Unaligned Sampling Research Articles

Spatial Variability of Sodium Adsorption Ratio and Sodicity in Salt-Affected Soils of Northeast Thailand

Information on spatial variability of Sodium Adsorption Ratio (SAR) is useful for implementation of appropriate control measures for the salt-affected soils. The major objective of this study was to use geostatistics to describe the spatial variability of (i) the SAR and consequently (ii) the soil sodicity, in areas of different classes of salt-affected soils. Attention was on areas of very severely salt-affected soils (class 1), severely salt-affected soils (class 2), and moderately salt-affected soils (class 3). For each class, 2 study sites were chosen, totally 6 sites were taken into consideration. In each site, 100 soil samples were collected at 0-30 cm depth according to the stratified systematic unaligned sampling method in the dry season of 2012, and analyzed for the SAR in the laboratory. Descriptive statistics and Geostatistics were applied to describe the variability and spatial variability of SAR and soil sodicity, respectively. The result revealed very high variability of SAR. Descriptive statistics showed the CV values of ≥ 35% for every site of every class. When using semivariogram to describe the spatial correlation of SAR, it was found that in 3 study sites, the semivariogram models fitted well with the corresponding semivariogram samples indicating spatial correlation of SAR in the areas. In these cases, the Ordinary Kriging was applied to generate soil sodicity map. The relatively short range values especially for class 1 indicated very high variation of SAR. However, for the other 3 study sites, the linear models were fitted indicating no spatial correlation. Consequently, Trend Surface Analysis was applied instead. According to the soil sodicity maps generated in this study, the areas of class 1 were entirely occupied by strongly sodic soils. For classes 2 and 3, the soils in all study sites belonging to these classes included normal and slightly sodic soils of different proportions. Furthermore, inconsistency of the spatial variability patterns of SAR was found even in areas within the same class of salt-affected soils. As a result, prior to the intensive management of this problem soil in a particular area, investigation on the spatial variability pattern should be performed

CdSe quantum dot-dispersed DOBAMBC: an electro-optical study

Cadmium selenide quantum dot (CdSe QD) has been used as a dopant in ferroelectric liquid crystal (FLC) 2-methylbutyl 4-(4-decyloxybenzylideneamino) cinnamate (DOBAMBC). Effect of CdSe QD in DOBAMBC on its different electro-optical (E-O) properties has been studied in the SmC* phase. The optical micrographs recorded for the pure and composite material are showing good dispersion of QDs in the FLC matrix. Micrographs of unaligned sample cell revealed that CdSe QDs induce homeotropic alignment of FLC molecules. An appreciable change in the value of E-O parameters like tilt angle, spontaneous polarisation and response time with shifting of SmA–SmC* phase transition temperature has been observed for CdSe QD–DOBAMBC composite. The observed properties of composite system have been discussed on the basis of surface properties of QDs in FLC system.

Finer resolution observation and monitoring of global land cover: first mapping results with Landsat TM and ETM+ data

We have produced the first 30 m resolution global land-cover maps using Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+) data. We have classified over 6600 scenes of Landsat TM data after 2006, and over 2300 scenes of Landsat TM and ETM+ data before 2006, all selected from the green season. These images cover most of the world's land surface except Antarctica and Greenland. Most of these images came from the United States Geological Survey in level L1T (orthorectified). Four classifiers that were freely available were employed, including the conventional maximum likelihood classifier (MLC), J4.8 decision tree classifier, Random Forest (RF) classifier and support vector machine (SVM) classifier. A total of 91,433 training samples were collected by traversing each scene and finding the most representative and homogeneous samples. A total of 38,664 test samples were collected at preset, fixed locations based on a globally systematic unaligned sampling strategy. Two software tools, Global Analyst and Global Mapper developed by extending the functionality of Google Earth, were used in developing the training and test sample databases by referencing the Moderate Resolution Imaging Spectroradiometer enhanced vegetation index (MODIS EVI) time series for 2010 and high resolution images from Google Earth. A unique land-cover classification system was developed that can be crosswalked to the existing United Nations Food and Agriculture Organization (FAO) land-cover classification system as well as the International Geosphere-Biosphere Programme (IGBP) system. Using the four classification algorithms, we obtained the initial set of global land-cover maps. The SVM produced the highest overall classification accuracy (OCA) of 64.9% assessed with our test samples, with RF (59.8%), J4.8 (57.9%), and MLC (53.9%) ranked from the second to the fourth. We also estimated the OCAs using a subset of our test samples (8629) each of which represented a homogeneous area greater than 500 m × 500 m. Using this subset, we found the OCA for the SVM to be 71.5%. As a consistent source for estimating the coverage of global land-cover types in the world, estimation from the test samples shows that only 6.90% of the world is planted for agricultural production. The total area of cropland is 11.51% if unplanted croplands are included. The forests, grasslands, and shrublands cover 28.35%, 13.37%, and 11.49% of the world, respectively. The impervious surface covers only 0.66% of the world. Inland waterbodies, barren lands, and snow and ice cover 3.56%, 16.51%, and 12.81% of the world, respectively.

Determination of the translational order parameter for smectic liquid crystals using small-angle neutron scattering

A simple method to determine the translational order parameter of a smectic liquid crystal is presented. It is based on a measurement of the absolute intensity of the first-order layer reflection from an unaligned (powder) sample using small-angle neutron scattering. The Lorentz factor and molecular form factor are used to derive the order parameter from the intensity. The method is demonstrated for 4-octyl-4'-cyanobiphenyl (8CB), using two different isotopomers which give a consistent translational order parameter value of 0.5 in the smectic A phase.

Dry Contact Transfer Printing of Aligned Carbon Nanotube Patterns and Characterization of Their Optical Properties for Diameter Distribution and Alignment

A scalable and facile approach is demonstrated where as-grown patterns of well-aligned structures composed of single-walled carbon nanotubes (SWNT) synthesized via water-assisted chemical vapor deposition (CVD) can be transferred, or printed, to any host surface in a single dry, room-temperature step using the growth substrate as a stamp. We demonstrate compatibility of this process with multiple transfers for large-scale device and specifically tailored pattern fabrication. Utilizing this transfer approach, anisotropic optical properties of the SWNT films are probed via polarized absorption, Raman, and photoluminescence spectroscopies. Using a simple model to describe optical transitions in the large SWNT species present in the aligned samples, polarized absorption data are demonstrated as an effective tool for accurate assignment of the diameter distribution from broad absorption features located in the infrared. This can be performed on either well-aligned samples or unaligned doped samples, allowing simple and rapid feedback of the SWNT diameter distribution that can be challenging and time-consuming to obtain in other optical methods. Furthermore, we discuss challenges in accurately characterizing alignment in structures of long versus short carbon nanotubes through optical techniques, where SWNT length makes a difference in the information obtained in such measurements. This work provides new insight to the efficient transfer and optical properties of an emerging class of long, large diameter SWNT species typically produced in the CVD process.

Time Domain Reflectometry Studies on a Nematic Liquid Crystal

The complex dielectric permittivity spectra of p-pentyl phenyl-p-propylbenzoate (PPPB) , of a nematic liquid crystal are obtained using Time Domain Reflectometry (TDR) method over a frequency range 10 MHz–10 GHz at various temperatures covering both nematic and isotropic phases. The relaxation behavior at different temperatures was studied through cole–cole arc. The dielectric behavior in nematic (N) phase could be described by the Cole–Davidson model, while isotropic (I) phase is found to obey to a large extent Debye model. Two relaxation times, τ1 and τ2, are obtained for N phase which are the characteristic of Cole–Davidson model. τ1 and τ2 are interpreted as corresponding to different degrees of freedom in different direction in liquid crystalline state. The fact that τ1 and τ2 obtained for the I phase are almost equal favors Debye model. The results are presented over a temperature range, and these results are discussed to understand the phase transition involved. The work included in this article is useful as it provides information about the macroscopic structure of the liquid crystals in general and PPPB in particular. The N phase is the least ordered of liquid crystalline phases, and hence the studies even on an unaligned samples give information that is very close to aligned ones as far as those properties which are due to overall effects like dielectric behavior.

High-resolution calorimetric study of the nematic to smectic-Atransition in aligned liquid crystal–aerosil gels

High-resolution ac calorimetry has been used to study the nematic to smectic- A (N-SmA) phase transition in the liquid crystal octylcyanobiphenyl (8CB) confined in aligned colloidal aerosil gels. A stable and robust nematic alignment was achieved by repeated thermal cycling of the samples in the presence of a strong uniform magnetic field. In some ways (such as transition temperature and integrated enthalpy), the dependence of the specific heat peak associated with the N-SmA transition on the aerosil density for aligned gels is consistent with that observed in unaligned (random) gel samples. However, a power-law analysis reveals that the behavior of the critical exponent alpha is quite different. For random gels, alpha varies gradually with aerosil density, whereas we find that alpha for aligned gels shifts abruptly to an XY -like value for the lowest aerosil density studied and remains essentially constant as the sil density increases. This aerosil density independence of alpha is consistent with the critical behavior of the smectic correlation lengths obtained from an x-ray scattering study of 8CB in aligned aerosil gels. The combined calorimetric and x-ray results indicate that the role of quenched randomness in aligned gels of 8CB+sils differs significantly from that in random gels.

Kinetics of nanocolloids in the aligned domain of octylcyanobiphenyl and aerosil dispersion

In this study we explore the interesting kinetics of nanocolloids formed by the solvent dispersion method (SDM) in an aligned matrix of octylcyanobiphenyl (8CB) liquid crystals and aerosil nanoparticles. The presence of alignment changes the behaviour of the induced crystallisation (IC), and melting transition (K–SmA) observed in the aligned nanocolloidal liquid crystal samples when compared with unaligned samples. Heating‐rate‐dependent experiments were performed for the aligned and unaligned samples at various heating ramp rates varied from 20 to 1 K min−1 using a calorimetric technique. In the aligned samples, the IC transition peak shifts towards higher temperature, whereas the melting transition peak shifts towards lower temperature. The IC peak shows an increase in enthalpy whereas the melting transition shows a decrease following an Arrhenius behaviour. The presence of alignment increases the activated kinetics of the system. This behaviour can be explained in terms of molecular interaction between aligned domains of nanocolloids in the 8CB matrix which makes the material stiffer.

A two-phase sampling strategy for large-scale forest carbon budgets

The estimation of forest carbon sources and sinks is an important issue in forest inventories. For monitoring forest carbon budgets, a two-phase strategy is proposed. In the first phase, N points are thrown onto the study region by means of unaligned systematic sampling and then classified as forest or non-forest on the basis of aerial information. In the second phase, a sample of n points of those classified as forest is achieved by means of a sampling scheme with selection probabilities proportional to the sizes of an auxiliary variable. Subsequently, circular plots of adequate size are centred in the n selected points and visited in order to quantify the carbon amount within. Unbiased estimators of the forest area size as well as of the overall amount of carbon in that area and a conservative estimator of their variance–covariance matrix are derived. The strategy is applied to estimate carbon budgets in the forests of Trentino (North Italy).

Wormlike Micelle Formation and Flow Alignment of a Pluronic Block Copolymer in Aqueous Solution

The self-assembly into wormlike micelles of a poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) triblock copolymer Pluronic P84 in aqueous salt solution (2 M NaCl) has been studied by rheology, small-angle X-ray and neutron scattering (SAXS/SANS), and light scattering. Measurements of the flow curves by controlled stress rheometry indicated phase separation under flow. SAXS on solutions subjected to capillary flow showed alignment of micelles at intermediate shear rates, although loss of alignment was observed for high shear rates. For dilute solutions, SAXS and static light scattering data on unaligned samples could be superposed over three decades in scattering vector, providing unique information on the wormlike micelle structure over several length scales. SANS data provided information on even shorter length scales, in particular, concerning "blob" scattering from the micelle corona. The data could be modeled based on a system of semiflexible self-avoiding cylinders with a circular cross-section, as described by the wormlike chain model with excluded volume interactions. The micelle structure was compared at two temperatures close to the cloud point (47 degrees C). The micellar radius was found not to vary with temperature in this region, although the contour length increased with increasing temperature, whereas the Kuhn length decreased. These variations result in an increase of the low-concentration radius of gyration with increasing temperature. This was consistent with dynamic light scattering results, and, applying theoretical results from the literature, this is in agreement with an increase in endcap energy due to changes in hydration of the poly(ethylene oxide) blocks as the temperature is increased.

Estimating forest area at the year 1990 by two-phase sampling on historical remotely sensed imagery in Italy

Forest area in the year 1990 is a figure of great interest under the Kyoto Protocol. This note is devoted to a scientific exercise for the probabilistic ex post assessment of such a figure in Italy. Estimation was performed by two-phase point sampling, which made use of historical remotely sensed imagery. In the first phase, a sample of 12089 points was selected according to an unaligned systematic sampling and the selected points were classified in land-use categories by Landsat 5 TM imagery. In the second phase, a sample of 3000 points was selected by stratified sampling in which the strata were determined by the satellite classification and the selected points were classified by aerial photos, assumed as ground truth. A two-phase estimate of land-use coverage partitioning the Italian territory was obtained together with a conservative estimate of the sampling variance-covariance. The procedure has proved to be of relatively easy implementation and objective repeatability.

Thermal Conductivity of UltemTM/Carbon Nanofiller Blends

In an effort to improve polymer thermal conductivity (TC), UltemTM 1000 was compounded with nano-fillers of carbon allotropes. As-received and modified multiwalled carbon nanotubes (MWCNTs), vapor-grown carbon nanofibers (CNF) and expanded graphite (EG) were investigated. Functionalization of MWCNTs was performed to improve the TC compatibility between the resin and MWCNTs. It was postulated that this may provide an improved interface between the MWCNT and the polymer which would result in enhanced TC. The nano-fillers were mixed with UltemTM 1000 inthemeltandinsolution at concentrations ranging from 5 to 40 wt.%. Ribbons were extruded from the blends to form samples where the nano-fillers were aligned to some degree in the extrusion direction. Samples were also fabricated by compression molding resulting in random orientation of the nano-fillers. Thermal properties of the samples were evaluated by differential scanning calorimetry (DSC) and thermal gravimetric analyzer (TGA). Tensile properties of aligned samples were determined at room temperature. As expected, increased filler loading led to increased modulus and decreased elongation with respect to the neat polymer. The degree of dispersion and alignment of the nano-fillers was determined by high-resolution scanning electron microscopy (HRSEM). The HRSEM of the ribbons revealed that the MWCNTs and CNFs were predominantly aligned in the flow direction. The TC of the samples was measured using a NanoflashTM instrument. Since the MWCNTs and CNF are anisotropic, the TC was expected to be different in the longitudinal (parallel to the nanotube and fiber axis) and transverse (perpendicular to the nanotube and fiber axis) directions. The largest TC improvement was achieved for aligned samples when the measurement was performed in the direction of MWCNT and CNF alignment (i.e. longitudinal axis). Unaligned samples also showed a significant improvement in TC and may be potentially useful in applications when it is not possible to align the nano-filler. The results of this study will be presented.

Aerial assessment of landscape net change by means of two‐phase network sampling: an application to central Italy

AbstractA design‐based procedure for estimating the land cover net change between two dates in time is considered by means of aerial information. The aerial information in the first date consists of analogical photos while the aerial information in the second date consists of digital photos or satellite imagery. In the first phase of sampling a set of points is selected on the study area by means of unaligned systematic sampling. The digital imagery available for the second date may be readily adopted for spotting and classifying the first‐phase points, thus obtaining a first‐phase estimator of the areal extents in the second date. On the other hand, owing to the operational difficulties of spotting all the first‐phase points on the analogical photos, a second‐phase sample selected from these points is necessary to estimate the areal extents of the land categories in the first date. Finally, the land cover net changes may be estimated by means of the difference between the resulting estimates in the two dates. The use of stratified network sampling is considered in the second phase in order to handle the presence of analogical photos overlapping each other at their boundaries. An application of the procedure is considered for assessing the land cover net change in the Abruzzo Region (Central Italy) between the years 1954 and 2002. Copyright © 2006 John Wiley & Sons, Ltd.

A three-phase sampling strategy for large-scale multiresource forest inventories

This article considers a two-phase estimation for the areal extent of K land categories partitioning a study region and a three-phase estimation for the biomass of W forest categories out of the K. In the first phase, a sample of N points is selected according to the unaligned systematic sampling. In the second phase, the selected points are partitioned into L strata on the basis of aerial photos. Then, a total sample of n < N points is selected by stratified sampling and the selected points are visited on the ground and correctly classified into one of K categories. The information achieved in the second phase is sufficient for obtaining an unbiased estimator of the areal extent vector together with a conservative estimator of its variance-covariance matrix. As to the estimation of the biomass of the W forest categories, in the third phase the second-phase sample is further partitioned into substrata on the basis of ground information. Finally, a total sample of m < n points is selected by stratified sampling. Then a plot of adequate radius centered at each point is considered and the biomass is recorded within. An unbiased estimator of the biomass vector is derived together with a conservative estimator of its variance-covariance matrix. The proposed strategy also makes it possible to obtain the calibrated estimator of the areal extent vector as well as estimators for the sums or ratios of the areal extents and biomasses. The application of the strategy in the Italian National Forest Inventory is considered.

The magnetic behaviors of the metamagnetic and ferromagnetic phases of [Fe(C5Me5)2][TCNQ] (TCNQ = 7,7,8,8-tetracyano-p-quinodimethane). Determination of the phase diagram for the metamagnetic phase

The detailed magnetic behaviors of the ferro- (1FO) and metamagnetic (1MM) phases of [FeCp*2][TCNE] (Cp* = pentamethylcyclopentadienide; TCNE = tetracyanoethylene) aligned parallel to the applied magnetic field, H, were obtained using eicosane (E). The Tc for 1FO is 3.1 K from the maximum in the frequency independent χ′(T) data and 3.0 K from the maximum in the Cp(T) data, and exhibits a hysteresis with a coercive field, Hcr, ∼50 Oe, a remanent magnetization of 1900 emu Oe mol−1 at 2 K, and saturation magnetization of 16 740 emu Oe mol−1. Significant differences were observed between aligned 1MM (1MM + E) and unaligned samples. Metamagnetic 1MM + E saturates to 15 900 emu Oe mol−1, and has a 1300 Oe critical field at 2 K that decreases with increasing temperature. The 2 K M(H) of 1MM + E displays a small bump between |3000 and 4000| Oe that is not observed in 1MM. The Tc for 1MM + E is 2.5 ± 1 K from the maximum in the frequency independent χ′(T) data, and peak maximum in Cp(T) data. The lack of a χ″(T) response for H = 0 is in accord with 1MM + E having an antiferromagnetic ground state. Upon application of an applied field a χ″(T) signal appears and increases in intensity until 1500 Oe in accord with 1MM + E going from an antiferromagnetic to a ferromagnetic-like state. For H > 1500 Oe the χ″(T) signal decreases. In contrast to 1MM, between 2.2 and 2.8 K χ′(H) and χ″(H) exhibit peaks between 3000 and 4000 Oe. The temperature at which the peak maximum in Cp(T) occurs (2.4 K) for 1MM and is unexpectedly independent of H. The peak maxima observed in χ′(T,H) at 100 and 1000 Hz were use to construct a magnetic phase diagram, H(T), for metamagnet 1MM + E, which has three different magnetic phases: paramagnetic, antiferromagnetic, and an intermediate phase. The detailed magnetic characterization of the structurally similar 1MM and 1FO phases will provide a basis for theorists to understand the subtle spin exchange interactions that lead not only to magnetic ordering, but the type of the ordering.

Fabric variability associated with periglacial mass-wasting at Eagle Summit, Alaska

Fabric analysis is a frequently applied technique and, when used in concert with other tools, aids the interpretation of glacigenic and colluvial depositional environments. The research presented here focuses on its application to periglacial colluvium, using a stratified systematic unaligned sampling framework in order to assess the variation of fabrics generated. The range of possible variation in fabric is necessary information for its application to periglacial paleoenvironmental interpretation. Fabric strength and shape from 68 samples, of 50 stones each on a range of microgeomorphic settings across terrain influenced by periglacial mass-wasting in central Alaska, were analyzed in relation to local slope orientation, clast characteristics, organic mat thickness, stone density, distance downslope from the divide, soil texture and soil moisture. Principal components analysis (PCA) was used to reduce stone characteristics to three factors. Multiple regression analyses of the three factors and environmental variables, with the fabric strength parameters as dependent variables, indicate that stone characteristics, particularly size and platyness, are the most significant factors determining fabric strength. No distinct fabric strength or shape was associated with specific landforms. These results raise serious doubts as to the time-cost effectiveness of the application of fabric analysis as a paleoenvironmental tool to identify periglacial landforms from their deposits.

An NMR Study of Translational Diffusion and Structural Anisotropy in Magnetically Alignable Nonionic Surfactant Mesophases

The diffusion of both water and surfactant components in aqueous solutions of the nonionic surfactant "C12E6"--which includes hexagonal, cubic, lamellar, and micellar mesophases--has been studied by pulsed-field-gradient NMR. Diffusion coefficients were measured in unaligned samples in all of these phases. They were also obtained in the hexagonal and lamellar phases in oriented monodomain samples that were aligned by slow cooling from the micellar phase in an 11.7 T magnet. Measured water and soap diffusion coefficients in the NMR-isotropic cubic and (high-water-content) micellar phases as well as diffusion anisotropy measurements in the magnetically aligned hexagonal phase were quantitatively consistent with the constituent structures of these phases being identical surfactant cylinders, with only the fraction of surface-associated water varying with the water-soap molar ratio. The values of the water and soap diffusion coefficients in the oriented lamellar phase suggest an increase in defects and obstructions to soap diffusion as a function of increasing water content, while those in the low-water-content micellar phase rule out the presence of inverse micelles.

Variabilidade espacial dos atributos físicos do solo e da produtividade em um Latossolo Bruno distrófico da região de Cascavel, PR

Através de técnicas de geoestatística foram confeccionados mapas de contorno, produzidos por interpolação através da krigagem ordinária representando, desta forma, a variabilidade espacial dos atributos físicos densidade do solo [kg dm-3], teor de água do solo [g g-1] e resistência mecânica a penetração [MPa] nas camadas de 0-10,10-20 e 20-30 cm de profundidade, além da produtividade de soja [t ha-1]. Os atributos do solo e a produtividade se derivaram de um plano de amostragem estratificada sistemática desalinhada, do ano agrícola 1998/99, subdividido em parcelas sem manejo localizado (SML) e parcelas com manejo localizado (CML). De maneira geral, os mapas de produtividade apresentaram um padrão de variabilidade semelhante quanto à distribuição na área não respondendo, assim, ao tratamento químico diferenciado aplicado nas parcelas CML; já os atributos físicos mostraram comportamento semelhante para os dois métodos de cultivo. Dentre os atributos físicos estudados, a resistência à penetração na camada 0-10 cm de profundidade foi a variável que melhor se correlacionou com a produtividade.

A Generalized Model for the Molecular Arrangement in the Columnar Mesophases of Polycatenar Mesogens. Crystal and Molecular Structure of Two Hexacatenar Mesogens

The columnar mesophases of two series of hexacatenar palladium(II) mesogens have been studied in detail by a combination of X-ray diffraction on aligned and unaligned samples and dilatometry. The results of these studies, combined with the results of two single crystal structure determinations, have allowed a model of the molecular arrangement in the columnar phases to be proposed. This model differs in detail from that generally accepted for the arrangement of polycatenar mesogens in columnar phases, and a new model is proposed which accounts for both new and existing data.

Radiative transfer modeling within a heterogeneous canopy for estimation of forest fire fuel properties

Imaging spectrometer data were acquired over conifer stands to retrieve spatially distributed information on canopy structure and foliage water content, which may be used to assess fire risk and to manage the impact of forest fires. The study relied on a comprehensive field campaign using stratified systematic unaligned sampling ranging from full spectroradiometric characterization of the canopy to conventional measurements of biochemical and biophysical variables. Airborne imaging spectrometer data (DAIS7915 and ROSIS) were acquired parallel to the ground measurements, describing the canopy reflectance of the observed forest. Coniferous canopies are highly heterogeneous and thus the transfer of incident radiation within the canopy is dominated by its structure. We demonstrated the viability of radiative transfer representation and compared the performance of two hybrid canopy reflectance models, GeoSAIL and FLIGHT, within this heterogeneous medium. Despite the different nature and canopy representation of these models, they yielded similar results. Subsequently, the inversion of a hyperspectral GeoSAIL version demonstrated the feasibility of estimating structure and foliage water content of a coniferous canopy based on radiative transfer modeling. Estimates of the canopy variables showed reasonably accurate results and were validated through ground measurements.