1,210 research outputs found
Comments on spin operators and spin-polarization states of 2+1 fermions
In this brief article we discuss spin polarization operators and spin
polarization states of 2+1 massive Dirac fermions and find a convenient
representation by the help of 4-spinors for their description. We stress that
in particular the use of such a representation allows us to introduce the
conserved covariant spin operator in the 2+1 field theory. Another advantage of
this representation is related to the pseudoclassical limit of the theory.
Indeed, quantization of the pseudoclassical model of a spinning particle in 2+1
dimensions leads to the 4-spinor representation as the adequate realization of
the operator algebra, where the corresponding operator of a first-class
constraint, which cannot be gauged out by imposing the gauge condition, is just
the covariant operator previously introduced in the quantum theory.Comment: 6 page
Pancreatoblastoma: Cytologic and histologic analysis of 12 adult cases reveals helpful criteria in their diagnosis and distinction from common mimics
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/152894/1/cncy22187_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/152894/2/cncy22187.pd
An Exploration into Fern Genome Space
Ferns are one of the few remaining major clades of land plants for which a complete genome sequence is lacking. Knowledge of genome space in ferns will enable broad-‐scale comparative analyses of land plant genes and genomes, provide insights into genome evolution across green plants, and shed light on genetic and genomic features that characterize ferns, such as their high chromosome numbers and large genome sizes. As part of an initial exploration into fern genome space, we used a whole genome shotgun sequencing approach to obtain low-‐density coverage (~0.4X to 2X) for six fern species from the Polypodiales (Ceratopteris, Pteridium, Polypodium, Cystopteris), Cyatheales (Plagiogyria), and Gleicheniales (Dipteris). We explore these data to characterize the proportion of the nuclear genome represented by repetitive sequences (including DNA transposons, retrotransposons, rDNA, and simple repeats) and protein-‐coding genes, and to extract chloroplast and mitochondrial genome sequences. Such initial sweeps of fern genomes can provide information useful for selecting a promising candidate fern species for whole genome sequencing. We also describe variation of genomic traits across our sample and highlight some differences and similarities in repeat structure between ferns and seed plants
Low-energy Pion-nucleon Scattering
This paper contains the results of an analysis of recent low-energy
pion-nucleon scattering experiments. Obtained are phase shifts, the
pion-nucleon coupling constant and an estimate of the Sigma term.Comment: 30 pages, 11 figures, LaTe
Measurement of XUV-absorption spectra of ZnS radiatively heated foils
Time-resolved absorption of zinc sulfide (ZnS) and aluminum in the XUV-range
has been measured. Thin foils in conditions close to local thermodynamic
equilibrium were heated by radiation from laser-irradiated gold spherical
cavities. Analysis of the aluminum foil radiative hydrodynamic expansion, based
on the detailed atomic calculations of its absorption spectra, showed that the
cavity emitted flux that heated the absorption foils corresponds to a radiation
temperature in the range 55 60 eV. Comparison of the ZnS absorption spectra
with calculations based on a superconfiguration approach identified the
presence of species Zn6+ - Zn8+ and S5+ - S6+. Based on the validation of the
radiative source simulations, experimental spectra were then compared to
calculations performed by post-processing the radiative hydrodynamic
simulations of ZnS. Satisfying agreement is found when temperature gradients
are accounted for
Gendered Discourse in the Political Behavior of Adolescents
The roots of adult civic and political participation originate in pre-adult experiences (Verba et al. 1995) and high school extracurricular activities offer students opportunities to develop interpersonal and leadership skills. In this research, we ask whether adolescents also learn gendered norms of political discourse through extracurricular activities. This project assessed gender differences in participation at the 1999 Model United Nations of the Southwest (MUNSW) at the University of Oklahoma. Important differences in participation were observed in the number and character of speaking turns taken by male and female delegates. We find that contextual factors, such as the sex of the committee chair, the issue areas addressed by the committee, and the timing of the session in the conference significantly influence who participates in the discourse, but the percentage of female participants surprisingly does not. The character of the political discourse suggests norms dominated by masculinity.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline
- …