Three-dimensional microscopy data exploration by interactive volume visualization

This paper presents a new volume visualization approach for three-dimensional (3-D) interactive microscopy data exploration. Because of their unique image characteristics, 3-D microscopy data are often not able to be visualized effectively by conventional volume visualization techniques. In our approach, microscopy visualization is carried out in an interactive data exploration environment, based on a combination of interactive volume rendering techniques and image-based transfer function design methods. Interactive volume rendering is achieved by using two-dimensional (2-D) texture mapping in a Shear-Warp volume rendering algorithm. Image processing techniques are employed and integrated into the rendering pipeline for the definition and searching of appropriate transfer functions that best reflect the user's visualization intentions. These techniques have been implemented successfully in a prototype visualization system on low-end and middle-range SGI desktop workstations. Since only 2-D texture mapping is required, the system can also be easily ported to PC platforms.     

Information technology offshoring in India: a postcolonial perspective

In recent years India has become the information technology (IT) offshoring destination of choice for many Western organizations. From the perspective of vendor organizations in India, however, the IT offshoring phenomenon is more than just a business relationship with Western firms. It is also embedded within the context of the longstanding imbalances of power in the relationship between the West and the East, the implications of which have been largely ignored in empirical work on offshoring within the information systems (IS) discipline. Drawing on concepts from postcolonial theory and using data from our ethnographic fieldwork, we explore the experiences and responses of one Indian vendor organization to asymmetries of power in its relationship with Western client organizations. Our analysis demonstrates how a postcolonial reading and interpretation of IT offshoring adds an important new dimension to previous IS research and also helps to develop a more comprehensive understanding of the strategies deployed by vendor organizations.     

Traffic of dynamin within individual Drosophila synaptic boutons relative to compartment-specific markers

Presynaptic terminals contain several specialized compartments, which have been described by electron microscopy. We show in an identified Drosophila neuromuscular synapse that several of these compartments-synaptic vesicle clusters, presynaptic plasma membrane, presynaptic cytosol, and axonal cytoskeleton-labeled by specific reagents may be resolved from one another by laser scanning confocal microscopy. Using a panel of compartment-specific markers and Drosophila shibire(ts1) mutants to trap an intermediate stage in synaptic vesicle recycling, we have examined the localization and redistribution of dynamin within single synaptic varicosities at the larval neuromuscular junction. Our results suggest that dynamin is not a freely diffusible molecule in resting nerve terminals; rather, it appears localized to synaptic sites by association with yet uncharacterized presynaptic components. In shi(ts1) nerve terminals depleted of synaptic vesicles, dynamin is quantitatively redistributed to the plasma membrane. It is not, however, distributed uniformly over presynaptic plasmalemma; instead, fluorescence images show "hot spots" of dynamin on the plasma membrane of vesicle-depleted nerve terminals. We suggest that these dynamin-rich domains may mark the active zones for synaptic vesicle endocytosis first described at the frog neuromuscular junction.     

Neurochemical alterations in asymptomatic abstinent cocaine users: a proton magnetic resonance spectroscopy study

Cocaine can cause a variety of neuropsychiatric and neurobehavioral complications; however, it is uncertain whether cocaine causes persistent cerebral structural and neurochemical abnormalities in asymptomatic users. We studied 52 African-American men (26 human immunodeficiency virus-negative asymptomatic heavy cocaine users and 26 normal subjects). Ventricle-to-brain ratio (VBR) and white matter lesions (WML) were quantified on magnetic resonance imaging. N-acetyl-containing compounds (NA), total creatine, choline-containing compounds, myo-inositol, and glutamate + glutamine were measured with in vivo proton magnetic resonance spectroscopy, VBR and WML were not significantly different in the cocaine users compared to the normal controls. Elevated creatine (+7%; p = .05) and myo-inositol (+18%; p = .01) in the white matter were associated with cocaine use. NA, primarily a measure of N-acetyl aspartate and neuronal content, was normal. Normal NA suggest no neuronal loss or damage in the brain regions examined in these cocaine users. Therefore, we conclude that neurochemical abnormalities observed might result from alterations in nonneuronal brain tissue.     

X-ray microtomography shows pore structure and tortuosity in alkali-activated binders

Durability of alkali-activated binders is of vital importance in their commercial application, and depends strongly on microstructure and pore network characteristics. X-ray microtomography (μCT) offers, for the first time, direct insight into microstructural and pore structure characteristics in three dimensions. Here, μCT is performed on a set of sodium metasilicate-activated fly ash/slag blends, using a synchrotron beamline instrument. Segmentation of the samples into pore and solid regions is then conducted, and pore tortuosity is calculated by a random walker method. Segmented porosity and diffusion tortuosity are correlated, and vary as a function of slag content (slag addition reduces porosity and increases tortuosity), and sample age (extended curing gives lower porosity and higher tortuosity). This is particularly notable for samples with ≥ 50% slag content, where a space-filling calcium (alumino)silicate hydrate gel provides porosity reductions which are not observed for the sodium aluminosilicate (‘geopolymer’) gels which do not chemically bind water of hydration.     

Agitator design for solids suspension under gassed conditions

Design of mechanical agitators for solids suspension under gassed conditions can be achieved using a constant ungassed torque criterion if the solids suspension task is more difficult than the gas dispersion task. When gas dispersion is the more difficult task, design for complete gas dispersion will ensure solids suspension. Evidence supporting this approach is very strong for radial-flow impellers, but less so for up-pumping and down-pumping axial-flow impellers.