Zig-zag instability of an Ising wall in liquid crystals

We present a theoretical explanation for the interfacial zigzag instability that appears in anisotropic systems. Such an instability has been experimentally highlighted for an Ising wall formed in a nematic liquid crystal cell under homeotropic anchoring conditions. From an envelope equation, relevant close to the Freedericksz transition, we have derived an asymptotic equation describing the interface dynamics in the vicinity of its bifurcation. The asymptotic limit used accounts for a strong difference between two of the elastic constants. The model is characterized by a conservative order parameter which satisfies a Cahn-Hilliard equation. It provides a good qualitative understanding of the experiments.Comment: 4 pagess, 4 figures, lette

Pearling and Pinching: Propagation of Rayleigh Instabilities

A new category of front propagation problems is proposed in which a spreading instability evolves through a singular configuration before saturating. We examine the nature of this front for the viscous Rayleigh instability of a column of one fluid immersed in another, using the marginal stability criterion to estimate the front velocity, front width, and the selected wavelength in terms of the surface tension and viscosity contrast. Experiments are suggested on systems that may display this phenomenon, including droplets elongated in extensional flows, capillary bridges, liquid crystal tethers, and viscoelastic fluids. The related problem of propagation in Rayleigh-like systems that do not fission is also considered.Comment: Revtex, 7 pages, 4 ps figs, PR

Molecular simulation of chevrons in confined smectic liquid crystals

Chevron structures adopted by confined smectic liquid crystals are investigated via molecular dynamics simulations of the Gay-Berne model. The chevrons are formed by quenching nematic films confined between aligning planar substrates whose easy axes have opposing azimuthal components. When the substrates are perfectly smooth, the chevron formed migrates rapidly towards one of the confining walls to yield a tilted layer structure. However, when substrate roughness is included, by introducing a small-amplitude modulation to the particle- substrate interaction well-depth, a symmetric chevron is formed which remains stable over sufficiently long runtimes for detailed structural information, such as the relevant order parameters and director orien- tation, to be determined. For both smooth and rough boundaries, the smectic order parameter remains non-zero across the entire chevron, implying that layer identity is maintained across the chevron tip. Also, when the surface-stabilised chevron does eventually revert to a tilted layer structure, it does so via surface slippage, such that layer integrity is maintained throughout the chevron to tilted layer relaxation process. </p

Spermidine Promotes Human Hair Growth and Is a Novel Modulator of Human Epithelial Stem Cell Functions

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Chemotherapeutic errors in hospitalised cancer patients: attributable damage and extra costs

<p>Abstract</p> <p>Background</p> <p>In spite of increasing efforts to enhance patient safety, medication errors in hospitalised patients are still relatively common, but with potentially severe consequences. This study aimed to assess antineoplastic medication errors in both affected patients and intercepted cases in terms of frequency, severity for patients, and costs.</p> <p>Methods</p> <p>A 1-year prospective study was conducted in order to identify the medication errors that occurred during chemotherapy treatment of cancer patients at a French university hospital. The severity and potential consequences of intercepted errors were independently assessed by two physicians. A cost analysis was performed using a simulation of potential hospital stays, with estimations based on the costs of diagnosis-related groups.</p> <p>Results</p> <p>Among the 6, 607 antineoplastic prescriptions, 341 (5.2%) contained at least one error, corresponding to a total of 449 medication errors. However, most errors (n = 436) were intercepted before medication was administered to the patients. Prescription errors represented 91% of errors, followed by pharmaceutical (8%) and administration errors (1%). According to an independent estimation, 13.4% of avoided errors would have resulted in temporary injury and 2.6% in permanent damage, while 2.6% would have compromised the vital prognosis of the patient, with four to eight deaths thus being avoided. Overall, 13 medication errors reached the patient without causing damage, although two patients required enhanced monitoring. If the intercepted errors had not been discovered, they would have resulted in 216 additional days of hospitalisation and cost an estimated annual total of 92, 907€, comprising 69, 248€ (74%) in hospital stays and 23, 658€ (26%) in additional drugs.</p> <p>Conclusion</p> <p>Our findings point to the very small number of chemotherapy errors that actually reach patients, although problems in the chemotherapy ordering process are frequent, with the potential for being dangerous and costly.</p

Minimising treatment-associated risks in systemic cancer therapy

Aim of the review To review the consequences of drug-related problems (DRP) in systemic cancer therapy and identify specific contributions of the pharmacist to minimise treatment-associated risks. Method Searches in PubMed, Embase and the Cochrane Library were conducted. Bibliographies of retrieved articles were examined for additional references. Only papers in English between 1980 and 2007 were included. Results In systemic cancer therapy there is an enormous potential for DRP due to the high toxicity and the complexity of most therapeutic regimens. The most frequently reported DRP can be classified into adverse effects, drug–drug interactions, medication errors, and non-adherence. Pharmacists have enhanced efforts to assure quality and safety in systemic cancer therapy together with other health care providers. In consequence, oncology pharmacy has evolved as a novel specialist discipline. The endeavour to merge and co-ordinate individual activities and services of the pharmacist has led to pharmaceutical care concepts which aim at offering novel solutions to the various DRP. Conclusion Pharmaceutical care for cancer patients should be developed within research projects and integrated into disease management programs in order to ensure broad implementation

Anti-inflammatory agents and monoHER protect against DOX-induced cardiotoxicity and accumulation of CML in mice

Cardiac damage is the major limiting factor for the clinical use of doxorubicin (DOX). Preclinical studies indicate that inflammatory effects may be involved in DOX-induced cardiotoxicity. Nɛ-(carboxymethyl) lysine (CML) is suggested to be generated subsequent to oxidative stress, including inflammation. Therefore, the aim of this study was to investigate whether CML increased in the heart after DOX and whether anti-inflammatory agents reduced this effect in addition to their possible protection on DOX-induced cardiotoxicity. These effects were compared with those of the potential cardioprotector 7-monohydroxyethylrutoside (monoHER)

The inhibition of the Rayleigh-Taylor instability by rotation

It is well-established that the Coriolis force that acts on fluid in a rotating system can act to stabilise otherwise unstable flows. Chandrasekhar considered theoretically the effect of the Coriolis force on the Rayleigh-Taylor instability, which occurs at the interface between a dense fluid lying on top of a lighter fluid under gravity, concluding that rotation alone could not stabilise this system indefinitely. Recent numerical work suggests that rotation may, nevertheless, slow the growth of the instability. Experimental verification of these results using standard techniques is problematic, owing to the practical difficulty in establishing the initial conditions. Here, we present a new experimental technique for studying the Rayleigh-Taylor instability under rotation that side-steps the problems encountered with standard techniques by using a strong magnetic field to destabilize an otherwise stable system. We find that rotation about an axis normal to the interface acts to retard the growth rate of the instability and stabilise long wavelength modes; the scale of the observed structures decreases with increasing rotation rate, asymptoting to a minimum wavelength controlled by viscosity. We present a critical rotation rate, dependent on Atwood number and the aspect ratio of the system, for stabilising the most unstable mode

Zig-zag walls in the chevron layer structure of smectic liquid crystals: Line energy and selection of the wall orientation

The cooling of thin cells containing a smectic liquid crystal (layers normal to the plates) often leads to a “chevron": to match the decreasing layer thickness in the bulk with that “frozen" near the plates, the layers tilt and fold in the middle plane of the cell, the two possible chevron directions being separated by walls of typical “zig-zag" shape. A simple model of these walls combines a paper-folding description with qualitative estimates of the folding energy. Different wall orientations are discussed: “thick walls" parallel to the layers, "thin walls" perpendicular to the layers, or inside the zig-zag patterns, slightly inclined with respect to the layer normal of an angle α. A geometrical argument suggests that α is proportional to the layer tilt angle θ, and presumably given by $\alpha=\theta/\sqrt{3}$