558 research outputs found

    Fe, Zn, Mn and N transfer between size classes in a coastal phytoplankton community: Trace metal and major nutrient recycling compared

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    Experiments were performed to investigate transfer of 59Fe, 65Zn, 54Mn, and 15N from labeled cyanobacteria to the large (\u3e8 μm or \u3e5 μm) phytoplankton size class from Monterey Bay, California. Transfer of metal isotope activity was measured from and into total (for all isotopes) and intracellular (59Fe only) pools. Results demonstrated rapid and efficient transfer of nitrogen to the large phytoplankton size class; intracellular 59Fe was transferred into the intracellular and total pools of the \u3e8 μm phytoplankton size class 70% and 130% as efficiently as nitrogen, respectively. 65Zn and 54Mn were transferred between size classes 48% and 23% as efficiently as N. Extracellular 59Fe and 65Zn from the added cyanobacteria also appeared quickly in the large size fraction, although most of the Fe transfer appeared to be the result of surface adsorption rather than biological uptake. These data are discussed in relation to the biological recycling efficiencies of the four elements and the resulting implications for biogeochemical cycling of trace and major nutrient elements

    Spatial distances affect temporal prediction and interception.

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    The more distant two consecutive stimuli are presented, the longer the temporal interstimulus interval (ISI) between their presentations is perceived (kappa effect). The present study aimed at testing whether the kappa effect not only affects perceptual estimates of time, but also motor action, more specifically, interception. In a first step, the original kappa paradigm was adapted to assess the effect in temporal prediction. Second, the task was further modified to an interception task, requiring participants to spatially and temporally predict and act. In two online experiments, a white circle was successively presented at three locations moving from left to right with constant spatial and temporal ISIs in between. Participants were asked to either (i) indicate the time of appearance of the predicted fourth stimulus (Exp. 1) or to (ii) intercept the predicted fourth location at the correct time (Exp. 2). In both experiments the temporal response depended on the spatial intervals. In line with the kappa effect, participants predicted the final stimulus to appear later (Exp. 1) or intercepted it later (Exp. 2), the more distant the stimuli were presented. Together, these results suggest that perceptual biases such as the kappa effect impact motor interception performance. [Abstract copyright: © 2022. The Author(s).

    Effects of visual blur and contrast on spatial and temporal precision in manual interception.

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    The visual system is said to be especially sensitive towards spatial but lesser so towards temporal information. To test this, in two experiments, we systematically reduced the acuity and contrast of a visual stimulus and examined the impact on spatial and temporal precision (and accuracy) in a manual interception task. In Experiment 1, we blurred a virtual, to-be-intercepted moving circle (ball). Participants were asked to indicate (i.e., finger tap) on a touchscreen where and when the virtual ball crossed a ground line. As a measure of spatial and temporal accuracy and precision, we analyzed the constant and variable errors, respectively. With increasing blur, the spatial and temporal variable error, as well as the spatial constant error increased, while the temporal constant error decreased. Because in the first experiment, blur was potentially confounded with contrast, in Experiment 2, we re-ran the experiment with one difference: instead of blur, we included five levels of contrast matched to the blur levels. We found no systematic effects of contrast. Our findings confirm that blurring vision decreases spatial precision and accuracy and that the effects were not mediated by concomitant changes in contrast. However, blurring vision also affected temporal precision and accuracy, thereby questioning the generalizability of the theoretical predictions to the applied interception task. [Abstract copyright: © 2021. The Author(s).

    Examination of precipitation chemistry and improvements in precision using the Mg(OH)2 preconcentration ICP-MS method for high-throughput analysis of open-ocean Fe and Mn in seawater

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    Author Posting. © Elsevier B.V., 2006. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Analytica Chimica Acta 565 (2006): 222-233, doi:10.1016/j.aca.2006.02.028.The chemistry of magnesium precipitation preconcentration of Fe, Mn and Co from seawater was investigated, and this analytical technique was adapted for use with the Element-2 inductively coupled plasma mass spectrometer (E2 ICP-MS). Experiments revealed that the scavenging efficiency of Mn using the precipitation protocol described here was ~95% and similar to that previously observed with Fe. In contrast, the scavenging efficiency of Co was three-fold lower than that of Fe and Mn, resulting in poor recovery. An increase in sample size to 13mL led to several desired effects: 1) an increase in the Fe and Mn signals allowing a final dilution of samples to 0.5mL and the use of an autosampler, 2) an increase in precision to ~1-2.5% RSD, 3) an increase in signal relative to the blank. Experiments suggest metal concentration from seawater occurs during the formation of Mg(OH)2 precipitate, whereas P was scavenged by adsorption onto the Mg(OH)2 particles. Example vertical profiles are shown for dissolved Fe and Mn from the Equatorial Pacific.This research was supported by NSF grants OCE-0327225, OCE-0452883, and the Center for Environmental Bioinorganic Chemistry at Princeton

    Converging Technologies - Shaping the Future of European Societies

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    The European Commission and Member States are called upon to recognise the novel potential of Converging Technologies (CTs) to advance the Lisbon Agenda. Wise investment in CTs stimulates science and technology research, strengthens economic competitiveness, and addresses the needs of European societies and their citizens. Preparatory action should be taken to implement CT as a thematic research priority, to develop Converging Technologies for the European Knowledge Society (CTEKS) as a specifically European approach to CTs, and to establish a CTEKS research communit

    Alkaline phosphatase in metastatic castration-resistant prostate cancer: reassessment of an older biomarker

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    Since most patients with metastatic castration-resistant prostate cancer (mCRPC) have bone metastases, it is important to understand the potential impact of therapies on prognostic biomarkers, such as ALP. Clinical studies involving mCRPC life-prolonging agents (i.e., sipuleucel-T, abiraterone, enzalutamide, docetaxel, cabazitaxel, and radium-223) have shown that baseline ALP level is prognostic for overall survival, and may be a better prognostic marker for overall survival than prostate-specific antigen in patients with bone-dominant mCRPC. Mechanism of action differences between therapies may partly explain ALP dynamics during treatment. ALP changes can be interpreted within the context of other parameters while monitoring disease activity to better understand the underlying pathology. This review evaluates the current role of ALP in mCRPC

    Inverse correlation between PDGFC expression and lymphocyte infiltration in human papillary thyroid carcinoma

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    Background: Members of the PDGF family have been suggested as potential biomarkers for papillary thyroid carcinomas (PTC). However, it is known that both expression and stimulatory effect of PDGF ligands can be affected by inflammatory cytokines. We have performed a microarray study in a collection of PTCs, of which about half the biopsies contained tumour-infiltrating lymphocytes or thyroiditis. To investigate the expression level of PDGF ligands and receptors in PTC we measured the relative mRNA expression of all members of the PDGF family by qRT-PCR in 10 classical PTC, eight clinically aggressive PTC, and five non-neoplastic thyroid specimens, and integrated qRT-PCR data with microarray data to enable us to link PDGF-associated gene expression profiles into networks based on recognized interactions. Finally, we investigated potential influence on PDGF mRNA levels by the presence of tumour-infiltrating lymphocytes. Methods: qRT-PCR was performed on PDGFA, PDGFB, PDGFC, PDGFD, PDGFRA PDGFRB and a selection of lymphocyte specific mRNA transcripts. Semiquantitative assessment of tumourinfiltrating lymphocytes was performed on the adjacent part of the biopsy used for RNA extraction for all biopsies, while direct quantitation by qRT-PCR of lymphocyte-specific mRNA transcripts were performed on RNA also subjected to expression analysis. Relative expression values of PDGF family members were combined with a cDNA microarray dataset and analyzed based on clinical findings and PDGF expression patterns. Ingenuity Pathway Analysis (IPA) was used to elucidate potential molecular interactions and networks. Results: PDGF family members were differentially regulated at the mRNA level in PTC as compared to normal thyroid specimens. Expression of PDGFA (p = 0.003), PDGFB (p = 0.01) and PDGFC (p = 0.006) were significantly up-regulated in PTCs compared to non-neoplastic thyroid tissue. In addition, expression of PDGFC was significantly up-regulated in classical PTCs as compared to clinically aggressive PTCs (p = 0.006), and PDGFRB were significantly up-regulated in clinically aggressive PTCs (p = 0.01) as compared to non-neoplastic tissue. Semiquantitative assessment of lymphocytes correlated well with quantitation of lymphocyte-specific gene expression. Further more, by combining TaqMan and microarray data we found a strong inverse correlation between PDGFC expression and the expression of lymphocyte specific mRNAs. Conclusion: At the mRNA level, several members of the PDGF family are differentially expressed in PTCs as compared to normal thyroid tissue. Of these, only the PDGFC mRNA expression level initially seemed to distinguish classical PTCs from the more aggressive PTCs. However, further investigation showed that PDGFC expression level correlated inversely to the expression of several lymphocyte specific genes, and to the presence of lymphocytes in the biopsies. Thus, we find that PDGFC mRNA expression were down-regulated in biopsies containing infiltrated lymphocytes or thyroiditis. No other PDGF family member could be linked to lymphocyte specific gene expression in our collection of PTCs biopsies

    Avoiding Quantum Chaos in Quantum Computation

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    We study a one-dimensional chain of nuclear 1/21/2-spins in an external time-dependent magnetic field. This model is considered as a possible candidate for experimental realization of quantum computation. According to the general theory of interacting particles, one of the most dangerous effects is quantum chaos which can destroy the stability of quantum operations. According to the standard viewpoint, the threshold for the onset of quantum chaos due to an interaction between spins (qubits) strongly decreases with an increase of the number of qubits. Contrary to this opinion, we show that the presence of a magnetic field gradient helps to avoid quantum chaos which turns out to disappear with an increase of the number of qubits. We give analytical estimates which explain this effect, together with numerical data supportingComment: RevTex, 5 pages including 3 eps-figure
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