1,456 research outputs found
Analytical solution of the tooling/workpiece contact interface shape during a flow forming operation
Flow forming involves complicated tooling/workpiece interactions. Purely
analytical models of the tool contact area are difficult to formulate,
resulting in numerical approaches that are case-specific. Provided are the
details of an analytical model that describes the steady-state
tooling/workpiece contact area allowing for easy modification of the dominant
geometric variables. The assumptions made in formulating this analytical model
are validated with experimental results attained from physical modelling. The
analysis procedure can be extended to other rotary forming operations such as
metal spinning, shear forming, thread rolling and crankshaft fillet rolling.Comment: 28 pages, 11 figure
Multiaxial Kitagawa analysis of A356-T6
Experimental Kitagawa analysis has been performed on A356-T6 containing
natural and artificial defects. Results are obtained with a load ratio of R =
-1 for three different loadings: tension, torsion and combined tension-torsion.
The critical defect size determined is 400 \pm 100 \mum in A356-T6 under
multiaxial loading. Below this value, the microstructure governs the endurance
limit mainly through Secondary Dendrite Arm Spacing (SDAS). Four theoretical
approaches are used to simulate the endurance limit characterized by a Kitagawa
relationship are compared: Murakami relationships [Y Murakami, Metal Fatigue:
Effects of Small Defects and Nonmetallic Inclusions, Elsevier, 2002.],
defect-crack equivalency via Linear Elastic Fracture Mechanics (LEFM), the
Critical Distance Method (CDM) proposed by Susmel and Taylor [L. Susmel, D.
Taylor. Eng. Fract. Mech. 75 (2008) 15.] and the gradient approach proposed by
Nadot [Y. Nadot, T. ~Billaudeau. Eng. Fract. Mech. 73 (2006) 1.]. It is shown
that the CDM and gradient methods are accurate; however fatigue data for three
loading conditions is necessary to allow accurate identification of an
endurance limit.Comment: 27 pages, 11 figure
Constitutive behavior of as-cast A356
The constitutive behavior of aluminum alloy A356 in the as-cast condition has
been characterized using compression tests performed over a wide range of
deformation temperatures (30-500{\deg}C) and strain rates (\approx0.1-10 /s).
This work is intended to support the development of process models for a wide
range of conditions including those relevant to casting, forging and machining.
The flow stress behavior as a function of temperature and strain rate has been
fit to a modified Johnson-Cook and extended Ludwik-Hollomon expression. The
data has also been assessed with both the strain-independent Kocks-Mecking and
Zener-Hollomon frameworks. The predicted plastic flow stress for each
expression are compared. The results indicate that the extended Ludwik-Hollomon
is best suited to describe small strain conditions (stage III hardening), while
the Kocks-Mecking is best employed for large strain (stage IV). At elevated
temperatures, it was found that the Zener-Hollomon model provides the best
prediction of flow stress.Comment: 34 pages, 12 figure
Greenberger-Horne-Zeilinger nonlocality for continuous variable systems
As a development of our previous work, this paper is concerned with the
Greenberger-Horne-Zeilinger (GHZ) nonlocality for continuous variable cases.
The discussion is based on the introduction of a pseudospin operator, which has
the same algebra as the Pauli operator, for each of the modes of a light
field. Then the Bell-CHSH (Clauser, Horne, Shimony and Holt) inequality is
presented for the modes, each of which has a continuous degree of freedom.
Following Mermin's argument, it is demonstrated that for -mode
parity-entangled GHZ states (in an infinite-dimensional Hilbert space) of the
light field, the contradictions between quantum mechanics and local realism
grow exponentially with , similarly to the usual -spin cases.Comment: RevTEX; comments are welcomed; new version with minor change
Clozapine once- versus multiple-daily dosing: a two-center cross-sectional study, systematic review and meta-analysis.
Evidence regarding effectiveness and safety of clozapine once- vs. multiple-daily dosing is limited. We compared demographic and clinical parameters between patients with once- vs. multiple-daily dosing in the Department of Psychiatry and Psychotherapy, University of Regensburg, Germany (AGATE dataset), and the Department of Psychiatry, Lausanne University Hospital, Switzerland, using non-parametric tests. Effectiveness and safety outcomes were available in the AGATE dataset. We performed a systematic review in PubMed/Embase until February 2022, meta-analyzing studies comparing clozapine once- vs. multiple-daily-dosing. We estimated a pooled odds ratio for adverse drug-induced reactions (ADRs) and meta-analyzed differences regarding clinical symptom severity, age, percentage males, smokers, clozapine dose, and co-medications between patients receiving once- vs. multiple-daily dosing. Study quality was assessed using the Newcastle-Ottawa-Scale. Of 1494 and 174 patients included in AGATE and Lausanne datasets, clozapine was prescribed multiple-daily in 74.8% and 67.8%, respectively. In the AGATE cohort, no differences were reported for the clinical symptoms severity or ADR rate (p > 0.05). Meta-analyzing eight cohorts with a total of 2810 clozapine-treated individuals, we found more severe clinical symptoms (p = 0.036), increased ADR risk (p = 0.01), higher clozapine doses (p < 0.001), more frequent co-medication with other antipsychotics (p < 0.001), benzodiazepines (p < 0.001), anticholinergics (p = 0.039), and laxatives (p < 0.001) in patients on multiple- vs. once-daily dosing. Of six studies, five were rated as good, and one as poor quality. Patients responding less well to clozapine may be prescribed higher doses multiple-daily, also treated with polypharmacy, potentially underlying worse safety outcomes. Patient preferences and adherence should be considered during regimen selection
Single-cell profiling of human megakaryocyte-erythroid progenitors identifies distinct megakaryocyte and erythroid differentiation pathways
Background
Recent advances in single-cell techniques have provided the opportunity to finely dissect cellular heterogeneity within populations previously defined by “bulk” assays and to uncover rare cell types. In human hematopoiesis, megakaryocytes and erythroid cells differentiate from a shared precursor, the megakaryocyte-erythroid progenitor (MEP), which remains poorly defined.
Results
To clarify the cellular pathway in erythro-megakaryocyte differentiation, we correlate the surface immunophenotype, transcriptional profile, and differentiation potential of individual MEP cells. Highly purified, single MEP cells were analyzed using index fluorescence-activated cell sorting and parallel targeted transcriptional profiling of the same cells was performed using a specifically designed panel of genes. Differentiation potential was tested in novel, single-cell differentiation assays. Our results demonstrate that immunophenotypic MEP comprise three distinct subpopulations: “Pre-MEP,” enriched for erythroid/megakaryocyte progenitors but with residual myeloid differentiation capacity; “E-MEP,” strongly biased towards erythroid differentiation; and “MK-MEP,” a previously undescribed, rare population of cells that are bipotent but primarily generate megakaryocytic progeny. Therefore, conventionally defined MEP are a mixed population, as a minority give rise to mixed-lineage colonies while the majority of cells are transcriptionally primed to generate exclusively single-lineage output.
Conclusions
Our study clarifies the cellular hierarchy in human megakaryocyte/erythroid lineage commitment and highlights the importance of using a combination of single-cell approaches to dissect cellular heterogeneity and identify rare cell types within a population. We present a novel immunophenotyping strategy that enables the prospective identification of specific intermediate progenitor populations in erythro-megakaryopoiesis, allowing for in-depth study of disorders including inherited cytopenias, myeloproliferative disorders, and erythromegakaryocytic leukemias
Polarization Entangled W State using Parametric Down-Conversion
An experimental scheme for preparing a polarization entangled W states from
four photons emitted by parametric down-conversion is proposed. We consider two
different configurations and a method of improving the yield by using single
photon sources. In the proposed scheme, one uses only linear optical elements
and photon detectors, so that this scheme is feasible by current technologies.Comment: 4 pages, 3 figure
Use of the Generalized Gradient Approximation in Pseudopotential Calculations of Solids
We present a study of the equilibrium properties of -bonded solids within
the pseudopotential approach, employing recently proposed generalized gradient
approximation (GGA) exchange correlation functionals. We analyze the effects of
the gradient corrections on the behavior of the pseudopotentials and discuss
possible approaches for constructing pseudopotentials self-consistently in the
context of gradient corrected functionals. The calculated equilibrium
properties of solids using the GGA functionals are compared to the ones
obtained through the local density approximation (LDA) and to experimental
data. A significant improvement over the LDA results is achieved with the use
of the GGA functionals for cohesive energies. For the lattice constant, the
same accuracy as in LDA can be obtained when the nonlinear coupling between
core and valence electrons introduced by the exchange correlation functionals
is properly taken into account. However, GGA functionals give bulk moduli that
are too small compared to experiment.Comment: 15 pages, latex, no figure
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