Surface resonance of the (2×1) reconstructed lanthanum hexaboride (001)-cleavage plane : a combined STM and DFT study

We performed a combined study of the (001)-cleavage plane of lanthanum hexaboride (LaB6) using scanning tunneling microscopy and density-functional theory (DFT). Experimentally, we found a (2×1) reconstructed surface on a local scale. The reconstruction is only short-range ordered and tends to order perpendicularly to step edges. At larger distances from surface steps, the reconstruction evolves to a labyrinthlike pattern. These findings are supported by low-energy electron diffraction experiments. Slab calculations within the framework of DFT show that the atomic structure consists of parallel lanthanum chains on top of boron octahedra. Scanning tunneling spectroscopy shows a prominent spectral feature at −0.6eV. Using DFT, we identify this structure as a surface resonance of the (2×1) reconstructed LaB6 (100) surface which is dominated by boron dangling bond states and lanthanum d states

Verbesserte Risikostratifizierung von Patienten mit Verdacht auf ein akutes Koronarsyndrom ohne ST-Streckenhebung durch hochsensitiv gemessenes Troponin T und Copeptin

Das akute Koronarsyndrom (ACS) stellt eine kritische Phase der KHK dar, die mit hoher Morbidität und Mortalität verbunden ist. Anhand des EKGs werden die Patienten in ACS mit ST-Streckenhebung (STEMI) und ohne ST-Streckenhebung (NSTE-ACS) eingeteilt. In letzterer Gruppe unterscheidet man Patienten mit NSTEMI und instabiler Angina (IAP). Hierbei gilt die Troponinbestimmung als Goldstandard bei der Diagnosestellung und Risikostratifizierung. Mit der Einführung hochsensitiver Troponinassays konnte die Identifizierung von Hochrisikopatienten weiter verbessert werden. Allerdings erlauben auch diese immer noch nicht die Erkennung von Patienten mit erst kurz zurückliegendem Brustschmerz und erfordern meist eine sequentielle Testung. Deshalb sind zusätzliche Biomarker wie zum Beispiel das Copeptin von Interesse, um die Diagnostik von Patienten mit Verdacht auf ACS zu verbessern. Copeptin wird als c-terminales Fragment des Arginin-Vasopressin- Prohormons zusammen mit Vasopressin unter akuten Stressbedingungen wie dem AMI von der Neurohypophyse sezerniert. Das Ziel der vorliegenden Arbeit war es, die diagnostische und prognostische Wertigkeit von Copeptin und hochsensitivem c-TnT (hs-cTnT) bei Patienten mit Verdacht auf ein NSTE-ACS zu untersuchen. Bei 321 Patienten mit vermutetem NSTE-ACS wurden hs-cTnT, cTnT und Copeptin zum Aufnahmezeitpunkt bestimmt. Hiervon wurden 137 (42,6%) Patienten aus einer anderen Klinik zugewiesen. Bei 201 (62,6%) Patienten wurde die Diagnose NSTEMI gestellt, 87 (27,1%) hatten eine instabile Angina pectoris und 33 (10,3%) Patienten hatten kein ACS. Die diagnostische Genauigkeit von hs-cTnT zur Diskriminierung von Patienten mit NSTEMI war der von konventionell gemessenem cTnT und Copeptin überlegen. Copeptin bot keinen zusätzlichen Gewinn gegenüber hs-cTnT in der Diagnosestellung des NSTEMI in der vorliegenden Untersuchung („rule in“). Wenn die initiale Troponinkonzentration kleiner der 99. Perzentile gemessen wird und die additive Copeptinbestimmung ebenfalls kleiner der 99. Perzentile ist, so kann allerdings ein AMI mit sehr hoher Wahrscheinlichkeit ausgeschlossen werden („rule out“). In der gegenwärtigen Arbeit war jedoch der Patientenanteil mit einer Troponinkonzentration kleiner der 99. Perzentile im Vergleich zu anderen ACS-Populationen sehr gering. Lediglich 46 Patienten der in der vorliegenden Arbeit untersuchten Patienten hatten eine Troponinkonzentration 14 pmol/L und somit ein erhöhtes Risiko. Die Copeptinkonzentration war im Median bei NSTEMI-Patienten höher als die bei Patienten mit instabiler AP. Allerdings war nur bei 59,2% der NSTEMI-Patienten eine Copeptinkonzentration oberhalb der 99. Perzentile messbar. Patienten, die aus anderen Krankenhäusern zugewiesen wurden, hatten weniger häufig eine erhöhte Copeptinkonzentration. Die Zeit von Symptombeginn bis zur Blutentnahme war bei diesen Patienten länger. Die Cox-Regressionsanalyse veranschaulicht, dass die Copeptinkonzentration direkt von der Zeitverzögerung des Transfers abhängen. Die Zeitverzögerung von Symptombeginn bis zur Blutentnahme muss deshalb in die Interpretation der Copeptinwerte bei Patienten mit Verdacht auf ACS einbezogen werden. Ein diagnostischer Vorteil von Copeptin in der Diagnostik von Patienten mit Verdacht auf ein NSTE-ACS konnte in dieser retrospektiven Analyse nicht gezeigt werden. Jedoch stellt sich Copeptin, neben kardialem Troponin T, als prädiktiver Faktor für die Mortalität innerhalb der ersten 6 Monate und 5 Jahre nach ursprünglicher Hospitalisierung heraus. Die endgültige Bewertung des Stellenwertes von Copeptin in der Diagnostik des ACS wird derzeit in einer multizentrisch-randomisierten Studie untersucht.The acute coronary syndrome (ACS) represents the critical phase of the coronary artery disease, which is associated with high morbidity and mortality. Based on the ECG, patients are subdivided in ACS with ST-Elevation (STEMI) and without ST-Elevation (NSTE-ACS). In the latter group patients with non-ST-elevation myocardial infarction (NSTEMI) and unstable angina (UA) are differentiated. In this setting, troponin (cTnT) measurements are regarded as gold standard for diagnosis finding and risk stratification. The introduction of high-sensitive troponin (hs-cTnT) assays allowed improving identification of high-risk patients. However, in patients presenting early after chest pain onset, sequential testing is still necessary. Accordingly, additional biomarkers like copeptin are of interest to improve early diagnosis and risk stratification of patients with ACS. Copeptin, the c-terminal fragment of the arginine-vasopressin-prohormon, is released under stress conditions, e.g. AMI, from the pituitary gland. The aim of this study was to investigate the diagnostic and prognostic role of copeptin and hs-cTnT in patients presenting with symptoms suggestive of ACS. In 321 patients with suspected NSTE-ACS hs-cTnT, cTnT and copeptin were determined on hospital admission. Out of these, 137 (42,6%) patients were transferred from other hospitals. In total, 201 (62,6%) had the discharge diagnosis of NSTEMI, 87 (27,1%) presented with UA, and in 33 (10,3%) patients ACS could be excluded. The diagnostic accuracy of hs-cTnT for discriminating patients with NSTEMI was superior compared to cTnT and copeptin. Accordingly, the measurement of copeptin alone did not provide any additional benefit in diagnosing NSTEMI compared to hs-cTnT in our cohort („rule in“). This is in contrast to other published data demonstrating that the measurement of copeptin improves early “rule-out” of AMI. When copeptin and troponin values were below the 99.percentile on admission, AMI could reliably be excluded. However, in contrast to published ACS populations the proportion of patients with troponin concentrations below the 99. percentile was very low in our study cohort. Only 46 (14.3%) patients had troponin values <14ng/L, but in 1/3 of these patients with later diagnosed ACS had elevated copeptin levels at presentation. The median copeptin concentration was higher in patients with NSTEMI than in patients with UA. However only 60% of the patients with NSTEMI had elevated copeptin levels. In patients referred from other hospitals copeptin was less frequently elevated, which was linked to longer time delay from symptom onset until first blood sample. Cox-regression analysis confirmed that copeptin concentrations are directly related to time delay of transfer. In conclusion time delay from symptom onset until first blood sample should be considered for the interpretation of copeptin level in general. The improvement in diagnosing ACS by adding copeptin could not be demonstrated in this retrospective analysis. However copeptin proved to carry independent value in predicting mortality 6 month and 5 years after initial hospitalization. The clinical role of copeptin for diagnosing ACS is currently analyzed further in a randomized multicenter trial

On the robustness of entanglement in analogue gravity systems

We investigate the possibility of generating quantum-correlated quasi-particles utilizing analogue gravity systems. The quantumness of these correlations is a key aspect of analogue gravity effects and their presence allows for a clear separation between classical and quantum analogue gravity effects. However, experiments in analogue systems, such as Bose–Einstein condensates (BECs) and shallow water waves, are always conducted at non-ideal conditions, in particular, one is dealing with dispersive media at non-zero temperatures. We analyse the influence of the initial temperature on the entanglement generation in analogue gravity phenomena. We lay out all the necessary steps to calculate the entanglement generated between quasi-particle modes and we analytically derive an upper bound on the maximal temperature at which given modes can still be entangled. We further investigate a mechanism to enhance the quantum correlations. As a particular example, we analyse the robustness of the entanglement creation against thermal noise in a sudden quench of an ideally homogeneous BEC, taking into account the super-sonic dispersion relations

The entangling side of the Unruh-Hawking effect

We show that the Unruh effect can create net quantum entanglement between inertial and accelerated observers depending on the choice of the inertial state. This striking result banishes the extended belief that the Unruh effect can only destroy entanglement and furthermore provides a new and unexpected source for finding experimental evidence of the Unruh and Hawking effects.Comment: 4 pages, 4 figures. Added Journal referenc

The one-dimensional Keller-Segel model with fractional diffusion of cells

We investigate the one-dimensional Keller-Segel model where the diffusion is replaced by a non-local operator, namely the fractional diffusion with exponent $0<\alpha\leq 2$. We prove some features related to the classical two-dimensional Keller-Segel system: blow-up may or may not occur depending on the initial data. More precisely a singularity appears in finite time when $\alpha<1$ and the initial configuration of cells is sufficiently concentrated. On the opposite, global existence holds true for $\alpha\leq1$ if the initial density is small enough in the sense of the $L^{1/\alpha}$ norm.Comment: 12 page

Combined Evaluation of FDG-PET and MRI Improves Detection and Differentiation of Dementia

INTRODUCTION: Various biomarkers have been reported in recent literature regarding imaging abnormalities in different types of dementia. These biomarkers have helped to significantly improve early detection and also differentiation of various dementia syndromes. In this study, we systematically applied whole-brain and region-of-interest (ROI) based support vector machine classification separately and on combined information from different imaging modalities to improve the detection and differentiation of different types of dementia. METHODS: Patients with clinically diagnosed Alzheimer's disease (AD: n = 21), with frontotemporal lobar degeneration (FTLD: n = 14) and control subjects (n = 13) underwent both [F18]fluorodeoxyglucose positron emission tomography (FDG-PET) scanning and magnetic resonance imaging (MRI), together with clinical and behavioral assessment. FDG-PET and MRI data were commonly processed to get a precise overlap of all regions in both modalities. Support vector machine classification was applied with varying parameters separately for both modalities and to combined information obtained from MR and FDG-PET images. ROIs were extracted from comprehensive systematic and quantitative meta-analyses investigating both disorders. RESULTS: Using single-modality whole-brain and ROI information FDG-PET provided highest accuracy rates for both, detection and differentiation of AD and FTLD compared to structural information from MRI. The ROI-based multimodal classification, combining FDG-PET and MRI information, was highly superior to the unimodal approach and to the whole-brain pattern classification. With this method, accuracy rate of up to 92% for the differentiation of the three groups and an accuracy of 94% for the differentiation of AD and FTLD patients was obtained. CONCLUSION: Accuracy rate obtained using combined information from both imaging modalities is the highest reported up to now for differentiation of both types of dementia. Our results indicate a substantial gain in accuracy using combined FDG-PET and MRI information and suggest the incorporation of such approaches to clinical diagnosis and to differential diagnostic procedures of neurodegenerative disorders

On an exponential attractor for a class of PDEs with degenerate diffusion and chemotaxis

In this article we deal with a class of strongly coupled parabolic systems that encompasses two different effects: degenerate diffusion and chemotaxis. Such classes of equations arise in the mesoscale level modeling of biomass spreading mechanisms via chemotaxis. We show the existence of an exponential attractor and, hence, of a finite-dimensional global attractor under certain 'balance conditions' on the order of the degeneracy and the growth of the chemotactic function