Ubiquitous defect-induced density wave instability in monolayer graphene.

Quantum materials are notoriously sensitive to their environments, where small perturbations can tip a system toward one of several competing ground states. Graphene hosts a rich assortment of such competing phases, including a bond density wave instability ("Kekulé distortion") that couples electrons at the K/K' valleys and breaks the lattice symmetry. Here, we report observations of a ubiquitous Kekulé distortion across multiple graphene systems. We show that extremely dilute concentrations of surface atoms (less than three adsorbed atoms every 1000 graphene unit cells) can self-assemble and trigger the onset of a global Kekulé density wave phase. Combining complementary momentum-sensitive angle-resolved photoemission spectroscopy (ARPES) and low-energy electron diffraction (LEED) measurements, we confirm the presence of this density wave phase and observe the opening of an energy gap. Our results reveal an unexpected sensitivity of the graphene lattice to dilute surface disorder and show that adsorbed atoms offer an attractive route toward designing novel phases in two-dimensional materials.

[The new Parkinson's disease pain classification system (PD-PCS)]. / Die neue Parkinson-Schmerzklassifikation (PSK).

BACKGROUND: Chronic pain is a common non-motor symptom in patients with Parkinson's disease (PD). AIM: To facilitate the diagnosis of pain in PD, we developed a new classification system the Parkinson's disease pain classification system (PD-PCS) and translated the corresponding validated questionnaire into German. METHODS: A causal relationship of the respective pain syndrome with PD can be determined by four questions before assigning it hierarchically into one of three pain categories (neuropathic, nociceptive and nociplastic). RESULTS: In the initial validation study 77% of the patients (122/159) had PD-associated pain comprising 87 (55%) with nociceptive, 36 (22%) with nociplastic and 24 (16%) with neuropathic pain. The study revealed a high validity of the questionnaire and a moderate intrarater and interrater reliability. The questionnaire has been adapted into German and employed in 30 patients. DISCUSSION: The PD-PCS questionnaire is a valid and reliable tool to determine the relationship of a pain syndrome with PD before classifying it according to the underlying category, facilitating further diagnostics and treatment.

Room temperature strain-induced Landau levels in graphene on a wafer-scale platform.

Graphene is a powerful playground for studying a plethora of quantum phenomena. One of the remarkable properties of graphene arises when it is strained in particular geometries and the electrons behave as if they were under the influence of a magnetic field. Previously, these strain-induced pseudomagnetic fields have been explored on the nano- and micrometer-scale using scanning probe and transport measurements. Heteroepitaxial strain, in contrast, is a wafer-scale engineering method. Here, we show that pseudomagnetic fields can be generated in graphene through wafer-scale epitaxial growth. Shallow triangular nanoprisms in the SiC substrate generate strain-induced uniform fields of 41 T, enabling the observation of strain-induced Landau levels at room temperature, as detected by angle-resolved photoemission spectroscopy, and confirmed by model calculations and scanning tunneling microscopy measurements. Our work demonstrates the feasibility of exploiting strain-induced quantum phases in two-dimensional Dirac materials on a wafer-scale platform, opening the field to new applications.

Dual-comb spectroscopy of water vapor with a free-running semiconductor disk laser.

Dual-comb spectroscopy offers the potential for high accuracy combined with fast data acquisition. Applications are often limited, however, by the complexity of optical comb systems. Here we present dual-comb spectroscopy of water vapor using a substantially simplified single-laser system. Very good spectroscopy measurements with fast sampling rates are achieved with a free-running dual-comb mode-locked semiconductor disk laser. The absolute stability of the optical comb modes is characterized both for free-running operation and with simple microwave stabilization. This approach drastically reduces the complexity for dual-comb spectroscopy. Band-gap engineering to tune the center wavelength from the ultraviolet to the mid-infrared could optimize frequency combs for specific gas targets, further enabling dual-comb spectroscopy for a wider range of industrial applications.

Optical efficiency and gain dynamics of modelocked semiconductor disk lasers.

Compact optically pumped passively modelocked semiconductor disk lasers (SDLs) based on active quantum wells (QWs) such as vertical external-cavity surface-emitting lasers (VECSELs) or modelocked integrated external-cavity surface-emitting lasers (MIXSELs) are wavelength-versatile sources that offer a unique combination of gigahertz pulse repetition rates and short pulse durations. In this paper, we present record-short pulses of 184 fs from a gigahertz MIXSEL emitting at a center wavelength of 1048 nm. This result comes at the expense of low optical-to-optical pump efficiency (<1%) and average output power limited to 115 mW. We experimentally observe that shorter pulses significantly reduce the macroscopic gain saturation fluence and develop a QW model based on rate equations to reproduce the gain saturation behavior and quantitatively explain the VECSEL and MIXSEL modelocking performances. We identify spectral hole burning as the main cause of the reduced gain at shorter pulse durations, which in combination with the short lifetime of the excited carriers strongly reduces the optical pump efficiency. Our better understanding will help to address these limitations in future ultrafast SDL designs.

Pyridostigmine bromide versus fludrocortisone in the treatment of orthostatic hypotension in Parkinson's disease - a randomized controlled trial.

BACKGROUND AND PURPOSE: Evidence for effective treatment options for orthostatic hypotension (OH) in Parkinson's disease (PD) is scarce. Elevation of cholinergic tone with pyridostigmine bromide has been reported as a way to improve blood pressure (bp) regulation in neurogenic hypotension without causing supine hypertension. METHODS: This was a double-centre, double-blind, randomized, active-control, crossover, phase II non-inferiority trial of pyridostigmine bromide for OH in PD (clinicaltrials.gov NCT01993680). Patients with confirmed OH were randomized to 14 days 3 × 60 mg/day pyridostigmine bromide or 1 × 0.2 mg/day fludrocortisone before crossover. Outcome was measured by peripheral and central bp monitoring during the Schellong manoeuvre and questionnaires. RESULTS: Thirteen participants were enrolled between April 2013 and April 2015 with nine participants completing each trial arm. Repeated measures comparison showed a significant 37% improvement with fludrocortisone for the primary outcome diastolic bp drop on orthostatic challenge (baseline 22.9 ± 13.6 vs. pyridostigmine bromide 22.1 ± 17.0 vs. fludrocortisone 14.0 ± 12.6 mmHg; P = 0.04), whilst pyridostigmine bromide had no effect. Fludrocortisone caused an 11% peripheral systolic supine bp rise (baseline 128.4 ± 12.8 vs. pyridostigmine bromide 130.4 ± 18.3 vs. fludrocortisone 143.2 ± 10.1 mmHg; P = 0.01) but no central mean arterial supine bp rise (baseline 107.2 ± 7.8 vs. pyridostigmine bromide 97.0 ± 12.0 vs. fludrocortisone 107.3 ± 6.3 mmHg; P = 0.047). Subjective OH severity, motor score and quality of life remained unchanged by both study interventions. CONCLUSIONS: Pyridostigmine bromide is inferior to fludrocortisone in the treatment of OH in PD. This trial provides first objective evidence of the efficacy of 0.2 mg/day fludrocortisone for OH in PD, causing minor peripheral but no central supine hypertension. In addition to peripheral bp, future trials should include central bp measurements, known to correlate more closely with cardiovascular risk.

Self-reference in psychosis and depression: a language marker of illness.

BACKGROUND: Language use is of increasing interest in the study of mental illness. Analytical approaches range from phenomenological and qualitative to formal computational quantitative methods. Practically, the approach may have utility in predicting clinical outcomes. We harnessed a real-world sample (blog entries) from groups with psychosis, strong beliefs, odd beliefs, illness, mental illness and/or social isolation to validate and extend laboratory findings about lexical differences between psychosis and control subjects. METHOD: We describe the results of two experiments using Linguistic Inquiry and Word Count software to assess word category frequencies. In experiment 1, we compared word use in psychosis and control subjects in the laboratory (23 per group), and related results to subject symptoms. In experiment 2, we examined lexical patterns in blog entries written by people with psychosis and eight comparison groups. In addition to between-group comparisons, we used factor analysis followed by clustering to discern the contributions of strong belief, odd belief and illness identity to lexical patterns. RESULTS: Consistent with others' work, we found that first-person pronouns, biological process words and negative emotion words were more frequent in psychosis language. We tested lexical differences between bloggers with psychosis and multiple relevant comparison groups. Clustering analysis revealed that word use frequencies did not group individuals with strong or odd beliefs, but instead grouped individuals with any illness (mental or physical). CONCLUSIONS: Pairing of laboratory and real-world samples reveals that lexical markers previously identified as specific language changes in depression and psychosis are probably markers of illness in general.

Structural and Electronic Properties of Nitrogen-Doped Graphene.

We investigate the structural and electronic properties of nitrogen-doped epitaxial monolayer graphene and quasifreestanding monolayer graphene on 6H-SiC(0001) by the normal incidence x-ray standing wave technique and by angle-resolved photoelectron spectroscopy supported by density functional theory simulations. With the location of various nitrogen species uniquely identified, we observe that for the same doping procedure, the graphene support, consisting of substrate and interface, strongly influences the structural as well as the electronic properties of the resulting doped graphene layer. Compared to epitaxial graphene, quasifreestanding graphene is found to contain fewer nitrogen dopants. However, this lack of dopants is compensated by the proximity of nitrogen atoms at the interface that yield a similar number of charge carriers in graphene.

Tracking Primary Thermalization Events in Graphene with Photoemission at Extreme Time Scales.

Direct and inverse Auger scattering are amongst the primary processes that mediate the thermalization of hot carriers in semiconductors. These two processes involve the annihilation or generation of an electron-hole pair by exchanging energy with a third carrier, which is either accelerated or decelerated. Inverse Auger scattering is generally suppressed, as the decelerated carriers must have excess energies higher than the band gap itself. In graphene, which is gapless, inverse Auger scattering is, instead, predicted to be dominant at the earliest time delays. Here, <8 fs extreme-ultraviolet pulses are used to detect this imbalance, tracking both the number of excited electrons and their kinetic energy with time-and angle-resolved photoemission spectroscopy. Over a time window of approximately 25 fs after absorption of the pump pulse, we observe an increase in conduction band carrier density and a simultaneous decrease of the average carrier kinetic energy, revealing that relaxation is in fact dominated by inverse Auger scattering. Measurements of carrier scattering at extreme time scales by photoemission will serve as a guide to ultrafast control of electronic properties in solids for petahertz electronics.

Word use in first-person accounts of schizophrenia.

BACKGROUND: Language use is often disrupted in patients with schizophrenia; novel computational approaches may provide new insights. AIMS: To test word use patterns as markers of the perceptual, cognitive and social experiences characteristic of schizophrenia. METHOD: Word counting software was applied to first-person accounts of schizophrenia and mood disorder. RESULTS: More third-person plural pronouns ('they') and fewer first-person singular pronouns ('I') were used in schizophrenia than mood disorder accounts. Schizophrenia accounts included fewer words related to the body and ingestion, and more related to religion. Perceptual and causal language were negatively correlated in schizophrenia accounts but positively correlated in mood disorder accounts. CONCLUSIONS: Differences in pronouns suggest decreased self-focus or perhaps even an understanding of self as other in schizophrenia. Differences in how perceptual and causal words are correlated suggest that long-held delusions represent a decreased coupling of explanations with sensory experience over time.

Detection of nickel and palladium contact hypersensitivity by a flow cytometric lymphocyte proliferation test.

We established a flow cytometric lymphocyte proliferation test (LPT) for the detection of nickel (Ni) and palladium (Pd) sensitization. Eighty-one consecutive patients with an indication for patch test (PT) were tested by LPT with Ni (NiSO4 ) and Pd (Na2 PdCl4 and PdCl2 ) salts. The imprecision of the LPT was low (coefficient of variation 7.2%). Using PT as a diagnostic reference, the sensitivity and specificity of LPT were 74.4% and 80% for NiSO4 , 74.4% and 78.3% for Na2 PdCl4 , and 57.2% and 85.4% for PdCl2 , respectively. For both Ni and Pd, the likelihood ratio for a positive PT markedly increased with increasing LPT value. With medical history as a reference, the sensitivity and specificity were 40.6% and 82.1% for LPT and 59.4% and 89.7% for PT, respectively. Combination of LPT and PT resulted in a higher specificity of 95%, albeit lower sensitivity of 34.4%. In conclusion, flow cytometric LPT represents a reliable and useful method for the detection of Ni and Pd sensitization. LPT values correlate with PT results and, when used in combination with PT, increase test specificity.

Probing a century old prediction one plasmonic particle at a time.

In 1908, Gustav Mie solved Maxwell's equations to account for the absorption and scattering of spherical plasmonic particles. Since then much attention has been devoted to the size dependent optical properties of metallic nanoparticles. However, ensemble measurements of colloidal solutions generally only yield the total extinction cross sections of the nanoparticles. Here, we show how Mie's prediction on the size dependence of the surface absorption and scattering can be probed separately for the same gold nanoparticle by using two single particle spectroscopy techniques, (1) dark-field scattering and (2) photothermal imaging, which selectively only measure scattering and absorption, respectively. Combining the optical measurements with correlated scanning electron microscopy furthermore allowed us to measure the size of the spherical gold nanoparticles, which ranged from 43 to 274 nm in diameter. We found that even though the trend predicted by Mie theory is followed well by the experimental data over a large range of nanoparticle diameters, for small size variations changes in scattering and absorption intensities are dominated by factors other than those considered by Mie theory. In particular, spectral shifts of the plasmon resonance due to deviations from a spherical particle shape alone cannot explain the observed variation in absorption and scattering intensities.

Evaluation of the autonomic nervous system using the FAN device -- range of normal and examples of abnormal.

Different components of the autonomic nervous system may be affected by different disorders to varying degrees. The aim of this study is to report first experiences with a new device (FAN(R), Schwarzer, Germany) which measures heart rate variability (HRV), sympathetic skin responses (SSR) and the pulse wave transit time (PTT). We examined 190 healthy volunteers (102 men, 88 women) and in 89 subjects (46 men, 43 women) PTT during VM was investigated. In a subset of 24 subjects PTT was compared to conventional blood pressure recording. Thereafter, normal data were compared to patients with polyneuropathy (PNP) and Parkinson syndromes. All parameters of HRV decreased with age. 6 parameters for HRV at rest, during deep respiration and the valsalva ratio were reclassified into three age categories: under 40 (n=96), 40 - 60 (n=71) and 60 or older (n=23). Applying the lower limits of normal (5%-tile) subjects did not have more than 2 of these 6 parameters in the pathological range PTT reduction during phase IV of the valsalva manoeuvre was greater than 7.7 ms (5%-tile) but not age dependent. Patients with PNP had reduced HRV and SSR, Parkinson patients had more frequently impaired blood pressure regulation according to PTT assessment. Our investigation shows that the FAN(R) might be useful for clinicians to detect autonomic disorders.

[Three-dimensional echocardiography in cardiac surgery. Current status and perspectives]. / Klinischer Einsatz der 3D-Echokardiographie in der Herzchirurgie. Aktueller Stand und Perspektiven.

Three-dimensional (3D) echocardiography is a new imaging technique that can provide useful information about cardiovascular morphology, pathology, and function. Recent refinements in instrumentation, data acquisition, post-processing, and computation speed allow 3D echocardiography to play an important role in cardiac imaging. These modalities provide comprehensive information on ventricular and valve morphology and function. Combined with 3D color Doppler sonography, further assessment of valvular function and determination of flow in the left ventricular outflow tract and cross-septal defects are now possible. Three-dimensional color flow imaging also makes echocardiography accurate for assessing the severity of mitral regurgitation. The purpose of this review is to describe technical developments in 3D echocardiography and its clinical application in cardiac surgery. Moreover, based on clinical studies at our centre, we describe the morphology of the mitral valve, its flow pattern, and function of the mitral annulus.

Structure and dynamics of conjugated polymers in liquid crystalline solvents.

A combination of single-molecule spectroscopy and analysis with simulations is used to provide detailed information about the structural and dynamic properties of a fluorescent polymer MEH-PPV (poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene]) immersed in a nematic and smectic solvent. In nematic solvents, single-polymer molecules are oriented strongly along the solvent director, much more so than the solvent molecules, confirming Onsager's old prediction. The diffusion anisotropy parallel and perpendicular to the solvent director, however, is less than two, which is similar to that of a spherical colloid in a nematic solvent. In smectic solvents, there is a second orientation of the dissolved polymer perpendicular to the solvent director, which we hypothesize is caused by the polymer occupying the interlayer volume. The research discussed here emphasizes the importance of organization in complex fluids and suggests that the interplay of order on different length scales could be exploited to fabricate novel nanostructured materials.

Three-dimensional assessment of left ventricular geometry and annular dilatation provides new mechanistic insights into the surgical correction of ischemic mitral regurgitation.

BACKGROUND: The aim of this study was to investigate the relationship between LV geometry, annular shape and the amount of regurgitation in patients with ischemic mitral regurgitation (group 1, n = 30) compared to patients with primary mitral valve lesions (group 2, n = 30). METHODS: LV geometry was assessed by the sphericity index, i.e., LV volume divided by the volume of a sphere with a diameter equal to the longest axis. Annular geometry was evaluated by diameters, areas and their percentual shortening. The degree of mitral regurgitation was assessed as jet volumes by 3D-echocardiography. RESULTS: Group 1 showed significantly larger longitudinal (54.3 +/- 3.1 vs. 40.9 +/- 2.6 mm) and antero-posterior (32.2 +/- 3.3 vs. 27.1 +/- 2.9 mm) annulus diameters and areas (993.3 +/- 66.6 vs. 702.1 +/- 47.9 mm (2)) than group 2. No asymmetric annular enlargement was found in either group. Annular enlargement correlated to the degree of mitral regurgitation in group 1 but not in group 2. Annular area shortening was significantly impaired in group 2 and the sphericity index was larger in group 1 than in group 2. In group 1, the sphericity index was significantly correlated to the degree of mitral regurgitation (r = 0.87; P < 0.001). CONCLUSIONS: These findings suggest that ischemic mitral regurgitation was mostly associated with a global left ventricular enlargement, in which annulus dilatation and its reduced contraction play a significant role.

Nematic solvation of segmented polymer chains.

We examine the effect of polymer chain segmentation on the recently discovered ability of nematic solvents to elongate and align polymer chain solutes. Coordinated single molecule spectroscopy and beads-on-a-chain simulations are used to study the orientational and conformational order of a series of segmented conjugated polymers, dissolved in the nematic liquid crystal 5CB. The order parameters for alignment and elongation are both observed to decrease with increasing segmentation, reflecting an interplay among conformational entropy, solvation anisotropy, and bending energy of the chain.