Vertical Homogeneity Research Articles

Atomic-Level Customization of 4 in. Transition Metal Dichalcogenide Multilayer Alloys for Industrial Applications.

Despite many encouraging properties of transition metal dichalcogenides (TMDs), a central challenge in the realm of industrial applications based on TMD materials is to connect the large-scale synthesis and reproducible production of highly crystalline TMD materials. Here, the primary aim is to resolve simultaneously the two inversely related issues through the synthesis of MoS2(1- x ) Se2 x ternary alloys with customizable bichalcogen atomic (S and Se) ratio via atomic-level substitution combined with a solution-based large-area compatible approach. The relative concentration of bichalcogen atoms in the 2D alloy can be effectively modulated by altering the selenization temperature, resulting in 4 in. scale production of MoS1.62 Se0.38 , MoS1.37 Se0.63 , MoS1.15 Se0.85 , and MoS0.46 Se1.54 alloys, as well as MoS2 and MoSe2 . Comprehensive spectroscopic evaluations for vertical and lateral homogeneity in terms of heteroatom distribution in the large-scale 2D TMD alloys are implemented. Se-stimulated strain effects and a detailed mechanism for the Se substitution in the MoS2 crystal are further explored. Finally, the capability of the 2D alloy for industrial application in nanophotonic devices and hydrogen evolution reaction (HER) catalysts is validated. Substantial enhancements in the optoelectronic and HER performances of the 2D ternary alloy compared with those of its binary counterparts, including pure-phase MoS2 and MoSe2 , are unambiguously achieved.

Development of a Homogenous Cement Slurry Using Synthetic Modified Phyllosilicate while Cementing HPHT Wells

Cement slurry segregation has a detrimental impact on the cement matrix efficiency in term of zonal isolation. In this study, synthetic modified phyllosilicate (SMP) dispersant, which is known as laponite RD is suggested to reduce the slurry segregation and enhance the vertical homogeneity of the cement matrix in term of density distribution. Seven cement slurries were prepared with different SMP concentrations using molds with different dimensions based on the targeted test, then cured for 24 h at 140 °C and 3000 psi using a high-pressure and high-temperature curing chamber. After that, the samples’ density distribution was evaluated using a direct density measurement and computer tomography (CT) scan imaging technique, and the effect of SMP on the cement rheological parameters, permeability, and compressive strength and were also evaluated. The performance of SMP was then compared with a commercial dispersant. As a result, 0.3% by weight of cement (BWOC) of SMP is found to considerably reduce the vertical density variation along the cement column to 0.46% compared with a density variation of 4.78% for the slurry with the commercial dispersant. The CT scan images confirmed the vertical homogeneity of the slurry with 0.3% BWOC of SMP. Addition of 0.3% BWOC of SMP increased the yield point of the cement slurry to 60.6 MPa compared with 20.5 MPa for the slurry with 0.25% of the commercial dispersant. Adding 0.3% BWOC of SMP into the cement formulation decreased the permeability by 37.1% compared with the commercial dispersant. The sample with 0.3% BWOC of SMP has a compressive strength of 43.9 MPa.

Front delineation and tracking with multiple underwater vehicles

AbstractThis study describes a method for detecting and tracking ocean fronts using multiple autonomous underwater vehicles (AUVs). Multiple vehicles, equally spaced along the expected frontal boundary, complete near parallel transects orthogonal to the front. Two different techniques are used to determine the location of the front crossing from each individual vehicle transect. The first technique uses lateral gradients to detect when a change in the observed water property occurs. The second technique uses a measure of the vertical temperature structure over a single dive to detect when the vehicle is in upwelling water. Adaptive control of the vehicles ensure they remain perpendicular to the estimated front boundary as it evolves over time. This method was demonstrated in several experiment periods totaling weeks, in and around Monterey Bay, CA, in May and June of 2017. We compare the two front detection methods, a lateral gradient front detector and an upwelling front detector using the Vertical Temperature Homogeneity Index. We introduce two metrics to evaluate the adaptive control techniques presented. We show the capability of this method for repeated sampling across a dynamic ocean front using a fleet of three types of platforms: short‐range Iver AUVs, Tethys‐class long‐range AUVs, and Seagliders. This method extends to tracking gradients of different properties using a variety of vehicles.

A simplified energetics based planetary boundary layer (ePBL) approach for ocean climate simulations.

This paper presents a method to parameterize vertical turbulent mixing coefficients within the ocean surface boundary layer (OSBL) for climate applications. The new method is specifically constructed to satisfy two requirements. The first aspect is to explicitly consider the mechanical energy budget of the turbulence that drives mixing. This constraint ensures a realistic and robust simulation of the OSBL, which is critical for coupled climate simulations. The second aspect is that the model should be formulated so that it is not sensitive to the numerical limitations common to climate simulations, such as long time-steps and coarse vertical grids. This goal is achieved by combining an existing resolved shear-driven mixing parameterization (here Jackson et al., 2008) with a new method to avoid time step sensitivity. The new method is motivated by the Kraus-Turner-Niiler type bulk boundary layer parameterization, but relaxes the requirement for vertical homogeneity. The non-dimensional coefficients m* and n* from the Kraus-Turner-Niiler approach are parameterized for the new method based on results of simulations using a previously tested parameterization at high resolution. The resulting parameterization is evaluated by comparing simulations with the new parameterization to simulations with the k−ϵ parameterization over a wide range of combinations of surface wind stress, surface buoyancy flux, and latitudes. The new method for vertical turbulent OSBL mixing is therefore proposed as a computationally efficient, implicitly energetically constrained option appropriate for ocean climate modeling applications.

Site characterization and evaluation of the stability of the Yesilyurt Landslide (Trabzon, NE Turkey) using back analysis method

The aim of this study was to determine the soil profile of the Yesilyurt Landslide Area (NE Turkey) and to investigate the stability of the landslide area after the excavation planned by back analysis for support design. For these purposes, after the 1/1000 scaled engineering geological map was prepared, seismic refraction, electrical resistivity tomography and ground penetrating radar measurements were performed on different profiles to understand vertical and horizontal homogeneity of the landslide materials and undisturbed/disturbed soil samples were obtained from the test pits to determine the geotechnical properties of the soil. The results of the geophysical measurements showed that the landslide material was composed of two different soil zones. While the maximum thickness of the upper zone is 2.5, the thickness of the lower zone is about 5 m. The depth of dasidic rock mass is about 7 m. Residual cohesions of the soil samples obtained upper and lower zones were determined as 38 kPa and 44 kPa, and their residual friction angles were determined as 18° and 15° respectively. Unit weight values of the soil samples obtained from both zones were 16.9 kN m−3. The data obtained from laboratory tests showed that the landslide material is a uniform lithology. The geophysical measurements indicate that the wave velocity and resistivity values of these profiles differ from each other due to groundwater at a depth of 2.5 m. Limit equilibrium analysis were carried out with Slide v5.0 software using data obtained from the field measurements and laboratory tests to evaluate current and supported cases of the studied area. Because the safety factor of the slope obtained from the LE analyses is 0.99 and the studied soil environment is considered as unstable, the reliable and economical reinforcement was suggested using the retaining wall. The back-analysis method was evaluated to ensure the stability for a 1.5 safety factor and finally the lateral active forces for the retaining wall were calculated in the LE analysis as 718 kN and 1839 kN for without and with seismic load respectively.

Comparative assessment of GRASP algorithm for a dust event over Granada (Spain) during ChArMEx-ADRIMED 2013 campaign

Abstract. In this study, vertical profiles and column-integrated aerosol properties retrieved by the GRASP (Generalized Retrieval of Atmosphere and Surface Properties) algorithm are evaluated with in situ airborne measurements made during the ChArMEx-ADRIMED field campaign in summer 2013. In the framework of this campaign, two different flights took place over Granada (Spain) during a desert dust episode on 16 and 17 June. The GRASP algorithm, which combines lidar and sun–sky photometer data measured at Granada, was used to retrieve aerosol properties. Two sun-photometer datasets are used: one co-located with the lidar system and the other in the Cerro Poyos station, approximately 1200 m higher than the lidar system but at a short horizontal distance. Column-integrated aerosol microphysical properties retrieved by GRASP are compared with AERONET products showing a good agreement. Differences between GRASP retrievals and airborne extinction profiles are in the range of 15 to 30 %, depending on the instrument on board the aircraft used as reference. On 16 June, a case where the dust layer was coupled to the aerosol layer close to surface, the total volume concentration differences between in situ data and GRASP retrieval are 15 and 36 % for Granada and Cerro Poyos retrievals, respectively. In contrast, on 17 June the dust layer was decoupled from the aerosol layer close to the surface, and the differences are around 17 % for both retrievals. In general, all the discrepancies found are within the uncertainly limits, showing the robustness and reliability of the GRASP algorithm. However, the better agreement found for the Cerro Poyos retrieval with the aircraft data and the vertical homogeneity of certain properties retrieved with GRASP, such as the scattering Ångström exponent, for cases with aerosol layers characterized by different aerosol types, shows that uncertainties in the vertical distribution of the aerosol properties have to be considered. The comparison presented here between GRASP and other algorithms (i.e. AERONET and LIRIC) and with airborne in situ measurements shows the potential to retrieve the optical and microphysical profiles of the atmospheric aerosol properties. Also, the advantage of GRASP versus LIRIC is that GRASP does not assume the results of the AERONET inversion as a starting point.

Amplitude calibration of an acoustic backscattered signal from a bottom-moored ADCP based on long-term measurement series

A possible approach to, and preliminary results of, amplitude calibration of acoustic signals backscattered from an ADCP moored at the bottom of the near-shelf zone of the Black Sea is considered. The aim of this work is to obtain vertical profiles of acoustic scattering signal levels, showing the real characteristics of the volume content of suspended sediments in sea water in units of conventional acoustic turbidity for a given signal frequency. In this case, the assumption about the intervals of maximum acoustic transparency and vertical homogeneity of the marine environment in long-term series of ADCP measurements is used. According to this hypothesis, the intervals of the least values of acoustic backscattered signals are detected, an empirical transfer function of the ADCP reception path is constructed, and it is calibrated. Normalized sets of acoustic backscattered signals relative to a signal from a level of conventionally clear water are obtained. New features in the behavior of vertical profiles of an acoustic echo-signal are revealed due to the calibration. The results of this work will be used in subsequent analysis of the vertical and time variations in suspended sediment content in the near-shelf zone of the Black Sea.

RETRACTED ARTICLE: The highest power conversion efficiencies in poly(3-hexylthiophene)/fullerene photovoltaic cells modified by rod-coil block copolymers under different annealing conditions

A best-performing morphology was proposed for poly(3-hexylthiophene):phenyl-C71-butyric acid methyl ester (P3HT:PC71BM) bulk heterojunction (BHJ) solar cells by thermal and solvent annealings in the presence of rod-coil block copolymers subsuming hydrophilic and hydrophobic coily blocks. Unlike uncompatibilized photovoltaic cells, the power conversion efficiency (PCE) dropping during both thermal and solvent annealings was prevented for all BHJ devices compatibilized with either hydrophobic- or hydrophilic-based copolymers. The observed behavior was assigned to ever increasing trend of the fill factor (FF) and increasing or marginally decreasing trend of short circuit current density (J sc ). Although PCEs were higher in untreated hydrophobic-compatibilized devices (e.g., 4.07 vs. 1.52%), the hydrophilic-compatibilized systems further benefited from thermal and solvent annealings (e.g., 4.78 vs. 3.71%). The J sc and PCE peaked at 12.10 mA/cm2 and 4.85%, respectively, within 1 h under solvent annealing by 20 wt% of P3HT7150-b-polystyrene compatibilizer. Based on dynamic secondary ion mass spectrometry (DSIMS) analyses, the vertical homogeneity increased for compatibilized BHJs during both thermal and solvent annealings, leading to very high FFs (~69%).

Micromechanics-Based Analysis of the Effect of Aggregate Homogeneity on the Uniaxial Penetration Test of Asphalt Mixtures

AbstractBased on the microstructure-based discrete-element method (DEM), this study aims to investigate the effect of vertical aggregate homogeneity, i.e., aggregate homogeneity in vertical cross sections, on the uniaxial penetration test of asphalt mixtures. An aggregate homogeneity index, which can be used to evaluate aggregate homogeneity in a two-dimensional (2D) cross section, was briefly introduced. The vertical aggregate distribution was evaluated by the index. Microstructure-based discrete-element modeling of a uniaxial penetration test was accomplished by a discrete-element program called particle flow code in two dimensions. The effect of vertical aggregate homogeneity on penetration strengths regarding a uniaxial penetration test was simulated by the DEM. The obtained results were verified by uniaxial penetration testing. Results show that the effect of vertical aggregate homogeneity on penetration strengths can be numerically simulated by the microstructure-based DEM. The penetration strengths...

Stability and biodegradability of organic matter from Arctic soils of Western Siberia: insights from <sup>13</sup>C-NMR spectroscopy and elemental analysis

Abstract. Arctic soils contain large amounts of organic matter which, globally, exceed the amount of carbon stored in vegetation biomass and in the atmosphere. Recent studies emphasise the potential sensitivity for this soil organic matter (SOM) to be mineralised when faced with increasing ambient temperatures. In order to better refine the predictions about the response of SOM to climate warming, there is a need to increase the spatial coverage of empirical data on SOM quantity and quality in the Arctic area. This study provides, for the first time, a characterisation of SOM from the Gydan Peninsula in the Yamal Region, Western Siberia, Russia. On the one hand, soil humic acids and their humification state were characterised by measuring the elemental composition and diversity of functional groups using solid-state 13C-nuclear magnetic resonance (NMR) spectroscopy. Also, the total mineralisable carbon was measured. Our results indicate that there is a predominance of aliphatic carbon structures, with a minimal variation of their functional-group composition both regionally and within soil depth. This vertical homogeneity and low level of aromaticity reflects the accumulation in soil of lowly decomposed organic matter due to cold temperatures. Mineralisation rates were found to be independent of SOM quality, and to be mainly explained solely by the total carbon content. Overall, our results provide further evidence on the sensitivity that the soils of Western Siberia may have to increasing ambient temperatures and highlight the important role that this region can play in the global carbon balance under the effects of climate warming.

Convective boundary layer evolution from lidar backscatter and its relationship with surface aerosol concentration at a location of a central China megacity

AbstractBased on the 1 min backscatter ratio R profiles from the all‐day lidar measurements in Wuhan, China (30.5°N, 114.4°E), hourly convective boundary layer (CBL) height was calculated with the variance method. The calculated CBL height sequence displays the regular diurnal cycle of the CBL top. The prevalent mixing process within the CBL is also revealed. During the CBL growth period, the backscatter ratio R falls visibly with increasing altitude and has large variance within the CBL, suggesting that more abundant aerosol particles from lower altitudes are being transported upward and being mixed with the local background or advected aerosol layers. During the CBL quasistationary period, R tends to be vertically uniform, and its variance reaches a daytime minimum within the CBL, indicating that the vertical homogenization of aerosol particles produced by the convectively driven mixing reaches its maximum. During the afternoon and early evening transition period, the vertical uniformity of R weakens and the variance enlarges again, implying that the reduced convectively driven mixing fails to maintain a high vertical homogeneity. When the 1 min R profiles were plotted together in terms of each 1 h interval, the fluctuating R curves at heights around the CBL top looked like a “node”, representing the structure of the entrainment zone between the CBL and the free troposphere. The moving node depicts the evolution of the entrainment zone. The diurnal variation of the CBL height shows an obvious seasonal dependence which coincides with the annual variation of the local surface temperature. The surface fine particle concentration generally has a more complex diurnal cycle than that expected from the CBL‐dilution/CBL‐accumulation effect. But, it shows a strong annual variation which is out of phase with respect to that of the monthly mean maximum CBL height. This tends to suggest that the seasonal behavior of the surface fine particle concentration mainly depends on the seasonal variation in available volume (determined by the CBL height) for aerosol dispersion.

Salinity minimum in the subsurface layers of the Japan Sea

Seasonal variability of vertical salinity distribution in the Japan Sea is considered. On the base of high accuracy data from the databases WODC-2013 (USA), JODC (Japan), and the databases of Far-Eastern State Hydrometeorological Institute and Pacific Oceanological Institute (Russia), several cases of salinity minimums are analyzed and interpreted taking into account seasonal variability of salinity profiles. High vertical homogeneity by salinity is noted for the Japan Sea waters, and the subsurface salinity minimum can be considered as a result of continuous changes of freshwater balance. It could be formed in the layers from the sea surface to 150-250 m as a temporary local extreme caused by prevalence of evaporation over precipitation on the sea surface in some seasons - that’s why it is observed seasonally. There is concluded that such conservative patterns as water masses are absent in the sea, at least in its active upper layers, but vertical salinity profiles are changing permanently under influence of changing freshwater fluxes, and their extremes appear or disappear in compliance with the dialectic laws.

Spatial‐Scale Prediction of the SVAT Soil Hydraulic Variables Characterizing Stratified Soils on the Tibetan Plateau from an EnKF Analysis of SAR Soil Moisture

In highly stratified soils as on the Tibetan Plateau, uncertainty associated with a vertical profile of soil and hydraulic properties largely restricts the performance of Soil Vegetation Atmosphere Transfer (SVAT) model. In lieu of commonly used pedotransfer functions (PTFs) or artificial neural networks (ANNs), soil hydraulic properties in this study were inverted from an Ensemble Kalman filter (EnKF) analysis of Synthetic Aperture Radar (SAR) surface soil moisture. The calibrated SVAT scheme using inverted soil hydraulic variables C1 and θgeq was better matched with in situ field measurements than the uncalibrated SVAT scheme using soil maps–based PTFs on a local point scale. It was shown that the inverse calibration of two soil hydraulic variables solved the forecast bias (underestimation) in surface soil moisture due to the assumption of vertical homogeneity and the site‐specificity of empirical PTFs. Additionally, at a SAR spatial scale, the calibrated SVAT scheme appropriately captured a high vertical gradient between surface and subsurface soil moisture, while the uncalibrated SVAT scheme could not. This suggests that it is possible to infer the SVAT soil hydraulic variables that are the main error source in SVAT scheme from the SAR soil moisture data assimilation analysis.

Seasonal dynamics of light absorption by chromophoric dissolved organic matter (CDOM) in the NW Mediterranean Sea (BOUSSOLE site)

We analyze a two-year time-series of chromophoric dissolved organic matter (CDOM) light absorption measurements in the upper 400m of the water column at the BOUSSOLE site in the NW Mediterranean Sea. The seasonal dynamics of the CDOM light absorption coefficients at 440nm (acdom(440)) is essentially characterized by (i) subsurface maxima forming in spring and progressively reinforcing throughout summer, (ii) impoverishment in the surface layer throughout summer and (iii) vertical homogeneity in winter. Seasonal variations of the spectral dependence of CDOM absorption, as described by the exponential slope value (Scdom), are characterized by highest values in summer and autumn at the surface and low values at the depths of acdom(440) subsurface maxima or just below them. Variations of acdom(440) are likely controlled by microbial digestion of phytoplankton cells, which leads to CDOM production, and by photochemical destruction (photobleaching), which leads to CDOM degradation. Photobleaching is also the main driver of Scdom variations. Consistently with previous observations, acdom(440) for a given chlorophyll a concentration is higher than expected from Case I waters bio-optical models. The total non-water light absorption budget shows that surface waters at the BOUSSOLE site are largely dominated by CDOM during all seasons but the algal bloom in March and April. These results improve the knowledge of CDOM absorption dynamics in the Mediterranean Sea, which is scarcely documented. In addition, they open the way to improved algorithms for the retrieval of CDOM absorption from field or satellite radiometric measurements.

Numerical ellipsometry: High accuracy modeling of thin absorbing films in the n–k plane

A major challenge for those utilizing ellipsometry is numerical processing of the measured data. Our recent work shows how the transcendental, multivalued equations arising from the physics of reflection from layers can be solved in the n–k plane. This approach applies the mathematics of Complex Analysis to solve the equations numerically. The work presented extends the n–k method to obtain solutions within the accuracy limit of each measurement. The system treated here is that of a thin absorbing film (chromium) overlying a known substrate (silicon). Solutions for a three-layer model of the chromium film including film–substrate and film–air interfacial layers result in a mean square error (MSE) on the order of 0.01, a significant improvement over a single-layer model. Relaxing the constraint of vertical homogeneity provides a six-layer model with the same interfacial layers and four sublayers of chromium. The chromium layers have near-identical values of optical properties and an MSE of essentially zero (10−13). It is anticipated that additional methods will be needed for other classes of problems.

Shape‐induced gravitational sorting of Saharan dust during transatlantic voyage: Evidence from CALIOP lidar depolarization measurements

Motivated by the physical picture of shape‐dependent air resistance and, consequently, shape‐induced differential sedimentation of dust particles, we searched for and found evidence of dust particle asphericity affecting the evolution and distribution of dust‐scattered light depolarization ratio (δ). Specifically, we examined a large data set of Cloud‐Aerosol Lidar with Orthogonal Polarization (CALIOP) observations of Saharan dust from June to August 2007. Observing along a typical transatlantic dust track, we find that (1) median δ is uniformly distributed between 2 and 5 km altitudes as the elevated dust leaves the west coast of Africa, thereby indicating uniformly random mixing of particle shapes with height; (2) vertical homogeneity of median δ breaks down during the westward transport: between 2 and 5 km δ increases with altitude and this increase becomes more pronounced with westward progress; (3) δ tends to increase at higher altitude (>4 km) and decrease at lower altitude (<4 km) during the westward transport. All these features are captured qualitatively by a minimal model (two shapes only), suggesting that shape‐induced differential settling and consequent sorting indeed contribute significantly to the observed temporal evolution and vertical stratification of dust properties. By implicating particle shape as a likely cause of gravitational sorting, these results will affect the estimates of radiative transfer through Saharan dust layers.

Intra-tidal variation of stratification in a semi-arid estuary under the impact of flow regulation

The Jaguaribe River is the largest semi-arid Brazilian river and represents an important water source for the state of Ceará. The Castanhão Weir, built to regulate the flow of the Jaguaribe, began operating successfully in the 1990s. As a result, the hydrodynamic regime of the estuary has undergone alteration and is no longer subject to the former annual climatological variability of the dry and rainy seasons. This paper introduces an assessment of the changes in the hydrological conditions resulting from the construction of the weir and investigates the structure of the density stratification in the estuary. A field experiment was conducted at the end of the dry season in November 2009, during which salinity and temperature were monitored at different levels for three tidal cycles. The temporal variations in salinity and temperature during the tidal cycles were 16 psu and 1.5°C, respectively. The salinity exhibited a vertical variation of four units, while the temperature variation was much lower. Several stratification indicators were calculated from the observed density: the stratification coefficient, the Brunt-Väisälä frequency and the potential energy anomaly. The results showed that the parameters behave similarly, differences being observed only in their relative magnitudes. The vertical structure of the estuary exhibited marked stratification during the ebb tide but vertical homogeneity during both flood and high tide. With the regularized flow existing under present conditions, the estuary exhibits hyposaline and a partially mixed structure for the period studied, despite the typical expectation of a hypersaline and well-mixed vertical structure.

Soil microbial community structure in a rice paddy field and its relationships to CH4 and N2O fluxes

Soil microbial community structure and gas exchange (CH4, N2O) were investigated in a rice paddy field, located in the Po plain, Italy. At eight sampling dates—representative for different soil conditions and crop stages—microbial community structure was characterized by phospholipid fatty acid (PLFA) analysis. Principal component analyses revealed differences in community composition as well as in soil fluxes during the monitored year. The vertical distribution of PLFAs was investigated by sampling at 0–15 and 15–30 cm; the uniformity in soil properties through the soil profile resulted in a vertical homogeneity of microbial biomass and community composition. Only temporary variations of soil conditions led to a distinction in microbial populations with depth. The ratio of Gram-positive to Gram-negative bacteria was higher in flooded than in non-flooded soils. The saturated and methyl-branched fatty acids typically present in Gram-positive bacteria appeared to be indicators of flooded and waterlogged conditions, which were favourable for CH4 emission as well as for N2O consumption. Gram-negative bacteria were instead most important for characterization of aerobic conditions and for the decomposition of fresh residues. In terms of microbial processes, the 16:1ω9 fatty acid appeared to be correlated with N2O fluxes.

Magnetoelastic response of La0.7Sr0.3MnO3/SrTiO3superlattices to reversible strain

The influence of an electrically controlled biaxial in-plane strain on the magnetization of superlattices of ferromagnetic La${}_{0.7}$Sr${}_{0.3}$MnO${}_{3}$ and SrTiO${}_{3}$ was studied for single-layer thicknesses of $d$ = 1.5--13 nm. Superlattices were grown by pulsed laser deposition on both SrTiO${}_{3}$(001) and piezoelectric 0.72Pb(Mg${}_{1/3}$Nb${}_{2/3}$)O${}_{3}$--0.28PbTiO${}_{3}$(001), or PMN-PT(001), substrates and have been structurally characterized by x-ray diffraction (XRD) and transmission electron microscopy. Grazing-incidence XRD reveals the vertical homogeneity of the piezoelectrically controlled reversible in-plane strain, even in a 600-nm-thick superlattice containing 100 oxide interfaces. The as-grown strain is almost identical in all superlattices that are coherently grown, with small variations resulting from the partially relaxed growth of the first La${}_{0.7}$Sr${}_{0.3}$MnO${}_{3}$ layer on PMN-PT(001). The magnetic transition temperature decreases with the layer thickness $d$ as a consequence of the finite layer thickness, and the strain-induced response of the magnetization changes its character from that of a long-range-ordered ferromagnet to that of a magnetically disordered (possibly electronically phase-separated) manganite. The strain response of a modified interface layer (``dead layer'') of the thickness ${d}_{I}$ is distinguished from that of the layer's interior by its different temperature dependence, allowing an estimation of 10 \AA{} ${d}_{I}$ 16 \AA{} for the superlattices on PMN-PT.

Nanorod decorated nanowires as highly efficient SERS-active hybrids

In order to propel surface enhanced Raman scattering (SERS)-based sensing into the real world, novel SERS-active nanostructure designs that enable facile, scalable, cost-effective, highly efficient and homogenous SERS substrates are paramount. We demonstrate the facile fabrication of highly efficient SERS-active 3D nanohybrids based on vertically aligned zinc oxide nanowires uniformly decorated with gold nanorods. The dramatic enhancement of the surface area (nearly 20 times) and hence the number of plasmonic nanostructures within the incident laser foot print results in more than three orders of magnitude increase in SERS intensity compared to planar SERS substrates. The SERS enhancement factor was found to be ∼3 × 107 with a detection limit of sub-pM for a non-resonant analyte. Apart from excellent sensitivity, the nanohybrids also exhibited excellent lateral and vertical homogeneity in SERS activity. We believe that under optimal conditions these nanohybrids can surpass the best 2D substrate designs in SERS enhancement and homogeneity.