8,581 research outputs found
Deeply Virtual Compton Scattering on the Deuteron
We study deeply virtual Compton scattering (DVCS) on a deuteron target. We
model the Generalized Quark Distributions in the deuteron by using the impulse
approximation for the lowest Fock-space state. Numerical predictions are given
for the unpolarized cross sections for the kinematical regimes relevant for
JLab and HERMES at HERA. Differential cross sections show the same pattern as
for the proton case and at low values of t they are of comparable size.Comment: 6 pages, 4 eps figures. Contribution to the European Workshop on the
QCD Structure of the Nucleon (QCD-N'02), Ferrara, Italy, 3-6 Apr 200
Plusiotis ericsmithi (Coleoptera: Scarabaeidae) : a new metallic species from eastern Guatemala
Se describe Plusiotis ericsmithi sp. nov. de un bosque nuboso de baja altitud (1100 msnm) en la Sierra del Merend6n, Guatemala, cerca de la front era con Honduras. Ademas, se incluyen ilustraciones de los genitales masculinos y femeninos.Plusiotis ericsmithii n. sp. is described from a low altitude cloud forest (1100 m) in the Guatemalan
Merend6n mountain chain near the Honduran border. Male and female genitalia are illustrated
Properties of five toughened matrix composite materials
The use of toughened matrix composite materials offers an attractive solution to the problem of poor damage tolerance associated with advanced composite materials. In this study, the unidirectional laminate strengths and moduli, notched (open-hole) and unnotched tension and compression properties of quasi-isotropic laminates, and compression-after-impact strengths of five carbon fiber/toughened matrix composites, IM7/E7T1-2, IM7/X1845, G40-800X/5255-3, IM7/5255-3, and IM7/5260 have been evaluated. The compression-after-impact (CAI) strengths were determined primarily by impacting quasi-isotropic laminates with the NASA Langley air gun. A few CAI tests were also made with a drop-weight impactor. For a given impact energy, compression after impact strengths were determined to be dependent on impactor velocity. Properties and strengths for the five materials tested are compared with NASA data on other toughened matrix materials (IM7/8551-7, IM6/1808I, IM7/F655, and T800/F3900). This investigation found that all five materials were stronger and more impact damage tolerant than more brittle carbon/epoxy composite materials currently used in aircraft structures
Strong Pionic Decays From a Spectroscopic Quark Model
From a refined non-relativistic quark model that fits the baryonic low-energy
spectrum the study of strong pion decay processes within an elementary emission
model scheme points out the need of incorporating size-contributing components
into the baryon wave functions. In particular the effect of a (qqq qantiq)
component is investigated in the framework of a quark pair creation model.Comment: 26 pages, 9 figures (1 postscript file), LaTe
Disconnected Elementary Band Representations, Fragile Topology, and Wilson Loops as Topological Indices: An Example on the Triangular Lattice
In this work, we examine the topological phases that can arise in triangular
lattices with disconnected elementary band representations. We show that,
although these phases may be "fragile" with respect to the addition of extra
bands, their topological properties are manifest in certain nontrivial
holonomies (Wilson loops) in the space of nontrivial bands. We introduce an
eigenvalue index for fragile topology, and we show how a nontrivial value of
this index manifests as the winding of a hexagonal Wilson loop; this remains
true even in the absence of time-reversal or sixfold rotational symmetry.
Additionally, when time-reversal and twofold rotational symmetry are present,
we show directly that there is a protected nontrivial winding in more
conventional Wilson loops. Crucially, we emphasize that these Wilson loops
cannot change without closing a gap to the nontrivial bands. By studying the
entanglement spectrum for the fragile bands, we comment on the relationship
between fragile topology and the "obstructed atomic limit" of B. Bradlyn et
al., Nature 547, 298--305 (2017). We conclude with some perspectives on
topological matter beyond the K-theory classification.Comment: 13 pages, 10 figures v2. accepted versio
Notes on Guatemalan Plusiotis (Coleoptera: Scarabaeidae; Rutelinae)
Dos especies nuevas de escarabajos del genero Plusiotis se describen de un bosque nuboso, 1560-1900 m en el departamento de San Marcos, Guatemala. Tambien se describen las hembras de P. turhheimi Ohaus, P. auropunctata Ohaus y P. quiche Moron. Ademas, se registra pOI' primera vez a P. turhheimi para Guatemala.Two new species of Plusiotis are described from a cloud forest between 1560-1900 m in the Department of San Marcos, Guatemala. Females of P. turhheimi Ohaus, P. auropunctata Ohaus and P. quiche Moron are described. Plusiotis turhheimi is reported from Guatemala for the first time
Cracking Control in Mezzanine Floor Slabs using Rice Husk Ash and Polypropylene Fibers
The continuous population increase in recent years requires a greater number of households to be built quickly, with good materials and produced under quality standards that guarantee their manufacturing process. The prefabricated concrete, produced and supplied by concrete plants, is poured into the different structural elements, the mezzanine slabs being the most careful surfaces in the appearance of fissures; because being horizontal and having larger dimensions, the dimensional changes in the concrete appear more frequently due to the rapid loss of water from the surface of the concrete before setting; which generates superior stresses to the resistant capacity of the concrete at early ages, which affect the durability and reduce the resistance of the structures, causing greater economic expenses in maintenance and repairs. In the present investigation, 5%, 10% and 15% of rice husk ash was used as a replacement for cement and 900g/m3 of polypropylene fiber; The results indicate that as the percentage of rice husk ash increases, there is a reduction in the slump and the crack fissures, and that the resistance to compression and flexion decreases, with respect to the concrete pattern
A (p/E) Calculation of Strong Pionic Decays of Baryons
Strong pionic decays of baryons are studied in a non-relativistic quark model
framework via a convergent (p/E) expansion of the transition operator. Results
are compared to the ones obtained within a more conventional (p/m) expansion.Comment: 16 pages, LaTeX, using amssymb.st
A new \u3ci\u3eAnomiopus\u3c/i\u3e Westwood (Coleoptera: Scarabaeidae: Scarabaeinae) from the Mayan Biosphere Reserve, Petén, Guatemala
Anomiopus cirulito Cano n. sp., from the tropical forest of the Mayan Biosphere Reserve, Petén, Guatemala is described. This is the northernmost known species of the genus Anomiopus Westwood (Coleoptera: Scarabaeidae: Scarabaeinae) and is related to the Costa Rican and Panamanian Anomiopus panamensis (Paulian).
Se describe Anomiopus cirulito Cano n. sp. del bosque tropical de la Reserva de la Biósfera Maya, Petén, Guatemala. Es la especie más norteña conocida del género Anomiopus Westwood (Coleoptera: Scarabaeidae: Scarabaeinae) y está relacionada a la especie costarricense y panameña Anomiopus panamensis (Paulian)
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