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The skull base is a highly complex anatomical region that provides passage for important nerves and vessels as they course into and out of the cranial cavity. Key to the management of pathology in this region is a thorough understanding of the anatomy, with its variations, and the relationship of various neurovascular structures to the pathology in question. Targeted high-resolution magnetic resonance imaging on high field strength magnets can enable the skull base surgeon to understand this intricate relationship and deal with the pathology from a position of relative advantage.
With the help of case studies, this paper illustrates the application of specialised magnetic resonance techniques to study pathology of the orbital apex in particular.
The fine anatomical detail provided gives surgeons the ability to design an endonasal endoscopic procedure appropriate to the anatomy of the pathology.
Three-dimensional (3D) nondestructive microstructural characterization was performed using full-field transmission X-ray microscopy on an Sn-rich alloy, at a spatial resolution of 60 nm. This study highlights the use of synchrotron radiation along with Fresnel zone plate optics to perform absorption contrast tomography for analyzing nanoscale features of fine second phase particles distributed in the tin matrix, which are representative of the bulk microstructure. The 3D reconstruction was also used to quantify microstructural details of the analyzed volume.
Colquitt, Murphy, and Ollander-Krane (Adler et al., 2016) argue that performance ratings are problematic in part because of the problems associated with feedback: Ratees dislike and dismiss performance feedback, raters are reluctant to provide tough feedback, and organizations do not enact research findings about improving feedback processes (Adler et al.). Discarding performance ratings on these grounds is effectively “throwing out the baby with the bath water,” given that we know quite a lot about how to improve the delivery and receptivity of feedback. Our commentary is intended to briefly illustrate ways to leverage research on feedback receptivity to improve performance management systems. Specifically, we focus on (a) cultivating supportive feedback environments, (b) integrating employee coaching into performance management systems, and (c) attending to the characteristics of feedback recipients to understand how they process feedback.
A fundamental goal of systems biology is to create models that describe relationships between biological components. Networks are an increasingly popular approach to this problem. However, a scientist interested in modeling biological (e.g., gene expression) data as a network is quickly confounded by the fundamental problem: how to construct the network? It is fairly easy to construct a network, but is it the network for the problem being considered? This is an important problem with three fundamental issues: How to weight edges in the network in order to capture actual biological interactions? What is the effect of the type of biological experiment used to collect the data from which the network is constructed? How to prune the weighted edges (or what cut-off to apply)? Differences in the construction of networks could lead to different biological interpretations.
Indeed, we find that there are statistically significant dissimilarities in the functional content and topology between gene co-expression networks constructed using different edge weighting methods, data types, and edge cut-offs. We show that different types of known interactions, such as those found through Affinity Capture-Luminescence or Synthetic Lethality experiments, appear in significantly varying amounts in networks constructed in different ways. Hence, we demonstrate that different biological questions may be answered by the different networks. Consequently, we posit that the approach taken to build a network can be matched to biological questions to get targeted answers. More study is required to understand the implications of different network inference approaches and to draw reliable conclusions from networks used in the field of systems biology.
Socio-behavioural factors and pathogens associated with childhood diarrhoea are of global public health concern. Our survey in 696 children aged ⩽2 years in rural West Bengal detected rotavirus as sole pathogen in 8% (17/199) of diarrhoeic stool specimens. Other organisms were detected along with rotavirus in 11% of faecal specimens. A third of the children with rotavirus diarrhoea, according to Vesikari score, had severe illness. The top four rotavirus genotypes were G9P (28%), G1P (19%), G2P (14%) and G8P (8%). In the multivariate model, the practice of ‘drawing drinking water by dipping a pot in the storage vessel’ [adjusted odds ratio (aOR) 2·21, 95% confidence interval (CI) 1·03–4·74, P = 0·041], and ‘children aged ⩽6 months with non-exclusive breastfeeding’ (aOR 2·07, 95% CI 1·1–3·82, P = 0·024) had twice the odds of having diarrhoea. Incidence of rotavirus diarrhoea was 24/100 child-years in children aged >6–18 months, 19/100 child-years in children aged >18–24 months and 5/100 child-years in those aged ⩽6 months. Results have translational implications for future interventions including vaccine development.
To evaluate the peri-operative usefulness of dexmedetomidine in obstructive sleep apnoea surgery.
In a clinical audit, patients were divided into a study group (dexmedetomidine used; n = 125; 82.9 per cent males, 17.1 per cent females; mean age 48.1 years) and a control group (dexmedetomidine not used; n = 143; 85.5 per cent males, 14.5 per cent females; mean age 47.4 years). The selected outcome measures were mean arterial pressure, use of anti-hypertensives and use of opioids.
Mean arterial pressure was stable (i.e. below 100 mmHg) in 93.3 per cent of the study group and 72.0 per cent of the control group (relative risk 1.30, 95 per cent confidence interval 1.14–1.47). The use of glyceryl trinitrate and hydralazine was significantly less in the study group, compared with controls (p = 0.005 and <0.001, respectively). Study group patients underwent more procedures than control patients (p < 0.001) and were more likely to require morphine. No difference was noted in the median dose of opioids.
Dexmedetomidine improves haemodynamic stability in patients undergoing surgery for obstructive sleep apnoea. It is reliable and reduces the need for polypharmacy. Its opioid-sparing action has been established in the literature; however, this was not demonstrated in our study.
1. ABSTRACT: This study was performed to evaluate the in-vitro and in-vivo tumor-cellular uptake and biodistribution pattern of tamoxifen when administered intravenously as a simple solution and upon encapsulation into biodegradable, surface-modified poly(ε-caprolactone) (PCL) nanoparticles. PCL (MW ∼ 15, 000) nanoparticles were prepared by the solvent displacement method and characterized for particle size/charge and surface morphology (by scanning electron microscopy). We investigated the nanoparticle-surface modification potential of the hydrophilic stabilizer (Pluronic® F-68 and F-108) employed during the preparation by electron spectroscopy for chemical analysis (ESCA). Quantitative in-vitro cellular uptake of tritiated (3H) tamoxifen in solution form and as nanoparticulate formulation was assessed in MCF-7 breast cancer cells. In-vivo biodistribution studies for the same formulations were carried out in Nu/Nu mice bearing MDA-MB-231 human breast carcinoma xenograft. Spherical nanoparticles having positive zeta potential (∼25 mV) were obtained in the size range of 200-300 nm. Pluronics (both F-68 and F-108), the triblock copolymers of poly(ethylene oxide) (PEO) and poly(propylene oxide) induced surface hydrophilization of the nanoparticles via adsorption as evident by ESCA. Nanoparticulate formulations of tamoxifen achieved higher intracellular concentrations when exposed at therapeutic concentrations to tumor cells in-vitro compared to solutions. The in-vivo biodistribution studies carried out in nude mice bearing experimental breast tumor suggested increased tumor concentrations for the drug administered as nanoparticulate formulations besides longer retention times within tumor mass. This type of delivery system is expected to provide better therapeutic benefit by dual means: preferential concentration within the tumor mass via enhanced permeation and retention pathway, and; subsequent controlled release, thus maintaining the local drug concentration for longer periods of time to achieve maximal cell-kill.
Two polyols were prepared from soybean oil, one by epoxidation route and the other via hydroformylation. The polyol obtained by epoxidation has secondary groups and has a gel time of more than one hour when reacted with crude MDI to produce polyurethanes. Hydroformylated polyol has a gel time with MDI of several minutes and is more suitable for reinforced reaction injection molding (RRIM). The first group of polyurethanes had a glass transition close to 80 °C while the hydroformylated gave about 30 degrees lower Tg and comparable strength but higher elongation. Adding glycerin as the crosslinker could increase both Tg and strength. Two series of laminates were prepared using several types of glass fabric, carbon fiber, polyester, cotton and jute fabrics r as reinforcements. Hydroformylated polyol based polyurethane composites were softer, with lower Tg, modulus and strength. Composites with organic fibers were lighter and more flexible than the glass reinforced samples. For comparison glass reinforced epoxy and polyester were prepared and tested. Organic fibers gave lower stiffness and strength than the corresponding glass or carbon fiber. Although the neat polyester and epoxy resins had somewhat higher strengths than the polyurethanes from soybean oil, mainly due to the higher crosslinking density, the composites from the soy oil-based resin displayed comparable or better properties. Glass transition and mechanical properties of the soy-based polyurethanes was varied from about 70 °C to 140 °C with added crosslinkers. Processing time of the soy-polyurethanes resins was shorter than that of the other two resins.
Interface and torsional shear stresses in the fiber twist test (FTT) were computed using the ABAQUS finite element program. Interface stress singularities were compared with an elasticity solution for the torsion of a fiber embedded in an elastic half space . Single fiber composite systems having perfectly bonded interfaces and fiber/matrix shear modulus ratios of Gf /Gm = 1 – 3 were considered. The decay rates and depths of the interface shear stress σrθ and the torsional shear stress σZθ in the fiber and matrix were evaluated for each Gf/Gm ratio.
The role of the material parameters on the fracture and creep behavior of discontinuous ductile fiber reinforced brittle matrix composite system was numerically investigated. For simulation of fracture behavior, the ductile fibers were modeled using a constitutive relationship that accounts for strength degradation resulting from nucleation and growth of the voids. The matrix is assumed to be elastic and fails according to requirements of a stress criterion. Results indicate that the contribution of ductile reinforcement to the work of fracture value (toughness) of the composite increases with less exhaustion of its work hardening capacity before the onset of matrix failure. At creep regime, for rigidly bonded interfaces, the creep rate of the composite is not significantly influenced by the material properties of the ductile reinforcing phase due to development of large hydrostatic stress and constrained deformation in the reinforcement. Significant increases in room temperature fracture toughness can be achieved without extensively sacrificing the creep strength by ductile discontinuous reinforcements.
Since the Lanxide process was advanced for forming of Al2O3 ceramic composite by directed oxidation of Al alloys, much work has been done with various mechanisms being proposed. The mechanisms have claimed that only certain dopants are essential to the growth process. Nevertheless, no united consensus has yet been reached. In the present work, Al alloy containing 5% Mg was oxidised in air for 12 hours at 1150°C with or without surface dopants of MgO or Pd. The resultant composites showed very different microstructures. Without any surface doping, the alloy did not develop any portion of composite as the initial intimate oxide film stops further oxidation. This intimate oxide film can either be broken off by mechanical means or penetrated by reaction with surface dopants, so that the composite can grow and develop. The results show that the previously reported incubation time is not only related to reaction processes but also to the initial mechanical disturbances. Doping with Pd made the composite darker in colour as the grains of the alumina ceramic matrix and inclusions of Al metal are finer. This shows that Pd may make the top oxide layer less intimate, and more nucleation sites are therefore available for oxidation. A new model is presented for oxide sustained growth based on the existence of oxygen active top surface layer and the capillary flow of molten metal around ceramic phase.
A set of numerical analyses of crack growth was performed to elucidate the influence of microcracking on the fracture behavior of microcracking ceramic and ceramic composites. The random nucleation, orientation and size effects of discrete nucleating microcracks and resulting interactions are fully accounted for in a hybrid finite element model. The results obtained from the finite element analysis are compared with the continuum description of the microcracking. Although continuum description can provide a reasonable estimation of shielding, it fails to resolve the details of the micromechanism of toughening resulting from microcracking, since not every shielding event during the course of crack extension corresponds to an increase in the Rcurve. Moreover, as seen in the composite cases, the local events leading to toughening behavior may not be associated with the microcracking, even in the presence of large population of microcracks.
Si powders synthesized by the laser pyrolysis of silane can be nitrided at 1200–1250°C, producing an improved reaction bonded silicon nitride. This RBSN is a potential matrix for composites since it can be formed at temperatures which do not degrade the strengths of commercially available amorphous ceramic fibers. However, the density of the RBSN matrix has been limited to about 75% using the silane-derived Si powder. Combining Si powders and preceramic polymers offers an approach for increasing the density and mechanical properties of the reaction-formed Si3N4 matrix. The incorporation of polysilazanes inhibited the nitridation at 1250°C, but samples could be effectively nitrided at 1400°C. These higher nitriding temperatures are compatible with SCS-6 and other lowoxygen, crystalline SiC fibers which can be used as reinforcements for ceramic composites.
Partial reduction reactions in the Ni-Al-O system, starting with the spinel compound NiAl2O4, are used to form metal-ceramic microstructures in situ. Two different morphologies of nearly pure Ni particles, equiaxed and rod-like, form within a ceramic matrix depending on the choice of processing parameters. Electron microscopy studies were performed for microstructural characterization, phase identification and chemical analysis. The fracture toughness of the Ni-Al2O3 mixture was significantly improved with respect to that of the original spinel phase. It is shown that cracking at the original spinel grain boundaries, likely due to the large volume changes associated with the reduction reaction, can be avoided by the addition of small amounts of ZrO2. It is seen that ZrO2 also acts as a nucleation site for the precipitating metal and hence allows morphology control in microstructures obtained by partial reduction reactions.
Oxide - carbon multilayer coatings were continuously applied to various fibers of nominal SiC composition. A liquid-phase coating system that allows application of the coatings in a controlled atmosphere at relatively rapid rates was employed. Sugar - ammonium hydroxide solutions were used for carbon coatings, and aqueous sols were used for the oxides. Carbon was also deposited simultaneously with alumina by chemical vapor deposition of a hydrocarbon in the coating furnace. The coatings were extensively characterized by optical microscopy and TEM. Problems with embrittlement by oxide coatings and poor adherence of oxide coatings on carbon, and some possible solutions to these problems, are discussed.