Analytical and numerical studies of disordered spin-1 Heisenberg chains with aperiodic couplings

We investigate the low-temperature properties of the one-dimensional spin-1 Heisenberg model with geometric fluctuations induced by aperiodic but deterministic coupling distributions, involving two parameters. We focus on two aperiodic sequences, the Fibonacci sequence and the 6-3 sequence. Our goal is to understand how these geometric fluctuations modify the physics of the (gapped) Haldane phase, which corresponds to the ground state of the uniform spin-1 chain. We make use of different adaptations of the strong-disorder renormalization-group (SDRG) scheme of Ma, Dasgupta and Hu, widely employed in the study of random spin chains, supplemented by quantum Monte Carlo and density-matrix renormalization-group numerical calculations, to study the nature of the ground state as the coupling modulation is increased. We find no phase transition for the Fibonacci chain, while we show that the 6-3 chain exhibits a phase transition to a gapless, aperiodicity-dominated phase similar to the one found for the aperiodic spin-1/2 XXZ chain. Contrary to what is verified for random spin-1 chains, we show that different adaptations of the SDRG scheme may lead to different qualitative conclusions about the nature of the ground state in the presence of aperiodic coupling modulations.Comment: Accepted for publication in Physical Review

Angular dependence of the magnetization of isotropic superconductors: which is the vortex direction?

We present studies of the dc magnetization of thin platelike samples of the isotropic type II superconductor PbTl(10%), as a function of the angle between the normal to the sample and the applied magnetic field ${\bf H}$. We determine the magnetization vector ${\bf M}$ by measuring the components both parallel and normal to ${\bf H}$ in a SQUID magnetometer, and we further decompose it in its reversible and irreversible contributions. The behavior of the reversible magnetization is well understood in terms of minimization of the free energy taking into account geometrical effects. In the mixed state at low fields, the dominant effect is the line energy gained by shortening the vortices, thus the flux lines are almost normal to the sample surface. Due to the geometrical constrain, the irreversible magnetization ${\bf M}_{irr}$ remains locked to the sample normal over a wide range of fields and orientations, as already known. We show that in order to undestand the angle and field dependence of the modulus of ${\bf M}_{irr}$, which is a measure of the vortex pinning, and to correctly extract the field dependent critical current density, the knowledge of the modulus and orientation of the induction field ${\bf B}$ is required.Comment: 11 pages, 6 figure

Primary gas thermometry by means of laser-absorption spectroscopy: Determination of the Boltzmann constant

We report on a new optical implementation of primary gas thermometry based on laser absorption spectrometry in the near infrared. The method consists in retrieving the Doppler broadening from highly accurate observations of the line shape of the R(12) $\nu_{1} + 2 \nu_{2}^{\phantom{1}0} + \nu_{3}$ transition in CO$_{2}$ gas at thermodynamic equilibrium. Doppler width measurements as a function of gas temperature, ranging between the triple point of water and the gallium melting point, allowed for a spectroscopic determination of the Boltzmann constant with a relative accuracy of $\sim1.6\times10^{-4}$.Comment: Submitted to Physical Review Letter

Equilibrium tuned by a magnetic field in phase separated manganite

We present magnetic and transport measurements on La5/8-yPryCa3/8MnO3 with y = 0.3, a manganite compound exhibiting intrinsic multiphase coexistence of sub-micrometric ferromagnetic and antiferromagnetic charge ordered regions. Time relaxation effects between 60 and 120K, and the obtained magnetic and resistive viscosities, unveils the dynamic nature of the phase separated state. An experimental procedure based on the derivative of the time relaxation after the application and removal of a magnetic field enables the determination of the otherwise unreachable equilibrium state of the phase separated system. With this procedure the equilibrium phase fraction for zero field as a function of temperature is obtained. The presented results allow a correlation between the distance of the system to the equilibrium state and its relaxation behavior.Comment: 13 pages, 5 figures. Submited to Journal of Physics: Condensed Matte

Surgical treatment of early breast cancer in day surgery

Quadrantectomy and associated sentinel lymph node biopsy (SLNB) is currently employed in most breast surgery centres as the gold standard in the treatment of early breast cancer. This approach has a modest morbidity and can usually be performed in a day-surgery regimen, leading to best acceptance by the patients. This reports outlines the experience of our Breast Unit with quadrantectomy and SLNB in day surgery for early breast cancer. One hundred patients presenting to our institution with primary invasive breast cancer measuring less than 3 cm and clinically negative axillary nodes underwent quadrantectomy and SLNB in day surgery. For 60 women with breast cancer the sentinel node was negative, so the only definitive surgical treatment was performed in the day-surgery regimen; 40 patients with positive sentinel nodes were hospitalised a second time for axillary dissection. In these patients that needed clearance of the axilla, SLNB was performed on the only positive node in 22 cases (55%). None of the patients admitted for quadrantectomy and SLNB in day surgery required re-hospitalisation after discharge. All patients proved to be fully satisfied with early discharge from hospital when questioned on the occasion of subsequent monitoring. Short-stay surgical programs in early invasive breast cancer treatment are feasible today owing to the availability of less invasive approaches such as quadrantectomy and SLNB. There are two main pointers to a distinct advantage for this kind of approach, i.e. recovery and psychological adjustment. Recovery from surgery is faster and the patient tends to play down the seriousness of the operation and to have a better mental attitude to neoplastic disease. Moreover, when performing quadrantectomy with SLNB in day surgery fewer than 50% of breast cancer patients (40% in our experience) require another surgical treatment, concluding the surgery in a single sessio

Secondary spontaneous pneumothorax and bullous lung disease in cannabis and tobacco smokers. A case-control study.

Background The notion that smoking cannabis may damage the respiratory tract has been introduced in recent years but there is still a paucity of studies on this subject. The aim of this study was to investigate the relationship between cannabis smoking, pneumothorax and bullous lung disease in a population of operated patients. Methods and findings We performed a retrospective study on patients operated on for spontaneous pneumothorax. Patients were divided into three groups according to their smoking habit: cannabis smokers, only-tobacco smokers and nonsmokers. Cannabis lifetime exposure was expressed in dose-years (1d/y = 1 gram of cannabis/week for one year). Clinical, radiological and perioperative variables were collected. The variables were analyzed to find associations with smoking habit. The impact of the amount of cannabis consumption was also investigated by ROC curves analysis. Of 112 patients, 39 smoked cannabis, 23 smoked only tobacco and 50 were nonsmokers. Median cannabis consumption was 28 dose/years, median tobacco consumption was 6 pack/years. Cannabis smokers presented with more severe chronic respiratory symptoms and bullous lung disease and with a higher incidence of tension pneumothorax than both tobacco smokers and nonsmokers. Cannabis smokers also developed a larger pneumothorax, experienced prolonged postoperative stay and demonstrated a higher incidence of pneumothorax recurrence after the operation than nonsmokers did. The risk of occurrence of chronic respiratory symptoms and bullous lung disease in cannabis smokers was dose-related. Conclusions Cannabis smoking seems to increase the risk of suffering from respiratory complaints and can have detrimental effects on lung parenchyma, in a dose-dependent manner. Cannabis smoking also negatively affected the outcome of patients operated for spontaneous pneumothorax. A history of cannabis abuse should always be taken in patients with pneumothorax. There may be need for a specific treatment for pneumothorax in cannabis smokers

The Effects of Heat Acclimatization, Heat Acclimation, and Intermittent Heat Training on Maximal Oxygen Uptake

Maximal oxygen uptake (VO2max) is an important determinant of endurance performance. Heat acclimation/acclimatization (HA/HAz) strategies elicit improvements in endurance performance. When heat exposure is reduced, intermittent heat training (IHT) is potentially beneficial to alleviate HA/HAz adaptation decay, however corresponding VO2max responses are unknown. PURPOSE: To determine the effects of HA/HAz and IHT on VO2max in endurance runners and identify how long VO2max adaptations remain following removal of repeated heat exposure. METHODS: Twenty-seven male endurance runners (mean ± SD; age, 36 ± 12 years; body mass, 73.03 ± 8.97 kg; height, 178.81 ± 6.39 cm; VO2max, 57.48 ± 7.03 ml.kg-1.min-1) completed VO2max and exercise testing at five time points; baseline, pre-HA, post-HA, week 4 of IHT (IHT4), and week 8 of IHT (IHT8). Exercise testing and HA environmental conditions were the same (ambient temperature, 35.42 ± 1.06°C; relative humidity, 46.35 ± 2.48%). Following baseline testing, participants completed HAz, proceeded by 5 days of HA involving exercise to induce hyperthermia (38.50 - 39.50°C) for 60 minutes. Participants were then randomly assigned to one of three IHT groups: once weekly (n = 9), twice weekly (n = 10), or no IHT (n = 8). Differences in VO2max and maximal heart rate at VO2max (HRmax) for baseline, pre-HA, post-HA, IHT4, and IHT8 were analyzed using repeated-measures ANOVAs with Bonferroni corrections post-hoc. RESULTS: No significant VO2max differences were observed between baseline (57.92 ± 6.82 ml.kg-1.min-1), pre-HA (59.65 ± 8.24 ml.kg-1.min-1), and post-HA (59.49 ± 7.18 ml.kg-1.min-1, p = 0.36). No significant group or time effects were identified for VO2max at post-HA, IHT4, and IHT8 (p = 0.67). However, significant HRmax differences were observed between baseline (180 ± 11 beats.min-1), pre-HA (177 ± 10 beats.min-1), and post-HA tests (175 ± 10 beats.min-1, p = 0.01). No significant group or time HRmax differences were shown for post-HA, IHT4, and IHT8 (p = 0.59). CONCLUSION: No changes in VO2max were identified among endurance runners following HA/HAz, potentially due to participants’ high aerobic fitness levels. As IHT maintained VO2max following 8 weeks without repeated heat exposure, it is potentially a beneficial strategy to minimize VO2max adaptation decay in endurance athletes

Foot-to-Foot Contact Among Initial Goal-Directed Movements Supports the Prognostic Value of Fidgety Movements in HIE-Cooled Infants

Background: Few studies conducted to date have observed general movements in infants affected by hypoxic–ischemic encephalopathy (HIE) who underwent therapeutic hypothermia. We investigated whether foot-to-foot contact (FF) could support the predictive value of fidgety movements (FMs) in infants affected by HIE and treated with brain cooling. Methods: Spontaneous motility was video recorded for 3–5 min at 12 weeks post-term age in 58 full-term newborn infants affected by perinatal asphyxia who were cooled due to moderate to severe HIE. FF and FMs were blindly scored by three independent observers. At 24 months, each patient underwent a neurological examination by Amiel-Tison and Grenier. Results: At 24 months, 47 infants had developed typically at neurological examination, eight had developed mild motor impairment, and three developed cerebral palsy (CP). At 12 weeks, 34 (58.6%) infants had shown normal FMs, four of whom developed mild motor impairment. Twenty-four infants (41.4%) exhibited abnormal or no FMs, four of whom developed mild motor impairment and three developed CP. FF was present in 20 infants (34.5%), two of whom developed mild motor impairment. FF was absent in 38 infants (65.5%), six of whom developed mild motor impairment and three developed CP. Both FMs and FF, considered separately, were 100% sensitive for predicting CP at 24 months, but only 61 and 36%, respectively, were specific. Summing the two patterns together, the specificity increases to 73%, considering only CP as an abnormal outcome, and increases to 74% when considering CP plus mild motor impairment. Unexpectedly, fidgety movements were absent in 24 infants with typical motor outcomes, 17 of whom showed a typical motor outcome. Conclusions: FF is already part of motor repertoire at 12 weeks and allows a comparison of spontaneous non-voluntary movements (FMs) to pre-voluntary movements (FF). FF supports FMs for both sensitivity and specificity. A second video recording at 16–18 weeks, when pedipulation is present in healthy infants, is suggested: it may better define the presence or absence of goal-directed motility