302 research outputs found
Spatially Anisotropic Heisenberg Kagome Antiferromagnet
We study the quasi-one-dimensional limit of the spin-1/2 quantum Heisenberg
antiferromagnet on the kagome lattice. The lattice is divided into
antiferromagnetic spin-chains (exchange J) that are weakly coupled via
intermediate "dangling" spins (exchange J'). Using one-dimensional
bosonization, renormalization group methods, and current algebra techniques the
ground state is determined in the limit J'<<J. We find that the dangling spins
and chain spins form a spiral with O(1) and O(J'/J) static moments,
respectively, atop of which the chain spins exhibit a smaller O[(J'/J)^2]
antiferromagnetically ordered component along the axis perpendicular to the
spiral plane.Comment: 17 pages, 3 figures, corrected sign error, corrected typos, updated
reference
Defect in lung growth Comparative study of three diagnostic criteria.
Traduction anglaise de l'article Arch Pediatr. 2004 Jun;11(6):515-7 Référence pubmed : 15158815A systematic analysis was made of the autopsies of 74 newborns and fetuses (49 pathological cases and 25 controls) to detect defects in lung growth. In each case lung/body (L/B) weight ratio was calculated, and radial alveolar (RA) count and histological assessment were performed. The L/B ratio is of diagnostic value when lower than 0.012 but not when there is intercurrent disease. RA count is low in lung hypoplasia but is not an entirely reliable diagnostic criterion since it change throughout pregnancy and the earlier the gestational age the wider the range of variation. Histological assessment showed an abnormally high number of bronchi and bronchi in distal location with in some cases delayed differentiation of distal airways. If any one of the above three critera fails to determine lung hypoplasia the other two can be used to arrive at diagnosis
CD73 expression and clinical significance in human metastatic melanoma.
CD73 is an ectoenzyme involved in the production of adenosine. It exerts immunosuppressive and protumoral roles and has emerged as a potential immuno-oncology target.
CD73 expression was detected in TC in 54% of melanoma metastases, involving < 50% TC in the majority of the cases, with variable intensity. CD73 expression was significantly associated with a lower Breslow's depth of the primary lesion and was more frequent in patients having received prior non-surgical therapies. In an adjusted analysis, CD73 expression in TC (H-score > 37.5 or intensity > 1) significantly correlated to decreased overall survival (OS) from biopsy. Of the samples containing TIMC, 35% presented CD73+ TIMC. Highly infiltrated tumors were more likely to contain CD73+ TIMC. CD73 expression in TIMC (percentage ≥1%) significantly correlated with improved OS from biopsy.
Immunohistochemistry detected CD73 expression in more than half of metastatic melanomas. While CD73 expression in TC significantly correlated with decreased OS, CD73 expression in TIMC significantly associated with improved OS. These results encourage the study of anti-CD73 therapies for metastatic melanoma patients.
CD73 expression was assessed by immunohistochemistry in metastatic melanomas from 114 patients. Immunostainings were evaluated in tumor cells (TC) (percentage, intensity (1-3) and H-score) and in tumor-infiltrating mononuclear cells (TIMC) (percentage)
Synchronous machine parameter identification in frequency and time domain
This paper presents the results of a frequency and time-domain identification procedure to estimate the linear parameters of a salient-pole synchronous machine at standstill. The objective of this study is to use several input signals to identify the model structure and parameters of a salient-pole synchronous machine from standstill test data. The procedure consists to define, to conduct the standstill tests and also to identify the model structure. The signals used for identification are the different excitation voltages at standstill and the flowing current in different windings. We estimate the parameters of operational impedances, or in other words the reactance and the time constants. The tests were carried out on synchronous machine of 1.5 kVA 380V 1500 rpm
Dynamics of the attractive 1D Bose gas: analytical treatment from integrability
The physics of the attractive one-dimensional Bose gas (Lieb-Liniger model)
is investigated with techniques based on the integrability of the system.
Combining a knowledge of particle quasi-momenta to exponential precision in the
system size with determinant representations of matrix elements of local
operators coming from the Algebraic Bethe Ansatz, we obtain rather general
analytical results for the zero-temperature dynamical correlation functions of
the density and field operators. Our results thus provide quantitative
predictions for possible future experiments in atomic gases or optical
waveguides.Comment: 26 pages, 5 figure
Scaling Exponents in the Incommensurate Phase of the Sine-Gordon and U(1) Thirring Models
In this paper we study the critical exponents of the quantum sine-Gordon and
U(1) Thirring models in the incommensurate phase. This phase appears when the
chemical potential exceeds a critical value and is characterized by a
finite density of solitons. The low-energy sector of this phase is critical and
is described by the Gaussian model (Tomonaga-Luttinger liquid) with the
compactification radius dependent on the soliton density and the sine-Gordon
model coupling constant .
For a fixed value of , we find that the Luttinger parameter is
equal to 1/2 at the commensurate-incommensurate transition point and approaches
the asymptotic value away from it. We describe a possible phase
diagram of the model consisting of an array of weakly coupled chains. The
possible phases are Fermi liquid, Spin Density Wave, Spin-Peierls and Wigner
crystal.Comment: 10pages; Improved version; Submitted to Physical Review
Form factor approach to dynamical correlation functions in critical models
We develop a form factor approach to the study of dynamical correlation
functions of quantum integrable models in the critical regime. As an example,
we consider the quantum non-linear Schr\"odinger model. We derive
long-distance/long-time asymptotic behavior of various two-point functions of
this model. We also compute edge exponents and amplitudes characterizing the
power-law behavior of dynamical response functions on the particle/hole
excitation thresholds. These last results confirm predictions based on the
non-linear Luttinger liquid method. Our results rely on a first principles
derivation, based on the microscopic analysis of the model, without invoking,
at any stage, some correspondence with a continuous field theory. Furthermore,
our approach only makes use of certain general properties of the model, so that
it should be applicable, with possibly minor modifications, to a wide class of
(not necessarily integrable) gapless one dimensional Hamiltonians.Comment: 33 page
Linear response theory for a pair of coupled one-dimensional condensates of interacting atoms
We use quantum sine-Gordon model to describe the low energy dynamics of a
pair of coupled one-dimensional condensates of interacting atoms. We show that
the nontrivial excitation spectrum of the quantum sine-Gordon model, which
includes soliton and breather excitations, can be observed in experiments with
time-dependent modulation of the tunneling amplitude, potential difference
between condensates, or phase of tunneling amplitude. We use the form-factor
approach to compute structure factors corresponding to all three types of
perturbations.Comment: 11 pages, 7 figure
- …