Relative Accumulation Rate Research Articles

Morphological and physiological response of amphibious Rotala rotundifolia from emergent to submerged form.

Rotala rotundifolia is an amphibious aquatic plant that can live in submerged and emergent forms. It is superior in nitrogen and phosphorus removal. To elucidate its adaptation strategies from emergent to submerged conditions, phenotypic and physiological responses of R. rotundifolia were investigated during three months of submergence, at water levels of 0cm (CK), 50cm (W50), and 90cm (W90). Results showed that submergence stress reduced the relative growth rate of plant height, fresh weight, and biomass accumulation, leading to root degradation and a significant decline in the root-shoot ratio. The amounts of soluble protein (SP), soluble sugar (SS), and starch in the aerial leaves of W50 and W90 decreased during the early stages of submergence compared to CK, whereas the total chlorophyll and proline contents, and activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) increased. The contents of endogenous hormones, including abscisic acid (ABA), gibberellin (GA), and indole-3-acetic acid (IAA), decreased during the change in leaf shape; the decline in ABA was more obvious. The leaf primordium generated transition leaves and submerged leaves to resolve the "carbon starvation" of plants. The maximum values of non-structural carbohydrates (NSC) in the leaves of W50 and W90 occurred at day 30, reaching 14.0 mg g- 1and 10.5 mg g- 1, respectively. The contents of SP and starch, activities of SOD and CAT of the roots in submerged treatments increased, while SS and proline content decreased at day 7. These results demonstrated that developing heterophyllous leaves, increasing chlorophyll content, and regulating plant carbon allocation and consumption were important mechanisms of R. rotundifolia to adapt to underwater habitats.

Historical declines in parrotfish on Belizean coral reefs linked to shifts in reef exploitation following European colonization

Humans have utilized the Mesoamerican Reef (MAR) for millennia but the effects of prehistorical and historical fishing on this ecosystem remain understudied. To assess the long-term coupling of reef ecosystem and human dynamics in this region, we tracked trends in the structure and functioning of lagoonal reefs within the Belizean portion of the MAR using fish teeth fossils and sediment accumulation rates within reef sediment cores. We then paired this with a timeline of demographic and cultural changes in this region’s human populations. The ∼1,300-year timeline encompassed in the core record shows that declines in the relative abundance and accumulation rate of teeth from parrotfish, a key reef herbivore, occurred at all three reef sites and began between ∼1500 and 1800 AD depending on site and metric of abundance. A causality analysis showed that parrotfish relative abundance had a positive causal effect on reef accretion rates, a proxy of coral growth, reconfirming the important role of these fish in reef ecosystem functioning. The timing of initial declines in parrotfish teeth occurred during a time of relatively low human population density in Belize. However, declines were synchronous with cultural and demographic upheaval resulting from European colonization of the New World. The more recent declines at these sites (∼1800 AD) occurred in tandem with increased subsistence fishing on reefs by multiple immigrant groups, a pattern that was likely necessitated by the establishment of an import economy controlled by a small group of land-owning European elites. These long-term trends from the paleoecological record reveal that current parrotfish abundances in central Belize are well below their pre-European contact peaks and that increased fishing pressure on parrotfish post-contact has likely caused a decline in reef accretion rates. The origins of reef degradation in the Belizean portion of the MAR began hundreds of years before the onset of modern declines resulting from the combined effects of local human disturbances and climate change.

Flue-cured tobacco (Nicotiana tabacum L.) leaf quality can be improved by grafting with potassium-efficient rootstock

The low Potassium (K) content in flue-cured tobacco leaves severely restricts the development of China's high-quality cigarette industry. To determine whether the quality of flue-cured tobacco leaves can be improved by grafting, a cross-grafting experiment of two different K-efficiency tobacco strain (Yunyan 87, main cultivar. WuFeng No.2, K-efficient genotype) was carried out. Measurement data from a field experiment with three K supply levels (0,135 and 270 kg K2O ha−1) and four grafting combinations [‘Wufeng No. 2’(W), ‘Yunyan 87’(Y), Y/W (Y grafted onto W) and W/Y (W grafted onto Y)] from 2018 to 2019 were used to evaluate the effect of grafting on flue-cured tobacco quality. The results demonstrated that the average leaf maturity in the grafted tobacco ‘Yunyan 87’ increased by 7.69 %. Meanwhile, maximum accumulation, rapid accumulation duration, and maximum relative accumulation rates of K and biomass in the grafting treatments were all improved over the growth period, and the K levels in the grafted tobacco leaves increased by 95.4 % on average. In addition, when potassium supply level was insufficient, the proportion of K+ in grafted tobacco leaves was higher than that in other treatments. In terms of commercial quality, the chemical and smoking quality of grafted tobacco leaves were 32.2 % and 7.1 % higher than those of ungrafted tobacco leaves. The grafted ‘Yunyan 87’ inherited the advantages of the scion in terms of flavor. At the same time, the combustibility of Y/W was improved by the characteristics of the rootstock, and its total score of quality was highest. The correlation analysis revealed that K accumulation was significantly related to the improvement of tobacco leaf quality. Therefore, increasing the K content and improving the quality of tobacco leaves through grafting is a feasible approach for the production of high quality flue-cured tobacco.

Species Abundance and Reaction Off-Rate Regulate Product Formation in Reactions Accelerated Using Isotachophoresis.

We present a model for second-order and pseudo-first-order reversible chemical reactions accelerated using peak-mode isotachophoresis (ITP). In such systems, ITP preconcentrates and co-locates the reactants between the leading and trailing electrolyte zones, and this significantly accelerates chemical reactions. Our model quantifies the effects of reaction rate constants and species abundance on product formation rate. We identify two key non-dimensional parameters, which are specific groupings of reaction rate constants, species concentrations, and influx rates. We then use a regular perturbation to study the effects of reverse reaction rate and relative species abundance (and relative rates of species accumulation) on production rate. We also use this perturbation method to derive an analytical expression for the quasi-steady-state production rate achievable by ITP. Our analytical models and numerical solutions are generally applicable to a wide range of systems, which use ITP to enhance reactions. The model is also an interesting case study of the complex coupling of electric field-driven species transport and reaction kinetics.

An optogenetic switch for the Set2 methyltransferase provides evidence for transcription-dependent and -independent dynamics of H3K36 methylation.

Histone H3 lysine 36 methylation (H3K36me) is a conserved histone modification associated with transcription and DNA repair. Although the effects of H3K36 methylation have been studied, the genome-wide dynamics of H3K36me deposition and removal are not known. We established rapid and reversible optogenetic control for Set2, the sole H3K36 methyltransferase in yeast, by fusing the enzyme with the light-activated nuclear shuttle (LANS) domain. Light activation resulted in efficient Set2-LANS nuclear localization followed by H3K36me3 deposition in vivo, with total H3K36me3 levels correlating with RNA abundance. Although genes showed disparate levels of H3K36 methylation, relative rates of H3K36me3 accumulation were largely linear and consistent across genes, suggesting that H3K36me3 deposition occurs in a directed fashion on all transcribed genes regardless of their overall transcription frequency. Removal of H3K36me3 was highly dependent on the demethylase Rph1. However, the per-gene rate of H3K36me3 loss weakly correlated with RNA abundance and followed exponential decay, suggesting H3K36 demethylases act in a global, stochastic manner. Altogether, these data provide a detailed temporal view of H3K36 methylation and demethylation that suggests transcription-dependent and -independent mechanisms for H3K36me deposition and removal, respectively.

Production and Transport of Supraglacial Debris: Insights From Cosmogenic 10Be and Numerical Modeling, Chhota Shigri Glacier, Indian Himalaya

AbstractMany mountain glaciers carry some amount of rocky debris on them, which modifies surface ablation rates. The debris is typically derived from erosion of the surrounding topography and its supraglacial extent is predominantly controlled by the relative accumulation rates of debris versus snow. Because Global Warming results in shrinking glaciers as well as thawing permafrost worldwide, changes in both rates will most likely affect the evolution of supraglacial debris cover and thus the response of glaciers to climate change. Here we report 10Be concentrations measured in five amalgamated debris samples collected from the main medial moraine of the Chhota Shigri Glacier, India. Results suggest headwall erosion rates that are ~0.5–1 mm year−1, and apparently increasing (10Be concentrations are decreasing) toward the present. We employed a numerical ice flow model that we combined with a new Lagrangian particle tracing routine to explore the impact of spatial and temporal variability in erosion rates and source areas on 10Be concentrations in the medial moraine. Our modeling results show that neither changes in source areas, related to the transient response of the glacier to ongoing climate change, nor four different scenarios of spatial and temporal variability in erosion rates could explain the observed trend in 10Be concentrations. Although not accounted for in our modeling explicitly, we suggest that the observed trend could be due to transiently enhanced erosion of recently deglaciated areas, or to greater spatial variability in erosion rates than explored in our models.

Key Growth Stage of Pb Accumulation in Rice Through a Hydroponic Experiment with Pb Stress

Pb accumulation in rice varies significantly at different growth stages. In this study, a hydroponic experiment was conducted to study the effects of exogenous Pb stress on Pb accumulation and transportation in rice plants and determine the key rice growth stages of Pb accumulation and their contribution to the Pb content in brown rice. For the hydroponic experiment, 0.5 mg ·L-1 of exogenous Pb was added to rice at different growth stages, including the tillering stage, jointing stage, booting stage, filling stage, dough stage, maturing stage, and whole growth stage (103 d) of the rice plant. Another treatment of the whole growth stage without Pb stress was established as the control. The results showed that: ① There were no significant effects of Pb stress in any single stage on the plant height, tiller number, and biomass, but the rice plant height and biomass significantly decreased under the Pb stress for the whole growth period. ② Pb contents in different tissues at the maturing stage of the rice plant were in the order of root > stem node 1 > other stem nodes > root rhizome > sti > leaf > ear > husk > brown rice. Pb contents in brown rice ranged from 0.1 to 1.2 mg ·kg-1 for all exogenous Pb treatments, and ranked in the growth stages as booting stage > jointing stage > tillering stage > filling stage > maturing stage > dough stage. ③ The relative contribution rates of Pb accumulation in the whole rice plants were relatively high during the reproductive growth period (filling stage, dough stage, and maturing stage), while those in the above-ground parts of the rice plants were relatively high during the vegetative growth stage (tillering stage, jointing stage, booting stage). ④ The booting stage was the key growth period for Pb accumulation in brown rice. Pb stress at this stage contributed 43.3% of Pb content in brown rice, followed by Pb stress at the jointing stage and the tillering stage, with contribution rates of 24.4% and 21.3%, respectively. ⑤ Water management regimes, application of amendments, or leaf resistance control techniques should be applied appropriately at the booting stage of the rice plants to reduce Pb accumulation in brown rice and to realize the safe use of rice paddies polluted with Pb.

A novel rate based methodology for creep fatigue life estimation of superalloys

In this present work, we present an accumulated inelastic strain rate based methodology to predict creep fatigue life of two different superalloys i.e. Haynes 282 and IN 718. The evolution of differential strain rate during creep and fatigue respectively motivated the present work. As creep is the rate controlling damage process in creep fatigue interaction, present mean strain rate based approach considers creep strain rate as a kinetic variable controlling the process. The other variable considered for this approach is accumulative cyclic strain during Creep-fatigue interaction. Our prediction method is purely based upon a relative accumulation rate of creep and fatigue strain. This method correlates the creep fatigue life with rate of interaction in strain-controlled regions successfully from the data of creep fatigue tests on those superalloys at two temperatures, 650 °C and 760 °C. We found suitable microstructure sensitive constants in a lifing model.

Dynamic time warping of palaeomagnetic secular variation data

SUMMARY We present and make publicly available a dynamic programming algorithm to simultaneously align the inclination and declination vector directions of sedimentary palaeomagnetic secular variation data. This algorithm generates a library of possible alignments through the systematic variation of assumptions about the relative accumulation rate and shared temporal overlap of two or more time-series. The palaeomagnetist can then evaluate this library of reproducible and objective alignments using available geological constraints, statistical methods and expert knowledge. We apply the algorithm to align previously (visually) correlated medium to high accumulation rate northern North Atlantic Holocene deposits (101–102 cm ka–1) with strong radiocarbon control. The algorithm generates plausible alignments that largely conform with radiocarbon and magnetic acquisition process uncertainty. These alignments illustrate the strengths and limitations of this numerical approach.

1980-2018年中国东部主要木本植物展叶始期的温度相关时段变化

PDF HTML阅读 XML下载 导出引用 引用提醒 1980-2018年中国东部主要木本植物展叶始期的温度相关时段变化 DOI: 10.5846/stxb202004070821 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41901014，41871032）；中国博士后科学基金面上项目（2018M640172） Changes in temperature-relevant period for the leaf unfolding date of main woody plants in eastern China during 1980-2018 Author: Affiliation: Fund Project: National Natural Science Foundation of China (41901014, 41871032)； China Postdoctoral Science Foundation (2018M640172) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:木本植物春季展叶始期的年际变化通常受其发生前一段时间的气温影响，这个时段被称作温度相关时段（temperature-relevant period，TRP）。TRP开始时间和长度的变化反映了气候增暖对植物发育过程的影响。利用中国物候网观测数据，分析了1980-2018年中国东部8个代表性站点162种木本植物展叶始期的TRP开始时间、结束时间和长度变化。结果显示：（1）亚热带站点比温带站点木本植物的平均TRP开始时间早约43 d，长度长约13 d。（2）TRP开始时间在温带地区北部（哈尔滨和牡丹江）变化不显著，在南部（北京、西安和民勤）以0.41-0.53 d/a的速度显著提前。在亚热带，除桂林外，其他站点展叶始期TRP长度延长和缩短的物种比例相近。这表明气候增暖对不同站点植物TRP的影响不仅取决于增暖的幅度，还和站点的背景气候条件相关。（3）乔木TRP平均开始时间和结束时间分别比灌木晚6.49 d和3.92 d，TRP长度略短于灌木。这与灌木采取机会主义的生存策略有关，而乔木在春季的展叶期较为保守以降低霜冻风险。（4）无论在亚热带还是温带地区，展叶越早的物种，TRP开始时间越早，长度越短，展叶始期与季前温度的相关性越强。研究结果可为研究气候变化对植物物候的影响及物候模型的发展提供科学参考。 Abstract:The variation in spring leaf unfolding date of woody plants is commonly influenced by air temperature in a prior period, which is called the temperature-relevant period (TRP). The shifts in start and length of TRP reflect how climate warming influence plants development. Using the phenological data from China Phenological Observation Network, our study analyzes the changes in start, end, length, and temperature-phenophase relationship (RTRP) of TRP for 162 woody plants in 8 representative sites of eastern China during 1980-2018. The following results are drawn. (1) Compared with temperate sites, the mean start and length of TRP in subtropical sites are 43 days earlier and 13 days longer, respectively, which is related to the higher forcing requirement and relative slower temperature accumulation rate during TRP of plants in subtropics. (2) The starts of TRP have changed slightly in the northern part of temperate zone (Harbin and Mudanjiang), but have significantly advanced in the southern part (Beijing, Xi'an and Minqin) at 0.41-0.53 d/a. In subtropical sites, except for Guilin, the proportion of plants showing an extended TRP and a shortened TRP is similar in the other sites. It suggests that the effect of climate warming on the chilling process in different sites not only depends on the magnitude of warming, but also is closely related to the background climatic conditions of the sites. (3) The start and end of TRP for tree species is 6.49 days and 3.92 days later than that of shrubs on average, respectively. The length of TRP for trees is a little shorter than that of shrubs. This is related to the opportunistic survival strategies adopted by shrubs, while trees are more conservative in spring to reduce frost risk. (4) In general, the species with an early leaf unfolding date exhibit an early start and a longer length of TRP, as well as a stronger RTRP in both temperate and subtropical sites. The results can provide scientific reference for studies about the influence of climate change on plant phenology and the development of phenological models. 参考文献 相似文献 引证文献

Separation of cancer cells using vortical microfluidic flows.

Label-free separation of viable cancer cells using vortical microfluidic flows has been introduced as a feasible cell collection method in oncological studies. Besides the clinical importance, the physics of particle interactions with the vortex that forms in a wall-confined geometry of a microchannel is a relatively new area of fluid dynamics. In our previous work [Haddadi and Di Carlo, J. Fluid. Mech. 811, 436-467 (2017)], we have introduced distinct aspects of inertial flow of dilute suspensions over cavities in a microchannel such as breakdown of the separatrix and formation of stable limit cycle orbits for finite size polystyrene particles. In this work, we extend our experiments to address the engineering-physics of cancer cell entrapment in microfluidic cavities. We begin by studying the effects of the channel width and device height on the morphology of the vortex, which has not been discussed in our previous work. The stable limit cycle orbits of finite size cancer cells are then presented. We demonstrate effects of the separatrix breakdown and the limit cycle formation on the operation of the cancer cell separation platform. By studying the flow of dilute cell suspensions over the cavities, we further develop the notion of the cavity capacity and the relative rate of cell accumulation as optimization criteria which connect the device geometry with the flow. Finally, we discuss the proper placement of multiple cavities inside a microchannel for improved cell entrapment.

Secondary rock structures and the regional hydrogeology of claystone-rich cretaceous strata, Williston Basin, Saskatchewan, Canada

The geometry and spatial distribution of a polygonal fault system (PFS) and collapse features within Cretaceous strata (predominantly mudstones and claystones) were investigated using three high-resolution three-dimensional seismic datasets of the Williston Basin, Saskatchewan, Canada. Mapping of the planform geometry and fault throw distributions (throw–depth (T–z) profiling) shows that the PFS present in the Colorado Group and Pierre Fm has a vertical extent of 200–330 m. Variation in the lateral planform geometry is attributed to the relative rates of stress accumulation during early development of the planar faults and is constrained using sequence stratigraphic principles. The mean fault dip is 60° ± 12° (number of measurements, n = 225). The T–z profiles appear as partial C-type profiles, demonstrating that at least half of the total height of the PFS was removed during post-Cretaceous erosion. The presence of polygonal faults in equivalent strata of the Western Interior Sedimentary Basin (WISB) suggests the PFS described in the current study (1510 km2) may be present across the WISB. Collapse features, formed in response to dissolution cavities within underlying strata, crosscut the entire Cretaceous sequence and are subcircular in plan view with typical diameters of 350–450 m. These features are present in each of the datasets at a rate of 0.02–0.11 collapses/km2. The prevalence of collapses in areas where faults display modified throw distributions may suggest post-Cretaceous fault reactivation associated with Pleistocene glacial periods. Although these secondary rock structures likely affect groundwater and solute transport at the basin scale, the impact remains to be determined.

Interactions of A Paleocene River, A Rising Fold, and Early-Diagenetic Concretions

Abstract: The relative rates of sediment accumulation, erosion, and structural uplift determine whether a growing fold develops positive topographic relief, is beveled by antecedent streams, or is buried under thick growth strata. When folds rise in subsiding basins, upward, convergent flow of groundwater through the permeable growth strata that underlie antecedent streams enhances the flux of ions required for concretion growth. Early diagenetic concretions that grow in such alluvial strata may constitute the only clasts larger than sand size available for transport when antecedent streams become erosive. The first reworked concretions deposited by these streams should accurately mark the transition from aggradation to erosion as folds rise into the paths of streams. In this situation, the ability to differentiate reworked from in situ concretions is crucial. The west-vergent Simpson Ridge anticline, a N–S-trending, thick-skinned Laramide structure in east-central Wyoming, separates the larger Hanna basin from the Carbon basin. Near the north nose of this anticline, in situ iron-oxide-rich concretions are abundant in folded Paleocene strata (Ferris Formation) and, just to the east, large, reworked , iron-rich concretions are abundant in younger, more gently dipping conglomerates in the basal Hanna Formation of the backlimb. Smaller reworked concretions are also present near the base of the Hanna Formation at least 7 km south of the anticlinal nose and just east of the fold9s axis. At the anticlinal nose, in situ (non-reworked) concretions up to 3 m × 1 m × 1 m are abundant at the top of an ∼ 7-km-thick sequence of sandstones and siltstones that constitute the Late Cretaceous–early Paleocene Ferris Formation. Reworked concretions are absent in the strata hosting these in situ concretions, but reworked concretionary clasts up to 2 m in diameter are present in exposures of conglomerates in the lowermost Hanna Formation that lie just above the in situ Ferris concretions and southeast of the anticlinal nose. These early-diagenetic concretions were originally cemented by siderite (FeCO 3 ). Oxidation of some small, rinded siderite-cemented clasts took place after their fluvial transport into the Hanna Formation, but abundant angular, un-rinded, iron-oxide-cemented clasts indicate that many large, in situ siderite concretions had resided in the vadose zone before they were entrained. The distribution of reworked concretions and the orientations of crossbeds show that antecedent Hanna streams eroded a swath at least 5 km wide across the rising structure. These streams transported Ferris Formation concretions southeastward into the Carbon basin, and deposited them in a conglomeratic sandstone body in the Hanna Formation. Large calcite-cemented concretions, many with a pipe-like morphology, then grew within Hanna crossbeds. In many cases, these in situ concretions enclose transported, iron-rich concretions, but there is no evidence any calcite-cemented concretions were reworked. The NW–SE alignment of the pipes record southeastward flow of groundwater and thus also provide evidence (together with the orientation of the crossbeds) of the original continuity of the Hanna Formation across the anticline. Reworked concretions reveal the interplay of deposition, diagenesis, and erosion. Due to convergent groundwater flow over growing anticlines, early diagenetic concretions, both in situ and as reworked clasts, are especially likely to be found in growth strata.

Graphic correlation: A powerful tool for biostratigraphic correlation of petroleum exploration and production in the Cenozoic deep offshore Niger Delta, Nigeria

The graphic correlation method provides better and higher resolution to the stratigraphic problems than zonation biostratigraphy. The measured total stratigraphic ranges of 44 palynomorphs present in five wells from the Niger Delta Basin have been assembled by graphic correlation method into a chronostratigraphic framework. The analysis by graphic correlation reveals that for a meter of sediment accumulation in Well E, correspondingly amounted to only 0.8794 m, 0.7586 m, 0.8677 m and 0.8686 m of sediments that were deposited in wells A, B, C and D, respectively. These relative rates of sediment accumulation indicate that either there was less erosion taking place and/or more accommodation space in Well E than Wells A, B, C and D. A graphic correlation horizontal terrace was recorded in each of the Wells A, C and D, which are interpreted as condensation of sediments that had truncated the sediments accumulation profile in these wells. These condensed sections are interpreted as sediment starvation and very slow rates of sedimentation during the Early Pliocene, Late Pliocene and Late Pleistocene due to marine transgression(s) at these stages in the Niger Delta Basin. The generated correlation equations, slopes and intercept values from graphic correlation plots allow the correlation of six biostratigraphic and sedimentological events in Wells A, B, C, D and E. The resulting chronostratigraphic framework in this study is essential for sequence stratigraphic interpretations and basin analysis, and in particular, to correlate widely separated wells.

The southern coastal Beringian land bridge: cryptic refugium or pseudorefugium for woody plants during the Last Glacial Maximum?

AbstractAimThe Bering Land Bridge (BLB) connected Asia and North America during glacial periods, supported a diverse ecosystem of now‐vanished megafauna, and is a proposed glacial refugium. This study tests whether southern coastal Beringia was a refugium for woody taxa during the Last Glacial Maximum (LGM) and hypotheses about habitats available on the BLB before and after megafaunal extinction.LocationSt. Paul Island, Alaska.MethodsWe analysed sediment cores from the Lake Hill, with a new age model anchored by 18 radiocarbon dates and multiple palaeoecological indicators (sedimentary ancient DNA [sedaDNA], macrobotanical fossils, and pollen) for the presence/absence of four woody genera: Picea, Betula, Alnus and Salix. We reconstructed vegetation history and compare St. Paul tundra composition to mainland counterparts.ResultsSt. Paul has been continuously occupied by graminoid‐forb tundra with prostrate shrubs (Salix, Ericaceae) since 18,000 years before present (yr bp). Fossil pollen of Picea, Pinus, Betula and Alnus is present in the Lake Hill sediments at low relative abundances and accumulation rates, consistent with long‐distance transport. Macrobotanical fossils and sedaDNA analyses do not support Picea, Betula and Alnus presence. The St. Paul modern and fossil pollen assemblages are compositionally unlike mainland counterparts, but most closely resemble Arctic herbaceous tundra. Stratigraphically constrained cluster analysis indicates no major change in the vegetation after woolly mammoth extinction at 5600 yr bp, although Poaceae, Cyperaceae, Equisetum and forb abundances increase.Main conclusionsThis study strongly indicates that St. Paul and, by implication, southern coastal Beringia were not refugia for woody taxa during the LGM. The persistence of prostrate shrub‐graminoid tundra supports interpretations that herbaceous tundra prevailed on southern Beringia during the LGM, whilst not ruling out the possibility of mesic shrub tundra in the interior. This herbaceous tundra supported an island refugium for woolly mammoth for 8000 years, showing no major vegetation composition changes after extinction.

The reasons for the nonmonotonic influence of extracellular calcium ion concentrations on the capacity of CD4+ T cells in human peripheral blood to polyclonal activation

Extracellular calcium ion concentrations ([Ca2+]o) nonlinearly affected the capacity of CD4+ T cells in human peripheral blood (HPB) to polyclonal activation in vitro. The dependencies of the tested parameters of CD4+ T cell activation on [Ca2+]o values corresponded to a curve with two maxima and one local minimum in between. One of the maxima was in the area of the HPB lower [Ca2+]o normal level, whereas the other was even lower, which is characteristic for pathological states of various origin. Such a pattern could be explained by some differences in T cell surface receptors. For the confirmation of this hypothesis we compared receptor-dependent (a mixture of monoclonal antibodies (mAbs) to CD3 and CD28 molecules) and receptor-independent (a mixture of phorbol myristate acetate and ionomycin) T cell activation pathways in HPB at varied [Ca2+]o values. The results evidenced a key role of the T cell intracellular signaling system for the differentiation of their sensitivity to calcium ions. Another reason can be related to the different in vitro rates of CD4+ T cell activation and differentiation stages. To check this assumption, we measured the time dependencies of activated CD4+CD69, CD4+(Tyr-P)high, CD4+CD29+ and CD4+(HLA-DR)+ T cell portions as well as their [Ca2+]o dependencies. The [Ca2+]o concentration was shown to influence the activation and differentiation stages of CD4+ T cell activation in vitro to the same degree. Hence, the earliest induction stages play a key role for the unequal sensitivity to calcium ions of CD4+ T cells in vitro. It was additionally supported by the analysis of the relative accumulation rates of activated CD4+CD69+ T cells in the presence of 0.4, 0.8, and 1.2 mM EGTA. A comparative role of CD4+ T memory cells and their naive precursors was studied in a separate series of experiments. First, we performed the phenotypical analysis of CD4+CD69+ T cells within the curve maxima. The first maximum of the CD4+ T cell portion dependence on calcium ion concentrations was formed on average by 85% CD4+CD45R0highCD69+ memory T cells, whereas the remaining 15% was constituted by naive CD4+CD45RAlowCD69+ T cells. The second maximum was nearly completely formed by CD4+CD45R0+CD69+ memory T cells. A portion of naive CD4+CD45RAlowCD69+ T cells rarely exceeded 2%. The content of CD4+CD69 T cells in these maxima was proportional to the donor age and was expressed as a straight line with R2 = 0.9077. Ionomycin-resistant (IR) memory T lymphocytes are the most probable candidates for the role of CD4+ T cells capable of being activated in the conditions of hypocalcemia. For the confirmation of this assumption we isolated mononuclear cells and their IR fraction from donor peripheral blood. Both cell populations were activated with a mAbs mixture at varied EGTA concentrations. In the first maximum only a small portion of the IR fraction of CD4+CD45RA-CD45R0+ memory T cells was activated. It was the second maximum that demonstrated the activation of the majority of CD4+CD45RA-CD45R0+ memory T cells. Hence, the presence of two activation maxima of CD4+ T cell in the conditions of hypocalcemia could be accounted for by the presence in HPB of two CD4+ memory Tcell populations differing in the calcium-dependent systems of intracellular signaling.

Diurnal and seasonal variations in photosynthetic characteristics of switchgrass in semiarid region on the Loess Plateau of China

In order to use rationally switchgrass (Panicum virgatum L.) introduced in a large scale in semiarid regions on the Loess Plateau of China, we investigated and compared soil water storage dynamics, diurnal and seasonal changes in leaf photosynthetic characteristics, and biomass production of switchgrass grown under three different row spacing (20, 40, and 60 cm). Results indicated that photosynthetic parameters showed a pronounced seasonality. Diurnal course of net photosynthetic rate (PN) was bimodal, showing obvious midday depression, which was mainly due to stomatal limitation in May and June, by nonstomatal limitation in August, and both stomatal and nonstomatal factors in September. Generally, PN, stomatal conductance, instantaneous water-use efficiency, light-saturated net photosynthetic rate, saturation irradiance, and compensation irradiance increased with increasing row spacing. Plant height, leaf width, and a relative growth rate of biomass accumulation were significantly higher at the row spacing of 60 cm, while 20 cm spacing showed significantly higher aboveground biomass production and the biomass water-use efficiency. All these confirmed that soil water is the key limiting factor influencing switchgrass photosynthesis, and suggested that the wide row plantation (i.e., 60 cm) was more beneficial to switchgrass growth, while narrow spacing was in favor of improving switchgrass productivity and water-use efficiency.

A more accurate method using MOVES (Motor Vehicle Emission Simulator) to estimate emission burden for regional-level analysis

The U.S. Environmental Protection Agency’s (EPA) Motor Vehicle Emission Simulator (MOVES) is required by the EPA to replace Mobile 6 as an official on-road emission model. Incorporated with annual vehicle mile traveled (VMT) by Highways Performance Monitoring System (HPMS) vehicle class, MOVES allocates VMT from HPMS to MOVES source (vehicle) types and calculates emission burden by MOVES source type. However, the calculated running emission burden by MOVES source type may be deviated from the actual emission burden because of MOVES source population, specifically the population fraction by MOVES source type in HPMS vehicle class. The deviation is also the result of the use of the universal set of parameters, i.e., relative mileage accumulation rate (relativeMAR), packaged in MOVES default database. This paper presents a novel approach by adjusting the relativeMAR to eliminate the impact of MOVES source population on running exhaust emission and to keep start and evaporative emissions unchanged for both MOVES2010b and MOVES2014. Results from MOVES runs using this approach indicated significant improvements on VMT distribution and emission burden estimation for each MOVES source type. The deviation of VMT by MOVES source type is minimized by using this approach from 12% to less than 0.05% for MOVES2010b and from 50% to less than 0.2% for MOVES2014 except for MOVES source type 53. Source type 53 still remains about 30% variation. The improvement of VMT distribution results in the elimination of emission burden deviation for each MOVES source type. For MOVES2010b, the deviation of emission burdens decreases from −12% for particulate matter less than 2.5 μm (PM2.5) and −9% for carbon monoxide (CO) to less than 0.002%. For MOVES2014, it drops from 80% for CO and 97% for PM2.5 to 0.006%.Implications: This approach is developed to more accurately estimate the total emission burdens using EPA’s MOVES, both MOVES2010b and MOVES2014, by redistributing vehicle mile traveled (VMT) by Highways Performance Monitoring System (HPMS) class to MOVES source type on the basis of comprehensive traffic study, local link-by-link VMT broken down into MOVES source type.

Pastejo e nitrogênio sobre o crescimento de raízes na mistura de aveia preta e azevém

This study evaluated the effect of grazing and its absence, and the nitrogen on the morphology of roots of black oat ( Avena strigosa Schreb.) mixed with Italian ryegrass ( Lolium multiflorum Lam.). The experimental design was a randomized block design in split-split, the main portion was study the effects of grazing and its absence, in the subplots the nitrogen doses of 75 and 150 kg ha-1 and in the sub-subplots were at sampling period. There was used the cylinder method to collect the root, being measured the length, surface area, mean diameter and volume by image analysis system Win / MacRizho (4.1c). Determined the dry mass of roots and shoot, and estimated the density of the root tissue and shoot:root ratio. From these results we determined the rate of root growth relative (RGR), relative root expansion rate (RRER) and rate of accumulation of dry matter daily (RADM). In the first period, was higher RGR, RRER, the second period there was a reduction of the same, probably due to the period of drought and plant senescence. There was also reduced due to grazing RADM. With grazing, the length, surface area, mean diameter and root volume were higher, indicating that there was greater root growth of plants grazed compared to ungrazed. The systems studied had no effect on the dry weight of roots. There were found greater specific mass and shot:root ratio in the system without grazing. There was no significant difference between the nitrogen studied. At mixed of black oat and ryegrass, the grazing and nitrogen dose until 150 kg ha-1 little affect root growth. The nitrogen dose changed a little the growth rates and expansion of the roots. On the other hand, the grazing favored the length, area, volume and root diameter.

Mn accumulation and tolerance in Celosia argentea Linn.: A new Mn-hyperaccumulating plant species

Identifying a hyperaccumulator is an important groundwork for the phytoextraction of heavy metal-contaminated soil. Celosia argentea Linn., which grew on a Mn tailing wasteland, was found to hyperaccumulate Mn (14 362mgkg−1 in leaf dry matter) in this study. To investigate Mn tolerance and accumulation in C. argentea, a hydroponic culture experiment was conducted in a greenhouse. Results showed that the biomass and the relative growth rate of C. argentea were insignificantly different (p>0.05) at the Mn supply level ranging from 2.5mgL−1 (control) to 400mgL−1. Manganese concentrations in leaves, stems, and roots reached maxima of 20228, 8872, and 2823mgkg−1 at 600mgMnL−1, respectively. The relative rate of Mn accumulation increased by 91.2% at 400mgMnL−1. Over 95% of the total Mn taken up by C. argentea was translocated to shoots. Thus, C. argentea exhibits the basic characteristics of a Mn-hyperaccumulator. This species has great potential to remediate Mn-contaminated soil cheaply and can also aid the studies of Mn uptake, translocation, speciation, distribution and detoxification in plants.