Electric-Field Control of a Single-Atom Polar Bond.

We expose the polar covalent bond between a single Au atom terminating the apex of an atomic force microscope tip and a C atom of graphene on SiC(0001) to an external electric field. For one field orientation, the Au─C bond is strong enough to sustain the mechanical load of partially detached graphene, while for the opposite orientation, the bond breaks easily. Calculations based on density-functional theory and nonequilibrium Green's function methods support the experimental observations by unveiling bond forces that reflect the polar character of the bond. Field-induced charge transfer between the atomic orbitals modifies the polarity of the different electronegative reaction partners and the Au─C bond strength.

Virtual monoenergetic images from spectral detector computed tomography facilitate washout assessment in arterially hyper-enhancing liver lesions.

OBJECTIVES: To investigate whether the increased soft tissue contrast of virtual monoenergetic images (VMIs) obtained from a spectral detector computed tomography (SDCT) system improves washout assessment of arterially hyper-enhancing liver lesions. METHODS: Fifty-nine arterially hyper-enhancing lesions in 31 patients (age 65 ± 9 years, M/W 20/11) were included in this IRB-approved study. All patients underwent multi-phase SDCT for HCC screening. MRI, CEUS or biopsy within 3 months served as standard of reference to classify lesions as LiRADS 3 or 4/5. VMIs and conventional images (CIs) were reconstructed. Visual analysis was performed on 40, 60, and 80 kiloelectronvolt (keV) and CIs by 3 radiologists. Presence and visibility of washout were assessed; image quality and confidence of washout evaluation were evaluated on 5-point Likert scales. Signal-to-noise ratio (SNR), lesion-to-liver contrast-to-noise ratio (CNR) (|HUlesion-HUliver|/SDliver) and washout (|HUlesion-HUliver|) were calculated. Statistical assessment was performed using ANOVA and Wilcoxon test. RESULTS: On subjective lesion analysis, the highest level of diagnostic confidence and highest sensitivity for the detection of lesion washout were found for 40-keV VMIs (40 keV vs. CI, 81.3 vs. 71.3%). Image quality parameters were significantly better in low-kiloelectronvolt VMIs than in CIs (p < 0.05; e.g. SNRliver: 40 keV vs. CIs, 12.5 ± 4.1 vs. 5.6 ± 1.6). In LiRADS 4/5 lesions, CNR and quantitative washout values were significantly higher in 40-keV VMIs compared to CIs (p < 0.05; e.g. CNR and washout in 40 keV vs. CIs, 2.3 ± 1.6 vs. 0.8 ± 0.5 and 29.0 ± 19.1 vs. 12.9 ± 6.9 HU, respectively). CONCLUSION: By increasing lesion contrast, low-kiloelectronvolt VMIs obtained from SDCT improve washout assessment of hyper-enhancing liver lesions with respect to washout visibility and diagnostic confidence. KEY POINTS: • Low-kiloelectronvolt virtual monoenergetic images from spectral detector CT facilitate washout assessment in arterially hyper-enhancing liver lesions. • Image quality and quantitative washout parameters as well as subjective washout visibility and diagnostic confidence benefit from low-kiloelectronvolt virtual monoenergetic images.

Could FreeStyle Libre™ sensor glucose data support decisions for safe driving?

AIM: Many countries require individuals with diabetes to adhere to standards regarding blood glucose testing in order to be granted or retain a driving licence. Currently, interstitial glucose results may not be used. The aim of this study was to determine whether interstitial glucose measurements using flash glucose-sensing technology can provide additional information to augment safe driving. METHODS: Sensor data from two European studies (NCT02232698 and NCT02082184) of the FreeStyle Libre Glucose Monitoring System™ in insulin-treated Type 1 and Type 2 diabetes, 241 and 224 participants respectively, were used to determine the frequency of a low interstitial sensor glucose result (< 3.9 mmol/l) up to 4 h subsequent to a daytime (07:00-21:00 h) capillary blood glucose result ≥ 5 mmol/l. RESULTS: Within 4 h of a capillary blood glucose result ≥ 5 mmol/l a sensor glucose result of < 3.9 mmol/l occurred on 22.0% of occasions (2573 of 11 706 blood glucose readings) for those with Type 1 diabetes, and 8.4% of occasions (699/8352) for those with Type 2 diabetes; 13.8% (1610/11 628) and 4.4% (365/8203) within 2 h, and 10.0% (1160/11 601) and 3.1% (254/8152) within 1.5 h. Analysis of sensor glucose results 5-7 mmol/l demonstrated the glucose trend arrow descending on 14.7% (1163/7894, Type 1 diabetes) and 9.4% (305/3233, Type 2 diabetes) of occasions. CONCLUSIONS: Sensor-based glucose information with directional arrows has the potential to support assessment of safe glucose levels associated with driving and offers distinct advantages over blood glucose testing for individuals with Type 1 and Type 2 diabetes to concord with driving safety standards.

Impact of Atomic-Scale Contact Geometry on Andreev Reflection.

Charge transport has been examined in junctions comprising the normal-metal tip of a low-temperature scanning tunneling microscope, the surface of a conventional superconductor, and adsorbed C_{60} molecules. The Bardeen-Cooper-Schrieffer energy gap gradually evolves into a zero-bias peak with decreasing electrode separation. The peak is assigned to the spectroscopic signature of Andreev reflection. The conductance due to Andreev reflection is determined by the atomic termination of the tip apex and the molecular adsorption orientation. Transport calculations unveil the finite temperature and the strong molecule-electrode hybridization as the origin to the surprisingly good agreement between spectroscopic data and the Blonder-Tinkham-Klapwijk model that was conceived for macroscopic point contacts.

Ordered Superstructures of a Molecular Electron Donor on Au(111).

The molecular donor tetraphenyldibenzoperiflanthene (DBP) forms coverage-dependent superstructures on Au(111). At submonolayer coverage, the molecules align parallel to each other. They arrange in row-like structures, which exhibit a nearly rectangular primitive unit cell. By contrast, the molecular monolayer is characterized by a herringbone-type DBP arrangement spanned by an almost square unit cell containing two molecules. Both superstructures occur simultaneously in a narrow coverage range close to completion of the molecular monolayer. The adsorbate-substrate interaction is similar to other physisorbed molecular films on Au(111), but differs for the two adsorption phases as inferred from the different modification of the Au(111) surface reconstruction. Structural properties were consistently probed in real and reciprocal space by scanning tunneling microscopy and low-energy electron diffraction, respectively.

Ballistic Anisotropic Magnetoresistance of Single-Atom Contacts.

Anisotropic magnetoresistance, that is, the sensitivity of the electrical resistance of magnetic materials on the magnetization direction, is expected to be strongly enhanced in ballistic transport through nanoscale junctions. However, unambiguous experimental evidence of this effect is difficult to achieve. We utilize single-atom junctions to measure this ballistic anisotropic magnetoresistance (AMR). Single Co and Ir atoms are deposited on domains and domain walls of ferromagnetic Fe layers on W(110) to control their magnetization directions. They are contacted with nonmagnetic tips in a low-temperature scanning tunneling microscope to measure the junction conductances. Large changes of the magnetoresistance occur from the tunneling to the ballistic regime due to the competition of localized and delocalized d-orbitals, which are differently affected by spin-orbit coupling. This work shows that engineering the AMR at the single atom level is feasible.

Lateral Electron Confinement with Open Boundaries: Quantum Well States above Nanocavities at Pb(111).

We have studied electron states present at the Pb(111) surface above Ar-filled nanocavities created by ion beam irradiation and annealing. Vertical confinement between the parallel crystal and nanocavity surfaces creates a series of quantum well state subbands. Differential conductance data measured by scanning tunneling spectroscopy contain a characteristic spectroscopic fine structure within the highest occupied subband, revealing additional quantization. Unexpectedly, reflection at the open boundary where the thin Pb film recovers its bulk thickness gives rise to the lateral confinement of electrons.

Superstructures and Electronic Properties of Manganese-Phthalocyanine Molecules on Au(110) from Submonolayer Coverage to Ultrathin Molecular Films.

The adsorption of manganese-phthalocyanine molecules on Au(110) was investigated using a low-temperature scanning tunneling microscope. A rich variety of commensurate superstructures was observed upon increasing the molecule coverage from submonolayers to ultrathin films. All structures were associated with reconstructions of the Au(110) substrate. Molecules adsorbed in the second molecular layer exhibited negative differential conductance occurring symmetrically around zero bias voltage. A double-barrier tunneling model rationalized this observation in terms of a peaked molecular resonance at the Fermi energy together with a voltage drop across the molecular film.

Associated factors of estimated desaturase activity in the EPIC-Potsdam study.

BACKGROUND AND AIMS: Altered activity of desaturase enzymes may be involved in the development of metabolic diseases like type 2-diabetes. Desaturase activities might be modifiable by diet and lifestyle-related factors, but no study has systematically investigated such factors so far. We aimed to evaluate the association of demographic, anthropometric, dietary and lifestyle characteristics with estimated Δ5-, Δ6- and Δ9-desaturase activity. METHODS AND RESULTS: A subsample (n = 1782) of the EPIC-Potsdam study was used for a cross-sectional analysis, involving men and women, mainly aged 35-65 years. Fatty acid (FA) product-to-precursor ratios, derived from the FA composition of erythrocyte membrane phospholipids, were used to estimate desaturase activities. Multiple linear regression models were used with estimated Δ5-, Δ6- and Δ9-desaturase activity as outcome and demographic (age, sex), anthropometric (BMI, WHR), dietary intake (FAs, carbohydrates) and lifestyle (physical activity, smoking, alcohol consumption) factors as exposure variables. Alcohol intake was positively associated with estimated Δ6- (explained variance in desaturase activity: 1.52%) and estimated Δ9-desaturase activity (explained variance: 5.53%). BMI and WHR showed a weak inverse association with estimated Δ5-desaturase activity (explained variance: BMI: 1.07%; WHR: 1.02%) and weak positive associations with estimated Δ6-(explained variance: BMI: 1.17%; WHR: 1.19%) and estimated Δ9-desaturase activities (explained variance: BMI: 0.70%; WHR: 0.96%). Age, sex, physical activity, smoking and dietary factors were only weakly associated with the estimated desaturase activities. CONCLUSION: Our findings suggest that alcohol intake as well as obesity measures are associated with the FA ratios reflecting desaturase activity.

Phthalocyanine adsorption to graphene on Ir(111): evidence for decoupling from vibrational spectroscopy.

Phthalocyanine molecules have been adsorbed to Ir(111) and to graphene on Ir(111). From a comparison of scanning tunneling microscopy images of individual molecules adsorbed to the different surfaces alone it is difficult to discern potential differences in the molecular adsorption geometry. In contrast, vibrational spectroscopy using inelastic electron scattering unequivocally hints at strong molecule deformations on Ir(111) and at a planar adsorption geometry on graphene. The spectroscopic evidence for the different adsorption configurations is supported by density functional calculations.

Tunneling anisotropic magnetoresistance at the single-atom limit.

The tunneling anisotropic magnetoresistance (TAMR) of single Co atoms adsorbed on a double-layer Fe film on W(110) is observed by scanning tunneling spectroscopy. Without applying an external magnetic field the TAMR is found by comparing spectra of atoms that are adsorbed on the domains and domain walls of the Fe film. The TAMR can be as large as 12% and repeatedly changes sign as a function of bias voltage. First-principles calculations show that the hybridization between Co d states of different orbital symmetries depends on the magnetization direction via spin-orbit coupling. This leads to an anisotropy of the density of states and thus induces a TAMR.

An integrated solar battery based on a charge storing 2D carbon nitride.

Solar batteries capable of harvesting sunlight and storing solar energy present an attractive vista to transition our energy infrastructure into a sustainable future. Here we present an integrated, fully earth-abundant solar battery based on a bifunctional (light absorbing and charge storing) carbon nitride (K-PHI) photoanode, combined with organic hole transfer and storage materials. An internal ladder-type hole transfer cascade via a transport layer is used to selectively shuttle the photogenerated holes to the PEDOT:PSS cathode. This concept differs from previous designs such as light-assisted battery schemes or photocapacitors and allows charging with light during both electrical charge and discharge, thus substantially increasing the energy output of the cell. Compared to battery operation in the dark, light-assisted (dis)charging increases charge output by 243%, thereby increasing the electric coulombic efficiency from 68.3% in the dark to 231%, leading to energy improvements of 94.1% under illumination. This concept opens new vistas towards compact, highly integrated devices based on multifunctional, carbon-based electrodes and separators, and paves the way to a new generation of earth-abundant solar batteries.

Body adiposity index, body fat content and incidence of type 2 diabetes.

AIMS/HYPOTHESIS: The aim of this study was to compare estimates of body fat content, i.e. body adiposity index (BAI), BMI and waist and hip circumferences, with respect to their ability to predict the percentage of body fat (PBF; confirmed by magnetic resonance tomography) and incident type 2 diabetes. METHODS: Associations between anthropometric measurements and PBF were evaluated in the Tübingen Lifestyle Intervention Program (TULIP; 138 men, 222 women), and between these measurements and incident type 2 diabetes in the European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam study (9,729 men, 15,438 women) and the Cooperative Health Research in the Region of Augsburg (KORA) study (5,573 men, 5,628 women), using correlation and multivariate Cox regression analyses. RESULTS: BMI more strongly correlated with PBF (men: r = 0.81, women: r = 0.84) than BAI (r = 0.68 and 0.81, respectively), while waist circumference among men (r = 0.84) and hip circumference among women (r = 0.88) showed the strongest correlations. BAI overestimated PBF among men (mean difference -3.0%), and this error was dependent on the value of PBF. BAI was more weakly associated with diabetes risk (RRs for 1 SD, EPIC-Potsdam men: 1.62 [95% CI 1.52, 1.72], women: 1.67 [95% CI 1.55, 1.80]; KORA men: 1.62 [95% CI 1.48, 1.78], women: 1.82 [95% CI 1.65, 2.02]) compared with BMI (RRs, EPIC-Potsdam men: 1.95 [95% CI 1.83, 2.09], women 1.88 [95% CI 1.76, 2.02], KORA men 1.75 [95% CI 1.62, 1.89], women 2.00 [95% CI 1.81, 2.22]), while waist circumference showed the strongest associations (RRs: 2.17 [95% CI 2.01, 2.35], 2.33 [95% CI 2.15, 2.53], 1.81 [95% CI 1.66, 1.96] and 2.29 [95% CI 2.05, 2.57] for EPIC-Potsdam men and women and KORA men and women, respectively). CONCLUSIONS/INTERPRETATION: Waist circumference in men and hip circumference in women are better predictors of PBF than BAI and BMI. BAI was not as strong a predictor of diabetes as BMI, while waist circumference was the strongest predictor.

Local gating of an Ir(111) surface resonance by graphene islands.

The influence of graphene islands on the electronic structure of the Ir(111) surface is investigated. Scanning tunneling spectroscopy (STS) indicates the presence of a two-dimensional electron gas with a binding energy of -160 meV and an effective mass of -0.18me underneath single-layer graphene on the Ir(111) surface. Density functional calculations reveal that the STS features are predominantly due to a holelike surface resonance of the Ir(111) substrate. Nanometer-sized graphene islands act as local gates, which shift and confine the surface resonance.

Two-level conductance fluctuations of a single-molecule junction.

The conductance of a single-molecule junction in a low-temperature scanning tunneling microscope has been measured at nanosecond time resolution. In a transition region between tunneling and contact the conductance exhibits rapid two-level fluctuations which are attributed to different geometries of the junction. The voltage dependence of the fluctuations indicates that electrons injected into the lowest unoccupied molecular orbital may efficiently couple to molecular vibrations.

Two-site Kondo effect in atomic chains.

Linear CoCu(n)Co clusters on Cu(111) fabricated by atomic manipulation represent a two-site Kondo system with tunable interaction. Scanning tunneling spectroscopy reveals oscillations of the Kondo temperature T(K) with the number n of Cu atoms for n≥3. Density functional calculations show that the Ruderman-Kittel-Kasuya-Yosida interaction mediated by the Cu chains causes the oscillations. Calculations find ferromagnetic and antiferromagnetic interaction for n=1 and 2, respectively. Both interactions lead to a decrease of T(K) as experimentally observed.

Electronic superstructure of lead phthalocyanine on lead islands.

Lead phthalocyanine (PbPc) deposited on lead islands on Ag(111) forms two-dimensional crystals of densely packed molecules. For particular orientations, the molecular arrays exhibit an electronic superstructure with an extraordinarily large unit cell. The molecules induce a shift of quantum well states, which are confined to the Pb islands. Patterns formed by PbPc on Ag(111) are drastically different.

Periodontal disease in patients with ankylosing spondylitis.

OBJECTIVE: Ankylosing spondylitis (AS) and periodontal disease (PD) are characterised by dysregulation of the host inflammatory response, resulting in soft and hard connective tissue destruction. AS has been related to other inflammatory diseases, however, there is a paucity of data on whether AS is associated with inflammatory PD. METHODS: The association between AS and PD was examined in 48 patients with AS and 48 healthy controls, matched for age and gender. AS was diagnosed according to the modified New York criteria. Periodontal examination included probing pocket depth (PPD), clinical attachment loss (CAL), plaque index (PI) and bleeding on probing (BOP). Potential risk factors of PD such as smoking, low education, alcohol consumption, body mass index (BMI), as well as chronic diseases associated with PD and AS were assessed through questionnaires. RESULTS: In stepwise logistic regression, including AS status, age, gender, education, smoking, alcohol consumption and BMI, only AS status, age and education remained significant predictors of PD. Patients with AS had significant 6.81-fold increased odds (95% CI 1.96 to 23.67) of PD (defined as mean attachment loss >3 mm) compared to controls. The strength of the association was attenuated but remained statistically significant after further adjustment for plaque accumulation (odds ratio (OR) 5.48, 95% CI 1.37 to 22.00). CONCLUSIONS: The present study shows that patients with AS have a significantly higher risk of PD, strongly suggesting the need for close collaboration between rheumatologists, periodontists and dental hygienists when treating patients with AS.

Graphene on Ru(0001): contact formation and chemical reactivity on the atomic scale.

Graphene on Ru(0001) is contacted with Au tips of a cryogenic scanning tunneling microscope. The formation and conductance of single-atom contacts vary within the moiré unit cell. Density functional calculations reveal that elastic distortions of the graphene lattice occur at contact due to a selectively enhanced chemical reactivity of C atoms at hollow sites of Ru(0001). Concomitant quantum transport calculations indicate that the graphene-Ru distance determines the conductance variations.

Atomic-scale control of electron transport through single molecules.

Tin-phthalocyanine molecules adsorbed on Ag(111) were contacted with the tip of a cryogenic scanning tunneling microscope. Orders-of-magnitude variations of the single-molecule junction conductance were achieved by controllably dehydrogenating the molecule and by modifying the atomic structure of the surface electrode. Nonequilibrium Green's function calculations reproduce the trend of the conductance and visualize the current flow through the junction, which is guided through molecule-electrode chemical bonds.