Faster Rate Of Accumulation Research Articles

Fate and potential ecological risk of rare earth elements in 3000-year reclaimed soil chronosequences

The introduction of anthropogenic inputs into natural systems may lead to enduring alterations in the innate characteristics of Rare Earth Elements (REEs). Against this backdrop, the evolutionary processes and environmental drivers of REEs in soil remain uncertain. A 3000-year soil chronosequence with uniform parent material was established in reclaimed farmland along the Yangtze River, reconstructing, for the first time, the dynamic processes of REE accumulation and fractionation over a long-time scale. Analysis of 122 soil samples showed REE concentrations ranging from 146.00 to 216.56 μg/g. Based on reclamation duration, three significant stages of REE evolution were identified: natural leaching, rapid accumulation, and stable accumulation with differentiation. Reclaimed soil after 3000 years exhibited a 14.1 % increase in REE concentrations compared to fresh sediments, attributed to anthro -pedogenic processes. Moreover, Heavy Rare Earth Elements (HREEs) accumulated faster than Light Rare Earth Elements (LREEs), particularly in deeper soils (60–100 cm), where HREE concentrations rose by 34.3 %, mainly due to acidic environments promoting HREE fixation. Additionally, the potential ecological risk posed by REEs heightened with reclamation duration, with HREEs exhibiting a sensitivity of 83 % to 94 %. Our findings stress the urgency of carefully monitoring exogenous REEs introduced through anthropogenic activities, particularly HREEs.

Selenate and selenite uptake, accumulation and toxicity in Lemna minuta.

The kinetics of Se uptake and toxicity to Lemna were studied over a period of 14 days of exposure to Se(IV) or Se(VI). The growth of Lemna stopped immediately after exposure to 5.0 mg/L of Se(IV) or Se(VI). The content of chlorophyll and phaeopigments of Lemna exposed to 5.0 mg/L of Se(IV) was two to three times less than in the control after 3 d exposure. Lemna took up Se rapidly within the first 3 d. The Se content in Lemna along with the exposure time fitted well the two-compartment and the hyperbolic model, which demonstrates that the mechanism of Se(IV) and Se(VI) uptake in Lemna is not only through passive diffusion, but also through other processes such as ion channel proteins or transporters. The kinetic bioconcentration factors (BCFs) were 231 and 42 for 0.5 mg/L Se(IV) and Se(VI) exposure, respectively. The uptake rate of Lemna reached 263 mg/kg/d and 28 mg/kg/d in the Se(IV) and Se(VI) treatments, respectively. This study showed that Se(IV) has a faster accumulation rate than Se(VI), but a higher toxicity, indicating Lemna could be a good candidate to remove Se(IV) from water, producing Se-enriched biomass which may eventually also be considered for use as Se-enriched feed supplement or fertilizer.

Variation of Anthocyanin Content and Profile Throughout Fruit Development and Ripening of Highbush Blueberry Cultivars Grown at Two Different Altitudes.

Blueberry (Vaccinium corymbosum L.) is a widely consumed fruit and a rich source of bioactive compounds, namely, the polyphenol class of anthocyanins. Little information is available about the influence of internal (genetic and developmental) and external (environmental) factors on the levels of phenolic metabolites in blueberry fruit. In light of this consideration, total polyphenolic and flavonoid content, anthocyanin accumulation and composition were evaluated in cv. “Duke” and “Brigitta” grown at two different altitudes in Valtellina, a valley of the Alps in Northern Italy. During berry ripening, there is a developmentally coordinated shift from cyanidin-type, di-substituted anthocyanins toward delphinidin-based, tri-substituted pigments. At the lower altitude location, higher temperatures, not exceeding optimum, resulted in a more quickly berry developmental pattern and in higher anthocyanin concentrations in the early phases of ripening. At later stages of ripening, berries of both cultivars at higher altitude compensate for these initial temperature effects, and no differences were recorded in ripe fruit grown in the two locations. We conclude that anthocyanin accumulation is strongly regulated by development and genotype, and the environmental factors, associated to the altitude gradient, exert in the trial conditions only a fine-tuning influence. Fruits reach the full-ripening stage simultaneously at both sites because the initial gap in pigment levels is counterbalanced at the higher altitude by a faster rate of accumulation at later phases of the ripening process.

Human Capital Differentials Across Urban and Rural Areas in Italy. The Role of Migrations

Differences in human capital endowment between the standard partition of Italy (North–South) are pronounced. The divide between urban and rural areas is even more remarkable, with the former showing also faster accumulation rate. Using data from civil registries and survey on graduates, we show that mobility plays a crucial role in explaining this accumulation gap. Urban areas of the North drain human capital from rural and urban locations of the South, but they lose graduates in favor of foreign countries. Urban movers are positively selected according to familiar background and secondary school grades. Moreover, in comparison to stayers, they are more likely to hold a university degree associated with better labour market prospects. Migrations of graduates are responsive to labour market conditions, to university supply, to house prices and—most importantly—to local human capital endowment.

Atomoxetine improves attentional orienting in a predictive context

The role of norepinephrine (NE) in visuo-spatial attention remains poorly understood. Our goal was to identify the attentional processes influenced by atomoxetine (ATX) injections, a NE-reuptake inhibitor that boosts the level of NE in the brain, and to characterize these influences. We tested the effects of ATX injections, on seven monkeys performing a saccadic cued task in which cues and distractors were used to manipulate spatial attention. We found that when the cue accurately predicted the location of the upcoming cue in 80% of the trials, ATX consistently improved attentional orienting, as measured from reaction times (RTs). These effects were best accounted for by a faster accumulation rate in the valid trials, rather than by a change in the decision threshold. By contrast, the effect of ATX on alerting and distractor interference was more inconsistent. Finally, we also found that, under ATX, RTs to non-cued targets were longer when these were presented separately from cued targets. This suggests that the impact of NE on visuo-spatial attention depends on the context, such that the adaptive changes elicited by the highly informative value of the cues in the most frequent trials were accompanied by a cost in the less frequent trials.

A Cenozoic seawater redox record derived from 238U/235U in ferromanganese crusts

Oceanic oxygen levels are projected to drop in certain areas due to warming climate, but the net effect to the overall ocean redox state is difficult to predict. Here we measured the “stable” uranium isotope composition (238U/235U) in globally representative hydrogenous ferromanganese crusts in order to reconstruct the redox evolution of the global ocean throughout the Cenozoic. Samples averaging ∼3 Myr intervals have analytically indistinguishable 238U/235U throughout the Cenozoic. Combined with a U isotope mass balance model, we suggest that the overall ocean redox state has remained remarkably stable on million year time scales throughout the Cenozoic, despite large surface temperature fluctuations during this time. This suggests that stabilizing feedbacks (for example, nutrient limitation in low oxygen zones) may have prevented dramatic large-scale shifts in oxygen levels in the ocean. However, the Fe-Mn crust record will be unlikely to reflect rapid perturbations in ocean redox state. To investigate these events, sediment archives with faster accumulation rates and redox proxies with faster response time must be explored.

Production of PHAs from mixed and pure cultures of Pseudomonas sp. using short-chain fatty acids as carbon source under nitrogen limitation

An enriched culture of polyhydroxyalkanoates (PHAs)-forming bacteria was developed using activated sludge from a municipal wastewater treatment plant as inoculum. The culture was developed under alternating cycling between carbon and nitrogen limitation. After several cycles, the predominant bacteria were identified and it was shown that a consortium of Pseudomonas sp. had been formed. The PHAs production efficiency of the mixed culture was studied under nonaseptic, nitrogen limitation conditions, whereas two isolates were studied in terms of PHAs accumulation under both nitrogen limitation and simultaneous nitrogen- and oxygen-limiting conditions. A synthetic medium with volatile fatty acids (VFAs) was used in all cases as carbon source. The mixed culture led to better final yields of PHAs/VFAs consumed as well as faster accumulation rates. Regarding the effect of dissolved oxygen (DO) concentration, it was shown that PHAs production was strongly favored by the limiting conditions in isolate A, whereas isolate B did not seem to be affected.

Modeling microbial survival in buildup biofilm for complex medical devices

BackgroundFlexible endoscopes undergo repeated rounds of patient-use and reprocessing. Some evidence indicates that there is an accumulation or build-up of organic material that occurs over time in endoscope channels. This "buildup biofilm" (BBF) develops as a result of cyclical exposure to wet and dry phases during usage and reprocessing. This study investigated whether the BBF matrix represents a greater challenge to disinfectant efficacy and microbial eradication than traditional biofilm (TBF), which forms when a surface is constantly bathed in fluid.MethodsUsing the MBEC (Minimum Biofilm Eradication Concentration) system, a unique modelling approach was developed to evaluate microbial survival in BBF formed by repetitive cycles of drying, disinfectant exposure and re-exposure to the test organism. This model mimics the cumulative effect of the reprocessing protocol on flexible endoscopes. Glutaraldehyde (GLUT) and accelerated hydrogen peroxide (AHP) were evaluated to assess the killing of microbes in TBF and BBF.ResultsThe data showed that the combination of an organic matrix and aldehyde disinfection quickly produced a protective BBF that facilitated high levels of organism survival. In cross-linked BBF formed under high nutrient conditions the maximum colony forming units (CFU) reached ~6 Log10 CFU/peg. However, if an oxidizing agent was used for disinfection and if organic levels were kept low, organism survival did not occur. A key finding was that once established, the microbial load of BBF formed by GLUT exposure had a faster rate of accumulation than in TBF. The rate of biofilm survival post high-level disinfection (HLD) determined by the maximum Log10CFU/initial Log10CFU for E. faecalis and P. aeruginosa in BBF was 10 and 8.6 respectively; significantly different compared to a survival rate in TBF of ~2 for each organism. Data from indirect outgrowth testing demonstrated for the first time that there is organism survival in the matrix. Both TBF and BBF had surviving organisms when GLUT was used. For AHP survival was seen less frequently in BBF than in TBF.ConclusionThis BBF model demonstrated for the first time that survival of a wide range of microorganisms does occur in BBF, with significantly more rapid outgrowth compared to TBF. This is most pronounced when GLUT is used compared to AHP. The data supports the need for meticulous cleaning of reprocessed endoscopes since the presence of organic material and microorganisms prevents effective disinfection when GLUT and AHP are used. However, cross-linking agents like GLUT are not as effective when there is BBF. The data from the MBEC model of BBF suggest that for flexible endoscopes that are repeatedly used and reprocessed, the assurance of effective high-level disinfection may decrease if BBF develops within the channels.

Pay-As-You-Go versus funded systems. Some critical considerations

Longer life expectancy and lower fertility rates will lead to an ageing population in most Western countries. This is thought to make earnings-based defined-benefit pay-as-you-go pension schemes unviable in the near future. Some economists suggest shifting towards a capitalized funded system grounding their proposal on the following advantages: (i) it raises national saving, thus leading to a faster rate of accumulation and a larger per capita income; (ii) it offers a higher rate of return on savings; (iii) it is immune to demographic shifts. In this paper we explore the fundamentals of these advantages, and conclude that the theoretical basis supporting them is very weak. We base our theoretical standpoint on the Sraffian-based capital critique and the theory of endogenous money. Additionally, we defend a parametric reform of a standard PAYG using figures that correspond to the Spanish economy for the period 2001–70.

An Alternative Explanation of Differences in Relative Wages among Developed Economies by Endogenizing Invention, Innovation and Diffusion

I develop a model for a small, open, technology-lagging economy that imports leading-edge knowledge from the technology leader by paying high-skilled researchers from the leading country their opportunity cost to train the lagging country's future high-skilled workers while adding to a local appropriate stock of skill-biased knowledge. The laggard may also import only as share of leading-edge knowledge at a reduced licensing fee. I use as the large, technology-leading country the closed economy from an endogenous growth model that endogenizes invention, innovation and diffusion of knowledge that is capable of matching inverse movements of the relative wage and the detrended relative supply of skilled workers plus the various growth experiences of the U.S. over the last 40 years. Innovation is modeled as diffusing skill-biased knowledge (created by what is termed the inventive sector) to adoptive knowledge (accessible by low-skilled intensive sectors), consistent with the diffusion literature. By forgoing a homegrown inventive sector, the technology lagging country has a larger percentage of high-skilled workers in the innovative sector resulting in what I call the specialization in innovation effect. Since the lagging country specializes in innovation, it has more of its resources devoted to innovation which tends to diffuse a larger share of any given amount of imported skill-biased knowledge to adoptive knowledge and thus tends to decrease its relative wage. This effect may help explain the higher wage premium in the U.S. and the U.K. (countries that arguably specialize in inventive rather than innovative activities) than in other developed such as Germany, France, and Italy since the 1980s. Importing a smaller share of leading-edge knowledge contributes to even lower wage inequality in the laggard without sacrificing economic growth because the lower cost of human capital accumulation allows for a faster accumulation rate and more diffusion of knowledge throughout its economy. The specialization effect will be in evidence as long as the effect is not dominated by differential accumulation rates between the leader and laggard economies. If the developed laggard has a threshold level of human capital to access leading-edge technologies, a slower human capital accumulation rate relative to the leader may allow the laggard to import a stock of skill-biased knowledge each period that is much larger that it is capable of producing itself if it did not import technology. This raises the share of total knowledge that is skill-biased and tends to raise the relative wage.

Analysis of Ripening Process of Spikelets in Rice Cultivars with Different Grain Size

Cultivars with different spikelet weight were compared with the ripening characteristics of primary and secondary spikelets at different positions in panicle and discussed the relation of the ripening process and dry matter production. The objectives were to know the variations of grain filling process of both primary and secondary spikelets among different grain size cultivars. Second, to find out the main ripening period (MRP, the accumulation period from 15.9-84.1% of the maximum grain weight) with the rate of grain filling and which factor between these two are important for the determination of final grain weight. The MRP of different grain size cultivars groups varied from 14-21 (small), 15-21 (medium), and 16-21 d (large) . The dry weight accumulation rate of a spikelet (DWAR-S) during MRP ranged 0.404-0.720, 0.624-0.981 and 0.703-1.297 mg/spikelet/d in small, medium and large grain cultivars, respectively. Among all cultivars MRP of primary and secondary branch spikelets were 13-16 and 14-23 d where DWAR-S were 0.672-1.544 and 0.334-0.939 mg/spikelet/d, respectively. The larger spikelet weight was accompanied with the faster rate of accumulation and a slower rate enhances the MRP. The relations between DWAR-S during MRP and a final spikelet dry weight showed significant positive correlation (r=0.834***) but no significant correlation was observed between the days of MRP and the final spikelet dry weight (FSDW) . Further, the temperature and radiation showed insignificant relationship with DWAR-S during MRP and for the same temperature the DWAR-S varied much among the cultivars which indicated that the FSDW was controlled mainly genetically with a partial impact of environment. It could be concluded that the large grain cultivars gained the higher spikelet weight at a faster rate of accumulation and not to the long period of accumulation.

Copper accumulation in soils from two different‐aged apricot orchards in Central Otago, New Zealand

In recent years there has been a move in New Zealand to convert small, uneconomic orchards to other agricultural uses. Overseas research has demonstrated that copper from fungicide sprays often accumulates in the soils of orchards and can cause certain problems for plant growth and livestock. To date, no assessments appear to have been made of the degree of copper accumulation in such older orchards in New Zealand. This study presents the results of an assessment of two well‐established apricot orchards in the Central Otago region of South Island, New Zealand. Two aspects of the results are surprising. The first is the relatively low levels of copper in the soil when compared with results from another orchard in the region. That orchard is 18 years old and mean soil copper has already reached 100.0 μg/g, indicating a much faster rate of accumulation than in the two orchards in the current study. The second unexpected result is that the younger orchard has a significantly higher level of copper than the ol...

NMR imaging of 15N at natural abundance

*‘N observation at natural abundance (0.37% of total nitrogen) has become conventional in NMR spectroscopic studies on liquids since the first report in 197 1 ( 1) . This technique has also been useful for solving problems in solids (2). Experiments involving enriched material have proved to be important in labeling studies in chemical applications (3)) in determination of protein structure (4)) and in improving the understanding of plant metabolism (5,6). In the case of plants, crude spatial selection has previously been achieved by physical sectioning of plants which had been fed with “N-labeled nutrients ( 5 ) . No 15N NMR images from samples at either natural abundance or enriched concentration have previously been reported, and only one 14N image (of liquid nitrogen) had been published ( 7) until recently (8). Given the ubiquity of nitrogen in metabolic processes and the interest in the processes of nitrogen fixation and nitrogen turnover in the environment, it seemed sensible to tackle the particular problems associated with ‘*N NMR imaging. These, as in 15N NMR spectroscopic studies, arise from the low isotopic abundance and the low magnetogyric ratio, which give the 15N isotope a receptivity of only 3.85 X 10e6 compared to ‘H. An additional drawback is the long relaxation times frequently encountered ( 9). This renders accumulation difficult but does at least ensure that “N lines are normally narrow. A faster accumulation rate may, however, become beneficial if relaxation times are shortened by the use of paramagnetic reagents or if steady-state techniques are employed. The maximum concentration of 15N spins at natural abundance occurs in liquid nitrogen, for which the molarity of i5N nuclei is 0.2 1 M. Additionally, low temperature (77 K) gives a favorable Boltzmann gain relative to 298 K of about 4 as well as reduced thermal noise to give an overall gain of approximately 7.5. The signal-to-noise ratio was measured to be approximately 10: 1 following a single 90” pulse and the linewidth was less than 70 Hz. The relaxation times are presumably shortened by contamination with oxygen, the amount of which varies from sample to sample. The sample was contained in a two-section, unsilvered Dewar and was bubbling while under investigation so that the signal-to-noise ratio was reduced by removal of magnetized material from the active volume of the RF coil. The upper section functioned as a reservoir and was 8 cm high (od, 6.5 cm) and ended in a finger (id, 1.7 cm and height, 7.5 cm) which was inserted into a lo-turn surface coil (id, 3.0 cm) made of 0.8 mm insulated copper wire. There was sufficient volume of liquid nitrogen in the reservoir to keep the finger full for 3 1 hours.

Molecular Species of Choline and Ethanolamine Phospholipids in Rat Cerebellum During Development

The molecular species composition of rat cerebellar phospholipid subclasses has been studied by HPLC after phospholipase C treatment and dinitrophenyl derivatization. During rat cerebellum development (3-90 days postpartum), cholinephosphoglycerides and ethanolamine phosphoglycerides represented approximately 80% of all phospholipids, with their relative amount changing after 1 month. Among ethanolamine phosphoglycerides, the molar ratio of diacylglycerophosphoethanolamine (diacylGPE) to alkenylacylGPE decreased from approximately 1.4 at 3 days to approximately 0.5 after 10 days. The phospholipids investigated contained up to 12 different molecular species. The rate of accumulation of the various molecular species of diacylglycerophosphocholine (diacylGPC), diacylGPE, and alkenylacylGPE during cerebellar development allowed a classification into three main groups. The overall increase of the molecular species of the first group (6-diacylGPC, 5-diacylGPE, and 4-alkenylacylGPE) was approximately 18-fold between 3 and 90 days, with a faster rate of accumulation between 3 and 30 days. Those of the second group (3-diacylGPC, 5-diacylGPE, and 5-akenylacylGPE) increased by approximately 45-fold during the same developmental period, at a slow rate before day 15 and a faster one thereafter. The molecular species of the third group (3-alkenylacylGPE) increased by greater than 250-fold between 3 and 90 days, at a very slow rate before day 21 and more quickly thereafter. The different rates of accumulation of the components of the three groups during cerebellar development suggest a preferential location of the first group in membranes of neuronal perikaryons, glial cells, and synaptosomal structures. Those of the second group appear to be located in both synaptosomal membranes and myelin sheets, and those of the third group can be considered as myelin markers.