Emission and absorption noise in the fractional quantum Hall effect

We compute the high-frequency emission and absorption noise in a fractional quantum Hall effect (FQHE) sample at arbitrary temperature. We model the edges of the FQHE as chiral Luttinger liquids (LL) and we use the non-equilibrium perturbative Keldysh formalism. We find that the non-symmetrized high frequency noise contains important signatures of the electron-electron interactions that can be used to test the Luttinger liquid physics, not only in FQHE edge states, but possibly also in other one-dimensional systems such as carbon nanotubes. In particular we find that the emission and absorption components of the excess noise (defined as the difference between the noise at finite voltage and at zero voltage) are different in an interacting system, as opposed to the non-interacting case when they are identical. We study the resonance features which appear in the noise at the Josephson frequency (proportional to the applied voltage), and we also analyze the effect of the distance between the measurement point and the backscattering site. Most of our analysis is performed in the weak backscattering limit, but we also compute and discuss briefly the high-frequency noise in the tunneling regime.Comment: 26 pages, 11 figure

Gait analysis in patients with idiopathic scoliosis

Introduction: The goal of this study was to observe scoliotic subjects during level walking to identify asymmetries—which may be related to a neurological dysfunction or the spinal deformity itself—and to correlate these to the severity of the scoliotic curve. Methods: We assessed the gait pattern of ten females (median age 14.4) with idiopathic scoliosis characterised by a left-lumbar and a right-thoracic curve component. Gait analysis consisted of 3D kinematic (VICON) and kinetic (Kistler force plates) measurements. The 3D-segment positions of the head, trunk and pelvis, as well as the individual joint angles of the upper and lower extremities, were computed during walking and static standing. Calculation of pertinent kinetic and kinematic parameters allowed statistical comparison. Results: All subjects walked at a normal velocity (median: 1.22m/s; range:1.08-1.30m/s; height-adjusted velocity: 0.75m/s; range: 0.62-0.88m/s). The timing of the individual gait phases was normal and symmetrical for the whole group. Sagittal plane hip, knee and ankle motion followed a physiological pattern. Significant asymmetry was observed in the trunk's rotational behaviour in the transverse plane. During gait, the pelvis and the head rotated symmetrically to the line of progression, whereas trunk rotation was asymmetric, with increased relative forward rotation of the right upper body in relation to the pelvis. This produced a torsional offset to the line of progression. Minimal torsion (at right heel strike) measured: median 1.0° (range: 5.1°-8.3°), and maximal torsion (at left heel strike) measured 11.4° (range 6.9°-17.9°). The magnitude of the torsional offset during gait correlated to the severity of the thoracic deformity and to the standing posture, whereas the range of the rotational movement was not affected by the severity of the deformity. The ground reaction forces revealed a significant asymmetry of [Msz], the free rotational moment around the vertical axis going through the point of equivalent force application. On the right side, the initial endo-rotational moment was lower, followed by a higher exo-rotational moment than on the left. All the other force parameters (vertical, medio-lateral, anterior-posterior), did not show a significant side difference for the whole group. The use of a brace stiffened torsional motion. However the torsional offset and the asymmetry of the free rotational moment remained unchanged. Conclusion: The most significant and marked asymmetry was seen in the transverse plane, denoted as a torsional offset of the upper trunk in relation to the symmetrically rotating pelvis. This motion pattern was reflected by a ground-reaction-force asymmetry of the free rotational moment. Further studies are needed to investigate whether this behaviour is solely an expression of the structural deformity or whether it could enhance the progression of the torsional deformit

AC conductance and non-symmetrized noise at finite frequency in quantum wires and carbon nanotubes

We calculate the AC conductance and the finite-frequency non-symmetrized noise in interacting quantum wires and single-wall carbon nanotubes in the presence of an impurity. We observe a strong asymmetry in the frequency spectrum of the non-symmetrized excess noise, even in the presence of the metallic leads. We find that this asymmetry is proportional to the differential excess AC conductance of the system, defined as the difference between the AC differential conductances at finite and zero voltage, and thus disappears for a linear system. In the quantum regime, for temperatures much smaller than the frequency and the applied voltage, we find that the emission noise is exactly equal to the impurity partition noise. For the case of a weak impurity we expand our results for the AC conductance and the noise perturbatively. In particular, if the impurity is located in the middle of the wire or at one of the contacts, our calculations show that the noise exhibits oscillations with respect to frequency, whose period is directly related to the value of the interaction parameter $g$

Optimization of heat- and ultrasound-assisted extraction of anthocyanins from Hibiscus sabdariffa calyces for natural food colorants

calyces. The extraction variables, time (t), ethanol proportion (S), and temperature (T) or ultrasonic power (P), were combined in a 5-level experimental design and analysed by response surface methodology for process optimization. The delphinidin-3-O-sambubioside (C1) and cyanidin-3-O-sambubioside (C2) levels were monitored by LC-DAD-ESI/MSn and used as response criteria. The developed models were successfully fitted to the experimental data and used to determine optimal extraction conditions. UAE was the most efficient method yielding 51.76 mg C1+C2/g R under optimal conditions (t=26.1 min, P=296.6W and S=39.1% ethanol, v/ v). The dose-response effects of the solid/liquid ratio on the extraction rate were also determined. The anthocyanin levels herein reported are higher than those found in the literature, which support the potential use of H. sabdariffa as a sustainable source of natural colorants with application in different industrial sectors.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) and FEDER under Programme PT2020 for financial support to CIMO (UID/AGR/00690/2013), FEDER through POCI-COMPETE2020 and FCT for financial support to LA LSRE-LCM (POCI-01-0145-FEDER-006984), J. Pinela (UID/AGR/00690/ 2013_DNAABN) and L. Barros contract. This work is funded by the European Regional Development Fund (ERDF) through the Regional Operational Program North 2020, within the scope of Project NORTE- 01-0145-FEDER-023289: DeCodE and project Mobilizador Norte-01- 0247-FEDER-024479: ValorNatural®. The authors are also grateful to FEDER-Interreg España-Portugal programme for financial support through the project 0377_Iberphenol_6_E. To the Xunta de Galicia for financial support to M.A. Prieto.info:eu-repo/semantics/publishedVersio

Resonance in a Tomonaga-Luttinger liquid

We study a homogeneous Tomonaga-Luttinger liquid with backscattering potential. A perturbative computation of the conductance at and near resonance is given. We find that the backscattering of one electron dominates that of two electrons for an interaction parameter $K\geq 1/3$ and that the resonance point depends on temperature. Our results may be relevant for recent experiments on shot-noise in FQHE, where the charge 1/3 and not $2*1/3$ is measured on resonance.Comment: 15 pages, three Figures. v2: Definite version, Citations added, presentation improved. To appear in Phys. Rev. B, Rapid Co

Ethnic differences in cardiometabolic risk profile in an overweight/obese paediatric cohort in the Netherlands: a cross-sectional study

<p>Abstract</p> <p>Background</p> <p>Differences in prevalence of cardiometabolic risk factors between different ethnic groups are largely unknown. We determined the variation in cardiometabolic risk profile according to ethnicity in a cohort overweight/obese Dutch children.</p> <p>Methods</p> <p>An oral glucose tolerance test was performed in 516 overweight/obese Dutch children of multi-ethnic origin, attending an obesity out-patient clinic of an urban general hospital (mean age 10.6 ± 3.2; 55.2% boys). Anthropometric parameters and blood samples were collected, and the prevalence of (components of) the metabolic syndrome (MetS) and insulin resistance were determined in each ethnic group.</p> <p>Results</p> <p>Major ethnic groups were Dutch native (18.4%), Turkish (28.1%), and Moroccan (25.8%). The remaining group (27.7%) consisted of children with other ethnicities. Turkish children had the highest mean standardized BMI compared to Dutch native children (<it>P </it>< 0.05). As compared to Moroccan children, they had a higher prevalence of MetS (22.8% vs. 12.8%), low HDL-cholesterol (37.9% vs. 25.8%), hypertension (29.7% vs. 18.0%) and insulin resistance (54.9% vs. 37.4%, all <it>P </it>< 0.05). Although Turkish children also had higher prevalences of forementioned risk factors than Dutch native children, these differences were not statistically significant. Insulin resistance was associated with MetS in the Turkish and Moroccan subgroup (OR 6.6; 95%CI, 2.4–18.3 and OR 7.0; 95%CI, 2.1–23.1, respectively).</p> <p>Conclusion</p> <p>In a Dutch cohort of overweight/obese children, Turkish children showed significantly higher prevalences of cardiometabolic risk factors relative to their peers of Moroccan descent. The prospective value of these findings needs to be established as this may warrant the need for differential ethnic-specific preventive measures.</p

Contribution of the phenolic composition to the antioxidant, anti-inflammatory and antitumor potential of Equisetum giganteum L. and Tilia platyphyllos Scop.

Naturally-occurring phytochemicals have received pivotal attention in the last few years, due to the increasing evidence of biological activities. Thus, in the present study, the antioxidant, anti-inflammatory and antitumor potentials of hydroethanolic extracts rich in phenolic compounds obtained from Equisetum giganteum L. and Tilia platyphyllos Scop. were assessed and directly correlated with their content of phenolic compounds, by using HPLC-DAD-ESI/MS analysis. T. platyphyllos showed the higher bioactive potential, evaluated in terms of antioxidant (radical scavenging effects-105 µg mL -1 , reducing power-123 µg mL -1 , ß-carotene bleaching inhibition-167 µg mL -1 , and lipid peroxidation inhibition-56 µg mL -1 ), anti-inflammatory (225 µg mL -1 inhibited 50% of nitric oxide production) and antitumor (breast-224 µg mL -1 ; lung-247 µg mL -1 ; cervical-195 µg mL -1 and hepatocellular-173 µg mL -1 carcinoma cells) activity, without having cytotoxic effects ( > 400 µg mL -1 ). These biological properties were positively correlated with its content and composition of phenolic compounds. Flavonoid contents were markedly higher than the content of phenolic acids, in both samples, being respectively 50.4 mg g -1 and 11.65 mg g -1 for T. platyphyllos, and 21.7 mg g -1 and 4.98 mg g -1 for E. giganteum. Moreover, while in E. giganteum extract, kaempferol-O-glucoside-O-rutinoside was the most abundant flavonoid, in T. platyphyllos extract protocatechuic acid and (-)-epicatechin were the most abundant phenolic acid and flavonoid, respectively. In relation to their content of phenolic acids, protocatechuic and caffeic acids existed in higher abundance in T. platyphyllos and E. giganteum hydroethanolic extracts, respectively. However, it would be interesting to evaluate the in vivo efficacy of both plant extracts to unveil the involved modes of action and to establish effective therapeutic doses.The authors are grateful to Fundação para a Ciência e a Tecnologia (FCT, Portugal) for financial support to CIMO (Pest-OE/AGR/UI0690/2015) and to POCI-01-0145-FEDER- 006984 (LA LSRE-LCM) funded by ERDF through POCICOMPETE2020 and FCT. L. Barros and N. Martins thank FCT for their grants (SFRH/BPD/107855/2015 and SFRH/BD/87658/ 2012, respectively). The GIP-USAL is financially supported by the Spanish Government through the project AGL2015-64522- C2-2-R.info:eu-repo/semantics/publishedVersio

Transport properties of single channel quantum wires with an impurity: Influence of finite length and temperature on average current and noise

The inhomogeneous Tomonaga Luttinger liquid model describing an interacting quantum wire adiabatically coupled to non-interacting leads is analyzed in the presence of a weak impurity within the wire. Due to strong electronic correlations in the wire, the effects of impurity backscattering, finite bias, finite temperature, and finite length lead to characteristic non-monotonic parameter dependencies of the average current. We discuss oscillations of the non-linear current voltage characteristics that arise due to reflections of plasmon modes at the impurity and quasi Andreev reflections at the contacts, and show how these oscillations are washed out by decoherence at finite temperature. Furthermore, the finite frequency current noise is investigated in detail. We find that the effective charge extracted in the shot noise regime in the weak backscattering limit decisively depends on the noise frequency $\omega$ relative to $v_F/gL$, where $v_F$ is the Fermi velocity, $g$ the Tomonaga Luttinger interaction parameter, and $L$ the length of the wire. The interplay of finite bias, finite temperature, and finite length yields rich structure in the noise spectrum which crucially depends on the electron-electron interaction. In particular, the excess noise, defined as the change of the noise due to the applied voltage, can become negative and is non-vanishing even for noise frequencies larger than the applied voltage, which are signatures of correlation effects.Comment: 28 pages, 19 figures, published version with minor change