Observation of depolarized ZnO(0001) monolayers: formation of unreconstructed planar sheets

A novel nonpolar structure of 2 monolayer (ML) thick ZnO(0001) films grown on Ag(111) has been revealed, using surface x-ray diffraction and scanning tunneling microscopy. Zn and O atoms are arranged in planar sheets like in the hexagonal boron-nitride prototype structure. The observed depolarization is accompanied by a significant lateral 1.6% expansion of the lattice parameter and a 3% reduced Zn-O bond length within the sheets. The nonpolar structure stabilizes an atomically flat surface morphology unseen for ZnO surfaces thus far. The transition to the bulk wurtzite structure occurs in the 3-4 ML coverage range, connected to considerable roughening.

A prospective, comparative trial of three anesthetics for elective supratentorial craniotomy. Propofol/fentanyl, isoflurane/nitrous oxide, and fentanyl/nitrous oxide

BACKGROUND

Different anesthetic agents have different effects on cerebrovascular physiology. However, the importance of these differences in neuroanesthetic practice are unclear. In an effort to determine whether important clinical differences are present, the authors compared three anesthetic techniques in 121 adults undergoing elective surgical removal of a supratentorial, intracranial mass lesion.

METHODS

Patients were assigned randomly to one of three groups. In group 1 (n = 40), anesthesia was induced with propofol and maintained with fentanyl (approximately 10 micrograms/kg load, 2-3 micrograms.kg-1.h-1 infusion) and propofol (50-300 micrograms.kg-1.min-1). In group 2 (n = 40), anesthesia was induced with thiopental and maintained with isoflurane and nitrous oxide. Up to 2 micrograms/kg fentanyl was given after replacement of the bone flap. In group 3 (n = 41), anesthesia was induced with thiopental and maintained with fentanyl (approximately 10 micrograms/kg load, 2-3 micrograms.kg-1.h-1 infusion), nitrous oxide, and low-dose isoflurane, if required. Blood pressure, heart rate, expired gas concentrations, and ventilatory parameters were recorded automatically in all patients. Epidural intracranial pressure (ICP) was measured via the first burr hole, brain swelling was rated at the time of dural opening, and emergence was monitored closely. Preoperative computed tomography or magnetic resonance imaging scans were evaluated, and pre- and postoperative neurologic exams were performed by a neurosurgeon unaware of group assignments. Total hospital stay (days) and total hospital cost (exclusive of physician charges) also were reviewed.

RESULTS

During induction, higher heart rates were seen in isoflurane/nitrous oxide patients, whereas mean arterial pressure was approximately 10 mmHg less during the maintenance phase (compared with both other groups). Otherwise, there were few intergroup hemodynamic differences. While there were no clinically important intergroup differences in mean ICP (+/- SD)-group 1, ICP = 12 +/- 7 mmHg; group 2, 15 +/- 12 mmHg; group 3, ICP = 11 +/- 8 mmHg-more isoflurane/nitrous oxide patients (nine, group 2) had an ICP > or = 24 mmHg than in the other groups (two each). Emergence was, overall, more rapid with fentanyl/nitrous oxide. For example, the median time until the patient could be awakened by quiet verbal command, e.g., "Open your eye," was 5 min, versus 10 min in the other groups. There were no relationships between ICP and any measurement of emergence (e.g., time to response to commands). Seven of 41 (17%) fentanyl/nitrous oxide patients vomited in the early postoperative period, compared with only 1 of 40 (2.5%) of those given propofol/fentanyl and 2 of 40 (5%) receiving isoflurane/nitrous oxide (P = 0.03). There were no differences in the incidence of new postoperative deficits, total hospital stay, or cost.

CONCLUSIONS

Although there are modest differences among the three tested anesthetics, short-term outcome was not affected. These results indicate that, despite their respective cerebrovascular effects, all of the anesthetic regimens used were acceptable in these patients undergoing elective surgery.

Clinical presentation and course of childhood Guillain-Barré syndrome: a prospective multicentre study

Presenting symptoms, clinical course and paraclinical findings in childhood Guillain-Barré syndrome (GBS) have rarely been investigated prospectively. We performed a multicentre study in GBS diagnosed according to international criteria. Clinical findings were recorded using an ordinal GBS score and additional scores for arm, cranial nerve and vegetative function, and pain. Electrophysiological and CSF investigations followed individual procedures in the local hospitals. Ninety-five children with a median age of 6.2 years were registered over 40 months (53 boys, 42 girls). 70 had suffered an infection and 8 had been vaccinated during the previous 6 weeks. The first symptom was usually a disturbance of gait or neuropathic pain. The symptoms progressed for a median of 7 days. At the height of the disease, 60% of patients were unable to walk and 24% could not use their arms. 46% showed cranial nerve involvement, and 51% autonomous dysfunction. 13% required artificial ventilation. 79% complained of neuropathic pain, half of them to a severe degree. Electrophysiological examination showed demyelination in 74%, and 26% of these presented with very low amplitude compound action potentials. Purely axonal changes were found in 11%. All but eight were treated with I.V. immunoglobulin. Improvement began on day 13 after the first symptom (median). Ability to walk unaided returned after 27 days. In the children observed over the long-term, it took 118 days for them to be free of symptoms. Transient deterioration after immunoglobulin treatment occurred in seven patients, two suffered relapsing GBS, and three developed CIDP. At the end of the observation period (288 days), 75% of patients were free of symptoms. 21% suffered residual symptoms having no effect on daily functioning. The more severely disabled 4% either suffered from CIDP or concurrent myelitis. With this prospective study, the results of earlier retrospective investigations are confirmed. Besides pareses and respiratory compromise, severe neuropathic pain frequently is a therapeutic challenge during the acute phase of the disease. The long-term prognosis is good for most children. However, a change to CIDP and concurrent myelitis can give rise to a worse prognosis.

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.

Asymmetric spin-wave dispersion on Fe(110): direct evidence of the Dzyaloshinskii-Moriya interaction

The influence of the Dzyaloshinskii-Moriya interaction on the spin-wave dispersion in an Fe double layer grown on W(110) is measured for the first time. It is demonstrated that the Dzyaloshinskii-Moriya interaction breaks the degeneracy of spin waves and leads to an asymmetric spin-wave dispersion relation. An extended Heisenberg spin Hamiltonian is employed to obtain the longitudinal component of the Dzyaloshinskii-Moriya vectors from the experimentally measured energy asymmetry.

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.

Development of a momentum microscope for time resolved band structure imaging

We demonstrate the use of a novel design of a photoelectron microscope in combination to an imaging energy filter for momentum resolved photoelectron detection. Together with a time resolved imaging detector, it is possible to combine spatial, momentum, energy, and time resolution of photoelectrons within the same instrument. The time resolution of this type of energy analyzer can be reduced to below 100 ps. The complete ARUPS pattern of a Cu(111) sample excited with He I, is imaged in parallel and energy resolved up to the photoelectron emission horizon. Excited with a mercury light source (h nu=4.9 eV), the Shockley surface state at the energy threshold is clearly imaged in k-space. Electron-electron interactions are observed in momentum space as a correlation hole in two-electron photoemission. With the high transmission and the time resolution of this instrument, possible new measurements are discussed: Time and polarization resolved ARUPS measurements, probing change of bandstructure due to chemical reaction, growth of films, or phase transitions, e.g., melting or martensitic transformations.

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.

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.