In this paper we compare 2D and 3D face models along three axes: (1) representational power, (2) construction, and (3) real-time fitting. For each axis in turn, we outline the differences that result from using a 2D or a 3D face model.     

Porometry, porosimetry, image analysis and void network modelling in the study of the pore-level properties of filters

We present fundamental and quantitative comparisons between the techniques of porometry (or flow permporometry), porosimetry, image analysis and void network modelling for seven types of filter, chosen to encompass the range of simple to complex void structure. They were metal, cellulose and glass fibre macro- and meso-porous filters of various types. The comparisons allow a general re-appraisal of the limitations of each technique for measuring void structures. Porometry is shown to give unrealistically narrow void size distributions, but the correct filtration characteristic when calibrated. Shielded mercury porosimetry can give the quaternary (sample-level anisotropic) characteristics of the void structure. The first derivative of a mercury porosimetry intrusion curve is shown to underestimate the large number of voids, but this error can be largely corrected by the use of a void network model. The model was also used to simulate the full filtration characteristic of each sample, which agreed with the manufacturer's filtration ratings. The model was validated through its correct a priori simulation of absolute gas permeabilities for track etch, cellulose nitrate and sintered powder filters.     

PEO coatings obtained on an Mg-Mn type alloy under unipolar and bipolar modes in silicate-containing electrolytes

Protective surface layers with high corrosion resistance (R_p = 3.3·105 ohm cm²) and significant microhardness (H = 4.8 GPa), as compared to the substrate material, were obtained on MA8 magnesium alloy by bipolar Plasma Electrolytic Oxidation (PEO) in a silicate-fluoride electrolyte. The phase and elemental composition and morphology of the coatings were investigated. It was found that the application of the bipolar PEO mode enables one to synthesise on the alloy's surface a high-temperature phase of magnesium silicate, forsterite (Mg₂SiO₄) having good anticorrosion and mechanical properties.     

Subconjunctival mitomycin C for the treatment of ocular cicatricial pemphigoid

PURPOSE: The authors performed a prospective evaluation of the efficacy of treating ocular cicatricial pemphigoid (OCP) with subconjunctival mitomycin C. DESIGN: Unmasked, prospective, internally controlled case series. METHODS: Patients were eligible for treatment with subconjunctival mitomycin C under three criteria: (1) significant complications of systemic immunosuppressant therapy; (2) markedly asymmetric conjunctival disease; and (3) end-stage OCP. All patients received monocular subconjunctival injections of 0.25 ml of 0.2 mg/ml mitomycin C to both the superior and inferior bulbar conjunctivae in the eye with the more severe disease. RESULTS: Nine eyes of nine patients (mean age, 74 years) were treated with subconjunctival mitomycin C to the more-involved eye and were followed for a mean of 23.5 months (range, 12-40 months). Eight of nine patients showed quiescence of their OCP in the treated eye based on serial evaluation of conjunctival cicatrization and grading of conjunctival erythema. Five of the nine untreated eyes showed progression of the conjunctival disease. One patient required concomitant systemic immunosuppressive therapy after subconjunctival mitomycin C. Two patients underwent successful visual rehabilitative surgery in the mitomycin C-treated eye. CONCLUSION: The use of subconjunctival mitomycin C may be effective in preventing progression of conjunctival cicatrization and erythema in patients with OCP. No complications of mitomycin C treatment were noted. Long-term follow-up and further investigation into the efficacy of subconjunctival mitomycin C in the management of OCP is warranted.     

Effects of hostility on ambulatory blood pressure and mood during daily living in healthy adults.

This study (a) tested the effects of hostile attributes on ambulatory blood pressure (BP), heart rate, and mood monitored repeatedly over 3 days in 100 healthy men and women and (b) determined whether the cardiovascular effects of trait hostility were moderated by mood. Multilevel random-coefficients regression analyses showed that hostile individuals exhibited higher systolic and diastolic BP and rated their current moods as more negative and less positive throughout the monitoring. Individuals low in hostility exhibited high BP only during the few occasions when they experienced negative mood. However, these patterns were true only when participants were classified by Potential for Hostility ratings from the Structured Interview (R. H. Rosenman, 1978), not by the Cynical Hostile Attitudes score derived from the Cook-Medley scale. Results provide convergent and ecological validity of interview rating of hostility and illuminate one possible dynamic mechanism by which overt hostile behaviors might contribute to the rates of increased cardiovascular morbidity and mortality. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Light-dependent changes in outer segment free-Ca2+ concentration in salamander cone photoreceptors

Simultaneous measurements of photocurrent and outer segment Ca2+ were made from isolated salamander cone photoreceptors. While recording the photocurrent from the inner segment, which was drawn into a suction pipette, a laser spot confocal technique was employed to evoke fluorescence from the outer segment of a cone loaded with the Ca2+ indicator fluo-3. When a dark-adapted cone was exposed to the intense illumination of the laser, the circulating current was completely suppressed and fluo-3 fluorescence rapidly declined. In the more numerous red-sensitive cones this light-induced decay in fluo-3 fluorescence was best fitted as the sum of two decaying exponentials with time constants of 43 +/- 2.4 and 640 +/- 55 ms (mean +/- SEM, n = 25) and unequal amplitudes: the faster component was 1.7-fold larger than the slower. In blue-sensitive cones, the decay in fluorescence was slower, with time constants of 140 +/- 30 and 1,400 +/- 300 ms, and nearly equal amplitudes. Calibration of fluo-3 fluorescence in situ from red-sensitive cones allowed the calculation of the free-Ca2+ concentration, yielding values of 410 +/- 37 nM in the dark-adapted outer segment and 5.5 +/- 2.4 nM after saturating illumination (mean +/- SEM, n = 8). Photopigment bleaching by the laser resulted in a considerable reduction in light sensitivity and a maintained decrease in outer segment Ca2+ concentration. When the photopigment was regenerated by applying exogenous 11-cis-retinal, both the light sensitivity and fluo-3 fluorescence recovered rapidly to near dark-adapted levels. Regeneration of the photopigment allowed repeated measurements of fluo-3 fluorescence to be made from a single red-sensitive cone during adaptation to steady light over a range of intensities. These measurements demonstrated that the outer segment Ca2+ concentration declines in a graded manner during adaptation to background light, varying linearly with the magnitude of the circulating current.