Revisiting model relations between T-odd transverse-momentum dependent parton distributions and generalized parton distributions

We revisit the connection between generalized parton distributions in impact parameter space and T-odd effects in single spin asymmetries of the semi-inclusive deep inelastic process. We show that nontrivial relations can be established only under very specific conditions, typically realized only in models that describe hadrons as two-body bound systems and involving a helicity-conserving coupling between the gauge boson and the spectator system. Examples of these models are the the scalar-diquark spectator model or the quark-target model for the nucleon, and relativistic models for the pion at the lowest order in the Fock-space expansion.Comment: 15 pages, 2 figures, 1 table, v2: list of references has been correcte

Mass sum rules of the electron in quantum electrodynamics

Different decompositions of the nucleon mass, in terms of the masses and energies of the underlying constituents, have been proposed in the literature. We explore the corresponding sum rules in quantum electrodynamics for an electron at one-loop order in perturbation theory. To this end we compute the form factors of the energy-momentum tensor, by paying particular attention to the renormalization of ultraviolet divergences, operator mixing and scheme dependence. We clarify the expressions of all the proposed sum rules in the electron rest frame in terms of renormalized operators. Furthermore, we consider the same sum rules in a moving frame, where they become energy decompositions. Finally, we discuss some implications of our study on the mass sum rules for the nucleon.Comment: 21 pages, 1 figure; V2: minor changes, references added, to appear in JHE

Revisiting model relations between T -odd transverse-momentum-dependent parton distributions and generalized parton distributions

We revisit the connection between generalized parton distributions in impact parameter space and T-odd effects in single spin asymmetries of the semi-inclusive deep inelastic process. We show that nontrivial relations can be established only under very specific conditions, typically realized only in models that describe hadrons as two-body bound systems and involving a helicity-conserving coupling between the gauge boson and the spectator system. Examples of these models are the scalar-diquark spectator model or the quark-target model for the nucleon, and relativistic models for the pion at the lowest order in the Fock-space expansion

Twist-3 TMDs within a light-front model

We discuss the two twist-3 Transverse Momentum Dependent parton distributions for unpolarized proton. We review their general, model independent decomposition, which follows from the QCD equations of motion. Then, we present results for the twist-3 distributions, using a light-front model for the Fock-states of three quark and three-quark plus one gluon

First Concurrent Extraction of the Leading-Order Scalar and Spin Proton Polarizabilities

We performed the first simultaneous extraction of the six leading-order proton polarizabilities. We reached this milestone thanks to both new high-quality experimental data and an innovative bootstrap-based fitting method. These new results provide a self-consistent and fundamental benchmark for all future theoretical and experimental polarizability estimates

Uniaxial Tensile Properties of AS4 3D Woven Composites with Four Different Resin Systems: Experimental Results and Analysis: Property Computations

As a part of the NASA Composite Technology for Exploration project, eight different AS4 3D orthogonal woven composite panels were manufactured and were subjected to mechanical testing including uniaxial tension along the weaves' warp direction. Each set, with four different resin systems (KCR-IR6070, EP2400, RTM6, and RS-50), included weave architectures designed using 12K and 6K AS4 carbon fiber yarns. For the tension testing conducted at Room Temperature Ambient (RTA) conditions, the elastic modulus and strength of these eight panels (as-processed and thermally-cycled) were measured and compared while the potential evolution of micro-cracking before and after thermal cycling were monitored via optical microscopy and X-Ray Computed Tomography. The data set also included test results of the as-processed materials at Elevated Temperature Wet (ETW) conditions. In the second part of this study, efforts were made to compute elastic constants for AS4 6K/RTM6 and AS4 12K/RTM6 materials by implementing a finite element approach and the Multiscale Generalized Method of Cells (MSGMC) technique developed at NASA Glenn Research Center. Digimat-FE was used to model the weave architectures, assign properties, calculate yarn properties, create the finite element mesh, and compute the elastic properties by applying periodic boundary conditions to finite element models of each repeating unit cell. The required input data for MSGMC was generated using Matlab from Digimat exported weave information. Experimental and computational results were compared, and the differences and limitations in correlating to the test data were briefly discussed

Contamination of Mesenchymal Stem-Cells with Fibroblasts Accelerates Neurodegeneration in an Experimental Model of Parkinson’s Disease

Pre-clinical studies have supported the use of mesenchymal stem cells (MSC) to treat highly prevalent neurodegenerative diseases such as Parkinson’s disease (PD) but preliminary trials have reported controversial results. In a rat model of PD induced by MPTP neurotoxin, we first observed a significant bilateral preservation of dopaminergic neurons in the substantia nigra and prevention of motor deficits typically observed in PD such as hypokinesia, catalepsy, and bradykinesia, following intracerebral administration of human umbilical cord-derived MSC (UC-MSC) early after MPTP injury. However, surprisingly, administration of fibroblasts, mesenchymal cells without stem cell properties, as a xenotransplantation control was highly detrimental, causing significant neurodegeneration and motor dysfunction independently of MPTP. This observation prompted us to further investigate the consequences of transplanting a MSC preparation contaminated with fibroblasts, a plausible circumstance in cell therapy since both cell types display similar immunophenotype and can be manipulated in vitro under the same conditions. Here we show for the first time, using the same experimental model and protocol, that transplantation of UC-MSC induced potent neuroprotection in the brain resulting in clinical benefit. However, co-transplantation of UC-MSC with fibroblasts reverted therapeutic efficacy and caused opposite damaging effects, significantly exacerbating neurodegeneration and motor deficits in MPTP-exposed rats. Besides providing a rationale for testing UC-MSC transplantation in early phases of PD aiming at delaying disease progression, our pre-clinical study suggests that fibroblasts may be common cell contaminants affecting purity of MSC preparations and clinical outcome in stem cell therapy protocols, which might also explain discrepant clinical results