Analysis Of Distribution Data Research Articles

Solvent extraction of Zn(II) by Cyanex 923 and its application to a solid‐supported liquid membrane system

AbstractThe extraction of zinc(II) by Cyanex 923 (phosphine oxides mixture) in Solvesso 100 from hydrochloric acid solution has been investigated. The extraction reaction is exothermic. The numerical analysis of metal distribution data suggests the formation of ZnCl2·L2,HZnCl3·2L and H2ZnCl4·2L(L = ligand) in the organic phase with formation constants Kext = 4.1,5.6 × 109 and 6.7 × 109, respectively. The results obtained for zinc(II) distribution have been implemented in a solid‐supported liquid membrane system. The influence of source phase stirring speed, membrane composition and metal concentration on zinc transport have been investigated.© 2001 Society of Chemical Industry

Progressive invasion and allopatric speciation can also explain distribution patterns of rock-dwelling cichlids from southern Lake Victoria: a comment on Seehausen and van Alphen (1999)

I show that distribution patterns of rock-dwelling haplochromine cichlids in the south-eastern part of Lake Victoria can be explained by allopatric speciation alone. Observed patterns are consistent with a progressive invasion of different lineages from older ( = deeper) parts of the lake, after which some lineages speciate more frequently than others. Based on a quantitative analysis of distribution data, Seehausen and van Alphen conclude that a high percentage of sympatric speciation (17.5%) is essential to explain the patterns. In my view this conclusion has its origins in an unjustifiable assumption. Seehausen and van Alphen assume that the unresolved phylogeny is balanced. However, allopatric speciation would typically result in imbalanced phylogenies.

A Dynamical Model for the Growth and Size Distribution of Multiple Metastatic Tumors

Metastasis is the spread of tumors culminating in the establishment of one or more secondary tumors at remote sites. In deciding the best treatment for cancer therapy, estimations of the colony size of metastatic tumors and predictions of the future spread of colonies are needed. A dynamical model for the colony size distribution of multiple metastatic tumors is presented here. The dynamics is described by equations that incorporate both the colonization by metastasis and the growth of each colony. When the colony growth is subject to the Gompertz function, the explicit solution obtained tends to an asymptotic stable distribution that shows a monotonically decreasing or U-shaped pattern according to the values of clinically significant parameters, such as the colonization coefficient and the fractal dimension of blood vessels. This predicted colony size distribution agrees well with successive data of a clinically observed size distribution of multiple metastatic tumors of liver cancer. The combined analysis of the theoretical colony size distribution and clinical data will give useful information on the diagnosis and the therapy for cancer patients.

Influence of Matrix Toughness on Damage Initiation and Growth in Carbon Fiber Fabric Composites

Progression of fatigue damage in toughened carbon fiber fabric composites by using matrix material of high toughness has been examined with hole-notched specimens. The matrix is toughened by impregnating solid rubber particles a fraction of a micron in diameter. The damage progression in the materials is mainly investigated as two-dimensional information by using analyses of stress distribution data obtained through the thermoelastic stress analysis (TSA). In particular, a new TDA technique developed by improving ordinary TSA has been applied to ascertain smaller (mesoscopic) failure. With the TDA data, improved matrix resin toughness actually influences to inhibit damage development in early fatigue process in the laminates. In addition, the finite element analysis is discussed in terms of a stress distribution and a strain level of damage initiation in the laminated materials.

Specific and Quantized Antigen−Antibody Interaction Measured by Atomic Force Microscopy

An atomic force microscope (AFM) has been used to directly monitor specific interactions between antigens and antibodies. By using AFM probes functionalized with the Fab fragment of an antiferritin antibody, the adhesion forces between the probe and the ferritin-coated substrates were monitored. Fourier analysis of the adhesion forces distribution data suggests quantization of the forces, with a period of approximately 63 pN. The work estimated from this unitary force and its estimated working distance was about half the free energy difference (ΔF0) relevant to the intrinsic affinity constant (K0), derived from the kinetic analysis using isothermal titration calorimetry (ITC) of the antibody−antigen interactions. This periodic force was attributed to a single unbinding event between individual antigen and antibody molecules. The probability of adhesive events was strongly influenced by the functionalization mode of the probes. Probes on which vectorially oriented Fab molecules were immobilized, without any spacers, gave much more distinct unbinding force curves than those on which the Fab molecules were randomly fixed.

EFFECT OF Y(III) DISTRIBUTION BETWEEN AQUEOUS NITRATE AND ORGANIC D2EHPA SOLUTIONS ON THE Y(III) PRECIPITATION STRIPPING USING OXALIC ACID.

ABSTRACT The solvent extraction process of yttrium (HI) from nitrate media by di(2-ethylhexyl) phosphoric acid (D2EHPA, represented as HA) has been studied as a first step to accomplish the homogeneous precipitation of yttrium oxalate from an organic metal loaded D2EHPA solution. The analysis of liquid-liquid distribution data at low metal concentrations determined YA3.2HA as the only metal organic species formed during the extraction, with a formation constant of logβ = 16·410 ± 0·055. A polymerisation of such organic metal species was observed at high metal loading of the organic phase. A comparison of these results with previous studies carried out in chloride or perchlorate media reveals a strong influence of the aqueous medium on the metal species formed in the organic phase, affecting mostly the stoichiometry of such species. The homogeneous precipitation of yttrium as yttrium oxalate using oxalic acid has been carried out as direct recovery of the metal from the organic solution. The observed precipitation-stripping kinetics has been related to the formation of organic yttrium species. The acidity of the stripping solution and the

SOLVENT EXTRACTION OF Pt(IV) BY ALIQUAT 336 AND ITS APPLICATION TO A SOLID SUPPORTED LIQUID MEMBRANE SYSTEM

ABSTRACT The extraction of Pt(IV) by Aliquat 336 (R3R'N+Cl−) in dodecane modified with 4% dodecanol from hydrochloric acid solutions has been investigated. The analysis of metal distribution data by numerical calculations suggested the formation of the species (R3R'N+)2PtCl6 2− in the organic phase with formation constant log β=5.26±0.02. The results obtained on Pt(IV) distribution have been implemented in a solid supported liquid membrane system, being NaClO4 solutions the most effective to strip the metal from the organic solution. Influence of membrane composition and metal concentration on platinum transport have also been studied.

Large angle scattering of α-particles from 32S

The elastic scattering of α-particles from 32S was studied in the incident energy range between 4 and 8.9 MeV. In order to ascertain whether quasi-molecular states exist, as predicted in the α- 32S system, excitation functions were measured, and angular distribution measurements were carried out using targets with different thicknesses in the angular range from θ lab = 30° to 175° at each extreme in the excitation functions. The analysis of the angular distribution data at back angles was performed using the Regge-pole method. A resonance with J = 3 was observed at 7.7 MeV in the α- 32S system. Evidence was also found for both a broad resonance which can be characterized by an angular momentum J = 1, and for a narrow J = 2 resonance.

A cloud-removal algorithm for SSM/I data

Microwave radiometers, while traditionally utilized in atmospheric and oceanic studies, can also be used in land surface applications. However, the problem of undesirable atmospheric effects caused by clouds and precipitation must be addressed. In this paper, temporal composite surface brightness images are generated from special sensor microwave/imager (SSM/I) data with the aid of new algorithms to eliminate small-scale distortion caused by clouds or precipitation. Mean, second-highest value, modified maximum average (MMA), and hybrid compositing algorithms are compared. The effectiveness of each algorithm is illustrated through simulation and real data distribution analysis. The results show that the second-highest value algorithm is biased high. MMA provides a more accurate brightness temperature estimate in areas of atmospheric distortion, while the mean is superior in regions with little or no distortion. A hybrid algorithm is developed that is a combination of MMA and mean. It utilizes the strengths of both to create a superior algorithm for regions with varying levels of distortion. Uses of composite images produced by these algorithms include studies of vegetation change, land cover classification, and surface parameter extraction.

Electronic properties of diamond for high-power device applications

The generation and transport of impact-ionized electrons in diamond are investigated using secondary electron emission spectroscopy. By studying secondary electron emission from diamond surfaces having a negative electron affinity (NEA), the total transmitted intensity and the full energy spectrum of the internal electrons are revealed in the measurements. Electron yield and energy distribution measurements from C(100) and CVD diamond samples are analyzed as a function of incident beam energy and information is obtained on both the internal gain and electron energy distribution following impact ionization as well as the effects of the transport process on the internal electron distribution. High internal gain and efficient electron transport are inferred from an analysis of the very high yields measured from both samples. In fact, by fitting calculated yield curves to the measured yield data, we deduce a lower limit on the electron escape depth of ∼5 μm and ∼1.3 μm in the C(100) and CVD diamond samples, respectively. Energy spectra measured from the diamond samples contain an intense, low-energy peak whose energy position and width are independent of incident beam energy. Based on an analysis of the energy distribution data, a model of the impact-ionization process in diamond is presented.

An Aggregation Index for Monitoring the State of the Suspensions

The state of aggregation in alumina, zirconia, and mixed alumina-zirconia suspensions is determined by particle size analysis of particles/aggregates in suspensions. An aggregation index is derived using principal component analysis of the size distribution data. The first principal component is shown to be an adequate single-value measure of the extent of aggregation in the suspension. Aggregation indices are obtained for suspensions prepared at different pH with and without the addition of different polymeric surfactants of varying dosage and molecular weight and employed for analyzing the state of the suspensions.

Thermodynamic characterization of the liquid–liquid extraction of silver by acyclic dithia benzene derivatives

A study of the liquid–liquid extraction equilibria between aqueous Ag(I) and 1,3-bis[(ethylthio)methyl]benzene, 1,3-bis[(pentylthio)methyl]benzene and 1,3-bis[(octylthio)methyl]benzene in chloroform solution, is reported. The results have been expressed in terms of solvent extraction reactions between Ag(I) in aqueous solution and the ligands in the organic phase. A numerical analysis of the metal distribution data has determined the following reactions to be responsible for the extraction process in all cases: Ag ++L(org)+NO − 3→[LAg(NO 3)](org) Ag ++2L(org)+NO − 3→[L 2Ag(NO 3)](org) From this analysis polynuclear species have also been found to be formed in the aqueous phase. Thus, trinuclear species [L 3Ag 3(NO 3) 3] were found to give the best interpretation of the experimental data.

Improvement of plant parameters of the ROBO gamma irradiation facility due to design modification

Two industrial scale, “ROBO” type 60Co gamma irradiation facilities have recently been put into operation in Syria and Peru, and the dosimetry commissioning of both plants have been carried out to determine dose distribution within products and to calculate plant parameters such as efficiency, dose uniformity ratio and throughput. There are some design modifications between the two plants in connection with the location of the carriers with respect to the source plaque and also to each other. The effect of these construction modifications on the plant parameters is discussed in the analysis of the dose distribution data measured in the carriers with depth and height among the four irradiation rows on both sides of the source plaque. The plant parameters were also calculated for different product densities using the technical data of the facilities, and the calculated and measured results were compared to each other.

Minor Elements Distribution between Iron-Silicate Base Slag and Ni<SUB>3</SUB>S<SUB>2</SUB>–FeS Matte under High Partial Pressures of SO<SUB>2</SUB>

As a fundamental study to elucidate the behavior of several minor elements in the oxygen-smelting process of nickel sulfide ore, equilibrium distributions of Cu, Ag, Co, As, Sb and Bi between the iron-silicate base slag with saturated silica and Ni 3 S 2 -FeS matte phases in a magnesia crucible were investigated at 1573 K under controlled partial pressures of S 2 , O 2 and SO 2 with 10.1, 50.7 and 101.3 kPa. The distribution ratio of X, L s/m X defined as (mass%X in slag)/ {mass%X in matte}, were plotted in relation to the nickel content in the matte (matte grade) and compared with the available data. At a fixed pso 2 , the distribution ratios of Cu, Co, As and Sb increase slightly with increasing matte grade, and in the cases of Ag and Bi, L s/m X decrease with increasing matte grade up to about 45 mass%Ni and then increase in the higher range. When the matte grade is specified, the distribution ratios of Co, As, Sb and Bi increase with increasing pso 2 while L s/m Cu and L s/m Ag are almost independent of p SO2 . The Raoultian activity coefficients of either metallic or sulfide species of the minor elements in the matte phase were derived, based on a thermodynamic analysis of the experimental distribution data. The sulfide species of cobalt in the matte was estimated to be CoS 2/3 .

THERMODYNAMIC EQUILIBRIA OF THE EXTRACTION OF CHROMIUM(VI) WITH TRI-N-OCTYLPHOSPHINE OXIDE FROM AQUEOUS SOLUTIONS

ABSTRACT The distribution of chromium( VI ) between aqueous solutions and the kerosene solutions of tri-n-octyl-phosphine oxide (TOPO) have been studied at 25 °C and pH 2-4, in which range the predominant forms of Cr(VI) are HCrO4 and Cr2O7 2−. The extraction equilibrium is influenced by the total chromium(VI) concentration, aqueous pH value, and total extractant concentration. The thermodynamic equilibria among all species in the aqueous phase were used for the analysis of distribution data, and the activity coefficients of ionic species were estimated according to Debye-Hiickel or Bromley equation. By numerical method, the complexes of Cr(VI ) with TOPO formed in the organic phase were found to be H2CrO4 (TOPO) and H2Cr2O7 (TOPO) 3. The corresponding extraction constants were 2019 and 3.69× 108, respectively.

Detection of antigen-antibody binding events with the atomic force microscope.

An atomic force microscope (AFM) has been used to directly monitor specific interactions between antibodies and antigens employed in an immunoassay system. Results were achieved using AFM probes functionalized with ferritin, and monitoring the adhesive forces between the probe and anti-ferritin antibody-coated substrates. Analysis of the force distribution data suggests a quantization of the forces, with a period of 49 +/- 10 pN. This periodic force may be attributed to single unbinding events between individual antigen and antibody molecules. These results demonstrate that the AFM could be employed as an analytical tool to study the interactions between the molecules involved in biosensor systems. The potential of the technique to provide information relating to the manner in which the antibody molecule binds to its specific antigen is also discussed.

Patterns of plant species endemism in Ecuador

Distribution patterns of plant species endemic to Ecuador and adjacent parts of southern Colombia and northern Peru are analysed on the basis of information in the Flora of Ecuador. A total of 827 restricted-range species were found, many of which are known from extremely small areas, often only one or a few localities. A total of 27% of the species treated in the Flora of Ecuador are endemic to that country. The overall proportion of endemic and restricted-range species is greater in the Andes than in the lowland areas on either side of these mountains; particularly the southern Andes appears to be very rich in endemic species. Spatial analysis of distribution data results in the recognition of 15 floristic elements and 18 geographical endemism regions in Ecuador, the characteristics of which are discussed. Comparison with distribution patterns of restricted-range bird species show a general correspondence, with the main difference that birds tend to be more widely distributed than plants along the Andes. Comparison of the results with the location of national parks and other protected areas shows that the endemic floras in the northern and eastern parts of the country are much better protected than those of the southern and western parts.

Modern Benthic Foraminifer Distribution in the Amerasian Basin, Arctic Ocean

A total of 38 box cores were collected from the Amerasian Basin, Arctic Ocean during the U.S. Geological Survey 1992 (PI92-AR) and 1993 (PI93-AR) Arctic Cruises aboard the U.S. Coast Guard Icebreaker Polar Star. In addition, the cruises collected geophysical data, piston cores and hydrographic data to address the geologic and oceanographic history of the western Arctic Ocean. This paper reports the results of the quantitative analyses of benthic foraminifer distribution data of the total (live + dead) assemblages derived from 22 box core-top samples. The results show that a distinct depth distribution of three dominant benthic foraminifer assemblages, the Textularia spp. - Spiroplectammina biformis, Cassidulina teretis and Oridorsalis tener - Eponides tumidulus Biofacies are strongly controlled by the dominant water masses within the Canada Basin: the Arctic Surface Water, Arctic Intermediate Water and Canada Basin Deep Water. The faunal distributions and their oceanographic associations in the Canada Basin are consistent with observations of benthic foraminifer distributions from other regions within the Arctic Ocean.

SCN − effect on the palladium(II) transfer in two and three phases systems using triphenylphosphine sulfide as a carrier

The extraction of Pd(II) by triphenylphosphine sulfide (TPPS) in toluene from hydrochloric acid solutions containing small amounts of SCN − has been investigated. The role of thiocyanate on the Pd(II) extraction is explained as a trans-effect with the formation of mixed complexes PdC l4− n (SCN) n 2−, less inert to ligand substitution than the chloride complexes. The analysis of metal distribution data by numerical calculations suggested the formation of the species Pd(SCN) 2·TPPS and Pd(SCN) 2·2TPPS in the organic phase with formation constants log K 021 = 13.00 and log K 022 = 14.24, respectively. A comparison of the results with those obtained using triisobutylphosphine sulfide (TIBPS) under similar conditions reveals a lower influence of SCN − concentration and also lower values for Pd(II) extraction, which can be attributed to the electron withdrawing characteristics of the aromatic ring with a decrease of the solvating power of the S atom for TPPS. The results obtained on Pd(II) distribution have been exploited in a three phases system by implementing a solid supported liquid membrane, being thiocyanate concentration the driving force of the mass transfer process. The behavior of the system is similar to that observed in the two phases.

Infrared Microspectroscopy of Bauxitic Pisoliths

Bauxite ore in the deposit at Weipa, Queensland, Australia occurs as pisoliths which are small, approximately spherical, pebbles with diameters in the range 0.5 to 2 cm. The distribution of various mineral species within the pisoliths has been determined by the use of reflectance infrared microspectroscopy of a large suite of pisoliths obtained from different parts of the Weipa orebody. The method allows the significant minerals of the bauxite to be analyzed including gibbsite (aluminium trihydroxide), boehmite (aluminium oxyhydroxide), quartz, and the clay, kaolinite. These minerals are readily distinguished by their IR spectrum. The iron minerals, present in small amounts, could not be detected. Specular reflectance spectra of sectioned pisoliths were measured, and the spectrum was utilized directly without the application of the Kramers–Kronig transformation. Polished pisolith sections were also mapped at a spatial resolution of 100 μm with the use of a computer-controlled microscope stage, and the mineral composition at any point was estimated by measuring relevant areas of the spectrum. Semi-quantitative results were obtained by relating the reflectance spectra for a particular pisolith thin section to the transmittance spectra for the same points. The transmittance spectra of the pisoliths were correlated with spectra of pure standards by application of a multicomponent Q-matrix approach. Principal component analysis of the mineral distribution data allowed the suite of pisoliths to be subdivided into groups with similar mineralization.