Magnetic light

Spherical silicon nanoparticles with sizes of a few hundreds of nanometers represent a unique optical system. According to theoretical predictions based on Mie theory they can exhibit strong magnetic resonances in the visible spectral range. The basic mechanism of excitation of such modes inside the nanoparticles is very similar to that of split-ring resonators, but with one important difference that silicon nanoparticles have much smaller losses and are able to shift the magnetic resonance wavelength down to visible frequencies. We experimentally demonstrate for the first time that these nanoparticles have strong magnetic dipole resonance, which can be continuously tuned throughout the whole visible spectrum varying particle size and visually observed by means of dark-field optical microscopy. These optical systems open up new perspectives for fabrication of low-loss optical metamaterials and nanophotonic devices.Comment: 24 pages with 6 figure

Evidence of lasting impact of the Deepwater Horizon oil spill on a deep Gulf of Mexico coral community

A coral community 11 km southwest of the site of the Deepwater Horizon blowout at 1,370 m water depth was discovered 3.5 months after the well was capped on 3 November 2010. Gorgonian corals at the site were partially covered by a brown flocculent material (floc) that contained hydrocarbons fingerprinted to the oil spill. Here we quantify the visible changes to the corals at this site during five visits over 17 months by digitizing images of individual branches of each colony and categorizing their condition. Most of the floc visible in November 2010 was absent from the corals by the third visit in March 2011, and there was a decrease in the median proportions of the colonies showing obvious signs of impact after the first visit. During our second visit in 2010, about six weeks after the first, we documented the onset of hydroid colonization (a sign of coral deterioration) on impacted coral branches that increased over the remainder of the study. Hydroid colonization of impacted portions of coral colonies by the last visit in March 2012 correlated positively with the proportion of the colony covered by floc during the first two visits in late 2010. Similarly, apparent recovery of impacted portions of the coral by March 2012 correlated negatively with the proportion of the coral covered with floc in late 2010. A notable feature of the impact was its patchy nature, both within and among colonies, suggesting that the impacting agent was not homogeneously dispersed during initial contact with the corals. While the median level of obvious visible impact decreased over time, the onset of hydroid colonization and the probability of impacts that were not visually obvious suggest that future visits may reveal additional deterioration in the condition of these normally long-lived corals

A Metalens with Near-Unity Numerical Aperture

The numerical aperture (NA) of a lens determines its ability to focus light and its resolving capability. Having a large NA is a very desirable quality for applications requiring small light-matter interaction volumes or large angular collections. Traditionally, a large NA lens based on light refraction requires precision bulk optics that ends up being expensive and is thus also a specialty item. In contrast, metasurfaces allow the lens designer to circumvent those issues producing high NA lenses in an ultra-flat fashion. However, so far, these have been limited to numerical apertures on the same order of traditional optical components, with experimentally reported values of NA <0.9. Here we demonstrate, both numerically and experimentally, a new approach that results in a diffraction limited flat lens with a near-unity numerical aperture (NA>0.99) and sub-wavelength thickness (~{\lambda}/3), operating with unpolarized light at 715 nm. To demonstrate its imaging capability, the designed lens is applied in a confocal configuration to map color centers in sub-diffractive diamond nanocrystals. This work, based on diffractive elements able to efficiently bend light at angles as large as 82{\deg}, represents a step beyond traditional optical elements and existing flat optics, circumventing the efficiency drop associated to the standard, phase mapping approach.Comment: 12 pages, 5 figure

Generalized Brewster-Kerker effect in dielectric metasurfaces

Polarization is one of the key properties defining the state of light. It was discovered in the early 19th century by Brewster, among others, while studying light reflected from materials at different angles. These studies led to the first polarizers, based on Brewster's effect. One of the most active trends in photonics now is devoted to the study of miniaturized, sub-wavelength devices exhibiting similar, or even improved, functionalities compared to those achieved with bulk optical elements. In the present work, it is theoretically predicted that a properly designed all-dielectric metasurface exhibits a generalized Brewster effect potentially for any angle, wavelength and polarization of choice. The effect is experimentally demonstrated for an array of silicon nanodisks at visible wavelengths. The underlying physics of this effect can be understood in terms of the suppressed scattering at certain angles that results from the interference between the electric and magnetic dipole resonances excited in the nanoparticles, predicted by Kerker in early 80s. This reveals deep connection of Kerker's and Brewster's legacies and opens doors for Brewster phenomenon to new applications in photonics, which are not bonded to a specific polarization or angle of incidence.Comment: 12 pages, 5 figures, and supplementary information (22 pages

The potential impact of primary headache disorders on stroke risk

Distribution of PHDs. (DOC 55 kb

Early iron production in the Levant: Smelting and smithing at early 1st millennium BC Tell Hammeh, Jordan, and Tel Beth-Shemesh, Israel

The use of iron in the Near East is first attested by the sporadic occurrence of iron artefacts during the Bronze Age. By the end of the Late Bronze Age, however, use of iron metal gradually increases to such a level that one can assume a reasonably regular production of iron metal from terrestrial ores by smelting. However, very few iron metallurgical workshops or installations have been discovered in the Near East thus far. Of these, most are apparently related to secondary smithing, and very few if any have clear evidence for iron smelting. Recent fieldwork at Tell Hammeh, Jordan, identified a major iron smelting operation dated to ca. 930 Cal BC. Excavations in 2001 and 2003 at Tel Beth- Shemesh, Israel, uncovered remains of a full-scale smithing operation, dating to ca. 900 Cal BC. Dedicated excavation techniques were developed and refined for both sites, aiming at optimal recovery of both technological and archaeological information. The excavated materials were comprehensively analysed using relevant scientific analytical techniques, which included the development and application of a calibration method for quantitative bulk chemical analysis of iron- rich materials by XRF. Combining laboratory data and fieldwork, this thesis explores the particular lime- rich and iron-oxide-poor nature of the Hammeh slags as a function of the composition of the local ore and the sacrificial contribution of technical ceramics (tuyeres and furnace wall). Furthermore, it compares the smelting operations at Tell Hammeh with the smithing at Tel Beth-Shemesh, both in terms of their respective archaeological contexts as well as of their technological residues. This aims at the identification and reconstruction of the chaine operatoire of the technologies at both sites. The reconstructed technological processes are discussed in terms of their place in the socio-economic and cultural context of the early first millennium BC of the Levant. Beyond providing new data about early iron metallurgy, the integrated archaeological and laboratory approach, the excavation methods applied, the analytical methodology, as well as the archaeometric data presented here may serve as a model for the excavation, interpretation, or comparison of future (and previous) discoveries of iron metallurgy in the Near East

The optimal pulse pressures for healthy adults with different ages and sexes correlate with cardiovascular health metrics

BackgroundPulse pressure (PP) may play a role in the development of cardiovascular disease, and the optimal PP for different ages and sexes is unknown. In a prospective cohort, we studied subjects with favorable cardiovascular health (CVH), proposed the mean PP as the optimal PP values, and demonstrated its relationship with healthy lifestyles.Methods and resultsBetween 1996 and 2016, a total of 162,636 participants (aged 20 years or above; mean age 34.9 years; 26.4% male subjects; meeting criteria for favorable health) were recruited for a medical examination program. PP in male subjects was 45.6 ± 9.4 mmHg and increased after the age of 50 years. PP in female subjects was 41.8 ± 9.5 mmHg and increased after the age of 40 years, exceeding that of male subjects after the age of 50 years. Except for female subjects with a PP of 40–70 mmHg, PP increase correlates with both systolic blood pressure (BP) increase and diastolic BP decrease. Individuals with mean PP values are more likely to meet health metrics, including body mass index (BMI) &lt;25 kg/m2 (chi-squared = 9.35, p&lt;0.01 in male subjects; chi-squared = 208.79, p &lt; 0.001 in female subjects) and BP &lt;120/80 mmHg (chi-squared =1,300, p &lt; 0.001 in male subjects; chi-squared =11,000, p &lt; 0.001 in female subjects). We propose a health score (Hscore) based on the sum of five metrics (BP, BMI, being physically active, non-smoking, and healthy diet), which significantly correlates with the optimal PP.ConclusionThe mean PP (within ±1 standard deviation) could be proposed as the optimal PP in the adult population with favorable CVH. The relationship between health metrics and the optimal PP based on age and sex was further demonstrated to validate the Hscore

Efficacy of Femarelle for the treatment of climacteric syndrome in postmenopausal women: An open label trial

AbstractObjectiveTo assess the effects of 2 months of treatment with Femarelle for climacteric syndrome in Taiwanese postmenopausal women.Materials and methodsA multi-center, open-label trial of 260 postmenopausal women, age ≥ 45 years with vasomotor symptoms. Women were enrolled after obtaining a detailed medical history and a thorough physical examination. They then received Femarelle (640 mg/d) twice daily for 8 weeks. The primary outcome was the changes in the frequency and severity of hot flushes from baseline to 4 weeks (1 month) and 8 weeks (2 months). Changes of general climacteric syndrome were assessed using a modified climacteric scale designed by Greene.ResultsThe frequency and severity of hot flushes were significantly improved with Femarelle use (p < 0.001). After 8 weeks of treatment, the percentage of women with various climacteric syndromes was reduced (from 100% to 20.9% for hot flushes, from 97.7% to 87.9% for psychological symptoms, from 93.8% to 78.8% for somatic symptoms, and from 87.8% to 74.9% for sexual symptoms). General climacteric syndrome scores also significantly decreased, from 20.8 ± 0.7 at the time of enrollment to 12.9 ± 0.7 after 8 weeks of Femarelle treatment (p < 0.0001). Participants experienced improvement of various climacteric symptoms and signs after 8 weeks of treatment (75.1% for hot flushes, 68.7% for psychological symptoms, 70.6% for somatic symptoms, and 69.0% for sexual problems respectively). After 4 weeks and 8 weeks of treatment with Femarelle, patients showed statistically significant improvement in climacteric symptoms (p < 0.0001). Three women (1.2%) withdrew from the study after 4 weeks of treatment due to adverse effects.ConclusionFemarelle significantly improved climacteric symptoms in Taiwanese postmenopausal women. However, further evaluation is needed regarding the safety of long-term consumption