Cross-shelf and out-of-bay transport driven by an open-ocean current

Author Posting. © American Meteorological Society, 2011. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 41 (2011): 2168–2186, doi:10.1175/JPO-D-11-08.1.This paper studies the interaction of an Antarctic Circumpolar Current (ACC)–like wind-driven channel flow with a continental slope and a flat-bottomed bay-shaped shelf near the channel’s southern boundary. Interaction between the model ACC and the topography in the second layer induces local changes of the potential vorticity (PV) flux, which further causes the formation of a first-layer PV front near the base of the topography. Located between the ACC and the first-layer slope, the newly formed PV front is constantly perturbed by the ACC and in turn forces the first-layer slope with its own variability in an intermittent but persistent way. The volume transport of the slope water across the first-layer slope edge is mostly directly driven by eddies and meanders of the new front, and its magnitude is similar to the maximum Ekman transport in the channel. Near the bay’s opening, the effect of the topographic waves, excited by offshore variability, dominates the cross-isobath exchange and induces a mean clockwise shelf circulation. The waves’ propagation is only toward the west and tends to be blocked by the bay’s western boundary in the narrow-shelf region. The ensuing wave–coast interaction amplifies the wave amplitude and the cross-shelf transport. Because the interaction only occurs near the western boundary, the shelf water in the west of the bay is more readily carried offshore than that in the east and the mean shelf circulation is also intensified along the bay’s western boundary.Y. Zhang acknowledges the support of the MIT-WHOI Joint Program in Physical Oceanography and NSF OCE-9901654 and OCE- 0451086. J. Pedlosky acknowledges the support of NSF OCE-9901654 and OCE-0451086

Probability Distribution Characteristics for Surface Air–Sea Turbulent Heat Fluxes over the Global Ocean

To analyze the probability density distributions of surface turbulent heat fluxes, the authors apply the twoparametric modified Fisher–Tippett (MFT) distribution to the sensible and latent turbulent heat fluxes recomputed from 6-hourly NCEP–NCAR reanalysis state variables for the period from 1948 to 2008. They derived the mean climatology and seasonal cycle of the location and scale parameters of the MFT distribution. Analysis of the parameters of probability distributions identified the areas where similar surface turbulent fluxes are determined by the very different shape of probability density functions. Estimated extreme turbulent heat fluxes amount to 1500–2000 W m22 (for the 99th percentile) and can exceed 2000 W m22 for higher percentiles in the subpolar latitudes and western boundary current regions. Analysis of linear trends and interannual variability in the mean and extreme fluxes shows that the strongest trends in extreme fluxes (more than 15 W m22 decade21) in the western boundary current regions are associated with the changes in the shape of distribution. In many regions changes in extreme fluxes may be different from those for the mean fluxes at interannual and decadal time scales. The correlation between interannual variability of themean and extreme fluxes is relatively low in the tropics, the SouthernOcean, and the Kuroshio Extension region.Analysis of probability distributions in turbulent fluxes has also been used in assessing the impact of sampling errors in theVoluntaryObserving Ship (VOS)-based surface flux climatologies, allowed for the estimation of the impact of sampling in extreme fluxes. Although sampling does not have a visible systematic effect onmean fluxes, sampling uncertainties result in the underestimation of extreme flux values exceeding 100 W m22 in poorly sampled regions

Examination of Countermovement Jump Performance Changes in Collegiate Female Volleyball in Fatigued Conditions

The purpose of this investigation was to examine changes in countermovement vertical jump performance after a single sport-specific training session in a sample of collegiate female volleyball athletes. Eleven NCAA Division I volleyball athletes performed countermovement vertical jumps with and without an arm swing prior to and immediately after a sport-specific training session. Each participant completed two jumps in each condition using a portable force platform. Paired samples t-tests were performed within each jump condition. When using an arm swing, mean braking force was the only variable to display a statistically significant change (p p p < 0.05). Additionally, a single-subject analysis was performed across all eleven participants resulting in general trends seen in the no-arm-swing condition, whereas the arm-swing condition displayed inconsistent findings across participants

COMPARISON OF INSTABILITY DEVICES ON MEASURES OF SINGLE LIMB POSTURE SWAY PARAMETERS

BACKGROUND: Single limb balance training is an integral part of both the prevention and rehabilitation process of lower extremity injuries. Practitioners use instability devices to provide a progressive overload to an individual during single limb balance training sessions. Previous investigations have shown that when using instability devices differences may or may not exist in postural sway parameters during use depending on the specific devices being assessed. Thus, this investigation sought to examine differences between a commonly used foam pad and a novel instability device (block) in measures of postural sway. METHODS: 22 healthy individuals with no history of lower extremity injury and neurological disorders participated in this investigation (age 21.66 ± 0.74 years, height 167.07 ± 10.74 cm, body 67.76 ± 13.45 kg). Participants performed three conditions of single limb static balance on a force platform sampling at 120 Hz. Each condition contained three 20 second trials separated by thirty seconds. The mean center of pressure (CoP) values of the three trials in each condition were then compared using a within-subjects repeated measures analysis of variance. RESULTS: Statistically significant differences were seen in sway area between conditions (f(2,42) = 5.28, p = 0.009), with the control (9.64 ± 4.53 cm) being significantly lower than both the foam pad (13.05 cm ± 4.25 cm) and block (12.33 ± 3.37 cm). Statistically significant differences were seen in CoP path length between conditions (f(2,42) = 5.52, p = 0.007), with the control (67.51 ± 9.49 cm) being significantly lower than both the foam pad (74.36 cm ± 9.76 cm) and block (76.38 ± 14.84 cm). Maximal medial-lateral CoP displacements were significantly different between conditions (f(2,42) = 6.24, p = 0.004). Lower displacements were seen in the control (1.39 ± 0.20 cm), which was statistically different from both foam pad (1.59 ± 0.24 cm) and block (1.53 ± 0.25 cm). Maximal anterior-posterior CoP displacements were not significantly different between conditions (f(2,42) = 1.50, p = 0.23). CONCLUSIONS: This investigation provides supporting evidence that different instability devices may provide similar changes in postural sway parameters in comparison to control conditions. The novel block instability device used in this investigation may be used in a similar fashion to the traditional foam pad in both prevention and rehabilitation settings based on no differences being found between the two devices

Air-sea interaction and circulation changes in the northeast Atlantic

The upper ocean of the Rockall Trough exhibits coherent interannual variations in temperature and salinity over the past 26 years, with highs in the mid-1980s and late 1990s and lows in the late 1970s and early 1990s, and with ranges of ±0.5°C and ±0.05 in salinity. The origins of the interannual changes are discussed, covering three potential influencing factors: the propagation of anomalies developed upstream of the basin, the effect of local air-sea interaction, and the result of changes of regional circulation bringing different water masses into the region. The changes in heat and freshwater content of the upper ocean are directly compared to observed variations in air-sea heat and freshwater fluxes over the period of the time series. It is shown that the role of the atmosphere in locally altering the oceanic properties, particularly salinity, is relatively small and insufficient to explain the changes. Two recent hydrographic surveys are analyzed to ascertain how the distribution of water masses to the south of the basin may influence the properties of the northern Rockall Trough upper ocean, and the results are reviewed in the context of historical analyses. It is found that the critical factor in determining the properties is the varying amount of relatively cool and fresh North Atlantic Current water mixing with the dominant water mass, the warm saline Eastern North Atlantic Central Water at the entrance to the basin. Variations of inflowing water masses are caused by east-west changes in the location of the subpolar front, and the relationship of these changes in regional circulation to the North Atlantic wind stress field is discussed

Enamel alteration following tooth bleaching and remineralization

The purpose of this study was to compare the effects of professional tooth whitening agents containing highly concentrated hydrogen peroxide (with and without laser activation), on the enamel surface; and the potential of four different toothpastes to remineralize any alterations. The study was performed on 50 human molars, divided in two groups: treated with Opalescence® Boost and Mirawhite® Laser Bleaching. Furthermore, each group was divided into five subgroups, a control one and 4 subgroups remineralized with: Mirasensitive® hap+, Mirawhite® Gelleѐ, GC Tooth Mousse™ and Mirafluor® C. The samples were analysed by SEM/3D-SEM-micrographs, SEM/EDX-qualitative analysis and SEM/EDX-semiquantitative analysis. The microphotographs show that both types of bleaching cause alterations: emphasized perikymata, erosions, loss of interprizmatic substance; the laser treatment is more aggressive and loss of integrity of the enamel is determined by shearing off the enamel rods. In all samples undergoing remineralization deposits were observed, those of toothpastes based on calcium phosphate technologies seem to merge with each other and cover almost the entire surface of the enamel. Loss of integrity and minerals were detected only in the line-scans of the sample remineralized with GC Tooth Mousse™. The semiquantitative EDX analysis of individual elements in the surface layer of the enamel indicates that during tooth-bleaching with HP statistically significant loss of Na and Mg occurs, whereas the bleaching in combination with a laser leads to statistically significant loss of Ca and P. The results undoubtedly confirm that teeth whitening procedures lead to enamel alterations. In this context, it must be noted that laser bleaching is more aggressive for dental substances. However, these changes are reversible and can be repaired by application of remineralization toothpastes

Assessing the Potential Roles of Silicon and Germanium Phthalocyanines in Planar Heterojunction Organic Photovoltaic Devices and How Pentafluoro Phenoxylation Can Enhance π–π Interactions and Device Performance

In this study, we have assessed the potential application of dichloro silicon phthalocyanine (Cl₂-SiPc) and dichloro germanium phthalocyanine (Cl₂-GePc) in modern planar heterojunction organic photovoltaic (PHJ OPV) devices. We have determined that Cl₂-SiPc can act as an electron donating material when paired with C₆₀ and that Cl₂-SiPc or Cl₂-GePc can also act as an electron acceptor material when paired with pentacene. These two materials enabled the harvesting of triplet energy resulting from the singlet fission process in pentacene. However, contributions to the generation of photocurrent were observed for Cl₂-SiPc with no evidence of photocurrent contribution from Cl₂-GePc. The result of our initial assessment established the potential for the application of SiPc and GePc in PHJ OPV devices. Thereafter, bis­(pentafluoro phenoxy) silicon phthalocyanine (F₁₀-SiPc) and bis­(pentafluoro phenoxy) germanium phthalocyanine (F₁₀-GePc) were synthesized and characterized. During thermal processing, it was discovered that F₁₀-SiPc and F₁₀-GePc underwent a reaction forming small amounts of difluoro SiPc (F₂-SiPc) and difluoro GePc (F₂-GePc). This undesirable reaction could be circumvented for F₁₀-SiPc but not for F₁₀-GePc. Using single crystal X-ray diffraction, it was determined that F₁₀-SiPc has significantly enhanced π–π interactions compared with that of Cl₂-SiPc, which had little to none. Unoptimized PHJ OPV devices based on F₁₀-SiPc were fabricated and directly compared to those constructed from Cl₂-SiPc, and in all cases, PHJ OPV devices based on F₁₀-SiPc had significantly improved device characteristics compared to Cl₂-SiPc