Plexiform Neurofibroma: A Rare Tumor of Submandibular Salivary Gland

A 15-year-old boy presented with swelling in the submandibular region. X-ray of the swollen part showed faint radio opaque shadow. A provisional diagnosis of sialadenitis with sialolithiasis was made. Excised mass was reported histopathologically as plexiform neurofibroma of submandibular salivary gland. Plexiform neurofibroma of the salivary gland is a rare benign tumor often present in the parotid gland. It is very rare in submandibular salivary gland. It is a slow growing, locally infiltrating tumor. Key words: Plexiform neurofibroma, sialadenitis, sialolithiasis, submandibular salivary glan

Phase cascade bridge rectifier array in a 2-D lattice

We report on a novel rectification phenomenon in a 2-D lattice network consisting of N×N sites with diode and AC source elements with controllable phases. A phase cascade configuration is described in which the current ripple in a load resistor goes to zero in the large N limit, enhancing the rectification efficiency without requiring any external capacitor or inductor based filters. The integrated modular configuration is qualitatively different from conventional rectenna arrays in which the source, rectifier and filter systems are physically disjoint. Exact analytical results derived using idealized diodes are compared to a realistic simulation of commercially available diodes. Our results on nonlinear networks of source-rectifier arrays are potentially of interest to a fast evolving field of distributed power networks

Phase cascade lattice rectifier array: an exactly solvable nonlinear network circuit

An exact analysis of a 2-D lattice network consisting of N × N sites with rectifier and AC source elements with controllable phases reveals a method for generating ripple-free DC power without the use of any filtering circuit elements. A phase cascade configuration is described in which the current ripple in a load resistor goes to zero in the large N limit, enhancing the rectification efficiency without requiring any additional capacitor or inductor based filters. The integrated modular configuration is qualitatively different from conventional rectenna arrays in which the source, rectifier and filter systems are physically disjoint. Nonlinear networks in the large N limit of source-rectifier arrays are potentially of interest to a fast evolving field of distributed power networks.MNacknowledges support from a Graduate Fellowship in the ECE department at Boston University. We thank CMaedler, R Averitt, and members of the Photonics Center staff for assistance. JC acknowledges support from the Boston University RISE summer program. (Graduate Fellowship in the ECE department at Boston University; Boston University RISE summer program)Published versio

Variation in viscous fingering pattern morphology due to surfactant-mediated interfacial recognition events

The study of the formation of finger-like patterns during displacement of a viscous fluid by a less viscous one is of technological importance. The morphology of the viscous-finger patterns generated is a function of many parameters such as the flow rate, difference in viscosities of the two fluids and the interfacial tension. We demonstrate herein that the morphology of patterns formed during viscous fingering in a Hele-Shaw cell during displacement of paraffin oil by aqueous solutions of the surfactant sodium dodecyl sulphate (SDS), is extremely sensitive to interfacial tension variation brought about by complexation of divalent cations with the surfactant SDS. The variation in morphology of the patterns formed has been quantified by measuring the fractal dimensions of structures formed in a radial Hele-Shaw cell as well as the average finger width in a linear Hele-Shaw cell. This technique shows promise for studying other interfacial phenomena in chemistry such as biorecognition as well as dynamic processes occurring at interfaces

Impacts of urbanisation on the native avifauna of Perth, Western Australia

Urban development either eliminates, or severely fragments, native vegetation, and therefore alters the distribution and abundance of species that depend on it for habitat. We assessed the impact of urban development on bird communities at 121 sites in and around Perth, Western Australia. Based on data from community surveys, at least 83 % of 65 landbirds were found to be dependent, in some way, on the presence of native vegetation. For three groups of species defined by specific patterns of habitat use (bushland birds), there were sufficient data to show that species occurrences declined as the landscape changed from variegated to fragmented to relictual, according to the percentage of vegetation cover remaining. For three other groups (urban birds) species occurrences were either unrelated to the amount of vegetation cover, or increased as vegetation cover declined. In order to maximise the chances of retaining avian diversity when planning for broad-scale changes in land-use (i.e. clearing native vegetation for housing or industrial development), land planners should aim for a mosaic of variegated urban landscapes (\u3e60 % vegetation retention) set amongst the fragmented and relictual urban landscapes (% vegetation retention) that are characteristic of most cities and their suburbs. Management actions for conserving remnant biota within fragmented urban landscapes should concentrate on maintaining the integrity and quality of remnant native vegetation, and aim at building awareness among the general public of the conservation value of remnant native vegetation

Simulation-based optimisation of LCC-HVDC controller parameters using surrogate model solvers

This paper proposes the use of surrogate model optimisation methods to solve box constrained LCC-HVDC controller tuning problems. The tuning problem is the selection of the proportional-integral controller gains and voltage-dependant current order limiter parameters of an LCC-HVDC link subject to two operational scenarios and a set of large-signal disturbances. The solvers using recently proposed surrogate model methods performed either similarly to or significantly better than solvers using mature methods of the types found in PSCAD/EMTDC, thus confirming the suitability of these surrogate model solvers for simulation-based optimisation of LCC-HVDC controllers

Economic liberalization and the antecedents of top management teams: evidence from Turkish 'big' business

There has been an increased interest in the last two decades in top management teams (TMTs) of business firms. Much of the research, however, has been US-based and concerned primarily with TMT effects on organizational outcomes. The present study aims to expand this literature by examining the antecedents of top team composition in the context of macro-level economic change in a late-industrializing country. The post-1980 trade and market reforms in Turkey provided the empirical setting. Drawing upon the literatures on TMT and chief executive characteristics together with punctuated equilibrium models of change and institutional theory, the article develops the argument that which firm-level factors affect which attributes of TMT formations varies across the early and late stages of economic liberalization. Results of the empirical investigation of 71 of the largest industrial firms in Turkey broadly supported the hypotheses derived from this premise. In the early stages of economic liberalization the average age and average organizational tenure of TMTs were related to the export orientation of firms, whereas in later stages, firm performance became a major predictor of these team attributes. Educational background characteristics of teams appeared to be under stronger institutional pressures, altering in different ways in the face of macro-level change

The structures underpinning vulnerability: examining landscape-society interactions in a smallholder coffee agroforestry system

Smallholder farmers dependent on rain-fed agriculture are particularly vulnerable to extreme climate events and, therefore, it is necessary to identify adaptive measures that would increase farmer resilience to these shocks. The management options in a low-input system, like forest coffee (Coffea arabica), are limited and there are several factors out of farmers' control driving their vulnerability to changing climatic conditions. These can relate to social structures and landscape factors, which can interact to reduce farmers' adaptive capacity, creating a state of contextual vulnerability. We explored the potential synergies of this interaction across elevation, patch area and shade management gradients for smallholder coffee farms around the UNESCO Yayu Coffee Forest Biosphere Reserve in Ethiopia before, during and immediately following the 2015/16 El Niño. We documented a dramatic collapse in coffee yields across all farms, resulting in coffee incomes 29.5 ± 18.0 % and 19.5 ± 10.0 % of 2014 incomes in 2015 and 2016, respectively. We identified farms at elevations between 1500-1600 m with canopy openness between 40-45 % as being consistently low yielding over our study period. We found these farmers had the highest rates of income diversification and, therefore, were already exhibiting adaptive capacity. Farmers with the largest income losses were spatially concentrated between 1600-1700 m, located in larger patch areas with lower canopy openness. Farmers at this elevation have access to poor infrastructure, restrictions on shade management and reported higher dependence on income from coffee, indicating an interaction of biotic and social factors exacerbating their vulnerability. Unfortunately, due to a nationally declared state of emergency, we were unable to survey farmers on the adaptive measures they undertook; therefore, we are limited in assessing their resilience. However, we do show the importance of considering both biotically and socially-mediated influences for assessing smallholder vulnerability, particularly barriers to diversifying incomes