Low-Temperature Quantum Critical Behaviour of Systems with Transverse Ising-like Intrinsic Dynamics

The low-temperature properties and crossover phenomena of $d$-dimensional transverse Ising-like systems within the influence domain of the quantum critical point are investigated solving the appropriate one-loop renormalization group equations. The phase diagram is obtained near and at $d=3$ and several sets of critical exponents are determined which describe different responses of a system to quantum fluctuations according to the way of approaching the quantum critical point. The results are in remarkable agreement with experiments for a wide variety of compounds exhibiting a quantum phase transition, as the ferroelectric oxides and other displacive systems.Comment: 36 pages, 2 figures, accepted in Physica

Quantum tricriticality in transverse Ising-like systems

The quantum tricriticality of d-dimensional transverse Ising-like systems is studied by means of a perturbative renormalization group approach focusing on static susceptibility. This allows us to obtain the phase diagram for 3<d<4, with a clear location of the critical lines ending in the conventional quantum critical points and in the quantum tricritical one, and of the tricritical line for temperature T \geq 0. We determine also the critical and the tricritical shift exponents close to the corresponding ground state instabilities. Remarkably, we find a tricritical shift exponent identical to that found in the conventional quantum criticality and, by approaching the quantum tricritical point increasing the non-thermal control parameter r, a crossover of the quantum critical shift exponents from the conventional value \phi = 1/(d-1) to the new one \phi = 1/2(d-1). Besides, the projection in the (r,T)-plane of the phase boundary ending in the quantum tricritical point and crossovers in the quantum tricritical region appear quite similar to those found close to an usual quantum critical point. Another feature of experimental interest is that the amplitude of the Wilsonian classical critical region around this peculiar critical line is sensibly smaller than that expected in the quantum critical scenario. This suggests that the quantum tricriticality is essentially governed by mean-field critical exponents, renormalized by the shift exponent \phi = 1/2(d-1) in the quantum tricritical region.Comment: 9 pages, 2 figures; to be published on EPJ

Classical transverse Ising spin glass with short- range interaction beyond the mean field approximation

The classical transverse field Ising spin- glass model with short-range interactions is investigated beyond the mean- field approximation for a real d- dimensional lattice. We use an appropriate nontrivial modification of the Bethe- Peierls method recently formulated for the Ising spin- glass. The zero- temperature critical value of the transverse field and the linear susceptibility in the paramagnetic phase are obtained analytically as functions of dimensionality d. The phase diagram is also calculated numerically for different values of d. In the limit d -> infinity, known mean- field results are consistently reproduced.Comment: LaTex, 11 pages, 2 figure

Field-Induced Quantum Criticality of Systems with Ferromagnetically Coupled Structural Spin Units

The field-induced quantum criticality of compounds with ferromagnetically coupled structural spin units (as dimers and ladders) is explored by applying Wilson's renormalization group framework to an appropriate effective action. We determine the low-temperature phase boundary and the behavior of relevant quantities decreasing the temperature with the applied magnetic field fixed at its quantum critical point value. In this context, a plausible interpretation of some recent experimental results is also suggested.Comment: to be published in Physics Letters

Application of different DNA extraction procedures, library preparation protocols and sequencing platforms: impact on sequencing results

In this study three DNA extraction procedures, two library preparation protocols and two sequencing platforms were applied to analyse six bacterial cultures and their corresponding DNA obtained as part of a proficiency test. The impact of each variable on sequencing results was assessed using the following parameters: reads quality, assembly and alignment statistics; number of single nucleotide polymorphisms (SNPs), detected applying assembly- and alignment-based strategies; antimicrobial resistance genes (ARGs), identified on de novo assemblies of all sequenced genomes. The investigated nucleic acid extraction procedures, library preparation kits and sequencing platforms do not significantly affect de novo assembly statistics and number of SNPs and ARGs. The only exception was observed for two duplicates, which were associated to one PCR-based library preparation kit. Results from this comparative study can support researchers in the choice toward the available pre-sequencing and sequencing options, and might suggest further comparisons to be performed

En defensa de los indios norteamericanos. : Traducción y presentación editorial de un capítulo de 'A century of dishonor', de Helen Hunt Jackson

El presente trabajo se ha realizado a partir de la traducción del inglés al castellano de un capítulo de la obra de A Century of Dishonor de Helen Hunt Jackson. La traducción es acompañada por un trabajo suplementario de investigación acerca del contexto sociopolítico de la época, la obra y su autora con el fin de contextualizar la traducción y de obtener un panorama más amplio sobre la historia de los indios norteamericanos y su relación con el gobierno de los Estados Unidos, marcada por innumerables injusticias e abusos perpetrados durante un siglo. En este trabajo se puede encontrar un extracto del texto traducido correspondiente al Capítulo VIII del texto original y cuyo argumento trata sobre la tribu indígena de los indios cheroquis, desde el primer encuentro con los colonos británicos del general Oglethorpe en 1733, pasando por contacto con la religión cristiana a través de los misionarios wesleyanos en 1735, hasta los efectos del nuevo gobierno real de Georgia. Los últimos episodios se centran en los acontecimientos relativos a la participación de los indios cheroquis en la revolución americana y las primeras relaciones diplomáticas con el gobierno de Estados Unidos iniciadas con la firma del tratado de Hopewell en 1785 y descritas en 1789 por el secretario de Guerra, el general KnoxEl present treball s'ha realitzat a partir de la traducció de l'anglès al castellà d'un capítol de l'obra A Century of Dishonor d'Helen Hunt Jackson. La traducció és acompanyada per un treball suplementari d'investigació sobre el context sociopolític de l'època, l'obra i la seva autora per tal de contextualitzar la traducció i d'obtenir un panorama més ampli sobre la història dels indis nord-americans i la seva relació amb el govern dels Estats Units, marcada per innombrables injustícies i abusos perpetrats durant un segle. En aquest treball es pot trobar un extracte del text traduït corresponent al Capítol VIII del text original; l'argument tracta sobre la tribu indígena dels indis cheroquis, des la primera trobada amb els colons britànics del general Oglethorpe en 1733, passant pel contacte amb la religió cristiana amb els missioners wesleyans en 1735, fins als efectes del nou govern reial de Geòrgia. Els últims episodis es centren en els esdeveniments relatius a la participació dels indis cheroquis en la revolució americana i les primeres relacions diplomàtiques amb el govern dels Estats Units iniciades amb la signatura del tractat de Hopewell en 1785 i descrites en 1789 pel secretari de Guerra, el general KnoxThis work consists of a translation from English into Spanish of a chapter of the book A Century of Dishonor by Helen Hunt Jackson. The translation is accompanied by an additional research about the socio-political context of the time and Jackson's life and work in order to contextualize the translation and offer a broader overview of the history of American Indians and their relationship with the United States government, marked by countless injustices and abuses perpetrated during a century. It is included an excerpt of the translated text corresponding to Chapter VIII of the original text and whose plot development is based on the history of the Cherokees Indians: their first meeting with the British settlers of General Oglethorpe in 1733, their contact with Christian religion introduced by the Wesleyan missionaries in 1735, until the effects of the new royal government of Georgia. The last episodes focus on the facts related to the participation of the Cherokees in the American Revolution and their first diplomatic relations with the US government initiated with the signing of Hopewell's treaty in 1785 and described in 1789 by the Secretary of War General Kno

Sediment Evacuation from Reservoirs through Intakes by Jet-Induced Flow

Reservoir sedimentation is considered as a sustainability problem. A concept getting down to the root of the cause was developed and tested in laboratory experiments. The idea is to maintain sediment in suspension, i.e., avoiding its settling near the dam by generating a jet induced artificial flow field and related turbulence (rotational flow), enabling the release of suspended sediment through the power intake. Therefore, a perpendicular jet configuration consisting of four jets arranged in a horizontal plane was investigated in a rectangular basin equipped with an outlet structure. The influence of its geometric parameters and the jet discharge on the sediment release was analyzed in detail. The flow pattern and its effect on the sediment release efficiency were evaluated, by measurements of turbidity and flow velocity. Depending on experiment duration and discharge, an ideal parameter set was identified resulting in a release efficiency between 1.5 and 2 compared to the reference case without jets. (C) 2014 American Society of Civil Engineers

Targeted capture and sequencing of Orientia tsutsugamushi genomes from chiggers and humans

Scrub typhus is a febrile disease caused by Orientia tsutsugamushi, transmitted by larval stage Trombiculid mites (chiggers), whose primary hosts are small mammals. The phylogenomics of O. tsutsugamushi in chiggers, small mammals and humans remains poorly understood. To combat the limitations imposed by the low relative quantities of pathogen DNA in typical O. tsutsugamushi clinical and ecological samples, along with the technical, safety and cost limitations of cell culture, a novel probe-based target enrichment sequencing protocol was developed. The method was designed to capture variation among conserved genes and facilitate phylogenomic analysis at the scale of population samples. A whole-genome amplification step was incorporated to enhance the efficiency of sequencing by reducing duplication rates. This resulted in on-target capture rates of up to 93% for a diverse set of human, chigger, and rodent samples, with the greatest success rate in samples with real-time PCR Ct values below 35. Analysis of the best-performing samples revealed phylogeographic clustering at local, provincial and international scales. Applying the methodology to a comprehensive set of samples could yield a more complete understanding of the ecology, genomic evolution and population structure of O. tsutsugamushi and other similarly challenging organisms, with potential benefits in the development of diagnostic tests and vaccines