Microstructured blood vessel surrogates reveal structural tropism of motile malaria parasites

Plasmodium sporozoites, the highly motile forms of the malaria parasite, are transmitted naturally by mosquitoes and traverse the skin to find, associate with, and enter blood capillaries. Research aimed at understanding how sporozoites select blood vessels is hampered by the lack of a suitable experimental system. Arrays of uniform cylindrical pillars can be used to study small cells moving in controlled environments. Here, an array system displaying a variety of pillars with different diameters and shapes is developed in order to investigate how Plasmodium sporozoites associate to the pillars as blood vessel surrogates. Investigating the association of sporozoites to pillars in arrays displaying pillars of different diameters reveals that the crescent-shaped parasites prefer to associate with and migrate around pillars with a similar curvature. This suggests that after transmission by a mosquito, malaria parasites may use a structural tropism to recognize blood capillaries in the dermis in order to gain access to the blood stream

Stable Isotope Phosphate Labelling of Diverse Metabolites is Enabled by a Family of O-18-Phosphoramidites**

A family of 18O2-phosphoramidites facilitates synthetic access on gram-scale to various isotopically pure 18O-labelled phosphate products, like nucleotides, inositol phosphates, polyphosphates, and DNA. The utility of these 18O-natural products is underlined in the assignment of various metabolites from biological matrices using capillary electrophoresis electrospray ionisation triple quadrupole mass spectrometry. Stable isotope labelling is state-of-the-art in quantitative mass spectrometry, yet often accessing the required standards is cumbersome and very expensive. Here, a unifying synthetic concept for 18O-labelled phosphates is presented, based on a family of modified 18O2-phosphoramidite reagents. This toolbox offers access to major classes of biologically highly relevant phosphorylated metabolites as their isotopologues including nucleotides, inositol phosphates, -pyrophosphates, and inorganic polyphosphates. 18O-enrichment ratios >95 % and good yields are obtained consistently in gram-scale reactions, while enabling late-stage labelling. We demonstrate the utility of the 18O-labelled inositol phosphates and pyrophosphates by assignment of these metabolites from different biological matrices. We demonstrate that phosphate neutral loss is negligible in an analytical setup employing capillary electrophoresis electrospray ionisation triple quadrupole mass spectrometry

Adaptive working memory training does not produce transfer effects in cognition and neuroimaging

Despite growing interest in cognitive interventions from academia and industry, it remains unclear if working memory (WM) training, one of the most popular cognitive interventions, produces transfer effects. Transfer effects are training-induced gains in performance in untrained cognitive tasks, while practice effects are improvements in trained task. The goal of this study was to evaluate potential transfer effects by comprehensive cognitive testing and neuroimaging. In this prospective, randomized-controlled, and single-blind study, we administered an 8-week n-back training to 55 healthy middle-aged (50–64 years) participants. State-of-the-art multimodal neuroimaging was used to examine potential anatomic and functional changes. Relative to control subjects, who performed non-adaptive WM training, no near or far transfer effects were detected in experimental subjects, who performed adaptive WM training. Equivalently, no training-related changes were observed in white matter integrity, amplitude of low frequency fluctuations, glucose metabolism, functional and metabolic connectivity. Exploratory within-group comparisons revealed some gains in transfer tasks, which, however, cannot be attributed to an increased WM capacity. In conclusion, WM training produces transfer effects neither at the cognitive level nor in terms of neural structure or function. These results speak against a common view that training-related gains reflect an increase in underlying WM capacity. Instead, the presently observed practice effects may be a result of optimized task processing strategies, which do not necessarily engage neural plasticity

Measurement of Leptonic Asymmetries and Top Quark Polarization in ttbar Production

We present measurements of lepton (l) angular distributions in ttbar -> W+ b W- b -> l+ nu b l- nubar bbar decays produced in ppbar collisions at a center-of-mass energy of sqrt(s)=1.96TeV, where l is an electron or muon. Using data corresponding to an integrated luminosity of 5.4fb^-1, collected with the D0 detector at the Fermilab Collider, we find that the angular distributions of l- relative to anti-protons and l+ relative to protons are in agreement with each other. Combining the two distributions and correcting for detector acceptance we obtain the forward-backward asymmetry A^l_FB = (5.8 +- 5.1(stat) +- 1.3(syst))%, compared to the standard model prediction of A^l_FB (predicted) = (4.7 +- 0.1)%. This result is further combined with the measurement based on the analysis of the l+jets final state to obtain A^l_FB = (11.8 +- 3.2)%. Furthermore, we present a first study of the top-quark polarization.Comment: submitted versio

Search for B0→π0π0B^{0}\to \pi^{0}\pi^{0} Decay

We have searched for the charmless hadronic decay of B0 mesons into two neutral pions. Using 9.13fb^-1 taken at the Upsilon(4S) with the CLEO detector, we obtain an improved upper limit for the branching fraction BR(B0-->pi0pi0) < 5.7*10^-6 at the 90% confidence level.Comment: pages postscript, also available through http://w4.lns.cornell.edu/public/CLN

A search for charged massive long-lived particles

We report on a search for charged massive long-lived particles (CMLLPs), based on 5.2 fb$^{-1}$ of integrated luminosity collected with the D0 detector at the Fermilab Tevatron $p\bar{p}$ collider. We search for events in which one or more particles are reconstructed as muons but have speed and ionization energy loss $(dE/dx)$ inconsistent with muons produced in beam collisions. CMLLPs are predicted in several theories of physics beyond the standard model. We exclude pair-produced long-lived gaugino-like charginos below 267 GeV and higgsino-like charginos below 217 GeV at 95% C.L., as well as long-lived scalar top quarks with mass below 285 GeV.Comment: submitted to Phys. Rev. Letter

Search for Zgamma events with large missing transverse energy in ppbar collisions at sqrt(s)=1.96 TeV

We present the first search for supersymmetry (SUSY) in Zgamma final states with large missing transverse energy using data corresponding to an integrated luminosity of 6.2 fb-1 collected with the D0 experiment in ppbar collisions at sqrt(s)=1.96 TeV. This signature is predicted in gauge-mediated SUSY-breaking models, where the lightest neutralino is the next-to-lightest supersymmetric particle (NLSP) and is produced in pairs, possibly through decay from heavier supersymmetric particles. The NLSP can decay either to a Z boson or a photon and an associated gravitino that escapes detection. We exclude this model at the 95% C.L. for SUSY breaking scales of Lambda < 87 TeV, corresponding to neutralino masses of < 151 GeV.Comment: submitted to Phys. Rev. Let

Search for WHWH associated production in ppˉp \bar{p} collisions at s=1.96 TeV\sqrt{s}=1.96\,{\rm TeV}

This report describes a search for associated production of $W$ and Higgs bosons based on data corresponding to an integrated luminosity of $\cal{L}$$\approx 5.3 \rm fb^{-1}$ collected with the D0 detector at the Fermilab Tevatron $p\bar{p}$ Collider. Events containing a $W\rightarrow \ell \nu$ candidate (with $\ell$ corresponding to $e$ or $\mu$) are selected in association with two or three reconstructed jets. One or two of the jets are required to be consistent with having evolved from a $b$ quark. A multivariate discriminant technique is used to improve the separation of signal and backgrounds. Expected and observed upper limits are obtained for the product of the $WH$ production cross section and branching ratios and reported in terms of ratios relative to the prediction of the standard model as a function of the mass of the Higgs boson ($M_{H}$). The observed and expected 95% C.L. upper limits obtained for an assumed $M_{H}=115 \rm GeV$ are, respectively, factors of 4.5 and 4.8 larger than the value predicted by the standard model.Comment: 25 pages, 14 figure