757 research outputs found

    Loss and revival of phase coherence in a Bose-Einstein condensate moving through an optical lattice

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    We investigate the phase coherence of a trapped Bose-Einstein condensate that undergoes a dynamical superfluid-insulator transition in the presence of a one-dimensional optical lattice. We study the evolution of the condensate after a sudden displacement of the harmonic trapping potential by solving the Gross-Pitaevskii equation, and comparing the results with the prediction of two effective 1D models. We show that, owing to the 3D nature of the system, the breakdown of the superfluid current above a critical displacement is not associated to a sharp transition, but there exists a range of displacements for which the condensate can recover a certain degree of coherence. We also discuss the implications on the interference pattern after the ballistic expansion as measured in recent experiments at LENS.Comment: 7 pages, 9 figure

    Three-Dimensional Printable Enzymatically Active Plastics

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    [Image: see text] Here, we describe a facile route to the synthesis of enzymatically active highly fabricable plastics, where the enzyme is an intrinsic component of the material. This is facilitated by the formation of an electrostatically stabilized enzyme–polymer surfactant nanoconstruct, which, after lyophilization and melting, affords stable macromolecular dispersions in a wide range of organic solvents. A selection of plastics can then be co-dissolved in the dispersions, which provides a route to bespoke 3D enzyme plastic nanocomposite structures using a wide range of fabrication techniques, including melt electrowriting, casting, and piston-driven 3D printing. The resulting constructs comprising active phosphotriesterase (arPTE) readily detoxify organophosphates with persistent activity over repeated cycles and for long time periods. Moreover, we show that the protein guest molecules, such as arPTE or sfGFP, increase the compressive Young’s modulus of the plastics and that the identity of the biomolecule influences the nanomorphology and mechanical properties of the resulting materials. Overall, we demonstrate that these biologically active nanocomposite plastics are compatible with state-of-the-art 3D fabrication techniques and that the methodology could be readily applied to produce robust and on-demand smart nanomaterial structures

    CMBPol Mission Concept Study: Probing Inflation with CMB Polarization

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    We summarize the utility of precise cosmic microwave background (CMB) polarization measurements as probes of the physics of inflation. We focus on the prospects for using CMB measurements to differentiate various inflationary mechanisms. In particular, a detection of primordial B-mode polarization would demonstrate that inflation occurred at a very high energy scale, and that the inflaton traversed a super-Planckian distance in field space. We explain how such a detection or constraint would illuminate aspects of physics at the Planck scale. Moreover, CMB measurements can constrain the scale-dependence and non-Gaussianity of the primordial fluctuations and limit the possibility of a significant isocurvature contribution. Each such limit provides crucial information on the underlying inflationary dynamics. Finally, we quantify these considerations by presenting forecasts for the sensitivities of a future satellite experiment to the inflationary parameters.Comment: 107 pages, 14 figures, 17 tables; Inflation Working Group contribution to the CMBPol Mission Concept Study; v2: typos fixed and references adde

    Prevention and management of adverse events of novel agents in multiple myeloma: a consensus of the European Myeloma Network

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    During the last few years, several new drugs have been introduced for treatment of patients with multiple myeloma, which have significantly improved the treatment outcome. All of these novel substances differ at least in part in their mode of action from similar drugs of the same drug class, or are representatives of new drug classes, and as such present with very specific side effect profiles. In this review, we summarize these adverse events, provide information on their prevention, and give practical guidance for monitoring of patients and for management of adverse events

    Degradation of Cdc25A by \u3b2-TrCP during S phase and in response to DNA damage

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    The Cdc25A phosphatase is essential for cell-cycle progression because of its function in dephosphorylating cyclin-dependent kinases. In response to DNA damage or stalled replication, the ATM and ATR protein kinases activate the checkpoint kinases Chk1 and Chk2, which leads to hyperphosphorylation of Cdc25A1\u20133. These events stimulate the ubiquitin-mediated pro- teolysis of Cdc25A1,4,5 and contribute to delaying cell-cycle progression, thereby preventing genomic instability1\u20137. Here we report that b-TrCP is the F-box protein that targets phosphory- lated Cdc25A for degradation by the Skp1/Cul1/F-box protein complex. Downregulation of b-TrCP1 and b-TrCP2 expression by short interfering RNAs causes an accumulation of Cdc25A in cells progressing through S phase and prevents the degradation of Cdc25A induced by ionizing radiation, indicating that b-TrCP may function in the intra-S-phase checkpoint. Consistent with this hypothesis, suppression of b-TrCP expression results in radioresistant DNA synthesis in response to DNA damage\u2014a phenotype indicative of a defect in the intra-S-phase checkpoint that is associated with an inability to regulate Cdc25A properly. Our results show that b-TrCP has a crucial role in mediating the response to DNA damage through Cdc25A degradation

    Pregnancy Does Not Affect HIV Incidence Test Results Obtained Using the BED Capture Enzyme Immunoassay or an Antibody Avidity Assay

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    Accurate incidence estimates are needed for surveillance of the HIV epidemic. HIV surveillance occurs at maternal-child health clinics, but it is not known if pregnancy affects HIV incidence testing.We used the BED capture immunoassay (BED) and an antibody avidity assay to test longitudinal samples from 51 HIV-infected Ugandan women infected with subtype A, C, D and intersubtype recombinant HIV who were enrolled in the HIVNET 012 trial (37 baseline samples collected near the time of delivery and 135 follow-up samples collected 3, 4 or 5 years later). Nineteen of 51 women were also pregnant at the time of one or more of the follow-up visits. The BED assay was performed according to the manufacturer's instructions. The avidity assay was performed using a Genetic Systems HIV-1/HIV-2 + O EIA using 0.1M diethylamine as the chaotropic agent.During the HIVNET 012 follow-up study, there was no difference in normalized optical density values (OD-n) obtained with the BED assay or in the avidity test results (%) when women were pregnant (n = 20 results) compared to those obtained when women were not pregnant (n = 115; for BED: p = 0.9, generalized estimating equations model; for avidity: p = 0.7, Wilcoxon rank sum). In addition, BED and avidity results were almost exactly the same in longitudinal samples from the 18 women who were pregnant at only one study visit during the follow-up study (p = 0.6, paired t-test).These results from 51 Ugandan women suggest that any changes in the antibody response to HIV infection that occur during pregnancy are not sufficient to alter results obtained with the BED and avidity assays. Confirmation with larger studies and with other HIV subtypes is needed

    Parp1 Localizes within the Dnmt1 Promoter and Protects Its Unmethylated State by Its Enzymatic Activity

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    Aberrant hypermethylation of CpG islands in housekeeping gene promoters and widespread genome hypomethylation are typical events occurring in cancer cells. The molecular mechanisms behind these cancer-related changes in DNA methylation patterns are not well understood. Two questions are particularly important: (i) how are CpG islands protected from methylation in normal cells, and how is this protection compromised in cancer cells, and (ii) how does the genome-wide demethylation in cancer cells occur. The latter question is especially intriguing since so far no DNA demethylase enzyme has been found.Our data show that the absence of ADP-ribose polymers (PARs), caused by ectopic over-expression of poly(ADP-ribose) glycohydrolase (PARG) in L929 mouse fibroblast cells leads to aberrant methylation of the CpG island in the promoter of the Dnmt1 gene, which in turn shuts down its transcription. The transcriptional silencing of Dnmt1 may be responsible for the widespread passive hypomethylation of genomic DNA which we detect on the example of pericentromeric repeat sequences. Chromatin immunoprecipitation results show that in normal cells the Dnmt1 promoter is occupied by poly(ADP-ribosyl)ated Parp1, suggesting that PARylated Parp1 plays a role in protecting the promoter from methylation.In conclusion, the genome methylation pattern following PARG over-expression mirrors the pattern characteristic of cancer cells, supporting our idea that the right balance between Parp/Parg activities maintains the DNA methylation patterns in normal cells. The finding that in normal cells Parp1 and ADP-ribose polymers localize on the Dnmt1 promoter raises the possibility that PARylated Parp1 marks those sequences in the genome that must remain unmethylated and protects them from methylation, thus playing a role in the epigenetic regulation of gene expression

    Substantial hysteresis in emergent temperature sensitivity of global wetland CH4 emissions

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    Wetland methane (CH4) emissions (FCH4) are important in global carbon budgets and climate change assessments. Currently, FCH4 projections rely on prescribed static temperature sensitivity that varies among biogeochemical models. Meta-analyses have proposed a consistent FCH4 temperature dependence across spatial scales for use in models; however, site-level studies demonstrate that FCH4 are often controlled by factors beyond temperature. Here, we evaluate the relationship between FCH4 and temperature using observations from the FLUXNET-CH4 database. Measurements collected across the globe show substantial seasonal hysteresis between FCH4 and temperature, suggesting larger FCH4 sensitivity to temperature later in the frost-free season (about 77% of site-years). Results derived from a machine-learning model and several regression models highlight the importance of representing the large spatial and temporal variability within site-years and ecosystem types. Mechanistic advancements in biogeochemical model parameterization and detailed measurements in factors modulating CH4 production are thus needed to improve global CH4 budget assessments. Wetland methane emissions contribute to global warming, and are oversimplified in climate models. Here the authors use eddy covariance measurements from 48 global sites to demonstrate seasonal hysteresis in methane-temperature relationships and suggest the importance of microbial processes.Peer reviewe
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