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showing 10 items of 1317 documents
A Combined Experimental and Theoretical Study on Bis(μ‐alkoxo)diiron(III) Complexes with Hydroxybenzylaminoethanol [O,N,O] Donor Ligands: Syntheses, …
2011
Three new neutral bis(μ-alkoxo)diiron(III) complexes were prepared from N(R),N-(2-methylene-4,6-di-tert-butylphenol)aminoethan-1-ol ligands (H2L1, R = Me and H2L2, R = H). In these complexes, the ligand wraps around the metal center exhibiting a tridentate facial coordination mode with alkoxo-bridging oxygen, amine nitrogen and phenoxo oxygen donor atoms. In the complex [Fe(acac)L1]2·MeCN (1) acetylacetonato coligand complete the distorted octahedral coordination spheres of the iron(III) ions, whereas in the five-coordinate iron(III) chloride complexes [FeClL1]2 (2) and [FeClL2]2 (3) the ligands induce a geometry that is intermediate between square pyramidal and trigonal bipyramidal. Magnet…
Synthesis, Structure, and Electrical Properties of Ta 4 FeTe 4
1995
Ta4FeTe4 has been synthesized and its structure determined by single-crystal X-ray methods. It crystallizes in the ortho-rhombic space group Pbam with Z = 4 and a = 10.514(5), b = 18.275(7), and c = 4.815(1) A. Ta4FeTe4 has a chain structure built up by Fe-centered Ta8-square antiprisms sharing common square faces. The resistivity of Ta4FeTe4 has been measured by a two-point method. Ta4FeTe4 shows metallic behavior. The structure of Ta4FeTe4 is discussed in relation to other early transition metal cluster compounds. A rational approach to the synthesis of related compounds is proposed.
Synthesis and Crystal Structure of Ln3(OH)(CrO4)4 · 3.5H2O (Ln = Pr, Nd) and Ln2(OH)2(CrO4)2 (Ln = Tb, Gd): Thermal Behavior and Infrared Spectra of …
1993
Abstract Crystal structures of Ln 2 (OH) 2 (CrO 4 ) 2 ( Ln = Gd, Tb) and Ln 3 (OH)(CrO 4 ) 4 · 3.5H 2 O ( Ln = Pr, Nd) were determined by a conventional single-crystal X-ray diffraction technique. Crystals of Ln 2 (OH) 2 (CrO 4 ) 2 ( Ln = Gd, Tb) are monoclinic, space group P 2 1 / c (no. 14) with lattice parameters a = 8.2454(4) A, b = 11.3834(5) A, C = 12.1420(8) A, and β = 136,590(5)°, Z = 4, D x = 4.92 mg · m -3 for Gd 2 (OH) 2 (CrO 4 ) 2 and a = 8.214(1) A, b = 11.348(1) A, c = 12.094(2) A, and β = 136.59(1)°, Z = 4, D x = 5.01 Mg · m -3 for Tb 2 (OH) 2 (CrO 4 ) 2 . Crystals of Ln 3 (OH)(CrO 4 )) 4 · 3.5H 2 O ( Ln = Pr, Nd) are monoclinic, space group C 2/ c (No. 15) with lattice param…
One-dimensional oxalato-bridged copper(II) complexes with 3-hydroxypyridine and 2-amino-4-methylpyridine
2001
Two new one-dimensional oxalato-bridged copper(II) compounds of formula [Cu(ox)L2]n (1) and {[Cu2(ox)2L%3]·L%}n (2) [ox oxalate dianion, L3-hydroxypyridine (pyOH) and L% 2-amino-4-methylpyridine (ampy)] have been synthesized and characterized by FT-IR spectroscopy, variable-temperature magnetic measurements and single-crystal X-ray diffraction. The crystal structure of 1 comprises chains of copper atoms in which cis-[Cu(pyOH)2] 2 units are sequentially bridged by asymmetric bis-bidentate oxalato ligands with an intrachain copper‐copper separation of 5.548(1) A, . Each copper atom is six-coordinated: four oxygen atoms belonging to two bridging oxalato ligands and two nitrogen atoms from two …
Evaluation of infrared spectroscopy as a screening tool for serum analysis
2013
Abstract The application of attenuated total reflectance Fourier transform infrared (ATR-FT-IR) spectroscopy to the determination of clinical parameters in serum using partial least squares (PLS) has been evaluated as a point-of-care diagnostic tool. In this study the effect of using an increased size of the calibration set and the influence of the origin of samples and their interyear variation on the prediction capability of the method were considered. PLS-ATR-FT-IR provides a green, fast and cheap point-of-care tool for the determination of total protein. Albumin, glucose, urea, HDL, LDL and total cholesterol were predicted with relative errors between 15 and 32%. The analytical predicti…
Multivariate data analysis and bivariate regression studies applied to comparison of two multi-elemental methods for analysing wine samples
2002
Two inductively coupled plasma mass spectrometry (ICP-MS) methods which permit multi-elemental analysis in wine samples have been compared following two strategies. First, a multivariate tool based on principal component analysis (PCA) was employed for a global (all analytes) qualitative comparison of the two methods. A single plot based on the confidence limits of the Q and T2 PCA model statistics corresponding to the ‘standard’ method results (calibration set) was used to check the comparability of the ‘candidate’ method (test samples). The residual matrix (after test matrix interpolation into the PCA model) gives qualitative information about the nature of the main errors. This approach …
Quantitative determination of surface area of silica gel particles by near infrared spectroscopy and chemometrics
2008
Abstract Surface areas of silica gel particles have been quantitatively determined by using near infrared spectrometry and chemometrics. Surface areas of six silica gel samples with varying surface area (300–750 m2/g) have been determined by the common Brunauer–Emmett–Teller (BET) method and used in preparing mixtures of silica gel samples with varying surface area in the ranges 300–474 and 500–750 m2/g. The near infrared spectra of the mixtures were measured and the spectral profiles calibrated against the calculated surface area of the mixtures as dependent variable using partial least squares (PLS) technique. The models obtained from the calibrations were then used in predicting the surf…
Dynamics and risk assessment of pesticides in cucumber through field experiments and model simulation
2020
Abstract Pesticides are often applied multiple times during cucumber cultivation in China. In order to obtain the residue concentrations and subsequently human health risk assessment after pesticide multiple applications, plenty of field trials have been conducted, consuming a lot of labor force and funds. The application of kinetic models can address this problem to some extent by predicting the residue values of pesticides in cucumber. In this study, a dynamic model (dynamiCROP) was applied in combination with field experiments to investigate the distribution, translocation, and dissipation after the one-time application of seven pesticides in a cucumber-soil environment. Moreover, the re…
Evaluation of Sentinel-2 Red-Edge Bands for Empirical Estimation of Green LAI and Chlorophyll Content
2011
ESA’s upcoming satellite Sentinel-2 will provide Earth images of high spatial, spectral and temporal resolution and aims to ensure continuity for Landsat and SPOT observations. In comparison to the latter sensors, Sentinel-2 incorporates three new spectral bands in the red-edge region, which are centered at 705, 740 and 783 nm. This study addresses the importance of these new bands for the retrieval and monitoring of two important biophysical parameters: green leaf area index (LAI) and chlorophyll content (Ch). With data from several ESA field campaigns over agricultural sites (SPARC, AgriSAR, CEFLES2) we have evaluated the efficacy of two empirical methods that specifically make use of the…
Partial least squares attenuated total reflectance IR spectroscopy versus chromatography: the greener method
2012
Method election is a complex task that must be done carefully in order to ensure the capability of analytical methodologies to provide appropriate data for problem solving. This is a real challenge in all fields, but especially with bioanalysis, which in many cases involves the need to do a large number of determinations in complex