Origin of the Magnetic Exciton in the van der Waals Antiferromagnet NiPS_{3}.

An ultrasharp photoluminescence line intimately related to antiferromagnetic order has been found in NiPS_{3}, a correlated van der Waals material, opening prospects for magneto-optical coupling schemes and spintronic applications. Here we unambiguously clarify the singlet origin of this excitation, confirming its roots in the spin structure. Based on a comprehensive investigation of the electronic structure using angle-resolved photoemission and q-dependent electron energy loss spectroscopy as experimental tools we develop, in a first step, an adequate theoretical understanding using density functional theory (DFT). In a second step the DFT is used as input for a dedicated multiplet theory by which we achieve excellent agreement with available multiplet spectroscopy. Our Letter connects the understanding of the electronic structure and of optical processes in NiPS_{3} and related materials as a prerequisite for further progress of the field.

Reevaluating limits of detection of 12 lateral flow immunoassays for the detection of Yersinia pestis, Francisella tularensis, and Bacillus anthracis spores using viable risk group-3 strains.

AIM: Rapid detection of biological agents in biodefense is critical for operational, tactical and strategic levels as well as for medical countermeasures. Yersinia pestis, Francisella tularensis, and Bacillus anthracis are high priority agents of biological warfare or bioterrorism and many response forces use lateral flow assays (LFAs) for their detection. Several companies produce these assays, which offer results in short time and are easy to use. Despite their importance, only few publications on the limits of detection (LOD) for LFAs are available. Most of these studies used inactivated bacteria or risk group-2 strains. As the inactivation process in previous studies might have affected the tests' performances, it was our aim in this study to determine and compare the LOD of several commercially available LFAs using viable risk group-3 strains. METHODS AND RESULTS: Lateral flow assays from four different companies for the detection of following bacteria were evaluated: Y. pestis, F. tularensis and B. anthracis spores. Two independent quantification methods for each target organism were applied, in order to ensure high quantification accuracy. LODs varied greatly between tests and organisms and ranged between 104 for Y. pestis-tests and as high as >109 for one B. anthracis-test. CONCLUSION: This work precisely determined the LODs of LFAs from four commercial suppliers. The herein determined LODs differed from results of previous studies. This illustrates the need for using accurately quantified viable risk group 3-strains for determining such LODs. SIGNIFICANCE AND IMPACT OF THE STUDY: Our work bridges an important knowledge gap with regard to LFA LOD. The LODs determined in this study will facilitate better assessment of LFA-results. They illustrate that a negative LFA result is not suited to exclude the presence of the respective agent in the analyzed sample.

[Prevalence of Gastroschisis, Omphalocele, Spina Bifida and Orofacial Clefts of Neonates from January 2000 to December 2010 in Leipzig, Saxony, Saxony-Anhalt and Germany]. / Prävalenz von Gastroschisis, Omphalozele, Spina bifida und orofazialen Spaltbildungen bei Neugeborenen im Zeitraum Januar 2000­Dezember 2010 in Leipzig, Sachsen, Sachsen-Anhalt und Deutschland.

BACKGROUND: Malformations are the most common cause of death in infancy. Numerous studies indicate an increased prevalence of malformations in neonates in recent years in some countries around the world. This study analyzed local and national trends of the prevalences of gastroschisis, omphalocele, spina bifida and orofacial clefts during 2000 till 2010 in Leipzig, Saxony, Saxony-Anhalt and Germany. METHODS: The prevalence of neonatal malformations was studied retrospectively from January 2000 till December 2010 using 4 sources from Leipzig, Saxony, Saxony-Anhalt and Germany. RESULTS: Between 2000 and 2010, the prevalence in Germany and in Saxony, respectively was 1.97/2.12 (gastroschisis), 1.63/1.48 (omphalocele), 5.80/8.11 (orofacial clefts) and 2.92/2.50 (spina bifida) of 10 000 live births. In Saxony, a small increase in prevalence was detected (OR/year: 1.01-1.09). In Germany, the prevalence of malformations also increased significantly (OR/year: 1.01-1.04) with the exception of the prevalence of spina bifida which seemed to decline (OR/year 0.986 (0.97-1.0), p-adjust=0.04). CONCLUSION: Whether or not there has been an actual increase in the prevalence of neonatal malformations in Germany over the years or the apparent increase is just due to bias, coding errors, multiple reporting and/or false registration and codification remains unclear. Importantly, in Germany, since prevalence of malformations is monitored prospectively only in Saxony-Anhalt and Rhineland-Palatinate, only in these states is it possible to recognize recent changes. For early identification of changes in prevalence and timely implementation of preventive measures, a nationwide register or additional regional registers are deemed necessary.

Polarization driven conductance variations at charged ferroelectric domain walls.

Conducting domain walls (CDWs) in ferroelectric materials are promising candidates for applications in a manifold of nanoscale, optoelectronic devices. Characterization of their microscopic properties, however, remains challenging due to their small dimension and highly insulating environment. Here, we inspect individual CDWs in single-crystalline LiNbO3 by the combination of photoemission electron microscopy (PEEM) and second harmonic generation (SHG) microscopy. While SHG unveils the overall domain wall inclination angle α, PEEM is sensitive to local conductance variations, both at and away from the domain wall. Thus, the two imaging techniques deliver complementary information over a large field of view. In agreement with earlier theoretical predictions we find that the local conductance is dictated by α and reveal a quantitative connection between them. Our results help to elucidate the electronic structure of CDWs and underline the value of PEEM as a non-contact characterization tool for mapping local conductance variations in highly resistive environments.

J_{eff} Description of the Honeycomb Mott Insulator α-RuCl_{3}.

Novel ground states might be realized in honeycomb lattices with strong spin-orbit coupling. Here we study the electronic structure of α-RuCl_{3}, in which the Ru ions are in a d^{5} configuration and form a honeycomb lattice, by angle-resolved photoemission, x-ray photoemission, and electron energy loss spectroscopy supported by density functional theory and multiplet calculations. We find that α-RuCl_{3} is a Mott insulator with significant spin-orbit coupling, whose low energy electronic structure is naturally mapped onto J_{eff} states. This makes α-RuCl_{3} a promising candidate for the realization of Kitaev physics. Relevant electronic parameters such as the Hubbard energy U, the crystal field splitting 10 Dq, and the charge transfer energy Δ are evaluated.

Tunable charge transfer properties in metal-phthalocyanine heterojunctions.

Organic materials such as phthalocyanine-based systems present a great potential for organic device applications due to the possibility of integrating films of different organic materials to create organic heterostructures which combine the electrical capabilities of each material. This opens the possibility to precisely engineer and tune new electrical properties. In particular, similar transition metal phthalocyanines demonstrate hybridization and charge transfer properties which could lead to interesting physical phenomena. Although, when considering device dimensions, a better understanding and control of the tuning of the transport properties still remain in the focus of research. Here, by employing conductive atomic force microscopy techniques, we provide an insight about the nanoscale electrical properties and transport mechanisms of MnPc and fluorinated phthalocyanines such as F16CuPc and F16CoPc. We report a transition from typical diode-like transport mechanisms for pure MnPc thin films to space-charge-limited current transport regime (SCLC) for Pc-based heterostructures. The controlled addition of fluorinated phthalocyanine also provides highly uniform and symmetric-polarized transport characteristics with conductance enhancements up to two orders of magnitude depending on the polarization. We present a method to spatially map the mobility of the MnPc/F16CuPc structures with a nanoscale resolution and provide theoretical calculations to support our experimental findings. This well-controlled nanoscale tuning of the electrical properties for metal transition phthalocyanine junctions stands as key step for future phthalocyanine-based electronic devices, where the low dimension charge transfer, mediated by transition metal atoms could be intrinsically linked to a transfer of magnetic moment or spin.

Nesting-driven multipolar order in CeB6 from photoemission tomography.

Some heavy fermion materials show so-called hidden-order phases which are invisible to many characterization techniques and whose microscopic origin remained controversial for decades. Among such hidden-order compounds, CeB6 is of model character due to its simple electronic configuration and crystal structure. Apart from more conventional antiferromagnetism, it shows an elusive phase at low temperatures, which is commonly associated with multipolar order. Here we show that this phase roots in a Fermi surface instability. This conclusion is based on a full 3D tomographic sampling of the electronic structure by angle-resolved photoemission and comparison with inelastic neutron scattering data. The hidden order is mediated by itinerant electrons. Our measurements will serve as a paradigm for the investigation of hidden-order phases in f-electron systems, but also generally for situations where the itinerant electrons drive orbital or spin order.

The role of elevated central-peripheral temperature difference in early detection of late-onset sepsis in preterm infants.

AIMS: The study investigated the association between clinical symptoms and late-onset sepsis (LOS) in preterm infants with the aim of identifying a non-invasive tool for the early detection of LOS. METHODS: This was a prospective study of 83 episodes of suspected LOS in 67 preterm infants. At the time LOS was suspected, we recorded a standardized set of clinical symptoms. A diagnosis of "clinical LOS" (Clin-LOS), "culture-proven LOS" (Prov-LOS) or "LOS not present" (No-LOS) was made on the basis of C-reactive protein (CrP) and blood culture results where Clin-LOS was defined as CrP>10mg/l, Prov-LOS was defined as CrP>10mg/l AND positive blood cultures, or it was established that there was no sepsis present (No-LOS). We examined univariable associations between clinical signs and LOS using odds ratio (OR) analysis and then adjusted the odds ratio (adOR) through binary regression analysis. RESULTS: Clin-LOS was diagnosed in 20/83 episodes, 19 cases were found to have Prov-LOS. Clinical signs which had a significant association with Clin-LOS were capillary refill time >2s (OR 2.9) and decreased responsiveness (OR 5.2), whereas there was a negative association between gastric residuals and LOS (OR 0.35). However, the most marked association was found for a greater central-peripheral temperature difference (cpTD) >2°C (OR 9). In Prov-LOS an increased heart rate (OR 3.1), prolonged capillary refill time (OR 3.3) and again an increased cpTD (OR 16) had a significant association with LOS, whereas gastric residuals were negatively associated (OR 0.29). Regression analysis showed that cpTD was the most striking clinical sign associated with both Clin- (adOR 6.3) and Prov-LOS (adOR 10.5). CONCLUSIONS: Prolonged capillary refill time and - more impressive - elevated cpTD were the most useful clinical symptoms for detection of LOS in preterm infants. We especially suggest using cpTD as a predictor of LOS. It is a cheap, non-invasive and readily available tool for daily routines.

Cesarean section increases the risk of respiratory adaptive disorders in healthy late preterm and two groups of mature newborns.

The rates of delivery by Cesarean section (CS) have been trending upwards in recent decades, perhaps leading to higher rates of dysfunction in respiratory adaptation in newborns. We present epidemiological data for pulmonary adaptation by mode of delivery for healthy late preterm and term infants born at a regional tertiary care center. The overall CS rate was 22% with the largest proportion of these in late preterms (39%). This drops to 30% in infants born after 37 weeks gestation and to 11% for those born after 40 weeks. Infants needing respiratory support decreased significantly as gestational age increased: 88% at 34 weeks, 67% at 35 weeks, 28% at 36 weeks, 17% at 37 weeks and 8% at 40 weeks. The risk of respiratory morbidity following CS as compared to vaginal delivery (VD) was substantially higher. 50% of infants born by CS needed respiratory support compared to only 12% following VD. 82% of all late preterm infants born by CS developed respiratory morbidity compared to 36% following VD. Comparable data for infants born after 37 and 40 weeks gestation were 33% compared to 9% and 26% compared to 6% respectively. Late preterm infants born after 36 weeks gestation showed the most marked difference by mode of birth with 66% needing respiratory support following CS as compared to only 9% following VD. Our data could be useful in counselling parents about risk associated with delivery by Cesarean section. A critical view should be taken of increasing CS rates worldwide because of a clear correlation in increased morbidity in infants, especially late preterm infants.

Anisotropic Particle-Hole Excitations in Black Phosphorus.

We report on the energy- and momentum-resolved optical response of black phosphorus (BP) in its bulk form. Along the armchair direction of the puckered layers, we find a highly dispersive mode that is strongly suppressed in the perpendicular (zigzag) direction. This mode emerges out of the single-particle continuum for finite values of momentum and is therefore interpreted as an exciton. We argue that this exciton, which has already been predicted theoretically for phosphorene-the monolayer form of BP-can be detected by conventional optical spectroscopy in the two-dimensional case and might pave the way for optoelectronic applications of this emerging material.

X-ray photoemission study of CeTIn(5) (T = Co, Rh, Ir).

We investigated CeTIn5 (T = Co, Rh, Ir) using temperature- and angle-dependent x-ray photoemission spectroscopy. The Ce 3d core level has a very similar shape for all three materials and is indicative of weak f-hybridization. The spectra were analyzed using a simplified version of the Anderson impurity model, which yields a Ce 4f occupancy that is larger than 0.9. The temperature dependence shows a continuous, irreversible and exclusive broadening of the Ce 3d peaks, due to oxidation of Ce at the surface.

Hypertrophic intraventricular flow obstruction after very-low-dose dexamethasone (Minidex) in preterm infants: case presentation and review of the literature.

The use of dexamethasone in preterm infants developing bronchopulmonary dysplasia has been proven to be effective. Hypertrophic cardiomyopathy is a frequently reported, although transient, side effect of high-dose dexamethasone administration. The recent introduction of very low dexamethasone dose, called 'Minidex', promised equal effectiveness compared to high-dose dexamethasone without relevant side effects. Our study presents two patients developing hypertrophic cardiomyopathy with intraventricular cardiac obstruction after administration of 'Minidex'. Marked cardiac side effects may occur even during very-low-dose dexamethasone treatment in preterm neonates. Betablocker and discontinuation of dexamethasone seem to allow spontaneous reversal of myocardial hypertrophy and obstruction. After all, systematic surveys of the incidence of cardiac complications in a larger population of preterm infants treated with very low doses of dexamethasone are needed.

Observation of a universal donor-dependent vibrational mode in graphene.

Electron-phonon coupling and the emergence of superconductivity in intercalated graphite have been studied extensively. Yet, phonon-mediated superconductivity has never been observed in the 2D equivalent of these materials, doped monolayer graphene. Here we perform angle-resolved photoemission spectroscopy to try to find an electron donor for graphene that is capable of inducing strong electron-phonon coupling and superconductivity. We examine the electron donor species Cs, Rb, K, Na, Li, Ca and for each we determine the full electronic band structure, the Eliashberg function and the superconducting critical temperature Tc from the spectral function. An unexpected low-energy peak appears for all dopants with an energy and intensity that depend on the dopant atom. We show that this peak is the result of a dopant-related vibration. The low energy and high intensity of this peak are crucially important for achieving superconductivity, with Ca being the most promising candidate for realizing superconductivity in graphene.

π and π + σ plasmon localization in single-walled carbon nanotube meta-materials.

We have investigated the plasmon excitations and interband transitions in nematic nanotube meta-materials with different nanotube mean diameters. While the characteristic optical low-energy transitions give testimony to the differing mean diameters, the full momentum resolved π as well as π + σ plasmon response of the meta-materials is found to be entirely invariant with the nanotube diameters 1 nm < d < 2 nm. We hence demonstrate that plasmons on single-walled carbon nanotubes are fully channeled to be one dimensional in the typical range of nanotube diameters. The internal morphology of the meta-material offers a knob to uniformly tune the plasmon resonances.

Changes in regional tissue oxygenation saturation and desaturations after red blood cell transfusion in preterm infants.

OBJECTIVE: The study investigated the ability of near-infrared spectroscopy (NIRS) to detect subgroups of preterm infants who benefit most from red blood cell (RBC) transfusion in regard to cerebral/renal tissue oxygenation (i) and the number of general oxygen desaturation below 80% (SaO(2) <80%) (ii). STUDY DESIGN: Cerebral regional (crSO(2)) and peripheral regional (prSO(2)) NIRS parameters were recorded before, during, immediately after and 24 h after transfusion in 76 infants. Simultaneously, SaO(2) <80% were recorded by pulse oximetry. To answer the basic question of the study, all preterm infants were divided into two subgroups according to their pretransfusion crSO(2) values (<55% and ≥55%). This cutoff was determined by a k-means clustering analysis. RESULT: crSO(2) and prSO(2) increased significantly in the whole study population. A stronger increase (P<0.0005) of both was found in the subgroup with pretransfusion crSO(2) values <55%. Regarding the whole population, a significant decrease (P<0.05) of episodes with SaO(2) <80% was observed. The subgroup with crSO(2) baselines <55% had significant (P<0.05) more episodes with SaO(2) <80% before transfusion. During and after transfusion, the frequency of episodes with SaO(2) <80% decreased more in this group compared with the group with crSO(2) baselines ≥55%. CONCLUSION: NIRS measurement is a simple, non-invasive method to monitor regional tissue oxygenation and the efficacy of RBC transfusion. Infants with low initial NIRS values benefited most from blood transfusions regarding SaO(2) <80%, which may be important for their general outcome.

Transition metal phthalocyanines: insight into the electronic structure from soft x-ray spectroscopy.

Transition metal phthalocyanines (MPc's) are an interesting class of material, and their magnetic and electronic properties are determined by the orbital occupation of the transition metal 3d orbitals incorporated in the molecules center. Thus, the ground state configuration of the transition metal center is very important for a complete understanding of these materials. We present experimental data taken using x-ray absorption and x-ray photoemission spectroscopy together with a theoretical interpretation of MPc series with M=Zn, Cu, Ni, Co, Fe, and Mn. The combination of these methods allows us to narrow down possible dominating ground state configurations and shed a brighter light on the electronic structure of these complexes.

[Prediction of extubation failure in ELBW preterm infants]. / Prädiktion von Extubationsversagen bei ELBW-Frühgeborenen.

BACKGROUND: The accurately timed extubation of ventilated ELBW preterm infants is still a problem. With different data systems the attempt has been made to more accurately predict the successful extubation of these infants. However, there do not yet exist any satisfying solutions. PATIENTS/METHODS: We retrospectively analysed 66 ELBW preterm infants who were endotracheal intubated and ventilated within 24 h postnatal. Basic data, clinical and ventilation data immediately before planned extubation and in several intervals during the following 24 h, as well as outcome variables at discharge were interpreted. RESULTS: 51 patients were successfully extubated (EE-group), 15 (22.7%) failed extubation (reintubation within 48 h after extubation, EV-group). Immediately before extubation in the EE-group there was found a significantly higher inspiratory oxygen concentration (FiO2) in comparison to the EV-group (0.25 vs. 0.3; p=0.01). After the extubation attempt the inspiratory oxygen concentration stayed lower in the EE-group, whereas in the EV-group it rose remarkably (2 h after ext.: 0.26 vs. 0.4; p<0.001). Neither of the basic data showed any significant difference. The outcome analysis indicated a longer intensive care in the EV-group and a trend towards increased BPD and ROP. CONCLUSION: The study shows that for ELBW preterm infants the inspiratory oxygen concentration is especially important to predict a successful extubation. According to our data, the inspiratory oxygen demand before and immediately after extubation establishes the essential difference between successfully extubated and reintubated infants.

Unoccupied electronic structure of TiOCl studied using x-ray absorption near-edge spectroscopy.

We study the unoccupied electronic structure of the spin-1/2 quantum magnet TiOCl using x-ray absorption near-edge spectroscopy (XANES) at the Ti L and O K edges. We acquire data both in total electron and fluorescence yield modes (TEY and FY, respectively). While only the latter allows us to access the unconventional low-temperature spin-Peierls (SP) phase of TiOCl, the signal is found to suffer from significant self-absorption in this case. Nevertheless, we conclude from FY data that effects of the SP distortion on the electronic structure are absent in the incommensurate intermediate phase within experimental accuracy. The similarity of room-temperature FY and TEY data, the latter not being obscured by self-absorption, allows us to use TEY spectra for comparison with simulations. These are performed by means of cluster calculations in D(4h) and D(2h) symmetries using two different codes. We extract values of the crystal-field splitting and parameterize our results using the commonly seen notation of Slater, Racah and Butler. In all cases, good agreement with published values from other studies is found.

Electronic states and the influence of oxygen addition on the optical absorption behaviour of manganese phthalocyanine.

The effects of electronic states and air exposure on the spectroscopic properties of manganese phthalocyanine (MnPc) have been examined. The observed features of the Q-band in the absorption spectra can be explained by intrinsic electronic properties of MnPc, i.e., the formation of singly charged molecules by charge transfer excitations. However, the reaction of MnPc with atmospheric molecular oxygen leads to deviations in peak intensities but does not change the fundamental characteristics of the spectra. Nevertheless, the reaction with oxygen changes the spin state from S = 3/2 to S = 1/2. X-ray diffraction measurements also indicate a slow diffusion process of the oxygen into the MnPc crystal. We discuss both influences to explain the behaviour of MnPc in various spectroscopic methods (EELS, ellipsometry, PES). Furthermore, we support the experimental investigations by detailed ab-initio calculations of spectroscopic properties using methods of the density functional theory framework.