Nanoscale structures and dynamics of a boundary liquid layer.

Our long term scientific interest is the understanding of the interface properties of flowing liquids on a microscopic level. Various mechanisms have been introduced to explain the origin of slip at a solid-liquid interface like the formation of a thin depletion layer or a molecular ordering of the liquid near the interface. Reflectometry (using x-rays or neutrons) is a powerful technique to probe structures in this surface region. However, to date much less attention has been paid to the dynamical properties. In the first part of this paper we show that a different ordering of water exists next to a hydrophobic substrate in comparison to a hydrophilic interface. Furthermore, we find that shear has no effect on the depletion layer on hydrophobic substrates, while no depletion layer exists for hydrophilic surfaces. The second part of the paper addresses the dynamical properties of the boundary layer, and we present a new method which enables the observation of the diffusion dynamics of polymers next to a solid substrate. As a proof of concept, the dynamics of micelles next to the interface has been explored using grazing incidence neutron spin-echo spectroscopy. We were able to verify that investigation of the dynamics of the sample is feasible with this grazing incidence technique and we present data taken near the critical angle of total reflection. It appears that the diffusive motion of micelles at the hydrophobic (repulsive) interface is faster than at a hydrophilic interface or in the bulk. Furthermore, neutron spin-echo spectroscopy was extended to a first evaluation of the Doppler shift which occurs under flow.

Recrafting the neighbor-joining method.

BACKGROUND: The neighbor-joining method by Saitou and Nei is a widely used method for constructing phylogenetic trees. The formulation of the method gives rise to a canonical Theta(n3) algorithm upon which all existing implementations are based. RESULTS: In this paper we present techniques for speeding up the canonical neighbor-joining method. Our algorithms construct the same phylogenetic trees as the canonical neighbor-joining method. The best-case running time of our algorithms are O(n2) but the worst-case remains O(n3). We empirically evaluate the performance of our algoritms on distance matrices obtained from the Pfam collection of alignments. The experiments indicate that the running time of our algorithms evolve as Theta(n2) on the examined instance collection. We also compare the running time with that of the QuickTree tool, a widely used efficient implementation of the canonical neighbor-joining method. CONCLUSION: The experiments show that our algorithms also yield a significant speed-up, already for medium sized instances.

Surgical approach to kinking and coiling of the internal carotid artery.

AIM: Whether kinking or coiling of the internal carotid artery (ICA) simply represents a morphological variation without clinical relevance still remains an object of debate. While most patients are incidentally diagnosed in an asymptomatic state due to the broad use of non-invasive investigations (like colour coded Doppler sonography), associated neurological deficits are often unspecific and might be related to coexisting proximal stenotic lesions. Its etiology is unclear. Beside artherosclerotic genesis, a persistent embryological condition or underlying fibromuscular dysplasia is discussed. Moreover, in contrast to precise recommendations concerning the indication for endarteriectomy in carotid artery stenosis, general guidelines for surgical intervention in case of kinking or coiling are not yet established. METHODS: The characteristics of 16 patients who underwent a total of 21 reconstructive operations for isolated kinking or coiling of the ICA during 5 years of observation were retrospectively analyzed. RESULTS: In 10 out of 14 kinkings and 5 out of 7 coilings central nervous symptoms were noted including unspecific vertigo, syncope, tinnitus synchronous to pulse, transient ischemic attacks and manifest cerebral infarction. All these individual complaints disappeared postoperatively. In 1 patient presenting with an ICA coiling histological examination revealed signs of fibromuscular dysplasia. The other specimens showed typical changes of artherosclerotic disease. CONCLUSION: By precluding significant proximal stenosis and effective elimination of symptoms after surgical correction, a causal connection between cerebral dysfunction and severe ICA kinking or coiling can be supposed. An actual abnormality of the arterial wall structure only exists in exceptional cases. Rather, a sequential development from kinking to coiling was noticed.

Antibodies to chlamydial lipopolysaccharides in unstable angina pectoris.

Patients with coronary artery disease frequently have elevated antibody titers against Chlamydia pneumoniae, but whether antichlamydial antibody titers are correlated with prognosis in unstable angina remains unclear. We therefore investigated the sera of 1,096 patients with unstable angina regarding immunoglobulin (Ig) IgG, IgA, and IgM antibody titers against chlamydial lipopolysaccharides (LPS) and the concentrations of C-reactive protein (CRP) and troponin T (TnT). Anti-LPS IgG titers were increased in 45% of patients at enrollment and in 48% of patients at discharge (p <0.0001). Anti-LPS IgA titers were increased in 27% of patients at enrollment and in 33% of patients at discharge (p <0.0001). Patients who subsequently died had significantly lower IgM titers at enrollment than patients without events (p = 0.016). IgG, IgA, or IgM titers did not correlate with concentrations of CRP or TnT. In this large-scale study of patients with unstable angina, we frequently found elevated antichlamydial antibody titers. Patients with low IgM anti-LPS titers were at risk for subsequent death. However, there was no correlation between antichlamydial antibody titers and CRP or TnT.