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Davis RC, Jensen CJ, Burgette L, Burnett K. Working Smarter on Cold Cases: Identifying Factors Associated with Successful Cold Case Investigations. J Forensic Sci 2014; 59:375-82. [DOI: 10.1111/1556-4029.12384] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2011] [Revised: 12/03/2012] [Accepted: 12/23/2012] [Indexed: 11/27/2022]
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Hung CH, Wiest LA, Singh B, Diwan A, Valentim MJC, Christensen JM, Davis RC, Miles AJ, Jensen DS, Vail MA, Dadson AE, Linford MR. Improved efficiency of reversed-phase carbon/nanodiamond/polymer core-shell particles for HPLC using carbonized poly(divinylbenzene) microspheres as the core materials. J Sep Sci 2013; 36:3821-9. [DOI: 10.1002/jssc.201300988] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Revised: 09/30/2013] [Accepted: 10/01/2013] [Indexed: 11/10/2022]
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Gupta V, Tuscano JA, Romriell NR, Davis RC, Linford MR. Data and device protection: A ToF-SIMS, wetting, and XPS study of an Apple iPod nano. SURF INTERFACE ANAL 2013. [DOI: 10.1002/sia.5352] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Wang H, Lunt BM, Gates RJ, Asplund MC, Shutthanandan V, Davis RC, Linford MR. Carbon/ternary alloy/carbon optical stack on mylar as an optical data storage medium to potentially replace magnetic tape. ACS APPLIED MATERIALS & INTERFACES 2013; 5:8407-8413. [PMID: 23964822 DOI: 10.1021/am401693u] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
A novel write-once-read-many (WORM) optical stack on Mylar tape is proposed as a replacement for magnetic tape for archival data storage. This optical tape contains a cosputtered bismuth-tellurium-selenium (BTS) alloy as the write layer sandwiched between thin, protective films of reactively sputtered carbon. The composition and thickness of the BTS layer were confirmed by Rutherford Backscattering (RBS) and atomic force microscopy (AFM), respectively. The C/BTS/C stack on Mylar was written to/marked by 532 nm laser pulses. Under the same conditions, control Mylar films without the optical stack were unaffected. Marks, which showed craters/movement of the write material, were characterized by optical microscopy and AFM. The threshold laser powers for making marks on C/BTS/C stacks with different thicknesses were explored. Higher quality marks were made with a 60× objective compared to a 40× objective in our marking apparatus. The laser writing process was simulated with COMSOL.
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Pearson AC, Linford MR, Harb JN, Davis RC. Dual patterning of a poly(acrylic acid) layer by electron-beam and block copolymer lithographies. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:7433-7438. [PMID: 23342948 DOI: 10.1021/la304486x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We show the controllable patterning of palladium nanoparticles in both one and two dimensions using electron-beam lithography and reactive ion etching of a thin film of poly(acrylic acid) (PAA). After the initial patterning of the PAA, a monolayer of polystyrene-b-poly-2-vinylpyridine micelles is spun cast onto the surface. A short reactive ion etch is then used to transfer the micelle pattern into the patterned poly(acrylic acid). Finally, PdCl2 is loaded from solution into the patterned poly(acrylic acid) features, and a reactive-ion etching process is used to remove the remaining polymer and form Pd nanoparticles. This method yields location-controlled patches of nanoparticles, including single- and double-file lines and nanoparticle pairs. A locational accuracy of 9 nm or less in one direction was achieved by optimizing the size of the PAA features.
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Pearson AC, Jamieson S, Linford MR, Lunt BM, Davis RC. Oxidation of graphene 'bow tie' nanofuses for permanent, write-once-read-many data storage devices. NANOTECHNOLOGY 2013; 24:135202. [PMID: 23478811 DOI: 10.1088/0957-4484/24/13/135202] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We have fabricated nanoscale fuses from CVD graphene sheets with a 'bow tie' geometry for write-once-read-many data storage applications. The fuses are programmed using thermal oxidation driven by Joule heating. Fuses that were 250 nm wide with 2.5 μm between contact pads were programmed with average voltages and powers of 4.9 V and 2.1 mW, respectively. The required voltages and powers decrease with decreasing fuse sizes. Graphene shows extreme chemical and electronic stability; fuses require temperatures of about 400 °C for oxidation, indicating that they are excellent candidates for permanent data storage. To further demonstrate this stability, fuses were subjected to applied biases in excess of typical read voltages; stable currents were observed when a voltage of 10 V was applied to the devices in the off state and 1 V in the on state for 90 h each.
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Geng Y, Pearson AC, Gates EP, Uprety B, Davis RC, Harb JN, Woolley AT. Electrically conductive gold- and copper-metallized DNA origami nanostructures. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:3482-3490. [PMID: 23419143 DOI: 10.1021/la305155u] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
This work demonstrates the use of a circuit-like DNA origami structure as a template to fabricate conductive gold and copper nanostructures on Si surfaces. We improved over previous results by using multiple Pd seeding steps to increase seed uniformity and density. Our process has also been characterized through atomic force microscopy, particle size distribution analysis, and scanning electron microscopy. We found that four successive Pd seeding steps yielded the best results for electroless metal plating on DNA origami. Electrical resistance measurements were done on both Au- and Cu-metallized nanostructures, with each showing ohmic behavior. Gold-plated DNA origami structures made under optimal conditions had an average resistivity of 7.0 × 10(-5) Ω·m, whereas copper-metallized structures had a resistivity as low as 3.6 × 10(-4) Ω·m. Importantly, this is the first demonstration of electrically conductive Cu nanostructures fabricated on either DNA or DNA origami templates. Although resistivities for both gold and copper samples were larger than those of the bulk metal, these metal nanostructures have the potential for use in electrically connecting small structures. In addition, these metallized objects might find use in surface-enhanced Raman scattering experiments.
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Jensen DS, Kanyal SS, Gupta V, Vail MA, Dadson AE, Engelhard M, Vanfleet R, Davis RC, Linford MR. Stable, microfabricated thin layer chromatography plates without volume distortion on patterned, carbon and Al2O3-primed carbon nanotube forests. J Chromatogr A 2012; 1257:195-203. [DOI: 10.1016/j.chroma.2012.07.086] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Revised: 07/21/2012] [Accepted: 07/23/2012] [Indexed: 11/28/2022]
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Davis B, Conley H, Jones D, Harb JN, Davis RC. Scaling parallel dielectrophoresis of carbon nanotubes: an enabling geometry. NANOTECHNOLOGY 2012; 23:185308. [PMID: 22513525 DOI: 10.1088/0957-4484/23/18/185308] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Dielectrophoresis has been used as a technique for the parallel localization and alignment of both semiconducting and metallic carbon nanotubes (CNTs) at junctions between electrodes. A variation of this technique known as floating potential dielectrophoresis (FPD) allows for a self-limiting number of CNTs to be localized at each junction, on a massively parallel scale. However, the smallest FPD geometries to date are restricted to conductive substrates and have a lower limit on floating electrode size. We present a geometry which eliminates this lower limit and enables FPD to be performed on non-conducting substrates. We also discuss experiments clarifying the self-limiting mechanism of CNT localization and how it can be used advantageously as devices are scaled downwards to smaller sizes.
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Pearson AC, Liu J, Pound E, Uprety B, Woolley AT, Davis RC, Harb JN. DNA origami metallized site specifically to form electrically conductive nanowires. J Phys Chem B 2012; 116:10551-60. [PMID: 22578334 DOI: 10.1021/jp302316p] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
DNA origami is a promising tool for use as a template in the design and fabrication of nanoscale structures. The ability to engineer selected staple strands on a DNA origami structure provides a high density of addressable locations across the structure. Here we report a method using site-specific attachment of gold nanoparticles to modified staple strands and subsequent metallization to fabricate conductive wires from DNA origami templates. We have modified DNA origami structures by lengthening each staple strand in select regions with a 10-base nucleotide sequence and have attached DNA-modified gold nanoparticles to the lengthened staple strands via complementary base-pairing. The high density of extended staple strands allowed the gold nanoparticles to pack tightly in the modified regions of the DNA origami, where the measured median gap size between neighboring particles was 4.1 nm. Gold metallization processes were optimized so that the attached gold nanoparticles grew until gaps between particles were filled and uniform continuous nanowires were formed. Finally, electron beam lithography was used to pattern electrodes in order to measure the electrical conductivity of metallized DNA origami, which showed an average resistance of 2.4 kΩ per metallized structure.
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Visser J, McCarthy I, Marks L, Davis RC. Is hip muscle strength the key to walking as a bilateral amputee, whatever the level of the amputations? Prosthet Orthot Int 2011; 35:451-8. [PMID: 21983043 DOI: 10.1177/0309364611422268] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
BACKGROUND Little data have been reported on the factors that are important in bilateral amputee walking ability especially the role of hip strength. STUDY DESIGN Observational, case-control study where participants were evaluated at a single point in time. OBJECTIVES The aim of this study was to investigate the factors involved in bilateral amputee walking ability by assessment of walking speed, perceived exertion, exercise intensity, physiological cost index (PCI) and hip muscle strength. METHODS For a group of 10 bilateral amputees, with different levels of amputation, and a non-pathological reference group, walking ability was assessed using the two-minute walk test. Hip muscle strength was assessed using isokinetic strength tests. RESULTS Bilateral amputees were found to have slower walking speeds and increased PCI of walking which were correlated to higher levels of amputation. Peak hip torques were reduced in the amputees, which was only significant for concentric extension torque (p = 0.029), and approaching significance for concentric flexion (p = 0.061) and abduction (p = 0.057). Bilateral amputee peak hip strength suggested a positive trend with increasing walking ability. CONCLUSIONS Bilateral amputee walking ability was reduced and mainly related to level of amputation. The role of hip strength in bilateral amputee walking ability requires further investigation.
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Wiest LA, Jensen DS, Hung CH, Olsen RE, Davis RC, Vail MA, Dadson AE, Nesterenko PN, Linford MR. Pellicular Particles with Spherical Carbon Cores and Porous Nanodiamond/Polymer Shells for Reversed-Phase HPLC. Anal Chem 2011; 83:5488-501. [DOI: 10.1021/ac200436a] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Pearson AC, Pound E, Woolley AT, Linford MR, Harb JN, Davis RC. Chemical alignment of DNA origami to block copolymer patterned arrays of 5 nm gold nanoparticles. NANO LETTERS 2011; 11:1981-7. [PMID: 21473607 DOI: 10.1021/nl200306w] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
We have used block copolymer patterned arrays of 5 nm gold nanoparticles (AuNPs) for chemically aligned surface attachment of DNA origami. Addition of single-stranded DNA-thiol to AuNPs allowed a base paired attachment of sticky end modified DNA origami. Results indicate a stable, selective attachment between the DNA origami and ssDNA modified AuNPs. Yield data showed 74% of AuNP binding sites forming an attachment with a DNA origami rectangle, and control surfaces showed less than 0.5% nonspecific adsorption.
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Zhang F, Sautter K, Larsen AM, Findley DA, Davis RC, Samha H, Linford MR. Chemical vapor deposition of three aminosilanes on silicon dioxide: surface characterization, stability, effects of silane concentration, and cyanine dye adsorption. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:14648-14654. [PMID: 20731334 DOI: 10.1021/la102447y] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Covalently bonded monolayers of two monofunctional aminosilanes (3-aminopropyldimethylethoxysilane, APDMES, and 3-aminopropyldiisopropylethoxysilane, APDIPES) and one trifunctional aminosilane (3-aminopropyltriethoxysilane, APTES) have been deposited on dehydrated silicon substrates by chemical vapor deposition (CVD) at 150 °C and low pressure (a few Torr) using reproducible equipment. Standard surface analytical techniques such as x-ray photoelectron spectroscopy (XPS), contact angle goniometry, spectroscopic ellipsometry, atomic force microscopy, and time-of-flight secondary ion mass spectroscopy (ToF-SIMS) have been employed to characterize the resulting films. These methods indicate that essentially constant surface coverages are obtained over a wide range of gas phase concentrations of the aminosilanes. XPS data further indicate that the N1s/Si2p ratio is higher after CVD with the trifunctional silane (APTES) compared to the monofunctional ones, with a higher N1s/Si2p ratio for APDMES compared to that for APDIPES. AFM images show an average surface roughness of 0.12- 0.15 nm among all three aminosilane films. Stability tests indicate that APDIPES films retain most of their integrity at pH 10 for several hours and are more stable than APTES or APDMES layers. The films also showed good stability against storage in the laboratory. ToF-SIMS of these samples showed expected peaks, such as CN(-), as well as CNO(-), which may arise from an interaction between monolayer amine groups and silanols. Optical absorption measurements on adsorbed cyanine dye at the surface of the aminosilane films show the formation of dimer aggregates on the surface. This is further supported by ellipsometry measurements. The concentration of dye on each surface appears to be consistent with the density of the amines.
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Zhang F, Sautter K, Larsen AM, Findley DA, Davis RC, Samha H, Linford MR. Chemical vapor deposition of three aminosilanes on silicon dioxide: surface characterization, stability, effects of silane concentration, and cyanine dye adsorption. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:14648-14654. [PMID: 20731334 DOI: 10.1021/la.102447y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Covalently bonded monolayers of two monofunctional aminosilanes (3-aminopropyldimethylethoxysilane, APDMES, and 3-aminopropyldiisopropylethoxysilane, APDIPES) and one trifunctional aminosilane (3-aminopropyltriethoxysilane, APTES) have been deposited on dehydrated silicon substrates by chemical vapor deposition (CVD) at 150 °C and low pressure (a few Torr) using reproducible equipment. Standard surface analytical techniques such as x-ray photoelectron spectroscopy (XPS), contact angle goniometry, spectroscopic ellipsometry, atomic force microscopy, and time-of-flight secondary ion mass spectroscopy (ToF-SIMS) have been employed to characterize the resulting films. These methods indicate that essentially constant surface coverages are obtained over a wide range of gas phase concentrations of the aminosilanes. XPS data further indicate that the N1s/Si2p ratio is higher after CVD with the trifunctional silane (APTES) compared to the monofunctional ones, with a higher N1s/Si2p ratio for APDMES compared to that for APDIPES. AFM images show an average surface roughness of 0.12- 0.15 nm among all three aminosilane films. Stability tests indicate that APDIPES films retain most of their integrity at pH 10 for several hours and are more stable than APTES or APDMES layers. The films also showed good stability against storage in the laboratory. ToF-SIMS of these samples showed expected peaks, such as CN(-), as well as CNO(-), which may arise from an interaction between monolayer amine groups and silanols. Optical absorption measurements on adsorbed cyanine dye at the surface of the aminosilane films show the formation of dimer aggregates on the surface. This is further supported by ellipsometry measurements. The concentration of dye on each surface appears to be consistent with the density of the amines.
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Pearlstein RM, Davis RC, Ditson SL. Giant circular dichroism of high molecular weight chlorophyllide-apomyoglobin complexes. Proc Natl Acad Sci U S A 2010; 79:400-2. [PMID: 16593144 PMCID: PMC345750 DOI: 10.1073/pnas.79.2.400] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Chlorophyllide a and the apoprotein of myoglobin (Mb) spontaneously form three types of complex. The M (M(r) approximately 3 x 10(5)) and H (M(r) >/= 4 x 10(6)) complexes, but not the L (M(r) approximately 1.7 x 10(4)), display a circular dichroism (CD) spectrum that is highly red-shifted, nonconservative, and very intense-characteristics shared by the CD spectra of reaction center complexes from purple photosynthetic bacteria. At its 710-nm peak, the H complex CD spectrum has a larger magnitude, 0.06 differential absorbance per unit total absorbance, than has been reported for chlorophyll in any medium.
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Bamburg JR, Bernstein BW, Davis RC, Flynn KC, Goldsbury C, Jensen JR, Maloney MT, Marsden IT, Minamide LS, Pak CW, Shaw AE, Whiteman I, Wiggan O. ADF/Cofilin-actin rods in neurodegenerative diseases. Curr Alzheimer Res 2010; 7:241-50. [PMID: 20088812 PMCID: PMC4458070 DOI: 10.2174/156720510791050902] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2009] [Accepted: 11/24/2009] [Indexed: 11/22/2022]
Abstract
Dephosphorylation (activation) of cofilin, an actin binding protein, is stimulated by initiators of neuronal dysfunction and degeneration including oxidative stress, excitotoxic glutamate, ischemia, and soluble forms of beta-amyloid peptide (Abeta). Hyperactive cofilin forms rod-shaped cofilin-saturated actin filament bundles (rods). Other proteins are recruited to rods but are not necessary for rod formation. Neuronal cytoplasmic rods accumulate within neurites where they disrupt synaptic function and are a likely cause of synaptic loss without neuronal loss, as occurs early in dementias. Different rod-inducing stimuli target distinct neuronal populations within the hippocampus. Rods form rapidly, often in tandem arrays, in response to stress. They accumulate phosphorylated tau that immunostains for epitopes present in "striated neuropil threads," characteristic of tau pathology in Alzheimer disease (AD) brain. Thus, rods might aid in further tau modifications or assembly into paired helical filaments, the major component of neurofibrillary tangles (NFTs). Rods can occlude neurites and block vesicle transport. Some rod-inducing treatments cause an increase in secreted Abeta. Thus rods may mediate the loss of synapses, production of excess Abeta, and formation of NFTs, all of the pathological hallmarks of AD. Cofilin-actin rods also form within the nucleus of heat-shocked neurons and are cleared from cells expressing wild type huntingtin protein but not in cells expressing mutant or silenced huntingtin, suggesting a role for nuclear rods in Huntington disease (HD). As an early event in the neurodegenerative cascade, rod formation is an ideal target for therapeutic intervention that might be useful in treatment of many different neurological diseases.
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Wickard TD, Nelsen E, Madaan N, ten Brummelhuis N, Diehl C, Schlaad H, Davis RC, Linford MR. Attachment of polybutadienes to hydrogen-terminated silicon and post-derivatization of the adsorbed species. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:1923-1928. [PMID: 19835363 DOI: 10.1021/la902760r] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We report the first attachment of polymers with pendant vinyl groups to hydrogen-terminated silicon(111) (Si(111)-H); 1,2-polybutadiene (M(w) = 3200-3500 g/mol) was attached to Si(111)-H under mild conditions at room temperature with visible light. We also report the partial functionalization, in solution, of 1,2-polybutadiene with various thiols using thiol-ene chemistry and the subsequent attachments of these compounds to Si(111)-H. The partially functionalized or unfunctionalized polybutadienes allow further functionalization at the surface through their unreacted carbon-carbon double bonds. We present this as a useful strategy for silicon surface modification. Surfaces were characterized with contact angle goniometry, spectroscopic ellipsometry, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and atomic force microscopy (AFM).
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Gale GD, Yazdi RD, Khan AH, Lusis AJ, Davis RC, Smith DJ. A genome-wide panel of congenic mice reveals widespread epistasis of behavior quantitative trait loci. Mol Psychiatry 2009; 14:631-45. [PMID: 18379576 PMCID: PMC3014058 DOI: 10.1038/mp.2008.4] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Understanding the genetics of behavioral variation remains a fascinating but difficult problem with considerable theoretical and practical implications. We used the genome-tagged mice (GTM) and an extensive test battery of well-validated behavioral assays to scan the genome for behavioral quantitative trait loci (QTLs). The GTM are a panel of 'speed congenic' mice consisting of over 60 strains spanning the entire autosomal genome. Each strain harbors a small (approximately 23 cM) DBA/2J donor segment on a uniform C57BL/6J background. The panel allows for mapping to regions as small as 5 cM and provides a powerful new tool for increasing mapping power and replicability in the analysis of QTLs. A total of 97 loci were mapped for a variety of complex behavioral traits including hyperactivity, anxiety, prepulse inhibition, avoidance and conditional fear. A larger number of loci were recovered than generally attained from standard mapping crosses. In addition, a surprisingly high proportion of loci, 63%, showed phenotypes unlike either of the parental strains. These data suggest that epistasis decreases sensitivity of locus detection in traditional crosses and demonstrate the utility of the GTM for mapping complex behavioral traits with high sensitivity and precision.
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Hayamizu Y, Davis RC, Yamada T, Futaba DN, Yasuda S, Yumura M, Hata K. Mechanical properties of beams from self-assembled closely packed and aligned single-walled carbon nanotubes. PHYSICAL REVIEW LETTERS 2009; 102:175505. [PMID: 19518795 DOI: 10.1103/physrevlett.102.175505] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2009] [Indexed: 05/27/2023]
Abstract
To demonstrate the potential for microelectromechanical systems, nanotube beams composed from self-assembled closely packed and aligned single-walled carbon nanotubes were fabricated and their mechanical properties were measured. We found that the nanotube beams behave as a cohesive, rigid, and elastic body with a sound velocity of 10,100 m/s.
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Zhang F, Sautter K, Davis RC, Linford MR. Subsurface oxidation for micropatterning silicon (SOMS). LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:1289-1291. [PMID: 19133726 DOI: 10.1021/la803408x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Here we present a straightforward patterning technique for silicon: subsurface oxidation for micropatterning silicon (SOMS). In this method, a stencil mask is placed above a silicon surface. Radio-frequency plasma oxidation of the substrate creates a pattern of thicker oxide in the exposed regions. Etching with HF or KOH produces very shallow or much higher aspect ratio features on silicon, respectively, where patterning is confirmed by atomic force microscopy, scanning electron microscopy, and optical microscopy. The oxidation process itself is studied under a variety of reaction conditions, including higher and lower oxygen pressures (2 and 0.5 Torr), a variety of powers (50-400 W), different times and as a function of reagent purity (99.5 or 99.994% oxygen). SOMS can be easily executed in any normal chemistry laboratory with a plasma generator. Because of its simplicity, it may have industrial viability.
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Hayamizu Y, Yamada T, Mizuno K, Davis RC, Futaba DN, Yumura M, Hata K. Integrated three-dimensional microelectromechanical devices from processable carbon nanotube wafers. NATURE NANOTECHNOLOGY 2008; 3:289-294. [PMID: 18654526 DOI: 10.1038/nnano.2008.98] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2008] [Accepted: 04/01/2008] [Indexed: 05/26/2023]
Abstract
In order to be useful as microelectromechanical devices, carbon nanotubes with well-controlled properties and orientations should be made at high density and be placed at predefined locations. We address this challenge by hierarchically assembling carbon nanotubes into closely packed and highly aligned three-dimensional wafer films from which a wide range of complex and three-dimensional nanotube structures were lithographically fabricated. These include carbon nanotube islands on substrates, suspended sheets and beams, and three-dimensional cantilevers, all of which exist as single cohesive units with useful mechanical and electrical properties. Every fabrication step is both parallel and scalable, which makes it easy to further integrate these structures into functional three-dimensional nanodevice systems. Our approach opens up new ways to make economical and scalable devices with unprecedented structural complexity and functionality.
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Blake RB, Pei L, Yang L, Lee MV, Conley HJ, Davis RC, Shirahata N, Linford MR. Macromol. Rapid Commun. 8/2008. Macromol Rapid Commun 2008. [DOI: 10.1002/marc.200890013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Blake RB, Pei L, Yang L, Lee MV, Conley HJ, Davis RC, Shirahata N, Linford MR. One-Step Growth of ca. 2-15 nm Polymer Thin Films on Hydrogen-Terminated Silicon. Macromol Rapid Commun 2008. [DOI: 10.1002/marc.200700752] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Mahadevan G, Davis RC, Frenneaux MP, Hobbs FDR, Lip GYH, Sanderson JE, Davies MK. Left ventricular ejection fraction: are the revised cut-off points for defining systolic dysfunction sufficiently evidence based? Heart 2008; 94:426-8. [PMID: 18347374 DOI: 10.1136/hrt.2007.123877] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
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