Bulk Phosphorus Research Articles

Controlled doping of silicon nanocrystals investigated by solution-processed field effect transistors.

The doping of semiconductor nanocrystals (NCs), which is vital for the optimization of NC-based devices, remains a significant challenge. While gas-phase plasma approaches have been successful in incorporating dopant atoms into NCs, little is known about their electronic activation. Here, we investigate the electronic properties of doped silicon NC thin films cast from solution by field effect transistor analysis. We find that, analogous to bulk silicon, boron and phosphorus electronically dope Si NC thin films; however, the dopant activation efficiency is only ∼10(-2)-10(-4). We also show that surface doping of Si NCs is an effective way to alter the carrier concentrations in Si NC films.

Integrated Nutrient Management to Improve Finger Millet Productivity and Soil Conditions in Hilly Region of Eastern India

Studies on effective integrated nutrient management (INM) modules for marginal landholders of eastern India relying upon crops, such as finger millet (Eleusine coracana L. Gaertn), are lacking. Thus, an experiment was conducted on farmer's field for three years (2002−2004) at Malipungar watershed in the Koraput district of Odisha, India, to evaluate various INM combinations and select the most remunerative INM option relative to productivity and profitability of finger millet crop and soil properties. The seven INM treatments consisted of different combinations of Gliricidia green-leaf manure, farmyard manure (FYM), synthetic fertilizers, and bio-fertilizers and compared with farmer's practice. The treatments were arranged in a randomized complete-block design replicated three times. Yield and net returns from Gliricidia-amended plots were greater than those from the FYM-amended plots. Soil-moisture status during crop period and bulk density, soil pH, organic carbon (C), and phosphorus (P) at the end of the three-year experiment were comparable between Gliricidia-and FYM-amended plots. Residual amounts of N and K were significantly higher in the plots amended with Gliricidia. Overall, the treatment receiving 50% recommended dose of fertilizers (RDF), Gliricidia at 2.5 t ha−1, and 2.5 kg ha−1 each of Azotobactor and phosphorus solubilizing bacteria (PSB) as soil inoculants (INM7) produced the highest grain yield (3.95 t ha−1), net returns (US$ 400 ha−1), and highest benefit:cost ratio (2.39). Year x INM interaction effects for growth parameters, such as shoots plant−1, dry matter plant−1, dry root weight plant−1, and straw yield were significant. The INM7 was significantly better than most of the other INM treatments for growth parameters and straw yield during two (2003 and 2004) out of three study years and hence was consistently better. Therefore, integrated use of 50% RDF, 2.5 t ha− 1 Gliricidia, and 2.5 kg ha−1 each of Azotobactor and PSB (INM7) is recommended for improving productivity of finger millet in eastern India.

Will hydrologic restoration of Mississippi River riparian wetlands improve their critical biogeochemical functions?

Riparian wetlands are essential components of the landscape, providing critical functions including buffers for floodwaters, wildlife habitat and improvement of surface water quality. Many riparian wetlands have been hydrologically disconnected from the Mississippi River by a vast system of levees, altering the ecosystem services provided by these riparian zones. Efforts are underway to restore these ecosystem services, however previous research demonstrated that the statutory requirements guiding wetland restoration do not adequately consider soil biogeochemical cycling. We examined soil properties and biogeochemical indicators of nitrogen cycling to assess soil recovery in a recently hydrologically restored riparian wetland. This restored wetland, reconnected with the river for approximately two years, was compared to a nearby reference wetland where the river connection has been constant. Seasonal measurements included bulk density, total carbon, nitrogen and phosphorus, microbial biomass nitrogen, potentially mineralizable nitrogen (PMN) and potential denitrification. There were significant differences found for nearly all measured soil properties with higher bulk density and lower total C, total N, microbial biomass, PMN and potential denitrification at the restored compared to the reference site. The PMN and potential denitrification at the restored site plots were 27–46% and 2% (respectively) of the values measured at the reference site. This clearly demonstrates that while the regulatory indicators of success are improving, some critical biogeochemical functions of the restored sites are significantly lower than the reference site two years after hydrologic restoration.

The high PT stability of apatite and Cl partitioning between apatite and hydrous potassic phases in peridotite: an experimental study to 19 GPa with implications for the transport of P, Cl and K in the upper mantle

High PT experiments were performed in the range 2.5–19 GPa and 800–1,500°C using a synthetic peridotite doped with trace elements and OH-apatite or with Cl-apatite + phlogopite. The aim of the study was (1) to investigate the stability and phase relations of apatite and its high PT breakdown products, (2) to study the compositional evolution with P and T of phosphate and coexisting silicate phases and (3) to measure the Cl-OH partitioning between apatite and coexisting calcic amphibole, phlogopite and K-richterite. Apatite is stable in a garnet-lherzolite assemblage in the range 2.5–8.7 GPa and 800–1,100°C. The high-P breakdown product of apatite is tuite γ-Ca3 (PO4)2, which is stable in the range 8–15 GPa and 1,100–1,300°C. Coexisting apatite and tuite were observed at 8 GPa/1,050°C and 8.7 GPa/1,000°C. MgO in apatite increases with P from 0.8 wt% at 2.5 GPa to 3.2 wt% at 8.7 GPa. Both apatite and tuite may contain significant Na, Sr and REE with a correlation indicating 2 Ca2+=Na+ + REE3+. Tuite has always higher Sr and REE and lower Fe and Mg than apatite. Phosphorus in the peridotite phases decreases in the order Pmelt ≫ Pgrt ≫ PMg2SiO4 > Pcpx > Popx. The phosphate-saturated P2O5 content of garnet increases from 0.07 wt% at 2.5 GPa to 1.5 wt% at 12.8 GPa. Due to the low bulk Na content of the peridotite, [8]Na[4]P[8]M2+−1[4]Si−1 only plays a minor role in controlling the phosphorus content of garnet. Instead, element correlations indicate a major contribution of [6]M2+[4]P[6]M3+−1[4]Si−1. Pyroxenes contain ~200–500 ppm P and olivine has 0.14–0.23 wt% P2O5 in the P range 4–8.7 GPa without correlation with P, T or XMg. At ≥12.7 GPa, all Mg2SiO4 polymorphs have <200 ppm P. Coexisting olivine and wadsleyite show an equal preference for phosphorus. In case of coexisting wadsleyite and ringwoodite, the latter fractionates phosphorus. Although garnet shows by far the highest phosphorus concentrations of any peridotite silicate phase, olivine is no less important as phosphorus carrier and could store the entire bulk phosphorus budget of primitive mantle. In the Cl-apatite + phlogopite-doped peridotite, apatite contains 0.65–1.35 wt% Cl in the PT range 2.5–8.7 GPa/800–1,000°C. Apatite coexists with calcic amphibole at 2.5 GPa, phlogopite at 2.5–5 GPa and K-richterite at 7 GPa, and all silicates contain between 0.2 and 0.6 wt% Cl. No solid potassic phase is stable between 5 and 8.7 GPa. Cl strongly increases the solubility of K in hydrous fluids. This may lead to the breakdown of phlogopite and give rise to the local presence in the mantle of fluids strongly enriched in K, Cl, P and incompatible trace elements. Such fluids may get trapped as micro-inclusions in diamonds and provide bulk compositions suitable for the formation of unusual phases such as KCl or hypersilicic Cl-rich mica.

Grain Boundary Segregation of Phosphorus and Columnar Grain Growth during Decarburization in Plain Carbon Steels

During decarburization of plain carbon steels, the grain boundary segregation concentration of phosphorus increased with increasing bulk phosphorus content and with decreasing decarburization temperature. The grain growth kinetics decreased with increasing bulk phosphorus content which is due to the grain boundary pinning effect of highly segregated phosphorus. After decarburization at 973 K for 24 h, the columnar grain growth following the abnormal grain growth was observed in the steel containing a low bulk phosphorus content, while the steel containing a high bulk phosphorus content showed only the abnormal grain growth behavior. Such grain growth behaviors can be understood in the light of the abnormal grain growth driven by the grain boundary carbides and the solute drag effect of highly segregated phosphorus on moving grain boundaries. During decarburization at 1173 K, only the normal grain growth was observed due to the absence of grain boundary carbides, regardless of the bulk phosphorus content. The decarburization reaction in the present study can be expressed by the parabolic relationship x = k(Dt)1⁄2 where x is the decarburization depth, k the reaction coefficient, D the diffusivity of carbon and t the decarburization time.

Observing Changes in Riparian Buffer Strip Soil Properties Related to Land Use Activities in the River Njoro Watershed, Kenya

Riparian buffer strip guidelines are under scrutiny in the River Njoro Watershed in Kenya. This study investigated soil properties (bulk density, carbon, nitrogen, and phosphorus) in different land use types (small scale agriculture in recent settlements, mixed agriculture in established peri-urban settlements, large- scale commercial agriculture, and the gazetted forest reference condition) and their adjacent buffer strips. Bulk density, carbon, nitrogen, and phosphorus within 30-m riparian buffer strips adjacent to recent settlement landuseareasweresimilar tothoseofthegazettedforest reference condition, but only bulk density of the buffer strips adjacent to peri-urban and commercial agriculture land use areas were similar to the gazetted forest reference condition. Phosphorus is a sensitive indicator of the impacts of human activity, as increased concen- trations were observed with increasing scale of land use activity. For riparian buffers adjacent to recent settle- ments, soil phosphorus was significantly higher in buffers narrower than 30 m (5.01 mg P kg −1 )t han gazetted forest (3.40 mg P kg −1 )b ut not significantly different for riparian buffers wider than 30 m (3.81 mg P kg −1 ) compared to gazetted forest. Based on the research, it is recommended that policies governing riparian buffer strips become (1) stricter, with the current "maximum" of 30 m considered a minimum; and (2) adaptive, with 30 m used in small- scale agricultural areas, and wider riparian buffer strips used in medium- and large-scale agricultural areas.

Geoestatística aplicada ao estudo das características físico-químicas do solo em áreas de Floresta Estacional Decidual

Utilizaram-se métodos da geoestatística na identificação do tamanho e da estrutura da variabilidade espacial de alguns atributos físico-químicos do solo em áreas de Floresta Estacional Decidual as quais foram denominadas floresta madura, floresta secundária e capoeirão. As áreas, localizadas no município de Santa Tereza, RS, foram amostradas durante o período de 2002 a 2003, compreendendo as classes de solo: Chernossolo Argilúvico, Cambissolo Ta e Neossolo Litólico. Realizou-se amostragem sistemática com grid de espaçamento regular entre os pontos variando de 30 m para o capoeirão e 40 m para floresta madura e secundária, totalizando oitenta pontos amostrais em uma área total de 7,34 ha. Foram coletadas amostras de solo "in situ" para análise em laboratório dos atributos densidade do solo, argila, pH, potássio, matéria orgânica e fósforo. A estrutura da variabilidade espacial foi identificada por meio dos semivariogramas, definindo-se os parâmetros necessários para a krigagem. O atributo mais variável foi a matéria orgânica, não obtendo ajuste a nenhum modelo teórico de semivariograma, enquanto que o pH foi o menor. Na análise de estrutura da variabilidade espacial por meio da geoestatística, a argila e densidade, ambas em área de floresta secundária, e o pH nas áreas experimentais apresentaram a maior dependência espacial. O modelo gaussiano para o atributo argila obteve o maior alcance da dependência espacial, sendo 400 e 388 m, nas áreas de floresta secundária e madura respectivamente. A validação cruzada mostrou acuracidade no ajuste dos modelos variográficos, tendo a variável pH apresentado o melhor desempenho, 0,87; 0,94 e 0,92 nas áreas de floresta madura, secundária e capoeirão respectivamente.

Issue of the relationship between primary productivity of organic carbon in ocean and phosphate accumulation (Holocene-Late Jurassic)

By analogy with the present-day ocean, the primary productivity of paleoceans can be reconstructed using calculations based on the content of organic carbon in sediments and their accumulation rates. Results of calculations based on literature data show that the primary productivity of organic carbon, the mass of phosphorus involved in the process, and the content of phosphorus in oceanic waters were relatively stable in the Mesozoic and Late Mesozoic. Prior to precipitation on the seafloor together with the biogenic detritus, the dissolved phosphorus could repeatedly be involved in the biogeochemical cycle. Therefore, only less than 0.1% of phosphorus is retained in bottom sediments. The bulk phosphorus accumulation rate in oceanic sediments is partly consistent with the calculated primary productivity. Some epochs of phosphate accumulation also coincide with maximums of primary productivity and minimums of the fossilization coefficient of organic carbon. The latter fact can testify to episodes of the acceleration of organic matter mineralization and the release of phosphorus from sediments, leading to increase in the phosphorus reserve in paleoceans and phosphate accumulation in some places.

Characterization of Active Phosphorus Surface Sites at Synthetic Carbonate-Free Fluorapatite Using Single-Pulse 1H, 31P, and 31P CP MAS NMR

The chemically active phosphorus surface sites defined as PO(x), PO(x)H, and PO(x)H2, where x = 1, 2, or 3, and the bulk phosphorus groups of PO4(3-) at synthetic carbonate-free fluorapatite (Ca5(PO4)3F) have been studied by means of single-pulse 1H,31P, and 31P CP MAS NMR. The changes in composition and relative amounts of each surface species are evaluated as a function of pH. By combining spectra from single-pulse 1H and 31P MAS NMR and data from 31P CP MAS NMR experiments at varying contact times in the range 0.2-3.0 ms, it has been possible to distinguish between resonance lines in the NMR spectra originating from active surface sites and bulk phosphorus groups and also to assign the peaks in the NMR spectra to the specific phosphorus species. In the 31P CP MAS NMR experiments, the spinning frequency was set to 4.2 kHz; in the single-pulse 1H MAS NMR experiments, the spinning frequency was 10 kHz. The 31P CP MAS NMR spectrum of fluorapatite at pH 5.9 showed one dominating resonance line at 2.9 ppm assigned to originate from PO4(3-) groups and two weaker shoulder peaks at 5.4 and 0.8 ppm which were assigned to the unprotonated PO(x) (PO, PO2-, and PO3(2-)) and protonated PO(x)H (PO2H and PO3H-) surface sites. At pH 12.7, the intensity of the peak representing unprotonated PO(x) surface sites has increased 1.7% relative to the bulk peak, while the intensity of the peaks of the protonated species PO(x)H have decreased 1.4% relative to the bulk peak. At pH 3.5, a resonance peak at -4.5 ppm has appeared in the 31P CP MAS NMR spectrum assigned to the surface species PO(x)H2 (PO3H2). The results from the 1H MAS and 31P CP MAS NMR measurements indicated that H+, OH-, and physisorbed H2O at the surface were released during the drying process at 200 degrees C.

Genotypic Variation in Root Systems of Chickpea (Cicer arietinum L.) across Environments

AbstractRoot systems of various chickpea genotypes were studied over time and in diverse environments, – varying in soil bulk density, phosphorus (P) levels and moisture regimes. In a pot study comparing a range of chickpea genotypes, ICC 4958 and ICCV 94916‐4 produced higher root length density (RLD) and root dry weight (RDW), which were better expressed under P stress conditions. In two field experiments in soils of intermediate and high soil bulk densities, ICC 4958 also had greater RLD and RDW, particularly under soil moisture stress conditions. The expression of greater rooting ability of ICC 4958 under a wide range of environmental conditions confirms its suitability as a parent for genetically enhancing drought resistance and P acquisition ability. The superiority of ICC 4958 over other genotypes was for root proliferation expressed through RLD. Thus, the variation in RLD can be the most relevant root trait that reflects chickpea's potential for soil moisture or P acquisition.

Effect of Grain Boundary Segregation on Mechanical Properties of P-Doped Fe-Si Base Alloys

Abstract The grain boundary segregation in two Fe-Si base alloys with the different bulk phosphorus contents was investigated. The phosphorus grain boundary concentrations determined with the use of Auger electron spectroscopy were related to the microstructure, fracture mode, and mechanical properties of the alloys. Transgranular cleavage was found to be the dominant fracture mode of the samples tested by impact at room temperature. The correlations between the phosphorus grain boundary concentration, the portion of intergranular fracture, and the dynamic fracture toughness were presented, which fulfil the theoretical expectation. Two possibilities were proposed to explain a discrepancy in the temperature dependence of the phosphorus grain boundary concentration for the alloy with the higher bulk phosphorus content. Introduction Impurity segregation and precipitation of secondary phases at the grain boundaries are the fundamental diffusion-controlled processes contributing to the intergranular embrittlement of commercial steels [1]. With intention to quantify the particular effects of the above processes, simple alloys have been investigated. In this respect the P-doped Fe-Si alloys, mostly free of precipitates, are suitable for the segregation studies [2,3]. As was described by McLean [4], the equilibrium grain boundary concentration of the impurity depends directly on its bulk concentration and the annealing temperature. The segregation kinetics can also be influenced by other factors as are grain size, type of the microstructure etc. [5]. It is generally known that small changes in the grain boundary chemistry can provide significant changes in mechanical properties of the alloy steels. This process was excellently characterised on the phenomenological level [6]. However, the precise quantification of the relationship between the grain boundary composition and the energy of intergranular fracture is still missing [7].

Impacts of small amounts of sandy sediment on wetland soils and vegetation: Results from field and greenhouse studies

This project used three different experiments to test the hypothesis that deposition of small amounts of sediment in wetlands alters plant diversity and soil properties. Greenhouse experiments using potting soil and Sagittaria latifolia were used with 0.5-2 cm sediment treatments and controls. Thirty 2 m X 2 m plots were established in a freshwater palustrine marsh, and the plots were monitored before and after the addition of 1, 2, or 4 cm of sediment to half of the plots. Large vegetated cores of native soil were removed from the wetland and monitored in the greenhouse before and after the addition of 2 cm of sediment. Greenhouse experiments showed that less than 2 cm of sediment had no effects on the growth of S. latifolia, while 2 cm of sediment significantly increased aboveground biomass but had no effect on matrix potential or oxidation-reduction potential. Field plots showed significant differences in bulk density, organic matter, and phosphorus resulting from addition of sediment but did not show differences in water levels, temperature, plant diversity, biomass, or stem density under any amount of added sediment. Soil cores showed a significant difference in bulk density and in matrix potential near the soil surface under wetter conditions but showed no significant differences in temperature, evapotranspiration, oxidation-reduction potential, or aboveground biomass. The lack of effect seen in the field plots is likely the result of a low effective loading rate relative to the greenhouse experiments and the dense plant cover and thick debris layer of the wetland. Observed changes in bulk density would alter the hydrologic functions of the wetland if these depths of sediment occurred over a larger area. The tolerable level of sediment for a wetland depends on the structure and function of the individual wetland.

The geochemistry of phosphorus in different granite suites of the Western Carpathians, Slovakia: the role of apatite and P-bearing feldspar

The geochemical behaviour of phosphorus in granites, coupled with compositional variations in apatite, discriminate the different genetic suites of Variscan granitic rocks in the West-Carpathian orogenic belt. Meso-Variscan granites, mostly of S-type affinity, show a good correlation between SiO 2 and P 2O 5, with decreasing amounts of P in the poorly and moderated fractionated granites, and increasing phosphorus in the most evolved and late differentiation products. The aluminium saturation index (ASI) correlates negatively with bulk P contents in I-type granites, and positively with P in S-type granites. The phosphorus content of alkali feldspar (mainly Kfs) is usually very low (typically <0.05 wt.% P 2O 5), or not detected in the slightly differentiated granites. In the lateVariscan I/S-type granitoids, phosphorus is hosted mainly in the early-magmatic apatite, but is present also in the late K-feldspar (up to 0.15 wt.% of P 2O 5) that formed from the residual melts. In the post-orogenic S-type granites, the bulk of the phosphorus occurs in alkali feldspar (∼0.3 wt.% P 2O 5), with a minor proportion present in primary early-magmatic apatite. Clusters of small secondary apatite grains with a distinctive composition are distributed in alkali feldspar grains of the post-orogenic S-type granites. This apatite has formed post-magmatically from P released from P-rich alkali feldspar during decreasing temperature, by reaction with a fluid rich in volatiles (including F and B), and alkali and alkali earth metals. A-type granites have the lowest bulk phosphorus contents. Consequently, phosphate minerals are relatively rare in this granite type, and the alkali feldspar has negligible P 2O 5 contents. Except for Sr, the minor element contents in apatite partly correlate with the bulk composition of their host rocks and partly reflect some thermodynamic properties of melt. The Mn contents of apatite increase with the peraluminous character of the melt and with decreasing fO 2 and so apatite from the S-type granites has significantly higher Mn contents than apatite from the I-type granites. Apatite from A-type granites is enriched in Fe and HREE, reflecting the higher bulk Fe and HREE content of this granite type. Apatite from specialized S-type granites is enriched in Y and HREE. In general, the Cl and S content of apatite is higher in the basic members of the I-type affinity granitic rocks.

Effects of agriculture and wetland restoration on hydrology, soils, and water quality of a Carolina bay complex

We compared hydrology, soils, and water quality of an agricultural field (AG), a two-year-old restored wetland (RW), and two reference ecosystems (a non-riverine swamp forest (NRSF) and a high pocosin forest (POC)) located at the Barra Farms Regional Wetland Mitigation Bank, a Carolina bay complex in Cumberland County, North Carolina. Our main objectives were to: 1) determine if the RW exhibited hydrology comparable to a reference ecosystem, 2) characterize the soils of the AG, RW, and reference ecosystems, and 3) assess differences in water quality in the surface outflow from the AG, RW, and reference ecosystems. Water table data indicated that the hydrology of the RW has been successfully reestablished as the hydroperiod of the RW closely matched that of the NRSF in 1998 and 1999. Jurisdictional hydrologic success criterion was also met by the RW in both years. To characterize soil properties, soil cores from each ecosystem were analyzed for bulk density (Db), total carbon (Ct), nitrogen (Nt), and phosphorus (Pt), extractable phosphate (PO4w), nitrogen (Nex), and cations (Caex, Mgex, Kex, Naex), as well as pH. Bulk density, Pt, Caex, Mgex, and pH were greatly elevated in the AG and RW compared to the reference ecosystems. Water quality monitoring consisted of measuring soluble reactive phosphorus (SRP), total phosphorus (TP), nitrate + nitrite (NOX), and total nitrogen (TN) concentrations in surface water from the AG, RW, and reference outflows. Outflow concentrations of SRP, TP, and NOX were highest and most variable in the AG, while TN was highest in the reference. This study suggested that while restoration of wetland hydrology has been successful in the short term, alteration of wetland soil properties by agriculture was so intense, that changes due to restoration were not apparent for most soil parameters. Restoration also appeared to provide water quality benefits, as outflow concentrations of SRP, TP, NOX, and TN were lower in the RW than the AG.

Non‐equilibrium intergranular segregation and embrittlement in neutron‐irradiated ferritic alloys

AbstractThis study describes intergranular segregation and embrittlement in several model ferritic alloys doped with Mn, P, S and/or Cu subjected to neutron irradiation, irradiation‐equivalent thermal ageing (ETA) and post‐irradiation annealing (PIA). Neutron irradiation produced a larger amount of intergranular phosphorus segregation than sulfur segregation. Irradiation‐induced phosphorus segregation became more prominent with decreasing bulk phosphorus content. Intergranular carbon segregation remained small in all the as‐irradiated alloys, which was enhanced by the ETA except for the high phosphorus‐containing alloy. A PIA study has shown that the phosphorus segregation in phosphorus‐doped alloys subjected to lower temperature PIA proceeds via mobile phosphorus–interstitial complexes, whereas the sulfur segregation, which occurs over a wide PIA temperature range, is controlled by vacancy‐enhanced diffusion. The mechanisms of non‐equilibrium intergranular segregation induced by neutron irradiation are discussed in light of coupled fluxes of point defects and impurities and changes in the segregation capacity of grain boundaries. Small punch tests demonstrated how the impurity segregation or desegregation and hardening or softening induced by the irradiation, ETA and PIA influence intergranular embrittlement in the various ferritic alloys. Copyright © 2001 John Wiley &amp; Sons, Ltd.

Propriedades físicas e químicas e produtividade de milho afetadas pelo manejo do solo com tração animal, numa terra bruna estruturada

A degradação física do solo é um dos principais processos responsáveis pelo aumento da erosão hídrica. Os preparos convencionais normalmente são aceleradores desse processo, enquanto a semeadura direta apresenta-se como um sistema de manejo conservacionista, pois mantém os resíduos culturais na superfície e preserva a matéria orgânica do solo. Contudo, a semeadura direta pode também aumentar a densidade e diminuir a porosidade total na superfície do solo. O trabalho foi desenvolvido numa Terra Bruna estruturada, no município de Lebon Régis - SC, no perí odo de junho de 1995 a maio de 1999. Os tratamentos de preparo do solo, preparo convencional com uma aração com arado "fuçador" de tração de animal + uma gradagem com tração mecânica e semeadura direta com semeadora "saraquá", foram executados em quatro repetições. No início, a área experimental foi cultivada com aveia e, a partir do segundo cultivo, milho e aveia em semeadura direta e milho e pousio no preparo convencional, ambos em sucessão. Em maio de 1999, foram avaliadas a densidade do solo, macroporosidade, microporosidade, porosidade total, fósforo extraível, potássio trocável e carbono orgânico nas camadas de 0-2,5; 2,5-5,0; 5,0-10,0 e 10,0-15,0cm de profundidade. A densidade do solo, macroporosidade e microporosidade no solo sob semeadura direta foram semelhantes aos valores do solo sob preparo convencional, em todas as profundidades. O carbono orgânico, fósforo extraível e potássio trocável apresentaram maiores valores na semeadura direta do que no preparo convencional, na camada de 0-5,0cm.

Effect of Bulk Phosphorus Content on Hardening, Non-Equilibrium Segregation and Embrittlement in Neutron Irradiated Iron-Based Alloys

ABSTRACTThe effect of bulk P contents on hardening, non-equilibrium intergranular segregation and embrittlement has been studied in Mn-doped ferritic alloys subjected to neutron irradiation (E&gt;0.1MeV: fluence of 1 × 1025 n/m2 at 711K for 2120 h) or irradiation-equivalent thermal aging. Neutron irradiation-induced intergranular P segregation became more prominent with decreasing bulk P content. Thermal aging slightly enhanced the amount of segregated P independent of the bulk P content. Intergranular C segregation in all the alloys was suppressed by the irradiation. An alloy with low bulk P content showed only moderate irradiation-induced hardening. The ductile-brittle transition temperature (DBTT) in alloys with low and intermediate amounts of P increased by the same shift during the irradiation but not at all during the thermal aging. Doping high bulk P led to a high DBTT in the as-heat-treated alloy while the irradiation decreased the DBTT. The irradiation effect on the DBTT in the model ferritic alloys containing the different levels of P is discussed in light of embrittling or toughening effects caused by the changes in the P or C segregation, and hardness.

Reverse temper embrittlement, RTE, in low alloy steels: a substantive study concerning the influences of grain size, bulk phosphorus and accumulated service strain

This article describes a large in-service embrittlement study concerning six separate series of steam turbine casing bolts involving nearly four hundred individual bolts. The bolts, which ranged in size from 300 to 1400 mm in length, were fabricated from low alloy steels which were subjected to operating temperatures of 450°C –490°C for service times varying from 60 000 to over 200 000 h. The principal effects of grain size, d, bulk phosphorus, %P, and accumulated service strain, % ε, on the occurrence of reverse temper embrittlement, RTE, are reasonably established. Indeed, a general embrittlement threshold expression, or condition, is evolved which can be expressed as a product of these three important parameters which dictated RTE effects, viz., d×(%P)×(% ε) b = α where b and α are scaling constants of value 0.64 and 0.0772 respectively. Effectively, when this product was numerically greater than the constant α bolt embrittlement was predicted; when less, no service embrittlement was predicted.

Embrittlement observed in Cr–Mo turbine bolts after service

The present paper describes a study aimed at investigating the extent of service related embrittlement suffered by a series of Cr–Mo steel turbine bolts after over 200,000 h at 450°C. A small section of material was removed from a non-critical location of all the 51 bolts. From this section, the chemical composition, average hardness and average prior austenite grain size were measured. The toughness of the bolts was measured by Charpy impact testing and/or Auger electron spectroscopy. From the various parameters investigated, it was established that grain size and phosphorus level were the only factors which consistently identified whether a bolt was embrittled or non-embrittled. Indeed it was established that bolt embrittlement could be predicted using the simple product of microstructure grain size d (μm's) and bulk phosphorus content. Finally, it was observed that bolt embrittlement could be predicted using the simple product of microstructure grain size and bulk phosphorus level and that such a trend indicated the importance of grain boundary area available for service induced phosphorus segregation.

Inhibitory effects of 1-hydroxyethylidene-1,1-bisphosphonate and Chinese traditional (kampo) medicines on calcification of the heart and tongue in DBA/2NCrj mice.

The effects of 1-hydroxyethylidene-1, 1-bisphosphonate (HEBP) and two Chinese traditional (Kampo) medicines, Dai-saiko-to and Saiko-ka-ryukotsu-borei-to on spontaneous soft tissue (heart and tongue) mineralization in DBA/2NCrj mice were studied. These agents were given orally for 4 weeks to DBA/2NCrj mice. After 2 weeks of administration in the heart, 0.006 and 0.03% (w/v) HEBP decreased calcium content by 90 and 30%, respectively, while 0.27 and 2.7 mg/ml Dai-saiko-to reduced calcium content by 30 and 45%, respectively. Saiko-ka-ryukotsu-borei-to (0.27 mg/ml) reduced both calcium and phosphorus content by 50 and 35%, respectively. However, their inhibitory effects on the heart were not observed after 4 weeks of administration. The compounds delayed the onset of increases of bulk calcium and phosphorus content. In the tongue, at 4 weeks, 0.006 and 0.03% (w/v) HEBP reduced calcium content by 30 and 45%, respectively, while two Kampo medicines (at both concentrations used) significantly reduced the content of calcium (by 27-79%) and phosphorus (by 24-32%). These results strongly suggest that two Kampo medicines as well as HEBP may be useful in preventing and curing soft tissue calcification.