bluuebunny/crossref_metadata_2025 huggingface dataset:
Serotonin differentially modulates the intrinsic properties of spinal motoneurons from the adult turtle
Authors: Perrier Jean‐François , Cotel Florence
Published: December 2007

This report considers serotonergic (5‐HT) effects on spinal motoneurons, reviewing previous data and presenting a new study showing distinct effects of two 5‐HT receptor subtypes. We previously investigated the effects of 5‐HT on motoneurons in a slice preparation from the spinal cord of the adult turtle. In agreement with previous studies, we had found that 5‐HT applied to the extracellular medium promoted a voltage sensitive plateau potential. However, we also reported that this effect was only observed in half of the motoneurons; 5‐HT inhibited the firing of the other half of the motoneurons recorded from. To investigate the reasons for this, we applied 5‐HT focally by means of the microiontophoresis technique. Facilitation of plateau potentials was observed when 5‐HT was released at sites throughout the somatodendritic region. However, motoneurons were inhibited by 5‐HT when selectively applied in the perisomatic region. These two effects could be induced in the same motoneuron. With pharmacological tools, we demonstrate here that the facilitation of plateau potentials is mediated by 5‐HT2 receptors and the inhibitory effect is due to the activation of 5‐HT1A/7 receptors.
Blunted response to low oxygen of rat respiratory network after perinatal ethanol exposure: involvement of inhibitory control
Authors: Dubois C. , Houchi H. , Naassila M. , Daoust M. , Pierrefiche O.
Published: December 2007

Acute ethanol depresses respiration, but little is known about chronic ethanol exposure during gestation and breathing, while the deleterious effects of ethanol on CNS development have been clearly described. In a recent study we demonstrated that pre‐ and postnatal ethanol exposure induced low minute ventilation in juvenile rats. The present study analysed in juvenile rats the respiratory response to hypoxiain vivoby plethysmography and the phrenic (Phr) nerve response to ischaemiain situ. Glycinergic neurotransmission was assessedin situwith strychnine application and [3H]strychnine binding experiments performed in the medulla. After chronic ethanol exposure, hyperventilation during hypoxia was bluntedin vivo.In situPhr nerve response to ischaemia was also impaired, while gasping activity occurred earlier and recovery was delayed. Strychnine applicationsin situ(0.05–0.5 μm) demonstrated a higher sensitivity of expiratory duration in ethanol‐exposed animals compared to control animals. Moreover, [3H]strychnine binding density was increased after ethanol and was associated with higher affinity. Furthermore, 0.2 μmstrychnine in ethanol‐exposed animals restored the low basal Phr nerve frequency, but also the Phr nerve response to ischaemia and the time to recovery, while gasping activity appeared even earlier with a higher frequency. Polycythaemia was present after ethanol exposure whereas lung and heart weights were not altered. We conclude that chronic ethanol exposure during rat brain development (i) induced polycythaemia to compensate for low minute ventilation at rest; (ii) impaired the respiratory network adaptive response to low oxygen because of an increase in central glycinergic tonic inhibitions, and (iii) did not affect gasping mechanisms. We suggest that ethanol exposure during early life can be a risk factor for the newborn respiratory adaptive mechanisms to a low oxygen environment.
GTP up‐regulated persistent Na+ current and enhanced nociceptor excitability require NaV1.9
Authors: Östman Johan A. R. , Nassar Mohammed A. , Wood John N. , Baker Mark D.
Published: December 2007

Persistent tetrodotoxin‐resistant (TTX‐r) sodium currents up‐regulated by intracellular GTP have been invoked as the site of action of peripheral inflammatory mediators that lower pain thresholds, and ascribed to the NaV1.9 sodium channel. Here we describe the properties of a global knock‐out of NaV1.9 produced by replacing exons 4 and 5 in SCN11A with a neomycin resistance cassette, deleting the domain 1 voltage sensor and introducing a frameshift mutation. Recordings from small (< 25 μm apparent diameter) sensory neurones indicated that channel loss eliminates a TTX‐r persistent current. Intracellular dialysis of GTP‐γ‐S did not cause an up‐regulation of persistent Na+ current in NaV1.9‐null neurones and the concomitant negative shift in voltage‐threshold seen in wild‐type and heterozygous neurones. Heterologous hNaV1.9 expression in NaV1.9 knock‐out sensory neurones confirms that the human clone can restore the persistent Na+ current. Taken together, these findings demonstrate that NaV1.9 underlies the G‐protein pathway‐regulated TTX‐r persistent Na+ current in small diameter sensory neurones that may drive spontaneous discharge in nociceptive nerve fibres during inflammation.
Spectral Collocation-Based Optimization in Parameter Estimation for Nonlinear Time-Varying Dynamical Systems
Authors: Deshmukh Venkatesh
Published: December 2007

A constructive optimization algorithm using Chebyshev spectral collocation and quadratic programming is proposed for unknown parameter estimation in nonlinear time-varying dynamic system models to be constructed from available data. The parameters to be estimated are assumed to be identifiable from the data, which also implies that the assumed system models with known parameter values have a unique solution corresponding to every initial condition and parameter set. The nonlinear terms in the dynamic system models are assumed to have a known form, and the models are assumed to be parameter affine. Using an equivalent algebraic description of dynamical systems by Chebyshev spectral collocation and data, a residual quadratic cost is set up, which is a function of unknown parameters only. The minimization of this cost yields the unique solution for the unknown parameters since the models are assumed to have a unique solution for a particular parameter set. An efficient algorithm is presented stepwise and is illustrated using suitable examples. The case of parameter estimation with incomplete or partial data availability is also illustrated with an example.
Growth and printability of multilayer phase defects on extreme ultraviolet mask blanks
Authors: Liang Ted , Ultanir Erdem , Zhang Guojing , Park Seh-Jin , Anderson Erik , Gullikson Eric , Naulleau Patrick , Salmassi Farhad , Mirkarimi Paul , Spiller Eberhard , Baker Sherry
Published: December 2007

The ability to fabricate defect-free reflective Mo–Si multilayer (ML) blanks is a well-recognized challenge in enabling extreme ultraviolet (EUV) lithography for semiconductor manufacturing. Both the specification and reduction of defects necessitate the understanding of their printability and how they are generated and grow during ML deposition. A ML phase defect can be depicted by its topographical profile on the surface as either a bump or pit, which is then characterized by height or depth and width. These phase defects are complex in nature and their impact to resist printing. The authors developed an effective way to study phase defects with programmed defect mask (PDM) as “model” test vehicle. The defects are produced with tuned ML deposition process and placed in varying proximity to absorber patterns on the mask. This article describes the recent study of ML phase defect printability from exposures of a ML PDM on the EUV microexposure tool with annular, monopole, and dipole illuminations.
Measurements of acid generation by extreme ultraviolet irradiation in lithographic films
Authors: Glodde Martin , Goldfarb Dario L. , Medeiros David R. , Wallraff Gregory M. , Denbeaux Gregory P.
Published: December 2007

Extreme ultraviolet (EUV) lithography requires photoresist materials that incorporate highly efficient photoacid generators (PAGs) due to the low intensity of the currently available EUV light sources. It is therefore necessary to understand the parameters that control acid generation mechanisms in photoresists under EUV irradiation, such as photoacid generator and base quencher structure, polymer matrix effects, and the interaction of ionizing radiation with the resist components. In this study, a known acid detection technique based on a dye indicator (coumarin 6) has been optimized for the quantification of the amount of photoacid produced by irradiation of lithographic resist films. Incorporation of acid-base indicators to solid polymer matrices has already been employed in previous studies; however, the environmental stability of the reactive species and the influence of the polymer resin have not been considered to date. Here, the authors present a comprehensive evaluation of PAGs that were exposed to 13.5nm radiation and compared to 248nm exposures. For some specific cases studied, it was possible to correlate the acid generation efficiency to the PAG structure and polymer matrix effects. Moreover, it is found that environmental effects such as humidity have a significant impact on acid strength, acid detection, and acid generation efficiency. The acid generation efficiency experiments were complemented with dose to clear exposures for selected resist systems. The results obtained indicate that the use of acid detection methods implemented for the design of EUV resist compositions with optimized photospeed requires careful attention to the complex role of the reactivity of all formulation components and photoreaction products in the presence of ionizing radiation.
Emission characteristics of Au60Be40 and Au62Si23Be15 liquid metal ion sources
Authors: Schwind G. A. , Swanson L. W.
Published: December 2007

The angular current densities, relative abundance, and total energy distributions (TEDs) of the various ion species from the binary Au60Be40 and ternary Au62Si23Be15 liquid metal ion sources (LMISs) have been measured. The results support a postionization mechanism for the formation of the various monoatomic M+2 species, while the M+ species are formed by a combination of field evaporation, field ionization, and charge exchange mechanisms. All ion species show an increase in the full width at half maximum of the TEDs with total emission current, mass, and charge. The dominant monoatomic species at 5μA total emission current are Au+ (64%), Au+2 (15%), Be+2 (10%), and Be+ (3.2%) for the binary LMIS and Au+ (63%), Au+2 (13%), Si+2 (3.2%), Be+2 (2.1%), and Be+ (0.71%) for the ternary LMIS. The predicted beam sizes for Au+2 and Be+2 for the binary LMIS at a beam current of 5pA in a typical focusing column are 15 and 8nm, respectively.
Imaging with surface sensitive backscattered electrons
Authors: Luo T. , Khursheed A.
Published: December 2007

This article presents simulation and experimental results of an angle-filtered backscattered electron (BSE) technique in the scanning electron microscope (SEM). Simulation results predict that for an incident primary beam energy of 5keV, BSEs with low emission angles (90°–91°) contain scattering information coming mostly from within 2nm below the specimen surface. A buried layer track is tested with a 10keV primary beam inside a normal SEM. The BSE image at low emission angles (between 90° and 91°) provides only surface contamination details while the buried layer is not present. This result indicates that the low emission angle BSEs can be used for surface sensitive imaging.
Effect of process parameters on via formation in Si using deep reactive ion etching
Authors: Abhulimen I. U. , Polamreddy S. , Burkett S. , Cai L. , Schaper L.
Published: December 2007

The effect of process parameters on blind via formation for vertical interconnects using an STS deep reactive ion etch tool is reported. A modified Bosch process is used to create vias (20 and 25μm in diameter) with varying depths and sidewall angles on 125mm diameter silicon wafers using a photoresist mask. The effect of changing the flow rates of SF6 and C4F8 gases, the automatic pressure control angle, and coil and platen powers on via profile and sidewall morphology is studied. The effect of chamber cleaning and conditioning on controlling the diameter growth at the top surface of the via is also reported. The various via profiles are examined using an environmental scanning electron microscope and by observing via cross sections. Each parameter plays a critical role in obtaining a specified via profile. A sloped via sidewall is required for our application of fabricating vertical interconnects. After etching, vias are insulated by depositing 2μm of silicon dioxide by plasma enhanced chemical vapor deposition at 250°C. A barrier film of TaN is reactively sputtered after insulation deposition followed by a Cu sputtered seed film allowing electroplated Cu to fill the via. The sloped via sidewall is required due to the weak step coverage obtained by sputter deposition.
Study of fluorine bombardment on the electrical properties of AlGaN∕GaN heterostructures
Authors: Basu Anirban , Kumar Vipan , Adesida Ilesanmi
Published: December 2007

The effects of fluorine ion bombardment on the channel transport properties of AlGaN∕GaN heterostructures have been investigated. Ion bombardment of the heterostructure was carried out within a CF4 plasma in a reactive ion etching system at various self-bias voltages. Hall mobility and sheet electron concentration for the two-dimensional electron gas showed strong dependence on bombardment duration and postbombardment annealing. A systematic study of the behavior of implanted fluorine ions in the annealed heterostructure reveals diffusion followed by accumulation of the ions at the heterointerface. Implications of such behavior on the performance of high electron mobility transistors are briefly discussed.
High throughput defect detection with multiple parallel electron beams
Authors: van Himbergen H. M. P. , Nijkerk M. D. , de Jager P. W. H. , Hosman T. C. , Kruit P.
Published: December 2007

A new concept for high throughput defect detection with multiple parallel electron beams is described. As many as 30 000 beams can be placed on a footprint of a in.2, each beam having its own microcolumn and detection system without cross-talk. Based on the International Technology Roadmap for Semiconductors requirements, some high level properties of the implementation of this concept were derived. A projection lens was designed that can both focus the primary beam into a small spot and simultaneously collect 75% of the secondary electrons. Conceptual design studies were performed for three crucial components of the detector chain: the scintillator, the light optics, and the detection array. The throughput of this concept is expected to be at least a factor of 300 higher than standard electron beam based defect detection systems.
Extracting the Boersch effect contribution from experimental energy spread measurements for Schottky electron emitters
Authors: Bronsgeest M. S. , Barth J. E. , Schwind G. A. , Swanson L. W. , Kruit P.
Published: December 2007

Energy spread is critical to the performance of probe forming systems working at high resolution. The energy spread in the probe is the convolution of the intrinsic spread upon emission and the broadening due to Coulomb interactions in the beam. In order to optimize the design, the two need to be distinguished. The Boersch effect in a Schottky electron gun is difficult to calculate because of the low initial velocity at emission and the strong potential gradient. This article presents a method to extract it from experimental data. Extracting the Boersch effect by deconvoluting the experimental spectrum with the intrinsic distribution is difficult because of noise in the data. Instead, the Boersch effect was determined by fitting convolutions to the measured spectra. A bell shaped function with two free parameters was selected to describe the Boersch contribution. By fitting the convolution of the intrinsic energy distribution and this bell with its free parameters as fitting parameters, the Boersch contribution of experimental spectra could be adequately determined.
Deep ultraviolet photolithography capability of ZEP520A electron beam resist for mix and match lithography
Authors: Brown Devin K.
Published: December 2007

ZEP520A is a positive high resolution electron beam resist enabling nanometer scale features; however, electron beam lithography (EBL) is a characteristically slow process. It is demonstrated that ZEP520A can be exposed by deep ultraviolet (DUV) photolithography and is useful for mix and match lithography schemes. Submicron resolution was achieved, an optical pattern was successfully aligned to an EBL pattern, and 1cm2 was exposed in 11min with DUV compared to 27h with EBL.
High brightness 100-electron-beam source for high-resolution applications
Authors: Zhang Yanxia , Kruit P.
Published: December 2007

The design of a 100-beam source for high-resolution applications is presented, comprising a Schottky emitter, an aperture lens array, an accelerator lens, and a conjugate blanker array. The beamlets emerge at 30kV, compatible with most scanning electron microscope-type systems commercially available. The aberrations due to the aperture lens array and the accelerator lens are carefully minimized. For a Schottky source with a brightness of 1.5×108A∕m2srV, the multibeam source is designed to allow a transmission of more than 1000nA current to the reduction optics with uniform spot sizes.
Fabrication of a needle array using a Si gray mask for x-ray lithography
Authors: Mekaru Harutaka , Takano Takayuki , Awazu Koichi , Takahashi Masaharu , Maeda Ryutaro
Published: December 2007

The authors fabricated a gray mask for x-ray lithography using a silicon-on-insulator wafer by employing microelectronic mechanical system fabrication technologies. Generally, when a three-dimensional (3D) resist structure is fabricated using x-ray lithography, an x-ray mask is rotated or scanned to adjust the exposure time of x ray irradiating the resist. However, the authors maintain that 3D resist structure can be made not only by manipulating the x-ray exposure time but also it could be accomplished rather more effectively by making basic changes in the very structure of x-ray masks. Here they present a procedure for making such a mask. Moreover, the use of such a mask could simplify the x-ray lithography process and make it operator friendly. The structure proposed here is known as gray mask and comprises of Si x-ray absorber on SU-8 membrane. Such a structure, unlike stencil mask structure, allows the formation of pattern with isolated features. The x-ray gray mask was evaluated on a beam line BL-4 at TERAS Synchrotron Radiation Facility at the AIST. By using the x-ray gray mask, the authors fabricated cone shaped and gimlet shaped polymethylmethacrylate (PMMA) resist structures. The base diameter and the maximum height of the cone shaped structure were 32 and 75μm; the base width and the maximum height of the gimlet were 34 and 76μm. They also showed that cross-sectional shape of PMMA resist structures matched quite well with the simulation results.
Fabrication of three dimensional structures for an UV curable nanoimprint lithography mold using variable dose control with critical-energy electron beam exposure
Authors: Mohamed K. , Alkaisi M. M. , Blaikie R. J.
Published: December 2007

In three dimensional (3D) printing the most challenging aspect is in the mold making process. The authors have developed a process for making 3D structures in a simple two-step process. The 3D profiles are created on a negative tone photoresist using electron beam lithography with variable dose and critical-energy electron beam exposure. Resist contrast profiles have been obtained with a negative tone photoresist from Microresist (ma-N2403) and subsequently have been utilized as the 3D masking layer. The 3D patterns have been transferred into a quartz mold by single-step reactive ion etching (RIE) with suitable resist-to-substrate selectivity. The precision of the fabricated structures is important, especially for micro-optic devices. Surface roughness below 2nm has been achieved when the RIE process pressure is lower than 6mTorr. The differences between intended and final dimensions are also analyzed. By employing this technique, complex structures for 3D quartz molds can be fabricated with simplified steps.
Formation of single crystal sulfur supersaturated silicon based junctions by pulsed laser melting
Authors: Tabbal Malek , Kim Taegon , Warrender Jeffrey M. , Aziz Michael J. , Cardozo B. L. , Goldman R. S.
Published: December 2007

The authors demonstrate the formation of pn and nn+ junctions based on silicon supersaturated with sulfur (up to 0.46at.%) using a combination of ion implantation and pulsed laser melting. Silicon wafers were implanted at 200keV S+32 to doses ranging from 1×1015to1×1016ions∕cm2 and subsequently melted and resolidified by using a homogenized excimer laser pulse. Above a threshold laser fluence of ∼1.4J∕cm2, the process produces a single crystal supersaturated alloy, free of extended defects, with a sharp junction between the laser melted layer and the underlying substrate, located near the maximum penetration of the melt front. Hall effect measurements indicate that the laser melted layers are n doped with a free carrier density up to 8×1018∕cm3 that decreases by one-third upon postirradiation furnace annealing at 550°C. Dark current-voltage measurements performed on these structures show good rectifying behavior. The photovoltaic characteristics of the junctions were enhanced by postirradiation annealing at 550–800°C. These effects are attributed to the evolution of a population of point defects that survive the laser treatment. The influence of ion implantation dose, laser fluence, and annealing temperature on the properties of the junctions is also presented and discussed.
Oxygen assisted focused electron beam induced deposition of Si-containing materials: Growth dynamics
Authors: Perentes A. , Hoffmann P.
Published: December 2007

The growth dynamics of oxygen assisted focused electron beam induced deposition of Si-containing materials (from SiOxCy to SiO2) were investigated as a function of relevant process parameters. The results obtained from organosilanes of different families (alkoxy, alkyl, and isocyanatosilanes) are compared. Residual water molecules in the SEM chamber were found to be responsible for side reactions leading to carbon etching and oxygen incorporation in focused electron beam induced deposition (FEBID) materials and ruled the deposition process during conventional FEBID. Depending on the precursor reactivity to oxygen, the material growth rate either increased or decreased with increasing additional O2 until it remained constant from 1SCCM. Accounting for the FEBID material density, oxygen always increased the deposition efficiency in terms of Si atoms deposited per second. Less carbon residues in the deposits were obtained at large replenishment times (above 50μs) and low dwell times (below 15μs), which hint to relatively slow process steps in the complex deposition mechanism in our deposition equipment. O2 assisted FEBID showed to be insensitive to electron density variations, and secondary electrons were demonstrated to have sufficient energy to initiate the oxidation reaction and achieve 90% of the deposition process.
Bit-array patterns with density over 1Tbit∕in.2 fabricated by extreme ultraviolet interference lithography
Authors: Solak Harun H. , Ekinci Yasin
Published: December 2007

The use of patterned magnetic media in future data storage devices requires the fabrication of two-dimensional periodic patterns with resolution well below 35nm in terms of the pattern period. The authors have used extreme ultraviolet interference lithography based on transmission diffraction gratings to demonstrate arrays of structures in negative resists calixarene and hydrogen silsesquioxane. The produced patterns have density exceeding 1Tbit∕in.2. Analysis of structure size and position on one of the patterns indicates variations of subnanometer magnitude.
In situ visualization of local electric field in an ultrasharp tungsten emitter under a low voltage scanning transmission electron microscope
Authors: Fujita Jun-Ichi , Ikeda Yuta , Okada Satoshi , Higashi Kodai , Nakasawa Shotaro , Ishida Masahiko , Matsui Shinji
Published: December 2007

Field emissions from a multiwalled carbon nanotube embedded in a conventional electropolished tungsten probe soften the tip of the tungsten by Joule heating, and the Coulomb attraction to the nanotube finery pulled from the tungsten tip resulted in an ultrasharp apex of the tungsten probe having a curvature of 5nm radius. We also found that scanning transmission electron microscopy (STEM), when operated at low accelerating voltage, can visualize a local electric field at the probe apex. This local electric field, induced around the probe apex, deflected the primary electron beam of the STEM, producing a dark circular shadow surrounding the probe apex in the STEM image. The authors analyzed the distribution of this local field using a simple Rutherford scattering model.
Evaluation of surface roughness of Zerodur® substrates machined by Ar+ ion beam with energy of 3–10keV
Authors: Kurashima Yuichi , Uozumi Ryou , Miyamoto Iwao , Ando Manabu , Numata Atsushi
Published: December 2007

Ion beam figuring is suitable for the final correction of the surface figure error of aspherical substrates in an extreme ultraviolet lithography apparatus. In ion beam processing, however, the surfaces are considered to become rougher. This paper reports the investigation of the surface roughness of Zerodur® machined with an Ar+ ion beam having an energy of 3–10keV. For an Ar+ ion beam with energies in the range of 3–10keV, the mid-spatial frequency roughness of the surfaces machined to a depth of less than 50nm was comparable to the surface roughness of an unprocessed one. The high-spatial frequency roughness of the unprocessed surface was 0.26nm rms; whereas the high-spatial frequency roughness of the surface machined with energies of 3, 5, 7, and 10keV was 0.46, 0.54, 0.63, and 0.65nm rms, respectively. The HSFR of the machined surface increases with an increase in the energy of the ion beam.
Micro-nano mixture patterning by thermal-UV novel nanoimprint
Authors: Okuda Keisuke , Niimi Naoyuki , Kawata Hiroaki , Hirai Yoshihiko
Published: December 2007

Hybrid patterning by thermal and UV nanoimprint lithography (NIL) is demonstrated to fabricate micro and nano mixed structures. The SU-8 resist is thermally imprinted using a quartz mold, which has fine nanostructures and micro Cr mask patterns. After the thermal nanoimprint, UV light is exposed to the resist through the mold. Then, the mold is released and the resist is developed to fabricate microstructures. Using this process, nanodots having 200nm feature sizes are successfully demonstrated on the microgratings with 40μm width and 20μm height. Also, fabrication of nanocorn array on the bottom of the deep microwell is demonstrated using Ni mold replicated from the resist master structure fabricated by the hybrid NIL.
Nanoscale patterning in high resolution HSQ photoresist by interferometric lithography with tabletop extreme ultraviolet lasers
Authors: Wachulak P. W. , Capeluto M. G. , Marconi M. C. , Patel D. , Menoni C. S. , Rocca J. J.
Published: December 2007

Arrays of nanodots and nanoholes were patterned with a highly coherent tabletop 46.9nm laser on high resolution hydrogen silsesquioxane photoresist using multiple exposure interferometric lithography. The authors observed for λ=46.9nm radiation a penetration depth in excess of 150nm. This laser-based extreme ultraviolet interferometric setup allows printing of 0.5×0.5mm2 areas with different nanoscale patterns using a compact tabletop system and exposure times of tens of seconds.
Using high-contrast salty development of hydrogen silsesquioxane for sub-10-nm half-pitch lithography
Authors: Yang Joel K. W. , Berggren Karl K.
Published: December 2007

When used as a negative-tone electron-beam resist, hydrogen silsesquioxane (HSQ) is typically developed in an aqueous alkali solution such as tetramethyl ammonium hydroxide. This development process results in low contrast. In this work, the authors instead used a mixture of salt and alkali to significantly increase the contrast of HSQ. Contrast values as high as 10 in a 115-nm-thick resist were achieved by developing HSQ in an aqueous mixture of NaOH alkali and NaCl salt. Remarkably, this salty developer resulted in contrast enhancement without significant decrease in resist sensitivity. The improved contrast of HSQ enabled the fabrication of 7nm half-pitch nested-“L” structures in a 35-nm-thick resist with minimal loss in thickness using a 30kV electron-beam acceleration voltage. They noticed a strong dependence of contrast enhancement on the concentration and type of cations and anions in the aqueous developer solution.
Electrospun DNA nanofibers
Authors: Bellan Leon M. , Strychalski Elizabeth A. , Craighead Harold G.
Published: December 2007

The authors have electrospun fluorescently labeled DNA molecules into nanofibers with diameters of approximately 27nm. They were able to image the nanofibers via fluorescence microscopy, scanning electron microscopy, and atomic force microscopy. Fibers were deposited over prepatterned features such as electrodes and trenches, allowing future measurement and manipulation of the DNA nanofibers. As an example of such a measurement, they have used an atomic force microscope to measure the Young’s modulus of a single DNA nanofiber.
Photoresist cross-sectioning with negligible damage using a dual-beam FIB-SEM: A high throughput method for profile imaging
Authors: Clarke James S. , Schmidt Michael B. , Orji Ndubuisi G.
Published: December 2007

Imaging of photoresist cross sections in a focused ion beam (FIB)–scanning electron microscope (SEM) is demonstrated with negligible damage. An in situ chromium sputtering technique is used to deposit metal on the site of interest, replacing the conventional and more damaging metal deposition by high energy ion decomposition of metal-organic precursors. Here, a high current ion beam is rastered over a small chromium target suspended over the wafer surface resulting in a less damaging metal deposition step. The subsequent resist critical dimensions measured via FIB-SEM are calibrated against profile measurements taken by critical dimension atomic force microscopy, implemented here as a reference measurement system (RMS) without the influence of beam exposure. The use of a nondamaging RMS allows an accurate measurement of resist damage during imaging. As a practical demonstration of this sputtering method, a 50nm 1:1 line/space array in extreme ultraviolet photoresist is analyzed through focus and exposure.
Subwavelength proximity nanolithography using a plasmonic lens
Authors: Seo Sungkyu , Kim Hyun Chul , Ko Hyungduk , Cheng Mosong
Published: December 2007

This article presents a novel device, the plasmonic lens (PL), consisting of equally spaced ring apertures in a metal film deposited on a fused silica substrate. It was fabricated by electron-beam lithography (EBL) and reactive-ion etching (RIE). When illuminated by a collimated laser, a cylindrical surface plasmon (SP) is excited in the PL, scattered by the structure, and propagates. As a result, the PL focuses a subwavelength spot in the midfield, i.e., the focal length is several microns. The authors experiment demonstrated that 90–300 nm spots (up to λ∕4) with pitches of 400–500 nm, focal length of 1.7 μm, were printed by a PL using 405 nm laser. The authors three-dimensional electromagnetic simulation predicted a full width at half maximum (FWHM) of 210 nm, equivalent to an aberration-free lens having an unity numerical aperture (NA=1). The experimental result agreed well with the simulation. A theoretical model is also presented. Given its small footprint and subwavelength resolution, the PL holds great promise in direct-writing and scanning microscopy.
Mechanisms of porous dielectric film modification induced by reducing and oxidizing ash plasmas
Authors: Posseme N. , Chevolleau T. , David T. , Darnon M. , Louveau O. , Joubert O.
Published: December 2007

This work focuses on the impact of oxidizing and reducing ash chemistries on the modifications of two porous SiOCH films with varied porosities (8% [low porosity (lp)-SiOCH] and 45% [high porosity (hp)-SiOCH]). The ash processes have been performed on SiOCH blanket wafers in either reactive ion etching (RIE) or downstream (DS) reactors. The modifications of the remaining film after plasma exposures have been investigated using different analysis techniques such as x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy (FTIR), x-ray reflectometry, mercury probe capacitance measurement (C-V), and spectroscopic ellipsometry (SE). FTIR analyses show that the lp-SiOCH film is not significantly altered by any of the ash processes investigated (DS-H2∕He, RIE-O2, and RIE-NH3), except by downstream oxidizing plasmas (DS-O2 or DS-N2∕O2) which induce some carbon depletion and moisture uptake, resulting in a slight increase of the k value. The porosity amplifies the sensitivity of the material to plasma treatments. Indeed, hp-SiOCH is fully modified (moisture uptake and carbon depletion) under oxidizing downstream plasma exposures (DS-O2 and DS-N2∕O2), while it is partially altered with the formation of a denser and modified layer (40–60nm thick), which is carbon depleted, hydrophilic, and composed of SiOxNyHz with RIE-NH3 and DS-N2∕H2 plasmas and SiOxHy with RIE-O2 plasma. In all the cases, the k value increase is mainly attributed to the moisture uptake rather than methyl group consumption. hp-SiOCH material is not altered using reducing DS chemistries (H2∕He and H2∕Ar). The porous SiOCH film degradation is presented and discussed with respect to chemistry, plasma parameters, and plasma mode in terms of film modification mechanism.
Visualization of mold filling stages in thermal nanoimprint by using pressure gradients
Authors: Schift Helmut , Bellini Sandro , Mikkelsen Morten Bo , Gobrecht Jens
Published: December 2007

A method for the visualization of mold filling during a thermoplastic imprint at a microscopic level was developed, which is based on superposition of images of a series of different states of imprint. The animated movie sequence gives an insight into the complex flow of polymer and shows how voids are forming and vanishing during the imprint process. It can therefore be used as a tool for optimization of processes and improvement of stamp design.
A Comprehensive Phylogeny of Beetles Reveals the Evolutionary Origins of a Superradiation
Authors: Hunt Toby , Bergsten Johannes , Levkanicova Zuzana , Papadopoulou Anna , John Oliver St. , Wild Ruth , Hammond Peter M. , Ahrens Dirk , Balke Michael , Caterino Michael S. , Gómez-Zurita Jesús , Ribera Ignacio , Barraclough Timothy G. , Bocakova Milada , Bocak Ladislav , Vogler Alfried P.
Published: December 2007

Beetles represent almost one-fourth of all described species, and knowledge about their relationships and evolution adds to our understanding of biodiversity. We performed a comprehensive phylogenetic analysis of Coleoptera inferred from three genes and nearly 1900 species, representing more than 80% of the world's recognized beetle families. We defined basal relationships in the Polyphaga supergroup, which contains over 300,000 species, and established five families as the earliest branching lineages. By dating the phylogeny, we found that the success of beetles is explained neither by exceptional net diversification rates nor by a predominant role of herbivory and the Cretaceous rise of angiosperms. Instead, the pre-Cretaceous origin of more than 100 present-day lineages suggests that beetle species richness is due to high survival of lineages and sustained diversification in a variety of niches.
A Sulfur Dioxide Climate Feedback on Early Mars
Authors: Halevy Itay , Zuber Maria T. , Schrag Daniel P.
Published: December 2007

Ancient Mars had liquid water on its surface and a CO
2
-rich atmosphere. Despite the implication that massive carbonate deposits should have formed, these have not been detected. On the basis of fundamental chemical and physical principles, we propose that climatic conditions enabling the existence of liquid water were maintained by appreciable atmospheric concentrations of volcanically degassed SO
2
and H
2
S. The geochemistry resulting from equilibration of this atmosphere with the hydrological cycle is shown to inhibit the formation of carbonates. We propose an early martian climate feedback involving SO
2
, much like that maintained by CO
2
on Earth.
Comparison between rectal and infrared skin temperature in the newborn
Authors: De Curtis Mario , Calzolari Flaminia , Marciano Alessandra , Cardilli Viviana , Barba Gianvincenzo
Published: December 2007

The reliability of measurement of body temperature using a new infrared skin thermometer was evaluated in 107 newborns. The use of the device was associated with low operator-related variability and acceptable limits of agreement with the temperature measured with a rectal mercury thermometer. Use of the infrared skin thermometer is a comfortable and reliable way of measurement of body temperature in newborns.
Effect of social support on informed consent in older adults with Parkinson disease and their caregivers
Authors: Ford M E , Kallen M , Richardson P , Matthiesen E , Cox V , Teng E J , Cook K F , Petersen N J
Published: December 2007

PURPOSE:

To evaluate the effects of social support on comprehension and recall of consent form information in a study of Parkinson disease patients and their caregivers.

DESIGN and METHODS:

Comparison of comprehension and recall outcomes among participants who read and signed the consent form accompanied by a family member/friend versus those of participants who read and signed the consent form unaccompanied. Comprehension and recall of consent form information were measured at one week and one month respectively, using Part A of the Quality of Informed Consent Questionnaire (QuIC).

RESULTS:

The mean age of the sample of 143 participants was 71 years (SD = 8.6 years). Analysis of covariance was used to compare QuIC scores between the intervention group (n = 70) and control group (n = 73). In the 1-week model, no statistically significant intervention effect was found (p = 0.860). However, the intervention status by patient status interaction was statistically significant (p = 0.012). In the 1-month model, no statistically significant intervention effect was found (p = 0.480). Again, however, the intervention status by patient status interaction was statistically significant (p = 0.040). At both time periods, intervention group patients scored higher (better) on the QuIC than did intervention group caregivers, and control group patients scored lower (worse) on the QuIC than did control group caregivers.

IMPLICATIONS:

Social support played a significant role in enhancing comprehension and recall of consent form information among patients.
Informed consent in Ghana: what do participants really understand?
Authors: Hill Z , Tawiah-Agyemang C , Odei-Danso S , Kirkwood B
Published: December 2007

Objectives:

To explore how subjects in a placebo-controlled vitamin A supplementation trial among Ghanaian women aged 15–45 years perceive the trial and whether they know that not all trial capsules are the same, and to identify factors associated with this knowledge.

Methods:

60 semistructured interviews and 12 focus groups were conducted to explore subjects’ perceptions of the trial. Steps were taken to address areas of low comprehension, including retraining fieldworkers. 1971 trial subjects were randomly selected for a survey measuring their knowledge that not all trial capsules are the same. The subjects’ fieldworkers were also interviewed about their characteristics and trial knowledge. Factors associated with knowledge were explored using multi-level modeling.

Results:

Although subjects knew they were taking part in research, most thought they were receiving an active and beneficial medication. Variables associated with knowledge were education and district of residence. Radio broadcasts benefited those with some schooling. Fieldworkers’ characteristics were not associated with subjects’ knowledge.

Conclusions:

Research and debate on new or improved consent procedures are urgently required, particularly for subjects with little education.
ON SOME INCONSISTENCIES IN MODELING CREDIT PORTFOLIO PRODUCTS
Authors: FABOZZI FRANK J. , TUNARU RADU
Published: December 2007

The survival probability term structure has become the main concept in modeling credit risk for pricing, risk management, and investment decisions. The Kth-to-default contract is not only a relatively liquid credit risk instrument but also a vehicle that credit rating agencies employ to determine the rating of more esoteric credit risky positions. In this paper, we point out some subtleties in credit risk modeling of default baskets and also identify some potential bias in the pricing formula of the Kth-to-default contract. The numerical examples suggest that this bias increases with the correlation. The results in this paper emphasize the important role of conditioning the information regarding arrival of default.
Biogenicity of gold- and silver-bearing siliceous sinters forming in hot (75°C) anaerobic spring-waters of Champagne Pool, Waiotapu, North Island, New Zealand
Authors: JONES BRIAN , RENAUT ROBIN W. , ROSEN MICHAEL R.
Published: December 2007

Champagne Pool, a large hot spring at Waiotapu in North Island, New Zealand, is rimmed by a subaerial sinter dam and a shallow subaqueous shelf that is composed of orange sinter rich in metallic sulphides. Orange siliceous flocs, also rich in sulphides, are in constant circulation in the spring pool and form loose sediment on the shelf. The orange sinters and flocs are rich in As, Sb, Tl, and Hg, and have high concentrations of Au (>100 ppm) and Ag (>330 ppm). Most metallic sulphides are amorphous and disseminated throughout the sinter, instead of forming distinct mineral phases.

The shelf sinters are domal and resemble stromatolites. The neutral chloride waters (pH 5.5; temperature 75°C), however, are virtually anaerobic. Examination of the sinters by scanning electron microscopy confirms that they are laminated and contain an abundant, low-diversity assemblage of filamentous, bacilliform, and coccoid microbes. The flocs are similarly composed of very small, silicified filaments. Silicification involved replacement of the cell walls and extensive encrustation by opal-A. Based on size and morphology, these microbes are probably anaerobic bacteria or archaea. By providing substrates for nucleation of the silica, the microbes are indirectly contributing to the formation of the gold-bearing sinters.
A combined zircon SHRIMP and Sm–Nd isotope study of high-grade paragneisses from the Mid-German Crystalline Rise: evidence for northern Gondwanan and Grenvillian provenance
Authors: ZEH A. , BRÄTZ H. , MILLAR I. L. , WILLIAMS I. S.
Published: December 2007

SHRIMP analyses of detrital zircon cores from high-grade metasediments from the Mid-German Crystalline Rise, which is situated between Eastern Avalonia in the NW and Saxo-Thuringia in the SE, yield mostly ages of
c.
 550 Ma and
c.
 2.06 Ga, with minor
c.
 1.0 and 2.4–2.9 Ga components. The sedimentary protoliths were deposited during the Late Proterozoic to Early Cambrian, probably prior to the break up of the northern Gondwana margin at 460–500 Ma. These data are consistent with the sediments’ high
ϵ
Nd values (0.9 to −3.0), which are comparable to those of well-documented Late Proterozoic sediments from other parts of Europe. The combined isotopic data suggest derivation of the sediments from at least three distinct crustal source regions. Dominant sources were the Avalonian–Cadomian orogenic belt (
c.
 45%), situated at the northern margin of Gondwana during the Neoproterozoic, and the West African and/or eastern Amazonian cratons (
c.
 45%). The Grenvillian belt was a minor source (
c.
 10%).
High-resolution correlation of Anglo-Welsh Middle to Upper Ordovician sequences and its relevance to international chronostratigraphy
Authors: BETTLEY R. M. , FORTEY R. A. , SIVETER D. J.
Published: December 2007

Continuously fossiliferous sections in south Wales and Shropshire spanning the base of the Upper Ordovician permit precise correlation of the
Nemagraptus gracilis
Biozone, a horizon currently under scrutiny for the selection of a Global Stratotype Section and Point (GSSP). Using graphic correlation we have compiled a new composite global standard for the Middle–Upper Ordovician, which shows that the first occurrence of the key graptolite
N. gracilis
is not everywhere of the same age, appearing earlier in North American successions than it does in Britain. Species of
Dicellograptus
, by contrast, appear to be almost synchronous in their first appearance. The status and correlation of standard British biozones through the Llandeilian–Caradoc interval, based on graptolites and trilobites, are revised. Suitable sections for the definition of bases of biozones are proposed. If the base of the
N. gracilis
Biozone is accepted internationally as the base of the Upper Ordovician, this biozone being coincident with the base of the Caradoc Series, there are sections suitable for its precise definition in the British succession.
Relationships between very low‐grade metamorphism and tectonic deformation: examples from the southern Central Iberian Zone (Iberian Massif, Variscan Belt)
Authors: MARTÍNEZ POYATOS DAVID , NIETO FERNANDO , AZOR ANTONIO , SIMANCAS JOSÉ FERNANDO
Published: December 2007

We have studied the syn‐kinematic very low‐grade metamorphism in a polyphase Variscan deformed region using X‐ray diffraction techniques. Two phases of regional metamorphism are related to their respective episodes of penetrative deformation in the southern Central Iberian Zone. The data obtained suggest that the rocks did not reach metamorphic equilibrium, but strain favoured the progress of mineral reactions in the more deformed parts. The first deformation is Devonian in age and consists in a heterogeneous ductile shearing coeval with large‐scale recumbent folding that were produced under high‐anchizone to epizone metamorphic conditions. The heterogeneity of the shearing originated strain gradients that can be said to enhance the growth of new minerals and the illite polytype transformation in the highly strained overturned limb of the preserved pile of recumbent folds, but illite crystallinity remained constant throughout the structure. The second deformation is Mid‐Carboniferous in age and consists in an upright folding that took place under late diagenesis to low‐anchizone metamorphic conditions. The distribution of mineral parageneses and illite crystallinity across one of the upright folds suggests that strain gradients favoured the metamorphic reaction progress from the hinge (low strain) towards the limbs (high strain). Other characteristics of the region such as a metamorphic gap associated with an unconformity at the base of the Lower Carboniferous rocks, or cryptic contacts aureoles surrounding volcanic intercalations and a large granitic batholith, are also studied.