Unaligned Sampling Research Articles

Dutch forest monitoring network, design and results

The new Dutch forest monitoring network is a policy-guided, multiple-use, GIS-oriented forest monitoring network. It is designed to provide the Dutch government, on a cyclic 8-year basis, with actual information about Dutch forests. Variables that reflect the information needs of policy makers and interest groups were selected by means of interviews and workshops. High-ranking variables are: wood stock, ownership, stand age, management status, biodiversity, carbon stock, and recreational use. These and other variables are being measured in 3622 forest sites, selected according to an unaligned systematic sampling design. The data are stored in an ORACLE data base, made accessible through the internet. The Dutch forest area approximates a total of 360 000 ha; 46% is owned by private owners and organisations for nature conservation. Coniferous forests dominate (60%). Most forests were planted in 1940-1980. The total above ground volume of living trunk wood amounts to 56.3 million m3. The most common tree sp...

Spatial sampling design for sediment quality assessment in estuaries

Unusual difficulties are encountered when characterizing the spatial distribution of the properties that collectively define the state of estuaries. Due to the variability of these estuarine conditions, greater sampling efforts are often necessary to describe estuarine environments, as compared to other aquatic systems. That is why in coastal management studies, where the collection of data is sometimes very difficult and time-consuming, a robust sampling strategy is essential. The aim of this study is to design a spatial sampling strategy for estuarine sediments, using prior information on the spatial variation of sediment granulometry. Systematic unaligned sampling with a grid cell size of 750×500 m was chosen on the basis of semi-variogram analysis, and was shown to have distinct advantages. This design was sampled for sediment parameters using a GPS-receiver and mapped within the digitized shoreline of the estuary. The estuary shoreline was digitized on the basis of aerial ortho-photography with tidal ebb determination. The sampling is intended to define the boundaries of environmental management areas for the Sado Estuary, situated on the west coast of Portugal. The research represents one of the initial phases in the development of a Sado Estuary environmental management system integrated into a Geographic Information System.

Optical Bit Stability and Relaxation Processes in a Liquid Crystal Polymer with a Photosensitive Azo Dye Molecule as Side Group

We present a study of optically-induced molecular relaxation and optical writing processes in a photosensitive liquid crystalline polymer, containing the azobenzene moiety in the side chain. Linear and non linear ESR spectroscopies, thermal analysis and rheology investigations carried on azo polymethacrylate (PMA) samples subjected to different thermal treatments have allowed to single out a suitable procedure to get stable, homogeneous substrates. Optical studies on micrometer length scale, adopting the selected procedure, have confirmed the stability conditions in both unaligned and aligned samples. The temperature dependence of the bit stability has been determined. The writing threshold power and writing rate have been measured. The results are discussed within the perspective of extension to the nanometer length scale.

STATISTICAL VERIFICATION OF SOIL DISCONTINUITIES IN VIRGINIA

Soil discontinuities, defined by significant texture and mineralogical, and/or age differences, are usually verified from a small number of pedons without producing information about the local distribution of properties that define the discontinuity. A discontinuity has geomorphic significance as well as important implications for interpretations. Along the western footslopes of the Virginia Blue Ridge, Typic Paleudults and Typic Fragiudults seem to have two depositional sequences in the sola: soil texture differences and abrupt color changes are present. Our objective was to show the discontinuity occurring in the soils using data analysis and multivariate statistics. Stratified systematic unaligned sampling within a 50-m2 area, the Wilcoxon Signed-Rank test, principal component analysis, and discriminant analysis were used to verify the discontinuities at four locations. Twenty-five soil properties were evaluated by the Wilcoxon Signed-Rank test. Nineteen significantly different properties (P = 0.10) were detected at Site 1, 17 at Site 2, 13 at Site 3, and 15 at Site 4. The first principal component (PC) loadings showed most properties contributed about equally to the first PC, with the exception of clay-free properties at Site 2 and Site 4. The second component loadings also identified clay-free properties as the best indices for defining the discontinuities. Discriminant analysis of scores from the first five principal components showed the components contributed from 91 to 96% to the discriminant functions. Discriminant functions clearly separated Unit A from Unit B at each site. Hotelling's T2 test showed the distances were significant (P ≤ 0.001) between Unit A and Unit B multivariate means. We conclude discontinuities are present at the four locations, and they can be differentiated spatially by textural differences and clay-free indices.

On the Dielectric Behavior of Unaligned Samples of 4-n-Octyl-4'-cyanobiphenyl (8CB)

On the Dielectric Behavior of Unaligned Samples of 4-n-Octyl-4'-cyanobiphenyl (8CB)

On the Dielectric Behavior of Unaligned Samples of 4-n-Octyl-4′-cyanobiphenyl (8CB)

On the Dielectric Behavior of Unaligned Samples of 4-n-Octyl-4′-cyanobiphenyl (8CB)

Peculiar behaviour of the spin susceptibility in Bi 2Sr 2Ca 2Cu 3O 10

The temperature dependence of the 63 Cu NMR shifts and spin lattice relaxation rates was measured for a (Bi 0.93Pb 0.07) 2.1Sr 2Ca 2Cu 3O 10 sample, in a powder and a magnetically aligned form. In the last case, two resonance lines were observed from Cu in the inner and the outer Cu–O planes. The inner plane Cu, which is in a symmetric local environment, has a small quadrupolar frequency ν Q=5.4 MHz ( ν Q= e 2 qQ/2 h), while the outer plane one has ν Q>15 MHz. Comparison of the 63 Cu ⊥ with the 17 O iso shifts from the same Cu–O planes shows that they are proportional to the same spin susceptibility. The temperature dependence of ( T 1,(u) T) −1 for the unaligned sample (inner plane resonance) shows a peak at 160 K, while ( T 1c,(o) T) −1 for the outer Cu–O planes peaks at 95 K. Strong antiferromagnetic fluctuations of the electron spins exist in the inner Cu–O planes.

In Situ Observation of Texture of a Dimesogenic Liquid Crystal Compound under Hydrostatic Pressure

In situ observation of microscopic texture of an unaligned sample of a dimesogenic liquid crystal compound, N-[4-(6-cholesteryloxycarbonyl)pentyloxy-benzylidene]-4-n-butylaniline, called as KI5, was performed under hydrostatic pressures up to 250 MPa by a polarized optical microscope equipped with a high-pressure optical hot-stage. The spherulites of the pressure-induced crystal polymorph(CII) of the KI5 compound, different from those of the normal crystal (CI), were confirmed directly at 100 MPa and higher pressures. The CII spherulites were grown up from the dark field (homeotropic orientation) of the supercooled smectic phase under high pressures. This observation coincides with the experimental results by high-pressure X-ray diffraction and thermal analysis already reported. The temperature region of homeotropic orientation including partial homeotropic region decreases from ca. 70°C at 0.1 MPa to ca. 47°C at 100 MPa, and then the homeotropic state persists to higher temperatures of about 40 ± 5°C under higher pressures. The homeotropic region shifts to high temperature with the CII-S1 transition line by applying pressures above 60 MPa, suggesting that homeotropic orientation of the KI5 compound occurs immediately after the CII-S1 transition(melting) at high pressure.

The utility of multi-sensor data for mapping eroded lands

The availability of remote sensing data with improved spatial, spectral and radiometric resolution is now available to fully exploit their potential for a specific application subject to the relative merits and the limitations of each sensor's data. Presented here is a case study where Landsat MSS and TM; and SPOT MLA data for part of the Bijapur district, southern India, which were acquired on the same day, have been evaluated for mapping eroded lands. The approach involves the geometric registration of all three data to a common map grid using tie points and third order polynomial transform; and resampling the MSS and TM data to a 20m by 20 m pixel dimension and radiometric normalization. Thematic maps showing eroded lands were generated on a micro-VAXbased DIPIX system using a maximum likelihood classifier. Accuracy estimates were made for the thematic maps following stratified unaligned random sampling technique, and subsequently, computing overall accuracy and Kappa coefficient. Spectral separability and classification accuracy was maximum from SPOT-MLA data followed by a combination of Landsat MSS band 1, SPOT-MLA band 2 and Landsat TM band 4; Landsat TM, a combination of Landsat MSS, TM and SPOT MLA; and Landsat MSS data.

Induced Circular Dichroism of Isotropic and Magnetically-Oriented Chiral Nematic Suspensions of Cellulose Crystallites

Stable colloidal suspensions of rodlike cellulose crystallites, prepared by acid hydrolysis of cellulose fibers, form a chiral nematic phase above a critical concentration. The direction of the chiral nematic axis may be controlled by applying a strong magnetic field. In the presence of Congo red, a dye with strong affinity for cellulose, the suspensions show induced circular dichroism (ICD) at the dye absorption wavelengths, indicating that the dye molecules are in a chiral environment. The isotropic suspension shows a relatively weak positive ICD peak, while the chiral nematic phase shows a very strong negative ICD peak when viewed along the chiral nematic axis. The peak is weaker for unaligned chiral nematic samples and is very small when viewed at right angles to the chiral nematic axis. Thus the ICD in the chiral nematic phase results from the orientation of the dye molecules in a chiral nematic array. The ICD band intensity increases with chiral nematic pitch.

2H-Labeling of Silk Fibroin Fibers and Their Structural Characterization by Solid-State 2H NMR

Three kinds of 2H-labeled Bombyx mori silk fibroin samples (with [2,2-2H2]Gly, [3,3,3-2H3]Ala, or [2,3,5,6-2H4]Tyr) were obtained by oral administration of either the labeled amino acid or 2H2O to 5th instar larvae. The administration of 2H2O alone yielded a high degree of selective deuteration at the alanine methyl group, since the incorporation of 2H2O occurs between fumarate and malate in the tricarboxylic acid (TCA) cycle of the silk fibroin synthetic pathway. Uniaxially oriented silk fibers were prepared as samples for 2H-NMR spectroscopy. An analysis of the quadrupole echo line shape was carried out in order to determine the angle of the deuterium-labeled group relative to the fiber axis, i.e., of the Cα−2H bond vectors in glycine and of Cα−Cβ2H3 in alanine. With the fiber axis aligned parallel to the magnetic field, quadrupole splittings were obtained as 117.8 and 39.8 kHz for [2,2-2H2]Gly- and [3,3,3-2H3]Ala-labeled silk, respectively. These values are identical with those obtained from the 2H-NMR powder patterns of the unaligned samples, within experimental error. From the angular dependence of the quadrupole splittings, it was thus calculated that the Cα−2H bonds of glycine as well as the Cα−Cβ2H3 bond of alanine make an angle of approximately 90° relative to the fiber axis. These steric constraints were then used to evaluate the torsion angles, φ and ψ, for the glycine and alanine residues within the protein backbone. These data, determined independently by solid-state 2H NMR, thus verified and narrowed down the allowed region in the Ramachandran (φ, ψ) map obtained from previous solid-state 13C- and 15N-NMR studies.

Superconductivity and spin fluctuations in the electron-doped infinitely-layered high T c superconductor Sr 0.9La 0.1CuO 2 ( Tc = 42 K)

We report 63Cu NMR studies on uniaxially aligned and unaligned powder samples of an electron-doped infinitely-layered high T c cuprate superconductor Sr 0.9 La 0.1 CuO 2 ( T c = 42 K). We measured the nuclear spin-lattice relaxation rate 1 T 1 up to 800 K. We found from the temperature dependence of 1 T 1 T that the wave-vector-averaged spin susceptibility is highly enhanced by spin-fluctuations in the normal state, resulting in a Curie-Weiss behavior. Below T c, we did not observe a Hebel-Slichter coherence peak of 1 T 1 , suggesting an unconventional nature of the symmetry of the superconducting order parameter. These results are quite similar to those observed for some hole-doped high T c cuprates.

Dielectric relaxation spectroscopy and molecular dynamics of a liquid-crystalline polyacrylate containing spiropyran groups

The dielectric properties of a liquid-crystalline (LC) copolymer containing photochromic spiropyran groups have been determined over wide ranges of frequency and temperature. The observed loss curves contain a component from the dipole reorientations of the mesogenic groups and a further component from a conductivity-related process. An electrical cleaning method was used to reduce the contribution from the latter process and a subtraction method was devised to separate the overall loss curves into the two components. Using electrical/thermal treatments it was found possible to align the copolymer homeotropically but not planarly. The dielectric loss spectra for unaligned and homeotropically aligned samples were very different. The data were analysed to yield two relaxation parameters for unaligned and aligned samples and were interpreted in terms of the anisotropic motions of dipolar mesogenic groups as have been discussed previously. In addition, the temporal stability of alignment of homeotropic samples at temperatures close to the clearing temperature was determined using the dielectric method.

Strategies for Sampling Spatially Heterogeneous Phenomena: the Example of River Gravels

ABSTRACT The paucity of critical results in the field sciences is partly the result of ineffective data collection. Multiple samples must be collected to take advantage of the power of inferential statistics, but the number of samples needed may be minimized by using efficient sampling methods. This study shows that for gravel river bars characterized by the presence of several unevenly distributed facies, the grid technique for sample selection is one of the best and easiest to use in the field. A special combination of grid and random techniques, known as systematic unaligned sampling, performs slightly better, but site selection and navigation in the field are more complex. Random sampling performs less well than either of the other methods. If the sampling question requires estimation of a statistic to represent the entire area or volume, rather than estimates of the variability within and between different zones of the area or volume, then the use of composite sampling further reduces the sampling effort required. A few replications of these composite samples will provide an estimate of the mean and standard deviation of a population statistic which can be used to construct confidence limits about the estimated statistic.

Transport critical current of aligned polycrystalline Y1Ba2Cu3O7−δ and evidence for a nonweak-linked component of intergranular current conduction

A study of grain alignment and its effect on the dc transport critical current in fine-grained bulk Y1Ba2Cu3O7−δ is reported in magnetic fields from 10−4 T to 26 T. Two features distinguish the critical current density Jc of aligned bulk Y1Ba2Cu3O7−δ from unaligned material. First, the effective critical field where the intergranular Jc approaches zero is about four times higher (30 T) for aligned samples with field parallel to the a, b planes, than it is for polycrystalline unaligned samples (7 T). Second, the nearly field independent plateau value of Jc between 10 mT and 1 T is one to two orders of magnitude higher than typical plateau values of Jc in unaligned bulk-sintered Y1Ba2Cu3O7−δ, for field parallel to the a, b planes. A low-field (<10 mT) weak-link decrease in Jc with magnetic field is still observed, but it is much smaller than for unaligned material. These data clearly demonstrate that alignment alone significantly reduces the weak-link problem in fine-grained polycrystalline samples with low-aspect-ratio (4:1) grains (unlike melt-grown samples where there has been some ambiguity as to the relative importance of alignment versus large grain growth). Furthermore, the results provide strong evidence that there are two parallel components of intergranular current conduction, one consisting of weak-linked material, the other behaving like intrinsic intragranular material that is not weak-linked. A comparison with unaligned Y1Ba2Cu3O7−δ indicates that the volume fraction of such nonweak-linked material is significantly enhanced by grain alignment, but still only 0.01%–0.1% of the grain boundary area. Field-cooled and force-free Jc data are also presented, along with detailed measurements of the shapes of the voltage-current characteristics.

Reflectivity of surface-aligned blue phase III of chiral liquid crystals.

We have performed the first measurements on surface-aligned samples of the blue phase III of chiral liquid crystals and have tested proposed icosahedral, cubic-domain, and double-twist structures for blue phase III. Angular-reflection studies on surface-aligned samples show no evidence of expected icosahedral structure; uv reflection measurements on unaligned samples show no evidence of expected cubic-domain structure; and attempts to observe Cano fringes show no evidence for any spatial periodicity.

Systematic geographic sampling with UTM coordinates

Abstract A geographic sampling method that incorporates the advantages of systematic sampling while preserving randomness is described. The method, stratified systematic unaligned sampling, is suited to both random surveys of any size area and systematic coverage of large areas such as might be required when mapping fallout patterns or determining land use for environmental impact studies. In our application, the Universal Transverse Mercator (UTM) grid coordinate system is used. The UTM grid system is well suited to this sampling method because of its rectangular nature, decimal basis, universal nature, and relative ease of use for determining grid coordinates in the field from standard topographic maps. An application of this method to a statewide survey of indoor radon levels in Pennsylvania is described in detail.

Zero field N.M.R. of uniaxial and biaxial smectic liquid crystals

A study of three smectic liquid crystal systems is made through a comparison of the high field and zero field N.M.R. spectra of probe molecules. The motional averaging of the proton dipolar interaction of a CH2Cl2 solute molecule reflects the local symmetry of Smectic A, B and E phases. In the Smectic E system, the onset of the biaxiality of the phase is clearly evident even in an unaligned sample.

Stratégie d'échantillonnage des données de terrain intégrées dans l'analyse des images satellitaires

Sampling strategy of integrated ground data for remote sensing. — When the integration of ground data with remote sensing is concerned, decisions about the design of the sampling scheme are of great importance. One of the problems is to choose a kind of probability sampling. This paper first introduces the advantages of the unaligned systematic sampling in the case of autocorrelated satellite data. It then determines the optimal size and shape of the sampling units as a response to the resolution of the imagery and the variability of the terrain. Finally, the minimum dimensions of the sample are estimated.

Optimal Randomization for Experiments in which Autocorrelation is Present

For a linear or spatial ordering of the experimental units, systematic methods of applying the treatments to the experimental units minimize the variance of linear contrasts of treatment means. In the linear ordering the optimal randomization scheme for the application of k treatments is to apply a treatment to every kth experimental unit, the equivalent of systematic sampling in the sampling literature. In the spatial ordering the optimal randomization schemes are equivalent to Quenouille's (1949) systematic aligned or unaligned spatial sampling schemes.