Institute for Critical Technology and Applied Science (ICTAS)
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ICTAS Vision:
To be a premier institute to advance transformative, interdisciplinary research for a sustainable future.
ICTAS Mission:
To serve Virginia Tech, the Commonwealth of Virginia, the nation, and the world through high-impact research and scholarship at the intersections of engineering, the sciences -- physical, life, and social -- and the humanities. To this end, advance the frontiers of knowledge and education, enhance the educational experience of undergraduate, graduate, and professional students, and promote economic development through the creation and application of innovative research that enhances the quality of life and preserves our natural resources.
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- ICTAS Connection, May 2007(Virginia Tech, 2007-05)This newsletter details new developments in staff and programs for ICTAS. In this issue: Message from VT President Charles Steger, SBES, and more about developing ICTAS facilities.
- Laser-induced exfoliation of amorphous carbon layer on an individual multiwall carbon nanotubeSingh, G.; Rice, P.; Hurst, K. E.; Lehman, John H.; Mahajan, R. L. (AIP Publishing, 2007-07)Pulsed laser treatment of an individual multiwall carbon nanotube induced selective exfoliation of the amorphous carbon contamination layer. The multiwall carbon nanotube (MWCNT) was exposed to a 248 nm excimer laser. After the treatment, transmission electron microscopy images show that the amorphous layer has expanded and separated from the crystalline MWCNT walls. This interesting observation has implications for laser cleaning and possible thinning of MWCNTs to reduce the radial dimensions. (C) 2007 American Institute of Physics.
- ICTAS Connection, August 2007(Virginia Tech, 2007-08)This newsletter details new developments in staff and programs for ICTAS. In this issue: Introduction of NCFL (then called ICTAS A) and initial staff introductions.
- ICTAS Connection, November 2007(Virginia Tech, 2007-11)This newsletter details new developments in staff and programs for ICTAS. In this issue: Opening of the NCFL (then called ICTAS A) and the inaugural doctoral scholar class.
- Foam-based optical absorber for high-power laser radiometryRamadurai, Krishna; Cromer, Christopher L.; Li, Xiaoyu; Mahajan, Roop L.; Lehman, John H. (Optical Society of America, 2007-12-01)We report damage threshold measurements of novel absorbers comprised of either liquid-cooled silicon carbide or vitreous carbon foams. The measurements demonstrate damage thresholds up to 1.6 x 104 W/cm(2) at an incident circular spot size of 2 mm with an absorbance of 96% at 1.064 mu m. We present a summary of the damage threshold as a function of the water flow velocity and the absorbance measurements. We also present a qualitative description of a damage mechanism based on a two-phase heat transfer between the foam and the flowing water. (c) 2007 Optical Society of America.
- High-performance carbon nanotube coatings for high-power laser radiometryRamadurai, Krishna; Cromer, Christopher L.; Lewis, Laurence A.; Hurst, Katherine E.; Dillon, Anne C.; Mahajan, Roop L.; Lehman, John H. (American Institute of Physics, 2008-01-01)Radiometry for the next generation of high-efficiency, high-power industrial lasers requires thermal management at optical power levels exceeding 10 kW. Laser damage and thermal transport present fundamental challenges for laser radiometry in support of common manufacturing processes, such as welding, cutting, ablation, or vaporization. To address this growing need for radiometry at extremely high power densities, we demonstrate multiwalled carbon nanotube (MWCNT) coatings with damage thresholds exceeding 15 000 W/cm(2) and absorption efficiencies over 90% at 1.06 mu m. This result demonstrates specific design advantages not possible with other contemporary high-power laser coatings. Furthermore, the results demonstrate a performance difference between MWCNTs and single-walled carbon nanotube coatings, which is attributed to the lower net thermal resistance of the MWCNT coatings. We explore the behavior of carbon nanotubes at two laser wavelengths (1.06 and 10.6 mu m) and also evaluate the optical-absorption efficiency and bulk properties of the coatings. (c) 2008 American Institute of Physics.
- ICTAS Connection, February 2008(Virginia Tech, 2008-02)This newsletter details new developments in staff and programs for ICTAS. In this issue: Microfossils, funding awards, and the arrival of Professor Padma Rajagopalan.
- Nanodispersed DO(3)-phase nanostructures observed in magnetostrictive Fe-19% Ga Galfenol alloysBhattacharyya, Somnath; Jinschek, J. R.; Khachaturyan, Armen G.; Cao, Hu; Li, Jiefang; Viehland, Dwight D. (American Physical Society, 2008-03-10)Few nanometer large (<2 nm) inclusions of DO(3)-phase structure have been identified in the A2 matrix of highly magnetostrictive Fe-19% Ga alloys by high-resolution transmission electron microscopy (HRTEM). In addition, we have found that these nanostructures include a high density of {100} line defects with a Burgers vector of a(bcc)/2 < 100 >. This dispersion of DO(3)-phase nanostructures formed within the main A2 matrix and the lifting of their coherency by defects are consistent with a recent theory for the structure and properties of magnetostrictive Fe-Ga and Fe-Al alloys.
- ICTAS Connection, November 2008(Virginia Tech, 2008-11)This newsletter details new developments in staff and programs for ICTAS. In this issue: Updates on construction of ICTAS I, 2008 Doctoral Scholars, arrival of Chris Cornelius.
- Antibacterial efficacy of core-shell nanostructures encapsulating gentamicin against an in vivo intracellular Salmonella modelRanjan, Ashish; Pothayee, Nikorn; Seleem, Mohamed N.; Tyler, Ronald D.; Brenseke, Bonnie; Sriranganathan, Nammalwar; Riffle, Judy S.; Kasimanickam, Ramanathan K. (Dove Medical Press, 2009-01-01)Pluronic based core-shell nanostructures encapsulating gentamicin were designed in this study. Block copolymers of (PAA(+/-)Na-b-(PEO-b-PPO-b-PEO)-b-PAA(+/-)Na) were blended with PAA(-) Na(+) and complexed with the polycationic antibiotic gentamicin to form nanostructures. Synthesized nanostructures had a hydrodynamic diameter of 210 nm, zeta potentials of -0.7 (+/-0.2), and incorporated approximately 20% by weight of gentamicin. Nanostructures upon co-incubation with J774A.1 macrophage cells showed no adverse toxicity in vitro. Nanostructures administered in vivo either at multiple dosage of 5 microg g(-1) or single dosage of 15 microg g(-1) in AJ-646 mice infected with Salmonella resulted in significant reduction of viable bacteria in the liver and spleen. Histopathological evaluation for concentration-dependent toxicity at a dosage of 15 microg g(-1) revealed mineralized deposits in 50% kidney tissues of free gentamicin-treated mice which in contrast was absent in nanostructure-treated mice. Thus, encapsulation of gentamicin in nanostructures may reduce toxicity and improve in vivo bacterial clearance.
- Large piezoresistivity phenomenon in SiCN-(La,Sr)MnO3 compositesKarmarkar, Makarand; Singh, Gurpreet; Shah, Sandeep; Mahajan, Roop L.; Priya, Shashank (AIP Publishing, 2009-02-01)We present the results on SiCN-(La,Sr)MnO3 (LSMO) composites correlating the observed large piezoresistance behavior with the microstructural features and defect chemistry. Scanning electron microscopy characterization revealed the presence of self-assembled periodic microvalleys in the microstructure with width of 1-5 mu m and depth of 600-1000 nm. The microvalleys act as stress concentration points providing change in volume with applied stress. High resolution transmission electron microscopy measurements conducted on composites showed that LSMO grains consist of SiCN phase but no inclusions were observed.
- ICTAS Connection, March 2009(Virginia Tech, 2009-03)This newsletter details new developments in staff and programs for ICTAS. In this issue: An agreement with Dahlgren, news on the move into ICTAS I, 2009 research awards, cancer research at VT.
- Thermal transport in composites of self-assembled nickel nanoparticles embedded in yttria stabilized zirconiaShukla, Nitin C.; Liao, Hao-Hsiang; Abiade, Jeremiah T.; Murayama, Mitsuhiro; Kumar, Dhananjay; Huxtable, Scott T. (AIP Publishing, 2009-04-01)We investigate the effect of nickel nanoparticle size on thermal transport in multilayer nanocomposites consisting of alternating layers of nickel nanoparticles and yttria stabilized zirconia (YSZ) spacer layers that are grown with pulsed laser deposition. Using time-domain thermoreflectance, we measure thermal conductivities of k=1.8, 2.4, 2.3, and 3.0 W m(-1) K(-1) for nanocomposites with nickel nanoparticle diameters of 7, 21, 24, and 38 nm, respectively, and k=2.5 W m(-1) K(-1) for a single 80 nm thick layer of YSZ. We use an effective medium theory to estimate the lower limits for interface thermal conductance G between the nickel nanoparticles and the YSZ matrix (G>170 MW m(-2) K(-1)), and nickel nanoparticle thermal conductivity.
- Overexpression and simple purification of the Thermotoga maritima 6-phosphogluconate dehydrogenase in Escherichia coli and its application for NADPH regenerationWang, Yiran; Zhang, Y. H. Percival (2009-06-04)Background Thermostable enzymes from thermophilic microorganisms are playing more and more important roles in molecular biology R&D and industrial applications. However, over-production of recombinant soluble proteins from thermophilic microorganisms in mesophilic hosts (e.g. E. coli) remains challenging sometimes. Results An open reading frame TM0438 from a hyperthermophilic bacterium Thermotoga maritima putatively encoding 6-phosphogluconate dehydrogenase (6PGDH) was cloned and expressed in E. coli. The purified protein was confirmed to have 6PGDH activity with a molecular mass of 53 kDa. The kcat of this enzyme was 325 s-1 and the Km values for 6-phosphogluconate, NADP+, and NAD+ were 11, 10 and 380 μM, respectively, at 80°C. This enzyme had half-life times of 48 and 140 h at 90 and 80°C, respectively. Through numerous approaches including expression vectors, hosts, cultivation conditions, inducers, and codon-optimization of the 6pgdh gene, the soluble 6PGDH expression levels were enhanced to ~250 mg per liter of culture by more than 500-fold. The recombinant 6PGDH accounted for >30% of total E. coli cellular proteins when lactose was used as a low-cost inducer. In addition, this enzyme coupled with glucose-6-phosphate dehydrogenase for the first time was demonstrated to generate two moles of NADPH per mole of glucose-6-phosphate. Conclusion We have achieved a more than 500-fold improvement in the expression of soluble T. maritima 6PGDH in E. coli, characterized its basic biochemical properties, and demonstrated its applicability for NADPH regeneration by a new enzyme cocktail. The methodology for over-expression and simple purification of this thermostable protein would be useful for the production of other thermostable proteins in E. coli.
- Cell-free protein synthesis energized by slowly-metabolized maltodextrinWang, Yiran; Zhang, Y. H. Percival (2009-06-28)Background Cell-free protein synthesis (CFPS) is a rapid and high throughput technology for obtaining proteins from their genes. The primary energy source ATP is regenerated from the secondary energy source through substrate phosphorylation in CFPS. Results Distinct from common secondary energy sources (e.g., phosphoenolpyruvate - PEP, glucose-6-phosphate), maltodextrin was used for energizing CFPS through substrate phosphorylation and the glycolytic pathway because (i) maltodextrin can be slowly catabolized by maltodextrin phosphorylase for continuous ATP regeneration, (ii) maltodextrin phosphorylation can recycle one phosphate per reaction for glucose-1-phosphate generation, and (iii) the maltodextrin chain-shortening reaction can produce one ATP per glucose equivalent more than glucose can. Three model proteins, esterase 2 from Alicyclobacillus acidocaldarius, green fluorescent protein, and xylose reductase from Neurospora crassa were synthesized for demonstration. Conclusion Slowly-metabolized maltodextrin as a low-cost secondary energy compound for CFPS produced higher levels of proteins than PEP, glucose, and glucose-6-phospahte. The enhancement of protein synthesis was largely attributed to better-controlled phosphate levels (recycling of inorganic phosphate) and a more homeostatic reaction environment.
- ICTAS Doctoral Students ReceptionMahajan, R. L. (Institute for Critical Technology and Applied Science (ICTAS), Virginia Tech, 2009-09-01)
- ICTAS Connection, November 2009(Virginia Tech, 2009-11)This newsletter details new developments in staff and programs for ICTAS. In this issue: 2009 Doctoral Scholars, new additions to the ICTAS team, first picture of the construction of ICTAS II.
- ICTAS Scientific Report 2010(Virginia Tech, 2010)This 172-page report, published in 2010, compiles many of the research projects that ICTAS awards helped to fund.
- Ted and Karyn Hume Center for National Security and TechnologyReed, Jeffrey H. (Institute for Critical Technology and Applied Science (ICTAS), Virginia Tech, 2010)
- Interdisciplinary Research and Innovation for A Sustainable Energy FutureMahajan, R. L. (Institute for Critical Technology and Applied Science (ICTAS), Virginia Tech, 2010-01-20)