Localized surface plasmon resonance (LSPR) in semiconductor nanocrystals (NCs) that results in resonant absorption, scattering, and near field enhancement around the NC can be tuned across a wide ...optical spectral range from visible to far-infrared by synthetically varying doping level, and post synthetically via chemical oxidation and reduction, photochemical control, and electrochemical control. In this review, we will discuss the fundamental electromagnetic dynamics governing light matter interaction in plasmonic semiconductor NCs and the realization of various distinctive physical properties made possible by the advancement of colloidal synthesis routes to such NCs. Here, we will illustrate how free carrier dielectric properties are induced in various semiconductor materials including metal oxides, metal chalcogenides, metal nitrides, silicon, and other materials. We will highlight the applicability and limitations of the Drude model as applied to semiconductors considering the complex band structures and crystal structures that predominate and quantum effects that emerge at nonclassical sizes. We will also emphasize the impact of dopant hybridization with bands of the host lattice as well as the interplay of shape and crystal structure in determining the LSPR characteristics of semiconductor NCs. To illustrate the discussion regarding both physical and synthetic aspects of LSPR-active NCs, we will focus on metal oxides with substantial consideration also of copper chalcogenide NCs, with select examples drawn from the literature on other doped semiconductor materials. Furthermore, we will discuss the promise that LSPR in doped semiconductor NCs holds for a wide range of applications such as infrared spectroscopy, energy-saving technologies like smart windows and waste heat management, biomedical applications including therapy and imaging, and optical applications like two photon upconversion, enhanced luminesence, and infrared metasurfaces.
Abstract Objective A validated measure of daytime sleepiness for adolescents is needed to better explore emerging relationships between sleepiness and the mental and physical health of adolescents. ...The Epworth Sleepiness Scale (ESS) is a widely used scale for daytime sleepiness in adults but contains references to alcohol and driving. The Epworth Sleepiness Scale for Children and Adolescents (ESS-CHAD) has been proposed as the official modified version of the ESS for children and adolescents. This study describes the psychometric analysis of the ESS-CHAD as a measure of daytime sleepiness for adolescents. Methods The ESS-CHAD was completed by 297 adolescents, 12−18 years old, from two independent schools in Victoria, Australia. Exploratory factor analysis and Rasch analysis was conducted to determine the validity of the scale. Results Exploratory factor analysis and Rasch analysis indicated that ESS-CHAD has internal validity and a unidimensional structure with good model fit. Rasch analysis of four subgroups based on gender and year-level were consistent with the overall results. The results were consistent with published ESS results, which strongly indicates that the changes to the scale do not affect the scale’s capacity to measure daytime sleepiness. Conclusions It is concluded that the ESS-CHAD is a reliable and internally valid measure of daytime sleepiness in adolescents 12−18 years old. Further studies are needed to establish the internal validity of the ESS-CHAD for children under 12 years, and to establish external validity and accurate cut-off points for children and adolescents.
The Atlantic Meridional Overturning Circulation (AMOC) is responsible for a variable and climatically important northward transport of heat. Using data from an array of instruments that span the ...Atlantic at 26°N, we show that the AMOC has been in a state of reduced overturning since 2008 as compared to 2004–2008. This change of AMOC state is concurrent with other changes in the North Atlantic such as a northward shift and broadening of the Gulf Stream and altered patterns of heat content and sea surface temperature. These changes resemble the response to a declining AMOC predicted by coupled climate models. Concurrent changes in air‐sea fluxes close to the western boundary reveal that the changes in ocean heat transport and sea surface temperature have altered the pattern of ocean‐atmosphere heat exchange over the North Atlantic. These results provide strong observational evidence that the AMOC is a major factor in decadal‐scale variability of North Atlantic climate.
Key Points
New data from the RAPID 26°N array show that the AMOC has been in a state of reduced overturning since mid‐2008
Observations of heat content and SSH indicate that the impact of the reduction in the AMOC is similar to that predicted by climate models
The results indicate that changes in ocean heat transport have altered ocean‐atmosphere heat exchange over the North Atlantic
Continuous estimates of the oceanic meridional heat transport in the Atlantic are derived from the Rapid Climate Change–Meridional Overturning Circulation (MOC) and Heatflux Array ...(RAPID–MOCHA)observing system deployed along 26.5°N, for the period from April 2004 to October 2007. The basinwide meridional heat transport (MHT) is derived by combining temperature transports (relative to a common reference) from 1) the Gulf Stream in the Straits of Florida; 2) the western boundary region offshore of Abaco, Bahamas; 3) the Ekman layer derived from Quick Scatterometer (QuikSCAT) wind stresses; and 4) the interior ocean monitored by “endpoint” dynamic height moorings. The interior eddy heat transport arising from spatial covariance of the velocity and temperature fields is estimated independently from repeat hydrographic and expendable bathythermograph (XBT) sections and can also be approximated by the array.
The results for the 3.5 yr of data thus far available show a mean MHT of 1.33 ± 0.40 PW for 10-day-averaged estimates, on which time scale a basinwide mass balance can be reasonably assumed. The associated MOC strength and variability is 18.5 ± 4.9 Sv (1 Sv ≡ 10⁶ m³ s−1). The continuous heat transport estimates range from a minimum of 0.2 to a maximum of 2.5 PW, with approximately half of the variance caused by Ekman transport changes and half caused by changes in the geostrophic circulation. The data suggest a seasonal cycle of the MHT with a maximum in summer (July–September) and minimum in late winter (March–April), with an annual range of 0.6 PW. A breakdown of the MHT into “overturning” and “gyre” components shows that the overturning component carries 88% of the total heat transport. The overall uncertainty of the annual mean MHT for the 3.5-yr record is 0.14 PW or about 10% of the mean value.
The Atlantic meridional overturning circulation (MOC) plays a critical role in the climate system and is responsible for much of the heat transported by the ocean. A mooring array, nominally at 26°N ...between the Bahamas and the Canary Islands, deployed in Apr 2004 provides continuous measurements of the strength and variability of this circulation. With seven full years of measurements, we now examine the interannual variability of the MOC. While earlier results highlighted substantial seasonal and shorter timescale variability, there had not been significant interannual variability. The mean MOC from 1 Apr 2004 to the 31 March 2009 was 18.5 Sv with the annual means having a standard deviation of only 1.0 Sv. From 1 April 2009 to 31 March 2010, the annually averaged MOC strength was just 12.8 Sv, representing a 30% decline. This downturn persisted from early 2009 to mid‐2010. We show that the cause of the decline was not only an anomalous wind‐driven event from Dec 2009–Mar 2010 but also a strengthening of the geostrophic flow. In particular, the southward flow in the top 1100 m intensified, while the deep southward return transport—particularly in the deepest layer from 3000–5000 m—weakened. This rebalancing of the transport from the deep overturning to the upper gyre has implications for the heat transported by the Atlantic.
Key Points
New observations of the interannual variability of the Atlantic MOC in 2009‐10
The 30% weakening of the MOC driven by extreme winds and increased upper ocean flow
This variability has a large impact on the heat transported in the Atlantic
To provide an observational basis for the Intergovernmental Panel on Climate Change projections of a slowing Atlantic meridional overturning circulation (MOC) in the 21st century, the Overturning in ...the Subpolar North Atlantic Program (OSNAP) observing system was launched in the summer of 2014. The first 21-month record reveals a highly variable overturning circulation responsible for the majority of the heat and freshwater transport across the OSNAP line. In a departure from the prevailing view that changes in deep water formation in the Labrador Sea dominate MOC variability, these results suggest that the conversion of warm, salty, shallow Atlantic waters into colder, fresher, deep waters that move southward in the Irminger and Iceland basins is largely responsible for overturning and its variability in the subpolar basin.
Doped metal oxides are plasmonic materials that boast both synthetic and postsynthetic spectral tunability. They have already enabled promising smart window and optoelectronic technologies and have ...been proposed for use in surface enhanced infrared absorption spectroscopy (SEIRA) and sensing applications. Herein, we report the first step toward realization of the former utilizing cubic F and Sn codoped In2O3 nanocrystals (NCs) to couple to the C–H vibration of surface-bound oleate ligands. Electron energy loss spectroscopy is used to map the strong near-field enhancement around these NCs that enables localized surface plasmon resonance (LSPR) coupling between adjacent nanocrystals and LSPR-molecular vibration coupling. Fourier transform infrared spectroscopy measurements and finite element simulations are applied to observe and explain the nature of the coupling phenomena, specifically addressing coupling in mesoscale assembled films. The Fano line shape signatures of LSPR-coupled molecular vibrations are rationalized with two-port temporal coupled mode theory. With this combined theoretical and experimental approach, we describe the influence of coupling strength and relative detuning between the molecular vibration and LSPR on the enhancement factor and further explain the basis of the observed Fano line shape by deconvoluting the combined response of the LSPR and molecular vibration in transmission, absorption and reflection. This study therefore illustrates various factors involved in determining the LSPR–LSPR and LSPR–molecular vibration coupling for metal oxide materials and provides a fundamental basis for the design of sensing or SEIRA substrates.
The pathways and transports of Labrador Sea Water (LSW) within the southward‐flowing lower limb of the Atlantic Meridional Overturning Circulation are studied using 12 years of Argo profiles and ...subsurface Argo drift data. Consistent with previous studies, the results show clear evidence for interior pathways of LSW that separate from the western boundary near the Grand Banks and flow eastward and then southward around a large‐scale deep anticyclonic gyre in the northern subtropical Atlantic. Most of the LSW exported into the interior recirculates in the Newfoundland Basin (9.3 ± 3.5 Sv). However, approximately 3.2 ± 0.4 Sv cross the Mid‐Atlantic Ridge and flow southward east of the Azores. This branch feeds a westward quasi‐zonal pathway that recrosses the Ridge and returns to the western boundary around 30°N.
Key Points
A large‐scale anticyclonic gyre (30‐52°N) shapes the interior pathways of Labrador Sea Water and reveals its transformation regions
Part of equatorward‐flowing Labrador Sea Water's interior pathway (3 Sv) takes place in the eastern North Atlantic Basin
Robust analysis of Labrador Sea Water interior pathways and transports can be performed from the Argo array and subsurface drift data
The Atlantic meridional overturning circulation (AMOC) makes the strongest oceanic contribution to the meridional redistribution of heat. Here, an observation-based, 48-month-long time series of the ...vertical structure and strength of the AMOC at 26.5°N is presented. From April 2004 to April 2008, the AMOC had a mean strength of 18.7 ± 2.1 Sv (1 Sv ≡ 10⁶ m³ s−1)with fluctuations of 4.8 Sv rms. The best guess of the peak-to-peak amplitude of the AMOC seasonal cycle is 6.7 Sv, with a maximum strength in autumn and a minimum in spring. While seasonality in the AMOC was commonly thought to be dominated by the northward Ekman transport, this study reveals that fluctuations of the geostrophic midocean and Gulf Stream transports of 2.2 and 1.7 Sv rms, respectively, are substantially larger than those of the Ekman component (1.2 Sv rms). A simple model based on linear dynamics suggests that the seasonal cycle is dominated by wind stress curl forcing at the eastern boundary of the Atlantic. Seasonal geostrophic AMOC anomalies might represent an important and previously underestimated component of meridional transport and storage of heat in the subtropical North Atlantic. There is evidence that the seasonal cycle observed here is representative of much longer intervals. Previously, hydrographic snapshot estimates between 1957 and 2004 had suggested a long-term decline of the AMOC by 8 Sv. This study suggests that aliasing of seasonal AMOC anomalies might have accounted for a large part of the inferred slowdown.
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