Pressure effect of growing with electron beam-induced deposition with tungsten hexafluoride and tetraethylorthosilicate precursor

Electron beam-induced deposition (EBID) provides a simple way to fabricate submicron- or nanometer-scale structures from various elements in a scanning electron microscope (SEM). The growth rate and shape of the deposits are influenced by many factors. We have studied the growth rate and morphology of EBID-deposited nanostructures as a function of the tungsten hexafluoride (WF6) and tetraethylorthosilicate (TEOS) precursor gas pressure and growth time, and we have used Monte Carlo simulations to model the growth of tungsten and silicon oxide to elucidate the mechanisms involved in the EBID growth. The lateral radius of the deposit decreases with increasing pressure because of the enhanced vertical growth rate which limits competing lateral broadening produced by secondary and forward-scattered electrons. The morphology difference between the conical SiO(x) and the cylindrical W nanopillars is related to the difference in interaction volume between the two materials. A key parameter is the residence time of the precursor gas molecules. This is an exponential function of the surface temperature; it changes during nanopillar growth and is a function of the nanopillar material and the beam conditions.     

Building the Connection Between Housing Needs and Metropolitan Planning in Sydney,Australia

The theme of a more compact city has been a central feature of planning policy for Sydney's development over the last two decades. Urban consolidation, in the form of attached dwellings in medium- and high-density configurations, has become the predominant form of new residential development since the early 1990s. One of the largely untested claims for this policy is that it provides more housing choice for an increasingly diverse population and that simply building larger amounts of smaller housing in high-density concentrations will be sufficient to meet that demand. As a result, planning for higher density housing has been undertaken with little explicit recognition of the housing sub-markets higher density housing caters for or their specific spatial characteristics within the city. These issues are examined by an analysis of the socio-economic characteristics of areas with high concentrations of attached housing. These data are processed by factor analysis to identify and locate the range of sub-markets within attached housing and additional small area data used to fill out the market profiling. The results reveal that a range of specific housing needs are met by this form of housing with discriminative characteristics in certain locations. In other words, higher density housing is associated with a range of locationally specific and spatially distinctive sub-markets. These findings are particularly relevant and timely as a new metropolitan strategy is in preparation for Sydney where an estimated 60–70 per cent of new dwelling provision in the next 30 years will take place within existing suburbs through higher density redevelopment. Planning for such development must take into account the local markets for such accommodation which have very different characteristics in different parts of the city.     

Exact and approximate analytic solutions of the nonlinear convective fin problem with temperature-dependent thermal conductivity

This article shows that the well-known nonlinear boundary value problem of the differential equation for temperature distribution of convective straight fins with temperature-dependent thermal conductivity is exactly solvable in an implicit form. Furthermore, an exact solution in an explicit form is derived. Also, an accurate analytic solution (series solution) is obtained by a new variation of the Adomian decomposition method.     

In situ probing of the growth and morphology in electron-beam-induced deposited nanostructures

Three series of nanofiber structures were grown via electron-beam-induced deposition as a function of beam energy (1, 5 and 20?keV) using a W(CO)(6) precursor. At each beam energy a time series ranging from 0.5 to 128?s was performed and the sample current during each growth was monitored versus growth time. The subsequent current traces have been correlated to the nanostructure morphology. For the 1 and 5?keV beam energy, two distinct lateral growth regimes were observed. Initially there is a rapid base broadening consistent with the electron beam interaction region. Secondly, a lateral 'platelet' type growth was observed. At 20?keV beam energy, there is an initial rapid broadening: however, no 'platelet' growth is observed. For each beam energy, the measured current trace is correlated to the observed growth regimes.     

Ultrasensitive detection and characterization of posttranslational modifications using surface-enhanced Raman spectroscopy

Posttranslational modification (PTM) of proteins is likely to be the most common mechanism of altering the expression of genetic information. It is essential to characterize PTMs to establish a complete understanding of the activities of proteins. Here, we present a sensitive detection method using surface-enhanced Raman spectroscopy (SERS) that can detect PTMs from as little as zeptomoles of peptide. We demonstrate, using model peptides, the ability of SERS to detect a variety of protein modifications, such as acetylation, trimethylation, phosphorylation, and ubiquitination. In addition, we show the capability to obtain positional information for modifications such as trimethylation and phosphorylation using SERS and wavelet decomposition data analysis techniques. We further show that it is possible to apply SERS to detect PTMs from biological samples such as histones. We envision that this detection method might be a valuable technique that is complementary to mass spectrometry in obtaining orthogonal chemical and modification-specific information from biological samples at sensitive levels.     

Photothermal nanoblade for large cargo delivery into mammalian cells

It is difficult to achieve controlled cutting of elastic, mechanically fragile, and rapidly resealing mammalian cell membranes. Here, we report a photothermal nanoblade that utilizes a metallic nanostructure to harvest short laser pulse energy and convert it into a highly localized explosive vapor bubble, which rapidly punctures a lightly contacting cell membrane via high-speed fluidic flows and induced transient shear stress. The cavitation bubble pattern is controlled by the metallic structure configuration and laser pulse duration and energy. Integration of the metallic nanostructure with a micropipet, the nanoblade generates a micrometer-sized membrane access port for delivering highly concentrated cargo (5 × 10(8) live bacteria/mL) with high efficiency (46%) and cell viability (>90%) into mammalian cells. Additional biologic and inanimate cargo over 3-orders of magnitude in size including DNA, RNA, 200 nm polystyrene beads, to 2 μm bacteria have also been delivered into multiple mammalian cell types. Overall, the photothermal nanoblade is a new approach for delivering difficult cargo into mammalian cells.     

Large-scale quantum mechanical simulations of high- Z metals

High-Z metals constitute a particular challenge for large-scale ab initio electronic-structure calculations, as they require high resolution due to the presence of strongly localized states and require many eigenstates to be computed due to the large number of electrons and need to accurately resolve the Fermi surface. Here, we report recent findings on high-Z metals, using an efficient massively parallel planewave implementation on some of the largest computational architectures currently available. We discuss the particular architectures employed and methodological advances required to harness them effectively. We present a pair-correlation function for U, calculated using quantum molecular dynamics, and discuss relaxations of Pu atoms in the vicinity of defects in aged and alloyed Pu. We find that the self-irradiation associated with aging has a negligible effect on the compressibility of Pu relative to other factors such as alloying. The US Goverment’s right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged.