1,051 research outputs found
Enhancement of entanglement in one-dimensional disordered systems
The pairwise quantum entanglement of sites in disordered electronic
one-dimensional systems (rings) is studied. We focus on the effect of diagonal
and off diagonal disorder on the concurrence between electrons on
neighbor and non neighbor sites as a function of band filling. In the
case of diagonal disorder, increasing the degree of disorder leads to a
decrease of the concurrence with respect to the ordered case. However,
off-diagonal disorder produces a surprisingly strong enhancement of
entanglement. This remarkable effect occurs near half filling, where the
concurrence becomes up to 15% larger than in the ordered system.Comment: 21 pages, 9 figure
Genetic algorithm optimization of entanglement
We present an application of a genetic algorithmic computational method to
the optimization of the concurrence measure of entanglement for the cases of
one dimensional chains, as well as square and triangular lattices in a simple
tight-binding approach in which the hopping of electrons is much stronger than
the phonon dissipationComment: 26 pages with 13 figures, based on Chapter 3 of the Master thesis of
the first author defended at IPICyT, San Luis Potosi, Mx, on 22nd of February
2006, similar to the published version [Fig. 5 left out but contains the
Appendix figure
Density-Matrix functional theory of strongly-correlated lattice fermions
A density functional theory (DFT) of lattice fermion models is presented,
which uses the single-particle density matrix gamma_{ij} as basic variable. A
simple, explicit approximation to the interaction-energy functional W[gamma] of
the Hubbard model is derived from exact dimer results, scaling properties of
W[gamma] and known limits. Systematic tests on the one-dimensional chain show a
remarkable agreement with theBethe-Ansatz exact solution for all interaction
regimes and band fillings. New results are obtained for the ground-state
energyand charge-excitation gap in two dimensions. A successful description of
strong electron correlations within DFT is achieved.Comment: 15 pages, 6 figures Submitted to PR
Interaction energy functional for lattice density functional theory: Applications to one-, two- and three-dimensional Hubbard models
The Hubbard model is investigated in the framework of lattice density
functional theory (LDFT). The single-particle density matrix with
respect the lattice sites is considered as the basic variable of the many-body
problem. A new approximation to the interaction-energy functional
is proposed which is based on its scaling properties and which recovers exactly
the limit of strong electron correlations at half-band filling. In this way, a
more accurate description of is obtained throughout the domain of
representability of , including the crossover from weak to strong
correlations. As examples of applications results are given for the
ground-state energy, charge-excitation gap, and charge susceptibility of the
Hubbard model in one-, two-, and three-dimensional lattices. The performance of
the method is demonstrated by comparison with available exact solutions, with
numerical calculations, and with LDFT using a simpler dimer ansatz for .
Goals and limitations of the different approximations are discussed.Comment: 25 pages and 8 figures, submitted to Phys. Rev.
Achieving the food security strategy by quantifying food loss and waste. A case study of the chinese economy
Undernourished and food insecurity are recognized as two highly relevant topics. Approx-imately 820 million people in the world are undernourished and 2 billion people have moderate or severe food insecurity (FAO). In addition, globally roughly one-third of food is not consumed and is wasted. This article aims to provide an updated estimate of food loss and waste (FLW) in China as, in the period 2016–2018, there were still 122 million people in this country experiencing undernourishment. In this research, we use a top-down mass balance approach, discuss how it affects the achievement of SDG 2, Zero Hunger, that it is linked also to target 12.3 that “seeks to halve global food waste at retail and consumer levels, as well as to reduce food loss during production and supply” (United Nations). We point out some challenges that private and public policies still need to overcome to reduce FLW. The results of this research may contribute a more accurate baseline for the design of public policies and strategies related to FLW and the corresponding SDG
COMPORTAMIENTO FISIOLÓGICO POSTCOSECHA DE TALLOS FLORALES DE ROSA (Rosa hybrida L.) EN RESPUESTA AL FÓSFORO APLICADO EN PRECOSECHA
Durante el crecimiento y desarro- llo de las flores, la nutrición fosforada es un factor que puede influir en la vida en flore- ro. El objetivo de este trabajo fue evaluar el efecto de cinco niveles de fósforo (P): 0, 0.5, 1.0, 1.5 y 2.0 me·L-1 de P aplicados en precosecha, mediante un sistema hidropóni- co abierto, en el comportamiento fisiológico postcosecha de tallos florales de rosa (Rosa hybrida L.) ‘Classy’ y ‘Vega’. Las variables evaluadas durante la vida de florero de los tallos florales fueron: transpiración foliar y floral, potencial de turgencia foliar y de pétalos. Además, se evaluó la concentración de antocianinas en pétalos al momento de la cosecha. Las aplicaciones de P en precose- cha tuvieron efecto significativo únicamente en la transpiración foliar; sin embargo, se demostró que la mayor vida en florero (15.8 días) de ‘Classy’ en comparación con ‘Vega’ (11.7 días) estuvo directamente asociada con mayores potenciales de turgencia foliar y de pétalos, mayor tasa transpiratoria floral y menor tasa transpiratoria foliar en ‘Classy’
Surgical treatment of benign parapharyngeal space tumours : presentation of two clinical cases and revision of the literature
Parapharyngeal space (PPS) tumours, most of them benign, account for some 0.5% of tumours of the head and neck. The importance of these tumours lies mainly in two aspects: on the one hand, the difficulty of early diagnosis, due to the lack of symptoms in the initial stages and, on the other, the extreme complications of performing surgery in the parapharyngeal region. This article discusses two clinical cases of parapharyngeal space tumours: a 45 year old man and a 60 year old woman. We revise the scientific literature and analyse the diagnostic and therapeutic procedures used, placing special emphasis on describing the different surgical approaches to the parapharyngeal space: transcervical, transcervical-transparotid, transpalatal or transoral, transmandibular and orbitozygomatic, all of which, used alone or combined with others, allow for complete resection of these tumours with minimum morbidity
Angiosarcoma del muslo: diagnóstico diferencial
Se presenta un caso de angiosarcoma de partes blandas en un paciente de
92 años localizado en extremidad inferior de seis meses de evolución. Estos tipos de tumores
muestran probabilidades de ser confundidos con hematomas, incluso con estudios
de Resonancia Nuclear. Se destaca la ayuda que ofrece para el diagnóstico la arteriografía,
así como la agresividad de dichos tumores y los posibles abordajes terapéuticos actuales.A case of angiosarcoma is presented. The patient was 92 years old. The tumor
was present 6 months before diagnosis. The tumor was diagnosed by MRN as haematoma
of the muscle. Arteriography is a good diagnostic tool before the biopsy in that
type of lesions. Alternative treatments of such letal neoplasms are discussed
Use of cavity ring-down spectrometry to quantify 13C-primary productivity in oligotrophic waters
Cavity ring-down spectroscopy (CRDS) is a highly sensitive laser technique that allows the analysis of
isotopic signals and absolute concentration of individual molecular species in small-volume samples. Here, we
describe a protocol to quantify photosynthetic 13C-uptake rates of marine phytoplankton by using the CRDS
technique (13C-CRDS-PP). We validated our method by comparing the 13C-PP rates measured between CRDS
and isotope ratio mass spectrometry (IRMS) in samples with different carbon content (30–160 μgC). The comparison
revealed that 13C-CRDS-PP rates were highly correlated with those obtained by IRMS (Spearman correlation
coefficient, ρ = 0.95, p < 0.0001, n = 15), with a mean difference between the two estimates of +- 0.08 mgC
m−3 h−1. Moreover, the slope of the relationship between CRDS and IRMS results was not significantly different
from 1 (F = 0.03, p = 0.86), and the intercept did not differ from 0 (F = 1.4, p = 0.24), indicating that there was
no bias in the CRDS relative to the IRMS-based measurements. A separate analysis also showed that despite the
difference in volume and carbon content between samples (40 +- 10 μgC and 160 +- 40 μgC, respectively), the
13C-CRDS-PP technique provides similar results (Mann–Whitney test, U = 30.5, p = 0.90, n = 8). In addition,
13C-CRDS-PP rates measured along the Red Sea (~ 176 mgC m−2 d−1) agreed with 14C-based PP rates previously
reported for similar locations. Thus, this study evidenced that the 13C-CRDS-PP method is sensitive enough to
quantify carbon fixation rates in oligotrophic regions
Microscopic study of the morphology and metabolic activity of Fusarium oxysporum f. sp. gladioli treated with Jatropha curcas oil and derivatives
AbstractThe fungus Fusarium oxysporum f. sp. gladioli is one of the main pathogenic microorganisms of the ornamental genus Gladiolus. The attack of this microorganism includes corms and different plant phenological stages. In this study, different microscopic techniques and fluorochromes were used to evaluate the effect of J. curcas oil and acylglycerides, namely trilinolein, triolein, monomyristin and dimyristin, on the morphology, membrane integrity (%), viability (%) and germination (%) of F. oxsporum f sp. gladioli. Phase-contrast optical photomicrographs and scanning microscopy showed that J. curcas oil and the triglycerides triolein and trilinolein caused the formation of numerous vacuoles, alterations in the morphology of the outer covering of the mycelium and conidia, and inhibition of membrane activity in the fungus during 24h of incubation. The fluorochromes used detected no permanent damage to the viability of the conidia. The high germination percentage of the conidia of Fusarium oxysporum f. sp. gladioli indicates that the damage caused by the application of the treatments was fungistatic rather than fungicidal and did not cause cell death
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