Optical determination and identification of organic shells around nanoparticles: application to silver nanoparticles

We present a simple method to prove the presence of an organic shell around silver nanoparticles. This method is based on the comparison between optical extinction measurements of isolated nanoparticles and Mie calculations predicting the expected wavelength of the Localized Surface Plasmon Resonance of the nanoparticles with and without the presence of an organic layer. This method was applied to silver nanoparticles which seemed to be well protected from oxidation. Further experimental characterization via Surface Enhanced Raman Spectroscopy (SERS) measurements allowed to identify this protective shell as ethylene glycol. Combining LSPR and SERS measurements could thus give proof of both presence and identification for other plasmonic nanoparticles surrounded by organic shells

Bayesian evidence synthesis to estimate HIV prevalence in men who have sex with men in Poland at the end of 2009.

HIV spread in men who have sex with men (MSM) is an increasing problem in Poland. Despite the existence of a surveillance system, there is no direct evidence to allow estimation of HIV prevalence and the proportion undiagnosed in MSM. We extracted data on HIV and the MSM population in Poland, including case-based surveillance data, diagnostic testing prevalence data and behavioural data relating to self-reported prior diagnosis, stratified by age (⩽35, >35 years) and region (Mazowieckie including the capital city of Warsaw; other regions). They were integrated into one model based on a Bayesian evidence synthesis approach. The posterior distributions for HIV prevalence and the undiagnosed fraction were estimated by Markov Chain Monte Carlo methods. To improve the model fit we repeated the analysis, introducing bias parameters to account for potential lack of representativeness in data. By placing additional constraints on bias parameters we obtained precisely identified estimates. This family of models indicates a high undiagnosed fraction [68·3%, 95% credibility interval (CrI) 53·9-76·1] and overall low prevalence (2·3%, 95% CrI 1·4-4·1) of HIV in MSM. Additional data are necessary in order to produce more robust epidemiological estimates. More effort is urgently needed to ensure timely diagnosis of HIV in Poland

Impedimetric and Plasmonic Sensing of Collagen I Using a Half-Antibody-Supported, Au-Modified, Self-Assembled Monolayer System

This research presents an electrochemical immunosensor for collagen I detection using a self-assembled monolayer (SAM) of gold nanoparticles (AuNPs) and covalently immobilized half-reduced monoclonal antibody as a receptor; this allowed for the validation of the collagen I concentration through two different independent methods: electrochemically by Electrochemical Impedance Spectroscopy (EIS), and optically by Surface Plasmon Resonance (SPR). The high unique advantage of the proposed sensor is based on the performance of the stable covalent immobilization of the AuNPs and enzymatically reduced half-IgG collagen I antibodies, which ensured their appropriate orientation onto the sensor’s surface, good stability, and sensitivity properties. The detection of collagen type I was performed in a concentration range from 1 to 5 pg/mL. Moreover, SPR was utilized to confirm the immobilization of the monoclonal half-antibodies and sensing of collagen I versus time. Furthermore, EIS experiments revealed a limit of detection (LOD) of 0.38 pg/mL. The selectivity of the performed immunosensor was confirmed by negligible responses for BSA. The performed approach of the immunosensor is a novel, innovative attempt that enables the detection of collagen I with very high sensitivity in the range of pg/mL, which is significantly lower than the commonly used enzyme-linked immunosorbent assay (ELISA)

Accommodation functions: co-dependency and relationship to refractive error

We assessed the extent to which different accommodative functions are correlated and whether accommodative functions predict the refractive error or the progression of myopia over a 12 month period in 64 young adults (30 myopes and 34 non-myopes). The functions were: amplitude of accommodation; monocular and binocular accommodative facility (6 m and 40 cm); monocular and binocular accommodative response to target distance; AC/A and CA/C ratios, tonic accommodation (dark focus and pinhole), accommodative hysteresis, and nearwork-induced transient myopia. Within groups of related accommodative functions (such as facility measures or open-loop measures) measurements on individuals were generally significantly correlated, however correlations between functions from different groups were generally not significant. Although accommodative amplitude and pinhole (open loop) accommodation were significantly different in myopes than in non-myopes, these functions were unrelated to myopia progression. Facility of accommodation and accommodative lag was independent predictors of myopia progression

Icebergs in the North Atlantic: Modelling circulation changes and glacio-marine deposition

In order to investigate meltwater events in the North Atlantic, a simple iceberg generation, drift, and melting routine was implemented in a high-resolution OGCM. Starting from the modelled last glacial state, every 25th day cylindrical model icebergs 300 meters high were released at 32 specific points along the coasts. Icebergs launched at the Barents Shelf margin spread a light meltwater lid over the Norwegian and Greenland Seas, shutting down the deep convection and the anti-clockwise circulation in this area. Due to the constraining ocean circulation, the icebergs produce a tongue of relatively cold and fresh water extending eastward from Hudson Strait that must develop at this location, regardless of iceberg origin. From the total amount of freshwater inferred by the icebergs, the thickness of the deposited IRD could be calculated in dependance of iceberg sediment concentration. In this way, typical extent and thickness of Heinrich layers could be reproduced, running the model for 250 years of steady state with constant iceberg meltwater inflow

Spatial contrast sensitivity in adolescents with autism spectrum disorders

Adolescents with autism spectrum disorders (ASD) and typically developing (TD) controls underwent a rigorous psychophysical assessment that measured contrast sensitivity to seven spatial frequencies (0.5-20 cycles/degree). A contrast sensitivity function (CSF) was then fitted for each participant, from which four measures were obtained: visual acuity, peak spatial frequency, peak contrast sensitivity, and contrast sensitivity at a low spatial frequency. There were no group differences on any of the four CSF measures, indicating no differential spatial frequency processing in ASD. Although it has been suggested that detail-oriented visual perception in individuals with ASD may be a result of differential sensitivities to low versus high spatial frequencies, the current study finds no evidence to support this hypothesis

The influence of cycloplegic in objective refraction

The purpose of this study was to compare refractions measured with an autorefractor and retinoscopy in cycloplegic and non-cycloplegic eyes. The objective refractions were performed in 199 right eyes from 199 healthy young adults with a mean age of 21.6 ±2.66 years. The measurements were performed first without cycloplegia and repeated 30 minutes later with cycloplegia. Data were analyzed using Fourier decomposition of the power profile. More negative values of component M and J0 were give by non-cycloplegic autorefraction compared to cycloplegic autorefraction (p<0.001). However more positive values were given by non-cycloplegic autorefraciton regarding to the J45 vector, althought this differences were not statistically significant (p=0.233). Regarding retinoscopy, more negative values of component M where obtained with non-cycloplegic retinoscopy (p<0.001); for the cylindrical vectors J0 and J45 the retinoscopy without cycloplegic yields more negative values (p= 0.234; p= 0.112, respectively). Accepting that differences between cycloplegic and non-cycloplegic retinoscopy are only due to accommodative response, present results confirm that when performed by an experienced clinician, retinoscopy is a more reliable method to obtain objective start point for refraction under non-cycloplegic conditions

Potential links between surging ice sheets, circulation changes and the Dansgaard Oeschger cycles in the Irminger Sea, 60-18 kyr.

Surface and deepwater paleoclimate records in Irminger Sea core SO82-5 (59°N, 31°W) and Icelandic Sea core PS2644 (68°N, 22°W) exhibit large fluctuations in thermohaline circulation (THC) from 60 to 18 calendar kyr B.P., with a dominant periodicity of 1460 years from 46 to 22 calendar kyr B.P., matching the Dansgaard-Oeschger (D-O) cycles in the Greenland Ice Sheet Project 2 (GISP2) temperature record [Grootes and Stuiver, 1997]. During interstadials, summer sea surface temperatures (SST<inf>su</inf>) in the Irminger Sea averaged to 8°C, and sea surface salinities (SSS) averaged to ∼36.5, recording a strong Irminger Current and Atlantic THC. During stadials, SST<inf>su</inf> dropped to 2°-4°C, in phase with SSS drops by ∼1-2. They reveal major meltwater injections along with the East Greenland Current, which turned off the North Atlantic deepwater convection and hence the heat advection to the north, in harmony with various ocean circulation and ice models. On the basis of the IRD composition, icebergs came from Iceland, east Greenland, and perhaps Svalbard and other northern ice sheets. However, the southward drifting icebergs were initially jammed in the Denmark Strait, reaching the Irminger Sea only with a lag of 155-195 years. We also conclude that the abrupt stadial terminations, the D-O warming events, were tied to iceberg melt via abundant seasonal sea ice and brine water formation in the meltwater-covered northwestern North Atlantic. In the 1/1460-year frequency band, benthic δ18O brine water spikes led the temperature maxima above Greenland and in the Irminger Sea by as little as 95 years. Thus abundant brine formation, which was induced by seasonal freezing of large parts of the northwestern Atlantic, may have finally entrained a current of warm surface water from the subtropics and thereby triggered the sudden reactivation of the THC. In summary, the internal dynamics of the east Greenland ice sheet may have formed the ultimate pacemaker of D-O cycles

Active mud volcanoes on the continental slope of the Canadian Beaufort Sea

The major geochemical characteristics of Red Sea brine are summarized for 11 brine-filled deeps located along the central graben axis between 19°N and 27°N. The major element composition of the different brine pools is mainly controlled by variable mixing situations of halite-saturated solution (evaporite dissolution) with Red Sea deep water. The brine chemistry is also influenced by hydrothermal water/rock interaction, whereas magmatic and sedimentary rock reactions can be distinguished by boron, lithium, and magnesium/calcium chemistry. Moreover, hydrocarbon chemistry (concentrations and δ 13 C data) of brine indicates variable injection of light hydrocarbons from organic source rocks and strong secondary (bacterial or thermogenic) degradation processes. A simple statistical cluster analysis approach was selected to look for similarities in brine chemistry and to classify the various brine pools, as the measured chemical brine compositions show remarkably strong concentration variations for some elements. The cluster analysis indicates two main classes of brine. Type I brine chemistry (Oceanographer and Kebrit Deeps) is controlled by evaporite dissolution and contributions from sediment alteration. The Type II brine (Suakin, Port Sudan, Erba, Albatross, Discovery, Atlantis II, Nereus, Shaban, and Conrad Deeps) is influenced by variable contributions from volcanic/ magmatic rock alteration. The chemical brine classification can be correlated with the sedimentary and tectonic setting of the related depressions. Type I brine-filled deeps are located slightly off-axis from the central Red Sea graben. A typical " collapse structure formation " which has been defined for the Kebrit Deep by evaluating seismic and geomorphological data probably corresponds to our Type I brine. Type II brine located in depressions in the northern Red Sea (i.e., Conrad and Shaban Deeps) could be correlated to " volcanic intrusion-/extrusion-related " deep formation. The chemical indications for hydrothermal influence on Conrad and Shaban Deep brine can be related to brines from the multi-deeps region in the central Red Sea, where volcanic/magmatic fluid/rock interaction is most obvious. The strongest hydrothermal influence is observed in Atlantis II brine (central multi-deeps region), which is also the hottest Red Sea brine body in 2011 (*68.2 °C)

The haptic perception of spatial orientations

This review examines the isotropy of the perception of spatial orientations in the haptic system. It shows the existence of an oblique effect (i.e., a better perception of vertical and horizontal orientations than oblique orientations) in a spatial plane intrinsic to the haptic system, determined by the gravitational cues and the cognitive resources and defined in a subjective frame of reference. Similar results are observed from infancy to adulthood. In 3D space, the haptic processing of orientations is also anisotropic and seems to use both egocentric and allocentric cues. Taken together, these results revealed that the haptic oblique effect occurs when the sensory motor traces associated with exploratory movement are represented more abstractly at a cognitive level