Design and performance of a spin-polarized electron energy loss spectrometer with high momentum resolution

We describe a new "complete" spin-polarized electron energy loss spectrometer comprising a spin-polarized primary electron source, an imaging electron analyzer, and a spin analyzer of the "spin-polarizing mirror" type. Unlike previous instruments, we have a high momentum resolution of less than 0.04 Å(-1), at an energy resolution of 90-130 meV. Unlike all previous studies which reported rather broad featureless data in both energy and angle dependence, we find richly structured spectra depending sensitively on small changes of the primary energy, the kinetic energy after scattering, and of the angle of incidence. The key factor is the momentum resolution.

Electron-Vibration Coupling in Molecular Materials: Assignment of Vibronic Modes from Photoelectron Momentum Mapping

Electron-phonon coupling is one of the most fundamental effects in condensed matter physics. We here demonstrate that photoelectron momentum mapping can reveal and visualize the coupling between specific vibrational modes and electronic excitations. When imaging molecular orbitals with high energy resolution, the intensity patterns of photoelectrons of the vibronic sidebands of molecular states show characteristic changes due to the distortion of the molecular frame in the vibronically excited state. By comparison to simulations, an assignment of specific vibronic modes is possible, thus providing unique information on the coupling between electronic and vibronic excitation.

Development of a spin polarized low energy electron diffraction system

We have designed and constructed a spin polarized low energy electron diffraction system working in the reflected electron pulse counting mode. This system is capable of measuring asymmetries due to spin-orbit and exchange interactions. Photoemission from a strained GaAs/GaAsP super lattice is used as the source of spin polarized electrons. Spin-orbit asymmetry is evaluated for Ir(100) single crystal at various energies. Subsequently, exchange asymmetry has been evaluated on 40 monolayer Fe deposited on Ir(100). This instrument proves to be useful in understanding structure and magnetism at surfaces.

Core-resonant double photoemission from palladium films

We studied the core-resonant double photoemission process from palladium films with linearly polarized synchrotron radiation. We excited either the 3d or 4p core level and focused on the Auger transitions which leave two holes in the valence band. We find that the two-dimensional energy distributions are markedly different for the 3d and 4p decay. The 3d decay can be understood by a sequential emission of the two electrons while the 4p decay proceeds in a single step. Despite the large differences in the two-dimensional energy spectra we find the shape of the energy sum spectra rather similar. For the description of the 4p decay we propose a model which uses available single electron spectra, but suggest an alternative interpretation of these data. With this we are able to explain the range over which the available energy is shared. Key assumptions of the model are verified by our experiments on the 3d decay.

TPM3 deletions cause a hypercontractile congenital muscle stiffness phenotype

OBJECTIVE

Mutations in TPM3, encoding Tpm3.12, cause a clinically and histopathologically diverse group of myopathies characterized by muscle weakness. We report two patients with novel de novo Tpm3.12 single glutamic acid deletions at positions ΔE218 and ΔE224, resulting in a significant hypercontractile phenotype with congenital muscle stiffness, rather than weakness, and respiratory failure in one patient.

METHODS

The effect of the Tpm3.12 deletions on the contractile properties in dissected patient myofibers was measured. We used quantitative in vitro motility assay to measure Ca(2+) sensitivity of thin filaments reconstituted with recombinant Tpm3.12 ΔE218 and ΔE224.

RESULTS

Contractility studies on permeabilized myofibers demonstrated reduced maximal active tension from both patients with increased Ca(2+) sensitivity and altered cross-bridge cycling kinetics in ΔE224 fibers. In vitro motility studies showed a two-fold increase in Ca(2+) sensitivity of the fraction of filaments motile and the filament sliding velocity concentrations for both mutations.

INTERPRETATION

These data indicate that Tpm3.12 deletions ΔE218 and ΔE224 result in increased Ca(2+) sensitivity of the troponin-tropomyosin complex, resulting in abnormally active interaction of the actin and myosin complex. Both mutations are located in the charged motifs of the actin-binding residues of tropomyosin 3, thus disrupting the electrostatic interactions that facilitate accurate tropomyosin binding with actin necessary to prevent the on-state. The mutations destabilize the off-state and result in excessively sensitized excitation-contraction coupling of the contractile apparatus. This work expands the phenotypic spectrum of TPM3-related disease and provides insights into the pathophysiological mechanisms of the actin-tropomyosin complex.

Improvement of liver function parameters in advanced HCV-associated liver cirrhosis by IFN-free antiviral therapies

BACKGROUND

Successful antiviral treatment of decompensated hepatitis B with HBV polymerase inhibitors is associated with improvement of liver function. To what extent liver function also improves in cirrhotic patients with chronic hepatitis C receiving novel interferon-free (IFN-free) therapies is unknown.

AIM

To study liver function in cirrhotic HCV patients receiving IFN-free therapies.

METHODS

We here studied 80 consecutive patients with advanced HCV associated liver cirrhosis including 34 patients (43%) with Child B/C cirrhosis and 42 patients (53%) with platelet counts of <90.000/μL receiving different combinations of direct acting antivirals without interferon [sofosbuvir/ribavirin (n = 56), sofosbuvir/simeprevir ± ribavirin (n = 15) and sofosbuvir/daclatasvir ± ribavirin (n = 9)]. The majority of patients was infected with HCV genotype 1 (n = 50); HCV genotypes 2, 3 and 4 were present in 4, 24 and 2 patients, respectively.

RESULTS

Liver function parameters including albumin, bilirubin, cholinesterase and prothrombin time all improved in the majority of patients during antiviral therapy irrespectively of the underlying HCV genotype, however, with different kinetics. MELD scores improved until post-treatment week 12 in 44% of the patients but worsened in 15%. A sustained virological response was achieved in 63% of the patients. HCV RNA relapse led to moderate ALT increases in 15/23 patients but was not associated with hepatic decompensations.

CONCLUSION

This real-world single centre study showed that interferon-free treatment of hepatitis C patients with advanced liver cirrhosis restores liver function, and may thereby reduce the need for liver transplantations.

Anomalous d-like surface resonances on Mo(110) analyzed by time-of-flight momentum microscopy

The electronic surface states on Mo(110) have been investigated using time-of-flight momentum microscopy with synchrotron radiation (hν=35 eV). This novel angle-resolved photoemission approach yields a simultaneous acquisition of the E-vs-k spectral function in the full surface Brillouin zone and several eV energy interval. (kx,ky,EB)-maps with 3.4 Å(-1) diameter reveal a rich structure of d-like surface resonances in the spin-orbit induced partial band gap. Calculations using the one-step model in its density matrix formulation predict an anomalous state with Dirac-like signature and Rashba spin texture crossing the bandgap at Γ¯ and EB=1.2 eV. The experiment shows that the linear dispersion persists away from the Γ¯-point in an extended energy- and k∥-range. Analogously to a similar state previously found on W(110) the dispersion is linear along H¯-Γ¯-H¯ and almost zero along N¯-Γ¯-N¯. The similarity is surprising since the spin-orbit interaction is 5 times smaller in Mo. A second point with unusual topology is found midway between Γ¯ and N¯. Band symmetries are probed by linear dichroism.

Correction of the deterministic part of space-charge interaction in momentum microscopy of charged particles

Ultrahigh spectral brightness femtosecond XUV and X-ray sources like free electron lasers (FEL) and table-top high harmonics sources (HHG) offer fascinating experimental possibilities for analysis of transient states and ultrafast electron dynamics. For electron spectroscopy experiments using illumination from such sources, the ultrashort high-charge electron bunches experience strong space-charge interactions. The Coulomb interactions between emitted electrons results in large energy shifts and severe broadening of photoemission signals. We propose a method for a substantial reduction of the effect by exploiting the deterministic nature of space-charge interaction. The interaction of a given electron with the average charge density of all surrounding electrons leads to a rotation of the electron distribution in 6D phase space. Momentum microscopy gives direct access to the three momentum coordinates, opening a path for a correction of an essential part of space-charge interaction. In a first experiment with a time-of-flight momentum microscope using synchrotron radiation at BESSY, the rotation in phase space became directly visible. In a separate experiment conducted at FLASH (DESY), the energy shift and broadening of the photoemission signals were quantified. Finally, simulations of a realistic photoemission experiment including space-charge interaction reveals that a gain of an order of magnitude in resolution is possible using the correction technique presented here.

Diagnostic algorithms in Charcot-Marie-Tooth neuropathies: experiences from a German genetic laboratory on the basis of 1206 index patients

We present clinical features and genetic results of 1206 index patients and 124 affected relatives who were referred for genetic testing of Charcot-Marie-Tooth (CMT) neuropathy at the laboratory in Aachen between 2001 and 2012. Genetic detection rates were 56% in demyelinating CMT (71% of autosomal dominant (AD) CMT1/CMTX), and 17% in axonal CMT (24% of AD CMT2/CMTX). Three genetic defects (PMP22 duplication/deletion, GJB1/Cx32 or MPZ/P0 mutation) were responsible for 89.3% of demyelinating CMT index patients in whom a genetic diagnosis was achieved, and the diagnostic yield of the three main genetic defects in axonal CMT (GJB1/Cx32, MFN2, MPZ/P0 mutations) was 84.2%. De novo mutations were detected in 1.3% of PMP22 duplication, 25% of MPZ/P0, and none in GJB1/Cx32. Motor nerve conduction velocity was uniformly <38 m/s in median or ulnar nerves in PMP22 duplication, >40 m/s in MFN2, and more variable in GJB1/Cx32, MPZ/P0 mutations. Patients with CMT2A showed a broad clinical severity regardless of the type or position of the MFN2 mutation. Out of 75 patients, 8 patients (11%) with PMP22 deletions were categorized as CMT1 or CMT2. Diagnostic algorithms are still useful for cost-efficient mutation detection and for the interpretation of large-scale genetic data made available by next generation sequencing strategies.

The LVV Auger line shape of sulfur on copper studied by Auger photoelectron coincidence spectroscopy

We have studied the line shapes of Cu(0 0 1)-p (2 × 2)S L2VV and L3VV Auger decay by means of Auger photoelectron coincidence spectroscopy. Measuring the LVV Auger spectrum in coincidence with S 2p1/2 and 2p3/2 photoelectrons respectively, we have been able to separate the two overlapping Auger spectra and determine their intrinsic line shapes. The two Auger transitions, though shifted in energy, display an identical line shape whose main features can be qualitatively understood considering a single particle approximation but are better described within a Cini-Sawatzky (CS) approach. Comparison between the experimental and the CS calculated spectra confirms that a substantial part of the Auger lines (∼20%) can be ascribed to decay events accompanied by the excitation of one additional electron-hole pair in the valence band. For the first time, the locality of the Auger process combined with the surface sensitivity of the APECS technique and its ability to separate overlapping structures are used to study Auger transitions taking place at the the surface states of a S/noble-metal interface.

Cantilever stress measurements for pulsed laser deposition of perovskite oxides at 1000 K in an oxygen partial pressure of 10(-4) millibars

An in situ stress measurement setup using an optical 2-beam curvature technique is described which is compatible with the stringent growth conditions of pulsed laser deposition (PLD) of perovskite oxides, which involves high substrate temperatures of 1000 K and oxygen partial pressures of up to 1 × 10(-4) millibars. The stress measurements are complemented by medium energy electron diffraction (MEED), Auger electron spectroscopy, and additional growth rate monitoring by a quartz microbalance. A shielded filament is used to allow for simultaneous stress and MEED measurements at high substrate temperatures. A computer-controlled mirror scans an excimer laser beam over a stationary PLD target. This avoids mechanical noise originating from rotating PLD targets, and the setup does not suffer from limited lifetime issues of ultra high vacuum (UHV) rotary feedthroughs.

Analysis of knowledge and attitude surveys to identify barriers and enablers of appropriate antimicrobial prescribing in three Australian tertiary hospitals

BACKGROUND

Antimicrobial stewardship programmes aim to optimise use of antibiotics and are now mandatory in all Australian hospitals.

AIM

We aimed to identify barriers to and enablers of appropriate antimicrobial prescribing among hospital doctors.

METHODS

Two paper-based and one web-based surveys were administered at three Australian university teaching hospitals from March 2010 to May 2011. The 18-item questionnaire recorded doctors’ level of experience, their knowledge regarding the use of common antimicrobials and their attitudes regarding antimicrobial prescribing. Local survey modifications allowed inclusion of specific questions on: infections in intensive care unit patients, clinical microbiology and use of local guidelines.

RESULTS

The respondents (n = 272) were comprised of 96 (35%) registrars, 67 (25%)residents, 57 (21%) interns and 47 (17%) consultant hospital doctors. Forty-one per cent were working in a medical specialty. Identified barriers included: gaps in antimicrobial prescribing knowledge (especially among interns), a lack of awareness about which antimicrobials were restricted and a reliance on senior colleagues to make antimicrobial prescribing decisions. Enablers of optimal prescribing included: an acknowledgement of the need for assistance in prescribing and reported readiness to consult national prescribing guidelines. These results were used to help guide and prioritise interventions to improve prescribing practices.

CONCLUSION

A transferable knowledge and attitudes survey tool can be used to highlight barriers and facilitators to optimal hospital antimicrobial prescribing in order to inform tailored antimicrobial stewardship interventions.

Dynamic screening probed by core-resonant double photoemission from surfaces

The universal response of a sudden created core hole, predicted to occur on an attosecond (10(-18)  s) time scale, lacks an experimental demonstration. With a two-dimensional coincidence spectrometer, we demonstrate an extensive energy sharing between the Ag 4p photoelectron and the N2,3VV Auger electron exceeding 10 eV. This energy width provides access to the time scale of the emission process. This is the fingerprint of the dynamic fluctuation process 4p(-1)⇌4d(-2)4f. The shakeup induced interband transitions from the Ag(100) surface are also identified by comparing the coincidence spectrum with the M4,5VV Auger transitions.

Hepatitis C virus core antigen testing in liver and kidney transplant recipients

HCV RNA levels correlate with the long-term outcome of hepatitis C in liver transplant recipients. Nucleic acid testing (NAT) is usually used to confirm HCV reinfection and to examine viral loads after liver transplantation. HCV core antigen (HCVcoreAg) testing could be an alternative to NAT with some potential advantages including very low intra- and interassay variabilities and lower costs. The performance of HCVcoreAg testing in organ transplant recipients is unknown. We prospectively studied 1011 sera for HCV RNA and HCVcoreAg in a routine real-world setting including 222 samples obtained from patients after liver or kidney transplantation. HCV RNA and HCVcoreAg test results showed a consistency of 98% with a very good correlation in transplanted patients (r > 0.85). The correlation between HCV RNA and HCVcoreAg was higher in sera with high viral loads and in samples from patients with low biochemical disease. Patients treated with tacrolimus showed a better correlation between both parameters than individuals receiving cyclosporine A. HCV RNA/HCVcoreAg ratios did not differ between transplanted and nontransplanted patients, and HCV RNA and HCVcoreAg kinetics were almost identical during the first days after liver transplantation. HCVcoreAg testing can be used to monitor HCV viral loads in patients after organ transplantation. However, the assay is not recommended to monitor antiviral therapies.

Tuning the Dirac point position in Bi(2)Se(3)(0001) via surface carbon doping

Angular resolved photoemission spectroscopy in combination with ab initio calculations show that trace amounts of carbon doping of the Bi_{2}Se_{3} surface allows the controlled shift of the Dirac point within the bulk band gap. In contrast to expectation, no Rashba-split two-dimensional electron gas states appear. This unique electronic modification is related to surface structural modification characterized by an expansion of the top Se-Bi spacing of ≈11% as evidenced by surface x-ray diffraction. Our results provide new ways to tune the surface band structure of topological insulators.

Energy relations of positron-electron pairs emitted from surfaces

The impact of a primary positron onto a surface may lead to the emission of a correlated positron-electron pair. By means of a lab-based positron beam we studied this pair emission from various surfaces. We analyzed the energy spectra in a symmetric emission geometry. We found that the available energy is shared in an unequal manner among the partners. On average the positron carries a larger fraction of the available energy. The unequal energy sharing is a consequence of positron and electron being distinguishable particles. We provide a model which explains the experimental findings.

Oscillations of the orbital magnetic moment due to d-band quantum well states

The effect of electron confinement on the magnetocrystalline anisotropy of ultrathin bcc Fe films is explored by combining photoemission spectroscopy, x-ray magnetic circular dichroism, and magneto-optical Kerr effect measurements. Pronounced thickness-dependent variations in the magnetocrystalline anisotropy are ascribed to periodic changes in the density of states at the Fermi level, induced by quantization of d(xz), d(yz) out-of-plane orbitals. Our results reveal a direct correlation between quantum well states, the orbital magnetic moment, and the magnetocrystalline anisotropy.