Assessment of fibrinolytic activity by measuring the lysis time of a tissue-factor-induced clot: a feasibility evaluation.

A clot lysis time assay in which a tissue factor—induced fibrin clot is lysed by exogenously added tissue plasminogen activator has been recently reported. We evaluated the feasibility of clot lysis time in a routine hemostasis laboratory, and its correlation with thrombin activatable fibrinolysis inhibitor and plasminogen activator inhibitor-1 levels and changes with aging in 185 healthy participants. Clot lysis time was assessed by monitoring changes in turbidity during clot formation and subsequent lysis using a computerized kinetic spectrophotometric microtiter plate. After preliminary experiments, 100 and 160 ng/mL tissue plasminogen activator concentrations were chosen for the study. Clot lysis time was calculated by a new mathematical analysis of the lysis curve based on discrete derivative. Clot lysis time, thrombin activatable fibrinolysis inhibitor, and plasminogen activator inhibitor-1 plasma levels showed a normal distribution. For both concentrations of tissue plasminogen activator, clot lysis time progressively increased with increase in age (P < .0001) and was significantly correlated with thrombin activatable fibrinolysis inhibitor antigen, thrombin activatable fibrinolysis inhibitor activity, and plasminogen activator inhibitor-1 antigen (at least P < .01). During linear regression analysis, thrombin activatable fibrinolysis inhibitor and plasminogen activator inhibitor-1 antigen were found to significantly influence clot lysis time (at least P < .01). Clot lysis time determination has a good laboratory performance. Our new method of calculation is independent of the time of reading and allows a more accurate and consistent detection of both short and prolonged lysis times. Our data suggest the feasibility of the use of this test in the work of routine hemostasis laboratory

Observation of Hadronic W Decays in t-tbar Events with the Collider Detector at Fermilab

We observe hadronic W decays in t-tbar -> W (-> l nu) + >= 4 jet events using a 109 pb-1 data sample of p-pbar collisions at sqrt{s} = 1.8 TeV collected with the Collider Detector at Fermilab (CDF). A peak in the dijet invariant mass distribution is obtained that is consistent with W decay and inconsistent with the background prediction by 3.3 standard deviations. From this peak we measure the W mass to be 77.2 +- 4.6 (stat+syst) GeV/c^2. This result demonstrates the presence of two W bosons in t-tbar candidates in the W (-> l nu) + >= 4 jet channel.Comment: 20 pages, 4 figures, submitted to PR

Measurement of the Associated γ+μ±\gamma + \mu^\pm Production Cross Section in ppˉp \bar p Collisions at s=1.8\sqrt{s} = 1.8 TeV

We present the first measurement of associated direct photon + muon production in hadronic collisions, from a sample of 1.8 TeV $p \bar p$ collisions recorded with the Collider Detector at Fermilab. Quantum chromodynamics (QCD) predicts that these events are primarily from the Compton scattering process $cg \to c\gamma$, with the final state charm quark producing a muon. Hence this measurement is sensitive to the charm quark content of the proton. The measured cross section of $29\pm 9 pb^{-1}$ is compared to a leading-order QCD parton shower model as well as a next-to-leading-order QCD calculation.Comment: 12 pages, 4 figures Added more detailed description of muon background estimat

Measurement of the B0 B0-bar oscillation frequency using pi-B meson charge-flavor correlations in p p-bar collisions at sqrt{s} = 1.8 TeV

We present a measurement of the B0 B0-bar oscillation frequency using a flavor tagging method based on correlations of B meson flavor with the charge of other particles produced in p p-bar collisions at sqrt{s} = 1.8 TeV. Such correlations are expected to arise from b quark hadronization and from B** decays. We partially reconstruct B mesons using the semileptonic decays B0 -> lepton D(*)- X. and B+ -> lepton D0-bar X$. From the oscillation frequency, we obtain the mass difference between the two B0 mass eigenstates, Delta m_d = 0.471 {+0.078} {-0.068}(stat) +- 0.034 (syst) hbar ps-1, and measure the efficiency and purity of this flavor tagging method for both charged and neutral B mesons.Comment: 16 pages, 2 figures. Submitted to Physical Review Letters. Also available at http://www-cdf.fnal.gov/physics/pub97/cdf4244_lepd_mix_sst_prl.p

Observation of the B_c Meson in p-bar p Collisions at sqrt{s} = 1.8 TeV

We have observed bottom-charm mesons B_c via the decay mode Bc -> J/psi lepton neutrino in 1.8 TeV p-bar p collisions using the CDF detector at the Fermilab Tevatron. A fit of background and signal contributions to the J/psi + lepton mass distribution yielded 20.4 +6.2 -5.5 events from B_c mesons. A fit to the same distribution with background alone was rejected at the level of 4.8 standard deviations. We measured the B_c mass to be 6.40 +- 0.39 +- 0.13 GeVc^2 and the B_c lifetime to be tau(B_c) = 0.46 +0.18 -0.16 +- 0.03 ps. We measured the production cross section times branching ratio for B_c -> J/psi lepton neutrino relative to that for B+ -> J/psi K to be 0.132 +0.041 -0.037 (stat) +- 0.031 (syst) +0.032 -0.020 (lifetime).Comment: 13 pages, 3 figures. Submitted to Physical Review Letters. Available at http://www-cdf.fnal.gov/physics/pub98/cdf4496_Bc_PRL.p

Search for Heavy Top-like Quarks t' -> Wq Using Lepton Plus Jets Events in 1.96 TeV Proton-Antiproton Collisions

We present the results of a search for pair production of a new heavy top-like quark t' decaying to a W boson and another quark using the CDF II detector in Run II of the Tevatron proton-antiproton collider. Using a data sample corresponding to 760 pb^-1 of integrated luminosity, we fit the observed spectrum of total transverse energy and reconstructed t' quark mass to a combination of standard model processes and t' pair production. We see no evidence for t' pair production, and we infer a lower limit of 256 GeV/c^2 on the mass of the t' at 95% C.L. assuming standard strong couplings for the t'.Comment: 7 pages, 2 figure

Multiple stimulus presentation yields larger deficits in children with developmental dyslexia: a study with reading and RAN-type tasks

In this study, we examined the effect of multiple versus single stimulus presentation in typically devel- oping readers and children with developmental dyslexia. The tasks involved either reading single words or arrays of words or naming single or multiple colors and digits (rapid automatized nam- ing or RAN). To be able to compare these sets of conditions, we recorded total response times (i.e., the time between stimulus onset and the end of the participant’s vocal response) in all cases. The study included 43 typically developing readers and 25 children with dyslexia. Results indicate that typically developing readers have a clear advantage with multiple over single items on both RAN and reading tasks. The children with dyslexia showed a moderate advantage for multiple stimuli in naming colors and digits but presented the opposite pattern in reading. With regard to reading, the disproportionate impairment of the children with dyslexia in dealing with multiple arrays suggests difficulty in integrating the multiple subcomponents of the reading task over and above the basic nuclear deficit in decoding words. Regarding the RAN tasks, results confirm that the requirement of integrating multiple subcomponents may be critical in mediating the predictive value of these measures on reading

Bridging the gap between different measures of the reading speed deficit in developmental dyslexia.

The study assessed how decoding and pronunciation times contribute to total reading time in reading aloud and how these measures change in the presence of developmental dyslexia. Vocal reaction times (RTs), pronunciation times, and total reading times were measured while 25 children with dyslexia and 43 age-matched typically developing readers read singly presented words and non-words that varied for length. Group differences were large for vocal RTs; children with dyslexia were increasingly slower as a function of condition difficulty (over-additivity effect); lexicality and length influenced RTs even when over-additivity was controlled for by z-score transformation. The group differences were also large for vocal total reading times, but the effect of over-additivity was smaller than that of vocal RTs and no selective influence of lexicality and length was detected. Pronunciation times showed very small individual differences and no over-additivity effect; children with dyslexia were more sensitive to the effect of lexicality and length than controls. To assess the contribution of the cognitive and sensory–motor compartments in determining group differences, we applied the difference engine model. As for RTs, the relationship between means and standard deviations closely supported the prediction of a general cognitive delay in the slow group, with no group difference in the sensory–motor compartment. The variance in total reading times was predicted by combining the model results for RTs with the linear relationship between pronunciation times and task difficulty. The results help clarify the internal structure of reading times, a measure largely used in clinical testing to assess reading rate

Venous thromboembolism secondary to hospitalization for COVID-19: patient management and long-term outcomes

Background: Venous thromboembolism (VTE) is a complication of COVID-19 in hospitalized patients. Little information is available on long-term outcomes of VTE in this population.Objectives: We aimed to compare the characteristics, management strategies, and long-term clinical outcomes between patients with COVID-19-associated VTE and patients with VTE provoked by hospitalization for other acute medical illnesses.Methods: This is an observational cohort study, with a prospective cohort of 278 patients with COVID-19-associated VTE enrolled between 2020 and 2021 and a comparison cohort of 300 patients without COVID-19 enrolled in the ongoing START2-Register between 2018 and 2020. Exclusion criteria included age &lt;18 years, other indications to anticoagulant treatment, active cancer, recent (&lt;3 months) major surgery, trauma, pregnancy, and participation in interventional studies. All patients were followed up for a minimum of 12 months after treatment discontinuation. Primary end point was the occurrence of venous and arterial thrombotic events.Results: Patients with VTE secondary to COVID-19 had more frequent pulmonary embolism without deep vein thrombosis than controls (83.1% vs 46.2%, P &lt;.001), lower prevalence of chronic inflammatory disease (1.4% and 16.3%, P &lt;.001), and history of VTE (5.0% and 19.0%, P &lt;.001). The median duration of anticoagulant treatment (194 and 225 days, P = 0.9) and the proportion of patients who discontinued anticoagulation (78.0% and 75.0%, P = 0.4) were similar between the 2 groups. Thrombotic event rates after discontinuation were 1.5 and 2.6 per 100 patient-years, respectively (P = 0.4). Conclusion: The risk of recurrent thrombotic events in patients with COVID-19- associated VTE is low and similar to the risk observed in patients with VTE secondary to hospitalization for other medical diseases