Delineation of Emitter-Collector Shorts in Bipolar Test Structures by Voltage Contrast Scanning Electron Microscopy

In examining emitter-collector shorts and their relationship to structural defects, we desire a nondestructive method for locating the short-circuited devices in large test arrays. Voltage contrast scanning electron microscopy (VC-SEM) and an established electrochemical anodization technique have been used to identify electrically faulty bipolar transistors. Direct comparison of these approaches was achieved by examining the same emitters with each method. The results indicate that VC-SEM may serve as a useful technique for delineating E-C shorts because of its nondestructive and purely electrical nature. In our qualitative investigation, the sensitivity and voltage resolution available by VC-SEM were not sufficient to differentiate device leakage levels as is often possible with anodization. Such information may, however, be obtainable by utilizing image subtraction and more sophisticated detector systems. Transmission electron microscopy of the transistor structures revealed dislocations in many short-circuited emitters and occasionally in unshorted devices. This confirmed prior observations that crystallographic defects in silicon devices may sometimes be, but are not always, electrically active. Deleterious effects may depend on factors such as junction penetration and dopant-defect interactions

Keratocystic odontogenic tumour masquerading as a mucosal antral cyst

Keratocystic odontogenic tumour (KCOT) is of clinical importance because of its pronounced tendency to recur. Among the factors that complicate KCOT management are its protean radiological presentations. KCOT showing involvement of the maxillary antrum in the absence of an associated impacted tooth is exceptionally rare. In these instances an odontogenic source of the lesion is often not suspected and the clinico-radiological features may be misinterpreted. We report such a case and highlight pertinent clinical and radiological features of antral KCOT.http://www.sada.co.zaam201

Optically tunable mesoscale CdSe morphologies via inorganic phototropic growth

Inorganic phototropic growth using only spatially conformal illumination generated Se–Cd films that exhibited precise light-defined mesoscale morphologies including highly ordered, anisotropic, and periodic ridge and trench nanotextures over entire macroscopic substrates. Growth was accomplished via a light-induced electrochemical method using an optically and chemically isotropic solution, an unpatterned substrate, and unstructured, incoherent, low-intensity illumination in the absence of chemical directing agents or physical templates and masks. The morphologies were defined by the illumination inputs: the nanotexture long axes aligned parallel to the optical E-field vector, and the feature sizes and periods scaled with the wavelength. Optically based modeling of the growth closely reproduced the experimental results, confirming the film morphologies were fully determined by the light–matter interactions during growth. Solution processing of the Se–Cd films resulted in stoichiometric, crystalline CdSe films that also exhibited ordered nanotextures, demonstrating that inorganic phototropic growth can effect tunable, template-free generation of ordered CdSe nanostructures over macroscopic length scales

Optically tunable mesoscale CdSe morphologies via inorganic phototropic growth

Inorganic phototropic growth using only spatially conformal illumination generated Se–Cd films that exhibited precise light-defined mesoscale morphologies including highly ordered, anisotropic, and periodic ridge and trench nanotextures over entire macroscopic substrates. Growth was accomplished via a light-induced electrochemical method using an optically and chemically isotropic solution, an unpatterned substrate, and unstructured, incoherent, low-intensity illumination in the absence of chemical directing agents or physical templates and masks. The morphologies were defined by the illumination inputs: the nanotexture long axes aligned parallel to the optical E-field vector, and the feature sizes and periods scaled with the wavelength. Optically based modeling of the growth closely reproduced the experimental results, confirming the film morphologies were fully determined by the light–matter interactions during growth. Solution processing of the Se–Cd films resulted in stoichiometric, crystalline CdSe films that also exhibited ordered nanotextures, demonstrating that inorganic phototropic growth can effect tunable, template-free generation of ordered CdSe nanostructures over macroscopic length scales

Stability of Solid State Reaction Fronts

We analyze the stability of a planar solid-solid interface at which a chemical reaction occurs. Examples include oxidation, nitridation, or silicide formation. Using a continuum model, including a general formula for the stress-dependence of the reaction rate, we show that stress effects can render a planar interface dynamically unstable with respect to perturbations of intermediate wavelength

Template-Free Synthesis of Periodic Three-Dimensional PbSe Nanostructures via Photoelectrodeposition

Highly periodic, geometrically directed, anisotropic Se–Pb films have been synthesized at room temperature from an isotropic aqueous solution without the use of physical templates by photoelectrodeposition using a series of discrete input illumination polarizations and wavelengths from an unstructured, uncorrelated, incoherent light source. Dark growth did not generate deposits with substantial long-range order, but growth using unpolarized illumination resulted in an ordered, nanoscale, mesh-type morphology. Linearly polarized illumination generated Se–Pb deposits that displayed an ordered, highly anisotropic lamellar pattern wherein the long axes of the lamellae were aligned parallel to the light polarization vector. The pitch of the lamellar features was proportional to the input light wavelength, as confirmed by Fourier analysis. Full-wave electromagnetic and Monte Carlo growth simulations that incorporated only the fundamental light–matter interactions during growth successfully reproduced the experimentally observed morphologies and quantitatively matched the pattern periodicities. Electrochemical postprocessing of the as-deposited Se–Pb structures resulted in the generation of stoichiometric, crystalline PbSe while preserving the nanopatterned morphology, thus broadening the genus of materials that can be prepared with controlled three-dimensional morphologies through maskless photoelectrodeposition

IPIP27 coordinates PtdIns(4,5)P2 homeostasis for successful cytokinesis

During cytokinesis, an actomyosin contractile ring drives the separation of the two daughter cells. A key molecule in this process is the inositol lipid PtdIns(4,5)P 2 , which recruits numerous factors to the equatorial region for contractile ring assembly. Despite the importance of PtdIns(4,5)P 2 in cytokinesis, the regulation of this lipid in cell division remains poorly understood. Here, we identify a role for IPIP27 in mediating cellular PtdIns(4,5)P 2 homeostasis. IPIP27 scaffolds the inositol phosphatase oculocerebrorenal syndrome of Lowe (OCRL) by coupling it to endocytic BAR domain proteins. Loss of IPIP27 causes accumulation of PtdIns(4,5)P 2 on aberrant endomembrane vacuoles, mislocalization of the cytokinetic machinery, and extensive cortical membrane blebbing. This phenotype is observed in Drosophila and human cells and can result in cytokinesis failure. We have therefore identified IPIP27 as a key modulator of cellular PtdIns(4,5)P 2 homeostasis required for normal cytokinesis. The results indicate that scaffolding of inositol phosphatase activity is critical for maintaining PtdIns(4,5)P 2 homeostasis and highlight a critical role for this process in cell division. Carim et al. reveal that the IPIP27 protein, which physically couples the inositol phosphatase OCRL to endocytic BAR domain proteins, is required for cellular phosphoinositide homeostasis and normal cell division. The results show the importance of physically scaffolding inositol phosphatase activity within cells

Regionalism and African agency : negotiating an Economic Partnership Agreement between the European Union and SADC-Minus

This article investigates the regional dynamics of African agency in the case of negotiations for an Economic Partnership Agreement (EPA) between the EU and a group of Southern African countries, known as SADC-Minus. I argue that these negotiations were shaped by a pattern of differentiated responses to the choice set on offer under the EPAs by SADC-Minus policymakers and by a series of strategic interactions and power plays between them. I offer two contributions to an emerging literature on the role of African agency in international politics. First, I argue for a clear separation between ontological claims about the structure-agency relationship and empirical questions about the preferences, strategies and influence of African actors. Second, I suggest that in order to understand the regional dynamics of African agency it is important to pay close attention to the diversity and contingency of African preferences and to the role of both power politics and rhetorical contestation in regional political processes