Deep Reactive Ion Research Articles

Polyoxometalate–Organic Hybrid Molecules as Amphiphilic Emulsion Catalysts for Deep Desulfurization

So emulsional: Two hexavanadate-organic hybrids were synthesized and their amphiphilic properties were confirmed by forming emulsions in mixtures of water and nonpolar organic solvents, and were utilized as "emulsion catalysts" in deep desulfurization reactions (see figure). Their catalytic activities show a pH-dependent behavior, which can be explained by the size-change of emulsions and the appearance of reverse emulsions.

Stencil mask methodology for the parallelized production of microscale mechanical test samples

A new methodology to parallelize the production of micromechanical test samples from bulk materials is reported. This methodology has been developed to produce samples with typical gage dimensions on the order of 20-200 μm, and also to minimize the reliance on conventional focused ion beam fabrication methods. The fabrication technique uses standard microelectronic process methods such as photolithography and deep-reactive ion etching to create high aspect ratio patterned templates-stencil masks-from a silicon wafer. In the present work, the stencil mask pattern consists of a linear row of tensile samples, where one grip of each sample is integrally attached to the bulk substrate. Once fabricated, the stencil mask is placed on top of a pre-thinned substrate, and the pattern and substrate are co-sputtered using a broad ion beam milling system, which ultimately results in the transfer of the mask pattern into the substrate. The methodology is demonstrated using a Si stencil mask and a polycrystalline Ni foil to manufacture an array of metallic micro-tensile samples.

A triple-layer protection process for high-aspect-ratio silicon micromachining by DRIE of SOI substrates

Using the buried oxide layer of silicon-on-insulator (SOI) wafers as the etch-stop layer, a triple-layer protection process integrating deep reaction ion etching (DRIE) and wet anisotropic bulk micromachining is demonstrated to fabricate various three-dimensional MEMS devices on SOI wafer. Several limitations of the DRIE process, including bottom grass formation, reactive ion etching lag and notching effects, are solved by modifying the process parameters to achieve satisfactory performance. This process is capable of various applications and is applied to fabricate a resonant pressure sensor in this study. In summary, the developed process possesses most existing merits and reduces many design constraints of the existing high-aspect-ratio micromachining process, contributing to a more competitive and convenient micromachining.

Deep Oxidations in the Oxidative Dehydrogenation Reaction of Propane over V2O5(001): Periodic Density Functional Theory Study

The oxidative dehydrogenation (ODH) of propane to propene over a vanadium-based catalyst suffers from side reactions of further and complete oxidations of propene and other intermediates, which limit the yield of propene. These further oxidation reactions are also referred to as deep oxidation reactions of ODH. In this paper, we present a comprehensive study of the deep oxidation reactions in the ODH of propane over the V2O5(001) surface using the periodic density functional theory method. It is shown that the main source of deep oxidation byproducts originates from the dehydrogenation reaction of the surface intermediate isopropoxide, leading to acetone and the following deep oxidation reactions of acetone and propene. Thorough oxidation of acetone is more difficult than that of propene. Noticeably, formation of acetone and deep oxidation of acetone and propene are only feasible on the terminal oxygen site O(1) of the V2O5(001) surface. The bridging site O(2) has similar reactivity for propene formation but is inert for the side reactions, showing its superiority for selectivity of propane ODH.

Wideband anti-reflective micro/nano dual-scale structures: fabrication and optical properties

This Letter reports the fabrication and optical characteristics of large-area wideband anti-reflective micro/nano dual-scale (MNDS) structures. Microstructures, including inverted pyramids and V-shaped grooves, with controllable geometry sizes (e.g. width, pitch and depth) are fabricated by anisotropic wet etching of silicon. Highly dense arrays of high-aspect-ratio nanostructures are then formed atop those microstructures by an improved maskless deep-reactive ion etching process. Compared with the black silicon surface made of nanostructures only, these MNDS structures further reduce the optical reflectance to less than 0.6%, and the total light absorption has almost reached 95%. More importantly, by combining the light trap of microstructures and the anti-reflectance of nanostructures, these MNDS structures can efficiently suppress the reflectance of incident light at a wideband range of wavelengths from the ultraviolet, through the solar spectrum, to the near-infrared region (i.e. from 200 to 2500 nm).

Geology, mineralogy, and sulfur isotope geochemistry of the Sargaz Cu–Zn volcanogenic massive sulfide deposit, Sanandaj–Sirjan Zone, Iran

The Sargaz Cu–Zn massive sulfide deposit is situated in the southeastern part of Kerman Province, in the southern Sanandaj–Sirjan Zone of Iran. The stratigraphic footwall of the Sargaz deposit is Upper Triassic to Lower Jurassic (?) pillowed basalt, whereas the stratigraphic hanging wall is andesite. Mafic volcanic rocks are overlain by andesitic volcaniclastics and volcanic breccias and locally by heterogeneous debris flows. Rhyodacitic flows and volcaniclastics overlie the sequence of basaltic and andesitic rocks. Based on the bimodal nature of volcanism, the regional geologic setting and petrochemistry of the volcanic rocks, we suggest massive sulfide mineralization in the Sargaz formed in a nascent ensialic back-arc basin. The current reserves (after ancient mining) of the Sargaz deposit are 3 Mt at 1.34% Cu, 0.38% Zn, 0.08%Pb, 0.24 g/t Au, and 7 g/t Ag. The structurally dismembered massive sulfide lens is zoned from a pyrite-rich base, to a pyrite ± chalcopyrite-rich central part, and a sphalerite–chalcopyrite-rich upper part, with a sphalerite-rich zone lateral to the upper part. The main sulfide mineral is pyrite, with lesser chalcopyrite and sphalerite. The feeder zone, comprised of a vein stockwork consists of quartz–sulfide–sericite pesudobreccia and, in the deepest part, chlorite–quartz–pyrite pesudobreccia. Footwall hydrothermal alteration extends at least 70–80 m below the massive sulfide lens and more than a hundred meters along strike from the massive sulfide lens. Jasper and Fe–Mn bearing chert horizons lateral to the sulfide deposit represent low-temperature hydrothermal precipitates of the evolving hydrothermal system. Based on mineral textures and paragenetic relationships, the growth history of the Sargaz deposit is complex and includes: (1) early precipitation of sulfides (protore) on the seafloor as precipitation of fine-grained anhedral pyrite, sphalerite, quartz, and barite; (2) anhydrite precipitation in open spaces and mineral interstices within the sulfide mound followed by its subsequent dissolution, formation of breccia textures, and mound clasts and precipitation of coarse-grained pyrite, sphalerite, tetrahedrite–tennantite, galena and barite; (3) replacement of pre-existing sulfides by chalcopyrite precipitated at higher temperatures (zone refining); (4) continued “refining” led to the dissolution of stage 3 chalcopyrite and formation of a base-metal-depleted pyrite body in the lowermost part of the massive sulfide lens; (5) carbonate veins were emplaced into the sulfide lens, replacing stage 2 barite. The δ34S composition of the sulfides ranges from +2.8‰ to +8.5‰ (average, +5.6‰) with a general increase of δ34S ratios with depth within the massive sulfide lens and underlying stockwork zone. The heavier values indicate that some of the sulfur was derived from seawater sulfate that was ultimately thermochemically reduced in deep hydrothermal reaction zones.

Fabrication of sloped sidewalls by inductively coupled plasma etching for silicon micro-optic structures

Current work on deep-reactive ion etching has primarily focused on creating vertical sidewalls for microelectromechanical system and electronics applications. For micro-optical and micro-optoelectromechanical system structures control of the sidewall angles other than vertical is as important as the ultimate depth. In this work, we investigate the control of sidewall profiles using an inductively coupled plasma technique. The material systems being investigated on blanket samples are silicon and silicon dioxide with CF4, CHF3, and SF6 chemistries. Micro-optic structures are created by photolithography and CHF3 gas has been explored to achieve a wide range of etch rates, smooth etch profiles, and sidewall angles. The etch profiles are characterized by scanning electron microscopy.

Mechanochemical methods of activating processes of biomass pretreatment

This work deals with the fundamental problems of searching for and attaining synergetic effects manifested upon the mechanochemical pretreatment of plant material. Laws relating the intense physicomechanical effects on the raw material during its preprocessing to the deep hydrolytic reactions of hemicelluloses in the bulk of the structural units of plant biomass are established. It was shown earlier on models that mechanical effects are able to dramatically influence the reactivity of macromolecules by changing the hybridization of bonds. To discover similar regularities for plant structures, we performed experiments on the grinding of biomaterials. The best results were obtained in an extruder in the presence of catalysts for polysaccharide hydrolytic cleavage (acids, alkalies, and enzymes). Using birch wood, it was shown that the hydrolytic processes are accelerated by several orders of magnitude in the extruder force fields; the working temperature was considerably reduced (relative to thermohydrolysis) and neither furfural nor any other harmful side product was detected. Our results suggest that the use of mechanochemical methods allows processing time to be reduced by an order and of magnitude along with the formation of side products, testifying to the utility of this technique’s practical application.

Hydrothermal fluid geochemistry at the Iheya North field in the mid-Okinawa Trough: Implication for origin of methane in subseafloor fluid circulation systems

Geochemical characteristics of hydrothermal fluids in the Iheya North hydrothermal field, mid-Okinawa Trough, was investigated. Twelve-years observation reveals temporal variation of vent fluid chemistry potentially controlled by temporally varying pattern of the phase-separation and -segregation, while the constant Element/Cl ratios among the periods and chimneys indicate the stable chemical composition of the source hydrothermal fluid prior to undergoing phase-separation. The high K contents in the estimated source fluid are typical in the arc-backarc hydrothermal systems due to the hydrothermal reaction with the K-enriched felsic rocks. The high I, B and NH4 contents and alkalinity are derived from decomposition of the sedimentary organic matters. Compositional and isotopic properties of gas species, CH4, H2, CO2, and C2H6, strongly suggest a dominance of biogenic CH4 associated with the sedimentary organic matter. Based on the carbon mass balance calculation and the multidisciplinary investigations of the Iheya North hydrothermal system since the discovery, we hypothesized that the microbial methanogenesis occurs not only within the Central Valley where hydrothermal vents exist, but also in the spatially abundant and widespread basin-filling sediments surrounding the Iheya North Knoll, and that the microbially produced CH4 is recharged together with the source fluid into the deep hydrothermal reaction zone. This “Microbial Methanogenesis at Recharge area in hydrothermal circulation” (MMR) model would be an implication for the generation and incorporation of hydrothermal fluid CH4 in the deep-sea hydrothermal systems but also for those of cold seep CH4 and for the presently uncertain hydrothermal fluid paths in the subseafloor environments. In the near future, the IODP drilling will be conducted in the Iheya North hydrothermal system, and give an excellent opportunity to testify our MMR model.

共振型マイクロ化学センサへの感応膜塗布特性の制御のための表面微細パターンの利用

SUMMARY We propose a new processing method to form thin films on the predefined micro-areas of movable parts of microdevices by using trench frames on the device surfaces in the coating of solutions containing the membrane materials. We fabricated 500-nm-wide surficial trench frames additively on silicon microcantilevers to define the areas coated with the thin films by increasing the tolerance to protrusion of a liquid droplet from the edge in the coating process. The trench frames were fabricated on the silicon surfaces by deep-reactive ion etching with the resist mask patterned by electron beam lithography. We also fabricated the same trench frames on planar silicon substrates, and we examined the proper conditions for the formation of polybutadiene (PBD) thin films on the framed surfaces by coating PBD solution using a microdispenser system. When the n-dodecane solution of PBD was applied to the micro-area framed by the trenches, PBD film was successfully defined within the framed area. The trench frames fabricated on the cantilevers indicated the practical effectiveness to define the PBD thin films within the framed micro-areas. © 2013 Wiley Periodicals, Inc. Electron Comm Jpn, 96(10): 60–66, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.11379

The Stereoselectivity of the Dehydrogenation of Alkyl Groups on Pt(111) Single-Crystal Surfaces

The thermal chemistry of erythro- and threo-2-butyl-3-d1 species adsorbed on Pt(111) single-crystal surfaces was studied under ultrahigh vacuum (UHV) by temperature-programmed desorption (TPD). The alkyl intermediates were prepared via thermal activation of the appropriate erythro- and threo-2-iodobutane-3-d1 precursors, which were made in house via a three-step synthesis starting with cis- and trans-2,3-epoxybutanes, respectively. Several products were detected in the TPD experiments, including butenes and butanes with different degrees of isotope substitutions and hydrogen from deep dehydrogenation reactions. At least two distinct temperature regimes were identified at higher coverages for the β-hydride elimination steps that produce the olefins, the focus of this work, but one single high-temperature regime could be isolated by working with low coverages of the iodoalkanes. On clean Pt(111), an inverse kinetic isotope effect was observed for the conversion of 2-butyls to 2-butenes, and a slight preference for trans- (rather than cis-) 2-butene production. In addition, a reversal in relative rates for 2-butene-d0 versus 2-butene-d1 was detected in the high-temperature side of the TPD peaks obtained with the two alkyl epimers, an observation that we explain by a high degree of reversibility of the alkyl-to-alkene conversion. Coadsorption of hydrogen or deuterium on the surface reverses the kinetic isotope effect, but not the selectivity for trans olefin production. However, these effects, in particular, the preference for trans olefin formation, are small, indicating an early transition state for the β-hydride elimination step and a thermodynamic (rather than kinetic) control of selectivity in olefin isomerization reactions.

Ontogeny and phylogeny of a Scutellospora heterogama mutant, with implications for morphological recognition of species in Glomeromycota

A putative mutant of Scutellospora heterogama has been maintained for 19 pot culture generations over 15 y. The mutant differed phenotypically from the wild-type parental lineage in characteristics of the spore wall: albino versus pigmented red-brown color, high plasticity in acidic mutants versus rigid and finely laminate, deep red-purple reaction versus no reaction in Melzer's reagent, respectively. This variation was equivalent to or greater than that between any two species in Scutellospora or any other genus in Glomeromycota. Comparison of spore ontogenesis revealed that the terminal (mature) state of the albino mutant was similar to a transient intermediate stage in the wild-type. The albino phenotype, therefore, did not result from emergence of a unique morphological innovation. Rather, it arose from a mutation that led to premature termination of spore ontogenesis so that a unique transient juvenile stage became permanent in mature spores. Because this mutation was homogeneous in all progeny populations, it is hypothesized to be a recessive trait expressed only after the allele was distributed in all nuclei of the fungal thallus. Sampling of the genomes of the putative mutant and wild-type isolates by microsatellite-primed PCR suggested a local mutation. The profile of the mutant was identical to that of the wild-type parent and was 60–97 % similar to those of four other S. heterogama isolates. Phylogenetic analysis of the D1–D2 domains of the 25S rRNA gene and a β-tubulin gene with and without three variable introns placed the albino mutant solidly within the S. heterogama clade. These results suggest that stability of morphological traits is not a suitable criterion by itself to recognize species. The albino phenotype was a discrete and heritable mutation that became fixed in a population and was stable through time and space. In the absence of negative selection, this mutation could persist, disperse and then be misinterpreted as a new species in nature. Genetic markers expose this mutation as a population-level variant and therefore of no macroevolutionary significance. Assessment of genetic divergence amongst multiple isolates is important in ascertaining the contribution of morphological characters toward recognition of species in glomeromycotan clades.

Deep sub-barrier fusion reactions of the light nuclei 12C and 16O

Fusion reactions relevant for the carbon and oxygen burning cycles in highly evolved stars are investigated in a standard approach to fusion. We employ the double folding method to evaluate the ion-ion interactions with Gogny-D1 and M3Y-Paris n – n effective forces. The cross-section evaluation do not indicate a possible hindrance even at the lowest energies under the barrier. Reaction rates at temperatures relevant for the stellar processes are estimated and compared to the traditional and modern extrapolation formulas.

Fact-Totems and the Statistical Imagination: The Public Life of a Statistic in Argentina 2001

Statistics are key elements of contemporary life. They figure prominently in the media, in political discourse, and in daily conversations. They also weigh heavily within the economic and political spheres of modern societies. Yet, the study of statistics in the public sphere has been neglected by social scientists in favor of a focus on their production and history. This article remedies this lacuna by focusing on the public life of statistics. Through a case study of a financial indicator—country risk—that exhibited a rich public life in Argentina in 2001, it argues that statistics are not simply transparent fragments of information, but rich symbols and collective representations able to condense multiple meanings and generate deep emotional reactions. Using in-depth interviews, newspaper covers, headlines, and leads, cartoons and archival materials, this article shows that country risk became a powerful collective representation and introduces a new concept, the fact-totem, to make visible the cultural life of statistics. A fact-totem is a statistic with high media presence that captures the imagination of diverse publics and becomes articulated with basic identity narratives of a collectivity. This article begins to elaborate dramatic dimensions of statistics in public.

Germanium–silicon fractionation in a tropical, granitic weathering environment

Germanium–silicon (Ge/Si) ratios were determined on quartz diorite bedrock, saprolite, soil, primary and secondary minerals, phytolith, soil and saprolite pore waters, and spring water and stream waters in an effort to understand Ge/Si fractionation during weathering of quartz diorite in the Rio Icacos watershed, Puerto Rico. The Ge/Si ratio of the bedrock is 2 μmol/mol, with individual primary mineral phases ranging between 0.5 and 7 μmol/mol. The ratios in the bulk saprolite are higher (∼3 μmol/mol) than values measured in the bedrock. The major saprolite secondary mineral, kaolinite, has Ge/Si ratios ranging between 4.8 and 6.1 μmol/mol. The high Ge/Si ratios in the saprolite are consistent with preferential incorporation of Ge during the precipitation of kaolinite. Bulk shallow soils have lower ratios (1.1–1.6 μmol/mol) primarily due to the residual accumulation of Ge-poor quartz. Ge/Si ratios measured on saprolite and soil pore waters reflect reactions that take place during mineral transformations at discrete depths. Spring water and baseflow stream waters have the lowest Ge/Si ratios (0.27–0.47 μmol/mol), reflecting deep initial weathering reactions resulting in the precipitation of Ge-enriched kaolinite at the saprolite–bedrock interface. Mass-balance calculations on saprolite require significant loss of Si and Al even within 1 m above the saprolite–bedrock interface. Higher pore water Ge/Si ratios (∼1.2 μmol/mol) are consistent with partial dissolution of this Ge-enriched kaolinite. Pore water Ge/Si ratios increase up through the saprolite and into the overlying soil, but never reach the high values predicted by mass balance, perhaps reflecting the influence of phytolith recycling in the shallow soil.

Structural basis for biosynthetic programming of fungal aromatic polyketide cyclization

Polyketides are a class of natural products with diverse structures and biological activities. The structural variability of aromatic products of fungal nonreducing, multidomain iterative polyketide synthases (NR-PKS group of IPKSs) results from regiospecific cyclizations of reactive poly-beta-keto intermediates. How poly-beta-keto species are synthesized and stabilized, how their chain lengths are determined, and, in particular, how specific cyclization patterns are controlled have been largely inaccessible and functionally unknown until recently. A product template (PT) domain is responsible for controlling specific aldol cyclization and aromatization of these mature polyketide precursors, but the mechanistic basis is unknown. Here we present the 1.8 A crystal structure and mutational studies of a dissected PT monodomain from PksA, the NR-PKS that initiates the biosynthesis of the potent hepatocarcinogen aflatoxin B(1) in Aspergillus parasiticus. Despite having minimal sequence similarity to known enzymes, the structure displays a distinct 'double hot dog' (DHD) fold. Co-crystal structures with palmitate or a bicyclic substrate mimic illustrate that PT can bind both linear and bicyclic polyketides. Docking and mutagenesis studies reveal residues important for substrate binding and catalysis, and identify a phosphopantetheine localization channel and a deep two-part interior binding pocket and reaction chamber. Sequence similarity and extensive conservation of active site residues in PT domains suggest that the mechanistic insights gleaned from these studies will prove general for this class of IPKSs, and lay a foundation for defining the molecular rules controlling NR-PKS cyclization specificity.

Microelectromechanical system assembled ion optics: An advance to miniaturization and assembly of electron and ion optics

Deep-reactive ion etching of n-doped silicon-on-insulator is utilized to make ion optical components to aid in the miniaturization of mass analyzers. The microelectromechanical system components are bound to aluminum nitride substrates and employed three-dimensional assembly. The assembly methods are tested for breakdown (V(b)), durability, and alignment. Demonstration of ion manipulation is shown with a 1 mm Bradbury-Nielsen gate, 500 mum Einzel lens, 500 mum coaxial ring ion trap, and reflectron optics. Data are presented showing the resolution, attenuation, and performance of each of these devices. We demonstrate advantages and disadvantages of this technology and its applications to mass analysis.

Afghanistan and multiculturalism in Khaled Hosseini's novels: study of place and diversity

PurposeThe purpose of this paper is to frame Khaled Hosseini's novels, The Kite Runner and A Thousand Splendid Suns, as literature to expand and enhance the American secondary curriculum with multicultural themes based on Afghanistan as a geographical and cultural place in a dynamic, diverse, and complex world more mediated than ever before by computer technologies.Design/methodology/approachThe methodological approach to the study is a synthesis of geographic education grounded in the concept of place and diversity pedagogy.FindingsKhaled Hosseini's web site has become the cyber place where hundreds of readers from around the world come to express their deep emotional reactions to The Kite Runner and A Thousand Splendid Suns. At the same time, that so many diverse international readers are responding favorably to Hosseini's novels, his works are being censored in classrooms in the USA. The research outlines geographical and cultural geographic features of Afghanistan – a place torn by military efforts of several nations. In the context of diversity pedagogy, the power of the novels portrays “difference,” yet humanity in need of understanding. Further attention is given to the censorship of ideas in American education, with Hosseini's books as one example.Originality/valueThis paper frames Hosseini's novels as place‐based literature illustrating the homeland of Afghanistan now more accessible than ever before to international and US classrooms.

Iron isotope electroplating: Diffusion-limited fractionation

Electron-transfer related isotope fractionation may produce large stable isotope geochemical signatures as a result of a variety of Earth processes, including biology, chemical weathering, fluid–rock interactions, and deep Earth redox reactions. In the laboratory, isotope fractionation at a charged electrode has been observed for electroplating of Fe and Zn; however these can arise from a variety of effects besides the electron transfer process. Here, we examine the effect of mass transport on observed isotope fractionation during potentiostatic electroplating of iron. We examine the observed isotope fractionation as a function of the ratio of the observed plating current to the mass-transport limited current (the Cottrell current). When the electroplating experiments are run at currents greater than the Cottrell current, the observed fractionation is ~− 1.15(± 0.40) ‰, and the extent of fractionation shows a tendency to decrease with increasing plating rate. When electroplating experiments are run at currents below the Cottrell current, observed fractionations are strongly dependent on the plating rate, with a maximum value of δ 56Fe = − 4.8. The data set demonstrates that mass transport to the electrode tends to attenuate a large fractionation factor associated with other, non-mass transport, processes at the electrode.

The fabrication of silicon nanostructures by local gallium implantation and cryogenic deepreactive ion etching

We show that gallium-ion-implanted silicon serves as an etch mask for fabrication of highaspect ratio nanostructures by cryogenic plasma etching (deep reactive ion etching). Thespeed of focused ion beam (FIB) patterning is greatly enhanced by the fact that only a thinapprox. 30 nm surface layer needs to be modified to create a mask for the etching step. Etchselectivity between gallium-doped and undoped material is at least 1000:1, greatlydecreasing the mask erosion problems. The resolution of the combined FIB-DRIE process is20 lines µm−1 with the smallest masked feature size of 40 nm. The maximum achieved aspect ratio is 15:1(e.g. 600 nm high pillars 40 nm in diameter).