Undetected Blooms in Prince William Sound: Using Multiple Techniques to Elucidate the Base of the Summer Food Web

© 2015, Coastal and Estuarine Research Federation. Prince William Sound supports many commercially and culturally important species. The phytoplankton community dynamics which support and sustain the high biomass and diversity of this ecosystem are largely unknown. The aim of this study was to describe the phytoplankton community composition during the summer, the time at which this system supports many additional migrants and commercially important fisheries. Phytoplankton community composition (pigments), dissolved nutrients, Secchi depth, total and particulate organic carbon and nitrogen, and export to deep water were measured during the summers of 2008–2010. In addition, natural abundance stable isotopes (δ13C and δ15N) of particulate organic matter (POM) and faunal samples were measured in 2010. The analysis of the phytoplankton community composition using multivariate statistics showed that changes over the summer were driven by changes in the proportion of the dominant groups: diatoms, dinoflagellates, cyanobacteria, cryptophytes, chlorophytes, and prasinophytes. These changes were driven by changes in nutrients including an organic nitrogen source, phosphate, and silica and correspond to shifts in particulate concentrations. A consistent pattern was observed each year: a large Noctiluca sp. bloom in June concurrent with low nutrients, low diversity, and high particulate organic carbon (POC) concentrations was followed by a shift in the phytoplankton community to a more diverse smaller size class community in July and equilibrating in August. This annual summer bloom could be an important contributor to the energy and nutrient inputs at the base of the regional marine food web

Factors controlling tropospheric O3, OH, NOx, and SO2 over the tropical Pacific during PEM-Tropics B

Observations over the tropical Pacific during the Pacific Exploratory Mission (PEM)-Tropics B experiment (March-April 1999) are analyzed. Concentrations of CO and long-lived nonmethane hydrocarbons in the region are significantly enhanced due to transport of pollutants from northern industrial continents. This pollutant import also enhances moderately O3 concentrations but not NOx concentrations. It therefore tends to depress OH concentrations over the tropical Pacific. These effects contrast to the large enhancements of O3 and NOx concentrations and the moderate increase of OH concentrations due to biomass burning outflow during the PEM-Tropics A experiment (September-October 1996). Observed CH3I concentrations, as in PEM-Tropics A, indicate that convective mass outflux in the middle and upper troposphere is largely independent of altitude over the tropical Pacific. Constraining a one-dimensiohal model with CH3I observations yields a 10-day timescale for convective turnover of the free troposphere, a factor of 2 faster than during PEM-Tropics A. Model simulated HO2, CH2O, H2O2, and CH3OOH concentrations are generally in agreement with observations. However, simulated OH concentrations are lower (∼25%) than observations above 6 km. Whereas models tend to overestimate previous field measurements, simulated HNO3 concentrations during PEM-Tropics B are too low (a factor of 2-4 below 6 km) compared to observations. Budget analyses indicate that chemical production of O3 accounts for only 50% of chemical loss; significant transport of O3 into the region appears to take place within the tropics. Convective transport of CH3OOH enhances the production of HOx and O3 in the upper troposphere, but this effect is offset by HOx loss due to the scavenging of H2O2. Convective transport and scavenging of reactive nitrogen species imply a necessary source of 0.4-1 Tg yr-1 of NOx in the free troposphere (above 4 km) over the tropics. A large fraction of the source could be from marine lightning. Oxidation of DMS transported by convection from the boundary layer could explain the observed free tropospheric SO2 concentrations over the tropical Pacific. This source of DMS due to convection, however, would imply in the model free tropospheric concentrations much higher than observed. The model overestimate cannot be reconciled using recent kinetics measurements of the DMS-OH adduct reaction at low pressures and temperatures and may reflect enhanced OH oxidation of DMS during convection. Copyright 2001 by the American Geophysical Union

Quantum whistling in superfluid 4He

Fundamental considerations predict that macroscopic quantum systems such as superfluids and the electrons in superconductors will exhibit oscillatory motion when pushed through a small constriction. Here we report the observation of these oscillations between two reservoirs of superfluid 4He partitioned by an array of nanometer-sized apertures. They obey the Josephson frequency equation and are coherent amongst all the apertures. This discovery at the relatively high temperature of 2K (2000 times higher than related phenomena in 3He) may pave the way for a new class of practical rotation sensors of unprecedented precision.Comment: 6 pages, 3 figures, to be published in Natur

Seasonal differences in the photochemistry of the South Pacific: A comparison of observations and model results from PEM-Tropics A and B

A time-dependent photochemical box model is used to examine the photochemistry of the equatorial and southern subtropical Pacific troposphere with aircraft data obtained during two distinct seasons: the Pacific Exploratory Mission-Tropics A (PEM-Tropics A) field campaign in September and October of 1996 and the Pacific Exploratory Mission-Tropics B (PEM-Tropics B) campaign in March and April of 1999. Model-predicted values were compared to observations for selected species (e.g., NO2, OH, HO2) with generally good agreement. Predicted values of HO2 were larger than those observed in the upper troposphere, in contrast to previous studies which show a general underprediction of HO2 at upper altitudes. Some characteristics of the budgets of HOx, NOx, and peroxides are discussed. The integrated net tendency for O3 is negative over the remote Pacific during both seasons, with gross formation equal to no more than half of the gross destruction. This suggests that a continual supply of O3 into the Pacific region throughout the year must exist in order to maintain O3 levels. Integrated net tendencies for equatorial O3 showed a seasonality, with a net loss of 1.06×1011 molecules cm-2 s-1 during PEM-Tropics B (March) increasing by 50% to 1.60×1011 molecules cm-2 s-1 during PEM-Tropics A (September). The seasonality over the southern subtropical Pacific was somewhat lower, with losses of 1.21×1011 molecules cm-2 s-1 during PEM-Tropics B (March) increasing by 25% to 1.51×1011 molecules cm-2 s-1 during PEM-Tropics A (September). While the larger net losses during PEM-Tropics A were primarily driven by higher concentrations of O3, the ability of the subtropical atmosphere to destroy O3 was ∼30% less effective during the PEM-Tropics A (September) campaign due to a drier atmosphere and higher overhead O3 column amounts. Copyright 2001 by the American Geophysical Union

Computer skills and internet use in adults aged 50-74 years: influence of hearing difficulties

BACKGROUND The use of personal computers (PCs) and the Internet to provide health care information and interventions has increased substantially over the past decade. Yet the effectiveness of such an approach is highly dependent upon whether the target population has both access and the skill set required to use this technology. This is particularly relevant in the delivery of hearing health care because most people with hearing loss are over 50 years (average age for initial hearing aid fitting is 74 years). Although PC skill and Internet use by demographic factors have been examined previously, data do not currently exist that examine the effects of hearing difficulties on PC skill or Internet use in older adults. OBJECTIVE To explore the effect that hearing difficulty has on PC skill and Internet use in an opportunistic sample of adults aged 50-74 years. METHODS Postal questionnaires about hearing difficulty, PC skill, and Internet use (n=3629) were distributed to adults aged 50-74 years through three family physician practices in Nottingham, United Kingdom. A subsample of 84 respondents completed a second detailed questionnaire on confidence in using a keyboard, mouse, and track pad. Summed scores were termed the "PC confidence index." The PC confidence index was used to verify the PC skill categories in the postal questionnaire (ie, never used a computer, beginner, and competent). RESULTS The postal questionnaire response rate was 36.78% (1298/3529) and 95.15% (1235/1298) of these contained complete information. There was a significant between-category difference for PC skill by PC confidence index (P<.001), thus verifying the three-category PC skill scale. PC and Internet use was greater in the younger respondents (50-62 years) than in the older respondents (63-74 years). The younger group's PC and Internet use was 81.0% and 60.9%, respectively; the older group's PC and Internet use was 54.0% and 29.8%, respectively. Those with slight hearing difficulties in the older group had significantly greater odds of PC use compared to those with no hearing difficulties (odds ratio [OR]=1.57, 95% confidence interval [CI] 1.06-2.30, P=.02). Those with moderate+ hearing difficulties had lower odds of PC use compared with those with no hearing difficulties, both overall (OR=0.58, 95% CI 0.39-0.87, P=.008) and in the younger group (OR=0.49, 95% CI 0.26-0.86, P=.008). Similar results were demonstrated for Internet use by age group (older: OR=1.57, 95% CI 0.99-2.47, P=.05; younger: OR=0.32, 95% CI 0.16-0.62, P=.001). CONCLUSIONS Hearing health care is of particular relevance to older adults because of the prevalence of age-related hearing loss. Our data show that older adults experiencing slight hearing difficulty have increased odds of greater PC skill and Internet use than those reporting no difficulty. These findings suggest that PC and Internet delivery of hearing screening, information, and intervention is feasible for people between 50-74 years who have hearing loss, but who would not typically present to an audiologist

HVOF and laser cladded Fe-Cr-B coating in simulated biomass combustion: microstructure and fireside corrosion

Biomass is often considered as a low carbon alternative to fossil fuels in the power industry. However the heat exchangers in biomass plants can suffer from chloride based aggressive fireside corrosion. A commercially available amorphous Fe-Cr-B alloy was deposited onto a stainless steel substrate by HVOF thermal spray and laser cladding. The controlled environment corrosion tests were conducted in a HCl rich environment at 700°C for 250 h with and without KCl deposits. The samples were examined with XRD, SEM and EDX mapping to understand the corrosion mechanisms. In the absence of any deposits, the amorphous HVOF coating performed very well with a thin oxide growth whereas the crystalline laser cladding suffered from ~350 μm metal loss. The scales were composed of MnWO₄, Fe₂O₃, Fe₃O₄ and Cr₂O₃. When a KCl deposit was present, the HVOF sprayed coating delaminated from the substrate and MnCl₂ was found in the scale