The Effect of Prestrain Temperature on Kinetics of Static Recrystallization, Microstructure Evolution, and Mechanical Properties of Low Carbon Steel

NASA Astrophysics Data System (ADS)

Akbari, Edris; Karimi Taheri, Kourosh; Karimi Taheri, Ali

2018-05-01

In this research, the samples of a low carbon steel sheet were rolled up to a thickness prestrain of 67% at three different temperatures consisted of room, blue brittleness, and subzero temperature. Microhardness, SEM, and tensile tests were carried out to evaluate the static recrystallization kinetics defined by the Avrami equation, microstructural evolution, and mechanical properties. It was found that the Avrami exponent is altered with change in prestrain temperature and it achieves the value of 1 to 1. 5. Moreover, it was indicated that prestraining at subzero temperature followed by annealing at 600 °C leads to considerable enhancement in tensile properties and kinetics of static recrystallization compared to room and blue brittleness temperatures. The prestraining at blue brittleness temperature followed by annealing treatment caused, however, a higher strength and faster kinetics compared with that at room temperature. It was concluded that although from the steel ductility point of view, the blue brittleness temperature is called an unsuitable temperature, but it can be used as prestraining temperature to develop noticeable combination of strength and ductility in low carbon steel.

Half-life of the electron-capture decay of {sup 97}Ru: Precision measurement shows no temperature dependence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goodwin, J. R.; Golovko, V. V.; Iacob, V. E.

2009-10-15

We have measured the half-life of the electron-capture (ec) decay of {sup 97}Ru in a metallic environment, both at low temperature (19 K), and also at room temperature. We find the half-lives at both temperatures to be the same within 0.1%. This demonstrates that a recent claim that the ec decay half-life for {sup 7}Be changes by 0.9%{+-}0.2% under similar circumstances certainly cannot be generalized to other ec decays. Our results for the half-life of {sup 97}Ru, 2.8370(14) d at room temperature and 2.8382(14) d at 19 K, are consistent with, but much more precise than, previous room-temperature measurements. Inmore » addition, we have also measured the half-lives of the {beta}{sup -}-emitters {sup 103}Ru and {sup 105}Rh at both temperatures, and found them also to be unchanged.« less

Tungsten Inert Gas and Friction Stir Welding Characteristics of 4-mm-Thick 2219-T87 Plates at Room Temperature and -196 °C

NASA Astrophysics Data System (ADS)

Lei, Xuefeng; Deng, Ying; Yin, Zhimin; Xu, Guofu

2014-06-01

2219-T87 aluminum alloy is widely used for fabricating liquid rocket propellant storage tank, due to its admirable cryogenic property. Welding is the dominant joining method in the manufacturing process of aerospace components. In this study, the tungsten inert gas welding and friction stir welding (FSW) characteristics of 4-mm-thick 2219-T87 alloy plate at room temperature (25 °C) and deep cryogenic temperature (-196 °C) were investigated by property measurements and microscopy methods. The studied 2219 base alloy exhibits a low strength plane anisotropy and excellent room temperature and cryogenic mechanical properties. The ultimate tensile strength values of TIG and FSW welding joints can reach 265 and 353 MPa at room temperature, and 342 and 438 MPa at -196 °C, respectively. The base metal consists of elongated deformed grains and many nano-scaled θ (Al2Cu) aging precipitates. Fusion zone and heat-affected zone (HAZ) of the TIG joint are characterized by coarsening dendritic grains and equiaxed recrystallized grains, respectively. The FSW-welded joint consists of the weld nugget zone, thermo-mechanically affected zone (TMAZ), and HAZ. In the weld nugget zone, a micro-scaled sub-grain structure is the main microstructure characteristic. The TMAZ and HAZ are both characterized by coarsened aging precipitates and elongated deformed grains. The excellent FSW welding properties are attributed to the preservation of the working structures and homogenous chemical compositions.

The effect of side-chain substitution and hot processing on diketopyrrolopyrrole-based polymers for organic solar cells.

PubMed

Heintges, Gaël H L; Leenaers, Pieter J; Janssen, René A J

2017-07-14

The effects of cold and hot processing on the performance of polymer-fullerene solar cells are investigated for diketopyrrolopyrrole (DPP) based polymers that were specifically designed and synthesized to exhibit a strong temperature-dependent aggregation in solution. The polymers, consisting of alternating DPP and oligothiophene units, are substituted with linear and second position branched alkyl side chains. For the polymer-fullerene blends that can be processed at room temperature, hot processing does not enhance the power conversion efficiencies compared to cold processing because the increased solubility at elevated temperatures results in the formation of wider polymer fibres that reduce charge generation. Instead, hot processing seems to be advantageous when cold processing is not possible due to a limited solubility at room temperature. The resulting morphologies are consistent with a nucleation-growth mechanism for polymer fibres during drying of the films.

An 57Fe Mössbauer study of the ordinary chondrite meteorite Lynch 001

NASA Astrophysics Data System (ADS)

Elewa, Nancy N.; Cadogan, J. M.

2017-11-01

The Lynch 001 meteorite was found in the Nullarbor Plain region of Western Australia in 1977. This meteorite is classified as an ordinary chondrite of the petrologic group L5/6 that has undergone `minor to moderate' terrestrial weathering. Here, we characterize the Fe-bearing phases in this chondrite using 57Fe Mössbauer spectroscopy carried out over the temperature range 13 K to room temperature (295 K). The paramagnetic doublets of olivine, pyroxene and a superparamagnetic ferric phase dominate the room temperature Mössbauer spectrum. On the basis of the room temperature quadrupole splitting of the olivine component, we estimate its composition to be Fa 30(5). Besides the paramagnetic ferric component, accounting for ˜15 % of the spectral area at room temperature, magnetically ordered ferric phases were also detected. The total relative proportion of the Fe 3+ components allows us to estimate the terrestrial age of Lynch 001 to be 6,500 ± 1,500 yr, consistent with the value of 6,700 ± 1,300 yr determined by 14C dating.

Crystal cryocooling distorts conformational heterogeneity in a model Michaelis complex of DHFR

PubMed Central

Keedy, Daniel A.; van den Bedem, Henry; Sivak, David A.; Petsko, Gregory A.; Ringe, Dagmar; Wilson, Mark A.; Fraser, James S.

2014-01-01

Summary Most macromolecular X-ray structures are determined from cryocooled crystals, but it is unclear whether cryocooling distorts functionally relevant flexibility. Here we compare independently acquired pairs of high-resolution datasets of a model Michaelis complex of dihydrofolate reductase (DHFR), collected by separate groups at both room and cryogenic temperatures. These datasets allow us to isolate the differences between experimental procedures and between temperatures. Our analyses of multiconformer models and time-averaged ensembles suggest that cryocooling suppresses and otherwise modifies sidechain and mainchain conformational heterogeneity, quenching dynamic contact networks. Despite some idiosyncratic differences, most changes from room temperature to cryogenic temperature are conserved, and likely reflect temperature-dependent solvent remodeling. Both cryogenic datasets point to additional conformations not evident in the corresponding room-temperature datasets, suggesting that cryocooling does not merely trap pre-existing conformational heterogeneity. Our results demonstrate that crystal cryocooling consistently distorts the energy landscape of DHFR, a paragon for understanding functional protein dynamics. PMID:24882744

Mechanical Alloying for Making Thermoelectric Compounds

NASA Technical Reports Server (NTRS)

Huang, Chen-Kuo; Fleurial, Jean-Pierre; Snyder, Jeffrey; Blair, Richard; May, Andrew

2007-01-01

An economical room-temperature mechanical alloying process has been shown to be an effective means of making a homogeneous powder that can be hot-pressed to synthesize a thermoelectric material having reproducible chemical composition. The synthesis of a given material consists of the room temperature thermomechanical-alloying process followed b y a hot-pressing process. Relative to synthesis of nominally the same material by a traditional process that includes hot melting, this s ynthesis is simpler and yields a material having superior thermoelect ric properties.

Static and transport properties of alkyltrimethylammonium cation-based room-temperature ionic liquids.

PubMed

Seki, Shiro; Tsuzuki, Seiji; Hayamizu, Kikuko; Serizawa, Nobuyuki; Ono, Shimpei; Takei, Katsuhito; Doi, Hiroyuki; Umebayashi, Yasuhiro

2014-05-01

We have measured physicochemical properties of five alkyltrimethylammonium cation-based room-temperature ionic liquids and compared them with those obtained from computational methods. We have found that static properties (density and refractive index) and transport properties (ionic conductivity, self-diffusion coefficient, and viscosity) of these ionic liquids show close relations with the length of the alkyl chain. In particular, static properties obtained by experimental methods exhibit a trend complementary to that by computational methods (refractive index ∝ [polarizability/molar volume]). Moreover, the self-diffusion coefficient obtained by molecular dynamics (MD) simulation was consistent with the data obtained by the pulsed-gradient spin-echo nuclear magnetic resonance technique, which suggests that computational methods can be supplemental tools to predict physicochemical properties of room-temperature ionic liquids.

Iron-aluminum alloys having high room-temperature and method for making same

DOEpatents

Sikka, V.K.; McKamey, C.G.

1993-08-24

A wrought and annealed iron-aluminum alloy is described consisting essentially of 8 to 9.5% aluminum, an effective amount of chromium sufficient to promote resistance to aqueous corrosion of the alloy, and an alloying constituent selected from the group of elements consisting of an effective amount of molybdenum sufficient to promote solution hardening of the alloy and resistance of the alloy to pitting when exposed to solutions containing chloride, up to about 0.05% carbon with up to about 0.5% of a carbide former which combines with the carbon to form carbides for controlling grain growth at elevated temperatures, and mixtures thereof, and the balance iron, wherein said alloy has a single disordered [alpha] phase crystal structure, is substantially non-susceptible to hydrogen embrittlement, and has a room-temperature ductility of greater than 20%.

Room-Temperature Synthesis of Mn-Doped Cesium Lead Halide Quantum Dots with High Mn Substitution Ratio.

PubMed

Zhu, Jingrun; Yang, Xiaoling; Zhu, Yihua; Wang, Yuanwei; Cai, Jin; Shen, Jianhua; Sun, Luyi; Li, Chunzhong

2017-09-07

Here we report the room-temperature, atmospheric synthesis of Mn-doped cesium lead halide (CsPbX 3 ) perovskite quantum dots (QDs). The synthesis is performed without any sort of protection, and the dual-color emission mechanism is revealed by density functional theory. The Mn concentration reaches a maximum atomic percentage of 37.73 at%, which is significantly higher in comparison to those achieved in earlier reports via high temperature hot injection method. The optical properties of as-prepared nanocrystals (NCs) remain consistent even after several months. Therefore, red-orange LEDs were fabricated by coating the composite of PS and as-prepared QDs onto ultraviolet LED chips. Additionally, the present approach may open up new methods for doping other ions in CsPbX 3 QDs under room temperature, the capability of which is essential for applications such as memristors and other devices.

Pulse echo and combined resonance techniques: a full set of LGT acoustic wave constants and temperature coefficients.

PubMed

Sturtevant, Blake T; Davulis, Peter M; da Cunha, Mauricio Pereira

2009-04-01

This work reports on the determination of langatate elastic and piezoelectric constants and their associated temperature coefficients employing 2 independent methods, the pulse echo overlap (PEO) and a combined resonance technique (CRT) to measure bulk acoustic wave (BAW) phase velocities. Details on the measurement techniques are provided and discussed, including the analysis of the couplant material in the PEO technique used to couple signal to the sample, which showed to be an order of magnitude more relevant than the experimental errors involved in the data extraction. At room temperature, elastic and piezoelectric constants were extracted by the PEO and the CRT methods and showed results consistent to within a few percent for the elastic constants. Both raw acquired data and optimized constants, based on minimization routines applied to all the modes involved in the measurements, are provided and discussed. Comparison between the elastic constants and their temperature behavior with the literature reveals the recent efforts toward the consistent growth and characterization of LGT, in spite of significant variations (between 1 and 30%) among the constants extracted by different groups at room temperature. The density, dielectric permittivity constants, and respective temperature coefficients used in this work have also been independently determined based on samples from the same crystal boule. The temperature behavior of the BAW modes was extracted using the CRT technique, which has the advantage of not relying on temperature dependent acoustic couplants. Finally, the extracted temperature coefficients for the elastic and piezoelectric constants between room temperature and 120 degrees C are reported and discussed in this work.

Potential of energy harvesting in barium titanate based laminates from room temperature to cryogenic/high temperatures: measurements and linking phase field and finite element simulations

NASA Astrophysics Data System (ADS)

Narita, Fumio; Fox, Marina; Mori, Kotaro; Takeuchi, Hiroki; Kobayashi, Takuya; Omote, Kenji

2017-11-01

This paper studies the energy harvesting characteristics of piezoelectric laminates consisting of barium titanate (BaTiO3) and copper (Cu) from room temperature to cryogenic/high temperatures both experimentally and numerically. First, the output voltages of the piezoelectric BaTiO3/Cu laminates were measured from room temperature to a cryogenic temperature (77 K). The output power was evaluated for various values of load resistance. The results showed that the maximum output power density is approximately 2240 nW cm-3. The output voltages of the BaTiO3/Cu laminates were also measured from room temperature to a higher temperature (333 K). To discuss the output voltages of the BaTiO3/Cu laminates due to temperature changes, phase field and finite element simulations were combined. A phase field model for grain growth was used to generate grain structures. The phase field model was then employed for BaTiO3 polycrystals, coupled with the time-dependent Ginzburg-Landau theory and the oxygen vacancies diffusion, to calculate the temperature-dependent piezoelectric coefficient and permittivity. Using these properties, the output voltages of the BaTiO3/Cu laminates from room temperature to both 77 K and 333 K were analyzed by three dimensional finite element methods, and the results are presented for several grain sizes and oxygen vacancy densities. It was found that electricity in the BaTiO3 ceramic layer is generated not only through the piezoelectric effect caused by a thermally induced bending stress but also by the temperature dependence of the BaTiO3 piezoelectric coefficient and permittivity.

Tensile properties to 650 C and deformation structures in a precipitation strengthened titanium-aluminum alloy

NASA Technical Reports Server (NTRS)

Mendiratta, M. G.

1973-01-01

Appreciable strength levels were retained to 650 C in a Ti-10Al-1Si alloy aged in the (alpha + alpha sub 2) phase field to yield optimum room temperature strength and ductility. The aging treatment precipitated a uniform distribution of alpha sub 2-particles such that, at room temperature, dislocations bypassed instead of shearing the particles at low strains. Specimens fractured at room temperature exhibited fine uniform dimples even for those aging conditions that imparted no macroscopic ductility. The main crack appeared to propagate through the planar slip bands that had cut through the alpha sub 2-particles. A two-step aging process produced a higher volume fraction of bimodally distributed alpha sub 2-particles that led to higher strength levels at elevated temperatures. Both for the single size and the bimodal alpha sub 2-particle distributions, elevated-temperature deformation structures consisted mainly of planar slip bands that sheared through the alpha sub 2-particles.

Effect of Time and Temperature on Transformation Toughened Zirconias.

DTIC Science & Technology

1987-06-01

room temperature. High temperature mechanical tests performed vere stress rupture and stepped temperature stress rupture. The results of the tests...tetragonal precipitates will spontaneously transform to the monoclinic phae due to the lattice mismatch stress if they become larger than about 0.2 on, with...specimens, including fast fracture and fracture toughness testing. High temper- ture testing consisting of stress rupture and stepped temperature stress

Determination of temperature dependence of full matrix material constants of PZT-8 piezoceramics using only one sample.

PubMed

Zhang, Yang; Tang, Liguo; Tian, Hua; Wang, Jiyang; Cao, Wenwu; Zhang, Zhongwu

2017-08-15

Resonant ultrasound spectroscopy (RUS) was used to determine the temperature dependence of full matrix material constants of PZT-8 piezoceramics from room temperature to 100 °C. Property variations from sample to samples can be eliminated by using only one sample, so that data self-consistency can be guaranteed. The RUS measurement system error was estimated to be lower than 2.35%. The obtained full matrix material constants at different temperatures all have excellent self-consistency, which can help accurately predict device performance at high temperatures using finite element simulations.

New Flexible Channels for Room Temperature Tunneling Field Effect Transistors.

PubMed

Hao, Boyi; Asthana, Anjana; Hazaveh, Paniz Khanmohammadi; Bergstrom, Paul L; Banyai, Douglas; Savaikar, Madhusudan A; Jaszczak, John A; Yap, Yoke Khin

2016-02-05

Tunneling field effect transistors (TFETs) have been proposed to overcome the fundamental issues of Si based transistors, such as short channel effect, finite leakage current, and high contact resistance. Unfortunately, most if not all TFETs are operational only at cryogenic temperatures. Here we report that iron (Fe) quantum dots functionalized boron nitride nanotubes (QDs-BNNTs) can be used as the flexible tunneling channels of TFETs at room temperatures. The electrical insulating BNNTs are used as the one-dimensional (1D) substrates to confine the uniform formation of Fe QDs on their surface as the flexible tunneling channel. Consistent semiconductor-like transport behaviors under various bending conditions are detected by scanning tunneling spectroscopy in a transmission electron microscopy system (in-situ STM-TEM). As suggested by computer simulation, the uniform distribution of Fe QDs enable an averaging effect on the possible electron tunneling pathways, which is responsible for the consistent transport properties that are not sensitive to bending.

High-temperature magnetostructural transition in van der Waals-layered α - MoCl 3

DOE PAGES

McGuire, Michael A.; Yan, Jiaqiang; Lampen-Kelley, Paula; ...

2017-11-07

Here, the crystallographic and magnetic properties of the cleavable 4d 3 transition metal compound α–MoCl 3 are reported, with a focus on the behavior above room temperature. Crystals were grown by chemical vapor transport and characterized using temperature dependent x-ray diffraction, Raman spectroscopy, and magnetization measurements. A structural phase transition occurs near 585 K, at which the Mo-Mo dimers present at room temperature are broken. A nearly regular honeycomb net of Mo is observed above the transition, and an optical phonon associated with the dimerization instability is identified in the Raman data and in first-principles calculations. The crystals are diamagneticmore » at room temperature in the dimerized state, and the magnetic susceptibility increases sharply at the structural transition. Moderately strong paramagnetism in the high-temperature structure indicates the presence of local moments on Mo. This is consistent with results of spin-polarized density functional theory calculations using the low- and high-temperature structures. Above the magnetostructural phase transition the magnetic susceptibility continues to increase gradually up to the maximum measurement temperature of 780 K, with a temperature dependence that suggests two-dimensional antiferromagnetic correlations.« less

High-temperature magnetostructural transition in van der Waals-layered α -MoCl3

NASA Astrophysics Data System (ADS)

McGuire, Michael A.; Yan, Jiaqiang; Lampen-Kelley, Paula; May, Andrew F.; Cooper, Valentino R.; Lindsay, Lucas; Puretzky, Alexander; Liang, Liangbo; KC, Santosh; Cakmak, Ercan; Calder, Stuart; Sales, Brian C.

2017-11-01

The crystallographic and magnetic properties of the cleavable 4 d3 transition metal compound α -MoCl3 are reported, with a focus on the behavior above room temperature. Crystals were grown by chemical vapor transport and characterized using temperature dependent x-ray diffraction, Raman spectroscopy, and magnetization measurements. A structural phase transition occurs near 585 K, at which the Mo-Mo dimers present at room temperature are broken. A nearly regular honeycomb net of Mo is observed above the transition, and an optical phonon associated with the dimerization instability is identified in the Raman data and in first-principles calculations. The crystals are diamagnetic at room temperature in the dimerized state, and the magnetic susceptibility increases sharply at the structural transition. Moderately strong paramagnetism in the high-temperature structure indicates the presence of local moments on Mo. This is consistent with results of spin-polarized density functional theory calculations using the low- and high-temperature structures. Above the magnetostructural phase transition the magnetic susceptibility continues to increase gradually up to the maximum measurement temperature of 780 K, with a temperature dependence that suggests two-dimensional antiferromagnetic correlations.

Cu/Nitroxyl Catalyzed Aerobic Oxidation of Primary Amines into Nitriles at Room Temperature

PubMed Central

Kim, Jinho; Stahl, Shannon S.

2013-01-01

An efficient catalytic method has been developed for aerobic oxidation of primary amines to the corresponding nitriles. The reactions proceed at room temperature and employ a catalyst consisting of (4,4′-tBu2bpy)CuI/ABNO (ABNO = 9-azabicyclo[3.3.1]nonan-3-one N-oxyl). The reactions exhibit excellent functional group compatibility and substrate scope, and are effective with benzylic, allylic and aliphatic amines. Preliminary mechanistic studies suggest that aerobic oxidation of the Cu catalyst is the turnover-limiting step of the reaction. PMID:24015373

Cu/Nitroxyl Catalyzed Aerobic Oxidation of Primary Amines into Nitriles at Room Temperature.

PubMed

Kim, Jinho; Stahl, Shannon S

2013-07-05

An efficient catalytic method has been developed for aerobic oxidation of primary amines to the corresponding nitriles. The reactions proceed at room temperature and employ a catalyst consisting of (4,4'- t Bu 2 bpy)CuI/ABNO (ABNO = 9-azabicyclo[3.3.1]nonan-3-one N -oxyl). The reactions exhibit excellent functional group compatibility and substrate scope, and are effective with benzylic, allylic and aliphatic amines. Preliminary mechanistic studies suggest that aerobic oxidation of the Cu catalyst is the turnover-limiting step of the reaction.

Hydrothermal deformation of granular quartz sand

NASA Astrophysics Data System (ADS)

Karner, Stephen L.; Kronenberg, Andreas K.; Chester, Frederick M.; Chester, Judith S.; Hajash, Andrew

2008-05-01

Isotropic and triaxial compression experiments were performed on porous aggregates of St Peter quartz sand to explore the influence of temperature (to 225°C). During isotropic stressing, samples loaded at elevated temperature exhibit the same sigmoidal stress-strain curves and non-linear acoustic emission rates as have previously been observed from room temperature studies on sands, sandstones, and soils. However, results from our hydrothermal experiments show that the critical effective pressure (P*) associated with the onset of significant pore collapse and pervasive cataclastic flow is lower at increased temperature. Samples subjected to triaxial loading at elevated temperature show yield behavior resembling that observed from room temperature studies on granular rocks and soils. When considered in terms of distortional and mean stresses, the yield strength data for a given temperature define an elliptical envelope consistent with critical state and CAP models from soil mechanics. For the conditions we tested, triaxial yield data at low effective pressure are essentially temperature-insensitive whereas yield levels at high effective pressure are lowered as a function of elevated temperature. We interpret our yield data in a manner consistent with Arrhenius behavior expected for thermally assisted subcritical crack growth. Taken together, our results indicate that increased stresses and temperatures associated with subsurface burial will significantly alter the yield strength of deforming granular media in systematic and predictable ways.

Friction Durability of Extremely Thin Diamond-Like Carbon Films at High Temperature

PubMed Central

Miyake, Shojiro; Suzuki, Shota; Miyake, Masatoshi

2017-01-01

To clarify the friction durability, both during and after the high-temperature heating of nanometer-thick diamond-like carbon (DLC) films, deposited using filtered cathodic vacuum arc (FCVA) and plasma chemical vapor deposition (P-CVD) methods, the dependence of the friction coefficient on the load and sliding cycles of the DLC films, were evaluated. Cluster-I consisted of a low friction area in which the DLC film was effective, while cluster-II consisted of a high friction area in which the lubricating effect of the DLC film was lost. The friction durability of the films was evaluated by statistical cluster analysis. Extremely thin FCVA-DLC films exhibited an excellent wear resistance at room temperature, but their friction durability was decreased at high temperatures. In contrast, the durability of the P-CVD-DLC films was increased at high temperatures when compared with that observed at room temperature. This inverse dependence on temperature corresponded to the nano-friction results obtained by atomic force microscopy. The decrease in the friction durability of the FCVA-DLC films at high temperatures, was caused by a complex effect of temperature and friction. The tribochemical reaction produced by the P-CVD-DLC films reduced their friction coefficient, increasing their durability at high temperatures. PMID:28772520

Friction Durability of Extremely Thin Diamond-Like Carbon Films at High Temperature.

PubMed

Miyake, Shojiro; Suzuki, Shota; Miyake, Masatoshi

2017-02-10

To clarify the friction durability, both during and after the high-temperature heating of nanometer-thick diamond-like carbon (DLC) films, deposited using filtered cathodic vacuum arc (FCVA) and plasma chemical vapor deposition (P-CVD) methods, the dependence of the friction coefficient on the load and sliding cycles of the DLC films, were evaluated. Cluster-I consisted of a low friction area in which the DLC film was effective, while cluster-II consisted of a high friction area in which the lubricating effect of the DLC film was lost. The friction durability of the films was evaluated by statistical cluster analysis. Extremely thin FCVA-DLC films exhibited an excellent wear resistance at room temperature, but their friction durability was decreased at high temperatures. In contrast, the durability of the P-CVD-DLC films was increased at high temperatures when compared with that observed at room temperature. This inverse dependence on temperature corresponded to the nano-friction results obtained by atomic force microscopy. The decrease in the friction durability of the FCVA-DLC films at high temperatures, was caused by a complex effect of temperature and friction. The tribochemical reaction produced by the P-CVD-DLC films reduced their friction coefficient, increasing their durability at high temperatures.

Effect of Fe substitution on the structural, magnetic and electron-transport properties of half-metallic Co 2TiSi

DOE PAGES

Jin, Y.; Waybright, J.; Kharel, P.; ...

2017-01-11

The structural, magnetic and electron-transport properties of Co 2Ti 1-xFe xSi (x = 0, 0.25, 0.5) ribbons prepared by arc-melting and melt-spinning were investigated. The rapidly quenched Co 2Ti 0.5Fe 0.5Si crystallized in the cubic L2 1 structure whereas Co 2Ti 0.75Fe 0.25Si and Co 2TiFe 0Si showed various degrees of B2-type disorder. At room temperature, all the samples are ferromagnetic, and the Curie temperature increased from 360 K for Co 2TiSi to about 800 K for Co 2Ti 0.5Fe 0.5Si. The measured magnetization also increased due to partial substitution of Fe for Ti atoms. The ribbons are moderately conductingmore » and show positive temperature coefficient of resistivity with the room temperature resistivity being between 360 μΩcm and 440 μΩcm. The experimentally observed structural and magnetic properties are consistent with the results of first-principle calculations. Our calculations also indicate that the Co 2Ti 1-xFe xSi compound remains nearly half-metallic for x ≤ 0.5. In conclusion, the predicted large band gaps and high Curie temperatures much above room temperature make these materials promising for room temperature spintronic and magnetic applications.« less

Survival of Salmonella and Staphylococcus aureus in mexican red salsa in a food service setting.

PubMed

Franco, Wendy; Hsu, Wei-Yea; Simonne, Amarat H

2010-06-01

Mexican red salsa is one of the most common side dishes in Mexican cuisine. According to data on foodborne illnesses collected by the Centers for Disease Control and Prevention, salsa was associated with 70 foodborne illness outbreaks between 1990 and 2006. Salsa ingredients such as tomatoes, cilantro, and onions often have been implicated in foodborne illness outbreaks. Mexican-style restaurants commonly prepare a large batch of red salsa, store it at refrigeration temperatures, and then serve it at room temperature. Salmonella is one of the top etiologies in foodborne illness outbreaks associated with salsa, and our preliminary studies revealed the consistent presence of Staphylococcus aureus in restaurant salsa. In the present study, we evaluated the survival of Salmonella Enteritidis and S. aureus inoculated into restaurant-made salsa samples stored at ambient (20 degrees C) and refrigeration (4 degrees C) temperatures. These test temperature conditions represent best-case and worst-case scenarios in restaurant operations. Salmonella survived in all samples stored at room temperature, but S. aureus populations significantly decreased after 24 h of storage at room temperature. No enterotoxin was detected in samples inoculated with S. aureus at 6.0 log CFU/g. Both microorganisms survived longer in refrigerated samples than in samples stored at room temperature. Overall, both Salmonella and S. aureus survived a sufficient length of time in salsa to pose a food safety risk.

Mechanical Properties of the TiAl IRIS Alloy

NASA Astrophysics Data System (ADS)

Voisin, Thomas; Monchoux, Jean-Philippe; Thomas, Marc; Deshayes, Christophe; Couret, Alain

2016-12-01

This paper presents a study of the mechanical properties at room and high temperature of the boron and tungsten containing IRIS alloy (Ti-48Al-2W-0.08B at. pct). This alloy was densified by Spark Plasma Sintering (SPS). The resultant microstructure consists of small lamellar colonies surrounded by γ regions containing B2 precipitates. Tensile tests are performed from room temperature to 1273 K (1000 °C). Creep properties are determined at 973 K (700 °C)/300 MPa, 1023 K (750 °C)/120 MPa, and 1023 K (750 °C)/200 MPa. The tensile strength and the creep resistance at high temperature are found to be very high compared to the data reported in the current literature while a plastic elongation of 1.6 pct is preserved at room temperature. A grain size dependence of both ductility and strength is highlighted at room temperature. The deformation mechanisms are studied by post-mortem analyses on deformed samples and by in situ straining experiments, both performed in a transmission electron microscope. In particular, a low mobility of non-screw segments of dislocations at room temperature and the activation of a mixed-climb mechanism during creep have been identified. The mechanical properties of this IRIS alloy processed by SPS are compared to those of other TiAl alloys developed for high-temperature structural applications as well as to those of similar tungsten containing alloys obtained by more conventional processing techniques. Finally, the relationships between mechanical properties and microstructural features together with the elementary deformation mechanisms are discussed.

Complex hydrides as room-temperature solid electrolytes for rechargeable batteries

NASA Astrophysics Data System (ADS)

de Jongh, P. E.; Blanchard, D.; Matsuo, M.; Udovic, T. J.; Orimo, S.

2016-03-01

A central goal in current battery research is to increase the safety and energy density of Li-ion batteries. Electrolytes nowadays typically consist of lithium salts dissolved in organic solvents. Solid electrolytes could facilitate safer batteries with higher capacities, as they are compatible with Li-metal anodes, prevent Li dendrite formation, and eliminate risks associated with flammable organic solvents. Less than 10 years ago, LiBH4 was proposed as a solid-state electrolyte. It showed a high ionic conductivity, but only at elevated temperatures. Since then a range of other complex metal hydrides has been reported to show similar characteristics. Strategies have been developed to extend the high ionic conductivity of LiBH4 down to room temperature by partial anion substitution or nanoconfinement. The present paper reviews the recent developments in complex metal hydrides as solid electrolytes, discussing in detail LiBH4, strategies towards for fast room-temperature ionic conductors, alternative compounds, and first explorations of implementation of these electrolytes in all-solid-state batteries.

Infrared absorptivities of transition metals at room and liquid-helium temperatures.

NASA Technical Reports Server (NTRS)

Jones, M. C.; Palmer, D. C.; Tien, C. L.

1972-01-01

Evaluation of experimental data concerning the normal spectral absorptivities of the transition metals, nickel, iron, platinum, and chromium, at both room and liquid-helium temperatures in the wavelength range from 2.5 to 50 microns. The absorptivities were derived from reflectivity measurements made relative to a room-temperature vapor-deposited gold reference mirror. The absorptivity of the gold reference mirror was measured calorimetrically, by use of infrared laser sources. Investigation of various methods of sample-surface preparation resulted in the choice of a vacuum-annealing process as the final stage. The experimental results are discussed on the basis of the anomalous-skin-effect theory modified for multiple conduction bands. As predicted, the results approach a single-band model toward the longer wavelengths. Agreement between theory and experiment is considerably improved by taking into account the modification of the relaxation time due to the photon-electron-phonon interaction proposed by Holstein (1954) and Gurzhi (1958); but, particularly at helium temperatures, the calculated curve is consistently below the experimental results.

Enhanced magnetic Purcell effect in room-temperature masers

PubMed Central

Breeze, Jonathan; Tan, Ke-Jie; Richards, Benjamin; Sathian, Juna; Oxborrow, Mark; Alford, Neil McN

2015-01-01

Recently, the world’s first room-temperature maser was demonstrated. The maser consisted of a sapphire ring housing a crystal of pentacene-doped p-terphenyl, pumped by a pulsed rhodamine-dye laser. Stimulated emission of microwaves was aided by the high quality factor and small magnetic mode volume of the maser cavity yet the peak optical pumping power was 1.4 kW. Here we report dramatic miniaturization and 2 orders of magnitude reduction in optical pumping power for a room-temperature maser by coupling a strontium titanate resonator with the spin-polarized population inversion provided by triplet states in an optically excited pentacene-doped p-terphenyl crystal. We observe maser emission in a thimble-sized resonator using a xenon flash lamp as an optical pump source with peak optical power of 70 W. This is a significant step towards the goal of continuous maser operation. PMID:25698634

Accessing protein conformational ensembles using room-temperature X-ray crystallography

PubMed Central

Fraser, James S.; van den Bedem, Henry; Samelson, Avi J.; Lang, P. Therese; Holton, James M.; Echols, Nathaniel; Alber, Tom

2011-01-01

Modern protein crystal structures are based nearly exclusively on X-ray data collected at cryogenic temperatures (generally 100 K). The cooling process is thought to introduce little bias in the functional interpretation of structural results, because cryogenic temperatures minimally perturb the overall protein backbone fold. In contrast, here we show that flash cooling biases previously hidden structural ensembles in protein crystals. By analyzing available data for 30 different proteins using new computational tools for electron-density sampling, model refinement, and molecular packing analysis, we found that crystal cryocooling remodels the conformational distributions of more than 35% of side chains and eliminates packing defects necessary for functional motions. In the signaling switch protein, H-Ras, an allosteric network consistent with fluctuations detected in solution by NMR was uncovered in the room-temperature, but not the cryogenic, electron-density maps. These results expose a bias in structural databases toward smaller, overpacked, and unrealistically unique models. Monitoring room-temperature conformational ensembles by X-ray crystallography can reveal motions crucial for catalysis, ligand binding, and allosteric regulation. PMID:21918110

Stability of sotalol hydrochloride in extemporaneously prepared oral suspension formulations.

PubMed

Sidhom, Madiha B; Rivera, Nadya; Almoazen, Hassan; Taft, David R; Kirschenbaum, Harold L

2005-01-01

The physical, chemical, and microbial stabilities of extemporaneously compounded oral liquid formulations of sotalol hydrochloride were studied. Sotalol hydrochloride oral liquid suspensions (5mg/mL) were prepared from commercially available tablets (Betapace) in a 1:1 mixture of Ora-Plus: Ora-Sweet, a 1:1 mixture of Ora-Plus:Ora-Sweet SF, and a 1:2.4 mixture of simple syrup:methylcellulose vehicle. Six batches of each formulation were prepared; three were stored at refrigerated temperature (2 deg to 8 deg C) and three at room temperature (20 deg to 25 deg C). Samples were collected from each batch weekly for 6 weeks, and again at 12 weeks. Samples were analyzed by means of a high-performance liquid chromatographic method, and the concentrations obtained were compared to the theoretical time zero value. Samples were examined for pH, odor, color, and consistency changes. The suspensions also were evaluated for their microbial stability. Sotalol hydrochloride oral liquid suspensions (5mg/mL) were chemically stable for 12 weeks regardless of storage conditions (room temperature or refrigerated). Bacterial growth was not supported by any of the formulations. Suspensions stored at refrigerated temperature retained better physical quality (e.g., odor, color, and consistency) than suspensions stored at room temperature. Overall, this study demonstrates that oral formulations of sotalol hydrochloride can be readily prepared with commercially available vehicles. The method of preparation is relatively simple, the materials are relatively inexpensive, and the products have a shelf-life of at least 12 weeks.

Is the boundary layer of an ionic liquid equally lubricating at higher temperature?

PubMed

Hjalmarsson, Nicklas; Atkin, Rob; Rutland, Mark W

2016-04-07

Atomic force microscopy has been used to study the effect of temperature on normal forces and friction for the room temperature ionic liquid (IL) ethylammonium nitrate (EAN), confined between mica and a silica colloid probe at 25 °C, 50 °C, and 80 °C. Force curves revealed a strong fluid dynamic influence at room temperature, which was greatly reduced at elevated temperatures due to the reduced liquid viscosity. A fluid dynamic analysis reveals that bulk viscosity is manifested at large separation but that EAN displays a nonzero slip, indicating a region of different viscosity near the surface. At high temperatures, the reduction in fluid dynamic force reveals step-like force curves, similar to those found at room temperature using much lower scan rates. The ionic liquid boundary layer remains adsorbed to the solid surface even at high temperature, which provides a mechanism for lubrication when fluid dynamic lubrication is strongly reduced. The friction data reveals a decrease in absolute friction force with increasing temperature, which is associated with increased thermal motion and reduced viscosity of the near surface layers but, consistent with the normal force data, boundary layer lubrication was unaffected. The implications for ILs as lubricants are discussed in terms of the behaviour of this well characterised system.

Submilliampere continuous-wave room-temperature lasing operation of a GaAs mushroom structure surface-emitting laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Y.J.; Dziura, T.G.; Wang, S.C.

1990-05-07

We report a GaAs mushroom structure surface-emitting laser at 900 nm with submilliampere (0.2--0.5 mA) threshold under room-temperature cw operation for the first time. The very low threshold current was achieved on devices which consisted of a 2--4 {mu}m diameter active region formed by chemical selective etching, and sandwiched between two Al{sub 0.05}Ga{sub 0.95} As/ Al{sub 0.53}Ga{sub 0.47} As distributed Bragg reflectors of very high reflectivity (98--99%) grown by metalorganic chemical vapor deposition.

Submilliampere continuous-wave room-temperature lasing operation of a GaAs mushroom structure surface-emitting laser

NASA Astrophysics Data System (ADS)

Yang, Ying Jay; Dziura, Thaddeus G.; Wang, S. C.; Hsin, Wei; Wang, Shyh

1990-05-01

We report a GaAs mushroom structure surface-emitting laser at 900 nm with submilliampere (0.2-0.5 mA) threshold under room-temperature cw operation for the first time. The very low threshold current was achieved on devices which consisted of a 2-4 μm diameter active region formed by chemical selective etching, and sandwiched between two Al0.05Ga0.95 As/ Al0.53Ga0.47 As distributed Bragg reflectors of very high reflectivity (98-99%) grown by metalorganic chemical vapor deposition.

Hybrid systems of AlInP microdisks and colloidal CdSe nanocrystals showing whispering-gallery modes at room temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strelow, Christian; Weising, Simon; Bonatz, Dennis

2014-09-01

We report on the realization of hybrid systems composed of passive optical microdisk resonators prepared from epitaxial layer systems and nanocrystal quantum emitters synthesized by colloidal chemistry. The AlInP disk material allows for the operation in the visible range, as probed by CdSe-based nanocrystals. Photoluminescence spectra at room temperature reveal sets of whispering-gallery modes consistent with finite-difference time-domain simulations. In the experiments, a special sample geometry renders it possible to detect resonant optical modes perpendicular to the disk plane.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oda, H., E-mail: h-oda@photon.chitose.ac.jp; Yamanaka, A.; Ozaki, N.

The development of small sized laser operating above room temperature is important in the realization of optical integrated circuits. Recently, micro-lasers consisting of photonic crystals (PhCs) and whispering gallery mode cavities have been demonstrated. Optically pumped laser devices could be easily designed using photonic crystal-slab waveguides (PhC-WGs) with an air-bridge type structure. In this study, we observe lasing at 1.3μm from two-photon pumped InAs-quantum-dots embedded GaAs PhC-WGs above room temperature. This type of compact laser shows promise as a new light source in ultra-compact photonics integrated circuits.

Effects of reduced nocturnal temperature on pig performance and energy consumption in swine nursery rooms.

PubMed

Johnston, L J; Brumm, M C; Moeller, S J; Pohl, S; Shannon, M C; Thaler, R C

2013-07-01

The objective of this investigation was to determine the effect of a reduced nocturnal temperature (RNT) regimen on performance of weaned pigs and energy consumption during the nursery phase of production. The age of weaned pigs assigned to experiments ranged from 16 to 22 d. In Exp. 1, 3 stations conducted 2 trials under a common protocol that provided data from 6 control rooms (CON; 820 pigs) and 6 RNT rooms (818 pigs). Two mirror-image nursery rooms were used at each station. Temperature in the CON room was set to 30°C for the first 7 d, then reduced by 2°C per week through the remainder of the experiment. Room temperature settings were held constant throughout the day and night. The temperature setting in the RNT room was the same as CON during the first 7 d, but beginning on the night of d 7, the room temperature setting was reduced 6°C from the daytime temperature from 1900 to 0700 h. The use of heating fuel and electricity were measured weekly in each room. Overall, ADG (0.43 kg), ADFI (0.62 kg), and G:F (0.69) were identical for CON and RNT rooms. Consumption of heating fuel [9,658 vs. 7,958 British thermal units (Btu)·pig(-1)·d(-1)] and electricity (0.138 vs. 0.125 kilowatt-hour (kWh)·pig(-1)·d(-1)] were not statistically different for CON and RNT rooms, respectively. In Exp. 2, 4 stations conducted at least 2 trials that provided data from 9 CON rooms (2,122 pigs) and 10 RNT rooms (2,176 pigs). Experimental treatments and protocols were the same as Exp. 1, except that the RNT regimen was imposed on the night of d 5 and the targeted nighttime temperature reduction was 8.3°C. Neither final pig BW (21.8 vs. 21.5 kg; SE = 0.64), ADG (0.45 vs. 0.44 kg; SE = 0.016), ADFI (0.61 vs. 0.60 kg; SE = 0.019), nor G:F (0.75 vs. 0.75; SE = 0.012) were different for pigs housed in CON or RNT rooms, respectively. Consumption of heating fuel and electricity was consistently reduced in RNT rooms for all 4 stations. Consumption of heating fuel (10,019 vs. 7,061 Btu·pig(-1)·d(-1); SE = 1,467) and electricity (0.026 vs. 0.021 kWh·pig-1·d-1; SE = 0.004) were lower (P < 0.05) in the RNT rooms compared with CON rooms. This represents a 30% reduction in heating fuel use and a 20% reduction in electrical use with no differences in pig growth performance or health. From these experiments, we conclude that imposing a RNT regimen from 1900 to 0700 h is effective in reducing energy costs in the nursery without compromising pig performance, which will reduce production costs and decrease emissions of greenhouse gases.

Growth of pentacene on α -Al2O3 (0001) studied by in situ optical spectroscopy

NASA Astrophysics Data System (ADS)

Zhang, Lei; Fu, X.; Hohage, M.; Zeppenfeld, P.; Sun, L. D.

2017-09-01

The growth of pentacene thin films on a sapphire α -Al2O3 (0001) surface was investigated in situ using differential reflectance spectroscopy (DRS). Two different film structures are observed depending on the substrate temperature. If pentacene is deposited at room temperature, a wetting layer consisting of flat-lying molecules is formed after which upright-standing molecular layers with a herringbone structure start to grow. At low substrate temperature of 100 K, the long molecular axis of the pentacene molecules remains parallel to the surface plane throughout the entire growth regime up to rather large thicknesses. Heating thin films deposited at 100 K to room temperature causes the pentacene molecules beyond the wetting layer to stand up and assemble into a herringbone structure. Another interesting observation is the dewetting of the first flat-lying monolayer upon exposure to air, leading to the condensation of islands consisting of upright-standing molecules. Our results emphasize the interplay between growth kinetics and thermodynamics and its influence on the molecular orientation in organic thin films.

In-situ infrared spectra of OH in rutile up to 1000 °C

NASA Astrophysics Data System (ADS)

Guo, Haihao

2017-09-01

The infrared spectra of hydrous, oriented single crystals of synthetic Al-doped and pure rutile were measured from room temperature to 1000 °C at 1 bar using a heating stage. At room temperature, the spectra show only one band at 3278 cm-1 in pure rutile, and two additional bands at 3303 and 3323 cm-1 in Al-doped rutile. The main band associated with Al at 3323 cm-1 loses intensity as temperature increases and nearly disappears already at 300 °C. This suggests that the corresponding defect only forms during cooling and, therefore, water speciation in rutile at room temperature is not representative of subduction zone or upper mantle conditions. All OH bands shift to lower wavenumbers at elevated temperatures with dν/d T = -0.0831 cm-1 K-1 for the main band at 3278 cm-1. This strong low-frequency shift is unexpected for an OH bond involved in hydrogen bonding, indicating decreasing O-O distance for the OH band. Together with the extreme broadening of the band at high temperature, it suggests some weakening of the OH bond strength and a rapid exchange of protons, consistent with rapid hydrogen diffusion in rutile.

Stability of E-type prostaglandins in triacetin.

PubMed

Yalkowsky, S H; Roseman, T J

1979-01-01

A drug delivery system for E-type prostaglandins is described. In this system, consisting of drug dissolved in triacetin and filled into soft gelatin capsules, normally unstable prostaglandins show excellent stability at room temperature.

New Flexible Channels for Room Temperature Tunneling Field Effect Transistors

PubMed Central

Hao, Boyi; Asthana, Anjana; Hazaveh, Paniz Khanmohammadi; Bergstrom, Paul L.; Banyai, Douglas; Savaikar, Madhusudan A.; Jaszczak, John A.; Yap, Yoke Khin

2016-01-01

Tunneling field effect transistors (TFETs) have been proposed to overcome the fundamental issues of Si based transistors, such as short channel effect, finite leakage current, and high contact resistance. Unfortunately, most if not all TFETs are operational only at cryogenic temperatures. Here we report that iron (Fe) quantum dots functionalized boron nitride nanotubes (QDs-BNNTs) can be used as the flexible tunneling channels of TFETs at room temperatures. The electrical insulating BNNTs are used as the one-dimensional (1D) substrates to confine the uniform formation of Fe QDs on their surface as the flexible tunneling channel. Consistent semiconductor-like transport behaviors under various bending conditions are detected by scanning tunneling spectroscopy in a transmission electron microscopy system (in-situ STM-TEM). As suggested by computer simulation, the uniform distribution of Fe QDs enable an averaging effect on the possible electron tunneling pathways, which is responsible for the consistent transport properties that are not sensitive to bending. PMID:26846587

New Flexible Channels for Room Temperature Tunneling Field Effect Transistors

DOE PAGES

Hao, Boyi; Asthana, Anjana; Hazaveh, Paniz Khanmohammadi; ...

2016-02-05

Tunneling field effect transistors (TFETs) have been proposed to overcome the fundamental issues of Si based transistors, such as short channel effect, finite leakage current, and high contact resistance. Unfortunately, most if not all TFETs are operational only at cryogenic temperatures. Here we report that iron (Fe) quantum dots functionalized boron nitride nanotubes (QDs-BNNTs) can be used as the flexible tunneling channels of TFETs at room temperatures. The electrical insulating BNNTs are used as the one-dimensional (1D) substrates to confine the uniform formation of Fe QDs on their surface as the flexible tunneling channel. Consistent semiconductor-like transport behaviors under variousmore » bending conditions are detected by scanning tunneling spectroscopy in a transmission electron microscopy system (insitu STM-TEM). Ultimately, as suggested by computer simulation, the uniform distribution of Fe QDs enable an averaging effect on the possible electron tunneling pathways, which is responsible for the consistent transport properties that are not sensitive to bending.« less

New Flexible Channels for Room Temperature Tunneling Field Effect Transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hao, Boyi; Asthana, Anjana; Hazaveh, Paniz Khanmohammadi

Tunneling field effect transistors (TFETs) have been proposed to overcome the fundamental issues of Si based transistors, such as short channel effect, finite leakage current, and high contact resistance. Unfortunately, most if not all TFETs are operational only at cryogenic temperatures. Here we report that iron (Fe) quantum dots functionalized boron nitride nanotubes (QDs-BNNTs) can be used as the flexible tunneling channels of TFETs at room temperatures. The electrical insulating BNNTs are used as the one-dimensional (1D) substrates to confine the uniform formation of Fe QDs on their surface as the flexible tunneling channel. Consistent semiconductor-like transport behaviors under variousmore » bending conditions are detected by scanning tunneling spectroscopy in a transmission electron microscopy system (insitu STM-TEM). Ultimately, as suggested by computer simulation, the uniform distribution of Fe QDs enable an averaging effect on the possible electron tunneling pathways, which is responsible for the consistent transport properties that are not sensitive to bending.« less

Strengths of serpentinite gouges at elevated temperatures

USGS Publications Warehouse

Moore, Diane E.; Lockner, D.A.; Ma, S.; Summers, R.; Byerlee, J.D.

1997-01-01

Serpentinite has been proposed as a cause of both low strength and aseismic creep of fault zones. To test these hypotheses, we have measured the strength of chrysotile-, lizardite-, and antigorite-rich serpentinite gouges under hydrothermal conditions, with emphasis on chrysotile, which has thus far received little attention. At 25??C, the coefficient of friction, ??, of chrysotile gouge is roughly 0.2, whereas the lizardite- and antigorite-rich gouges are at least twice as strong. The very low room temperature strength of chrysotile is a consequence of its unusually high adsorbed water content. When the adsorbed water is removed, chrysotile is as strong as pure antigorite gouge at room temperature. Heating to ???200??C causes the frictional strengths of all three gouges to increase. Limited data suggest that different polytypes of a given serpentine mineral have similar strengths; thus deformation-induced changes in polytype should not affect fault strength. At 25??C, the chrysotile gouge has a transition from velocity strengthening at low velocities to velocity weakening at high velocities, consistent with previous studies. At temperatures up to ???200??C, however, chrysotile strength is essentially independent of velocity at low velocities. Overall, chrysotile has a restricted range of velocity-strengthening behavior that migrates to higher velocities with increasing temperature. Less information on velocity dependence is available for the lizardite and antigorite gouges, but their behavior is consistent with that outlined for chrysotile. The marked changes in velocity dependence and strength of chrysotile with heating underscore the hazards of using room temperature data to predict fault behavior at depth. The velocity behavior at elevated temperatures does not rule out serpentinite as a cause of aseismic slip, but in the presence of a hydrostatic fluid pressure gradient, all varieties of serpentine are too strong to explain the apparent weakness of faults such as the San Andreas.

Wear Characteristic of Stellite 6 Alloy Hardfacing Layer by Plasma Arc Surfacing Processes

PubMed Central

Zhou, Xiaowei

2017-01-01

The microstructure and wear resistance of Stellite 6 alloy hardfacing layer at two different temperatures (room temperature and 300°C) were investigated by plasma arc surfacing processes on Q235 Steel. Tribological test was conducted to characterize the wear property. The microstructure of Stellite 6 alloy coating mainly consists of α-Co and (Cr, Fe)7C3 phases. The friction coefficient of Stellite 6 alloys fluctuates slightly under different loads at 300°C. The oxide layer is formed on the coating surface and serves as a special lubricant during the wear test. Abrasive wear is the dominant mechanism at room temperature, and microploughing and plasticity are the key wear mechanisms at 300°C. PMID:29359005

Radiation-induced hydroxyl addition to purine molecules: EPR and ENDOR study of hypoxanthine hydrochloride monohydrate single crystals.

PubMed

Tokdemir, Sibel; Nelson, William H

2005-06-01

Three radical species were detected in an EPR/ENDOR study of X-irradiated hypoxanthine.HCl.H2O single crystals at room temperature: RI was identified as the product of net H addition to C8, RII was identified as the product of net H addition to C2, and RIII was identified as the product of OH addition to C8. The observed set of radicals was the same for room-temperature irradiation as for irradiation at 10 K followed by warming the crystals to room temperature; however, the C2 H-addition and C8 OH-addition radicals were not detectable after storage of the crystals for about 2 months at room temperature. Use of selectively deuterated crystals permitted unique assignment of the observed hyperfine couplings, and results of density functional theory calculations on each of the radical structures were consistent with the experimental results. Comparison of these experimental results with others from previous crystal-based systems and model system computations provides insight into the mechanisms by which the biologically important purine C8 hydroxyl addition products are formed. The evidence from solid systems supports the mechanism of net water addition to one-electron oxidized purine bases and demonstrates the importance of a facial approach between the reactants.

Giant room temperature magnetoelectric response in strain controlled nanocomposites

NASA Astrophysics Data System (ADS)

Rafique, Mohsin; Herklotz, Andreas; Dörr, Kathrin; Manzoor, Sadia

2017-05-01

We report giant magnetoelectric coupling at room temperature in a self-assembled nanocomposite of BiFeO3-CoFe2O4 (BFO-CFO) grown on a BaTiO3 (BTO) crystal. The nanocomposite consisting of CFO nanopillars embedded in a BFO matrix exhibits weak perpendicular magnetic anisotropy due to a small out-of-plane compression (˜0.3%) of the magnetostrictive (CFO) phase, enabling magnetization rotation under moderate in-plane compression. Temperature dependent magnetization measurements demonstrate strong magnetoelastic coupling between the BaTiO3 substrate and the nanocomposite film, which has been exploited to produce a large magnetoelectric response in the sample. The reorientation of ferroelectric domains in the BTO crystal upon the application of an electric field (E) alters the strain state of the nanocomposite film, thus enabling control of its magnetic anisotropy. The strain mediated magnetoelectric coupling coefficient α = μ o d M / d E calculated from remnant magnetization at room temperature is 2.6 × 10-7 s m-1 and 1.5 × 10-7 s m-1 for the out-of-plane and in-plane orientations, respectively.

Fabrication and Microstructure of Hydroxyapatite Coatings on Zirconia by Room Temperature Spray Process.

PubMed

Seo, Dong Seok; Chae, Hak Cheol; Lee, Jong Kook

2015-08-01

Hydroxyapatite coatings were fabricated on zirconia substrates by a room temperature spray process and were investigated with regards to their microstructure, composition and dissolution in water. An initial hydroxyapatite powder was prepared by heat treatment of bovine-bone derived powder at 1100 °C for 2 h, while dense zirconia substrates were fabricated by pressing 3Y-TZP powder and sintering it at 1350 °C for 2 h. Room temperature spray coating was performed using a slit nozzle in a low pressure-chamber with a controlled coating time. The phase composition of the resultant hydroxyapatite coatings was similar to that of the starting powder, however, the grain size of the hydroxyapatite particles was reduced to about 100 nm due to their formation by particle impaction and fracture. All areas of the coating had a similar morphology, consisting of reticulated structure with a high surface roughness. The hydroxyapatite coating layer exhibited biostability in a stimulated body fluid, with no severe dissolution being observed during in vitro experimentation.

A bioactive coating of a silica xerogel/chitosan hybrid on titanium by a room temperature sol-gel process.

PubMed

Jun, Shin-Hee; Lee, Eun-Jung; Yook, Se-Won; Kim, Hyoun-Ee; Kim, Hae-Won; Koh, Young-Hag

2010-01-01

A bioactive coating consisting of a silica xerogel/chitosan hybrid was applied to Ti at room temperature as a novel surface treatment for metallic implants. A crack-free thin layer (<2 microm) was coated on Ti with a chitosan content of >30 vol.% through a sol-gel process. The coating layer became more hydrophilic with increasing silica xerogel content, as assessed by contact angle measurement. The hybrid coatings afforded excellent bone bioactivity by inducing the rapid precipitation of apatite on their surface when immersed in a simulated body fluid (SBF). Osteoblastic cells cultured on the hybrid coatings were more viable than those on a pure chitosan coating. Furthermore, the alkaline phosphate activity of the cells was significantly higher on the hybrid coatings than on a pure chitosan coating, with the highest level being achieved on the hybrid coating containing 30% chitosan. These results indicate that silica xerogel/chitosan hybrids are potentially useful as room temperature bioactive coating materials on titanium-based medical implants.

Highly reliable contacts for lead-salt diode lasers

NASA Astrophysics Data System (ADS)

Lo, W.

1981-02-01

In order to improve the long term reliability of lead-salt diode lasers, ohmic contacts of multilayer, thin-film structures consisting of In plus Au, Pt, Ni, and Pd have been studied. Diode lasers of PbSnTe fabricated with a variety of contacts were tested during room-temperature storage and during accelerated aging tests. The results show that contact reliability can be improved when multiple overlapping films are used. After 4500 h of baking at 60 C, lasers with In-Au-Pd-Au contacts on both sides showed the least resistance increase (10%). For lasers with In-Au-Pt-Au contacts, 1 h of baking at 60 C is equivalent to 2 d storage at room temperature. Extrapolating these results, a 70% increase in contact resistance is expected for this type of laser after 9000 d of storage at room temperature. The data also suggests that a smaller increase in contact resistance can be expected for lasers fabricated with In-Au-Ni and In-Au-Pd-Au contacts.

Microstructure development during equal channel angular drawing of Al at room temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chakkingal, U.; Suriadi, A.B.; Thomson, P.F.

1998-08-11

In this study 3004 aluminum alloy can-stock remelt (composition 99.9% Al) was subjected to Equal Channel Angular Drawing (ECAD) at room temperature. Tests were conducted to an applied true strain of 2.95. Mechanical properties like tensile strength, ductility at fracture, and microhardness were measured. The development of the substructure was studied using optical and transmission electron microscopy. Subgrain sizes and their angular misorientations were measured as a function of the applied strain. In general, a substructure that consists of cells and subgrains was seen to evolve, as is expected for the case of high SFE fcc metals.

Room temperature chemical synthesis of lead selenide thin films with preferred orientation

NASA Astrophysics Data System (ADS)

Kale, R. B.; Sartale, S. D.; Ganesan, V.; Lokhande, C. D.; Lin, Yi-Feng; Lu, Shih-Yuan

2006-11-01

Room temperature chemical synthesis of PbSe thin films was carried out from aqueous ammoniacal solution using Pb(CH3COO)2 as Pb2+ and Na2SeSO3 as Se2- ion sources. The films were characterized by a various techniques including, X-ray diffraction (XRD), energy dispersive X-ray analysis (EDAX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED), Fast Fourier transform (FFT) and UV-vis-NIR techniques. The study revealed that the PbSe thin film consists of preferentially oriented nanocubes with energy band gap of 0.5 eV.

Experimental Demonstration of xor Operation in Graphene Magnetologic Gates at Room Temperature

NASA Astrophysics Data System (ADS)

Wen, Hua; Dery, Hanan; Amamou, Walid; Zhu, Tiancong; Lin, Zhisheng; Shi, Jing; Žutić, Igor; Krivorotov, Ilya; Sham, L. J.; Kawakami, Roland K.

2016-04-01

We report the experimental demonstration of a magnetologic gate built on graphene at room temperature. This magnetologic gate consists of three ferromagnetic electrodes contacting a single-layer graphene spin channel and relies on spin injection and spin transport in the graphene. We utilize electrical bias tuning of spin injection to balance the inputs and achieve "exclusive or" (xor) logic operation. Furthermore, a simulation of the device performance shows that substantial improvement towards spintronic applications can be achieved by optimizing the device parameters such as the device dimensions. This advance holds promise as a basic building block for spin-based information processing.

Phase Interrogation Used for a Wireless Passive Pressure Sensor in an 800 °C High-Temperature Environment

PubMed Central

Zhang, Huixin; Hong, Yingping; Liang, Ting; Zhang, Hairui; Tan, Qiulin; Xue, Chenyang; Liu, Jun; Zhang, Wendong; Xiong, Jijun

2015-01-01

A wireless passive pressure measurement system for an 800 °C high-temperature environment is proposed and the impedance variation caused by the mutual coupling between a read antenna and a LC resonant sensor is analyzed. The system consists of a ceramic-based LC resonant sensor, a readout device for impedance phase interrogation, heat insulating material, and a composite temperature-pressure test platform. Performances of the pressure sensor are measured by the measurement system sufficiently, including pressure sensitivity at room temperature, zero drift from room temperature to 800 °C, and the pressure sensitivity under the 800 °C high temperature environment. The results show that the linearity of sensor is 0.93%, the repeatability is 6.6%, the hysteretic error is 1.67%, and the sensor sensitivity is 374 KHz/bar. The proposed measurement system, with high engineering value, demonstrates good pressure sensing performance in a high temperature environment. PMID:25690546

Spreading of mercury droplets on thin silver films at room temperature.

PubMed

Be'er, Avraham; Lereah, Yossi; Frydman, Aviad; Taitelbaum, Haim

2007-05-01

We study the spreading characteristics of a reactive-wetting system of mercury (Hg) droplets on silver (Ag) films in room temperature. This is done using our recently developed method for reconstructing the dynamical three-dimensional shape of spreading droplets from two-dimensional microscope images [A. Be'er and Y. Lereah, J. Microsc. 208, 148 (2002)]. We study the time evolution of the droplet radius and its contact angle, and find that the spreading process consists of two stages: (i) the "bulk propagation" regime, controlled by chemical reaction on the surface, and (ii) the "fast-flow" regime, which occurs within the metal film as well as on the surface and consists of both reactive and diffusive propagation. We show that the transition time between the two main time regimes depends solely on the thickness of the Ag film. We also discuss the chemical structure of the intermetallic compound formed in this process.

Thermal power generation during heat cycle near room temperature

NASA Astrophysics Data System (ADS)

Shibata, Takayuki; Fukuzumi, Yuya; Kobayashi, Wataru; Moritomo, Yutaka

2018-01-01

We demonstrate that a sodium-ion secondary battery (SIB)-type thermocell consisting of two types of Prussian blue analogue (PBA) with different electrochemical thermoelectric coefficients (S EC ≡ ∂V/∂T V and T are the redox potential and temperature, respectively) produces electrical energy during heat cycles. The device produces an electrical energy of 2.3 meV/PBA per heat cycle between 295 K (= T L) and 323 K (= T H). The ideal thermal efficiency (η = 1.0%), which is evaluated using the heat capacity (C = 4.16 meV/K) of ideal Na2Co[Fe(CN)6], reaches 11% of the Carnot efficiency (ηth = 8.7%). Our SIB-type thermocell is a promising thermoelectric device that harvests waste heat near room temperature.

Abrasion-Resistant Coating for Flexible Insulation

NASA Technical Reports Server (NTRS)

Mui, D.; Headding, R. E.

1986-01-01

Ceramic coating increases durability and heat resistance of flexible high-temperature insulation. Coating compatible with quartz-fabric insulation allowing it to remain flexible during and after repeated exposures to temperatures of 1,800 degree F (982 degree C). Prevents fabric from becoming brittle while increasing resistance to aerodynamic abrasion and loading. Coating consists of penetrating precoat and topcoat. Major ingredients high-purity colloidal silica binder and ground silica filler, which ensure stability and compatibility with fabric at high temperatures. Both precoat and topcoat cured at room temperature.

Lithium ion conducting electrolytes

DOEpatents

Angell, C. Austen; Liu, Changle

1996-01-01

A liquid, predominantly lithium-conducting, ionic electrolyte having exceptionally high conductivity at temperatures of 100.degree. C. or lower, including room temperature, and comprising the lithium salts selected from the group consisting of the thiocyanate, iodide, bromide, chloride, perchlorate, acetate, tetrafluoroborate, perfluoromethane sulfonate, perfluoromethane sulfonamide, tetrahaloaluminate, and heptahaloaluminate salts of lithium, with or without a magnesium-salt selected from the group consisting of the perchlorate and acetate salts of magnesium. Certain of the latter embodiments may also contain molecular additives from the group of acetonitrile (CH.sub.3 CN) succinnonitrile (CH.sub.2 CN).sub.2, and tetraglyme (CH.sub.3 --O--CH.sub.2 --CH.sub.2 --O--).sub.2 (or like solvents) solvated to a Mg.sup.+2 cation to lower the freezing point of the electrolyte below room temperature. Other particularly useful embodiments contain up to about 40, but preferably not more than about 25, mol percent of a long chain polyether polymer dissolved in the lithium salts to provide an elastic or rubbery solid electrolyte of high ambient temperature conductivity and exceptional 100.degree. C. conductivity. Another embodiment contains up to about but not more than 10 mol percent of a molecular solvent such as acetone.

Lithium ion conducting electrolytes

DOEpatents

Angell, C.A.; Liu, C.

1996-04-09

A liquid, predominantly lithium-conducting, ionic electrolyte is described having exceptionally high conductivity at temperatures of 100 C or lower, including room temperature, and comprising the lithium salts selected from the group consisting of the thiocyanate, iodide, bromide, chloride, perchlorate, acetate, tetrafluoroborate, perfluoromethane sulfonate, perfluoromethane sulfonamide, tetrahaloaluminate, and heptahaloaluminate salts of lithium, with or without a magnesium-salt selected from the group consisting of the perchlorate and acetate salts of magnesium. Certain of the latter embodiments may also contain molecular additives from the group of acetonitrile (CH{sub 3}CN), succinnonitrile (CH{sub 2}CN){sub 2}, and tetraglyme (CH{sub 3}--O--CH{sub 2}--CH{sub 2}--O--){sub 2} (or like solvents) solvated to a Mg{sup +2} cation to lower the freezing point of the electrolyte below room temperature. Other particularly useful embodiments contain up to about 40, but preferably not more than about 25, mol percent of a long chain polyether polymer dissolved in the lithium salts to provide an elastic or rubbery solid electrolyte of high ambient temperature conductivity and exceptional 100 C conductivity. Another embodiment contains up to about but not more than 10 mol percent of a molecular solvent such as acetone. 2 figs.

CO2 sensing of La0.875Ca0.125FeO3 in wet vapor: a comparison of experimental results and first-principles calculations.

PubMed

Wang, Xiaofeng; Chen, Yanping; Qin, Hongwei; Li, Ling; Shi, Changmin; Liu, Liang; Hu, Jifan

2015-05-28

Experimental results show that with an increase of relative humidity, the resistance of La0.875Ca0.125FeO3 decreases at room temperature but increases at higher temperatures (140-360 °C). The humid effect at room temperature is due to the movement of H(+) or H3O(+) inside of the condensed water layer on the surface of La0.875Ca0.125FeO3. Regarding the humid effect at high temperatures, the density functional theory (DFT) calculations show that H2O can be adsorbed onto the La0.875Ca0.125FeO3 surface in the molecular and dissociative adsorption configurations, where the La0.875Ca0.125FeO3 surface gains some electrons from H2O or its dissociative products, consistent with our observation. Experimental results also show that CO2 sensing response at high temperatures decreases with an increase of room-temperature relative humidity. DFT calculations indicate that CO2 adsorbed onto the La0.875Ca0.125FeO3(010) surface, where high concentration oxygen adsorption occurs without water adsorption nearby, releases some electrons into the semiconductor surface, playing the role of a donor. The interaction between CO2 and the local La0.875Ca0.125FeO3(010) surface with pre-adsorption of H2O nearby results in some electron transfer from the La0.875Ca0.125FeO3 surface to CO2, which is responsible for the weakening of CO2 response at high temperatures for La0.875Ca0.125FeO3 with an increase of room-temperature relative humidity.

Does Z' equal 1 or 2? Enhanced powder NMR crystallography verification of a disordered room temperature crystal structure of a p38 inhibitor for chronic obstructive pulmonary disease.

PubMed

Widdifield, Cory M; Nilsson Lill, Sten O; Broo, Anders; Lindkvist, Maria; Pettersen, Anna; Svensk Ankarberg, Anna; Aldred, Peter; Schantz, Staffan; Emsley, Lyndon

2017-06-28

The crystal structure of the Form A polymorph of N-cyclopropyl-3-fluoro-4-methyl-5-[3-[[1-[2-[2-(methylamino)ethoxy]phenyl]cyclopropyl]amino]-2-oxo-pyrazin-1-yl]benzamide (i.e., AZD7624), determined using single-crystal X-ray diffraction (scXRD) at 100 K, contains two molecules in the asymmetric unit (Z' = 2) and has regions of local static disorder. This substance has been in phase IIa drug development trials for the treatment of chronic obstructive pulmonary disease, a disease which affects over 300 million people and contributes to nearly 3 million deaths annually. While attempting to verify the crystal structure using nuclear magnetic resonance crystallography (NMRX), we measured 13 C solid-state NMR (SSNMR) spectra at 295 K that appeared consistent with Z' = 1 rather than Z' = 2. To understand this surprising observation, we used multinuclear SSNMR ( 1 H, 13 C, 15 N), gauge-including projector augmented-wave density functional theory (GIPAW DFT) calculations, crystal structure prediction (CSP), and powder XRD (pXRD) to determine the room temperature crystal structure. Due to the large size of AZD7624 (ca. 500 amu, 54 distinct 13 C environments for Z' = 2), static disorder at 100 K, and (as we show) dynamic disorder at ambient temperatures, NMR spectral assignment was a challenge. We introduce a method to enhance confidence in NMR assignments by comparing experimental 13 C isotropic chemical shifts against site-specific DFT-calculated shift distributions established using CSP-generated crystal structures. The assignment and room temperature NMRX structure determination process also included measurements of 13 C shift tensors and the observation of residual dipolar coupling between 13 C and 14 N. CSP generated ca. 90 reasonable candidate structures (Z' = 1 and Z' = 2), which when coupled with GIPAW DFT results, room temperature pXRD, and the assigned SSNMR data, establish Z' = 2 at room temperature. We find that the polymorphic Form A of AZD7624 is maintained at room temperature, although dynamic disorder is present on the NMR timescale. Of the CSP-generated structures, 2 are found to be fully consistent with the SSNMR and pXRD data; within this pair, they are found to be structurally very similar (RMSD 16 = 0.30 Å). We establish that the CSP structure in best agreement with the NMR data possesses the highest degree of structural similarity with the scXRD-determined structure (RMSD 16 = 0.17 Å), and has the lowest DFT-calculated energy amongst all CSP-generated structures with Z' = 2.

Room-Temperature Multiferroics and Thermal Conductivity of 0.85BiFe1-2xTixMgxO3-0.15CaTiO3 Epitaxial Thin Films (x = 0.1 and 0.2).

PubMed

Zhang, Ji; Sun, Wei; Zhao, Jiangtao; Sun, Lei; Li, Lei; Yan, Xue-Jun; Wang, Ke; Gu, Zheng-Bin; Luo, Zhen-Lin; Chen, Yanbin; Yuan, Guo-Liang; Lu, Ming-Hui; Zhang, Shan-Tao

2017-08-02

Thin films of 0.85BiFe 1-2x Ti x Mg x O 3 -0.15CaTiO 3 (x = 0.1 and 0.2, abbreviated to C-1 and C-2, respectively) have been fabricated on (001) SrTiO 3 substrate with and without a conductive La 0.7 Sr 0.3 MnO 3 buffer layer. The X-ray θ-2θ and ϕ scans, atomic force microscopy, and cross-sectional transmission electron microscopy confirm the (001) epitaxial nature of the thin films with very high growth quality. Both the C-1 and C-2 thin films show well-shaped magnetization-magnetic field hysteresis at room temperature, with enhanced switchable magnetization values of 145.3 and 42.5 emu/cm 3 , respectively. The polarization-electric loops and piezoresponse force microscopy measurements confirm the room-temperature ferroelectric nature of both films. However, the C-1 films illustrate a relatively weak ferroelectric behavior and the poled states are easy to relax, whereas the C-2 films show a relatively better ferroelectric behavior with stable poled states. More interestingly, the room-temperature thermal conductivity of C-1 and C-2 films are measured to be 1.10 and 0.77 W/(m·K), respectively. These self-consistent multiferroic properties and thermal conductivities are discussed by considering the composition-dependent content and migration of Fe-induced electrons and/or charged point defects. This study not only provides multifunctional materials with excellent room-temperature magnetic, ferroelectric, and thermal conductivity properties but may also stimulate further work to develop BiFeO 3 -based materials with unusual multifunctional properties.

Structural and optical studies of nitrogen incorporation into GaSb-based GaInSb quantum wells

NASA Astrophysics Data System (ADS)

Nair, Hari P.; Crook, Adam M.; Yu, Kin M.; Bank, Seth R.

2012-01-01

We investigate the incorporation of nitrogen into (Ga,In)Sb grown on GaSb and report room temperature photoluminescence from GaInSb(N) quantum wells. X-ray diffraction and channeling nuclear reaction analysis, together with Rutherford backscattering, were employed to identify the optimal molecular beam epitaxial growth conditions that minimized the incorporation of non-substitutional nitrogen into GaNSb. Consistent with this hypothesis, GaInSb(N) quantum wells grown under the conditions that minimized non-substitutional nitrogen exhibited room temperature photoluminescence, indicative of significantly improved radiative efficiency. Further development of this material system could enable type-I laser diodes emitting throughout the (3-5 μm) wavelength range.

Stable room temperature magnetocurrent in electrodeposited permeable n-type metal base transistor

NASA Astrophysics Data System (ADS)

Silva, G. V. O.; Teixeira, H. A.; Mello, S. L. A.; de Araujo, C. I. L.

2018-02-01

We investigated a permeable metal base transistor consisting of a ZnO/NiFe/Si heterostructure. Both ZnO and NiFe layers were grown by electrodeposition techniques, using only adhesive tape masks to define deposition regions. The base permeability can thus be controlled by varying the NiFe deposition time. We report here our best results obtained for the permeable NiFe base close to the electrical percolation threshold, which gives reasonable sensitivity to the device. Magnetocurrent measurements carried out at room temperature show that this permeable metal base transistor is stable and sensitive under applied magnetic fields of low intensities, ˜100 Oe, required for electronics integration.

The cold and atmospheric-pressure air surface barrier discharge plasma for large-area sterilization applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang Dacheng; Department of Aeronautics, Fujian Key Laboratory for Plasma and Magnetic Resonance, School of Physics and Mechanical and Electrical Engineering, Xiamen University, Xiamen, Fujian 361005; Zhao Di

2011-04-18

This letter reports a stable air surface barrier discharge device for large-area sterilization applications at room temperature. This design may result in visually uniform plasmas with the electrode area scaled up (or down) to the required size. A comparison for the survival rates of Escherichia coli from air, N{sub 2} and O{sub 2} surface barrier discharge plasmas is presented, and the air surface plasma consisting of strong filamentary discharges can efficiently kill Escherichia coli. Optical emission measurements indicate that reactive species such as O and OH generated in the room temperature air plasmas play a significant role in the sterilizationmore » process.« less

[Studies on the health standard for room temperature in cold regions].

PubMed

Meng, Z L

1990-03-01

The microclimate of 205 rooms of single storey houses in four new rural residential districts in coastal and inland Shandong was monitored and studied the blood circulation of the finger, skin temperature, sweating function and other physiological indexes among 2,401 peasants. We interrogated their personal sensation to cold and warmth. The count was done by the application of thermal equilibrium index (TEI), predicted 4-hour Sweat Rate (P4SR) and the uncomfortable index. The standard room temperature is recommended as follows. In rural area in winter the appropriate room temperature is 14-16 degrees C, the comfortable room temperature is 16-20 degrees C, the lowest room temperature must not be below 14 degrees C. In summer the appropriate room temperature is 25-28 degrees C, the comfortable room temperature is 26-27 degrees C, the highest temperature must not be above 28 degrees C.

Low-temperature magnetic properties of greigite (Fe3S4)

NASA Astrophysics Data System (ADS)

Chang, Liao; Roberts, Andrew P.; Rowan, Christopher J.; Tang, Yan; Pruner, Petr; Chen, Qianwang; Horng, Chorng-Shern

2009-01-01

We provide comprehensive low-temperature magnetic results for greigite (Fe3S4) across the spectrum from superparamagnetic (SP) to multidomain (MD) behavior. It is well known that greigite has no low-temperature magnetic transitions, but we also document that it has strong domain-state dependence of magnetic properties at low temperatures. Blocking of SP grains and increasing thermal stability with decreasing temperature is apparent in many magnetic measurements. Thermally stable single-domain greigite undergoes little change in magnetic properties below room temperature. For pseudo-single-domain (PSD)/MD greigite, hysteresis properties and first-order reversal curve diagrams exhibit minor changes at low temperatures, while remanence continuously demagnetizes because of progressive domain wall unpinning. The low-temperature demagnetization is grain size dependent for PSD/MD greigite, with coarser grains undergoing larger remanence loss. AC susceptibility measurements indicate consistent blocking temperatures (TB) for all synthetic and natural greigite samples, which are probably associated with surficial oxidation. Low-temperature magnetic analysis provides much more information about magnetic mineralogy and domain state than room temperature measurements and enables discrimination of individual components within mixed magnetic mineral assemblages. Low-temperature rock magnetometry is therefore a useful tool for studying magnetic mineralogy and granulometry of greigite-bearing sediments.

Room-temperature spin-orbit torque in NiMnSb

NASA Astrophysics Data System (ADS)

Ciccarelli, C.; Anderson, L.; Tshitoyan, V.; Ferguson, A. J.; Gerhard, F.; Gould, C.; Molenkamp, L. W.; Gayles, J.; Železný, J.; Šmejkal, L.; Yuan, Z.; Sinova, J.; Freimuth, F.; Jungwirth, T.

2016-09-01

Materials that crystallize in diamond-related lattices, with Si and GaAs as their prime examples, are at the foundation of modern electronics. Simultaneously, inversion asymmetries in their crystal structure and relativistic spin-orbit coupling led to discoveries of non-equilibrium spin-polarization phenomena that are now extensively explored as an electrical means for manipulating magnetic moments in a variety of spintronic structures. Current research of these relativistic spin-orbit torques focuses primarily on magnetic transition-metal multilayers. The low-temperature diluted magnetic semiconductor (Ga, Mn)As, in which spin-orbit torques were initially discovered, has so far remained the only example showing the phenomenon among bulk non-centrosymmetric ferromagnets. Here we present a general framework, based on the complete set of crystallographic point groups, for identifying the potential presence and symmetry of spin-orbit torques in non-centrosymmetric crystals. Among the candidate room-temperature ferromagnets we chose to use NiMnSb, which is a member of the broad family of magnetic Heusler compounds. By performing all-electrical ferromagnetic resonance measurements in single-crystal epilayers of NiMnSb we detect room-temperature spin-orbit torques generated by effective fields of the expected symmetry and of a magnitude consistent with our ab initio calculations.

A Multi-Scale Framework for Multi-Field Analyses of Smart Composites

DTIC Science & Technology

2015-01-15

purchased from Advanced Cerametrics Incorporated, consist of PZT 5A fibers dispersed in an epoxy matrix. Kapton layers and electrode fingers are placed...tests in the longitudinal fiber direction, at different rates and temperatures: 25oC, 50oC, and 75oC. Figure 2 shows examples of PZT Positive... PZT and active fiber composites at various frequencies at temperatures 25oC and 75oC. Figure 4 Hysteretic polarization at room temperature with

POSS Ionic Liquid.

PubMed

Tanaka, Kazuo; Ishiguro, Fumiyasu; Chujo, Yoshiki

2010-12-22

We report the synthesis of a stable room-temperature ionic liquid consisting of an octacarboxy polyhedral oligomeric silsesquioxane (POSS) anion and an imidazolium cation. The introduction of the POSS moiety enhances the thermal stability and reduces the melting temperature. From an evaluation of the thermodynamic parameters during the melting, it was found that the rigidity and cubic structure of POSS can contribute to the enhancement of these thermal properties.

High-resolution absorption cross section measurements of carbon monoxide at 20 K between 96.7 and 98.8 nanometers

NASA Technical Reports Server (NTRS)

Stark, G.; Yoshino, K.; Smith, P. L.; Esmond, J. R.; Ito, K.; Stevens, M. H.

1993-01-01

Photoabsorption cross sections for five CO bands, at wavelengths between 96.7 and 98.8 nm, have been measured at high-resolution in a supersonic jet-cooled source at the Photon Factory synchrotron facility. New integrated cross sections are reported for the K-X, L(prime)-X, and L-X bands. Low-temperature spectra of the J-X and W-X bands, which were used in the determination of the absorbing CO column densities, are also presented. The rotational structures of the K-X, L(prime)-X, and L-X bands do not overlap in the low-temperature spectra, allowing for the first unambiguous determination of these band oscillator strengths. We also report revised room temperature measurements of integrated cross sections for the K-X, L(prime)-X, and L-X bands, in which distortions in the measured spectra due to insufficient instrumental resolution have been minimized; the revised room temperature integrated cross sections are consistent with the low-temperature results.

Microstructure and properties of laser-clad high-temperature wear-resistant alloys

NASA Astrophysics Data System (ADS)

Yang, Yongqiang

1999-02-01

A 2-kW CO 2 laser with a powder feeder was used to produce alloy coatings with high temperature-wear resistance on the surface of steel substrates. To analyze the microstructure and microchemical composition of the laser-clad layers, a scanning electron microscope (SEM) equipped with an energy dispersive X-ray microanalysis system was employed. X-ray diffraction techniques were applied to characterize the phases formed during the cladding process. The results show that the microstructure of the cladding alloy consists mainly of many dispersed particles (W 2C, (W,Ti)C 1- x, WC), a lamellar eutectic carbide M 12C, and an (f.c.c) matrix. Hardness tested at room and high temperature showed that the laser-clad zone has a moderate room temperature hardness and relatively higher elevated temperature hardness. The application of the laser-clad layer to a hot tool was very successful, and its operational life span was prolonged 1 to 4 times.

Synthesis of low-moment CrVTiAl: a potential room temperature spin filter

NASA Astrophysics Data System (ADS)

Stephen, Gregory; Wolfsberg, Jacob; McDonald, Ian; Lejeune, Brian; Lewis, Laura; Heiman, Don

The efficient production of spin-polarized currents at room temperature is fundamental to the advancement of spintronics. Spin-filter materials - semiconductors with unequal band gaps for each spin channel - can generate spin-polarized current without the need for spin-polarizing electrodes. In addition, a spin-filter material with zero magnetic moment would have the advantage of not producing fringing fields to interfere with neighboring components. Several quaternary Heusler compounds have recently been predicted to have spin-filter properties and Curie temperatures TC >1000 K. In this work, CrVTiAl has been synthesized in the Y-type Heusler structure, as confirmed by X-ray diffractometry. Magnetization measurements exhibit an exceptionally small temperature-independent moment of 10-3μB /f.u. up to 400 K, a result that is consistent with zero-moment ferrimagnetism. In addition, temperature dependent resistivity measurements reveal the existence of a semiconducting conduction channel. These results suggest that CrVTiAl is a promising candidate for future spintronic devices.

Self-Assembled Layered Supercell Structure of Bi2AlMnO6 with Strong Room-Temperature Multiferroic Properties.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Leigang; Boullay, Philippe; Lu, Ping

2017-02-01

Room-temperature (RT) multiferroics, possessing ferroelectricity and ferromagnetism simultaneously at RT, hold great promise in miniaturized devices including sensors, actuators, transducers, and multi-state memories. In this work, we report a novel 2D layered RT multiferroic system with self-assembled layered supercell structure consisting of two mismatch-layered sub-lattices of [Bi 3O 3+δ] and [MO 2] 1.84 (M=Al/Mn, simply named as BAMO), i.e., alternative layered stacking of two mutually incommensurate sublattices made of a three-layer-thick Bi-O slab and a one-layer-thick Al/Mn-O octahedra slab along the out-of-plane direction. Strong room-temperature multiferroic responses, e.g., ferromagnetic and ferroelectric properties, have been demonstrated and attributed to the highlymore » anisotropic 2D nature of the non-ferromagnetic and ferromagnetic sublattices which are highly mismatched. The work demonstrates an alternative design approach for new 2D layered oxide materials that hold promises as single-phase multiferroics, 2D oxides with tunable bandgaps, and beyond.« less

Length scale selects directionality of droplets on vibrating pillar ratchet

DOE PAGES

Agapov, Rebecca L.; Boreyko, Jonathan B.; Briggs, Dayrl P.; ...

2014-09-22

Directional control of droplet motion at room temperature is of interest for applications such as microfluidic devices, self-cleaning coatings, and directional adhesives. Here, arrays of tilted pillars ranging in height from the nanoscale to the microscale are used as structural ratchets to directionally transport water at room temperature. Water droplets deposited on vibrating chips with a nanostructured ratchet move preferentially in the direction of the feature tilt while the opposite directionality is observed in the case of microstructured ratchets. This remarkable switch in directionality is consistent with changes in the contact angle hysteresis. To glean further insights into the lengthmore » scale dependent asymmetric contact angle hysteresis, the contact lines formed by a nonvolatile room temperature ionic liquid placed onto the tilted pillar arrays were visualized and analyzed in situ in a scanning electron microscope. As a result, the ability to tune droplet directionality by merely changing the length scale of surface features all etched at the same tilt angle would be a versatile tool for manipulating multiphase flows and for selecting droplet directionality in other lap-on-chip applications.« less

Use of radiometer to reform and repair an old living house to passive solar one

NASA Astrophysics Data System (ADS)

Okamoto, Yoshizo; Inagaki, Terumi; Suzuki, Takakazu; Kurokawa, Takashi

1994-03-01

Japanese living houses mainly consist of wooden elements in high-temperature and moist conditions. To modify the hot and humid environment, a conventional old house was partially rebuilt and repaired. Especially in the winter season, a diagnostic thermographic test was used to find deteriorated and leaking parts of interior and exterior walls. Macroscopic deteriorated parts were checked again in detail. The deteriorated element was then removed. During the reconstruction process, a new solar heat and air conditioning system using a silica-gel adsorber and underground water was installed to cool and warm up the living room. Thermography tests of this remodeled house show that room temperature is always constant and mild to human beings, especially in the winter. Temperature and heat flow distribution of flowing air in the living room was measured using thermal net and wire methods. Leaking thermal streak flow of the gap was locally visualized by the IR radiometer and a highly sensitive video camera. It was verified that IR thermography is a useful measuring instrument to check thermal defects of a house.

Time-dependent strength degradation of a siliconized silicon carbide determined by dynamic fatigue

DOE Office of Scientific and Technical Information (OSTI.GOV)

Breder, K.

1995-10-01

Both fast-fracture strength and strength as a function of stressing rate at room temperature, 1,100, and 1,400 C were measured for a siliconized SiC. The fast-fracture strength increased slightly from 386 MPa at room temperature to 424 MPa at 1,100 C and then dropped to 308 MPa at 1,400 C. The Weibull moduli at room temperature and 1,100 were 10.8 and 7.8, respectively, whereas, at 1,400 C, the Weibull modulus was 2.8. The very low Weibull modulus at 1,400 C was due to the existence of two exclusive flaw populations with very different characteristic strengths. The data were reanalyzed usingmore » two exclusive flaw populations. The ceramic showed no slow crack growth (SCG), as measured by dynamic fatigue at 1,100 C, but, at 1,400 C, an SCG parameter, n, of 15.5 was measured. Fractography showed SCG zones consisting of cracks grown out from silicon-rich areas. Time-to-failure predictions at given levels of failure probabilities were performed.« less

Room Temperature Tensile Behavior and Damage Accumulation of Hi-Nicalon Reinforced SiC Matrix Composites

NASA Technical Reports Server (NTRS)

Morscher, G. N.; Gyekenyesi, J. Z.

1998-01-01

Composites consisting of woven Hi-Nicalon fibers, BN interphases, and different SiC matrices were studied in tension at room temperature. Composites with SiC matrices processed by CVI and melt infiltration were compared. Monotonic and load/unload/reload tensile hysteresis experiments were performed. A modal acoustic emission (AE) analyzer was used to monitor damage accumulation during the tensile test. Post test polishing of the tensile gage sections was performed to determine the extent of cracking. The occurrence and location of cracking could easily be determined using modal AE. The loss of modulus could also effectively be determined from the change in the velocity of sound across the sample. Finally, the stresses where cracks appear to intersect the load-bearing fibers correspond with high temperature low cycle fatigue run out stresses for these materials.

Near-band-edge optical responses of solution-processed organic-inorganic hybrid perovskite CH3NH3PbI3 on mesoporous TiO2 electrodes

NASA Astrophysics Data System (ADS)

Yamada, Yasuhiro; Nakamura, Toru; Endo, Masaru; Wakamiya, Atsushi; Kanemitsu, Yoshihiko

2014-03-01

We studied the near-band-edge optical responses of solution-processed CH3NH3PbI3 on mesoporous TiO2 electrodes, which is utilized in mesoscopic heterojunction solar cells. Photoluminescence (PL) and PL excitation spectra peaks appear at 1.60 and 1.64 eV, respectively. The transient absorption spectrum shows a negative peak at 1.61 eV owing to photobleaching at the band-gap energy, indicating a direct band-gap semiconductor. On the basis of the temperature-dependent PL and diffuse reflectance spectra, we clarified that the absorption tail at room temperature is explained in terms of an Urbach tail and consistently determined the band-gap energy to be ˜1.61 eV at room temperature.

Use of Recirculating Ventilation with Dust Filtration to Improve Wintertime Air Quality in a Swine Farrowing Room

PubMed Central

Anthony, T. Renée; Altmaier, Ralph; Jones, Samuel; Gassman, Rich; Park, Jae Hong; Peters, Thomas M.

2016-01-01

The performance of a recirculating ventilation system with dust filtration was evaluated to determine its effectiveness to improve the air quality in a swine farrowing room of a concentrated animal feeding operation (CAFO). Air was exhausted from the room (0.47 m3sec−1; 1000 cfm), treated with a filtration unit (Shaker-Dust Collector), and returned to the farrowing room to reduce dust concentrations while retaining heat necessary for livestock health. The air quality in the room was assessed over a winter, during which time limited fresh air is traditionally brought into the building. Over the study period, dust concentrations ranged from 0.005 to 0.31 mg m−3 (respirable) and 0.17 to 2.09 mg m−3 (inhalable). In-room dust concentrations were reduced (41% for respirable and 33% for inhalable) with the system in operation, while gas concentrations (ammonia [NH3], hydrogen sulfide [H2S], carbon monoxide [CO], carbon dioxide [CO2]) were unchanged. The position of the exhaust and return air systems provided reasonably uniform contaminant distributions, although the respirable dust concentrations nearest one of the exhaust ducts was statistically higher than other locations in the room, with differences averaging only 0.05 mg m−3. Throughout the study, CO2 concentrations consistently exceeded 1540 ppm (industry recommendations) and on eight of the 18 study days it exceeded 2500 ppm (50% of the ACGIH TLV), with significantly higher concentrations near a door to a temperature-controlled hallway that was typically often left open. Alternative heaters are recommended to reduce CO2 concentrations in the room. Contaminant concentrations were modeled using production and environmental factors, with NH3 related to the number of sow in the room and outdoor temperatures and CO2 related to the number of piglets and outdoor temperatures. The recirculating ventilation system provided dust reduction without increasing concentrations of hazardous gases. PMID:25950713

Reference breast temperature: proposal of an equation.

PubMed

Souza, Gladis Aparecida Galindo Reisemberger de; Brioschi, Marcos Leal; Vargas, José Viriato Coelho; Morais, Keli Cristiane Correia; Dalmaso Neto, Carlos; Neves, Eduardo Borba

2015-01-01

To develop an equation to estimate the breast reference temperature according to the variation of room and core body temperatures. Four asymptomatic women were evaluated for three consecutive menstrual cycles. Using thermography, the temperature of breasts and eyes was measured as indirect reference of core body and room temperatures. To analyze the thermal behavior of the breasts during the cycle, the core body and room temperatures were normalized by means of a mathematical equation. We performed 180 observations and the core temperature had the highest correlation with the breast temperature, followed by room temperature. The proposed prediction model could explain 45.3% of the breast temperature variation, with variable room temperature variable; it can be accepted as a way to estimate the reference breast temperature at different room temperatures. The average breast temperature in healthy women had a direct relation with the core and room temperature and can be estimated mathematically. It is suggested that an equation could be used in clinical practice to estimate the normal breast reference temperature in young women, regardless of the day of the cycle, therefore assisting in evaluation of anatomical studies.

Shell structures in aluminum nanocontacts at elevated temperatures

PubMed Central

2012-01-01

Aluminum nanocontact conductance histograms are studied experimentally from room temperature up to near the bulk melting point. The dominant stable configurations for this metal show a very early crossover from shell structures at low wire diameters to ionic subshell structures at larger diameters. At these larger radii, the favorable structures are temperature-independent and consistent with those expected for ionic subshell (faceted) formations in face-centered cubic geometries. When approaching the bulk melting temperature, these local stability structures become less pronounced as shown by the vanishing conductance histogram peak structure. PMID:22325572

Room Temperature Ferromagnetism of Fe Doped Indium Tin Oxide Based on Dispersed Fe3O4 Nanoparticles

NASA Astrophysics Data System (ADS)

Okada, Koichi; Kohiki, Shigemi; Nishi, Sachio; Shimooka, Hirokazu; Deguchi, Hiroyuki; Mitome, Masanori; Bando, Yoshio; Shishido, Toetsu

2007-09-01

Transmission electron microscopy revealed that Fe3O4 nanoparticles with diameter of ≈200 nm dispersed in Fe doped indium tin oxide (Fe@ITO) powders exhibiting co-occurrence of room temperature ferromagnetism and superparamagnetism. Although we observed no X-ray diffraction peak from Fe related compounds for Fe0.19@ITO (ITO: In1.9Sn0.1O3) powders, the powders showed both hysteresis loop in field dependent magnetization at 300 K and divergence of zero-field-cooled magnetization from field-cooled magnetization. Scanning transmission electron microscopy with energy dispersive X-ray spectroscopy demonstrated that the nanoparticle with diameter of ≈200 nm consists of Fe and oxygen. Transmission electron diffraction revealed that crystal structure of the nanoparticle is inverse spinel type Fe3O4. The Fe3O4 crystalline phase by electron diffraction is consistent with the saturation magnetization of 1.3 μB/Fe and magnetic anomaly at ≈110 K observed for the powders.

Sterilization of medical equipment and contaminated articles by making use of a resistive barrier discharge

NASA Astrophysics Data System (ADS)

Uhm, Han S.; Kang, Jung G.; Choi, Eun H.; Cho, Guang S.

2012-08-01

Presented here is an apparatus consisting of an atmospheric resistive-barrier discharge for the sterilization of medical tools wrapped in typical hospital cloths, for the sterilization of manufactured drugs in typical packaging materials, and for the sterilization of biologically-contaminated articles. The sterilization apparatus consists of layers of the resistive-barrier discharge device operating at room temperature, a sterilization chamber, and an ozone destruction device. An electrical discharge in the resistive-barrier discharge system generates an atmospheric plasma in oxygen gas, generating ozone, which in turn efficiently sterilizes medical tools and biologically contaminated articles at room temperature. A sterilization experiment was carried out at an apparatus volume of 100 liters, with a sterilization chamber volume of 60 liters, and a discharge device volume of 40 liters. The sterilization in this experiment required 60 W of power for 5 hours of residence time. For a given sterilization time, the required electrical power was proportional to the apparatus volume. Ozone in the sterilization chamber was destroyed safely after sterilization.

Room temperature synthesis of rutile nanorods and their applications on cloth

NASA Astrophysics Data System (ADS)

Fei, Bin; Deng, Zhaoxiang; Xin, John H.; Zhang, Yihe; Pang, Geoffrey

2006-04-01

In order to achieve better photocatalytic performance, rutile nanorods dispersed in anatase and brookite phases were synthesized from titanium isopropoxide (TIP) in a concentrated HNO3 solution at room temperature (23 °C). X-ray diffraction results indicated that the percentage of rutile increased with increasing peptization time. Scanning electron microscopy and and high-resolution transmission electron microscopy measurements revealed that the nanosized titania particles mainly consisted of granular anatase and brookite, and rod-like rutile. It was interesting that the stability of the colloid increased with increasing nanoparticle concentration, and the tricrystalline titania showed a photocatalytic activity higher than that of pure anatase. These nanocrystals were applied onto cotton fabrics, and achieved a promising bactericidal photocatalytic activity and excellent protection against UV radiation.

High-Temperature Crystal-Growth Cartridge Tubes Made by VPS

NASA Technical Reports Server (NTRS)

Holmes, Richard; O'Dell, Scott; McKechnie, Timothy; Power, Christopher

2008-01-01

Cartridge tubes for use in a crystal growth furnace at temperatures as high as 1,600 deg. C have been fabricated by vacuum plasma spraying (VPS). These cartridges consist mainly of an alloy of 60 weight percent molybdenum with 40 weight percent rhenium, made from molybdenum powder coated with rhenium. This alloy was selected because of its high melting temperature (approximately equal.2,550 C) and because of its excellent ductility at room temperature. These cartridges are intended to supplant tungsten/nickel-alloy cartridges, which cannot be used at temperatures above approximately equal 1,300 C.

Angle-resolved and core-level photoemission study of interfacing the topological insulator Bi1.5Sb0.5Te1.7Se1.3 with Ag, Nb, and Fe

NASA Astrophysics Data System (ADS)

de Jong, N.; Frantzeskakis, E.; Zwartsenberg, B.; Huang, Y. K.; Wu, D.; Hlawenka, P.; Sańchez-Barriga, J.; Varykhalov, A.; van Heumen, E.; Golden, M. S.

2015-08-01

Interfaces between a bulk-insulating topological insulator (TI) and metallic adatoms have been studied using high-resolution, angle-resolved, and core-level photoemission. Fe, Nb, and Ag were evaporated onto Bi1 .5Sb0 .5Te1 .7Se1 .3 (BSTS) surfaces both at room temperature and 38 K. The coverage and temperature dependence of the adsorption and interfacial formation process have been investigated, highlighting the effects of the overlayer growth on the occupied electronic structure of the TI. For all coverages at room temperature and for those equivalent to less than 0.2 monolayer at low temperature all three metals lead to a downward shift of the TI bands with respect to the Fermi level. At room temperature Ag appears to intercalate efficiently into the van der Waals gap of BSTS, accompanied by low-level substitution for the Te/Se atoms of the termination layer of the crystal. This Te/Se substitution with silver increases significantly for low temperature adsorption, and can even dominate the electrostatic environment of the Bi/Sb atoms in the BSTS near-surface region. On the other hand, Fe and Nb evaporants remain close to the termination layer of the crystal. On room temperature deposition, they initially substitute isoelectronically for Bi as a function of coverage, before substituting for Te/Se atoms. For low temperature deposition, Fe and Nb are too immobile for substitution processes and show a behavior consistent with clustering on the surface. For both Ag and Fe/Nb, these differing adsorption pathways still lead to the qualitatively similar and remarkable behavior for low temperature deposition that the chemical potential first moves downward (p -type dopant behavior) and then upward (n -type behavior) on increasing coverage.

Reference breast temperature: proposal of an equation

PubMed Central

de Souza, Gladis Aparecida Galindo Reisemberger; Brioschi, Marcos Leal; Vargas, José Viriato Coelho; Morais, Keli Cristiane Correia; Dalmaso, Carlos; Neves, Eduardo Borba

2015-01-01

ABSTRACT Objective To develop an equation to estimate the breast reference temperature according to the variation of room and core body temperatures. Methods Four asymptomatic women were evaluated for three consecutive menstrual cycles. Using thermography, the temperature of breasts and eyes was measured as indirect reference of core body and room temperatures. To analyze the thermal behavior of the breasts during the cycle, the core body and room temperatures were normalized by means of a mathematical equation. Results We performed 180 observations and the core temperature had the highest correlation with the breast temperature, followed by room temperature. The proposed prediction model could explain 45.3% of the breast temperature variation, with variable room temperature variable; it can be accepted as a way to estimate the reference breast temperature at different room temperatures. Conclusion The average breast temperature in healthy women had a direct relation with the core and room temperature and can be estimated mathematically. It is suggested that an equation could be used in clinical practice to estimate the normal breast reference temperature in young women, regardless of the day of the cycle, therefore assisting in evaluation of anatomical studies. PMID:26761549

A proposed mechanism for Pt/SnO(x)-catalyzed CO oxidation

NASA Technical Reports Server (NTRS)

Schryer, David R.; Upchurch, Billy T.; Sidney, Barry D.; Brown, Kenneth G.; Hoflund, Gar B.; Herz, Richard K.

1991-01-01

A mechanism for Pt/SnO(x)-catalyzed CO oxidation is proposed, which is consistent with a broad range of experimental observations. CO oxidation catalysts with high activity at or near room temperature are used in closed-cycle CO2 lasers and air purification.

Adequacy of solar energy to keep babies warm.

PubMed

Daga, S R; Sequera, D; Goel, S; Desai, B; Gajendragadkar, A

1996-02-01

Solar energy could be used as an alternate energy source for keeping neonates warm especially in tropical countries. The present study investigated the efficacy of solar powered room heating system. Referral center for neonatal care. A fluid system heated by solar panels and circulated into a room was used to maintain room temperature. A servocontrolled heating device was used to regulate and maintain desired room temperature. Neonatal rectal temperature and room temperature. Infants between 1750-2250 g were observed to require a mean room temperature of 32.5 degrees C to maintain normothermia. In 85 infants less than 1500 g, of the 5050 infant temperature records, only 3% showed a record less than 36 degrees C. Solar powered room heating is effective in maintaining infant temperature and is cost-effective as compared to the existing warming devices.

Polaron physics and crossover transition in magnetite probed by pressure-dependent infrared spectroscopy.

PubMed

Ebad-Allah, J; Baldassarre, L; Sing, M; Claessen, R; Brabers, V A M; Kuntscher, C A

2013-01-23

The optical properties of magnetite at room temperature were studied by infrared reflectivity measurements as a function of pressure up to 8 GPa. The optical conductivity spectrum consists of a Drude term, two sharp phonon modes, a far-infrared band at around 600 cm(-1) and a pronounced mid-infrared absorption band. With increasing pressure both absorption bands shift to lower frequencies and the phonon modes harden in a linear fashion. Based on the shape of the MIR band, the temperature dependence of the dc transport data, and the occurrence of the far-infrared band in the optical conductivity spectrum, the polaronic coupling strength in magnetite at room temperature should be classified as intermediate. For the lower energy phonon mode an abrupt increase of the linear pressure coefficient occurs at around 6 GPa, which could be attributed to minor alterations of the charge distribution among the different Fe sites.

Enhanced thermoelectric transport in modulation-doped GaN/AlGaN core/shell nanowires.

PubMed

Song, Erdong; Li, Qiming; Swartzentruber, Brian; Pan, Wei; Wang, George T; Martinez, Julio A

2016-01-08

The thermoelectric properties of unintentionally n-doped core GaN/AlGaN core/shell N-face nanowires are reported. We found that the temperature dependence of the electrical conductivity is consistent with thermally activated carriers with two distinctive donor energies. The Seebeck coefficient of GaN/AlGaN nanowires is more than twice as large as that for the GaN nanowires alone. However, an outer layer of GaN deposited onto the GaN/AlGaN core/shell nanowires decreases the Seebeck coefficient at room temperature, while the temperature dependence of the electrical conductivity remains the same. We attribute these observations to the formation of an electron gas channel within the heavily-doped GaN core of the GaN/AlGaN nanowires. The room-temperature thermoelectric power factor for the GaN/AlGaN nanowires can be four times higher than the GaN nanowires. Selective doping in bandgap engineered core/shell nanowires is proposed for enhancing the thermoelectric power.

Producing >60,000-fold room-temperature 89Y NMR signal enhancement

NASA Astrophysics Data System (ADS)

Lumata, Lloyd; Jindal, Ashish; Merritt, Matthew; Malloy, Craig; Sherry, A. Dean; Kovacs, Zoltan

2011-03-01

89 Y in chelated form is potentially valuable in medical imaging because its chemical shift is sensitive to local factors in tumors such as pH. However, 89 Y has a low gyromagnetic ratio γn thus its NMR signal is hampered by low thermal polarization. Here we show that we can enhance the room-temperature NMR signal of 89 Y up to 65,000 times the thermal signal, which corresponds to 10 % nuclear polarization, via fast dissolution dynamic nuclear polarization (DNP). The relatively long spin-lattice relaxation time T1 (~ 500 s) of 89 Y translates to a long polarization lifetime. The 89 Y NMR enhancement is optimized by varying the glassing matrices and paramagnetic agents as well as doping the samples with a gadolinium relaxation agent. Co-polarization of 89 Y-DOTA with a 13 C sample shows that both nuclear spin species acquire the same spin temperature Ts , consistent with thermal mixing mechanism of DNP. The high room-temperature NMR signal enhancement places 89 Y, one of the most challenging nuclei to detect by NMR, in the list of viable magnetic resonance imaging (MRI) agents when hyperpolarized under optimized conditions. This work is supported in part by the National Institutes of Health grant numbers 1R21EB009147-01 and RR02584.

Real-time modeling of heat distributions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamann, Hendrik F.; Li, Hongfei; Yarlanki, Srinivas

Techniques for real-time modeling temperature distributions based on streaming sensor data are provided. In one aspect, a method for creating a three-dimensional temperature distribution model for a room having a floor and a ceiling is provided. The method includes the following steps. A ceiling temperature distribution in the room is determined. A floor temperature distribution in the room is determined. An interpolation between the ceiling temperature distribution and the floor temperature distribution is used to obtain the three-dimensional temperature distribution model for the room.

The influence of room temperature on Mg isotope measurements by MC-ICP-MS.

PubMed

Zhang, Xing-Chao; Zhang, An-Yu; Zhang, Zhao-Feng; Huang, Fang; Yu, Hui-Min

2018-03-24

We observed that the accuracy and precision of magnesium (Mg) isotope analyses could be affected if the room temperature oscillated during measurements. To achieve high quality Mg isotopic data, it is critical to evaluate how the unstable room temperature affects Mg isotope measurements by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). We measured the Mg isotopes for the reference material DSM-3 using MC-ICP-MS under oscillating room temperatures in spring. For a comparison, we also measured the Mg isotopes under stable room temperatures, which was achieved by the installation of an improved temperature control system in the laboratory. The δ 26 Mg values measured under oscillating room temperatures have a larger deviation (δ 26 Mg from -0.09 to 0.08‰, with average δ 26 Mg = 0.00 ± 0.08 ‰) than those measured under a stable room temperature (δ 26 Mg from -0.03 to 0.03‰, with average δ 26 Mg = 0.00 ± 0.02 ‰) using the same MC-ICP-MS system. The room temperature variation can influence the stability of MC-ICP-MS. Therefore, it is critical to keep the room temperature stable to acquire high precise and accurate isotopic data when using MC-ICP-MS, especially when using the sample-standard bracketing (SSB) correction method. This article is protected by copyright. All rights reserved.

Research on thermal conductivity of HGMs at vacuum in room temperature

NASA Astrophysics Data System (ADS)

Wang, Ping; Liao, Bin; An, Zhenguo; Yan, Kaiqi; Zhang, Jingjie

2018-05-01

Hollow glass microspheres (HGMs) can be used as thermal insulation materials owing to its hollow structure which brings excellent thermal insulation property and low density. At present, most researches on thermal conductivity of HGMs are focused on polymer matrix/HGMs composite materials. However, thermal conductivity of HGMs at vacuum in room temperature has rarely been investigated. In this work, thermal conductivity of six types of HGMs (T17 (0.17g/cm3), T20 (0.20g/cm3), T22 (0.22g/cm3), T25 (0.25g/cm3), T32 (0.32g/cm3) and T40 (0.40g/cm3)) at vacuum in room temperature were calculated by heat transfer of solid conduction and radiation. The calculation results showed that thermal conductivity of HGMs would be decreased by an order of magnitude compared with no vacuum. In order to verify the calculation and study vacuum thermal insulation properties of HGMs, thermal conductivity of above-mentioned HGMs at no vacuum and high vacuum in room temperature were measured by a self-made thermal conductivity measuring apparatus which was based on the transient plane source (TPS) method. The experimental results showed that thermal conductivity of HGMs were in the range of 4.2030E-02 to 6.3300E-02 W/m.K (at no vacuum) and 3.8160E-03 to 4.9660E-03 W/m.K (at high vacuum). The results indicated that experimental thermal conductivity was consistent with the calculation results and both of them were all decreased by 8-13 times at vacuum compared with no vacuum. In addition, the relationship with physical properties and thermal conductivity of HGMs has been discussed in detail. In conclusion, HGMs possess excellent thermal insulation performance at high vacuum in room temperature and have potential to further reduce thermal conductivity at the same conditions.

Room-Temperature-Processed Flexible Amorphous InGaZnO Thin Film Transistor.

PubMed

Xiao, Xiang; Zhang, Letao; Shao, Yang; Zhou, Xiaoliang; He, Hongyu; Zhang, Shengdong

2017-12-13

A room-temperature flexible amorphous indium-gallium-zinc oxide thin film transistor (a-IGZO TFT) technology is developed on plastic substrates, in which both the gate dielectric and passivation layers of the TFTs are formed by an anodic oxidation (anodization) technique. While the gate dielectric Al 2 O 3 is grown with a conventional anodization on an Al:Nd gate electrode, the channel passivation layer Al 2 O 3 is formed using a localized anodization technique. The anodized Al 2 O 3 passivation layer shows a superior passivation effect to that of PECVD SiO 2 . The room-temperature-processed flexible a-IGZO TFT exhibits a field-effect mobility of 7.5 cm 2 /V·s, a subthreshold swing of 0.44 V/dec, an on-off ratio of 3.1 × 10 8 , and an acceptable gate-bias stability with threshold voltage shifts of 2.65 and -1.09 V under positive gate-bias stress and negative gate-bias stress, respectively. Bending and fatigue tests confirm that the flexible a-IGZO TFT also has a good mechanical reliability, with electrical performances remaining consistent up to a strain of 0.76% as well as after 1200 cycles of fatigue testing.

Revisiting the formation of cyclic clusters in liquid ethanol

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balanay, Mannix P.; Fan, Haiyan, E-mail: haiyan.fan@nu.edu.kz; Kim, Dong Hee

2016-04-21

The liquid phase of ethanol in pure and in non-polar solvents was studied at room temperature using Fourier transform infrared (FT-IR) and {sup 1}H nuclear magnetic resonance (NMR) spectroscopies together with theoretical approach. The FT-IR spectra for pure ethanol and solution in cyclohexane at different dilution stages are consistent with {sup 1}H NMR results. The results from both methods were best explained by the results of the density functional theory based on a multimeric model. It is suggested that cyclic trimers and tetramers are dominated in the solution of cyclohexane/hexane with the concentration greater than 0.5M at room temperature. Inmore » liquid ethanol, while the primary components at room temperature are cyclic trimers and tetramers, there is a certain amount (∼14%) of open hydroxide group representing the existence of chain like structures in the equilibria. The cyclic cluster model in the liquid and concentrated solution phase (>0.5M) can be used to explain the anomalously lower freezing point of ethanol (159 K) than that of water (273 K) at ambient conditions. In addition, {sup 1}H NMR at various dilution stages reveals the dynamics for the formation of cyclic clusters.« less

A highly sensitive solid substrate room temperature phosphorimetry for carbaryl detection based on its activating effect on NaIO4 oxidizing fluorescein.

PubMed

Liu, Jiaming; Huang, Qitong; Liu, Zhen-bo; Lin, Xiaofeng; Zhang, Li-Hong; Lin, Chang-Qing; Zheng, Zhi-Yong

2014-11-01

Fluorescein (HFin) could emit strong and stable room temperature phosphorescence (RTP) signal on polyamide membrane (PAM) using Pb(2+) as the ion perturber. Carbaryl could activate effect on NaIO4 oxidating HFin, which caused the RTP signal of the system to quench sharply. The phosphorescence intensity (ΔI p) of activating system higher 3.3 times (119.4/36.0) than that of non-activating system, and is directly proportional to the content of carbaryl. Thus, an activating solid substrate room temperature phosphorimetry (SSRTP) for carbaryl detection has been established. This sensitive (the limit of quantification (LOQ) was 2.0 × 10(-13) g mL(-1)), selective, simple and rapid method has been applied to determine trace carbaryl in water samples with the results consisting with those obtained by fluorimetry, showing its high accuracy. The apparent activation energy (E) and rate constant (k) of this activating reaction were 20.77 kJ mol(-1) and 1.85 × 10(-4) s(-1), respectively. Meanwhile, the mechanism of activating SSRTP for carbaryl detection was also discussed using infrared spectra (IR).

Continuous-wave mid-infrared photonic crystal light emitters at room temperature

NASA Astrophysics Data System (ADS)

Weng, Binbin; Qiu, Jijun; Shi, Zhisheng

2017-01-01

Mid-infrared photonic crystal enhanced lead-salt light emitters operating under continuous-wave mode at room temperature were investigated in this work. For the device, an active region consisting of 9 pairs of PbSe/Pb0.96Sr0.04Se quantum wells was grown by molecular beam epitaxy method on top of a Si(111) substrate which was initially dry-etched with a two-dimensional photonic crystal structure in a pattern of hexagonal holes. Because of the photonic crystal structure, an optical band gap between 3.49 and 3.58 µm was formed, which matched with the light emission spectrum of the quantum wells at room temperature. As a result, under optical pumping, using a near-infrared continuous-wave semiconductor laser, the device exhibited strong photonic crystal band-edge mode emissions and delivered over 26.5 times higher emission efficiency compared to the one without photonic crystal structure. The output power obtained was up to 7.68 mW (the corresponding power density was 363 mW/cm2), and a maximum quantum efficiency reached to 1.2%. Such photonic crystal emitters can be used as promising light sources for novel miniaturized gas-sensing systems.

Characteristics of indium-gallium-nitride multiple-quantum-well blue laser diodes grown by MOCVD

NASA Astrophysics Data System (ADS)

Mack, M. P.; Abare, A. C.; Hansen, M.; Kozodoy, P.; Keller, S.; Mishra, U.; Coldren, L. A.; DenBaars, S. P.

1998-06-01

Room temperature (RT) pulsed operation of blue (420 nm) nitride-based multi-quantum well (MQW) laser diodes grown on c-plane sapphire substrates has been demonstrated. Atmospheric pressure MOCVD was used to grow the active region of the device which consisted of a 10 pair In 0.21Ga 0.79N (2.5 nm)/In 0.07Ga 0.93N (5 nm) InGaN MQW. Threshold current densities as low as 12.6 kA/cm 2 were observed for 10×1200 μm lasers with uncoated reactive ion etched (RIE) facets. The emission is strongly TE polarized and has a sharp transition in the far-field pattern above threshold. Laser diodes were tested under pulsed conditions lasted up to 6 h at room temperature.

Room-temperature low-voltage electroluminescence in amorphous carbon nitride thin films

NASA Astrophysics Data System (ADS)

Reyes, R.; Legnani, C.; Ribeiro Pinto, P. M.; Cremona, M.; de Araújo, P. J. G.; Achete, C. A.

2003-06-01

White-blue electroluminescent emission with a voltage bias less than 10 V was achieved in rf sputter-deposited amorphous carbon nitride (a-CN) and amorphous silicon carbon nitride (a-SiCN) thin-film-based devices. The heterojunction structures of these devices consist of: Indium tin oxide (ITO), used as a transparent anode; amorphous carbon film as an emission layer, and aluminum as a cathode. The thickness of the carbon films was about 250 Å. In all of the produced diodes, a stable visible emission peaked around 475 nm is observed at room temperature and the emission intensity increases with the current density. For an applied voltage of 14 V, the luminance was about 3 mCd/m2. The electroluminescent properties of the two devices are discussed and compared.

Sealed head access area enclosure

DOEpatents

Golden, Martin P.; Govi, Aldo R.

1978-01-01

A liquid-metal-cooled fast breeder power reactor is provided with a sealed head access area enclosure disposed above the reactor vessel head consisting of a plurality of prefabricated structural panels including a center panel removably sealed into position with inflatable seals, and outer panels sealed into position with semipermanent sealant joints. The sealant joints are located in the joint between the edge of the panels and the reactor containment structure and include from bottom to top an inverted U-shaped strip, a lower layer of a room temperature vulcanizing material, a separator strip defining a test space therewithin, and an upper layer of a room temperature vulcanizing material. The test space is tapped by a normally plugged passage extending to the top of the enclosure for testing the seal or introducing a buffer gas thereinto.

Glancing angle deposition of sculptured thin metal films at room temperature

NASA Astrophysics Data System (ADS)

Liedtke, S.; Grüner, Ch; Lotnyk, A.; Rauschenbach, B.

2017-09-01

Metallic thin films consisting of separated nanostructures are fabricated by evaporative glancing angle deposition at room temperature. The columnar microstructure of the Ti and Cr columns is investigated by high resolution transmission electron microscopy and selective area electron diffraction. The morphology of the sculptured metallic films is studied by scanning electron microscopy. It is found that tilted Ti and Cr columns grow with a single crystalline morphology, while upright Cr columns are polycrystalline. Further, the influence of continuous substrate rotation on the shaping of Al, Ti, Cr and Mo nanostructures is studied with view to surface diffusion and the shadowing effect. It is observed that sculptured metallic thin films deposited without substrate rotation grow faster compared to those grown with continuous substrate rotation. A theoretical model is provided to describe this effect.

Tunable transport gap in narrow bilayer graphene nanoribbons

PubMed Central

Yu, Woo Jong; Duan, Xiangfeng

2013-01-01

The lack of a bandgap makes bulk graphene unsuitable for room temperature transistors with a sufficient on/off current ratio. Lateral constriction of charge carriers in graphene nanostructures or vertical inversion symmetry breaking in bilayer graphene are two potential strategies to mitigate this challenge, but each alone is insufficient to consistently achieve a large enough on/off ratio (e.g. > 1000) for typical logic applications. Herein we report the combination of lateral carrier constriction and vertical inversion symmetry breaking in bilayer graphene nanoribbons (GNRs) to tune their transport gaps and improve the on/off ratio. Our studies demonstrate that the on/off current ratio of bilayer GNRs can be systematically increased upon applying a vertical electric field, to achieve a largest on/off current ratio over 3000 at room temperature. PMID:23409239

Isothermal Fatigue, Damage Accumulation, and Life Prediction of a Woven PMC

NASA Technical Reports Server (NTRS)

Gyekenyesi, Andrew L.

1998-01-01

This dissertation focuses on the characterization of the fully reversed fatigue behavior exhibited by a carbon fiber/polyimide resin, woven laminate at room and elevated temperatures. Nondestructive video edge view microscopy and destructive sectioning techniques were used to study the microscopic damage mechanisms that evolved. The residual elastic stiffness was monitored and recorded throughout the fatigue life of the coupon. In addition, residual compressive strength tests were conducted on fatigue coupons with various degrees of damage as quantified by stiffness reduction. Experimental results indicated that the monotonic tensile properties were only minimally influenced by temperature, while the monotonic compressive and fully reversed fatigue properties displayed noticeable reductions due to the elevated temperature. The stiffness degradation, as a function of cycles, consisted of three stages; a short-lived high degradation period, a constant degradation rate segment composing the majority of the life, and a final stage demonstrating an increasing rate of degradation up to failure. Concerning the residual compressive strength tests at room and elevated temperatures, the elevated temperature coupons appeared much more sensitive to damage. At elevated temperatures, coupons experienced a much larger loss in compressive strength when compared to room temperature coupons with equivalent damage. The fatigue damage accumulation law proposed for the model incorporates a scalar representation for damage, but admits a multiaxial, anisotropic evolutionary law. The model predicts the current damage (as quantified by residual stiffness) and remnant life of a composite that has undergone a known load at temperature. The damage/life model is dependent on the applied multiaxial stress state as well as temperature. Comparisons between the model and data showed good predictive capabilities concerning stiffness degradation and cycles to failure.

In-situ neutron diffraction characterization of temperature dependence deformation in α-uranium

NASA Astrophysics Data System (ADS)

Calhoun, C. A.; Garlea, E.; Sisneros, T. A.; Agnew, S. R.

2018-04-01

In-situ strain neutron diffraction measurements were conducted at temperature on specimens coming from a clock-rolled α-uranium plate, and Elasto-Plastic Self-Consistent (EPSC) modeling was employed to interpret the findings. The modeling revealed that the active slip systems exhibit a thermally activated response, while deformation twinning remains athermal over the temperature ranges explored (25-150 °C). The modeling also allowed assessment of the effects of thermal residual stresses on the mechanical response during compression. These results are consistent with those from a prior study of room-temperature deformation, indicating that the thermal residual stresses strongly influence the internal strain evolution of grain families, as monitored with neutron diffraction, even though accounting for these residual stresses has little effect on the macroscopic flow curve, except in the elasto-plastic transition.

Room temperature single-photon detectors for high bit rate quantum key distribution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Comandar, L. C.; Patel, K. A.; Engineering Department, Cambridge University, 9 J J Thomson Ave., Cambridge CB3 0FA

We report room temperature operation of telecom wavelength single-photon detectors for high bit rate quantum key distribution (QKD). Room temperature operation is achieved using InGaAs avalanche photodiodes integrated with electronics based on the self-differencing technique that increases avalanche discrimination sensitivity. Despite using room temperature detectors, we demonstrate QKD with record secure bit rates over a range of fiber lengths (e.g., 1.26 Mbit/s over 50 km). Furthermore, our results indicate that operating the detectors at room temperature increases the secure bit rate for short distances.

Structure of water clusters on graphene: A classical molecular dynamics approach

NASA Astrophysics Data System (ADS)

Maekawa, Yuki; Sasaoka, Kenji; Yamamoto, Takahiro

2018-03-01

The microscopic structure of surface water adsorbed on graphene is elucidated theoretically by classical molecular dynamics simulation. At a low temperature (100 K), the main polygon consisting of hydrogen bonds in single-layered water on graphene is tetragonal, whereas the dominant polygons in double-layered water are tetragonal, pentagonal, and hexagonal. On the other hand, at room temperature, the tetragonal, pentagonal, and hexagonal water clusters are the main structures in both single- and double-layered water.

Photophysical properties of ortho-metalated monomeric and dimeric complexes containing rhodium(III) and iridium(III) metal centers

NASA Astrophysics Data System (ADS)

Marshall, Jason Alexander

Photophysical properties of dichloro-bridged dimers and monomeric tris complexes of the type [M(NC)2Cl]2 and M(NC)3, where NC refers to the ortho-metalating ligands 2-phenylpyridine (ppy), benzo[h]quinoline (bzq), or 2-(p-tolyl)pyridine (ptpy) and M is Rh(III) or Ir(III), were investigated. Excited-state emission of Rh(III) complexes are highly structured and independent of temperature from 4--100 K in glassy media, with long lifetimes (102 mus to ms). Emission is not observed from the pale yellow, fluid solutions of Rh(III) complexes at room temperature. Below 7K, decay kinetics are sensitive to temperature and are complicated, requiring multi-exponential fits in 4:1 EtOH/MeOH. The spectroscopic properties are consistent with the assignment of a lowest 3pipi* excited-state manifold perturbed by an admixture of higher-lying states possessing strong spin-orbit interactions. The complicated decays are attributed to spin-relaxation-limited behavior between spin-levels in the 3pipi* manifold. Deep yellow solutions of Ir(III) complexes in 4:1 EtOH/MeOH are observed to emit in both glassy media and in fluid solution, displaying severe changes in spectral shape as the glass softens which are not attributable to rigidochromic shifts. Low-temperature spectra are structured with emission origins in the range 496--520 nm whereas room-temperature emission of complexes in fluid solution are characteristically broad structureless bands with maxima redshifted from spectra measured in rigid media. Both the emission and the excited-state lifetimes display temperature dependence, with lifetimes in the microsecond to tens of microseconds range at 77 K, increasing by more than an order of magnitude as the temperature is decreased to 4 K. Each of these characteristic band shapes arises from separate components of the emission which have been time-resolved from the low-temperature spectrum. A long-lived, structured component of the emission, only observed in rigid media, has been assigned as 3pipi*. The spectroscopic properties of the short-lived component, observed in the time-resolved low-temperature emission spectrum and in the room-temperature fluid-solution emission spectrum, are consistent with a lowest 3MLCT excited state manifold.

How mothers keep their babies warm.

PubMed Central

Bacon, C J; Bell, S A; Clulow, E E; Beattie, A B

1991-01-01

Details of room temperature, clothing, and bedding used by night and by day and in winter and in summer were recorded for 649 babies aged 8 to 26 weeks. Room temperature at night was significantly related to outside temperature and duration of heating. Total insulation was significantly related to outside temperature and to minimum room temperature, but there was wide variation in insulation at the same room temperature. High levels of insulation for a given room temperature were found particularly at night and in winter, and were associated with the use of thick or doubled duvets and with swaddling. At least half the babies threw off some or all of their bedding at night, and at least a quarter sweated. Younger mothers and mothers in the lower social groups put more bedclothes over their babies, and the latter also kept their rooms warmer. Many mothers kept their babies warmer during infections. PMID:2039255

Evolution of interphase and intergranular strain in zirconium-niobium alloys during deformation at room temperature

NASA Astrophysics Data System (ADS)

Cai, Song

Zr-2.5Nb is currently used for pressure tubes in the CANDU (CANada Deuterium Uranium) reactor. A complete understanding of the deformation mechanism of Zr-2.5Nb is important if we are to accurately predict the in-reactor performance of pressure tubes and guarantee normal operation of the reactors. This thesis is a first step in gaining such an understanding; the deformation mechanism of ZrNb alloys at room temperature has been evaluated through studying the effect of texture and microstructure on deformation. In-situ neutron diffraction was used to monitor the evolution of the lattice strain of individual grain families along both the loading and Poisson's directions and to track the development of interphase and intergranular strains during deformation. The following experiments were carried out with data interpreted using elasto-plastic modeling techniques: (1) Compression tests of a 100%betaZr material at room temperature. (2) Tension and compression tests of hot rolled Zr-2.5Nb plate material. (3) Compression of annealed Zr-2.5Nb. (4) Cyclic loading of the hot rolled Zr-2.5Nb. (5) Compression tests of ZrNb alloys with different Nb and oxygen contents. The experimental results were interpreted using a combination of finite element (FE) and elasto-plastic self-consistent (EPSC) models. The phase properties and phase interactions well represented by the FE model, the EPSC model successfully captured the evolution of intergranular constraint during deformation and provided reasonable estimates of the critical resolved shear stress and hardening parameters of different slip systems under different conditions. The consistency of the material parameters obtained by the EPSC model allows the deformation mechanism at room temperature and the effect of textures and microstructures of ZrNb alloys to be understood. This work provides useful information towards manufacturing of Zr-2.5Nb components and helps in producing ideal microstructures and material properties for pressure tubes. Also it is helpful in guiding the development of new materials for the next generation of nuclear reactors. Furthermore, the large data set obtained from this study can be used in evaluation and improving current and future polycrystalline deformation models.

Formation of porous silicon oxide from substrate-bound silicon rich silicon oxide layers by continuous-wave laser irradiation

NASA Astrophysics Data System (ADS)

Wang, Nan; Fricke-Begemann, Th.; Peretzki, P.; Ihlemann, J.; Seibt, M.

2018-03-01

Silicon nanocrystals embedded in silicon oxide that show room temperature photoluminescence (PL) have great potential in silicon light emission applications. Nanocrystalline silicon particle formation by laser irradiation has the unique advantage of spatially controlled heating, which is compatible with modern silicon micro-fabrication technology. In this paper, we employ continuous wave laser irradiation to decompose substrate-bound silicon-rich silicon oxide films into crystalline silicon particles and silicon dioxide. The resulting microstructure is studied using transmission electron microscopy techniques with considerable emphasis on the formation and properties of laser damaged regions which typically quench room temperature PL from the nanoparticles. It is shown that such regions consist of an amorphous matrix with a composition similar to silicon dioxide which contains some nanometric silicon particles in addition to pores. A mechanism referred to as "selective silicon ablation" is proposed which consistently explains the experimental observations. Implications for the damage-free laser decomposition of silicon-rich silicon oxides and also for controlled production of porous silicon dioxide films are discussed.

Room temperature synthesis of silver nanowires from tabular silver bromide crystals in the presence of gelatin

NASA Astrophysics Data System (ADS)

Liu, Suwen; Wehmschulte, Rudolf J.; Lian, Guoda; Burba, Christopher M.

2006-03-01

Long silver nanowires were synthesized at room temperature by a simple and fast process derived from the development of photographic films. A film consisting of an emulsion of tabular silver bromide grains in gelatin was treated with a photographic developer (4-(methylamino)phenol sulfate (metol), citric acid) in the presence of additional aqueous silver nitrate. The silver nanowires have lengths of more than 50 μm, some even more than 100 μm, and average diameters of about 80 nm. Approximately, 70% of the metallic silver formed in the reduction consists of silver nanowires. Selected area electron diffraction (SAED) results indicate that the silver nanowires grow along the [111] direction. It was found that the presence of gelatin, tabular silver bromide crystals and silver ions in solution are essential for the formation of the silver nanowires. The nanowires appear to originate from the edges of the silver bromide crystals. They were characterized by transmission electron microscopy (TEM), SAED, scanning electron microscopy (SEM), and powder X-ray diffraction (XRD).

Room temperature infrared imaging sensors based on highly purified semiconducting carbon nanotubes.

PubMed

Liu, Yang; Wei, Nan; Zhao, Qingliang; Zhang, Dehui; Wang, Sheng; Peng, Lian-Mao

2015-04-21

High performance infrared (IR) imaging systems usually require expensive cooling systems, which are highly undesirable. Here we report the fabrication and performance characteristics of room temperature carbon nanotube (CNT) IR imaging sensors. The CNT IR imaging sensor is based on aligned semiconducting CNT films with 99% purity, and each pixel or device of the imaging sensor consists of aligned strips of CNT asymmetrically contacted by Sc and Pd. We found that the performance of the device is dependent on the CNT channel length. While short channel devices provide a large photocurrent and a rapid response of about 110 μs, long channel length devices exhibit a low dark current and a high signal-to-noise ratio which are critical for obtaining high detectivity. In total, 36 CNT IR imagers are constructed on a single chip, each consists of 3 × 3 pixel arrays. The demonstrated advantages of constructing a high performance IR system using purified semiconducting CNT aligned films include, among other things, fast response, excellent stability and uniformity, ideal linear photocurrent response, high imaging polarization sensitivity and low power consumption.

Room temperature synthesis of silver nanowires from tabular silver bromide crystals in the presence of gelatin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu Suwen; Wehmschulte, Rudolf J.; Lian Guoda

2006-03-15

Long silver nanowires were synthesized at room temperature by a simple and fast process derived from the development of photographic films. A film consisting of an emulsion of tabular silver bromide grains in gelatin was treated with a photographic developer (4-(methylamino)phenol sulfate (metol), citric acid) in the presence of additional aqueous silver nitrate. The silver nanowires have lengths of more than 50 {mu}m, some even more than 100 {mu}m, and average diameters of about 80 nm. Approximately, 70% of the metallic silver formed in the reduction consists of silver nanowires. Selected area electron diffraction (SAED) results indicate that the silvermore » nanowires grow along the [111] direction. It was found that the presence of gelatin, tabular silver bromide crystals and silver ions in solution are essential for the formation of the silver nanowires. The nanowires appear to originate from the edges of the silver bromide crystals. They were characterized by transmission electron microscopy (TEM), SAED, scanning electron microscopy (SEM), and powder X-ray diffraction (XRD)« less

Rapid and high throughput fabrication of high temperature stable structures through PDMS transfer printing

NASA Astrophysics Data System (ADS)

Hohenberger, Erik; Freitag, Nathan; Korampally, Venumadhav

2017-07-01

We report on a facile and low cost fabrication approach for structures—gratings and enclosed nanochannels, through simple solution processed chemistries in conjunction with nanotransfer printing techniques. The ink formulation primarily consisting of an organosilicate polymeric network with a small percentage of added 3-aminopropyl triethoxysilane crosslinker allows one to obtain robust structures that are not only stable towards high temperature processing steps as high as 550 °C but also exhibit exceptional stability against a host of organic solvent washes. No discernable structure distortion was observed compared to the as-printed structures (room temperature processed) when printed structures were subjected to temperatures as high as 550 °C. We further demonstrate the applicability of this technique towards the fabrication of more complex nanostructures such as enclosed channels through a double transfer method, leveraging the exceptional room temperature cross-linking ability of the printed structures and their subsequent resistance to dissolution in organic solvent washes. The exceptional temperature and physico-chemical stability of the nanotransfer printed structures makes this a useful fabrication tool that may be applied as is, or integrated with conventional lithographic techniques for the large area fabrication of functional nanostructures and devices.

Performance evaluation of a piezoactuator-based single-stage valve system subjected to high temperature

NASA Astrophysics Data System (ADS)

Jeon, Juncheol; Han, Chulhee; Chung, Jye Ung; Choi, Seung-Bok

2015-01-01

In this paper, a novel single-stage valve system activated by a piezostack actuator is proposed and experimentally evaluated at both room temperature (20 °C) and high temperature (100 °C) conditions. A hinge-lever displacement amplifier is adopted in the valve system to magnify the displacement generated from the piezostack actuator. After explaining the operating principle of the proposed piezostack-driven single-stage valve system, the geometric dimensions and mechanical properties of the valve components are discussed in details. An experimental apparatus is then manufactured to evaluate the performances of the valve system such as flow rate. The experimental apparatus consists of a heat chamber, which can regulate the temperature of the valve system and oil, pneumatic-hydraulic cylinders, a hydraulic circuit, a pneumatic circuit, electronic devices, an interface card, and a high voltage amplifier. The pneumatic-hydraulic cylinder transforms the pneumatic pressure into hydraulic pressure. The performances of the valve system regarding spool response, pressure drop, and flow rate are evaluated and presented. In addition, the performance of the valve system under high temperature condition is compared with that under room temperature condition. The experimental results are plotted in both frequency and time domains.

The impact of morning light intensity and environmental temperature on body temperatures and alertness.

PubMed

Te Kulve, Marije; Schlangen, Luc J M; Schellen, Lisje; Frijns, Arjan J H; van Marken Lichtenbelt, Wouter D

2017-06-01

Indoor temperature and light exposure are known to affect body temperature, productivity and alertness of building occupants. However, not much is known about the interaction between light and temperature exposure and the relationship between morning light induced alertness and its effect on body temperature. Light intensity and room temperature during morning office hours were investigated under strictly controlled conditions. In a randomized crossover study, two white light conditions (4000K, either bright 1200lx or dim 5lx) under three different room temperatures (26, 29 and 32°C) were investigated. A lower room temperature increased the core body temperature (CBT) and lowered skin temperature and the distal-proximal temperature gradient (DPG). Moreover, a lower room temperature reduced the subjective sleepiness and reaction time on an auditory psychomotor vigilance task (PVT), irrespective of the light condition. Interestingly, the morning bright light exposure did affect thermophysiological parameters, i.e. it decreased plasma cortisol, CBT and proximal skin temperature and increased the DPG, irrespective of the room temperature. During the bright light session, subjective sleepiness decreased irrespective of the room temperature. However, the change in sleepiness due to the light exposure was not related to these physiological changes. Copyright © 2017 Elsevier Inc. All rights reserved.

Effect of a heat and moisture exchanger on heat loss in isoflurane-anesthetized dogs undergoing single-limb orthopedic procedures.

PubMed

Hofmeister, Erik H; Brainard, Benjamin M; Braun, Christina; Figueiredo, Juliana P

2011-12-15

To determine whether a heat and moisture exchange device (HME) prevents a decrease in body temperature in isoflurane-anesthetized dogs undergoing orthopedic procedures. Blinded randomized controlled clinical trial. 60 privately owned dogs weighing at least 15 kg (33 lb). Dogs were randomly assigned to 1 of 3 treatment groups (n = 20/group): HME placed immediately after anesthetic induction with isoflurane, after transfer to the operating room, or not at all. The device consisted of a hygroscopic filter placed between the endotracheal tube and the Y piece of the anesthesia circuit. Each dog was positioned on a circulating warm water blanket and had a forced-air warming blanket placed over its body. Body temperature was monitored after transfer to the operating room with a probe placed in the thoracic aspect of the esophagus. Study groups did not differ significantly with respect to body weight, body condition score, reproductive status, breed, surgical procedure, preoperative sedative and opioid administration, anesthetic induction drug, local nerve block technique, or operating room assignment. There were no significant differences among groups in esophageal temperature variables, interval between anesthetic induction and surgery, surgery duration, anesthesia duration, or oxygen flow rate. However, the relationship between temperature delta and body weight was significant and relevant (R(2) = 0.23), as was the association between temperature nadir and body weight (R(2)= 0.10). As body weight increased, the temperature delta decreased and temperature nadir increased. No other significant relationships were identified. Inclusion of an HME in healthy dogs undergoing anesthesia for an elective orthopedic surgery did not facilitate maintenance of body temperature throughout the procedure.

Electron-Transfer Ion/Ion Reactions of Doubly Protonated Peptides: Effect of Elevated Bath Gas Temperature

PubMed Central

Pitteri, Sharon J.; Chrisman, Paul A.; McLuckey, Scott A.

2005-01-01

In this study, the electron-transfer dissociation (ETD) behavior of cations derived from 27 different peptides (22 of which are tryptic peptides) has been studied in a 3D quadrupole ion trap mass spectrometer. Ion/ion reactions between peptide cations and nitrobenzene anions have been examined at both room temperature and in an elevated temperature bath gas environment to form ETD product ions. From the peptides studied, the ETD sequence coverage tends to be inversely related to peptide size. At room temperature, very high sequence coverage (~100%) was observed for small peptides (≤7 amino acids). For medium-sized peptides composed of 8–11 amino acids, the average sequence coverage was 46%. Larger peptides with 14 or more amino acids yielded an average sequence coverage of 23%. Elevated-temperature ETD provided increased sequence coverage over room-temperature experiments for the peptides of greater than 7 residues, giving an average of 67% for medium-sized peptides and 63% for larger peptides. Percent ETD, a measure of the extent of electron transfer, has also been calculated for the peptides and also shows an inverse relation with peptide size. Bath gas temperature does not have a consistent effect on percent ETD, however. For the tryptic peptides, fragmentation is localized at the ends of the peptides suggesting that the distribution of charge within the peptide may play an important role in determining fragmentation sites. A triply protonated peptide has also been studied and shows behavior similar to the doubly charged peptides. These preliminary results suggest that for a given charge state there is a maximum size for which high sequence coverage is obtained and that increasing the bath gas temperature can increase this maximum. PMID:16131079

Room Temperature Curing Resin Systems for Graphite/Epoxy Composite Repair.

DTIC Science & Technology

1979-12-01

ROOM TEMPERATURE CURING RESIN SYSTEMS FOR GRAPHITE/EPOXY COMPOS--ETC(UI DEC 79 0 J CRABTREE N62269-79-C-G224 UNCLASSIFIE O80-46 NADC -781 1-6 NL END...Room Temperature Curing Resin Sys-U3 linal for Graphite/Epoxy Composite Repair •.Dec *79 NOR- -46h: V111IT NUM8ER(s) 4362269-79- ,722 S. PERFORMING...repair, composite repair room temperature cure resin , moderate temperature cure resins , epoxies, adhesives, vinyl eater polymers, anaerobic curing polymers

A charge-density-wave oscillator based on an integrated tantalum disulfide-boron nitride-graphene device operating at room temperature.

PubMed

Liu, Guanxiong; Debnath, Bishwajit; Pope, Timothy R; Salguero, Tina T; Lake, Roger K; Balandin, Alexander A

2016-10-01

The charge-density-wave (CDW) phase is a macroscopic quantum state consisting of a periodic modulation of the electronic charge density accompanied by a periodic distortion of the atomic lattice in quasi-1D or layered 2D metallic crystals. Several layered transition metal dichalcogenides, including 1T-TaSe 2 , 1T-TaS 2 and 1T-TiSe 2 exhibit unusually high transition temperatures to different CDW symmetry-reducing phases. These transitions can be affected by the environmental conditions, film thickness and applied electric bias. However, device applications of these intriguing systems at room temperature or their integration with other 2D materials have not been explored. Here, we demonstrate room-temperature current switching driven by a voltage-controlled phase transition between CDW states in films of 1T-TaS 2 less than 10 nm thick. We exploit the transition between the nearly commensurate and the incommensurate CDW phases, which has a transition temperature of 350 K and gives an abrupt change in current accompanied by hysteresis. An integrated graphene transistor provides a voltage-tunable, matched, low-resistance load enabling precise voltage control of the circuit. The 1T-TaS 2 film is capped with hexagonal boron nitride to provide protection from oxidation. The integration of these three disparate 2D materials in a way that exploits the unique properties of each yields a simple, miniaturized, voltage-controlled oscillator suitable for a variety of practical applications.

Screening out the non-Arrhenius behaviour of nematic-isotropic transition by room temperature ionic liquid.

PubMed

Dan, K; Datta, A; Yoshida, Y; Saito, G; Yoshikawa, K; Roy, M

2016-02-28

Differential Scanning Calorimetry (DSC) and optical polarization microscopy of a mixture of the liquid crystalline material (N-(4-methoxybenzylidene)-4-butylaniline, MBBA) and a Fe-based room temperature ionic liquid 1-ethyl-3-methylimidazolium tetrachloroferrate ([Emim](+) [FeCl4](-), EMIF) indicate a decrease in the nematic-isotropic (N-I) phase transition temperature (T(NI)) with an increase in EMIF concentration, explained by a proposed model of Coulomb "screening" of MBBA quadrupoles by the EMIF ions along with ionic "self screening." DSC studies of EMIF-MBBA and pure EMIF and comparison with pure MBBA results show that the major transitions in pure EMIF have Arrhenius behaviour, but more importantly the previously found convex Arrhenius behaviour of the pristine MBBA [K. Dan et al., Europhys. Lett. 108, 36007 (2014)] becomes Arrhenius in the mixture, indicating a conversion of the entropic N-I activation barrier to an enthalpic one. In presence of EMIF, a drastic decrease in the intensity of out-of-plane distortions of benzene rings in MBBA is found from Fourier transform infrared spectroscopy, consistent with significant reduction in the conformational states of MBBA. This suppression of large amplitude motion is again consistent with a Coulomb screening and gives a molecular basis for the entropic-to-enthalpic conversion of the N-I activation barrier.

Anion exchange membrane crosslinked in the easiest way stands out for fuel cells

NASA Astrophysics Data System (ADS)

Hossain, Md. Masem; Wu, Liang; Liang, Xian; Yang, Zhengjin; Hou, Jianqiu; Xu, Tongwen

2018-06-01

Covalent crosslinking is an effective method to stabilize anion exchange membranes (AEMs) against water swelling and high alkaline environment, yet complicated process is required. We report herein a straightforward approach to prepare highly crosslinked, transparent and flexible AEM by simply immersing a halo-alkylated polymer (e.g., brominated poly-(2,6-dimethyl-phenylene oxide)) based membrane in aqueous dimethylamine solution at room temperature and the following methylation. During this crosslinking process, a robust self-crosslinking network is formed which shows a gel fraction in N-methyl-2-pyrrolidone of (up to) 94%. Self-crosslinked membranes show low water uptakes (20-42%) and dimensional swelling (9-16%) compared to non-crosslinked membrane but good hydroxide conductivities (up to 26 mS cm-1) at room temperature. Besides, the resulting membranes show some interesting features: the membranes do not immensely change its room temperature water swelling properties at high temperature but exhibits good hydroxide conductivities (up to 60 mS cm-1 at 80 °C). Noting that, the self-crosslinked AEM reported here has no β-hydrogens, exhibiting extremely high alkaline stability (no decline in hydroxide conductivity in 1 M KOH at 60 °C for 360h). Membrane electrode assembly consists of fabricated membrane shows moderate fuel cell performance reaching peak power density 31 mW cm-2 at 60 °C in a H2/O2 alkaline fuel cell.

Reducing pain with genetic amniocentesis-A randomized trial of subfreezing versus room temperature needles.

PubMed

Wax, Joseph R; Pinette, Michael G; Carpenter, Molly; Chard, Renée; Blackstone, Jacquelyn; Cartin, Angelina

2005-10-01

To determine whether pain associated with second trimester genetic amniocentesis is decreased by using subfreezing rather than room temperature needles. Subjects were randomized to a -14 degrees C or room temperature (20-22 degrees C) 22-gauge spinal needle. Patients, blinded to allocation, recorded anticipated and actual pain before and after the procedure, respectively, using a 0-10 visual analog scale with 0 = no pain and 10 = excruciating pain. Thirty-three subjects were randomized to room temperature and 29 subjects to subfreezing needles. Anticipated pain was similar in room temperature, 5.1 +/- 1.7, and subfreezing groups, 4.9 +/- 2.0, respectively (p = 0.6). Actual pain was also similar in the room temperature, 3.6 +/- 2.0, and subfreezing groups, 2.8 +/- 2.0, respectively (p = 0.14). Similar numbers of subjects in the room temperature and subfreezing groups reported less actual pain (20 vs. 18), greater actual pain (4 vs. 4) or no difference in pain (9 vs. 5) than anticipated (p = 0.6). A subfreezing 22-gauge spinal needle does not decrease perceived pain associated with second trimester genetic amniocentesis.

Room Temperature and Elevated Temperature Composite Sandwich Joint Testing

NASA Technical Reports Server (NTRS)

Walker, Sandra P.

1998-01-01

Testing of composite sandwich joint elements has been completed to verify the strength capacity of joints designed to carry specified running loads representative of a high speed civil transport wing. Static tension testing at both room and an elevated temperature of 350 F and fatigue testing at room temperature were conducted to determine strength capacity, fatigue life, and failure modes. Static tension test results yielded failure loads above the design loads for the room temperature tests, confirming the ability of the joint concepts tested to carry their design loads. However, strength reductions as large as 30% were observed at the elevated test temperature, where all failure loads were below the room temperature design loads for the specific joint designs tested. Fatigue testing resulted in lower than predicted fatigue lives.

Novel room temperature ferromagnetic semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gupta, Amita

2004-06-01

Today's information world, bits of data are processed by semiconductor chips, and stored in the magnetic disk drives. But tomorrow's information technology may see magnetism (spin) and semiconductivity (charge) combined in one 'spintronic' device that exploits both charge and 'spin' to carry data (the best of two worlds). Spintronic devices such as spin valve transistors, spin light emitting diodes, non-volatile memory, logic devices, optical isolators and ultra-fast optical switches are some of the areas of interest for introducing the ferromagnetic properties at room temperature in a semiconductor to make it multifunctional. The potential advantages of such spintronic devices will bemore » higher speed, greater efficiency, and better stability at a reduced power consumption. This Thesis contains two main topics: In-depth understanding of magnetism in Mn doped ZnO, and our search and identification of at least six new above room temperature ferromagnetic semiconductors. Both complex doped ZnO based new materials, as well as a number of nonoxides like phosphides, and sulfides suitably doped with Mn or Cu are shown to give rise to ferromagnetism above room temperature. Some of the highlights of this work are discovery of room temperature ferromagnetism in: (1) ZnO:Mn (paper in Nature Materials, Oct issue, 2003); (2) ZnO doped with Cu (containing no magnetic elements in it); (3) GaP doped with Cu (again containing no magnetic elements in it); (4) Enhancement of Magnetization by Cu co-doping in ZnO:Mn; (5) CdS doped with Mn, and a few others not reported in this thesis. We discuss in detail the first observation of ferromagnetism above room temperature in the form of powder, bulk pellets, in 2-3 mu-m thick transparent pulsed laser deposited films of the Mn (<4 at. percent) doped ZnO. High-resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS) spectra recorded from 2 to 200nm areas showed homogeneous distribution of Mn substituting for Zn a 2 + state in the ZnO lattice. Ferromagnetic Resonance (FMR) technique is used to confirm the existence of ferromagnetic ordering at temperatures as high as 425K. The ab initio calculations were found to be consistent with the observation of ferromagnetism arising from fully polarized Mn 2 + state. The key to observed room temperature ferromagnetism in this system is the low temperature processing, which prevents formation of clusters, secondary phases and the host ZnO from becoming n-type. The electronic structure of the same Mn doped ZnO thin films studied using XAS, XES and RIXS, revealed a strong hybridization between Mn 3d and O 2p states, which is an important characteristic of a Dilute magnetic Semiconductor (DMS). It is shown that the various processing conditions like sintering temperature, dopant concentration and the properties of precursors used for making of DMS have a great influence on the final properties. Use of various experimental techniques to verify the physical properties, and to understand the mechanism involved to give rise to ferromagnetism is presented. Methods to improve the magnetic moment in Mn doped ZnO are also described. New promising DMS materials (such as Cu doped ZnO are explored). The demonstrated new capability to fabricate powder, pellets, and thin films of room temperature ferromagnetic semiconductors thus makes possible the realization of a wide range of complex elements for a variety of new multifunctional phenomena related to Spintronic devices as well as magneto-optic components.« less

Photoluminescence study of MBE grown InGaN with intentional indium segregation

NASA Astrophysics Data System (ADS)

Cheung, Maurice C.; Namkoong, Gon; Chen, Fei; Furis, Madalina; Pudavar, Haridas E.; Cartwright, Alexander N.; Doolittle, W. Alan

2005-05-01

Proper control of MBE growth conditions has yielded an In0.13Ga0.87N thin film sample with emission consistent with In-segregation. The photoluminescence (PL) from this epilayer showed multiple emission components. Moreover, temperature and power dependent studies of the PL demonstrated that two of the components were excitonic in nature and consistent with indium phase separation. At 15 K, time resolved PL showed a non-exponential PL decay that was well fitted with the stretched exponential solution expected for disordered systems. Consistent with the assumed carrier hopping mechanism of this model, the effective lifetime, , and the stretched exponential parameter, , decrease with increasing emission energy. Finally, room temperature micro-PL using a confocal microscope showed spatial clustering of low energy emission.

Microstructure and wear behaviors of laser clad NiCr/Cr3C2-WS2 high temperature self-lubricating wear-resistant composite coating

NASA Astrophysics Data System (ADS)

Yang, Mao-Sheng; Liu, Xiu-Bo; Fan, Ji-Wei; He, Xiang-Ming; Shi, Shi-Hong; Fu, Ge-Yan; Wang, Ming-Di; Chen, Shu-Fa

2012-02-01

The high temperature self-lubricating wear-resistant NiCr/Cr3C2-30%WS2 coating and wear-resistant NiCr/Cr3C2 coating were fabricated on 0Cr18Ni9 austenitic stainless steel by laser cladding. Phase constitutions and microstructures were investigated, and the tribological properties were evaluated using a ball-on-disc wear tester under dry sliding condition at room-temperature (17 °C), 300 °C and 600 °C, respectively. Results indicated that the laser clad NiCr/Cr3C2 coating consisted of Cr7C3 primary phase and γ-(Fe,Ni)/Cr7C3 eutectic colony, while the coating added with WS2 was mainly composed of Cr7C3 and (Cr,W)C carbides, with the lubricating WS2 and CrS sulfides as the minor phases. The wear tests showed that the friction coefficients of two coatings both decrease with the increasing temperature, while the both wear rates increase. The friction coefficient of laser clad NiCr/Cr3C2-30%WS2 is lower than the coating without WS2 whatever at room-temperature, 300 °C, 600 °C, but its wear rate is only lower at 300 °C. It is considered that the laser clad NiCr/Cr3C2-30%WS2 composite coating has good combination of anti-wear and friction-reducing capabilities at room-temperature up to 300 °C.

Circular dichroism studies of the mitochondrial channel, VDAC, from Neurospora crassa.

PubMed Central

Shao, L; Kinnally, K W; Mannella, C A

1996-01-01

The protein that forms the voltage-gated channel VDAC (or mitochondrial porin) has been purified from Neurospora crassa. At room temperature and pH 7, the circular dichoism (CD) spectrum of VDAC suspended in octyl beta-glucoside is similar to those of bacterial porins, consistent with a high beta-sheet content. When VDAC is reconstituted into phospholipid liposomes at pH 7, a similar CD spectrum is obtained and the liposomes are rendered permeable to sucrose. Heating VDAC in octyl beta-glucoside or in liposomes results in thermal denaturation. The CD spectrum irreversibly changes to one consistent with total loss of beta-sheet content, and VDAC-containing liposomes irreversibly lose sucrose permeability. When VDAC is suspended at room temperature in octyl beta-glucoside at pH < 5 or in sodium dodecyl sulfate at pH 7, its CD spectrum is consistent with partial loss of beta-sheet content. The sucrose permeability of VDAC-containing liposomes is decreased at low pH and restored at pH 7. Similarly, the pH-dependent changes in the CD spectrum of VDAC suspended in octyl beta-glucoside also are reversible. These results suggest that VDAC undergoes a reversible conformational change at low pH involving reduced beta-sheet content and loss of pore-forming activity. Images FIGURE 1 PMID:8842216

Microcontroller based automatic temperature control for oyster mushroom plants

NASA Astrophysics Data System (ADS)

Sihombing, P.; Astuti, T. P.; Herriyance; Sitompul, D.

2018-03-01

In the cultivation of Oyster Mushrooms need special treatment because oyster mushrooms are susceptible to disease. Mushroom growth will be inhibited if the temperature and humidity are not well controlled because temperature and inertia can affect mold growth. Oyster mushroom growth usually will be optimal at temperatures around 22-28°C and humidity around 70-90%. This problem is often encountered in the cultivation of oyster mushrooms. Therefore it is very important to control the temperature and humidity of the room of oyster mushroom cultivation. In this paper, we developed an automatic temperature monitoring tool in the cultivation of oyster mushroom-based Arduino Uno microcontroller. We have designed a tool that will control the temperature and humidity automatically by Android Smartphone. If the temperature increased more than 28°C in the room of mushroom plants, then this tool will turn on the pump automatically to run water in order to lower the room temperature. And if the room temperature of mushroom plants below of 22°C, then the light will be turned on in order to heat the room. Thus the temperature in the room oyster mushrooms will remain stable so that the growth of oyster mushrooms can grow with good quality.

Enhanced and selective ammonia sensing of reduced graphene oxide based chemo resistive sensor at room temperature

NASA Astrophysics Data System (ADS)

Kumar, Ramesh; Kaur, Amarjeet

2016-05-01

The reduced graphene oxide thin films were fabricated by using the spin coating method. The reduced graphene oxide samples were characterised by Raman studies to obtain corresponding D and G bands at 1360 and 1590 cm-1 respectively. Fourier transform infra-red (FTIR) spectra consists of peak corresponds to sp2 hybridisation of carbon atoms at 1560 cm-1. The reduced graphene oxide based chemoresistive sensor exhibited a p-type semiconductor behaviour in ambient conditions and showed good sensitivity to different concentration of ammonia from 25 ppm to 500 ppm and excellent selectivity at room temperature. The sensor displays selectivity to several hazardous vapours such as methanol, ethanol, acetone and hydrazine hydrate. The sensor demonstrated a sensitivity of 9.8 at 25 ppm concentration of ammonia with response time of 163 seconds.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Azadi, Sam, E-mail: s.azadi@ucl.ac.uk; Cohen, R. E.; Department of Earth- and Environmental Sciences, Ludwig Maximilians Universität, Munich 80333

We studied the low-pressure (0–10 GPa) phase diagram of crystalline benzene using quantum Monte Carlo and density functional theory (DFT) methods. We performed diffusion quantum Monte Carlo (DMC) calculations to obtain accurate static phase diagrams as benchmarks for modern van der Waals density functionals. Using density functional perturbation theory, we computed the phonon contributions to the free energies. Our DFT enthalpy-pressure phase diagrams indicate that the Pbca and P2{sub 1}/c structures are the most stable phases within the studied pressure range. The DMC Gibbs free-energy calculations predict that the room temperature Pbca to P2{sub 1}/c phase transition occurs at 2.1(1)more » GPa. This prediction is consistent with available experimental results at room temperature. Our DMC calculations give 50.6 ± 0.5 kJ/mol for crystalline benzene lattice energy.« less

Colossal internal barrier layer capacitance effect in polycrystalline copper (II) oxide

NASA Astrophysics Data System (ADS)

Sarkar, Sudipta; Jana, Pradip Kumar; Chaudhuri, B. K.

2008-01-01

Dielectric spectroscopy analysis of the high permittivity (κ˜104) copper (II) oxide (CuO) ceramic shows that the grain contribution plays a major role for the giant-κ value at low temperature, whereas grain boundary (GB) contribution dominates around room temperature and above. Moreover, impedance spectroscopy analysis reveals electrically heterogeneous microstructure in CuO consisting of semiconducting grains and insulating GBs. Finally, the giant dielectric phenomenon exhibited by CuO is attributed to the internal barrier layer (due to GB) capacitance mechanism.

Structural versus electrical properties of an organic-inorganic hybrid material based on sulfate

NASA Astrophysics Data System (ADS)

Ben Rached, Asma; Guionneau, Philippe; Lebraud, Eric; Mhiri, Tahar; Elaoud, Zakaria

2017-01-01

A new organo-sulfate compound is obtained by slow evaporation at room temperature and is characterized by powder and single-crystal X-ray diffraction (XRD) at variable temperatures. The benzylammonium monohydrogenosulfate of formula C6H5CH2NH3+. HSO4-, denoted (BAS), crystallizes in the monoclinic system P21/c space group with the following parameters at room temperature: a=5.623(5)Å, b=20.239(5) Å, c=8.188(5)Å, β=94.104(5)°. The crystal structure consists of infinite parallel two-dimensional planes built by HSO4- anions and C6H5CH2NH3+ cations interconnected by strong O-H….. O and N-H….. O hydrogen bonds. A phase transition is detected at 350 K by differential scanning calorimetry (DSC) and confirmed by powder XRD. Conductivity measurements using the impedance spectroscopy technique allow to determine the conductivity relaxation parameters associated with the H+ conduction from an analysis of the M"/M"max spectrum measured in a wide temperature range. Transport properties of this material appear to be due to an H+ ion hopping mechanism.

Enhanced thermoelectric transport in modulation-doped GaN/AlGaN core/shell nanowires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Erdong; Li, Qiming; Swartzentruber, Brian

2015-11-25

The thermoelectric properties of unintentionally n-doped core GaN/AlGaN core/shell N-face nanowires are reported. We found that the temperature dependence of the electrical conductivity is consistent with thermally activated carriers with two distinctive donor energies. The Seebeck coefficient of GaN/AlGaN nanowires is more than twice as large as that for the GaN nanowires alone. However, an outer layer of GaN deposited onto the GaN/AlGaN core/shell nanowires decreases the Seebeck coefficient at room temperature, while the temperature dependence of the electrical conductivity remains the same. We attribute these observations to the formation of an electron gas channel within the heavily-doped GaN coremore » of the GaN/AlGaN nanowires. The room-temperature thermoelectric power factor for the GaN/AlGaN nanowires can be four times higher than the GaN nanowires. As a result, selective doping in bandgap engineered core/shell nanowires is proposed for enhancing the thermoelectric power.« less

Effect of Specimen Thickness on Mechanical Behavior of SiC/SiC Composites

NASA Technical Reports Server (NTRS)

Morscher, Gregory N.; Singh, Mrityunjay; Freedman, Marc

2004-01-01

Potential composite applications in aerospace and transportation application systems have different thickness requirements. For example, space applications such as nozzle ramps or heat exchangers use very thin (less than 1 mm) structures whereas turbine blades need very thick parts greater than or equal to cm). There has been little investigation into the effect of thickness on stress-strain behavior or elevated temperature tensile properties controlled by oxidation. In this study, composites consisting of woven Hi-NicalonTM fibers, a carbon interphase, and CVI Sic matrix were fabricated with different numbers of plies to provide variable thickness. The composites ranged from a single ply (approximately 0.4 mm) to thirty-six plies (approximately 1 cm). Tensile tests were performed at room temperature with acoustic emission used to monitor matrix crack behavior. Elevated temperature tensile stress-rupture tests were performed in air. Considerably different room and elevated temperature tensile behavior was observed that will be discussed with respect to the effect of thickness on matrix crack formation, matrix crack growth and oxidation diffusion kinetics.

Properties of melt-spun Co15Fe5Cu80, a bulk granular magnetic solid (abstract)

NASA Astrophysics Data System (ADS)

Rubenstein, M.; Das, B. N.; Koon, N. C.

1993-05-01

We have investigated the magnetic and transport properties of melt-spun Co15Fe5Cu80 as a function of heat treatment. Recently Xiao, Jiang, and Chien1 reported clustering and giant magnetoresistance in thin films of related alloys prepared by sputtering. We report qualitatively similar phenomena in these rapidly quenched ribbons. The unannealed samples exhibited saturation magnetoresistance of 0.2%. Annealing at 500 °C for 15 min in hydrogen increases the room temperature for magnetoresistance to 3%, and lowering the temperature to 77 K increased the magnetoresistance to 12.6%. Ferromagnetic resonance measurements at 35 GHz were also made. At room temperature the unannealed sample displayed a very broad resonance centered at 10 kG, consistent with a broad distribution of single domain particles of roughly spherical shape and an overall global magnetization 4πM=3.5 kOe. As the annealing temperature increases, the single domain particles with an inhomogeneous linewidth of ˜2 kOe grow into multidomain particles with a linewidth of ˜6 kOe.

Influence of perfusate temperature on nasal potential difference.

PubMed

Bronsveld, Inez; Vermeulen, François; Sands, Dorotha; Leal, Teresinha; Leonard, Anissa; Melotti, Paola; Yaakov, Yasmin; de Nooijer, Roel; De Boeck, Kris; Sermet, Isabelle; Wilschanski, Michael; Middleton, Peter G

2013-08-01

Nasal potential difference (NPD) quantifies abnormal ion transport in cystic fibrosis. It has gained acceptance as an outcome measure for the investigation of new therapies. To quantify the effect of solution temperature on NPD, we first examined the effect of switching from room temperature (20-25°C) to warmed (32-37°C) solutions and vice versa during each perfusion step. Secondly, standard protocols were repeated at both temperatures in the same subjects. Changing solution temperature did not alter NPD during perfusion with Ringer's solution (<1 mV) (p>0.1). During perfusion with zero chloride solution, changing from room temperature to warmed solutions tended to decrease absolute NPD (i.e. it became less negative) by 0.9 mV (p>0.1); changing from warmed to room temperature increased NPD by 2.1 mV (p<0.05). During isoprenaline perfusion, changing from room temperature to warmed solutions increased NPD by 1.5 mV (p<0.01) and from warmed to room temperature decreased NPD by 1.4 mV (p<0.05). For full protocols at room temperature or warmed in the same subjects, mean values were similar (n = 24). During warmed perfusion, group results for total chloride response had a larger standard deviation. As this increased variability will probably decrease the power of trials, this study suggests that solutions at room temperature should be recommended for the measurement of NPD.

Metallurgical characterization of controlled memory wire nickel-titanium rotary instruments.

PubMed

Shen, Ya; Zhou, Hui-Min; Zheng, Yu-Feng; Campbell, Les; Peng, Bin; Haapasalo, Markus

2011-11-01

To improve the fracture resistance of nickel-titanium (NiTi) files, manufacturers have introduced new alloys and developed new manufacturing processes for the fabrication of NiTi files. This study aimed to examine the phase transformation behavior and microstructure of NiTi instruments from a novel controlled memory NiTi wire (CM wire). Instruments of EndoSequence (ES), ProFile (PF), ProFile Vortex (Vortex), Twisted Files (TF), Typhoon (TYP), and Typhoon™ CM (TYP CM), all size 25/.04, were examined by differential scanning calorimetry (DSC) and x-ray diffraction (XRD). Microstructures of etched instruments were observed by optical microscopy and scanning electron microscopy with x-ray energy-dispersive spectrometric (EDS) analyses. The DSC analyses showed that each segment of the TYP CM and Vortex instruments had an austenite transformation completion or austenite-finish (A(f)) temperature exceeding 37°C, whereas the NiTi instruments made from conventional superelastic NiTi wire (ES, PF, and TYP) and TF had A(f) temperatures substantially below mouth temperature. The higher A(f) temperature of TYP CM instruments was consistent with a mixture of austenite and martensite structure, which was observed at room temperature with XRD. All NiTi instruments had room temperature martensite microstructures consisting of colonies of lenticular features with substantial twinning. EDS analysis indicated that the precipitates in all NiTi instruments were titanium-rich, with an approximate composition of Ti(2)Ni. The TYP CM and Vortex instruments with heat treatment contribute to increase austenite transformation temperature. The CM instrument has significant changes in the phase transformation behavior, compared with conventional superelastic NiTi instruments. Copyright © 2011 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

H2O2-assisted photocatalysis on flower-like rutile TiO2 nanostructures: Rapid dye degradation and inactivation of bacteria

NASA Astrophysics Data System (ADS)

Kőrösi, László; Prato, Mirko; Scarpellini, Alice; Kovács, János; Dömötör, Dóra; Kovács, Tamás; Papp, Szilvia

2016-03-01

Hierarchically assembled flower-like rutile TiO2 (FLH-R-TiO2) nanostructures were successfully synthesized from TiCl4 at room temperature without the use of surfactants or templates. An initial sol-gel synthesis at room temperature allowed long-term hydrolysis and condensation of the precursors. The resulting FLH-R-TiO2 possessed relatively high crystallinity (85 wt%) and consisted of rod-shaped subunits assembling into cauliflower-like nanostructures. Hydrothermal evolution of FLH-R-TiO2 at different temperatures (150, 200 and 250 °C) was followed by means of X-ray diffraction, transmission and scanning electron microscopy. These FLH-R-TiO2 nanostructures were tested as photocatalysts under simulated daylight (full-spectrum lighting) in the degradation of methyl orange and in the inactivation of a multiresistant bacterium, Klebsiella pneumoniae. The effects of hydrothermal treatment on the structure, photocatalytic behavior and antibacterial activity of FLH-R-TiO2 are discussed.

Real-time monitoring of barrel thickness and barrel/screw separation using ultrasound

NASA Astrophysics Data System (ADS)

Jen, Cheng-Kuei; Zun, Zhigang; Kobayashi, Makiko

2005-03-01

Ultrasonic sensors together with a fast data acquisition system have been used to monitor the barrel thickness and barrel/screw separation during low-density polyethylene as well as high-density polyethylene extrusion in 30 mm and 50 mm twin-screw extruders. The sensors include sol-gel sprayed high temperature (HT) piezoelectric thick ceramic film ultrasonic transducers (UTs), stand-alone HTUTs and air-cooled buffer rod type sensors consisting of a room temperature UT and a non-clad or clad buffer rod to which the room temperature UT is attached. The installation and use of these sensors are non-intrusive to the extruder and non-destructive to the polymers being processed. This study has demonstrated the capability of appropriately designed ultrasonic sensors in monitoring the barrel and screw integrity at the melting, mixing and pumping zones of the extruder via barrel or flange. The merits and limitations of these sensors are discussed. The measurement speed and analysis of the sensitivity for quantitative wear measurements are also presented.

Interface between fatigue, creep and stress-corrosion cracking on Ti6246 titanium alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarrazin-Baudoux, C.; Chabanne, Y.; Petit, J.

1999-07-01

The influence of mean stress on the fatigue crack growth behavior of a Ti6246 alloy has been studied in the near-threshold area at room temperature and at 500 C. Tests were performed at various constant K{sub max} levels in ambient air, high vacuum and humidified Argon. Conditions for the occurrence of an abnormal behavior consisting in the disappearance of the threshold for sufficiently high K{sub max} level, are discussed with respect to environment and temperature. This effect is observed in air and in vacuum for K{sub max} higher than 52 MPa{radical}m, and is related to an intrinsic creep damage processmore » which appears more efficient at room temperature than at 500 C and more accentuated in air than in vacuum. In humidified Argon, the critical Kmax level is reduced at 22 MPa{radical}m at 500 C, such a detrimental effect being related to a Stress Corrosion Cracking process induced by water vapor.« less

Heterodyne Receiver for Laboratory Spectrosocpy of Molecules of Astrophysical Importance

NASA Astrophysics Data System (ADS)

Wehres, Nadine; Lewen, Frank; Endres, Christian; Hermanns, Marius; Schlemmer, Stephan

2016-06-01

We present first results of a heterodyne receiver built for high-resolution emission laboratory spectroscopy of molecules of astrophysical interest. The room-temperature receiver operates at frequencies between 80 and 110 GHz, consistent with ALMA band 3. Many molecules have been identified in the interstellar and circumstellar medium at exactly these frequencies by comparing emission spectra obtained from telescopes to high-resolution laboratory absorption spectra. Taking advantage of the recent progresses in the field of mm/submm technology in the astronomy community, we have built a room-temperature emission spectrometer making use of heterodyne receiver technology at an instantaneous bandwidth of currently 2.5 GHz. The system performance, in particular the noise temperature and systematic errors, is presented. The proof-of-concept is demonstrated by comparing the emission spectrum of methyl cyanide to respective absorption spectra and to the literature. Future prospects as well as limitations of the new laboratory receiver for the spectroscopy of complex organic molecules or transient species in discharges will be discussed.

Single-electron quantization at room temperature in a-few-donor quantum dot in silicon nano-transistors

NASA Astrophysics Data System (ADS)

Samanta, Arup; Muruganathan, Manoharan; Hori, Masahiro; Ono, Yukinori; Mizuta, Hiroshi; Tabe, Michiharu; Moraru, Daniel

2017-02-01

Quantum dots formed by donor-atoms in Si nanodevices can provide a breakthrough for functionality at the atomic level with one-by-one control of electrons. However, single-electron effects in donor-atom devices have only been observed at low temperatures mainly due to the low tunnel barriers. If a few donor-atoms are closely coupled as a molecule to form a quantum dot, the ground-state energy level is significantly deepened, leading to higher tunnel barriers. Here, we demonstrate that such an a-few-donor quantum dot, formed by selective conventional doping of phosphorus (P) donors in a Si nano-channel, sustains Coulomb blockade behavior even at room temperature. In this work, such a quantum dot is formed by 3 P-donors located near the center of the selectively-doped area, which is consistent with a statistical analysis. This finding demonstrates practical conditions for atomic- and molecular-level electronics based on donor-atoms in silicon nanodevices.

Microwave SQUID Multiplexing of Metallic Magnetic Calorimeters: Status of Multiplexer Performance and Room-Temperature Readout Electronics Development

NASA Astrophysics Data System (ADS)

Wegner, M.; Karcher, N.; Krömer, O.; Richter, D.; Ahrens, F.; Sander, O.; Kempf, S.; Weber, M.; Enss, C.

2018-02-01

To our present best knowledge, microwave SQUID multiplexing (μ MUXing) is the most suitable technique for reading out large-scale low-temperature microcalorimeter arrays that consist of hundreds or thousands of individual pixels which require a large readout bandwidth per pixel. For this reason, the present readout strategy for metallic magnetic calorimeter (MMC) arrays combining an intrinsic fast signal rise time, an excellent energy resolution, a large energy dynamic range, a quantum efficiency close to 100% as well as a highly linear detector response is based on μ MUXing. Within this paper, we summarize the state of the art in MMC μ MUXing and discuss the most recent results. This particularly includes the discussion of the performance of a 64-pixel detector array with integrated, on-chip microwave SQUID multiplexer, the progress in flux ramp modulation of MMCs as well as the status of the development of a software-defined radio-based room-temperature electronics which is specifically optimized for MMC readout.

Room temperature organic magnets derived from sp3 functionalized graphene.

PubMed

Tuček, Jiří; Holá, Kateřina; Bourlinos, Athanasios B; Błoński, Piotr; Bakandritsos, Aristides; Ugolotti, Juri; Dubecký, Matúš; Karlický, František; Ranc, Václav; Čépe, Klára; Otyepka, Michal; Zbořil, Radek

2017-02-20

Materials based on metallic elements that have d orbitals and exhibit room temperature magnetism have been known for centuries and applied in a huge range of technologies. Development of room temperature carbon magnets containing exclusively sp orbitals is viewed as great challenge in chemistry, physics, spintronics and materials science. Here we describe a series of room temperature organic magnets prepared by a simple and controllable route based on the substitution of fluorine atoms in fluorographene with hydroxyl groups. Depending on the chemical composition (an F/OH ratio) and sp 3 coverage, these new graphene derivatives show room temperature antiferromagnetic ordering, which has never been observed for any sp-based materials. Such 2D magnets undergo a transition to a ferromagnetic state at low temperatures, showing an extraordinarily high magnetic moment. The developed theoretical model addresses the origin of the room temperature magnetism in terms of sp 2 -conjugated diradical motifs embedded in an sp 3 matrix and superexchange interactions via -OH functionalization.

Room temperature organic magnets derived from sp3 functionalized graphene

PubMed Central

Tuček, Jiří; Holá, Kateřina; Bourlinos, Athanasios B.; Błoński, Piotr; Bakandritsos, Aristides; Ugolotti, Juri; Dubecký, Matúš; Karlický, František; Ranc, Václav; Čépe, Klára; Otyepka, Michal; Zbořil, Radek

2017-01-01

Materials based on metallic elements that have d orbitals and exhibit room temperature magnetism have been known for centuries and applied in a huge range of technologies. Development of room temperature carbon magnets containing exclusively sp orbitals is viewed as great challenge in chemistry, physics, spintronics and materials science. Here we describe a series of room temperature organic magnets prepared by a simple and controllable route based on the substitution of fluorine atoms in fluorographene with hydroxyl groups. Depending on the chemical composition (an F/OH ratio) and sp3 coverage, these new graphene derivatives show room temperature antiferromagnetic ordering, which has never been observed for any sp-based materials. Such 2D magnets undergo a transition to a ferromagnetic state at low temperatures, showing an extraordinarily high magnetic moment. The developed theoretical model addresses the origin of the room temperature magnetism in terms of sp2-conjugated diradical motifs embedded in an sp3 matrix and superexchange interactions via –OH functionalization. PMID:28216636

Compositional changes at the interface between thorium-doped uranium dioxide and zirconium due to high-temperature annealing

NASA Astrophysics Data System (ADS)

Youn, Young-Sang; Lee, Jeongmook; Kim, Jandee; Kim, Jong-Yun

2018-06-01

Compositional changes at the interface between thorium-doped uranium dioxide (U0.97Th0.03O2) and Zr before and after annealing at 1700 °C for 18 h were studied by X-ray photoelectron spectroscopy, X-ray diffraction, and Raman spectroscopy. At room temperature, the U0.97Th0.03O2 pellet consisted of hyperstoichiometric UO2+x with UO2 and ThO2, and the Zr sample contained Zr with ZrO2. After annealing, the former contained stoichiometric UO2 with ThO2 and the latter consisted of ZrO2 along with ZrO2·2H2O.

Phase analysis of Košice meteorite: Preliminary results

NASA Astrophysics Data System (ADS)

Sitek, J.; Dekan, J.; Degmová, J.; Sedlačková, K.

2012-10-01

Meteorite fall was observed by the Košice town in Slovakia in February 2010 and it was classified as an ordinary chondrite H5. The samples were prepared in powder form scratched from the surface. Mossbauer spectra were measured at room temperature and liquid nitrogen temperature. Spectra consist of components related to iron-bearing phases with different content. Non-magnetic part was fitted with three quadrupole doublets. According to its parameters, we identified olivine, pyroxene, and traces of Fe3+ phases. Magnetic part consists of an iron-rich Fe-Ni alloy with hyperfine magnetic field similar to kamacite α-Fe(Ni,Co) and troilite. Main elements were also determined by X-ray fluorescence spectroscopy.

Long tailed trions in monolayer MoS2: Temperature dependent asymmetry and resulting red-shift of trion photoluminescence spectra.

PubMed

Christopher, Jason W; Goldberg, Bennett B; Swan, Anna K

2017-10-25

Monolayer molybdenum disulfide (MoS 2 ) has emerged as a model system for studying many-body physics because the low dimensionality reduces screening leading to tightly bound states stable at room temperature. Further, the many-body states possess a pseudo-spin degree of freedom that corresponds with the two direct-gap valleys of the band structure, which can be optically manipulated. Here we focus on one bound state, the negatively charged trion. Unlike excitons, trions can radiatively decay with non-zero momentum by kicking out an electron, resulting in an asymmetric trion photoluminescence (PL) peak with a long low-energy tail and peak position that differs from the zero momentum trion energy. The asymmetry of the trion PL peak and resulting peak red-shift depends both on the trion size and a temperature-dependent contribution. Ignoring the trion asymmetry will result in over estimating the trion binding energy by nearly 20 meV at room temperature. We analyze the temperature-dependent PL to reveal the effective trion size, consistent with the literature, and the temperature dependence of the band gap and spin-orbit splitting of the valence band. This is the first time the temperature-dependence of the trion PL has been analyzed with such detail in any system.

Processing of MnBi bulk magnets with enhanced energy product

DOE PAGES

Poudyal, Narayan; Liu, Xubo; Wang, Wei; ...

2016-02-23

Here, we report magnetic properties and microstructure of high energy-product MnBi bulk magnets fabricated by low-temperature ball-milling and warm compaction technique. A maximum energy product (BH) max of 8.4 MGOe and a coercivity of 6.2 kOe were obtained in the bulk MnBi magnet at room temperature. Magnetic characterization at elevated temperatures showed an increase in coercivity to 16.2 kOe while (BH) max value decreased to 6.8 MGOe at 400 K. Microstructure characterization revealed that the bulk magnets consist of oriented uniform nanoscale grains with average size about 50 nm.

Fabrication and characterization of a germanium nanowire light emitting diode

NASA Astrophysics Data System (ADS)

Greil, Johannes; Bertagnolli, Emmerich; Salem, Bassem; Baron, Thierry; Gentile, Pascal; Lugstein, Alois

2017-12-01

In this letter, we demonstrate the feasibility of a germanium nanowire light emitting diode as a reasonable approach for downscaling of CMOS compatible light sources. We show room-temperature direct bandgap electroluminescence from axial p-n junction nanowire devices. The electron population in the Γ valley, necessary for direct bandgap emission, is achieved by high injection current densities. Carrier temperature is consistently found to be higher than the lattice temperature, indicating inhibited carrier cooling in small diameter wires. Strong polarization of the emission parallel to the nanowire axis is observed and attributed to dielectric contrast phenomena.

Stability of selected hematology variables in canine blood kept at room temperature in EDTA for 24 and 48 hours.

PubMed

Médaille, C; Briend-Marchal, A; Braun, J P

2006-03-01

Most hematologic analyses are performed within a short time of blood sampling, but samples collected at the end of a week may have to be stored for up to 2 days. The stability of hematologic constituents is poorly documented. The objective of this study was to compare the results of RBC, WBC and platelet counts, hemoglobin (Hgb) concentration, and MCV before and after storage of canine blood at room temperature for 24 and 48 hours. One hundred fifty-two K3-EDTA canine blood specimens from 2 veterinary hospitals were analyzed within 4 hours of collection, then 24 and 48 hours later with a Coulter T540 hematology analyzer. Results were compared by Passing-Bablock agreement, difference plots, and according to their classification as normal or abnormal based on reference intervals. RBC count and Hgb concentration were stable for the duration of the study. Differences in WBC and platelet counts varied with the specimen, independently of the initial value. MCV increased consistently over the 2 days. However, only a few results were misclassified. Whole blood specimens stored for up to 2 days at room temperature are suitable for cell counts and Hgb measurement. However, potential variations have to be known to avoid misinterpretations, especially near the decision limits.

Effects of Texture and Grain Size on the Yield Strength of ZK61 Alloy Rods Processed by Cyclic Extrusion and Compression

PubMed Central

Zhang, Lixin; Zhang, Wencong; Cao, Biao; Chen, Wenzhen; Duan, Junpeng; Cui, Guorong

2017-01-01

The ZK61 alloy rods with different grain sizes and crystallographic texture were successfully fabricated by cyclic extrusion and compression (CEC). Their room-temperature tension & compression yield strength displayed a significant dependence on grain size and texture, essentially attributed to {10-12} twinning. The texture variations were characterized by the angle θ between the c-axis of the grain and the extrusion direction (ED) during the process. The contour map of room-temperature yield strength as a function of grain size and the angle θ was obtained. It showed that both the tension yield strength and the compression yield strength of ZK61 alloy were fully consistent with the Hall-Patch relationship at a certain texture, but the change trends of the tension yield strength and the compression yield strength were completely opposite at the same grain size while texture altered. The friction stresses of different deformation modes calculated based on the texture confirmed the tension yield strength of the CECed ZK61 alloy rods, which was determined by both the basal slip and the tension twinning slip during the tension deformation at room temperature, while the compression yield strength was mainly determined by the basal slip during the compression deformation. PMID:29072616

Effects of room temperature aging on two cryogenic temperature sensor models used in aerospace applications

NASA Astrophysics Data System (ADS)

Courts, S. Scott; Krause, John

2012-06-01

Cryogenic temperature sensors used in aerospace applications are typically procured far in advance of the mission launch date. Depending upon the program, the temperature sensors may be stored at room temperature for extended periods as installation and groundbased testing can take years before the actual flight. The effects of long term storage at room temperature are sometimes approximated by the use of accelerated aging at temperatures well above room temperature, but this practice can yield invalid results as the sensing material and/or electrical contacting method can be increasingly unstable with higher temperature exposure. To date, little data are available on the effects of extended room temperature aging on sensors commonly used in aerospace applications. This research examines two such temperature sensors models - the Lake Shore Cryotronics, Inc. model CernoxTM and DT-670-SD temperature sensors. Sample groups of each model type have been maintained for ten years or longer with room temperature storage between calibrations. Over an eighteen year period, the CernoxTM temperature sensors exhibited a stability of better than ±20 mK for T<30 K and better than ±0.1% of temperature for T>30 K. Over a ten year period the model DT-670-SD sensors exhibited a stability of better than ±140 mK for T<25 K and better than ±75 mK for T>25 K.

A novel method for room temperature distribution and conservation of RNA and DNA reference materials for guaranteeing performance of molecular diagnostics in onco-hematology: A GBMHM study.

PubMed

Cayuela, Jean-Michel; Mauté, Carole; Fabre, Anne-Lise; Nibourel, Olivier; Dulucq, Stéphanie; Delabesse, Eric; Villarèse, Patrick; Hayette, Sandrine; Mozziconacci, Marie-Joelle; Macintyre, Elizabeth

2015-10-01

Performance of methods used for molecular diagnostics must be closely controlled by regular analysis of internal quality controls. However, conditioning, shipping and long lasting storage of nucleic acid controls remain problematic. Therefore, we evaluated the minicapsule-based innovative process developed by Imagene (Evry, France) for implementing DNA and RNA controls designed for clonality assessment of lymphoproliferations and BCR-ABL1 mRNA quantification, respectively. DNA samples were extracted from 12 cell lines selected for giving specific amplifications with most BIOMED-2 PCR tubes. RNA samples were extracted from 8 cell line mixtures expressing various BCR-ABL1 transcript levels. DNA and RNA were encapsulated by Imagene and shipped at room temperature to participating laboratories. Biologists were asked to report quality data of recovered nucleic acids as well as PCR results. Encapsulated nucleic acids samples were easily and efficiently recovered from minicapsules. The expected rearrangements at immunoglobulin, T-cell receptor and BCL2 loci were detected in DNA samples by all laboratories. Quality of RNA was consistent between laboratories and met the criteria requested for quantification of BCR-ABL1 transcripts. Expression levels measured by the 5 laboratories were within ±2 fold interval from the corresponding pre-encapsulation reference value. Moreover aging studies of encapsulated RNA simulating up to 100 years storage at room temperature show no bias in quantitative outcome. Therefore, Imagene minicapsules are suitable for storage and distribution at room temperature of genetic material designed for proficiency control of molecular diagnostic methods based on end point or real-time quantitative PCR. Copyright © 2014 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.

Thermomechanical Behavior of Developmental Thermal Barrier Coating Bond Coats

NASA Astrophysics Data System (ADS)

Pandey, Amit; Tolpygo, Vladimir K.; Hemker, Kevin J.

2013-04-01

Thermal expansion, microtensile, and stress relaxation experiments have been performed to contrast and compare the thermal and mechanical response of two experimental (L1 and H1) coatings provided by Honeywell Corporation (Morristown, NY). Thermal expansion experiments reveal that both coatings have coefficients of thermal expansion (CTE) that vary with temperature and that the CTE mismatch between the coatings and superalloy substrate is significant in the case of L1 as compared to H1. Values of the 0.2% offset yield stress (YS), Young's modulus ( E), and hardening exponent ( n) are reported. Room-temperature microtensile experiments show higher strain hardening and a very low value of failure strain for L1 as compared to H1. At elevated temperatures, there is a significant decrease in the YS of as-received L1 for (924 MPa at room temperature to 85 MPa at 1000°C) as compared to H1. Finally, a power law creep description for high-temperature stress relaxation is developed and the measured values of the stress exponent ( n = 3) and activation energies ( Q creep = 200-250 kJ/mol) are shown to be consistent with power law creep.

High temperature superconductor dc SQUID micro-susceptometer for room temperature objects

NASA Astrophysics Data System (ADS)

Faley, M. I.; Pratt, K.; Reineman, R.; Schurig, D.; Gott, S.; Atwood, C. G.; Sarwinski, R. E.; Paulson, D. N.; Starr, T. N.; Fagaly, R. L.

2004-05-01

We have developed a scanning magnetic microscope (SMM) with 25 µm resolution in spatial position for the magnetic features of room temperature objects. The microscope consists of a high-temperature superconductor (HTS) dc SQUID sensor, suspended in vacuum with a self-adjusting standoff, close spaced liquid nitrogen Dewar, X-Y scanning stage and a computer control system. The HTS SQUIDs were optimized for better spatial and field resolutions for operation at liquid nitrogen temperature. Measured inside a magnetic shield, the 10 pT Hz-1/2 typical noise of the SQUIDs is white down to frequencies of about 10 Hz, increasing up to about 20 pT Hz-1/2 at 1 Hz. The microscope is mounted on actively damped platforms, which negate vibrations from the environment as well as damping internal stepper motor noises. A high-resolution video telescope and a 1 µm precision z-axis positioning system allow a close positioning of the sample under the sensor. The ability of the sensors to operate in unshielded environmental conditions with magnetic fields up to about 15 G allowed us to perform 2D mapping of the local ac and dc susceptibility of the objects.

Microfluidic channel flow cell for simultaneous cryoelectrochemical electron spin resonance.

PubMed

Wain, Andrew J; Compton, Richard G; Le Roux, Rudolph; Matthews, Sinead; Fisher, Adrian C

2007-03-01

A novel microfluidic electrochemical channel flow cell has been constructed for in situ operation in a cylindrical TE011 resonant ESR cavity under variable temperature conditions. The cell has a U-tube configuration, consisting of an inlet and outlet channel which run parallel and contain evaporated gold film working, pseudo-reference, and counter electrodes. This geometry was employed to permit use in conjunction with variable temperature apparatus which does not allow a flow-through approach. The cell is characterized qualitatively and quantitatively using the one-electron reduction of p-bromonitrobenzene in acetonitrile at room temperature as a model system, and the ESR signal-flow rate response is validated by use of three-dimensional digital simulation of the concentration profile for a stable electrogenerated radical species under hydrodynamic conditions. The cell is then used to obtain ESR spectra for a number of radical species in acetonitrile at 233 K, including the radical anions of m- and p-iodonitrobenzene, o-bromonitrobenzene, and m-nitrobenzyl chloride, the latter three being unstable at room temperature. Spectra are also presented for the radical anion of 2-chloranthraquinone and the crystal violet radical, which display improved resolution at low temperatures.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weese, R K; Burnham, A K

Dimensional changes related to temperature cycling of the {beta} and {delta} polymorphs of HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) are important for a variety of applications. The coefficient of thermal expansion (CTE) of the {beta} and {delta} phases are measured over a temperature range of -20 C to 215 C by thermo-mechanical analysis (TMA). Dimensional changes associated with the phase transition were also measured, and the time-temperature dependence of the dimensional change is consistent with phase transition kinetics measured earlier by differential scanning calorimetry (DSC). One HMX sample measured by TMA during its initial heating and again three days later during a second heatingmore » showed the {beta}-to-{delta} phase transition a second time, thereby indicating back conversion from {delta}-to-{beta} phase HMX during those three days. DSC was used to measure kinetics of the {delta}-to-{beta} back conversion. The most successful approach was to first heat the material to create the {delta} phase, then after a given period at room temperature, measure the heat absorbed during a second pass through the {beta}-to-{delta} phase transition. Back conversion at room temperature follows nucleation-growth kinetics.« less

Transient natural ventilation of a room with a distributed heat source

NASA Astrophysics Data System (ADS)

Fitzgerald, Shaun D.; Woods, Andrew W.

We report on an experimental and theoretical study of the transient flows which develop as a naturally ventilated room adjusts from one temperature to another. We focus on a room heated from below by a uniform heat source, with both high- and low-level ventilation openings. Depending on the initial temperature of the room relative to (i) the final equilibrium temperature and (ii) the exterior temperature, three different modes of ventilation may develop. First, if the room temperature lies between the exterior and the equilibrium temperature, the interior remains well-mixed and gradually heats up to the equilibrium temperature. Secondly, if the room is initially warmer than the equilibrium temperature, then a thermal stratification develops in which the upper layer of originally hot air is displaced upwards by a lower layer of relatively cool inflowing air. At the interface, some mixing occurs owing to the effects of penetrative convection. Thirdly, if the room is initially cooler than the exterior, then on opening the vents, the original air is displaced downwards and a layer of ambient air deepens from above. As this lower layer drains, it is eventually heated to the ambient temperature, and is then able to mix into the overlying layer of external air, and the room becomes well-mixed. For each case, we present new laboratory experiments and compare these with some new quantitative models of the transient flows. We conclude by considering the implications of our work for natural ventilation of large auditoria.

Instantaneous radioiodination of rose bengal at room temperature and a cold-kit therefor. [DOE patent application

DOEpatents

O'Brien, H. Jr.; Hupf, H.B.; Wanek, P.M.

The disclosure relates to the radioiodination of rose bengal at room temperature and a cold-kit therefor. A purified rose bengal tablet is stirred into acidified ethanol at or near room temperature, until a suspension forms. Reductant-free /sup 125/I/sup -/ is added and the resulting mixture stands until the exchange label reaction occurs at room temperature. A solution of sterile isotonic phosphate buffer and sodium hydroxide is added and the final resulting mixture is sterilized by filtration.

Instantaneous radioiodination of rose bengal at room temperature and a cold kit therefor

DOEpatents

O'Brien, Jr., Harold A.; Hupf, Homer B.; Wanek, Philip M.

1981-01-01

The disclosure relates to the radioiodination of rose bengal at room temperature and a cold-kit therefor. A purified rose bengal tablet is stirred into acidified ethanol at or near room temperature, until a suspension forms. Reductant-free .sup.125 I.sup.- is added and the resulting mixture stands until the exchange label reaction occurs at room temperature. A solution of sterile isotonic phosphate buffer and sodium hydroxide is added and the final resulting mixture is sterilized by filtration.

Room-temperature d0 ferromagnetism in carbon-doped Y2O3 for spintronic applications: A density functional theory study

NASA Astrophysics Data System (ADS)

Chakraborty, Brahmananda; Nandi, Prithwish K.; Kawazoe, Yoshiyuki; Ramaniah, Lavanya M.

2018-05-01

Through density functional theory simulations with the generalized gradient approximation, confirmed by the more sophisticated hybrid functional, we predict the triggering of d0 ferromagnetism in C doped Y2O3 at a hole density of 3.36 ×1021c m-3 (one order less than the critical hole density of ZnO) having magnetic moment of 2.0 μB per defect with ferromagnetic coupling large enough to promote room-temperature ferromagnetism. The persistence of ferromagnetism at room temperature is established through computation of the Curie temperature by the mean field approximation and ab initio molecular dynamics simulations. The induced magnetic moment is mainly contributed by the 2 p orbital of the impurity C and the 2 p orbital of O and we quantitatively and extensively demonstrate through the analysis of density of states and ferromagnetic coupling that the Stoner criterion is satisfied to activate room-temperature ferromagnetism. As the system is stable at room temperature, C doped Y2O3 has feasible defect formation energy and ferromagnetism survives for the choice of hybrid exchange functional, and at room temperature we strongly believe that C doped Y2O3 can be tailored as a room-temperature diluted magnetic semiconductor for spintronic applications.

Design of the thermal insulating test system for doors and windows of buildings

NASA Astrophysics Data System (ADS)

Yu, Yan; Qi, Jinqing; Xu, Yunwei; Wu, Hao; Ou, Jinping

2011-04-01

Thermal insulating properties of doors and widows are important parameter to measure the quality of windows and doors. This paper develops the thermal insulating test system of doors and windows for large temperature difference in winter in north of China according to national standards. This system is integrated with temperature measurement subsystem, temperature control subsystem, the heating power measurement subsystem, and heat transfer coefficient calculated subsystem. The temperature measurement subsystem includes temperature sensor which is implemented by sixty-four thermocouple sensors to measure the key positions of cold room and hot room, and the temperature acquisition unit which adopts Agilent 34901A data acquisition card to achieve self-compensation and accurate temperature capture. The temperature control subsystem including temperature controller and compressor system is used to control the temperature between 0 degree to 20 degree for hot room and -20 degree to 0 degree for cold room. The hot room controller uses fuzzy control algorithm to achieve accurate control of temperature and the cold room controller firstly uses compressor to achieve coarse control and then uses more accurate temperature controller unit to obtain constant temperature(-20 degree). The heating power measurement is mainly to get the heat power of hot room heating devices. After above constant temperature environment is constructed, software of the test system is developed. Using software, temperature data and heat power data can be accurately got and then the heat transfer coefficient, representing the thermal insulating properties of doors and widows, is calculated using the standard formula. Experimental results show that the test system is simple, reliable and precise. It meets the testing requirements of national standard and has a good application prospect.

Factors affecting the energy consumption of two refrigerator-freezers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kao, J.Y.; Kelley, G.E.

Two refrigerator-freezers, one with a top-mounted freezer and one with side-by-side doors, were tested in the laboratory to determine the sensitivity of their energy consumption to various operational factors. Room temperature, room humidity, door openings, and the setting of the anti-sweat heater switch were the factors examined. The results indicated that the room temperature and door openings had a significantly greater effect on energy consumption than the other two factors. More detailed tests were then performed under different room temperature and door-opening combinations. The relationship of door openings and the equivalent test room temperature was established. Finally, the effect onmore » energy of different temperature settings was studied. Test results are presented and discussed.« less

Consistency of signal intensity and T2* in frozen ex vivo heart muscle, kidney, and liver tissue.

PubMed

Kaye, Elena A; Josan, Sonal; Lu, Aiming; Rosenberg, Jarrett; Daniel, Bruce L; Pauly, Kim Butts

2010-03-01

To investigate tissue dependence of the MRI-based thermometry in frozen tissue by quantification and comparison of signal intensity and T2* of ex vivo frozen tissue of three different types: heart muscle, kidney, and liver. Tissue samples were frozen and imaged on a 0.5 Tesla MRI scanner with ultrashort echo time (UTE) sequence. Signal intensity and T2* were determined as the temperature of the tissue samples was decreased from room temperature to approximately -40 degrees C. Statistical analysis was performed for (-20 degrees C, -5 degrees C) temperature interval. The findings of this study demonstrate that signal intensity and T2* are consistent across three types of tissue for (-20 degrees C, -5 degrees C) temperature interval. Both parameters can be used to calculate a single temperature calibration curve for all three types of tissue and potentially in the future serve as a foundation for tissue-independent MRI-based thermometry.

57Fe Mössbauer study of Lu 2Fe 3Si 5 iron silicide superconductor

DOE PAGES

Ma, Xiaoming; Ran, Sheng; Pang, Hua; ...

2015-03-28

With the advent of Fe–As based superconductivity it has become important to study how superconductivity manifests itself in details of 57Fe Mössbauer spectroscopy of conventional, Fe-bearing superconductors. The iron-based superconductor Lu 2Fe 3Si 5 has been studied by 57Fe Mössbauer spectroscopy over the temperature range from 4.4 K to room temperature with particular attention to the region close to the superconducting transition temperature (T c=6.1 K). Consistent with the two crystallographic sites for Fe in this structure, the observed spectra appear to have a pattern consisting of two doublets over the whole temperature range. Furthermore, the value of Debye temperaturemore » was estimated from temperature dependence of the isomer shift and the total spectral area and compared with the specific heat capacity data. Neither abnormal behavior of the hyperfine parameters at or near T c, nor phonon softening were observed.« less

Physical properties of ionic liquids consisting of the 1-butyl-3-methylimidazolium cation with various anions and the bis(trifluoromethylsulfonyl)imide anion with various cations.

PubMed

Jin, Hui; O'Hare, Bernie; Dong, Jing; Arzhantsev, Sergei; Baker, Gary A; Wishart, James F; Benesi, Alan J; Maroncelli, Mark

2008-01-10

Physical properties of 4 room-temperature ionic liquids consisting of the 1-butyl-3-methylimidazolium cation with various perfluorinated anions and the bis(trifluoromethylsulfonyl)imide (Tf2N-) anion with 12 pyrrolidinium-, ammonium-, and hydroxyl-containing cations are reported. Electronic structure methods are used to calculate properties related to the size, shape, and dipole moment of individual ions. Experimental measurements of phase-transition temperatures, densities, refractive indices, surface tensions, solvatochromic polarities based on absorption of Nile Red, 19F chemical shifts of the Tf2N- anion, temperature-dependent viscosities, conductivities, and cation diffusion coefficients are reported. Correlations among the measured quantities as well as the use of surface tension and molar volume for estimating Hildebrand solubility parameters of ionic liquids are also discussed.

Ordered iron aluminide alloys having an improved room-temperature ductility and method thereof

DOEpatents

Sikka, Vinod K.

1992-01-01

A process is disclosed for improving the room temperature ductility and strength of iron aluminide intermetallic alloys. The process involves thermomechanically working an iron aluminide alloy by means which produce an elongated grain structure. The worked alloy is then heated at a temperature in the range of about 650.degree. C. to about 800.degree. C. to produce a B2-type crystal structure. The alloy is rapidly cooled in a moisture free atmosphere to retain the B2-type crystal structure at room temperature, thus providing an alloy having improved room temperature ductility and strength.

Effect of 50 MeV Li3 + irradiation on structural and electrical properties of Mn-doped ZnO

NASA Astrophysics Data System (ADS)

Neogi, S. K.; Chattopadhyay, S.; Banerjee, Aritra; Bandyopadhyay, S.; Sarkar, A.; Kumar, Ravi

2011-05-01

The present work aims to study the effect of ion irradiation on structural and electrical properties and their correlation with the defects in the Zn1 - xMnxO-type system. Zn1 - xMnxO (x = 0.02, 0.04) samples have been synthesized by the solid-state reaction method and have been irradiated with 50 MeV Li3 + ions. The concomitant changes have been probed by x-ray diffraction (XRD), temperature-dependent electrical resistivity and positron annihilation lifetime (PAL) spectroscopy. The XRD result shows a single-phase wurtzite structure for Zn0.98Mn0.02O, whereas for the Zn0.96Mn0.04O sample an impurity phase has been found, apart from the usual peaks of ZnO. Ion irradiation removes this impurity peak. The grain size of the samples is found to be uniform. For Zn0.98Mn0.02O, the observed sharp decrease in room temperature resistivity (ρRT) with irradiation is consistent with the lowering of the full width at half maximum of the XRD peaks. However, for Zn0.96Mn0.04O, ρRT decreases for the initial fluence but increases for a further increase in fluence. All the irradiated Zn0.98Mn0.02O samples show a metal-semiconductor transition in temperature-dependent resistivity measurements at low temperature. But all the irradiated Zn0.96Mn0.04O samples show a semiconducting nature in the whole range of temperatures. Results of room temperature resistivity, XRD and PAL measurements are consistent with each other.

Effect of 50 MeV Li3+ irradiation on structural and electrical properties of Mn-doped ZnO.

PubMed

Neogi, S K; Chattopadhyay, S; Banerjee, Aritra; Bandyopadhyay, S; Sarkar, A; Kumar, Ravi

2011-05-25

The present work aims to study the effect of ion irradiation on structural and electrical properties and their correlation with the defects in the Zn(1 - x)Mn(x)O-type system. Zn(1 - x)Mn(x)O (x = 0.02, 0.04) samples have been synthesized by the solid-state reaction method and have been irradiated with 50 MeV Li(3+) ions. The concomitant changes have been probed by x-ray diffraction (XRD), temperature-dependent electrical resistivity and positron annihilation lifetime (PAL) spectroscopy. The XRD result shows a single-phase wurtzite structure for Zn(0.98)Mn(0.02)O, whereas for the Zn(0.96)Mn(0.04)O sample an impurity phase has been found, apart from the usual peaks of ZnO. Ion irradiation removes this impurity peak. The grain size of the samples is found to be uniform. For Zn(0.98)Mn(0.02)O, the observed sharp decrease in room temperature resistivity (ρ(RT)) with irradiation is consistent with the lowering of the full width at half maximum of the XRD peaks. However, for Zn(0.96)Mn(0.04)O, ρ(RT) decreases for the initial fluence but increases for a further increase in fluence. All the irradiated Zn(0.98)Mn(0.02)O samples show a metal-semiconductor transition in temperature-dependent resistivity measurements at low temperature. But all the irradiated Zn(0.96)Mn(0.04)O samples show a semiconducting nature in the whole range of temperatures. Results of room temperature resistivity, XRD and PAL measurements are consistent with each other.

Characterization of biologic response modifiers in the supernatant of conventional, refrigerated, and cryopreserved platelets.

PubMed

Johnson, Lacey; Tan, Shereen; Jenkins, Emily; Wood, Ben; Marks, Denese C

2018-04-01

Alternatives to room temperature storage of platelets (PLTs) are of interest to support blood banking logistics. The aim of this study was to compare the presence of biologic response modifiers (BRMs) in PLT concentrates stored under conventional room temperature conditions with refrigerated or cryopreserved PLTs. A three-arm pool-and-split study was carried out using buffy coat-derived PLTs stored in 30% plasma/70% SSP+. The three matched treatment arms were as follows: room temperature (20-24°C), cold (2-6°C), and cryopreserved (-80°C with DMSO). Liquid-stored PLTs were tested over a 21-day period, while cryopreserved PLTs were tested immediately after thawing and reconstitution in 30% plasma/70% SSP+ and after storage at room temperature. Coagulation factor activity was comparable between room temperature and cold PLTs, with the exception of protein S, while cryopreserved PLTs had reduced Factor (F)V and FVIII activity. Cold-stored PLTs retained α-granule proteins better than room temperature or cryopreserved PLTs. Cryopreservation resulted in 10-fold higher microparticle generation than cold-stored PLTs, but both groups contained significantly more microparticles than those stored at room temperature. The supernatant from both cold and cryopreserved PLTs initiated faster clot formation and thrombin generation than room temperature PLTs. Cold storage and cryopreservation alter the composition of the soluble fraction of stored PLTs. These differences in coagulation proteins, cytokines, and microparticles likely influence both the hemostatic capacity of the components and the auxiliary functions. © 2017 AABB.

Wide bandgap BaSnO3 films with room temperature conductivity exceeding 104 S cm−1

PubMed Central

Prakash, Abhinav; Xu, Peng; Faghaninia, Alireza; Shukla, Sudhanshu; Ager, Joel W.; Lo, Cynthia S.; Jalan, Bharat

2017-01-01

Wide bandgap perovskite oxides with high room temperature conductivities and structural compatibility with a diverse family of organic/inorganic perovskite materials are of significant interest as transparent conductors and as active components in power electronics. Such materials must also possess high room temperature mobility to minimize power consumption and to enable high-frequency applications. Here, we report n-type BaSnO3 films grown using hybrid molecular beam epitaxy with room temperature conductivity exceeding 104 S cm−1. Significantly, these films show room temperature mobilities up to 120 cm2 V−1 s−1 even at carrier concentrations above 3 × 1020 cm−3 together with a wide bandgap (3 eV). We examine the mobility-limiting scattering mechanisms by calculating temperature-dependent mobility, and Seebeck coefficient using the Boltzmann transport framework and ab-initio calculations. These results place perovskite oxide semiconductors for the first time on par with the highly successful III–N system, thereby bringing all-transparent, high-power oxide electronics operating at room temperature a step closer to reality. PMID:28474675

Proposal for a room-temperature diamond maser

PubMed Central

Jin, Liang; Pfender, Matthias; Aslam, Nabeel; Neumann, Philipp; Yang, Sen; Wrachtrup, Jörg; Liu, Ren-Bao

2015-01-01

The application of masers is limited by its demanding working conditions (high vacuum or low temperature). A room-temperature solid-state maser is highly desirable, but the lifetimes of emitters (electron spins) in solids at room temperature are usually too short (∼ns) for population inversion. Masing from pentacene spins in p-terphenyl crystals, which have a long spin lifetime (∼0.1 ms), has been demonstrated. This maser, however, operates only in the pulsed mode. Here we propose a room-temperature maser based on nitrogen-vacancy centres in diamond, which features the longest known solid-state spin lifetime (∼5 ms) at room temperature, high optical pumping efficiency (∼106 s−1) and material stability. Our numerical simulation demonstrates that a maser with a coherence time of approximately minutes is feasible under readily accessible conditions (cavity Q-factor ∼5 × 104, diamond size ∼3 × 3 × 0.5 mm3 and pump power <10 W). A room-temperature diamond maser may facilitate a broad range of microwave technologies. PMID:26394758

Wide bandgap BaSnO 3 films with room temperature conductivity exceeding 10 4 S cm -1

DOE PAGES

Prakash, Abhinav; Xu, Peng; Faghaninia, Alireza; ...

2017-05-05

Wide bandgap perovskite oxides with high room temperature conductivities and structural compatibility with a diverse family of organic/inorganic perovskite materials are of sign ificant interest as transparent conductors and as active components in power electronics. Such materials must also possess high room temperature mobility to minimize power consumption and to enable high-frequency applications. Here, we report n-type BaSnO 3 films grown using hybrid molecular beam epitaxy with room temperature conductivity exceeding 10 4 S cm -1 . Significantly, these films show room temperature mobilities up to 120 cm 2 V -1 s -1 even at carrier concentrations abovemore » 3 × 10 20 cm -3 together with a wide bandgap (3 eV). We examine the mobility-limiting scattering mechanisms by calculating temperature-dependent mobility, and Seebeck coefficient using the Boltzmann transport framework and ab-initio calculations. These results place perovskite oxide semiconductors for the first time on par with the highly successful III-N system, thereby bringing all-transparent, high-power oxide electronics operating at room temperature a step closer to reality.« less

Mechanism-Based Modeling for Low Cycle Fatigue of Cast Austenitic Steel

NASA Astrophysics Data System (ADS)

Wu, Xijia; Quan, Guangchun; Sloss, Clayton

2017-09-01

A mechanism-based approach—the integrated creep-fatigue theory (ICFT)—is used to model low cycle fatigue behavior of 1.4848 cast austenitic steel over the temperature range from room temperature (RT) to 1173 K (900 °C) and the strain rate range from of 2 × 10-4 to 2 × 10-2 s-1. The ICFT formulates the material's constitutive equation based on the physical strain decomposition into mechanism strains, and the associated damage accumulation consisting of crack nucleation and propagation in coalescence with internally distributed damage. At room temperature, the material behavior is controlled by plasticity, resulting in a rate-independent and cyclically stable behavior. The material exhibits significant cyclic hardening at intermediate temperatures, 673 K to 873 K (400 °C to 600 °C), with negative strain rate sensitivity, due to dynamic strain aging. At high temperatures >1073 K (800 °C), time-dependent deformation is manifested with positive rate sensitivity as commonly seen in metallic materials at high temperature. The ICFT quantitatively delineates the contribution of each mechanism in damage accumulation, and predicts the fatigue life as a result of synergistic interaction of the above identified mechanisms. The model descriptions agree well with the experimental and fractographic observations.

Impacts of exhalation flow on the microenvironment around the human body under different room temperatures

NASA Astrophysics Data System (ADS)

Jafari, Mohammad Javad; Gharari, Noradin; Azari, Mansour Rezazade; Ashrafi, Khosro

2018-04-01

Exhalation flow and room temperature can have a considerable effect on the microenvironment in the vicinity of human body. In this study, impacts of exhalation flow and room temperature on the microenvironment around a human body were investigated using a numerical simulation. For this purpose, a computational fluid dynamic program was applied to study thermal plume around a sitting human body at different room temperatures of a calm indoor room by considering the exhalation flow. The simulation was supported by some experimental measurements. Six different room temperatures (18 to 28 °C) with two nose exhalation modes (exhalation and non-exhalation) were investigated. Overhead and breathing zone velocities and temperatures were simulated in different scenarios. This study finds out that the exhalation through the nose has a significant impact on both quantitative and qualitative features of the human microenvironment in different room temperatures. At a given temperature, the exhalation through the nose can change the location and size of maximum velocity at the top of the head. In the breathing zone, the effect of exhalation through the nose on velocity and temperature distribution was pronounced for the point close to mouth. Also, the exhalation through the nose strongly influences the thermal boundary layer on the breathing zone while it only minimally influences the convective boundary layer on the breathing zone. Overall results demonstrate that it is important to take the exhalation flow into consideration in all areas, especially at a quiescent flow condition with low temperature.

Influence of Starting Powders on Hydroxyapatite Coatings Fabricated by Room Temperature Spraying Method.

PubMed

Seo, Dong Seok; Lee, Jong Kook; Hwang, Kyu Hong; Hahn, Byung Dong; Yoon, Seog Young

2015-08-01

Three types of raw materials were used for the fabrication of hydroxyapatite coatings by using the room temperature spraying method and their influence on the microstructure and in vitro characteristics were investigated. Starting hydroxyapatite powders for coatings on titanium substrate were prepared by a heat treatment at 1100 °C for 2 h of bovine bone, bone ash, and commercial hydroxyapatite powders. The phase compositions and Ca/P ratios of the three hydroxyapatite coatings were similar to those of the raw materials without decomposition or formation of a new phase. All hydroxyapatite coatings showed a honeycomb structure, but their surface microstructures revealed different features in regards to surface morphology and roughness, based on the staring materials. All coatings consisted of nano-sized grains and had dense microstructure. Inferred from in vitro experiments in pure water, all coatings have a good dissolution-resistance and biostability in water.

Room-Temperature Quantum Cloning Machine with Full Coherent Phase Control in Nanodiamond

PubMed Central

Chang, Yan-Chun; Liu, Gang-Qin; Liu, Dong-Qi; Fan, Heng; Pan, Xin-Yu

2013-01-01

In contrast to the classical world, an unknown quantum state cannot be cloned ideally, as stated by the no-cloning theorem. However, it is expected that approximate or probabilistic quantum cloning will be necessary for different applications, and thus various quantum cloning machines have been designed. Phase quantum cloning is of particular interest because it can be used to attack the Bennett-Brassard 1984 (BB84) states used in quantum key distribution for secure communications. Here, we report the first room-temperature implementation of quantum phase cloning with a controllable phase in a solid-state system: the nitrogen-vacancy centre of a nanodiamond. The phase cloner works well for all qubits located on the equator of the Bloch sphere. The phase is controlled and can be measured with high accuracy, and the experimental results are consistent with theoretical expectations. This experiment provides a basis for phase-controllable quantum information devices. PMID:23511233

High Strength-High Ductility Combination Ultrafine-Grained Dual-Phase Steels Through Introduction of High Degree of Strain at Room Temperature Followed by Ultrarapid Heating During Continuous Annealing of a Nb-Microalloyed Steel

NASA Astrophysics Data System (ADS)

Deng, Yonggang; Di, Hongshuang; Hu, Meiyuan; Zhang, Jiecen; Misra, R. D. K.

2017-07-01

Ultrafine-grained dual-phase (UFG-DP) steel consisting of ferrite (1.2 μm) and martensite (1 μm) was uniquely processed via combination of hot rolling, cold rolling and continuous annealing of a low-carbon Nb-microalloyed steel. Room temperature tensile properties were evaluated and fracture mechanisms studied and compared to the coarse-grained (CG) counterpart. In contrast to the CG-DP steel, UFG-DP had 12.7% higher ultimate tensile strength and 10.7% greater uniform elongation. This is partly attributed to the increase in the initial strain-hardening rate, decrease in nanohardness ratio of martensite and ferrite. Moreover, a decreasing number of ferrite grains with {001} orientation increased the cleavage fracture stress and increased the crack initiation threshold stress with consequent improvement in ductility UFG-DP steel.

Three-dimensional scanning force/tunneling spectroscopy at room temperature.

PubMed

Sugimoto, Yoshiaki; Ueda, Keiichi; Abe, Masayuki; Morita, Seizo

2012-02-29

We simultaneously measured the force and tunneling current in three-dimensional (3D) space on the Si(111)-(7 × 7) surface using scanning force/tunneling microscopy at room temperature. The observables, the frequency shift and the time-averaged tunneling current were converted to the physical quantities of interest, i.e. the interaction force and the instantaneous tunneling current. Using the same tip, the local density of states (LDOS) was mapped on the same surface area at constant height by measuring the time-averaged tunneling current as a function of the bias voltage at every lateral position. LDOS images at negative sample voltages indicate that the tip apex is covered with Si atoms, which is consistent with the Si-Si covalent bonding mechanism for AFM imaging. A measurement technique for 3D force/current mapping and LDOS imaging on the equivalent surface area using the same tip was thus demonstrated.

Robust, Self-Healing Superhydrophobic Fabrics Prepared by One-Step Coating of PDMS and Octadecylamine

PubMed Central

Xue, Chao-Hua; Bai, Xue; Jia, Shun-Tian

2016-01-01

A robust, self-healing superhydrophobic poly(ethylene terephthalate) (PET) fabric was fabricated by a convenient solution-dipping method using an easily available material system consisting of polydimethylsiloxane and octadecylamine (ODA). The surface roughness was formed by self-roughening of ODA coating on PET fibers without any lithography steps or adding any nanomaterials. The fabric coating was durable to withstand 120 cycles of laundry and 5000 cycles of abrasion without apparently changing the superhydrophobicity. More interestingly, the fabric can restore its super liquid-repellent property by 72 h at room temperature even after 20000 cycles of abrasion. Meanwhile, after being damaged chemically, the fabric can restore its superhydrophobicity automatically in 12 h at room temperature or by a short-time heating treatment. We envision that this simple but effective coating system may lead to the development of robust protective clothing for various applications. PMID:27264995

Optomechanical terahertz detection with single meta-atom resonator.

PubMed

Belacel, Cherif; Todorov, Yanko; Barbieri, Stefano; Gacemi, Djamal; Favero, Ivan; Sirtori, Carlo

2017-11-17

Most of the common technologies for detecting terahertz photons (>1 THz) at room temperature rely on slow thermal devices. The realization of fast and sensitive detectors in this frequency range is indeed a notoriously difficult task. Here we propose a novel device consisting of a subwavelength terahertz meta-atom resonator, which integrates a nanomechanical element and allows energy exchange between the mechanical motion and the electromagnetic degrees of freedom. An incident terahertz wave thus produces a nanomechanical signal that can be read out optically with high precision. We exploit this concept to demonstrate a terahertz detector that operates at room temperature with high sensitivity and a much higher frequency response compared to standard detectors. Beyond the technological issue of terahertz detection, our architecture opens up new perspectives for fundamental science of light-matter interaction at terahertz frequencies, combining optomechanical approaches with semiconductor quantum heterostructures.

Enhanced and selective ammonia sensing of reduced graphene oxide based chemo resistive sensor at room temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Ramesh, E-mail: rameshphysicsdu@gmail.com; Kaur, Amarjeet, E-mail: amarkaur@physics.du.ac.in

The reduced graphene oxide thin films were fabricated by using the spin coating method. The reduced graphene oxide samples were characterised by Raman studies to obtain corresponding D and G bands at 1360 and 1590 cm{sup −1} respectively. Fourier transform infra-red (FTIR) spectra consists of peak corresponds to sp{sup 2} hybridisation of carbon atoms at 1560 cm{sup −1}. The reduced graphene oxide based chemoresistive sensor exhibited a p-type semiconductor behaviour in ambient conditions and showed good sensitivity to different concentration of ammonia from 25 ppm to 500 ppm and excellent selectivity at room temperature. The sensor displays selectivity to several hazardous vapours such asmore » methanol, ethanol, acetone and hydrazine hydrate. The sensor demonstrated a sensitivity of 9.8 at 25 ppm concentration of ammonia with response time of 163 seconds.« less

Nanoparticles of nickel oxide: growth and organization on zinc-substituted anionic clay matrix by one-pot route at room temperature

NASA Astrophysics Data System (ADS)

Carja, Gabriela; Nakajima, Akira; Dranca, Cristian; Okada, Kiyoshi

2010-10-01

A room temperature nanocarving strategy is developed for the fabrication of nanoparticles of nickel oxide on zinc-substituted anionic clay matrix (Ni/ZnLDH). It is based on the growth and organization of nanoparticles of nickel oxide which occur during the structural reconstruction of the layered structure of the anionic clay in NiSO4 aqueous solution. No organic compounds are used during the fabrication. The described material was characterized by X-ray diffraction (XRD), IR spectroscopy (FTIR), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) spectroscopy, and X-ray photoelectron spectroscopy (XPS). Results show that the nickel-clay nanoarchitecture consists of small nanoparticles of nickel oxide (average size 7 nm) deposited on the larger nanoparticles (average size 90 nm) of zinc-substituted clay. The optical properties of the new nickel-zinc formulation are studied by UV-Vis.

Room temperature electroluminescence from the n-ZnO/p-GaN heterojunction device grown by MOCVD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, T.P.; Zhu, H.C.; Bian, J.M.

2008-12-01

The heterojunction light-emitting diode with n-ZnO/p-GaN structure was grown on (0 0 0 1) sapphire substrate by metalorganic chemical vapor deposition (MOCVD) technique. The heterojunction structure was consisted of an Mg-doped p-type GaN layer with a hole concentration of {approx}10{sup 17} cm{sup -3} and a unintentionally doped n-type ZnO layer with an electron concentration of {approx}10{sup 18} cm{sup -3}. A distinct blue-violet electroluminescence with a dominant emission peak centered at {approx}415 nm was observed at room temperature from the heterojunction structure under forward bias conditions. The origins of the electroluminescence (EL) emissions are discussed in comparison with the photoluminescence spectra,more » and it was supposed to be attributed to a radiative recombination in both n-ZnO and p-GaN sides.« less

Broadband multiresonator quantum memory-interface.

PubMed

Moiseev, S A; Gerasimov, K I; Latypov, R R; Perminov, N S; Petrovnin, K V; Sherstyukov, O N

2018-03-05

In this paper we experimentally demonstrated a broadband scheme of the multiresonator quantum memory-interface. The microwave photonic scheme consists of the system of mini-resonators strongly interacting with a common broadband resonator coupled with the external waveguide. We have implemented the impedance matched quantum storage in this scheme via controllable tuning of the mini-resonator frequencies and coupling of the common resonator with the external waveguide. Proof-of-principal experiment has been demonstrated for broadband microwave pulses when the quantum efficiency of 16.3% was achieved at room temperature. By using the obtained experimental spectroscopic data, the dynamics of the signal retrieval has been simulated and promising results were found for high-Q mini-resonators in microwave and optical frequency ranges. The results pave the way for the experimental implementation of broadband quantum memory-interface with quite high efficiency η > 0.99 on the basis of modern technologies, including optical quantum memory at room temperature.

Aqueous, Room Temperature Deposition of Silicon, Molybdenum and Germanium onto Aluminum Substrates

NASA Astrophysics Data System (ADS)

Krishnamurthy, Aarti Krishna

Electrochemical deposition of active materials such as Si, Mo and Ge is notoriously difficult, so they are typically deposited using expensive vacuum methods such as chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), and magnetron sputtering. However, for most materials, electrochemical deposition has significant advantages of cost, scalability, and manufacturability. There are two main challenges in depositing these materials from aqueous electrolytes at room temperature, namely their highly cathodic standard reduction potential and the formation of native oxides. This has led researchers to use non-aqueous electrolytes such as organic solvents, room temperature ionic liquids (RTILs), and high temperature molten salts. However, these have drawbacks over aqueous electrolytes such as high cost, low conductivity, flammability, and corrosive behavior. During my PhS studies, these two challenges were overcome by using the galvanic method of deposition and by including HF in the electrolyte. Si thin films are employed in a variety of technologies, including microelectronic and photovoltaic devices, Li ion battery anodes, and corrosion-resistant coatings. A galvanic and a combined galvanic/electroless method of Si deposition were developed using aqueous electrolytes at room temperature to obtain nanoporous and compact films, respectively. These films were characterized to understand the surface morphology, thickness, crystallinity, growth rate, composition and nucleation behavior. Approximately 7-10 µm thick compact Si films were achieved with a deposition time of around 28 hours. The galvanic method of deposition was also extended to deposit compact Mo films. Mo thin films have a number of technological applications, including back contacts for CIGS/CZTS photovoltaic devices and corrosion-resistant coatings. Mo thin films were also thoroughly characterized and approximately 4.5 µm thick films were obtained after 3 hours. Similar to Si depostion, a galvanic method of deposition and the galvanic/electroless method of deposition was tested for the deposition of Ge. However no Ge deposit could be consistently obtained, probably due to oxyanion formation in aqueous hexaflurogermante solution.

Silicon-germanium and platinum silicide nanostructures for silicon based photonics

NASA Astrophysics Data System (ADS)

Storozhevykh, M. S.; Dubkov, V. P.; Arapkina, L. V.; Chizh, K. V.; Mironov, S. A.; Chapnin, V. A.; Yuryev, V. A.

2017-05-01

This paper reports a study of two types of silicon based nanostructures prospective for applications in photonics. The first ones are Ge/Si(001) structures forming at room temperature and reconstructing after annealing at 600°C. Germanium, being deposited from a molecular beam at room temperature on the Si(001) surface, forms a thin granular film composed of Ge particles with sizes of a few nanometers. A characteristic feature of these films is that they demonstrate signs of the 2 x 1 structure in their RHEED patterns. After short-term annealing at 600°C under the closed system conditions, the granular films reconstruct to heterostructures consisting of a Ge wetting layer and oval clusters of Ge. A mixed type c(4x2) + p(2x2) reconstruction typical to the low-temperature MBE (Tgr < 600°C) forms on the wetting layer. Long-term annealing of granular films at the same conditions results in formation of c(4x2)-reconstructed wetting layer typical to high-temperature MBE (Tgr < 600°C) and huge clusters of Ge. The other type of the studied nanostructures is based on Pt silicides. This class of materials is one of the friendliest to silicon technology. But as silicide film thickness reaches a few nanometers, low resistivity becomes of primary importance. Pt3Si has the lowest sheet resistance among the Pt silicides. However, the development of a process of thin Pt3Si films formation is a challenging task. This paper describes formation of a thin Pt3Si/Pt2Si structures at room temperature on poly-Si films. Special attention is paid upon formation of poly-Si and amorphous Si films on Si3N4 substrates at low temperatures.

OXIDATION OF TRANSURANIC ELEMENTS

DOEpatents

Moore, R.L.

1959-02-17

A method is reported for oxidizing neptunium or plutonium in the presence of cerous values without also oxidizing the cerous values. The method consists in treating an aqueous 1N nitric acid solution, containing such cerous values together with the trivalent transuranic elements, with a quantity of hydrogen peroxide stoichiometrically sufficient to oxidize the transuranic values to the hexavalent state, and digesting the solution at room temperature.

A single electron nanomechanical Y-switch.

PubMed

Kim, Chulki; Kim, Hyun-Seok; Prada, Marta; Blick, Robert H

2014-08-07

We demonstrate current switching in the frequency domain using a nanomechanical shuttle with three terminals operating at room temperature. The shuttle consists of a metallic island on top of a Si nanopillar forming the Y-junction. A flexural mode of the nanopillar is excited by applying an external bias to one of the contacts, allowing electrons to be shuttled across the oscillating island.

Fabrication method for a room temperature hydrogen sensor

NASA Technical Reports Server (NTRS)

Shukla, Satyajit V. (Inventor); Cho, Hyoung (Inventor); Seal, Sudipta (Inventor); Ludwig, Lawrence (Inventor)

2011-01-01

A sensor for selectively determining the presence and measuring the amount of hydrogen in the vicinity of the sensor. The sensor comprises a MEMS device coated with a nanostructured thin film of indium oxide doped tin oxide with an over layer of nanostructured barium cerate with platinum catalyst nanoparticles. Initial exposure to a UV light source, at room temperature, causes burning of organic residues present on the sensor surface and provides a clean surface for sensing hydrogen at room temperature. A giant room temperature hydrogen sensitivity is observed after making the UV source off. The hydrogen sensor of the invention can be usefully employed for the detection of hydrogen in an environment susceptible to the incursion or generation of hydrogen and may be conveniently used at room temperature.

Quasi-Solid-State Rechargeable Li-O2 Batteries with High Safety and Long Cycle Life at Room Temperature.

PubMed

Cho, Sung Man; Shim, Jimin; Cho, Sung Ho; Kim, Jiwoong; Son, Byung Dae; Lee, Jong-Chan; Yoon, Woo Young

2018-05-09

As interest in electric vehicles and mass energy storage systems continues to grow, Li-O 2 batteries are attracting much attention as a candidate for next-generation energy storage systems owing to their high energy density. However, safety problems related to the use of lithium metal anodes have hampered the commercialization of Li-O 2 batteries. Herein, we introduced a quasi-solid polymer electrolyte with excellent electrochemical, chemical, and thermal stabilities into Li-O 2 batteries. The ion-conducting QSPE was prepared by gelling a polymer network matrix consisting of poly(ethylene glycol) methyl ether methacrylate, methacrylated tannic acid, lithium trifluoromethanesulfonate, and nanofumed silica with a small amount of liquid electrolyte. The quasi-solid-state Li-O 2 cell consisted of a lithium powder anode, a quasi-solid polymer electrolyte, and a Pd 3 Co/multiwalled carbon nanotube cathode, which enhanced the electrochemical performance of the cell. This cell, which exhibited improved safety owing to the suppression of lithium dendrite growth, achieved a lifetime of 125 cycles at room temperature. These results show that the introduction of a quasi-solid electrolyte is a potentially new alternative for the commercialization of solid-state Li-O 2 batteries.

Flexible interfaces between Si anodes and composite electrolytes consisting of poly(propylene carbonates) and garnets for solid-state batteries

NASA Astrophysics Data System (ADS)

Huo, Hanyu; Sun, Jiyang; chen, Cheng; Meng, Xianglu; He, Minghui; Zhao, Ning; Guo, Xiangxin

2018-04-01

Flexible interfaces between Si anodes and composite electrolytes consisting of poly(propylene carbonates) (PPCs) and garnets have been fabricated. The solid polymer electrolytes (SPEs) of PPC/garnet/LiTFSI show the conductivity of 4.2 × 10-4 S cm-1 at room temperature. Their combination with the Si layer anodes allows great alleviation of internal stress resulting from the large volume variation during lithiation and delithiation process of Si anodes. As a result, the Si/SPE/Li cells exhibit 2520 mAh g-1, 2260 mAh g-1, 1902 mAh g-1, 1342 mAh g-1 at 0.1 C, 0.2 C, 0.5 C, and 1 C, respectively. Furthermore, with such compatible and stable interfaces of Si/SPE and the LiFePO4 cathodes in solid-state batteries, the specific capacity of 2296 mAh g-1 in terms of Si is obtained, which remains 82.6% after 100 cycles at room temperature and 0.1 C. The results here indicate that constructing of flexible interfaces between Si anodes and SPEs is a promising strategy to develop high performance solid-state batteries.

Microstructure and Mechanical Properties of Reaction-Formed Joints in Reaction Bonded Silicon Carbide Ceramics

NASA Technical Reports Server (NTRS)

Singh, M.

1998-01-01

A reaction-bonded silicon carbide (RB-SiC) ceramic material (Carborundum's Cerastar RB-SIC) has been joined using a reaction forming approach. Microstructure and mechanical properties of three types of reaction-formed joints (350 micron, 50-55 micron, and 20-25 micron thick) have been evaluated. Thick (approximately 350 micron) joints consist mainly of silicon with a small amount of silicon carbide. The flexural strength of thick joints is about 44 plus or minus 2 MPa, and fracture always occurs at the joints. The microscopic examination of fracture surfaces of specimens with thick joints tested at room temperature revealed the failure mode to be typically brittle. Thin joints (<50-55 micron) consist of silicon carbide and silicon phases. The room and high temperature flexural strengths of thin (<50-55 micron) reaction-formed joints have been found to be at least equal to that of the bulk Cerastar RB-SIC materials because the flexure bars fracture away from the joint regions. In this case, the fracture origins appear to be inhomogeneities inside the parent material. This was always found to be the case for thin joints tested at temperatures up to 1350C in air. This observation suggests that the strength of Cerastar RB-SIC material containing a thin joint is not limited by the joint strength but by the strength of the bulk (parent) materials.

Precipitation hardening behaviour of Al-Mg-Si alloy processed by cryorolling and room temperature rolling

NASA Astrophysics Data System (ADS)

Hussain, Maruff; Nageswara rao, P.; Singh, Dharmendra; Jayaganthan, R.

2018-04-01

The precipitation hardenable aluminium alloy (Al-Mg-Si) plates were solutionized and subjected to rolling at room temperature and liquid nitrogen temperature (RTR, CR) up to a true strain of ∼2.7. The rolled sheets were uniformly aged at room temperature and above room temperature (125 °C) to induce precipitation. The rolled and aged samples were analysed using differential scanning calorimetry (DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM), hardness and tensile tests. The strength and ductility were simultaneously improved after controlled ageing of the cryorolled (CR) and room temperature rolled (RTR) samples. However, the increment in strength is more in RTR material than CR material with same ductility. Transmission electron microscopy analysis revealed the formation of ultrafine grains (UFG) filled with dislocations and nanosized precipitates in the CR and RTR conditions after ageing treatment. The behaviour of CR and RTR alloy is same under natural ageing conditions.

Giant Polarization Rotation in BiFeO3/SrTiO3 Thin Films.

NASA Astrophysics Data System (ADS)

Langner, M. C.; Chu, Y. H.; Martin, L. M.; Gajek, M.; Ramesh, R.; Orenstein, J.

2008-03-01

We use optical second harmonic generation to probe dynamics of the ferroelectric polarization in (111) oriented BiFeO3 thin films grown on SrTiO3 substrates. The second harmonic response indicates 3m point group symmetry and is consistent with a spontaneous polarization normal to the surface of the film. We measure large changes in amplitude and lowering of symmetry, consistent with polarization rotation, when modest electric fields are applied in the plane of the film. At room temperature the rotation is an order of magnitude larger than expected from reported values of the dielectric constant and increases further (as 1/T) as temperature is lowered. We propose a substrate interaction model to explain these results.

Near-room-temperature Mid-infrared Photoconductor Signal and Noise Characterization

DTIC Science & Technology

2012-09-01

Near-room-temperature Mid-infrared Photoconductor Signal and Noise Characterization by Justin R. Bickford, Neal K. Bambha, and Wayne H. Chang...Adelphi, MD 20783-1197 ARL-TR-6169 September 2012 Near-room-temperature Mid-infrared Photoconductor Signal and Noise Characterization...temperature Mid-infrared Photoconductor Signal and Noise Characterization 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6

Visible GaAs/0.7/P/0.3/ CW heterojunction lasers

NASA Technical Reports Server (NTRS)

Kressel, H.; Olsen, G. H.; Nuese, C. J.

1977-01-01

The paper reports the first low-threshold red-light-emitting heterojunction laser diodes consisting of lattice-matched Ga(As,P)/(In,Ga)P heteroepitaxial layers. A room-temperature threshold current of 3400 A/sq cm was obtained at a wavelength of about 7000 A; this value is substantially lower than those achieved at this wavelength with (Al,Ga)As lasers. For the first time, continuous-wave laser operation at temperatures as high as 10 C has been obtained for GaAs(1-x)P(x).

Internally Consistent Single-Crystal Elasticity of (Mg0.89Fe0.11)2SiO4 Wadsleyite at High Pressures and High Temperatures

NASA Astrophysics Data System (ADS)

Buchen, J.; Marquardt, H.; Kurnosov, A.; Boffa Ballaran, T.; Speziale, S.; Kawazoe, T.

2016-12-01

The transition zone in Earth's upper mantle attains a pivotal role in deep Earth dynamics. Various scenarios for the fate of subducted lithospheric slabs have been identified from seismic tomographic images while petrological observations point to potential reservoirs of volatile elements in the transition zone. Among the mineral phases expected to assemble a mantle rock at depths between 410 km and 520 km, wadsleyite stands out with a remarkable hydrogen storage capacity of several weight percent H2O, a volume fraction of about 60 % for a pyrolitic mantle composition, and the potential to cause seismic anisotropy. Interpretations of seismological observations in terms of the thermal and mineralogical state of the upper transition zone rely on the elastic properties of wadsleyite at the prevailing conditions of pressure and temperature including its elastic anisotropy. We have determined internally consistent single-crystal elastic constants for wadsleyite with a relevant composition ((Mg0.89Fe0.11)1.98H0.04SiO4, 0.25(3) wt-% H2O) up to a pressure of 16 GPa at room temperature and conducted first measurements at combined high pressures and high temperatures. Single-crystal segments were cut from oriented thin sections with a focused ion beam and complementary orientations loaded together into the same pressure chamber of resistively heated diamond anvil cells. Using this two-sample approach and a combination of Brillouin spectroscopy and single-crystal X-ray diffraction, all nine independent elastic constants can be obtained under consistent conditions of pressure and temperature. Comparison of our room temperature results with those reported for wadsleyites with different iron contents suggests a very small effect of Fe-Mg substitution on the bulk modulus while the shear modulus decreases with increasing iron content. This differential effect of iron on the elastic moduli bears the potential to be seismically distinguishable from the signatures of temperature or other chemical substituents like volatile elements. The two-sample approach is currently being extended to four crystal segments to directly quantify the effect of hydrogen incorporation on the elastic behavior of iron-bearing wadsleyite.

Thermal effects on the mechanical properties of SiC fiber reinforced reaction bonded silicon nitride matrix (SiC/RBSN) composites

NASA Technical Reports Server (NTRS)

Bhatt, R. T.; Phillips, R. E.

1988-01-01

The elevated temperature four-point flexural strength and the room temperature tensile and flexural strength properties after thermal shock were measured for ceramic composites consisting of 30 vol pct uniaxially aligned 142 micron diameter SiC fibers in a reaction bonded Si3N4 matrix. The elevated temperature strengths were measured after 15 min of exposure in air at temperatures to 1400 C. Thermal shock treatment was accomplished by heating the composite in air for 15 min at temperatures to 1200 C and then quenching in water at 25 C. The results indicate no significant loss in strength properties either at temperature or after thermal shock when compared with the strength data for composites in the as-fabricated condition.

Structural and elastic properties of InX (X = P, As, Sb) at pressure and room temperature

NASA Astrophysics Data System (ADS)

Pawar, Pooja; Singh, Sadhna

2018-06-01

We have investigated the pressure-induced phase transition of InX (X = P, As, Sb) from Zinc-Blende (ZB) to NaCl structure by using realistic interaction potential model involving the effect of temperature. This model consists of Coulomb interaction, three-body interaction and short-range overlap repulsive interaction upto the second nearest neighbor involving temperature. Phase-transition pressure is associated with a sudden collapse in volume, showing the incidence of first-order phase transition. The phase-transition pressure is associated with volume collapses, and the elastic constants obtained from the present model indicate good agreement with the available experimental and theoretical data.

High-throughput resistivity apparatus for thin-film combinatorial libraries

NASA Astrophysics Data System (ADS)

Hewitt, K. C.; Casey, P. A.; Sanderson, R. J.; White, M. A.; Sun, R.

2005-09-01

An apparatus, capable of measuring the dc resistance versus temperature of a 49-member library prepared by thin-film deposition techniques was designed and tested. The library is deposited by dc magnetron sputtering onto 10.16cm×10.16cm alumina substrates on which are placed aluminum masks consisting of 8mm diam holes cut on a 7×7 grid, the center-to-center spacing being 10.15mm. Electrical contact to the library is made in a standard van der Pauw geometry using 196 spring-loaded, gold-coated pins, four pins for each member of the library. The temperature is controlled using a helium refrigerator in combination with a liquid-nitrogen radiation shield that greatly reduces radiative heating of the sample stage. With the radiation shield, the cold finger is able to sustain a minimum temperature of 7K and the sample stage a minimum temperature of 27K. The temperature (27-291K) dependent dc resistivity of a thin-film silver library of varying thickness (48-639nm) is presented to highlight the capabilities of the apparatus. The thickness dependence of both the resistivity and the temperature coefficient of resistivity are quantitatively consistent with the literature. For thicknesses greater than about 100nm, the room-temperature resistivity (3.4μΩcm) are consistent with Matthiessen's rule for 1%-2% impurity content, and the temperature coefficient of resistivity is consistent with the bulk value. For thicknesses less than 100nm, an increase in resistivity by a factor of 8 is found, which may be due to surface and boundary scattering effects; a corresponding increase in the temperature coefficient of resistivity is consistent with a concomitant decrease in the magnitude of the elastic constants and surface scattering effects.

Pt/ZnO nanoarray nanogenerator as self-powered active gas sensor with linear ethanol sensing at room temperature.

PubMed

Zhao, Yayu; Lai, Xuan; Deng, Ping; Nie, Yuxin; Zhang, Yan; Xing, Lili; Xue, Xinyu

2014-03-21

A self-powered gas sensor that can actively detect ethanol at room temperature has been realized from a Pt/ZnO nanoarray nanogenerator. Pt nanoparticles are uniformly distributed on the whole surface of ZnO nanowires. The piezoelectric output of Pt/ZnO nanoarrays can act not only as a power source, but also as a response signal to ethanol at room temperature. Upon exposure to dry air and 1500 ppm ethanol at room temperature, the piezoelectric output of the device under the same compressive strain is 0.672 and 0.419 V, respectively. Moreover, a linear dependence of the sensitivity on the ethanol concentration is observed. Such a linear ethanol sensing at room temperature can be attributed to the atmosphere-dependent variety of the screen effect on the piezoelectric output of ZnO nanowires, the catalytic properties of Pt nanoparticles, and the Schottky barriers at Pt/ZnO interfaces. The present results can stimulate research in the direction of designing new material systems for self-powered room-temperature gas sensing.

Critical role of the coupling between the octahedral rotation and A -site ionic displacements in PbZr O3 -based antiferroelectric materials investigated by in situ neutron diffraction

NASA Astrophysics Data System (ADS)

Lu, Teng; Studer, Andrew J.; Yu, Dehong; Withers, Ray L.; Feng, Yujun; Chen, Hua; Islam, S. S.; Xu, Zhuo; Liu, Yun

2017-12-01

This in situ neutron-diffraction study on antiferroelectric (AFE) P b0.99(N b0.02Z r0.65S n0.28T i0.05 ) O3 polycrystalline materials describes systematic structural and associated preferred orientation changes as a function of applied electric field and temperature. It is found that the pristine AFE phase can be poled into the metastable ferroelectric (FE) phase at room temperature. At this stage, both AFE and FE phases consist of modes associated with octahedral rotation and A -site ionic displacements. The temperature-induced phase transition indicates that the octahedral rotation and ionic displacements are weakly coupled in the room-temperature FE phase and decoupled in the high-temperature FE phase. However, both temperature and E -field-induced phase transitions between the AFE and high-temperature FE phase demonstrate the critical role of coupling between octahedral rotation and A -site ionic displacements in stabilizing the AFE structure, which provides not only experimental evidence to support previous theoretical calculations, but also an insight into the design and development of AFE materials. Moreover, the associated preferred orientation evolution in both AFE and FE phases is studied during the phase transitions. It is found that the formation of the preferred orientation can be controlled to tune the samples' FE and AFE properties.

Magnetic Properties of Fe-49Co-2V Alloy and Pure Fe at Room and Elevated Temperatures

NASA Technical Reports Server (NTRS)

De Groh, Henry C., III; Geng, Steven M.; Niedra, Janis M.; Hofer, Richard R.

2018-01-01

The National Aeronautics and Space Administration (NASA) has a need for soft magnetic materials for fission power and ion propulsion systems. In this work the magnetic properties of the soft magnetic materials Hiperco 50 (Fe-49wt%Cr-2V) and CMI-C (commercially pure magnetic iron) were examined at various temperatures up to 600 C. Toroidal Hiperco 50 samples were made from stacks of 0.35 mm thick sheet, toroidal CMI-C specimens were machined out of solid bar stock, and both were heat treated prior to testing. The magnetic properties of a Hiperco 50 sample were measured at various temperatures up to 600 C and then again after returning to room temperature; the magnetic properties of CMI-C were tested at temperatures up to 400 C. For Hiperco 50 coercivity decreased as temperature increased, and remained low upon returning to room temperature; maximum permeability improved (increased) with increasing temperature and was dramatically improved upon returning to room temperature; remanence was not significantly affected by temperature; flux density at H = 0.1 kA/m increased slightly with increasing temperature, and was about 20% higher upon returning to room temperature; flux density at H = 0.5 kA/m was insensitive to temperature. It appears that the properties of Hiperco 50 improved with increasing temperature due to grain growth. There was no significant magnetic property difference between annealed and aged CMI-C iron material; permeability tended to decrease with increasing temperature; the approximate decline in the permeability at 400 C compared to room temperature was 30%; saturation flux density, B(sub S), was approximately equal for all temperatures below 400 C; B(sub S) was lower at 400 C.

Dimer formation and surface alloying: a STM study of lead on Cu(211)

NASA Astrophysics Data System (ADS)

Bartels, L.; Zöphel, S.; Meyer, G.; Henze, E.; Rieder, K.-H.

1997-02-01

We present a STM investigation of Pb adsorption on the Cu(211) surface in the temperature range between 30 K and room temperature. We observe three different kinds of ordered 1D Pb and PbCu chains (nanowires) located at the intrinsic step edges of the Cu(211) surface. On room temperature prepared samples, Pb is found to be incorporated into the step edges of the (211) surface. The first ordered structure consists of CuPb chains at the step edges (p(2 × disorder)) and is followed with increasing coverage by a close packed row of Pb-atoms (p(4 × disorder)). Preparation at low temperature yields Pb-dimers, and the first ordered structure is a row of Pb-dimers at the step edge (p(3 × disorder)) followed with increased coverage by a structure as described above. By systematic manipulation with the tunneling tip, we could get additional insight into the structural elements of the PbCu layer on the atomic scale. Furthermore, by measuring the threshold resistance to detach atoms from different ad-sites, we can approximately determine the binding energy and gain some insight into the thermodynamical parameters involved.

Landau theory and giant room-temperature barocaloric effect in M F 3 metal trifluorides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Corrales-Salazar, A.; Brierley, R. T.; Littlewood, P. B.

The structural phase transitions of MF 3 (M = Al, Cr, V, Fe, Ti, Sc) metal trifluorides are studied within a simple Landau theory consisting of tilts of rigid MF 6 octahedra associated with soft antiferrodistortive optic modes that are coupled to long-wavelength strain generating acoustic phonons. We calculate the temperature and pressure dependence of several quantities such as the spontaneous distortions, volume expansion, and shear strains as well as T - P phase diagrams. By contrasting our model to experiments we quantify the deviations from mean-field behavior and find that the tilt fluctuations of the MF 6 octahedra increasemore » with metal cation size. We apply our model to predict giant barocaloric effects in Sc-substituted TiF 3 of up to about 15 JK -1 kg -1 for modest hydrostatic compressions of 0.2GPa. The effect extends over a wide temperature range of over 140K (including room temperature) due to a large predicted rate, dT c/dP = 723K GPa -1, which exceeds those of typical barocaloric materials. Our results suggest that open lattice frameworks such as the trifluorides are an attractive platform to search for giant barocaloric effects.« less

LiMn2O4–yBryNanoparticles Synthesized by a Room Temperature Solid-State Coordination Method

PubMed Central

2009-01-01

LiMn2O4–yBrynanoparticles were synthesized successfully for the first time by a room temperature solid-state coordination method. X-ray diffractometry patterns indicated that the LiMn2O4–yBrypowders were well-crystallized pure spinel phase. Transmission electron microscopy images showed that the LiMn2O4–yBrypowders consisted of small and uniform nanosized particles. Synthesis conditions such as the calcination temperature and the content of Br−were investigated to optimize the ideal condition for preparing LiMn2O4–yBrywith the best electrochemical performances. The optimized synthesis condition was found in this work; the calcination temperature is 800 °C and the content of Br−is 0.05. The initial discharge capacity of LiMn2O3.95Br0.05obtained from the optimized synthesis condition was 134 mAh/g, which is far higher than that of pure LiMn2O4, indicating introduction of Br−in LiMn2O4is quite effective in improving the initial discharge capacity. PMID:20628635

Luminescent Thermochromism of 2D Coordination Polymers Based on Copper(I) Halides with 4-Hydroxythiophenol

PubMed Central

Troyano, Javier; Perles, Josefina; Amo-Ochoa, Pilar; Martínez, Jose Ignacio; Concepción Gimeno, Maria; Fernández-Moreira, Vanesa; Zamora, Félix; Delgado, Salomé

2016-01-01

Solvothermal reactions between copper(I) halides and 4-mercaptophenol give rise to the formation of three coordination polymers with general formula [Cu3X(HT)2]n (X= Cl, 1; Br, 2; and I, 3). The structures of these coordination polymers have been determined by X-ray diffraction at both room temperature and low temperature (110 K), showing a general shortening in Cu-S, Cu-X and Cu···Cu bond distances at low temperatures. 1 and 2 are isostructural consisting of layers in which the halogen ligands act as μ3-bridges joining two Cu1 and one Cu2 atoms whereas in 3 the iodine ligands is as μ4-mode but the layers are quasi-isostructural with 1 or 2. These compounds show a reversible thermochromic luminescence, with strong orange emission for 1 and 2, but weaker for 3 at room temperature, while upon cooling at 77 K 1 and 2 show stronger yellow as well as 3 displays stronger green emission. DFT calculations have been used to rationalise these observations. These results suggest a high potential for this novel and promising stimuli-responsive materials. PMID:27809369

A Practical Method for the Vinylation of Aromatic Halides using Inexpensive Organosilicon Reagents

PubMed Central

Denmark, Scott E.; Butler, Christopher R.

2009-01-01

The preparation of styrenes by palladium-catalyzed cross-coupling of aromatic iodides and bromides with divinyltetramethyldisiloxane (DVDS) in the presence of inexpensive silanolate activators has been developed. To facilitate the discovery of optimal reaction conditions, Design of Experiment protocols were used. By the guided selection of reagents, stoichiometries, temperatures, and solvents the vinylation reaction was rapidly optimized with three stages consisting of ca. 175 experiments (of a possible 1440 combinations). A variety of aromatic iodides undergo cross-coupling at room temperature in the presence of potassium trimethylsilanoate using Pd(dba)2 in DMF in good yields. Triphenylphosphine oxide is needed to extend catalyst lifetime. Application of these conditions to aryl bromides was accomplished by the development of two complementary protocols. First, the direct implementation of the successful reaction conditions using aryl iodides at elevated temperature in THF provided the corresponding styrenes in good to excellent yields. Alternatively, the use of potassium triethylsilanolate and a bulky “Buchwald-type” ligand allows for the vinylation reactions to occur at or just above room temperature. A wide range of bromides underwent coupling in good yields for each of the protocols described. PMID:18303892

Light-trapping for room temperature Bose-Einstein condensation in InGaAs quantum wells.

PubMed

Vasudev, Pranai; Jiang, Jian-Hua; John, Sajeev

2016-06-27

We demonstrate the possibility of room-temperature, thermal equilibrium Bose-Einstein condensation (BEC) of exciton-polaritons in a multiple quantum well (QW) system composed of InGaAs quantum wells surrounded by InP barriers, allowing for the emission of light near telecommunication wavelengths. The QWs are embedded in a cavity consisting of double slanted pore (SP2) photonic crystals composed of InP. We consider exciton-polaritons that result from the strong coupling between the multiple quantum well excitons and photons in the lowest planar guided mode within the photonic band gap (PBG) of the photonic crystal cavity. The collective coupling of three QWs results in a vacuum Rabi splitting of 3% of the bare exciton recombination energy. Due to the full three-dimensional PBG exhibited by the SP2 photonic crystal (16% gap to mid-gap frequency ratio), the radiative decay of polaritons is eliminated in all directions. Due to the short exciton-phonon scattering time in InGaAs quantum wells of 0.5 ps and the exciton non-radiative decay time of 200 ps at room temperature, polaritons can achieve thermal equilibrium with the host lattice to form an equilibrium BEC. Using a SP2 photonic crystal with a lattice constant of a = 516 nm, a unit cell height of 2a=730nm and a pore radius of 0.305a = 157 nm, light in the lowest planar guided mode is strongly localized in the central slab layer. The central slab layer consists of 3 nm InGaAs quantum wells with 7 nm InP barriers, in which excitons have a recombination energy of 0.944 eV, a binding energy of 7 meV and a Bohr radius of aB = 10 nm. We take the exciton recombination energy to be detuned 35 meV above the lowest guided photonic mode so that an exciton-polariton has a photonic fraction of approximately 97% per QW. This increases the energy range of small-effective-mass photonlike states and increases the critical temperature for the onset of a Bose-Einstein condensate. With three quantum wells in the central slab layer, the strong light confinement results in light-matter coupling strength of ℏΩ = 13.7 meV. Assuming an exciton density per QW of (15aB)^-2, well below the saturation density, in a 2-D box-trap with a side length of 10 to 500 µm, we predict thermal equilibrium Bose-Einstein condensation well above room temperature.

Power supply system for the superconducting outsert of the CHMFL hybrid magnet

NASA Astrophysics Data System (ADS)

Fang, Z.; Zhu, J.; Chen, W.; Jiang, D.; Huang, P.; Chen, Z.; Tan, Y.; Kuang, G.

2017-12-01

The construction of a new hybrid magnet, consisting of a 11 T superconducting outsert and a 34 T resistive insert magnet, has been finished at the Chinese High Magnetic Field Laboratory (CHMFL) in Hefei. With a room temperature bore of 800 mm in diameter, the hybrid magnet superconducting outsert is composed of four separate Nb3Sn-based Cable-in-Conduit Conductor (CICC) coils electrically connected in series and powered by a single power supply system. The power supply system for the superconducting outsert consists of a 16 kA DC power supply, a quench protection system, a pair of 16 kA High Temperature Superconducting (HTS) current leads, and two Low Temperature Superconducting bus-lines. The design and manufacturing of the power supply system have been completed at the CHMFL. This paper describes the design features of the power supply system as well as the current fabrication condition of its main components.

Evidence for Kinetic Limitations as a Controlling Factor of Ge Pyramid Formation: a Study of Structural Features of Ge/Si(001) Wetting Layer Formed by Ge Deposition at Room Temperature Followed by Annealing at 600 °C.

PubMed

Storozhevykh, Mikhail S; Arapkina, Larisa V; Yuryev, Vladimir A

2015-12-01

The article presents an experimental study of an issue of whether the formation of arrays of Ge quantum dots on the Si(001) surface is an equilibrium process or it is kinetically controlled. We deposited Ge on Si(001) at the room temperature and explored crystallization of the disordered Ge film as a result of annealing at 600 °C. The experiment has demonstrated that the Ge/Si(001) film formed in the conditions of an isolated system consists of the standard patched wetting layer and large droplike clusters of Ge rather than of huts or domes which appear when a film is grown in a flux of Ge atoms arriving on its surface. We conclude that the growth of the pyramids appearing at temperatures greater than 600 °C is controlled by kinetics rather than thermodynamic equilibrium whereas the wetting layer is an equilibrium structure. Primary 68.37.Ef; 68.55.Ac; 68.65.Hb; 81.07.Ta; 81.16.Dn.

Stability of headspace volatiles in a ‘Fallglo’ tangerine juice matrix system at room temperature

USDA-ARS?s Scientific Manuscript database

Gas chromatography systems are usually equipped with autosamplers. Samples held in the autosampler tray can stay up to one day or longer at room temperature, if the tray is not equipped with a cooling mechanism. The objective of this research was to determine if holding samples at room temperature i...

Biogas utilization for drying sweet potato chips by using infrared dryer

NASA Astrophysics Data System (ADS)

Sriharti, Rahayuningtyas, Ari; Susanti, Novita Dwi; Sitompul, Rislima Febriani

2017-11-01

This study aims to utilize biogas, that produced from organic waste, as fuel for infrared dryers. The digester was dome type, which made from fiberglass, 5.5 m3 capacities, gas container made from soft PVC, 5.6 m3 capacities. The infrared dryer was household scale which have dimension 2000 mm x 2000 mm x 2000 mm, it is consist of 2 racks, which have size 1500 mm x 500 mm x 1400 mm, and consist of 44 baking pans (600 mm X 400 mm x 30 mm), the dryer has 36 kg of capacity. The parameters observed include ambient temperature, temperature inside the digester, pH value, biogas production, drying room temperature, moisture content of sweet potato and biogas consumption for drying. Infrared dryer is used to dry the sweet potato slices thickness of 2 mm with total amount 12 kg, at room temperature dryer ± 60 °C. The results showed that the average biogas production was 1.335 m3 per day, at a temperature of 26 - 35 °C and the neutral pH value was 6.99 - 7.7. 12 kg of sweet potato sliced dried for 4 hours, the initial moisture content of 79.68 % decreased to 8.98 %, the consumption of biogas used 4,952 m3. The final result of drying process of sweet potato slices of 3.5 kg, there was a shrinkage of 70.83 %. Characterization of sweet potato slices is 3 % protein, 0,6 % fat, 94 % carbohydrate and 2 % ash. These sweet potato can be used as flour for cookies and cake raw materials, the use of sweet potato flour can reach 50 - 100 %.

Water vapor self-continuum absorption measurements in the 4.0 and 2.1 μm transparency windows

NASA Astrophysics Data System (ADS)

Richard, L.; Vasilchenko, S.; Mondelain, D.; Ventrillard, I.; Romanini, D.; Campargue, A.

2017-11-01

In a recent contribution [A. Campargue, S. Kassi, D. Mondelain, S. Vasilchenko, D. Romanini, Accurate laboratory determination of the near infrared water vapor self-continuum: A test of the MT_CKD model. J. Geophys. Res. Atmos., 121,13,180-13,203, doi:10.1002/2016JD025531], we reported accurate water vapor absorption continuum measurements by Cavity Ring-down Spectroscopy (CRDS) and Optical-Feedback-Cavity Enhanced Absorption Spectroscopy (OF-CEAS) at selected spectral points of 4 near infrared transparency windows. In the present work, the self-continuum cross-sections, CS, are determined for two new spectral points. The 2491 cm-1 spectral point in the region of maximum transparency of the 4.0 μm window was measured by OF-CEAS in the 23-52 °C temperature range. The 4435 cm-1 spectral point of the 2.1 μm window was measured by CRDS at room temperature. The self-continuum cross-sections were determined from the pressure squared dependence of the continuum absorption. Comparison to the literature shows a reasonable agreement with 1970 s and 1980 s measurements using a grating spectrograph in the 4.0 μm window and a very good consistency with our previous laser measurements in the 2.1 μm window. For both studied spectral points, our values are much smaller than previous room temperature measurements by Fourier Transform Spectroscopy. Significant deviations (up to about a factor 4) are noted compared to the widely used semi empirical MT_CKD model of the absorption continuum. The measured temperature dependence at 2491 cm-1 is consistent with previous high temperature measurements in the 4.0 μm window and follows an exp(D0/kT) law, D0 being the dissociation energy of the water dimer.

Room-temperature multiferroic and magnetocapacitance effects in M-type hexaferrite BaFe10.2Sc1.8O19

NASA Astrophysics Data System (ADS)

Tang, Rujun; Zhou, Hao; You, Wenlong; Yang, Hao

2016-08-01

The room-temperature multiferroic and magnetocapacitance (MC) effects of polycrystalline M-type hexaferrite BaFe10.2Sc1.8O19 have been investigated. The results show that the magnetic moments of insulating BaFe10.2Sc1.8O19 can be manipulated by the electric field at room temperature, indicating the existence of magnetoelectric coupling. Moreover, large MC effects are also observed around the room temperature. A frequency dependence analysis shows that the Maxwell-Wagner type magnetoresistance effect is the dominant mechanism for MC effects at low frequencies. Both the magnetoelectric-type and non-magnetoelectric-type spin-phonon couplings contribute to the MC effects at high frequencies with the former being the dominant mechanism. The above results show that the hexaferrite BaFe10.2Sc1.8O19 is a room-temperature multiferroic material that can be potentially used in magnetoelectric devices.

On-site chemical pre-lithiation of S cathode at room temperature on a 3D nano-structured current collector

NASA Astrophysics Data System (ADS)

Wu, Yunwen; Momma, Toshiyuki; Ahn, Seongki; Yokoshima, Tokihiko; Nara, Hiroki; Osaka, Tetsuya

2017-10-01

This work reports a new chemical pre-lithiation method to fabricate lithium sulfide (Li2S) cathode. This pre-lithiation process is taken place simply by dropping the organolithium reagent lithium naphthalenide (Li+Naph-) on the prepared sulfur cathode. It is the first time realizing the room temperature chemical pre-lithaition reaction attributed by the 3D nanostructured carbon nanotube (CNT) current collector. It is confirmed that the Li2S cathode fabricated at room temperature showing higher capacity and lower hysteresis than the Li2S cathode fabricated at high temperature pre-lithiation. The pre-lithiated Li2S cathode at room temperature shows stable cycling performance with a 600 mAh g-1 capacity after 100 cycles at 0.1 C-rate and high capacity of 500 mAh g-1 at 2 C-rate. This simple on-site pre-lithiation method at room temperature is demonstrated to be applicable for the in-situ pre-lithiation in a Li metal free battery.

Interim report on nuclear waste depository thermal analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Altenbach, T.J.

1978-07-25

A thermal analysis of a deep geologic depository for spent nuclear fuel is being conducted. The TRUMP finite difference heat transfer code is used to analyze a 3-dimensional model of the depository. The model uses a unit cell consisting of one spent fuel canister buried in salt beneath a ventilated room in the depository. A base case was studied along with several parametric variations. It is concluded that this method is appropriate for analyzing the thermal response of the system, and that the most important parameter in determining the maximum temperatures is the canister heat generation rate. The effects ofmore » room ventilation and different depository media are secondary.« less

Hydrogen-atmosphere induction furnace has increased temperature range

NASA Technical Reports Server (NTRS)

Caves, R. M.; Gresslin, C. H.

1966-01-01

Improved hydrogen-atmosphere induction furnace operates at temperatures up to 5,350 deg F. The furnace heats up from room temperature to 4,750 deg F in 30 seconds and cools down to room temperature in 2 minutes.

Highly sensitive response of solution-processed bismuth sulfide nanobelts for room-temperature nitrogen dioxide detection.

PubMed

Kan, Hao; Li, Min; Song, Zhilong; Liu, Sisi; Zhang, Baohui; Liu, Jingyao; Li, Ming-Yu; Zhang, Guangzu; Jiang, ShengLin; Liu, Huan

2017-11-15

Low dimensional nanomaterials have emerged as candidates for gas sensors owing to their unique size-dependent properties. In this paper, Bi 2 S 3 nanobelts were synthesized via a facile solvothermal process and spin-coated onto alumina substrates at room temperature. The conductometric devices can even sensitively response to the relatively low concentrations of NO 2 at room temperature, and their sensing performance can be effectively enhanced by the ligand exchange treatment with inorganic salts. The Pb(NO 3 ) 2 -treated device exhibited superior sensing performance of 58.8 under 5ppm NO 2 at room-temperature, with the response and recovery time of 28 and 106s. The competitive adsorption of NO 2 against O 2 on Bi 2 S 3 nanobelts, with the enhancement both in gas adsorption and charge transfer caused by the porous network of the very thin Bi 2 S 3 nanobelts, can be a reasonable explanation for the improved performance at room temperature. Their sensitive room-temperature response behaviors combined with the excellent solution processability, made Bi 2 S 3 nanobelts very attractive for the construction of low-cost gas sensors with lower power consumption. Copyright © 2017 Elsevier Inc. All rights reserved.

Investigation of tension-compression fatigue behavior of a cross-ply metal matrix composite at room and elevated temperatures. Master's thesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boyum, E.A.

1993-12-01

This research, the first load-controlled tension-compression fatigue testing to be performed on a MMC, extends the existing knowledge of MMC fatigue damage mechanisms to include the tension compression loading condition. To accomplish this, a (0/90)2, SCS-6/Ti-15-3 laminate was subjected to tension-tension fatigue at room temperature, and tension-compression fatigue at both room temperature and 427 deg C. Stress and strain data was taken to evaluate the macro-mechanic behavior of the material. Microscopy and fractography were performed to characterize the damage on a micro-mechanic level. On a maximum applied stress basis, the room temperature tension-tension specimens had longer fatigue lives than themore » room temperature tension-compression specimens. The room and high temperature tension-compression fatigue lives were nearly identical in the fiber-dominated high stress region of the SN curve. However, the increased ductility and diffused plasticity of the titanium matrix at 427 deg C delayed the onset and severity of matrix cracking, and thus increased the elevated temperature fatigue lives in the matrix dominated region of the SN curve. In all cases, matrix damage initiated at reaction zone cracks which nucleated both matrix plasticity and matrix cracking. Metal matrix composite, Elevated temperature, Fatigue testing, Compression, Fully-reversed, Titanium, Silicon carbide.« less

Room-temperature electron spin relaxation of nitroxides immobilized in trehalose: Effect of substituents adjacent to NO-group

NASA Astrophysics Data System (ADS)

Kuzhelev, Andrey A.; Strizhakov, Rodion K.; Krumkacheva, Olesya A.; Polienko, Yuliya F.; Morozov, Denis A.; Shevelev, Georgiy Yu.; Pyshnyi, Dmitrii V.; Kirilyuk, Igor A.; Fedin, Matvey V.; Bagryanskaya, Elena G.

2016-05-01

Trehalose has been recently promoted as efficient immobilizer of biomolecules for room-temperature EPR studies, including distance measurements between attached nitroxide spin labels. Generally, the structure of nitroxide influences the electron spin relaxation times, being crucial parameters for room-temperature pulse EPR measurements. Therefore, in this work we investigated a series of nitroxides with different substituents adjacent to NO-moiety including spirocyclohexane, spirocyclopentane, tetraethyl and tetramethyl groups. Electron spin relaxation times (T1, Tm) of these radicals immobilized in trehalose were measured at room temperature at X- and Q-bands (9/34 GHz). In addition, a comparison was made with the corresponding relaxation times in nitroxide-labeled DNA immobilized in trehalose. In all cases phase memory times Tm were close to 700 ns and did not essentially depend on structure of substituents. Comparison of temperature dependences of Tm at T = 80-300 K shows that the benefit of spirocyclohexane substituents well-known at medium temperatures (∼100-180 K) becomes negligible at 300 K. Therefore, unless there are specific interactions between spin labels and biomolecules, the room-temperature value of Tm in trehalose is weakly dependent on the structure of substituents adjacent to NO-moiety of nitroxide. The issues of specific interactions and stability of nitroxide labels in biological media might be more important for room temperature pulsed dipolar EPR than differences in intrinsic spin relaxation of radicals.

Determining temperature limits of drilling fluids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thuren, J.B.; Chenevert, M.E.; Huang, W.T.W.

A capillary three tube viscometer has been designed which allows the measurement of rheological properties of time dependent non-Newtonian fluids in laminar flow at high temperture and pressure. The objective of this investigation is to determine the temperature stability of clay-water suspensions containing various drilling fluid additives. The additives studied consisted of viscosifiers, filtrate reducers, and chemical thinners. The temperature range studied is from room temperature to 550{sup 0}F. The system pressure is consistently maintained above the vapor pressure. The Bentonite and water standardized base mud used is equivalent to a 25 ppB fluid. Stabilization of the base mud ismore » necessary to obtain steady state laminar flow conditions and to obtain reliable temperature thinning effects with each temperature interval under investigation. Generally the temperature levels are maintained for one hour until 550{sup 0}F is attained. The last interval is then maintained until system fluid degradation occurs. Rheological measurements are obtained from differential pressure transducers located in a three diameter tube test section and externally at ambient conditions from a Baroid Rotational Viscometer. The power law model for non-Newtonian fluids is used to correlate the data.« less

Progressive failure site generation in AlGaN/GaN high electron mobility transistors under OFF-state stress: Weibull statistics and temperature dependence

NASA Astrophysics Data System (ADS)

Sun, Huarui; Bajo, Miguel Montes; Uren, Michael J.; Kuball, Martin

2015-01-01

Gate leakage degradation of AlGaN/GaN high electron mobility transistors under OFF-state stress is investigated using a combination of electrical, optical, and surface morphology characterizations. The generation of leakage "hot spots" at the edge of the gate is found to be strongly temperature accelerated. The time for the formation of each failure site follows a Weibull distribution with a shape parameter in the range of 0.7-0.9 from room temperature up to 120 °C. The average leakage per failure site is only weakly temperature dependent. The stress-induced structural degradation at the leakage sites exhibits a temperature dependence in the surface morphology, which is consistent with a surface defect generation process involving temperature-associated changes in the breakdown sites.

Murder or Not? Cold Temperature Makes Criminals Appear to Be Cold-Blooded and Warm Temperature to Be Hot-Headed

PubMed Central

Gockel, Christine; Kolb, Peter M.; Werth, Lioba

2014-01-01

Temperature-related words such as cold-blooded and hot-headed can be used to describe criminal behavior. Words associated with coldness describe premeditated behavior and words associated with heat describe impulsive behavior. Building on recent research about the close interplay between physical and interpersonal coldness and warmth, we examined in a lab experiment how ambient temperature within a comfort zone influences judgments of criminals. Participants in rooms with low temperature regarded criminals to be more cold-blooded than participants in rooms with high temperature. Specifically, they were more likely to attribute premeditated crimes, ascribed crimes resulting in higher degrees of penalty, and attributed more murders to criminals. Likewise, participants in rooms with high temperature regarded criminals to be more hot-headed than participants in rooms with low temperature: They were more likely to attribute impulsive crimes. Results imply that cognitive representations of temperature are closely related to representations of criminal behavior and attributions of intent. PMID:24788725

Murder or not? Cold temperature makes criminals appear to be cold-blooded and warm temperature to be hot-headed.

PubMed

Gockel, Christine; Kolb, Peter M; Werth, Lioba

2014-01-01

Temperature-related words such as cold-blooded and hot-headed can be used to describe criminal behavior. Words associated with coldness describe premeditated behavior and words associated with heat describe impulsive behavior. Building on recent research about the close interplay between physical and interpersonal coldness and warmth, we examined in a lab experiment how ambient temperature within a comfort zone influences judgments of criminals. Participants in rooms with low temperature regarded criminals to be more cold-blooded than participants in rooms with high temperature. Specifically, they were more likely to attribute premeditated crimes, ascribed crimes resulting in higher degrees of penalty, and attributed more murders to criminals. Likewise, participants in rooms with high temperature regarded criminals to be more hot-headed than participants in rooms with low temperature: They were more likely to attribute impulsive crimes. Results imply that cognitive representations of temperature are closely related to representations of criminal behavior and attributions of intent.

Short-term hot hardness characteristics of rolling-element steels

NASA Technical Reports Server (NTRS)

Chevalier, J. L.; Dietrich, M. W.; Zaretsky, E. V.

1972-01-01

Short-term hot hardness studies were performed with five vacuum-melted steels at temperatures from 294 to 887 K (70 to 1140 F). Based upon a minimum Rockwell C hardness of 58, the temperature limitation on all materials studied was dependent on the initial room temperature hardness and the tempering temperature of each material. For the same room temperature hardness, the short-term hot hardness characteristics were identical and independent of material composition. An equation was developed to predict the short-term hardness at temperature as a function of initial room temperature hardness for AISI 52100, as well as the high-speed tool steels.

Diuretic‐sensitive electroneutral Na+ movement and temperature effects on central axons

PubMed Central

Kanagaratnam, Meneka; Pendleton, Christopher; Souza, Danilo Almeida; Pettit, Joseph; Howells, James

2017-01-01

Key points Optic nerve axons get less excitable with warming.F‐fibre latency does not shorten at temperatures above 30°C.Action potential amplitude falls when the Na+‐pump is blocked, an effect speeded by warming.Diuretics reduce the rate of action potential fall in the presence of ouabain.Our data are consistent with electroneutral entry of Na+ occurring in axons and contributing to setting the resting potential. Abstract Raising the temperature of optic nerve from room temperature to near physiological has effects on the threshold, refractoriness and superexcitability of the shortest latency (fast, F) nerve fibres, consistent with hyperpolarization. The temperature dependence of peak impulse latency was weakened at temperatures above 30°C suggesting a temperature‐sensitive process that slows impulse propagation. The amplitude of the supramaximal compound action potential gets larger on warming, whereas in the presence of bumetanide and amiloride (blockers of electroneutral Na+ movement), the action potential amplitude consistently falls. This suggests a warming‐induced hyperpolarization that is reduced by blocking electroneutral Na+ movement. In the presence of ouabain, the action potential collapses. This collapse is speeded by warming, and exposure to bumetanide and amiloride slows the temperature‐dependent amplitude decline, consistent with a warming‐induced increase in electroneutral Na+ entry. Blocking electroneutral Na+ movement is predicted to be useful in the treatment of temperature‐dependent symptoms under conditions with reduced safety factor (Uhthoff's phenomenon) and provide a route to neuroprotection. PMID:28213919

Identification of modes of fracture in a 2618-T6 aluminum alloy using stereophotogrammetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Salas Zamarripa, A., E-mail: a.salaszamarripa@gmail.com; Pinna, C.; Brown, M.W.

2011-12-15

The identification and the development of a quantification technique of the modes of fracture in fatigue fracture surfaces of a 2618-T6 aluminum alloy were developed during this research. Fatigue tests at room and high temperature (230 Degree-Sign C) were carried out to be able to compare the microscopic fractographic features developed by this material under these testing conditions. The overall observations by scanning electron microscopy (SEM) of the fracture surfaces showed a mixture of transgranular and ductile intergranular fracture. The ductile intergranular fracture contribution appears to be more significant at room temperature than at 230 Degree-Sign C. A quantitative methodologymore » was developed to identify and to measure the contribution of these microscopic fractographic features. The technique consisted of a combination of stereophotogrammetry and image analysis. Stereo-pairs were randomly taken along the crack paths and were then analyzed using the profile module of MeX software. The analysis involved the 3-D surface reconstruction, the trace of primary profile lines in both vertical and horizontal directions within the stereo-pair area, the measurements of the contribution of the modes of fracture in each profile, and finally, the calculation of the average contribution in each stereo-pair. The technique results confirmed a higher contribution of ductile intergranular fracture at room temperature than at 230 Degree-Sign C. Moreover, there was no indication of a direct relationship between this contribution and the strain amplitudes range applied during the fatigue testing. - Highlights: Black-Right-Pointing-Pointer Stereophotogrammetry and image analysis as a measuring tool of modes of fracture in fatigue fracture surfaces. Black-Right-Pointing-Pointer A mixture of ductile intergranular and transgranular fracture was identified at room temperature and 230 Degree-Sign C testing. Black-Right-Pointing-Pointer Development of a quantitative methodology to obtain the percentage of modes of fracture within the fracture surface.« less

Stability and accuracy of total and free PSA values in samples stored at room temperature.

PubMed

Forde, J C; Blake, O; Crowley, V E; Lynch, T H

2016-11-01

In 2010, an estimated 476,076 total PSA tests were performed in Ireland, at a cost of €3.6 million with the majority ordered by general practitioners. We aimed to replicate storage conditions at room temperature and see if prolonged storage affected total and free PSA values. Blood samples were taken from 20 male patients in four VACUETTE ® Serum Separator tubes (Greiner-Bio-One, Austria) and stored at room temperature (22 °C) for different time intervals (4, 8, 24, 48 h) before being centrifuged and analyzed. Total PSA (tPSA) and free PSA (fPSA) values were determined using the Tosoh AIA 1800 assay (Tokyo, Japan). Mean tPSA values were measured at 4, 8, 24 and 48 h with values of 7.9, 8.1, 7.8 and 8.0 μg/L, respectively. Values ranged from -1.26 to +2.53 % compared to the initial 4 h interval reading, indicating tPSA remained consistent at room temperature. The tPSA showed no significance between groups (ANOVA, p = 0.283). Mean fPSA values at 4, 8, 24 and 48 h were 2.05, 2.04, 1.83, 1.82 μg/L, respectively. At 24 and 48 h there was 10.73 and 11.22 % reduction, respectively, in fPSA compared to the 4-h time interval, indicating prolonged storage resulted in reduced fPSA values. After 24 h, there was an 8.8 % reduction in the free/total PSA %. The fPSA showed significant differences between groups (ANOVA, p = 0.024). Our recommendation is that samples that have been stored for prolonged amounts of time (greater than 24 h) should not be used for free PSA testing.

Impact of environmental factors on efficacy of upper-room air ultraviolet germicidal irradiation for inactivating airborne mycobacteria.

PubMed

Xu, Peng; Kujundzic, Elmira; Peccia, Jordan; Schafer, Millie P; Moss, Gene; Hernandez, Mark; Miller, Shelly L

2005-12-15

This study evaluated the efficacy of an upper-room air ultraviolet germicidal irradiation (UVGI) system for inactivating airborne bacteria, which irradiates the upper part of a room while minimizing radiation exposure to persons in the lower part of the room. A full-scale test room (87 m3), fitted with a UVGI system consisting of 9 louvered wall and ceiling fixtures (504 W all lamps operating) was operated at 24 and 34 degrees C, between 25 and 90% relative humidity, and at three ventilation rates. Mycobacterium parafortuitum cells were aerosolized into the room such that their numbers and physiologic state were comparable both with and without the UVGI system operating. Airborne bacteria were collected in duplicate using liquid impingers and quantified with direct epifluorescent microscopy and standard culturing assay. Performance of the UVGI system degraded significantly when the relative humidity was increased from 50% to 75-90% RH, the horizontal UV fluence rate distribution was skewed to one side compared to being evenly dispersed, and the room air temperature was stratified from hot at the ceiling to cold at the floor. The inactivation rate increased linearly with effective UV fluence rate up to 5 microW cm(-2); an increase in the fluence rate above this level did not yield a proportional increase in inactivation rate.

Static and Dynamic Disorder in Bacterial Light-Harvesting Complex LH2: A 2DES Simulation Study.

PubMed

Rancova, Olga; Abramavicius, Darius

2014-07-10

Two-dimensional coherent electronic spectroscopy (2DES) is a powerful technique in distinguishing homogeneous and inhomogeneous broadening contributions to the spectral line shapes of molecular transitions induced by environment fluctuations. Using an excitonic model of a double-ring LH2 aggregate, we perform simulations of its 2DES spectra and find that the model of a harmonic environment cannot provide a consistent set of parameters for two temperatures: 77 K and room temperature. This indicates the highly anharmonic nature of protein fluctuations for the pigments of the B850 ring. However, the fluctuations of B800 ring pigments can be assumed as harmonic in this temperature range.

Process for forming retrograde profiles in silicon

DOEpatents

Weiner, K.H.; Sigmon, T.W.

1996-10-15

A process is disclosed for forming retrograde and oscillatory profiles in crystalline and polycrystalline silicon. The process consisting of introducing an n- or p-type dopant into the silicon, or using prior doped silicon, then exposing the silicon to multiple pulses of a high-intensity laser or other appropriate energy source that melts the silicon for short time duration. Depending on the number of laser pulses directed at the silicon, retrograde profiles with peak/surface dopant concentrations which vary are produced. The laser treatment can be performed in air or in vacuum, with the silicon at room temperature or heated to a selected temperature.

Dose Rate Effects in Linear Bipolar Transistors

NASA Technical Reports Server (NTRS)

Johnston, Allan; Swimm, Randall; Harris, R. D.; Thorbourn, Dennis

2011-01-01

Dose rate effects are examined in linear bipolar transistors at high and low dose rates. At high dose rates, approximately 50% of the damage anneals at room temperature, even though these devices exhibit enhanced damage at low dose rate. The unexpected recovery of a significant fraction of the damage after tests at high dose rate requires changes in existing test standards. Tests at low temperature with a one-second radiation pulse width show that damage continues to increase for more than 3000 seconds afterward, consistent with predictions of the CTRW model for oxides with a thickness of 700 nm.

The effects of heated and room-temperature abdominal lavage solutions on core body temperature in dogs undergoing celiotomy.

PubMed

Nawrocki, Michael A; McLaughlin, Ron; Hendrix, P K

2005-01-01

To document the magnitude of temperature elevation obtained with heated lavage solutions during abdominal lavage, 18 dogs were lavaged with sterile isotonic saline intraoperatively (i.e., during a celiotomy). In nine dogs, room-temperature saline was used. In the remaining nine dogs, saline heated to 43+/-2 degrees C (110+/-4 degrees F) was used. Esophageal, rectal, and tympanic temperatures were recorded every 60 seconds for 15 minutes after initiation of the lavage. Temperature levels decreased in dogs lavaged with room-temperature saline. Temperature levels increased significantly in dogs lavaged with heated saline after 2 to 6 minutes of lavage, and temperatures continued to increase throughout the 15-minute lavage period.

Use of infrared thermography to assess the influence of high environmental temperature on rabbits.

PubMed

de Lima, V; Piles, M; Rafel, O; López-Béjar, M; Ramón, J; Velarde, A; Dalmau, A

2013-10-01

The aim of this work was to ascertain if infrared thermography (IRT) can be used on rabbits to assess differences in surface body temperature when they are subjected to two different environmental temperatures outside the comfort zone. Rabbits housed in room A were maintained at a temperature of below 30°C and rabbits in room B at a temperature of above 32°C for a year. Faeces were collected six times during the year to assess stress by means of faecal cortisol metabolites (FCM). The assessment of IRT was carried out to assess maximum and minimum temperatures on the eyes, nose and ears. FCM concentration was higher in room B than A, to confirm that stress conditions were higher in room B. Significant differences in IRT were found between the animals housed in both rooms. It was observed that it was more difficult for animals from room B to maintain a regular heat loss. Although all the body zones used to assess temperature with IRT gave statistical differences, the correlations found between the eyes, nose and ears were moderate, suggesting that they were giving different information. In addition, differences up to 3.36°C were found in the eye temperature of rabbits housed in the same room, with a clear effect of their position in relation to extractors and heating equipments. Therefore, IRT could be a good tool to assess heat stress in animals housed on typical rabbit farm buildings, giving a measure of how the animal is perceiving a combination of humidity, temperature and ventilation. Some face areas were better for analysing images. Minimum temperature on eyes and temperatures on nose are suggested to assess heat losses and critical areas of the farm for heat stress in rabbits. Copyright © 2013 Elsevier Ltd. All rights reserved.

Energy transfer simulation for radiantly heated and cooled enclosures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chapman, K.S.; Zhang, P.

1996-11-01

This paper presents the development of a three-dimensional mathematical model to compute heat transfer within a radiantly heated or cooled room, which then calculates the mass-averaged room air temperature and the wall surface temperature distributions. The radiation formulation used in the model accommodates arbitrary placement of walls and objects within the room. The convection model utilizes Nusselt number correlations published in the open literature. The complete energy transfer model is validated by comparing calculated room temperatures to temperatures measured in a radiantly heated room. This three-dimensional model may be applied to a building to assist the heating/cooling system design engineermore » in sizing a radiant heating/cooling system. By coupling this model with a thermal comfort model, the comfort levels throughout the room can be easily and efficiently mapped for a given radiant heater/cooler location. In addition, obstacles such as airplanes, trucks, furniture, and partitions can be easily incorporated to determine their effect on the radiant heating system performance.« less

Unattended Radiation Sensor Systems for Remote Terrestrial Applications and Nuclear Nonproliferation

DTIC Science & Technology

2002-01-01

liquid nitrogen is not available, or frequent attention is inconvenient and time-consuming. The “box” section contains a Stirling engine cryocooler and...sponsorship of the Defense Threat Reduction Agency (DTRA). The first is a system consisting of a mechanical cryocooler coupled with a high-purity...amplifier, a multichannel analyzer, and gated integrator electronics to process the slow signal pulses generated by room temperature solid state detectors

Development of a Filament-Overwrapped Cryoformed Metal Pressure Vessel

DTIC Science & Technology

1971-01-01

ABSTRACT High performance ARDEFORM cryoformed 301 stainless steel glass fiber reinforced (GFR) vessels were demonstrated by room temperature tests of 13 1...Appendix 6 - Vessel Testing ........... . A-54 7.7 Appendix 7 - Increased Ductility Liner High Performance Spherical GFR Vessel A-62 7.8 Appendix 8...vessel consisting of a load-bearing cryogenically stretched ARDEFORM 301 stainless steel liner overwrapped with fiber- glass for high pressure fluid

Fracture toughness of advanced ceramics at room temperature

NASA Technical Reports Server (NTRS)

Quinn, George D.; Salem, Jonathan; Bar-On, Isa; Cho, Kyu; Foley, Michael; Fang, HO

1992-01-01

Results of round-robin fracture toughness tests on advanced ceramics are reported. A gas-pressure silicon nitride and a zirconia-toughened alumina were tested using three test methods: indentation fracture, indentation strength, and single-edge precracked beam. The latter two methods have produced consistent results. The interpretation of fracture toughness test results for the zirconia alumina composite is shown to be complicated by R-curve and environmentally assisted crack growth phenomena.

Infrared Pyrometry From Room Temperature To 700 Degrees C

NASA Technical Reports Server (NTRS)

Wheeler, Donald R.; Jones, William R., Jr.; Pepper, Stephen V.

1989-01-01

Consistent readings obtained when specimens prepared appropriately. New method largely overcomes limitations. Transmission of infrared increased by replacing customary metal-coated glass viewing port with quartz viewing port covered with tantalum mesh. Commercially available infrared microscope with focal distance of 53 cm focuses on spot only 1 mm wide on specimen. Microscope operated as radiometer. Output of detector varies by several orders of magnitude, processed by logarithmic amplifier before reading.

P-type conductivity in annealed strontium titanate

DOE PAGES

Poole, Violet M.; Corolewski, Caleb D.; McCluskey, Matthew D.

2015-12-17

In this study, Hall-effect measurements indicate p-type conductivity in bulk, single-crystal strontium titanate (SrTiO 3, or STO) samples that were annealed at 1200°C. Room temperature mobilities above 100 cm 2/Vs were measured, an order of magnitude higher than those for electrons (5-10 cm 2/Vs). Average hole densities were in the 10 9-10 10 cm -3 range, consistent with a deep acceptor.

The reduction and oxidation of ceria: A natural abundance triple oxygen isotope perspective

NASA Astrophysics Data System (ADS)

Hayles, Justin; Bao, Huiming

2015-06-01

Ceria (CeO2) is a heavily studied material in catalytic chemistry for use as an oxygen storage medium, oxygen partial pressure regulator, fuel additive, and for the production of syngas, among other applications. Ceria powders are readily reduced and lose structural oxygen when subjected to low pO2 and/or high temperature conditions. Such dis-stoichiometric ceria can then re-oxidize under higher pO2 and/or lower temperature by incorporating new oxygen into the previously formed oxygen site vacancies. Despite extensive studies on ceria, the mechanisms for oxygen adsorption-desorption, dissociation-association, and diffusion of oxygen species on ceria surface and within the crystal structure are not well known. We predict that a large kinetic oxygen isotope effect should accompany the release and incorporation of ceria oxygen. As the first attempt to determine the existence and the degree of the isotope effect, this study focuses on a set of simple room-temperature re-oxidation experiments that are also relevant to a laboratory procedure using ceria to measure the triple oxygen isotope composition of CO2. Triple-oxygen-isotope labeled ceria powders are heated at 700 °C and cooled under vacuum prior to exposure to air. By combining results from independent experimental sets with different initial oxygen isotope labels and using a combined mass-balance and triangulation approach, we have determined the isotope fractionation factors for both high temperature reduction in vacuum (⩽10-4 mbar) and room temperature re-oxidation in air. Results indicate that there is a 1.5‰ ± 0.8‰ increase in the δ18O value of ceria after being heated in vacuum at 700 °C for 1 h. When the vacuum is broken at room temperature, the previously heated ceria incorporates 3-19% of its final structural oxygen from air, with a δ18O value of 2.1-4.1+7.7 ‰ for the incorporated oxygen. The substantial incorporation of oxygen from air supports that oxygen mobility is high in vacancy-rich ceria during re-oxidation at room temperature. The quantified oxygen isotope fractionation factors are consistent with the direct involvement of O2 in the rate limiting step for ceria reoxidation in air at room temperature. While additional parameters may reduce some of the uncertainties in our approach, this study demonstrates that isotope effects can be an encouraging tool for studying oxygen transport kinetics in ceria and other oxides. In addition, our finding warns of the special cares and limits in using ceria as an exchange medium for laboratory triple oxygen isotope analysis of CO2 or other oxygen-bearing gases.

Physical and Chemical Stability of Budesonide Mucoadhesive Oral Suspensions (MucoLox).

PubMed

Ip, Kendice; Carvalho, Maria; Shan, Ashley; Banov, Daniel

2017-01-01

Budesonide is a corticosteroid that has been shown effective in the treatment of eosinophilic esophagitis, but there are currently no commercial medicines to treat this chronic allergic/immune condition, despite its prevalence in the U.S. Therefore, pharmaceutical compounding is the alternative choice to meet the therapeutic need of eosinophilic esophagitis patients. Two budesonide mucoadhesive oral suspensions (1 mg/10 mL and 2 mg/10 mL) were developed using the compounding vehicle MucoLox, a proprietary mucoadhesive polymer blend that promotes mucosal adhesion. The physical and chemical stability of the oral suspensions was tested over a period of 182 days, at room temperature and refrigerated conditions, in order to determine the corresponding beyond-use date. The physical characterization consisted in observing all samples for color/appearance and odor, and testing for pH and density, whereas the chemical characterization consisted in ultra-performance liquid chromatography assay testing. Both oral suspensions were proven physically and chemically stable, and the ultra-performance liquid chromatography method was proven stability indicating. As a result, the beyond-use date of the budesonide 1-mg/10-mL and 2-mg/10-mL mucoadhesive oral suspensions (MucoLox), in amber plastic bottles, is six months at both room temperature and refrigerated conditions. Copyright© by International Journal of Pharmaceutical Compounding, Inc.

Room-Temperature Processing of TiOx Electron Transporting Layer for Perovskite Solar Cells.

PubMed

Deng, Xiaoyu; Wilkes, George C; Chen, Alexander Z; Prasad, Narasimha S; Gupta, Mool C; Choi, Joshua J

2017-07-20

In order to realize high-throughput roll-to-roll manufacturing of flexible perovskite solar cells, low-temperature processing of all device components must be realized. However, the most commonly used electron transporting layer in high-performance perovskite solar cells is based on TiO 2 thin films processed at high temperature (>450 °C). Here, we demonstrate room temperature solution processing of the TiO x layer that performs as well as the high temperature TiO 2 layer in perovskite solar cells, as evidenced by a champion solar cell efficiency of 16.3%. Using optical spectroscopy, electrical measurements, and X-ray diffraction, we show that the room-temperature processed TiO x is amorphous with organic residues, and yet its optical and electrical properties are on par with the high-temperature TiO 2 . Flexible perovskite solar cells that employ a room-temperature TiO x layer with a power conversion efficiency of 14.3% are demonstrated.

Room-temperature photomagnetism in the spinel ferrite (Mn,Zn,Fe)3O4 as seen via soft x-ray magnetic circular dichroism

NASA Astrophysics Data System (ADS)

Bettinger, J. S.; Piamonteze, C.; Chopdekar, R. V.; Liberati, M.; Arenholz, E.; Suzuki, Y.

2009-10-01

We have used x-ray magnetic circular dichroism (XMCD) in conjunction with multiplet simulations to directly probe the origin of photomagnetism in nanocrystalline (Mn,Zn,Fe)3O4 . A photomagnetic effect at room temperature has been observed in these films with HeNe illumination. We have verified an intervalence charge transfer among octahedral Fe cations to account for the increase in magnetization observed at and above room temperature in small magnetic fields. Using XMCD, we demonstrate that the dichroism of Fe in octahedral sites increases by 18% at room temperature, while the dichroism of Fe in tetrahedral sites does not change.

Room-temperature ferromagnetism observed in C-/N-/O-implanted MgO single crystals

NASA Astrophysics Data System (ADS)

Li, Qiang; Ye, Bonian; Hao, Yingping; Liu, Jiandang; Zhang, Jie; Zhang, Lijuan; Kong, Wei; Weng, Huimin; Ye, Bangjiao

2013-01-01

MgO single crystals were implanted with 70 keV C/N/O ions at room temperature with respective doses of 2 × 1016 and 2 × 1017 ions/cm2. All samples with high-dose implantation showed room temperature hysteresis in magnetization loops. Magnetization and slow positron annihilation measurements confirmed that room temperature ferromagnetism in O-implanted samples was attributed to the presence of Mg vacancies. Furthermore, the introduction of C or N played more effective role in ferromagnetic performance than Mg vacancies. Moreover, the magnetic moment possibly occurred from the localized wave function of unpaired electrons and the exchange interaction formed a long-range magnetic order.

Room Temperature ppb Level Chlorine Gas Sensor Based on Copper (II) 1, 4, 8, 11, 15, 18, 22, 25-octabutoxy-29 H, 31 H-phthalocyanine Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bedi, R. K.; Saini, Rajan; Mahajan, Aman

2010-12-01

Spin coating technique has been used to fabricate room temperature chlorine gas sensor based on copper (II) 1, 4, 8, 11, 15, 18, 22, 25-octabutoxy-29 H, 31 H-phthalocyanine (CuPc(OBu){sub 8}) films. Gas sensor shows a response of 185% to few parts per billion level of Cl{sub 2} gas with response time of 9.5 minutes at room temperature. The interactions between sensor and analytes followed first order kinetics with rate constant 0.01{<=}k{<=}0.02. The chemiresistive sensor showed very good stability at room temperature over a long period of time.

Room Temperature Hard Radiation Detectors Based on Solid State Compound Semiconductors: An Overview

NASA Astrophysics Data System (ADS)

Mirzaei, Ali; Huh, Jeung-Soo; Kim, Sang Sub; Kim, Hyoun Woo

2018-05-01

Si and Ge single crystals are the most common semiconductor radiation detectors. However, they need to work at cryogenic temperatures to decrease their noise levels. In contrast, compound semiconductors can be operated at room temperature due to their ability to grow compound materials with tunable densities, band gaps and atomic numbers. Highly efficient room temperature hard radiation detectors can be utilized in biomedical diagnostics, nuclear safety and homeland security applications. In this review, we discuss room temperature compound semiconductors. Since the field of radiation detection is broad and a discussion of all compound materials for radiation sensing is impossible, we discuss the most important materials for the detection of hard radiation with a focus on binary heavy metal semiconductors and ternary and quaternary chalcogenide compounds.

Room-Temperature Determination of Two-Dimensional Electron Gas Concentration and Mobility in Heterostructures

NASA Technical Reports Server (NTRS)

Schacham, S. E.; Mena, R. A.; Haugland, E. J.; Alterovitz, S. A.

1993-01-01

A technique for determination of room-temperature two-dimensional electron gas (2DEG) concentration and mobility in heterostructures is presented. Using simultaneous fits of the longitudinal and transverse voltages as a function of applied magnetic field, we were able to separate the parameters associated with the 2DEG from those of the parallel layer. Comparison with the Shubnikov-de Haas data derived from measurements at liquid helium temperatures proves that the analysis of the room-temperature data provides an excellent estimate of the 2DEG concentration. In addition we were able to obtain for the first time the room-temperature mobility of the 2DEG, an important parameter to device application. Both results are significantly different from those derived from conventional Hall analysis.

The α-γ-ɛ triple point and phase boundaries of iron under shock compression

NASA Astrophysics Data System (ADS)

Li, Jun; Wu, Qiang; Xue, Tao; Geng, Huayun; Yu, Jidong; Jin, Ke; Li, Jiabo; Tan, Ye; Xi, Feng

2017-07-01

The phase transition of iron under shock compression has attracted much attention in recent decades because of its importance in fields such as condensed matter physics, geophysics, and metallurgy. At room temperature, the transition of iron from the α-phase (bcc) to the ɛ-phase (hpc) occurs at a stress of 13 GPa. At high temperature, a triple point followed by transformation to the γ-phase (fcc) is expected. However, the details of the high-temperature phase transitions of iron are still under debate. Here, we investigate the phase-transition behavior of polycrystalline iron under compression from room temperature to 820 K. The results show that the shock-induced phase transition is determined unequivocally from the measured three-wave-structure profiles, which clearly consist of an elastic wave, a plastic wave, and a phase-transition wave. The phase transition is temperature-dependent, with an average rate Δσtr/ΔT of -6.91 MPa/K below 700 K and -34.7 MPa/K at higher temperatures. The shock α-ɛ and α-γ phase boundaries intersect at 10.6 ± 0.53 GPa and 763 K, which agrees with the α-ɛ-γ triple point from early shock wave experiments and recent laser-heated diamond-anvil cell resistivity and in situ X-ray diffraction data but disagrees with the shock pressure-temperature phase diagram reported in 2009 by Zaretsky [J. Appl. Phys. 106, 023510 (2009)].

Mechanochemical Synthesis of Carbon Nanothread Single Crystals.

PubMed

Li, Xiang; Baldini, Maria; Wang, Tao; Chen, Bo; Xu, En-Shi; Vermilyea, Brian; Crespi, Vincent H; Hoffmann, Roald; Molaison, Jamie J; Tulk, Christopher A; Guthrie, Malcolm; Sinogeikin, Stanislav; Badding, John V

2017-11-15

Synthesis of well-ordered reduced dimensional carbon solids with extended bonding remains a challenge. For example, few single-crystal organic monomers react under topochemical control to produce single-crystal extended solids. We report a mechanochemical synthesis in which slow compression at room temperature under uniaxial stress can convert polycrystalline or single-crystal benzene monomer into single-crystalline packings of carbon nanothreads, a one-dimensional sp 3 carbon nanomaterial. The long-range order over hundreds of microns of these crystals allows them to readily exfoliate into fibers. The mechanochemical reaction produces macroscopic single crystals despite large dimensional changes caused by the formation of multiple strong, covalent C-C bonds to each monomer and a lack of reactant single-crystal order. Therefore, it appears not to follow a topochemical pathway, but rather one guided by uniaxial stress, to which the nanothreads consistently align. Slow-compression room-temperature synthesis may allow diverse molecular monomers to form single-crystalline packings of polymers, threads, and higher dimensional carbon networks.

Magnetic vortices in nanocaps induced by curvature

NASA Astrophysics Data System (ADS)

Abdelgawad, Ahmed M.; Nambiar, Nikhil; Bapna, Mukund; Chen, Hao; Majetich, Sara A.

2018-05-01

Magnetic nanoparticles with room temperature remanent magnetic vortices stabilized by their curvature are very intriguing due to their potential use in biomedicine. In the present study, we investigate room temperature magnetic chirality in 100 nm diameter permalloy spherical caps with 10 nm and 30 nm thicknesses. Micromagnetic OOMMF simulations predict the equilibrium spin structure for these caps to form a vortex state. We fabricate the permalloy caps by sputtering permalloy on both close-packed and sparse arrays of polystyrene nanoparticles. Magnetic force microscopy scans show a clear signature of a vortex state in close-packed caps of both 10 nm and 30 nm thicknesses. Alternating gradient magnetometry measurements of the caps are consistent with a remnant vortex state in 30 nm thick caps and a transition to an onion state followed by a vortex state in 10 nm thick caps. Out-of-plane measurements supported by micromagnetic simulations shows that an out-of-plane field can stabilize a vortex state down to a diameter of 15 nm.

Intrinsic phonon-limited charge carrier mobilities in thermoelectric SnSe

NASA Astrophysics Data System (ADS)

Ma, Jinlong; Chen, Yani; Li, Wu

2018-05-01

Within the past few years, tin selenide (SnSe) has attracted intense interest due to its remarkable thermoelectric potential for both n - and p -type crystals. In this work, the intrinsic phonon-limited electron/hole mobilities of SnSe are investigated using a Boltzmann transport equation based on first-principles calculated electron-phonon interactions. We find that the electrons have much larger mobilities than the holes. At room temperature, the mobilities of electrons along the a , b , and c axes are 325, 801, and 623 cm2/V s, respectively, whereas those of holes are 100, 299, and 291 cm2/V s, respectively. The anisotropy of mobilities is consistent with the reciprocal effective mass at band edges. The mode-specific analysis shows that the highest longitudinal optical phonons, rather than previously assumed acoustic phonons, dominate the scattering processes and consequently the mobilities in SnSe. The room-temperature largest mean free paths of electrons and holes in SnSe are about 21 and 13 nm, respectively.

Ultra-Low-Power Smart Electronic Nose System Based on Three-Dimensional Tin Oxide Nanotube Arrays.

PubMed

Chen, Jiaqi; Chen, Zhuo; Boussaid, Farid; Zhang, Daquan; Pan, Xiaofang; Zhao, Huijuan; Bermak, Amine; Tsui, Chi-Ying; Wang, Xinran; Fan, Zhiyong

2018-06-04

In this work, we present a high-performance smart electronic nose (E-nose) system consisting of a multiplexed tin oxide (SnO 2 ) nanotube sensor array, read-out circuit, wireless data transmission unit, mobile phone receiver, and data processing application (App). Using the designed nanotube sensor device structure in conjunction with multiple electrode materials, high-sensitivity gas detection and discrimination have been achieved at room temperature, enabling a 1000 times reduction of the sensor's power consumption as compared to a conventional device using thin film SnO 2 . The experimental results demonstrate that the developed E-nose can identify indoor target gases using a simple vector-matching gas recognition algorithm. In addition, the fabricated E-nose has achieved state-of-the-art sensitivity for H 2 and benzene detection at room temperature with metal oxide sensors. Such a smart E-nose system can address the imperative needs for distributed environmental monitoring in smart homes, smart buildings, and smart cities.

A new (Ba, Ca) (Ti, Zr)O3 based multiferroic composite with large magnetoelectric effect

PubMed Central

Naveed-Ul-Haq, M.; Shvartsman, Vladimir V.; Salamon, Soma; Wende, Heiko; Trivedi, Harsh; Mumtaz, Arif; Lupascu, Doru C.

2016-01-01

The lead-free ferroelectric 0.5Ba(Zr0.2Ti0.8)O3 − 0.5(Ba0.7Ca0.3)TiO3 (BCZT) is a promising component for multifunctional multiferroics due to its excellent room temperature piezoelectric properties. Having a composition close to the polymorphic phase boundary between the orthorhombic and tetragonal phases, it deserves a case study for analysis of its potential for modern electronics applications. To obtain magnetoelectric coupling, the piezoelectric phase needs to be combined with a suitable magnetostrictive phase. In the current article, we report on the synthesis, dielectric, magnetic, and magnetoelectric characterization of a new magnetoelectric multiferroic composite consisting of BCZT as a piezoelectric phase and CoFe2O4 (CFO) as the magnetostrictive phase. We found that this material is multiferroic at room temperature and manifests a magnetoelectric effect larger than that of BaTiO3 −CoFe2O4 bulk composites with similar content of the ferrite phase. PMID:27555563

Modification of molybdenum surface by low-energy oxygen implantation at room temperature

NASA Astrophysics Data System (ADS)

Kavre Piltaver, Ivna; Jelovica Badovinac, Ivana; Peter, Robert; Saric, Iva; Petravic, Mladen

2017-12-01

We have studied the initial stages of oxide formation on molybdenum surfaces under 1 keV O2+ ion bombardment at room temperature (RT), using x-ray photoelectron spectroscopy around Mo 3d or O 1s core-levels and the valence band photoemission. The results are compared with the oxidation mechanism of thermally oxidized Mo at RT. The thermal oxidation reveals the formation of a very thin MoO2 layer that prevents any further adsorption of oxygen at higher oxygen doses. Oxygen implantation is more efficient in creating thicker oxide films with the simultaneous formation of several oxide compounds. The oxidation rates of MoO2 and Mo2O5 follow the parabolic growth rate consistent with the mass transport driven by diffusion of either neutral or singly and doubly charged oxygen interstitials. The oxidation of MoO3, which occurs at a later oxidation stage, follows the logarithmic rate driven by the diffusion of cations in an electric field.

A new (Ba, Ca) (Ti, Zr)O3 based multiferroic composite with large magnetoelectric effect

NASA Astrophysics Data System (ADS)

Naveed-Ul-Haq, M.; Shvartsman, Vladimir V.; Salamon, Soma; Wende, Heiko; Trivedi, Harsh; Mumtaz, Arif; Lupascu, Doru C.

2016-08-01

The lead-free ferroelectric 0.5Ba(Zr0.2Ti0.8)O3 - 0.5(Ba0.7Ca0.3)TiO3 (BCZT) is a promising component for multifunctional multiferroics due to its excellent room temperature piezoelectric properties. Having a composition close to the polymorphic phase boundary between the orthorhombic and tetragonal phases, it deserves a case study for analysis of its potential for modern electronics applications. To obtain magnetoelectric coupling, the piezoelectric phase needs to be combined with a suitable magnetostrictive phase. In the current article, we report on the synthesis, dielectric, magnetic, and magnetoelectric characterization of a new magnetoelectric multiferroic composite consisting of BCZT as a piezoelectric phase and CoFe2O4 (CFO) as the magnetostrictive phase. We found that this material is multiferroic at room temperature and manifests a magnetoelectric effect larger than that of BaTiO3 -CoFe2O4 bulk composites with similar content of the ferrite phase.

Tunable Fano Resonance and Plasmon-Exciton Coupling in Single Au Nanotriangles on Monolayer WS2 at Room Temperature.

PubMed

Wang, Mingsong; Krasnok, Alex; Zhang, Tianyi; Scarabelli, Leonardo; Liu, He; Wu, Zilong; Liz-Marzán, Luis M; Terrones, Mauricio; Alù, Andrea; Zheng, Yuebing

2018-05-01

Tunable Fano resonances and plasmon-exciton coupling are demonstrated at room temperature in hybrid systems consisting of single plasmonic nanoparticles deposited on top of the transition metal dichalcogenide monolayers. By using single Au nanotriangles (AuNTs) on monolayer WS 2 as model systems, Fano resonances are observed from the interference between a discrete exciton band of monolayer WS 2 and a broadband plasmonic mode of single AuNTs. The Fano lineshape depends on the exciton binding energy and the localized surface plasmon resonance strength, which can be tuned by the dielectric constant of surrounding solvents and AuNT size, respectively. Moreover, a transition from weak to strong plasmon-exciton coupling with Rabi splitting energies of 100-340 meV is observed by rationally changing the surrounding solvents. With their tunable plasmon-exciton interactions, the proposed WS 2 -AuNT hybrids can open new pathways to develop active nanophotonic devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High-quality RNA extracted from biopsied samples dehydrated and stored dried at room temperature without chemical preservation for up to 3 months as evidenced by RT-PCR results.

PubMed

Sadler, Theodore R; Khodavirdi, Ani C

2015-07-01

Handling and maintenance of biological tissues for nucleic acid and/or protein analysis has long been a challenge because of the perceived instability of these molecules at room temperature if not preserved or processed. Structural damage and compromised integrity of aforementioned biomolecules subsequent to preservation have also posed difficulties in their use in research. The development of technologies employing nonfixative methods with the capability to store at room temperature have been of growing interest. Our previous publication exploring preservation of proteins by desiccation challenged the convention of their unstable nature. Herein, we report the results of quantitative and qualitative analyses of RNA from tissue samples that were desiccated and stored at room temperature for up to 3 months. Our results indicate that viable RNA can be obtained from dehydrated ex vivo tissue samples that have been stored at room temperature.

Room-temperature processed tin oxide thin film as effective hole blocking layer for planar perovskite solar cells

NASA Astrophysics Data System (ADS)

Tao, Hong; Ma, Zhibin; Yang, Guang; Wang, Haoning; Long, Hao; Zhao, Hongyang; Qin, Pingli; Fang, Guojia

2018-03-01

Tin oxide (SnO2) film with high mobility and good transmittance has been reported as a promising semiconductor material for high performance perovskite solar cells (PSCs). In this study, ultrathin SnO2 film synthesized by radio frequency magnetron sputtering (RFMS) method at room temperature was employed as hole blocking layer for planar PSCs. The room-temperature sputtered SnO2 film not only shows favourable energy band structure but also improves the surface topography of fluorine doped SnO2 (FTO) substrate and perovskite (CH3NH3PbI3) layer. Thus, this SnO2 hole blocking layer can efficiently promote electron transport and suppress carrier recombination. Furthermore, the best efficiency of 13.68% was obtained for planar PSC with SnO2 hole blocking layer prepared at room temperature. This research highlights the room-temperature preparation process of hole blocking layer in PSC and has a certain reference significance for the usage of flexible and low-cost substrates.

Structure determination of an integral membrane protein at room temperature from crystals in situ

DOE Office of Scientific and Technical Information (OSTI.GOV)

Axford, Danny; Foadi, James; Imperial College London, London SW7 2AZ

2015-05-14

The X-ray structure determination of an integral membrane protein using synchrotron diffraction data measured in situ at room temperature is demonstrated. The structure determination of an integral membrane protein using synchrotron X-ray diffraction data collected at room temperature directly in vapour-diffusion crystallization plates (in situ) is demonstrated. Exposing the crystals in situ eliminates manual sample handling and, since it is performed at room temperature, removes the complication of cryoprotection and potential structural anomalies induced by sample cryocooling. Essential to the method is the ability to limit radiation damage by recording a small amount of data per sample from many samplesmore » and subsequently assembling the resulting data sets using specialized software. The validity of this procedure is established by the structure determination of Haemophilus influenza TehA at 2.3 Å resolution. The method presented offers an effective protocol for the fast and efficient determination of membrane-protein structures at room temperature using third-generation synchrotron beamlines.« less

Broad-gain (Δλ/λ0

PubMed

Fujita, Kazuue; Furuta, Shinichi; Dougakiuchi, Tatsuo; Sugiyama, Atsushi; Edamura, Tadataka; Yamanishi, Masamichi

2011-01-31

Broad-gain operation of λ~8.7 μm quantum cascade lasers based on dual-upper-state to multiple-lower-state transition design is reported. The devices exhibit surprisingly wide (~500 cm(-1)) electroluminescence spectra which are very insensitive to voltage and temperature changes above room temperature. With recourse to the temperature-insensitivity of electroluminescence spectra, the lasers demonstrate an extremely-weak temperature-dependence of laser performances: T0-value of 510 K, associated with a room temperature threshold current density of 2.6 kA/cm2. In addition, despite such wide gain spectra, room temperature, continuous wave operation of the laser with buried hetero structure is achieved.

Ultra-Low-Cost Room Temperature SiC Thin Films

NASA Technical Reports Server (NTRS)

Faur, Maria

1997-01-01

The research group at CSU has conducted theoretical and experimental research on 'Ultra-Low-Cost Room Temperature SiC Thin Films. The effectiveness of a ultra-low-cost room temperature thin film SiC growth technique on Silicon and Germanium substrates and structures with applications to space solar sells, ThermoPhotoVoltaic (TPV) cells and microelectronic and optoelectronic devices was investigated and the main result of this effort are summarized.

Negative differential resistance in GaN nanocrystals above room temperature.

PubMed

Chitara, Basant; Ivan Jebakumar, D S; Rao, C N R; Krupanidhi, S B

2009-10-07

Negative differential resistance (NDR) has been observed for the first time above room temperature in gallium nitride nanocrystals synthesized by a simple chemical route. Current-voltage characteristics have been used to investigate this effect through a metal-semiconductor-metal (M-S-M) configuration on SiO2. The NDR effect is reversible and reproducible through many cycles. The threshold voltage is approximately 7 V above room temperature.

Neutron absorbing room temperature vulcanizable silicone rubber compositions

DOEpatents

Zoch, Harold L.

1979-11-27

A neutron absorbing composition comprising a one-component room temperature vulcanizable silicone rubber composition or a two-component room temperature vulcanizable silicone rubber composition in which the composition contains from 25 to 300 parts by weight based on the base silanol or vinyl containing diorganopolysiloxane polymer of a boron compound or boron powder as the neutron absorbing ingredient. An especially useful boron compound in this application is boron carbide.

Novel Nanocomposite Structures as Active and Passive Barrier Materials

DTIC Science & Technology

2010-06-01

during the course of this ARO-funded project. The development of a novel polymer material based on a diol-functionalized room-temperature ionic liquid ...material based on a diol-functionalized room- temperature ionic liquid (RTIL) monomer led to fabrication of membranes, which were tested for their...stimulant vapor. Technical Report A polymerizable room-temperature ionic liquid (4, Figure 1) was chosen as the starting material for making poly(RTIL

Development of Pasteuria penetrans in Meloidogyne javanica females as affected by constantly high vs fluctuating temperature in an in-vivo system.

PubMed

Darban, D A; Gowen, S R; Pembroke, B; Mahar, A N

2005-03-01

Growth room and glasshouse experiment was conducted to investigate the effect of constant and fluctuating temperatures on the development of Pasteuria penetrans a hyperparasite of root-knot nematodes. Tomato plants (Lycopersicon esculentum Mill) were inoculated with Meloidogyne javanica second-stage juveniles attached with endospores of P. penetrans and were grown in growth room at 26-29 degrees C and in glasshouse at 20-32 degrees C. The tomato plants were sampled from the growth room after 600 degree-days based on 17 degrees C/d, accumulating each day above a base temperature of 10 degrees C and from the glasshouse after 36 calendar days. Temperature affected the development of P. penetrans directly. The rate of development at constant temperature in growth room was faster than that in the glasshouse at fluctuating temperatures.

Development of Pasteuria penetrans in Meloidogyne javanica females as affected by constantly high vs fluctuating temperature in an in-vivo system

PubMed Central

Darban, D.A.; Gowen, S.R.; Pembroke, B.; Mahar, A.N.

2005-01-01

Growth room and glasshouse experiment was conducted to investigate the effect of constant and fluctuating temperatures on the development of Pasteuria penetrans a hyperparasite of root-knot nematodes. Tomato plants (Lycopersicon esculentum Mill) were inoculated with Meloidogyne javanica second-stage juveniles attached with endospores of P. penetrans and were grown in growth room at 26–29 °C and in glasshouse at 20–32 °C. The tomato plants were sampled from the growth room after 600 degree-days based on 17 °C/d, accumulating each day above a base temperature of 10 °C and from the glasshouse after 36 calendar days. Temperature affected the development of P. penetrans directly. The rate of development at constant temperature in growth room was faster than that in the glasshouse at fluctuating temperatures. PMID:15682497

Practical and efficient magnetic heat pump

NASA Technical Reports Server (NTRS)

Brown, G. V.

1978-01-01

Method for pumping heat magnetically at room temperature is more economical than existing refrigeration systems. Method uses natural magneto-thermal effect of gadolinium metal to establish temperature gradient across length of tube. Regenerative cyclic process in which gadolinium sample is magnetized and gives off heat at one end of tube, and then is demagnetized at other end to absorb heat has established temperature gradients of 144 degrees F in experiments near room temperature. Other materials with large magnetothermal effects can be used below room temperature. Possible commercial applications include freeze-drying and food processing, cold storage, and heating and cooling of buildings, plants, and ships.

An easy tool to assess ventilation in health facilities as part of air-borne transmission prevention: a cross-sectional survey from Uganda.

PubMed

Brouwer, Miranda; Katamba, Achilles; Katabira, Elly Tebasoboke; van Leth, Frank

2017-05-03

No guidelines exist on assessing ventilation through air changes per hour (ACH) using a vaneometer. The objective of the study was to evaluate the position and frequency for measuring air velocity using a vaneometer to assess ventilation with ACH; and to assess influence of ambient temperature and weather on ACH. Cross-sectional survey in six urban health facilities in Kampala, Uganda. Measurements consisted of taking air velocity on nine separate moments in five positions in each opening of the TB clinic, laboratory, outpatient consultation and outpatient waiting room using a vaneometer. We assessed in addition the ventilation with the "20% rule", and compared this estimation with the ventilation in ACH assessed using the vaneometer. A total of 189 measurements showed no influence on air velocity of the position and moment of the measurement. No significant influence existed of ambient temperature and a small but significant influence of sunny weather. Ventilation was adequate in 17/24 (71%) of all measurements. Using the "20% rule", ventilation was adequate in 50% of rooms assessed. Agreement between both methods existed in 13/23 (56%) of the rooms assessed. Most rooms had adequate ventilation when assessed using a vaneometer for measuring air velocity. A single vaneometer measurement of air velocity is adequate to assess ventilation in this setting. These findings provide practical input for clear guidelines on assessing ventilation using a vaneometer. Assessing ventilation with a vaneometer differs substantially from applying the "20% rule".

First-principles study of lattice thermal conductivity in ZrTe5 and HfTe5

NASA Astrophysics Data System (ADS)

Wang, Cong; Wang, Haifeng; Chen, Y. B.; Yao, Shu-Hua; Zhou, Jian

2018-05-01

Recently, the layered transition-metal pentatellurides ZrTe5 and HfTe5 have attracted increasing attention because of their interesting topological electronic properties. Nevertheless, some of their other good physical properties seem to be ignored now. Actually, both ZrTe5 and HfTe5 have high electric conductivities (>105 Ω-1 m-1) and Seebeck coefficients (> 100 μV/K) at room temperature, thus making them promising thermoelectric materials. However, the disadvantage is that the thermal conductivities of the two materials are relatively high according to the few available experiments; meanwhile, the detailed mechanism of the intrinsic thermal conductivity has not been studied yet. Based on the density functional theory and the Boltzmann transport theory, we present here the theoretical study of the intrinsic lattice thermal conductivities of ZrTe5 and HfTe5, which are found to be in the range of 5-8 W/mṡK at room temperature and well consistent with the experimental results. We also find that the thermal conductivities of the two materials are anisotropic, which are mainly caused by their anisotropic crystal structures. Based on the detailed analysis, we proposed that the thermal conductivities of the two materials could possibly be reduced by different kinds of structural engineering at the atomic and mesoscopic scales, such as alloying, doping, nano-structuring, and polycrystalline structuring, which could make ZrTe5 and HfTe5 good thermoelectric materials for room temperature thermoelectric applications.

A study of photomodulated reflectance on staircase-like, n-doped GaAs/AlxGa1−xAs quantum well structures

PubMed Central

2012-01-01

In this study, photomodulated reflectance (PR) technique was employed on two different quantum well infrared photodetector (QWIP) structures, which consist of n-doped GaAs quantum wells (QWs) between undoped AlxGa1−xAs barriers with three different x compositions. Therefore, the barrier profile is in the form of a staircase-like barrier. The main difference between the two structures is the doping profile and the doping concentration of the QWs. PR spectra were taken at room temperature using a He-Ne laser as a modulation source and a broadband tungsten halogen lamp as a probe light. The PR spectra were analyzed using Aspnes’ third derivative functional form. Since the barriers are staircase-like, the structure has different ground state energies; therefore, several optical transitions take place in the spectrum which cannot be resolved in a conventional photoluminescence technique at room temperature. To analyze the experimental results, all energy levels in the conduction and in the valance band were calculated using transfer matrix technique, taking into account the effective mass and the parabolic band approximations. A comparison of the PR results with the calculated optical transition energies showed an excellent agreement. Several optical transition energies of the QWIP structures were resolved from PR measurements. It is concluded that PR spectroscopy is a very useful experimental tool to characterize complicated structures with a high accuracy at room temperature. PMID:23146126

A study of photomodulated reflectance on staircase-like, n-doped GaAs/AlxGa1-xAs quantum well structures.

PubMed

Donmez, Omer; Nutku, Ferhat; Erol, Ayse; Arikan, Cetin M; Ergun, Yuksel

2012-11-12

In this study, photomodulated reflectance (PR) technique was employed on two different quantum well infrared photodetector (QWIP) structures, which consist of n-doped GaAs quantum wells (QWs) between undoped AlxGa1-xAs barriers with three different x compositions. Therefore, the barrier profile is in the form of a staircase-like barrier. The main difference between the two structures is the doping profile and the doping concentration of the QWs. PR spectra were taken at room temperature using a He-Ne laser as a modulation source and a broadband tungsten halogen lamp as a probe light. The PR spectra were analyzed using Aspnes' third derivative functional form.Since the barriers are staircase-like, the structure has different ground state energies; therefore, several optical transitions take place in the spectrum which cannot be resolved in a conventional photoluminescence technique at room temperature. To analyze the experimental results, all energy levels in the conduction and in the valance band were calculated using transfer matrix technique, taking into account the effective mass and the parabolic band approximations. A comparison of the PR results with the calculated optical transition energies showed an excellent agreement. Several optical transition energies of the QWIP structures were resolved from PR measurements. It is concluded that PR spectroscopy is a very useful experimental tool to characterize complicated structures with a high accuracy at room temperature.

A study of photomodulated reflectance on staircase-like, n-doped GaAs/Al x Ga1- x As quantum well structures

NASA Astrophysics Data System (ADS)

Donmez, Omer; Nutku, Ferhat; Erol, Ayse; Arikan, Cetin M.; Ergun, Yuksel

2012-11-01

In this study, photomodulated reflectance (PR) technique was employed on two different quantum well infrared photodetector (QWIP) structures, which consist of n-doped GaAs quantum wells (QWs) between undoped Al x Ga1- x As barriers with three different x compositions. Therefore, the barrier profile is in the form of a staircase-like barrier. The main difference between the two structures is the doping profile and the doping concentration of the QWs. PR spectra were taken at room temperature using a He-Ne laser as a modulation source and a broadband tungsten halogen lamp as a probe light. The PR spectra were analyzed using Aspnes' third derivative functional form. Since the barriers are staircase-like, the structure has different ground state energies; therefore, several optical transitions take place in the spectrum which cannot be resolved in a conventional photoluminescence technique at room temperature. To analyze the experimental results, all energy levels in the conduction and in the valance band were calculated using transfer matrix technique, taking into account the effective mass and the parabolic band approximations. A comparison of the PR results with the calculated optical transition energies showed an excellent agreement. Several optical transition energies of the QWIP structures were resolved from PR measurements. It is concluded that PR spectroscopy is a very useful experimental tool to characterize complicated structures with a high accuracy at room temperature.

Effect of Embedded Pd Microstructures on the Flat-Band-Voltage Operation of Room Temperature ZnO-Based Liquid Petroleum Gas Sensors

PubMed Central

Ali, Ghusoon M.; Thompson, Cody V.; Jasim, Ali K.; Abdulbaqi, Isam M.; Moore, James C.

2013-01-01

Three methods were used to fabricate ZnO-based room temperature liquid petroleum gas (LPG) sensors having interdigitated metal-semiconductor-metal (MSM) structures. Specifically, devices with Pd Schottky contacts were fabricated with: (1) un-doped ZnO active layers; (2) Pd-doped ZnO active layers; and (3) un-doped ZnO layers on top of Pd microstructure arrays. All ZnO films were grown on p-type Si(111) substrates by the sol-gel method. For devices incorporating a microstructure array, Pd islands were first grown on the substrate by thermal evaporation using a 100 μm mesh shadow mask. We have estimated the sensitivity of the sensors for applied voltage from –5 to 5 V in air ambient, as well as with exposure to LPG in concentrations from 500 to 3,500 ppm at room temperature (300 K). The current-voltage characteristics were studied and parameters such as leakage current, barrier height, reach-through voltage, and flat-band voltage were extracted. We include contributions due to the barrier height dependence on the electric field and tunneling through the barrier for the studied MSM devices. The Pd-enhanced devices demonstrated a maximum gas response at flat-band voltages. The study also revealed that active layers consisting of Pd microstructure embedded ZnO films resulted in devices exhibiting greater gas-response as compared to those using Pd-doped ZnO thin films or un-doped active layers.

Low-temperature operation of a Buck DC/DC converter

NASA Technical Reports Server (NTRS)

Ray, Biswajit; Gerber, Scott S.; Patterson, Richard L.; Myers, Ira T.

1995-01-01

Low-temperature (77 K) operation of a 42/28 V, 175 W, 50 kHz PWM Buck DC/DC converter designed with commercially available components is reported. Overall, the converter losses decreased at 77 K compared to room temperature operation. A full-load efficiency of 97 percent was recorded at liquid-nitrogen temperature, compared to 95.8 percent at room temperature. Power MOSFET operation improved significantly where as the output rectifier operation deteriorated at low-temperature. The performance of the output filter inductor and capacitor did not change significantly at 77 K compared to room temperature performance. It is possible to achieve high-density and high efficiency power conversion at low-temperatures due to improved electronic, electrical and thermal properties of materials.

Packaging Technology Developed for High-Temperature Silicon Carbide Microsystems

NASA Technical Reports Server (NTRS)

Chen, Liang-Yu; Hunter, Gary W.; Neudeck, Philip G.

2001-01-01

High-temperature electronics and sensors are necessary for harsh-environment space and aeronautical applications, such as sensors and electronics for space missions to the inner solar system, sensors for in situ combustion and emission monitoring, and electronics for combustion control for aeronautical and automotive engines. However, these devices cannot be used until they can be packaged in appropriate forms for specific applications. Suitable packaging technology for operation temperatures up to 500 C and beyond is not commercially available. Thus, the development of a systematic high-temperature packaging technology for SiC-based microsystems is essential for both in situ testing and commercializing high-temperature SiC sensors and electronics. In response to these needs, researchers at Glenn innovatively designed, fabricated, and assembled a new prototype electronic package for high-temperature electronic microsystems using ceramic substrates (aluminum nitride and aluminum oxide) and gold (Au) thick-film metallization. Packaging components include a ceramic packaging frame, thick-film metallization-based interconnection system, and a low electrical resistance SiC die-attachment scheme. Both the materials and fabrication process of the basic packaging components have been tested with an in-house-fabricated SiC semiconductor test chip in an oxidizing environment at temperatures from room temperature to 500 C for more than 1000 hr. These test results set lifetime records for both high-temperature electronic packaging and high-temperature electronic device testing. As required, the thick-film-based interconnection system demonstrated low (2.5 times of the room-temperature resistance of the Au conductor) and stable (decreased 3 percent in 1500 hr of continuous testing) electrical resistance at 500 C in an oxidizing environment. Also as required, the electrical isolation impedance between printed wires that were not electrically joined by a wire bond remained high (greater than 0.4 GW) at 500 C in air. The attached SiC diode demonstrated low (less than 3.8 W/mm2) and relatively consistent dynamic resistance from room temperature to 500 C. These results indicate that the prototype package and the compatible die-attach scheme meet the initial design standards for high-temperature, low-power, and long-term operation. This technology will be further developed and evaluated, especially with more mechanical tests of each packaging element for operation at higher temperatures and longer lifetimes.

Chemically engineered graphene-based 2D organic molecular magnet.

PubMed

Hong, Jeongmin; Bekyarova, Elena; de Heer, Walt A; Haddon, Robert C; Khizroev, Sakhrat

2013-11-26

Carbon-based magnetic materials and structures of mesoscopic dimensions may offer unique opportunities for future nanomagnetoelectronic/spintronic devices. To achieve their potential, carbon nanosystems must have controllable magnetic properties. We demonstrate that nitrophenyl functionalized graphene can act as a room-temperature 2D magnet. We report a comprehensive study of low-temperature magnetotransport, vibrating sample magnetometry (VSM), and superconducting quantum interference (SQUID) measurements before and after radical functionalization. Following nitrophenyl (NP) functionalization, epitaxially grown graphene systems can become organic molecular magnets with ferromagnetic and antiferromagnetic ordering that persists at temperatures above 400 K. The field-dependent, surface magnetoelectric properties were studied using scanning probe microscopy (SPM) techniques. The results indicate that the NP-functionalization orientation and degree of coverage directly affect the magnetic properties of the graphene surface. In addition, graphene-based organic magnetic nanostructures were found to demonstrate a pronounced magneto-optical Kerr effect (MOKE). The results were consistent across different characterization techniques and indicate room-temperature magnetic ordering along preferred graphene orientations in the NP-functionalized samples. Chemically isolated graphene nanoribbons (CINs) were observed along the preferred functionality directions. These results pave the way for future magnetoelectronic/spintronic applications based on promising concepts such as current-induced magnetization switching, magnetoelectricity, half-metallicity, and quantum tunneling of magnetization.

Phase stability of iron germanate, FeGeO3, to 127 GPa

NASA Astrophysics Data System (ADS)

Dutta, R.; Tracy, S. J.; Stan, C. V.; Prakapenka, V. B.; Cava, R. J.; Duffy, T. S.

2018-04-01

The high-pressure behavior of germanates is of interest as these compounds serve as analogs for silicates of the deep Earth. Current theoretical and experimental studies of iron germanate, FeGeO3, are limited. Here, we have examined the behavior of FeGeO3 to 127 GPa using the laser-heated diamond anvil cell combined with in situ synchrotron X-ray diffraction. Upon compression at room temperature, the ambient-pressure clinopyroxene phase transforms to a disordered triclinic phase [FeGeO3 (II)] at 18 GPa in agreement with earlier studies. An additional phase transition to FeGeO3 (III) occurs above 54 GPa at room temperature. Laser-heating experiments ( 1200-2200 K) were conducted at three pressures (33, 54, and 123 GPa) chosen to cover the stability regions of different GeO2 polymorphs. In all cases, we observe that FeGeO3 dissociates into GeO2 + FeO at high pressure and temperature conditions. Neither the perovskite nor the post-perovskite phase was observed up to 127 GPa at ambient or high temperatures. The results are consistent with the behavior of FeSiO3, which also dissociates into a mixture of the oxides (FeO + SiO2) at least up to 149 GPa.

ESR identification of gamma-irradiated albendazole

NASA Astrophysics Data System (ADS)

Çolak, Seyda

2010-01-01

The use of ionizing radiation for sterilization of pharmaceuticals is a well-established technology. In the present work, the spectroscopic and kinetic features of the radicals induced in gamma-irradiated solid albendazole samples is investigated at different temperatures in the dose range of 3-34 kGy by electron spin resonance (ESR) spectroscopy. Irradiation with gamma radiation produced two different radical species in albendazole. They were fairly stable at room temperature but relatively unstable above room temperature, giving rise to an unresolved ESR spectrum consisting of three resonance peaks centered at g=2.0057. Decay activation energies of the contributing radical species were calculated to be 47.8 (±13.5) and 50.5 (±9.7) kJ/mol using the signal intensity decay data derived from annealing studies performed at high temperatures. A linear function of the applied dose was found to best describe the experimental dose-response data. Albendazole does not present the characteristics of good dosimetric materials. However, the discrimination of irradiated albendazole from its unirradiated form was possible even 6 months after storage in normal conditions. Based on these findings, it is concluded that albendazole and albendazole-containing drugs can be safely sterilized by gamma radiation and that ESR spectroscopy could be successfully used as a potential technique for monitoring their radiosterilization.

Synthesis of low-moment CrVTiAl: A potential room temperature spin filter

NASA Astrophysics Data System (ADS)

Stephen, G. M.; McDonald, I.; Lejeune, B.; Lewis, L. H.; Heiman, D.

2016-12-01

The efficient production of spin-polarized currents at room temperature is fundamental to the advancement of spintronics. Spin-filter materials—semiconductors with unequal band gaps for each spin channel—can generate spin-polarized current without the need for spin-polarized contacts. In addition, a spin-filter material with zero magnetic moment would have the advantage of not producing strong fringing fields that would interfere with neighboring electronic components and limit the volume density of devices. The quaternary Heusler compound CrVTiAl has been predicted to be a zero-moment spin-filter material with a Curie temperature in excess of 1000 K. In this work, CrVTiAl has been synthesized with a lattice constant of a = 6.15 Å. Magnetization measurements reveal an exceptionally low moment of μ = 2.3 × 10-3 μB/f.u. at a field of μ0H = 2 T that is independent of temperature between T = 10 K and 400 K, consistent with the predicted zero-moment ferrimagnetism. Transport measurements reveal a combination of metallic and semiconducting components to the resistivity. Combining a zero-moment spin-filter material with nonmagnetic electrodes would lead to an essentially nonmagnetic spin injector. These results suggest that CrVTiAl is a promising candidate for further research in the field of spintronics.

Electric Field Dependence of Quantum Efficiencies of Ag/n-Si Composites in the Infrared at Room Temperature

DTIC Science & Technology

2009-09-10

Howard University 2300 6th Street NW, Room 1016 Washington, D.C. 20059 Air Force Office of Scientific Research 875 North Randolph Street Room 3112...Department of Electrical Engineering, Howard University , Washington, DC 20059 Room temperature quantum efficiencies of Ag/n-Si composite...at the Howard University CREST Center for Nanomaterials Characterization Science and Processing Technology were used in this investigation. The

46 CFR 111.01-15 - Temperature ratings.

Code of Federal Regulations, 2010 CFR

2010-10-01

... Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS... assumed for all rotating electrical machinery in boiler rooms, engine rooms, auxiliary machinery rooms...-rotating electrical equipment in boiler rooms, in engine rooms, in auxiliary machinery rooms, and on...

46 CFR 111.01-15 - Temperature ratings.

Code of Federal Regulations, 2011 CFR

2011-10-01

... Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS... assumed for all rotating electrical machinery in boiler rooms, engine rooms, auxiliary machinery rooms...-rotating electrical equipment in boiler rooms, in engine rooms, in auxiliary machinery rooms, and on...

Performance of "Waterless Concrete"

NASA Technical Reports Server (NTRS)

Toutanji, H. A.; Grugel, R. N.

2009-01-01

Waterless concrete consists of molten elementary sulfur and aggregate. The aggregates in a lunar environment will be lunar rocks and soil. Sulfur is present on the Moon in Troilite soil (FeS) and, by oxidation of the soil, iron and sulfur can be produced. Sulfur concrete specimens were cycled between liquid nitrogen (approx.]91 C) and room temperature (^21 C) to simulate exposure to a lunar environment. Cycled and control specimens were subsequently tested in compression at room temperatures (^21 C) and ^-101 C. Test results showed that due to temperature cycling, the compressive strength of cycled specimens was 20% of those non-cycled. This reduction in strength can be attributed to the large differences in thermal coefficients of expansion of the materials constituting the concrete which promoted cracking. Similar sulfur concrete mixtures were strengthened with short and long glass fibres. The lunar regolith simulant was melted in a 25 cc Pt- Rh crucible in a Sybron Thermoline high temperature MoSi2 furnace at melting temperatures of 1450 to 1600 C for times of 30 min to i hour. Glass fibres and small rods were pulled from the melt. The glass fibres were used to reinforce sulfur concrete plated to improve the flexural strength of the sulfur concrete. Beams strengthened with glass fibres showed to exhibit an increase in the flexural strength by as much as 45%.

Correlation between structural, electrical and magnetic properties of GdMnO3 bulk ceramics

NASA Astrophysics Data System (ADS)

Samantaray, S.; Mishra, D. K.; Pradhan, S. K.; Mishra, P.; Sekhar, B. R.; Behera, Debdhyan; Rout, P. P.; Das, S. K.; Sahu, D. R.; Roul, B. K.

2013-08-01

This paper reports the effect of sintering temperature on ferroelectric properties of GdMnO3 (GMO) bulk ceramics at room temperature prepared by the conventional solid state reaction route following slow step sintering schedule. Ferroelectric hysteresis loop as well as sharp dielectric anomaly in pure (99.999%) GMO sintered ceramics has been clearly observed. Samples sintered at 1350 °C become orthorhombic with Pbnm space group and showed frequency independent sharp dielectric anomalies at 373 K and a square type of novel ferroelectric hysteresis loop was observed at room temperature. Interestingly, dielectric anomalies and ferroelectric behavior were observed to be dependent upon sintering temperature of GdMnO3. Room temperature dielectric constant (ɛr) value at different frequencies is observed to be abnormally high. The magnetic field and temperature dependent magnetization show antiferromagnetic behavior at 40 K for both 1350 °C and 1700 °C sintered GMO. Present findings showed the possibility of application of GdMnO3 at room temperature as multifunctional materials.

Evaluation, construction and endurance testing of compression sealed pyrolytic boron nitride slot insulation

NASA Technical Reports Server (NTRS)

Grant, W. L.

1969-01-01

A high-temperature statorette, consisting of an iron-27 percent cobalt magnetic lamination stack and nickel-clad silver conductors, was tested with pyrolytic boron nitride slot insulation. Temperatures were measured in each test to determine characteristics of slot linear heat conductance from statorette conductors. Testing was carried out to temperatures of approximately 1500 F in a vacuum environment of 10-8 torr. Three assemblies were built and tested, each having a different room temperature slot clearance. The final statorette assembly was subjected to a 100-hour vacuum aging test at 1400 F followed by 25 thermal cycles. Temperature data from the three assemblies showed that decreasing slot clearance and increasing compression loading did enhance heat transfer. The temperature difference between slot and lamination at 1400 F increased 4 F during the thermal aging and an additional 10 F during the 25 thermal cycles.

Miniature optical fiber temperature sensor based on FMF-SCF structure

NASA Astrophysics Data System (ADS)

Zhang, Chuanbiao; Ning, Tigang; Zheng, Jingjing; Gao, Xuekai; Lin, Heng; Li, Jing; Pei, Li; Wen, Xiaodong

2018-03-01

We proposed and experimentally demonstrated a miniature optical fiber temperature sensor consisting of a seven core fiber (SCF) and a few mode fiber (FMF). The device is fabricated by splicing a section of FMF with a segment of SCF to form a FMF-SCF based sensing structure, and during the FMF region, few modes can be excited and will propagate within the SCF. In experiment, the proposed device has good quality interferometric spectra, and the highest extinction ratio of 27 dB was achieved. When the temperature increases from room temperature to 110 °C, the temperature response properties of the sensor have been investigated, the wavelength sensitivity of about 91.8 pm/°C and the amplitude sensitivity of about 1.57 × 10-2 a.u./°C are obtained, respectively. Due to its easy and controllable fabrication, the sensor can be a suitable candidate in temperature sensing applications.

A study of elevated temperature testing techniques for the fatigue behavior of PMCS: Application to T650-35/AMB21

NASA Technical Reports Server (NTRS)

Gyekenyesi, Andrew L.; Gastelli, Michael G.; Ellis, John R.; Burke, Christopher S.

1995-01-01

An experimental study was conducted to investigate the mechanical behavior of a T650-35/AMB21 eight-harness satin weave polymer composite system. Emphasis was placed on the development and refinement of techniques used in elevated temperature uniaxial PMC testing. Issues such as specimen design, gripping, strain measurement, and temperature control and measurement were addressed. Quasi-static tensile and fatigue properties (R(sub sigma) = 0.1) were examined at room and elevated temperatures. Stiffness degradation and strain accumulation during fatigue cycling were recorded to monitor damage progression and provide insight for future analytical modeling efforts. Accomplishments included an untabbed dog-bone specimen design which consistently failed in the gage section, accurate temperature control and assessment, and continuous in-situ strain measurement capability during fatigue loading at elevated temperatures. Finally, strain accumulation and stiffness degradation during fatigue cycling appeared to be good indicators of damage progression.

Progressive failure site generation in AlGaN/GaN high electron mobility transistors under OFF-state stress: Weibull statistics and temperature dependence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Huarui, E-mail: huarui.sun@bristol.ac.uk; Bajo, Miguel Montes; Uren, Michael J.

2015-01-26

Gate leakage degradation of AlGaN/GaN high electron mobility transistors under OFF-state stress is investigated using a combination of electrical, optical, and surface morphology characterizations. The generation of leakage “hot spots” at the edge of the gate is found to be strongly temperature accelerated. The time for the formation of each failure site follows a Weibull distribution with a shape parameter in the range of 0.7–0.9 from room temperature up to 120 °C. The average leakage per failure site is only weakly temperature dependent. The stress-induced structural degradation at the leakage sites exhibits a temperature dependence in the surface morphology, which ismore » consistent with a surface defect generation process involving temperature-associated changes in the breakdown sites.« less

Design of a Tunable, Room Temperature, Continuous-Wave Terahertz Source and Detector using Silicon Waveguides

DTIC Science & Technology

2008-01-30

that will use conventional diode- or hotomultiplier-tube-based optical detectors , which are xtremely sensitive . . HEATING AND FREE-CARRIER IMITATIONS...CONTRACT NUMBER IN-HOUSE Design of a tunable, room temperature, continuous-wave terahertz source and detector using silicon waveguides 5b. GRANT...B 261Design of a tunable, room temperature, continuous-wave terahertz source and detector using silicon waveguides T. Baehr-Jones,1,* M. Hochberg,1,3

Room temperature polariton light emitting diode with integrated tunnel junction.

PubMed

Brodbeck, S; Jahn, J-P; Rahimi-Iman, A; Fischer, J; Amthor, M; Reitzenstein, S; Kamp, M; Schneider, C; Höfling, S

2013-12-16

We present a diode incorporating a large number (12) of GaAs quantum wells that emits light from exciton-polariton states at room temperature. A reversely biased tunnel junction is placed in the cavity region to improve current injection into the device. Electroluminescence studies reveal two polariton branches which are spectrally separated by a Rabi splitting of 6.5 meV. We observe an anticrossing of the two branches when the temperature is lowered below room temperature as well as a Stark shift of both branches in a bias dependent photoluminescence measurement.

Discrimination between spin-dependent charge transport and spin-dependent recombination in π-conjugated polymers by correlated current and electroluminescence-detected magnetic resonance

NASA Astrophysics Data System (ADS)

Kavand, Marzieh; Baird, Douglas; van Schooten, Kipp; Malissa, Hans; Lupton, John M.; Boehme, Christoph

2016-08-01

Spin-dependent processes play a crucial role in organic electronic devices. Spin coherence can give rise to spin mixing due to a number of processes such as hyperfine coupling, and leads to a range of magnetic field effects. However, it is not straightforward to differentiate between pure single-carrier spin-dependent transport processes which control the current and therefore the electroluminescence, and spin-dependent electron-hole recombination which determines the electroluminescence yield and in turn modulates the current. We therefore investigate the correlation between the dynamics of spin-dependent electric current and spin-dependent electroluminescence in two derivatives of the conjugated polymer poly(phenylene-vinylene) using simultaneously measured pulsed electrically detected (pEDMR) and optically detected (pODMR) magnetic resonance spectroscopy. This experimental approach requires careful analysis of the transient response functions under optical and electrical detection. At room temperature and under bipolar charge-carrier injection conditions, a correlation of the pEDMR and the pODMR signals is observed, consistent with the hypothesis that the recombination currents involve spin-dependent electronic transitions. This observation is inconsistent with the hypothesis that these signals are caused by spin-dependent charge-carrier transport. These results therefore provide no evidence that supports earlier claims that spin-dependent transport plays a role for room-temperature magnetoresistance effects. At low temperatures, however, the correlation between pEDMR and pODMR is weakened, demonstrating that more than one spin-dependent process influences the optoelectronic materials' properties. This conclusion is consistent with prior studies of half-field resonances that were attributed to spin-dependent triplet exciton recombination, which becomes significant at low temperatures when the triplet lifetime increases.

Wide temperature range (T = 295 K and 770-1305 K) study of the kinetics of the reactions HCO + NO and HCO + NO2 using frequency modulation spectroscopy.

PubMed

Dammeier, J; Colberg, M; Friedrichs, G

2007-08-21

The rate constants for , HCO + NO --> HNO + CO, and , HCO + NO(2)--> products, have been measured at temperatures between 770 K < T < 1305 K behind reflected shock waves and, for the purpose of a consistency check, in a slow flow reactor at room temperature. HCO radicals were generated by 193 nm excimer laser photolysis of diluted gas mixtures containing glyoxal, (CHO)(2), and NO or NO(2) in argon and were monitored using frequency modulation (FM) absorption spectroscopy. Kinetic simulations based on a comprehensive reaction mechanism showed that the rate constants for the title reactions could be sensitively extracted from the measured HCO profiles. The determined high temperature rate constants are k(1)(769-1307 K) = (7.1 +/- 2.7) x 10(12) cm(3) mol(-1) s(-1) and k(2)(804-1186 K) = (3.3 +/- 1.8) x 10(13) cm(3) mol(-1) s(-1). The room temperature values were found to be in very good agreement with existing literature data and show that both reactions are essentially temperature independent. The weak temperature dependence of can be explained by the interplay of a dominating direct abstraction pathway and a complex-forming mechanism. Both pathways yield the products HNO + CO. In contrast to , no evidence for a significant contribution of a direct high temperature abstraction channel was found for . Here, the observed temperature independent overall rate constant can be described by a complex-forming mechanism with several product channels. Detailed information on the strongly temperature dependent channel branching ratios is provided. Moreover, the high temperature rate constant of , OH + (CHO)(2), has been determined to be k(7) approximately 1.1 x 10(13) cm(3) mol(-1) s(-1).

A study of room-temperature LixMn1.5Ni0.5O4 solid solutions

NASA Astrophysics Data System (ADS)

Saravanan, Kuppan; Jarry, Angelique; Kostecki, Robert; Chen, Guoying

2015-01-01

Understanding the kinetic implication of solid-solution vs. biphasic reaction pathways is critical for the development of advanced intercalation electrode materials. Yet this has been a long-standing challenge in materials science due to the elusive metastable nature of solid solution phases. The present study reports the synthesis, isolation, and characterization of room-temperature LixMn1.5Ni0.5O4 solid solutions. In situ XRD studies performed on pristine and chemically-delithiated, micron-sized single crystals reveal the thermal behavior of LixMn1.5Ni0.5O4 (0 <= x <= 1) cathode material consisting of three cubic phases: LiMn1.5Ni0.5O4 (Phase I), Li0.5Mn1.5Ni0.5O4 (Phase II) and Mn1.5Ni0.5O4 (Phase III). A phase diagram capturing the structural changes as functions of both temperature and Li content was established. The work not only demonstrates the possibility of synthesizing alternative electrode materials that are metastable in nature, but also enables in-depth evaluation on the physical, electrochemical and kinetic properties of transient intermediate phases and their role in battery electrode performance.

Evidence for Kinetic Limitations as a Controlling Factor of Ge Pyramid Formation: a Study of Structural Features of Ge/Si(001) Wetting Layer Formed by Ge Deposition at Room Temperature Followed by Annealing at 600 °C

NASA Astrophysics Data System (ADS)

Storozhevykh, Mikhail S.; Arapkina, Larisa V.; Yuryev, Vladimir A.

2015-07-01

The article presents an experimental study of an issue of whether the formation of arrays of Ge quantum dots on the Si(001) surface is an equilibrium process or it is kinetically controlled. We deposited Ge on Si(001) at the room temperature and explored crystallization of the disordered Ge film as a result of annealing at 600 °C. The experiment has demonstrated that the Ge/Si(001) film formed in the conditions of an isolated system consists of the standard patched wetting layer and large droplike clusters of Ge rather than of huts or domes which appear when a film is grown in a flux of Ge atoms arriving on its surface. We conclude that the growth of the pyramids appearing at temperatures greater than 600 °C is controlled by kinetics rather than thermodynamic equilibrium whereas the wetting layer is an equilibrium structure. PACS: Primary 68.37.Ef; 68.55.Ac; 68.65.Hb; 81.07.Ta; 81.16.Dn

Initial stages of ion beam-induced phase transformations in Gd2O3 and Lu2O3

NASA Astrophysics Data System (ADS)

Chen, Chien-Hung; Tracy, Cameron L.; Wang, Chenxu; Lang, Maik; Ewing, Rodney C.

2018-02-01

The atomic-scale evolution of lanthanide sesquioxides Gd2O3 and Lu2O3 irradiated with 1 MeV Kr ions at room temperature and 120 K, up to fluences of 1 × 1016 ions/cm2 (˜20 dpa), has been characterized by in situ transmission electron microscopy. At room temperature, both oxides exhibited high radiation tolerance. Irradiation did not cause any observable structural change in either material, likely due to the mobility of irradiation-induced point defects, causing efficient defect annihilation. For Gd2O3, having the larger cation ionic radius of the two materials, an irradiation-induced stacking fault structure appeared at low fluences in the low temperature irradiation. As compared with the cubic-to-monoclinic phase transformations known to result from higher energy (˜GeV) ion irradiation, Kr ions of lower energies (˜MeV) yield much lower rates of damage accumulation and thus less extensive structural modification. At a fluence of 2.5 × 1015 ions/cm2, only the initial stages of the cubic-to-monoclinic (C to B) phase transformation process, consisting of the formation and aggregation of defects, have been observed.

Dielectric properties of polyhedral oligomeric silsesquioxane (POSS)-based nanocomposites at 77k

NASA Astrophysics Data System (ADS)

Pan, Ming-Jen; Gorzkowski, Edward; McAllister, Kelly

2011-10-01

The goal of this study is to develop dielectric nanocomposites for high energy density applications at liquid nitrogen temperature by utilizing a unique nano-material polyhedral oligomeric silsesquioxanes (POSS). A POSS molecule is consisted of a silica cage core with 8 silicon and 12 oxygen atoms and organic functional groups attached to the corners of the cage. In this study, we utilize POSS for the fabrication of nanocomposites both as a silica nanoparticle filler to enhance the breakdown strength and as a surfactant for effective dispersion of high permittivity ceramic nanoparticles in a polymer matrix. The matrix materials selected for the study are polyvinylidene fluoride (PVDF) and poly(methyl methacrylate) (PMMA). The ceramic nanoparticles are barium strontium titanate (BST 50/50) and strontium titanate. The dielectric properties of the solution-cast nanocomposites films were correlated to the composition and processing conditions. We determined that the addition of POSS did not provide enhanced dielectric performance in PVDF- and PMMA-based materials at either room temperature or 77K. In addition, we found that the dielectric breakdown strength of PMMA is lower at 77K than at room temperature, contradicting literature data.

Luminescent Thermochromism of 2D Coordination Polymers Based on Copper(I) Halides with 4-Hydroxythiophenol.

PubMed

Troyano, Javier; Perles, Josefina; Amo-Ochoa, Pilar; Martínez, Jose Ignacio; Concepción Gimeno, Maria; Fernández-Moreira, Vanesa; Zamora, Félix; Delgado, Salomé

2016-12-12

Solvothermal reactions between copper(I) halides and 4-mercaptophenol give rise to the formation of three coordination polymers with general formula [Cu 3 X(HT) 2 ] n (X=Cl, 1; Br, 2; and I, 3). The structures of these coordination polymers have been determined by X-ray diffraction at both room- and low temperature (110 K), showing a general shortening in Cu-S, Cu-X and Cu-Cu bond lengths at low temperatures. 1 and 2 are isostructural, consisting of layers in which the halogen ligands act as μ 3 -bridges joining two Cu1 and one Cu2 atoms whereas in 3 the iodine ligands is as μ 4 -mode but the layers are quasi-isostructural with 1 or 2. These compounds show a reversible thermochromic luminescence, with strong orange emission for 1 and 2, but weaker for 3 at room temperature, whereas upon cooling at 77 K 1 and 2 show stronger yellow emission, and 3 displays stronger green emission. DFT calculations have been used to rationalize these observations. These results suggest a high potential for this novel and promising stimuli-responsive materials. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Numerical investigations on the effect of slenderness ratio of matrix elements in cryogenic chill down process

NASA Astrophysics Data System (ADS)

Reby Roy, K. E.; Mohammed, Jesna; Abhiroop, V. M.; Thekkethil, S. R.

2017-02-01

Cryogenic fluids have many applications in space, medicine, preservation etc. The chill-down of cryogenic fluid transfer line is a complicated phenomenon occurring in most of the cryogenic systems. The cryogenic fluid transfer line, which is initially at room temperature, has to be cooled to the temperature of the cryogen as fast as possible. When the cryogenic fluid at liquid state passes along the line, transient heat transfer between the cryogen and the transfer line causes voracious evaporation of the liquid. This paper makes a contribution to the two-phase flow along a rectangular flow passage consisting of an array of elliptically shaped matrix elements. A simplified 2D model is considered and the problem is solved using ANSYS FLUENT. The present analysis aims to study the influence of the slenderness ratio of matrix elements on the heat transfer rate and chill down time. For a comparative study, matrix elements of slenderness ratios 5 and 10 are considered. Liquid nitrogen at 74K flows through the matrix. The material of the transfer line is assumed to be aluminium which is initially at room temperature. The influence of Reynolds numbers from 800 to 3000 on chill-down is also investigated.

Intersubband Transitions in InAs/AlSb Quantum Wells

NASA Technical Reports Server (NTRS)

Li, J.; Koloklov, K.; Ning, C. Z.; Larraber, D. C.; Khodaparast, G. A.; Kono, J.; Ueda, K.; Nakajima, Y.; Sasa, S.; Inoue, M.

2003-01-01

We have studied intersubband transitions in InAs/AlSb quantum wells experimentally and theoretically. Experimentally, we performed polarization-resolved infrared absorption spectroscopy to measure intersubband absorption peak frequencies and linewidths as functions of temperature (from 4 K to room temperature) and quantum well width (from a few nm to 10 nm). To understand experimental results, we performed a self-consistent 8-band k-p band-structure calculation including spatial charge separation. Based on the calculated band structure, we developed a set of density matrix equations to compute TE and TM optical transitions self-consistently, including both interband and intersubband channels. This density matrix formalism is also ideal for the inclusion of various many-body effects, which are known to be important for intersubband transitions. Detailed comparison between experimental data and theoretical simulations is presented.

Initial evaluation tests of General Electric Company 12.0 ampere hour nickel cadmium spacecraft cells with design variables

NASA Technical Reports Server (NTRS)

Harkness, J. D.

1979-01-01

All evaluation tests were performed at room ambient pressure and temperature, with discharges at a 2 hour rate. Tests consisted of phenolphthalein leak tests, three capacity tests, an auxiliary electrode test, a charge retention test, an internal short test, a charge efficiency test, overcharge tests, and a pressure versus capacity test. Results of the tests and recommendations for improvements in manufacturing are presented.

Batteryless Electroencephalography (EEG): Subthreshold Voltage System-on-a-Chip (SoC) Design for Neurophysiological Measurement

DTIC Science & Technology

2015-03-01

example, be harvested via thermoelectric coupling requiring only a 1 °C temperature gradient (supplied by the human scalp at ambient room...controller. The amplifier chain will consist of a differential low-noise amplifier (LNA) with digitally modulated , voltage-offset control and a variable...result in decreased vertical resolution of the digitized signal, even in conjunction with the VOC/VGA modulation described above. Figure 4 shows

Long-term room temperature preservation of corpse soft tissue: an approach for tissue sample storage

PubMed Central

2011-01-01

Background Disaster victim identification (DVI) represents one of the most difficult challenges in forensic sciences, and subsequent DNA typing is essential. Collected samples for DNA-based human identification are usually stored at low temperature to halt the degradation processes of human remains. We have developed a simple and reliable procedure for soft tissue storage and preservation for DNA extraction. It ensures high quality DNA suitable for PCR-based DNA typing after at least 1 year of room temperature storage. Methods Fragments of human psoas muscle were exposed to three different environmental conditions for diverse time periods at room temperature. Storage conditions included: (a) a preserving medium consisting of solid sodium chloride (salt), (b) no additional substances and (c) garden soil. DNA was extracted with proteinase K/SDS followed by organic solvent treatment and concentration by centrifugal filter devices. Quantification was carried out by real-time PCR using commercial kits. Short tandem repeat (STR) typing profiles were analysed with 'expert software'. Results DNA quantities recovered from samples stored in salt were similar up to the complete storage time and underscored the effectiveness of the preservation method. It was possible to reliably and accurately type different genetic systems including autosomal STRs and mitochondrial and Y-chromosome haplogroups. Autosomal STR typing quality was evaluated by expert software, denoting high quality profiles from DNA samples obtained from corpse tissue stored in salt for up to 365 days. Conclusions The procedure proposed herein is a cost efficient alternative for storage of human remains in challenging environmental areas, such as mass disaster locations, mass graves and exhumations. This technique should be considered as an additional method for sample storage when preservation of DNA integrity is required for PCR-based DNA typing. PMID:21846338

Assessment of tautomer distribution using the condensed reaction graph approach

NASA Astrophysics Data System (ADS)

Gimadiev, T. R.; Madzhidov, T. I.; Nugmanov, R. I.; Baskin, I. I.; Antipin, I. S.; Varnek, A.

2018-03-01

We report the first direct QSPR modeling of equilibrium constants of tautomeric transformations (logK T ) in different solvents and at different temperatures, which do not require intermediate assessment of acidity (basicity) constants for all tautomeric forms. The key step of the modeling consisted in the merging of two tautomers in one sole molecular graph ("condensed reaction graph") which enables to compute molecular descriptors characterizing entire equilibrium. The support vector regression method was used to build the models. The training set consisted of 785 transformations belonging to 11 types of tautomeric reactions with equilibrium constants measured in different solvents and at different temperatures. The models obtained perform well both in cross-validation (Q2 = 0.81 RMSE = 0.7 logK T units) and on two external test sets. Benchmarking studies demonstrate that our models outperform results obtained with DFT B3LYP/6-311 ++ G(d,p) and ChemAxon Tautomerizer applicable only in water at room temperature.

Magnetic properties of co-precipitated hexaferrite powders with Sm-Co substitutions optimized with the molten flux method

NASA Astrophysics Data System (ADS)

Serletis, C.; Litsardakis, G.; Pavlidou, E.; Efthimiadis, K. G.

2017-11-01

In this work, using the chemical coprecipitation method, Sr1-xSmxFe12-xCoxO19 (x = 0, 0.1, 0.2) hexaferrite powders were prepared. Major magnetization loops were recorded at room temperature in order to determine the correct calcination temperature for optimum hard magnetic properties. It is found that a small degree of substitution increases substantially the coercive field. Also, the use of the molten flux calcination method increases the remanent magnetization. SEM/EDXS and XRD measurements were performed at the calcined powders: the results show that a single hexaferrite phase is formed and that the substituted powders consist of an assembly of grains with a mean diameter of 40 nm. Measurements of minor magnetization loops and of the temperature and time dependence of the magnetization confirm that the powders consist of a non-oriented single domain magnetic particles assembly. The results indicate that Sm could be a viable replacement for La in the manufacturing of hexaferrites with a high-energy product.

Comparing cooling systems for the COBE 2991 cell separator used in the purification of human pancreatic islets of Langerhans.

PubMed

Adewola, A; Mage, R; Hansen, M; Barbaro, B; Mendoza-Elias, J; Harvat, T; Morel, P H; Oberholzer, J; Wang, Y

2010-01-01

Two different approaches of controlled cooling of the COBE 2991 cell-separator for islet purification were evaluated. The first method is the new Geneva COBE cooling system (GCCS), which consists of an electronically controlled liquid nitrogen injection system. The second is the University of Illinois at Chicago cooling system (UICCS), which consists of a specially designed "Cold Room" maintained at 1-8 C. For the GCCS, the mean temperatures of the gradient solutions were measured at the beginning and end of centrifugation were found to be 7 +/-0.7 C and 6.8 +/-0.6 C respectively. For the UICCS, the mean temperature of the gradients at the beginning and end of centrifugation were 4.7 +/-0.53 C and 7.03 C+/-0.91 C respectively. The presented COBE cooling systems can easily be adapted to a COBE 2991 cell-separator and are efficient in maintaining gradient solutions at a defined low temperature during centrifugation.

Entanglement and Bell's inequality violation above room temperature in metal carboxylates

NASA Astrophysics Data System (ADS)

Souza, A. M.; Soares-Pinto, D. O.; Sarthour, R. S.; Oliveira, I. S.; Reis, M. S.; Brandão, P.; Dos Santos, A. M.

2009-02-01

In the present work we show that a particular family of materials, the metal carboxylates, may have entangled states up to very high temperatures. From magnetic-susceptibility measurements, we have estimated the critical temperature below which entanglement exists in the copper carboxylate {Cu2(O2CH)4}{Cu(O2CH)2(2-methylpyridine)2} , and we have found this to be above room temperature (Te˜630K) . Furthermore, the results show that the system remains maximally entangled until close to ˜100K and the Bell’s inequality is violated up to nearly room temperature (˜290K) .

Entanglement and Bell's inequality violation above room temperature in metal carboxylates.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Souza, A M; Soares-Pinto, D O; Sarthour, R S

In the present work we show that a particular family of materials, the metal carboxylates, may have entangled states up to very high temperatures. From magnetic-susceptibility measurements, we have estimated the critical temperature below which entanglement exists in the copper carboxylate {Cu-2(O2CH)(4)}{Cu(O2CH)(2)(2-methylpyridine)(2)}, and we have found this to be above room temperature (T-e similar to 630 K). Furthermore, the results show that the system remains maximally entangled until close to similar to 100 K and the Bell's inequality is violated up to nearly room temperature (similar to 290 K).

Tailoring the magnetostructural transition and magnetocaloric properties around room temperature: In-doped Ni-Mn-Ga alloys

NASA Astrophysics Data System (ADS)

Zhang, Linfang; Wang, Jingmin; Hua, Hui; Jiang, Chengbao; Xu, Huibin

2014-09-01

Some off-stoichiometric Ni-Mn-Ga alloys undergo a coupled magnetostructural transition from ferromagnetic martensite to paramagnetic austenite, giving rise to the large magnetocaloric effect. However, the magnetostructural transitions of Ni-Mn-Ga alloys generally take place at temperatures higher than room temperature. Here, we report that by the partial substitution of In for Ga, the paramagnetic austenite phase is well stabilized, and the magnetostructural transition can be tailored around room temperature. Sizable magnetic entropy change and adiabatic temperature change were induced by magnetic field change in the vicinity of the magnetostructural transition of the In-doped Ni-Mn-Ga alloys.

Evaluation of Ultra High Pressure (UHP) Firefighting in a Room-and-Contents Fire

DTIC Science & Technology

2017-03-15

Burn Room and Hangar Temperature Prior to Ignition ............................................... 18 Figure 12. Effect of Temperature on Normalized...Figure 20. Maximum Average Temperature and Heat Flux ......................................................... 22 Figure 21. Effect of Maximum Average...Aspirated Ceiling Temperature .................................... 23 Figure 22. Effect of Maximum Average Floor Heat Flux on Extinguishment Quantity

Cryogenic characterization of LEDs for space application

NASA Astrophysics Data System (ADS)

Carron, Jérôme; Philippon, Anne; How, Lip Sun; Delbergue, Audrey; Hassanzadeh, Sahar; Cillierre, David; Danto, Pascale; Boutillier, Mathieu

2017-09-01

In the frame of EUCLID project, the Calibration Unit of the VIS (VISible Imager) instrument must provide an accurate and well characterized light source for in-flight instrument calibration without noise when it is switched off. The Calibration Unit consists of a set of LEDs emitting at various wavelengths in the visible towards an integrating sphere. The sphere's output provides a uniform illumination over the entire focal plane. Nine references of LEDs from different manufacturers were selected, screened and qualified under cryogenic conditions. Testing this large quantity of samples led to the implementation of automated testing equipment with complete in-situ monitoring of optoelectronic parameters as well as temperature and vacuum values. All the electrical and optical parameters of the LED have been monitored and recorded at ambient and cryogenic temperatures. These results have been compiled in order to show the total deviation of the LED electrical and electro-optical properties in the whole mission and to select the best suitable LED references for the mission. This qualification has demonstrated the robustness of COTS LEDs to operate at low cryogenic temperatures and in the space environment. Then 6 wavelengths were selected and submitted to an EMC sensitivity test at room and cold temperature by counting the number of photons when LEDs drivers are OFF. Characterizations were conducted in the full frequency spectrum in order to implement solutions at system level to suppress the emission of photons when the LED drivers are OFF. LEDs impedance was also characterized at room temperature and cold temperature.

Outstanding compressive creep strength in Cr/Ir-codoped (Mo0.85Nb0.15)Si2 crystals with the unique cross-lamellar microstructure.

PubMed

Hagihara, Koji; Ikenishi, Takaaki; Araki, Haruka; Nakano, Takayoshi

2017-06-21

A (Mo 0.85 Nb 0.15 )Si 2 crystal with an oriented, lamellar, C40/C11 b two-phase microstructure is a promising ultrahigh-temperature (UHT) structural material, but its low room-temperature fracture toughness and low high-temperature strength prevent its practical application. As a possibility to overcome these problems, we first found a development of unique "cross-lamellar microstructure", by the cooping of Cr and Ir. The cross-lamellar microstructure consists of a rod-like C11 b -phase grains that extend along a direction perpendicular to the lamellar interface in addition to the C40/C11 b fine lamellae. In this study, the effectiveness of the cross-lamellar microstructure for improving the high-temperature creep deformation property, being the most essential for UHT materials, was examined by using the oriented crystals. The creep rate significantly reduced along a loading orientation parallel to the lamellar interface. Furthermore, the degradation in creep strength for other loading orientation that is not parallel to the lamellar interface, which has been a serious problem up to now, was also suppressed. The results demonstrated that the simultaneous improvement of high-temperature creep strength and room temperature fracture toughness can be first accomplished by the development of unique cross-lamellar microstructure, which opens a potential avenue for the development of novel UHT materials as alternatives to existing Ni-based superalloys.

[Association between ambient temperature and hospital emergency room visits for cardiovascular diseases: a case-crossover study].

PubMed

Guo, Yu-Ming; Wang, Jia-Jia; Li, Guo-Xing; Zheng, Ya-An; He, Wichmann; Pan, Xiao-Chuan

2009-08-01

To explore the association between ambient average temperature and hospital emergency room visits for cardiovascular diseases (International Classification of Diseases, Tenth Vision ICD-10: I00 - I99) in Beijing, China. Data was collected on daily hospital emergency room visits for cardiovascular diseases from Peking University Third Hospital, including meteorological data (daily average temperature, relative humidity, wind speed, and atmospheric pressure) from the China Meteorological Data Sharing Service System, and on air pollution from the Beijing Municipal Environmental Monitoring Center. Time-stratified case-crossover design was used to analyze data on 4 seasons. After adjusting data on air pollution, 1 degree ( degrees C) increase of ambient average temperature would associate with the emergency room visits of odds ratio (ORs) as 1.282 (95%CI: 1.250 - 1.315), 1.027 (95%CI: 1.001 - 1.055), 0.661 (95%CI: 0.637 - 0.687), and 0.960 (95%CI: 0.937 - 0.984) in spring, summer, autumn, and winter respectively. After controlling the influence of relative humidity, wind speed, and atmospheric pressure, 1 degrees C increase in the ambient average temperature would be associated with the emergency room visits on ORs value as 1.423 (95%CI: 1.377 - 1.471), 1.082 (95%CI: 1.041 - 1.124), 0.633 (95%CI: 0.607 - 0.660) and 0.971 (95%CI: 0.944 - 1.000) in spring, summer, autumn, and winter respectively. These data on outcomes suggested that the elevated level of ambient temperature would increase the hospital emergency room visits for cardiovascular diseases in spring and summer while the elevated level of ambient temperature would decrease the hospital emergency room visits for the cardiovascular diseases in autumn and winter, suggesting that patients with cardiovascular diseases should pay attention to the climate change.

The effect of preheated versus room-temperature skin disinfection on bacterial colonization during pacemaker device implantation: a randomized controlled non-inferiority trial.

PubMed

Wistrand, Camilla; Söderquist, Bo; Magnusson, Anders; Nilsson, Ulrica

2015-01-01

In clinical practice, patients who are awake often comment that cold surgical skin disinfectant is unpleasant. This is not only a problem of patients' experience; heat loss during the disinfection process is a problem that can result in hypothermia. Evidence for the efficacy of preheated disinfection is scarce. We tested whether preheated skin disinfectant was non-inferior to room-temperature skin disinfectant on reducing bacterial colonization during pacemaker implantation. This randomized, controlled, non-inferiority trial included 220 patients allocated to skin disinfection with preheated (36 °C) or room-temperature (20 °C) chlorhexidine solution in 70 % ethanol. Cultures were obtained by swabbing at 4 time-points; 1) before skin disinfection (skin surface), 2) after skin disinfection (skin surface), 3) after the incision (subcutaneously in the wound), and 4) before suturing (subcutaneously in the wound). The absolute difference in growth between patients treated with preheated versus room-temperature skin disinfectant was zero (90 % CI -0.101 to 0.101; preheated: 30 of 105 [28.6 %] vs. room-temperature: 32 of 112 [28.6 %]). The pre-specified margin for statistical non-inferiority in the protocol was set at 10 % for the preheated disinfectant. There were no significant differences between groups regarding SSIs three month postoperatively, which occurred in 0.9 % (1 of 108) treated with preheated and 1.8 % (2 of 112) treated with room-temperature skin disinfectant. Preheated skin disinfection is non-inferior to room-temperature disinfection in bacterial reduction. We therefore suggest that preheated skin disinfection become routine in clean surgery. The study is registered at ClinicalTrials.gov (NCTO2260479).

Stability of procalcitonin at room temperature.

PubMed

Milcent, Karen; Poulalhon, Claire; Fellous, Christelle Vauloup; Petit, François; Bouyer, Jean; Gajdos, Vincent

2014-01-01

The aim was to assess procalcitonin (PCT) stability after two days of storage at room temperature. Samples were collected from febrile children aged 7 to 92 days and were rapidly frozen after sampling. PCT levels were measured twice after thawing: immediately (named y) and 48 hours later after storage at room temperature (named x). PCT values were described with medians and interquartile ranges or by categorizing them into classes with thresholds 0.25, 0.5, and 2 ng/mL. The relationship between x and y PCT levels was analyzed using fractional polynomials in order to predict the PCT value immediately after thawing (named y') from x. A significant decrease in PCT values was observed after 48 hours of storage at room temperature, either in median, 30% lowering (p < 0.001), or as categorical variable (p < 0.001). The relationship between x and y can be accurately modeled with a simple linear model: y = 1.37 x (R2 = 0.99). The median of the predicted PCT values y' was quantitatively very close to the median of y and the distributions of y and y' across categories were very similar and not statistically different. PCT levels noticeably decrease after 48 hours of storage at room temperature. It is possible to pre- dict accurately effective PCT values from the values after 48 hours of storage at room temperature with a simple statistical model.

Cystic fibrosis transmembrane conductance regulator: temperature-dependent cysteine reactivity suggests different stable conformers of the conduction pathway.

PubMed

Liu, Xuehong; Dawson, David C

2011-11-29

Cysteine scanning has been widely used to identify pore-lining residues in mammalian ion channels, including the cystic fibrosis transmembrane conductance regulator (CFTR). These studies, however, have been typically conducted at room temperature rather than human body temperature. Reports of substantial effects of temperature on gating and anion conduction in CFTR channels as well as an unexpected pattern of cysteine reactivity in the sixth transmembrane segment (TM6) prompted us to investigate the effect of temperature on the reactivity of cysteines engineered into TM6 of CFTR. We compared reaction rates at temperatures ranging from 22 to 37 °C for cysteines placed on either side of an apparent size-selective accessibility barrier previously defined by comparing reactivity toward channel-permeant and channel-impermeant, thiol-directed reagents. The results indicate that the reactivity of cysteines at three positions extracellular to the position of the accessibility barrier, 334, 336, and 337, is highly temperature-dependent. At 37 °C, cysteines at these positions were highly reactive toward MTSES(-), whereas at 22 °C, the reaction rates were 2-6-fold slower to undetectable. An activation energy of 157 kJ/mol for the reaction at position 337 is consistent with the hypothesis that, at physiological temperature, the extracellular portion of the CFTR pore can adopt conformations that differ significantly from those that can be accessed at room temperature. However, the position of the accessibility barrier defined empirically by applying channel-permeant and channel-impermeant reagents to the extracellular aspect of the pore is not altered. The results illuminate previous scanning results and indicate that the assay temperature is a critical variable in studies designed to use chemical modification to test structural models for the CFTR anion conduction pathway.

Airway humidification during high-frequency percussive ventilation.

PubMed

Allan, Patrick F; Hollingsworth, Michael J; Maniere, Gordon C; Rakofsky, Anthony K; Chung, Kevin K; Naworol, Gregory A; Ward, John A; Perello, Michelle; Morris, Michael J

2009-03-01

We were concerned about the risk of inadequate humidification during high-frequency percussive ventilation (HFPV). We studied 5 humidifiers during HFPV with a lung model, at bias gas flows of 10 L/min, 30 L/min, and 50 L/min, and compared the results to those from a comparator ventilator/humidifier setup and to the minimum temperature (30 degrees C) and humidity (30 mg/L) [corrected] recommended by the American Association for Respiratory Care, at both regular room temperature and a high ambient temperature. Temperature was measured at the humidifier outflow point and at the artificial carina. Humidity was measured at the artificial carina. Of the 7 HFPV/humidifier combinations, 2 (the MR850 at a bias flow of 50 L/min, and the ConchaTherm Hi-Flow with VDR nebulizer) provided a carinal temperature equivalent to the comparator setup at room temperature, whereas one HFPV/humidifier combination (the ConchaTherm Hi-Flow with modified programming, at bias flows of 30 L/min and 50 L/min) provided a higher carinal temperature. At high ambient temperature, all of the setups delivered lower carinal temperature than the comparator setup. Only 2 setups (the ConchaTherm with modified programming at a bias flow of 50 L/min, and the ConchaTherm Hi-Flow with VDR nebulizer) provided carinal humidification equivalent to the comparator setup, without regard to ambient temperature; the other humidifiers were less effective. The ConchaTherm with modified programming, and the ConchaTherm with the VDR nebulizer provided the most consistent humidification. HFPV's distinctive gas-flow mechanism may impair gas heating and humidification, so all humidification systems should be tested with HFPV prior to clinical use.

Graphene-based room-temperature implementation of a modified Deutsch-Jozsa quantum algorithm.

PubMed

Dragoman, Daniela; Dragoman, Mircea

2015-12-04

We present an implementation of a one-qubit and two-qubit modified Deutsch-Jozsa quantum algorithm based on graphene ballistic devices working at room temperature. The modified Deutsch-Jozsa algorithm decides whether a function, equivalent to the effect of an energy potential distribution on the wave function of ballistic charge carriers, is constant or not, without measuring the output wave function. The function need not be Boolean. Simulations confirm that the algorithm works properly, opening the way toward quantum computing at room temperature based on the same clean-room technologies as those used for fabrication of very-large-scale integrated circuits.

Thermal responses from repeated exposures to severe cold with intermittent warmer temperatures.

PubMed

Ozaki, H; Enomoto-Koshimizu, H; Tochihara, Y; Nakamura, K

1998-09-01

This study was conducted to evaluate physiological reaction and manual performance during exposure to warm (30 degrees C) and cool (10 degrees C) environments after exposure to very low temperatures (-25 degrees C). Furthermore, this experiment was conducted to study whether it is desirable to remove cold-protective jackets in warmer rooms after severe cold exposure. Eight male students remained in an extremely cold room for 20 min, after which they transferred into either the warm room or the cool room for 20 min. This pattern was repeated three times, and the total cold exposure time was 60 min. In the warm and cool rooms, the subjects either removed their cold-protective jackets (Condition A), or wore them continuously (Condition B). Rectal temperature, skin temperatures, manual performance, blood pressure, thermal, comfort and pain sensations were measured during the experiment. The effects of severe cold on almost all measurements in the cool (10 degrees C) environment were greater than those in the warm (30 degrees C) environment under both clothing conditions. The effects of severe cold on all measurements under Condition A except rectal temperature and toe skin temperature were significantly greater than those under Condition B in the cool environment but, not at all differences between Condition A and Condition B in the warm environments were significant. It was recognized that to remove cold-protective jackets in the cool room (10 degrees C) after severe cold exposure promoted the effects of severe cold. When rewarming in the warm resting room (30 degrees C), the physiological and psychological responses and manual performance were not influenced by the presence or absence of cold-protective clothing. These results suggest that it is necessary for workers to make sure to rewarm in the warm room outside of the cold storage and continue to wear cold-protective clothing in the cool room.

Iron aluminide alloys with improved properties for high temperature applications

DOEpatents

McKamey, Claudette G.; Liu, Chain T.

1990-01-01

An improved iron aluminide alloy of the DO.sub.3 type that has increased room temperature ductility and improved high elevated temperature strength. The alloy system further is resistant to corrosive attack in the environments of advanced energy corrosion systems such as those using fossil fuels. The resultant alloy is relatively inexpensive as contrasted to nickel based and high nickel steels currently utilized for structural components. The alloy system consists essentially of 26-30 at. % aluminum, 0.5-10 at. % chromium, 0.02-0.3 at. % boron plus carbon, up to 2 at. % molybdenum, up to 1 at. % niobium, up to 0.5 at. % zirconium, up to 0.1 at. % yttrium, up to 0.5 at. % vanadium and the balance iron.

Retention of Compressive Residual Stresses Introduced by Shot Peening in a Powder Metal Disk Superalloy

NASA Technical Reports Server (NTRS)

Gabb, Timothy P.; Danetti, Andrew; Draper, Susan L.; Locci, Ivan E.; Telesman, Jack

2016-01-01

The fatigue lives of disk superalloys can be increased by shot peening their surfaces, to induce compressive residual stresses near the surface that impede cracking there. As disk application temperatures increase for improved efficiency, the persistence of these beneficial stresses could be impaired, especially with continued fatigue cycling. The objective of this work was to study the retention of residual stresses introduced by shot peening, when subjected to fatigue and high temperatures. Fatigue specimens of powder metallurgy processed nickel-base disk superalloy ME3 were prepared with consistent processing and heat treatment. They were then shot peened using varied conditions. Strain-controlled fatigue cycles were run at room temperature and 704 C, to allow re-assessment of residual stresses.

Photoluminescence of ZnTe/ZnMgTe multiple quantum well structures grown on ZnTe substrates by molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Tanaka, Tooru; Ohshita, Hiroshi; Saito, Katsuhiko; Guo, Qixin

2018-02-01

Photoluminescence (PL) properties of ZnTe/ZnMgTe quantum well (QW) structures grown by molecular beam epitaxy (MBE) were investigated systematically with respect to well widths and Mg contents. Observed PL peak energies were consistent well with the calculated emission energies of the QWs considering a lattice distortion in the ZnTe well. From the temperature dependence of PL intensity, it was found that a suppression of a carrier escape from QW is crucial to obtain a PL at higher temperature in the ZnTe/ZnMgTe QW. Based on the results, multiple quantum well structures were designed and fabricated, which exhibited a green PL at room temperature.

Iron aluminide alloys with improved properties for high temperature applications

DOEpatents

McKamey, C.G.; Liu, C.T.

1990-10-09

An improved iron aluminide alloy of the DO[sub 3] type is described that has increased room temperature ductility and improved high elevated temperature strength. The alloy system further is resistant to corrosive attack in the environments of advanced energy conversion systems such as those using fossil fuels. The resultant alloy is relatively inexpensive as contrasted to nickel based and high nickel steels currently utilized for structural components. The alloy system consists essentially of 26--30 at. % aluminum, 0.5--10 at. % chromium, 0.02--0.3 at. % boron plus carbon, up to 2 at. % molybdenum, up to 1 at. % niobium, up to 0.5 at. % zirconium, up to 0.1 at. % yttrium, up to 0.5 at. % vanadium and the balance iron. 3 figs.

Formation of quasi-single crystalline porous ZnO nanostructures with a single large cavity

NASA Astrophysics Data System (ADS)

Cho, Seungho; Kim, Semi; Jung, Dae-Won; Lee, Kun-Hong

2011-09-01

We report a method for synthesizing quasi-single crystalline porous ZnO nanostructures containing a single large cavity. The microwave-assisted route consists of a short (about 2 min) temperature ramping stage (from room temperature to 120 °C) and a stage in which the temperature is maintained at 120 °C for 2 h. The structures produced by this route were 200-480 nm in diameter. The morphological yields of this method were very high. The temperature- and time-dependent evolution of the synthesized powders and the effects of an additive, vitamin C, were studied. Spherical amorphous/polycrystalline structures (70-170 nm in diameter), which appeared transitorily, may play a key role in the formation of the single crystalline porous hollow ZnO nanostructures. Studies and characterization of the nanostructures suggested a possible mechanism for formation of the quasi-single crystalline porous ZnO nanostructures with an interior space.We report a method for synthesizing quasi-single crystalline porous ZnO nanostructures containing a single large cavity. The microwave-assisted route consists of a short (about 2 min) temperature ramping stage (from room temperature to 120 °C) and a stage in which the temperature is maintained at 120 °C for 2 h. The structures produced by this route were 200-480 nm in diameter. The morphological yields of this method were very high. The temperature- and time-dependent evolution of the synthesized powders and the effects of an additive, vitamin C, were studied. Spherical amorphous/polycrystalline structures (70-170 nm in diameter), which appeared transitorily, may play a key role in the formation of the single crystalline porous hollow ZnO nanostructures. Studies and characterization of the nanostructures suggested a possible mechanism for formation of the quasi-single crystalline porous ZnO nanostructures with an interior space. Electronic supplementary information (ESI) available: TEM images and the corresponding SAED image of a ZnO nanostructure synthesized from the reaction without l(+)-ascorbic acid at the 85 °C time point (Fig. S1). See DOI: 10.1039/c1nr10609k

Room-temperature nine-µm-wavelength photodetectors and GHz-frequency heterodyne receivers.

PubMed

Palaferri, Daniele; Todorov, Yanko; Bigioli, Azzurra; Mottaghizadeh, Alireza; Gacemi, Djamal; Calabrese, Allegra; Vasanelli, Angela; Li, Lianhe; Davies, A Giles; Linfield, Edmund H; Kapsalidis, Filippos; Beck, Mattias; Faist, Jérôme; Sirtori, Carlo

2018-04-05

Room-temperature operation is essential for any optoelectronics technology that aims to provide low-cost, compact systems for widespread applications. A recent technological advance in this direction is bolometric detection for thermal imaging, which has achieved relatively high sensitivity and video rates (about 60 hertz) at room temperature. However, owing to thermally induced dark current, room-temperature operation is still a great challenge for semiconductor photodetectors targeting the wavelength band between 8 and 12 micrometres, and all relevant applications, such as imaging, environmental remote sensing and laser-based free-space communication, have been realized at low temperatures. For these devices, high sensitivity and high speed have never been compatible with high-temperature operation. Here we show that a long-wavelength (nine micrometres) infrared quantum-well photodetector fabricated from a metamaterial made of sub-wavelength metallic resonators exhibits strongly enhanced performance with respect to the state of the art up to room temperature. This occurs because the photonic collection area of each resonator is much larger than its electrical area, thus substantially reducing the dark current of the device. Furthermore, we show that our photonic architecture overcomes intrinsic limitations of the material, such as the drop of the electronic drift velocity with temperature, which constrains conventional geometries at cryogenic operation. Finally, the reduced physical area of the device and its increased responsivity allow us to take advantage of the intrinsic high-frequency response of the quantum detector at room temperature. By mixing the frequencies of two quantum-cascade lasers on the detector, which acts as a heterodyne receiver, we have measured a high-frequency signal, above four gigahertz (GHz). Therefore, these wide-band uncooled detectors could benefit technologies such as high-speed (gigabits per second) multichannel coherent data transfer and high-precision molecular spectroscopy.

Room-temperature nine-µm-wavelength photodetectors and GHz-frequency heterodyne receivers

NASA Astrophysics Data System (ADS)

Palaferri, Daniele; Todorov, Yanko; Bigioli, Azzurra; Mottaghizadeh, Alireza; Gacemi, Djamal; Calabrese, Allegra; Vasanelli, Angela; Li, Lianhe; Davies, A. Giles; Linfield, Edmund H.; Kapsalidis, Filippos; Beck, Mattias; Faist, Jérôme; Sirtori, Carlo

2018-04-01

Room-temperature operation is essential for any optoelectronics technology that aims to provide low-cost, compact systems for widespread applications. A recent technological advance in this direction is bolometric detection for thermal imaging, which has achieved relatively high sensitivity and video rates (about 60 hertz) at room temperature. However, owing to thermally induced dark current, room-temperature operation is still a great challenge for semiconductor photodetectors targeting the wavelength band between 8 and 12 micrometres, and all relevant applications, such as imaging, environmental remote sensing and laser-based free-space communication, have been realized at low temperatures. For these devices, high sensitivity and high speed have never been compatible with high-temperature operation. Here we show that a long-wavelength (nine micrometres) infrared quantum-well photodetector fabricated from a metamaterial made of sub-wavelength metallic resonators exhibits strongly enhanced performance with respect to the state of the art up to room temperature. This occurs because the photonic collection area of each resonator is much larger than its electrical area, thus substantially reducing the dark current of the device. Furthermore, we show that our photonic architecture overcomes intrinsic limitations of the material, such as the drop of the electronic drift velocity with temperature, which constrains conventional geometries at cryogenic operation. Finally, the reduced physical area of the device and its increased responsivity allow us to take advantage of the intrinsic high-frequency response of the quantum detector at room temperature. By mixing the frequencies of two quantum-cascade lasers on the detector, which acts as a heterodyne receiver, we have measured a high-frequency signal, above four gigahertz (GHz). Therefore, these wide-band uncooled detectors could benefit technologies such as high-speed (gigabits per second) multichannel coherent data transfer and high-precision molecular spectroscopy.

Mechanical properties of ZrB2- and HfB2-based ultra-high temperature ceramics fabricated by spark plasma sintering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zapata-Solvas, E.; Jayaseelan, D.; Lin, Hua-Tay

2013-01-01

Flexural strengths at room temperature, at 1400 C in air and at room temperature after 1 h oxidation at 1400 C were determined for ZrB2- and HfB2-based ultra-high temperature ceramics (UHTCs). Defects caused by electrical discharge machining (EDM) lowered measured strengths significantly and were used to calculate fracture toughness via a fracture mechanics approach. ZrB2 with 20 vol.% SiC had room temperature strength of 700 90 MPa, fracture toughness of 6.4 0.6 MPa, Vickers hardness at 9.8 N load of 21.1 0.6 GPa, 1400 C strength of 400 30 MPa and room temperature strength after 1 h oxidation at 1400more » C of 678 15 MPa with an oxide layer thickness of 45 5 m. HfB2 with 20 vol.% SiC showed room temperature strength of 620 50 MPa, fracture toughness of 5.0 0.4 MPa, Vickers hardness at 9.8 N load of 27.0 0.6 GPa, 1400 C strength of 590 150 MPa and room temperature strength after 1 h oxidation at 1400 C of 660 25 MPa with an oxide layer thickness of 12 1 m. 2 wt.% La2O3 addition to UHTCs slightly reduced mechanical performance while increasing tolerance to property degradation after oxidation and effectively aided internal stress relaxation during spark plasma sintering (SPS) cooling, as quantified by X-ray diffraction (XRD). Slow crack growth was suggested as the failure mechanism at high temperatures as a consequence of sharp cracks formation during oxidation.« less

Room-temperature multiferroic and magnetocapacitance effects in M-type hexaferrite BaFe{sub 10.2}Sc{sub 1.8}O{sub 19}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Rujun, E-mail: tangrj@suda.edu.cn, E-mail: yanghao@nuaa.edu.cn; Zhou, Hao; You, Wenlong

2016-08-22

The room-temperature multiferroic and magnetocapacitance (MC) effects of polycrystalline M-type hexaferrite BaFe{sub 10.2}Sc{sub 1.8}O{sub 19} have been investigated. The results show that the magnetic moments of insulating BaFe{sub 10.2}Sc{sub 1.8}O{sub 19} can be manipulated by the electric field at room temperature, indicating the existence of magnetoelectric coupling. Moreover, large MC effects are also observed around the room temperature. A frequency dependence analysis shows that the Maxwell-Wagner type magnetoresistance effect is the dominant mechanism for MC effects at low frequencies. Both the magnetoelectric-type and non-magnetoelectric-type spin-phonon couplings contribute to the MC effects at high frequencies with the former being the dominantmore » mechanism. The above results show that the hexaferrite BaFe{sub 10.2}Sc{sub 1.8}O{sub 19} is a room-temperature multiferroic material that can be potentially used in magnetoelectric devices.« less

Crystal induced phosphorescence from Benz(a)anthracene microcrystals at room temperature

NASA Astrophysics Data System (ADS)

Maity, Samir; Mazumdar, Prativa; Shyamal, Milan; Sahoo, Gobinda Prasad; Misra, Ajay

2016-03-01

Pure organic compounds that are also phosphorescent at room temperature are very rare in literature. Here, we report efficient phosphorescence emission from aggregated hydrosol of Benz(a)anthracene (BaA) at room temperature. Aggregated hydrosol of BaA has been synthesized by re-precipitation method and SDS is used as morphology directing agent. Morphology of the particles is characterized using optical and scanning electronic microcopy (SEM). Photophysical properties of the aggregated hydrosol are carried out using UV-vis, steady state and time resolved fluorescence study. The large stoke shifted structured emission from aggregated hydrosol of BaA has been explained due to phosphorescence emission of BaA at room temperature. In the crystalline state, the restricted intermolecular motions (RIM) such as rotations and vibrations are activated by crystal lattice. This rigidification effect makes the chromophore phosphorescent at room temperature. The possible stacking arrangement of the neighboring BaA within the aggregates has been substantiated by computing second order Fukui parameter as local reactivity descriptors. Computational study also reveals that the neighboring BaA molecules are present in parallel slipped conformation in its aggregated crystalline form.

Quantitative Investigation of Room-Temperature Breakdown Effects in Pixelated TlBr Detectors

NASA Astrophysics Data System (ADS)

Koehler, Will; He, Zhong; Thrall, Crystal; O'Neal, Sean; Kim, Hadong; Cirignano, Leonard; Shah, Kanai

2014-10-01

Due to favorable material properties such as high atomic number (Tl: 81, Br: 35), high density ( 7.56 g/cm3), and a wide band gap (2.68 eV), thallium-bromide (TlBr) is currently under investigation for use as an alternative room-temperature semiconductor gamma-ray spectrometer. TlBr detectors can achieve less than 1% FWHM energy resolution at 662 keV, but these results are limited to stable operation at - 20°C. After days to months of room-temperature operation, ionic conduction causes these devices to fail. This work correlates the varying leakage current with alpha-particle and gamma-ray spectroscopic performances at various operating temperatures. Depth-dependent photopeak centroids exhibit time-dependent transient behavior, which indicates trapping sites form near the anode surface during room-temperature operation. After refabrication, similar performance and functionality of failed detectors returned.

Giant Room-Temperature Magnetodielectric Response in a MOF at 0.1 Tesla.

PubMed

Chen, Li-Hong; Guo, Jiang-Bin; Wang, Xuan; Dong, Xin-Wei; Zhao, Hai-Xia; Long, La-Sheng; Zheng, Lan-Sun

2017-11-01

A giant room-temperature magnetodielectric (MD) response upon the application of a small magnetic field is of fundamental importance for the practical application of a new generation of devices. Here, the giant room-temperature magnetodielectric response is demonstrated in the metal-organic framework (MOF) of [NH 2 (CH 3 ) 2 ] n [Fe III Fe II (1- x ) Ni II x (HCOO) 6 ] n (x ≈ 0.63-0.69) (1) with its MD coefficient remaining between -20% and -24% in the 300-410 K temperature range, even at 0.1 T. Because a room-temperature magnetodielectric response has never been observed in MOFs, the present work not only provides a new type of magnetodielectric material but also takes a solid step toward the practical application of MOFs in a new generation of devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Room-temperature creation and spin-orbit torque-induced manipulation of skyrmions in thin film

NASA Astrophysics Data System (ADS)

Yu, Guoqiang; Upadhyaya, Pramey; Li, Xiang; Li, Wenyuan; Im, Se Kwon K.; Fan, Yabin; Wong, Kin L.; Tserkovnyak, Yaroslav; Amiri, Pedram Khalili; Wang, Kang L.

Magnetic skyrmions, which are topologically protected spin texture, are promising candidates for ultra-low energy and ultra-high density magnetic data storage and computing applications1, 2. To date, most experiments on skyrmions have been carried out at low temperatures. The choice of materials available is limited and there is a lack of electrical means to control of skyrmions. Here, we experimentally demonstrate a method for creating skyrmion bubbles phase in the ferromagnetic thin film at room temperature. We further demonstrate that the created skyrmion bubbles can be manipulated by electric current. This room-temperature creation and manipulation of skyrmion in thin film is of particular interest for applications, being suitable for room-temperature operation and compatible with existing semiconductor manufacturing tools. 1. Nagaosa, N., Tokura, Y. Nature Nanotechnology 8, 899-911 (2013). 2. Fert, A., et al., Nature Nanotechnology 8, 152-156 (2013).

Room-temperature ferroelectricity of SrTiO{sub 3} films modulated by cation concentration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Fang; Zhang, Qinghua; Yang, Zhenzhong

2015-08-24

The room-temperature ferroelectricity of SrTiO{sub 3} is promising for oxide electronic devices controlled by multiple fields. An effective way to control the ferroelectricity is highly demanded. Here, we show that the off-centered antisite-like defects in SrTiO{sub 3} films epitaxially grown on Si (001) play the determinative role in the emergence of room-temperature ferroelectricity. The density of these defects changes with the film cation concentration sensitively, resulting in a varied coercive field of the ferroelectric behavior. Consequently, the room-temperature ferroelectricity of SrTiO{sub 3} films can be effectively modulated by tuning the temperature of metal sources during the molecular beam epitaxy growth.more » Such an easy and reliable modulation of the ferroelectricity enables the flexible engineering of multifunctional oxide electronic devices.« less

A Stable Room-Temperature Luminescent Biphenylmethyl Radical.

PubMed

Ai, Xin; Chen, Yingxin; Feng, Yuting; Li, Feng

2018-03-05

There is only one family of room-temperature luminescent radicals, the triphenylmethyl radicals, to date. Herein, we synthesize a new stable room-temperature luminescent radical, (N-carbazolyl)bis(2,4,6-tirchlorophenyl)methyl radical (CzBTM), which has improved properties compared to the triphenylmethyl radicals. X-ray crystallography, electron paramagnetic resonance spectroscopy, and magnetic susceptibility measurements confirmed the radical structure. CzBTM shows room-temperature deep-red to near-infrared emission in various solutions. Both thermal and photo stability were significantly enhanced by the replacement of trichlorobenzene by the carbazole moiety. The electroluminescence results of CzBTM verify its potential application to circumvent the problem of triplet harvesting in traditional fluorescent OLEDs. A new family of stable luminescent radicals based on CzBTM is anticipated. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Collaborative Research: Polymeric Multiferroics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ren, Shenqiang

2017-04-20

The goal of this project is to investigate room temperature magnetism and magnetoelectric coupling of polymeric multiferroics. A new family of molecular charge-transfer crystals has been emerged as a fascinating opportunity for the development of all-organic electrics and spintronics due to its weak hyperfine interaction and low spin-orbit coupling; nevertheless, direct observations of room temperature magnetic spin ordering have yet to be accomplished in organic charge-transfer solids. Furthermore, room temperature magnetoelectric coupling effect hitherto known multiferroics, is anticipated in organic donor-acceptor complexes because of magnetic field effects on charge-transfer dipoles, yet this is also unexplored. The PI seeks to fundamentalmore » understanding of the control of organic crystals to demonstrate and explore room temperature multiferroicity. The experimental results have been verified through the theoretical modeling.« less

Preparation of Boron Nitride Nanoparticles with Oxygen Doping and a Study of Their Room-Temperature Ferromagnetism.

PubMed

Lu, Qing; Zhao, Qi; Yang, Tianye; Zhai, Chengbo; Wang, Dongxue; Zhang, Mingzhe

2018-04-18

In this work, oxygen-doped boron nitride nanoparticles with room-temperature ferromagnetism have been synthesized by a new, facile, and efficient method. There are no metal magnetic impurities in the nanoparticles analyzed by X-ray photoelectron spectroscopy. The boron nitride nanoparticles exhibit a parabolic shape with increase in the reaction time. The saturation magnetization value reaches a maximum of 0.2975 emu g -1 at 300 K when the reaction time is 12 h, indicating that the Curie temperature ( T C ) is higher than 300 K. Combined with first-principles calculation, the coupling between B 2p orbital, N 2p orbital, and O 2p orbital in the conduction bands is the main origin of room-temperature ferromagnetism and also proves that the magnetic moment changes according the oxygen-doping content change. Compared with other room temperature ferromagnetic semiconductors, boron nitride nanoparticles have widely potential applications in spintronic devices because of high temperature oxidation resistance and excellent chemical stability.

Oxidation and thermal fatigue of coated and uncoated NX-188 nickel-base alloy in a high velocity gas stream

NASA Technical Reports Server (NTRS)

Johnson, J. R.; Young, S. G.

1972-01-01

A cast nickel-base superalloy, NX-188, coated and uncoated, was tested in a high-velocity gas stream for resistance to oxidation and thermal fatigue by cycling between room temperature and 980, 1040, and 1090 C. Contrary to the behavior of more conventional nickel-base alloys, uncoated NX-188 exhibited the greatest weight loss at the lowest test temperature. In general, on the basis of weight change and metallographic observations a coating consisting of vapor-deposited Fe-Cr-Al-Y over a chromized substrate exhibited the best overall performance in resistance to oxidation and thermal fatigue.

Thermodynamic limits for solar energy conversion by a quantum-thermal hybrid system

NASA Technical Reports Server (NTRS)

Byvik, C. E.; Buoncristiani, A. M.; Smith, B. T.

1981-01-01

The limits are presented fo air mass 1.5 conditions. A maximum conversion efficiency of 74 percent is thermodynamically achievable for the quantum device operating at 3500 K and the heat engine in contact with a reservoir at 0 K. The efficiency drops to 56 percent for a cold reservoir at approximately room temperature conditions. Hybrid system efficiencies exceed 50 percent over receiver temperatures ranging from 1400 K to 4000 K, suggesting little benefit is gained in operating the system above 1400 K. The results are applied to a system consisting of a photovoltaic solar cell in series with a heat engine.

Charge and spin transport in metal-graphene-metal vertical junctions

NASA Astrophysics Data System (ADS)

Cobas, Enrique; van't Erve, Olaf; Cheng, Shu-Fan; Culbertson, James; Jernigan, Glenn; Bussman, Konrad; Jonker, Berry

We observe negative magnetoresistance(MR) in metallic NiFe(111)|multi-layer graphene|Fe heterostructures consistent with minority spin filtering. The MR is -5 percent at room temperature and -12 percent at 10 K. The transport properties and temperature dependence are metallic. We further investigate the out-of-plane (c-axis) resistivity and magnetoresistance of multi-layer graphene between metal surfaces. We fabricate various metal-graphene-metal vertical heterostructures via chemical vapor deposition directly on lattice-matched crystalline metal films including NiFe(111) and Co(0002) and in-situ electron beam evaporation of NiFe, Co, Ni, Fe, Cu and Au.

Leakage conduction behavior in electron-beam-cured nanoporous silicate films

NASA Astrophysics Data System (ADS)

Liu, Po-Tsun; Tsai, T. M.; Chang, T. C.

2005-05-01

This letter explores the application of electron-beam curing on nanoporous silicate films. The electrical conduction mechanism for the nanoporous silicate film cured by electron-beam radiation has been studied with metal-insulator-semiconductor capacitors. Electrical analyses over a varying temperature range from room temperature to 150°C provide evidence for space-charge-limited conduction in the electron-beam-cured thin film, while Schottky-emission-type leaky behavior is seen in the counterpart typically cured by a thermal furnace. A physical model consistent with electrical analyses is also proposed to deduce the origin of conduction behavior in the nanoporous silicate thin film.

Dielectric 1/f noise of proton glass on a hydrated protein surface

NASA Astrophysics Data System (ADS)

Careri, Giorgio; Consolini, Giuseppe

2000-09-01

From nonexponentiality of dielectric relaxation detected in hydrated lysozyme powder we evaluate the power spectrum x2ω of the fluctuating dipole moment x¯2 of one macromolecule, due to the glass of protons migrating on the protein surface. Near room temperature, the contribution to the total dipole moment by the integrated strength of the 1/fα noise in the frequency range from 104 to 106 Hz, is well consistent with early Kirkwood's predictions in solution and more recent computations. The biochemical significance of the nonequilibrium region near the Vogel-Fulcher temperature T0~268 K calls for further investigations.

Direct synthesis of ultrafine tetragonal BaTiO3 nanoparticles at room temperature

PubMed Central

2011-01-01

A large quantity of ultrafine tetragonal barium titanate (BaTiO3) nanoparticles is directly synthesized at room temperature. The crystalline form and grain size are checked by both X-ray diffraction and transmission electron microscopy. The results revealed that the perovskite nanoparticles as fine as 7 nm have been synthesized. The phase transition of the as-prepared nanoparticles is investigated by the temperature-dependent Raman spectrum and shows the similar tendency to that of bulk BaTiO3 materials. It is confirmed that the nanoparticles have tetragonal phase at room temperature. PMID:21781339

Room-temperature magnetoelectric multiferroic thin films and applications thereof

DOEpatents

Katiyar, Ram S; Kuman, Ashok; Scott, James F.

2014-08-12

The invention provides a novel class of room-temperature, single-phase, magnetoelectric multiferroic (PbFe.sub.0.67W.sub.0.33O.sub.3).sub.x (PbZr.sub.0.53Ti.sub.0.47O.sub.3).sub.1-x (0.2.ltoreq.x.ltoreq.0.8) (PFW.sub.x-PZT.sub.1-x) thin films that exhibit high dielectric constants, high polarization, weak saturation magnetization, broad dielectric temperature peak, high-frequency dispersion, low dielectric loss and low leakage current. These properties render them to be suitable candidates for room-temperature multiferroic devices. Methods of preparation are also provided.

Room temperature ferromagnetic and semiconducting properties of graphene adsorbed with cobalt oxide using electrochemical method

NASA Astrophysics Data System (ADS)

Park, Chang-Soo; Lee, Kyung Su; Chu, Dongil; Lee, Juwon; Shon, Yoon; Kim, Eun Kyu

2017-12-01

We report the room temperature ferromagnetic properties of graphene adsorbed by cobalt oxide using electrochemical method. The cobalt oxide doping onto graphene was carried out in 0.1 M LiCoO2/DI-water solution. The doped graphene thin film was determined to be a single layer from Raman analysis. The CoO doped graphene has a clear ferromagnetic hysteresis at room temperature and showed a remnant magnetization, 128.2 emu/cm3. The temperature dependent conductivity of the adsorbed graphene showed the semiconducting behavior and a band gap opening of 0.12 eV.

Long-term hot-hardness characteristics of five through-hardened bearing steels

NASA Technical Reports Server (NTRS)

Anderson, N. E.

1978-01-01

Five vacuum-melted bearing steels tempered to various room temperature hardnesses: AISI 52100 and the tool steels AISI M-1, AISI M-50, Halmo, and WB-49 were studied. Hardness measurements were taken on AISI 52100 at room temperature and at elevated temperatures after soaking it at temperatures to 478 K (400 F) for as long as 1000 hours. Hardness measurements were also taken on the tool steels after soaking them at temperatures to 700 K (800 F) for as long at 1000 hours. None of the tool steel tempered during soaking and AISI 52100 did not temper when soaked at 366 K (200 F) for 1000 hours. However, AISI 52100 that was initially hardened to room temperature hardness of 62.5 or 64.5 lost hardness during the first 500 hours of the 1000-hour soak tests at temperatures greater than 394 K (250 F), but it maintained its hardness during the final 500 hours of soaking. Similarly, AISI 52100 initially hardened to room temperature hardness of 60.5 lost hardness during the first 500 hours of the 1000-hour soaking at temperatures greater than 422 K (300 F), but it maintained its hardness during the final 500 hours of soaking.

46 CFR 111.01-15 - Temperature ratings.

Code of Federal Regulations, 2013 CFR

2013-10-01

... Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS... is assumed for all rotating electrical machinery in boiler rooms, engine rooms, auxiliary machinery...-rotating electrical equipment in boiler rooms, in engine rooms, in auxiliary machinery rooms, and on...

46 CFR 111.01-15 - Temperature ratings.

Code of Federal Regulations, 2012 CFR

2012-10-01

... Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS... is assumed for all rotating electrical machinery in boiler rooms, engine rooms, auxiliary machinery...-rotating electrical equipment in boiler rooms, in engine rooms, in auxiliary machinery rooms, and on...

46 CFR 111.01-15 - Temperature ratings.

Code of Federal Regulations, 2014 CFR

2014-10-01

... Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS... is assumed for all rotating electrical machinery in boiler rooms, engine rooms, auxiliary machinery...-rotating electrical equipment in boiler rooms, in engine rooms, in auxiliary machinery rooms, and on...

Self-locking threaded fasteners

DOEpatents

Glovan, Ronald J.; Tierney, John C.; McLean, Leroy L.; Johnson, Lawrence L.

1996-01-01

A threaded fastener with a shape memory alloy (SMA) coatings on its threads is disclosed. The fastener has special usefulness in high temperature applications where high reliability is important. The SMA coated fastener is threaded into or onto a mating threaded part at room temperature to produce a fastened object. The SMA coating is distorted during the assembly. At elevated temperatures the coating tries to recover its original shape and thereby exerts locking forces on the threads. When the fastened object is returned to room temperature the locking forces dissipate. Consequently the threaded fasteners can be readily disassembled at room temperature but remains securely fastened at high temperatures. A spray technique is disclosed as a particularly useful method of coating of threads of a fastener with a shape memory alloy.

Synthesis of isoflavones by room-temperature nickel-catalyzed cross-couplings of 3-iodo(bromo)chromones with arylzincs.

PubMed

Zhang, Zunting; Qiao, Jinfeng; Wang, Ding; Han, Ling; Ding, Ru

2014-05-01

A new concise, facile method for synthesis of isoflavones was accomplished in moderate to good yields for 3-iodochromones or 3-bromochromones and arylzinc bromides via Negishi cross-coupling reaction catalyzed by NiCl(2)/PPh(3) or NiCl(2)(PPh(3))(2) at room temperature. The Isoflavone core was synthesized in four steps in good yield, starting from commercially available 2-hydroxyacetophenone and aromatic bromide. Three steps of the procedure were carried out at room temperature.

Temperature autocontrol system for the coud%eacute; room of the 1.2 m telescope

NASA Astrophysics Data System (ADS)

Zhang, Jian-Hua

The setting up of temperature autocontrol system for the coudé room of the 1.2 m telescope at Yunnan Observatory and realizing the airflow autocirculation, purified the air, keeping the temperature in the coudé room constantly by autocontrol the heater, and then keeping the optical system in the best condition are introduced in this paper. The autocontrol system is designed and developed at the basis of having only the air circulator and the heater controlled by hand.

Advancing the Capabilities of an Authentic Ex Vivo Model of Primary Human Prostate Cancer

DTIC Science & Technology

2014-10-01

maintained the PTEN expression of the native tissues after 5 days in culture. Prostate-specific membrane antigen ( PSMA ) was detected in benign and malignant...room temperature 1 h room temperature 30 min room temperature Abcam, Cambridge, MA, USA p63 SMA CD68 PSMA Mouse monoclonal Mouse monoclonal Mouse...Prostate-specific membrane antigen ( PSMA ) was detected in benign and malignant glands as expected in both native tissue and in TSCs after 5 days.47

Room Temperature Intrinsic Ferromagnetism in Epitaxial Manganese Selenide Films in the Monolayer Limit

NASA Astrophysics Data System (ADS)

O'Hara, Dante J.; Zhu, Tiancong; Trout, Amanda H.; Ahmed, Adam S.; Luo, Yunqiu Kelly; Lee, Choong Hee; Brenner, Mark R.; Rajan, Siddharth; Gupta, Jay A.; McComb, David W.; Kawakami, Roland K.

2018-05-01

Monolayer van der Waals (vdW) magnets provide an exciting opportunity for exploring two-dimensional (2D) magnetism for scientific and technological advances, but the intrinsic ferromagnetism has only been observed at low temperatures. Here, we report the observation of room temperature ferromagnetism in manganese selenide (MnSe$_x$) films grown by molecular beam epitaxy (MBE). Magnetic and structural characterization provides strong evidence that in the monolayer limit, the ferromagnetism originates from a vdW manganese diselenide (MnSe$_2$) monolayer, while for thicker films it could originate from a combination of vdW MnSe$_2$ and/or interfacial magnetism of $\\alpha$-MnSe(111). Magnetization measurements of monolayer MnSe$_x$ films on GaSe and SnSe$_2$ epilayers show ferromagnetic ordering with large saturation magnetization of ~ 4 Bohr magnetons per Mn, which is consistent with density functional theory calculations predicting ferromagnetism in monolayer 1T-MnSe$_2$. Growing MnSe$_x$ films on GaSe up to high thickness (~ 40 nm) produces $\\alpha$-MnSe(111), and an enhanced magnetic moment (~ 2x) compared to the monolayer MnSe$_x$ samples. Detailed structural characterization by scanning transmission electron microscopy (STEM), scanning tunneling microscopy (STM), and reflection high energy electron diffraction (RHEED) reveal an abrupt and clean interface between GaSe(0001) and $\\alpha$-MnSe(111). In particular, the structure measured by STEM is consistent with the presence of a MnSe$_2$ monolayer at the interface. These results hold promise for potential applications in energy efficient information storage and processing.

High mobility, dual layer, c-axis aligned crystalline/amorphous IGZO thin film transistor

NASA Astrophysics Data System (ADS)

Chung, Chen-Yang; Zhu, Bin; Greene, Raymond G.; Thompson, Michael O.; Ast, Dieter G.

2015-11-01

We demonstrate a dual layer IGZO thin film transistor (TFT) consisting of a 310 °C deposited c-axis aligned crystal (CAAC) 20 nm thick channel layer capped by a second, 30 nm thick, 260 °C deposited amorphous IGZO layer. The TFT exhibits a saturation field-effect mobility of ˜20 cm2/V s, exceeding the mobility of 50 nm thick single layer reference TFTs fabricated with either material. The deposition temperature of the second layer influences the mobility of the underlying transport layer. When the cap layer is deposited at room temperature (RT), the mobility in the 310 °C deposited CAAC layer is initially low (6.7 cm2/V s), but rises continuously with time over 58 days to 20.5 cm2/V s, i.e., to the same value as when the second layer is deposited at 260 °C. This observation indicates that the two layers equilibrate at RT with a time constant on the order of 5 × 106 s. An analysis based on diffusive transport indicates that the room temperature diffusivity must be of the order of 1 × 10-18 cm2 s-1 with an activation enthalpy EA < 0.2 eV for the mobility limiting species. The findings are consistent with a hypothesis that the amorphous layer deposited on top of the CAAC has a higher solubility for impurities and/or structural defects than the underlying nanocrystalline transport layer, and that the equilibration of the mobility limiting species is rate limited by hydrogen diffusion, whose known diffusivity fits these estimates.

Surface conduction of topological Dirac electrons in bulk insulating Bi2Se3

NASA Astrophysics Data System (ADS)

Fuhrer, Michael

2013-03-01

The three dimensional strong topological insulator (STI) is a new phase of electronic matter which is distinct from ordinary insulators in that it supports on its surface a conducting two-dimensional surface state whose existence is guaranteed by topology. I will discuss experiments on the STI material Bi2Se3, which has a bulk bandgap of 300 meV, much greater than room temperature, and a single topological surface state with a massless Dirac dispersion. Field effect transistors consisting of thin (3-20 nm) Bi2Se3 are fabricated from mechanically exfoliated from single crystals, and electrochemical and/or chemical gating methods are used to move the Fermi energy into the bulk bandgap, revealing the ambipolar gapless nature of transport in the Bi2Se3 surface states. The minimum conductivity of the topological surface state is understood within the self-consistent theory of Dirac electrons in the presence of charged impurities. The intrinsic finite-temperature resistivity of the topological surface state due to electron-acoustic phonon scattering is measured to be ~60 times larger than that of graphene largely due to the smaller Fermi and sound velocities in Bi2Se3, which will have implications for topological electronic devices operating at room temperature. As samples are made thinner, coherent coupling of the top and bottom topological surfaces is observed through the magnitude of the weak anti-localization correction to the conductivity, and, in the thinnest Bi2Se3 samples (~ 3 nm), in thermally-activated conductivity reflecting the opening of a bandgap.

Mossbauer Study of Low Temperature Magnetic and magnetooptic Properties of Amorphous Tb/Fe Multilayers

NASA Astrophysics Data System (ADS)

Chowdhury, Ataur

Magnetic and magnetooptic properties of multilayers critically depend on detailed magnetic and structural ordering of the interface. To study these properties in Tb/Fe multilayers, samples with varying layer thicknesses were fabricated by planar magnetic sputtering on polyester substrates. Mossbauer effect spectra were recorded at different temperatures ranging between 20 K and 300 K. The results show that perpendicular magnetic anisotropy (PMA) increases as temperature decreases for samples that show parallel anisotropy at room temperature, and for samples that show strong PMA at room temperature, no significant change in PMA is observed at low temperature (<100 K). Hyperfine field of samples that display parallel anisotropy at room temperature shows oscillatory behavior, reminiscent of RKKY oscillations, at low temperatures (<100 K). Plausible causes of these properties will be discussed in the paper.

Conformational variation of proteins at room temperature is not dominated by radiation damage

DOE PAGES

Russi, Silvia; González, Ana; Kenner, Lillian R.; ...

2017-01-01

Protein crystallography data collection at synchrotrons is routinely carried out at cryogenic temperatures to mitigate radiation damage. Although damage still takes place at 100 K and below, the immobilization of free radicals increases the lifetime of the crystals by approximately 100-fold. Recent studies have shown that flash-cooling decreases the heterogeneity of the conformational ensemble and can hide important functional mechanisms from observation. These discoveries have motivated increasing numbers of experiments to be carried out at room temperature. However, the trade-offs between increased risk of radiation damage and increased observation of alternative conformations at room temperature relative to cryogenic temperature havemore » not been examined. A considerable amount of effort has previously been spent studying radiation damage at cryo-temperatures, but the relevance of these studies to room temperature diffraction is not well understood. Here, the effects of radiation damage on the conformational landscapes of three different proteins ( T. danielli thaumatin, hen egg-white lysozyme and human cyclophilin A) at room (278 K) and cryogenic (100 K) temperatures are investigated. Increasingly damaged datasets were collected at each temperature, up to a maximum dose of the order of 10 7 Gy at 100 K and 10 5 Gy at 278 K. Although it was not possible to discern a clear trend between damage and multiple conformations at either temperature, it was observed that disorder, monitored by B-factor-dependent crystallographic order parameters, increased with higher absorbed dose for the three proteins at 100 K. At 278 K, however, the total increase in this disorder was only statistically significant for thaumatin. A correlation between specific radiation damage affecting side chains and the amount of disorder was not observed. Lastly, this analysis suggests that elevated conformational heterogeneity in crystal structures at room temperature is observed despite radiation damage, and not as a result thereof.« less

Conformational variation of proteins at room temperature is not dominated by radiation damage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Russi, Silvia; González, Ana; Kenner, Lillian R.

Protein crystallography data collection at synchrotrons is routinely carried out at cryogenic temperatures to mitigate radiation damage. Although damage still takes place at 100 K and below, the immobilization of free radicals increases the lifetime of the crystals by approximately 100-fold. Recent studies have shown that flash-cooling decreases the heterogeneity of the conformational ensemble and can hide important functional mechanisms from observation. These discoveries have motivated increasing numbers of experiments to be carried out at room temperature. However, the trade-offs between increased risk of radiation damage and increased observation of alternative conformations at room temperature relative to cryogenic temperature havemore » not been examined. A considerable amount of effort has previously been spent studying radiation damage at cryo-temperatures, but the relevance of these studies to room temperature diffraction is not well understood. Here, the effects of radiation damage on the conformational landscapes of three different proteins ( T. danielli thaumatin, hen egg-white lysozyme and human cyclophilin A) at room (278 K) and cryogenic (100 K) temperatures are investigated. Increasingly damaged datasets were collected at each temperature, up to a maximum dose of the order of 10 7 Gy at 100 K and 10 5 Gy at 278 K. Although it was not possible to discern a clear trend between damage and multiple conformations at either temperature, it was observed that disorder, monitored by B-factor-dependent crystallographic order parameters, increased with higher absorbed dose for the three proteins at 100 K. At 278 K, however, the total increase in this disorder was only statistically significant for thaumatin. A correlation between specific radiation damage affecting side chains and the amount of disorder was not observed. Lastly, this analysis suggests that elevated conformational heterogeneity in crystal structures at room temperature is observed despite radiation damage, and not as a result thereof.« less

Reversible Dissolution of Microdomains in Detergent-Resistant Membranes at Physiological Temperature

PubMed Central

Cremona, Andrea; Orsini, Francesco; Corsetto, Paola A.; Hoogenboom, Bart W.; Rizzo, Angela M.

2015-01-01

The formation of lipid microdomains (“rafts”) is presumed to play an important role in various cellular functions, but their nature remains controversial. Here we report on microdomain formation in isolated, detergent-resistant membranes from MDA-MB-231 human breast cancer cells, studied by atomic force microscopy (AFM). Whereas microdomains were readily observed at room temperature, they shrunk in size and mostly disappeared at higher temperatures. This shrinking in microdomain size was accompanied by a gradual reduction of the height difference between the microdomains and the surrounding membrane, consistent with the behaviour expected for lipids that are laterally segregated in liquid ordered and liquid disordered domains. Immunolabeling experiments demonstrated that the microdomains contained flotillin-1, a protein associated with lipid rafts. The microdomains reversibly dissolved and reappeared, respectively, on heating to and cooling below temperatures around 37°C, which is indicative of radical changes in local membrane order close to physiological temperature. PMID:26147107

Octahedral cation partitioning in Mg,Fe2+-olivine. Mössbauer spectroscopic study of synthetic (Mg0.5 Fe2+ 0.5)2SiO4 (Fa50)

NASA Astrophysics Data System (ADS)

Morozov, Mikhail; Brinkmann, Christian; Grodzicki, Michael; Lottermoser, Werner; Tippelt, Gerold; Amthauer, Georg; Kroll, Herbert

2005-11-01

The high-temperature partitioning of Fe2+ and Mg between the two non-equivalent octahedral M1 and M2 sites in synthetic olivine (Fa50) was studied by Mössbauer spectroscopy. Powder samples have been equilibrated in annealing experiments performed under reducing oxygen fugacity at temperatures between 500 and 800°C followed by rapid quenching in order to prevent redistribution of cations. M-site ordering with Fe2+ preferring M1, Mg preferring M2 sites increases continuously with rising equilibrium temperature. K D values increase from 1.21 at 500°C to 1.48 at 750°C. The results are consistent with both room temperature as well as in situ high temperature single crystal X-ray diffraction experiments of Heinemann et al. [8, 9].

Phononic Crystal Tunable via Ferroelectric Phase Transition

NASA Astrophysics Data System (ADS)

Xu, Chaowei; Cai, Feiyan; Xie, Shuhong; Li, Fei; Sun, Rong; Fu, Xianzhu; Xiong, Rengen; Zhang, Yi; Zheng, Hairong; Li, Jiangyu

2015-09-01

Phononic crystals (PCs) consisting of periodic materials with different acoustic properties have potential applications in functional devices. To realize more smart functions, it is desirable to actively control the properties of PCs on demand, ideally within the same fabricated system. Here, we report a tunable PC made of Ba0.7Sr0.3Ti O3 (BST) ceramics, wherein a 20-K temperature change near room temperature results in a 20% frequency shift in the transmission spectra induced by a ferroelectric phase transition. The tunability phenomenon is attributed to the structure-induced resonant excitation of A0 and A1 Lamb modes that exist intrinsically in the uniform BST plate, while these Lamb modes are sensitive to the elastic properties of the plate and can be modulated by temperature in a BST plate around the Curie temperature. The study finds opportunities for creating tunable PCs and enables smart temperature-tuned devices such as the Lamb wave filter or sensor.

Low-temperature performance of semiconducting asymmetric nanochannel diodes

NASA Astrophysics Data System (ADS)

Akbas, Y.; Savich, G. R.; Jukna, A.; Plecenik, T.; Ďurina, P.; Plecenik, A.; Wicks, G. W.; Sobolewski, Roman

2017-10-01

We present our studies on fabrication and electrical and optical characterization of semiconducting asymmetric nanochannel diodes (ANCDs), focusing mainly on the temperature dependence of their current-voltage (I-V) characteristics in the range from room temperature to 77 K. These measurements enable us to elucidate the electron transport mechanism in a nanochannel. Our test devices were fabricated in a GaAs/AlGaAs heterostructure with a two-dimensional electron gas layer and were patterned using electron-beam lithography. The 250-nm-wide, 70-nm-deep trenches that define the nanochannel were ion-beam etched using the photoresist as a mask, so the resulting nanostructure consisted of approximately ten ANCDs connected in parallel with 2-µm-long, 230-nm-wide nanochannels. The ANCD I-V curves collected in the dark exhibited nonlinear, diode-type behavior at all tested temperatures. Their forward-biased regions were fitted to the classical diode equation with a thermionic barrier, with the ideality factor n and the saturation current as fitting parameters. We have obtained very good fits, but with n as large as ˜50, suggesting that there must be a substantial voltage drop likely at the contact pads. The thermionic energy barrier was determined to be 56 meV at high temperatures. We have also observed that under optical illumination our ANCDs at low temperatures exhibited, at low illumination powers, a very strong photoresponse enhancement that exceeded that at room temperature. At 78 K, the responsivity was of the order of 104 A/W at the nW-level light excitation.

Low-Temperature Photochemically Activated Amorphous Indium-Gallium-Zinc Oxide for Highly Stable Room-Temperature Gas Sensors.

PubMed

Jaisutti, Rawat; Kim, Jaeyoung; Park, Sung Kyu; Kim, Yong-Hoon

2016-08-10

We report on highly stable amorphous indium-gallium-zinc oxide (IGZO) gas sensors for ultraviolet (UV)-activated room-temperature detection of volatile organic compounds (VOCs). The IGZO sensors fabricated by a low-temperature photochemical activation process and exhibiting two orders higher photocurrent compared to conventional zinc oxide sensors, allowed high gas sensitivity against various VOCs even at room temperature. From a systematic analysis, it was found that by increasing the UV intensity, the gas sensitivity, response time, and recovery behavior of an IGZO sensor were strongly enhanced. In particular, under an UV intensity of 30 mW cm(-2), the IGZO sensor exhibited gas sensitivity, response time and recovery time of 37%, 37 and 53 s, respectively, against 750 ppm concentration of acetone gas. Moreover, the IGZO gas sensor had an excellent long-term stability showing around 6% variation in gas sensitivity over 70 days. These results strongly support a conclusion that a low-temperature solution-processed amorphous IGZO film can serve as a good candidate for room-temperature VOCs sensors for emerging wearable electronics.

The effect of ultraviolet irradiation on the ultra-thin HfO{sub 2} based CO gas sensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karaduman, Irmak; Barin, Özlem; Acar, Selim

2015-11-07

In this work, an effort has been made to fabricate ultrathin HfO{sub 2}/Al{sub 2}O{sub 3} sample by atomic layer deposition method for the fast detection of CO gas at room temperature. The effect of the operating temperature and the UV light on the gas sensing characteristics has been studied. We investigated the optimum operating temperature for the sample by sensing 25 ppm CO and CO{sub 2} gases from room temperature to 150 °C for 10 °C steps. The maximum response was obtained at 150 °C for both gases in the measurement temperature range. Also, the photoresponse measurements clearly show the effect of UV lightmore » on the sample. At room temperature, sensor showed superior response (14%) for 5 ppm CO gas. The response time of sensor is 6 s to 5 ppm CO gas concentration. The ultrathin HfO{sub 2} based sample shows acceptable gas sensitivity for 5 ppm CO gas at room temperature under UV light irradiation.« less

Pretest reference calculation for the 18-W/m/sup 2/ Mockup for Defense High-Level Waste (WIPP Room A in situ experiment)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morgan, H.S.; Stone, C.M.

A pretest reference calculation for the 18-W/m/sup 2/ Mockup for Defense High-Level Waste (DHLW) or Room A experiment is presented in this report. The mockup is one of several large scale in situ experiments currently under construction near Carlsbad, New Mexico, at the site of the Waste Isolation Pilot Plant (WIPP). The 18-W/m/sup 2/ test is an in situ experiment developed to simulate closely the Reference Repository Conditions (RRC) for DHLW in salt. The test consists of three long, parallel rooms (A1, A2, A3) which are heated by canister heaters placed in the floor of each room. These heaters producemore » thermal loading which simulates an areal heat output of 18-W/m/sup 2/ for Room A2, which is the focus of the experiment. This load will be supplied for a period of three years. Rooms A1, A2, and A3 are heavily instrumented for monitoring both temperature increases due to the thermal loading and deformations due to creep of the salt. Data from the experiment are not available at the present time, but the measurements for Room A2 will eventually be compared to the results for Room A2 presented here to assess and improve thermal and mechanical modeling capabilities for the WIPP. The thermal/structural model used here represents the state-of-the-art at the present time. A large number of plots are included since an appropriate result is presented for every Room A2 gauge location. 55 refs., 70 figs., 4 tabs.« less

A room temperature operating cryogenic cell for in vivo monitoring of dry snow metamorphism by X-ray microtomography

NASA Astrophysics Data System (ADS)

Calonne, N.; Flin, F.; Lesaffre, B.; Dufour, A.; Roulle, J.; Puglièse, P.; Philip, A.; Lahoucine, F.; Rolland du Roscoat, S.; Geindreau, C.

2013-12-01

Three-dimensional (3D) images of snow offer the possibility of studying snow metamorphism at the grain scale by analysing the time evolution of its complex microstructure. Such images are also particularly useful for providing physical effective properties of snow arising in macroscopic models. In the last 15 years, several experiments have been developed in order to get 3D images of snow by X-ray microtomography. Up to now, two different approaches have been used: a static and an in vivo approach. The static method consists in imaging a snow sample whose structural evolution has been stopped by impregnation and/or very cold temperature conditions. The sample is placed in a cryogenic cell that can operate at the ambient temperature of the tomograph room (e.g. Brzoska et al., 1999, Coléou et al., 2001). The in vivo technique uses a non impregnated sample which continues to undergo structural evolutions and is put in a cell that controls the temperature conditions at the boundaries of the sample. This kind of cell requires a cold environnement and the whole tomographic acquisition process takes place in a cold room (e.g. Schneebeli and Sokratov, 2004, Pinzer and Schneebeli, 2009). The 2nd approach has the major advantage to provide the time evolution of the microstructure of a same snow sample but requires a dedicated cold-room tomographic scanner, whereas the static method can be used with any tomographic scanner operating at ambient conditions. We developed a new in vivo cryogenic cell which benefits from the advantages of each of the above methods: it (1) allows to follow the evolution of the same sample with time and (2) is usable with a wide panel of tomographic scanners provided with large cabin sizes, which has many advantages in terms of speed, resolution, and availability of new technologies. The thermal insulation between the snow sample and the outside is ensured by a double wall vacuum system of thermal conductivity of about 0.0015 Wm-1K-1. An air pumping system is thus permanently active during the experiment. Two Peltier cells are used to regulate the temperature at the top and bottom of the snow sample, allowing to impose the conditions of metamorphism (isothermal, temperature gradient). The snow sample consists of a cylinder of 1 cm radius and 1 cm height. During its positioning into the cryogenic cell, it is protected from the room conditions by a sealed and cold copper sample holder. The whole apparatus (cell, pumping system) is able to rotate of 360° synchronously during the tomographic acquisition. After X-ray tomography and image processing, this cell provides a set of 3D images showing the time evolution of the microstructure of a snow sample during its metamorphism under well-defined imposed conditions. Preliminary results give promising outlooks for the study of snow and firn physical processes. Brzoska, J.-B. and 7 others. 1999. ESRF Newsletter, 32, 22-23. Coléou, C., B. Lesaffre, J.-B. Brzoska, W. Ludwig and E. Boller. 2001. Ann. Glaciol., 32, 75-81. Pinzer, B. and M. Schneebeli. 2009. Meas. Sci. Technol., 20, 095705. Schneebeli, M. and S. A. Sokratov. 2004. Hydrol. Process., 18, 3655 - 3665.

Effect of deep cryogenic temperature on silicon-on-insulator CMOS mismatch: A circuit designer’s perspective

NASA Astrophysics Data System (ADS)

Das, Kushal; Lehmann, Torsten

2014-07-01

The effect of ultra low operating temperature on mismatch among identically designed Silicon-on-Sapphire CMOS devices is investigated in detail from a circuit design view point. The evolution of transistor matching properties for different operating conditions at both room and 4.2 K temperature are presented. The statistical analysis reveals that mismatch at low temperature is effectively unrelated to that at room temperature, which disagrees with previously published literature. The measurement data was used to extract key transistor parameters and the consequence of temperature lowering on their respective variance is estimated. We find that standard deviation of the threshold-voltage mismatch deteriorates by a factor ∼2 at 4.2 K temperature. Similar to room temperature operation, mismatch at 4.2 K is bias point dependent and the degradation of matching at very low temperature depends to some extent on how the bias point shifts upon cooling.

Magnetic excitations in the itinerant antifferromagnet Mn sub 90 Cu sub 10

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fernandez-Baca, J.A.; Nicklow, R.M.; Hagen, M.E.

1991-01-01

We have performed a neutron scattering experiment in order to study the spin dynamics of the itinerant-electron-antiferromagnet Mn{sub 90}Cu{sub 10} at room temperature. Strongly-damped spin waves of energies up to 68 MeV have been observed. These excitations have been found to be consistent with a linear dispersion relation with a stiffness constant of about 140 MeV -- {Angstrom} and an energy gap of 8.2 MeV. The spin-wave damping is consistent with theoretical calculations that predict a damping linear in the wavevector q. These results are qualitatively consistent with recent measurements by Nicklow and Tsunoda, and with earlier measurements by Wiltshiremore » and collaborators. 5 refs., 1 fig.« less

[In vitro evaluation of the gels properties prepared thermosensitive polymers as vehicles for administration substance by injection].

PubMed

Karolewicz, Bozena; Owczarek, Artur; Pluta, Janusz

2011-01-01

The aim of this study was to prepare a thermoresponsive formulations, which are a carrier for substance administered directly into site of action and which obtain sol-gel transitions at physiological ranges of temperature. The investigated formulations of liquid consistency at room temperature were obtained in sterile conditions on the basis of nonionic polymers Pluronic F-127, Pluronic F-68 and anionic polymer hyaluronic acid in different concentrations. The sol-gel transition temperature of the formulations was investigated and their physicochemical properties such as pH, density, osmotic pressure, sol-gel transition temperature, texture and release of vancomycin hydrochloride were studied. In vitro release experiments indicated that the optimised platform was able to prolong vancomycin hydrochloride release and their physico-chemical properties allow for application by injection form.

Improvement of GRCop-84 Through the Addition of Zirconium

NASA Technical Reports Server (NTRS)

Ellis, David L.; Lerch, Bradley A.

2012-01-01

GRCop-84 (Cu-8 at.% Cr-4 at.% Nb) has excellent strength, creep resistance, low cycle fatigue (LCF) life and stability at elevated temperatures. It suffers in comparison to many commercially available precipitation-strengthened alloys below 500 C (932 F). It was observed that the addition of Zr consistently improved the mechanical properties of Cu-based alloys especially below 500 C. In an effort to improve the low temperature properties of GRCop-84, 0.35 wt.% Zr was added to the alloy. Limited tensile, creep, and LCF testing was conducted to determine if improvements occur. The results showed some dramatic increases in the tensile and creep properties at the conditions tested with the probability of additional improvements being possible through cold working. LCF testing at room temperature did not show an improvement, but improvements might occur at elevated temperatures.

Validation of time and temperature values as critical limits for Salmonella and background flora growth during the production of fresh ground and boneless pork products.

PubMed

Mann, J E; Smith, L; Brashears, M M

2004-07-01

To provide pork processors with valuable data to validate the critical limits set for temperature during pork fabrication and grinding, a study was conducted to determine the growth of Salmonella serotypes and background flora at various temperatures. Growth of Salmonella Typhimurium and Salmonella Enteritidis and of background flora was monitored in ground pork and boneless pork chops held at various temperatures to determine growth patterns. Case-ready modified atmosphere packaged ground pork and fresh whole pork loins were obtained locally. Boneless chops and ground pork were inoculated with a cocktail mixture of streptomycin-resistant Salmonella to facilitate recovery in the presence of background flora. Samples were held at 4.4, 7.2C, and 10 degrees C and at room temperature (22.2 to 23.3 degrees C) to mimic typical processing and holding temperatures observed in pork processing environments. Salmonella counts were determined at regular intervals over 12 and 72 h for both room and refrigeration temperatures. No significant growth of Salmonella (P < 0.05) was observed in boneless pork chops held at refrigeration temperatures. However, Salmonella in boneless pork chops held at room temperature had grown significantly by 8 h. Salmonella grew at faster rates in ground pork. Significant growth was observed at 6, 24. and 72 h when samples were held at room temperature, 10 degrees C, and 7.2 degrees C, respectively. No significant growth was observed at 4.4 degrees C. Background flora in ground pork samples increased significantly after 10 h at room temperature and after 12 h for samples held at 10 and 7.2 degrees C. Background flora in samples held at refrigeration temperatures did not increase until 72 h. Background flora in the boneless chops increased significantly after 6 h at room temperature and after 24 h when held at 10 and 4.4 degrees C. These results illustrate that meat processors can utilize a variety of time and temperature combinations as critical limits to minimize Salmonella growth during production and storage of raw pork products.

Ambient temperature influences the neural benefits of exercise.

PubMed

Maynard, Mark E; Chung, Chasity; Comer, Ashley; Nelson, Katharine; Tran, Jamie; Werries, Nadja; Barton, Emily A; Spinetta, Michael; Leasure, J Leigh

2016-02-15

Many of the neural benefits of exercise require weeks to manifest. It would be useful to accelerate onset of exercise-driven plastic changes, such as increased hippocampal neurogenesis. Exercise represents a significant challenge to the brain because it produces heat, but brain temperature does not rise during exercise in the cold. This study tested the hypothesis that exercise in cold ambient temperature would stimulate hippocampal neurogenesis more than exercise in room or hot conditions. Adult female rats had exercise access 2h per day for 5 days at either room (20 °C), cold (4.5 °C) or hot (37.5 °C) temperature. To label dividing hippocampal precursor cells, animals received daily injections of BrdU. Brains were immunohistochemically processed for dividing cells (Ki67+), surviving cells (BrdU+) and new neurons (doublecortin, DCX) in the hippocampal dentate gyrus. Animals exercising at room temperature ran significantly farther than animals exercising in cold or hot conditions (room 1490 ± 400 m; cold 440 ± 102 m; hot 291 ± 56 m). We therefore analyzed the number of Ki67+, BrdU+ and DCX+ cells normalized for shortest distance run. Contrary to our hypothesis, exercise in either cold or hot conditions generated significantly more Ki67+, BrdU+ and DCX+ cells compared to exercise at room temperature. Thus, a limited amount of running in either cold or hot ambient conditions generates more new cells than a much greater distance run at room temperature. Taken together, our results suggest a simple means by which to augment exercise effects, yet minimize exercise time. Copyright © 2015 Elsevier B.V. All rights reserved.

Protocols for dry DNA storage and shipment at room temperature

PubMed Central

Ivanova, Natalia V; Kuzmina, Masha L

2013-01-01

The globalization of DNA barcoding will require core analytical facilities to develop cost-effective, efficient protocols for the shipment and archival storage of DNA extracts and PCR products. We evaluated three dry-state DNA stabilization systems: commercial Biomatrica® DNAstable® plates, home-made trehalose and polyvinyl alcohol (PVA) plates on 96-well panels of insect DNA stored at 56 °C and at room temperature. Controls included unprotected samples that were stored dry at room temperature and at 56 °C, and diluted samples held at 4 °C and at −20 °C. PCR and selective sequencing were performed over a 4-year interval to test the condition of DNA extracts. Biomatrica® provided better protection of DNA at 56 °C and at room temperature than trehalose and PVA, especially for diluted samples. PVA was the second best protectant after Biomatrica® at room temperature, whereas trehalose was the second best protectant at 56 °C. In spite of lower PCR success, the DNA stored at −20 °C yielded longer sequence reads and stronger signal, indicating that temperature is a crucial factor for DNA quality which has to be considered especially for long-term storage. Although it is premature to advocate a transition to DNA storage at room temperature, dry storage provides an additional layer of security for frozen samples, protecting them from degradation in the event of freezer failure. All three forms of DNA preservation enable shipment of dry DNA and PCR products between barcoding facilities. PMID:23789643

Fast detection and low power hydrogen sensor using edge-oriented vertically aligned 3-D network of MoS2 flakes at room temperature

NASA Astrophysics Data System (ADS)

Agrawal, A. V.; Kumar, R.; Venkatesan, S.; Zakhidov, A.; Zhu, Z.; Bao, Jiming; Kumar, Mahesh; Kumar, Mukesh

2017-08-01

The increased usage of hydrogen as a next generation clean fuel strongly demands the parallel development of room temperature and low power hydrogen sensors for their safety operation. In this work, we report strong evidence for preferential hydrogen adsorption at edge-sites in an edge oriented vertically aligned 3-D network of MoS2 flakes at room temperature. The vertically aligned edge-oriented MoS2 flakes were synthesised by a modified CVD process on a SiO2/Si substrate and confirmed by Scanning Electron Microscopy. Raman spectroscopy and PL spectroscopy reveal the signature of few-layer MoS2 flakes in the sample. The sensor's performance was tested from room temperature to 150 °C for 1% hydrogen concentration. The device shows a fast response of 14.3 s even at room temperature. The sensitivity of the device strongly depends on temperature and increases from ˜1% to ˜11% as temperature increases. A detail hydrogen sensing mechanism was proposed based on the preferential hydrogen adsorption at MoS2 edge sites. The proposed gas sensing mechanism was verified by depositing ˜2-3 nm of ZnO on top of the MoS2 flakes that partially passivated the edge sites. We found a decrease in the relative response of MoS2-ZnO hybrid structures. This study provides a strong experimental evidence for the role of MoS2 edge-sites in the fast hydrogen sensing and a step closer towards room temperature, low power (0.3 mW), hydrogen sensor development.

Digital Optical Circuit Technology.

DTIC Science & Technology

1985-03-01

ordinateurs ct des syst~mcs de diffusion de donn’es qui soient I la fois numcriques, entierement optiques. tres rapides etI I’abri des interferences et des...F.A.Hopf SESSION 11 - OPTICAL LOGIC PROSPECTS FOR PARALLEL NONLINEAR OPTICAL SIGNAL PROCESSING USING GaAs ETALONS AND ZnS INTERFERENCE FILTERS by...talks 1, 8, and 9) interference filters for room-temperature parallel processing. If one imposes a maximum heat load of 100 W/cm 2 , consistent with

Catalyst-free, III-V nanowire photovoltaics

NASA Astrophysics Data System (ADS)

Davies, D. G.; Lambert, N.; Fry, P. W.; Foster, A.; Krysa, A. B.; Wilson, L. R.

2014-05-01

We report on room temperature, photovoltaic operation of catalyst-free GaAs p-i-n junction nanowire arrays. Growth studies were first performed to determine the optimum conditions for controlling the vertical and lateral growth of the nanowires. Following this, devices consisting of axial p-i-n junctions were fabricated by planarising the nanowire arrays with a hard baked polymer. We discuss the photovoltaic properties of this proof-of-concept device, and significant improvements to be made during the growth.

Reversible photoinduced spectral change in Eu2O3 at room temperature

NASA Astrophysics Data System (ADS)

Mochizuki, Shosuke; Nakanishi, Tauto; Suzuki, Yuya; Ishi, Kimihiro

2001-12-01

When Eu2O3 powder compact and film are irradiated with ultraviolet (UV) laser light in a vacuum, their photoluminescence (PL) spectra change from a red sharp-line structure to a white broad band, which can be clearly seen with the naked eye. After removing the UV laser light, the white PL continues for more than several months at room temperature under room light, in spite of any changes of atmosphere. By irradiating with the same UV laser light at room temperature under O2 gas atmosphere, the original red PL state reappears. Such a reversible phenomenon may well yield materials for white-light-emitting devices and erasable optical storage.

Method of solution preparation of polyolefin class polymers for electrospinning processing included

NASA Technical Reports Server (NTRS)

Rabolt, John F. (Inventor); Givens, Steven R. (Inventor); Lee, Keun-Hyung (Inventor)

2011-01-01

A process to make a polyolefin fiber which has the following steps: mixing at least one polyolefin into a solution at room temperature or a slightly elevated temperature to form a polymer solution and electrospinning at room temperature said polymer solution to form a fiber.

Stability of three commonly compounded extemporaneous enrofloxacin suspensions for oral administration to exotic animals.

PubMed

Petritz, Olivia A; Guzman, David Sanchez-Migallon; Wiebe, Valerie J; Papich, Mark G

2013-07-01

To evaluate the stability of 3 extemporaneous oral suspensions of enrofloxacin mixed with readily available flavoring vehicles when stored at room temperature (approx 22°C). Evaluation study. 3 commonly compounded oral suspensions of enrofloxacin. On day 0, commercially available enrofloxacin tablets were compounded with a mixture of distilled water and corn syrup (formulation A) or cherry syrup (formulation B) flavoring vehicles to create suspensions with a nominal enrofloxacin concentration of 22.95 mg/mL, and 2.27% enrofloxacin injectable solution was compounded with a liquid sweetener (formulation C) to create a suspension with a nominal enrofloxacin concentration of 11.35 mg/mL. Preparations were stored in amber-colored vials at room temperature for 56 days. For each preparation, the enrofloxacin concentration was evaluated with high-performance liquid chromatography at prespecified intervals during the study. The pH, odor, and consistency for all suspensions were recorded at the start and completion of the study. Relative to the nominal enrofloxacin concentration, the enrofloxacin concentration strength ranged from 95.80% to 100.69% for formulation A, 108.44% to 111.06% for formulation B, and 100.99% to 103.28% for formulation C. A mild pH increase was detected in all 3 suspensions during the study. Results indicated that, when stored in amber-colored vials at room temperature for 56 days, the enrofloxacin concentration strength in all 3 formulations was retained within acceptance criteria of 90% to 110%. Subjectively, cherry syrup flavoring was better at masking the smell and taste of enrofloxacin than were the other mixing vehicles.

Room temperature synthesis of biodiesel using sulfonated graphitic carbon nitride

EPA Science Inventory

Sulfonation of graphitic carbon nitride (g-CN) affords a polar and strongly acidic catalyst, Sg-CN, which displays unprecedented reactivity and selectivity in biodiesel synthesis and esterification reactions at room temperature.

Room temperature synthesis of biodiesel using sulfonated graphitic carbon nitride

DOE PAGES

Baig, R. B. Nasir; Verma, Sanny; Nadagouda, Mallikarjuna N.; ...

2016-12-19

Sulfonation of graphitic carbon nitride (g-CN) affords a polar and strongly acidic catalyst, Sg-CN, which displays unprecedented reactivity and selectivity in biodiesel synthesis and esterification reactions at room temperature.

An Elevated-Temperature Tension-Compression Test and Its Application to Magnesium AZ31B

NASA Astrophysics Data System (ADS)

Piao, Kun

Many metals, particularly ones with HCP crystal structures, undergo deformation by combinations of twinning and slip, the proportion of which depends on variables such as temperature and strain rate. Typical techniques to reveal such mechanisms rely on metallography, x-ray diffraction, or electron optics. Simpler, faster, less expensive mechanical tests were developed in the current work and applied to Mg AZ31B. An apparatus was designed, simulated, optimized, and constructed to enable the large-strain, continuous tension/compression testing of sheet materials at elevated temperature. Thermal and mechanical FE analyses were used to locate cartridge heaters, thus enabling the attainment of temperatures up to 350°C within 15 minutes of start-up, and ensuring temperature uniformity throughout the gage length within 8°C. The low-cost device also makes isothermal testing possible at strain rates higher than corresponding tests in air. Analysis was carried out to predict the attainable compressive strains using novel finite element (FE) modeling and a single parameter characteristic of the machine and fixtures. The limits of compressive strain vary primarily with the material thickness and the applied-side-force-to-material-strength ratio. Predictions for a range of sheet alloys with measured buckling strains from -0.04 to -0.17 agreed within a standard deviation of 0.025 (0.015 excluding one material that was not initially flat). In order to demonstrate the utility of the new method, several sheet materials were tested over a range of temperatures. Some of the data obtained is the first of its kind. Magnesium AZ31B sheets were tested at temperatures up to 250°C with strain rate of 0.001/s. The inflected stress-strain curve observed in compression at room temperature disappeared between 125°C and 150°C, corresponding to the suppression of twinning, and suggesting a simple method for identifying the deformation mechanism transition temperature. The temperature-dependent behavior of selected advanced high strength steels (TWIP and DP) was revealed by preliminary tests at room temperature, 150°C and 250°C. For Mg AZ31B alloy sheets, the curvature of compressive stress-strain plots over a fixed strain range was found to be a consistent indicator of twinning magnitude, independent of temperature and strain rate. The relationship between curvature and areal fraction of twins is presented. Transition temperatures determined based on stress-strain curvature were consistent with ones determined by metallographic analysis and flow stresses, and depended on strain rate by the Zener-Hollomon parameter, a critical value for which was measured. The transition temperature was found to depend significantly on grain size, a relationship for which was established. Finally, it was shown that the transition temperature can be determined consistently, and much faster, using a single novel "Step-Temperature" test.

Simulation of effects of direction and air flow speed on temperature distribution in the room covered by various roof materials

NASA Astrophysics Data System (ADS)

Sukanto, H.; Budiana, E. P.; Putra, B. H. H.

2016-03-01

The objective of this research is to get a comparison of the distribution of the room temperature by using three materials, namely plastic-rubber composite, clay, and asbestos. The simulation used Ansys Fluent to get the temperature distribution. There were two conditions in this simulations, first the air passing beside the room and second the air passing in front of the room. Each condition will be varied with the air speed of 1 m/s, 2 m/s, 3 m/s, 4 m/s, 5 m/s for each material used. There are three heat transfers in this simulation, namely radiation, convection, and conduction. Based on the ANSI/ ASHRAE Standard 55-2004, the results of the simulation showed that the best temperature distribution was the roof of plastic-rubber composites.

Aspects of fracture mechanics in cryogenic model design. Part 2: NTF materials

NASA Technical Reports Server (NTRS)

Newman, J. C., Jr.; Lisagor, W. B.

1983-01-01

Results of fatigue crack growth and fracture toughness tests conducted on three candidate materials are presented. Fatigue crack growth and fracture toughness tests were conducted on NITRONIC 40 at room temperature and -275 F. Fracture toughness tests were also conducted on Vascomax 200 and 250 maraging steel from room temperature to -320 F. NITRONIC 40 was used to make the Pathfinder 1 model. The fatigue crack growth rate tests were conducted at room temperature and -275 F on three-point notch bend specimens. The fracture toughness tests on the as received and stress relieved materials at -275 F were conducted on the center crack tension specimens. Toughness tests were also conducted on Vascomax CVM-200 and CVM-250 maraging steel from room temperature to -320 F using round and rectangular compact specimens.

Beneficial effects of warmed humidified oxygen combined with nebulized albuterol and ipratropium in pediatric patients with acute exacerbation of asthma in winter months.

PubMed

Nibhanipudi, Kumara; Hassen, Getaw Worku; Smith, Arthur

2009-11-01

The objective of this study was to determine whether a combination of nebulized albuterol and ipratropium with warmed humidified oxygen would be more beneficial when compared to the same combination with humidified oxygen at room temperature. Albuterol alone was tested in the same settings. All patients between 6 and 17 years of age who presented to a pediatric emergency department in the winter months with acute exacerbation of bronchial asthma were given a combination of nebulized albuterol and ipratropium with warmed or room temperature humidified oxygen. Peak flow was measured before and after the treatment. Sixty patients were enrolled in the study, with 15 subjects in each group. The mean increase in peak flow in the albuterol-ipratropium with warm humidified oxygen group was 52.6, and in the albuterol-ipratropium with humidified oxygen at room temperature group, it was 26.2. The results of the albuterol with warmed humidified oxygen and with humidified oxygen at room temperature groups were 20.6 and 34.3, respectively. The differences between the groups were statistically significant. Our study shows that warmed humidified oxygen given along with the combination of nebulized albuterol and ipratropium is more beneficial for pediatric patients having an acute exacerbation of bronchial asthma in the winter months when compared to nebulized albuterol alone with warmed humidified oxygen, nebulized albuterol alone with room temperature humidified oxygen, or a combination of nebulized albuterol and ipratropium with room temperature humidified oxygen.

High Capacity Garnet-Based All-Solid-State Lithium Batteries: Fabrication and 3D-Microstructure Resolved Modeling.

PubMed

Finsterbusch, Martin; Danner, Timo; Tsai, Chih-Long; Uhlenbruck, Sven; Latz, Arnulf; Guillon, Olivier

2018-06-21

The development of high-capacity, high-performance all-solid-state batteries requires the specific design and optimization of its components, especially on the positive electrode side. For the first time, we were able to produce a completely inorganic mixed positive electrode consisting only of LiCoO 2 and Ta-substituted Li 7 La 3 Zr 2 O 12 (LLZ:Ta) without the use of additional sintering aids or conducting additives, which has a high theoretical capacity density of 1 mAh/cm 2 . A true all-solid-state cell composed of a Li metal negative electrode, a LLZ:Ta garnet electrolyte, and a 25 μm thick LLZ:Ta + LiCoO 2 mixed positive electrode was manufactured and characterized. The cell shows 81% utilization of theoretical capacity upon discharging at elevated temperatures and rather high discharge rates of 0.1 mA (0.1 C). However, even though the room temperature performance is also among the highest reported so far for similar cells, it still falls far short of the theoretical values. Therefore, a 3D reconstruction of the manufactured mixed positive electrode was used for the first time as input for microstructure-resolved continuum simulations. The simulations are able to reproduce the electrochemical behavior at elevated temperature favorably, however fail completely to predict the performance loss at room temperature. Extensive parameter studies were performed to identify the limiting processes, and as a result, interface phenomena occurring at the cathode active material/solid-electrolyte interface were found to be the most probable cause for the low performance at room temperature. Furthermore, the simulations are used for a sound estimation of the optimization potential that can be realized with this type of cell, which provides important guidelines for future oxide based all-solid-state battery research and fabrication.

Recommendations to Improve Employee Thermal Comfort When Working in 40°F Refrigerated Cold Rooms.

PubMed

Ceballos, Diana; Mead, Kenneth; Ramsey, Jessica

2015-01-01

Cold rooms are commonly used for food storage and preparation, and are usually kept around 40°F following food safety guidelines. Some food preparation employees may spend 8 or more hours inside cold rooms. These employees may not be aware of the risks associated with mildly cold temperatures, dampness, and limited ventilation. We performed an evaluation of cold rooms at an airline catering facility because of concerns with exposure to cold temperatures. We spoke with and observed employees in two cold rooms, reviewed daily temperature logs, evaluated employee's physical activity, work/rest schedule, and protective clothing. We measured temperature, percent relative humidity, and air velocities at different work stations inside the cold rooms. We concluded that thermal comfort concerns perceived by cold room employees may have been the result of air drafts at their workstations, insufficient use of personal protective equipment due to dexterity concerns, work practices, and lack of knowledge about good health and safety practices in cold rooms. These moderately cold work conditions with low air velocities are not well covered in current occupational health and safety guidelines, and wind chill calculations do not apply. We provide practical recommendations to improve thermal comfort of cold room employees. Engineering control recommendations include the redesigning of air deflectors and installing of suspended baffles. Administrative controls include the changing out of wet clothing, providing hand warmers outside of cold rooms, and educating employees on cold stress. We also recommended providing more options on personal protective equipment. However, there is a need for guidelines and educational materials tailored to employees in moderately cold environments to improve thermal comfort and minimize health and safety problems.

Recommendations to Improve Employee Thermal Comfort When Working in 40°F Refrigerated Cold Rooms

PubMed Central

Ceballos, Diana; Mead, Kenneth; Ramsey, Jessica

2015-01-01

Cold rooms are commonly used for food storage and preparation, and are usually kept around 40°F following food safety guidelines. Some food preparation employees may spend 8 or more hours inside cold rooms. These employees may not be aware of the risks associated with mildly cold temperatures, dampness, and limited ventilation. We performed an evaluation of cold rooms at an airline catering facility because of concerns with exposure to cold temperatures. We spoke with and observed employees in two cold rooms, reviewed daily temperature logs, evaluated employee’s physical activity, work/rest schedule, and protective clothing. We measured temperature, percent relative humidity, and air velocities at different work stations inside the cold rooms. We concluded that thermal comfort concerns perceived by cold room employees may have been the result of air drafts at their workstations, insufficient use of personal protective equipment due to dexterity concerns, work practices, and lack of knowledge about good health and safety practices in cold rooms. These moderately cold work conditions with low air velocities are not well covered in current occupational health and safety guidelines, and wind chill calculations do not apply. We provide practical recommendations to improve thermal comfort of cold room employees. Engineering control recommendations include the redesigning of air deflectors and installing of suspended baffles. Administrative controls include the changing out of wet clothing, providing hand warmers outside of cold rooms, and educating employees on cold stress. We also recommended providing more options on personal protective equipment. However, there is a need for guidelines and educational materials tailored to employees in moderately cold environments to improve thermal comfort and minimize health and safety problems. PMID:25961447

Fracture Sustainability Pressure, Temperature, Differential Pressure, and Aperture Closure Data

DOE Data Explorer

Tim Kneafsey

2016-09-30

In these data sets, the experiment time, actual date and time, room temperature, sample temperature, upstream and downstream pressures (measured independently), corrected differential pressure (measured independently and corrected for offset and room temperature) indication of aperture closure by linear variable differential transformer are presented. An indication of the sample is in the file name and in the first line of data.

Room-temperature storage of medications labeled for refrigeration.

PubMed

Cohen, Victor; Jellinek, Samantha P; Teperikidis, Leftherios; Berkovits, Elliot; Goldman, William M

2007-08-15

Data regarding the recommended maximum duration that refrigerated medications available in hospital pharmacies may be stored safely at room temperature were collected and compiled in a tabular format. During May and June of 2006, the prescribing information for medications labeled for refrigeration as obtained from the supplier were reviewed for data addressing room-temperature storage. Telephone surveys of the products' manufacturers were conducted when this information was not available in the prescribing information. Medications were included in the review if they were labeled to be stored at 2-8 degrees C and purchased by the pharmacy department for uses indicated on the hospital formulary. Frozen antibiotics thawed in the refrigerator and extemporaneously compounded medications were excluded. Information was compiled and arranged in tabular format. The U.S. Pharmacopeia's definition of room temperature (20-25 degrees C [68-77 degrees F]) was used for this review. Of the 189 medications listed in AHFS Drug Information 2006 for storage in a refrigerator, 89 were present in the pharmacy department's refrigerator. Since six manufacturers were unable to provide information for 10 medications, only 79 medications were included in the review. This table may help to avoid unnecessary drug loss and expenditures due to improper storage temperatures. Information regarding the room-temperature storage of 79 medications labeled for refrigerated storage was compiled.

Room temperature ferrimagnetism and ferroelectricity in strained, thin films of BiFe 0.5Mn 0.5O 3

DOE PAGES

Choi, Eun -Mi; Fix, Thomas; Kursumovic, Ahmed; ...

2014-10-14

In this study, highly strained films of BiFe 0.5Mn 0.5O 3 (BFMO) grown at very low rates by pulsed laser deposition were demonstrated to exhibit both ferrimagnetism and ferroelectricity at room temperature and above. Magnetization measurements demonstrated ferrimagnetism (T C ~ 600K), with a room temperature saturation moment (M S) of up to 90 emu/cc (~0.58μ B/f.u) on high quality (001) SrTiO 3. X-ray magnetic circular dichroism showed that the ferrimagnetism arose from antiferromagnetically coupled Fe 3+ and Mn 3+ . While scanning transmission electron microscope studies showed there was no long range ordering of Fe and Mn, the magneticmore » properties were found to be strongly dependent on the strain state in the films. The magnetism is explained to arise from one of three possible mechanisms with Bi polarization playing a key role. A signature of room temperature ferroelectricity in the films was measured by piezoresponse force microscopy and was confirmed using angular dark field scanning transmission electron microscopy. The demonstration of strain induced, high temperature multiferroism is a promising development for future spintronic and memory applications at room temperature and above.« less

Study on room temperature gas-sensing performance of CuO film-decorated ordered porous ZnO composite by In2O3 sensitization

NASA Astrophysics Data System (ADS)

Li, Tian-tian; Bao, Na; Geng, Ai-fang; Yu, Hui; Yang, Ying; Dong, Xiang-ting

2018-02-01

For the first time, ordered mesoporous ZnO nanoparticles have been synthesized by a template method. The electroplating after chemical plating method was creatively used to form copper film on the surface of the prepared ZnO, and then a CuO film-decorated ordered porous ZnO composite (CuO/ZnO) was obtained by a high-temperature oxidation method. In2O3 was loaded into the prepared CuO film-ZnO by an ultrasonic-assisted method to sensitize the room temperature gas-sensing performance of the prepared CuO/ZnO materials. The doped In2O3 could effectively improve the gas-sensing properties of the prepared materials to nitrogen oxides (NOx) at room temperature. The 1% In2O3 doped CuO/ZnO sample (1 wt% In2O3-CuO/ZnO) showed the best gas-sensing properties whose response to 100 ppm NOx reached 82%, and the detectable minimum concentration reached 1 ppm at room temperature. The prepared materials had a good selectivity, better response, very low detection limit, and high sensitivity to NOx gas at room temperature, which would have a great development space in the gas sensor field and a great research value.

Electrically tunable organic–inorganic hybrid polaritons with monolayer WS2

PubMed Central

Flatten, Lucas C.; Coles, David M.; He, Zhengyu; Lidzey, David G.; Taylor, Robert A.; Warner, Jamie H.; Smith, Jason M.

2017-01-01

Exciton-polaritons are quasiparticles consisting of a linear superposition of photonic and excitonic states, offering potential for nonlinear optical devices. The excitonic component of the polariton provides a finite Coulomb scattering cross section, such that the different types of exciton found in organic materials (Frenkel) and inorganic materials (Wannier-Mott) produce polaritons with different interparticle interaction strength. A hybrid polariton state with distinct excitons provides a potential technological route towards in situ control of nonlinear behaviour. Here we demonstrate a device in which hybrid polaritons are displayed at ambient temperatures, the excitonic component of which is part Frenkel and part Wannier-Mott, and in which the dominant exciton type can be switched with an applied voltage. The device consists of an open microcavity containing both organic dye and a monolayer of the transition metal dichalcogenide WS2. Our findings offer a perspective for electrically controlled nonlinear polariton devices at room temperature. PMID:28094281

Numerical simulation of magnetic field for compact electromagnet consisting of REBCO coils and iron yoke

NASA Astrophysics Data System (ADS)

You, Shuangrong; Chi, Changxin; Guo, Yanqun; Bai, Chuanyi; Liu, Zhiyong; Lu, Yuming; Cai, Chuanbing

2018-07-01

This paper presents the numerical simulation of a high-temperature superconductor electromagnet consisting of REBCO (RE-Ba2Cu3O7‑x, RE: rare earth) superconducting tapes and a ferromagnetic iron yoke. The REBCO coils with multi-width design are operating at 77 K, with the iron yoke at room temperature, providing a magnetic space with a 32 mm gap between two poles. The finite element method is applied to compute the 3D model of the studied magnet. Simulated results show that the magnet generates a 1.5 T magnetic field at an operating current of 38.7 A, and the spatial inhomogeneity of the field is 0.8% in a Φ–20 mm diameter sphere volume. Compared with the conventional iron electromagnet, the present compact design is more suitable for practical application.

Nanoindentation study of bulk zirconium hydrides at elevated temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cinbiz, Mahmut Nedim; Balooch, Mehdi; Hu, Xunxiang

Here, the mechanical properties of zirconium hydrides was studied using nano-indentation technique at a temperature range of 25 – 400 °C. Temperature dependency of reduced elastic modulus and hardness of δ- and ε-zirconium hydrides were obtained by conducting nanoindentation experiments on the bulk hydride samples with independently heating capability of indenter and heating stage. The reduced elastic modulus of δ-zirconium hydride (H/Zr ratio =1.61) decreased from ~113 GPa to ~109 GPa while temperature increased from room temperature to 400°C. For ε-zirconium hydrides (H/Zr ratio=1.79), the reduced elastic modulus decreased from 61 GPa to 54 GPa as temperature increased from roommore » temperature to 300 °C. Whereas, hardness of δ-zirconium hydride significantly decreased from 4.1 GPa to 2.41 GPa when temperature increased from room temperature to 400 °C. Similarly, hardness of ε-zirconium hydride decreased from 3.06 GPa to 2.19 GPa with temperature increase from room temperature to 300°C.« less

Nanoindentation study of bulk zirconium hydrides at elevated temperatures

DOE PAGES

Cinbiz, Mahmut Nedim; Balooch, Mehdi; Hu, Xunxiang; ...

2017-08-02

Here, the mechanical properties of zirconium hydrides was studied using nano-indentation technique at a temperature range of 25 – 400 °C. Temperature dependency of reduced elastic modulus and hardness of δ- and ε-zirconium hydrides were obtained by conducting nanoindentation experiments on the bulk hydride samples with independently heating capability of indenter and heating stage. The reduced elastic modulus of δ-zirconium hydride (H/Zr ratio =1.61) decreased from ~113 GPa to ~109 GPa while temperature increased from room temperature to 400°C. For ε-zirconium hydrides (H/Zr ratio=1.79), the reduced elastic modulus decreased from 61 GPa to 54 GPa as temperature increased from roommore » temperature to 300 °C. Whereas, hardness of δ-zirconium hydride significantly decreased from 4.1 GPa to 2.41 GPa when temperature increased from room temperature to 400 °C. Similarly, hardness of ε-zirconium hydride decreased from 3.06 GPa to 2.19 GPa with temperature increase from room temperature to 300°C.« less

High-Temperature Dielectric Properties of Aluminum Nitride Ceramic for Wireless Passive Sensing Applications

PubMed Central

Liu, Jun; Yuan, Yukun; Ren, Zhong; Tan, Qiulin; Xiong, Jijun

2015-01-01

The accurate characterization of the temperature-dependent permittivity of aluminum nitride (AlN) ceramic is quite critical to the application of wireless passive sensors for harsh environments. Since the change of the temperature-dependent permittivity will vary the ceramic-based capacitance, which can be converted into the change of the resonant frequency, an LC resonator, based on AlN ceramic, is prepared by the thick film technology. The dielectric properties of AlN ceramic are measured by the wireless coupling method, and discussed within the temperature range of 12 °C (room temperature) to 600 °C. The results show that the extracted relative permittivity of ceramic at room temperature is 2.3% higher than the nominal value of 9, and increases from 9.21 to 10.79, and the quality factor Q is decreased from 29.77 at room temperature to 3.61 at 600 °C within the temperature range. PMID:26370999

Self-locking threaded fasteners

DOEpatents

Glovan, R.J.; Tierney, J.C.; McLean, L.L.; Johnson, L.L.

1996-01-16

A threaded fastener with a shape memory alloy (SMA) coatings on its threads is disclosed. The fastener has special usefulness in high temperature applications where high reliability is important. The SMA coated fastener is threaded into or onto a mating threaded part at room temperature to produce a fastened object. The SMA coating is distorted during the assembly. At elevated temperatures the coating tries to recover its original shape and thereby exerts locking forces on the threads. When the fastened object is returned to room temperature the locking forces dissipate. Consequently the threaded fasteners can be readily disassembled at room temperature but remains securely fastened at high temperatures. A spray technique is disclosed as a particularly useful method of coating of threads of a fastener with a shape memory alloy. 13 figs.

Room temperature, air crystallized perovskite film for high performance solar cells

DOE PAGES

Dubey, Ashish; Kantack, Nicholas; Adhikari, Nirmal; ...

2016-05-31

For the first time, room temperature heating free growth and crystallization of perovskite films in ambient air without the use of thermal annealing is reported. Highly efficient perovskite nanorod-based solar cells were made using ITO/PEDOT:PSS/CH 3NH 3PbI 3 nanorods/PC 60BM/rhodamine/Ag. All the layers except PEDOT:PSS were processed at room temperature thereby eliminating the need for thermal treatment. Perovskite films were spin coated inside a N-2 filled glovebox and immediately were taken outside in air having 40% relative humidity (RH). Exposure to humid air was observed to promote the crystallization process in perovskite films even at room temperature. Perovskite films keptmore » for 5 hours in ambient air showed nanorod-like morphology having high crystallinity, with devices exhibiting the highest PCE of 16.83%, which is much higher than the PCE of 11.94% for traditional thermally annealed perovskite film based devices. Finally, it was concluded that moisture plays an important role in room temperature crystallization of pure perovskite nanorods, showing improved optical and charge transport properties, which resulted in high performance solar cells.« less

High-resolution ionization detector and array of such detectors

DOEpatents

McGregor, Douglas S [Ypsilanti, MI; Rojeski, Ronald A [Pleasanton, CA

2001-01-16

A high-resolution ionization detector and an array of such detectors are described which utilize a reference pattern of conductive or semiconductive material to form interaction, pervious and measurement regions in an ionization substrate of, for example, CdZnTe material. The ionization detector is a room temperature semiconductor radiation detector. Various geometries of such a detector and an array of such detectors produce room temperature operated gamma ray spectrometers with relatively high resolution. For example, a 1 cm.sup.3 detector is capable of measuring .sup.137 Cs 662 keV gamma rays with room temperature energy resolution approaching 2% at FWHM. Two major types of such detectors include a parallel strip semiconductor Frisch grid detector and the geometrically weighted trapezoid prism semiconductor Frisch grid detector. The geometrically weighted detector records room temperature (24.degree. C.) energy resolutions of 2.68% FWHM for .sup.137 Cs 662 keV gamma rays and 2.45% FWHM for .sup.60 Co 1.332 MeV gamma rays. The detectors perform well without any electronic pulse rejection, correction or compensation techniques. The devices operate at room temperature with simple commercially available NIM bin electronics and do not require special preamplifiers or cooling stages for good spectroscopic results.

Effect of storage temperature on endogenous GHB levels in urine.

PubMed

LeBeau, M A; Miller, M L; Levine, B

2001-06-15

Because gamma-hydroxybutyrate (GHB) is an endogenous substance present in the body and is rapidly eliminated after ingestion, toxicologists investigating drug-facilitated sexual assault cases are often asked to differentiate between endogenous and exogenous levels of GHB in urine samples. This study was designed to determine the effects of storage temperature on endogenous GHB levels in urine. Specifically, it was designed to ascertain whether endogenous levels can be elevated to a range considered indicative of GHB ingestion. Urine specimens from two subjects that had not been administered exogenous GHB were collected during a 24h period and individually pooled. The pooled specimens were separated into standard sample cups and divided into three storage groups: room temperature ( approximately 25 degrees C), refrigerated (5 degrees C), and frozen (-10 degrees C). Additionally, some specimens were put through numerous freeze/thaw cycles to mimic situations that may occur if multiple laboratories analyze the same specimen. Periodic analysis of the samples revealed increases in the levels of endogenous GHB over a 6-month period. The greatest increase (up to 404%) was observed in the samples maintained at room temperature. The refrigerated specimens showed increases of 140-208%, while the frozen specimens showed smaller changes (88-116%). The specimens subjected to multiple freeze/thaw cycles mirrored specimens that had been thawed only once. None of the stored urine specimens demonstrated increases in GHB concentrations that would be consistent with exogenous GHB ingestion.

On the transmission of terahertz radiation through silicon-based structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Persano, Anna, E-mail: anna.persano@le.imm.cnr.it; Francioso, Luca; Cola, Adriano

2014-07-28

We report on the transmission of a terahertz (THz) radiation through prototype structures based on a p-type silicon substrate. In particular, the bare substrate and progressively more complicated multilayer structures were investigated, allowing to address the effect on the transmission of different factors, such as the orientation of interdigitated contacts with respect to the polarized beam, the temperature, and the current flowing through a conductive SnO{sub 2} nanorods layer. A suitable experimental set-up was developed for the direct spectral measurement of transmission in the range of 0.75–1.1 THz at room and low temperatures. A simple Drude-Lorentz model was formulated, findingmore » a quantitative agreement with the experimental transmission spectrum of the bare substrate at room temperature. For the multilayer structures, the spectra variations observed with temperature are well accounted by the corresponding change of the mobility of holes in the silicon p-type substrate. The influence of the contact orientation is consistent with that of a polarizing metallic grating. Finally, Joule heating effects are observed in the spectra performed as a function of the current flowing through the SnO{sub 2} nanorods layer. The experimental results shown here, together with their theoretical interpretation, provide insights for the development of devices fabricated on conductive substrates aimed to absorb/modulate radiation in the THz range.« less

Phase stability of iron germanate, FeGeO 3, to 127 GPa

DOE PAGES

Dutta, R.; Tracy, S. J.; Stan, C. V.; ...

2017-11-15

The high-pressure behavior of germanates is of interest as these compounds serve as analogs for silicates of the deep Earth. Current theoretical and experimental studies of iron germanate, FeGeO 3, are limited. Here in this paper, we have examined the behavior of FeGeO 3 to 127 GPa using the laser-heated diamond anvil cell combined with in situ synchrotron X-ray diffraction. Upon compression at room temperature, the ambient-pressure clinopyroxene phase transforms to a disordered triclinic phase [FeGeO 3 (II)] at ~ 18 GPa in agreement with earlier studies. An additional phase transition to FeGeO 3 (III) occurs above 54 GPa atmore » room temperature. Laser-heating experiments (~ 1200–2200 K) were conducted at three pressures (33, 54, and 123 GPa) chosen to cover the stability regions of different GeO 2 polymorphs. In all cases, we observe that FeGeO 3 dissociates into GeO 2 + FeO at high pressure and temperature conditions. Neither the perovskite nor the post-perovskite phase was observed up to 127 GPa at ambient or high temperatures. The results are consistent with the behavior of FeSiO 3, which also dissociates into a mixture of the oxides (FeO + SiO 2) at least up to 149 GPa.« less

Room temperature synthesis of biodiesel using sulfonated graphitic carbon nitride

PubMed Central

Baig, R. B. Nasir; Verma, Sanny; Nadagouda, Mallikarjuna N.; Varma, Rajender S.

2016-01-01

Sulfonation of graphitic carbon nitride (g-CN) affords a polar and strongly acidic catalyst, Sg-CN, which displays unprecedented reactivity and selectivity in biodiesel synthesis and esterification reactions at room temperature. PMID:27991593

Thermoelectric Generator Used in Fire-Alarm Temperature Sensing

NASA Astrophysics Data System (ADS)

Wu, Wenchang; Du, Zhengliang; Cui, Jiaolin; Shi, Zhongtao; Deng, Yuan

2015-06-01

Here we present a thermoelectric (TE) generator used in fire-alarm temperature sensing. The TE module, a core component of this generator, has a sandwich-like structure consisting of a Cu/Sn95Ag5/coated Ni/sprayed Ni/TE/sprayed Ni/coated Ni/Sn95Ag5/Cu multilayer that exhibits a low internal resistance of 5.5 Ω to 5.9 Ω and a contact resistance of 0.51 Ω to 0.91 Ω at room temperature (RT), enabling the TE generator to attain an open-circuit voltage ( V op) of 1.50 V at RT and 2.97 V at ~90°C. Moreover, its maximum output power ( p max) was estimated to be 11.6 mW and 428.7 mW, respectively, for a temperature difference (Δ T) of 9.3°C and 52.9°C. These values are comparable to those for the bulk TE generator developed by Thermonamic. According to these figures, we obtain corresponding power densities of ~7.25 × 103 nW/mm2 and 2.68 × 105 nW/mm2, respectively. Although there is still much room to improve the performance of the generator when the source temperature rises above 90°C, the output voltages and maximum output powers attained in the current testing conditions are large enough to drive small electronic devices such as fire-alarm systems etc. Therefore, it is believed that the fabrication technology and designed structure of the generator are appropriate for such applications.

Equation of state, phase stability, and phase transformations of uranium-6 wt. % niobium under high pressure and temperature

NASA Astrophysics Data System (ADS)

Zhang, Jianzhong; Vogel, Sven; Brown, Donald; Clausen, Bjorn; Hackenberg, Robert

2018-05-01

In-situ time-of-flight neutron diffraction experiments were conducted on the uranium-niobium alloy with 6 wt. % Nb (U-6Nb) at pressures up to 4.7 GPa and temperatures up to 1073 K. Upon static compression at room temperature, the monoclinic structure of U-6Nb (α″ U-6Nb) remains stable up to the highest experimental pressure. Based on the pressure-volume measurements at room temperature, the least-squares fit using the finite-strain equation of state (EOS) yields an isothermal bulk modulus of B0 = 127 ± 2 GPa for the α″-phase of U-6Nb. The calculated zero-pressure bulk sound speed from this EOS is 2.706 ± 0.022 km/s, which is in good agreement with the linear extrapolation of the previous Hugoniot data above 12 GPa for α″ U-6Nb, indicating that the dynamic response under those shock-loading conditions is consistent with the stabilization of the initial monoclinic phase of U-6Nb. Upon heating at ambient and high pressures, the metastable α″ U-6Nb exhibits complex transformation paths leading to the diffusional phase decomposition, which are sensitive to applied pressure, stress state, and temperature-time path. These findings provide new insight into the behavior of atypical systems such as U-Nb and suggest that the different U-Nb phases are separated by rather small energies and hence highly sensitive to compositional, thermal, and mechanical perturbations.

Room-temperature serial crystallography at synchrotron X-ray sources using slowly flowing free-standing high-viscosity microstreams.

PubMed

Botha, Sabine; Nass, Karol; Barends, Thomas R M; Kabsch, Wolfgang; Latz, Beatrice; Dworkowski, Florian; Foucar, Lutz; Panepucci, Ezequiel; Wang, Meitian; Shoeman, Robert L; Schlichting, Ilme; Doak, R Bruce

2015-02-01

Recent advances in synchrotron sources, beamline optics and detectors are driving a renaissance in room-temperature data collection. The underlying impetus is the recognition that conformational differences are observed in functionally important regions of structures determined using crystals kept at ambient as opposed to cryogenic temperature during data collection. In addition, room-temperature measurements enable time-resolved studies and eliminate the need to find suitable cryoprotectants. Since radiation damage limits the high-resolution data that can be obtained from a single crystal, especially at room temperature, data are typically collected in a serial fashion using a number of crystals to spread the total dose over the entire ensemble. Several approaches have been developed over the years to efficiently exchange crystals for room-temperature data collection. These include in situ collection in trays, chips and capillary mounts. Here, the use of a slowly flowing microscopic stream for crystal delivery is demonstrated, resulting in extremely high-throughput delivery of crystals into the X-ray beam. This free-stream technology, which was originally developed for serial femtosecond crystallography at X-ray free-electron lasers, is here adapted to serial crystallography at synchrotrons. By embedding the crystals in a high-viscosity carrier stream, high-resolution room-temperature studies can be conducted at atmospheric pressure using the unattenuated X-ray beam, thus permitting the analysis of small or weakly scattering crystals. The high-viscosity extrusion injector is described, as is its use to collect high-resolution serial data from native and heavy-atom-derivatized lysozyme crystals at the Swiss Light Source using less than half a milligram of protein crystals. The room-temperature serial data allow de novo structure determination. The crystal size used in this proof-of-principle experiment was dictated by the available flux density. However, upcoming developments in beamline optics, detectors and synchrotron sources will enable the use of true microcrystals. This high-throughput, high-dose-rate methodology provides a new route to investigating the structure and dynamics of macromolecules at ambient temperature.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hanc, Emil; Zając, Wojciech, E-mail: wojciech.zajac@agh.edu.pl; Lu, Li

Ceramic oxides exhibiting high lithium-ion mobility at room temperature receive broad attention as candidate electrolytes for lithium batteries. Lithium-stuffed garnets from the Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12} group seem to be especially promising because of their high ionic conductivity at room temperature and their electrochemical stability. In this work, we discuss factors that affect formation of the garnet in its bulk form or in the form of thick and thin films. We demonstrate that zinc oxide can be applied as a sintering aid that facilitate the formation of the highly conducting cubic Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12} garnet phase inmore » a single-step sintering procedure. Based on our experience with the single-step sintering experiments, we successfully fabricated a thick-film membrane consisting of a garnet solid electrolyte using the tape casting technique. In order to reduce the thickness of the electrolyte even further we investigated the fabrication of a thin-film Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12} electrolyte by means of the pulsed laser deposition technique.« less

Nanosized thin SnO₂ layers doped with Te and TeO₂ as room temperature humidity sensors.

PubMed

Georgieva, Biliana; Podolesheva, Irena; Spasov, Georgy; Pirov, Jordan

2014-05-21

In this paper the humidity sensing properties of layers prepared by a new method for obtaining doped tin oxide are studied. Different techniques-SEM, EDS in SEM, TEM, SAED, AES and electrical measurements-are used for detailed characterization of the thin layers. The as-deposited layers are amorphous with great specific area and low density. They are built up of a fine grained matrix, consisting of Sn- and Te-oxides, and a nanosized dispersed phase of Te, Sn and/or SnTe. The chemical composition of both the matrix and the nanosized particles depends on the ratio R(Sn/Te) and the evaporation conditions. It is shown that as-deposited layers with R(Sn/Te) ranging from 0.4 to 0.9 exhibit excellent characteristics as humidity sensors operating at room temperature-very high sensitivity, good selectivity, fast response and short recovery period. Ageing tests have shown that the layers possess good long-term stability. Results obtained regarding the type of the water adsorption on the layers' surface help better understand the relation between preparation conditions, structure, composition and humidity sensing properties.

Ellipsometric characterization of MoSe2 thin layers obtained by thermal treatment of molybdenum in selenium vapor

NASA Astrophysics Data System (ADS)

Bayramov, Ayaz; Aliyeva, Yegana; Eyyubov, Gurban; Mammadov, Eldar; Jahangirli, Zakir; Lincot, Daniel; Mamedov, Nazim

2017-11-01

Submicron MoSe2 layers were prepared by thermal treatment of thick Mo layers on glass substrate in saturated selenium vapor. Spectroscopic ellipsometry was then applied to the obtained MoSe2/Mo/Glass structures and MoSe2 target sample at room temperature. Dielectric function for both the MoSe2 layer and MoSe2 target was retrieved in the spectral range 190-1700 nm by using the Kramers-Kronig consistent B-spline dispersion model. The obtained data were similar in both cases. Despite apparent red shift of the dielectric function spectra of the layer in high energy region the peculiarity at around 1 eV is manifested at the same energy for both, layer and target. Comparison of the ellipsometry-based dielectric function of the target and the one, obtained within calculated band structure of MoSe2 for room temperature lattice parameters, has shown that the former is a broadened counterpart of the latter. Above-mentioned peculiar feature is not reproduced in the calculated dielectric function and is assumed to have excitonic nature.

Giant reversible anisotropy changes at room temperature in a (La,Sr)MnO3/Pb(Mg,Nb,Ti)O3 magneto-electric heterostructure.

PubMed

Chopdekar, Rajesh Vilas; Buzzi, Michele; Jenkins, Catherine; Arenholz, Elke; Nolting, Frithjof; Takamura, Yayoi

2016-06-08

In a model artificial multiferroic system consisting of a (011)-oriented ferroelectric Pb(Mg,Nb,Ti)O3 substrate intimately coupled to an epitaxial ferromagnetic (La,Sr)MnO3 film, electric field pulse sequences of less than 6 kV/cm induce large, reversible, and bistable remanent strains. The magnetic anisotropy symmetry reversibly switches from a highly anisotropic two-fold state to a more isotropic one, with concomitant changes in resistivity. Anisotropy changes at the scale of a single ferromagnetic domain were measured using X-ray microscopy, with electric-field dependent magnetic domain reversal showing that the energy barrier for magnetization reversal is drastically lowered. Free energy calculations confirm this barrier lowering by up to 70% due to the anisotropic strain changes generated by the substrate. Thus, we demonstrate that an electric field pulse can be used to 'set' and 'reset' the magnetic anisotropy orientation and resistive state in the film, as well as to lower the magnetization reversal barrier, showing a promising route towards electric-field manipulation of multifunctional nanostructures at room temperature.

Photoinduced, copper-catalyzed alkylation of amides with unactivated secondary alkyl halides at room temperature.

PubMed

Do, Hien-Quang; Bachman, Shoshana; Bissember, Alex C; Peters, Jonas C; Fu, Gregory C

2014-02-05

The development of a mild and general method for the alkylation of amides with relatively unreactive alkyl halides (i.e., poor substrates for SN2 reactions) is an ongoing challenge in organic synthesis. We describe herein a versatile transition-metal-catalyzed approach: in particular, a photoinduced, copper-catalyzed monoalkylation of primary amides. A broad array of alkyl and aryl amides (as well as a lactam and a 2-oxazolidinone) couple with unactivated secondary (and hindered primary) alkyl bromides and iodides using a single set of comparatively simple and mild conditions: inexpensive CuI as the catalyst, no separate added ligand, and C-N bond formation at room temperature. The method is compatible with a variety of functional groups, such as an olefin, a carbamate, a thiophene, and a pyridine, and it has been applied to the synthesis of an opioid receptor antagonist. A range of mechanistic observations, including reactivity and stereochemical studies, are consistent with a coupling pathway that includes photoexcitation of a copper-amidate complex, followed by electron transfer to form an alkyl radical.

Single molecule quantum-confined Stark effect measurements of semiconductor nanoparticles at room temperature

NASA Astrophysics Data System (ADS)

Park, Kyoung Won; Deutsch, Zvicka; Li, J. Jack; Oron, Dan; Weiss, Shimon

2013-02-01

We investigate the quantum confined Stark effect (QCSE) of various nanoparticles (NPs) on the single molecule level at room temperature. We tested 8 different NPs with different geometry, material composition and electronic structure, and measured their QCSE by single molecule spectroscopy. This study reveals that suppressing the Coulomb interaction force between electron and hole by asymmetric type-II interface is critical for an enhanced QCSE. For example, ZnSe-CdS and CdSe(Te)-CdS-CdZnSe asymmetric nanorods (type-II) display respectively twice and more than three times larger QCSE than that of simple type-I nanorods (CdSe). In addition, wavelength blue-shift of QCSE and roughly linear Δλ-F (emission wavelength shift vs. the applied electric field) relation are observed for the type-II nanorods. Experimental results (Δλ-F or ΔE-F) are successfully reproduced by self-consistent quantum mechanical calculation. Intensity reduction in blue-shifted spectrum is also accounted for. Both calculations and experiments suggest that the magnitude of the QCSE is predominantly determined by the degree of initial charge separation in these structures.

Quantum-well states in thin Ag films grown on the Ga/Si(111)-√{3 }×√{3 } surface

NASA Astrophysics Data System (ADS)

Starfelt, S.; Zhang, H. M.; Johansson, L. S. O.

2018-05-01

Silver thin films have been created by room temperature deposition on a Ga/Si(111)-√{3 }×√{3 } surface and their valence band structures and core levels have been measured by angle-resolved photoelectron spectroscopy (ARPES). Discrete quantum-well states (QWSs) quantized from the Ag s p valence band are observed already at 3 monolayers (ML). The characteristics of the QWSs have been examined in the phase accumulation model for thicknesses between 3 and 12 ML. The phase shift and QWSs binding energies dependence with Ag film thicknesses have all been consistently derived. In-plane energy dispersion follows a parabolic curve, and the effective mass of the QWSs shows an increasing trend with binding energies as well as with reduced film thicknesses. Furthermore, the ARPES measurements reveal umklapp mediated QWSs around the M ¯ points of the Si(111) 1 ×1 surface Brillouin zone. The study confirms that the Ga/Si(111)-√{3 }×√{3 } surface is a good substrate for growing uniform ultrathin Ag films in room temperature conditions.

Visible photoluminescence of porous Si(1-x)Ge(x) obtained by stain etching

NASA Technical Reports Server (NTRS)

Ksendzov, A.; Fathauer, R. W.; George, T.; Pike, W. T.; Vasquez, R. P.; Taylor, A. P.

1993-01-01

We have investigated visible photoluminescence (PL) from thin porous Si(1-x)Ge(x) alloy layers prepared by stain etching of molecular-beam-epitaxy-grown material. Seven samples with nominal Ge fraction x varying from 0.04 to 0.41 were studied at room temperature and 80 K. Samples of bulk stain etched Si and Ge were also investigated. The composition of the porous material was determined using X-ray photoemission spectroscopy and Rutherford backscattering techniques to be considerably more Ge-rich than the starting epitaxial layers. While the luminescence intensity drops significantly with the increasing Ge fraction, we observe no significant variation in the PL wavelength at room temperature. This is clearly in contradiction to the popular model based on quantum confinement in crystalline silicon which predicts that the PL energy should follow the bandgap variation of the starting material. However, our data are consistent with small active units containing only a few Si atoms that are responsible for the light emission. Such units are present in many compounds proposed in the literature as the cause of the visible PL in porous Si.

Photoinduced, Copper-Catalyzed Carbon-Carbon Bond Formation with Alkyl Electrophiles: Cyanation of Unactivated Secondary Alkyl Chlorides at Room Temperature.

PubMed

Ratani, Tanvi S; Bachman, Shoshana; Fu, Gregory C; Peters, Jonas C

2015-11-04

We have recently reported that, in the presence of light and a copper catalyst, nitrogen nucleophiles such as carbazoles and primary amides undergo C-N coupling with alkyl halides under mild conditions. In the present study, we establish that photoinduced, copper-catalyzed alkylation can also be applied to C-C bond formation, specifically, that the cyanation of unactivated secondary alkyl chlorides can be achieved at room temperature to afford nitriles, an important class of target molecules. Thus, in the presence of an inexpensive copper catalyst (CuI; no ligand coadditive) and a readily available light source (UVC compact fluorescent light bulb), a wide array of alkyl halides undergo cyanation in good yield. Our initial mechanistic studies are consistent with the hypothesis that an excited state of [Cu(CN)2](-) may play a role, via single electron transfer, in this process. This investigation provides a rare example of a transition metal-catalyzed cyanation of an alkyl halide, as well as the first illustrations of photoinduced, copper-catalyzed alkylation with either a carbon nucleophile or a secondary alkyl chloride.

Superior Self-Powered Room-Temperature Chemical Sensing with Light-Activated Inorganic Halides Perovskites.

PubMed

Chen, Hongjun; Zhang, Meng; Bo, Renheng; Barugkin, Chog; Zheng, Jianghui; Ma, Qingshan; Huang, Shujuan; Ho-Baillie, Anita W Y; Catchpole, Kylie R; Tricoli, Antonio

2018-02-01

Hybrid halide perovskite is one of the promising light absorber and is intensively investigated for many optoelectronic applications. Here, the first prototype of a self-powered inorganic halides perovskite for chemical gas sensing at room temperature under visible-light irradiation is presented. These devices consist of porous network of CsPbBr 3 (CPB) and can generate an open-circuit voltage of 0.87 V under visible-light irradiation, which can be used to detect various concentrations of O 2 and parts per million concentrations of medically relevant volatile organic compounds such as acetone and ethanol with very quick response and recovery time. It is observed that O 2 gas can passivate the surface trap sites in CPB and the ambipolar charge transport in the perovskite layer results in a distinct sensing mechanism compared with established semiconductors with symmetric electrical response to both oxidizing and reducing gases. The platform of CPB-based gas sensor provides new insights for the emerging area of wearable sensors for personalized and preventive medicine. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Room temperature current-voltage (I-V) characteristics of Ag/InGaN/n-Si Schottky barrier diode

NASA Astrophysics Data System (ADS)

Erdoğan, Erman; Kundakçı, Mutlu

2017-02-01

Metal-semiconductors (MSs) or Schottky barrier diodes (SBDs) have a significant potential in the integrated device technology. In the present paper, electrical characterization of Ag/InGaN/n-Si Schottky diode have been systematically carried out by simple Thermionic method (TE) and Norde function based on the I-V characteristics. Ag ohmic and schottky contacts are deposited on InGaN/n-Si film by thermal evaporation technique under a vacuum pressure of 1×10-5 mbar. Ideality factor, barrier height and series resistance values of this diode are determined from I-V curve. These parameters are calculated by TE and Norde methods and findings are given in a comparetive manner. The results show the consistency for both method and also good agreement with other results obtained in the literature. The value of ideality factor and barrier height have been determined to be 2.84 and 0.78 eV at room temperature using simple TE method. The value of barrier height obtained with Norde method is calculated as 0.79 eV.

Apparatus for material tests using an internal loading system in high-pressure gas at room temperature.

PubMed

Imade, M; Fukuyama, S; Yokogawa, K

2008-07-01

A new type of apparatus for material tests using an internal loading system in high-pressure gas up to 100 MPa at room temperature without conventional material testing equipment was developed. The apparatus consists of a high-pressure control system and a pressure vessel, in which a piston is installed in the cylinder of the pressure vessel. The load caused by the pressure difference between spaces separated by the piston in the vessel cylinder is applied on the specimen connected to the piston in the vessel cylinder. The actual load on the specimen is directly measured by an external load cell and the displacement of the specimen is also measured by an external extensometer. As an example of the application of the apparatus, a tensile test on SUS316 stainless steel the Japanese Industrial Standard (JIS) G4303, which is comparable to the type 316 stainless steel ASTM A276, was conducted in 90 MPa hydrogen and argon. Hydrogen showed a marked effect on the tensile property of the material. The hydrogen gas embrittlement of the material was briefly discussed.

Apparatus for material tests using an internal loading system in high-pressure gas at room temperature

NASA Astrophysics Data System (ADS)

Imade, M.; Fukuyama, S.; Yokogawa, K.

2008-07-01

A new type of apparatus for material tests using an internal loading system in high-pressure gas up to 100MPa at room temperature without conventional material testing equipment was developed. The apparatus consists of a high-pressure control system and a pressure vessel, in which a piston is installed in the cylinder of the pressure vessel. The load caused by the pressure difference between spaces separated by the piston in the vessel cylinder is applied on the specimen connected to the piston in the vessel cylinder. The actual load on the specimen is directly measured by an external load cell and the displacement of the specimen is also measured by an external extensometer. As an example of the application of the apparatus, a tensile test on SUS316 stainless steel the Japanese Industrial Standard (JIS) G4303, which is comparable to the type 316 stainless steel ASTM A276, was conducted in 90MPa hydrogen and argon. Hydrogen showed a marked effect on the tensile property of the material. The hydrogen gas embrittlement of the material was briefly discussed.

Application of edible coating from cassava peel – bay leaf on avocado

NASA Astrophysics Data System (ADS)

Handayani, M. N.; Karlina, S.; Sugiarti, Y.; Cakrawati, D.

2018-05-01

Avocados have a fairly short shelf life and are included in climacteric fruits. Edible coating application is one alternative to maintain the shelf life of avocado. Cassava peel starch is potential to be used as raw material for edible coating making. Addition of bay leaf extract containing antioxidants can increase the functional value of edible coating. The purpose of this study is to know the shrinkage of weight, acid number, color change and respiration rate of avocado coated with edible coating from cassava peel starch with an addition of bay leaf extract. The study consisted of making cassava peel starch, bay leaf extraction, edible coating making, edible coating application on avocado, and analysis of avocado characteristics during storage at room temperature. The results showed that addition of bay leaf extract on cassava peel starch edible coating applied to avocado, an effect on characteristics of avocado. Avocado applied edible coating and stored at room temperatures had lower weight loss than avocado without edible coating, lower acid number, tend to be more able to maintain color rather than avocado without edible coating.

On fabrication procedures of Li-ion conducting garnets

NASA Astrophysics Data System (ADS)

Hanc, Emil; Zając, Wojciech; Lu, Li; Yan, Binggong; Kotobuki, Masashi; Ziąbka, Magdalena; Molenda, Janina

2017-04-01

Ceramic oxides exhibiting high lithium-ion mobility at room temperature receive broad attention as candidate electrolytes for lithium batteries. Lithium-stuffed garnets from the Li7La3Zr2O12 group seem to be especially promising because of their high ionic conductivity at room temperature and their electrochemical stability. In this work, we discuss factors that affect formation of the garnet in its bulk form or in the form of thick and thin films. We demonstrate that zinc oxide can be applied as a sintering aid that facilitate the formation of the highly conducting cubic Li7La3Zr2O12 garnet phase in a single-step sintering procedure. Based on our experience with the single-step sintering experiments, we successfully fabricated a thick-film membrane consisting of a garnet solid electrolyte using the tape casting technique. In order to reduce the thickness of the electrolyte even further we investigated the fabrication of a thin-film Li7La3Zr2O12 electrolyte by means of the pulsed laser deposition technique.

Synthesis, crystal structure and characterization of chiral, three-dimensional anhydrous potassium tris(oxalato)ferrate(III)

NASA Astrophysics Data System (ADS)

Saritha, A.; Raju, B.; Ramachary, M.; Raghavaiah, P.; Hussain, K. A.

2012-11-01

The synthesis, crystal structure and physical properties of chiral, three-dimensional anhydrous potassium tris(oxalato)ferrate(III) [K3Fe(C2O4)3] are described. X-ray analysis reveals that the compound crystallized in the chiral space group P4132 of cubic system with a=b=c=13.5970(2), Z=4. The structure of the complex consists of infinite anionic [Fe(C2O4)3]3- units with distorted octahedral environment of iron surrounded by six oxygen atoms of three oxalato groups. The anionic units are interlinked through K+ ions of three different coordination environments of distorted octahedral, bicapped trigonal prismatic and trigonal prismatic yielding a three-dimensional motif. The two broad absorption bands at 644 and 924 nm from UV-vis-NIR transmittance spectra were ascribed to a ligand-to-metal charge transfer. The room temperature crystalline EPR spectra indicate the high-spin (S=5/2) of Fe(III) ion. The vibrating sample magnetometer measurement shows the paramagnetic nature at room temperature. Thermal studies of the compound confirm the absence of water molecule.

The room-temperature synthesis of anisotropic CdHgTe quantum dot alloys: a "molecular welding" effect.

PubMed

Taniguchi, Shohei; Green, Mark; Lim, Teck

2011-03-16

The room-temperature chemical transformation of spherical CdTe nanoparticles into anisotropic alloyed CdHgTe particles using mercury bromide in a toluene/methanol system at room temperature has been investigated. The resulting materials readily dissolved in toluene and exhibited a significant red-shift in the optical properties toward the infrared region. Structural transformations were observed, with electron microscopy showing that the CdTe nanoparticles were chemically attached ('welded') to other CdTe nanoparticles, creating highly complex anisotropic heterostructures which also incorporated mercury.

Bend strengths of reaction bonded silicon nitride prepared from dry attrition milled silicon powder

NASA Technical Reports Server (NTRS)

Herbell, T. P.; Glasgow, T. K.

1979-01-01

Dry attrition milled silicon powder was compacted, sintered in helium, and reaction bonded in nitrogen-4 volume percent hydrogen. Bend strengths of bars with as-nitrided surfaces averaged as high as 210 MPa at room temperature and 220 MPa at 1400 C. Bars prepared from the milled powder were stronger than those prepared from as-received powder at both room temperature and at 1400 C. Room temperature strength decreased with increased milling time and 1400 C strength increased with increased milling time.

Synthesis and characterization of CoPt nanoparticles prepared by room temperature chemical reduction with PAMAM dendrimer as template.

PubMed

Wan, Haiying; Shi, Shifan; Bai, Litao; Shamsuzzoha, Mohammad; Harrell, J W; Street, Shane C

2010-08-01

We describe an approach to synthesize monodisperse CoPt nanoparticles with dendrimer as template by a simple chemical reduction method in aqueous solution using NaBH4 as reducing agent at room temperature. The as-made CoPt nanoparticles buried in the dendrimer matrix have the chemically disordered fcc structure and can be transformed to the fct phase after annealing at 700 degrees C. This is the first report of dendrimer-mediated room temperature synthesis of monodisperse magnetic nanoparticles in aqueous solution.

Room Temperature Monoclinic Phase in BaTiO3 Single Crystals

NASA Astrophysics Data System (ADS)

Denev, Sava; Kumar, Amit; Barnes, Andrew; Vlahos, Eftihia; Shepard, Gabriella; Gopalan, Venkatraman

2010-03-01

BaTiO3 is a well studied ferroelectric material for the last half century. It is well known to show phase transitions to tetragonal, orthorhombic and rhombohedral phases upon cooling. Yet, some old and some recent studies have argued that all these phases co-exist with a second phase with monoclinic distortion. Using optical second harmonic generation (SHG) at room temperature we directly present evidence for such monoclininc phase co-existing with tetragonal phase at room temperature. We observe domains with the expected tetragonal symmetry exhibiting 90^o and 180^o domain walls. However, at points of higher stress at the tips of the interpenetrating tetragonal domains we observe a well pronounced metastable ``staircase pattern'' with a micron-scale fine structure. Polarization studies show that this phase can be explained only by monoclinic symmetry. This phase is very sensitive to external perturbations such as temperature and fields, hence stabilizing this phase at room temperature could lead to large properties' tunability.

Storage stability and composition changes of three cold-pressed nut oils under refrigeration and room temperature conditions.

PubMed

Rabadán, Adrián; Álvarez-Ortí, Manuel; Pardo, José Emilio; Alvarruiz, Andrés

2018-09-01

Chemical composition and stability parameters of three cold-pressed nut oils (almond, walnut and pistachio) were monitored for up to 16 months of storage at 5 °C, 10 °C, 20 °C and room temperature. Freshly pressed pistachio oil had lower peroxide value than almond oil and higher induction period than almond and walnut oils, indicating a higher stability. The peroxide values increased faster at room temperature than at lower temperatures during the storage time, and the highest increase was for pistachio oil stored at room temperature exposed to daylight. The induction period decreased for all three nut oils during the storage time, regardless of the storage conditions. Pistachio oil remained the most stable oil at the end of the storage time, followed by almond oil. The percentage of polyunsaturated fatty acids decreased slightly throughout the storage. Copyright © 2018 Elsevier Ltd. All rights reserved.

High Temperature Tensile Properties of Unidirectional Hi-Nicalon/Celsian Composites In Air

NASA Technical Reports Server (NTRS)

Gyekenyesi, John Z.; Bansal, Narottam P.

2000-01-01

High temperature tensile properties of unidirectional BN/SiC-coated Hi-Nicalon SiC fiber reinforced celsian matrix composites have been measured from room temperature to 1200 C (2190 F) in air. Young's modulus, the first matrix cracking stress, and the ultimate strength decreased from room temperature to 1200 C (2190 F). The applicability of various micromechanical models, in predicting room temperature values of various mechanical properties for this CMC, has also been investigated. The simple rule of mixtures produced an accurate estimate of the primary composite modulus. The first matrix cracking stress estimated from ACK theory was in good agreement with the experimental value. The modified fiber bundle failure theory of Evans gave a good estimate of the ultimate strength.

Resonant Ultrasound Spectroscopy studies of Berea sandstone at high temperature

DOE PAGES

Davis, Eric S.; Sturtevant, Blake T.; Sinha, Dipen N.; ...

2016-09-04

Resonant Ultrasound Spectroscopy was used in this paper to determine the elastic moduli of Berea sandstone from room temperature to 478 K. Sandstone is a common component of oil reservoirs, and the temperature range was chosen to be representative of typical downhole conditions, down to about 8 km. In agreement with previous works, Berea sandstone was found to be relatively soft with a bulk modulus of approximately 6 GPa as compared to 37.5 GPa for α-quartz at room temperature and pressure. Finally, it was found that Berea sandstone undergoes a ~17% softening in bulk modulus between room temperature and 385more » K, followed by an abnormal behavior of similar stiffening between 385 K and 478 K.« less

Resonant Ultrasound Spectroscopy studies of Berea sandstone at high temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, Eric S.; Sturtevant, Blake T.; Sinha, Dipen N.

Resonant Ultrasound Spectroscopy was used in this paper to determine the elastic moduli of Berea sandstone from room temperature to 478 K. Sandstone is a common component of oil reservoirs, and the temperature range was chosen to be representative of typical downhole conditions, down to about 8 km. In agreement with previous works, Berea sandstone was found to be relatively soft with a bulk modulus of approximately 6 GPa as compared to 37.5 GPa for α-quartz at room temperature and pressure. Finally, it was found that Berea sandstone undergoes a ~17% softening in bulk modulus between room temperature and 385more » K, followed by an abnormal behavior of similar stiffening between 385 K and 478 K.« less

BURNER RIG TESTING OF A500 C/SiC

DTIC Science & Technology

2018-03-17

test program characterized the durability behavior of A500® C/SiC ceramic matrix composite material at room and elevated temperature . Specimens were...7 Figure 6. Typical Room- Temperature Tensile Stress-Versus-Strain Trace for As-Manufactured A500...Operation ......................................... 18 Figure 17. Example of the Burner Rig Temperature Profiles Used

Recrystallization in Si upon ion irradiation at room temperature in Co/Si(111) thin film systems

NASA Astrophysics Data System (ADS)

Banu, Nasrin; Satpati, B.; Dev, B. N.

2018-04-01

After several decades of research it was concluded that for a constant flux recrystallization in Si upon ion irradiation is possible only at high temperature. At low temperature or at room temperature only amorphization can take place. However we have observed recrystallization in Si upon ion irradiation at room temperature in a Co/Si thin film system. The Co/Si sample was prepared by deposition of 25 nm Co on clean Si(111) substrate. An oxide layer (˜ 2nm) of cobalt at the top of the film due to air exposure. The ion irradiation was done at room temperature under high vacuum with 1MeV Si+ ion with low beam current < 400 nA. Earlier we have shown similar ion induced recrystallization in Si(100) substrate which had a sandwich Si/Ni/Si structure. This system had an epitaxial buffer Si layer on Si substrate. This study also shows that the phenomenon is independent of substrate orientation and buffer layer. We have used transmission electron microscopy (TEM) to study the recrystallization behavior.

[Distribution of environmental temperature and relative humidity according to the number of conditioned air changes in laboratory animals rooms].

PubMed

Fujita, S; Obara, T; Tanaka, I; Yamauchi, C

1981-01-01

The relation of the rate of circulating air change to room temperature and relative humidity in animal quarters with a central air-conditioning system during heating and cooling seasons was investigated, with the results as follows: During the period of heating, the ambient temperature generally rose with a fall of relative humidity as the number of conditioned air changes per hour was increased. Vertical differences in temperature and humidity between levels of 0.5 and 1.5 m above the floor also diminished with increasing air change rate. This tendency was more conspicuous in small animals rooms with outer walls facing north and west. With increasing rate of air changes, the room temperature was prone to decline and the relative humidity to rise during the period of cooling. There were less vertical differences in temperature and humidity during this period. The velocity of air circulation within the animal quarters and its variations tended to increase progressively with increasing rate of ventilation, though the changes were modest.

Room temperature CO and H2 sensing with carbon nanoparticles.

PubMed

Kim, Daegyu; Pikhitsa, Peter V; Yang, Hongjoo; Choi, Mansoo

2011-12-02

We report on a shell-shaped carbon nanoparticle (SCNP)-based gas sensor that reversibly detects reducing gas molecules such as CO and H(2) at room temperature both in air and inert atmosphere. Crystalline SCNPs were synthesized by laser-assisted reactions in pure acetylene gas flow, chemically treated to obtain well-dispersed SCNPs and then patterned on a substrate by the ion-induced focusing method. Our chemically functionalized SCNP-based gas sensor works for low concentrations of CO and H(2) at room temperature even without Pd or Pt catalysts commonly used for splitting H(2) molecules into reactive H atoms, while metal oxide gas sensors and bare carbon-nanotube-based gas sensors for sensing CO and H(2) molecules can operate only at elevated temperatures. A pristine SCNP-based gas sensor was also examined to prove the role of functional groups formed on the surface of functionalized SCNPs. A pristine SCNP gas sensor showed no response to reducing gases at room temperature but a significant response at elevated temperature, indicating a different sensing mechanism from a chemically functionalized SCNP sensor.

Improvement of Superplasticity in High-Mg Aluminum Alloys by Sacrifice of Some Room Temperature Formability

NASA Astrophysics Data System (ADS)

Jin, H.; Amirkhiz, B. Shalchi; Lloyd, D. J.

2018-03-01

The mechanical properties of fully annealed Al-4.6 wt pct Mg alloys with different levels of Mn and Fe have been characterized at room and superplastic forming (SPF) temperatures. The effects of Mn and Fe on the intermetallic phase, grain structure, and cavitation were investigated and correlated to the formability at different temperatures. Although both Mn and Fe contribute to the formation of Al6(Mn,Fe) phase, which refines the grain structure by particle-stimulated nucleation and Zener pinning, their effects are different. An increasing Mn reduces the room temperature formability due to the increasing number of intermetallic particles, but significantly improves the superplasticity by fine grain size-induced grain boundary sliding. Meanwhile, the Fe makes the constituent particles very coarse, resulting in reduced formability at all temperatures due to extensive cavitation. A combination of high Mn and low Fe is therefore beneficial to SPF, while low levels of both elements are good for cold forming. Consequently, the superplasticity of high-Mg aluminum alloys can be significantly improved by modifying the chemical composition with sacrifice of some room temperature formability.

Fluorescence behaviour of 5,10-methenyltetrahydrofolate, 10-formyltetrahydrofolate, 10-formyldihydrofolate, and 10-formylfolate in aqueous solution at pH 8

NASA Astrophysics Data System (ADS)

Tyagi, A.; Penzkofer, A.; Batschauer, A.; Wolf, E.

2009-06-01

The fluorescence spectroscopic behaviour of (6R,S)-5,10-methenyltetrahydrofolate (MTHF), (6R,S)-10-formyltetrahydrofolate (10-HCO-H4folate), 10-formyldihydrofolate (10-HCO-H2folate), and 10-formylfolate (10-HCO-folate) in aqueous Tris-HCl buffer at pH 8 is studied. MTHF and 10-HCO-folate were commercially available. 10-HCO-H4folate was prepared from MTHF by hydrolysis at room temperature under anaerobic conditions. 10-HCO-H2folate was prepared by oxidation of 10-HCO-H4folate under aerobic conditions. Fluorescence quantum distributions at room temperature and fluorescence signal decays at room temperature and liquid nitrogen temperature were measured. The fluorescence lifetimes determined at room temperature (liquid nitrogen temperature) are 10 ps (2.9 ns) for MTHF, 38 ps (3.7 ns) for 10-HCO-H4folate, 80 ps (10.5 ns) for 10-HCO-H2folate, and 7.1 ns (20 ns) for 10-HCO-folate. The results are discussed in terms of dyadic (pterin-benzoyl-glutamate) photo-induced electron transfer and dyadic fluorescent dynamics.

Using sieving and pretreatment to separate plastics during end-of-life vehicle recycling.

PubMed

Stagner, Jacqueline A; Sagan, Barsha; Tam, Edwin Kl

2013-09-01

Plastics continue to be a challenge for recovering materials at the end-of-life for vehicles. However, it may be possible to improve the recovery of plastics by exploiting material characteristics, such as shape, or by altering their behavior, such as through temperature changes, in relation to recovery processes and handling. Samples of a 2009 Dodge Challenger front fascia were shredded in a laboratory-scale hammer mill shredder. A 2 × 2 factorial design study was performed to determine the effect of sample shape (flat versus curved) and sample temperature (room temperature versus cryogenic temperature) on the size of the particles exiting from the shredder. It was determined that sample shape does not affect the particle size; however, sample temperature does affect the particle size. At cryogenic temperatures, the distribution of particle sizes is much narrower than at room temperature. Having a more uniform particle size could make recovery of plastic particles, such as these more efficient during the recycling of end-of-life vehicles. Samples of Chrysler minivan headlights were also shredded at room temperature and at cryogenic temperatures. The size of the particles of the two different plastics in the headlights is statistically different both at room temperature and at cryogenic temperature, and the particles are distributed narrowly. The research suggests that incremental changes in end-of-life vehicle processing could be effective in aiding materials recovery.

Room temperature growth of ZnO nanorods by hydrothermal synthesis

NASA Astrophysics Data System (ADS)

Tateyama, Hiroki; Zhang, Qiyan; Ichikawa, Yo

2018-05-01

The effect of seed layer morphology on ZnO nanorod growth at room temperature was studied via hydrothermal synthesis on seed layers with different thicknesses and further annealed at different temperatures. The change in the thickness and annealing temperature enabled us to control over a diameter of ZnO nanorods which are attributed to the changing of crystallinity and roughness of the seed layers.

IMPROVED SYNTHESIS OF ROOM TEMPERATURE IONIC LIQUIDS

EPA Science Inventory

Room temperature ionic liquids (RTILs), molten salts comprised of N-alkylimidazolium cations and various anions, have received significant attention due to their commercial potential in a variety of chemical applications especially as substitutes for conventional volatile organic...

Nickel-catalyzed synthesis of aryl trifluoromethyl sulfides at room temperature.

PubMed

Zhang, Cheng-Pan; Vicic, David A

2012-01-11

Inexpensive nickel-bipyridine complexes were found to be active for the trifluoromethylthiolation of aryl iodides and aryl bromides at room temperature using the convenient [NMe(4)][SCF(3)] reagent. © 2011 American Chemical Society

Simulation of effects of direction and air flow speed on temperature distribution in the room covered by various roof materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sukanto, H., E-mail: masheher@uns.ac.id; Budiana, E. P., E-mail: budiana.e@gmail.com; Putra, B. H. H., E-mail: benedictus.hendy@gmail.com

The objective of this research is to get a comparison of the distribution of the room temperature by using three materials, namely plastic-rubber composite, clay, and asbestos. The simulation used Ansys Fluent to get the temperature distribution. There were two conditions in this simulations, first the air passing beside the room and second the air passing in front of the room. Each condition will be varied with the air speed of 1 m/s, 2 m/s, 3 m/s, 4 m/s, 5 m/s for each material used. There are three heat transfers in this simulation, namely radiation, convection, and conduction. Based on the ANSI/ ASHRAE Standard 55-2004,more » the results of the simulation showed that the best temperature distribution was the roof of plastic-rubber composites.« less

Quality of red blood cells isolated from umbilical cord blood stored at room temperature.

PubMed

Zhurova, Mariia; Akabutu, John; Acker, Jason

2012-01-01

Red blood cells (RBCs) from cord blood contain fetal hemoglobin that is predominant in newborns and, therefore, may be more appropriate for neonatal transfusions than currently transfused adult RBCs. Post-collection, cord blood can be stored at room temperature for several days before it is processed for stem cells isolation, with little known about how these conditions affect currently discarded RBCs. The present study examined the effect of the duration cord blood spent at room temperature and other cord blood characteristics on cord RBC quality. RBCs were tested immediately after their isolation from cord blood using a broad panel of quality assays. No significant decrease in cord RBC quality was observed during the first 65 hours of storage at room temperature. The ratio of cord blood to anticoagulant was associated with RBC quality and needs to be optimized in future. This knowledge will assist in future development of cord RBC transfusion product.

Electric field modulated ferromagnetism in ZnO films deposited at room temperature

NASA Astrophysics Data System (ADS)

Bu, Jianpei; Liu, Xinran; Hao, Yanming; Zhou, Guangjun; Cheng, Bin; Huang, Wei; Xie, Jihao; Zhang, Heng; Qin, Hongwei; Hu, Jifan

2018-04-01

The ZnO film deposited at room temperature, which is composed of the amorphous-phase background plus a few nanograins or nanoclusters (about 1-2 nm), exhibits room temperature ferromagnetism (FM). Such FM is found to be connected with oxygen vacancies. For the Ta/ZnO/Pt device based on the medium layer ZnO deposited at room temperature, the saturation magnetization not only is modulated between high and low resistive states by electric voltage with DC loop electric current but also increases/decreases through adjusting the magnitudes of positive/negative DC sweeping voltage. Meanwhile, the voltage-controlled conductance quantization is observed in Ta/ZnO/Pt, accompanying the voltage-controlled magnetization. However, the saturation magnetization of the Ta/ZnO/Pt device becomes smaller under positive electric voltage and returns in some extent under negative electric voltage, when the DC loop electric current is not applied.

Room Temperature Memory for Few Photon Polarization Qubits

NASA Astrophysics Data System (ADS)

Kupchak, Connor; Mittiga, Thomas; Jordan, Bertus; Nazami, Mehdi; Nolleke, Christian; Figueroa, Eden

2014-05-01

We have developed a room temperature quantum memory device based on Electromagnetically Induced Transparency capable of reliably storing and retrieving polarization qubits on the few photon level. Our system is realized in a vapor of 87Rb atoms utilizing a Λ-type energy level scheme. We create a dual-rail storage scheme mediated by an intense control field to allow storage and retrieval of any arbitrary polarization state. Upon retrieval, we employ a filtering system to sufficiently remove the strong pump field, and subject retrieved light states to polarization tomography. To date, our system has produced signal-to-noise ratios near unity with a memory fidelity of >80 % using coherent state qubits containing four photons on average. Our results thus demonstrate the feasibility of room temperature systems for the storage of single-photon-level photonic qubits. Such room temperature systems will be attractive for future long distance quantum communication schemes.

Transition from poor ductility to room-temperature superplasticity in a nanostructured aluminum alloy.

PubMed

Edalati, Kaveh; Horita, Zenji; Valiev, Ruslan Z

2018-04-30

Recent developments of nanostructured materials with grain sizes in the nanometer to submicrometer range have provided ground for numerous functional properties and new applications. However, in terms of mechanical properties, bulk nanostructured materials typically show poor ductility despite their high strength, which limits their use for structural applications. The present article shows that the poor ductility of nanostructured alloys can be changed to room-temperature superplastisity by a transition in the deformation mechanism from dislocation activity to grain-boundary sliding. We report the first observation of room-temperature superplasticity (over 400% tensile elongations) in a nanostructured Al alloy by enhanced grain-boundary sliding. The room-temperature grain-boundary sliding and superplasticity was realized by engineering the Zn segregation along the Al/Al boundaries through severe plastic deformation. This work introduces a new boundary-based strategy to improve the mechanical properties of nanostructured materials for structural applications, where high deformability is a requirement.

Enzyme catalysis captured using multiple structures from one crystal at varying temperatures.

PubMed

Horrell, Sam; Kekilli, Demet; Sen, Kakali; Owen, Robin L; Dworkowski, Florian S N; Antonyuk, Svetlana V; Keal, Thomas W; Yong, Chin W; Eady, Robert R; Hasnain, S Samar; Strange, Richard W; Hough, Michael A

2018-05-01

High-resolution crystal structures of enzymes in relevant redox states have transformed our understanding of enzyme catalysis. Recent developments have demonstrated that X-rays can be used, via the generation of solvated electrons, to drive reactions in crystals at cryogenic temperatures (100 K) to generate 'structural movies' of enzyme reactions. However, a serious limitation at these temperatures is that protein conformational motion can be significantly supressed. Here, the recently developed MSOX (multiple serial structures from one crystal) approach has been applied to nitrite-bound copper nitrite reductase at room temperature and at 190 K, close to the glass transition. During both series of multiple structures, nitrite was initially observed in a 'top-hat' geometry, which was rapidly transformed to a 'side-on' configuration before conversion to side-on NO, followed by dissociation of NO and substitution by water to reform the resting state. Density functional theory calculations indicate that the top-hat orientation corresponds to the oxidized type 2 copper site, while the side-on orientation is consistent with the reduced state. It is demonstrated that substrate-to-product conversion within the crystal occurs at a lower radiation dose at 190 K, allowing more of the enzyme catalytic cycle to be captured at high resolution than in the previous 100 K experiment. At room temperature the reaction was very rapid, but it remained possible to generate and characterize several structural states. These experiments open up the possibility of obtaining MSOX structural movies at multiple temperatures (MSOX-VT), providing an unparallelled level of structural information during catalysis for redox enzymes.

Protocols for dry DNA storage and shipment at room temperature.

PubMed

Ivanova, Natalia V; Kuzmina, Masha L

2013-09-01

The globalization of DNA barcoding will require core analytical facilities to develop cost-effective, efficient protocols for the shipment and archival storage of DNA extracts and PCR products. We evaluated three dry-state DNA stabilization systems: commercial Biomatrica(®) DNAstable(®) plates, home-made trehalose and polyvinyl alcohol (PVA) plates on 96-well panels of insect DNA stored at 56 °C and at room temperature. Controls included unprotected samples that were stored dry at room temperature and at 56 °C, and diluted samples held at 4 °C and at -20 °C. PCR and selective sequencing were performed over a 4-year interval to test the condition of DNA extracts. Biomatrica(®) provided better protection of DNA at 56 °C and at room temperature than trehalose and PVA, especially for diluted samples. PVA was the second best protectant after Biomatrica(®) at room temperature, whereas trehalose was the second best protectant at 56 °C. In spite of lower PCR success, the DNA stored at -20 °C yielded longer sequence reads and stronger signal, indicating that temperature is a crucial factor for DNA quality which has to be considered especially for long-term storage. Although it is premature to advocate a transition to DNA storage at room temperature, dry storage provides an additional layer of security for frozen samples, protecting them from degradation in the event of freezer failure. All three forms of DNA preservation enable shipment of dry DNA and PCR products between barcoding facilities. © 2013 The Authors. Molecular Ecology Resources published by John Wiley & Sons Ltd.

Comparisons of Damage Evolution between 2D C/SiC and SiC/SiC Ceramic-Matrix Composites under Tension-Tension Cyclic Fatigue Loading at Room and Elevated Temperatures

PubMed Central

Li, Longbiao

2016-01-01

In this paper, comparisons of damage evolution between 2D C/SiC and SiC/SiC ceramic-matrix composites (CMCs) under tension–tension cyclic fatigue loading at room and elevated temperatures have been investigated. Fatigue hysteresis loops models considering multiple matrix cracking modes in 2D CMCs have been developed based on the damage mechanism of fiber sliding relative to the matrix in the interface debonded region. The relationships between the fatigue hysteresis loops, fatigue hysteresis dissipated energy, fatigue peak stress, matrix multiple cracking modes, and interface shear stress have been established. The effects of fiber volume fraction, fatigue peak stress and matrix cracking mode proportion on fatigue hysteresis dissipated energy and interface debonding and sliding have been analyzed. The experimental fatigue hysteresis dissipated energy of 2D C/SiC and SiC/SiC composites at room temperature, 550 °C, 800 °C, and 1100 °C in air, and 1200 °C in vacuum corresponding to different fatigue peak stresses and cycle numbers have been analyzed. The interface shear stress degradation rate has been obtained through comparing the experimental fatigue hysteresis dissipated energy with theoretical values. Fatigue damage evolution in C/SiC and SiC/SiC composites has been compared using damage parameters of fatigue hysteresis dissipated energy and interface shear stress degradation rate. It was found that the interface shear stress degradation rate increases at elevated temperature in air compared with that at room temperature, decreases with increasing loading frequency at room temperature, and increases with increasing fatigue peak stress at room and elevated temperatures. PMID:28773966

Room temperature magnetism and metal to semiconducting transition in dilute Fe doped Sb1-xSex semiconducting alloy thin films

NASA Astrophysics Data System (ADS)

Agrawal, Naveen; Sarkar, Mitesh; Chawda, Mukesh; Ganesan, V.; Bodas, Dhananjay

2015-02-01

The magnetism was observed in very dilute Fe doped alloy thin film Fe0.008Sb1-xSex, for x = 0.01 to 0.10. These thin films were grown on silicon substrate using thermal evaporation technique. Structural, electrical, optical, charge carrier concentration measurement, surface morphology and magnetic properties were observed using glancing incidence x-ray diffraction (GIXRD), four probe resistivity, photoluminescence, Hall measurement, atomic force microscopy (AFM) and magnetic force microscopy (MFM) techniques, respectively. No peaks of iron were seen in GIXRD. The resistivity results show that activation energy increases with increase in selenium (Se) concentration. The Arrhenius plot reveals metallic behavior below room temperature. The low temperature conduction is explained by variable range-hopping mechanism, which fits very well in the temperature range 150-300 K. The decrease in density of states has been observed with increasing selenium concentration (x = 0.01 to 0.10). There is a metal-to-semiconductor phase transition observed above room temperature. This transition temperature is Se concentration dependent. The particle size distribution ˜47-61 nm is evaluated using AFM images. These thin films exhibit ferromagnetic interactions at room temperature.

Isotropic Elastic Stress Induced Large Temperature Range Liquid Crystal Blue Phase at Room Temperature.

PubMed

Manna, Suman K; Dupont, Laurent; Li, Guoqiang

2016-08-11

A thermodynamically stable blue phase (BP) based on the conventional rod like nematogen is demonstrated for the first time at room temperature by only diluting a chiral-nematic mixture with the help of some nonmesogenic isotropic liquid. It is observed that addition of this isotropic liquid does not only stabilize the BPs at room temperature, but also significantly improves the temperature range (reversible during heating and cooling) of the BPs to the level of more than 28 °C. Apart from that, we have observed its microsecond electro-optic response time and, external electric field induced wavelength tuning, which are the two indispensable requirements for next generation optical devices, photonic displays, lasers, and many more. Here we propose that the isotropic liquid plays two crucial roles simultaneously. On one hand, it reduces the effective elastic moduli (EEM) of the BP mixtures and stabilizes the BPs at room temperature, and on the other hand, it increases the symmetry of the mutual orientation ordering among the neighboring unit cells of the BP. Hence, the resultant mixture becomes better resistive to some microscopic change due to the change in temperature, even over a large range.

The structure and transformation of the nanomineral schwertmannite: a synthetic analog representative of field samples

NASA Astrophysics Data System (ADS)

French, Rebecca A.; Monsegue, Niven; Murayama, Mitsuhiro; Hochella, Michael F.

2014-04-01

The phase transformation of schwertmannite, an iron oxyhydroxide sulfate nanomineral synthesized at room temperature and at 75 °C using H2O2 to drive the precipitation of schwertmannite from ferrous sulfate (Regenspurg et al. in Geochim Cosmochim Acta 68:1185-1197, 2004), was studied using high-resolution transmission electron microscopy. The results of this study suggest that schwertmannite synthesized using this method should not be described as a single phase with a repeating unit cell, but as a polyphasic nanomineral with crystalline areas spanning less than a few nanometers in diameter, within a characteristic `pin-cushion'-like amorphous matrix. The difference in synthesis temperature affected the density of the needles on the schwertmannite surface. The needles on the higher-temperature schwertmannite displayed a dendritic morphology, whereas the needles on the room-temperature schwertmannite were more closely packed. Visible lattice fringes in the schwertmannite samples are consistent with the powder X-ray diffraction (XRD) pattern taken on the bulk schwertmannite and also matched d-spacings for goethite, indicating a close structural relationship between schwertmannite and goethite. The incomplete transformation from schwertmannite to goethite over 24 h at 75 °C was tracked using XRD and TEM. TEM images suggest that the sample collected after 24 h consists of aggregates of goethite nanocrystals. Comparing the synthetic schwertmannite in this study to a study on schwertmannite produced at 85 °C, which used ferric sulfate, reveals that synthesis conditions can result in significant differences in needle crystal structure. The bulk powder XRD patterns for the schwertmannite produced using these two samples were indistinguishable from one another. Future studies using synthetic schwertmannite should account for these differences when determining schwertmannite's structure, reactivity, and capacity to take up elements like arsenic. The schwertmannite synthesized by the Regenspurg et al. method produces a mineral that is consistent with the structure and morphology of natural schwertmannite observed in our previous study using XRD and TEM, making this an ideal synthetic method for laboratory-based mineralogical and geochemical studies that intend to be environmentally relevant.

Quenching and Partitioning Process Development to Replace Hot Stamping of High Strength Automotive Steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

De Moor, Emmanuel

The present project investigated Quenching and Partitioning (Q&P) to process cold rolled steels to develop high strength sheet steels that exhibit superior ductility compared to available grades with the intent to allow forming of high strength parts at room temperature to provide an alternative to hot stamping of parts. Hot stamping of boron alloyed steel is the current technology to manufacture thinner gauge sections in automotive structures to guarantee anti-intrusion during collisions whilst improving fuel efficiency by decreasing vehicle weight. Hot stamping involves reheating steel to 900 °C or higher followed by deformation and quenching in the die to producemore » ultra-high strength materials. Hot stamping requires significant energy to reheat the steel and is less productive than traditional room temperature stamping operations. Stamping at elevated temperature was developed due to the lack of available steels with strength levels of interest possessing sufficient ductility enabling traditional room temperature forming. This process is seeing growing demand within the automotive industry and, given the reheating step in this operation, increased energy consumption during part manufacturing results. The present research program focused on the development of steel grades via Q&P processing that exhibit high strength and formability enabling room temperature forming to replace hot stamping. The main project objective consisted of developing sheet steels exhibiting minimum ultimate tensile strength levels of 1200 MPa in combination with minimum tensile elongation levels of 15 pct using Q&P processing through judicious alloy design and heat treating parameter definition. In addition, detailed microstructural characterization and study of properties, processing and microstructure interrelationships were pursued to develop strategies to further enhance tensile properties. In order to accomplish these objectives, alloy design was conducted towards achieving the target properties. Twelve alloys were designed and laboratory produced involving melting, alloying, casting, hot rolling, and cold rolling to obtain sheet steels of approximately 1 mm thickness. Q&P processing of the samples was then conducted. Target properties were achieved and substantially exceeded demonstrating success in the developed and employed alloy design approaches. The best combinations of tensile properties were found at approximately 1550 MPa with a total elongation in excess of 20 pct clearly showing the potential for replacement of hot stamping to produce advanced high strength steels.« less

High pressure phase transitions in lawsonite at simultaneous high pressure and temperature: A single crystal study

NASA Astrophysics Data System (ADS)

O'Bannon, E. F., III; Vennari, C.; Beavers, C. C. G.; Williams, Q. C.

2015-12-01

Lawsonite (CaAl2Si2O7(OH)2.H2O) is a hydrous mineral with a high overall water content of ~11.5 wt.%. It is a significant carrier of water in subduction zones to depths greater than ~150 km. The structure of lawsonite has been extensively studied under room temperature, high-pressure conditions. However, simultaneous high-pressure and high-temperature experiments are scarce. We have conducted synchrotron-based simultaneous high-pressure and temperature single crystal experiments on lawsonite up to a maximum pressure of 8.4 GPa at ambient and high temperatures. We used a natural sample of lawsonite from Valley Ford, California (Sonoma County). At room pressure and temperature lawsonite crystallizes in the orthorhombic system with Cmcm symmetry. Room temperature compression indicates that lawsonite remains in the orthorhombic Cmcm space group up to ~9.0 GPa. Our 5.0 GPa crystal structure is similar to the room pressure structure, and shows almost isotropic compression of the crystallographic axes. Unit cell parameters at 5.0 GPa are a- 5.7835(10), b- 8.694(2), and c- 13.009(3). Single-crystal measurements at simultaneous high-pressure and temperature (e.g., >8.0 GPa and ~100 oC) can be indexed to a monoclinic P-centered unit cell. Interestingly, a modest temperature increase of ~100 oC appears to initiate the orthorhombic to monoclinic phase transition at ~0.6-2.4 GPa lower than room temperature compression studies have shown. There is no evidence of dehydration or H atom disorder under these conditions. This suggests that the orthorhombic to monoclinic transition could be kinetically impeded at 298 K, and that monoclinic lawsonite could be the dominant water carrier through much of the depth range of upper mantle subduction processes.

Advances in processing of NiAl intermetallic alloys and composites for high temperature aerospace applications

NASA Astrophysics Data System (ADS)

Bochenek, Kamil; Basista, Michal

2015-11-01

Over the last few decades intermetallic compounds such as NiAl have been considered as potential high temperature structural materials for aerospace industry. A large number of investigations have been reported describing complex fabrication routes, introducing various reinforcing/alloying elements along with theoretical analyses. These research works were mainly focused on the overcoming of main disadvantage of nickel aluminides that still restricts their application range, i.e. brittleness at room temperature. In this paper we present an overview of research on NiAl processing and indicate methods that are promising in solving the low fracture toughness issue at room temperature. Other material properties relevant for high temperature applications are also addressed. The analysis is primarily done from the perspective of NiAl application in aero engines in temperature regimes from room up to the operating temperature (over 1150 °C) of turbine blades.

Design of a superconducting volume coil for magnetic resonance microscopy of the mouse brain

NASA Astrophysics Data System (ADS)

Nouls, John C.; Izenson, Michael G.; Greeley, Harold P.; Johnson, G. Allan

2008-04-01

We present the design process of a superconducting volume coil for magnetic resonance microscopy of the mouse brain at 9.4 T. The yttrium barium copper oxide coil has been designed through an iterative process of three-dimensional finite-element simulations and validation against room temperature copper coils. Compared to previous designs, the Helmholtz pair provides substantially higher B1 homogeneity over an extended volume of interest sufficiently large to image biologically relevant specimens. A custom-built cryogenic cooling system maintains the superconducting probe at 60 ± 0.1 K. Specimen loading and probe retuning can be carried out interactively with the coil at operating temperature, enabling much higher through-put. The operation of the probe is a routine, consistent procedure. Signal-to-noise ratio in a mouse brain increased by a factor ranging from 1.1 to 2.9 as compared to a room-temperature solenoid coil optimized for mouse brain microscopy. We demonstrate images encoded at 10 × 10 × 20 μm for an entire mouse brain specimen with signal-to-noise ratio of 18 and a total acquisition time of 16.5 h, revealing neuroanatomy unseen at lower resolution. Phantom measurements show an effective spatial resolution better than 20 μm.

Investigation of irradiation effects induced by self-ion in 6H-SiC combining RBS/C, Raman and XRD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chaabane, Nihed; Debelle, Aurelien; Sattonnay, Gael

2012-01-01

Single crystals of 6H-SiC were irradiated at room temperature and 670 K with 4 MeV C ions at two fluences: 1015 and 1016 cm2 (0.16 and 1.6 dpa at the damage peak). Damage accumulation was studied by a combination of X-ray diffraction (XRD), Raman spectroscopy and Rutherford backscattering spectrometry in channelling geometry (RBS/C) along the [0001] direction. The irradiated layer is found to be composed of a low damage region up to 1.5 lm followed by a region where the disorder level is higher, consistent with SRIM predictions. At room temperature and low fluence, typically 1015 cm2, the strain depthmore » profile follows the dpa depth distribution (with a maximum value of 2%). The disorder is most likely due to small defect clusters. When increasing the fluence up to 1016 cm2, a buried amorphous layer forms, as indicated by e.g. Raman results where the Si C bands become broader or even disappear. At a higher irradiation temperature of 670 K, amorphization is not observed at the same fluence, revealing a dynamic annealing process. However, results tend to suggest that the irradiated layer is highly heterogeneous and composed of different types of defects.« less

A study of room-temperature LixMn1.5Ni0.5O4 solid solutions

PubMed Central

Saravanan, Kuppan; Jarry, Angelique; Kostecki, Robert; Chen, Guoying

2015-01-01

Understanding the kinetic implication of solid-solution vs. biphasic reaction pathways is critical for the development of advanced intercalation electrode materials. Yet this has been a long-standing challenge in materials science due to the elusive metastable nature of solid solution phases. The present study reports the synthesis, isolation, and characterization of room-temperature LixMn1.5Ni0.5O4 solid solutions. In situ XRD studies performed on pristine and chemically-delithiated, micron-sized single crystals reveal the thermal behavior of LixMn1.5Ni0.5O4 (0 ≤ x ≤ 1) cathode material consisting of three cubic phases: LiMn1.5Ni0.5O4 (Phase I), Li0.5Mn1.5Ni0.5O4 (Phase II) and Mn1.5Ni0.5O4 (Phase III). A phase diagram capturing the structural changes as functions of both temperature and Li content was established. The work not only demonstrates the possibility of synthesizing alternative electrode materials that are metastable in nature, but also enables in-depth evaluation on the physical, electrochemical and kinetic properties of transient intermediate phases and their role in battery electrode performance. PMID:25619504

A room temperature strategy towards enhanced performance and bias stability of oxide thin film transistor with a sandwich structure channel layer

NASA Astrophysics Data System (ADS)

Zeng, Yong; Ning, Honglong; Zheng, Zeke; Zhang, Hongke; Fang, Zhiqiang; Yao, Rihui; Xu, Miao; Wang, Lei; Lan, Linfeng; Peng, Junbiao; Lu, Xubing

2017-04-01

Thermal annealing is a conventional and effective way to improve the bias stress stability of oxide thin film transistors (TFT) on solid substrates. However, it is still a challenge for enhancing the bias stress stability of oxide TFTs on flexible substrates by high-temperature post-treatment due to the thermal sensitivity of flexible substrates. Here, a room temperature strategy is presented towards enhanced performance and bias stability of oxide TFTs by intentionally engineering a sandwich structure channel layer consisting of a superlattice with aluminum doped zinc oxide (AZO) and Al2O3 thin films. The Al2O3/AZO/Al2O3-TFTs not only exhibit a saturation mobility of 9.27 cm2 V-1 s-1 and a linear mobility of 11.38 cm2 V-1 s-1 but also demonstrate a better bias stress stability than AZO/Al2O3-TFT. Moreover, the underlying mechanism of this enhanced electrical performance of TFTs with a sandwich structure channel layer is that the bottom Al2O3 thin films can obviously improve the crystalline phase of AZO films while decreasing electrical trapping centers and adsorption sites for undesirable molecules such as water and oxygen.

A study of room-temperature Li xMn 1.5Ni 0.5O 4 solid solutions

DOE PAGES

Saravanan, Kuppan; Jarry, Angelique; Kostecki, Robert; ...

2015-01-26

Understanding the kinetic implication of solid-solution vs. biphasic reaction pathways is critical for the development of advanced intercalation electrode materials. Yet this has been a long-standing challenge in materials science due to the elusive metastable nature of solid solution phases. The present study reports the synthesis, isolation, and characterization of room-temperature Li xMn 1.5Ni 0.5O 4 solid solutions. In situ XRD studies performed on pristine and chemically-delithiated, micron-sized single crystals reveal the thermal behavior of Li xMn 1.5Ni 0.5O 4 (0 ≤ x ≤ 1) cathode material consisting of three cubic phases: LiMn 1.5Ni 0.5O 4 (Phase I), Li 0.5Mnmore » 1.5Ni 0.5O 4 (Phase II) and Mn 1.5Ni 0.5O 4 (Phase III). A phase diagram capturing the structural changes as functions of both temperature and Li content was established. In conclusion, the work not only demonstrates the possibility of synthesizing alternative electrode materials that are metastable in nature, but also enables in-depth evaluation on the physical, electrochemical and kinetic properties of transient intermediate phases and their role in battery electrode performance.« less

Design of a superconducting volume coil for magnetic resonance microscopy of the mouse brain.

PubMed

Nouls, John C; Izenson, Michael G; Greeley, Harold P; Johnson, G Allan

2008-04-01

We present the design process of a superconducting volume coil for magnetic resonance microscopy of the mouse brain at 9.4T. The yttrium barium copper oxide coil has been designed through an iterative process of three-dimensional finite-element simulations and validation against room temperature copper coils. Compared to previous designs, the Helmholtz pair provides substantially higher B(1) homogeneity over an extended volume of interest sufficiently large to image biologically relevant specimens. A custom-built cryogenic cooling system maintains the superconducting probe at 60+/-0.1K. Specimen loading and probe retuning can be carried out interactively with the coil at operating temperature, enabling much higher through-put. The operation of the probe is a routine, consistent procedure. Signal-to-noise ratio in a mouse brain increased by a factor ranging from 1.1 to 2.9 as compared to a room-temperature solenoid coil optimized for mouse brain microscopy. We demonstrate images encoded at 10x10x20mum for an entire mouse brain specimen with signal-to-noise ratio of 18 and a total acquisition time of 16.5h, revealing neuroanatomy unseen at lower resolution. Phantom measurements show an effective spatial resolution better than 20mum.

Room temperature LPG resistive sensor based on the use of a few-layer graphene/SnO2 nanocomposite.

PubMed

Goutham, Solleti; Bykkam, Satish; Sadasivuni, Kishor Kumar; Kumar, Devarai Santhosh; Ahmadipour, Mohsen; Ahmad, Zainal Arifin; Rao, Kalagadda Venkateswara

2017-12-20

A nanocomposite consisting of a few layers of graphene (FLG) and tin dioxide (SnO 2 ) was prepared by ultrasound-assisted synthesis. The uniform SnO 2 nanoparticles (NPs) on the FLG were characterized by X-ray diffraction in terms of lattice and phase structure. The functional groups present in the composite were analyzed by FTIR. Electron microscopy (HR-TEM and FE-SEM) was used to study the morphology. The effect of the fraction of FLG present in the nanocomposite was investigated. Sensitivity, selectivity and reproducibility towards resistive sensing of liquid propane gas (LPG) was characterized by the I-V method. The sensor with 1% of FLG on SnO 2 operated at a typical voltage of 1 V performs best in giving a rapid and sensitive response even at 27 °C. This proves that the operating temperature of such sensors can be drastically decreased which is in contrast to conventional metal oxide LPG sensors. Graphical abstract Schematic of a room temperature gas sensor for liquefied petroleum gas (LPG). It is based on the use of a few-layered graphene (1 wt%)/SnO 2 nanocomposite that was deposited on an interdigitated electrode (IDEs). A sensing mechanism for LPG detection has been established.

Storage and stability of IgG and IgM monoclonal antibodies dried on filter paper and utility in Neisseria meningitidis serotyping by Dot-blot ELISA.

PubMed

Ferraz, Aline S; Belo, Elza F T; Coutinho, Ligia M C C; Oliveira, Ana P; Carmo, Andréia M S; Franco, Daniele L; Ferreira, Tatiane; Yto, André Y; Machado, Marta S F; Scola, Monica C G; De Gaspari, Elizabeth

2008-03-06

A simple filter paper method was developed for, the transport and storage of monoclonal antibodies (Mabs) at room temperature or -20 degrees C after spotting on filter paper, for subsequent serotyping of outer membrane antigens of N.meningitidis by dot-blot ELISA. Monoclonal antibodies (Mabs) were spotted within a 0.5-1 cm diameter area of Whatman grade 903 paper, which were stored individually at room temperature or at -20 degrees C. These MAbs were stored and analyzed after periods of one week, 4 weeks, 12 months, or 13 years in the case of frozen Mab aliquots, or after 4 weeks at -20 degrees C or at room temperature (RT) in the case of Mabs dried on filter paper strips. Assays were performed in parallel using dot-blot ELISA. In addition to the MAbs specific for serotyping class 1, 2 or 3, we used a larger number of Mabs for polysaccharides, lipooligosaccharides (LOS), class 5 and cross-reactive antigens for native outer membrane of N.meningitidis. The Mabs dried on filter paper were eluted with phosphate-buffered saline (PBS) containing 0.2% gelatin. Mabs of the isotypes IgG and IgM dried on filter papers were not affected by duration of storage. The detection by serotyping Mabs was generally consistent for dried filter paper MAb samples stored frozen for over 1 year at -20 degrees C, and although decreased reactive antibody titers were found after storage, this did not interfere with the specificity of the Mabs used after 13 years as dry spots on filter paper. The use of filter paper is an inexpensive and convenient method for collecting, storing, and transporting Mab samples for serotyping studies. In addition, the samples occupy little space and can be readily transported without freezing. The efficiency of using immunoglobulin G (IgG) or M (IgM) eluted was found to be consistent with measurement of IgG or IgM titers in most corresponding, ascites Mabs stored frozen for over 1 year. The application of meningococcal typing methods and designations depend on the question being asked.

Protective layer formation on magnesium in cell culture medium.

PubMed

Wagener, V; Virtanen, S

2016-06-01

In the past, different studies showed that hydroxyapatite (HA) or similar calcium phosphates can be precipitated on Mg during immersion in simulated body fluids. However, at the same time, in most cases a dark grey or black layer is built under the white HA crystals. This layer seems to consist as well of calcium phosphates. Until now, neither the morphology nor its influence on Mg corrosion have been investigated in detail. In this work commercially pure magnesium (cp) was immersed in cell culture medium for one, three and five days at room temperature and in the incubator (37 °C, 5% CO2). In addition, the influence of proteins on the formation of a corrosion layer was investigated by adding 20% of fetal calf serum (FCS) to the cell culture medium in the incubator. In order to analyze the formed layers, SEM images of cross sections, X-ray Photoelectron Spectroscopy (XPS), X-ray diffraction (XRD), Energy Dispersive X-ray Spectroscopy (EDX) and Fourier Transformed Infrared Spectroscopy (FTIR) measurements were carried out. Characterization of the corrosion behavior was achieved by electrochemical impedance spectroscopy (EIS) and by potentio-dynamic polarization in Dulbecco's Modified Eagle's Medium (DMEM) at 37°C. Surface analysis showed that all formed layers consist mainly of amorphous calcium phosphate compounds. For the immersion at room temperature the Ca/P ratio indicates the formation of HA, while in the incubator probably pre-stages to HA are formed. The different immersion conditions lead to a variation in layer thicknesses. However, electrochemical characterization shows that the layer thickness does not influence the corrosion resistance of magnesium. The main influencing factor for the corrosion behavior is the layer morphology. Thus, immersion at room temperature leads to the highest corrosion protection due to the formation of a compact outer layer. Layers formed in the incubator show much worse performances due to completely porous structures. The existence of proteins in DMEM seems to hinder the formation of a corrosion layer. However, protein adsorption leads to similar results as concerns corrosion protection as the formed calcium phosphate layer. Copyright © 2016 Elsevier B.V. All rights reserved.

Generation of an ultrafast femtosecond soliton fiber laser by carbon nanotube as saturable absorber

NASA Astrophysics Data System (ADS)

Salim, M. A. M.; Ahmad, H.; Harun, S. W.; Bidin, N.; Krishnan, G.

2018-05-01

This paper reports the demonstration of ultrafast fiber laser in a simple erbium-doped fiber (EDF) laser that employed a carbon nanotube (CNT) thin film saturable absorber (SA) to generate a stable soliton pulse. The repetition rate of 10.8 MHz pulse consistently achieved has narrowest pulse width of 640 fs and 1555.78 nm central wavelength for an hour operation in room temperature. This proposed setup has the capability for reliable and stable system features.

Four-probe charge transport measurements on individual vertically aligned carbon nanofibers

NASA Astrophysics Data System (ADS)

Zhang, Lan; Austin, Derek; Merkulov, Vladimir I.; Meleshko, Anatoli V.; Klein, Kate L.; Guillorn, Michael A.; Lowndes, Douglas H.; Simpson, Michael L.

2004-05-01

We report four-probe I-V measurements on individual vertically aligned carbon nanofibers (VACNFs). These measurements were enabled by the fabrication of multiple Ti/Au ohmic contacts on individual fibers that exhibited resistance of only a few kilohms. These measurements demonstrate that VACNFs exhibit linear I-V behavior at room temperature, with a resistivity of approximately 4.2×10-3 Ω cm. Our measurements are consistent with a dominant transport mechanism of electrons traveling through intergraphitic planes in the VACNFs.

Intermolecular forces in acetonitrile + ethanol binary liquid mixtures

NASA Astrophysics Data System (ADS)

Elangovan, A.; Shanmugam, R.; Arivazhagan, G.; Mahendraprabu, A.; Karthick, N. K.

2015-10-01

FTIR spectral measurements have been carried out on the binary mixtures of acetonitrile with ethanol at 1:0 (acetonitrile:ethanol), 1:1, 1:2, 1:3 and 0:1 at room temperature. DFT and isosurface calculations have been performed. The acetonitrile + ethanol binary mixtures consist of 1:1, 1:2, 1:3 and 1:4 complexes formed through both the red and blue shifting H-bonds. Inter as well as intra molecular forces are found to exist in 1:3 and 1:4 complexes.

Stability of allopurinol and of five antineoplastics in suspension.

PubMed

Dressman, J B; Poust, R I

1983-04-01

The stability of allopurinol, azathioprine, chlorambucil, melphalan, mercaptopurine, and thioguanine each in an extemporaneously prepared suspension was studied. Tablets of each drug were crushed, mixed with a suspending agent, and brought to a final volume of 10, 15, or 20 ml with a 2:1 mixture of simple syrup and wild cherry syrup. Suspensions were prepared in the following concentrations: allopurinol (20 mg/ml), azathioprine (50 mg/ml), chlorambucil (2 mg/ml), melphalan (2 mg/ml), mercaptopurine (50 mg/ml), and thioguanine (40 mg/ml). Using high-performance liquid chromatography or ultraviolet scans, duplicate assays were performed on each suspension periodically during storage for up to 84 days at ambient room temperature or 5 degrees C. The time required for the suspensions to drop below 90% of labeled strength was used as an indicator of drug stability. Allopurinol and azathioprine were stable for at least 56 days at room temperature and at 5 degrees C. Chlorambucil decomposed rapidly at room temperature but was stable for seven days when stored at 5 degrees C. Melphalan suspensions did not meet the stated criteria for stability even at the time of initial assay. Mercaptopurine and thioguanine were stable for 14 and 84 days, respectively, at room temperature; at 5 degrees C, assay values dropped below those obtained at room temperature. In the suspension formulation tested, allopurinol, azathioprine, mercaptopurine, and thioguanine are stable for at least 14 days at room temperature; chlorambucil suspensions should be refrigerated and discarded after seven days. Melphalan decomposes too rapidly to make this suspension formulation feasible for extemporaneous compounding.

Room-Temperature-Cured Copolymers for Lithium Battery Gel Electrolytes

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B.; Tigelaar, Dean M.

2009-01-01

Polyimide-PEO copolymers (PEO signifies polyethylene oxide) that have branched rod-coil molecular structures and that can be cured into film form at room temperature have been invented for use as gel electrolytes for lithium-ion electric-power cells. These copolymers offer an alternative to previously patented branched rod-coil polyimides that have been considered for use as polymer electrolytes and that must be cured at a temperature of 200 C. In order to obtain sufficient conductivity for lithium ions in practical applications at and below room temperature, it is necessary to imbibe such a polymer with a suitable carbonate solvent or ionic liquid, but the high-temperature cure makes it impossible to incorporate and retain such a liquid within the polymer molecular framework. By eliminating the high-temperature cure, the present invention makes it possible to incorporate the required liquid.

Mechanical Behavior of AZ31B Mg Alloy Sheets under Monotonic and Cyclic Loadings at Room and Moderately Elevated Temperatures

PubMed Central

Nguyen, Ngoc-Trung; Seo, Oh Suk; Lee, Chung An; Lee, Myoung-Gyu; Kim, Ji-hoon; Kim, Heon Young

2014-01-01

Large-strain monotonic and cyclic loading tests of AZ31B magnesium alloy sheets were performed with a newly developed testing system, at different temperatures, ranging from room temperature to 250 °C. Behaviors showing significant twinning during initial in-plane compression and untwinning in subsequent tension at and slightly above room temperature were recorded. Strong yielding asymmetry and nonlinear hardening behavior were also revealed. Considerable Bauschinger effects, transient behavior, and variable permanent softening responses were observed near room temperature, but these were reduced and almost disappeared as the temperature increased. Different stress–strain responses were inherent to the activation of twinning at lower temperatures and non-basal slip systems at elevated temperatures. A critical temperature was identified to account for the transition between the twinning-dominant and slip-dominant deformation mechanisms. Accordingly, below the transition point, stress–strain curves of cyclic loading tests exhibited concave-up shapes for compression or compression following tension, and an unusual S-shape for tension following compression. This unusual shape disappeared when the temperature was above the transition point. Shrinkage of the elastic range and variation in Young’s modulus due to plastic strain deformation during stress reversals were also observed. The texture-induced anisotropy of both the elastic and plastic behaviors was characterized experimentally. PMID:28788514

Gas production in anaerobic dark-fermentation processes from agriculture solid waste

NASA Astrophysics Data System (ADS)

Sriwuryandari, L.; Priantoro, E. A.; Sintawardani, N.

2017-03-01

Approximately, Bandung produces agricultural solid waste of 1549 ton/day. This wastes consist of wet-organic matter and can be used for bio-gas production. The research aimed to apply the available agricultural solid waste for bio-hydrogen. Biogas production was done by a serial of batches anaerobic fermentation using mix-culture bacteria as the active microorganism. Fermentation was carried out inside a 30 L bioreactor at room temperature. The analyzed parameters were of pH, total gas, temperature, and COD. Result showed that from 3 kg/day of organic wastes, various total gases of O2, CH4, H2, CO2, and CnHn,O2 was produced.

Metal-insulator transition in nanocomposite VOx films formed by anodic electrodeposition

NASA Astrophysics Data System (ADS)

Tsui, Lok-kun; Hildebrand, Helga; Lu, Jiwei; Schmuki, Patrik; Zangari, Giovanni

2013-11-01

The ability to grow VO2 films by electrochemical methods would open a low-cost, easily scalable production route to a number of electronic devices. We have synthesized VOx films by anodic electrodeposition of V2O5, followed by partial reduction by annealing in Ar. The resulting films are heterogeneous, consisting of various metallic/oxide phases and including regions with VO2 stoichiometry. A gradual metal insulator transition with a nearly two order of magnitude change in film resistance is observed between room temperature and 140 °C. In addition, the films exhibit a temperature coefficient of resistance of ˜ -2.4%/ °C from 20 to 140 °C.

Properties of radiation stable, low viscosity impregnating resin for cryogenic insulation system

NASA Astrophysics Data System (ADS)

Wu, Zhixiong; Zhang, Hao; Yang, Huihui; Chu, Xinxin; Song, Yuntao; Wu, Weiyue; Liu, Huajun; Li, Laifeng

2011-06-01

Impregnating resins in fusion magnet technology are required to be radiation stable, low viscosity, long usable life and high toughness. To meet these objectives, we developed a new epoxy based composite which consists of triglycidyl-p-aminophenol (TGPAP) epoxy resin and isopropylidenebisphenol bis[(2-glycidyloxy-3-n-butoxy)-1-propylether] (IPBE). The ratio of TGPAP to IPBE can be varied to achieve desired viscosity and working time. The boron-free glass fiber reinforced composites were prepared by vacuum pressure impregnation. The radiation resistance was evaluated by 60Co γ-ray irradiation of 1 MGy at ambient temperature. The mechanical properties of the composites have been measured at room temperature and at 77 K.