Magnon interactions in a moderately correlated Mott insulator.

Quantum fluctuations in low-dimensional systems and near quantum phase transitions have significant influences on material properties. Yet, it is difficult to experimentally gauge the strength and importance of quantum fluctuations. Here we provide a resonant inelastic x-ray scattering study of magnon excitations in Mott insulating cuprates. From the thin film of SrCuO2, single- and bi-magnon dispersions are derived. Using an effective Heisenberg Hamiltonian generated from the Hubbard model, we show that the single-magnon dispersion is only described satisfactorily when including significant quantum corrections stemming from magnon-magnon interactions. Comparative results on La2CuO4 indicate that quantum fluctuations are much stronger in SrCuO2 suggesting closer proximity to a magnetic quantum critical point. Monte Carlo calculations reveal that other magnetic orders may compete with the antiferromagnetic Néel order as the ground state. Our results indicate that SrCuO2-due to strong quantum fluctuations-is a unique starting point for the exploration of novel magnetic ground states.

Multi-scale time-resolved electron diffraction: A case study in moiré materials.

Ultrafast-optical-pump - structural-probe measurements, including ultrafast electron and x-ray scattering, provide direct experimental access to the fundamental timescales of atomic motion, and are thus foundational techniques for studying matter out of equilibrium. High-performance detectors are needed in scattering experiments to obtain maximum scientific value from every probe particle. We deploy a hybrid pixel array direct electron detector to perform ultrafast electron diffraction experiments on a WSe2/MoSe2 2D heterobilayer, resolving the weak features of diffuse scattering and moiré superlattice structure without saturating the zero order peak. Enabled by the detector's high frame rate, we show that a chopping technique provides diffraction difference images with signal-to-noise at the shot noise limit. Finally, we demonstrate that a fast detector frame rate coupled with a high repetition rate probe can provide continuous time resolution from femtoseconds to seconds, enabling us to perform a scanning ultrafast electron diffraction experiment that maps thermal transport in WSe2/MoSe2 and resolves distinct diffusion mechanisms in space and time.

Gapped Collective Charge Excitations and Interlayer Hopping in Cuprate Superconductors.

We use resonant inelastic x-ray scattering to probe the propagation of plasmons in the electron-doped cuprate superconductor Sr_{0.9}La_{0.1}CuO_{2}. We detect a plasmon gap of ∼120 meV at the two-dimensional Brillouin zone center, indicating that low-energy plasmons in Sr_{0.9}La_{0.1}CuO_{2} are not strictly acoustic. The plasmon dispersion, including the gap, is accurately captured by layered t-J-V model calculations. A similar analysis performed on recent resonant inelastic x-ray scattering data from other cuprates suggests that the plasmon gap is generic and its size is related to the magnitude of the interlayer hopping t_{z}. Our work signifies the three dimensionality of the charge dynamics in layered cuprates and provides a new method to determine t_{z}.

Single-Crystal Alkali Antimonide Photocathodes: High Efficiency in the Ultrathin Limit.

The properties of photoemission electron sources determine the ultimate performance of a wide class of electron accelerators and photon detectors. To date, all high-efficiency visible-light photocathode materials are either polycrystalline or exhibit intrinsic surface disorder, both of which limit emitted electron beam brightness. In this Letter, we demonstrate the synthesis of epitaxial thin films of Cs_{3}Sb on 3C-SiC (001) using molecular-beam epitaxy. Films as thin as 4 nm have quantum efficiencies exceeding 2% at 532 nm. We also find that epitaxial films have an order of magnitude larger quantum efficiency at 650 nm than comparable polycrystalline films on Si. Additionally, these films permit angle-resolved photoemission spectroscopy measurements of the electronic structure, which are found to be in good agreement with theory. Epitaxial films open the door to dramatic brightness enhancements via increased efficiency near threshold, reduced surface disorder, and the possibility of engineering new photoemission functionality at the level of single atomic layers.

A kiloelectron-volt ultrafast electron micro-diffraction apparatus using low emittance semiconductor photocathodes.

We report the design and performance of a time-resolved electron diffraction apparatus capable of producing intense bunches with simultaneously single digit micrometer probe size, long coherence length, and 200 fs rms time resolution. We measure the 5d (peak) beam brightness at the sample location in micro-diffraction mode to be 7 × 10 13 A / m 2 rad 2 . To generate high brightness electron bunches, the system employs high efficiency, low emittance semiconductor photocathodes driven with a wavelength near the photoemission threshold at a repetition rate up to 250 kHz. We characterize spatial, temporal, and reciprocal space resolution of the apparatus. We perform proof-of-principle measurements of ultrafast heating in single crystal Au samples and compare experimental results with simulations that account for the effects of multiple scattering.

Low temperature hidden Fermi-liquid charge transport in under doped La x Sr1-x CuO2 infinite layer electron-doped thin films.

We have studied the low temperature electrical transport properties of La x Sr1-x CuO2 thin films grown by oxide molecular beam epitaxy on (1 1 0) GdScO3 and TbScO3 substrates. The transmission electron microscopy measurements and the x-ray diffraction analysis confirmed the epitaxy of the obtained films and the study of their normal state transport properties, removing the ambiguity regarding the truly conducting layer, allowed to highlight the presence of a robust hidden Fermi liquid charge transport in the low temperature properties of infinite layer electron doped cuprate superconductors. These results are in agreement with recent observations performed in other p  and n doped cuprate materials and point toward a general description of the superconducting and normal state properties in these compounds.

Nonequilibrium fluctuations as a distinctive feature of weak localization.

Two-dimensional materials, such as graphene, topological insulators, and two-dimensional electron gases, represent a technological playground to develop coherent electronics. In these systems, quantum interference effects, and in particular weak localization, are likely to occur. These coherence effects are usually characterized by well-defined features in dc electrical transport, such as a resistivity increase and negative magnetoresistance below a crossover temperature. Recently, it has been shown that in magnetic and superconducting compounds, undergoing a weak-localization transition, a specific low-frequency 1/f noise occurs. An interpretation in terms of nonequilibrium universal conductance fluctuations has been given. The universality of this unusual electric noise mechanism has been here verified by detailed voltage-spectral density investigations on ultrathin copper films. The reported experimental results validate the proposed theoretical framework, and also provide an alternative methodology to detect weak-localization effects by using electric noise spectroscopy.

Correlation between structural properties and resistivity critical behavior in SrRuO3 thin films.

SrRuO(3) is a strong itinerant ferromagnet showing many features of 'bad metals' together with Fermi liquid behavior at very low temperature. The intriguing magnetic and transport properties of SrRuO(3) are tightly related to structure, as commonly observed in transition metal oxides. Here we report on the correlation of structural parameters (lattice constant and surface roughness) with the critical behavior of resistivity at the Curie point in SrRuO(3) thin films deposited on (001) SrTiO(3) by PLD. By varying the deposition conditions we were able to obtain a wide variety of structural properties in our samples, thus allowing us to perform a systematic study. Our analysis demonstrates the direct correlation between the critical temperature T(P) and the lattice out-of-plane parameter. Furthermore, the value of the critical exponent λ is proved to be a good physical parameter to quantify the microscopic order of SrRuO(3) samples.

Pseudostenosis of axillary vein due to adduction of the upper limb.

Axillary vein stenosis is a well-documented complication in hemodialysis (HD) patients, but in adipose or athletic subjects, pseudostenosis of the axillary vein can be detected. We report a case of pseudostenosis in a fit dialysis patient who underwent phlebography of the right upper limb, performed to create a new vascular access (VA). The investigation demonstrated that the axillary vein appeared sharpened with a reduced lumen. Based on this exam, angioplasty of the right axillary vein was planned. The new phlebographic study, performed abducting the arm, demonstrated that the previously marked stenosis of the axillary vein disappeared. Our case illustrates how the reduction of the axillary vein lumen was secondary to ""muscular print"" and was present only if the arm was adducted. In uremic patients, the squeezing of the vascular nervous bundle of the upper limb is possible in fit patients at the time of phlebography, an examination that should be performed with the arm both in adduction and abduction.

Experimental technique for reducing contact and background noise in voltage spectral density measurements.

Electric noise measurements can give useful information on the conduction mechanisms and the dynamic behaviors of the charge carriers in new materials. However, it is well known that not all the electronic fluctuations are originated from the material itself, but some noise sources depend on the experimental procedures used for the measurements. In this article, an experimental technique to reduce "external" noise components, not associated with the bulk system, is presented. The proposed method is based on measurements of the voltage spectral density, using in sequence a four- and a two-probe technique. From the measurements it is possible to evaluate the contact and the background noise contributions and to recover the real spectral trace of the sample. The proposed procedure is demonstrated to be valid in spectral density measurements performed on La(0.7)Sr(0.3)MnO(3) thin films.

[MEN type 1 and chronic renal failure: a rarely reported association]. / MEN tipo 1 ed insufficienza renale: una associazione poco conosciuta.

BACKGROUND: Multiple endocrine neoplasia type 1 (MEN 1), or Wermer's syndrome, is a rare autosomal dominant genetic syndrome characterized by tumors or hyperplasia involving the pituitary, parathyroid, and pancreatic islet cells. Association between MEN 1 and nephrocalcinosis is well known, though data published in medical literature regarding Wermer's syndrome and chronic renal failure relation are still rare. CASE: A 70-year-old Caucasian female patient had a history of primitive hyperparathyroidism, prolactinoma, glucagonoma, adrenal adenoma and pulmonary neuroendocrine neoplasia. She presented at our clinic first when she was 62 years old because of hypertension, nephrolithiasis (calcium oxalate) and diabetes mellitus treated with oral agents. During the eight-year follow-up she developed chronic renal failure (serum creatinine 1.8 mg/dL, glomerular clearance 35 mL/min) and partial thrombosis of abdominal aortic wall. CONCLUSIONS: Although the association between renal failure and MEN 1 is rarely reported, patients affected by Wermer's syndrome have several risk factors of decreasing renal function such as hypertension, nephrolithiasis and diabetes mellitus. Moreover, hyperparathyroidism in MEN 1 is clinically similar to the kidney failure condition; indeed, diffuse hyper-plasia of more than one gland is common. Vitamin D should not be administered to these patients. Nephrologists should be involved in MEN 1 follow-up, with the aim to prevent kidney failure development by correcting risk factors.

Upper airway muscles dysfunction and levodopa responsiveness in Parkinson's disease.

Pulmonary function tests were performed before and at different times after 250 mg L-Dopa in 12 patients with Parkinson's disease (PD). Six were de-novo patients, the other six patients had been taking L-Dopa over different periods. All patients had an abnormal basal flow-volume loop, which significantly improved only in de-novo patients. This improvement occurred early and was independent on improvement of neurological symptoms. The effect of L-Dopa on pulmonary function could be a useful test in differentiating PD from related extrapyramidal syndromes.

High-dose intravenous immunoglobulin in the treatment of demyelinating neuropathy associated with monoclonal gammopathy.

We treated 2 patients with IgM monoclonal paraproteinemic demyelinating peripheral neuropathy (PPN) with monthly intravenous human immunoglobulin. Both patients had a steadily progressive course in spite of steroid and other immunosuppressive therapy for 3 years before starting the immunoglobulin therapy. Both had a rapid clinical improvement noticeable 5 to 10 days after the 1st immunoglobulin infusion lasting on the average of 3 to 6 weeks. Retreatment caused improvement after each consecutive infusion. There were no significant adverse side effects. High-dose IV human immunoglobulin can be a useful therapy in the treatment of PPN and warrants a large-scale controlled therapeutic trial.

An unusual case of carnitine palmitoyl transferase deficiency.

A 36-year-old man presented with episodic exertional dyspnea, fluctuating exercise intolerance, and myoglobinuria. He never experienced cramps or myalgias. Subsequent evaluation revealed carnitine palmitoyl transferase deficiency. The unusual features of this case suggested that carnitine palmitoyl transferase deficiency may have a more diverse clinical picture than previously described.

Paraneoplastic tonic pupils.

Tonic pupils developed in two patients with malignancies outside the nervous system. Symptoms and signs of more generalized somatic and autonomic nervous system involvement were also present. Although the exact morphologic basis for autonomic dysfunction in patients with paraneoplastic neurologic deterioration is uncertain, recent studies suggest that in some cases an autoimmune mechanism is responsible and may be directed against autonomic ganglion cells.

Lysosomal abnormalities in cultured schwann cells from a patient with peripheral neuropathy and continuous muscle fiber activity.

Schwann cell cultures were established from a sural nerve containing large membrane-bound vacuoles in its Schwann cells, obtained from a patient with neuropathy and continuous muscle fiber activity. Cultured Schwann cells contained many large membrane-bound vacuoles, presumably lysosomes, resembling those present in the biopsied nerve. The acid phosphatase reaction was excessive in the patient's cultured Schwann cells but practically negative in normal cultured Schwann cells. This study indicates that the patient's neuropathy is primary dysschwannian with abnormal lysosomes as a major abnormality.

Benign recurrent aseptic meningitis (Mollaret's meningitis): case report and clinical review.

Benign recurrent aseptic meningitis (Mollaret's meningitis) is rare. Only five cases have been reported in this country. This article reports another case and briefly reviews the characteristic manifestations of this disorder.

Essentials in the management of myasthenia gravis.

Myasthenia gravis is a disorder that most commonly affects young adults but occasionally appears in the elderly. Muscle weakness and easy fatigability, particularly of the ocular muscles, are characteristic. Diagnosis is confirmed by electromyography and the edrophonium (Tensilon) test. The pathology results from inability of acetylcholine to gain access to receptor sites at the neuromuscular junction, possibly because of a blocking antibody produced by the thymus. Initial treatment (in the absence of a thymoma) consists of administration of an anticholinesterase drug. If that is ineffective, thymectomy and/or corticosteroids may be useful.