Reinforcements in avian wing bones: Experiments, analysis, and modeling.

Almost all species of modern birds are capable of flight; the mechanical competency of their wings and the rigidity of their skeletal system evolved to enable this outstanding feat. One of the most interesting examples of structural adaptation in birds is the internal structure of their wing bones. In flying birds, bones need to be sufficiently strong and stiff to withstand forces during takeoff, flight, and landing, with a minimum of weight. The cross-sectional morphology and presence of reinforcing structures (struts and ridges) found within bird wing bones vary from species to species, depending on how the wings are utilized. It is shown that both morphology and internal features increases the resistance to flexure and torsion with a minimum weight penalty. Prototypes of reinforcing struts fabricated by 3D printing were tested in diametral compression and torsion to validate the concept. In compression, the ovalization decreased through the insertion of struts, while they had no effect on torsional resistance. An elastic model of a circular ring reinforced by horizontal and vertical struts is developed to explain the compressive stiffening response of the ring caused by differently oriented struts.

Triptans and third nerve paresis: a case series of three patients.

PurposeThe aim of this report is to increase awareness of a possible association between cranial nerve paresis and the use of sumatriptan in migraine sufferers, particularly in patients who have additional vascular risk factors.Patients and methodsWe describe a series of three cases where third nerve paresis developed in patients who were treated with the oral form of sumatriptan. All of the patients had a clear history of repetitive migraine headache and none of them had previous third nerve paresis.ConclusionAmong a variety of medications for the treatment of migraine, there are some drugs with vasoconstrictive effects, particularly triptans. These drugs may be a contributing factor for microvascular damage of the cranial nerves and other organs.

Pain score assessment in babies undergoing laser treatment for retinopathy of prematurity under sub-tenon anaesthesia.

PURPOSE: To assess the tolerability and outcomes of laser treatment for retinopathy of prematurity (ROP) under sub-tenon anaesthetic with oral or rectal sedation using a reliable, multidimensional, and internationally accepted tool for assessment of neonatal pain. METHODS: Sixty-two babies have had ROP laser treatment in our neonatal unit in the 7-year interval between 1 March 2005 and 28 February 2012; 44% (27 of the 62) were performed using sub-tenon anaesthesia. Pain scores were routinely assessed using the Neonatal Pain Agitation and Sedation Scale (N-PASS) every 10 min during laser treatment. The outcome and requirement for re-treatment in this group was compared with that in the intravenous sedation group. RESULTS: Pain scores were available in 19 of the 27 babies treated under sub-tenon anaesthesia. The mean pain score during treatment was 2.7 (SD ± 1.7, range 0.5-6.2). There was no statistically significant correlation between the mean pain score and duration of treatment (Spearman correlation coefficient (ρ) = 0.31; P = 0.09), number of laser burns (ρ = 0.32; P = 0.09), or post-menstrual age of the baby at the time of treatment (ρ = 0.38; P = 0.052). Treatments performed under sub-tenon anaesthesia were as successful as those performed under intravenous sedation. The mean pain scores during laser treatment under sub-tenon anaesthesia in our study were lower than those previously reported during ROP screening or heel-stick procedure.Conclusion Our study demonstrated that sub-tenon anaesthesia with oral or rectal sedation provides sufficient pain control for laser treatment for ROP without the need or risks of intravenous sedation and intubation.

Elastic moduli of untreated, demineralized and deproteinized cortical bone: validation of a theoretical model of bone as an interpenetrating composite material.

A theoretical experimentally based multi-scale model of the elastic response of cortical bone is presented. It portrays the hierarchical structure of bone as a composite with interpenetrating biopolymers (collagen and non-collagenous proteins) and minerals (hydroxyapatite), together with void spaces (porosity). The model involves a bottom-up approach and employs micromechanics and classical lamination theories of composite materials. Experiments on cortical bone samples from bovine femur include completely demineralized and deproteinized bones as well as untreated bone samples. Porosity and microstructure are characterized using optical and scanning electron microscopy, and micro-computed tomography. Compression testing is used to measure longitudinal and transverse elastic moduli of all three bone types. The characterization of structure and properties of these three bone states provides a deeper understanding of the contributions of the individual components of bone to its elastic response and allows fine tuning of modeling assumptions. Very good agreement is found between theoretical modeling and compression testing results, confirming the validity of the interpretation of bone as an interpenetrating composite material.

A novel method to study fluorescein staining of the ocular surface using the fluorescein angiogram setting of the fundus camera.

We present a case of a failed penetrating keratoplasty (PKP), comparing the fluorescein staining of the cornea with the conventional technique, and the new technique using the fluorescein filters of a standard fundus camera.