A theory of T-S curves as a method for studying the mixing of water masses in the sea

A sea or an ocean, according to Defant (1929), is composed of wat er masses which are more or less homogeneous volumes of water characterized by definite relationships of physico-chemical properties such as temperature and salinity…

Harmonics added to a flickering light can upset the balance between ON and OFF pathways to produce illusory colors

The neural signals generated by the light-sensitive photoreceptors in the human eye are substantially processed and recoded in the retina before being transmitted to the brain via the optic nerve. A key aspect of this recoding is the splitting of the signals within the two major cone-driven visual pathways into distinct ON and OFF branches that transmit information about increases and decreases in the neural signal around its mean level. While this separation is clearly important physiologically, its effect on perception is unclear. We have developed a model of the ON and OFF pathways in early color processing. Using this model as a guide, we can produce imbalances in the ON and OFF pathways by changing the shapes of time-varying stimulus waveforms and thus make reliable and predictable alterations to the perceived average color of the stimulus—although the physical mean of the waveforms does not change. The key components in the model are the early half-wave rectifying synapses that split retinal photoreceptor outputs into the ON and OFF pathways and later sigmoidal nonlinearities in each pathway. The ability to systematically vary the waveforms to change a perceptual quality by changing the balance of signals between the ON and OFF visual pathways provides a powerful psychophysical tool for disentangling and investigating the neural workings of human vision

Intimate partner violence among African American and African Caribbean women: prevalence, risk factors, and the influence of cultural attitudes.

BackgroundWomen of African descent are disproportionately affected by intimate partner abuse; yet, limited data exist on whether the prevalence varies for women of African descent in the United States and those in the US territories.ObjectiveIn this multisite study, we estimated lifetime and 2-year prevalence of physical, sexual, and psychological intimate partner abuse (IPA) among 1,545 women of African descent in the United States and US Virgin Islands (USVI). We also examined how cultural tolerance of physical and/or sexual intimate partner violence (IPV) influences abuse.DesignBetween 2009 and 2011, we recruited African American and African Caribbean women aged 18-55 from health clinics in Baltimore, MD, and St. Thomas and St. Croix, USVI, into a comparative case-control study. Screened and enrolled women completed an audio computer-assisted self-interview. Screening-based prevalence of IPA and IPV were stratified by study site and associations between tolerance of IPV and abuse experiences were examined by multivariate logistic regression analysis.ResultsMost of the 1,545 screened women were young, of low-income, and in a current intimate relationship. Lifetime prevalence of IPA was 45% in St. Thomas, 38% in St. Croix, and 37% in Baltimore. Lifetime prevalence of IPV was 38% in St. Thomas, 28% in St. Croix, and 30% in Baltimore. Past 2-year prevalence of IPV was 32% in St. Thomas, 22% in St. Croix, and 26% in Baltimore. Risk and protective factors for IPV varied by site. Community and personal acceptance of IPV were independently associated with lifetime IPA in Baltimore and St. Thomas.ConclusionsVariance across sites for risk and protective factors emphasizes cultural considerations in sub-populations of women of African descent when addressing IPA and IPV in given settings. Individual-based interventions should be coupled with community/societal interventions to shape attitudes about use of violence in relationships and to promote healthy relationships

Visual consequences of molecular changes in the guanylate cyclase activating protein

Purpose: In this study, we characterize and model changes in visual performance associated with a Tyr99Cys substitution in the guanylate cyclase activating protein (GCAP1) in four family members aged between 39 and 55 years. Guanylate cyclase and its activating protein are molecules in the visual transduction pathway that restore cyclic GMP (cGMP) following its light-activated hydrolysis. The mutation causes an excess of cGMP in the dark and results in progressive photoreceptor loss. Methods: L-cone temporal acuity was measured as a function of target irradiance; and L-cone temporal contrast-sensitivity was measured as a function of temporal frequency. Results: All four GCAP1-mutant family members show sensitivity or acuity losses relative to normal observers. The data for the youngest family member are consistent with an abnormal speeding up of the visual response relative to normals, but those for the older members show a progressive higher-frequency sensitivity loss consistent with a slowing down of their response. Conclusions: The speeding up of the visual response in the youngest observer is consistent with the Tyr99Cys-mutation resulting in the more rapid replacement of cGMP after light exposure, and thus in a reduction of temporal integration and relative improvement in high frequency sensitivity compared to normals. The high-frequency losses in the older observers are consistent with their vision being further limited by the interposition of some sluggish process. This might result from some residual or malfunctioning molecular process limiting transduction within damaged photoreceptors, or from an active or passive postreceptoral reorganization caused by the paucity of functioning photoreceptors

Characteristics of Ten Tropical Hardwoods from Certified Forests in Bolivia. Part II. Natural Durability to Decay Fungi

The natural durability of 10 lesser known, commercially available Bolivian hardwoods to decay fungi was evaluated using a modified ASTM soil-block analysis for 12 weeks. The blocks were then retested for an additional 12 weeks to determine their level of decay resistance, as determined by percentage of weight loss. Astronium urundeuva, Caesalpinia cf. pluviosa, Schinopsis quebrachocolorado, and Tabebuia sp. (Iapacho group) were found to be highly resistant to decay; Amburana cearensis, Anadenanthera colubrina (syn: A. macrocarpa), Aspidosperma cylindrocarpon, Diplotropis purpurea, and Guibourtia chodatiana, resistant to decay; and Phyllostylon rhamnoides, moderately resistant to decay. We conclude that an extended soil-bottle test is an effective tool for assessing the level of natural durability of these and other tropical species

Detection of Extended Polarized Ultraviolet Radiation from the z = 1.82 Radio Galaxy 3C 256

We have detected spatially extended linear polarized UV emission from the high-redshift radio galaxy 3C~256 ($z=1.82$). A spatially integrated ($7.8''$ diameter aperture) measurement of the degree of polarization of the $V-$band (rest frame 0.19 $\mu$m) emission yields a value of 16.4\% ($\pm 2.2$\%) with a position angle of $42{}\rlap{\rm .}^\circ 4$ ($\pm 3{}\rlap{\rm .}^\circ 9$), orthogonal to the position angle on the sky of the major axis of the extended emission. The peak emission measured with a $3.6''$ diameter circular aperture is 11.7\% ($\pm 1.5$\%) polarized with a position angle of $42{}\rlap{\rm .}^\circ 4$ ($\pm 3{}\rlap{\rm .}^\circ 6$). An image of the polarized flux is presented, clearly displaying that the polarized flux is extended and present over the entire extent of the object. While it has been suggested that the UV continuum of 3C~256 might be due to star formation (Elston 1988) or a protogalaxy (Eisenhardt \& Dickinson 1993) based on its extremely blue spectral energy distribution and similar morphology at UV and visible wavelengths, we are unable to reconcile the observed high degree of polarization with such a model. While the detection of polarized emission from HZRGs has been shown to be a common phenomena, 3C~256 is only the third object for which a measurement of the extended polarized UV emission has been presented. These data lend additional support to the suggestion first made by di Serego Alighieri and collaborators that the ``alignment effect'', the tendency for the extended UV continuum radiation and line emission from HZRGs to be aligned with the major axis of the extended radio emission, is in large part due to scattering of anisotropic nuclear emission.Comment: 11 pages, LaTeX (aaspp style) file. Figure available by request to [email protected]

Semimetallization of dielectrics in strong optical fields

At the heart of ever growing demands for faster signal processing is ultrafast charge transport and control by electromagnetic fields in semiconductors. Intense optical fields have opened fascinating avenues for new phenomena and applications in solids. Because the period of optical fields is on the order of a femtosecond, the current switching and its control by an optical field may pave a way to petahertz optoelectronic devices. Lately, a reversible semimetallization in fused silica on a femtosecond time scale by using a few-cycle strong field (~1 V/Å) is manifested. The strong Wannier-Stark localization and Zener-type tunneling were expected to drive this ultrafast semimetallization. Wider spread of this technology demands better understanding of whether the strong field behavior is universally similar for different dielectrics. Here we employ a carrier-envelope-phase stabilized, few-cycle strong optical field to drive the semimetallization in sapphire, calcium fluoride and quartz and to compare this phenomenon and show its remarkable similarity between them. The similarity in response of these materials, despite the distinguishable differences in their physical properties, suggests the universality of the physical picture explained by the localization of Wannier-Stark states. Our results may blaze a trail to PHz-rate optoelectronics

Carrier-envelope phase effects on the strong-field photoemission of electrons from metallic nanostructures

Sharp metallic nanotapers irradiated with few-cycle laser pulses are emerging as a source of highly confined coherent electron wavepackets with attosecond duration and strong directivity. The possibility to steer, control or switch such electron wavepackets by light is expected to pave the way towards direct visualization of nanoplasmonic field dynamics and real-time probing of electron motion in solid state nanostructures. Such pulses can be generated by strong-field induced tunneling and acceleration of electrons in the near-field of sharp gold tapers within one half-cycle of the driving laser field. Here, we show the effect of the carrier-envelope phase of the laser field on the generation and motion of strong-field emitted electrons from such tips. This is a step forward towards controlling the coherent electron motion in and around metallic nanostructures on ultrashort length and time scales

Colour and brightness encoded in a common L- and M-cone pathway with expansive and compressive nonlinearities?

Lights near 560 nm appear brighter when flickered, whereas lights near 520 or 650 nm appear yellower. Both effects are consistent with signal distortion within the visual pathway—brightness changes at an expansive nonlinearity, and hue shifts at a compressive one. We previously manipulated the distortion products generated by each nonlinearity to extract the temporal properties of stages of the L- and M-cone pathways that signal brightness and colour before (early stages) and after (late stages) each nonlinearity. We find that the attenuation characteristics of the early and late stages are virtually identical in both pathways: the early temporal stage acts like a band-pass filter peaking at 10-15 Hz, while the late stage acts like low-pass filter with a cut-off frequency near 3 Hz. We propose a physiologically-relevant model that accounts for the filter shapes and incorporates both nonlinearities within a common parvocellular pathway. The shape of the early bandpass filter is consistent with antagonism between “center” signals and more sluggish and delayed “surround” signals, while the late filter is consistent with a simple two-stage low-pass filter. Modelling suggests that the brightness-change and hue-shift are both initially caused by the half-wave rectification and partition of signals into ON and OFF components. However, the hue shift is probably caused by the additional effects of a later nonlinearity that compresses chromatic “red” and “green” signals. Plausible sites for the expansive half-wave rectifying nonlinearity are after surround antagonism, possibly from horizontal cells, but the compressive nonlinearity is likely to be after the late filter