Incommensurate phonon anomaly and the nature of charge density waves in cuprates

While charge density wave (CDW) instabilities are ubiquitous to superconducting cuprates, the different ordering wavevectors in various cuprate families have hampered a unified description of the CDW formation mechanism. Here we investigate the temperature dependence of the low energy phonons in the canonical CDW ordered cuprate La$_{1.875}$Ba$_{0.125}$CuO$_{4}$. We discover that the phonon softening wavevector associated with CDW correlations becomes temperature dependent in the high-temperature precursor phase and changes from a wavevector of 0.238 reciprocal space units (r.l.u.) below the ordering transition temperature up to 0.3~r.l.u. at 300~K. This high-temperature behavior shows that "214"-type cuprates can host CDW correlations at a similar wavevector to previously reported CDW correlations in non-"214"-type cuprates such as YBa$_{2}$Cu$_{3}$O$_{6+\delta}$. This indicates that cuprate CDWs may arise from the same underlying instability despite their apparently different low temperature ordering wavevectors.Comment: Accepted in Phys. Rev. X; 9 pages; 5 figures; 3 pages of supplementary materia

Leiomyosarcoma of the Larynx: A Complex Diagnosis

An 84-year-old man was referred to our institution for dysphonia present for 2 months. Fiberoptic laryngoscopy demonstrated a polypoid lesion of the right true vocal fold with normal motility. Excisional biopsy of a submucosal thickening of the right vocal fold with vocal ligament calcification was performed. Histology revealed squamous cell epithelium without malignancy. Postoperative endoscopic follow-up was regular. Six months after surgery, dysphonia and dyspnea occurred. Flexible laryngoscopy demonstrated right hemilaryngeal paralysis, edema, and partial airway obstruction. Necrotic tissue and purulent secretions were visible at the anterior commissure, right vocal fold, and ipsilateral vestibule. A second microlaryngoscopic surgery included multiple biopsies and debridement of the necrotic tissue. Histological report was negative for malignancy, and purulent chondritis was diagnosed. Intravenous antibiotic therapy was administered with improvement of infection, inflammation, dysphonia, and dyspnea. The patient was discharged

Magnetic properties of GdT2T_2Zn20_{20} (T = Fe, Co) investigated by X-ray diffraction and spectroscopy

We investigate the magnetic and electronic properties of the Gd$T_2$Zn$_{20}$ ($T$ = Fe and Co) compounds using X-ray resonant magnetic scattering (XRMS), X-ray absorption near-edge structure (XANES) and X-ray magnetic circular dichroism (XMCD) techniques. The XRMS measurements reveal that the GdCo$_2$Zn$_{20}$ compound has a commensurate antiferromagnetic spin structure with a magnetic propagation vector $\vec{\tau}$ = $(\frac{1}{2},\frac{1}{2},\frac{1}{2})$ below the N\'eel temperature ($T_N \sim$ 5.7 K). Only the Gd ions carry a magnetic moment forming an antiferromagnetic structure with magnetic representation $\Gamma_6$. For the ferromagnetic GdFe$_2$Zn$_{20}$ compound, an extensive investigation was performed at low temperature and under magnetic field using XANES and XMCD techniques. A strong XMCD signal of about 12.5 $\%$ and 9.7 $\%$ is observed below the Curie temperature ($T_C \sim$ 85 K) at the Gd-$L_2$ and $L_3$ edges, respectively. In addition, a small magnetic signal of about 0.06 $\%$ of the jump is recorded at the Zn $K$-edge suggesting that the Zn 4$p$ states are spin polarized by the Gd 5$d$ extended orbitals

Electronic and structural ground state of heavy alkali metals at high pressure

Alkali metals display unexpected properties at high pressure, including emergence of low symmetry crystal structures, that appear to occur due to enhanced electronic correlations among the otherwise nearly-free conduction electrons. We investigate the high pressure electronic and structural ground state of K, Rb, and Cs using x-ray absorption spectroscopy and x-ray diffraction measurements together with ab initio theoretical calculations. The sequence of phase transitions under pressure observed at low temperature is similar in all three heavy alkalis except for the absence of the oC84 phase in Cs. Both the experimental and theoretical results point to pressure-enhanced localization of the valence electrons characterized by pseudo-gap formation near the Fermi level and strong spd hybridization. Although the crystal structures predicted to host magnetic order in K are not observed, the localization process appears to drive these alkalis closer to a strongly correlated electron state.Comment: 10 pages, 8 figure

Development and Technology Assessment of the Analytical Performance of an Eight Position Dynamic Olfactometer

The European technical standard \u201cAir Quality\u2014Determination of Odour Concentration by Dynamic Olfactometry\u201d adopts dynamic olfactometry, a sensorial methodology based on the employment of a panel of human assessors, as the official methodology for the measurement of odour concentration in gas samples. The olfactometer is the device, useful to dilute the odor sample with neutral air, according to precise ratios and to present it to the panel for the analysis. The present paper describes the development of an Italian olfactometer, able to host eight assessors, designed to improve the instrumental performance of the devices actually present on the market, and to increase the accuracy and repeatability of the olfactometric measurement. In particular, in the paper the principal features of the instrumental device and the results of calibrations of dilution valves will be shown