bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metal‐complex‐bearing star polymers by metal‐catalyzed living radical polymerization: Synthesis and characterization of poly(methyl methacrylate) star polymers with Ru(II)‐embedded microgel cores
Authors: Terashima Takaya , Ouchi Makoto , Ando Tsuyoshi , Kamigaito Masami , Sawamoto Mitsuo 
Published: July 2006

AbstractOne‐pot, spontaneous, and in‐situ incorporation of Ru(II) complexes into a microgel (solubilized nanometer‐scale network) has been achieved in near quantitative efficiency by a polymer‐linking reaction of linear living poly(methyl methacrylate) (PMMA) with a bifunctional methacrylate (ethylene glycol dimethacrylate or bisphenol A dimethacrylate; linking agent) and a phosphine‐ligand monomer [diphenyl‐4‐styryl‐phosphine (3); i.e., CH2CHC6H4p‐PPh2] in the RuCl2(PPh3)3‐catalyzed living radical polymerization. The products were Ru‐bearing. PMMA‐armed star polymers with a microgel‐core that consisted of a copolymer network of the linking agent and 3. Upon the network formation, the phosphine ligands efficiently encapsulated RuCl2(PPh3)3, thus achieving a polymer catalyst directly from a polymerization catalyst. Colored dark brown‐red, the star polymers exhibited UV‐vis absorptions originating from the entrapped complex (3.1–7.4 × 10−5 mol Ru/g of polymer), the incorporation efficiency being close to 100% with respect to the original polymerization‐catalyst. Detailed spectroscopic characterization showed the following: an absolute molecular weight of 1.7 × 105 to 1.7 × 106, an arm number of 11–92 arms/polymer, and a radius of gyration of 8–19 nm (in DMF). Direct observation of the individual star molecules in solid state was achieved by transmission electron microscopy (unstained; 2–3 nm dark dots for the core) and atomic force microscopy (semi‐circular images). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4966–4980, 2006
In situ generation of nitroxide from alkoxyamines for controlled acrylate polymerization
Authors: Xia Qing , Grubbs Robert B. 
Published: July 2006

AbstractA general strategy for the controlled nitroxide‐mediated polymerization of acrylates from alkoxyamines without addition of excess free nitroxide is outlined. 2,2‐Dimethyl‐3‐(1‐phenylethoxy)‐4‐phenyl‐3‐azapentane (1), prepared in one pot by the addition of 1‐phenylethyl radicals to 2‐methyl‐2‐nitrosopropane, is heated prior to the addition of monomer to afford a mixture of alkoxyamine 1, free nitroxide, and 2,3‐diphenylbutane. With a 30 min preheating period at temperatures up to 125 °C, the kinetics of the subsequent polymerization of n‐butyl acrylate at 125 °C appear largely unaffected, though the ultimate molecular weight of the polymers is dependent upon the preheating temperature. The poly(n‐butyl acrylate) samples, that result from this process, have much narrower molecular weight distributions than those which result in the absence of the preheating process. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5128–5136, 2006
Self‐assembled lipid nanotube hosts: The dimension control for encapsulation of nanometer‐scale guest substances
Authors: Shimizu Toshimi 
Published: July 2006

AbstractSupramolecular nanotube hosts with precisely controlled inner or outer diameters have been synthesized by self‐assembly of unsymmetrical bolaamphiphilic monomers or glucopyranosylamide lipids, respectively. Time‐resolved fluorescent measurement using 8‐anilinonaphthalene‐1‐sulfonate (ANS) as a probe revealed that the water confined in a cardanyl‐β‐D‐glucopyranoside lipid nanotube has relatively lower solvent polarity corresponding to that of propanol than bulk water. Extensively developed hydrogen bond networks also characterize the confined water in comparison to the case in bulk water. Encapsulation ability of the glucopyranosylamide lipid nanotube has been examined by filling the lyophilized LNTs with gold or silver nanoparticles, ferritin, or magnetic crystals. Filling the unsymmetrical bolaamphiphile nanotube possessing positively charged inner surfaces with negatively charged polymer beads or ferritin proved to be successful without depending on capillary action. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5137–5152, 2006
The Accumulation of Oleosins Determines the Size of Seed Oilbodies inArabidopsis
Authors: Siloto Rodrigo M.P. , Findlay Kim , Lopez-Villalobos Arturo , Yeung Edward C. , Nykiforuk Cory L. , Moloney Maurice M. 
Published: July 2006

AbstractWe investigated the role of the oilbody proteins in developing and germinating Arabidopsis thaliana seeds. Seed oilbodies are simple organelles comprising a matrix of triacylglycerol surrounded by a phospholipid monolayer embedded and covered with unique proteins called oleosins. Indirect observations have suggested that oleosins maintain oilbodies as small single units preventing their coalescence during seed desiccation. To understand the role of oleosins during seed development or germination, we created lines of Arabidopsis in which a major oleosin is ablated or severely attenuated. This was achieved using RNA interference techniques and through the use of a T-DNA insertional event, which appears to interrupt the major (18 kD) seed oleosin gene of Arabidopsis and results in ablation of expression. Oleosin suppression resulted in an aberrant phenotype of embryo cells that contain unusually large oilbodies that are not normally observed in seeds. Changes in the size of oilbodies caused disruption of storage organelles, altering accumulation of lipids and proteins and causing delay in germination. The aberrant phenotypes were reversed by reintroducing a recombinant oleosin. Based on this direct evidence, we have shown that oleosins are important proteins in seed tissue for controlling oilbody structure and lipid accumulation.
A FIELD METHOD OF MEASURING THE SHEAR STRENGTH OF SOILS
Authors: PAYNE P. C. J. , FOUNTAINE E. R. 
Published: July 2006

SummarySoil shear strength is a property likely to affect the performance of cultivation implements. Existing methods of measuring this property have been found unsuitable for cultivated top soils, principally because of the difficulty of obtaining an undisturbed sample. A field method of determining shear strength is described in which a cylinder of soil is sheared in torsion and a moment/angle‐of‐twist (proportional to strain) curve obtained. From this the shear‐stress/angle‐of‐twist can be obtained mathematically. Where only the maximum shear strength is required a simplified method is given. A number of results using the apparatus on widely differing soil types is given, together with a comparison of some of these with results from the standard shear box.
MICROBIOLOGICAL STUDIES OF SOME SUBANTARCTIC SOILS
Authors: BUNT J. S. , ROVIRA A. D. 
Published: July 2006

SummaryA study has been made of the rhizosphere effect of four subantarctic plant associations at Macquarie Island. A stimulation occurred in each case in the rhizosphere, even in the more primitive Azorella selago and Dicranoweisia antarctica associations.No qualitative differences were found between rhizosphere and non‐rhizosphere isolates. The temperature range of most isolates was 10° to 25°C. with a high proportion giving maximum growth at 25° C.Respiration measurements were made on I I soils using the Warburg respirometer and a marked correlation was found between total carbon content of the soil and respiration. The variations in respiratory quotient which occurred were not related to carbon content and were probably due to differences in chemical constitution of the organic‐matter fractions and soil aeration.
THE EFFECT OF TEMPERATURE AND HEAT TREATMENT ON SOIL METABOLISM
Authors: BUNT J. S. , ROVIRA A. D. 
Published: July 2006

SummaryThe respiration of subantarctic and subtropical soils was found to increase as temperature increased from 100 to 37°C. The gas exchange decreased between 37° and 50°C., but increased with further increase in temperature.The oxygen uptake of soil subjected to various heat treatments showed an increase with the severity of treatment. The ratio of COa evolved to oxygen consumed of heat‐sterilized soil was always below 0.4, indicating a different oxidation process from that of unsterilized soils in which the ratio approximates 1.0. The activity of heat‐sterilized soil was not inhibited by NaCl, NaN3, or HgCl2, indicating that a non‐enzymic oxygen uptake and CO, evolution were occurring.Chemical oxidation also seems to occur in unsterilized soils at high temperatures, and is likely to be a factor in the decline in organic matter in dry, exposed soils.Oxidative enzymes of ‘dead’ micro‐organisms appear to be chiefly responsible for the immediate respiration on wetting an air‐dry soil.
COARSE PARTICLE DISTRIBUTION IN THE SKELETON OF SOME COARSE‐ TO MEDIUM‐TEXTURED SOILS1
Authors: SWANSON C. L. W. , RITCHIE A. , DOEHNE H. A. 
Published: July 2006

AbstractIn New England many of the soils are predominantly sandy and gravelly. Because of the intensive agriculture practised, costing as much as $2,000 per acre to produce some crops, obtaining quantitative data on the content and distribution of coarse particles in the profiles of these soils is useful in predicting their behaviour in the growing of highly specialized crops. For example, the highest quality cigar tobacco is grown on the coarser‐textured soils. A quantitative study of the coarse particles in ten profiles each of the Hinckley and Merrimac series and four profiles each of the Cheshire and Enfield series has been made. The Hinckley was outstanding in containing more than 60 per cent. gravel in the D1; the Merrimac was intermediate with 25 per cent. in the D2; the Cheshire and Enfield next in order with about 20 per cent. in the substratum. For the Cheshire and Enfield soils, the gravel content was about 2 per cent. greater in the Ap, horizon of the cultivated soil than in the forested counterpart. Organic matter losses and compaction decreased their total porosity 25 per cent. These factors plus removal of stones for cultivation are thought to account for about one‐half of the reduction in thickness of the solum; the remainder probably is due to soil removal by erosion.
PROFILE DEVELOPMENT IN THE SAND DUNES OF CULBIN FOREST, MORAYSHIRE
Authors: WRIGHT T. W. 
Published: July 2006

SummaryChanges in some physical properties of the sand dunes of Culbin Forest, Morayshire, brought about by fixation and afforestation of the sand, have been studied on sites ranging from bare sand to mature plantations. Trees appear to be having no measurable effect on the mechanical composition of the sand apart from the deposition of litter, but studies of soil moisture and temperature, using gypsum moisture blocks and thermistors, have shown that, while the moisture content of the unplanted dunes remains comparatively high throughout the growing season due to their coarse texture, the growth of trees dries out the sand considerably, although the total moisture‐holding capacity of the upper soil layers in the older stands is greatly increased by the incorporation of organic matter. The artificial fixation of the dunes by means of brushwood (“thatching”) has been found to be an efficient method of conserving soil moisture.
ION‐EXCHANGE PHENOMENA IN SOME SOILS CONTAINING AMORPHOUS MINERAL CONSTITUENTS
Authors: BIRRELL K. S. , GRADWELL M. 
Published: July 2006

SummarySoils containing allophane, “palagonite”, and amorphous oxides have been found to give cation‐exchange capacity values as determined by conventional methods, which depend markedly upon concentration of leaching solution, the cation in the solution, the volume of the washing alcohol, and its water content. Experiments in which the soil is brought to equilibrium with solutions of barium acetate adjusted to pH 7, and containing an excess of barium with respect to the cation‐exchange capacity value given by the leaching method, indicate that the uptake of cation conforms to the Brunauer, Emmett, and Teller theory of multilayer physical adsorption. Similar results are also given by barium‐chloride and lithium‐acetate solutions at pH 7. Adsorption does not take place in the absence of water, and it is thought that it is the hydrated cation which is effective in covering the surface. Adsorption is strongly influenced by equilibrium pH values of the solutions. The adsorption of cations by these soils closely resembles the behaviour of hydrated alumina prepared by precipitation from sodium aluminate with CO2. The acetate and chloride anions are taken up to a much smaller extent than the cations. Titration experiments indicate that soils containing allophane exhibit little if any tendency to hold exchangeable hydrogen ions in the same manner as montmorillonite.
A REVIEW OF TRACER STUDIES IN SASKATCHEWAN ON THE UTILIZATION OF PHOSPHATES BY GRAIN CROPS*
Authors: MITCHELL J. 
Published: July 2006

SummaryThe use of P32 as a tracer has been particularly valuable in studying the uptake of phosphorus from fertilizer and soil. It is a technique which may be used to differentiate between the availability of phosphorus in both soils and fertilizers.The work was done on soils well supplied with lime. The fertilizer was drilled with the seed unless otherwise stated.Results show that the wheat plant obtains most of its phosphorus from the fertilizer in the early stages of growth. The proportion obtained from the soil increases rapidly after the fourth week. Most of the phosphorus in the above‐ground part of the plant migrates to the head of the plant as it matures.Increasing the rate of application of the fertilizer results in a decreased utilization of soil phosphorus with a proportional increase in uptake of fertilizer phosphorus. The availability of phosphorus varies greatly in different carriers. Under the soil and climatic conditions to which the data apply mono‐ammonium phosphate had superior availability to calcium phosphates. Di‐calcium phosphates are relatively lower in availability than mono‐calcium phosphates. The availability of fertilizer phosphorus can be increased through the incorporation of small quantities of sulphur in the material. In drier areas at least the phosphatic fertilizers appear to be most effective when placed close to the seed. Under drought conditions a larger proportion of the phosphorus utilized by the plant comes from the fertilizer. Increased yields may result from the application of phosphates even under extreme drought conditions.Certain varieties of barley respond better to phosphatic fertilizer than do others. This differentiation did not appear in the wheat and oat varieties tested.The effect of different levels of radiation on plant growth and uptake of phosphorus has been studied in considerable detail. Deviations in results caused by radiation are considered unlikely to affect the type of experiments reported in this paper.
ISOTOPICALLY EXCHANGEABLE PHOSPHORUS IN SOILS
Authors: TALIBUDEEN O. 
Published: July 2006

SummaryMethods used to determine isotopically exchangeabIe phosphorus in soils are described and briefly analysed. The influence of soil: solution ratio, orthophosphate ions added with radio‐phosphorus, the equilibrium pH, and the removal of increasing amounts of phosphate from the soil are investigated. A scheme is suggested for the subdivision of the total soil phosphate into four fractions on the basis of their abilities to exchange PO4 ions with the phosphate in the soil solution. The relation between the labile pool of soil phosphate and this scheme is discussed.
A RECONNAISSANCE CLASSIFICATION OF THE SOILS OF THE SOUTH TURKANA DESERT
Authors: HEMMING C. F. , TRAPNELL C. G. 
Published: July 2006

Summary Development of the Soil Pattern As an outcome of an ecological reconnaissance this account provides a record of the occurrences of two major regional types, a system of consolidated sand dunes and derived sands, referred to here as the Chestnut Sands, and a wide assortment of stony truncated ‘desert pavement’ soils or soil remnants described as Stone Mantles. The latter involve areas both of basement complex and of lava origin. Briefer observations are also given on other soils of lesser extent, including flash‐flood, alluvial and lacustrine deposits.Although a present‐day desert or semi‐desert, the south Turkana region bears the stamp of successive erosion cycles, which have largely influenced its soil pattern. Modified remnants of the original end‐Tertiary surface are probably discernible in the higher‐lying stone mantles about the central hill ranges (Section 2, Introd.). Residual stone mantles of this class appear to be the last truncated remnants of an ancient soil cover. Ancient alluvial and lacustrine deposits, the former of conjectured and the latter of established Pleistocene age, have provided the material for other stone mantle areas (Section 2 (b)). The present surface of all these has been affected by more recent erosion and deflation.On top of these several types of stone mantle, or the stony soils from which they originated, seems to have been deposited the deep mantle of the Chestnut Sands, blanketing at one time the greater part of the Turkana plain. These dune sands are regarded as a mainly aeolian drift, deposited during a period of active arid erosion, though their materials may have been derived from older surfaces (Section I, Introd.). They must be subsequent to the deposits which they overlie, and may possibly be compared with the Goz or Kordofan Sands of the Sudan, which have been very tentatively referred to the late Pleistocene (Andrew, 1948).As with the Goz Sands, the dunes of the Chestnut Sands presumably became fixed under less arid conditions. Finally, in common with the rest of the Turkanalandscape, they have been subjected to the present régime of brief seasonal flash‐flood erosion and intervening wind action. Their formerly extensive dune structure has been greatly modified and from many areas they appear to have been removed wholesale. The redeposited Chestnut Sands, the flash‐flood deposits and sandy riverine alluvia are the outcome of this latest phase of erosion. At the same time tracts of comparatively recent lacustrine sands and possible deltaic silts (Section 4 (b) have been left in the east of the region as a result of the progressive retreat of Lake Rudolf.The influence of the resulting soil pattern on the vegetation of the region is very briefly indicated, with reference more particularly to the principal shrub components.
A RELATION BETWEEN PERMEABILITY AND SIZE DISTRIBUTION OF PORES
Authors: MARSHALL T. J. 
Published: July 2006

SummaryAn equation has been derived for the relation between permeability and the size distribution of the pores in isotropic material. If the mean radius of the pores in each of n equal fractions of the total pore space is represented in decreasing order of size by r1, r2., and rn cm. respectively, then permeability is given by
image
where is the porosity in cm.3/cm.2 of porous material, and K is in units of cm.2 By this means, permeability can be calculated from she curve relating water content to suction. This has been tested on published data for flow of air through porous stones and flow of water through saturated and unsaturated sands. Calculated values have been found to agree satisfactorily with measured values over a wide range of permeability.The Kozeny equation is discussed as a particular case of this equation
STUDIES ON THE BASALTIC SOILS OF NORTHERN IRELAND V. CATION‐EXCHANGE CAPACITIES AND MINERALOGY OF THE SILT SEPARATES (2–20μ)
Authors: McALEESE D. M. , MITCHELL W. A. 
Published: July 2006

SummaryX‐ray and chemical studies of silt separates (2–20μ) from basaltic soils were made to determine the origin of the rather high cation‐exchange capacities (C.E.C.) found for these separates. The silts as isolated by the usual method of mechanical analysis consisted in the main of quartz and feldspars with variable amounts of clay minerals which occurred as aggregates. These aggregates were of two types:(a) Composed of clay‐size particles, i.e. <2μ cemented or bound into silt‐size aggregates by ‘free’ sesquioxides of which the basaltic soils have a high content. The aggregates were disrupted by reduction and the clay particles subsequently released.(b) ‘Pseudo‐aggregates’ which were shown to be individual particles of silt‐size dimensions and having a flaky appearance. These particles were either vermiculitic (under good drainage conditions) or montmorillonitic (under poor drainage conditions), and it is suggested that they form intermediate products in the weathering of primary‐rock minerals to clay minerals.Whilst the major contributor to the C.E.C. of the silts was undoubtedly the ‘pseudo‐aggregates’ and to a lesser extent the true clay aggregates, most of the silt separates had a much higher C.E.C. than implied by their mineralogical composition.
CHEMICAL STUDIES OF PODZOLIC ILLUVIAL HORIZONS
Authors: MARTIN A.E. , REEVE R. 
Published: July 2006

SummaryTitration curves of humus suspensions (prepared from some representative podzol B horizons by acetylacetone extraction) in o.1 N KCL are Presented. The shape of each curve (in absence of added metal ions) and the apparent PK value (PKe) derived from it are affected by the amount of Al contained in the suspension. One soil extract (initial PH 3.6) had a C/Al ratio of 4.9 and gave PKe= 6.21, Whereas the amberlite‐treated extract (initial PH 2.6) had a C/Al ratio of 152 and PKe= 4.12. Extrapolation of PKe values to zero concentration of Al gave limiting values of 4.o and 3.8 for the humus extracted from a Queensland and a New Zealand podzol respectively. These figures are lower than those normally quoted for humic acid, but they may be characteristic of the translocated humus of podzols.Titration curves of fresh humus extracts with added Al+++, Fe+++ or divalent transition metal ions did not suggest the presence of complex sites although the results for Fe+++ are uncertain owing to the complexity of the equilibria involved Similar titrations with added Al+++ and Cu++ using amberlite‐treated extracts did not indicate potential complex sites and, as before, the Fe+++ data were inconclusive. By analogy with Cu++ it is unlikely that Fe complexes ate present in these systems. It is concluded that humus is immobilized in these horizons by elexctrostatic bonding with Al+++ (since free Fe+++ would not exist at the soil PH), and the residual Al contained in the organic micelles in suspension is probably also bound by Coulomb forces. It is pointed out that the approximate methods used in this study for practically metal‐free preparations may not reveal the presence of the type of complexes found by other workers for some synthetic Polyelectrolytes.
FACTORS AFFECTING THE ABILITY OF PLANTS TO ABSORB PHOSPHATE FROM SOIL
Authors: RUSSELL R. SCOTT , RUSSELL E. W. , MARAIS P. G. 
Published: July 2006

SummaryBarley, rye, and cabbage have been used as test plants to measure labile soil phosphate by the Larsen procedure. In some soils higher values are given by rye and cabbage than by barley. These differences are believed to reflect the greater ability of cabbage and rye to lower the free energy of phosphate in the external medium. Thus, in soils contai& ncaring large quantities of labile phosphate at a low potential, sources of phosphate that are inaccessible to barley are accessible to the other two species.