593 research outputs found
Quantum Quench in the Transverse Field Ising chain I: Time evolution of order parameter correlators
We consider the time evolution of order parameter correlation functions after
a sudden quantum quench of the magnetic field in the transverse field Ising
chain. Using two novel methods based on determinants and form factor sums
respectively, we derive analytic expressions for the asymptotic behaviour of
one and two point correlators. We discuss quenches within the ordered and
disordered phases as well as quenches between the phases and to the quantum
critical point. We give detailed account of both methods.Comment: 65 pages, 21 figures, some typos correcte
Corrections to scaling in entanglement entropy from boundary perturbations
We investigate the corrections to scaling of the Renyi entropies of a region
of size l at the end of a semi-infinite one-dimensional system described by a
conformal field theory when the corrections come from irrelevant boundary
operators. The corrections from irrelevant bulk operators with scaling
dimension x have been studied by Cardy and Calabrese (2010), and they found not
only the expected corrections of the form l^(4-2x) but also unusual corrections
that could not have been anticipated by finite-size scaling arguments alone.
However, for the case of perturbations from irrelevant boundary operators we
find that the only corrections that can occur to leading order are of the form
l^(2-2x_b) for boundary operators with scaling dimension x_b < 3/2, and l^(-1)
when x_b > 3/2. When x_b=3/2 they are of the form l^(-1)log(l). A marginally
irrelevant boundary perturbation will give leading corrections going as
log(l)^(-3). No unusual corrections occur when perturbing with a boundary
operator.Comment: 8 pages. Minor improvements and updated references. Published versio
Diversidade de bactérias diazotróficas endofíticas de milho em cultivos convencional e agroecológico.
Diferentes gêneros de bactérias diazotróficas, além de fixar N2 atmosférico, também promovem o crescimento de plantas pela produção de hormônios vegetais e disponibilização de outros nutrientes como o fósforo. O objetivo deste trabalho foi isolar e identificar bactérias diazotróficas endofíticas de milho (Zea mays L.) sob plantio direto e convencional, em sistema agroecológico e convencional. O isolamento foi realizado em meios de cultura livres de N (LGI, JNFb e JMV), totalizando 86 isolados. Por meio do sequenciamento do gene 16S DNAr foram identificadas bactérias dos gêneros Burkholderia spp., Agrobacterium spp., Enterobacter spp., Stenotrophomonas spp., Rhizobium spp., Pseudoxanthomonas sp., Microbacterium sp., Sphingomonas sp., Klebsiella spp., Bacillus sp., Xanthomonas sp., Leclercia sp., Pantoea sp., Dyella sp. e Pseudomonas spp. O gênero Burkholderia representou 30% dos isolados, seguido de Agrobacterium com 14%. O milho sob cultivo agroecológico apresentou mais isolados de bactérias endofíticas (24%). Assim, sistemas menos sujeitos a ações antrópicas parecem ser hotspots de diversidade para isolamento de microrganismos com potencial para promoção de crescimento vegetal.Fertbio
Entropy inequalities from reflection positivity
We investigate the question of whether the entropy and the Renyi entropies of
the vacuum state reduced to a region of the space can be represented in terms
of correlators in quantum field theory. In this case, the positivity relations
for the correlators are mapped into inequalities for the entropies. We write
them using a real time version of reflection positivity, which can be
generalized to general quantum systems. Using this generalization we can prove
an infinite sequence of inequalities which are obeyed by the Renyi entropies of
integer index. There is one independent inequality involving any number of
different subsystems. In quantum field theory the inequalities acquire a simple
geometrical form and are consistent with the integer index Renyi entropies
being given by vacuum expectation values of twisting operators in the Euclidean
formulation. Several possible generalizations and specific examples are
analyzed.Comment: Significantly enlarged and corrected version. Counterexamples found
for the most general form of the inequalities. V3: minor change
Quasi-local conserved charges and spin transport in spin-1 integrable chains
We consider the integrable one-dimensional spin-1 chain defined by the Zamolodchikov-Fateev (ZF) Hamiltonian. The latter is parametrized, analogously to the XXZ spin-1/2 model, by a continuous anisotropy parameter and at the isotropic point coincides with the well-known spin-1 Babujian-Takhtajan Hamiltonian. Following a procedure recently developed for the XXZ model, we explicitly construct a continuous family of quasi-local conserved operators for the periodic spin-1 ZF chain. Our construction is valid for a dense set of commensurate values of the anisotropy parameter in the gapless regime where the isotropic point is excluded. Using the Mazur inequality, we show that, as for the XXZ model, these quasi-local charges are enough to prove that the high-temperature spin Drude weight is non-vanishing in the thermodynamic limit, thus establishing ballistic spin transport at high temperature
Carbono orgânico e atributos microbiológicos em solo agrícola com diferentes níveis de produtividade de soja em sistema de plantio direto.
Atributos microbiológicos e bioquímicos do solo são geralmente negligenciados ao se relacionar a fertilidade do solo e a produtividade das culturas, em que o carbono orgânico (C) apresenta papel chave. O objetivo deste trabalho foi avaliar alguns bioindicadores de qualidade de solo e relacioná-los com o teor de C do solo em áreas de produção comercial com diferentes níveis de produtividade de soja sob sistema de plantio direto. Amostras compostas de solo foram obtidas na profundidade 0-10 cm, em 6 áreas agrícolas em Ponta Grossa, PR. Os dados foram submetidos à análise de correlação de Pearson e regressão múltipla. A regressão múltipla mostrou que a produtividade é influenciada principalmente pelo teor de C orgânico no solo, e a correlação simples de Pearson mostrou-se significativa entre o C orgânico e a biomassa microbiana de carbono (BMC), biomassa microbiana de nitrogênio (BMN), capacidade de troca de cátions (CTC) e atividades enzimáticas. Conclui-se que há uma relação entre a produtividade de grãos de soja e a atividade microbiana no solo, em que o C orgânico apresenta papel chave.Fertbio
Robotic treatment of colorectal endometriosis: technique, feasibility and short-term results
background: Deep infiltrating endometriosis (DIE) is a complex disease that impairs the quality of life and the fertility of women. Since
a medical approach is often insufficient, a minimally invasive approach is considered the gold standard for complete disease excision. Roboticassisted
surgery is a revolutionary approach, with several advantages compared with traditional laparoscopic surgery.
methods: From March 2010 to May 2011, we performed 22 consecutive robotic-assisted complete laparoscopic excisions of DIE endometriosis
with colorectal involvement. All clinical data were collected by our team and all patients were interviewed preoperatively and 3 and
6 months post-operatively and yearly thereafter regarding endometriosis-related symptoms. Dysmenorrhoea, dyschezia, dyspareunia and
dysuria were evaluated with a 10-point analog rating scale.
results: There were 12 patients, with a median larger endometriotic nodule of 35 mm, who underwent segmental resection, and 10
patients, with a median larger endometriotic nodule of 30 mm, who underwent complete nodule debulking by colorectal wall-shaving technique.
No laparotomic conversions were performed, nor was any blood transfusion necessary. No intra-operative complications were
observed and, in particular, there were no inadvertent rectal perforations in any of the cases treated by the shaving technique. None of
the patients had ileostomy or colostomy. No major post-operative complications were observed, except one small bowel occlusion 14
days post-surgery that was resolved in 3 days with medical treatment. Post-operatively, a statistically significant improvement of patient symptoms
was shown for all the investigated parameters.
conclusions: To our knowledge, this is the first study reporting the feasibility and short-term results and complications of laparoscopic
robotic-assisted treatment of DIE with colorectal involvement.We demonstrate that this approach is feasible and safe, without conversion to
laparotomy
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