Multiple equilibria in a simple elastocapillary system

We consider the elastocapillary interaction of a liquid drop placed between two flexible sheets, which are both clamped at one end to a rigid substrate. This is a simple model system relevant to the problem of surface tension-induced collapse of flexible micro-channels that has been observed in the manufacture of microelectromechanical systems(MEMS). We determine the conditions under which the flexible sheets remain separated, touch at a point, or stick along a portion of their length. Surprisingly, we show that in many circumstances multiple equilibrium states are possible. We develop a lubrication-type model for the flow of liquid out of equilibrium and thereby investigate the stability of the multiple equilibria. We demonstrate that for given material properties two stable equilibria may exist and show through numerical solutions of the dynamic model that it is the initial state of the system that determines which stable equilibrium is reached by the system; the system does not simply choose the equilibrium state of lowest energy

Lubricated wrinkles: imposed constraints affect the dynamics of wrinkle coarsening

We study the dynamic coarsening of wrinkles in an elastic sheet that is compressed while lying on a thin layer of viscous liquid. When the ends of the sheet are instantaneously brought together by a small distance, viscous resistance initially prevents the sheet from adopting a globally buckled shape. Instead, the sheet accommodates the compression by wrinkling. Previous scaling arguments suggested that a balance between the sheet's bending stiffness and viscous effects lead to a wrinkle wavelength $\lambda$ that increases with time $t$ according to $\lambda\propto t^{1/6}$. We show that taking proper account of the compression constraint leads to a logarithmic correction of this result, $\lambda\propto (t/\log t)^{1/6}$. This correction is significant over experimentally observable time spans, and leads us to reassess previously published experimental data.Comment: 12 pages. Version accepted in Phys. Rev. Fluids (with small correction to bibliography

A study of nano-particle based silane consolidants for Globigerina limestone

This STEPS funded study focuses on the application of hybrid and nanoparticle loaded hybrid silane consolidants for the treatment of 'Franka' type Globigerina Limestone. Consolidants act by gluing the deteriorated stone material to the underlying healthy stone (Dukes, 1972; Gutt, 1973; Alessandrini et al., 1975; Garrod, 2001). The consolidants evaluated in this work were a laboratory prepared hybrid silane based on a mixture of tetraethylorthosilicate (TEOS) and 3-(glycidoxypropyl) trimethoxysilane (GPTMS), the same hybrid consolidant loaded with silica nanoparticles and GPTMS-modified silica nanoparticles. In addition, a consolidant based on the hydrolysis product of TEOS was also tested. Prepared consolidants were applied to Globigerina Limestone test blocks by complete immersion. Untreated stone block were used as benchmarks. Following application of the consolidants, half of the treated limestone blocks were subjected to accelerated weathering. Non-weathered and weathered limestone blocks were then characterised by optical and electron microscopy and the stone colour before and after treatment with consolidants was assessed by a colorimetric technique. The pore size distribution before and after application of the different consolidant treatments was assessed by Mercury Intrusion Porosimetry. A water absorption by capillarity technique was also carried out to assess how the water uptake rate into the limestone alters with the different treatments. The mechanical properties of the consolidated limestone blocks were assessed by resistance to sodium sulfate crystallisation. Microscopy observations showed that the consolidants penetrated the stone to different extents depending on the consolidant and the method of application. The hybrid consolidant on its own led to yellowing of the limestone but the addition of nanoparticles to the hybrid (modified or not) appeared to help restore the original colour of the stone. The porosity of the limestone was only marginally affected by the different treatments but the somewhat hydrophobic nature of the consolidants led to a disruption in the capillary flow of water into the limestone.peer-reviewe

Cloaking by coating: How effectively does a thin, stiff coating hide a soft substrate?

From human tissue to fruits, many soft materials are coated by a thin layer of a stiffer material. While the primary role of such a coating is often to protect the softer material, the thin, stiff coating also has an important effect on the mechanical behaviour of the composite material, making it appear significantly stiffer than the underlying material. We study this cloaking effect of a coating for the particular case of indentation tests, which measure the `firmness' of the composite solid: we use a combination of theory and experiment to characterize the firmness quantitatively. We find that the indenter size plays a key role in determining the effectiveness of cloaking: small indenters feel a mixture of the material properties of the coating and of the substrate, while large indenters sense largely the unadulterated substrate

Murine and human myogenic cells identified by elevated aldehyde dehydrogenase activity: Implications for muscle regeneration and repair

Background: Despite the initial promise of myoblast transfer therapy to restore dystrophin in Duchenne muscular dystrophy patients, clinical efficacy has been limited, primarily by poor cell survival post-transplantation. Murine muscle derived stem cells (MDSCs) isolated from slowly adhering cells (SACs) via the preplate technique, induce greater muscle regeneration than murine myoblasts, primarily due to improved post-transplantation survival, which is conferred by their increased stress resistance capacity. Aldehyde dehydrogenase (ALDH) represents a family of enzymes with important morphogenic as well as oxidative damage mitigating roles and has been found to be a marker of stem cells in both normal and malignant tissue. In this study, we hypothesized that elevated ALDH levels could identify murine and human muscle derived cell (hMDC) progenitors, endowed with enhanced stress resistance and muscle regeneration capacity. Methodology/Principal Findings: Skeletal muscle progenitors were isolated from murine and human skeletal muscle by a modified preplate technique and unfractionated enzymatic digestion, respectively. ALDHhisubpopulations isolated by fluorescence activate cell sorting demonstrated increased proliferation and myogenic differentiation capacities compared to their ALDHlocounterparts when cultivated in oxidative and inflammatory stress media conditions. This behavior correlated with increased intracellular levels of reduced glutathione and superoxide dismutase. ALDHhimurine myoblasts were observed to exhibit an increased muscle regenerative potential compared to ALDHlomyoblasts, undergo multipotent differentiation (osteogenic and chondrogenic), and were found predominately in the SAC fraction, characteristics that are also observed in murine MDSCs. Likewise, human ALDHhihMDCs demonstrated superior muscle regenerative capacity compared to ALDHlohMDCs. Conclusions: The methodology of isolating myogenic cells on the basis of elevated ALDH activity yielded cells with increased stress resistance, a behavior that conferred increased regenerative capacity of dystrophic murine skeletal muscle. This result demonstrates the critical role of stress resistance in myogenic cell therapy as well as confirms the role of ALDH as a marker for rapid isolation of murine and human myogenic progenitors for cell therapy. © 2011 Vella et al

Antibiotic prescribing on two medical wards at St Luke’s Hospital : what scope for improvement?

Antibiotics are frequently prescribed drugs and form a significant part of the hospital budget. The literature suggests that prescribing is not without problems and may need constant review. We have no data relating to our hospital. This study aims to explore some aspects of antibiotic use in our setting. Records of all patients prescribed antibiotics on two medical wards over a 4 month period were analysed for indication, choice of antibiotic, outcome and cost. There were 126 patients: 54% males; 75.4%, >60 years old; 62% were admitted because of infection. Of the whole group, 8.7% received antibiotics with no evidence of infection and no indication for prophylaxis. There were 118 infections, 64% respiratory, 13.5% urinary and the rest of miscellaneous sites; 14% of infections were nosocomial. Microbiological studies were available in only 29% of infections. For 6 patients, the antibiotics prescribed were relatively contraindicated because of impaired hepatic and renal function. There was one adverse drug reaction. The total drug cost was Lm2181.79; i.v. treatment accounted for 93% of this cost and ceftazidime for 60%. There is room for improvement in the selection of antibiotics and their route of administration. The hospital microbiologists and the Antibiotic Policy should be consulted more often. Laboratory diagnosis of infection and biochemical patient monitoring are inadequate. Restricting i.v. treatment could reduce cost very substantially.peer-reviewe

Pharmacist-led diabetic patient monitoring

Objective: To assess pharmacist intervention in diabetic patients on patient compliance to medication and blood glucose self-monitoring and to evaluate patient therapeutic plans through monitoring of glycated haemoglobin (HbA1c) levels. Method: Thirty type 2 diabetic patients receiving their medication through the Pharmacy of Your Choice (POYC) scheme were assessed. Patient compliance to medication and to self-blood glucose monitoring was reported before (t=0) and following pharmacist intervention (t=1). The pharmacist intervention included an educational session and distribution of a ‘Diabetes Patient Information Leaflet’. HbA1c testing was performed and patients with out-of-range values were referred. Key findings: Patient compliance to medication improved following pharmacist intervention, with 24 patients claiming to ‘rarely miss a dose’ of medication prior to the intervention (t=0), decreasing to 8 patients at t=1. At t=0, 1 patient reported to ‘never miss a dose’ of medication which increased to 22 patients at t=1. Fifteen patients reported to monitor glucose levels less than once a month at t=0, while 23 patients claimed to monitor their glucose levels on a weekly basis at t=1. The mean value for HbA1c was 6.5%. Two patients obtained HbA1c values of 7.0 and 7.1% and were referred. Conclusion: Pharmacist-led medication reviews, through monitoring of blood glucose and HbA1c levels and suggesting optimal pharmacological treatment, can help diabetic patients use their medications more effectively to achieve maximal treatment benefits. Point-of-care HbA1c testing may be an accessible means of assessing glucose control and may motivate patients who seek to monitor glycaemia more closely.peer-reviewe

Evaluation of pharmacist clinical recommendations in a geriatric hospital

Objectives: This study was undertaken to record the number and type of recommendations made by pharmacists reviewing the drug treatment of older patients, to note acceptance of these recommendations by physicians and to assess clinical significance of pharmacist recommendations. Method: Three pharmacists providing inpatient services at Zammit Clapp Hospital were asked to record specific details of all recommendations given using a designed documentation form. The clinical impact of the pharmacists’ recommendations was assessed by the pharmacists making the recommendations together with a panel of two independent pharmacists and a medical doctor who had to rate the contribution of each recommendation as major, moderate, minor or of no clinical significance. Key findings: A total of 263 valid pharmacist recommendations were documented. The most frequent recommendations, accounting for 20.5% (n=54) of the total number of recommendations were adjustment to dosage, frequency and time of administration followed by discontinuation of a medication. The majority of recommendations were accepted by physicians (80%) and were rated by the panel to be of moderate (60.5%) clinical significance. Conclusion: Clinical pharmacists make a number of recommendations of significant clinical benefit to the care of hospitalised elderly patients, the majority of which are accepted by physicians.peer-reviewe