Science.gov

Sample records for minimum crystal size

  1. The minimum crystal size needed for a complete diffraction data set

    SciTech Connect

    Holton, James M.; Frankel, Kenneth A.

    2010-04-01

    A formula for absolute scattering power is derived to include spot fading arising from radiation damage and the crystal volume needed to collect diffraction data to a given resolution is calculated. In this work, classic intensity formulae were united with an empirical spot-fading model in order to calculate the diameter of a spherical crystal that will scatter the required number of photons per spot at a desired resolution over the radiation-damage-limited lifetime. The influences of molecular weight, solvent content, Wilson B factor, X-ray wavelength and attenuation on scattering power and dose were all included. Taking the net photon count in a spot as the only source of noise, a complete data set with a signal-to-noise ratio of 2 at 2 Å resolution was predicted to be attainable from a perfect lysozyme crystal sphere 1.2 µm in diameter and two different models of photoelectron escape reduced this to 0.5 or 0.34 µm. These represent 15-fold to 700-fold less scattering power than the smallest experimentally determined crystal size to date, but the gap was shown to be consistent with the background scattering level of the relevant experiment. These results suggest that reduction of background photons and diffraction spot size on the detector are the principal paths to improving crystallographic data quality beyond current limits.

  2. The minimum crystal size needed for a complete diffraction data set

    PubMed Central

    Holton, James M.; Frankel, Kenneth A.

    2010-01-01

    In this work, classic intensity formulae were united with an empirical spot-fading model in order to calculate the diameter of a spherical crystal that will scatter the required number of photons per spot at a desired resolution over the radiation-damage-limited lifetime. The influences of molecular weight, solvent content, Wilson B factor, X-ray wavelength and attenuation on scattering power and dose were all included. Taking the net photon count in a spot as the only source of noise, a complete data set with a signal-to-noise ratio of 2 at 2 Å resolution was predicted to be attainable from a perfect lysozyme crystal sphere 1.2 µm in diameter and two different models of photoelectron escape reduced this to 0.5 or 0.34 µm. These represent 15-fold to 700-fold less scattering power than the smallest experimentally determined crystal size to date, but the gap was shown to be consistent with the background scattering level of the relevant experiment. These results suggest that reduction of background photons and diffraction spot size on the detector are the principal paths to improving crystallographic data quality beyond current limits. PMID:20382993

  3. 50 CFR 648.143 - Minimum sizes.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 50 Wildlife and Fisheries 10 2011-10-01 2011-10-01 false Minimum sizes. 648.143 Section 648.143 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE FISHERIES OF THE NORTHEASTERN UNITED STATES Management Measures for the Black Sea Bass Fishery § 648.143 Minimum...

  4. 50 CFR 648.143 - Minimum sizes.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 50 Wildlife and Fisheries 8 2010-10-01 2010-10-01 false Minimum sizes. 648.143 Section 648.143 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION... retain black sea bass in or from U.S. waters of the western Atlantic Ocean from 35′ 15.3 N. Lat.,...

  5. 50 CFR 648.83 - Multispecies minimum fish sizes.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 50 Wildlife and Fisheries 10 2011-10-01 2011-10-01 false Multispecies minimum fish sizes. 648.83... Measures for the NE Multispecies and Monkfish Fisheries § 648.83 Multispecies minimum fish sizes. (a) Minimum fish sizes. (1) Minimum fish sizes for recreational vessels and charter/party vessels that are...

  6. 50 CFR 648.103 - Minimum fish sizes.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 50 Wildlife and Fisheries 8 2010-10-01 2010-10-01 false Minimum fish sizes. 648.103 Section 648... Summer Flounder Fisheries § 648.103 Minimum fish sizes. (a) The minimum size for summer flounder is 14... carrying more than five crew members. (c) The minimum sizes in this section apply to whole fish or to...

  7. 50 CFR 648.83 - Multispecies minimum fish sizes.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 50 Wildlife and Fisheries 8 2010-10-01 2010-10-01 false Multispecies minimum fish sizes. 648.83... Measures for the NE Multispecies and Monkfish Fisheries § 648.83 Multispecies minimum fish sizes. (a) Minimum fish sizes. (1) Minimum fish sizes for recreational vessels and charter/party vessels that are...

  8. 50 CFR 648.83 - Multispecies minimum fish sizes.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 50 Wildlife and Fisheries 12 2013-10-01 2013-10-01 false Multispecies minimum fish sizes. 648.83... Measures for the NE Multispecies and Monkfish Fisheries § 648.83 Multispecies minimum fish sizes. (a) Minimum fish sizes. (1) Minimum fish sizes for recreational vessels and charter/party vessels that are...

  9. 50 CFR 648.83 - Multispecies minimum fish sizes.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 50 Wildlife and Fisheries 12 2012-10-01 2012-10-01 false Multispecies minimum fish sizes. 648.83... Measures for the NE Multispecies and Monkfish Fisheries § 648.83 Multispecies minimum fish sizes. (a) Minimum fish sizes. (1) Minimum fish sizes for recreational vessels and charter/party vessels that are...

  10. 50 CFR 648.83 - Multispecies minimum fish sizes.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 50 Wildlife and Fisheries 12 2014-10-01 2014-10-01 false Multispecies minimum fish sizes. 648.83... Measures for the NE Multispecies and Monkfish Fisheries § 648.83 Multispecies minimum fish sizes. (a) Minimum fish sizes. (1) Minimum fish sizes for recreational vessels and charter/party vessels that are...

  11. 50 CFR 648.93 - Monkfish minimum fish sizes.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 50 Wildlife and Fisheries 10 2011-10-01 2011-10-01 false Monkfish minimum fish sizes. 648.93... Measures for the NE Multispecies and Monkfish Fisheries § 648.93 Monkfish minimum fish sizes. (a) General... fish size requirements established in this section. Minimum Fish Sizes (Total Length/Tail Length)...

  12. 50 CFR 648.93 - Monkfish minimum fish sizes.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 50 Wildlife and Fisheries 8 2010-10-01 2010-10-01 false Monkfish minimum fish sizes. 648.93... Measures for the NE Multispecies and Monkfish Fisheries § 648.93 Monkfish minimum fish sizes. (a) General... fish size requirements established in this section. Minimum Fish Sizes (Total Length/Tail Length)...

  13. 50 CFR 648.93 - Monkfish minimum fish sizes.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 50 Wildlife and Fisheries 12 2012-10-01 2012-10-01 false Monkfish minimum fish sizes. 648.93... Measures for the NE Multispecies and Monkfish Fisheries § 648.93 Monkfish minimum fish sizes. (a) General... fish size requirements established in this section. Minimum Fish Sizes (Total Length/Tail Length)...

  14. 50 CFR 648.93 - Monkfish minimum fish sizes.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 50 Wildlife and Fisheries 12 2013-10-01 2013-10-01 false Monkfish minimum fish sizes. 648.93... Measures for the NE Multispecies and Monkfish Fisheries § 648.93 Monkfish minimum fish sizes. (a) General... fish size requirements established in this section. Minimum Fish Sizes (Total Length/Tail Length)...

  15. 50 CFR 648.72 - Minimum surf clam size.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 50 Wildlife and Fisheries 8 2010-10-01 2010-10-01 false Minimum surf clam size. 648.72 Section 648... Atlantic Surf Clam and Ocean Quahog Fisheries § 648.72 Minimum surf clam size. (a) Minimum length. The minimum length for surf clams is 4.75 inches (12.065 cm). (b) Determination of compliance. No more than...

  16. 50 CFR 648.124 - Minimum fish sizes.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 50 Wildlife and Fisheries 8 2010-10-01 2010-10-01 false Minimum fish sizes. 648.124 Section 648... Scup Fishery § 648.124 Minimum fish sizes. (a) The minimum size for scup is 9 inches (22.9 cm) TL for... charter boat, or more than five crew members if a party boat. (c) The minimum size applies to whole...

  17. 50 CFR 648.162 - Minimum fish sizes.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 50 Wildlife and Fisheries 8 2010-10-01 2010-10-01 false Minimum fish sizes. 648.162 Section 648... Atlantic Bluefish Fishery § 648.162 Minimum fish sizes. If the Council determines through its annual review or framework adjustment process that minimum fish sizes are necessary to assure that the...

  18. 50 CFR 648.103 - Minimum fish sizes.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 50 Wildlife and Fisheries 10 2011-10-01 2011-10-01 false Minimum fish sizes. 648.103 Section 648... Summer Flounder Fisheries § 648.103 Minimum fish sizes. Link to an amendment published at 76 FR 60628... members. (c) The minimum sizes in this section apply to whole fish or to any part of a fish found...

  19. 50 CFR 648.124 - Minimum fish sizes.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 50 Wildlife and Fisheries 10 2011-10-01 2011-10-01 false Minimum fish sizes. 648.124 Section 648... Scup Fishery § 648.124 Minimum fish sizes. Link to an amendment published at 76 FR 60633, Sept. 29... if a party boat. (c) The minimum size applies to whole fish or any part of a fish found in...

  20. 50 CFR 648.162 - Minimum fish sizes.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 50 Wildlife and Fisheries 10 2011-10-01 2011-10-01 false Minimum fish sizes. 648.162 Section 648... Atlantic Bluefish Fishery § 648.162 Minimum fish sizes. Link to an amendment published at 76 FR 60639, Sept... minimum fish sizes are necessary to assure that the fishing mortality rate is not exceeded, or to...

  1. 50 CFR 648.165 - Bluefish minimum fish sizes.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 50 Wildlife and Fisheries 12 2014-10-01 2014-10-01 false Bluefish minimum fish sizes. 648.165... Measures for the Atlantic Bluefish Fishery § 648.165 Bluefish minimum fish sizes. If the MAFMC determines through its annual review or framework adjustment process that minimum fish sizes are necessary to...

  2. 50 CFR 648.126 - Scup minimum fish sizes.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 50 Wildlife and Fisheries 12 2014-10-01 2014-10-01 false Scup minimum fish sizes. 648.126 Section... Scup Fishery § 648.126 Scup minimum fish sizes. (a) Moratorium (commercially) permitted vessels. The... whole fish or any part of a fish found in possession, e.g., fillets. These minimum sizes may be...

  3. 50 CFR 648.104 - Summer flounder minimum fish sizes.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 50 Wildlife and Fisheries 12 2013-10-01 2013-10-01 false Summer flounder minimum fish sizes. 648... Measures for the Summer Flounder Fisheries § 648.104 Summer flounder minimum fish sizes. (a) Moratorium... minimum sizes in this section apply to whole fish or to any part of a fish found in possession,...

  4. 50 CFR 648.104 - Summer flounder minimum fish sizes.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 50 Wildlife and Fisheries 12 2014-10-01 2014-10-01 false Summer flounder minimum fish sizes. 648... Measures for the Summer Flounder Fisheries § 648.104 Summer flounder minimum fish sizes. (a) Moratorium... minimum sizes in this section apply to whole fish or to any part of a fish found in possession,...

  5. 50 CFR 648.165 - Bluefish minimum fish sizes.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 50 Wildlife and Fisheries 12 2013-10-01 2013-10-01 false Bluefish minimum fish sizes. 648.165... Measures for the Atlantic Bluefish Fishery § 648.165 Bluefish minimum fish sizes. If the MAFMC determines through its annual review or framework adjustment process that minimum fish sizes are necessary to...

  6. 50 CFR 648.126 - Scup minimum fish sizes.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 50 Wildlife and Fisheries 12 2013-10-01 2013-10-01 false Scup minimum fish sizes. 648.126 Section... Scup Fishery § 648.126 Scup minimum fish sizes. (a) Moratorium (commercially) permitted vessels. The... whole fish or any part of a fish found in possession, e.g., fillets. These minimum sizes may be...

  7. 50 CFR 648.165 - Bluefish minimum fish sizes.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 50 Wildlife and Fisheries 12 2012-10-01 2012-10-01 false Bluefish minimum fish sizes. 648.165... Measures for the Atlantic Bluefish Fishery § 648.165 Bluefish minimum fish sizes. If the MAFMC determines through its annual review or framework adjustment process that minimum fish sizes are necessary to...

  8. 50 CFR 648.93 - Monkfish minimum fish sizes.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 50 Wildlife and Fisheries 12 2014-10-01 2014-10-01 false Monkfish minimum fish sizes. 648.93... Measures for the NE Multispecies and Monkfish Fisheries § 648.93 Monkfish minimum fish sizes. (a) General provisions. All monkfish caught by vessels issued a valid Federal monkfish permit must meet the minimum...

  9. 24 CFR 984.105 - Minimum program size.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... (CONTINUED) OFFICE OF ASSISTANT SECRETARY FOR PUBLIC AND INDIAN HOUSING, DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT SECTION 8 AND PUBLIC HOUSING FAMILY SELF-SUFFICIENCY PROGRAM General § 984.105 Minimum program... size than the minimum. (b) How to determine FSS minimum program size—(1) Public housing. The...

  10. 24 CFR 984.105 - Minimum program size.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... (Continued) OFFICE OF ASSISTANT SECRETARY FOR PUBLIC AND INDIAN HOUSING, DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT SECTION 8 AND PUBLIC HOUSING FAMILY SELF-SUFFICIENCY PROGRAM General § 984.105 Minimum program... size than the minimum. (b) How to determine FSS minimum program size—(1) Public housing. The...

  11. 24 CFR 984.105 - Minimum program size.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... (CONTINUED) OFFICE OF ASSISTANT SECRETARY FOR PUBLIC AND INDIAN HOUSING, DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT SECTION 8 AND PUBLIC HOUSING FAMILY SELF-SUFFICIENCY PROGRAM General § 984.105 Minimum program... size than the minimum. (b) How to determine FSS minimum program size—(1) Public housing. The...

  12. 24 CFR 984.105 - Minimum program size.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... (CONTINUED) OFFICE OF ASSISTANT SECRETARY FOR PUBLIC AND INDIAN HOUSING, DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT SECTION 8 AND PUBLIC HOUSING FAMILY SELF-SUFFICIENCY PROGRAM General § 984.105 Minimum program... size than the minimum. (b) How to determine FSS minimum program size—(1) Public housing. The...

  13. 46 CFR 111.60-4 - Minimum cable conductor size.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 4 2013-10-01 2013-10-01 false Minimum cable conductor size. 111.60-4 Section 111.60-4...-GENERAL REQUIREMENTS Wiring Materials and Methods § 111.60-4 Minimum cable conductor size. Each cable conductor must be #18 AWG (0.82 mm2) or larger except— (a) Each power and lighting cable conductor must...

  14. 46 CFR 111.60-4 - Minimum cable conductor size.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 4 2012-10-01 2012-10-01 false Minimum cable conductor size. 111.60-4 Section 111.60-4...-GENERAL REQUIREMENTS Wiring Materials and Methods § 111.60-4 Minimum cable conductor size. Each cable conductor must be #18 AWG (0.82 mm2) or larger except— (a) Each power and lighting cable conductor must...

  15. 46 CFR 111.60-4 - Minimum cable conductor size.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 4 2011-10-01 2011-10-01 false Minimum cable conductor size. 111.60-4 Section 111.60-4...-GENERAL REQUIREMENTS Wiring Materials and Methods § 111.60-4 Minimum cable conductor size. Each cable conductor must be #18 AWG (0.82 mm2) or larger except— (a) Each power and lighting cable conductor must...

  16. 50 CFR 622.302 - Minimum mesh size.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Sargassum Habitat of the South Atlantic Region § 622.302 Minimum mesh size. (a) The minimum allowable mesh size for a net used to fish for pelagic sargassum in the South Atlantic EEZ is 4.0 inches (10.2 cm... possess any pelagic sargassum. (b)...

  17. 50 CFR 622.302 - Minimum mesh size.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Sargassum Habitat of the South Atlantic Region § 622.302 Minimum mesh size. (a) The minimum allowable mesh size for a net used to fish for pelagic sargassum in the South Atlantic EEZ is 4.0 inches (10.2 cm... possess any pelagic sargassum. (b)...

  18. 50 CFR 648.233 - Minimum Fish Sizes. [Reserved

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 50 Wildlife and Fisheries 8 2010-10-01 2010-10-01 false Minimum Fish Sizes. 648.233 Section 648.233 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND ATMOSPHERIC... Spiny Dogfish Fishery § 648.233 Minimum Fish Sizes....

  19. 50 CFR 622.454 - Minimum size limit.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Lobster Fishery of Puerto Rico and the U.S. Virgin Islands § 622.454 Minimum size limit. (a) The minimum size limit for Caribbean spiny lobster is 3.5 inches (8.9 cm), carapace length. (b) A spiny lobster not... operator of a vessel that fishes in the EEZ is responsible for ensuring that spiny lobster on board are...

  20. 50 CFR 622.454 - Minimum size limit.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Lobster Fishery of Puerto Rico and the U.S. Virgin Islands § 622.454 Minimum size limit. (a) The minimum size limit for Caribbean spiny lobster is 3.5 inches (8.9 cm), carapace length. (b) A spiny lobster not... operator of a vessel that fishes in the EEZ is responsible for ensuring that spiny lobster on board are...

  1. 46 CFR 111.60-4 - Minimum cable conductor size.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Minimum cable conductor size. 111.60-4 Section 111.60-4 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Wiring Materials and Methods § 111.60-4 Minimum cable conductor size. Each...

  2. CALCIUM SULFITE CRYSTAL SIZING STUDIES

    EPA Science Inventory

    The report describes a reliable experimental method that can be used routinely to determine the crystal size distribution function, a measure that is required for a mathematical representation of the nucleation and growth processes involved in the settling, dewatering, and dispos...

  3. 50 CFR 648.126 - Scup minimum fish sizes.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... ADMINISTRATION, DEPARTMENT OF COMMERCE FISHERIES OF THE NORTHEASTERN UNITED STATES Management Measures for the... whole fish or any part of a fish found in possession, e.g., fillets. These minimum sizes may be...

  4. Minimum Sample Size Recommendations for Conducting Factor Analyses

    ERIC Educational Resources Information Center

    Mundfrom, Daniel J.; Shaw, Dale G.; Ke, Tian Lu

    2005-01-01

    There is no shortage of recommendations regarding the appropriate sample size to use when conducting a factor analysis. Suggested minimums for sample size include from 3 to 20 times the number of variables and absolute ranges from 100 to over 1,000. For the most part, there is little empirical evidence to support these recommendations. This…

  5. 50 CFR 648.72 - Minimum surf clam size.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... surfclam and or ocean quahog quotas that differ from the annual quotas specified for the current 3-year... Atlantic Surf Clam and Ocean Quahog Fisheries § 648.72 Minimum surf clam size. Link to an amendment... the convenience of the user, the revised text is set forth as follows: § 648.72 Surfclam and...

  6. LDPC Codes with Minimum Distance Proportional to Block Size

    NASA Technical Reports Server (NTRS)

    Divsalar, Dariush; Jones, Christopher; Dolinar, Samuel; Thorpe, Jeremy

    2009-01-01

    Low-density parity-check (LDPC) codes characterized by minimum Hamming distances proportional to block sizes have been demonstrated. Like the codes mentioned in the immediately preceding article, the present codes are error-correcting codes suitable for use in a variety of wireless data-communication systems that include noisy channels. The previously mentioned codes have low decoding thresholds and reasonably low error floors. However, the minimum Hamming distances of those codes do not grow linearly with code-block sizes. Codes that have this minimum-distance property exhibit very low error floors. Examples of such codes include regular LDPC codes with variable degrees of at least 3. Unfortunately, the decoding thresholds of regular LDPC codes are high. Hence, there is a need for LDPC codes characterized by both low decoding thresholds and, in order to obtain acceptably low error floors, minimum Hamming distances that are proportional to code-block sizes. The present codes were developed to satisfy this need. The minimum Hamming distances of the present codes have been shown, through consideration of ensemble-average weight enumerators, to be proportional to code block sizes. As in the cases of irregular ensembles, the properties of these codes are sensitive to the proportion of degree-2 variable nodes. A code having too few such nodes tends to have an iterative decoding threshold that is far from the capacity threshold. A code having too many such nodes tends not to exhibit a minimum distance that is proportional to block size. Results of computational simulations have shown that the decoding thresholds of codes of the present type are lower than those of regular LDPC codes. Included in the simulations were a few examples from a family of codes characterized by rates ranging from low to high and by thresholds that adhere closely to their respective channel capacity thresholds; the simulation results from these examples showed that the codes in question have low

  7. Neutron star glitches have a substantial minimum size

    NASA Astrophysics Data System (ADS)

    Espinoza, C. M.; Antonopoulou, D.; Stappers, B. W.; Watts, A.; Lyne, A. G.

    2014-05-01

    Glitches are sudden spin-up events that punctuate the steady spin-down of pulsars and are thought to be due to the presence of a superfluid component within neutron stars. The precise glitch mechanism and its trigger, however, remain unknown. The size of glitches is a key diagnostic for models of the underlying physics. While the largest glitches have long been taken into account by theoretical models, it has always been assumed that the minimum size lay below the detectability limit of the measurements. In this paper we define general glitch detectability limits and use them on 29 yr of daily observations of the Crab pulsar, carried out at Jodrell Bank Observatory. We find that all glitches lie well above the detectability limits and by using an automated method to search for small events we are able to uncover the full glitch size distribution, with no biases. Contrary to the prediction of most models, the distribution presents a rapid decrease of the number of glitches below ˜0.05 μHz. This substantial minimum size indicates that a glitch must involve the motion of at least several billion superfluid vortices and provides an extra observable which can greatly help the identification of the trigger mechanism. Our study also shows that glitches are clearly separated from all the other rotation irregularities. This supports the idea that the origin of glitches is different to that of timing noise, which comprises the unmodelled random fluctuations in the rotation rates of pulsars.

  8. The best nanoparticle size distribution for minimum thermal conductivity

    PubMed Central

    Zhang, Hang; Minnich, Austin J.

    2015-01-01

    Which sizes of nanoparticles embedded in a crystalline solid yield the lowest thermal conductivity? Nanoparticles have long been demonstrated to reduce the thermal conductivity of crystals by scattering phonons, but most previous works assumed the nanoparticles to have a single size. Here, we use optimization methods to show that the best nanoparticle size distribution to scatter the broad thermal phonon spectrum is not a similarly broad distribution but rather several discrete peaks at well-chosen nanoparticle radii. For SiGe, the best size distribution yields a thermal conductivity below that of amorphous silicon. Further, we demonstrate that a simplified distribution yields nearly the same low thermal conductivity and can be readily fabricated. Our work provides important insights into how to manipulate the full spectrum of phonons and will guide the design of more efficient thermoelectric materials. PMID:25757414

  9. Minimum size of disc cams with radial translating roller followers

    NASA Astrophysics Data System (ADS)

    1992-11-01

    ESDU 92005 gives a direct method for finding the minimum allowable prime circle radius based on the criteria that the maximum pressure angle does not exceed a specified value and that profile undercutting is avoided. ESDU 82023 provides an alternative approach that handles offset followers as well, but it is a geometric iterative procedure. Two methods are given here: one finds the minimum radius and the corresponding maximum diameter of the roller follower while the other finds the minimum radius when the size of the follower is known. The methods apply to DRD or DRRD follower motion defined by a single law; a hand calculation may be used based on graphs provided, or a FORTRAN program (ESDUpac A9205) which is also supplied, and both apply to six cam laws (simple harmonic, cycloidal, modified trapezoidal acceleration, modified sine acceleration, and 3-4-5 or 4-5-6-7 polynomial). Notes on the derivation of the method are included, together with step-by-step design procedures and guidance on the use of the program with a detailed explanation of the input and the output. Worked examples illustrate the practical applications of the procedures during the design of such mechanism.

  10. 50 CFR 622.208 - Minimum mesh size applicable to rock shrimp off Georgia and Florida.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... mesh size applicable to rock shrimp off Georgia and Florida. (a) The minimum mesh size for the cod end...), stretched mesh. This minimum mesh size is required in at least the last 40 meshes forward of the cod...

  11. "PowerUp"!: A Tool for Calculating Minimum Detectable Effect Sizes and Minimum Required Sample Sizes for Experimental and Quasi-Experimental Design Studies

    ERIC Educational Resources Information Center

    Dong, Nianbo; Maynard, Rebecca

    2013-01-01

    This paper and the accompanying tool are intended to complement existing supports for conducting power analysis tools by offering a tool based on the framework of Minimum Detectable Effect Sizes (MDES) formulae that can be used in determining sample size requirements and in estimating minimum detectable effect sizes for a range of individual- and…

  12. The elusive minimum viable population size for white sturgeon

    SciTech Connect

    Jager, Yetta; Lepla, Ken B.; Van Winkle, Webb; James, Mr Brad; McAdam, Dr Steve

    2010-01-01

    Biological conservation of sturgeon populations is a concern for many species. Those responsible for managing the white sturgeon (Acipenser transmontanus) and similar species are interested in identifying extinction thresholds to avoid. Two thresholds that exist in theory are the minimum viable population size (MVP) and minimum amount of suitable habitat. In this paper, we present both model and empirical estimates of these thresholds. We modified a population viability analysis (PVA) model for white sturgeon to include two new Allee mechanisms. Despite this, PVA-based MVP estimates were unrealistically low compared with empirical estimates unless opportunities for spawning were assumed to be less frequent. PVA results revealed a trade-off between MVP and habitat thresholds; smaller populations persisted in longer river segments and vice versa. Our empirical analyses suggested (1) a MVP range based on population trends from 1,194 to 27,700 individuals, and (2) a MVP estimate of 4,000 individuals based on recruitment. Long-term historical population surveys are needed for more populations to pinpoint an MVP based on trends, whereas the available data were sufficient to estimate MVP based on recruitment. Beyond the MVP, we developed a hierarchical model for population status based on empirical data. Metapopulation support was the most important predictor of population health, followed by the length of free-flowing habitat, with habitat thresholds at 26 and 150 km. Together, these results suggest that habitat and connectivity are important determinants of population status that likely influence the site-specific MVP thresholds.

  13. Strong crystal size effect on deformation twinning.

    PubMed

    Yu, Qian; Shan, Zhi-Wei; Li, Ju; Huang, Xiaoxu; Xiao, Lin; Sun, Jun; Ma, Evan

    2010-01-21

    Deformation twinning in crystals is a highly coherent inelastic shearing process that controls the mechanical behaviour of many materials, but its origin and spatio-temporal features are shrouded in mystery. Using micro-compression and in situ nano-compression experiments, here we find that the stress required for deformation twinning increases drastically with decreasing sample size of a titanium alloy single crystal, until the sample size is reduced to one micrometre, below which the deformation twinning is entirely replaced by less correlated, ordinary dislocation plasticity. Accompanying the transition in deformation mechanism, the maximum flow stress of the submicrometre-sized pillars was observed to saturate at a value close to titanium's ideal strength. We develop a 'stimulated slip' model to explain the strong size dependence of deformation twinning. The sample size in transition is relatively large and easily accessible in experiments, making our understanding of size dependence relevant for applications. PMID:20090749

  14. Graphene single crystals: size and morphology engineering.

    PubMed

    Geng, Dechao; Wang, Huaping; Yu, Gui

    2015-05-13

    Recently developed chemical vapor deposition (CVD) is considered as an effective way to large-area and high-quality graphene preparation due to its ultra-low cost, high controllability, and high scalability. However, CVD-grown graphene film is polycrystalline, and composed of numerous grains separated by grain boundaries, which are detrimental to graphene-based electronics. Intensive investigations have been inspired on the controlled growth of graphene single crystals with the absence of intrinsic defects. As the two most concerned parameters, the size and morphology serve critical roles in affecting properties and understanding the growth mechanism of graphene crystals. Therefore, a precise tuning of the size and morphology will be of great significance in scale-up graphene production and wide applications. Here, recent advances in the synthesis of graphene single crystals on both metals and dielectric substrates by the CVD method are discussed. The review mainly covers the size and morphology engineering of graphene single crystals. Furthermore, recent progress in the growth mechanism and device applications of graphene single crystals are presented. Finally, the opportunities and challenges are discussed. PMID:25809643

  15. 48 CFR 52.247-61 - F.o.b. Origin-Minimum Size of Shipments.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 48 Federal Acquisition Regulations System 2 2013-10-01 2013-10-01 false F.o.b. Origin-Minimum Size... Clauses 52.247-61 F.o.b. Origin—Minimum Size of Shipments. As prescribed in 47.305-16(c), insert the following clause in solicitations and contracts when volume rates may apply: F.o.b. Origin—Minimum Size...

  16. AN EXPERIMENTAL ASSESSMENT OF MINIMUM MAPPING UNIT SIZE

    EPA Science Inventory

    Land-cover (LC) maps derived from remotely sensed data are often presented using a minimum mapping unit (MMU). The choice of a MMU that is appropriate for the projected use of a classification is important. The objective of this experiment was to determine the optimal MMU of a L...

  17. Gauging the Nearness and Size of Cycle Minimum

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.; Hathaway, David H.; Reichmann, Edwin J.

    1997-01-01

    By definition, the conventional onset for the start of a sunspot cycle is the time when smoothed sunspot number (i.e., the 12-month moving average) has decreased to its minimum value (called minimum amplitude) prior to the rise to its maximum value (called maximum amplitude) for the given sunspot cycle. On the basis (if the modern era sunspot cycles 10-22 and on the presumption that cycle 22 is a short-period cycle having a cycle length of 120 to 126 months (the observed range of short-period modern era cycles), conventional onset for cycle 23 should not occur until sometime between September 1996 and March 1997, certainly between June 1996 and June 1997, based on the 95-percent confidence level deduced from the mean and standard deviation of period for the sample of six short-pei-iod modern era cycles. Also, because the first occurrence of a new cycle, high-latitude (greater than or equal to 25 degrees) spot has always preceded conventional onset of the new cycle by at least 3 months (for the data-available interval of cycles 12-22), conventional onset for cycle 23 is not expected until about August 1996 or later, based on the first occurrence of a new cycle 23, high-latitude spot during the decline of old cycle 22 in May 1996. Although much excitement for an earlier-occurring minimum (about March 1996) for cycle 23 was voiced earlier this year, the present study shows that this exuberance is unfounded. The decline of cycle 22 continues to favor cycle 23 minimum sometime during the latter portion of 1996 to the early portion of 1997.

  18. 50 CFR 648.147 - Black sea bass minimum fish sizes.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 50 Wildlife and Fisheries 12 2012-10-01 2012-10-01 false Black sea bass minimum fish sizes. 648... Measures for the Black Sea Bass Fishery § 648.147 Black sea bass minimum fish sizes. (a) Moratorium... all vessels issued a moratorium permit under § 648.4(a)(7) that fish for, possess, land or...

  19. 50 CFR 648.147 - Black sea bass minimum fish sizes.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 50 Wildlife and Fisheries 12 2013-10-01 2013-10-01 false Black sea bass minimum fish sizes. 648... Measures for the Black Sea Bass Fishery § 648.147 Black sea bass minimum fish sizes. (a) Moratorium... all vessels issued a moratorium permit under § 648.4(a)(7) that fish for, possess, land or...

  20. 50 CFR 648.147 - Black sea bass minimum fish sizes.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 50 Wildlife and Fisheries 12 2014-10-01 2014-10-01 false Black sea bass minimum fish sizes. 648... Measures for the Black Sea Bass Fishery § 648.147 Black sea bass minimum fish sizes. (a) Moratorium... all vessels issued a moratorium permit under § 648.4(a)(7) that fish for, possess, land or...

  1. Transverse micro-erosion meter measurements; determining minimum sample size

    NASA Astrophysics Data System (ADS)

    Trenhaile, Alan S.; Lakhan, V. Chris

    2011-11-01

    Two transverse micro-erosion meter (TMEM) stations were installed in each of four rock slabs, a slate/shale, basalt, phyllite/schist, and sandstone. One station was sprayed each day with fresh water and the other with a synthetic sea water solution (salt water). To record changes in surface elevation (usually downwearing but with some swelling), 100 measurements (the pilot survey), the maximum for the TMEM used in this study, were made at each station in February 2010, and then at two-monthly intervals until February 2011. The data were normalized using Box-Cox transformations and analyzed to determine the minimum number of measurements needed to obtain station means that fall within a range of confidence limits of the population means, and the means of the pilot survey. The effect on the confidence limits of reducing an already small number of measurements (say 15 or less) is much greater than that of reducing a much larger number of measurements (say more than 50) by the same amount. There was a tendency for the number of measurements, for the same confidence limits, to increase with the rate of downwearing, although it was also dependent on whether the surface was treated with fresh or salt water. About 10 measurements often provided fairly reasonable estimates of rates of surface change but with fairly high percentage confidence intervals in slowly eroding rocks; however, many more measurements were generally needed to derive means within 10% of the population means. The results were tabulated and graphed to provide an indication of the approximate number of measurements required for given confidence limits, and the confidence limits that might be attained for a given number of measurements.

  2. Minimum Sample Size for Cronbach's Coefficient Alpha: A Monte-Carlo Study

    ERIC Educational Resources Information Center

    Yurdugul, Halil

    2008-01-01

    The coefficient alpha is the most widely used measure of internal consistency for composite scores in the educational and psychological studies. However, due to the difficulties of data gathering in psychometric studies, the minimum sample size for the sample coefficient alpha has been frequently debated. There are various suggested minimum sample…

  3. 48 CFR 52.247-61 - F.o.b. Origin-Minimum Size of Shipments.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... minimum weight, the Contractor agrees to ship such scheduled quantity in one shipment. The Contractor... of Shipments. 52.247-61 Section 52.247-61 Federal Acquisition Regulations System FEDERAL ACQUISITION... Clauses 52.247-61 F.o.b. Origin—Minimum Size of Shipments. As prescribed in 47.305-16(c), insert...

  4. Nanoscale size effects in crystallization of metallic glass nanorods.

    PubMed

    Sohn, Sungwoo; Jung, Yeonwoong; Xie, Yujun; Osuji, Chinedum; Schroers, Jan; Cha, Judy J

    2015-01-01

    Atomistic understanding of crystallization in solids is incomplete due to the lack of appropriate materials and direct experimental tools. Metallic glasses possess simple metallic bonds and slow crystallization kinetics, making them suitable to study crystallization. Here, we investigate crystallization of metallic glass-forming liquids by in-situ heating metallic glass nanorods inside a transmission electron microscope. We unveil that the crystallization kinetics is affected by the nanorod diameter. With decreasing diameters, crystallization temperature decreases initially, exhibiting a minimum at a certain diameter, and then rapidly increases below that. This unusual crystallization kinetics is a consequence of multiple competing factors: increase in apparent viscosity, reduced nucleation probability and enhanced heterogeneous nucleation. The first two are verified by slowed grain growth and scatter in crystallization temperature with decreasing diameters. Our findings provide insight into relevant length scales in crystallization of supercooled metallic glasses, thus offering accurate processing conditions for predictable metallic glass nanomolding. PMID:26323828

  5. Nanoscale size effects in crystallization of metallic glass nanorods

    PubMed Central

    Sohn, Sungwoo; Jung, Yeonwoong; Xie, Yujun; Osuji, Chinedum; Schroers, Jan; Cha, Judy J.

    2015-01-01

    Atomistic understanding of crystallization in solids is incomplete due to the lack of appropriate materials and direct experimental tools. Metallic glasses possess simple metallic bonds and slow crystallization kinetics, making them suitable to study crystallization. Here, we investigate crystallization of metallic glass-forming liquids by in-situ heating metallic glass nanorods inside a transmission electron microscope. We unveil that the crystallization kinetics is affected by the nanorod diameter. With decreasing diameters, crystallization temperature decreases initially, exhibiting a minimum at a certain diameter, and then rapidly increases below that. This unusual crystallization kinetics is a consequence of multiple competing factors: increase in apparent viscosity, reduced nucleation probability and enhanced heterogeneous nucleation. The first two are verified by slowed grain growth and scatter in crystallization temperature with decreasing diameters. Our findings provide insight into relevant length scales in crystallization of supercooled metallic glasses, thus offering accurate processing conditions for predictable metallic glass nanomolding. PMID:26323828

  6. Determining size and dispersion of minimum viable populations for land management planning and species conservation

    NASA Astrophysics Data System (ADS)

    Lehmkuhl, John F.

    1984-03-01

    The concept of minimum populations of wildlife and plants has only recently been discussed in the literature. Population genetics has emerged as a basic underlying criterion for determining minimum population size. This paper presents a genetic framework and procedure for determining minimum viable population size and dispersion strategies in the context of multiple-use land management planning. A procedure is presented for determining minimum population size based on maintenance of genetic heterozygosity and reduction of inbreeding. A minimum effective population size ( N e ) of 50 breeding animals is taken from the literature as the minimum shortterm size to keep inbreeding below 1% per generation. Steps in the procedure adjust N e to account for variance in progeny number, unequal sex ratios, overlapping generations, population fluctuations, and period of habitat/population constraint. The result is an approximate census number that falls within a range of effective population size of 50 500 individuals. This population range defines the time range of short- to long-term population fitness and evolutionary potential. The length of the term is a relative function of the species generation time. Two population dispersion strategies are proposed: core population and dispersed population.

  7. Fundamental limitations of LIGA x-ray lithography : sidewall offset, slope and minimum feature size.

    SciTech Connect

    Griffiths, Stewart K.

    2004-01-01

    Analytical and numerical methods are used to examine photoelectron doses and their effect on the dimensions of features produced by deep x-ray lithography. New analytical models describing electron doses are presented and used to compute dose distributions for several feature geometries. The history of development and final feature dimensions are also computed, taking into account the dose field, dissolution kinetics based on measured development rates, and the transport of PMMA fragments away from the dissolution front. We find that sidewall offsets, sidewall slope and producible feature sizes all exhibit at least practical minima and that these minima represent fundamental limitations of the LIGA process. The minimum values under optimum conditions are insensitive to the synchrotron spectrum, but depend strongly on resist thickness. This dependence on thickness is well approximated by simple analytical expressions describing the minimum offset, minimum sidewall slope, minimum producible size of positive and negative features, maximum aspect ratio and minimum radius of inside and outside corners.

  8. 50 CFR 622.208 - Minimum mesh size applicable to rock shrimp off Georgia and Florida.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... shrimp off Georgia and Florida. 622.208 Section 622.208 Wildlife and Fisheries FISHERY CONSERVATION AND... mesh size applicable to rock shrimp off Georgia and Florida. (a) The minimum mesh size for the cod end of a rock shrimp trawl net in the South Atlantic EEZ off Georgia and Florida is 17/8 inches (4.8...

  9. Maximizing Macromolecule Crystal Size for Neutron Diffraction Experiments

    NASA Technical Reports Server (NTRS)

    Judge, R. A.; Kephart, R.; Leardi, R.; Myles, D. A.; Snell, E. H.; vanderWoerd, M.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    A challenge in neutron diffraction experiments is growing large (greater than 1 cu mm) macromolecule crystals. In taking up this challenge we have used statistical experiment design techniques to quickly identify crystallization conditions under which the largest crystals grow. These techniques provide the maximum information for minimal experimental effort, allowing optimal screening of crystallization variables in a simple experimental matrix, using the minimum amount of sample. Analysis of the results quickly tells the investigator what conditions are the most important for the crystallization. These can then be used to maximize the crystallization results in terms of reducing crystal numbers and providing large crystals of suitable habit. We have used these techniques to grow large crystals of Glucose isomerase. Glucose isomerase is an industrial enzyme used extensively in the food industry for the conversion of glucose to fructose. The aim of this study is the elucidation of the enzymatic mechanism at the molecular level. The accurate determination of hydrogen positions, which is critical for this, is a requirement that neutron diffraction is uniquely suited for. Preliminary neutron diffraction experiments with these crystals conducted at the Institute Laue-Langevin (Grenoble, France) reveal diffraction to beyond 2.5 angstrom. Macromolecular crystal growth is a process involving many parameters, and statistical experimental design is naturally suited to this field. These techniques are sample independent and provide an experimental strategy to maximize crystal volume and habit for neutron diffraction studies.

  10. Crystal growth of large size Dy3Al5O12 garnet single crystals

    NASA Astrophysics Data System (ADS)

    Kimura, Hideo; Sakamoto, Masaru; Numazawa, Takenori; Sato, Mitsunori; Maeda, Hiroshi

    1990-01-01

    Crystal growth conditions using the Czochralski technique were examined in order to be able to grow large-size disprosium-aluminum-garnet single crystals; these are useful as a working material in a practical magnetic refrigeration system. Using the best conditions, large-size bubble-free Dy3Al5O12 single crystals 50 mm in diameter were grown from a stoichiometric melt composition using a seed of Y3Al5O12 single crystal.

  11. 48 CFR 52.247-61 - F.o.b. Origin-Minimum Size of Shipments.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 48 Federal Acquisition Regulations System 2 2012-10-01 2012-10-01 false F.o.b. Origin-Minimum Size of Shipments. 52.247-61 Section 52.247-61 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION (CONTINUED) CLAUSES AND FORMS SOLICITATION PROVISIONS AND CONTRACT CLAUSES Text of Provisions and Clauses 52.247-61 F.o.b....

  12. Size dependent compressibility of nano-ceria: Minimum near 33 nm

    NASA Astrophysics Data System (ADS)

    Rodenbough, Philip P.; Song, Junhua; Walker, David; Clark, Simon M.; Kalkan, Bora; Chan, Siu-Wai

    2015-04-01

    We report the crystallite-size-dependency of the compressibility of nanoceria under hydrostatic pressure for a wide variety of crystallite diameters and comment on the size-based trends indicating an extremum near 33 nm. Uniform nano-crystals of ceria were synthesized by basic precipitation from cerium (III) nitrate. Size-control was achieved by adjusting mixing time and, for larger particles, a subsequent annealing temperature. The nano-crystals were characterized by transmission electron microscopy and standard ambient x-ray diffraction (XRD). Compressibility, or its reciprocal, bulk modulus, was measured with high-pressure XRD at LBL-ALS, using helium, neon, or argon as the pressure-transmitting medium for all samples. As crystallite size decreased below 100 nm, the bulk modulus first increased, and then decreased, achieving a maximum near a crystallite diameter of 33 nm. We review earlier work and examine several possible explanations for the peaking of bulk modulus at an intermediate crystallite size.

  13. Effect of Minimum Cell Sizes and Confidence Interval Sizes for Special Education Subgroups on School-Level AYP Determinations. Synthesis Report 61

    ERIC Educational Resources Information Center

    Simpson, Mary Ann; Gong, Brian; Marion, Scott

    2006-01-01

    This study addresses three questions: First, considering the full group of students and the special education subgroup, what is the likely effect of minimum cell size and confidence interval size on school-level Adequate Yearly Progress (AYP) determinations? Second, what effects do the changing minimum cell sizes have on inclusion of special…

  14. On-line monitoring of the crystallization process: relationship between crystal size and electrical impedance spectra

    NASA Astrophysics Data System (ADS)

    Zhao, Yanlin; Yao, Jun; Wang, Mi

    2016-07-01

    On-line monitoring of crystal size in the crystallization process is crucial to many pharmaceutical and fine-chemical industrial applications. In this paper, a novel method is proposed for the on-line monitoring of the cooling crystallization process of L-glutamic acid (LGA) using electrical impedance spectroscopy (EIS). The EIS method can be used to monitor the growth of crystal particles relying on the presence of an electrical double layer on the charged particle surface and the polarization of double layer under the excitation of alternating electrical field. The electrical impedance spectra and crystal size were measured on-line simultaneously by an impedance analyzer and focused beam reflectance measurement (FBRM), respectively. The impedance spectra were analyzed using the equivalent circuit model and the equivalent circuit elements in the model can be obtained by fitting the experimental data. Two equivalent circuit elements, including capacitance (C 2) and resistance (R 2) from the dielectric polarization of the LGA solution and crystal particle/solution interface, are in relation with the crystal size. The mathematical relationship between the crystal size and the equivalent circuit elements can be obtained by a non-linear fitting method. The function can be used to predict the change of crystal size during the crystallization process.

  15. Minimum bar size for flexure testing of irradiated SiC/SiC composite

    SciTech Connect

    Youngblood, G.E.; Jones, R.H.

    1998-03-01

    This report covers material presented at the IEA/Jupiter Joint International Workshop on SiC/SiC Composites for Fusion structural Applications held in conjunction with ICFRM-8, Sendai, Japan, Oct. 23-24, 1997. The minimum bar size for 4-point flexure testing of SiC/SiC composite recommended by PNNL for irradiation effects studies is 30 {times} 6 {times} 2 mm{sup 3} with a span-to-depth ratio of 10/1.

  16. Skaergaard vs Sudbury: Solidification Times and Crystal Sizes

    NASA Astrophysics Data System (ADS)

    Marsh, B. D.; Mittal, T.; Currier, R. M.; Jordon, E.

    2010-12-01

    The overall cooling time of a batch of magma is intimately reflected in the nature of the crystal sizes. The thinner are dikes and sills the finer grained are the crystals they display. And the spatial variations in crystal size and abundance record the spatial progression of solidification. Chilled margins are fine grained because of rapid solidification, and a progressive inward increase in crystal size is perfectly predictable by coupling a law of crystal growth with a suitable solidification front-based cooling model. When observed crystal sizes are much larger than predicted, as in finding phenocrysts near or in chilled margins, this is a clear indication of crystals grown and entrained prior to final emplacement and solidification. This is exactly the process exhibited by volcanics carrying swarms of large crystals. But in plutonic rocks there is frequent confusion over what crystal sizes to expect, especially when the pluton size and shape is poorly known, and there is often an unexpressed feeling that fine grained (i.e., non-phenocryst bearing) bodies almost regardless of size somehow cool fundamentally different than large bodies, especially layered intrusions. An invaluable standard state body to which to compare the crystal sizes of other large bodies is the Sudbury impact melt sheet. Formed in a few minutes, the 3km thick 200 km wide superheated melt sheet cooled and crystallized to produce a systematic and predictable internal variation in crystal size and abundance (Zieg & Marsh, 2002, JPet). Buried by 3km of fallback debris, the sheet took about 100,000 to solidify. The Skaergaard intrusion is of a similar thickness (3.4-4 km), but is much less extensive, being more like a thin-edged elliptical laccolith (Norton et. al., 1984, JGR) or a fault-bounded loaf of bread (7.75 x 10.55 x 3.7 km; Nielsen, 2004, JPet). In spite of its limited extent, the extent is large enough for solidification of the thickest parts time to approach that of an infinite sheet

  17. Large-size germanium crystal growth for rare event physics

    NASA Astrophysics Data System (ADS)

    Mei, Dongming; Wang, Guojian; Mei, Hao; Guan, Yutong; Yang, Gang; Govani, Jayesh; Cubed Collaboration

    2014-09-01

    Cosmogenic production in germanium crystals grown on the surface can limit the sensitivity for the next generation deep underground experiments in searching for rare event physics beyond the Standard Model. One of the best solutions to eliminate unwanted cosmogenics is to produce the germanium crystals and detectors in an underground environment. The goal of this project is to create state-of-the-art detectors to advance neutrinoless double-beta decay and dark matter exploration research and technology while simultaneously paving the way for infrastructure to support an underground laboratory for zone refining, crystal growth, and detector fabrication. The greatest challenge in the growth of germanium crystals is a lack of precise control of individual crystal properties such as the impurity distribution, the dislocation density, and the crystalline structure. With knowledge gained from the pioneers in the field of crystal growth, the researchers have developed a novel technique to grow detector-grade crystals. In this paper, we will report detector-grade large-size germanium crystal growth at the University of South Dakota. Cosmogenic production in germanium crystals grown on the surface can limit the sensitivity for the next generation deep underground experiments in searching for rare event physics beyond the Standard Model. One of the best solutions to eliminate unwanted cosmogenics is to produce the germanium crystals and detectors in an underground environment. The goal of this project is to create state-of-the-art detectors to advance neutrinoless double-beta decay and dark matter exploration research and technology while simultaneously paving the way for infrastructure to support an underground laboratory for zone refining, crystal growth, and detector fabrication. The greatest challenge in the growth of germanium crystals is a lack of precise control of individual crystal properties such as the impurity distribution, the dislocation density, and the

  18. Does Nanoparticle Activity Depend upon Size and Crystal Phase?

    PubMed Central

    Jiang, Jingkun; Oberdörster, Günter; Elder, Alison; Gelein, Robert; Mercer, Pamela; Biswas, Pratim

    2010-01-01

    A method to investigate the dependence of the physicochemical properties of nanoparticles (e.g. size, surface area and crystal phase) on their oxidant generating capacity is proposed and demonstrated for TiO2 nanoparticles. Gas phase synthesis methods that allow for strict control of size and crystal phase were used to prepare TiO2 nanoparticles. The reactive oxygen species (ROS) generating capacity of these particles was then measured. The size dependent ROS activity was established using TiO2 nanoparticles of 9 different sizes (4 – 195 nm) but the same crystal phase. For a fixed total surface area, an S-shaped curve for ROS generation per unit surface area was observed as a function of particle size. The highest ROS activity per unit area was observed for 30 nm particles, and observed to be constant above 30 nm. There was a decrease in activity per unit area as size decreased from 30 nm to 10 nm; and again constant for particles smaller than 10 nm. The correlation between crystal phase and oxidant capacity was established using TiO2 nanoparticles of 11 different crystal phase combinations but similar size. The ability of different crystal phases of TiO2 nanoparticles to generate ROS was highest for amorphous, followed by anatase, and then anatase/rutile mixtures, and lowest for rutile samples. Based on evaluation of the entire dataset, important dose metrics for ROS generation are established. Their implications of these ROS studies on biological and toxicological studies using nanomaterials are discussed. PMID:20827377

  19. Fictive temperature-independent density and minimum indentation size effect in calcium aluminosilicate glass

    SciTech Connect

    Gross, T. M.; Tomozawa, M.

    2008-09-15

    Using the calcium aluminosilicate system a glass was developed that exhibits fictive temperature-independent density by creating an intermediate glass between normal and anomalous glasses. Normal glass, such as soda-lime silicate glass, exhibits decreasing density with increasing fictive temperature while anomalous glass, such as silica glass, exhibits increasing density with increasing fictive temperature. This intermediate glass composition was found to exhibit the minimum indentation size effect during indentation hardness testing. It appears that the indentation size effect is correlated with a deformation-induced fictive temperature increase, which is accompanied by a density change and hardness change in the vicinity of the indentation. It is suggested from these observations that indentation size effect originates from the energy required to create interfaces and defects such as shear bands, subsurface cracks, and point defects near the indenter-specimen boundary, which accompany the volume change.

  20. Size dependent compressibility of nano-ceria: Minimum near 33 nm

    SciTech Connect

    Rodenbough, Philip P.; Song, Junhua; Chan, Siu-Wai; Walker, David; Clark, Simon M.; Kalkan, Bora

    2015-04-20

    We report the crystallite-size-dependency of the compressibility of nanoceria under hydrostatic pressure for a wide variety of crystallite diameters and comment on the size-based trends indicating an extremum near 33 nm. Uniform nano-crystals of ceria were synthesized by basic precipitation from cerium (III) nitrate. Size-control was achieved by adjusting mixing time and, for larger particles, a subsequent annealing temperature. The nano-crystals were characterized by transmission electron microscopy and standard ambient x-ray diffraction (XRD). Compressibility, or its reciprocal, bulk modulus, was measured with high-pressure XRD at LBL-ALS, using helium, neon, or argon as the pressure-transmitting medium for all samples. As crystallite size decreased below 100 nm, the bulk modulus first increased, and then decreased, achieving a maximum near a crystallite diameter of 33 nm. We review earlier work and examine several possible explanations for the peaking of bulk modulus at an intermediate crystallite size.

  1. 'Crystal Collimator' Measurement of CESR particle-beam Source Size

    SciTech Connect

    Finkelstein, K.D.; Bazarov, Ivan; White, Jeffrey; Revesz, Peter

    2004-05-12

    We have measured electron and positron beam source size at CHESS when the Cornell Electron Storage Ring (CESR) is run dedicated for the production of synchrotron radiation. Horizontal source size at several beamlines is expected to shrink by a factor of two but synchrotron (visible) light measurements only provide the vertical size. Therefore a 'crystal collimator' using two Bragg reflection in dispersive (+,+) orientation has been built to image the horizontal (vertical) source by passing x-rays parallel to within 5 microradians to an imaging screen and camera. With the 'crystal collimator' we observe rms sizes of 1.2 mm horizontal by 0.28 mm vertical, in good agreement with the 1.27 mm size calculated from lattice functions, and 0.26 mm observed using a synchrotron light interferometer.

  2. Novel all-optical planar and compact minimum-stage switches of size >= 4x4

    NASA Astrophysics Data System (ADS)

    Giglmayr, Josef

    1997-01-01

    Throughout the paper, novel all-optical planar 1-stage k multiplied by k-switches and compact minimum-stage k multiplied by k-switches in double-layer and multi-layer technique, are presented and analyzed. In the first case, the number of k(k - 1)/2 switches of size 2 multiplied by 2 (equivalent minimum of the Spanke-Benes network) are arranged in parallel instead of the number of k (equivalent maximum) cascaded 2 multiplied by 2-switches of the Spanke- Benes network. In the second case, the number of 2 multiplied by 2-switches depends on the geometry of the 'pipes' of the switches formed by the layers and waveguides [for a square it is 3k/2(k/2 - 1) for rearrangeable nonblocking and 3(k - 1)k/2(k/2 - 1) for circuit switching networks]. The number of stages (NS) (horizontal cascaded) of the proposed compact switches for the nonblocking interconnection is NS equals n - 1 if the waveguides form an n-gon (n greater than or equal to 3) for any size of the k multiplied by k-switch. In this way, the attenuation of optical signals passing through a photonic network may be minimized. In particular, for any size of a k multiplied by k-switch, dependent on the n-gon, the minimum NS is n-1 equals 2 (triangle) or n - 1 equals 3 (square) etc. Thus the proposed switch concept is of complexity O(1), i.e. the NS is independent of the number of inputs/outputs. Additionally, the proposed switches are capable to operate in the circuit switching mode if and only if (iff) the parallelism increases by the factor k-1.

  3. Model based matching using simulated annealing and a minimum representation size criterion

    NASA Technical Reports Server (NTRS)

    Ravichandran, B.; Sanderson, A. C.

    1992-01-01

    We define the model based matching problem in terms of the correspondence and transformation that relate the model and scene, and the search and evaluation measures needed to find the best correspondence and transformation. Simulated annealing is proposed as a method for search and optimization, and the minimum representation size criterion is used as the evaluation measure in an algorithm that finds the best correspondence. An algorithm based on simulated annealing is presented and evaluated. This algorithm is viewed as a part of an adaptive, hierarchical approach which provides robust results for a variety of model based matching problems.

  4. [Theory and practice of electrospray crystallization in particle size reduction].

    PubMed

    Szunyogh, Tímea; Ambrus, Rita; Szabóné Révész, Piroska

    2015-01-01

    Nowdays, one of the most challenges for the researchers is the formulation of poorly water soluble drugs. Reduction of particle size of active agents to submicron range could result in a faster dissolution rate and higher bioavailability. Integration as crystallization process is an often used particle size decreasing technique. The aim of this study was to show the theoretical background and practical application of the electros pray crystallization as an innovative particle size decreasing technique. Our model drug was the niflumic acid (NIF), which belongs to the BCS Class II. After the optimization of the process parameters, the physico-chemical properties of the samples were characterized. Particle size and shape were visualized by scanning electron microscopy (SEM). Crystalline state of NIF and the samples were investigated using differential scanning calorimetry (DSC) and X-ray powder diffraction. Physico-chemical properties were determined using dissolution test from simulated media. The electrospray crytallization resulted in particle size reduction but the aggregation of nanonized NIF crystals (NIF-nano) could not avoid without excipient. Aggregates with poor secondary forces are suitable for production of the interactive physical mixture. It was found that NIF-nano could be well distributed on the surface of the mannitol as carrier and the Poloxamer R protected the NIF-nano crystals (320 nm)from aggregation. Consequently, the physical mixture resulted in product with higher polarity, better wettability and faster dissolution rate of NIF as raw NIF or NIF-nano. PMID:26390735

  5. Minimum-sized ideal reactor for continuous alcohol fermentation using immobilized microorganism

    SciTech Connect

    Yamane, T.; Shimizu, S.

    1982-12-01

    Recently, alcohol fermentation has gained considerable attention with the aim of lowering its production cost in the production processes of both fuel ethanol and alcoholic beverages. The over-all cost is a summation of costs of various subsystems such as raw material (sugar, starch, and cellulosic substances) treatment, fermentation process, and alcohol separation from water solutions; lowering the cost of the fermentation processes is very important in lowering the total cost. Several new techniques have been developed for economic continuous ethanol production, use of a continuous wine fermentor with no mechanical stirring, cell recycle combined with continuous removal of ethanol under vaccum, a technique involving a bed of yeast admixed with an inert carrier, and use of immobilized yeast reactors in packed-bed column and in a three-stage double conical fluidized-bed bioreactor. All these techniques lead to increases more or less, in reactor productivity, which in turn result in the reduction of the reactor size for a given production rate and a particular conversion. Since an improvement in the fermentation process often leads to a reduction of fermentor size and hence, a lowering of the initial construction cost, it is important to theoretically arrive at a solution to what is the minimum-size setup of ideal reactors from the viewpoint of liquid backmixing. In this short communication, the minimum-sized ideal reactor for continuous alcohol fermentation using immobilized cells will be specifically discussed on the basis of a mathematical model. The solution will serve for designing an optimal bioreactor. (Refs. 26).

  6. Metagenomic analysis of size-fractionated picoplankton in a marine oxygen minimum zone.

    PubMed

    Ganesh, Sangita; Parris, Darren J; DeLong, Edward F; Stewart, Frank J

    2014-01-01

    Marine oxygen minimum zones (OMZs) support diverse microbial communities with roles in major elemental cycles. It is unclear how the taxonomic composition and metabolism of OMZ microorganisms vary between particle-associated and free-living size fractions. We used amplicon (16S rRNA gene) and shotgun metagenome sequencing to compare microbial communities from large (>1.6 μm) and small (0.2-1.6 μm) filter size fractions along a depth gradient in the OMZ off Chile. Despite steep vertical redox gradients, size fraction was a significantly stronger predictor of community composition compared to depth. Phylogenetic diversity showed contrasting patterns, decreasing towards the anoxic OMZ core in the small size fraction, but exhibiting maximal values at these depths within the larger size fraction. Fraction-specific distributions were evident for key OMZ taxa, including anammox planctomycetes, whose coding sequences were enriched up to threefold in the 0.2-1.6 μm community. Functional gene composition also differed between fractions, with the >1.6 μm community significantly enriched in genes mediating social interactions, including motility, adhesion, cell-to-cell transfer, antibiotic resistance and mobile element activity. Prokaryotic transposase genes were three to six fold more abundant in this fraction, comprising up to 2% of protein-coding sequences, suggesting that particle surfaces may act as hotbeds for transposition-based genome changes in marine microbes. Genes for nitric and nitrous oxide reduction were also more abundant (three to seven fold) in the larger size fraction, suggesting microniche partitioning of key denitrification steps. These results highlight an important role for surface attachment in shaping community metabolic potential and genome content in OMZ microorganisms. PMID:24030599

  7. Metagenomic analysis of size-fractionated picoplankton in a marine oxygen minimum zone

    PubMed Central

    Ganesh, Sangita; Parris, Darren J; DeLong, Edward F; Stewart, Frank J

    2014-01-01

    Marine oxygen minimum zones (OMZs) support diverse microbial communities with roles in major elemental cycles. It is unclear how the taxonomic composition and metabolism of OMZ microorganisms vary between particle-associated and free-living size fractions. We used amplicon (16S rRNA gene) and shotgun metagenome sequencing to compare microbial communities from large (>1.6 μm) and small (0.2–1.6 μm) filter size fractions along a depth gradient in the OMZ off Chile. Despite steep vertical redox gradients, size fraction was a significantly stronger predictor of community composition compared to depth. Phylogenetic diversity showed contrasting patterns, decreasing towards the anoxic OMZ core in the small size fraction, but exhibiting maximal values at these depths within the larger size fraction. Fraction-specific distributions were evident for key OMZ taxa, including anammox planctomycetes, whose coding sequences were enriched up to threefold in the 0.2–1.6 μm community. Functional gene composition also differed between fractions, with the >1.6 μm community significantly enriched in genes mediating social interactions, including motility, adhesion, cell-to-cell transfer, antibiotic resistance and mobile element activity. Prokaryotic transposase genes were three to six fold more abundant in this fraction, comprising up to 2% of protein-coding sequences, suggesting that particle surfaces may act as hotbeds for transposition-based genome changes in marine microbes. Genes for nitric and nitrous oxide reduction were also more abundant (three to seven fold) in the larger size fraction, suggesting microniche partitioning of key denitrification steps. These results highlight an important role for surface attachment in shaping community metabolic potential and genome content in OMZ microorganisms. PMID:24030599

  8. SSZ-13 Crystallization by Particle Attachment and Deterministic Pathways to Crystal Size Control.

    PubMed

    Kumar, Manjesh; Luo, Helen; Román-Leshkov, Yuriy; Rimer, Jeffrey D

    2015-10-14

    Many synthetic and natural crystalline materials are either known or postulated to grow via nonclassical pathways involving the initial self-assembly of precursors that serve as putative growth units for crystallization. Elucidating the pathway(s) by which precursors attach to crystal surfaces and structurally rearrange (postattachment) to incorporate into the underlying crystalline lattice is an active and expanding area of research comprising many unanswered fundamental questions. Here, we examine the crystallization of SSZ-13, which is an aluminosilicate zeolite that possesses exceptional physicochemical properties for applications in separations and catalysis (e.g., methanol upgrading to chemicals and the environmental remediation of NO(x)). We show that SSZ-13 grows by two concerted mechanisms: nonclassical growth involving the attachment of amorphous aluminosilicate particles to crystal surfaces and classical layer-by-layer growth via the incorporation of molecules to advancing steps on the crystal surface. A facile, commercially viable method of tailoring SSZ-13 crystal size and morphology is introduced wherein growth modifiers are used to mediate precursor aggregation and attachment to crystal surfaces. We demonstrate that small quantities of polymers can be used to tune crystal size over 3 orders of magnitude (0.1-20 μm), alter crystal shape, and introduce mesoporosity. Given the ubiquitous presence of amorphous precursors in a wide variety of microporous crystals, insight of the SSZ-13 growth mechanism may prove to be broadly applicable to other materials. Moreover, the ability to selectively tailor the physical properties of SSZ-13 crystals through molecular design offers new routes to optimize their performance in a wide range of commercial applications. PMID:26376337

  9. Passive Rocket Diffuser Theory: A Re-Examination of Minimum Second Throat Size

    NASA Technical Reports Server (NTRS)

    Jones, Daniel R.

    2016-01-01

    Second-throat diffusers serve to isolate rocket engines from the effects of ambient back pressure during testing without using active control systems. Among the most critical design parameters is the relative area of the diffuser throat to that of the nozzle throat. A smaller second throat is generally desirable because it decreases the stagnation-to-ambient pressure ratio the diffuser requires for nominal operation. There is a limit, however. Below a certain size, the second throat can cause pressure buildup within the diffuser and prevent it from reaching the start condition that protects the nozzle from side-load damage. This paper presents a method for improved estimation of the minimum second throat area which enables diffuser start. The new 3-zone model uses traditional quasi-one-dimensional compressible flow theory to approximate the structure of two distinct diffuser flow fields observed in Computational Fluid Dynamics (CFD) simulations and combines them to provide a less-conservative estimate of the second throat size limit. It is unique among second throat sizing methods in that it accounts for all major conical nozzle and second throat diffuser design parameters within its limits of application. The performance of the 3-zone method is compared to the historical normal shock and force balance methods, and verified against a large number of CFD simulations at specific heat ratios of 1.4 and 1.25. Validation is left as future work, and the model is currently intended to function only as a first-order design tool.

  10. Estimates of minimum patch size depend on the method of estimation and the condition of the habitat.

    PubMed

    McCoy, Earl D; Mushinsky, Henry R

    2007-06-01

    Minimum patch size for a viable population can be estimated in several ways. The density-area method estimates minimum patch size as the smallest area in which no new individuals are encountered as one extends the arbitrary boundaries of a study area outward. The density-area method eliminates the assumption of no variation in density with size of habitat area that accompanies other methods, but it is untested in situations in which habitat loss has confined populations to small areas. We used a variant of the density area method to study the minimum patch size for the gopher tortoise (Gopherus polyphemus) in Florida, USA, where this keystone species is being confined to ever smaller habitat fragments. The variant was based on the premise that individuals within populations are likely to occur at unusually high densities when confined to small areas, and it estimated minimum patch size as the smallest area beyond which density plateaus. The data for our study came from detailed surveys of 38 populations of the tortoise. For all 38 populations, the areas occupied were determined empirically, and for 19 of them, duplicate surveys were undertaken about a decade apart. We found that a consistent inverse density area relationship was present over smaller areas. The minimum patch size estimated from the density-area relationship was at least 100 ha, which is substantially larger than previous estimates. The relative abundance of juveniles was inversely related to population density for sites with relatively poor habitat quality, indicating that the estimated minimum patch size could represent an extinction threshold. We concluded that a negative density area relationship may be an inevitable consequence of excessive habitat loss. We also concluded that any detrimental effects of an inverse density area relationship may be exacerbated by the deterioration in habitat quality that often accompanies habitat loss. Finally, we concluded that the value of any estimate of

  11. Discrete plasticity in sub-10-nm-sized gold crystals.

    PubMed

    Zheng, He; Cao, Ajing; Weinberger, Christopher R; Huang, Jian Yu; Du, Kui; Wang, Jianbo; Ma, Yanyun; Xia, Younan; Mao, Scott X

    2010-01-01

    Although deformation processes in submicron-sized metallic crystals are well documented, the direct observation of deformation mechanisms in crystals with dimensions below the sub-10-nm range is currently lacking. Here, through in situ high-resolution transmission electron microscopy (HRTEM) observations, we show that (1) in sharp contrast to what happens in bulk materials, in which plasticity is mediated by dislocation emission from Frank-Read sources and multiplication, partial dislocations emitted from free surfaces dominate the deformation of gold (Au) nanocrystals; (2) the crystallographic orientation (Schmid factor) is not the only factor in determining the deformation mechanism of nanometre-sized Au; and (3) the Au nanocrystal exhibits a phase transformation from a face-centered cubic to a body-centered tetragonal structure after failure. These findings provide direct experimental evidence for the vast amount of theoretical modelling on the deformation mechanisms of nanomaterials that have appeared in recent years. PMID:21266994

  12. Discrete plasticity in sub-10-nm-sized gold crystals

    PubMed Central

    Zheng, He; Cao, Ajing; Weinberger, Christopher R.; Huang, Jian Yu; Du, Kui; Wang, Jianbo; Ma, Yanyun; Xia, Younan; Mao, Scott X.

    2010-01-01

    Although deformation processes in submicron-sized metallic crystals are well documented, the direct observation of deformation mechanisms in crystals with dimensions below the sub-10-nm range is currently lacking. Here, through in situ high-resolution transmission electron microscopy (HRTEM) observations, we show that (1) in sharp contrast to what happens in bulk materials, in which plasticity is mediated by dislocation emission from Frank-Read sources and multiplication, partial dislocations emitted from free surfaces dominate the deformation of gold (Au) nanocrystals; (2) the crystallographic orientation (Schmid factor) is not the only factor in determining the deformation mechanism of nanometre-sized Au; and (3) the Au nanocrystal exhibits a phase transformation from a face-centered cubic to a body-centered tetragonal structure after failure. These findings provide direct experimental evidence for the vast amount of theoretical modelling on the deformation mechanisms of nanomaterials that have appeared in recent years. PMID:21266994

  13. On the origin of size-dependent and size-independent crystal growth: Influence of advection and diffusion

    USGS Publications Warehouse

    Kile, D.E.; Eberl, D.D.

    2003-01-01

    Crystal growth experiments were conducted using potassium alum and calcite crystals in aqueous solution under both non-stirred and stirred conditions to elucidate the mechanism for size-dependent (proportionate) and size-independent (constant) crystal growth. Growth by these two laws can be distinguished from each other because the relative size difference among crystals is maintained during proportionate growth, leading to a constant crystal size variance (??2) for a crystal size distribution (CSD) as the mean size increases. The absolute size difference among crystals is maintained during constant growth, resulting in a decrease in size variance. Results of these experiments show that for centimeter-sized alum crystals, proportionate growth occurs in stirred systems, whereas constant growth occurs in non-stirred systems. Accordingly, the mechanism for proportionate growth is hypothesized to be related to the supply of reactants to the crystal surface by advection, whereas constant growth is related to supply by diffusion. Paradoxically, micrometer-sized calcite crystals showed proportionate growth both in stirred and in non-stirred systems. Such growth presumably results from the effects of convection and Brownian motion, which promote an advective environment and hence proportionate growth for minute crystals in non-stirred systems, thereby indicating the importance of solution velocity relative to crystal size. Calcite crystals grown in gels, where fluid motion was minimized, showed evidence for constant, diffusion-controlled growth. Additional investigations of CSDs of naturally occurring crystals indicate that proportionate growth is by far the most common growth law, thereby suggesting that advection, rather than diffusion, is the dominant process for supplying reactants to crystal surfaces.

  14. On the relationship of minimum detectable contrast to dose and lesion size in abdominal CT.

    PubMed

    Zhou, Yifang; Scott, Alexander; Allahverdian, Janet; Lee, Christina; Kightlinger, Blake; Azizyan, Avetis; Miller, Joseph

    2015-10-01

    CT dose optimization is typically guided by pixel noise or contrast-to-noise ratio that does not delineate low contrast details adequately. We utilized the statistically defined low contrast detectability to study its relationship to dose and lesion size in abdominal CT. A realistically shaped medium sized abdomen phantom was customized to contain a cylindrical void of 4 cm diameter. The void was filled with a low contrast (1% and 2%) insert containing six groups of cylindrical targets ranging from 1.2 mm to 7 mm in size. Helical CT scans were performed using a Siemens 64-slice mCT and a GE Discovery 750 HD at various doses. After the subtractions between adjacent slices, the uniform sections of the filtered backprojection reconstructed images were partitioned to matrices of square elements matching the sizes of the targets. It was verified that the mean values from all the elements in each matrix follow a Gaussian distribution. The minimum detectable contrast (MDC), quantified by the mean signal to background difference equal to the distribution's standard deviation multiplied by 3.29, corresponding to 95% confidence level, was found to be related to the phantom specific dose and the element size by a power law (R^2  >  0.990). Independent readings on the 5 mm and 7 mm targets were compared to the measured contrast to the MDC ratios. The results showed that 93% of the cases were detectable when the measured contrast exceeds the MDC. The correlation of the MDC to the pixel noise and target size was also identified and the relationship was found to be the same for the scanners in the study. To quantify the impact of iterative reconstructions to the low contrast detectability, the noise structure was studied in a similar manner at different doses and with different ASIR blending fractions. The relationship of the dose to the blending fraction and low contrast detectability is presented. PMID:26389637

  15. On the relationship of minimum detectable contrast to dose and lesion size in abdominal CT

    NASA Astrophysics Data System (ADS)

    Zhou, Yifang; Scott, Alexander, II; Allahverdian, Janet; Lee, Christina; Kightlinger, Blake; Azizyan, Avetis; Miller, Joseph

    2015-10-01

    CT dose optimization is typically guided by pixel noise or contrast-to-noise ratio that does not delineate low contrast details adequately. We utilized the statistically defined low contrast detectability to study its relationship to dose and lesion size in abdominal CT. A realistically shaped medium sized abdomen phantom was customized to contain a cylindrical void of 4 cm diameter. The void was filled with a low contrast (1% and 2%) insert containing six groups of cylindrical targets ranging from 1.2 mm to 7 mm in size. Helical CT scans were performed using a Siemens 64-slice mCT and a GE Discovery 750 HD at various doses. After the subtractions between adjacent slices, the uniform sections of the filtered backprojection reconstructed images were partitioned to matrices of square elements matching the sizes of the targets. It was verified that the mean values from all the elements in each matrix follow a Gaussian distribution. The minimum detectable contrast (MDC), quantified by the mean signal to background difference equal to the distribution’s standard deviation multiplied by 3.29, corresponding to 95% confidence level, was found to be related to the phantom specific dose and the element size by a power law (R^2  >  0.990). Independent readings on the 5 mm and 7 mm targets were compared to the measured contrast to the MDC ratios. The results showed that 93% of the cases were detectable when the measured contrast exceeds the MDC. The correlation of the MDC to the pixel noise and target size was also identified and the relationship was found to be the same for the scanners in the study. To quantify the impact of iterative reconstructions to the low contrast detectability, the noise structure was studied in a similar manner at different doses and with different ASIR blending fractions. The relationship of the dose to the blending fraction and low contrast detectability is presented.

  16. An assessment of calcite crystal growth mechanisms based on crystal size distributions

    USGS Publications Warehouse

    Kile, D.E.; Eberl, D.D.; Hoch, A.R.; Reddy, M.M.

    2000-01-01

    Calcite crystal growth experiments were undertaken to test a recently proposed model that relates crystal growth mechanisms to the shapes of crystal size distributions (CSDs). According to this approach, CSDs for minerals have three basic shapes: (1) asymptotic, which is related to a crystal growth mechanism having constant-rate nucleation accompanied by surface-controlled growth; (2) lognormal, which results from decaying-rate nucleation accompanied by surface-controlled growth; and (3) a theoretical, universal, steady-state curve attributed to Ostwald ripening. In addition, there is a fourth crystal growth mechanism that does not have a specific CSD shape, but which preserves the relative shapes of previously formed CSDs. This mechanism is attributed to supply-controlled growth. All three shapes were produced experimentally in the calcite growth experiments by modifying nucleation conditions and solution concentrations. The asymptotic CSD formed when additional reactants were added stepwise to the surface of solutions that were supersaturated with respect to calcite (initial Ω = 20, where Ω = 1 represents saturation), thereby leading to the continuous nucleation and growth of calcite crystals. Lognormal CSDs resulted when reactants were added continuously below the solution surface, via a submerged tube, to similarly supersaturated solutions (initial Ω = 22 to 41), thereby leading to a single nucleation event followed by surface-controlled growth. The Ostwald CSD resulted when concentrated reactants were rapidly mixed, leading initially to high levels of supersaturation (Ω >100), and to the formation and subsequent dissolution of very small nuclei, thereby yielding CSDs having small crystal size variances. The three CSD shapes likely were produced early in the crystallization process, in the nanometer crystal size range, and preserved during subsequent growth. Preservation of the relative shapes of the CSDs indicates that a supply-controlled growth mechanism

  17. What is the optimum minimum segment size used in step and shoot IMRT for prostate cancer?

    PubMed

    Takahashi, Yutaka; Koizumi, Masahiko; Sumida, Iori; Ogata, Toshiyuki; Akino, Yuichi; Yoshioka, Yasuo; Konishi, Koji; Isohashi, Fumiaki; Ota, Seiichi; Inoue, Takehiro

    2010-01-01

    Although the use of small segments in step and shoot IMRT provides better dose distribution, extremely small segments decrease treatment accuracy. The purpose of this study was to determine the optimum minimum segment size (MSS) in two-step optimization in prostate step and shoot IMRT with regard to both planning quality and dosimetric accuracy. The XiO treatment planning system and Oncor Impression Plus were used. Results showed that the difference in homogeneity index (HI), defined as the ratio of maximum to minimum doses for planning target volume, between the MSS 1.0 cm and 1.5 cm plans, and 2.0 cm plans, was 0.1%, and 9.6%, respectively. With regard to V107 of PTV, the volume receiving 107% of the prescribed dose of the PTV, the difference between MSS 1.0 cm and 1.5 cm was 2%. However, the value of the MSS 2.0 cm or greater plans was more than 2.5-fold that of the MSS 1.0 cm plan. With regard to maximum rectal dose, a significant difference was seen between the MSS 1.5 cm and 2.0 cm plans, whereas no significant difference was seen between the MSS 1.0 cm and 1.5 cm plans. Composite plan verification revealed a greater than 5% dose difference between planned and measured dose in many regions with the MSS 1.0 cm plan, but in only limited regions in the MSS 1.5 cm plan. Our data suggest that the MSS should be determined with regard to both planning quality and dosimetric accuracy. PMID:20683175

  18. Next generation cooled long range thermal sights with minimum size, weight, and power

    NASA Astrophysics Data System (ADS)

    Breiter, R.; Ihle, T.; Wendler, J.; Rühlich, I.; Ziegler, J.

    2013-06-01

    Situational awareness and precise targeting at day, night and severe weather conditions are key elements for mission success in asymmetric warfare. To support these capabilities for the dismounted soldier, AIM has developed a family of stand-alone thermal weapon sights based on high performance cooled IR-modules which are used e.g. in the infantryman of the future program of the German army (IdZ). The design driver for these sights is a long ID range <1500m for the NATO standard target to cover the operational range of a platoon with the engagement range of .50 cal rifles, 40mm AGLs or for reconnaissance tasks. The most recent sight WBZG has just entered into serial production for the IdZ enhanced system of the German army with additional capabilities like a wireless data link to the soldier backbone computer. Minimum size, weight and power (SWaP) are most critical requirements for the dismounted soldiers' equipment and sometimes push a decision towards uncooled equipment with marginal performance referring to the outstanding challenges in current asymmetric warfare, e.g. the capability to distinguish between combatants and non-combatants in adequate ranges. To provide the uncompromised e/o performance with SWaP parameters close to uncooled, AIM has developed a new thermal weapon sight based on high operating temperature (HOT) MCT MWIR FPAs together with a new low power single piston stirling cooler. In basic operation the sight is used as a clip-on in front of the rifle scope. An additional eyepiece for stand-alone targeting with e.g. AGLs or a biocular version for relaxed surveillance will be available. The paper will present details of the technologies applied for such long range cooled sights with size, weight and power close to uncooled.

  19. Study of flutter related computational procedures for minimum weight structural sizing of advanced aircraft

    NASA Technical Reports Server (NTRS)

    Oconnell, R. F.; Hassig, H. J.; Radovcich, N. A.

    1976-01-01

    Results of a study of the development of flutter modules applicable to automated structural design of advanced aircraft configurations, such as a supersonic transport, are presented. Automated structural design is restricted to automated sizing of the elements of a given structural model. It includes a flutter optimization procedure; i.e., a procedure for arriving at a structure with minimum mass for satisfying flutter constraints. Methods of solving the flutter equation and computing the generalized aerodynamic force coefficients in the repetitive analysis environment of a flutter optimization procedure are studied, and recommended approaches are presented. Five approaches to flutter optimization are explained in detail and compared. An approach to flutter optimization incorporating some of the methods discussed is presented. Problems related to flutter optimization in a realistic design environment are discussed and an integrated approach to the entire flutter task is presented. Recommendations for further investigations are made. Results of numerical evaluations, applying the five methods of flutter optimization to the same design task, are presented.

  20. Size of a crystal nucleus in the isothermal crystallization of supercooled liquid

    NASA Astrophysics Data System (ADS)

    Lee, Heon Sang

    2013-09-01

    We present an alternative to classical nucleation theory (CNT). We introduce a size-dependent surface energy into the total Gibbs free-energy of formation of a crystal (ΔG). We consider the free-energy in the core part of the total volume of crystal and the free-energy in the surface-layer part of it, separately, for the evaluation of ΔG. As a result, we present an explicit model to evaluate a characteristic size of an initial nucleus that differs from the critical nucleus of CNT, but whose temperature dependence agrees well with that reported for the temperature dependency initial fold length of isotactic polystyrene and polyethylene in the literature. Our model has fitted the experimental data in the literature with only one adjustable parameter that is defined as nucleation constant. The nucleation constant is the Gibbs free-energy difference between the crystal and supercooled liquid phases for the volume of initial nucleus. We also present an expression to approximate the evolution of free-energy in the surface-layer part of crystal during the crystal growth.

  1. Multiscale sampling of plant diversity: Effects of minimum mapping unit size

    USGS Publications Warehouse

    Stohlgren, T.J.; Chong, G.W.; Kalkhan, M.A.; Schell, L.D.

    1997-01-01

    Only a small portion of any landscape can be sampled for vascular plant diversity because of constraints of cost (salaries, travel time between sites, etc.). Often, the investigator decides to reduce the cost of creating a vegetation map by increasing the minimum mapping unit (MMU), and/or by reducing the number of vegetation classes to be considered. Questions arise about what information is sacrificed when map resolution is decreased. We compared plant diversity patterns from vegetation maps made with 100-ha, 50-ha, 2-ha, and 0.02-ha MMUs in a 754-ha study area in Rocky Mountain National Park, Colorado, United States, using four 0.025-ha and 21 0.1-ha multiscale vegetation plots. We developed and tested species-log(area) curves, correcting the curves for within-vegetation type heterogeneity with Jaccard's coefficients. Total species richness in the study area was estimated from vegetation maps at each resolution (MMU), based on the corrected species-area curves, total area of the vegetation type, and species overlap among vegetation types. With the 0.02-ha MMU, six vegetation types were recovered, resulting in an estimated 552 species (95% CI = 520-583 species) in the 754-ha study area (330 plant species were observed in the 25 plots). With the 2-ha MMU, five vegetation types were recognized, resulting in an estimated 473 species for the study area. With the 50-ha MMU, 439 plant species were estimated for the four vegetation types recognized in the study area. With the 100-ha MMU, only three vegetation types were recognized, resulting in an estimated 341 plant species for the study area. Locally rare species and keystone ecosystems (areas of high or unique plant diversity) were missed at the 2-ha, 50-ha, and 100-ha scales. To evaluate the effects of minimum mapping unit size requires: (1) an initial stratification of homogeneous, heterogeneous, and rare habitat types; and (2) an evaluation of within-type and between-type heterogeneity generated by environmental

  2. Investigation of the size effect for photonic crystals.

    PubMed

    Liu, M; Xu, W; Bai, J; Chua, C K; Wei, J; Li, Z; Gao, Y; Kim, D H; Zhou, K

    2016-10-01

    Three types of photonic crystal (PC) thin films have been prepared for the investigation of their deformation behaviors by nanoindentation tests at the microscale and nanoscale. Each type of PC thin film was composed of poly(methyl methacrylate) (PMMA) nanoparticles with a uniform size. Another type of thin film was prepared by assembling nanoparticles with three different sizes. It was exciting to observe that the hardness and Young's modulus were significantly improved (more than 15 times) in well-ordered PC thin films than disordered ones. Furthermore, size-dependent mechanical properties were observed for the three types of PCs. Such a size effect phenomenon can be attributed to the special polycrystalline material having a periodical face-centered cubic structure of PC thin films. Furthermore, the indentation size effect that shows that the indentation hardness decreases with an increasing indentation depth has also been observed for all four types of thin films. It is conjectured that the application of the PC structure to other functional materials may enhance their mechanical properties. PMID:27577061

  3. Exciton-phonon interaction in crystals and quantum size structures

    NASA Astrophysics Data System (ADS)

    Yaremko, A. M.; Yukhymchuk, V. O.; Dzhagan, V. M.; Valakh, M. Ya; Baran, J.; Ratajczak, H.

    2007-12-01

    In this report, the problem of electron-phonon interaction (EPI) in bulk semiconductors and quantum dots (QDs) is considered. It is shown that the model of strong EPI developed for organic molecular crystals can be successfully applied to bulk and nano-sized semiconductors. The idea of the approach proposed is to describe theoretically the experimental Raman (IR) spectra, containing the phonon replicas, by varying the EPI constant. The main parameter of the theoretical expression (βS) is the ratio of EPI constant (χS) to the frequency of the corresponding phonon mode (ΩS). The theoretical results show that variation of the QD size can change the value of χS.

  4. 7 CFR 932.153 - Establishment of minimum quality and size requirements for processed olives for limited uses.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... for processed olives for limited uses. 932.153 Section 932.153 Agriculture Regulations of the..., Vegetables, Nuts), DEPARTMENT OF AGRICULTURE OLIVES GROWN IN CALIFORNIA Rules and Regulations § 932.153 Establishment of minimum quality and size requirements for processed olives for limited uses. (a)...

  5. 7 CFR 932.153 - Establishment of minimum quality and size requirements for processed olives for limited uses.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... for processed olives for limited uses. 932.153 Section 932.153 Agriculture Regulations of the..., Vegetables, Nuts), DEPARTMENT OF AGRICULTURE OLIVES GROWN IN CALIFORNIA Rules and Regulations § 932.153 Establishment of minimum quality and size requirements for processed olives for limited uses. (a)...

  6. 7 CFR 932.153 - Establishment of minimum quality and size requirements for processed olives for limited uses.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... for processed olives for limited uses. 932.153 Section 932.153 Agriculture Regulations of the..., VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE OLIVES GROWN IN CALIFORNIA Rules and Regulations § 932.153 Establishment of minimum quality and size requirements for processed olives for limited uses. (a)...

  7. 7 CFR 932.153 - Establishment of minimum quality and size requirements for processed olives for limited uses.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... for processed olives for limited uses. 932.153 Section 932.153 Agriculture Regulations of the..., Vegetables, Nuts), DEPARTMENT OF AGRICULTURE OLIVES GROWN IN CALIFORNIA Rules and Regulations § 932.153 Establishment of minimum quality and size requirements for processed olives for limited uses. (a)...

  8. 7 CFR 932.153 - Establishment of minimum quality and size requirements for processed olives for limited uses.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... for processed olives for limited uses. 932.153 Section 932.153 Agriculture Regulations of the..., VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE OLIVES GROWN IN CALIFORNIA Rules and Regulations § 932.153 Establishment of minimum quality and size requirements for processed olives for limited uses. (a)...

  9. 78 FR 32865 - Procedures To Establish Appropriate Minimum Block Sizes for Large Notional Off-Facility Swaps and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-31

    ... Establish Appropriate Minimum Block Sizes for Large Notional Off-Facility Swaps and Block Trades, 77 FR 15...), 75 FR 76171. The Real-Time Reporting Final Rule defines the term ``block trade'' as a publicly... commence at the time of execution of such trade or swap. See 75 FR 76176. Proposed Sec. 43.5(k)(2)...

  10. 77 FR 15459 - Procedures To Establish Appropriate Minimum Block Sizes for Large Notional Off-Facility Swaps and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-15

    ... minimum block trade size.\\18\\ \\11\\ See Real-Time Public Reporting of Swap Transaction Data, 75 FR 76,139... such trade or swap. See 75 FR 76,176. Proposed Sec. 43.5(k)(2) provided that the time delay for... Commission's proposed rulemakings,\\75\\ as well as a report issued by two industry trade associations on...

  11. 48 CFR 52.247-61 - F.o.b. Origin-Minimum Size of Shipments.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... be the highest applicable minimum weight which will result in the lowest freight rate (or per car charge) on file or published in common carrier tariffs or tenders as of date of shipment. In the...

  12. 48 CFR 52.247-61 - F.o.b. Origin-Minimum Size of Shipments.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... be the highest applicable minimum weight which will result in the lowest freight rate (or per car charge) on file or published in common carrier tariffs or tenders as of date of shipment. In the...

  13. Growth of high quality bulk size single crystals of inverted solubility lithium sulphate monohydrate

    NASA Astrophysics Data System (ADS)

    Silambarasan, A.; Rajesh, P.; Ramasamy, P.

    2015-06-01

    The paper summarizes the processes of growing large lithium sulfate monohydrate (LSMH) single crystals. We have established a procedure to grow high quality bulk size single crystals of inverted solubility LSMH by a newly developed unidirectional crystallization technique called the Sankeranarayenan - Ramasamy (SR) method. The convective flow of crystal growth processes from solution and the conditions of growing crystals of various aspects were discussed. Good quality LSMH single crystal is grown of the size 20 mmX80 mm without cracks, localized-defects and inclusions. The as-grown crystals are suitable for piezoelectric and nonlinear optical applications.

  14. Growth of high quality bulk size single crystals of inverted solubility lithium sulphate monohydrate

    SciTech Connect

    Silambarasan, A.; Rajesh, P. Ramasamy, P.

    2015-06-24

    The paper summarizes the processes of growing large lithium sulfate monohydrate (LSMH) single crystals. We have established a procedure to grow high quality bulk size single crystals of inverted solubility LSMH by a newly developed unidirectional crystallization technique called the Sankeranarayenan - Ramasamy (SR) method. The convective flow of crystal growth processes from solution and the conditions of growing crystals of various aspects were discussed. Good quality LSMH single crystal is grown of the size 20 mmX80 mm without cracks, localized-defects and inclusions. The as-grown crystals are suitable for piezoelectric and nonlinear optical applications.

  15. Coupled crystal orientation-size effects on the strength of nano crystals

    NASA Astrophysics Data System (ADS)

    Yuan, Rui; Beyerlein, Irene J.; Zhou, Caizhi

    2016-05-01

    We study the combined effects of grain size and texture on the strength of nanocrystalline copper (Cu) and nickel (Ni) using a crystal-plasticity based mechanics model. Within the model, slip occurs in discrete slip events exclusively by individual dislocations emitted statistically from the grain boundaries. We show that a Hall-Petch relationship emerges in both initially texture and non-textured materials and our values are in agreement with experimental measurements from numerous studies. We find that the Hall-Petch slope increases with texture strength, indicating that preferred orientations intensify the enhancements in strength that accompany grain size reductions. These findings reveal that texture is too influential to be neglected when analyzing and engineering grain size effects for increasing nanomaterial strength.

  16. Coupled crystal orientation-size effects on the strength of nano crystals

    PubMed Central

    Yuan, Rui; Beyerlein, Irene J.; Zhou, Caizhi

    2016-01-01

    We study the combined effects of grain size and texture on the strength of nanocrystalline copper (Cu) and nickel (Ni) using a crystal-plasticity based mechanics model. Within the model, slip occurs in discrete slip events exclusively by individual dislocations emitted statistically from the grain boundaries. We show that a Hall-Petch relationship emerges in both initially texture and non-textured materials and our values are in agreement with experimental measurements from numerous studies. We find that the Hall-Petch slope increases with texture strength, indicating that preferred orientations intensify the enhancements in strength that accompany grain size reductions. These findings reveal that texture is too influential to be neglected when analyzing and engineering grain size effects for increasing nanomaterial strength. PMID:27185364

  17. 50 CFR 648.75 - Shucking at sea and minimum surfclam size.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    .... 648.75 Section 648.75 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND... Measures for the Atlantic Surf Clam and Ocean Quahog Fisheries § 648.75 Shucking at sea and minimum... surfclams or ocean quahogs at sea if he/she determines that an observer carried aboard the vessel...

  18. 50 CFR 648.75 - Shucking at sea and minimum surfclam size.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    .... 648.75 Section 648.75 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND... Measures for the Atlantic Surf Clam and Ocean Quahog Fisheries § 648.75 Shucking at sea and minimum... surfclams or ocean quahogs at sea if he/she determines that an observer carried aboard the vessel...

  19. 50 CFR 648.75 - Shucking at sea and minimum surfclam size.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    .... 648.75 Section 648.75 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC AND... Measures for the Atlantic Surf Clam and Ocean Quahog Fisheries § 648.75 Shucking at sea and minimum... surfclams or ocean quahogs at sea if he/she determines that an observer carried aboard the vessel...

  20. 50 CFR 622.407 - Minimum size limits and other harvest limitations.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ..., AND SOUTH ATLANTIC Spiny Lobster Fishery of the Gulf of Mexico and South Atlantic § 622.407 Minimum... (c) of this section— (i) No person may possess a spiny lobster in or from the EEZ with a carapace length of 3.0 inches (7.62 cm) or less; and (ii) A spiny lobster, harvested in the EEZ by means...

  1. 50 CFR 622.407 - Minimum size limits and other harvest limitations.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ..., AND SOUTH ATLANTIC Spiny Lobster Fishery of the Gulf of Mexico and South Atlantic § 622.407 Minimum... (c) of this section— (i) No person may possess a spiny lobster in or from the EEZ with a carapace length of 3.0 inches (7.62 cm) or less; and (ii) A spiny lobster, harvested in the EEZ by means...

  2. Analysis of the Effect of Degree Correlation on the Size of Minimum Dominating Sets in Complex Networks

    PubMed Central

    2016-01-01

    Network controllability is an important topic in wide-ranging research fields. However, the relationship between controllability and network structure is poorly understood, although degree heterogeneity is known to determine the controllability. We focus on the size of a minimum dominating set (MDS), a measure of network controllability, and investigate the effect of degree-degree correlation, which is universally observed in real-world networks, on the size of an MDS. We show that disassortativity or negative degree-degree correlation reduces the size of an MDS using analytical treatments and numerical simulation, whereas positive correlations hardly affect the size of an MDS. This result suggests that disassortativity enhances network controllability. Furthermore, apart from the controllability issue, the developed techniques provide new ways of analyzing complex networks with degree-degree correlations. PMID:27327273

  3. Monochromaticity of orientation maps in v1 implies minimum variance for hypercolumn size.

    PubMed

    Afgoustidis, Alexandre

    2015-01-01

    In the primary visual cortex of many mammals, the processing of sensory information involves recognizing stimuli orientations. The repartition of preferred orientations of neurons in some areas is remarkable: a repetitive, non-periodic, layout. This repetitive pattern is understood to be fundamental for basic non-local aspects of vision, like the perception of contours, but important questions remain about its development and function. We focus here on Gaussian Random Fields, which provide a good description of the initial stage of orientation map development and, in spite of shortcomings we will recall, a computable framework for discussing general principles underlying the geometry of mature maps. We discuss the relationship between the notion of column spacing and the structure of correlation spectra; we prove formulas for the mean value and variance of column spacing, and we use numerical analysis of exact analytic formulae to study the variance. Referring to studies by Wolf, Geisel, Kaschube, Schnabel, and coworkers, we also show that spectral thinness is not an essential ingredient to obtain a pinwheel density of π, whereas it appears as a signature of Euclidean symmetry. The minimum variance property associated to thin spectra could be useful for information processing, provide optimal modularity for V1 hypercolumns, and be a first step toward a mathematical definition of hypercolumns. A measurement of this property in real maps is in principle possible, and comparison with the results in our paper could help establish the role of our minimum variance hypothesis in the development process. PMID:25859421

  4. Nanostructured magnonic crystals with size-tunable bandgaps.

    PubMed

    Wang, Zhi Kui; Zhang, Vanessa Li; Lim, Hock Siah; Ng, Ser Choon; Kuok, Meng Hau; Jain, Shikha; Adeyeye, Adekunle Olusola

    2010-02-23

    Just as a photonic crystal is a periodic composite composed of materials with different dielectric constants, its lesser known magnetic analogue, the magnonic crystal can be considered as a periodic composite comprising different magnetic materials. Magnonic crystals are excellent candidates for the fabrication of nanoscale microwave devices, as the wavelengths of magnons in magnonic crystals are orders of magnitude shorter than those of photons, of the same frequency, in photonic crystals. Using advanced electron beam lithographic techniques, we have fabricated a series of novel bicomponent magnonic crystals which exhibit well-defined frequency bandgaps. They are in the form of laterally patterned periodic arrays of alternating cobalt and permalloy stripes of various widths ranging from 150 to 500 nm. Investigations by Brillouin light scattering and computer modeling show that the dispersion spectrum of these crystals is strongly dependent on their structural dimensions. For instance, their first frequency bandgap is found to vary over a wide range of 1.4-2.6 gigahertz. Such a functionality permits the tailoring of the bandgap structure which controls the transmission of information-carrying spin waves in devices based on these crystals. Additionally, it is observed that the bandgap width decreases with increasing permalloy stripe width, but increases with increasing cobalt stripe width, and that the bandgap center frequency is more dependent on the stripe width of permalloy than that of cobalt. This information would be of value in the design of magnonic crystals for potential applications in the emerging field of magnonics. PMID:20099868

  5. Calcium oxalate toxicity in renal epithelial cells: the mediation of crystal size on cell death mode

    PubMed Central

    Sun, X-Y; Gan, Q-Z; Ouyang, J-M

    2015-01-01

    The cytotoxicity of calcium oxalate (CaOx) in renal epithelial cells has been studied extensively, but the cell death mode induced by CaOx with different physical properties, such as crystal size and crystal phase, has not been studied in detail. In this study, we comparatively investigated the differences of cell death mode induced by nano-sized (50 nm) and micron-sized (10 μm) calcium oxalate monohydrate (COM) and calcium oxalate dihydrate (COD) to explore the cell death mechanism. The effect of the exposure of nano-/micron-sized COM and COD crystals toward the African green monkey renal epithelial (Vero) cells were investigated by detecting cell cytoskeleton changes, lysosomal integrity, mitochondrial membrane potential (Δψm), apoptosis and/or necrosis, osteopontin (OPN) expression, and malondialdehyde (MDA) release. Nano-/micron-sized COM and COD crystals could cause apoptosis and necrosis simultaneously. Nano-sized crystals primarily caused apoptotic cell death, leading to cell shrinkage, phosphatidylserine ectropion, and nuclear shrinkage, whereas micron-sized crystals primarily caused necrotic cell death, leading to cell swelling and cell membrane and lysosome rupture. Nano-sized COM and COD crystals induced much greater cell death (sum of apoptosis and necrosis) than micron-sized crystals, and COM crystals showed higher cytotoxicity than the same-sized COD crystals. Both apoptosis and necrosis could lead to mitochondria depolarization and elevate the expression of OPN and the generation of lipid peroxidation product MDA. The amount of expressed OPN and generated MDA was positively related to cell injury degree. The physicochemical properties of crystals could affect the cell death mode. The results of this study may provide a basis for future studies on cell death mechanisms. PMID:27551481

  6. Impact of minimum catch size on the population viability of Strombus gigas (Mesogastropoda: Strombidae) in Quintana Roo, Mexico.

    PubMed

    Peel, Joanne R; Mandujano, María del Carmen

    2014-12-01

    The queen conch Strombus gigas represents one of the most important fishery resources of the Caribbean but heavy fishing pressure has led to the depletion of stocks throughout the region, causing the inclusion of this species into CITES Appendix II and IUCN's Red-List. In Mexico, the queen conch is managed through a minimum fishing size of 200 mm shell length and a fishing quota which usually represents 50% of the adult biomass. The objectives of this study were to determine the intrinsic population growth rate of the queen conch population of Xel-Ha, Quintana Roo, Mexico, and to assess the effects of a regulated fishing impact, simulating the extraction of 50% adult biomass on the population density. We used three different minimum size criteria to demonstrate the effects of minimum catch size on the population density and discuss biological implications. Demographic data was obtained through capture-mark-recapture sampling, collecting all animals encountered during three hours, by three divers, at four different sampling sites of the Xel-Ha inlet. The conch population was sampled each month between 2005 and 2006, and bimonthly between 2006 and 2011, tagging a total of 8,292 animals. Shell length and lip thickness were determined for each individual. The average shell length for conch with formed lip in Xel-Ha was 209.39 ± 14.18 mm and the median 210 mm. Half of the sampled conch with lip ranged between 200 mm and 219 mm shell length. Assuming that the presence of the lip is an indicator for sexual maturity, it can be concluded that many animals may form their lip at greater shell lengths than 200 mm and ought to be considered immature. Estimation of relative adult abundance and densities varied greatly depending on the criteria employed for adult classification. When using a minimum fishing size of 200 mm shell length, between 26.2% and up to 54.8% of the population qualified as adults, which represented a simulated fishing impact of almost one third of the

  7. Spatial, socio-economic, and ecological implications of incorporating minimum size constraints in marine protected area network design.

    PubMed

    Metcalfe, Kristian; Vaughan, Gregory; Vaz, Sandrine; Smith, Robert J

    2015-12-01

    Marine protected areas (MPAs) are the cornerstone of most marine conservation strategies, but the effectiveness of each one partly depends on its size and distance to other MPAs in a network. Despite this, current recommendations on ideal MPA size and spacing vary widely, and data are lacking on how these constraints might influence the overall spatial characteristics, socio-economic impacts, and connectivity of the resultant MPA networks. To address this problem, we tested the impact of applying different MPA size constraints in English waters. We used the Marxan spatial prioritization software to identify a network of MPAs that met conservation feature targets, whilst minimizing impacts on fisheries; modified the Marxan outputs with the MinPatch software to ensure each MPA met a minimum size; and used existing data on the dispersal distances of a range of species found in English waters to investigate the likely impacts of such spatial constraints on the region's biodiversity. Increasing MPA size had little effect on total network area or the location of priority areas, but as MPA size increased, fishing opportunity cost to stakeholders increased. In addition, as MPA size increased, the number of closely connected sets of MPAs in networks and the average distance between neighboring MPAs decreased, which consequently increased the proportion of the planning region that was isolated from all MPAs. These results suggest networks containing large MPAs would be more viable for the majority of the region's species that have small dispersal distances, but dispersal between MPA sets and spill-over of individuals into unprotected areas would be reduced. These findings highlight the importance of testing the impact of applying different MPA size constraints because there are clear trade-offs that result from the interaction of size, number, and distribution of MPAs in a network. PMID:26219669

  8. Minimum Temperatures, Diurnal Temperature Ranges and Temperature Inversions in Limestone Sinkholes of Different Sizes and Shapes

    SciTech Connect

    Whiteman, Charles D.; Haiden, Thomas S.; Pospichal, Bernhard; Eisenbach, Stefan; Steinacker, Reinhold

    2004-08-01

    Air temperature data from five enclosed limestone sinkholes of various sizes and shapes on the 1300 m MSL Duerrenstein Plateau near Lunz, Austria have been analyzed to determine the effect of sinkhole geometry on temperature minima, diurnal temperature ranges, temperature inversion strengths and vertical temperature gradients. Data were analyzed for a non-snow-covered October night and for a snow-covered December night when the temperature fell as low as -28.5°C. Surprisingly, temperatures were similar in two sinkholes with very different drainage areas and depths. A three-layer model was used to show that the sky-view factor is the most important topographic parameter controlling cooling for basins in this size range and that the cooling slows when net longwave radiation at the floor of the sinkhole is nearly balanced by the ground heat flux.

  9. Particle size distribution and estimated carbon flux across the Arabian Sea oxygen minimum zone

    NASA Astrophysics Data System (ADS)

    Roullier, F.; Berline, L.; Guidi, L.; Durrieu De Madron, X.; Picheral, M.; Sciandra, A.; Pesant, S.; Stemmann, L.

    2014-08-01

    The goal of the Arabian Sea section of the TARA oceans expedition was to study large particulate matter (LPM > 100 μm) distributions and possible impact of associated midwater biological processes on vertical carbon export through the oxygen minimum zone (OMZ) of this region. We propose that observed spatial patterns in LPM distribution resulted from the timing and location of surface phytoplankton bloom, lateral transport, microbial processes in the core of the OMZ, and enhanced biological processes mediated by bacteria and zooplankton at the lower oxycline. Indeed, satellite-derived net primary production maps showed that the northern stations of the transect were under the influence of a previous major bloom event while the most southern stations were in a more oligotrophic situation. Lagrangian simulations of particle transport showed that deep particles of the northern stations could originate from the surface bloom while the southern stations could be considered as driven by 1-D vertical processes. In the first 200 m of the OMZ core, minima in nitrate concentrations and the intermediate nepheloid layer (INL) coincided with high concentrations of 100 μm < LPM < 200 μm. These particles could correspond to colonies of bacteria or detritus produced by anaerobic microbial activity. However, the calculated carbon flux through this layer was not affected. Vertical profiles of carbon flux indicate low flux attenuation in the OMZ, with a Martin model b exponent value of 0.22. At three stations, the lower oxycline was associated to a deep nepheloid layer, an increase of calculated carbon flux and an increase in mesozooplankton abundance. Enhanced bacterial activity and zooplankton feeding in the deep OMZ is proposed as a mechanism for the observed deep particle aggregation. Estimated lower flux attenuation in the upper OMZ and re-aggregation at the lower oxycline suggest that OMZ may be regions of enhanced carbon flux to the deep sea relative to non OMZ regions.

  10. Particles size distribution and carbon flux across the Arabian Sea Oxygen Minimum Zone

    NASA Astrophysics Data System (ADS)

    Roullier, F.; Berline, L.; Guidi, L.; Sciandra, A.; Durrieu De Madron, X.; Picheral, M.; Pesant, S.; Stemmann, L.

    2013-12-01

    The goal of the Arabian Sea section of the TARA oceans expedition was to study Large Particulate Matter (LPM > 100 μm) distributions and possible impact of associated midwater biological processes on vertical carbon export through the Oxygen Minimum Zone (OMZ) of this region. We found that spatial patterns in LPM distribution resulted from the timing and location of surface phytoplankton bloom, lateral transport, microbial processes in the core of the OMZ, and zooplankton activity at the lower oxycline. Indeed, satellite-derived net primary production maps showed that the northern stations of the transect were under the influence of a previous major bloom event while, the most southern stations were in a more oligotrophic situation. Lagrangian simulations of particle transport showed that deep particles of the northern stations could originate from the surface bloom while the southern stations could be considered as driven by 1-D vertical processes. In the first 200 m of the OMZ core, minima in nitrate concentrations and the Intermediate Nepheloid Layer (INL) coincided with high concentrations of 100 μm < LPM < 200 μm. These particles could correspond to colonies of bacteria or detritus produced by anaerobic microbial activity. However, the calculated carbon flux through this layer was not affected. Vertical profiles of carbon flux indicate low flux attenuation in the OMZ, with a Martin model b exponent value of 0.22. At the lower oxycline, a deep nepheloid layer was associated to an increase of carbon flux and an increase in mesozooplankton abundance. Zooplankton feeding on un-mineralized sinking particles in the OMZ is proposed as a mechanism for the observed deep particle aggregation. These results suggest that OMZ may be regions of enhanced carbon flux to the deep sea relative to non-OMZ regions.

  11. Dependence of Raman Spectral Intensity on Crystal Size in Organic Nano Energetics.

    PubMed

    Patel, Rajen B; Stepanov, Victor; Qiu, Hongwei

    2016-08-01

    Raman spectra for various nitramine energetic compounds were investigated as a function of crystal size at the nanoscale regime. In the case of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), there was a linear relationship between intensity of Raman spectra and crystal size. Notably, the Raman modes between 120 cm(-1) and 220 cm(-1) were especially affected, and at the smallest crystal size, were completely eliminated. The Raman spectral intensity of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), like that of CL-20's, depended linearly on crystal size. The Raman spectral intensity of 1,3,5-trinitroperhydro-1,3,5-triazine (RDX), however, was not observably changed by crystal size. A non-nitramine explosive compound, 2,4,6-triamino-1,3,5- trinitrobenzene (TATB), was also investigated. Its spectral intensity was also found to correlate linearly with crystal size, although substantially less so than that of HMX and CL-20. To explain the observed trends, it is hypothesized that disordered molecular arrangement, originating from the crystal surface, may be responsible. In particular, it appears that the thickness of the disordered surface layer is dependent on molecular characteristics, including size and conformational flexibility. Furthermore, as the mean crystal size decreases, the volume fraction of disordered molecules within a specimen increases, consequently, weakening the Raman intensity. These results could have practical benefit for allowing the facile monitoring of crystal size during manufacturing. Finally, these findings could lead to deep insights into the general structure of the surface of crystals. PMID:27449371

  12. On the minimum size of drops composing the type of monodisperse microemulsions obtained via tip streaming

    NASA Astrophysics Data System (ADS)

    Gordillo, Jose Manuel; Sevilla, Alejandro; Castro-Hernandez, Elena

    2012-11-01

    On a recent paper, Castro et al. (JFM (2012), 698, 423-445, JFM12) reported the generation of concentrated monodisperse emulsions composed of drops with sizes even below 1 μm . Drops are generated from the capillary breakup of a long and thin ligament which strongly stretches downstream from the exit of an injector of radius Ri. The ligament is formed when a flow rate Qi of a fluid with a viscosity μi discharges into an immiscible liquid of viscosity μo flowing in parallel with the axis of the injector at a velocity qU0 , with q =Qi / (πRi2Uo) . It was theoretically found that the diameter of the drops obtained is Di ~Riq 1 / 2 . However, experiments showed that the predicted drop size is only found when the highly stretched ligament is formed. But this occurs for values of λ =μi /μo and the capillary number Cao =μoUo / σ , with σ the interfacial tension coefficient, above a certain threshold which depends on the flow rate ratio q. In this presentation we theoretically show that the boundaries in the (Cao , λ, q) space in which highly stretched long ligaments are formed, corresponds to the conditions under which the jet, calculated using the slender-body description of JFM12, is globally stable.

  13. Boundary effects in finite size plasmonic crystals: focusing and routing of plasmonic beams for optical communications

    NASA Astrophysics Data System (ADS)

    Benetou, M. I.; Bouillard, J.-S.; Segovia, P.; Dickson, W.; Thomsen, B. C.; Bayvel, P.; Zayats, A. V.

    2015-11-01

    Plasmonic crystals, which consist of periodic arrangements of surface features at a metal-dielectric interface, allow the manipulation of optical information in the form of surface plasmon polaritons. Here we investigate the excitation and propagation of plasmonic beams in and around finite size plasmonic crystals at telecom wavelengths, highlighting the effects of the crystal boundary shape and illumination conditions. Significant differences in broad plasmonic beam generation by crystals of different shapes are demonstrated, while for narrow beams, the propagation from a crystal onto the smooth metal film is less sensitive to the crystal boundary shape. We show that by controlling the boundary shape, the size and the excitation beam parameters, directional control of propagating plasmonic modes and their behaviour such as angular beam splitting, focusing power and beam width can be efficiently achieved. This provides a promising route for robust and alignment-independent integration of plasmonic crystals with optical communication components.

  14. Boundary effects in finite size plasmonic crystals: focusing and routing of plasmonic beams for optical communications.

    PubMed

    Benetou, M I; Bouillard, J-S; Segovia, P; Dickson, W; Thomsen, B C; Bayvel, P; Zayats, A V

    2015-11-01

    Plasmonic crystals, which consist of periodic arrangements of surface features at a metal-dielectric interface, allow the manipulation of optical information in the form of surface plasmon polaritons. Here we investigate the excitation and propagation of plasmonic beams in and around finite size plasmonic crystals at telecom wavelengths, highlighting the effects of the crystal boundary shape and illumination conditions. Significant differences in broad plasmonic beam generation by crystals of different shapes are demonstrated, while for narrow beams, the propagation from a crystal onto the smooth metal film is less sensitive to the crystal boundary shape. We show that by controlling the boundary shape, the size and the excitation beam parameters, directional control of propagating plasmonic modes and their behaviour such as angular beam splitting, focusing power and beam width can be efficiently achieved. This provides a promising route for robust and alignment-independent integration of plasmonic crystals with optical communication components. PMID:26469205

  15. Minimum size for a nanoscale temperature discriminator based on a thermochemical system.

    PubMed

    Gorecki, J; Nowakowski, B; Gorecka, J N; Lemarchand, A

    2016-02-14

    What are the limits of size reduction for information processing devices based on chemical reactions? In this paper, we partially answer this question. We show that a thermochemical system can be used to design a discriminator of the parameters associated with oscillations of the ambient temperature. Depending on the amplitude and frequency of the oscillations, the system exhibits sharp transitions between different types of its time evolutions. This phenomenon can be used to discriminate between different parameter values describing the oscillating environment. We investigate the reliability of the thermochemical discriminator as a function of the number of molecules involved in the reactions. A stochastic model of chemical reactions and heat exchange with the neighborhood, in which the number of molecules explicitly appears, is introduced. For the selected values of the parameters, thermochemical discriminators operating with less than 10(5) molecules appear to be unreliable. PMID:26807977

  16. Evolution of crystal sizes in the series of dissolution and precipitation events in open magma systems

    NASA Astrophysics Data System (ADS)

    Simakin, A. G.; Bindeman, I. N.

    2008-11-01

    We propose a model that describes the evolution of crystal sizes and crystal size distributions (CSD) of igneous phenocrysts in a sequence of dissolution and crystallization events. This model is based on the assumption that crystal dissolution is rate-limited by diffusion in melt while crystal growth is controlled by the slower kinetic of new nucleation and growth. As a result, the dissolution rate is inversely proportional to crystal size coming into effect through the curvature of the crystal's surface, but the growth rate does not depend on the crystal size. Closed-form analytical solution of equation for CSD is obtained. We apply results of modeling to quartz and zircon, two prime minerals in silicic igneous systems that are widely used in geochemical and isotopic investigations. The time-series of multiple solution-reprecipitation episodes generate concave-downward CSDs and this result fits well with experimental and natural observations on the abundant concave-down CSD in silicic igneous rocks. We suggest that maturation of crystal populations with sizes above several micrometers can not be caused by a size effect on the solubility of the crystals (Ostwald ripening), but is rather driven by thermal oscillations in experiments and in nature. The model predicts that mean crystal size increases with time proportionally to ˜ t0.20, which is very close to the published experimental results for quartz maturation with the exponent of 0.19-0.22. Our proposed model gives an opportunity to use natural CSDs for interpretation of pre-eruptive magma history, when solubilities and diffusion data are available for constituent elements of the dissolving mineral. In particular, we present time estimates for maturing zircon populations in large volume ignimbrites and estimate that it takes 100-1000 yrs to mature an initially exponential CSD to a lognormal CSD.

  17. Variation of Ice Crystal Size, Shape and Asymmetry Parameter in Tops of Convective Storm Systems Observed during SEAC4RS

    NASA Astrophysics Data System (ADS)

    van Diedenhoven, B.; Cairns, B.; Fridlind, A. M.; Ackerman, A. S.

    2014-12-01

    The sizes and shapes of ice particles in tops of convective storms have a significant impact on their radiative properties. Ice crystal sizes and shapes likely vary with altitude, environmental conditions and convective strength, but these relationships are not well characterized. The rich dataset of the NASA SEAC4RS field campaign offers unique perspectives to further identify variations of ice crystal sizes and shapes and their relations to environmental and dynamical conditions. Here we focus on data acquired with the Research Scanning Polarimeter (RSP), which was mounted on the high-altitude ER-2 aircraft during SEAC4RS. RSP's unique multi-angular, multi-wavelength total and polarized reflectance measurements allow retrieval of ice effective radius, the aspect ratio of components of ice crystals, the crystal distortion level and ice asymmetry parameter, as well as cloud optical thickness and cloud top height. Using RSP data, as well as data from the eMAS and CPL sensors and in situ probes, we explore the statistical variation of ice properties retrieved during SEAC4RS in tops of convective systems. The data indicates that, in general, ice crystal populations consistent with plate-like components with aspect ratios near 0.4 are prevalent at cloud tops. The asymmetry parameter is around 0.76-0.8 and generally decreases with increasing cloud top height, mainly because the ice crystal distortion increases with height. Below about 12 km height, the effective radius decreases with increasing altitude, as previously shown for convective clouds using satellite data, but at higher levels the SEAC4RS data indicate a transition to effective radii increasing with cloud top height. Here we explore some possible explanations for this transition, related to its approximate coincidence with the level of minimum stability and the homogeneous freezing level, either of which could affect ice crystal formation and evolution. Additionally, we will demonstrate some of the

  18. Energy surface and minimum energy paths for Fréedericksz transitions in bistable cholesteric liquid crystals

    NASA Astrophysics Data System (ADS)

    Ivanov, A. V.; Bessarab, P. F.; Aksenova, E. V.; Romanov, V. P.; Uzdin, V. M.

    2016-04-01

    The multidimensional energy surface of a cholesteric liquid crystal in a planar cell is investigated as a function of spherical coordinates determining the director orientation. Minima on the energy surface correspond to the stable states with particular director distribution. External electric and magnetic fields deform the energy surface and positions of minima. It can lead to the transitions between states, known as the Fréedericksz effect. Transitions can be continuous or discontinuous depending on parameters of the liquid crystal which determine an energy surface. In a case of discontinuous transition when a barrier between stable states is comparable with the thermal energy, the activation transitions may occur, and it leads to the modification of characteristics of the Fréedericksz effect with temperature without explicit temperature dependencies of liquid crystal parameters. A minimum energy path between stable states on the energy surface for the Fréedericksz transition is found using the geodesic nudged elastic band method. Knowledge of this path, which has maximal statistical weight among all other paths, gives the information about a barrier between stable states and configuration of director orientation during the transition. It also allows one to estimate the stability of states with respect to the thermal fluctuations and their lifetime when the system is close to the Fréedericksz transition.

  19. Laser damage dependence on the size and concentration of precursor defects in KDP crystals: view through differently sized filter pores.

    PubMed

    Wang, Yueliang; Zhao, Yuanan; Xie, Xiaoyi; Hu, Guohang; Yang, Liujiang; Xu, Ziyuan; Shao, Jianda

    2016-04-01

    We investigate the laser-induced damage performance at 1064 nm of potassium dihydrogen phosphate (KDP) crystals grown using filters of different pore sizes. The aim is to explore a novel method for understanding laser-matter interactions with regard to physical parameters affecting the ability of damage precursors to initiate damage. By reducing the pore size of filters in continuous filtration growth, we can improve laser damage resistance. Furthermore, we develop a model based on a Gaussian distribution of precursor thresholds and heat transfer to obtain a size distribution of the precursor defects. Smaller size and/or lower concentration of precursor defects could lead to better damage resistance. PMID:27192280

  20. On geological interpretations of crystal size distributions: Constant vs. proportionate growth

    USGS Publications Warehouse

    Eberl, D.D.; Kile, D.E.; Drits, V.A.

    2002-01-01

    Geological interpretations of crystal size distributions (CSDs) depend on understanding the crystal growth laws that generated the distributions. Most descriptions of crystal growth, including a population-balance modeling equation that is widely used in petrology, assume that crystal growth rates at any particular time are identical for all crystals, and, therefore, independent of crystal size. This type of growth under constant conditions can be modeled by adding a constant length to the diameter of each crystal for each time step. This growth equation is unlikely to be correct for most mineral systems because it neither generates nor maintains the shapes of lognormal CSDs, which are among the most common types of CSDs observed in rocks. In an alternative approach, size-dependent (proportionate) growth is modeled approximately by multiplying the size of each crystal by a factor, an operation that maintains CSD shape and variance, and which is in accord with calcite growth experiments. The latter growth law can be obtained during supply controlled growth using a modified version of the Law of Proportionate Effect (LPE), an equation that simulates the reaction path followed by a CSD shape as mean size increases.

  1. Verwey transition of nano-sized magnetite crystals investigated by 57Fe NMR

    NASA Astrophysics Data System (ADS)

    Lim, Sumin; Choi, Baek Soon; Lee, Soon Chil; Hong, Jaeyoung; Lee, Jisoo; Hyeon, Taeghwan; Kim, Taehun; Jeong, Jaehong; Park, Je-Geun

    It is well known that magnetite crystals undergo a metal-insulator transition at the Verwey transition temperature, TV = 123 K. In this work, we studied the Verwey transition of nano-sized crystals with 57Fe NMR. In the metallic state above Tv, the NMR spectrum shows a single sharp peak, which broadens below TV indicating the Verwey transition. We measured the spectra of the nano-crystals with radii of 16 nm, 25 nm, and 40 nm and compared with that of a bulk. The transition temperature obtained from the NMR spectra depends on both the crystal size and crystallinity. When the crystal size decreases from bulk to 16 nm, the transition temperature drops from 123 K to 100 K. The transition temperature of the samples kept dry air decrease due to aging.

  2. Size-fractionated diversity of eukaryotic microbial communities in the Eastern Tropical North Pacific oxygen minimum zone.

    PubMed

    Duret, Manon T; Pachiadaki, Maria G; Stewart, Frank J; Sarode, Neha; Christaki, Urania; Monchy, Sébastien; Srivastava, Ankita; Edgcomb, Virginia P

    2015-05-01

    Oxygen minimum zones (OMZs) caused by water column stratification appear to expand in parts of the world's ocean, with consequences for marine biogeochemical cycles. OMZ formation is often fueled by high surface primary production, and sinking organic particles can be hotspots of interactions and activity within microbial communities. This study investigated the diversity of OMZ protist communities in two biomass size fractions (>30 and 30-1.6 μm filters) from the world's largest permanent OMZ in the Eastern Tropical North Pacific. Diversity was quantified via Illumina MiSeq sequencing of V4 region of 18S SSU rRNA genes in samples spanning oxygen gradients at two stations. Alveolata and Rhizaria dominated the two size fractions at both sites along the oxygen gradient. Community composition at finer taxonomic levels was partially shaped by oxygen concentration, as communities associated with versus anoxic waters shared only ∼32% of operational taxonomic unit (OTU) (97% sequence identity) composition. Overall, only 9.7% of total OTUs were recovered at both stations and under all oxygen conditions sampled, implying structuring of the eukaryotic community in this area. Size-fractionated communities exhibited different taxonomical features (e.g. Syndiniales Group I in the 1.6-30 μm fraction) that could be explained by the microniches created on the surface-originated sinking particles. PMID:25873468

  3. Advancement of proprotor technology. Task 1: Design study summary. [aerodynamic concept of minimum size tilt proprotor research aircraft

    NASA Technical Reports Server (NTRS)

    1969-01-01

    A tilt-proprotor proof-of-concept aircraft design study has been conducted. The results are presented. The ojective of the contract is to advance the state of proprotor technology through design studies and full-scale wind-tunnel tests. The specific objective is to conduct preliminary design studies to define a minimum-size tilt-proprotor research aircraft that can perform proof-of-concept flight research. The aircraft that results from these studies is a twin-engine, high-wing aircraft with 25-foot, three-bladed tilt proprotors mounted on pylons at the wingtips. Each pylon houses a Pratt and Whitney PT6C-40 engine with a takeoff rating of 1150 horsepower. Empty weight is estimated at 6876 pounds. The normal gross weight is 9500 pounds, and the maximum gross weight is 12,400 pounds.

  4. In situ observation of crystal growth in a basalt melt and the development of crystal size distribution in igneous rocks

    NASA Astrophysics Data System (ADS)

    Ni, Huaiwei; Keppler, Hans; Walte, Nicolas; Schiavi, Federica; Chen, Yang; Masotta, Matteo; Li, Zhenjiang

    2014-05-01

    To understand the solidification processes of natural magma and the texture evolution of igneous rocks, we have carried out in situ observation of the crystallization of a high-K basaltic melt cooling from ~1,240 °C in a moissanite cell. In a series of experiments with different thermal history, olivine or clinopyroxene (cpx) appeared as the liquidus phase before the formation of plagioclase. During cooling at 100 °C/h, the morphology of olivine and cpx transited from tabular to hopper habit. To first order approximation, crystal grow rate (2 × 10-9 to 7 × 10-9 m/s for olivine and 6 × 10-9 to 17 × 10-9 m/s for cpx), probably limited by chemical diffusion, is proportional to crystal size. In one experiment dominated by olivine crystallization, the good image quality allows the analysis of texture evolution over an extended period. Nucleation of olivine occurred only in a narrow temperature and time interval below the liquidus. Two-dimensional length- and area-based crystal size distributions (CSDs) show counterclockwise rotation around axes of 8 μm and 100 μm2, which is consistent with the proportionate crystal growth. Both CSDs and direct observation show the dissolution of small crystals and Ostwald ripening. These data suggest that conventional analyses of crystal size distributions of igneous rocks may be in error—the slope of the CSD cannot be interpreted in terms of a uniform growth rate, and the intercept with the vertical axis does not correspond to a nucleation density.

  5. Effects of crystal shape- and size-modality on magma rheology

    NASA Astrophysics Data System (ADS)

    Moitra, P.; Gonnermann, H. M.

    2015-01-01

    magma often contains crystals over a wide range of sizes and shapes, potentially affecting magma viscosity over many orders of magnitude. A robust relation between viscosity and the modality of crystal sizes and shapes remains lacking, principally because of the dimensional complexity and size of the governing parameter space. We have performed a suite of shear viscosity measurements on liquid-particle suspensions of dynamical similarity to crystal-bearing magma. Our experiments encompass five suspension types, each consisting of unique mixtures of two different particle sizes and shapes. The experiments span two orthogonal subspaces of particle concentration, as well as particle size and shape for each suspension type, thereby providing insight into the topology of parameter space. For each suspension type, we determined the dry maximum packing fraction and measured shear rates across a range of applied shear stresses. The results were fitted using a Herschel-Bulkley model and augment existing predictive capabilities. We demonstrate that our results are consistent with previous work, including friction-based constitutive laws for granular materials. We conclude that predictions for ascent rates of crystal-rich magmas must take the shear-rate dependence of viscosity into account. Shear-rate dependence depends first and foremost on the volume fraction of crystals, relative to the maximum packing fraction, which in turn depends on crystal size and shape distribution.

  6. Crystal growth and detector performance of large size high-purity Ge crystals

    NASA Astrophysics Data System (ADS)

    Wang, Guojian; Amman, Mark; Mei, Hao; Mei, Dongming; Irmscher, Klaus; Guan, Yutong; Yang, Gang

    2015-03-01

    High-purity germanium crystals with 12 cm in diameter were grown in a hydrogen atmosphere using the Czochralski method. The dislocation density of the crystals was determined to be in the range of 2000 - 4200 cm-2, which meets a requirement for use as a radiation detector. The axial and radial distributions of impurities in the crystals were measured by Hall effect and Photo-thermal ionization spectroscopy (PTIS). Two detectors were also fabricated from one of the crystals with different techniques and then evaluated for electrical and spectral performance. Measurements of gamma-ray spectra from 137Cs, 241Am and 60Co sources demonstrate that the detectors have excellent energy resolution. Keywords: High-purity germanium crystal, Czochralski method This work is supported by DOE grant DE-FG02-10ER46709 and the state of South Dakota.

  7. Sensitivity Studies For Cirrus Effective Ice Crystal Size Retrieval In The Infrared

    NASA Astrophysics Data System (ADS)

    Radel, G.; Stubenrauch, C.; Holz, R.; Mitchell, D.

    During the last years, much effort has been made to find a realistic description of the single-scattering properties of non-spherical ice crystals of cirrus clouds explicitely in dependence of ice crystal shape and size distribution. By using single scattering properties of non-spherical ice crystals instead of ice spheres, one observes that the spectral region between 8 and 12 micron offers a possibility of effective ice crystal size retrieval. The difference between cirrus emissivities at these wavelengths is sen- sitive to the mean ice crystal size of the cirrus cloud. At present, we use two different sets of ice crystal single scattering properties in the infrared: one for randomly oriented planar polycrystals and the other for hexagonal columns. For planar polycrystals, mod- ified Anomalous Diffraction Approximation (mADA) is used to describe absorption coefficients as analytical expressions of size distribution parameters, ice crystal shape, wavelength and refractive index, taking into account a parameterized correction for internal reflection and refraction. As scattering cannot be calculated through mADA, scattering contributions are obtained from different combinations of Improved Geo- metric Optics and Finite Difference Time Domain. For hexagonal columns the single scattering properties have been computed using the Finite Difference Time Domain method. Retrievals of mean effective ice crystal sizes in the infrared have the advan- tage that they are less dependent on the assumed shape of the ice crystals, in contrary to retrievals from differences between the visible and near-infrared radiation. Several satellite instruments measure now emitted and scattered radiation from different lev- els of the atmosphere. The longest time period is covered by the TOVS instruments aboard the NOAA Polar Orbiting Environmental Satellites (since 1979). These obser- vations have been converted into atmospheric temperature and water vapor profiles as well as cloud and

  8. Finite particle size drives defect-mediated domain structures in strongly confined colloidal liquid crystals

    NASA Astrophysics Data System (ADS)

    Gârlea, Ioana C.; Mulder, Pieter; Alvarado, José; Dammone, Oliver; Aarts, Dirk G. A. L.; Lettinga, M. Pavlik; Koenderink, Gijsje H.; Mulder, Bela M.

    2016-06-01

    When liquid crystals are confined to finite volumes, the competition between the surface anchoring imposed by the boundaries and the intrinsic orientational symmetry-breaking of these materials gives rise to a host of intriguing phenomena involving topological defect structures. For synthetic molecular mesogens, like the ones used in liquid-crystal displays, these defect structures are independent of the size of the molecules and well described by continuum theories. In contrast, colloidal systems such as carbon nanotubes and biopolymers have micron-sized lengths, so continuum descriptions are expected to break down under strong confinement conditions. Here, we show, by a combination of computer simulations and experiments with virus particles in tailor-made disk- and annulus-shaped microchambers, that strong confinement of colloidal liquid crystals leads to novel defect-stabilized symmetrical domain structures. These finite-size effects point to a potential for designing optically active microstructures, exploiting the as yet unexplored regime of highly confined liquid crystals.

  9. Size dependent growth behaviour related to the mosaic spread in ammonium sulphate crystals

    NASA Astrophysics Data System (ADS)

    Meadhra, R. S. Ó.; Kramer, H. J. M.; van Rosmalen, G. M.

    1995-07-01

    The growth rate of small (1-120 μm) ammonium sulphate crystals, which were removed from a 970 L crystallizer via a fines classification line, were measured in a 2 L growth cell. An exponential size dependent growth (SDG) curve was used to model the data, revealing a size dependent growth rate up to a size of 220 μm. The same crystals were dried and sieved and the level of internal strain ("mosaic spread") measured using the high intensity synchrotron radiation source. The results showed that the average mosaic spread and also the spread in mosaic spreads reduced with increasing crystal length. These results are consistent with the SDG rate measured for the small particles in suspension and points to internal lattice strain as being the cause of the SDG.

  10. Director-configurational transitions around microbubbles of hydrostatically regulated size in liquid crystals.

    PubMed

    Völtz, C; Maeda, Y; Tabe, Y; Yokoyama, H

    2006-12-01

    A high-pressure technique is introduced which allows a continuous variation of the inclusion size in liquid crystal colloids. We use a nematic liquid crystal host into which micrometer-sized gas bubbles are injected. By applying hydrostatic pressures, the diameter of these gas bubbles can be continuously decreased via compression and absorption of gas into the host liquid crystal, so that the director configurations around a single bubble can be investigated as a function of the bubble size. The theoretically predicted transition from a hyperbolic hedgehog to a Saturn-ring configuration, on reduction of the particle size below a certain threshold, is confirmed to occur at the radius of a few micrometers. PMID:17155844

  11. Size-Topology Correlations and Crystallization in Tilings and Packings

    NASA Astrophysics Data System (ADS)

    Hilgenfeldt, Sascha

    2014-03-01

    Ever since its empirical formulation in 1928, Lewis`s law has intrigued scientists, postulating a linear correlation between the average in-plane area and the number of neighbors in a two-dimensional tiling. Many supporting and dissenting results have been reported in systems as diverse as foams, Voronoi tilings in glass models, and nanocrystals. A strong size-topology correlation is consistently observed, but it is often pronouncedly nonlinear. Recently, a variant of the granocentric model explained numerous cases of nonlinear correlations, but cannot account for the linear version of the law. We revisit Lewis's original work by conducting more extensive experiments on cucumber epidermis tissue. The data confirms the linear law, but also shows that the individual cells have a pronounced anisotropy, not present in systems with nonlinear correlation laws. We demonstrate how the granocentric model can be modified taking into account the cell anisotropy, and how this feature is capable of reproducing the linear Lewis law, as well as other characteristic differences in size-topology statistical quantities. The model should be generally applicable to jammed, plane-filling systems and identifies domain anisotropy as an important ingredient in their statistical description.

  12. Crystallization of sodium chloride from a concentrated calcium chloride-potassium chloride-sodium chloride solution in a CMSMPR crystallizer: Observation of crystal size distribution and model validation

    NASA Astrophysics Data System (ADS)

    Choi, Byung Sang

    Compared to overwhelming technical data available in other advanced technologies, knowledge about particle technology, especially in particle synthesis from a solution, is still poor due to the lack of available equipment to study crystallization phenomena in a crystallizer. Recent technical advances in particle size measurement such as Coulter counter and laser light scattering have made in/ex situ study of some of particle synthesis, i.e., growth, attrition, and aggregation, possible with simple systems. Even with these advancements in measurement technology, to grasp fully the crystallization phenomena requires further theoretical and technical advances in understanding such particle synthesis mechanisms. Therefore, it is the motive of this work to establish the general processing parameters and to produce rigorous experimental data with reliable performance and characterization that rigorously account for the crystallization phenomena of nucleation, growth, aggregation, and breakage including their variations with time and space in a controlled continuous mixed-suspension mixed-product removal (CMSMPR) crystallizer. This dissertation reports the results and achievements in the following areas: (1) experimental programs to support the development and validation of the phenomenological models and generation of laboratory data for the purpose of testing, refining, and validating the crystallization process, (2) development of laboratory well-mixed crystallizer system and experimental protocols to generate crystal size distribution (CSD) data, (3) the effects of feed solution concentration, crystallization temperature, feed flow rate, and mixing speed, as well as different types of mixers resulting in the evolution of CSDs with time from a concentrated brine solution, (4) with statistically designed experiments the effects of processing variables on the resultant particle structure and CSD at steady state were quantified and related to each of those operating

  13. Chemical Vapor Deposition of Large-Sized Hexagonal WSe₂ Crystals on Dielectric Substrates.

    PubMed

    Chen, Jianyi; Liu, Bo; Liu, Yanpeng; Tang, Wei; Nai, Chang Tai; Li, Linjun; Zheng, Jian; Gao, Libo; Zheng, Yi; Shin, Hyun Suk; Jeong, Hu Young; Loh, Kian Ping

    2015-11-01

    High-quality large-sized hexagoal WSe2 crystals can be grown on dielectric substrates using atmospheric chemical vapor deposition in the presence of hydrogen gas. These hexagonal crystals (lateral width >160 um) have a carrier mobility of 100 cm(2) V(-1) s(-1) and a photoresponsivity of ≈1100 mA W(-1), which is comparable to that of exfoliated flakes. PMID:26414106

  14. Finite size corrections to Madelung number. [for ion atoms in ionic crystals

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.; Heinbockel, J. H.; Outlaw, R. A.

    1986-01-01

    It is customary in the study of ionic crystals to assume that the ions are point charges at their respective lattice sites; the corresponding electrostatic energy of one such ion is reducible to Madelung's form, where the Madelung number has a value of 1.7467. This paper considers the modifications in the electrostatic energy when the atomic finite size is treated in more detail. The results are tabulated as a direct correction to Madelung's number for alkali halide cubic crystals.

  15. Deducing growth mechanisms for minerals from the shapes of crystal size distributions

    USGS Publications Warehouse

    Eberl, D.D.; Drits, V.A.; Srodon, J.

    1998-01-01

    Crystal size distributions (CSDs) of natural and synthetic samples are observed to have several distinct and different shapes. We have simulated these CSDs using three simple equations: the Law of Proportionate Effect (LPE), a mass balance equation, and equations for Ostwald ripening. The following crystal growth mechanisms are simulated using these equations and their modifications: (1) continuous nucleation and growth in an open system, during which crystals nucleate at either a constant, decaying, or accelerating nucleation rate, and then grow according to the LPE; (2) surface-controlled growth in an open system, during which crystals grow with an essentially unlimited supply of nutrients according to the LPE; (3) supply-controlled growth in an open system, during which crystals grow with a specified, limited supply of nutrients according to the LPE; (4) supply- or surface-controlled Ostwald ripening in a closed system, during which the relative rate of crystal dissolution and growth is controlled by differences in specific surface area and by diffusion rate; and (5) supply-controlled random ripening in a closed system, during which the rate of crystal dissolution and growth is random with respect to specific surface area. Each of these mechanisms affects the shapes of CSDs. For example, mechanism (1) above with a constant nucleation rate yields asymptotically-shaped CSDs for which the variance of the natural logarithms of the crystal sizes (??2) increases exponentially with the mean of the natural logarithms of the sizes (??). Mechanism (2) yields lognormally-shaped CSDs, for which ??2 increases linearly with ??, whereas mechanisms (3) and (5) do not change the shapes of CSDs, with ??2 remaining constant with increasing ??. During supply-controlled Ostwald ripening (4), initial lognormally-shaped CSDs become more symmetric, with ??2 decreasing with increasing ??. Thus, crystal growth mechanisms often can be deduced by noting trends in ?? versus ??2 of CSDs for

  16. Modulating crystal grain size and optoelectronic properties of perovskite films for solar cells by reaction temperature

    NASA Astrophysics Data System (ADS)

    Ren, Xiaodong; Yang, Zhou; Yang, Dong; Zhang, Xu; Cui, Dong; Liu, Yucheng; Wei, Qingbo; Fan, Haibo; Liu, Shengzhong (Frank)

    2016-02-01

    Regulating the temperature during the direction contact and intercalation process (DCIP) for the transition from PbI2 to CH3NH3PbI3 modulated the crystallinity, crystal grain size and crystal grain orientation of the perovskite films. Higher temperatures produced perovskite films with better crystallinity, larger grain size, and better photovoltaic performance. The best cell, which had a PCE of 12.9%, was obtained on a film prepared at 200 °C. Further open circuit voltage decay and film resistance characterization revealed that the larger grain size contributed to longer carrier lifetime and smaller carrier transport resistance, both of which are beneficial for solar cell devices.Regulating the temperature during the direction contact and intercalation process (DCIP) for the transition from PbI2 to CH3NH3PbI3 modulated the crystallinity, crystal grain size and crystal grain orientation of the perovskite films. Higher temperatures produced perovskite films with better crystallinity, larger grain size, and better photovoltaic performance. The best cell, which had a PCE of 12.9%, was obtained on a film prepared at 200 °C. Further open circuit voltage decay and film resistance characterization revealed that the larger grain size contributed to longer carrier lifetime and smaller carrier transport resistance, both of which are beneficial for solar cell devices. Electronic supplementary information (ESI) available: XRD patterns and statistic results of solar cell performance. See DOI: 10.1039/c5nr08935b

  17. Effects of increasing size and changing europium activator concentration in KCaI3 scintillator crystals

    NASA Astrophysics Data System (ADS)

    Lindsey, Adam C.; Zhuravleva, Mariya; Wu, Yuntao; Stand, Luis; Loyd, Matthew; Gokhale, Sasmit; Koschan, Merry; Melcher, Charles L.

    2016-09-01

    KCaI3:Eu crystals have been identified as very promising for use in spectroscopic detector applications related to nuclear nonproliferation and domestic security efforts. Initial studies have shown for small crystals a few mm3 in size with 3% europium dopant concentration, a high light yield of >70,000 ph/MeV and energy resolution of ≈3% at 662 keV is attainable which is comparable with the highest performance scintillators discovered. In this work, single crystals of KCaI3 with a range of Eu2+ doping between 0 and 5 at% substituting for Ca2+ were grown at 22 mm diameter and their performance for gamma-ray spectroscopy studied. Comparisons among crystals approximately Ø22 mm×22 mm (8.4 cm3 or ≈0.5 in3) provide a more accurate understanding of how scintillation performance changes with Eu doping and increased crystal size. KCaI3 in the undoped form is shown to be a highly efficient intrinsic scintillator with a defect-related emission at 404 nm which coexists with the Eu2+ 5d-4f emission in low dopant concentrations and is completely re-absorbed in more heavily doped crystals. For larger crystals, effects from self-absorption due to Eu activation become more evident by a near doubling of decay time for 0.5 in3 crystals as the activator is increased from 0.5 to 5.0 at% Eu. Comparisons of pulse-height spectra obtained for Ø22 mm×22 mm cylinders with varying Eu concentration suggests best performance is achieved using lower Eu additions closer to 0.5-1.0 at%. Using a modified crystal packaging featuring an offset reflector geometry, 0.5 in3 crystals of KCaI3:Eu can attain under 4% energy resolution at 662 keV.

  18. A Theory of the von Weimarn Rules Governing the Average Size of Crystals Precipitated from a Supersaturated Solution

    NASA Technical Reports Server (NTRS)

    Barlow, Douglas A.; Baird, James K.; Su, Ching-Hua

    2003-01-01

    More than 75 years ago, von Weimarn summarized his observations of the dependence of the average crystal size on the initial relative concentration supersaturation prevailing in a solution from which crystals were growing. Since then, his empirically derived rules have become part of the lore of crystal growth. The first of these rules asserts that the average crystal size measured at the end of a crystallization increases as the initial value of the relative supersaturation decreases. The second rule states that for a given crystallization time, the average crystal size passes through a maximum as a function of the initial relative supersaturation. Using a theory of nucleation and growth due to Buyevich and Mansurov, we calculate the average crystal size as a function of the initial relative supersaturation. We confirm the von Weimarn rules for the case where the nucleation rate is proportional to the third power or higher of the relative supersaturation.

  19. Size, crystal structure and morphology changes of IATO nanoparticles effect on its optical property

    NASA Astrophysics Data System (ADS)

    Hu, Te; Su, Yu-Chang; Liu, Si-Dong; Tang, Hong-Bo; Mu, Shi-Jia; Hu, Ze-Xing

    2014-09-01

    Controlling and changing size, crystal structure and morphology of antimony and tin-doped indium oxide (IATO) nanoparticles can effectively influence their specific optical properties. Nanocube-like, nanorod-like and nanosphere-like IATO nanoparticles have been fabricated from 20 to 200 nm in diameter by sintering as-prepared precursors with distinct crystallographic structures and morphologies. These nano-sized precursors are either cubic In(OH)3 or orthorhombic InOOH with different crystallographic sizes and shapes due to the use of different solvents (deionized water, absolute ethyl alcohol and ethylene glycol) in hydrothermal synthesis process. Characterization and comparison of experimental samples have detailedly demonstrated that desired optical properties of IATO nanoparticles should be attained by appropriate change of size, crystal structure and morphology of IATO nanoparticles.

  20. Gas promotes the crystallization of nano-sized metal-organic frameworks in ionic liquid.

    PubMed

    Liu, Chengcheng; Zhang, Bingxing; Zhang, Jianling; Peng, Li; Kang, Xinchen; Han, Buxing; Wu, Tianbin; Sang, Xinxin; Ma, Xue

    2015-07-21

    Herein it was found that gas can be utilized as an activator to promote metal-organic framework (MOF) crystallization in IL at room temperature. The ultra-small MOF nanoparticles were obtained, and their size and porosity properties can be easily modulated by controlling gas pressure. The as-synthesized nano-sized Cu-MOF is an excellent candidate catalyst for the solvent-free oxidation of cyclohexene with oxygen. PMID:26087458

  1. Modeling of Fano resonances in the reflectivity of photonic crystal cavities with finite spot size excitation.

    PubMed

    Vasco, J P; Vinck-Posada, H; Valentim, P T; Guimãraes, P S S

    2013-12-16

    We study the reflectivity spectra of photonic crystal slab cavities using an extension of the scattering matrix method that allows treating finite sizes of the spot of the excitation beam. The details of the implementation of the method are presented and then we show that Fano resonances arise as a consequence of the electromagnetic interference between the discrete contribution of the fundamental cavity mode and the continuum contribution of the light scattered by the photonic crystal pattern. We control the asymmetry lineshape of the Fano resonance through the polarization of the incident field, which determines the relative phase between the two electromagnetic contributions to the interference. We analyse the electric field profile inside and outside of the crystal to help in the understanding of the dependence on polarization of the reflectivity lineshape. We also study with our implementation the dependence of the Fano resonances on the size of the incident radiation spot. PMID:24514709

  2. Deformation twinning in small-sized face-centred cubic single crystals: Experiments and modelling

    NASA Astrophysics Data System (ADS)

    Liang, Z. Y.; Huang, M. X.

    2015-12-01

    Small-sized crystals generally show deformation behaviour distinct from their bulk counterparts. In addition to dislocation slip, deformation twinning in small-sized face-centred cubic (FCC) single crystals has been reported to follow a different mechanism which involves coherent emission of partial dislocations on successive { 111 } planes from free surface. The present work employed a twinning-induced plasticity (TWIP) steel with a low stacking fault energy to systematically investigate the twin evolution in small-sized FCC single crystals. Micrometre-sized single crystal pillars of TWIP steel were fabricated by focus ion beam and then strained to different levels by compression experiments. Detailed transmission electron microscopy characterization was carried out to obtain a quantitative evaluation of the deformation twins, which contribute to most of the plastic strain. Emissions of partial dislocations from free surface (surface sources) and pre-existing perfect dislocations inside the pillar (inner sources) are found as the essential processes for the formation of deformation twins. Accordingly, a physically-based model, which integrates source introduction methods and source activation criterions for partial dislocation emission, is developed to quantitatively predict the twin evolution. The model is able to reproduce the experimental twin evolution, in terms of the total twin formation, the twin morphology and the occurrence of twinning burst.

  3. Estimation by radiation inactivation of the minimum functional size of acrosome-reaction-inducing substance (ARIS) in the starfish, Asterias amurensis.

    PubMed

    Ushiyama, A; Chiba, K; Shima, A; Hoshi, M

    1995-11-01

    In the starfish Asterias amurensis, the jelly coat of the eggs contains a glycoprotein essential for the induction of the acrosome reaction in homologous spermatozoa that is termed the acrosome-reaction-inducing substance (ARIS). ARIS is a highly sulphated and fucose-rich glycoprotein of extremely high molecular mass (> 10(4) kDa). ARIS was irradiated with high-energy electrons in order to estimate the minimum size required for its biological activity. The minimum functional unit or target size of ARIS was estimated to be c. 14 kDa by target size analysis. ARIS was significantly disintegrated by the irradiation, yet the total sugar content was not apparently reduced. The binding of 125I-labelled ARIS to spermatozoa competed with that of irradiated ARIS, although the affinity of ARIS was much reduced after irradiation. PMID:8730900

  4. On the influence of crystal size and wavelength on native SAD phasing.

    PubMed

    Liebschner, Dorothee; Yamada, Yusuke; Matsugaki, Naohiro; Senda, Miki; Senda, Toshiya

    2016-06-01

    Native SAD is an emerging phasing technique that uses the anomalous signal of native heavy atoms to obtain crystallographic phases. The method does not require specific sample preparation to add anomalous scatterers, as the light atoms contained in the native sample are used as marker atoms. The most abundant anomalous scatterer used for native SAD, which is present in almost all proteins, is sulfur. However, the absorption edge of sulfur is at low energy (2.472 keV = 5.016 Å), which makes it challenging to carry out native SAD phasing experiments as most synchrotron beamlines are optimized for shorter wavelength ranges where the anomalous signal of sulfur is weak; for longer wavelengths, which produce larger anomalous differences, the absorption of X-rays by the sample, solvent, loop and surrounding medium (e.g. air) increases tremendously. Therefore, a compromise has to be found between measuring strong anomalous signal and minimizing absorption. It was thus hypothesized that shorter wavelengths should be used for large crystals and longer wavelengths for small crystals, but no thorough experimental analyses have been reported to date. To study the influence of crystal size and wavelength, native SAD experiments were carried out at different wavelengths (1.9 and 2.7 Å with a helium cone; 3.0 and 3.3 Å with a helium chamber) using lysozyme and ferredoxin reductase crystals of various sizes. For the tested crystals, the results suggest that larger sample sizes do not have a detrimental effect on native SAD data and that long wavelengths give a clear advantage with small samples compared with short wavelengths. The resolution dependency of substructure determination was analyzed and showed that high-symmetry crystals with small unit cells require higher resolution for the successful placement of heavy atoms. PMID:27303793

  5. Finite particle size drives defect-mediated domain structures in strongly confined colloidal liquid crystals

    PubMed Central

    Gârlea, Ioana C.; Mulder, Pieter; Alvarado, José; Dammone, Oliver; Aarts, Dirk G. A. L.; Lettinga, M. Pavlik; Koenderink, Gijsje H.; Mulder, Bela M.

    2016-01-01

    When liquid crystals are confined to finite volumes, the competition between the surface anchoring imposed by the boundaries and the intrinsic orientational symmetry-breaking of these materials gives rise to a host of intriguing phenomena involving topological defect structures. For synthetic molecular mesogens, like the ones used in liquid-crystal displays, these defect structures are independent of the size of the molecules and well described by continuum theories. In contrast, colloidal systems such as carbon nanotubes and biopolymers have micron-sized lengths, so continuum descriptions are expected to break down under strong confinement conditions. Here, we show, by a combination of computer simulations and experiments with virus particles in tailor-made disk- and annulus-shaped microchambers, that strong confinement of colloidal liquid crystals leads to novel defect-stabilized symmetrical domain structures. These finite-size effects point to a potential for designing optically active microstructures, exploiting the as yet unexplored regime of highly confined liquid crystals. PMID:27353002

  6. SU-F-18C-01: Minimum Detectability Analysis for Comprehensive Sized Based Optimization of Image Quality and Radiation Dose Across CT Protocols

    SciTech Connect

    Smitherman, C; Chen, B; Samei, E

    2014-06-15

    Purpose: This work involved a comprehensive modeling of task-based performance of CT across a wide range of protocols. The approach was used for optimization and consistency of dose and image quality within a large multi-vendor clinical facility. Methods: 150 adult protocols from the Duke University Medical Center were grouped into sub-protocols with similar acquisition characteristics. A size based image quality phantom (Duke Mercury Phantom) was imaged using these sub-protocols for a range of clinically relevant doses on two CT manufacturer platforms (Siemens, GE). The images were analyzed to extract task-based image quality metrics such as the Task Transfer Function (TTF), Noise Power Spectrum, and Az based on designer nodule task functions. The data were analyzed in terms of the detectability of a lesion size/contrast as a function of dose, patient size, and protocol. A graphical user interface (GUI) was developed to predict image quality and dose to achieve a minimum level of detectability. Results: Image quality trends with variations in dose, patient size, and lesion contrast/size were evaluated and calculated data behaved as predicted. The GUI proved effective to predict the Az values representing radiologist confidence for a targeted lesion, patient size, and dose. As an example, an abdomen pelvis exam for the GE scanner, with a task size/contrast of 5-mm/50-HU, and an Az of 0.9 requires a dose of 4.0, 8.9, and 16.9 mGy for patient diameters of 25, 30, and 35 cm, respectively. For a constant patient diameter of 30 cm, the minimum detected lesion size at those dose levels would be 8.4, 5, and 3.9 mm, respectively. Conclusion: The designed CT protocol optimization platform can be used to evaluate minimum detectability across dose levels and patient diameters. The method can be used to improve individual protocols as well as to improve protocol consistency across CT scanners.

  7. Preparation of large-sized hydroxyapatite single crystals using homogeneous releasing controls

    NASA Astrophysics Data System (ADS)

    Tao, Jinhui; Jiang, Wenge; Pan, Haihua; Xu, Xurong; Tang, Ruikang

    2007-10-01

    Hydroxyapatite (HAP) single crystals with size of tens of micrometer have been synthesized by a controlled homogeneous precipitation method. A complex of calcium bis(2-ethylhexyl) sulfosuccinate (Ca(AOT) 2) and Na 2HPO 4 used to supply the calcium and phosphate ions during the reactions. Hexamethylenetetramine (HMT) is applied as a pH regulator to control the homogeneous release of hydroxyl ions in the bulk solution. Since HAP formation is sensitive to pH, the controlled release of hydroxyl ions by the hydrolysis of HMT can trigger the crystallization of HAP, which is regulated by the solution temperature. The formed HAP crystals have large and smooth crystal facets and their lattice structure can be easily determined by using atomic force microscopy. The control experiments show that HMT plays an important role in the formation of the large HAP since it can provide the homogeneous supersaturation fields in the bulk solution. The application of Ca(AOT) 2 is another helpful factor which reduces the supersaturation level during the crystallization process. This synthesis strategy provides a facile pathway to obtain HAP single crystals at least one order in magnitude larger than the conventional ones.

  8. Elastic deformation of nanometer-sized metal crystals in graphitic shells

    SciTech Connect

    Sun, L.; Rodriguez-Manzo, J. A.; Banhart, F.

    2006-12-25

    The elastic deformation of nanometer-sized metal crystals is achieved by encapsulating them in carbon nanotubes or carbon onions. Electron irradiation of these core-shell particles leads to high pressure in their center due to a shrinkage of the graphitic shells. Pressures in the range of 10-30 GPa are found by measuring the decrease in lattice spacings in the encapsulated metal crystals. Hence, it is quantitatively shown how closed graphitic shells can be applied as compression cells on the nanoscale.

  9. Minimum size requirements for open-ended lasing from N two-level atoms in infinite cylindrical samples

    SciTech Connect

    Manassah, Jamal T.

    2010-10-15

    Using the threshold condition relating the rate of pumping with the transverse decay rate and the real part of the eigenvalue of the dominant eigenmode of the dipole-dipole interaction kernel, I obtain the minimum radius which a cloud of N two-level atoms in infinite-cylindrical geometrical configuration coherently excited must obey to permit open-ended cw lasing.

  10. Millimeter-size single-crystal graphene by suppressing evaporative loss of Cu during low pressure chemical vapor deposition.

    PubMed

    Chen, Shanshan; Ji, Hengxing; Chou, Harry; Li, Qiongyu; Li, Hongyang; Suk, Ji Won; Piner, Richard; Liao, Lei; Cai, Weiwei; Ruoff, Rodney S

    2013-04-11

    Millimeter-size single-crystal monolayer graphene is synthesized on polycrystalline Cu foil by a method that involves suppressing loss by evaporation of the Cu at high temperature under low pressure. This significantly diminishes the number of graphene domains, and large single crystal domains up to ∼2 mm in size are grown. PMID:23386288

  11. Role of Surface Area, Primary Particle Size, and Crystal Phase on Titanium Dioxide Nanoparticle Dispersion Properties

    PubMed Central

    2011-01-01

    Characterizing nanoparticle dispersions and understanding the effect of parameters that alter dispersion properties are important for both environmental applications and toxicity investigations. The role of particle surface area, primary particle size, and crystal phase on TiO2 nanoparticle dispersion properties is reported. Hydrodynamic size, zeta potential, and isoelectric point (IEP) of ten laboratory synthesized TiO2 samples, and one commercial Degussa TiO2 sample (P25) dispersed in different solutions were characterized. Solution ionic strength and pH affect titania dispersion properties. The effect of monovalent (NaCl) and divalent (MgCl2) inert electrolytes on dispersion properties was quantified through their contribution to ionic strength. Increasing titania particle surface area resulted in a decrease in solution pH. At fixed pH, increasing the particle surface area enhanced the collision frequency between particles and led to a higher degree of agglomeration. In addition to the synthesis method, TiO2 isoelectric point was found to be dependent on particle size. As anatase TiO2 primary particle size increased from 6 nm to 104 nm, its IEP decreased from 6.0 to 3.8 that also results in changes in dispersion zeta potential and hydrodynamic size. In contrast to particle size, TiO2 nanoparticle IEP was found to be insensitive to particle crystal structure. PMID:27502650

  12. Shape and feature size control of colloidal crystal-based patterns using stretched polydimethylsiloxane replica molds.

    PubMed

    Choi, Hong Kyoon; Im, Sang Hyuk; Park, O Ok

    2009-10-20

    In this work, we fabricated various patterns using colloidal crystals as master molds via the soft lithography method. Even though colloidal crystals consist of spherical colloidal particles, nonspherical shaped patterns such as rectangular or elongated hexagonal shaped patterns can be fabricated using a stretched polydimethylsiloxane (PDMS) replica mold. The pattern shape and feature size can be easily controlled by changing the stretching axis and ratio of the PDMS replica mold. The deformations of the PDMS mold were simulated using the finite element method, and they are consistent with experimental results. The elongated patterns were used as templates to offer new types of colloidal crystal superlattice structures. A proposed pattern-control method will significantly expand the usefulness and diversity of micro/nanopatterning technology. PMID:19821618

  13. Critical superparamagnetic/single-domain grain sizes in interacting magnetite particles: implications for magnetosome crystals

    PubMed Central

    Muxworthy, Adrian R.; Williams, Wyn

    2009-01-01

    Magnetotactic bacteria contain chains of magnetically interacting crystals (magnetosome crystals), which they use for navigation (magnetotaxis). To improve magnetotaxis efficiency, the magnetosome crystals (usually magnetite or greigite in composition) should be magnetically stable single-domain (SSD) particles. Smaller single-domain particles become magnetically unstable owing to thermal fluctuations and are termed superparamagnetic (SP). Previous calculations for the SSD/SP threshold size or blocking volume did not include the contribution of magnetic interactions. In this study, the blocking volume has been calculated as a function of grain elongation and separation for chains of identical magnetite grains. The inclusion of magnetic interactions was found to decrease the blocking volume, thereby increasing the range of SSD behaviour. Combining the results with previously published calculations for the SSD to multidomain threshold size in chains of magnetite reveals that interactions significantly increase the SSD range. We argue that chains of interacting magnetosome crystals found in magnetotactic bacteria have used this effect to improve magnetotaxis. PMID:19091684

  14. Critical superparamagnetic/single-domain grain sizes in interacting magnetite particles: implications for magnetosome crystals.

    PubMed

    Muxworthy, Adrian R; Williams, Wyn

    2009-12-01

    Magnetotactic bacteria contain chains of magnetically interacting crystals (magnetosome crystals), which they use for navigation (magnetotaxis). To improve magnetotaxis efficiency, the magnetosome crystals (usually magnetite or greigite in composition) should be magnetically stable single-domain (SSD) particles. Smaller single-domain particles become magnetically unstable owing to thermal fluctuations and are termed superparamagnetic (SP). Previous calculations for the SSD/SP threshold size or blocking volume did not include the contribution of magnetic interactions. In this study, the blocking volume has been calculated as a function of grain elongation and separation for chains of identical magnetite grains. The inclusion of magnetic interactions was found to decrease the blocking volume, thereby increasing the range of SSD behaviour. Combining the results with previously published calculations for the SSD to multidomain threshold size in chains of magnetite reveals that interactions significantly increase the SSD range. We argue that chains of interacting magnetosome crystals found in magnetotactic bacteria have used this effect to improve magnetotaxis. PMID:19091684

  15. Critical single domain grain sizes in chains of interacting greigite particles: Implications for magnetosome crystals

    NASA Astrophysics Data System (ADS)

    Muxworthy, Adrian R.; Williams, Wyn; Roberts, Andrew P.; Winklhofer, Michael; Chang, Liao; Pósfai, Mihály

    2013-12-01

    Magnetotactic bacteria contain chains of magnetically interacting crystals (magnetosomes), which aid navigation (magnetotaxis). To improve the efficiency of magnetotaxis, magnetosome crystals (which can consist of magnetite or greigite) should be magnetically stable single domain (SD) particles. Larger particles subdivide into nonuniform multidomain (MD) magnetic structures that produce weaker magnetic signals, while small SD particles become magnetically unstable due to thermal fluctuations and exhibit superparamagnetic (SP) behavior. In this study, we determined the stable SD range as a function of grain elongation and interparticle separation for chains of identical greigite grains using fundamental parameters recently determined for greigite. Interactions significantly increase the stable SD range. For example, for cube-shaped greigite grains the upper stable SD threshold size is increased from 107 nm for isolated grains to 204 nm for touching grains arranged in chains. The larger critical SD grain size for greigite means that, compared to magnetite magnetosomes, greigite magnetosomes can produce larger magnetic signals without the need for intergrain interactions.

  16. Crystal size of epidotes: A potentially exploitable geothermometer in geothermal fields

    SciTech Connect

    Patrier, P.; Beaufort, D.; Touchard, G. ); Fouillac, A.M. )

    1990-11-01

    Crystal size of epidotes crystallized in quartz + epidote veins is used as the basis for a new geothermometer from the fossil geothermal field of Saint Martin (Lesser Antilles). The epidote-bearing alteration paragenesis is developed as far as 3 km from a quartz diorite pluton at temperatures of 220-350C. The length/width ratio of the epidote grains is constant for all the analyzed samples and suggests isotropic growth environments. However, the length and width of the grains vary exponentially with temperature. The obtained results offer new perspectives for simple grain-size geothermomentry but must be extended to other geologic environments to clarify the influence of different rock types.

  17. Indentation Size Effects in Single Crystal Copper as Revealed by Synchrotron X-ray Microdiffraction

    SciTech Connect

    Feng, G.; Budiman, A. S.; Nix, W. D.; Tamura, N.; Patel, J. R.

    2007-11-19

    The indentation size effect (ISE) has been observed in numerous nanoindentation studies on crystalline materials; it is found that the hardness increases dramatically with decreasing indentation size - a 'smaller is stronger' phenomenon. Some have attributed the ISE to the existence of strain gradients and the geometrically necessary dislocations (GNDs). Since the GND density is directly related to the local lattice curvature, the Scanning X-ray Microdiffraction ({mu}SXRD) technique, which can quantitatively measure relative lattice rotations through the streaking of Laue diffractions, can used to study the strain gradients. The synchrotron {mu}SXRD technique we use - which was developed at the Advanced Light Source (ALS), Berkeley Lab - allows for probing the local plastic behavior of crystals with sub-micrometer resolution. Using this technique, we studied the local plasticity for indentations of different depths in a Cu single crystal. Broadening of Laue diffractions (streaking) was observed, showing local crystal lattice rotation due to the indentation-induced plastic deformation. A quantitative analysis of the streaking allows us to estimate the average GND density in the indentation plastic zones. The size dependence of the hardness, as found by nanoindentation, will be described, and its correlation to the observed lattice rotations will be discussed.

  18. A LiDAR study of the effective size of cirrus ice crystals over Chung-Li, Taiwan

    NASA Astrophysics Data System (ADS)

    Kumar Das, Subrata; Nee, Jan-Bai; Chiang, Chih-Wei

    2010-06-01

    In this paper, we estimated the effective size of ice crystals in cirrus clouds using fall velocity derived from LiDAR (light detection and ranging) measurements at Chung-Li (24.58°N, 121.1°E), Taiwan. Nine shapes of the ice crystals, viz. hexagonal plates, hexagonal columns, rimed long columns, crystals with sector-like branches, broad-branched crystals, stellar crystal with broad arms, side planes, bullet rosettes and assemblages of planar poly-crystals of specific dimensions have been analyzed. The results show that the lidar derived most probable mean effective size of ice crystals is 340±180 [mu]m with a dominant size range of 200-300 [mu]m. The lidar derived mean effective size of cirrus crystals are parameterized in terms of cloud mid-height temperature as well as optical depth. The discussed method will be useful to study the most probable effective size distribution of ice crystals in cirrus cloud.

  19. Crystal form control and particle size control of RG3487, a nicotinic α7 receptor partial agonist.

    PubMed

    Kuang, Shanming; Zhang, Pingsheng; Dong, Eric Z; Jennings, Geremia; Zhao, Baoshu; Pierce, Michael

    2016-07-11

    This paper describes solid form control and particle size control of RG3487, a nicotinic receptor partial agonist. Four crystal forms were identified by polymorph screen under ∼100 varying conditions. Form A and Form B are anhydrates, while Forms C and D are solvates. Forms A, which is enantiotropically related to Form B, is the more thermodynamically stable form under ambient conditions and the desired form selected for clinical development. The crystal form control of Form A was achieved by crystallization solvent selection which consistently produced the desired form. Several process parameters impacting particle size of Form A in the final crystallization step were identified and investigated through both online and offline particle size measurement. The investigation results were utilized to control crystallization processes which successfully produced Form A with different particle size in 500g scale. PMID:27167333

  20. The Influence of Grain Size and Crystal Content on Rheology and Deformation of Pyroclastic Material

    NASA Astrophysics Data System (ADS)

    Paquereau-Lebti, P.; Robert, G.; Grunder, A. L.; Russell, K. J.

    2007-12-01

    Pyroclastic deposits undergo variable degrees of sintering, viscous deformation of particles and loss of pore space, which combine to produce the dramatic textural variations that define welded facies. We here investigate the effects of grain size and crystal content on the rheology and welding of pyroclastic material.Uniaxial deformation experiments were conducted using sintered cores of natural rhyolite ash under conditions consistent with welding. Experiments were done in the University of British Columbia Volcanology Deformation Rig (VDR). This apparatus is designed to run experiments relevant to volcanology, by supporting low-load, high temperature, deformation experiments (Quane et al., 2004). We ran experiments at constant displacement rate (2.5.10-6 m.s-1), under ambient water pressure ("Dry"), at temperatures of 850 and 900°C and to maximal strain of 50%. Grain-size effect was investigated using sintered cores from three different sieving fractions of Rattlesnake Tuff (RST, Eastern Oregon, USA) ash: fine ash (grain size < 0.6 mm), coarse ash (0.6 to 2mm) and row unsieved ash. The effect of crystal content was explored using cores of sintered unsieved RST ash, variably enriched in crystals of feldspars and quartz.Unsieved and fine ash cores suffered higher total porosity reduction than coarse ash cores during deformation experiments. For cores of unsieved ash, porosity loss is facilitated by mechanical compaction, which includes orientation and organisation of different size clasts to a compact assemblage, without any deformation of individual particles. Isolated porosity decreases faster than connected porosity in coarse and fine ash cores, whereas cores of raw ash mainly loose connected porosity. This is also consistent with mechanical compaction for cores of unsieved ash, in which isolated porosity of weakly deformed individual pumice clasts or glass shards is maintained. Increasing strain causes a reduction in porosity and correlates with increase in

  1. Ice Crystal Size Retrivals using High Spectral Resolution Lidar and Millimeter Wave Radar Data.

    NASA Astrophysics Data System (ADS)

    Eloranta, E.

    2006-12-01

    The University of Wisconsin Arctic High Spectral Resolution Lidar(AHSRL) and the NOAA 8.6 mm radar(MMCR) are collecting data in the high Arctic at Eureka, Canada (79.94N, 85.56W). They have been deployed as part of the NOAA SEARCH program since August of 2005. AHSRL and MMCR data are distributed at http://lidar.ssec.wisc.edu. This web site allows visual scans of available data, composition of custom images and downloading of data in netCDF format. NetCDF files are prepared on demand with user specified time and altitude limits along with user specified altitude and time averaging. The ratio of the lidar and radar cross sections data can be used to measure the size of cloud and precipitation particles. Unfortunately, attenuation and multiple scattering make it difficult to measure the lidar scattering cross section. Standard lidar data does not contain sufficient information to correct for attenuation without the use of poorly supported assumptions. The multiply scattered signal is dependent on particle size and is often comparable in magnitude to the singly scattered signal. As a result, past lidar-radar particle size measurements have required use of complicated iterative solutions (Donovan and Lammeren, JGR, 106, Nov 16, 2001, pp 27425). These problems are avoided when using AHSRL data. It provides robustly calibrated measurements of the backscatter cross section. Furthermore, the lidar receiver accepts light from a very small angular field-of- view greatly limiting multiply scattered signals. Lidar-radar size retrievals provide the effective diameter prime. This quantity is proportional to the mass of the average particle squared divided by the projected area of the average particle. Conversion of effective diameter prime to commonly derived size measures such as effective diameter, mean diameter, median mass diameter, or mean mass of the ice particles requires knowledge of the ice crystal shape. Mitchell(J. Atmos. Sci V29 p153-163) and others have presented

  2. Glass bead size and morphology characteristics in support of Crystal Mist field experiments

    SciTech Connect

    Einfeld, W.

    1995-03-01

    One of the tasks of the Lethality Group within US Army Space and Strategic Defense Command (USASSDC) is the development of a capability to simulate various missile intercept scenarios using computer codes. Currently under development within USASSDC and its various contractor organizations is a group of codes collected under a master code called PEGEM for Post Event Ground Effects Model. Among the various components of the code are modules which are used to predict atmospheric dispersion and transport of particles or droplets following release at the altitude specified in the missile intercept scenario. The atmospheric transport code takes into account various source term data from the intercept such as: initial cloud size; droplet or particle size distribution; and, total mass of agent released. An ongoing USASSDC experimental program termed Crystal Mist involved release of precision glass beads under various altitude and meteorological conditions to assist in validation and refinement of various codes that are components of PEGEM used to predict particle atmospheric transport and diffusion following a missile intercept. Here, soda-lime glass beads used in the Crystal Mist series of atmospheric transport and diffusion tests were characterized by scanning electron microscopy and automated image processing routines in order to fully define their size distributions and morphology. Four bead size classifications ranging from a median count diameter of 45 to 200 micrometers were found to be approximately spherical and to fall within the supplier`s sizing specifications. Log-normal functions fit to the measured size distributions resulted in geometric standard deviations ranging from 1.08 to 1.12, thereby fulfilling the field trial requirements for a relatively narrow bead size distribution.

  3. Size-dependent energy in crystal plasticity and continuum dislocation models

    PubMed Central

    Mesarovic, Sinisa Dj.; Forest, Samuel; Jaric, Jovo P.

    2015-01-01

    In the light of recent progress in coarsening the discrete dislocation mechanics, we consider two questions relevant for the development of a mesoscale, size-dependent plasticity: (i) can the phenomenological expression for size-dependent energy, as quadratic form of Nye's dislocation density tensor, be justified from the point of view of dislocation mechanics and under what conditions? (ii) how can physical or phenomenological expressions for size-dependent energy be computed from dislocation mechanics in the general case of elastically anisotropic crystal? The analysis based on material and slip system symmetries implies the negative answer to the first question. However, the coarsening method developed in response to the second question, and based on the physical interpretation of the size-dependent energy as the coarsening error in dislocation interaction energy, introduces additional symmetries. The result is that the equivalence between the phenomenological and the physical expressions is possible, but only if the multiplicity of characteristic lengths associated with different slip systems, is sacrificed. Finally, we discuss the consequences of the assumption that a single length scale governs the plasticity of a crystal, and note that the plastic dissipation at interfaces has a strong dependence on the length scale embedded in the energy expression. PMID:25792963

  4. Growth and characterization of millimeter-sized single crystals of CaFeAsF

    NASA Astrophysics Data System (ADS)

    Ma, Yonghui; Zhang, Hui; Gao, Bo; Hu, Kangkang; Ji, Qiucheng; Mu, Gang; Huang, Fuqiang; Xie, Xiaoming

    2015-08-01

    High-quality and sizable single crystals are crucial for studying the intrinsic properties of unconventional superconductors, which are lacking in the 1111 phase of Fe-based superconductors. Here we report the successful growth of CaFeAsF single crystals with sizes of 1-2 mm using the self-flux method. Owing to the availability of the high-quality single crystals, the structure and transport properties were investigated with a high reliability. The structure was refined by using single-crystal x-ray diffraction data, which confirms earlier reports on the basis of powder data. A clear anomaly associated with the structural transition was observed at 121 K from the resistivity, magnetoresistance, and magnetic susceptibility measurements. Another kink-feature at 110 K, most likely an indication of antiferromagnetic transition, was also detected in the resistivity data. Our results supply a basis from which to propel physical investigations of the 1111 phase of Fe-based superconductors.

  5. Size effects in models for mechanically-stressed protein crystals and aggregates

    NASA Technical Reports Server (NTRS)

    Noever, David A.

    1992-01-01

    As protein aggregates increase in size, they become easier to disrupt mechanically. Using the scaling properties of models proposed to govern protein aggregation, the effect of thermal vibrations and gravity are investigated as deforming forces. For typical protein assemblies made of 30 A proteins, the assembled diameter must remain less than 100-10,000 times the molecular radius to survive in finite thermal and gravity fields. The analysis predicts the following experimental outcomes: (1) reductions in gravitational strain should favor larger protein aggregates; (2) in comparing the aggregate stability of different proteins, the addition of peptide chains should stabilize against thermal strain, but should not affect gravitational strain; (3) critical aggregate sizes should show significant (exponential) sensitivity to cluster geometry, solution preparation and growth conditions. The analysis is extended to consider qualitative size effects in crystal damage during X-ray exposure.

  6. Predicting Sizes of Hexagonal and Gyroid Metal Nanostructures from Liquid Crystal Templating.

    PubMed

    Asghar, Kaleem A; Rowlands, Daniel A; Elliott, Joanne M; Squires, Adam M

    2015-11-24

    We describe a method to predict and control the lattice parameters of hexagonal and gyroid mesoporous materials formed by liquid crystal templating. In the first part, we describe a geometric model with which the lattice parameters of different liquid crystal mesophases can be predicted as a function of their water/surfactant/oil volume fractions, based on certain geometric parameters relating to the constituent surfactant molecules. We demonstrate the application of this model to the lamellar (Lα), hexagonal (H1), and gyroid bicontinuous cubic (V1) mesophases formed by the binary Brij-56 (C16EO10)/water system and the ternary Brij-56/hexadecane/water system. In this way, we demonstrate predictable and independent control over the size of the cylinders (with hexadecane) and their spacing (with water). In the second part, we produce mesoporous platinum using as templates hexagonal and gyroid phases with different compositions and show that in each case the symmetry and lattice parameter of the metal nanostructure faithfully replicate those of the liquid crystal template, which is itself in agreement with the model. This demonstrates a rational control over the geometry, size, and spacing of pores in a mesoporous metal. PMID:26493862

  7. Size-selective crystallization of homochiral camphorate metal-organic frameworks for lanthanide separation.

    PubMed

    Zhao, Xiang; Wong, Matthew; Mao, Chengyu; Trieu, Thuong Xinh; Zhang, Jian; Feng, Pingyun; Bu, Xianhui

    2014-09-10

    Lanthanides (Ln) are a group of important elements usually found in nature as mixtures. Their separation is essential for technological applications but is made challenging by their subtly different properties. Here we report that crystallization of homochiral camphorate metal-organic frameworks (MOFs) is highly sensitive to ionic radii of lanthanides and can be used to selectively crystallize a lanthanide element into predesigned MOFs. Two series of camphorate MOFs were synthesized with acetate (Type 1 with early lanthanides La-Dy) or formate (Type 2 with late lanthanides Tb-Lu and Y) as the auxiliary ligand, respectively. The Ln coordination environment in each type exhibits selectivity for Ln(3+) of different sizes, which could form the basis for a new cost-effective method for Ln separation. PMID:25164942

  8. Evolution of genome size and chromosome number in the carnivorous plant genus Genlisea (Lentibulariaceae), with a new estimate of the minimum genome size in angiosperms

    PubMed Central

    Fleischmann, Andreas; Michael, Todd P.; Rivadavia, Fernando; Sousa, Aretuza; Wang, Wenqin; Temsch, Eva M.; Greilhuber, Johann; Müller, Kai F.; Heubl, Günther

    2014-01-01

    Background and Aims Some species of Genlisea possess ultrasmall nuclear genomes, the smallest known among angiosperms, and some have been found to have chromosomes of diminutive size, which may explain why chromosome numbers and karyotypes are not known for the majority of species of the genus. However, other members of the genus do not possess ultrasmall genomes, nor do most taxa studied in related genera of the family or order. This study therefore examined the evolution of genome sizes and chromosome numbers in Genlisea in a phylogenetic context. The correlations of genome size with chromosome number and size, with the phylogeny of the group and with growth forms and habitats were also examined. Methods Nuclear genome sizes were measured from cultivated plant material for a comprehensive sampling of taxa, including nearly half of all species of Genlisea and representing all major lineages. Flow cytometric measurements were conducted in parallel in two laboratories in order to compare the consistency of different methods and controls. Chromosome counts were performed for the majority of taxa, comparing different staining techniques for the ultrasmall chromosomes. Key Results Genome sizes of 15 taxa of Genlisea are presented and interpreted in a phylogenetic context. A high degree of congruence was found between genome size distribution and the major phylogenetic lineages. Ultrasmall genomes with 1C values of <100 Mbp were almost exclusively found in a derived lineage of South American species. The ancestral haploid chromosome number was inferred to be n = 8. Chromosome numbers in Genlisea ranged from 2n = 2x = 16 to 2n = 4x = 32. Ascendant dysploid series (2n = 36, 38) are documented for three derived taxa. The different ploidy levels corresponded to the two subgenera, but were not directly correlated to differences in genome size; the three different karyotype ranges mirrored the different sections of the genus. The smallest known plant genomes were not found in

  9. Artificial silver sulfide Ag2S: Crystal structure and particle size in deposited powders

    NASA Astrophysics Data System (ADS)

    Sadovnikov, S. I.; Gusev, A. I.; Rempel, A. A.

    2015-07-01

    Chemical deposition from aqueous solutions of silver nitrate and sodium sulfide was used for synthesis of coarse-crystalline and nanocrystalline silver sulfide Ag2S powders. Sodium citrate was used as a complexing and stabilizing agent during synthesis. X-ray diffraction study shows that synthesized Ag2S powders have monoclinic (space group P21/c) α-Ag2S acanthite type crystal structure. The unit cell of artificial monoclinic silver sulfide Ag2S contains four Ag2S formula units and has the following parameters: a = 0.42264 nm, b = 0.69282 nm, c = 0.95317 nm and β = 125.554°. The size of silver sulfide particles in deposited powders was estimated by the X-ray diffraction and BET methods. By varying the ratio between the concentrations of reagents in the initial reaction mixture it is possible to deposit Ag2S nanoparticles with average size ranging in the interval from ∼1000 to ∼30 nm. Ag2S nanopowders have no deformation distortions of the crystal lattice practically because the microstrains ε in the synthesized powders do not exceed 0.15%. All the Ag2S powders with different particle size have an identical morphology.

  10. Biphase micro/nanometer sized single crystals of organic semiconductors: Control synthesis and their strong phase dependent optoelectronic properties

    NASA Astrophysics Data System (ADS)

    Wang, Chengliang; Liu, Yaling; Wei, Zhongming; Li, Hongxiang; Xu, Wei; Hu, Wenping

    2010-04-01

    The control synthesis of α and β phase micro/nanometer sized single crystals of semiconductor 9,10-bis(phenylethynyl)anthracene were achieved; the device performance of individual α and β phase single crystals showed strong phase dependence; devices of β phase single crystals exhibited very high photoswitch performance (on/off current ratio ˜6×103, one of the highest values reported for organic materials), and those of α phase displayed high field-effect performance.

  11. Systems code assessment of innovations, major design drivers, and minimum sizes of INTOR (International Tokamak Reactor) and ETR-like designs

    SciTech Connect

    Galambos, J.D.; Peng, Y.K.M.; Strickler, D.J.; Reid, R.L.

    1987-10-01

    System studies of next-generation superconducting tokamaks are presented here. These studies include examining design changes suggested for the International Tokamak Reactor (INTOR) as a means of reducing the size and simplifying the device and assessing the impact of a series of more aggressive design assumptions suggested in recent Engineering Test Reactor (ETR) studies. Also, a set of candidate design points offering small machines (major radius = 4 m) with a relatively conservative mix of design assumptions is proposed. Some of the design assumptions found to have a major effect on the minimum size are TF coil current density, noninductive current drive, plasma elongation and edge q, plasma temperature for current drive, maximum allowable plasma beta, the minimum required wall load, and assumptions on fixed radial dimensions such as shield thickness, gaps, and plasma scrapeoff. Some design assumptions with less impact on the device size are the OH coil current density, PF configuration (limiter/divertor), and plasma current level. 22 refs., 5 figs., 6 tabs.

  12. Nano-sized fine droplets of liquid crystals for optical application

    SciTech Connect

    Matsumoto, Shiro; Houlbert, M.; Hayashi, Takayoshi; Kubodera, Kenichi

    1997-09-01

    Nano-sized fine droplets of liquid crystal (LC) were obtained by phase separation of nematic LC in UV curing polymer. The polymer composite had a high transparency in the infrared region. The fine droplets responded to an electric field causing a change in birefringence. Output power change was brought about by the generated retardation between two polarizations, parallel and perpendicular to the applied electric field. This differs from the composite containing much larger droplets, where output depends on the degree of scattering. The birefringence changed by 0.001 at the applied voltage of 7.5 V/{micro}m.

  13. Minimum wound size for clotting: flowing blood coagulates on a single collagen fiber presenting tissue factor and von Willebrand factor.

    PubMed

    Zhu, Shu; Tomaiuolo, Maurizio; Diamond, Scott L

    2016-08-01

    It is unknown if a lower size limit exists for human blood coagulation under flow over physiological vessel wall triggers as small as a single collagen fiber. Prior determinations of the smallest sized surface stimuli necessary for clotting of human blood, defined as the patch size threshold, have not deployed whole blood, hemodynamic flow, and platelet adhesive stimuli. For whole blood perfused in microfluidic devices, we report that steady venous flow (wall shear rate, 100 s(-1)) was sufficient to drive platelet deposition on 20 micron long zones of collagen fibers or on a single fiber. With tissue factor (TF)-coated collagen, flowing blood generated robust platelet deposits, platelet-localized thrombin, and fibrin on a single collagen fiber, thus demonstrating the absence of a physiological patch size threshold under venous flow. In contrast, at arterial wall shear rate (1000 s(-1)) with TF present, essentially no platelet or fibrin deposition occurred on 20 micron collagen zones or on a single collagen fiber, demonstrating a patch threshold, which was overcome by pre-coating the collagen with von Willebrand factor (vWF). For venous flows, human blood can clot on one of the smallest biological units of a single collagen fiber presenting TF. For arterial flows, vWF together with TF allows human blood to generate thrombin and fibrin on a patch stimulus as limited as a single collagen fiber. vWF-dependent platelet adhesion represents a particle-based sensing mechanism of micron-scale stimuli that then allows amplification of the molecular components of TF-driven thrombin and fibrin production under arterial flow. PMID:27339024

  14. A probabilistic explanation for the size-effect in crystal plasticity

    NASA Astrophysics Data System (ADS)

    Derlet, P. M.; Maaß, R.

    2015-06-01

    In this work, the well-known power-law relation between strength and sample size, d-n, is derived from the knowledge that a dislocation network exhibits scale-free behaviour and the extreme value statistical properties of an arbitrary distribution of critical stresses. This approach yields n = (τ + 1) / (α + 1), where α reflects the leading order algebraic exponent of the low-stress regime of the critical stress distribution and τ is the scaling exponent for intermittent plastic strain activity. This quite general derivation supports the experimental observation that the size effect paradigm is applicable to a wide range of materials, differing in crystal structure, internal microstructure and external sample geometry.

  15. Size-fraction partitioning of community gene transcription and nitrogen metabolism in a marine oxygen minimum zone.

    PubMed

    Ganesh, Sangita; Bristow, Laura A; Larsen, Morten; Sarode, Neha; Thamdrup, Bo; Stewart, Frank J

    2015-12-01

    The genetic composition of marine microbial communities varies at the microscale between particle-associated (PA; >1.6 μm) and free-living (FL; 0.2-1.6 μm) niches. It remains unclear, however, how metabolic activities differ between PA and FL fractions. We combined rate measurements with metatranscriptomics to quantify PA and FL microbial activity in the oxygen minimum zone (OMZ) of the Eastern Tropical North Pacific, focusing on dissimilatory processes of the nitrogen (N) cycle. Bacterial gene counts were 8- to 15-fold higher in the FL compared with the PA fraction. However, rates of all measured N cycle processes, excluding ammonia oxidation, declined significantly following particle (>1.6 μm) removal. Without particles, rates of nitrate reduction to nitrite (1.5-9.4nMNd(-1)) fell to zero and N2 production by denitrification (0.5-1.7nMNd(-1)) and anammox (0.3-1.9nMNd(-1)) declined by 53-85%. The proportional representation of major microbial taxa and N cycle gene transcripts in metatranscriptomes followed fraction-specific trends. Transcripts encoding nitrate reductase were uniform among PA and FL fractions, whereas anammox-associated transcripts were proportionately enriched up to 15-fold in the FL fraction. In contrast, transcripts encoding enzymes for N2O and N2 production by denitrification were enriched up to 28-fold in PA samples. These patterns suggest that the majority of N cycle activity, excluding N2O and N2 production by denitrification, is confined to a FL majority that is critically dependent on access to particles, likely as a source of organic carbon and inorganic N. Variable particle distributions may drive heterogeneity in N cycle activity and gene expression in OMZs. PMID:25848875

  16. Observation of nanometer-sized crystalline grooves in as-grown β-Ga2O3 single crystals

    NASA Astrophysics Data System (ADS)

    Hanada, Kenji; Moribayashi, Tomoya; Uematsu, Takumi; Masuya, Satoshi; Koshi, Kimiyoshi; Sasaki, Kohei; Kuramata, Akito; Ueda, Osamu; Kasu, Makoto

    2016-03-01

    On the surface of as-grown β-Ga2O3 single crystals that are cut and polished, we found nanometer-sized grooves elongated in the [001] direction. We confirmed that these grooves terminate within the crystals in the [010] direction. This proves that the grooves are different from micropipes penetrating crystals. Their typical length and width are 50-1200 nm in the [001] direction and ˜40 nm in the [100] direction, respectively. The grooves tend to form an array in the [001] direction. The type of nanometer-sized grooves should be essentially different from etch pits.

  17. Radiation damage in a micron-sized protein crystal studied via reciprocal space mapping and Bragg coherent diffractive imaging

    DOE PAGESBeta

    Coughlan, H. D.; Darmanin, C.; Phillips, N. W.; Hofmann, F.; Clark, J. N.; Harder, R. J.; Vine, D. J.; Abbey, B.

    2015-04-29

    For laboratory and synchrotron based X-ray sources, radiation damage has posed a significant barrier to obtaining high-resolution structural data from biological macromolecules. The problem is particularly acute for micron-sized crystals where the weaker signal often necessitates the use of higher intensity beams to obtain the relevant data. Here, we employ a combination of techniques, including Bragg coherent diffractive imaging to characterise the radiation induced damage in a micron-sized protein crystal over time. The approach we adopt here could help screen for potential protein crystal candidates for measurement at X-ray free election laser sources.

  18. Radiation damage in a micron-sized protein crystal studied via reciprocal space mapping and Bragg coherent diffractive imaging

    PubMed Central

    Coughlan, H. D.; Darmanin, C.; Phillips, N. W.; Hofmann, F.; Clark, J. N.; Harder, R. J.; Vine, D. J.; Abbey, B.

    2015-01-01

    For laboratory and synchrotron based X-ray sources, radiation damage has posed a significant barrier to obtaining high-resolution structural data from biological macromolecules. The problem is particularly acute for micron-sized crystals where the weaker signal often necessitates the use of higher intensity beams to obtain the relevant data. Here, we employ a combination of techniques, including Bragg coherent diffractive imaging to characterise the radiation induced damage in a micron-sized protein crystal over time. The approach we adopt here could help screen for potential protein crystal candidates for measurement at X-ray free election laser sources. PMID:26798804

  19. Crystal size distributions of plagioclase in lavas from the July-August 2001 Mount Etna eruption

    NASA Astrophysics Data System (ADS)

    Fornaciai, Alessandro; Perinelli, Cristina; Armienti, Pietro; Favalli, Massimiliano

    2015-08-01

    During the 2001 eruption of Mount Etna, two independent vent systems simultaneously erupted two different lavas. The Upper Vents system (UV), opened between 3100 and 2650 m a.s.l., emitted products that are markedly porphyritic and rich in plagioclase, while the Lower Vents system (LV), opened at 2100 and 2550 m a.s.l., emitted products that are sparsely porphyritic with scarce plagioclase. In this study, the crystal size distributions (CSDs) of plagioclase were measured for a series of 14 samples collected from all the main flows of the 2001 eruption. The coefficient of R 2 determination was used to evaluate the goodness of fit of linear models to the CSDs, and the results are represented as a grid of R 2 values by using a numerical code developed ad hoc. R 2 diagrams suggest that the 2001 products can be separated into two main groups with slightly different characteristics: plagioclase CSDs from the UVs can be modeled by three straight lines with different slopes while the plagioclase CSDs from the LVs are largely concave. We have interpreted the CSDs of the UVs as representing three different populations of plagioclases: (i) the large phenocrysts (type I), which started to crystallize at lower cooling rate in a deep reservoir from 13 to 8 months before eruption onset; (ii) the phenocrysts (type II), which crystallized largely during continuous degassing in a shallow reservoir; and (iii) the microlites, which crystallized during magma ascent immediately prior to the eruption. The plagioclase CSD curves for the LVs lava are interpreted to reflect strong and rapid changes in undercooling induced by strong and sudden degassing.

  20. High-efficiency space-based software radio architectures & algorithms (a minimum size, weight, and power TeraOps processor)

    SciTech Connect

    Dunham, Mark Edward; Baker, Zachary K; Stettler, Matthew W; Pigue, Michael J; Schmierer, Eric N; Power, John F; Graham, Paul S

    2009-01-01

    Los Alamos has recently completed the latest in a series of Reconfigurable Software Radios, which incorporates several key innovations in both hardware design and algorithms. Due to our focus on satellite applications, each design must extract the best size, weight, and power performance possible from the ensemble of Commodity Off-the-Shelf (COTS) parts available at the time of design. In this case we have achieved 1 TeraOps/second signal processing on a 1920 Megabit/second datastream, while using only 53 Watts mains power, 5.5 kg, and 3 liters. This processing capability enables very advanced algorithms such as our wideband RF compression scheme to operate remotely, allowing network bandwidth constrained applications to deliver previously unattainable performance.

  1. Crystallization Behavior of Amorphous Si3N4 and Particle Size Control of the Crystallized α-Si3N4.

    PubMed

    Chung, Yong-Kwon; Kim, Shin-A; Koo, Jae-Hong; Oh, Hyeon-Cheol; Chi, Eun-Ok; Hahn, Jee-Hyun; Park, Chan

    2016-05-01

    Amorphous silicon nitride powder prepared by low-temperature vapor-phase reaction was heat treated at various temperatures for different periods of time to examine the crystallization behavior. The effects of the heat-treatment temperature and duration on the degree of crystallization were investigated along with the effect of the heat-up rate on the particle size, and its distribution, of the crystallized α-phase silicon nitride powder. A phase transition from amorphous to α-phase occurred at a temperature above 1400 degrees C. The crystallization. process was completed after heat treatment at 1500 degrees C for 3 h or at 1550 degrees C for 1 h. The crystallization process starts at the surface of the amorphous particle: while the outer regions of the particle become crystalline, the inner part remains amorphous. The re-arrangement of the Si and N atoms on the surface of the amorphous particle leads to the formation of hexagonal crystals that are separated from the host amorphous particle. The particle size and size distribution can be controlled by varying the heat-treatment profile (namely, the heat-treatment temperature, heating rate, and heating duration at the specified temperature), which can be used to control the relative extent of the nucleation and growth. The completion of most of the nucleation process by lowering the heat-up rate can be used to achieve a singlet particle size distribution. Bimodal particle size distribution can be achieved by fast heat-up during the crystallization process. PMID:27483939

  2. Influence of particle aspect ratio on the midinfrared extinction spectra of wavelength-sized ice crystals.

    PubMed

    Wagner, Robert; Benz, Stefan; Möhler, Ottmar; Saathoff, Harald; Schnaiter, Martin; Leisner, Thomas

    2007-12-20

    We have used the T-matrix method and the discrete dipole approximation to compute the midinfrared extinction cross-sections (4500-800 cm(-1)) of randomly oriented circular ice cylinders for aspect ratios extending up to 10 for oblate and down to 1/6 for prolate particle shapes. Equal-volume sphere diameters ranged from 0.1 to 10 microm for both particle classes. A high degree of particle asphericity provokes a strong distortion of the spectral habitus compared to the extinction spectrum of compactly shaped ice crystals with an aspect ratio around 1. The magnitude and the sign (increase or diminution) of the shape-related changes in both the absorption and the scattering cross-sections crucially depend on the particle size and the values for the real and imaginary part of the complex refractive index. When increasing the particle asphericity for a given equal-volume sphere diameter, the values for the overall extinction cross-sections may change in opposite directions for different parts of the spectrum. We have applied our calculations to the analysis of recent expansion cooling experiments on the formation of cirrus clouds, performed in the large coolable aerosol and cloud chamber AIDA of Forschungszentrum Karlsruhe at a temperature of 210 K. Depending on the nature of the seed particles and the temperature and relative humidity characteristics during the expansion, ice crystals of various shapes and aspect ratios could be produced. For a particular expansion experiment, using Illite mineral dust particles coated with a layer of secondary organic matter as seed aerosol, we have clearly detected the spectral signatures characteristic of strongly aspherical ice crystal habits in the recorded infrared extinction spectra. We demonstrate that the number size distributions and total number concentrations of the ice particles that were generated in this expansion run can only be accurately derived from the recorded infrared spectra when employing aspect ratios as high as

  3. Radiation damage in protein crystals is reduced with a micron-sized X-ray beam

    PubMed Central

    Sanishvili, Ruslan; Yoder, Derek W.; Pothineni, Sudhir Babu; Rosenbaum, Gerd; Xu, Shenglan; Vogt, Stefan; Stepanov, Sergey; Makarov, Oleg A.; Corcoran, Stephen; Benn, Richard; Nagarajan, Venugopalan; Smith, Janet L.; Fischetti, Robert F.

    2011-01-01

    Radiation damage is a major limitation in crystallography of biological macromolecules, even for cryocooled samples, and is particularly acute in microdiffraction. For the X-ray energies most commonly used for protein crystallography at synchrotron sources, photoelectrons are the predominant source of radiation damage. If the beam size is small relative to the photoelectron path length, then the photoelectron may escape the beam footprint, resulting in less damage in the illuminated volume. Thus, it may be possible to exploit this phenomenon to reduce radiation-induced damage during data measurement for techniques such as diffraction, spectroscopy, and imaging that use X-rays to probe both crystalline and noncrystalline biological samples. In a systematic and direct experimental demonstration of reduced radiation damage in protein crystals with small beams, damage was measured as a function of micron-sized X-ray beams of decreasing dimensions. The damage rate normalized for dose was reduced by a factor of three from the largest (15.6 μm) to the smallest (0.84 μm) X-ray beam used. Radiation-induced damage to protein crystals was also mapped parallel and perpendicular to the polarization direction of an incident 1-μm X-ray beam. Damage was greatest at the beam center and decreased monotonically to zero at a distance of about 4 μm, establishing the range of photoelectrons. The observed damage is less anisotropic than photoelectron emission probability, consistent with photoelectron trajectory simulations. These experimental results provide the basis for data collection protocols to mitigate with micron-sized X-ray beams the effects of radiation damage. PMID:21444772

  4. Dislocation arrangement in small crystal volumes determines power-law size dependence of yield strength

    NASA Astrophysics Data System (ADS)

    Gu, R.; Ngan, A. H. W.

    2013-06-01

    It is by now well-known that micron-sized metallic crystals exhibit a smaller-being-stronger size effect: the yield strength σ varies with specimen size D approximately as a power-law σ˜D-m, and the exponent m has been found to vary within a range of ˜0.3-1.0 for different metals. However, little is known about why such a power-law comes into play, and what determines the actual value of the exponent m involved. This work shows that if the yield strength is determined by the Taylor interaction mechanism within the initial dislocation network, then for the size dependence of strength to be of the power-law relation observed, it is necessary for the mesh lengths L of the dislocation network to be power-law distributed, i.e. p(L)˜L-q. In such a case, the exponent m of the size effect is predicted to be inversely proportional to the sum of q the exponent of the mesh-length distribution and n the exponent of the dislocation velocity vs. stress law. To verify these predictions, compression experiments on aluminum micro-pillars with different pre-strains from 0% to 15% were carried out. The different pre-strains led to different initial dislocation networks, as well as different exponent m in the size dependence of strength. Box-counting analyses of transmission electron micrographs of the initial dislocation networks showed that the 2-D projected dislocation patterns were approximate fractals. On increasing pre-strain, the exponent m for the size dependence of strength was found to decrease while the fractal dimension of the initial dislocation patterns increased, thus verifying the inverse relationship between the two quantities. These findings show that the commonly observed power-law scaling of strength with size is due to an approximate power-law distribution of the initial dislocation mesh lengths, which also appears to be a robust feature in deformed metals. Furthermore, for a given metal, it is the exponent q of the initial mesh-length distribution which

  5. Sensitivity of cirrus cloud radiative properties to ice crystal size and shape in general circulation model simulations

    SciTech Connect

    Mitchell, D.L.; Kristjansson, J.E.; Newman, M.J.

    1995-04-01

    Recent research has shown that the radiative properties of cirrus clouds (i.e., optical depth, albedo, emissivity) depend on the shapes and sizes of ice crystals. For instance, the cloud albedo may vary by a factor of two, depending on whether hexagonal columns or bullet rosette ice crystals are assumed for a given ice water path (IWP). This variance occurs primarily because, at sizes characteristic of cirrus clouds, bullet rosettes have less mass than columns of the same size. However, their projected areas may be comparable. Thus, for a given IWP and mean cloud ice particle size, the optical depth will be considerably greater for rosettes, since many more rosettes are required to account for the IWP than are columns. The same could be said of hexagonal plates and columns, with plates exhibiting the greater optical depth. Satellite information suggests that the albedos of tropical cirrus clouds are greater than those of midlatitude cirrus, with albedos as high as 60%-80%. The reasons for this are not understood, but might be attributed in part to differences in ice particle size and shape. For instance, in the tropical western Pacific, ice crystal size distributions in cirrus near the tropopause exhibited median mass dimensions (D{sub m} around 30 {mu}m) and contained planar polycrystals. Very small ice crystals (typically 10 {mu}m, often ranging from about 2 {mu}m - 100 {mu}m) of indeterminate shape were sampled in anvil cirrus by an ice particle replicator in this region during the Tropical Ocean Global Atmosphere (TOGA) Coupled Ocean Atmosphere Response Experiment (COARE). If fewer columnar ice crystals were present in tropical versus midlatitude cirrus and/or sizes were smaller, tropical cirrus should exhibit greater size distribution projected area, producing greater optical depth, albedo, and emissivity for the same IWP. Smaller crystal sizes would also promote higher albedos via enhanced backscattering.

  6. The origin of felsic microgranitoid enclaves: Insights from plagioclase crystal size distributions and thermodynamic models

    NASA Astrophysics Data System (ADS)

    Alves, Adriana; Pereira, Giovanna de Souza; Janasi, Valdecir de Assis; Higgins, Michael; Polo, Liza Angelica; Juriaans, Orlando Stanley; Ribeiro, Bruno Vieira

    2015-12-01

    Magma mixing is widely recognized in contemporary petrology as one of the primary igneous processes. Microgranitoid enclaves (MEs) are considered to be remnants of such mixing processes, and the term has a well-established genetic implication. However, microgranitoid enclaves span a wide range of compositions, and felsic varieties are also frequently reported. Nd-Sr isotope and textural data from felsic microgranitoid enclaves (FMEs), mafic microgranitoid enclaves (MMEs) and host granites from the Salto pluton, Itu Granitic Province, show that the cm-sized MMEs are dioritic, have medium-grained igneous textures and xenocrysts of alkali feldspar and quartz. The FMEs are cm- to meter-sized, have spheric shapes, show corrugated contacts with the host granites, and have resorbed feldspars and deformed quartz crystals interpreted as xenocrysts set in a fine-grained groundmass. Compared to the host granites, both MME and FME samples have increased FeO, MgO, TiO2, P2O5 and Zr contents, but their Sr and Nd isotope signatures are identical: FME 87Sr/86Sri = 0.7088-0.7063, εNdi = - 10.0 to - 10.2; MME 87Sr/86Sri = 0.7070, εNdi = - 10.5; host granite 87Sr/86Sri 0.7056-0.7060, εNdi = - 10.2 to - 10.3. These indicate that the enclaves derive from a similar source, although the melts from which they formed were probably hotter and chemically more primitive than their host granites. Crystal size distributions (CSDs) of plagioclase in samples drilled from rinds and cores of three FMEs show that the rind samples are systematically finer-grained than the samples from the cores, which indicates that the FMEs cooled inwards and contradict interpretations that the FMEs are autoliths. Thermal modeling suggests that a slightly more primitive, hotter magma would be thermally equilibrated with an evolved resident melt within weeks after mixing/mingling. Upon thermal equilibrium, the FMEs would have an increased crystal cargo, and the resulting touching framework would impart a solid

  7. Simple thermal treatment for the size control of pore arrays in a polystyrene colloidal crystal films

    NASA Astrophysics Data System (ADS)

    Jamiolkowski, Ryan M.; Fiorenza, Shane A.; Chen, Kevin; Tate, Alyssa M.; Pfeil, Shawn H.; Goldman, Yale E.

    Nanosphere Lithography (NSL) offers an attractive route to fabricating periodic structures with nanoscale features, without e-beam or deep UV lithography. In particular, it is uniquely suited to the low cost fabrication of large repeated arrays pores or pillars created by taking advantage of the interstitial spaces in close-packed monolayers of nano to micro-scale beads. However pore size, shape, and spacing cannot be controlled independently. We present both a robust method for producing large, approximately 1 cm2, hexagonally close packed monolayer films of 1 micron diameter polystyrene beads on glass substrates, and thermal treatment of these films near the glass temperature, Tg, of polystyrene to modify the pore size. This builds on earlier work showing that pore size can be modified for colloidal crystals formed at a liquid gas interface [2]. These processes promise a simple, reproducible, and low cost route to periodic pore arrays for nano-photonic applications such as zero mode waveguides (ZMWs) Funding: F30 AI114187 (RMJ), R01-GM080376 (YEG).

  8. Effect of the Inhomogeneity of Ice Crystals on Retrieving Ice Cloud Optical Thickness and Effective Particle Size

    NASA Technical Reports Server (NTRS)

    Xie, Yu; Minnis, Patrick; Hu, Yong X.; Kattawar, George W.; Yang, Ping

    2008-01-01

    Spherical or spheroidal air bubbles are generally trapped in the formation of rapidly growing ice crystals. In this study the single-scattering properties of inhomogeneous ice crystals containing air bubbles are investigated. Specifically, a computational model based on an improved geometric-optics method (IGOM) has been developed to simulate the scattering of light by randomly oriented hexagonal ice crystals containing spherical or spheroidal air bubbles. A combination of the ray-tracing technique and the Monte Carlo method is used. The effect of the air bubbles within ice crystals is to smooth the phase functions, diminish the 22deg and 46deg halo peaks, and substantially reduce the backscatter relative to bubble-free particles. These features vary with the number, sizes, locations and shapes of the air bubbles within ice crystals. Moreover, the asymmetry factors of inhomogeneous ice crystals decrease as the volume of air bubbles increases. Cloud reflectance lookup tables were generated at wavelengths 0.65 m and 2.13 m with different air-bubble conditions to examine the impact of the bubbles on retrieving ice cloud optical thickness and effective particle size. The reflectances simulated for inhomogeneous ice crystals are slightly larger than those computed for homogenous ice crystals at a wavelength of 0.65 microns. Thus, the retrieved cloud optical thicknesses are reduced by employing inhomogeneous ice cloud models. At a wavelength of 2.13 microns, including air bubbles in ice cloud models may also increase the reflectance. This effect implies that the retrieved effective particle sizes for inhomogeneous ice crystals are larger than those retrieved for homogeneous ice crystals, particularly, in the case of large air bubbles.

  9. Ion Size Effect in Glow Peak Temperature in Binary Mixed Crystals Doped with Divalente Europium

    NASA Astrophysics Data System (ADS)

    Rodriguez-Mijangos, Ricardo; Perez-Salas, Raul

    2006-03-01

    Thermoluminiscence measurements at room temperature of ``beta'' irradiated divalent Europium doped binary mixed alkali halides with KCl and KBr components at several concentrations x in molar fraction. The experiments have been carried out to identify the effect of composition of glow peaks. A typical glow peak has been distinguished for each composition. A linear dependence of its temperature on the composition x has been found. This is associated with the size change of ions Cl and Br. Initial comparative cathodoluminiscent measurement was carried out irradiating a single sample with electrons in an electron microscopy using a 30 KV voltage. With the present results is speculated the behavior of the mixed binary crystals with components KCl and RbCl, doped with divalent Europium.

  10. Effect of crystal size on physical and catalytic properties of ZSM-5 type zeolites

    NASA Astrophysics Data System (ADS)

    Voogd, P.

    1991-09-01

    Diffusion of C6-alkanes in zeolite ZSM-5 and its aluminum free variant silicate-1 receives the greatest attention in the thesis. A physical property of zeolite like the ability to sorb, in particular, nonpolar compounds, was utilized in studying hydrocarbon diffusion by performing adsorption and desorption experiments. The diffusional behavior of the zeolite ZSM-5 and of aluminated silicate-1 at catalytically relevant temperatures was studied by way of a catalytic property of the zeolite. Descriptions of physical studies on nitrogen sorption in ZSM 5 type zeolites and of catalytic studies on the conversion of ethanol to hydrocarbons complete the thesis which tries to give a better understanding of adsorptive, diffusional, and catalytic behavior by describing experiments in which only one parameter has been varied, the zeolite crystal size. Discussions and conclusions are directed towards the industrial application of zeolite ZSM-5, as a catalyst.

  11. Surface plasmon resonance biosensor based on large size square-lattice photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Bing, Pibin; Li, Zhongyang; Yuan, Sheng; Yao, Jianquan; Lu, Ying

    2016-04-01

    A surface plasmon resonance biosensor based on large size square-lattice photonic crystal fiber has been designed and simulated by finite element method. The square-lattice airholes are first coated with a calcium fluoride layer to provide mode confinement, then a nanoscale gold layer is deposited to excite the plasmon mode, and finally, the sample is infiltrated into the holes. The numerical results reveal that the resonance properties are easily affected by many parameters. The refractive index resolution of corresponding sensor can reach 4.3 × 10-6 RIU when the optimum parameters are set as the radius of curvature of the airhole r = 2 μm, the thickness of the core struts c = 200 nm, the auxiliary dielectric layer s = 1 μm, and the gold film d = 40 nm. In addition, the effective area and nonlinear coefficient are calculated.

  12. Growth of large size <1 1 0> benzophenone crystal using uniaxially solution-crystallization method of Sankaranarayanan Ramasamy (SR)

    NASA Astrophysics Data System (ADS)

    Sankaranarayanan, K.

    2005-10-01

    <1 1 0> benzophenone single crystal of diameter 60 mm and length 50 mm was successfully grown by SR method using a seed fixed at the bottom of the ampoule. The obtained cylindrical morphology, solute-crystal conversion efficiency of 100%, growth at room temperature, less-sophisticated experimental set-up employed, growth in a chosen direction, possibility for avoidance of microbial growth and ease in scaling up of diameter are the vital advantages of this technique towards the growth of phase-matched SHG crystal for device application. The grown benzophenone crystal was characterized by XRD, phase-matching study and laser damage threshold measurement. The results evidence the suitability of this method for unidirectional growth of bulk single crystal.

  13. CrystalMoM: a tool for modeling the evolution of Crystals Size Distributions in magmas with the Method of Moments

    NASA Astrophysics Data System (ADS)

    Colucci, Simone; de'Michieli Vitturi, Mattia; Landi, Patrizia

    2016-04-01

    It is well known that nucleation and growth of crystals play a fundamental role in controlling magma ascent dynamics and eruptive behavior. Size- and shape-distribution of crystal populations can affect mixture viscosity, causing, potentially, transitions between effusive and explosive eruptions. Furthermore, volcanic samples are usually characterized in terms of Crystal Size Distribution (CSD), which provide a valuable insight into the physical processes that led to the observed distributions. For example, a large average size can be representative of a slow magma ascent, and a bimodal CSD may indicate two events of nucleation, determined by two degassing events within the conduit. The Method of Moments (MoM), well established in the field of chemical engineering, represents a mesoscopic modeling approach that rigorously tracks the polydispersity by considering the evolution in time and space of integral parameters characterizing the distribution, the moments, by solving their transport differential-integral equations. One important advantage of this approach is that the moments of the distribution correspond to quantities that have meaningful physical interpretations and are directly measurable in natural eruptive products, as well as in experimental samples. For example, when the CSD is defined by the number of particles of size D per unit volume of the magmatic mixture, the zeroth moment gives the total number of crystals, the third moment gives the crystal volume fraction in the magmatic mixture and ratios between successive moments provide different ways to evaluate average crystal length. Tracking these quantities, instead of volume fraction only, will allow using, for example, more accurate viscosity models in numerical code for magma ascent. Here we adopted, for the first time, a quadrature based method of moments to track the temporal evolution of CSD in a magmatic mixture and we verified and calibrated the model again experimental data. We also show how

  14. Effects of initial crystal size of diamond powder on surface residual stress and morphology in polycrystalline diamond (PCD) layer

    NASA Astrophysics Data System (ADS)

    Jia, HongSheng; Jia, XiaoPeng; Xu, Yue; Wan, LianRu; Jie, KaiKai; Ma, HongAn

    2011-01-01

    Polycrystalline diamond compacts (PDC) were synthesized using diamond powder of average crystal size 3-20 μm by the Ni70Mn25Co5 alloy infiltration technique at high temperature and high pressure (HPHT). The surface residual stress of polycrystalline diamond (PCD) layer was measured using micro-Raman spectroscopy with hydrostatic stress model and X-ray diffraction (XRD). Measurements of the stress levels of PCDs show that the residual compressive stresses range from 0.12 to 0.22 GPa, which increase with the crystal size of diamond. Scanning electron microscopy (SEM) was used to observe the morphology of initial diamond grains and PCD cross-section. The results indicate that PCD has a dense and interlaced microstructure with diamond-diamond (D-D) direct bonding. And the smaller the crystal size of diamond, the better the growth of diamond direct bonding and the smaller the binder metal between diamond boundaries will be.

  15. Growth and characterization of large size ADP single crystals and the effect of glycine on their growth and properties

    NASA Astrophysics Data System (ADS)

    Rajesh, P.; Ramasamy, P.

    2015-04-01

    80 × 50 × 50 mm3 size 1 mol% of glycine added ADP single crystals have been grown by ACRT technique. The grown crystals have been subjected to powder XRD, FTIR, UV-Vis, HRXRD, TG/DTA, microhardness, laser damage threshold, piezoelectric, dielectric and SHG studies. The crystallinity and the functional groups are confirmed by powder XRD and FTIR spectroscopy. Good transparency in the entire visible region which is an essential requirement for a nonlinear optical crystal is observed for the grown crystals. The structural perfection of the grown crystal has been analyzed by high resolution X-ray diffraction rocking curve measurements. Compared to pure ADP crystal higher hardness was observed from the Vickers hardness studies. Shift in the decomposition temperature has been observed from TG/DTA. Dielectric constant and dielectric loss were measured for the grown crystals for different frequencies and temperatures. Significant piezoelectric charge coefficient has been noted for the glycine doped crystals. Laser damage threshold value has been determined using Nd:YAG laser. Powder SHG measurements show the suitability of the ingot for nonlinear optical applications.

  16. Quantifying solubility enhancement due to particle size reduction and crystal habit modification: case study of acetyl salicylic acid.

    PubMed

    Hammond, Robert B; Pencheva, Klimentina; Roberts, Kevin J; Auffret, Tony

    2007-08-01

    The poor solubility of potential drug molecules is a significant problem in the design of pharmaceutical formulations. It is well known, however, that the solubility of crystalline materials is enhanced when the particle size is reduced to submicron levels and this factor can be expected to enhance drug product bioavailability. Direct estimation of solubility enhancement, as calculated via the Gibbs-Thompson relationship, demands reasonably accurate values for the particle/solution interfacial tension and, in particular, its anisotropy with respect to the crystal product's habit and morphology. In this article, an improved, more molecule-centered, approach is presented towards the calculation of solubility enhancement factors in which molecular modeling techniques are applied, and the effects associated with both crystal habit modification and solvent choice are examined. A case study for facetted, acetyl salicylic acid (aspirin) crystals in equilibrium with saturated aqueous ethanol solution reveals that their solubility will be enhanced in the range (7-58%) for a crystal size of 0.02 microm, with significantly higher enhancement for crystal morphologies in which the hydrophobic crystal faces are more predominant than the hydrophilic faces and for solvents in which the solubility is smaller. PMID:17323349

  17. Synthetic Hemozoin (β-Hematin) Crystals Nucleate at the Surface of Neutral Lipid Droplets that Control Their Sizes

    PubMed Central

    Ambele, Melvin A.; Sewell, B. Trevor; Cummings, Franscious R.; Smith, Peter J.; Egan, Timothy J.

    2013-01-01

    Emulsions of monopalmitoylglycerol (MPG) and of a neutral lipid blend (NLB), consisting of MPG, monostearoylglycerol, dipalmitoylglycerol, dioleoylglycerol and dilineoylglycerol (4:2:1:1:1), the composition associated with hemozoin from the malaria parasite Plasmodium falciparum, have been used to mediate the formation of β-hematin microcrystals. Transmission electron microscopy (TEM), electron diffraction and electron spectroscopic imaging/electron energy loss spectroscopy (ESI/EELS) have been used to characterize both the lipid emulsion and β-hematin crystals. The latter have been compared with β-hematin formed at a pentanol/aqueous interface and with hemozoin both within P. falciparum parasites and extracted from the parasites. When lipid and ferriprotoporphyrin IX solutions in 1:9 v/v acetone/methanol were thoroughly pre-mixed either using an extruder or ultrasound, β-hematin crystals were found formed in intimate association with the lipid droplets. These crystals resembled hemozoin crystals, with prominent {100} faces. Lattice fringes in TEM indicated that these faces made contact with the lipid surface. The average length of these crystals was 0.62 times the average diameter of NLB droplets and their size distributions were statistically equivalent after 10 min incubation, suggesting that the lipid droplets also controlled the sizes of the crystals. This most closely resembles hemozoin formation in the helminth worm Schistosoma mansoni, while in P. falciparum, crystal formation appears to be associated with the much more gently curved digestive vacuole membrane which apparently leads to formation of much larger hemozoin crystals, similar to those formed at the flat pentanol-water interface. PMID:24244110

  18. Thermal and structural behavior of milk fat. 3. Influence of cooling rate and droplet size on cream crystallization.

    PubMed

    Lopez, Christelle; Bourgaux, Claudie; Lesieur, Pierre; Bernadou, Sophie; Keller, Gérard; Ollivon, Michel

    2002-10-01

    , demonstrating the usefulness of the small-angle XRD technique. Reconstituted emulsions homogenized under different pressures are used to determine the influence of droplet size on crystallization. The decrease of droplet size induces (i) a higher supercooling/supersaturation and (ii) a higher disorder and/or a smaller size of TG crystals within the emulsion droplets. At the supramolecular scale, polarized light microscopy shows that various cooling rates applied in situ using a temperature-controlled stage directly influence crystal sizes and their type of organization within milk fat globules. The faster the cooling rate, the smaller the size of the crystals within the globules. PMID:12702426

  19. Rapid Z-plate seed regeneration of large size KDP crystal from solution

    NASA Astrophysics Data System (ADS)

    Li, Guohui

    2008-01-01

    Regeneration process of a 330×330×20 mm 3 Z-plate seed is carried out in a 1.5 metric tonnage volume crystallizer that placed in a water bath of temperature fluctuation less than ±0.02 °C within 10 days. The surface of the whole crystal was restored by the formation of a box-like structure filled with growth solution, and then the transparent layer of perfect tetragonal KDP crystal without inclusions, crack and milky regions just like those produced by traditional slow cooling technique can be grown from solution. After the regeneration, the height of KDP crystal is merely 0.5 times the side of plate seed. We found it that the optical transmission and laser damage threshold of the KDP crystals we grown are not significantly different from those of KDP crystals grown by traditional method.

  20. Size control of in vitro synthesized magnetite crystals by the MamC protein of Magnetococcus marinus strain MC-1.

    PubMed

    Valverde-Tercedor, C; Montalbán-López, M; Perez-Gonzalez, T; Sanchez-Quesada, M S; Prozorov, T; Pineda-Molina, E; Fernandez-Vivas, M A; Rodriguez-Navarro, A B; Trubitsyn, D; Bazylinski, Dennis A; Jimenez-Lopez, C

    2015-06-01

    Magnetotactic bacteria are a diverse group of prokaryotes that share the unique ability of biomineralizing magnetosomes, which are intracellular, membrane-bounded crystals of either magnetite (Fe3O4) or greigite (Fe3S4). Magnetosome biomineralization is mediated by a number of specific proteins, many of which are localized in the magnetosome membrane, and thus is under strict genetic control. Several studies have partially elucidated the effects of a number of these magnetosome-associated proteins in the control of the size of magnetosome magnetite crystals. However, the effect of MamC, one of the most abundant proteins in the magnetosome membrane, remains unclear. In this present study, magnetite nanoparticles were synthesized inorganically in free-drift experiments at 25 °C in the presence of different concentrations of the iron-binding recombinant proteins MamC and MamCnts (MamC without its first transmembrane segment) from the marine, magnetotactic bacterium Magnetococcus marinus strain MC-1 and three commercial proteins [α-lactalbumin (α-Lac), myoglobin (Myo), and lysozyme (Lyz)]. While no effect was observed on the size of magnetite crystals formed in the presence of the commercial proteins, biomimetic synthesis in the presence of MamC and MamCnts at concentrations of 10-60 μg/mL resulted in the production of larger and more well-developed magnetite crystals (~30-40 nm) compared to those of the control (~20-30 nm; magnetite crystals grown protein-free). Our results demonstrate that MamC plays an important role in the control of the size of magnetite crystals and could be utilized in biomimetic synthesis of magnetite nanocrystals. PMID:25874532

  1. Size-controlled anatase titania single crystals with octahedron-like morphology for dye-sensitized solar cells.

    PubMed

    Shiu, Jia-Wei; Lan, Chi-Ming; Chang, Yu-Cheng; Wu, Hui-Ping; Huang, Wei-Kai; Diau, Eric Wei-Guang

    2012-12-21

    A simple hydrothermal method with titanium tetraisopropoxide (TTIP) as a precursor and triethanolamine (TEOA) as a chelating agent enabled growth in the presence of a base (diethylamine, DEA) of anatase titania nanocrystals (HD1-HD5) of controlled size. DEA played a key role to expedite this growth, for which a biphasic crystal growth mechanism is proposed. The produced single crystals of titania show octahedron-like morphology with sizes in a broad range of 30-400 nm; a typical, extra large, octahedral single crystal (HD5) of length 410 nm and width 260 nm was obtained after repeating a sequential hydrothermal treatment using HD3 and then HD4 as a seed crystal. The nanocrystals of size ~30 nm (HD1) and ~300 nm (HD5) served as active layer and scattering layer, respectively, to fabricate N719-sensitized solar cells. These HD devices showed greater V(OC) than devices of conventional nanoparticle (NP) type; the overall device performance of HD attained an efficiency of 10.2% power conversion at a total film thickness of 28 μm, which is superior to that of a NP-based reference device (η = 9.6%) optimized at a total film thickness of 18-20 μm. According to results obtained from transient photoelectric and charge extraction measurements, this superior performance of HD devices relative to their NP counterparts is due to the more rapid electron transport and greater TiO(2) potential. PMID:23116194

  2. Upconversion, size analysis, and fiber filling of NaYF4: Ho3+, Yb3+ crystals and nanocolloids

    NASA Astrophysics Data System (ADS)

    Patel, Darayas; Lewis, Ashley; Wright, Donald; Velentine, Maucus; Lewis, Danielle; Valentine, Ruben; Sarkisov, Sergey

    2014-03-01

    Nano-colloids and nano-crystals doped with ions of rare-earth elements have recently attracted a lot of attention in the scientific community. This attention is due to unique physical, chemical and optical properties attributed to nanometer size of the particles. They have great potential of being used in applications spanning from new types of lasers, especially blue and UV ones, phosphorous display monitors, optical communications, and fluorescence imaging. In this paper we investigate the near-infrared upconversion luminescence in bulk crystals and nanocolloid filled photonic crystal fiber with ytterbium and holmium co-doped NaYF4 phosphor. The phosphor is prepared by using simple co-precipitation synthetic method. The initially prepared phosphor has very week upconversion fluorescence. The fluorescence significantly increased after the phosphor was annealed at a temperature of 600 °C. Nanocolloids of this phosphor were obtained using 1-propanol as solvent and they were utilized as laser filling medium in photonic crystal fibers. Under 980 nm diode laser excitation very strong upconversion signals were obtained for ytterbium and holmium co-doped phosphor at 541 nm, 646 nm and 751 nm. Pump power emissions, laser ablation and size analysis of the particles was conducted to understand the upconversion mechanisms. The particle sizes of the nanocolloids were analyzed using Atomic Force Microscope and Malvern Zetasizer instrument. The reported nanocolloids are good candidates for fluorescent biosensing applications and also as a new laser filling medium in fiber laser.

  3. Liquid crystal size selection of large-size graphene oxide for size-dependent N-doping and oxygen reduction catalysis.

    PubMed

    Lee, Kyung Eun; Kim, Ji Eun; Maiti, Uday Narayan; Lim, Joonwon; Hwang, Jin Ok; Shim, Jongwon; Oh, Jung Jae; Yun, Taeyeong; Kim, Sang Ouk

    2014-09-23

    Graphene oxide (GO) is aqueous-dispersible oxygenated graphene, which shows colloidal discotic liquid crystallinity. Many properties of GO-based materials, including electrical conductivity and mechanical properties, are limited by the small flake size of GO. Unfortunately, typical sonochemical exfoliation of GO from graphite generally leads to a broad size and shape distribution. Here, we introduce a facile size selection of large-size GO exploiting liquid crystallinity and investigate the size-dependent N-doping and oxygen reduction catalysis. In the biphasic GO dispersion where both isotropic and liquid crystalline phases are equilibrated, large-size GO flakes (>20 μm) are spontaneously concentrated within the liquid crystalline phase. N-Doping and reduction of the size-selected GO exhibit that N-dopant type is highly dependent on GO flake size. Large-size GO demonstrates quaternary dominant N-doping and the lowest onset potential (-0.08 V) for oxygen reduction catalysis, signifying that quaternary N-dopants serve as principal catalytic sites in N-doped graphene. PMID:25145457

  4. Effect of dislocation pile-up on size-dependent yield strength in finite single-crystal micro-samples

    SciTech Connect

    Pan, Bo; Shibutani, Yoji; Zhang, Xu; Shang, Fulin

    2015-07-07

    Recent research has explained that the steeply increasing yield strength in metals depends on decreasing sample size. In this work, we derive a statistical physical model of the yield strength of finite single-crystal micro-pillars that depends on single-ended dislocation pile-up inside the micro-pillars. We show that this size effect can be explained almost completely by considering the stochastic lengths of the dislocation source and the dislocation pile-up length in the single-crystal micro-pillars. The Hall–Petch-type relation holds even in a microscale single-crystal, which is characterized by its dislocation source lengths. Our quantitative conclusions suggest that the number of dislocation sources and pile-ups are significant factors for the size effect. They also indicate that starvation of dislocation sources is another reason for the size effect. Moreover, we investigated the explicit relationship between the stacking fault energy and the dislocation “pile-up” effect inside the sample: materials with low stacking fault energy exhibit an obvious dislocation pile-up effect. Our proposed physical model predicts a sample strength that agrees well with experimental data, and our model can give a more precise prediction than the current single arm source model, especially for materials with low stacking fault energy.

  5. Growth of large size diamond single crystals by plasma assisted chemical vapour deposition: Recent achievements and remaining challenges

    NASA Astrophysics Data System (ADS)

    Tallaire, Alexandre; Achard, Jocelyn; Silva, François; Brinza, Ovidiu; Gicquel, Alix

    2013-02-01

    Diamond is a material with outstanding properties making it particularly suited for high added-value applications such as optical windows, power electronics, radiation detection, quantum information, bio-sensing and many others. Tremendous progresses in its synthesis by microwave plasma assisted chemical vapour deposition have allowed obtaining single crystal optical-grade material with thicknesses of up to a few millimetres. However the requirements in terms of size, purity and crystalline quality are getting more and more difficult to achieve with respect to the forecasted applications, thus pushing the synthesis method to its scientific and technological limits. In this paper, after a short description of the operating principles of the growth technique, the challenges of increasing crystal dimensions both laterally and vertically, decreasing and controlling point and extended defects as well as modulating crystal conductivity by an efficient doping will be detailed before offering some insights into ways to overcome them.

  6. Large size LSO and LYSO crystal scintillators for future high-energy physics and nuclear physics experiments

    NASA Astrophysics Data System (ADS)

    Chen, Jianming; Zhang, Liyuan; Zhu, Ren-yuan

    2007-03-01

    The high energy and nuclear physics community is interested in fast bright heavy crystal scintillators, such as cerium-doped LSO and LYSO. An investigation is being carried out to explore the potential use of the LSO and LYSO crystals in future physics experiments. Optical and scintillation properties, including longitudinal transmittance, emission and excitation spectra, light output, decay kinetics and light response uniformity, were measured for three long (2.5×2.5×20 cm) LSO and LYSO samples from different vendors, and were compared to a long BGO sample of the same size. The degradation of optical and scintillation properties under γ-ray irradiations and the radiation-induced phosphorescence were also measured for two long LYSO samples. Possible applications for a crystal calorimeter in future high energy and nuclear physics experiments are discussed.

  7. Minimum Audible Angles Measured with Simulated Normally-Sized and Oversized Pinnas for Normal-Hearing and Hearing-Impaired Test Subjects.

    PubMed

    Rønne, Filip M; Laugesen, Søren; Jensen, Niels S; Pedersen, Julie H

    2016-01-01

    The human pinna introduces spatial acoustic cues in terms of direction-dependent spectral patterns that shape the incoming sound. These cues are specifically useful for localization in the vertical dimension. Pinna cues exist at frequencies above approximately 5 kHz, a frequency range where people with hearing loss typically have their highest hearing thresholds. Since increased thresholds often are accompanied by reduced frequency resolution, there are good reasons to believe that many people with hearing loss are unable to discriminate these subtle spectral pinna--cue details, even if the relevant frequency region is amplified by hearing aids.One potential solution to this problem is to provide hearing-aid users with artificially enhanced pinna cues-as if they were listening through oversized pinnas. In the present study, it was tested whether test subjects were better at discriminating spectral patterns similar to enlarged-pinna cues. The enlarged-pinna patterns were created by transposing (T) generic normal-sized pinna cues (N) one octave down, or by using the approach (W) suggested by Naylor and Weinrich (System and method for generating auditory spatial cues, United States Patent, 2011). The experiment was cast as a determination of simulated minimum audible angle (MAA) in the median saggital plane. 13 test subjects with sloping hearing loss and 11 normal-hearing test subjects participated. The normal-hearing test subjects showed similar discrimination performance with the T, W, and N-type simulated pinna cues, as expected. However, the results for the hearing-impaired test subjects showed only marginally lower MAAs with the W and T-cues compared to the N-cues, while the overall discrimination thresholds were much higher for the hearing-impaired compared to the normal-hearing test subjects. PMID:27080661

  8. Self-Assembly of Graphene Single Crystals with Uniform Size and Orientation: The First 2D Super-Ordered Structure.

    PubMed

    Zeng, Mengqi; Wang, Lingxiang; Liu, Jinxin; Zhang, Tao; Xue, Haifeng; Xiao, Yao; Qin, Zhihui; Fu, Lei

    2016-06-29

    The challenges facing the rapid developments of highly integrated electronics, photonics, and microelectromechanical systems suggest that effective fabrication technologies are urgently needed to produce ordered structures using components with high performance potential. Inspired by the spontaneous organization of molecular units into ordered structures by noncovalent interactions, we succeed for the first time in synthesizing a two-dimensional superordered structure (2DSOS). As demonstrated by graphene, the 2DSOS was prepared via self-assembly of high-quality graphene single crystals under mutual electrostatic force between the adjacent crystals assisted by airflow-induced hydrodynamic forces at the liquid metal surface. The as-obtained 2DSOS exhibits tunable periodicity in the crystal space and outstanding uniformity in size and orientation. Moreover, the intrinsic property of each building block is preserved. With simplicity, scalability, and continuously adjustable feature size, the presented approach may open new territory for the precise assembly of 2D atomic crystals and facilitate its application in structurally derived integrated systems. PMID:27313075

  9. Genetic variation in eggshell crystal size and orientation is large and these traits are correlated with shell thickness and are associated with eggshell matrix protein markers.

    PubMed

    Dunn, I C; Rodríguez-Navarro, A B; Mcdade, K; Schmutz, M; Preisinger, R; Waddington, D; Wilson, P W; Bain, M M

    2012-08-01

    The size and orientation of calcium carbonate crystals influence the structure and strength of the eggshells of chickens. In this study, estimates of heritability were found to be high (0.6) for crystal size and moderate (0.3) for crystal orientation. There was a strong positive correlation (0.65) for crystal size and orientation with the thickness of the shell and, in particular, with the thickness of the mammillary layer. Correlations with shell breaking strength were positive but with a high standard error. This was contrary to expectations, as in man-made materials smaller crystals would be stronger. We believe the results of this study support the hypothesis that the structural organization of shell, and in particular the mammillary layer, is influenced by crystal size and orientation, especially during the initial phase of calcification. Genetic associations for crystal measurements were observed between haplotype blocks or individual markers for a number of eggshell matrix proteins. Ovalbumin and ovotransferrin (LTF) markers for example were associated with crystal size, while ovocleidin-116 and ovocalyxin-32 (RARRES1) markers were associated with crystal orientation. The location of these proteins in the eggshell is consistent with different phases of the shell-formation process. In conclusion, the variability of crystal size, and to a lesser extent orientation, appears to have a large genetic component, and the formation of calcite crystals are intimately related to the ultrastructure of the eggshell. Moreover, this study also provides evidence that proteins in the shell influence the variability of crystal traits and, in turn, the shell's thickness profile. The crystal measurements and/or the associated genetic markers may therefore prove to be useful in selection programs to improve eggshell quality. PMID:22497523

  10. Collective spin excitation in finite size array of patterned magnonic crystals

    NASA Astrophysics Data System (ADS)

    Piao, H.-G.; Shim, J.-H.; Pan, L.; Yu, S.-C.; Kim, D.-H.

    2016-04-01

    We explore further details of the collectively excited spin wave mode in finite arrays of elliptically shaped ferromagnetic nanoelements as two-dimensional magnonic crystals by means of micromagnetic simulations. Under a pulsed magnetic driving field, collective spin wave modes were intensively investigated with variation of nanoelement dimensions and interelement separation as structural parameters of the magnonic crystal as well as changing the applied bias magnetic field. Via observing and analyzing the dynamic behavior of collective spin wave modes, we have found that the dynamic behavior strongly depends on the bias magnetic field with a quasi-linear dependency. The quasi-linear dependency of spin wave frequency transition can be achieved to a high sensitivity of the pT/Hz level. By modulating the magnonic crystal lattice structures and the bias magnetic field, the spin wave dynamic behavior is tunable which might be a promising property for a future magnonic crystal application and multifunctional sensors.

  11. Nondestructive evaluation of crystallized-particle size in lactose-powder by terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Yamauchi, Satoshi; Hatakeyama, Sakura; Imai, Yoh; Tonouchi, Masayoshi

    2014-03-01

    Transmission-type terahertz time-domain spectroscopy is applied to evaluate crystallized lactose particle of size below 30 μm, which is far too small compared to the wavelength of incident terahertz (THz)-wave. The THz-absorption spectrum of lactose is successfully deconvoluted by Lorentzian to two spectra with peaks at 17.1 cm-1 (0.53 THz) and 45.6 cm-1 (1.37 THz) derived from α-lactose monohydrate, and a spectrum at 39.7 cm-1 (1.19 THz) from anhydrous β-lactose after removal of the broad-band spectrum by polynomial cubic function. Lactose is mainly crystallized into α-lactose monohydrate from the supersaturated solution at room temperature with a small amount of anhydrous β-lactose below 4%. The absorption feature is dependent on the crystallized particle size and the integrated intensity ratio of the two absorptions due to α-lactose monohydrate is correlated in linear for the size.

  12. Size Effect on Deformation Mode in Micron-Sized Ti-5Al Single Crystal Loaded Along [2 /line 1 /line 1 0] and [0001

    NASA Astrophysics Data System (ADS)

    Xiao, Lin; Yu, Qian; Sun, Qiaoyan; Sun, Jun

    Free-standing sub-micron Ti-5Al single crystal square pillars were fabricated along [2 /line 1 /line 1 0] double slip and [0001] twinning orientations using FIB fabrication processes. Samples in range of 0.4 to 2.0µm were compressed. The yield stress increases much higher than their bulk counterpart as the specimen width decreases. The tendency of "smaller is stronger" is displayed in Ti-5Al single crystals loaded along [2 /line 1 /line 1 0] and [0001] orientations. The number of slip systems is restricted by specimen physical size as it declines from 2µm to 0.5µm, when the specimens were subjected to double slip loading. Meanwhile, when sample size is less than 1.0µm, micro-pillars along twinning orientation have to compensate the incomplete twinning deformation via shearing due to geometrical restriction and dislocation starvation effects. This variation of deformation mode could be attributed to the starvation effect of dislocations.

  13. Bone mineral crystal size and organization vary across mature rat bone cortex.

    PubMed

    Turunen, Mikael J; Kaspersen, Jørn D; Olsson, Ulf; Guizar-Sicairos, Manuel; Bech, Martin; Schaff, Florian; Tägil, Magnus; Jurvelin, Jukka S; Isaksson, Hanna

    2016-09-01

    The macro- and micro-features of bone can be assessed by using imaging methods. However, nano- and molecular features require more detailed characterization, such as use of e.g., vibrational spectroscopy and X-ray scattering. Nano- and molecular features also affect the mechanical competence of bone tissue. The aim of the present study was to reveal the effects of mineralization and its alterations on the mineral crystal scale, by investigating the spatial variation of molecular composition and mineral crystal structure across the cross-section of femur diaphyses in young rats, and healthy and osteoporotic mature rats (N=5). Fourier transform infrared spectroscopy and scanning small- and wide-angle X-ray scattering (SAXS/WAXS) techniques with high spatial resolution were used at identical locations over the whole cross-section. This allowed quantification of point-by-point information about the spatial distribution of mineral crystal volume. All measured parameters (crystal dimensions, degree of orientation and predominant orientation) varied across the cortex. Specifically, the crystal dimensions were lower in the central cortex than in the endosteal and periosteal regions. Mineral crystal orientation followed the cortical circumference in the periosteal and endosteal regions, but was less well-oriented in the central regions. Central cortex is formed rapidly during development through endochondral ossification. Since rats possess no osteonal remodeling, this bone remains (until old age). Significant linear correlations were observed between the dimensional and organizational parameters, e.g., between crystal length and degree of orientation (R(2)=0.83, p<0.001). Application of SAXS/WAXS provides valuable information on bone nanostructure and its constituents, effects of diseases and, prospectively, mechanical competence. PMID:27417019

  14. What can crystal size distributions and olivine compositions tell us about magma solidification processes inside Kilauea Iki lava lake, Hawaii?

    NASA Astrophysics Data System (ADS)

    Vinet, Nicolas; Higgins, Michael D.

    2011-12-01

    Lava lakes offer the opportunity to investigate magma solidification and can be considered as a proxy for small magma chambers. Here we present olivine compositions and crystal size distributions (CSDs) from scoria and drill core samples from Kilauea Iki lava lake, which formed during the 1959 eruption of Kilauea Volcano, Hawaii. Three chemically distinct olivine populations were distinguished, in the basis of their forsterite (Fo) content: (1) a high-Fo population (Fo 86-90); (2) an intermediate-Fo population (Fo 78-82); and (3) a minor low-Fo population (Fo 74-78). Populations 1 and 2 both have deformed and undeformed crystals. The third population may be the result of rejuvenation. Olivine in the lower 60 m of lake has a less Fo-rich composition and more crystals are deformed. The CSD analysis yields estimates of the average olivine residence time: 1-60 years. The shape of the olivine CSDs is fairly uniform with respect to depth. Curved CSDs are considered to be evidence of hybrid populations, partly or totally involving crystal or magma mixing. The turndown at the smallest sizes of most foundered crust and lake CSDs may be the result of coarsening, making this process active both before and after eruption. Our CSD modelling does not support significant crystal settling and overall convection in the lava lake, although small advective currents are known to have occurred. The olivine vertical stratification cannot be an original feature, which is consistent with supposed strong stirring of the lake magma due to intense activity over the 17 eruptive phases. It is also possible that independent basal feeding of the lake during the eruption may be needed to explain fully features of the chemical and mineralogical stratification.

  15. Toxicity of TiO2 nanoparticles to Escherichia coli: effects of particle size, crystal phase and water chemistry.

    PubMed

    Lin, Xiuchun; Li, Jingyi; Ma, Si; Liu, Gesheng; Yang, Kun; Tong, Meiping; Lin, Daohui

    2014-01-01

    Controversial and inconsistent results on the eco-toxicity of TiO2 nanoparticles (NPs) are commonly found in recorded studies and more experimental works are therefore warranted to elucidate the nanotoxicity and its underlying precise mechanisms. Toxicities of five types of TiO2 NPs with different particle sizes (10∼50 nm) and crystal phases were investigated using Escherichia coli as a test organism. The effect of water chemistry on the nanotoxicity was also examined. The antibacterial effects of TiO2 NPs as revealed by dose-effect experiments decreased with increasing particle size and rutile content of the TiO2 NPs. More bacteria could survive at higher solution pH (5.0-10.0) and ionic strength (50-200 mg L(-1) NaCl) as affected by the anatase TiO2 NPs. The TiO2 NPs with anatase crystal structure and smaller particle size produced higher content of intracellular reactive oxygen species and malondialdehyde, in line with their greater antibacterial effect. Transmission electron microscopic observations showed the concentration buildup of the anatase TiO2 NPs especially those with smaller particle sizes on the cell surfaces, leading to membrane damage and internalization. These research results will shed new light on the understanding of ecological effects of TiO2 NPs. PMID:25310452

  16. Toxicity of TiO2 Nanoparticles to Escherichia coli: Effects of Particle Size, Crystal Phase and Water Chemistry

    PubMed Central

    Lin, Xiuchun; Li, Jingyi; Ma, Si; Liu, Gesheng; Yang, Kun; Tong, Meiping; Lin, Daohui

    2014-01-01

    Controversial and inconsistent results on the eco-toxicity of TiO2 nanoparticles (NPs) are commonly found in recorded studies and more experimental works are therefore warranted to elucidate the nanotoxicity and its underlying precise mechanisms. Toxicities of five types of TiO2 NPs with different particle sizes (10∼50 nm) and crystal phases were investigated using Escherichia coli as a test organism. The effect of water chemistry on the nanotoxicity was also examined. The antibacterial effects of TiO2 NPs as revealed by dose-effect experiments decreased with increasing particle size and rutile content of the TiO2 NPs. More bacteria could survive at higher solution pH (5.0–10.0) and ionic strength (50–200 mg L−1 NaCl) as affected by the anatase TiO2 NPs. The TiO2 NPs with anatase crystal structure and smaller particle size produced higher content of intracellular reactive oxygen species and malondialdehyde, in line with their greater antibacterial effect. Transmission electron microscopic observations showed the concentration buildup of the anatase TiO2 NPs especially those with smaller particle sizes on the cell surfaces, leading to membrane damage and internalization. These research results will shed new light on the understanding of ecological effects of TiO2 NPs. PMID:25310452

  17. Lactose particle engineering: Influence of ultrasound and anti-solvent on crystal habit and particle size

    NASA Astrophysics Data System (ADS)

    Kougoulos, E.; Marziano, I.; Miller, P. R.

    2010-11-01

    This study focuses on ultrasound-assisted anti-solvent crystallization of lactose, expanding on previous studies and presenting, for the first time, the results of large scale implementation of sonocrystallization for lactose. The results further clarify the interplay between solution chemistry - namely the role of β-lactose - and crystallization, representing a step forward in the fine tuning of lactose properties for pharmaceutical manufacturing applications. Batches manufactured at laboratory and pilot scales were extensively characterised, including an approach for the quantification of β-lactose in α-lactose based on powder X-ray diffraction (PXRD), which is described here.

  18. Solar Minimum

    NASA Astrophysics Data System (ADS)

    Lopresto, James C.; Mathews, John; Manross, Kevin

    1995-12-01

    Calcium K plage, H alpha plage and sunspot area have been monitored daily on the INTERNET since November of 1992. The plage and sunspot area have been measured by image processing. The purpose of the project is to investigate the degree of correlation between plage area and solar irradiance. The plage variation shows the expected variation produced by solar rotation and the longer secular changes produced by the solar cycle. The H alpha and sunspot plage area reached a minimum in about late 1994 or early 1995. This is in agreement with the K2 spectral index obtained daily from Sacramento Peak Observatory. The Calcium K plage area minimum seems delayed with respect to the others mentioned above. The minimum of the K line plage area is projected to come within the last few months of 1995.

  19. Derivation of Physical and Optical Properties of Midlatitude Cirrus Ice Crystals for a Size-Resolved Cloud Microphysics Model

    NASA Technical Reports Server (NTRS)

    Fridlind, Ann M.; Atlas, Rachel; Van Diedenhoven, Bastiaan; Um, Junshik; McFarquhar, Greg M.; Ackerman, Andrew S.; Moyer, Elisabeth J.; Lawson, R. Paul

    2016-01-01

    Single-crystal images collected in mid-latitude cirrus are analyzed to provide internally consistent ice physical and optical properties for a size-resolved cloud microphysics model, including single-particle mass, projected area, fall speed, capacitance, single-scattering albedo, and asymmetry parameter. Using measurements gathered during two flights through a widespread synoptic cirrus shield, bullet rosettes are found to be the dominant identifiable habit among ice crystals with maximum dimension (Dmax) greater than 100µm. Properties are therefore first derived for bullet rosettes based on measurements of arm lengths and widths, then for aggregates of bullet rosettes and for unclassified (irregular) crystals. Derived bullet rosette masses are substantially greater than reported in existing literature, whereas measured projected areas are similar or lesser, resulting in factors of 1.5-2 greater fall speeds, and, in the limit of large Dmax, near-infrared single-scattering albedo and asymmetry parameter (g) greater by approx. 0.2 and 0.05, respectively. A model that includes commonly imaged side plane growth on bullet rosettes exhibits relatively little difference in microphysical and optical properties aside from approx. 0:05 increase in mid-visible g primarily attributable to plate aspect ratio. In parcel simulations, ice size distribution, and g are sensitive to assumed ice properties.

  20. Size/morphology induced tunable luminescence in upconversion crystals: ultra-strong single-band emission and underlying mechanisms

    NASA Astrophysics Data System (ADS)

    Wang, Zhaofeng; Zeng, Songshan; Yu, Jingfang; Ji, Xiaoming; Zeng, Huidan; Xin, Shuangyu; Wang, Yuhua; Sun, Luyi

    2015-05-01

    In this work, we present a two-step method to controllably synthesize novel and highly efficient upconversion materials, Lu5O4F7:Er3+,Yb3+ nano/micro-crystals, and investigate their size/morphology induced tunable upconversion properties. In addition to the common phenomenon aroused by a surface quenching effect, direct experimental evidence for the regulation of phonon modes is obtained in nanoparticles. The findings in this work advance the existing mechanisms for the general explanation of size/morphology induced upconversion features. Because of the adjustment of phonon energy and density as well as the surface quenching effect, the biocompatible Lu5O4F7:Er3+,Yb3+ nanoparticles exhibit an ultra-strong single-band red upconversion, rendering them promising for biomedical applications.In this work, we present a two-step method to controllably synthesize novel and highly efficient upconversion materials, Lu5O4F7:Er3+,Yb3+ nano/micro-crystals, and investigate their size/morphology induced tunable upconversion properties. In addition to the common phenomenon aroused by a surface quenching effect, direct experimental evidence for the regulation of phonon modes is obtained in nanoparticles. The findings in this work advance the existing mechanisms for the general explanation of size/morphology induced upconversion features. Because of the adjustment of phonon energy and density as well as the surface quenching effect, the biocompatible Lu5O4F7:Er3+,Yb3+ nanoparticles exhibit an ultra-strong single-band red upconversion, rendering them promising for biomedical applications. Electronic supplementary information (ESI) available: Crystal structure analysis, UV-Vis absorption spectra, SEM micrographs, surface micro-structure investigation, biocompatibility of Lu5O4F7: Er3+, Yb3+, as well as morphology and upconversion properties of the control sample NaYF4: Er3+, Yb3+. See DOI: 10.1039/c5nr01008j

  1. Effect of Gravity Level on the Particle Shape and Size During Zeolite Crystal Growth

    NASA Technical Reports Server (NTRS)

    Song, Hong-Wei; Ilebusi, Olusegun J.; Sacco, Albert, Jr.

    2003-01-01

    A microscopic diffusion model is developed to represent solute transport in the boundary layer of a growing zeolite crystal. This model is used to describe the effect of gravity on particle shape and solute distribution. Particle dynamics and crystal growth kinetics serve as the boundary conditions of flow and convection-diffusion equations. A statistical rate theory is used to obtain the rate of solute transport across the growing interface, which is expressed in terms of concentration and velocity of solute species. Microgravity can significantly decrease the solute velocity across the growing interface compared to its earth-based counterpart. The extent of this reduction highly depends on solute diffusion constant in solution. Under gravity, the flow towards the crystal enhances solute transport rate across the growing interface while the flow away from crystals reduces this rate, suggesting a non-uniform growth rate and thus an elliptic final shape. However, microgravity can significantly reduce the influence of flow and obtain a final product with perfect spherical shape. The model predictions compare favorably with the data of space experiment of zeolites grown in space.

  2. Sensitivity of Cirrus Bidirectional Reflectance at MODIS Bands to Vertical Inhomogeneity of Ice Crystal Habits and Size Distribution

    NASA Technical Reports Server (NTRS)

    Yang, P.; Gao, B.-C.; Baum, B. A.; Wiscombe, W.; Hu, Y.; Nasiri, S. L.; Soulen, P. F.; Heymsfield, A. J.; McFarquhar, G. M.; Miloshevich, L. M.

    2000-01-01

    A common assumption in satellite imager-based cirrus retrieval algorithms is that the radiative properties of a cirrus cloud may be represented by those associated with a specific ice crystal shape (or habit) and a single particle size distribution. However, observations of cirrus clouds have shown that the shapes and sizes of ice crystals may vary substantially with height within the clouds. In this study we investigate the sensitivity of the top-of-atmosphere bidirectional reflectances at two MODIS bands centered at 0.65 micron and 2.11 micron to the cirrus models assumed to be either a single homogeneous layer or three distinct but contiguous, layers. First, we define the single- and three-layer cirrus cloud models with respect to ice crystal habit and size distribution on the basis of in situ replicator data acquired during the First ISCCP Regional Experiment (FIRE-II), held in Kansas during the fall of 1991. Subsequently, fundamental light scattering and radiative transfer theory is employed to determine the single scattering and the bulk radiative properties of the cirrus cloud. Regarding the radiative transfer computations, we present a discrete form of the adding/doubling principle by introducing a direct transmission function, which is computationally straightforward and efficient an improvement over previous methods. For the 0.65 micron band, at which absorption by ice is negligible, there is little difference between the bidirectional reflectances calculated for the one- and three-layer cirrus models, suggesting that the vertical inhomogeneity effect is relatively unimportant. At the 2.11 micron band, the bidirectional reflectances computed for both optically thin (tau = 1) and thick (tau = 10) cirrus clouds show significant differences between the results for the one- and three-layer models. The reflectances computed for the three-layer cirrus model are substantially larger than those computed for the single-layer cirrus. Finally, we find that cloud

  3. Acoustical and optical investigations of the size effect in nematic-isotropic phase transition in liquid crystal microemulsions

    NASA Astrophysics Data System (ADS)

    Maksimochkin, G. I.; Pasechnik, S. V.; Lukin, A. V.

    2015-07-01

    The absorption of ultrasound (at a frequency of 2.7 MHz) and the depolarized light transmission and scattering (at a wavelength of 630 nm) in liquid crystal (LC) emulsions have been studied during the nematic-isotropic (N-I) phase transition in LC droplets with radii ranging from 150 to 2300 nm. The obtained acoustical and optical data are used to determine the influence of the droplet size on characteristics of the N-I phase transition. It is shown that the acoustical and optical characteristics of LC emulsions have good prospects to be used for the investigation of phase transitions in submicron samples.

  4. Specific features of the spectral properties of a photonic crystal with a nanocomposite defect with allowance for the size effects

    NASA Astrophysics Data System (ADS)

    Vetrov, S. Ya.; Pankin, P. S.; Timofeev, I. V.

    2015-07-01

    The spectral properties of a one-dimensional photonic crystal (PC) with a structure defect (a layer of isotropic nanocomposite inserted between two multilayer dielectric mirrors) have been investigated. The nanocomposite consists of spherical gold nanoparticles dispersed in a transparent matrix; it is characterized by effective resonant permittivity. The dependence of the transmission and absorption spectra on the size and concentration of nanoparticles is analyzed. It is shown that the transmission spectrum contains, along with the band gap caused by Bragg diffraction of light, an additional nontransmission band due to the nanocomposite absorption near the resonant frequency.

  5. What Can Crystal Size Distributions and Olivine Compositions Tell Us About Magma Solidification Processes in Kilauea Iki Lava Lake, Hawaii?

    NASA Astrophysics Data System (ADS)

    Vinet, N.; Higgins, M. D.

    2009-12-01

    Lava lakes offer the opportunity to investigate magma solidification and can be considered as a proxy for small magma chambers or layered intrusions. Here we present data from Kilauea Iki Lava Lake, which formed during the near-summit 1959 picritic eruption of Kilauea Volcano, Hawaii. Microprobe geochemical analyses and crystal size distributions (CSDs) of olivine were determined from three eruption scoria samples, and 34 drill core samples taken from 1967 to 1988. The data provide valuable information on the dynamics and timescales of the intra-lake solidification processes, along with origin of, and temporal constraints on, the distinct olivine populations. Based on their core and rim forsterite (Fo) content, three distinct olivine populations were distinguished: (1) a high-Fo population (Fo85-88); (2) an intermediate-Fo population (Fo77-81); and (3) a low-Fo population (Fo72-76). Groups 1 and 2 both have deformed and undeformed crystals indicating that they formed partly within Kilauea plumbing system before the eruption. The second group seems to be associated with the ‘vertical olivine-rich bodies’ (VORBs) of Helz (1980). These structures raise magma from the lower part of the lake; hence they may have a contrasting composition maintained from the initial filling of the lake. The third population may be the result of rejuvenation within the lake during its cooling. Although the shape of the olivine CSDs is fairly uniform, we note significant variations that allow the recognition and quantification of multiple solidification processes. Our data display evidence of minor accumulation occurring by settling modified by convection currents. The concave-up curvature of at least half of the CSDs is strong evidence for mixing of magmas or crystal populations. The turndown at smallest sizes of the CSD, particularly present for samples at the edge of the lake, is thought to be the result of coarsening. Our CSD and crystal chemistry data suggest that the early

  6. Influence of gold nanorods size on electro-optical and dielectric properties of ferroelectric liquid crystals

    SciTech Connect

    Podgornov, Fedor V.; Ryzhkova, Anna V.; Haase, Wolfgang

    2010-11-22

    The influence of the gold nanorods (GNRs) diameter on the electro-optic and dielectric properties of the ferroelectric liquid crystals (FLCs) was investigated. It was shown that dispersing of GNRs in FLCs could lead to an increase of the internal electric field inside the liquid crystalline layer. This effect results in a significant decrease of the switching time and the rotational viscosity of the FLC/GNRs nanodispersions independently on the GNRs diameter. Oppositely, the relaxation frequency and the dielectric strength of the Goldstone mode strongly depend on the GNRs diameter, which can be explained by the charge transfer between the GNRs and FLC molecules.

  7. Role of cationic size in the optical properties of the LiCl crystal surface: theoretical study.

    PubMed

    Abdel Halim, Wael Salah; Abdullah, Noha; Abdel-Aal, Safaa; Shalabi, A S

    2012-06-01

    The size of the cations (either Ca(2+), Sr(2+), Ga(+), or Au(+)) at the F(A1)-type color centers on the (100) surface of LiCl crystal plays an important role in the optical properties of this surface. In this work, double-well potentials at this surface were investigated using ab initio quantum mechanical methods. Quantum clusters were embedded in simulated Coulomb fields that closely approximate the Madelung fields of the host surface, and the ions that were the nearest neighbors to the F(A1) site were allowed to relax to equilibrium. The calculated Stokes-shifted optical transition bands, optical-optical conversion efficiency, and relaxed excited states of the defect-containing surface, as well as the orientational destruction of the color centers, recording sensitivity, exciton (energy) transfer, and the Glasner-Tompkins empirical relation were all found to be sensitive to the size of the dopant cation. PMID:22033757

  8. Conductivity of laser printed copper structures limited by nano-crystal grain size and amorphous metal droplet shell

    NASA Astrophysics Data System (ADS)

    Winter, Shoshana; Zenou, Michael; Kotler, Zvi

    2016-04-01

    We present a study of the morphology and electrical properties of copper structures which are printed by laser induced forward transfer from bulk copper. The percentage of voids and the oxidation levels are too low to account for the high resistivities (~4 to 14 times the resistivity of bulk monocrystalline copper) of these structures. Transmission electron microscope (TEM) images of slices cut from the printed areas using a focused ion beam (FIB) show nano-sized crystal structures with grain sizes that are smaller than the electron free path length. Scattering from such grain boundaries causes a significant increase in the resistivity and can explain the measured resistivities of the structures. The TEM images also show a nano-amorphous layer (~5 nm) at the droplet boundaries which also contributes to the overall resistivity. Such morphological characteristics are best explained by the ultrafast cooling rate of the molten copper droplets during printing.

  9. Size/morphology induced tunable luminescence in upconversion crystals: ultra-strong single-band emission and underlying mechanisms.

    PubMed

    Wang, Zhaofeng; Zeng, Songshan; Yu, Jingfang; Ji, Xiaoming; Zeng, Huidan; Xin, Shuangyu; Wang, Yuhua; Sun, Luyi

    2015-06-01

    In this work, we present a two-step method to controllably synthesize novel and highly efficient upconversion materials, Lu5O4F7:Er(3+),Yb(3+) nano/micro-crystals, and investigate their size/morphology induced tunable upconversion properties. In addition to the common phenomenon aroused by a surface quenching effect, direct experimental evidence for the regulation of phonon modes is obtained in nanoparticles. The findings in this work advance the existing mechanisms for the general explanation of size/morphology induced upconversion features. Because of the adjustment of phonon energy and density as well as the surface quenching effect, the biocompatible Lu5O4F7:Er(3+),Yb(3+) nanoparticles exhibit an ultra-strong single-band red upconversion, rendering them promising for biomedical applications. PMID:25948156

  10. A linear relationship between crystal size and fragment binding time observed crystallographically: implications for fragment library screening using acoustic droplet ejection.

    PubMed

    Cole, Krystal; Roessler, Christian G; Mulé, Elizabeth A; Benson-Xu, Emma J; Mullen, Jeffrey D; Le, Benjamin A; Tieman, Alanna M; Birone, Claire; Brown, Maria; Hernandez, Jesus; Neff, Sherry; Williams, Daniel; Allaire, Marc; Orville, Allen M; Sweet, Robert M; Soares, Alexei S

    2014-01-01

    High throughput screening technologies such as acoustic droplet ejection (ADE) greatly increase the rate at which X-ray diffraction data can be acquired from crystals. One promising high throughput screening application of ADE is to rapidly combine protein crystals with fragment libraries. In this approach, each fragment soaks into a protein crystal either directly on data collection media or on a moving conveyor belt which then delivers the crystals to the X-ray beam. By simultaneously handling multiple crystals combined with fragment specimens, these techniques relax the automounter duty-cycle bottleneck that currently prevents optimal exploitation of third generation synchrotrons. Two factors limit the speed and scope of projects that are suitable for fragment screening using techniques such as ADE. Firstly, in applications where the high throughput screening apparatus is located inside the X-ray station (such as the conveyor belt system described above), the speed of data acquisition is limited by the time required for each fragment to soak into its protein crystal. Secondly, in applications where crystals are combined with fragments directly on data acquisition media (including both of the ADE methods described above), the maximum time that fragments have to soak into crystals is limited by evaporative dehydration of the protein crystals during the fragment soak. Here we demonstrate that both of these problems can be minimized by using small crystals, because the soak time required for a fragment hit to attain high occupancy depends approximately linearly on crystal size. PMID:24988328

  11. A Linear Relationship between Crystal Size and Fragment Binding Time Observed Crystallographically: Implications for Fragment Library Screening Using Acoustic Droplet Ejection

    PubMed Central

    Birone, Claire; Brown, Maria; Hernandez, Jesus; Neff, Sherry; Williams, Daniel; Allaire, Marc; Orville, Allen M.; Sweet, Robert M.; Soares, Alexei S.

    2014-01-01

    High throughput screening technologies such as acoustic droplet ejection (ADE) greatly increase the rate at which X-ray diffraction data can be acquired from crystals. One promising high throughput screening application of ADE is to rapidly combine protein crystals with fragment libraries. In this approach, each fragment soaks into a protein crystal either directly on data collection media or on a moving conveyor belt which then delivers the crystals to the X-ray beam. By simultaneously handling multiple crystals combined with fragment specimens, these techniques relax the automounter duty-cycle bottleneck that currently prevents optimal exploitation of third generation synchrotrons. Two factors limit the speed and scope of projects that are suitable for fragment screening using techniques such as ADE. Firstly, in applications where the high throughput screening apparatus is located inside the X-ray station (such as the conveyor belt system described above), the speed of data acquisition is limited by the time required for each fragment to soak into its protein crystal. Secondly, in applications where crystals are combined with fragments directly on data acquisition media (including both of the ADE methods described above), the maximum time that fragments have to soak into crystals is limited by evaporative dehydration of the protein crystals during the fragment soak. Here we demonstrate that both of these problems can be minimized by using small crystals, because the soak time required for a fragment hit to attain high occupancy depends approximately linearly on crystal size. PMID:24988328

  12. Crystal size induced reduction in thermal hysteresis of Ni-Ti-Nb shape memory thin films

    NASA Astrophysics Data System (ADS)

    Li, K.; Li, Y.; Yu, K. Y.; Liu, C.; Gibson, D.; Leyland, A.; Matthews, A.; Fu, Y. Q.

    2016-04-01

    Ni41.7Ti38.8Nb19.5 shape memory alloy films were sputter-deposited onto silicon substrates and annealed at various temperatures. A narrow thermal hysteresis was obtained in the Ni-Ti-Nb films with a grain size of less than 50 nm. The small grain size, which means an increase in the volume fraction of grain boundaries, facilitates the phase transformation and reduces the hysteresis. The corresponding less transformation friction and lower heat transfer during the shear process, as well as reduced spontaneous lattice distortion, are responsible for this reduction of the thermal hysteresis.

  13. Colour Size Illusion on Liquid Crystal Displays and Design Guidelines for Bioinformatics Tools

    ERIC Educational Resources Information Center

    Yoo, Hyun Seung; Smith-Jackson, Tonya L.

    2011-01-01

    Although the influence of colour on size perception has been known for a century, there is only limited research on interventions that can reduce this effect. This study was therefore undertaken in order to identify appropriate interventions and propose design guidelines for information visualisation, especially in applications where size…

  14. All-benzene carbon nanocages: size-selective synthesis, photophysical properties, and crystal structure.

    PubMed

    Matsui, Katsuma; Segawa, Yasutomo; Itami, Kenichiro

    2014-11-19

    The design and synthesis of a series of carbon nanocages consisting solely of benzene rings are described. Carbon nanocages are appealing molecules not only because they represent junction unit structures of branched carbon nanotubes, but also because of their potential utilities as unique optoelectronic π-conjugated materials and guest-encapsulating hosts. Three sizes of strained, conjugated [n.n.n]carbon nanocages (1, n = 4; 2, n = 5; 3, n = 6) were synthesized with perfect size-selectivity. Cyclohexane-containing units and 1,3,5-trisubstituted benzene-containing units were assembled to yield the minimally strained bicyclic precursors, which were successfully converted into the corresponding carbon nanocages via acid-mediated aromatization. X-ray crystallography of 1 confirmed the cage-shaped structure with an approximately spherical void inside the cage molecule. The present studies revealed the unique properties of carbon nanocages, including strain energies, size-dependent absorption and fluorescence, as well as unique size-dependency for the electronic features of 1-3. PMID:25361385

  15. Size dependence of bandgaps in a two-dimensional plasmonic crystal with a hexagonal lattice.

    PubMed

    Saito, Hikaru; Yamamoto, Naoki

    2015-02-01

    The optical properties of surface plasmon polaritons (SPPs) are investigated at the Г point in a two-dimensional plasmonic crystal with a hexagonal lattice (Hex-PlC). The cathodoluminescence (CL) technique combined with a scanning transmission electron microscope (STEM) are used to produce spectral images of the SPP standing waves at the Г point and identify the four types of band-edge modes predicted by group theory. The systematic measurement of the band-edge energies employed here is used to determine the characteristic dependence of each band-edge mode on the structure parameters, which provides some criteria for the design of plasmonic devices with Hex-PlCs. PMID:25836118

  16. Minimum Hamiltonian Ascent Trajectory Evaluation (MASTRE) program (update to automatic flight trajectory design, performance prediction, and vehicle sizing for support of Shuttle and Shuttle derived vehicles) engineering manual

    NASA Technical Reports Server (NTRS)

    Lyons, J. T.

    1993-01-01

    The Minimum Hamiltonian Ascent Trajectory Evaluation (MASTRE) program and its predecessors, the ROBOT and the RAGMOP programs, have had a long history of supporting MSFC in the simulation of space boosters for the purpose of performance evaluation. The ROBOT program was used in the simulation of the Saturn 1B and Saturn 5 vehicles in the 1960's and provided the first utilization of the minimum Hamiltonian (or min-H) methodology and the steepest ascent technique to solve the optimum trajectory problem. The advent of the Space Shuttle in the 1970's and its complex airplane design required a redesign of the trajectory simulation code since aerodynamic flight and controllability were required for proper simulation. The RAGMOP program was the first attempt to incorporate the complex equations of the Space Shuttle into an optimization tool by using an optimization method based on steepest ascent techniques (but without the min-H methodology). Development of the complex partial derivatives associated with the Space Shuttle configuration and using techniques from the RAGMOP program, the ROBOT program was redesigned to incorporate these additional complexities. This redesign created the MASTRE program, which was referred to as the Minimum Hamiltonian Ascent Shuttle TRajectory Evaluation program at that time. Unique to this program were first-stage (or booster) nonlinear aerodynamics, upper-stage linear aerodynamics, engine control via moment balance, liquid and solid thrust forces, variable liquid throttling to maintain constant acceleration limits, and a total upgrade of the equations used in the forward and backward integration segments of the program. This modification of the MASTRE code has been used to simulate the new space vehicles associated with the National Launch Systems (NLS). Although not as complicated as the Space Shuttle, the simulation and analysis of the NLS vehicles required additional modifications to the MASTRE program in the areas of providing

  17. Characterization of synthetic nanocrystalline mackinawite: crystal structure, particle size, and specific surface area

    PubMed Central

    Jeong, Hoon Y.; Lee, Jun H.; Hayes, Kim F.

    2010-01-01

    Iron sulfide was synthesized by reacting aqueous solutions of sodium sulfide and ferrous chloride for 3 days. By X-ray powder diffraction (XRPD), the resultant phase was determined to be primarily nanocrystalline mackinawite (space group: P4/nmm) with unit cell parameters a = b = 3.67 Å and c = 5.20 Å. Iron K-edge XAS analysis also indicated the dominance of mackinawite. Lattice expansion of synthetic mackinawite was observed along the c-axis relative to well-crystalline mackinawite. Compared with relatively short-aged phase, the mackinawite prepared here was composed of larger crystallites with less elongated lattice spacings. The direct observation of lattice fringes by HR-TEM verified the applicability of Bragg diffraction in determining the lattice parameters of nanocrystalline mackinawite from XRPD patterns. Estimated particle size and external specific surface area (SSAext) of nanocrystalline mackinawite varied significantly with the methods used. The use of Scherrer equation for measuring crystallite size based on XRPD patterns is limited by uncertainty of the Scherrer constant (K) due to the presence of polydisperse particles. The presence of polycrystalline particles may also lead to inaccurate particle size estimation by Scherrer equation, given that crystallite and particle sizes are not equivalent. The TEM observation yielded the smallest SSAext of 103 m2/g. This measurement was not representative of dispersed particles due to particle aggregation from drying during sample preparation. In contrast, EGME method and PCS measurement yielded higher SSAext (276–345 m2/g by EGME and 424 ± 130 m2/g by PCS). These were in reasonable agreement with those previously measured by the methods insensitive to particle aggregation. PMID:21085620

  18. Seebeck Coefficient Measurements on Micron-Size Single-Crystal Zinc Germanium Nitride Rods

    NASA Astrophysics Data System (ADS)

    Dyck, J. S.; Colvin, J. R.; Quayle, P. C.; Peshek, T. J.; Kash, K.

    2016-06-01

    II-IV-nitride compounds are tetrahedrally bonded, heterovalent ternary semiconductors that have recently garnered attention for their potential technological applications. These materials are derived from the parent III-nitride compounds; ZnGeN2 is the II-IV-nitride analogue to the III-nitride GaN. Very little is known about the transport properties of ZnGeN2. In this work, we present Seebeck coefficient ( S) data on 3-micron-diameter, 70-micron-long, single-crystal ZnGeN2 rods, employing a novel measurement approach. The measurements of S show that the majority free carriers are electrons, and imply that the carrier gas is degenerate. Within a single-band model for the conduction band, a carrier concentration of order 1019 cm-3 was estimated for a measured S = -90 μV/K. Together with electrical transport measurements, a lower limit for the electron mobility is estimated to be ˜20 cm2/V-s. A discussion of this material as a thermoelectric is presented. The background level of free electrons in this unintentionally doped ZnGeN2 is very near the predicted optimum value for maximum thermoelectric performance.

  19. Seebeck Coefficient Measurements on Micron-Size Single-Crystal Zinc Germanium Nitride Rods

    NASA Astrophysics Data System (ADS)

    Dyck, J. S.; Colvin, J. R.; Quayle, P. C.; Peshek, T. J.; Kash, K.

    2016-01-01

    II-IV-nitride compounds are tetrahedrally bonded, heterovalent ternary semiconductors that have recently garnered attention for their potential technological applications. These materials are derived from the parent III-nitride compounds; ZnGeN2 is the II-IV-nitride analogue to the III-nitride GaN. Very little is known about the transport properties of ZnGeN2. In this work, we present Seebeck coefficient (S) data on 3-micron-diameter, 70-micron-long, single-crystal ZnGeN2 rods, employing a novel measurement approach. The measurements of S show that the majority free carriers are electrons, and imply that the carrier gas is degenerate. Within a single-band model for the conduction band, a carrier concentration of order 1019 cm-3 was estimated for a measured S = -90 μV/K. Together with electrical transport measurements, a lower limit for the electron mobility is estimated to be ˜20 cm2/V-s. A discussion of this material as a thermoelectric is presented. The background level of free electrons in this unintentionally doped ZnGeN2 is very near the predicted optimum value for maximum thermoelectric performance.

  20. Inverse gas chromatography a tool to follow physicochemical modifications of pharmaceutical solids: Crystal habit and particles size surface effects.

    PubMed

    Cares-Pacheco, M G; Calvet, R; Vaca-Medina, G; Rouilly, A; Espitalier, F

    2015-10-15

    Powders are complex systems and so pharmaceutical solids are not the exception. Nowadays, pharmaceutical ingredients must comply with well-defined draconian specifications imposing narrow particle size range, control on the mean particle size, crystalline structure, crystal habits aspect and surface properties of powders, among others. The different facets, physical forms, defects and/or impurities of the solid will alter its interaction properties. A powerful way of studying surface properties is based on the adsorption of an organic or water vapor on a powder. Inverse gas chromatography (IGC) appears as a useful method to characterize the surface properties of divided solids. The aim of this work is to study the sensitivity of IGC, in Henry's domain, in order to detect the impact of size and morphology in surface energy of two crystalline forms of an excipient, d-mannitol. Surface energy analyses using IGC have shown that the α form is the most energetically active form. To study size and shape influence on polymorphism, pure α and β mannitol samples were cryomilled (CM) and/or spray dried (SD). All forms showed an increase of the surface energy after treatment, with a higher influence for β samples (γs(d) of 40-62 mJ m(-2)) than for α mannitol samples (γs(d) of 75-86 mJ m(-2)). Surface heterogeneity analysis in Henry's domain showed a more heterogeneous β-CM sample (62-52 mJ m(-2)). Moreover, despite its spherical shape and quite homogeneous size distribution, β-SD mannitol samples showed a slightly heterogeneous surface (57-52 mJ m(-2)) also higher than the recrystallized β pure sample (∼40 mJ m(-2)). PMID:26248145

  1. Ion Size Effect on Glow Peak Temperature in Dielectric Binary Mixed Crystals Doped With Divalent Europium

    NASA Astrophysics Data System (ADS)

    Rodriguez-Mijangos, Ricardo; Perez-Salas, Raul

    2008-03-01

    Thermoluminiscence measurements at room temperature of ``beta'' irradiated divalent Europium doped binary mixed alkali halides with RbCl and KBr components at several concentrations x in molar fraction are carried out. The experiments have been carried out to identify the effect of composition in thermoluminiscense glow peaks. A typical glow peak has been distinguished for each composition. A linear dependence of its temperature on the composition x has been found. This is principally associated with the radii size change of halogen ions. Comparison with results in mixed KCl:KBr. KBr:RbBr and KCl:RbCl support that assertion.

  2. Effect of initial gamma prime size on the elevated temperature creep properties of single crystal nickel base superalloys

    NASA Technical Reports Server (NTRS)

    Nathal, M. V.

    1987-01-01

    The influence of initial gamma-prime size and shape on the high-temperature creep properties of two single-crystal Ni-base superalloys was investigated. The two alloys were chosen to represent different magnitudes of gamma/gamma-prime lattice mismatch. A range of initial microstructures was produced by various quenching and aging treatments. Creep-rupture testing at 1000 C was performed under stresses where gamma-prime directionally coarsens to form gamma/gamma-prime lamellae in the early portion of the creep life. Both alloys exhibited a peak in creep resistance as a function of initial gamma-prime size. The peak corresponded to an initial microstructure consisting of cuboidal precipitates aligned along 001 line directions. These aligned cuboidal gamma-prime particles directionally coarsened into a relatively perfect lamellar gamma/gamma-prime structure in the early stages of creep, whereas the more irregularly shaped and distributed gamma-prime particles in both under- and overaged material formed more irregular lamellae with more imperfections. The alloy with a lower magnitude of mismatch was less sensitive to initial gamma-prime size and shape.

  3. Minimum Hamiltonian ascent trajectory evaluation (MASTRE) program (update to automatic flight trajectory design, performance prediction, and vehicle sizing for support of shuttle and shuttle derived vehicles) users manual

    NASA Technical Reports Server (NTRS)

    Lyons, J. T.; Borchers, William R.

    1993-01-01

    Documentation for the User Interface Program for the Minimum Hamiltonian Ascent Trajectory Evaluation (MASTRE) is provided. The User Interface Program is a separate software package designed to ease the user input requirements when using the MASTRE Trajectory Program. This document supplements documentation on the MASTRE Program that consists of the MASTRE Engineering Manual and the MASTRE Programmers Guide. The User Interface Program provides a series of menus and tables using the VAX Screen Management Guideline (SMG) software. These menus and tables allow the user to modify the MASTRE Program input without the need for learning the various program dependent mnemonics. In addition, the User Interface Program allows the user to modify and/or review additional input Namelist and data files, to build and review command files, to formulate and calculate mass properties related data, and to have a plotting capability.

  4. Black Butte Dacitic Dome, Ca: A Study of Ascent Rates Using Amphibole and Plagioclase Reactions and Crystal Size Distribution

    NASA Astrophysics Data System (ADS)

    McCanta, M.; Rutherford, M.; Hammer, J.

    2001-12-01

    Magma ascent rate can be quantified petrologically utilizing measurement of (1) decompression-driven amphibole breakdown rims, (2) compositional changes in plagioclase phenocryst rims and (3) crystal size distribution (CSD) of groundmass plagioclase microlites, that are known to have grown during ascent and cooling. Measurements of these parameters in both natural and experimental samples allows for an investigation into the relative rates and correlations between amphibole breakdown, plagioclase growth (of both phenocrysts and microlites) and magma ascent. Black Butte, Ca provides a good opportunity to study the effects of ascent rate as determined using the above three methods. Black Butte consists of four overlapping dacitic domes on the southwest flank of Mt. Shasta. At Black Butte the natural phase assemblage consists of amphiboles with well developed breakdown rims, homogeneous An74 plagioclase phenocryst cores decreasing monotonically to An55 rims, and extensive groundmass plagioclase microphenocryst growth. Amphibole breakdown rim widths in natural samples are 30-45 μ m, consistent over all four domes. It is important to note that unlike any other studied dome, these samples exhibit a lack of variable rim thicknesses in any one section, indicating little to no magma mixing in the conduit. Plagioclase phenocryst rim widths, defined by a compositional change, are 10-30 μ m. Textural analysis of the groundmass indicates that crystallization of plagioclase microlites accounts for ~57 volume%, with little variation between samples. CSD plots are approximately log-linear over the size range 1-250 μ m. The characteristic microphenocryst size, volumetric number density, and growth rate are 33μ m, 1.5E-5, ~1.3E-5, respectively. Isothermal, constant rate decompression (P1=200 MPa, P2=2 MPa, dP/dt=6 MPa/day) experiments were run to determine the conditions necessary to produce the rims measured in the natural samples. The starting material was a partially crushed

  5. Size-dependent phase transition in methylammonium lead iodide perovskite microplate crystals

    NASA Astrophysics Data System (ADS)

    Li, Dehui; Wang, Gongming; Cheng, Hung-Chieh; Chen, Chih-Yen; Wu, Hao; Liu, Yuan; Huang, Yu; Duan, Xiangfeng

    2016-04-01

    Methylammonium lead iodide perovskite has attracted considerable recent interest for solution processable solar cells and other optoelectronic applications. The orthorhombic-to-tetragonal phase transition in perovskite can significantly alter its optical, electrical properties and impact the corresponding applications. Here, we report a systematic investigation of the size-dependent orthorhombic-to-tetragonal phase transition using a combined temperature-dependent optical, electrical transport and transmission electron microscopy study. Our studies of individual perovskite microplates with variable thicknesses demonstrate that the phase transition temperature decreases with reducing microplate thickness. The sudden decrease of mobility around phase transition temperature and the presence of hysteresis loops in the temperature-dependent mobility confirm that the orthorhombic-to-tetragonal phase transition is a first-order phase transition. Our findings offer significant fundamental insight on the temperature- and size-dependent structural, optical and charge transport properties of perovskite materials, and can greatly impact future exploration of novel electronic and optoelectronic devices from these materials.

  6. Size-dependent phase transition in methylammonium lead iodide perovskite microplate crystals.

    PubMed

    Li, Dehui; Wang, Gongming; Cheng, Hung-Chieh; Chen, Chih-Yen; Wu, Hao; Liu, Yuan; Huang, Yu; Duan, Xiangfeng

    2016-01-01

    Methylammonium lead iodide perovskite has attracted considerable recent interest for solution processable solar cells and other optoelectronic applications. The orthorhombic-to-tetragonal phase transition in perovskite can significantly alter its optical, electrical properties and impact the corresponding applications. Here, we report a systematic investigation of the size-dependent orthorhombic-to-tetragonal phase transition using a combined temperature-dependent optical, electrical transport and transmission electron microscopy study. Our studies of individual perovskite microplates with variable thicknesses demonstrate that the phase transition temperature decreases with reducing microplate thickness. The sudden decrease of mobility around phase transition temperature and the presence of hysteresis loops in the temperature-dependent mobility confirm that the orthorhombic-to-tetragonal phase transition is a first-order phase transition. Our findings offer significant fundamental insight on the temperature- and size-dependent structural, optical and charge transport properties of perovskite materials, and can greatly impact future exploration of novel electronic and optoelectronic devices from these materials. PMID:27098114

  7. Size-dependent phase transition in methylammonium lead iodide perovskite microplate crystals

    DOE PAGESBeta

    Li, Dehui; Wang, Gongming; Cheng, Hung -Chieh; Chen, Chih -Yen; Wu, Hao; Liu, Yuan; Huang, Yu; Duan, Xiangfeng

    2016-04-21

    Methylammonium lead iodide perovskite has attracted considerable recent interest for solution processable solar cells and other optoelectronic applications. The orthorhombic-to-tetragonal phase transition in perovskite can significantly alter its optical, electrical properties and impact the corresponding applications. Here, we report a systematic investigation of the size-dependent orthorhombic-to-tetragonal phase transition using a combined temperature-dependent optical, electrical transport and transmission electron microscopy study. Our studies of individual perovskite microplates with variable thicknesses demonstrate that the phase transition temperature decreases with reducing microplate thickness. The sudden decrease of mobility around phase transition temperature and the presence of hysteresis loops in the temperature-dependent mobility confirmmore » that the orthorhombic-to-tetragonal phase transition is a first-order phase transition. Lastly, our findings offer significant fundamental insight on the temperature-and size-dependent structural, optical and charge transport properties of perovskite materials, and can greatly impact future exploration of novel electronic and optoelectronic devices from these materials.« less

  8. Size-dependent phase transition in methylammonium lead iodide perovskite microplate crystals

    PubMed Central

    Li, Dehui; Wang, Gongming; Cheng, Hung-Chieh; Chen, Chih-Yen; Wu, Hao; Liu, Yuan; Huang, Yu; Duan, Xiangfeng

    2016-01-01

    Methylammonium lead iodide perovskite has attracted considerable recent interest for solution processable solar cells and other optoelectronic applications. The orthorhombic-to-tetragonal phase transition in perovskite can significantly alter its optical, electrical properties and impact the corresponding applications. Here, we report a systematic investigation of the size-dependent orthorhombic-to-tetragonal phase transition using a combined temperature-dependent optical, electrical transport and transmission electron microscopy study. Our studies of individual perovskite microplates with variable thicknesses demonstrate that the phase transition temperature decreases with reducing microplate thickness. The sudden decrease of mobility around phase transition temperature and the presence of hysteresis loops in the temperature-dependent mobility confirm that the orthorhombic-to-tetragonal phase transition is a first-order phase transition. Our findings offer significant fundamental insight on the temperature- and size-dependent structural, optical and charge transport properties of perovskite materials, and can greatly impact future exploration of novel electronic and optoelectronic devices from these materials. PMID:27098114

  9. Anatase-TiO2 Nanomaterials: Morphological/Size Dependence of the Crystallization and Phase Behavior Phenomena

    SciTech Connect

    Fernandez-Garcia,M.; Wang, X.; Belver, C.; Hanson, J.; Rodriguez, J.

    2007-01-01

    Nanoparticulated TiO{sub 2} materials with anatase structure were synthesized by using a microemulsion method. Three different syntheses with varying surfactant-to-water molar ratio ({omega}) were used to obtain amorphous solid precipitates at room temperature. The structural characteristics of these solid precursors were studied by using X-ray absorption structure (X-ray absorption near-edge structure and extended X-ray absorption fine structure) and Raman spectroscopies, which showed that all lack 3D (tridimensional) order but contain a different degree of 2D-confined connectivity. While heating such solid precursors under dry air, marked differences appeared in the phase behavior; the onset temperature for anatase crystallization increases ca. 150 {sup o}C while the {omega} parameter decreases and only one of the samples shows the anatase-to-rutile transformation below 900 {sup o}C. In all cases, the crystallization of the anatase structure does not follow a traditional nucleation and growth mechanism and its analysis using the Avrami formalism gives conclusive evidence of a surface nucleation-dominated process. This appears as a distinctive feature of anatase-TiO{sub 2} nanomaterials, far from the corresponding behavior of microsized or bulk materials. After nucleation, the grain growth of anatase nanoparticles was found to follow the kinetic equation D{sup 2}-D{sub 0}{sup 2} = k{sub 0} exp(-E{sub a}/RT), where the activation energy is a function of several structural properties of the solid materials mainly related to the hydration characteristics of the surface layer. A combined in situ X-ray diffraction/Raman/infrared study aimed to unveil the physical basis of the phase behavior and to interpret key variables allowing control of the crystallization mechanism and morphological properties, particularly primary particle size, in the nanometer regime.

  10. Organized Assemblies of Colloids Formed at the Poles of Micrometer-Sized Droplets of Liquid Crystal

    PubMed Central

    Wang, Xiaoguang; Miller, Daniel S.; de Pablo, Juan J.

    2014-01-01

    We report on the formation of organized assemblies of 1 μm-in-diameter colloids (polystyrene (PS)) at the poles of water-dispersed droplets (diameters 7 - 20 μm) of nematic liquid crystal (LC). For 4-cyano-4′-pentylbiphenyl droplets decorated with two to five PS colloids, we found 32 distinct arrangements of the colloids to form at the boojums of bipolar droplet configurations. Significantly, all but one of these configurations (a ring comprised of five PS colloids) could be mapped onto a local (non-close packed) hexagonal lattice. To provide insight into the origin of the hexagonal lattice, we investigated planar aqueous—LC interfaces, and found that organized assemblies of PS colloids did not form at these interfaces. Experiments involving the addition of salts revealed that a repulsive interaction of electrostatic origin prevented formation of assemblies at planar interfaces, and that regions of high splay near the poles of the LC droplets generated cohesive interactions between colloids that could overcome the repulsion. Support for this interpretation was obtained from a model that included (i) a long-range attraction between adsorbed colloids and the boojum due to the increasing rate of strain (splay) of LC near the boojum (splay attraction), (ii) an attractive inter-colloid interaction that reflects the quadrupolar symmetry of the strain in the LC around the colloids, and (iii) electrostatic repulsion between colloids. The model predicts that electrostatic repulsion between colloids can lead to a ∼1,000 kBT energy barrier at planar interfaces of LC films, and that the repulsive interaction can be overcome by splay attraction of the colloids to the boojums of the LC droplets. Overall, the results reported in this paper advance our understanding of the directed assembly of colloids at interfaces of LC droplets. PMID:25284139

  11. GV /m Single-Cycle Terahertz Fields from a Laser-Driven Large-Size Partitioned Organic Crystal

    NASA Astrophysics Data System (ADS)

    Vicario, Carlo; Monoszlai, Balazs; Hauri, Christoph P.

    2014-05-01

    We report on compact and efficient laser-based THz generation in the terahertz frequency gap (1-10 THz). The radiation is generated by optical rectification of a midinfrared laser in a large-size, partitioned nonlinear organic crystal assembly. This enables up-scaling of presently field-limited tabletop THz sources to GV /m electric and several tesla magnetic field at millijoule pulse energy. In agreement with simulations, the THz beam properties at focus are shown to be not deteriorated by the discontinuity of the emitter surface. The high laser-to-THz energy conversion efficiency exceeds the Manley-Rowe limit and is explained by a cascaded χ(2) process in the organic crystals accompanied by a significant redshift of the pump spectrum. The scheme provides a compact, tabletop THz source for single-cycle transients at field strength equivalent or even higher to linear accelerator and FEL-based THz sources. This opens an avenue toward novel nonlinear THz applications.

  12. Analysis of Wave Curvature and Rate Stick Experiments for Monomodal Explosives with Different Crystal Quality and Particle Size Characteristics

    NASA Astrophysics Data System (ADS)

    Sutherland, Gerrit

    2007-06-01

    Wood-Kirkwood theory and computer simulations of rate stick and wave curvature experiments of two sets of monomodal explosives are presented. One set [1] included two explosives composed of RDX or reduced sensitivity RDX representing a range of crystal quality. The second set [2] of explosives had mean particle sizes of 6, 134 and 428 μm. Wood-Kirkwood theory was used to calculate the reaction zone width from the wave curvature experiments. Two-term ignition and growth reactive model simulations for the first set of experiments were performed. Ignition and growth parameters were determined from embedded gauge experiments and critical diameter tests. The ability of the simulations to adequately predict shape of detonation velocity versus diameter curves and to replicate wave curvature data is presented. 1. G.T. Sutherland, 13^th International Detonation Symposium, to be published. 2. H. Moulard, 9^th International Detonation Symposium, pp. 18-24.

  13. An examination of polymorphic stability and molecular conformational flexibility as a function of crystal size associated with the nucleation and growth of benzophenone.

    PubMed

    Hammond, Robert B; Pencheva, Klimentina; Roberts, Kevin J

    2007-01-01

    The polymorphic behaviour of the aromatic ketone, benzophenone, which is a conformationally flexible molecule and forms crystal structures dominated by van der Waals intermolecular interactions, is examined. Crystallization of this material from the undercooled molten state yields the two known polymorphic forms, i.e. the stable alpha-form and the metastable beta-form. The relative, energetic stabilities are examined using both crystal lattice and molecular conformational modelling techniques. Examination of nano-sized faceted molecular clusters of these forms, with cluster sizes ranging from 3 to 100 molecules, reveals that at very small cluster size (< 5 molecules) the relative energetic stability of clusters representative for the two forms become very similar, indicating that for high melting undercooling (i.e. small critical cluster size for nucleation) crystallization of the metastable beta-phase becomes more likely. Detailed analysis of the variation in molecular conformations within the simulated molecular clusters reveals more disordered three-dimensional structures at small compared to larger cluster sizes. The conformational disorder was found to be higher for the metastable beta-form. This observation, together with the lower stability of clusters for this form is indicative of the difficulty in achieving crystallization of the metastable beta-form from the melt, which requires a considerable undercooling. PMID:17955805

  14. Effects of ternary mixed crystal and size on optical phonons in wurtzite nitride core-shell nanowires

    SciTech Connect

    Li, J.; Guan, J. Y.; Zhang, S. F.; Ban, S. L.; Qu, Y.

    2014-04-21

    Within the framework of dielectric continuum and Loudon's uniaxial crystal models, existence conditions dependent on components and frequencies for optical phonons in wurtzite nitride core-shell nanowires (CSNWs) are discussed to obtain dispersion relations and electrostatic potentials of optical phonons in In{sub x}Ga{sub 1−x}N/GaN CSNWs. The results show that there may be four types of optical phonons in In{sub x}Ga{sub 1−x}N/GaN CSNWs for a given ternary mixed crystal (TMC) component due to the phonon dispersion anisotropy. This property is analogous to wurtzite planar heterojunctions. Among the optical phonons, there are two types of quasi-confined optical (QCO) phonons (named, respectively, as QCO-A and QCO-B), one type of interface (IF) phonons and propagating (PR) phonons existing in certain component and frequency domains while the dispersion relations and electrostatic potentials of same type of optical phonons vary with components. Furthermore, the size effect on optical phonons in CSNWs is also discussed. The dispersion relations of IF and QCO-A are independent of the boundary location of CSNWs. Meanwhile, dispersion relations and electrostatic potentials of QCO-B and PR phonons vary obviously with size, especially, when the ratio of a core radius to a shell radius is small, and dispersion relation curves of PR phonons appear to be close to each other, whereas, this phenomenon disappears when the ratio becomes large. Based on our conclusions, one can further discuss photoelectric properties in nitride CSNWs consisting of TMCs associated with optical phonons.

  15. Size-dependent plasticity in KCl and LiF single crystals: influence of orientation, temperature, pre-straining and doping

    NASA Astrophysics Data System (ADS)

    Zou, Yu; Spolenak, Ralph

    2015-06-01

    Size effects in plasticity are mostly studied in metallic systems, but they are rarely investigated in ionic crystals. In this study, single-crystalline KCl and LiF pillars were fabricated by focused ion beam technique and compressed using a flat punch tip in a nanoindenter. The materials were investigated with regards to crystal orientation, test temperature, pre-straining and doping. The results show: (1) [1 1 1] LiF pillars do exhibit size effect with an exponent of -0.38, in contrary to no size effect in [1 1 1] LiF reported in literature; (2) [0 0 1] LiF, and [0 0 1] and [1 1 1] KCl have similar size-effect exponents of -0.68, -0.71 and -0.65, respectively; (3) the size effect of [1 1 1] LiF pillars is more sensitive to the temperature change than that of [0 0 1] LiF pillars; (4) pre-straining of [1 1 1] LiF pillars results in a reduced size effect; (5) the 0.05 mol% CaCl2 doping in [0 0 1] KCl slightly increases strength levels and does not change the size effect much. The magnitude of the size effects in ionic crystals can be attributed to the bulk stress level, but not the slip systems. In addition, a correlation between critical temperatures and size-effect slopes is illustrated, and the additivity of strengthening mechanisms is critically discussed.

  16. Mercury's inner core size and core-crystallization régime

    NASA Astrophysics Data System (ADS)

    Dumberry, M.; Rivoldini, A.

    2014-04-01

    Geodetic observations provide insights about the interior structure of Mercury. In particular, they constrain the radius of the core-mantle boundary and on the bulk densities of the core and mantle [5, 3]. Here, we show that they also yield information about the radius of the inner core and on the crystallization regime in the liquid core. Recently, the MESSENGER spacecraft has measured Mercury's internally generated magnetic field and shown that the magnetic field is about two orders of magnitude smaller than Earth's [4]. Dynamo models that agree with those observations require a magnetic field that is driven by chemical convection and generated in a thin spherical shell located deep inside the fluid core that is overlain by a stable thermallystratified layer [1]. We have build models of Mercury that include a sub-adiabatic temperature profile in the upper part of the liquid core. In those models, the dominant light element inside the core is sulfur. Unlike the Earth, upon cooling the core adiabat may first cross the liquidus near the core-mantle boundary resulting in the precipitation of solid iron snow from the liquid Fe - FeS liquid alloy. Cooling extends the precipitation zone to greater depth and produces a stable compositional gradient [2]. Depending on the thermal state of the core the snow zone could extent to the inner core boundary. In that case the inner core would grow through the sedimentation of solid iron snow. If, somewhere below the snow layer, the temperature crosses the liquidus, then inner core growth will proceed in an Earth-like manner. Our study shows that models that best agree with recently measured geodesy observations (88 - day libration and polar moment of inertia) require an inner core that is not larger than 1325 ± 250km. If the inner core radius is smaller than about 650km they have an iron snow layer in the upper part of the fluid core, consistent with a deep seated dynamo. However, if the inner core radius is larger than about 650

  17. Multi-minimum adiabatic potential in the single crystal normal spinel ZnAl(2)O(4), doped by Cu(2+) ions.

    PubMed

    Shapovalov, V A; Zhitlukhina, E S; Lamonova, K V; Shapovalov, V V; Rafailovich, M; Schwarz, S A; Jahoda, R; Reidy, V J; Orel, S M; Pashkevich, Yu G

    2010-06-23

    Spectroscopic investigations of a ZnAl(2)O(4) spinel doped with bivalent copper ions of 0.05% concentration have been carried out in the temperature range 4.2-290 K using a 3 cm(-1) range electron paramagnetic resonance (EPR) spectrometer having an operational frequency f = (9.241 ± 0.001) GHz. The spectrum can be represented as a superposition of two components: a low-temperature (LT) and a high-temperature (HT) one. Redistribution of integrated intensity between HT and LT components of the spectra occurs with temperature change that is typical of systems with multi-minimum adiabatic potential. Spectra observed are explained within the modified theory of crystalline field (MTCF). The electron levels of a Cu(2+) ion placed in an octahedral coordination center with trigonal distortion [CuO(6)](10-) have been calculated. The influence of possible types of oxygen octahedron distortions and possible displacement of copper ions from the symmetry center on the electron spectrum, as well as the shape of the adiabatic potential, has been analyzed. It is shown that in the low-temperature phase the multiple minima of the adiabatic potential occur due to tetragonal distortions while the depth of a minimum is determined by the degree of trigonal octahedron distortions. Tetragonal distortion values and multi-minimum potential barrier heights have been determined. PMID:21393785

  18. Two-Inch-Sized Perovskite CH3 NH3 PbX3 (X = Cl, Br, I) Crystals: Growth and Characterization.

    PubMed

    Liu, Yucheng; Yang, Zhou; Cui, Dong; Ren, Xiaodong; Sun, Jiankun; Liu, Xiaojing; Zhang, Jingru; Wei, Qingbo; Fan, Haibo; Yu, Fengyang; Zhang, Xu; Zhao, Changming; Liu, Shengzhong Frank

    2015-09-16

    Two-inch-sized perovskite crystals, CH3 NH3 PbX3 (X=I, Br, Cl), with high crystalline quality are prepared by a solution-grown strategy. The availability of large perovskite crystals is expected to transform its broad applications in photovoltaics, optoelectronics, lasers, photodetectors, LEDs, etc., just as crystalline silicon has done in revolutionizing the modern electronics and photovoltaic industries. PMID:26247401

  19. Not Seeing the Forest for the Trees: Size of the Minimum Spanning Trees (MSTs) Forest and Branch Significance in MST-Based Phylogenetic Analysis

    PubMed Central

    Teixeira, Andreia Sofia; Monteiro, Pedro T.; Carriço, João A; Ramirez, Mário; Francisco, Alexandre P.

    2015-01-01

    Trees, including minimum spanning trees (MSTs), are commonly used in phylogenetic studies. But, for the research community, it may be unclear that the presented tree is just a hypothesis, chosen from among many possible alternatives. In this scenario, it is important to quantify our confidence in both the trees and the branches/edges included in such trees. In this paper, we address this problem for MSTs by introducing a new edge betweenness metric for undirected and weighted graphs. This spanning edge betweenness metric is defined as the fraction of equivalent MSTs where a given edge is present. The metric provides a per edge statistic that is similar to that of the bootstrap approach frequently used in phylogenetics to support the grouping of taxa. We provide methods for the exact computation of this metric based on the well known Kirchhoff’s matrix tree theorem. Moreover, we implement and make available a module for the PHYLOViZ software and evaluate the proposed metric concerning both effectiveness and computational performance. Analysis of trees generated using multilocus sequence typing data (MLST) and the goeBURST algorithm revealed that the space of possible MSTs in real data sets is extremely large. Selection of the edge to be represented using bootstrap could lead to unreliable results since alternative edges are present in the same fraction of equivalent MSTs. The choice of the MST to be presented, results from criteria implemented in the algorithm that must be based in biologically plausible models. PMID:25799056

  20. Not seeing the forest for the trees: size of the minimum spanning trees (MSTs) forest and branch significance in MST-based phylogenetic analysis.

    PubMed

    Teixeira, Andreia Sofia; Monteiro, Pedro T; Carriço, João A; Ramirez, Mário; Francisco, Alexandre P

    2015-01-01

    Trees, including minimum spanning trees (MSTs), are commonly used in phylogenetic studies. But, for the research community, it may be unclear that the presented tree is just a hypothesis, chosen from among many possible alternatives. In this scenario, it is important to quantify our confidence in both the trees and the branches/edges included in such trees. In this paper, we address this problem for MSTs by introducing a new edge betweenness metric for undirected and weighted graphs. This spanning edge betweenness metric is defined as the fraction of equivalent MSTs where a given edge is present. The metric provides a per edge statistic that is similar to that of the bootstrap approach frequently used in phylogenetics to support the grouping of taxa. We provide methods for the exact computation of this metric based on the well known Kirchhoff's matrix tree theorem. Moreover, we implement and make available a module for the PHYLOViZ software and evaluate the proposed metric concerning both effectiveness and computational performance. Analysis of trees generated using multilocus sequence typing data (MLST) and the goeBURST algorithm revealed that the space of possible MSTs in real data sets is extremely large. Selection of the edge to be represented using bootstrap could lead to unreliable results since alternative edges are present in the same fraction of equivalent MSTs. The choice of the MST to be presented, results from criteria implemented in the algorithm that must be based in biologically plausible models. PMID:25799056

  1. Dependence on Crystal Size of the Nanoscale Chemical Phase Distribution and Fracture in LixFePO₄.

    PubMed

    Yu, Young-Sang; Kim, Chunjoong; Shapiro, David A; Farmand, Maryam; Qian, Danna; Tyliszczak, Tolek; Kilcoyne, A L David; Celestre, Rich; Marchesini, Stefano; Joseph, John; Denes, Peter; Warwick, Tony; Strobridge, Fiona C; Grey, Clare P; Padmore, Howard; Meng, Ying Shirley; Kostecki, Robert; Cabana, Jordi

    2015-07-01

    The performance of battery electrode materials is strongly affected by inefficiencies in utilization kinetics and cycle life as well as size effects. Observations of phase transformations in these materials with high chemical and spatial resolution can elucidate the relationship between chemical processes and mechanical degradation. Soft X-ray ptychographic microscopy combined with X-ray absorption spectroscopy and electron microscopy creates a powerful suite of tools that we use to assess the chemical and morphological changes in lithium iron phosphate (LiFePO4) micro- and nanocrystals that occur upon delithiation. All sizes of partly delithiated crystals were found to contain two phases with a complex correlation between crystallographic orientation and phase distribution. However, the lattice mismatch between LiFePO4 and FePO4 led to severe fracturing on microcrystals, whereas no mechanical damage was observed in nanoplates, indicating that mechanics are a principal driver in the outstanding electrode performance of LiFePO4 nanoparticles. These results demonstrate the importance of engineering the active electrode material in next generation electrical energy storage systems, which will achieve theoretical limits of energy density and extended stability. This work establishes soft X-ray ptychographic chemical imaging as an essential tool to build comprehensive relationships between mechanics and chemistry that guide this engineering design. PMID:26061698

  2. Defining the minimum size of a hydrophobic cluster in two-stranded α-helical coiled-coils: Effects on protein stability

    PubMed Central

    Lu, Stephen M.; Hodges, Robert S.

    2004-01-01

    The α-helical coiled-coil motif is characterized by a heptad repeat pattern (abcdefg)n in which residues a and d form the hydrophobic core. Long coiled-coils (e.g., tropomyosin, 284 residues per polypeptide chain) typically do not have a continuous hydrophobic core of stabilizing residues, but rather one that consists of alternating clusters of stabilizing and destabilizing residues. We have arbitrarily defined a cluster as a minimum of three consecutive stabilizing or destabilizing residues in the hydrophobic core. We report here on a series of two-stranded, disulfide-bridged parallel α-helical coiled-coils that contain a central cassette of three consecutive hydrophobic core positions (d, a, and d) with a destabilizing cluster of three consecutive Ala residues in the hydrophobic core on each side of the cassette. The effect of adding one to three stabilizing hydrophobes in these positions (Leu or Ile; denoted as •) was investigated. Alanine residues (denoted as ○) are used to represent destabilizing residues. The peptide with three Ala residues in the d a d cassette positions (○○○) was among the least stable coiled-coil (Tm = 39.3°C and Urea1/2 = 1.9 M). Surprisingly, the addition of one stabilizing hydrophobe (Leu) to the cassette or two stabilizing hydrophobes (Leu), still interspersed by an Ala in the cassette (•○•), also did not lead to any gain in stability. However, peptides with two adjacent hydrophobes in the cassette (••○)(○••) did show a gain in stability of 0.9 kcal/mole over the peptide with two interspersed hydrophobes (•○•). Because the latter three peptides have the same inherent hydrophobicity, the juxtaposition of stabilizing hydrophobes leads to a synergistic effect, and thus a clustering effect. The addition of a third stabilizing hydrophobe to the cassette (•••) resulted in a further synergistic gain in stability of 1.7 kcal/mole (Tm = 54.1°C and Urea1/2 = 3.3M). Therefore, the role of hydrophobicity

  3. Synthesis of KCa₂Nb₃O₁₀ Crystals with Varying Grain Sizes and Their Nanosheet Monolayer Films As Seed Layers for PiezoMEMS Applications.

    PubMed

    Yuan, Huiyu; Nguyen, Minh; Hammer, Tom; Koster, Gertjan; Rijnders, Guus; ten Elshof, Johan E

    2015-12-16

    The layered perovskite-type niobate KCa2Nb3O10 and its derivatives show advantages in several fields, such as templated film growth and (photo)catalysis. Conventional synthesis routes generally yield crystal size smaller than 2 μm. We report a flux synthesis method to obtain KCa2Nb3O10 crystals with significantly larger sizes. By using different flux materials (K2SO4 and K2MoO4), crystals with average sizes of 8 and 20 μm, respectively, were obtained. The KCa2Nb3O10 crystals from K2SO4 and K2MoO4 assisted synthesis were protonated and exfoliated into monolayer nanosheets, and the optimal exfoliation conditions were determined. Using pulsed laser deposition, highly (001)-oriented piezoelectric stacks (SrRuO3/PbZr0.52Ti0.48O3/SrRuO3, SRO/PZT/SRO) were deposited onto Langmuir-Blodgett films of Ca2Nb3O10(-) (CNO) nanosheets with varying lateral nanosheet sizes on Si substrates. The resulting PZT thin films showed high crystallinity irrespective of nanosheet size. The small sized nanosheets yielded a high longitudinal piezoelectric coefficient d33 of 100 pm/V, while the larger sized sheets had a d33 of 72 pm/V. An enhanced transverse piezoelectric coefficient d31 of -107 pm/V, an important input parameter for the actuation of active structures in microelectromechanical systems (MEMS) devices, was obtained for PZT films grown on CNO nanosheets with large lateral size, while the corresponding value on small sized sheets was -96 pm/V. PMID:26583282

  4. Growing Larger Crystals for Neutron Diffraction

    NASA Technical Reports Server (NTRS)

    Pusey, Marc

    2003-01-01

    Obtaining crystals of suitable size and high quality has been a major bottleneck in macromolecular crystallography. With the advent of advanced X-ray sources and methods the question of size has rapidly dwindled, almost to the point where if one can see the crystal then it was big enough. Quality is another issue, and major national and commercial efforts were established to take advantage of the microgravity environment in an effort to obtain higher quality crystals. Studies of the macromolecule crystallization process were carried out in many labs in an effort to understand what affected the resultant crystal quality on Earth, and how microgravity improved the process. While technological improvements are resulting in a diminishing of the minimum crystal size required, neutron diffraction structural studies still require considerably larger crystals, by several orders of magnitude, than X-ray studies. From a crystal growth physics perspective there is no reason why these 'large' crystals cannot be obtained: the question is generally more one of supply than limitations mechanism. This talk will discuss our laboratory s current model for macromolecule crystal growth, with highlights pertaining to the growth of crystals suitable for neutron diffraction studies.

  5. Preparation and stress evolution of sol-gel SiO2 antireflective coatings for small-size anisotropic lithium triborate crystals

    NASA Astrophysics Data System (ADS)

    Tian, Bingtao; Wang, Xiaodong; Niu, Yanyan; Zhang, Jinlong; Zhang, Qinghua; Zhang, Zhihua; Wu, Guangming; Zhou, Bin; Shen, Jun

    2016-04-01

    Lithium triborate (LiB3O5, LBO) crystal is now one of the most useful nonlinear optical materials for frequency conversion of high power lasers. The use of the crystal, however, has been hampered by the unavailability of antireflective (AR) coatings with high laser damage resistance. In this work, a "point contact" dip-coating method is developed to prepare sol-gel SiO2 AR coatings on small-size LBO crystals. Using this approach, we obtain a homogenous coating surface on an 8 mm×8 mm×3 mm LBO crystal. The stress measurements show that the stresses in sol-gel SiO2 coatings vary with the time of natural drying, which is beyond our expectation. The anisotropic Young's modulus of the LBO crystal and the different evolution tendency of the stress in the different SiO2 coating layers are found to be responsible for the crack of the double-layer AR coatings on anisotropic LBO crystal. Meanwhile, the resulting coatings on LBO crystal achieve a LIDT of over 15 J/cm2 (532 nm, 3ns) and the coated LBO is expected to have a transmittance of over 99% at 800 nm.

  6. Correction: Decrease in thermal conductivity in polymeric P3HT nanowires by size-reduction induced by crystal orientation: new approaches towards thermal transport engineering of organic materials.

    PubMed

    Muñoz Rojo, Miguel; Martín, Jaime; Grauby, Stéphane; Borca-Tasciuc, Theodorian; Dilhaire, Stefan; Martin-Gonzalez, Marisol

    2015-03-01

    Correction for 'Decrease in thermal conductivity in polymeric P3HT nanowires by size-reduction induced by crystal orientation: new approaches towards thermal transport engineering of organic materials' by Miguel Muñoz Rojo et al., Nanoscale, 2014, 6, 7858-7865. PMID:25668105

  7. Evaluation of minimum coverage size and orbital accuracy at different orbital regimes for one order of magnitude reduction of the catastrophic collision risk

    NASA Astrophysics Data System (ADS)

    Sánchez-Ortiz, Noelia; Domínguez-González, Raúl; Krag, Holger

    2015-03-01

    One of the main objectives of Space Surveillance and Tracking (SST) systems is to support space collision avoidance activities. This collision avoidance capability aims to significantly reduce the catastrophic collision risk of space objects. In particular, for the case of the future European SST, the objective is translated into a risk reduction of one order of magnitude whilst keeping a low number of false alarm events. In order to translate this aim into system requirements, an evaluation of the current catastrophic collision risk for different orbital regimes is addressed. The reduction of such risk depends on the amount of catalogued objects (coverage) and the knowledge of the associated orbits in the catalogue (accuracy). This paper presents an analysis of the impact of those two aspects in the capability to reduce the catastrophic collision risk at some orbital regimes. A reliable collision avoidance support depends on the accuracy of the predicted miss-events. The assessment of possible conjunctions is normally done by computing the estimated miss-distances between objects (which is compared with a defined distance threshold) or by computing the associated collision risk (which is compared with the corresponding accepted collision probability level). This second method is normally recommended because it takes into account the reliability of the orbits and allows reducing false alarm events. The collision risk depends on the estimated miss-distance, the object sizes and the accuracy of the two orbits at the time of event. This accuracy depends on the error of the orbits at the orbit determination epoch and the error derived from the propagation from that epoch up to the time of event. The modified DRAMA ARES (Domínguez-González et al., 2012, 2013a,b; Gelhaus et al., 2014) provides information on the expected number of encounters for a given mission and year. It also provides information on the capacity to reduce the risk of collision by means of avoidance

  8. Crystallization of nickel nanoclusters by molecular dynamics

    NASA Astrophysics Data System (ADS)

    Chamati, H.; Gaminchev, K.

    2012-12-01

    We investigated the melting properties of bulk nickel and the crystallization of nickel nanocrystals via molecular dynamics using a potential in the framework of the second moment approximation of tight-binding theory. The melting behavior was simulated with the hysteresis approach by subsequently heating and cooling gradually the system over a wide range of temperatures. The crystallization of nickel nanoclusters consisting of 55, 147 and 309 atoms was achieved after repeatedly annealing and quenching the corresponding quasicrystals several times to avoid being trapped in a local energy minimum. The time over which the global minimum was reached was found to increase with the cluster size.

  9. A model predicting the evolution of ice particle size spectra and radiative properties of cirrus clouds. Part 2: Dependence of absorption and extinction on ice crystal morphology

    NASA Technical Reports Server (NTRS)

    Mitchell, David L.; Arnott, W. Patrick

    1994-01-01

    This study builds upon the microphysical modeling described in Part 1 by deriving formulations for the extinction and absorption coefficients in terms of the size distribution parameters predicted from the micro-physical model. The optical depth and single scatter albedo of a cirrus cloud can then be determined, which, along with the asymmetry parameter, are the input parameters needed by cloud radiation models. Through the use of anomalous diffraction theory, analytical expressions were developed describing the absorption and extinction coefficients and the single scatter albedo as functions of size distribution parameters, ice crystal shapes (or habits), wavelength, and refractive index. The extinction coefficient was formulated in terms of the projected area of the size distribution, while the absorption coefficient was formulated in terms of both the projected area and mass of the size distribution. These properties were formulated as explicit functions of ice crystal geometry and were not based on an 'effective radius.' Based on simulations of the second cirrus case study described in Part 1, absorption coefficients predicted in the near infrared for hexagonal columns and rosettes were up to 47% and 71% lower, respectively, than absorption coefficients predicted by using equivalent area spheres. This resulted in single scatter albedos in the near-infrared that were considerably greater than those predicted by the equivalent area sphere method. Reflectances in this region should therefore be underestimated using the equivalent area sphere approach. Cloud optical depth was found to depend on ice crystal habit. When the simulated cirrus cloud contained only bullet rosettes, the optical depth was 142% greater than when the cloud contained only hexagonal columns. This increase produced a doubling in cloud albedo. In the near-infrared (IR), the single scatter albedo also exhibited a significant dependence on ice crystal habit. More research is needed on the

  10. Simulation of energetic stability of facetted l-glutamic acid nanocrystalline clusters in relation to their polymorphic phase stability as a function of crystal size.

    PubMed

    Hammond, R B; Pencheva, K; Roberts, K J

    2005-10-27

    A molecular modeling approach is used to study the stability of different polymorphic forms of l-glutamic acid through building and optimizing molecular clusters of different sizes and shapes with the latter corresponding to the predicted crystal growth morphologies. The results reveal that the initially nucleating (according to Oswald rule) metastable (alpha) form is the more energetically stable form at small cluster sizes of ca. 200 molecular units, whereas the stable (beta) form is more stable when the cluster size is larger. PMID:16853527

  11. Combined magnetic and structural investigation of nano crystalline iron oxides: The interplay between crystal size and phase composition during FeS 2 oxidation

    NASA Astrophysics Data System (ADS)

    Eneroth, Erik

    2007-01-01

    The oxides that form during thermal oxidation of natural FeS 2 (pyrite and marcasite) consist of nanometer-sized crystals of α-Fe 2O 3 and γ-Fe 2O 3. This is shown with heating experiments that were made up to 650 °C, which resembles temperatures used in metallurgical processes. It is shown that magnetic measurements can play a key role in the investigation of this reaction, due to the unwanted blurring effects associated with finite crystal sizes if other methods are used. According to Mössbauer spectra combined with pXRD, many α-Fe 2O 3 crystals are in a stable magnetic state only due to the formation of bridging superexchange interactions in between them, but the γ-Fe 2O 3 experiences super-paramagnetic relaxation ceasing first at 20 K. Magnetisation measurements were used for two main purposes (1) determination of the amounts of γ-Fe 2O 3 in the products, and (2) for characterization of γ-Fe 2O 3 with respect to crystal size and possible magnetic surface effects such as spin-glass. It is proven that fine FeS 2 grains produce more γ-Fe 2O 3 than coarse. At 500 °C the fine FeS 2 grains oxidised into c. 30% γ-Fe 2O 3 and ca. 70% α-Fe 2O 3. At 525 °C, the γ-Fe 2O 3 amounts were also estimated in coarse oxidised FeS 2, and results were ca. 20% and 10% γ-Fe 2O 3 for the fine and coarse FeS 2 respectively. The γ-Fe 2O 3 crystal sizes were a function of both temperature and grain size, and it decreased with decreasing grain size, and upon rising the temperature from 450 to 550 °C. It is argued that the estimated errors during γ-Fe 2O 3 amount determination are due mainly to disordered magnetic sublattices at the crystal faces of γ-Fe 2O 3, giving an error of ca. 15% for those samples that have the smallest crystals.

  12. Eruption of Deep Mushy Magma from the Searchlight Magma System, Southern Nevada (USA): a Crystal Size Distribution and Geochemical Analysis

    NASA Astrophysics Data System (ADS)

    Bazar, D.; Miller, J.; Miller, C.; Dodge, M.; Hodge, K.; Faulds, J.

    2006-12-01

    The Miocene Searchlight pluton and overlying volcanic rocks are exposed in the Eldorado Mountains of southern Nevada within the Colorado River Extensional Corridor. Steep tilting of the pluton and its cover provides an exceptional opportunity to study the magmatic plumbing system from bottom to top, including possible eruptions of magma from the Searchlight magma system. The pluton is approximately 10 km thick and divided into three compositionally distinct units that solidified in monotonic fashion: a 2 km thick upper fine-grained quartz monzonite (solidification front), a 6 km thick lower, more mafic quartz monzonite (cumulate), and a 2 km thick middle granite (extracted melt) [ref]. In addition, near E-W-striking rhyolite and trachydacite porphyry dikes intrude the upper quartz monzonite unit (but not the lower or middle units), and identical trachydacite porphyries (locally > 45 vol. % crystals) occur as irregular pods and masses in the roof area. The trachydacite porphyries superficially resemble trachydacite lavas in part of the overlying volcanic section. Ion probe zircon ages are identical within error for the upper unit, the lower unit, and the trachydacite dikes and pods (206Pb/238U age for samples of each ranging from 16.6±0.3 Ma to 16.9±0.2 Ma 2σ). Ages for the middle granite unit and rhyolite dikes are consistently younger (15.8-16.0 Ma). Crystal size distribution (CSD) analysis on plagioclase has been undertaken on samples from the upper Searchlight and overlying volcanic rocks in order to establish and corroborate linkages between the volcanic and intrusive units and to better understand the growth and solidification history of the Searchlight magma system. The CSD's for the intermediate porphyry dikes and pods that intrude upper Searchlight pluton are identical to trachydacite lava flows and domes erupted onto Proterozoic gneiss and earlier lava flows that comprise the roof of the pluton. The CSD's for these rocks are distinctly concave up and

  13. The role of hydrogen in oxygen-assisted chemical vapor deposition growth of millimeter-sized graphene single crystals

    NASA Astrophysics Data System (ADS)

    Zhao, Pei; Cheng, Yu; Zhao, Dongchen; Yin, Kun; Zhang, Xuewei; Song, Meng; Yin, Shaoqian; Song, Yenan; Wang, Peng; Wang, Miao; Xia, Yang; Wang, Hongtao

    2016-03-01

    Involving oxygen in the traditional chemical vapor deposition (CVD) process has proven a promising approach to achieve large-scale graphene single crystals (GSCs), but its many relevant fundamental aspects are still not fully understood. Here we report a systematic study on the role of hydrogen in the growth of millimeter-sized GSCs using enclosure-like Cu structures via the oxygen-assisted CVD process. Results show that GSCs have different first layer growth behaviors on the inside and outside surfaces of a Cu enclosure when the H2 environment is varied, and these behaviors will consequently and strongly influence the adlayer formation in these GSCs, leading to two entirely different growth modes. Low H2 partial pressure (PH2) tends to result in fast growth of dendritically shaped GSCs with multiple small adlayers, but high PH2 can modify the GSC shape into hexagons with single large adlayer nuclei. This difference of adlayers is attributed to the different C diffusion paths determined by the shapes of their host GSCs. On the basis of these observations, we developed an isothermal two-step method to obtain GSCs with significantly improved growth rate and sample quality, in which low PH2 is first set to accelerate the growth rate followed by high PH2 to restrict the adlayer nuclei. Our results prove that the growth of GSCs can reach a reasonable optimization between their growth rates and sample quality by simply adjusting the CVD H2 environment, which we believe will lead to more improvements in graphene synthesis and fundamental insight into the related growth mechanisms.Involving oxygen in the traditional chemical vapor deposition (CVD) process has proven a promising approach to achieve large-scale graphene single crystals (GSCs), but its many relevant fundamental aspects are still not fully understood. Here we report a systematic study on the role of hydrogen in the growth of millimeter-sized GSCs using enclosure-like Cu structures via the oxygen-assisted CVD

  14. Er(3+)-doped transparent glass ceramics containing micron-sized SrF2 crystals for 2.7 μm emissions.

    PubMed

    Jiang, Yiguang; Fan, Jintai; Jiang, Benxue; Mao, Xiaojian; Tang, Junzhou; Xu, Yinsheng; Dai, Shixun; Zhang, Long

    2016-01-01

    Er(3+)-doped transparent glass ceramics containing micron-sized SrF2 crystals were obtained by direct liquid-phase sintering of a mixture of SrF2 powders and precursor glass powders at 820 °C for 15 min. The appearance and microstructural evolution of the SrF2 crystals in the resulting glass ceramics were investigated using X-ray diffraction, field-emission scanning electron microscopy and transmission microscopy. The SrF2 crystals are ~15 μm in size and are uniformly distributed throughout the fluorophosphate glass matrix. The glass ceramics achieve an average transmittance of 75% in the visible region and more than 85% in the near-IR region. The high transmittance of the glass ceramics results from matching the refractive index of the SrF2 with that of the precursor glass. Energy dispersive spectroscopy, photoluminescence spectra, and photoluminescence lifetimes verified the incorporation of Er(3+) into the micron-sized SrF2 crystals. Intense 2.7 μm emissions due to the (4)I11/2 → (4)I13/2 transition were observed upon excitation at 980 nm using a laser diode. The maximum value of the emission cross section of Er(3+) around 2.7 μm is more than 1.2 × 10(-20) cm(2), which indicates the potential of using transparent glass ceramics containing micron-sized SrF2 crystals for efficient 2.7 μm lasers and amplifiers. PMID:27430595

  15. Er3+-doped transparent glass ceramics containing micron-sized SrF2 crystals for 2.7 μm emissions

    PubMed Central

    Jiang, Yiguang; Fan, Jintai; Jiang, Benxue; Mao, Xiaojian; Tang, Junzhou; Xu, Yinsheng; Dai, Shixun; Zhang, Long

    2016-01-01

    Er3+-doped transparent glass ceramics containing micron-sized SrF2 crystals were obtained by direct liquid-phase sintering of a mixture of SrF2 powders and precursor glass powders at 820 °C for 15 min. The appearance and microstructural evolution of the SrF2 crystals in the resulting glass ceramics were investigated using X-ray diffraction, field-emission scanning electron microscopy and transmission microscopy. The SrF2 crystals are ~15 μm in size and are uniformly distributed throughout the fluorophosphate glass matrix. The glass ceramics achieve an average transmittance of 75% in the visible region and more than 85% in the near-IR region. The high transmittance of the glass ceramics results from matching the refractive index of the SrF2 with that of the precursor glass. Energy dispersive spectroscopy, photoluminescence spectra, and photoluminescence lifetimes verified the incorporation of Er3+ into the micron-sized SrF2 crystals. Intense 2.7 μm emissions due to the 4I11/2 → 4I13/2 transition were observed upon excitation at 980 nm using a laser diode. The maximum value of the emission cross section of Er3+ around 2.7 μm is more than 1.2 × 10−20 cm2, which indicates the potential of using transparent glass ceramics containing micron-sized SrF2 crystals for efficient 2.7 μm lasers and amplifiers. PMID:27430595

  16. Er3+-doped transparent glass ceramics containing micron-sized SrF2 crystals for 2.7 μm emissions

    NASA Astrophysics Data System (ADS)

    Jiang, Yiguang; Fan, Jintai; Jiang, Benxue; Mao, Xiaojian; Tang, Junzhou; Xu, Yinsheng; Dai, Shixun; Zhang, Long

    2016-07-01

    Er3+-doped transparent glass ceramics containing micron-sized SrF2 crystals were obtained by direct liquid-phase sintering of a mixture of SrF2 powders and precursor glass powders at 820 °C for 15 min. The appearance and microstructural evolution of the SrF2 crystals in the resulting glass ceramics were investigated using X-ray diffraction, field-emission scanning electron microscopy and transmission microscopy. The SrF2 crystals are ~15 μm in size and are uniformly distributed throughout the fluorophosphate glass matrix. The glass ceramics achieve an average transmittance of 75% in the visible region and more than 85% in the near-IR region. The high transmittance of the glass ceramics results from matching the refractive index of the SrF2 with that of the precursor glass. Energy dispersive spectroscopy, photoluminescence spectra, and photoluminescence lifetimes verified the incorporation of Er3+ into the micron-sized SrF2 crystals. Intense 2.7 μm emissions due to the 4I11/2 → 4I13/2 transition were observed upon excitation at 980 nm using a laser diode. The maximum value of the emission cross section of Er3+ around 2.7 μm is more than 1.2 × 10‑20 cm2, which indicates the potential of using transparent glass ceramics containing micron-sized SrF2 crystals for efficient 2.7 μm lasers and amplifiers.

  17. The role of hydrogen in oxygen-assisted chemical vapor deposition growth of millimeter-sized graphene single crystals.

    PubMed

    Zhao, Pei; Cheng, Yu; Zhao, Dongchen; Yin, Kun; Zhang, Xuewei; Song, Meng; Yin, Shaoqian; Song, Yenan; Wang, Peng; Wang, Miao; Xia, Yang; Wang, Hongtao

    2016-04-14

    Involving oxygen in the traditional chemical vapor deposition (CVD) process has proven a promising approach to achieve large-scale graphene single crystals (GSCs), but its many relevant fundamental aspects are still not fully understood. Here we report a systematic study on the role of hydrogen in the growth of millimeter-sized GSCs using enclosure-like Cu structures via the oxygen-assisted CVD process. Results show that GSCs have different first layer growth behaviors on the inside and outside surfaces of a Cu enclosure when the H2 environment is varied, and these behaviors will consequently and strongly influence the adlayer formation in these GSCs, leading to two entirely different growth modes. Low H2 partial pressure (PH2) tends to result in fast growth of dendritically shaped GSCs with multiple small adlayers, but high PH2 can modify the GSC shape into hexagons with single large adlayer nuclei. This difference of adlayers is attributed to the different C diffusion paths determined by the shapes of their host GSCs. On the basis of these observations, we developed an isothermal two-step method to obtain GSCs with significantly improved growth rate and sample quality, in which low PH2 is first set to accelerate the growth rate followed by high PH2 to restrict the adlayer nuclei. Our results prove that the growth of GSCs can reach a reasonable optimization between their growth rates and sample quality by simply adjusting the CVD H2 environment, which we believe will lead to more improvements in graphene synthesis and fundamental insight into the related growth mechanisms. PMID:26987665

  18. Growth of high quality and large-sized Rb 0.3MoO 3 single crystals by molten salt electrolysis method

    NASA Astrophysics Data System (ADS)

    Wang, Junfeng; Xiong, Rui; Yi, Fan; Yin, Di; Ke, Manzhu; Li, Changzhen; Liu, Zhengyou; Shi, Jing

    2005-05-01

    High quality and large-sized Rb 0.3MoO 3 single crystals were synthesized by molten salt electrolysis method. X-ray diffraction (XRD) patterns and rocking curves, as well as the white beam Laue diffraction of X-ray images show the crystals grown by this method have high quality. The lattice constants evaluated from XRD patterns are a0=1.87 nm, b0=0.75 nm, c0=1.00 nm, β=118.83∘. The in situ selected area electron diffraction (SAED) patterns along the [101¯], [11¯1¯] and [103¯] zone axes at room temperature indicate that the Rb 0.3MoO 3 crystal possess perfect C-centered symmetry. Temperature dependence of the resistivity shows this compound undergoes a metal to semiconductor transition at 183 K.

  19. Polarized spectral properties and potential application of large-size Nd3+:Ba3Gd2(BO3)4 crystal

    NASA Astrophysics Data System (ADS)

    Gao, S. F.; Lv, S. Z.; Zhu, Z. J.; Wang, Y.; You, Z. Y.; Li, J. F.; Xu, J. L.; Wang, H. Y.; Tu, C. Y.

    2014-06-01

    The Nd3+-doped Ba3Gd2(BO3)4 crystal with high optical quality and large size is reported in this paper. The growing processes and characteristics of Nd3+:Ba3Gd2(BO3)4 crystal are discussed. The absorption and luminescence spectra of Nd3+ in Ba3Gd2(BO3)4 crystal were measured at room temperature. The luminescence decay curve in correspondence with the 4F3/2 →4I11/2 transition centered at 1062 nm was also measured. The JO intensity parameters Ωt (t = 2,4,6) were calculated to be Ω2 = 1.263, Ω4 = 2.496, Ω6 = 3.606. The radiative lifetime τr and fluorescence lifetime τf are 317.771 and 115 μs respectively, and the fluorescence quantum efficiency is 37.1%.

  20. Effect of Antifreeze Peptide Pretreatment on Ice Crystal Size, Drip Loss, Texture, and Volatile Compounds of Frozen Carrots.

    PubMed

    Kong, Charles H Z; Hamid, Nazimah; Liu, Tingting; Sarojini, Vijayalekshmi

    2016-06-01

    Ice crystal formation is of primary concern to the frozen food industry. In this study, the effects of antifreeze peptides (AFPs) on ice crystal formation were assessed in carrot during freezing and thawing. Three synthetic analogues based on naturally occurring antifreeze peptides were used in this study. The AFPs exhibited modification of ice crystal morphology, confirming their antifreeze activity in vitro. The ability of the synthetic AFPs to minimize drip loss and preserve color, structure, texture, and volatiles of frozen carrot was evaluated using the techniques of SEM, GC-MS, and texture analysis. The results prove the potential of these AFPs to preserve the above characteristics in frozen carrot samples. PMID:27138051

  1. From micro- to nano-scale molding of metals : size effect during molding of single crystal Al with rectangular strip punches.

    SciTech Connect

    Chen, K.; Meng, W. J.; Mei, F.; Hiller, J.; Miller, D. J.

    2011-02-01

    A single crystal Al specimen was molded at room temperature with long, rectangular, strip diamond punches. Quantitative molding response curves were obtained at a series of punch widths, ranging from 5 {micro}m to 550 nm. A significant size effect was observed, manifesting itself in terms of significantly increasing characteristic molding pressure as the punch width decreases to 1.5 {micro}m and below. A detailed comparison of the present strip punch molding results was made with Berkovich pyramidal indentation on the same single crystal Al specimen. The comparison reveals distinctly different dependence of the characteristic pressure on corresponding characteristic length. The present results show the feasibility of micro-/nano-scale compression molding as a micro-/nano-fabrication technique, and offer an experimental test case for size-dependent plasticity theories.

  2. Finite-size thermomechanical effects in smectic liquid crystals: The vapor pressure paradox as an anharmonic phenomenon

    NASA Astrophysics Data System (ADS)

    Gao, Lianghui; Golubović, Leonardo

    2003-10-01

    We pursue a systematic statistical mechanics study of finite smectic stacks of semiflexible manifolds bounded by interfaces under tension. We address, by analytic calculations and Monte Carlo simulations, the effects of the surface tension on smectic interlayer distances. We use our theoretical results to elucidate the so called vapor pressure paradox (VPP) in multilamellar membrane phases and explain the experiments of Katsaras [Biophys. J. 73, 2924 (1997); 75, 2157 (1998)]. We show that the effects of the interfacial tension are substantially weaker than suggested by the previous theoretical discussion of the VPP effects [R. Podgornik and V. A. Parsegian, Biophys. J. 72, 942 (1997)]. By consistently taking into account the discrete, layered character of smectic liquid crystals, and anharmonic phonon effects, we show that the essence of VPP effects is in spatially nonuniform thermal expansion of smectic interlayer separations. We find that the average period of the whole finite stack can be both smaller (ordinary VPP effect at high enough interfacial tensions) or bigger (a reverse VPP effect at low interfacial tensions, overlooked in previous studies), relative to the average period of the corresponding infinite smectic stack. Looking at stacks from outside, these two effects show up as if there is an attractive (for the ordinary VPP effect), or repulsive (for the reverse VPP effect) pseudo-Casimir force acting between the two stack interfaces. We show however that the physics of VPP effects is obscured by schematically invoking Casimir-like forces. Rather, the ordinary and the reverse VPP effects are to be both characterized as thermomechanical anharmonic effects caused by a spatially nonuniform thermal expansion of smectic interlayer distances. Interlayer distances close to stack surfaces expand less (more) for the ordinary (reverse) VPP effect than those deep in the stack. The reverse VPP prevails at low interfacial tensions, simply because the membrane at the

  3. Size effects in spin-crossover nanoparticles in framework of 2D and 3D Ising-like breathing crystal field model

    NASA Astrophysics Data System (ADS)

    Gudyma, Iu.; Maksymov, A.; Spinu, L.

    2015-10-01

    The spin-crossover nanoparticles of different sizes and stochastic perturbations in external field taking into account the influence of the dimensionality of the lattice was studied. The analytical tools used for the investigation of spin-crossover system are based on an Ising-like model described using of the breathing crystal field concept. The changes of transition temperatures characterizing the systems' bistable properties for 2D and 3D lattices, and their dependence on its size and fluctuations strength were obtained. The state diagrams with hysteretic and non-hysteretic behavior regions have also been determined.

  4. Finite-size scaling investigation of the liquid-liquid critical point in ST2 water and its stability with respect to crystallization

    NASA Astrophysics Data System (ADS)

    Kesselring, T. A.; Lascaris, E.; Franzese, G.; Buldyrev, S. V.; Herrmann, H. J.; Stanley, H. E.

    2013-06-01

    The liquid-liquid critical point scenario of water hypothesizes the existence of two metastable liquid phases—low-density liquid (LDL) and high-density liquid (HDL)—deep within the supercooled region. The hypothesis originates from computer simulations of the ST2 water model, but the stability of the LDL phase with respect to the crystal is still being debated. We simulate supercooled ST2 water at constant pressure, constant temperature, and constant number of molecules N for N ⩽ 729 and times up to 1 μs. We observe clear differences between the two liquids, both structural and dynamical. Using several methods, including finite-size scaling, we confirm the presence of a liquid-liquid phase transition ending in a critical point. We find that the LDL is stable with respect to the crystal in 98% of our runs (we perform 372 runs for LDL or LDL-like states), and in 100% of our runs for the two largest system sizes (N = 512 and 729, for which we perform 136 runs for LDL or LDL-like states). In all these runs, tiny crystallites grow and then melt within 1 μs. Only for N ⩽ 343 we observe six events (over 236 runs for LDL or LDL-like states) of spontaneous crystallization after crystallites reach an estimated critical size of about 70 ± 10 molecules.

  5. Effect of zinc-borate glass addition on the thermal properties of the cordierite/Al2O3 composites containing nano-sized spinel crystal.

    PubMed

    Jo, Sinae; Kang, Seunggu

    2013-11-01

    Low-melting zinc-borate glass was added to the cordierite/Al2O3 composite in order to improve the sintering facility of Al2O3 and formation of nano-sized spinel crystal of high thermal conductivity. Increasing the ZnO/B2O3 ratio in the zinc-borate glass increased the ZnAl2O4 spinel and decreased the Al4B2O9 crystal peak intensities in X-ray diffraction pattern. The XRD peak intensities of the ZnAl2O4 spinel and Al4B2O9 crystals in the specimen containing 10 wt% zinc-borate glass (10G series) are higher than that of the specimen containing 5 wt% zinc-borate glass (5G series). The microstructures of most 10G series specimens had the flower-shaped crystal which was composed of 50 nm wide and 250 nm long needle-like crystals and identified as ZnAl2O4 spinel phase. The thermal conductivity of the 10G series specimen was higher than that of the 5G series in any ZnO/B2O3 ratio due to the formation of plenty of nano-sized ZnAl2O4 spinel of high thermal conductivity. Particularly, the thermal conductivity of the cordierite/Al2O3 composite containing 10 wt% zinc-borate glass of ZnO/B2O3 weight ratio = 1.5 was 3.8 W/Km which is much higher than that of the published value (3.0 W/Km). PMID:24245313

  6. Synthesis and characterization of anatase TiO{sub 2} nanotubes with controllable crystal size by a simple MWCNT template method

    SciTech Connect

    Kim, Ju Hyung; Zhang, Xiao Hui; Kim, Jae Deuk; Park, Hoon Mo; Lee, Sang Bok; Yi, Jin Woo; Jung, Seung Il

    2012-12-15

    Highly crystalline phase-pure anatase TiO{sub 2} nanotubes were produced by performing a simple calcinations process in air of the TiO{sub 2} coated MWCNTs composite material prepared by an in situ sol-gel method. A homogeneous thin coating layer of TiO{sub 2} on the surface of MWCNTs is firstly obtained. Calcination in ambient air at appropriate temperatures is performed to transform phase of TiO{sub 2} into anatase and remove MWCNTs simultaneously, resulting in pure anatase TiO{sub 2} nanotubes. Both end tips of the nanotubes are observed to be closed, probably due to covering up MWCNTs with TiO{sub 2} particles. The crystallization of anatase phase was formed upon 350 Degree-Sign C, and MWCNTs are completely oxidized between 500 and 650 Degree-Sign C, leaving anatase TiO{sub 2} nanotubes with an average crystal size increasing from about 8 to 24 nm as the temperature rises. Moreover, the tubular structure was found to collapse after calcinations at 700 Degree-Sign C. - Graphical abstract: TGA analysis and TEM images of the samples after calcinations in air at different temperatures: (a) before calcinations, (b) 350 Degree-Sign C, (c) 500 Degree-Sign C, and (d) 650 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer Highly crystalline and stable phase-pure anatase TiO{sub 2} nanotubes were produced by a simply MWCNT template method. Black-Right-Pointing-Pointer A homogeneous thin coating layer of TiO{sub 2} on the surface of MWCNTs could be obtained. Black-Right-Pointing-Pointer Small crystal size of anatase is formed at lower temperatures and higher temperatures cause significant increase of crystal size from 8 to 24 nm. Black-Right-Pointing-Pointer Convex closed tip structure of TiO{sub 2} nanotubes is formed owing to the good coating of TiO{sub 2}.

  7. Social Security's special minimum benefit.

    PubMed

    Olsen, K A; Hoffmeyer, D

    beneficiaries are female retired workers. About 90 percent of special minimum beneficiaries are retired workers, and 77 percent of those retired workers are women. The special minimum benefit has never provided poverty-level benefits. Maximum payable special minimum benefits (unreduced for early retirement) equal 85 percent of the poverty level for aged persons, down from 96 percent at the provision's inception. Major public policy considerations raised by this analysis include the following: Social Security benefits alone do not protect all long-term low earners from poverty. Low earners with 30 years of earnings equal to the annual full-time minimum wage who retired in selected years from 1982 to 2000 received benefits that were 3.9 percent to 20.1 percent below the poverty threshold, depending on the year they retired. For 40-year earners, the range was 3.9 percent to 15.3 percent below poverty. Furthermore, in 1993, 29.2 percent of retired-worker beneficiaries who were poor had 30 or more years of coverage. The size of the universe of persistently low earners with significant attachment to the covered workforce is unknown. Available research that examines two 28-month periods suggests that only 4 percent to 6 percent of full-time, full-period earners had below-minimum wages for more than 12 consecutive months. Targeting enhanced benefits only toward long-term, regular workers who are low earners is difficult under the current Social Security program. All else being equal, if total wage-indexed lifetime covered earnings are the same for both a full-career low earner and for a high earner who has worked only occasionally, then their Social Security benefits will be identical. Social Security has no information on number of hours worked, hourly wages, or other information that could distinguish between two such persons. PMID:12428507

  8. Multiple plagioclase crystal populations identified by crystal size distribution and in situ chemical data: Implications for timescales of magma chamber processes associated with the 1915 eruption of Lassen Peak, CA

    USGS Publications Warehouse

    Salisbury, M.J.; Bohrson, W.A.; Clynne, M.A.; Ramos, F.C.; Hoskin, P.

    2008-01-01

    Products of the 1915 Lassen Peak eruption reveal evidence for a magma recharge-magma mixing event that may have catalyzed the eruption and from which four compositional members were identified: light dacite, black dacite, andesitic inclusion, and dark andesite. Crystal size distribution, textural, and in situ chemical (major and trace element and Sr isotope) data for plagioclase from these compositional products define three crystal populations that have distinct origins: phenocrysts (long axis > 0??5 mm) that typically have core An contents between 34 and 36 mol %, microphenocrysts (long axis between 0??1 and 0??5 mm) that have core An contents of 66-69, and microlites (long axis < 0??1 mm) with variable An core contents from 64 to 52. Phenocrysts are interpreted to form in an isolated dacitic magma chamber that experienced slow cooling. Based on textural, compositional, and isotopic data for the magma represented by the dacitic component, magma recharge was not an important process until just prior to the 1915 eruption. Average residence times for phenocrysts are in the range of centuries to millennia. Microphenocrysts formed in a hybrid layer that resulted from mixing between end-member reservoir dacite and recharge magma of basaltic andesite composition. High thermal contrast between the two end-member magmas led to relatively high degrees of undercooling, which resulted in faster crystal growth rates and acicular and swallowtail crystal habits. Some plagioclase phenocrysts from the dacitic chamber were incorporated into the hybrid layer and underwent dissolution-precipitation, seen in both crystal textures and rim compositions. Average microphenocryst residence times are of the order of months. Microlites may have formed in response to decompression and/ or syn-eruptive degassing as magma ascended from the chamber through the volcanic conduit. Chemical distinctions in plagioclase microlite An contents reveal that melt of the dark andesite was more mafic than

  9. Derivation of physical and optical properties of mid-latitude cirrus ice crystals for a size-resolved cloud microphysics model

    DOE PAGESBeta

    Fridlind, Ann M.; Atlas, Rachel; van Diedenhoven, Bastiaan; Um, Junshik; McFarquhar, Greg M.; Ackerman, Andrew S.; Moyer, Elisabeth J.; Lawson, R. Paul

    2016-06-10

    Single-crystal images collected in mid-latitude cirrus are analyzed to provide internally consistent ice physical and optical properties for a size-resolved cloud microphysics model, including single-particle mass, projected area, fall speed, capacitance, single-scattering albedo, and asymmetry parameter. Using measurements gathered during two flights through a widespread synoptic cirrus shield, bullet rosettes are found to be the dominant identifiable habit among ice crystals with maximum dimension (Dmax) greater than 100 µm. Properties are therefore first derived for bullet rosettes based on measurements of arm lengths and widths, then for aggregates of bullet rosettes and for unclassified (irregular) crystals. Derived bullet rosette massesmore » are substantially greater than reported in existing literature, whereas measured projected areas are similar or lesser, resulting in factors of 1.5–2 greater fall speeds, and, in the limit of large Dmax, near-infrared single-scattering albedo and asymmetry parameter (g) greater by  ∼  0.2 and 0.05, respectively. A model that includes commonly imaged side plane growth on bullet rosettes exhibits relatively little difference in microphysical and optical properties aside from  ∼ 0.05 increase in mid-visible g primarily attributable to plate aspect ratio. In parcel simulations, ice size distribution, and g are sensitive to assumed ice properties.« less

  10. Growth of Large-Size SnS Thin Crystals Driven by Oriented Attachment and Applications to Gas Sensors and Photodetectors.

    PubMed

    Wang, Jun; Lian, Gang; Xu, Zhenghao; Fu, Chen; Lin, Zhaojun; Li, Liyi; Wang, Qilong; Cui, Deliang; Wong, Ching-Ping

    2016-04-20

    Freestanding large-size SnS thin crystals are synthesized via two-dimensional oriented attachment (OA) growth of colloidal quantum dots (CQDs) in a novel high-pressure solvothermal reaction. The SnS thin crystals present a uniform rectangular shape with a lateral size of 20-30 um and thickness of <10 nm. The evolution process demonstrates that a synergetic effect of pressure, aging time and organic ligands results in polycrystal-to-monocrystal formation and defect annihilation. Furthermore, gas sensor and photodetector devices, based on SnS thin single crystals, are also prepared. The sensing devices present high sensitivity, superior selectivity, low detection limit (≪100 ppb) and reversibility to NO2 at room temperature. The fabricated photodetector devices exhibit a high responsivity of 2.04 × 10(3) A W(1-) and high external quantum efficiency of ∼4.75 × 10(5) % at 532 nm, which are much higher than most of the photodetector devices. PMID:27054920

  11. Derivation of physical and optical properties of mid-latitude cirrus ice crystals for a size-resolved cloud microphysics model

    DOE PAGESBeta

    Fridlind, Ann M.; Atlas, Rachel; van Diedenhoven, Bastiaan; Um, Junshik; McFarquhar, Greg M.; Ackerman, Andrew S.; Moyer, Elisabeth J.; Lawson, R. Paul

    2016-06-10

    Single-crystal images collected in mid-latitude cirrus are analyzed to provide internally consistent ice physical and optical properties for a size-resolved cloud microphysics model, including single-particle mass, projected area, fall speed, capacitance, single-scattering albedo, and asymmetry parameter. Using measurements gathered during two flights through a widespread synoptic cirrus shield, bullet rosettes are found to be the dominant identifiable habit among ice crystals with maximum dimension (Dmax) greater than 100 µm. Properties are therefore first derived for bullet rosettes based on measurements of arm lengths and widths, then for aggregates of bullet rosettes and for unclassified (irregular) crystals. Derived bullet rosette massesmore » are substantially greater than reported in existing literature, whereas measured projected areas are similar or lesser, resulting in factors of 1.5–2 greater fall speeds, and, in the limit of large Dmax, near-infrared single-scattering albedo and asymmetry parameter (g) greater by ~0.2 and 0.05, respectively. Furthermore, a model that includes commonly imaged side plane growth on bullet rosettes exhibits relatively little difference in microphysical and optical properties aside from ~0.05 increase in mid-visible g primarily attributable to plate aspect ratio. In parcel simulations, ice size distribution, and g are sensitive to assumed ice properties.« less

  12. Derivation of physical and optical properties of mid-latitude cirrus ice crystals for a size-resolved cloud microphysics model

    NASA Astrophysics Data System (ADS)

    Fridlind, Ann M.; Atlas, Rachel; van Diedenhoven, Bastiaan; Um, Junshik; McFarquhar, Greg M.; Ackerman, Andrew S.; Moyer, Elisabeth J.; Lawson, R. Paul

    2016-06-01

    Single-crystal images collected in mid-latitude cirrus are analyzed to provide internally consistent ice physical and optical properties for a size-resolved cloud microphysics model, including single-particle mass, projected area, fall speed, capacitance, single-scattering albedo, and asymmetry parameter. Using measurements gathered during two flights through a widespread synoptic cirrus shield, bullet rosettes are found to be the dominant identifiable habit among ice crystals with maximum dimension (Dmax) greater than 100 µm. Properties are therefore first derived for bullet rosettes based on measurements of arm lengths and widths, then for aggregates of bullet rosettes and for unclassified (irregular) crystals. Derived bullet rosette masses are substantially greater than reported in existing literature, whereas measured projected areas are similar or lesser, resulting in factors of 1.5-2 greater fall speeds, and, in the limit of large Dmax, near-infrared single-scattering albedo and asymmetry parameter (g) greater by ˜ 0.2 and 0.05, respectively. A model that includes commonly imaged side plane growth on bullet rosettes exhibits relatively little difference in microphysical and optical properties aside from ˜ 0.05 increase in mid-visible g primarily attributable to plate aspect ratio. In parcel simulations, ice size distribution, and g are sensitive to assumed ice properties.

  13. Positive frequency shifts observed upon adsorbing micron-sized solid objects to a quartz crystal microbalance from the liquid phase.

    PubMed

    Pomorska, Agata; Shchukin, Dmitry; Hammond, Richard; Cooper, Matthew A; Grundmeier, Guido; Johannsmann, Diethelm

    2010-03-15

    By specifically binding derivatized colloidal particles and physisorbing nonderivatized particles to the surface of a quartz crystal microbalance (QCM), we have observed positive shifts of frequency, Deltaf, in contrast to the negative frequency shifts typically found in adsorption experiments. Evidently, the Sauerbrey relation does not apply to this situation. A comparison of frequencies shifts and bandwidths on different overtones reveals a coupled resonance: at low overtones, Deltaf is negative, whereas it is positive at high overtones, with maximal resonance bandwidth observed at the crossover point. As predicted by the Dybwad model, the spheres bound to the surface form resonating systems on their own. A composite resonator is formed, consisting of a large crystal with resonance frequency omega and the adsorbed spheres with resonance frequency omega(S). In the case in which the resonance frequency of the small spheres (firmly attached to crystal), omega(S), is higher than the resonance frequency of the crystal, omega, Deltaf of the composite system is negative (leading to the Sauerbrey limit). In the opposite limit (that is, in the case of large adsorbed particles bound to the sensor surface via a sufficiently weak bridge) Deltaf is positive. Such a behavior is known from sphere-plate contacts in the dry state. Finite element calculation demonstrates that this phenomena is also plausible in liquid phase media, with Deltaf critically dependent on the strength of the sphere-plate contact. Operated in this mode, the QCM most likely probes the contact strength, rather than the mass of the particle. PMID:20166672

  14. High birefringent rectangular-lattice photonic crystal fibers with low confinement loss employing different sizes of elliptical air holes in the cladding and the core

    NASA Astrophysics Data System (ADS)

    Liao, Jianfei; Sun, Junqiang

    2012-12-01

    Based on the full-vector finite element method with anisotropic perfectly matched layers, modal birefringence and confinement loss for the fundamental mode in rectangular-lattice photonic crystal fibers with different sizes of elliptical air holes in the cladding and the core are investigated numerically. The results show that the modal birefringence in this proposed photonic crystal fibers can be up to 5.64 × 10-2 at the wavelength of 1.55 μm. Moreover, when the birefringence is higher than 4 × 10-2, the confinement loss of x-polarized mode can be kept less than 0.005 dB/km at 1.55 μm. It means that the tradeoff between the high birefringence and the low confinement loss is overcome.

  15. Size and chain length effects on structural behaviors of biphenylcyclohexane-based liquid crystal nanoclusters by a coarse-grained model.

    PubMed

    Liao, Ming-Liang; Ju, Shin-Pon; Chang, Chun-Yi; Huang, Wei-Lin

    2012-06-01

    Size and chain length effects on structural behaviors of liquid crystal nanoclusters were examined by a coarse-grained model and the configurational-bias Monte Carlo (CBMC) simulation. The nanoclusters investigated in this study are composed of the biphenylcyclohexane-based BCH5H liquid crystal molecule and its derivatives. Results of the study show that the average energy decreases (i.e., more negative) as the cluster size (i.e., the number of molecules) increases. With the increasing cluster size, the equilibrium conformation of the nanocluster changes gradually from a pipe-like structure (for the smaller systems) to a ball-like cluster (for the larger systems). The order parameter of the system reduces with the transition of the equilibrium conformation. Regarding the chain length effect, the pipe-like equilibrium conformation (for the smaller systems) was observed more close to a pipe as the length of the tail alkyl chain of the derivatives extended. However, due to the flexibility of the tail alkyl chain, the pipe conformation of the system deflects slightly about its cyclohexyl group as the tail extends further. PMID:21975541

  16. Effect of particle size and particle size distribution on physical characteristics, morphology and crystal structure of explosively compacted high-T(sub c) superconductors

    NASA Technical Reports Server (NTRS)

    Kotsis, I.; Enisz, M.; Oravetz, D.; Szalay, A.

    1995-01-01

    A superconductor, of composition Y(Ba,K,Na)2Cu3O(x)/F(y) and a composite of composition Y(Ba,K,Na)2Cu3O(x)/F(y) + Ag, with changing K, Na and F content but a constant silver content (Ag = 10 mass%) was prepared using a single heat treatment. the resulting material was ground in a corundum lined mill, separated to particle size fractions of 0-40 micron, 0-63 micron and 63-900 micron and explosively compacted, using an explosive pressure of 10(exp 4) MPa and a subsequent heat treatment. Best results were obtained with the 63-900 micron fraction of composition Y(Ba(1.95) K(0.01)Cu3O(x)F(0),(05)/Ag: porosity less than 0.01 cu cm/g and current density 2800 A/sq cm at 77K.

  17. Minimum Competency Testing. Update.

    ERIC Educational Resources Information Center

    Beard, Jacob G.

    During the last decade many school systems began to define minimum levels of competency for their students and to construct tests to measure whether students had achieved these minimums. Many states have passed laws which require high school students to pass minimum competency tests in order to graduate. This digest overviews four areas of…

  18. Effect of particle size and particle size distribution on physical characteristics, morphology and crystal strucutre of explosively compacted high-Tc superconductors

    SciTech Connect

    Kotsis, I.; Enisz, M.; Oravetz, D.

    1994-12-31

    A superconductor, of composition Y(Ba,K,Na){sub 2}Cu{sub 3}O{sub x}/F{sub y} and a composite, of composition Y(Ba,K,Na){sub 2}Cu{sub 3}O{sub x}/F{sub y}+Ag, with changing K, Na and F content, but a constant silver content (Ag=10 mass per cent) was prepared using a single heat treatment. The resulting material was ground in a corundum lined mill, separated to particle size fractions of 0-40 {mu}m, 0-63 {mu}m and 63-900 {mu}m and explosively compacted, using an explosive pressure of 10{sup 4} MPa and a subsequent heat treatment. Best results were obtained with the 63-900 {mu}m fraction of composition Y(Ba{sub 1,95}K{sub 0,01})Cu{sub 3}O{sub x}F{sub 0,05}/Ag: porosity <0.01 cm{sup 3}/g and current density 2800 A/cm{sup 2} at 77 K.

  19. Quantitative Research on the Minimum Wage

    ERIC Educational Resources Information Center

    Goldfarb, Robert S.

    1975-01-01

    The article reviews recent research examining the impact of minimum wage requirements on the size and distribution of teenage employment and earnings. The studies measure income distribution, employment levels and effect on unemployment. (MW)

  20. Colloidal Synthesis of Quantum Confined Single Crystal CsPbBr3 Nanosheets with Lateral Size Control up to the Micrometer Range

    PubMed Central

    2016-01-01

    We report the nontemplated colloidal synthesis of single crystal CsPbBr3 perovskite nanosheets with lateral sizes up to a few micrometers and with thickness of just a few unit cells (i.e., below 5 nm), hence in the strong quantum confinement regime, by introducing short ligands (octanoic acid and octylamine) in the synthesis together with longer ones (oleic acid and oleylamine). The lateral size is tunable by varying the ratio of shorter ligands over longer ligands, while the thickness is mainly unaffected by this parameter and stays practically constant at 3 nm in all the syntheses conducted at short-to-long ligands volumetric ratio below 0.67. Beyond this ratio, control over the thickness is lost and a multimodal thickness distribution is observed. PMID:27228475

  1. Colloidal Synthesis of Quantum Confined Single Crystal CsPbBr3 Nanosheets with Lateral Size Control up to the Micrometer Range.

    PubMed

    Shamsi, Javad; Dang, Zhiya; Bianchini, Paolo; Canale, Claudio; Stasio, Francesco Di; Brescia, Rosaria; Prato, Mirko; Manna, Liberato

    2016-06-15

    We report the nontemplated colloidal synthesis of single crystal CsPbBr3 perovskite nanosheets with lateral sizes up to a few micrometers and with thickness of just a few unit cells (i.e., below 5 nm), hence in the strong quantum confinement regime, by introducing short ligands (octanoic acid and octylamine) in the synthesis together with longer ones (oleic acid and oleylamine). The lateral size is tunable by varying the ratio of shorter ligands over longer ligands, while the thickness is mainly unaffected by this parameter and stays practically constant at 3 nm in all the syntheses conducted at short-to-long ligands volumetric ratio below 0.67. Beyond this ratio, control over the thickness is lost and a multimodal thickness distribution is observed. PMID:27228475

  2. Direct synthesis of size-tunable PbS nanocubes and octahedra and the pH effect on crystal shape control.

    PubMed

    Chen, Hsiang-Sheng; Wu, Szu-Chieh; Huang, Michael H

    2015-09-14

    A one-pot synthesis for the growth of PbS nanocubes and octahedra has been developed by heating an aqueous mixture of cetyltrimethylammonium bromide (CTAB), thioacetamide (TAA), lead acetate, and nitric acid at 90 °C for 3 h. The method allows for direct large-scale production of small and uniform PbS nanocubes. The PbS cubes and octahedra exhibit different surface properties, as evidenced by zeta potential measurements and stability tests in methyl orange and methylene blue solutions. Examination of the reagent introduction sequence indicates that early or late addition of nitric acid to tune the initial solution pH can strongly influence crystal growth rate and result in the formation of PbS crystals with different sizes and shapes. Remarkably, the use of pre-formed PbS nanocubes for further crystal growth under low TAA concentration can transform the cubes into large octahedra through a series of particle shape evolution. PMID:25536923

  3. The effects of CeO{sub 2} addition on crystallization behavior and pore size in microporous calcium titanium phosphate glass ceramics

    SciTech Connect

    Soleimani, F.; Rezvani, M.

    2012-06-15

    Highlights: ► We prepare a phosphate glass ceramic in the system of CaO–TiO{sub 2}–P{sub 2}O{sub 5} and add 2 to 6 mol% CeO{sub 2} to it. We determine the optimum percentage of CeO{sub 2} addition. ► We study phase separation, suitable time and temperature for crystallization in the microporous Calcium Titanium Phosphate Glass Ceramics utilizing DTA, SEM and XRD. ► We investigate on pore size utilizing BET and SEM techniques before and after CeO{sub 2} addition. ► CeO{sub 2} increases the pore size in the Calcium Titanium Phosphate Glass Ceramics. -- Abstract: In this research the effect of the addition of CeO{sub 2} to microporous Calcium Titanium Phosphate glass ceramics was studied. Different molar percentages of CeO{sub 2} were added to three samples of a base glass whose composition was P{sub 2}O{sub 5} 30, CaO 45, TiO{sub 2} 25 (mol%). The first sample had 2 mol% CeO{sub 2}, the second sample had 4 mol% CeO{sub 2}, and the third sample had 6 mol% CeO{sub 2}. The fourth sample did not contain any CeO{sub 2}. The glass samples were melted and crystallized to bulk glass ceramics by a conventional method. Differential Thermal Analysis (DTA) was utilized to determine the appropriate nucleation and crystallization temperatures. Among the samples, the DTA curve of the sample which had 2 mol% CeO{sub 2} had the sharpest crystallization peak. Therefore, this sample was chosen to prepare the glass ceramics. Using X-ray Diffraction (XRD) it was found that in all samples β-Ca{sub 3}(PO{sub 4}){sub 2} and CaTi{sub 4}(PO{sub 4}){sub 6} were the major phases. The β-Ca{sub 3}(PO{sub 4}){sub 2} phase was dissolved away by soaking the glass ceramics in HCl, leaving a porous skeleton of CaTi{sub 4}(PO{sub 4}){sub 6}. CeO{sub 2} addition increased the glass transition temperature and decreased the crystallization time and temperature. It was shown that CeO{sub 2} addition resulted in an increase in the mean pore diameter while the specific surface area decreased

  4. Synthesis of submicrometer-sized titania spherical particles with a sol-gel method and their application to colloidal photonic crystals.

    PubMed

    Mine, Eiichi; Hirose, Mitsuaki; Nagao, Daisuke; Kobayashi, Yoshio; Konno, Mikio

    2005-11-01

    A synthetic method for preparing submicrometer-sized titania particles is proposed, which is based on hydrolysis of titanium alkoxide with the use of a cosolvent and an amine catalyst for alkoxide hydrolysis. The preparation was performed with different amines of ammonia, methylamine (MA), and dimethylamine (DMA) in different solvents of ethanol/acetonitrile, ethanol/methanol, ethanol/acetone, ethanol/acetonitrile, and ethanol/formamide for 0.1-0.3 M water and 0.03 M titanium tetraisopropoxide (TTIP) at temperatures of 10-50 degrees C. The use of the ethanol/acetonitrile solvent with MA was required for preparing monodispersed, spherical particles. The number average of the titania particle sizes and their coefficient of variation were varied from 143 to 551 nm and from 5.7 to 20.6%, respectively, with reaction temperature and concentrations of water and MA. Colloidal crystals of titania particles fabricated with a sedimentation method revealed reflection peaks attributed to Bragg's diffraction. Annealing at 100-1000 degrees C led to shrinkage and crystallization of titania particles followed by an increase in the refractive index of titania particles. PMID:15949809

  5. Lung Injury Induced by TiO2 Nanoparticles Depends on Their Structural Features: Size, Shape, Crystal Phases, and Surface Coating

    PubMed Central

    Wang, Jiangxue; Fan, Yubo

    2014-01-01

    With the rapid development of nanotechnology, a variety of engineered nanoparticles (NPs) are being produced. Nanotoxicology has become a hot topic in many fields, as researchers attempt to elucidate the potential adverse health effects of NPs. The biological activity of NPs strongly depends on physicochemical parameters but these are not routinely considered in toxicity screening, such as dose metrics. In this work, nanoscale titanium dioxide (TiO2), one of the most commonly produced and widely used NPs, is put forth as a representative. The correlation between the lung toxicity and pulmonary cell impairment related to TiO2 NPs and its unusual structural features, including size, shape, crystal phases, and surface coating, is reviewed in detail. The reactive oxygen species (ROS) production in pulmonary inflammation in response to the properties of TiO2 NPs is also briefly described. To fully understand the potential biological effects of NPs in toxicity screening, we highly recommend that the size, crystal phase, dispersion and agglomeration status, surface coating, and chemical composition should be most appropriately characterized. PMID:25479073

  6. All-electron LCAO calculations of the LiF crystal phonon spectrum: Influence of the basis set, the exchange-correlation functional, and the supercell size.

    PubMed

    Evarestov, R A; Losev, M V

    2009-12-01

    For the first time the convergence of the phonon frequencies and dispersion curves in terms of the supercell size is studied in ab initio frozen phonon calculations on LiF crystal. Helmann-Feynman forces over atomic displacements are found in all-electron calculations with the localized atomic functions (LCAO) basis using CRYSTAL06 program. The Parlinski-Li-Kawazoe method and FROPHO program are used to calculate the dynamical matrix and phonon frequencies of the supercells. For fcc lattice, it is demonstrated that use of the full supercell space group (including the supercell inner translations) enables to reduce essentially the number of the displacements under consideration. For Hartree-Fock (HF), PBE and hybrid PBE0, B3LYP, and B3PW exchange-correlation functionals the atomic basis set optimization is performed. The supercells up to 216 atoms (3 x 3 x 3 conventional unit cells) are considered. The phonon frequencies using the supercells of different size and shape are compared. For the commensurate with supercell k-points the best agreement of the theoretical results with the experimental data is found for B3PW exchange-correlation functional calculations with the optimized basis set. The phonon frequencies at the most non-commensurate k-points converged for the supercell consisting of 4 x 4 x 4 primitive cells and ensures the accuracy 1-2% in the thermodynamic properties calculated (the Helmholtz free energy, entropy, and heat capacity at the room temperature). PMID:19382176

  7. Finite-Size Effects on Liquid-Solid Phase Coexistence and the Estimation of Crystal Nucleation Barriers

    NASA Astrophysics Data System (ADS)

    Statt, Antonia; Virnau, Peter; Binder, Kurt

    2015-01-01

    A fluid in equilibrium in a finite volume V with particle number N at a density ρ =N /V exceeding the onset density ρf of freezing may exhibit phase coexistence between a crystalline nucleus and surrounding fluid. Using a method suitable for the estimation of the chemical potential of dense fluids, we obtain the excess free energy due to the surface of the crystalline nucleus. There is neither a need to precisely locate the interface nor to compute the (anisotropic) interfacial tension. As a test case, a soft version of the Asakura-Oosawa model for colloid-polymer mixtures is treated. While our analysis is appropriate for crystal nuclei of arbitrary shape, we find the nucleation barrier to be compatible with a spherical shape and consistent with classical nucleation theory.

  8. Apatite (U-Th-Sm)/He age dispersion arising from analysis of variable grain sizes and broken crystals - examples from the Scottish Southern Uplands

    NASA Astrophysics Data System (ADS)

    Łuszczak, Katarzyna; Persano, Cristina; Stuart, Finlay; Brown, Roderick

    2016-04-01

    Apatite (U-Th-Sm)/He (AHe) thermochronometry is a powerful technique for deciphering denudation of the uppermost crust. However, the age dispersion of single grains from the same rock is typical, and this hampers establishing accurate thermal histories when low grain numbers are analysed. Dispersion arising from the analysis of broken crystal fragments[1] has been proposed as an important cause of age dispersion, along with grain size and radiation damage. A new tool, Helfrag[2], allows constraints to be placed on the low temperature history derived from the analysis of apatite crystal fragments. However, the age dispersion model has not been fully tested on natural samples yet. We have performed AHe analysis of multiple (n = 20-25) grains from four rock samples from the Scottish Southern Uplands, which were subjected to the same exhumation episodes, although, the amount of exhumation varied between the localities. This is evident from the range of AFT ages (˜60 to ˜200 Ma) and variable thermal histories showing either strong, moderate and no support for a rapid cooling event at ˜60 Ma. Different apatite size and fragment geometry were analysed in order to maximise age dispersion. In general, the age dispersion increases with increasing AFT age (from 47% to 127%), consistent with the prediction from the fragmentation model. Thermal histories obtained using Helfrag were compared with those obtained by standard codes based on the spherical approximation. In one case, the Helfrag model was capable of resolving the higher complexity of the thermal history of the rock, constraining several heating/cooling events that are not predicted by the standard models, but are in good agreement with the regional geology. In other cases, the thermal histories are similar for both Helfrag and standard models and the age predictions for the Helfrag are only slightly better than for standard model, implying that the grain size has the dominant role in generating the age dispersion

  9. High coercivity sized controlled cobalt–gold core–shell nano-crystals prepared by reverse microemulsion

    SciTech Connect

    Bahmanrokh, Ghazaleh; Hashim, Mansor; Soltani, Nayereh; Ismail, Ismayadi; Vaziri, Parisa; Navaseri, Manizheh; Erfani, Maryam; Kanagesan, Samikannu

    2013-10-15

    Graphical abstract: - Highlights: • Calculating the crystallinity percentage and percentage of phases presented in Co–Au core–shell nanoparticles. • Magnetic properties of four groups nanogarin: 5, 10, 15, 20 nm. • Single domain ferromagnetic materials with high coercivity at room temperature. • Intrinsic blocking temperature measured in zero field cooled-warmed (ZFC-W). - Abstract: Size-controlled cobalt–gold core–shell nanoparticles were synthesized via the reverse-micelle microemulsion method. In order to control the size of the nanoparticles, the nucleation and growth process were performed within a confined space by adjusting the water to surfactant ratio of reverse micelles solution during synthesis. The crystallinity percentage and percentage of phases presented in Co–Au core–shell nanoparticles were calculated using X-ray diffraction data. The results from transmission electron microscopy provide direct evidence for core–shell structure nanomaterials. Magnetic properties of the samples were investigated using a vibrating sample magnetometer. The as-prepared samples showed significant coercivity at room temperature. The intrinsic blocking temperature was experimentally deduced from zero-field-cooled warmed (ZFC-W) curves by a simple method without employing an external magnetic field. The B-field dependence temperature data of Co–Au nanoparticles exhibited an intrinsic blocking temperature at 45 K. Annealing these samples at 400 °C caused an increase in particle size, crystallinity percentage and further enhanced their magnetic properties.

  10. Remote sensing estimates of cirrus particle size for tropical and midlatitude cirrus: Hexagonal crystals and ice spheres

    NASA Technical Reports Server (NTRS)

    Wielicki, Bruce A.; Minnis, Patrick; Arduini, Robert; Parker, Lindsay; Tsay, Si-Chee; Takano, Yoshihide; Liou, Kuo-Nan

    1993-01-01

    A large discrepancy exists in current estimates of a mean cirrus particle size appropriate for calculations of the effects of these ice clouds on solar and thermal infrared radiative fluxes. For spheres with large size parameter (x = (2 pi r / lambda) is greater than 30, where r is particle radius), and moderate absorption (n(sup i) x less than 1, where n(sup i) is imaginary index of refraction for ice), the optimal effective particle radius is given by: r(sub e) = integral of r(exp 3)n(r)dr / integral of r(exp 2)n(r)dr. For the remote sensing of cirrus particle size at wavelengths of 0.83, 1.65, and 2.21 mu m, a 50 mu m ice sphere would have a size parameter of about 200, and values of n(sup i) x of 0, 0.045, and 0.06, satisfying the above conditions. However, while r(sub e) is a well-defined parameter for spheres, this cross-section area-weighted particle radius can only be extended to non-spherical particles by defining some equivalent sphere, typically an equivalent volume or equivalent cross-section area sphere. Using equivalent volume spheres, values of r(sub e) obtained over Lake Michigan on October 28, 1986, during FIRE phase I varied from 200 mu m (King Air 2D Imaging probes) to 60 mu m (Landsat reflectances at 0.83, 1.65, and 2.2 mu m), to 25 mu m (HIS spectrometer thermal emission between 8 and 12 mu m). Three major uncertainties were identified in this comparison: small ice particles missed by the 2D-C aircraft probes, uncertain ice refractive index, and uncertainties in the single scatter albedos and scattering phase functions used in the radiative calculations. Since the first FIRE cirrus results, advances have been made in all three areas. The present paper reports on improvements in the radiative modeling of ice particles at 0.83, 1.65, and 2.21 mu m wavelengths appropriate for comparisons to Landsat Thematic Mapper data. The paper also includes new results for Landsat observations of ice clouds in the eastern and western tropical Pacific.

  11. Correlation of the structure and the luminescence properties of Eu 3+-doped Gd 2O 3 oxide between fiber single crystal and the nano-size powders

    NASA Astrophysics Data System (ADS)

    Louis, C.; Lebbou, K.; Flores-Gonzalez, M. A.; Bazzi, R.; Hautefeuille, B.; Mercier, B.; Roux, S.; Perriat, P.; Olagnon, C.; Tillement, O.

    2004-05-01

    Gd 2- xEu xO 3 powder materials doped with Eu 3+ using different concentration from x=0 to 2 were prepared by a new sol-lyophilization synthesis and fiber single crystal (Gd 2O 3-Gd 2O 3/Eu 3+) oxides were grown using laser-heated pedestal growth (LHPG) technique. X-ray powder diffraction performed at room temperature showed that the materials obtained by lyophilization technique are cubic, lies in the nanometer range and different from bulk materials. The materials are a continued solid solution and the lattice parameter a-axis increases with Eu 3+ concentration. The fibers grown by LHPG technique were single crystal, transparent, red in color when Eu 3+ concentration is high, and the structure is monoclinic for Eu 3+<15%. The luminescence of Eu 3+ from C 2 crystallographic site was been detected. In the case of nano-particles oxide, an additional peak in emission spectral is obtained at λ=610 nm. The influence of Eu 3+, particles sizes and the structure on the luminescence spectral of Eu 3+ ions was been described.

  12. Influence of finite size and wetting on nematic and smectic phase behavior of liquid crystal confined to controlled-pore matrices

    NASA Astrophysics Data System (ADS)

    Kutnjak, Zdravko; Kralj, Samo; Lahajnar, Gojmir; Žumer, Slobodan

    2004-11-01

    The high-resolution calorimetric study was carried out on octylcyanobiphenyl liquid crystal (LC) confined to various controlled-pore glass (CPG) matrices with silane-treated surface. The diameter of the voids cross section ranged between 23.7 and 395nm . The results are compared to those obtained previously on CPG voids nontreated with silane. We found a striking similarity between the shifts in the isotropic to nematic and nematic to smectic- A phase transition temperatures as a function of the void radius in which order parameter variations at the LC-void interface play the dominant role. Weaker temperature shifts are observed in silane-treated samples, where surface ordering tendency is larger. In nontreated samples, a finite-size scaling law in the maximum value of the heat capacity at the nematic to smectic- A transition was observed for void diameters larger than 20nm . In silane-treated samples, this behavior is considerably changed by surface wetting interactions.

  13. New developments in nanoparticle-liquid crystal composites: from magic-sized semiconductor nanoclusters to alignment pattern formation via nanoparticle stenciling

    NASA Astrophysics Data System (ADS)

    Mirzaei, Javad; Sawatzky, Ryan; Sharma, Anshul; Urbanski, Martin; Yu, Kui; Kitzerow, Heinz-S.; Hegmann, Torsten

    2012-03-01

    We here report on the alignment and electro-optic properties of nematic liquid crystals (LCs) either containing nanoscale particles as additives or featuring particles patterned on substrates. The investigated nematic LCs or LC dispersions are doped or in contact with magic-sized semiconductor CdSe nanocrystals (MSNCs) or silane- and alkylthiol monolayercapped gold nanoparticles. Three single-sized CdSe quantum dots capped with myristic acid exhibiting bright bandgap photoluminescence (PL) at λmax ~ 463 nm were tested as additives. Two of the quantum dots only vary in the amount of defects as indicated by different bandgap and deep trap PL. The third MSNC sample is compositionally different, doped with Zn. These MSNCs with almost identical sizes were doped at different concentrations (1-5 wt%) into the nematic phase of the 2-phenylpyrimidine-based LC1. Only the Zn-doped MSNCs showed the formation of birefringent stripes surrounded by areas of homeotropic alignment between plain glass slides at all concentrations as observed for many other nanoparticle-doped nematic LCs reported earlier by our group. In polyimide-coated glass slides favoring planar orientation of the nematic director, planar alignment was observed. Similarly, siloxane-coated gold nanoparticle additives with narrow size distribution, but larger size, show homeotropic alignment between plain glass and planar alignment in rubbed polyimide-coated cells. Surprisingly then, we succeeded in creating alignment patterns using smaller, ~2 nm alkylthiol-capped gold nanoparticles using a process called stenciling that allowed us to generate patterns of homeotropic alignment in a continuum of planar alignment of the nematic LC. Finally, electro-optic investigations on some of these samples revealed that only the Zn-doped magic-sized MSNCs significantly lower the dielectric anisotropy as well as the splay elastic constant of the nematic host, despite identical size and surface functionality of the three used

  14. Crystal- and fragment- size distributions of quartz and zircon in pumice: growth and fragmentation conditions in large and small-volume magma chambers

    NASA Astrophysics Data System (ADS)

    Bindeman, I.

    2003-12-01

    I describe an acid (HF and HBF4) technique to extract phenocrysts from individual vesiculated pumice clasts, coupled with camera- and computer-assisted measurements of phenocryst length, width, 3D shape, and vol abundance. CSDs of quartz and zircon are presented for several well-known voluminous ash-flow tuffs and small-volume lavas: Bishop, Lava Creek, Lower Bandelier, Toba, Katmai, and Timber Mt. Measured CSDs of quartz and zircon from these clasts provide a quenched "snapshot" view of growth conditions in preclimactic magma chambers. A common feature of CSDs of unfragmented phenocrysts is a concave-down, lognormal shape in contrast to the reported linear CSDs in more mafic systems.In addition, there are no crystals smaller than a threshold size. These features in silicic magmas are interpreted to be a general result of surface-controlled crystal growth (with growth rate dispersion) by layer nucleation. CSD slopes on log-linear frequency- size graphs in large volume tuffs, and smaller volume intracaldera lavas are similar, and do not simply correlate to the eruptive volume, or SHRIMP-determined zircon ages. CSDs of quartz in clasts with known stratigraphic positions document single evolving reservoir, fingerprint different magma batches (L Bandelier and Lava Creek), and overgrowth and gravitational redistribution (Bishop). Fragment size distributions (FSDs) in the same clasts document fragmentation due to 1) decrepitation of melt inclusions decompression- and heating-induced), and 2)syneruptive breakage. FSDs are treated with lognormal, Weibull, and fractal distributions. Among studied clasts, asymptotic and fractal FSDs are found to be more common. However, the genesis mechanisms (e.g. fractal, scale-invariant vs. size-dependent lognormal) inferred from CSD or FSD should be treated with caution. Decrepitation results in a smaller number of fragments (2-6) than crushing and in shapes that can be distinguished on perimeter/area vs. length diagrams. CSD and FSD

  15. 2011 Sea Ice Minimum

    NASA Video Gallery

    This video shows Arctic sea ice from March 7, 2011, to Sept. 9, 2011, ending with a comparison of the 30-year average minimum extent, shown in yellow, and the Northwest Passage, in red. (no audio) ...

  16. Protein Crystallization

    NASA Technical Reports Server (NTRS)

    Chernov, Alexander A.

    2005-01-01

    Nucleation, growth and perfection of protein crystals will be overviewed along with crystal mechanical properties. The knowledge is based on experiments using optical and force crystals behave similar to inorganic crystals, though with a difference in orders of magnitude in growing parameters. For example, the low incorporation rate of large biomolecules requires up to 100 times larger supersaturation to grow protein, rather than inorganic crystals. Nucleation is often poorly reproducible, partly because of turbulence accompanying the mixing of precipitant with protein solution. Light scattering reveals fluctuations of molecular cluster size, its growth, surface energies and increased clustering as protein ages. Growth most often occurs layer-by-layer resulting in faceted crystals. New molecular layer on crystal face is terminated by a step where molecular incorporation occurs. Quantitative data on the incorporation rate will be discussed. Rounded crystals with molecularly disordered interfaces will be explained. Defects in crystals compromise the x-ray diffraction resolution crucially needed to find the 3D atomic structure of biomolecules. The defects are immobile so that birth defects stay forever. All lattice defects known for inorganics are revealed in protein crystals. Contribution of molecular conformations to lattice disorder is important, but not studied. This contribution may be enhanced by stress field from other defects. Homologous impurities (e.g., dimers, acetylated molecules) are trapped more willingly by a growing crystal than foreign protein impurities. The trapped impurities induce internal stress eliminated in crystals exceeding a critical size (part of mni for ferritin, lysozyme). Lesser impurities are trapped from stagnant, as compared to the flowing, solution. Freezing may induce much more defects unless quickly amorphysizing intracrystalline water.

  17. Unidirectional growth of large size urea doped L-cysteine hydrochloride monohydrate NLO organic crystal and investigations of its crystalline and optical properties.

    PubMed

    Verma, Sunil; Rao, K Ramachandra; Kar, S; Bartwal, K S

    2016-01-15

    Organic crystals of urea doped L-cysteine hydrochloride monohydrate have been grown by unidirectional solution growth technique. The crystal grown by this technique has high growth rate as compared to the crystals grown using conventional slow cooling method. This method is ideally suited to grow crystals along a specific direction. The growth process was monitored at regular intervals of time in a time-lapsed manner to estimate the growth rate and also monitor its quality visually. The grown crystal was subjected to different characterizations in order to confirm the phase of the grown crystal, its crystalline perfection and optical properties. The X-ray diffraction confirmed the phase of the crystal. The rocking curve recorded using high resolution X-ray diffraction (HRXRD) technique reveals that the crystal grown using conventional slow cooling method has internal gain boundaries whereas that grown by unidirectional technique has high degree of crystalline perfection. The bonding environment present in the crystal was characterized by FTIR spectroscopy where vibrational frequencies of the different functional groups present were identified. The optical quality of the crystal was characterized using UV-vis-NIR spectrophotometer and Mach-Zehnder interferometer. The nonlinear optical response of the crystal was measured using Kurtz-Perry method and found to be 1.4 times that of a KDP crystal. PMID:26282319

  18. Unidirectional growth of large size urea doped L-cysteine hydrochloride monohydrate NLO organic crystal and investigations of its crystalline and optical properties

    NASA Astrophysics Data System (ADS)

    Verma, Sunil; Ramachandra Rao, K.; Kar, S.; Bartwal, K. S.

    2016-01-01

    Organic crystals of urea doped L-cysteine hydrochloride monohydrate have been grown by unidirectional solution growth technique. The crystal grown by this technique has high growth rate as compared to the crystals grown using conventional slow cooling method. This method is ideally suited to grow crystals along a specific direction. The growth process was monitored at regular intervals of time in a time-lapsed manner to estimate the growth rate and also monitor its quality visually. The grown crystal was subjected to different characterizations in order to confirm the phase of the grown crystal, its crystalline perfection and optical properties. The X-ray diffraction confirmed the phase of the crystal. The rocking curve recorded using high resolution X-ray diffraction (HRXRD) technique reveals that the crystal grown using conventional slow cooling method has internal gain boundaries whereas that grown by unidirectional technique has high degree of crystalline perfection. The bonding environment present in the crystal was characterized by FTIR spectroscopy where vibrational frequencies of the different functional groups present were identified. The optical quality of the crystal was characterized using UV-vis-NIR spectrophotometer and Mach-Zehnder interferometer. The nonlinear optical response of the crystal was measured using Kurtz-Perry method and found to be 1.4 times that of a KDP crystal.

  19. Influence of rare earth cation size on the crystal structure in rare earth silicates, Na2RESiO4(OH) (RE = Sc, Yb) and NaRESiO4 (RE = La, Yb)

    NASA Astrophysics Data System (ADS)

    Latshaw, Allison M.; Wilkins, Branford O.; Chance, W. Michael; Smith, Mark D.; zur Loye, Hans-Conrad

    2016-01-01

    Crystals of Na2ScSiO4(OH) and Na2YbSiO4(OH) were synthesized at low temperatures using a sodium hydroxide based hydroflux, while crystals of NaLaSiO4 and NaYbSiO4 were grown at high temperatures using a sodium fluoride/sodium chloride eutectic flux. Both structure types were crystallized under reaction conditions that, when used for medium sized rare earths (RE = Pr, Nd, Sm - Tm) yield the Na5RE4X[SiO4]4 structure type, where X is OH in the hydroflux conditions and F in the eutectic flux conditions. Herein, we report the synthesis, structure, size effect, and magnetic properties of these compositions and introduce the new structure type of Na2RESiO4(OH), which crystallizes in the orthorhombic space group Pca21, of NaLaSiO4, which crystallizes in the orthorhombic space group Pna21, and of NaYbSiO4, which crystallizes in the orthorhombic space group Pnma, where both NaRESiO4 compounds have one silicon structural analog.

  20. Record Sea Ice Minimum

    NASA Technical Reports Server (NTRS)

    2007-01-01

    Arctic sea ice reached a record low in September 2007, below the previous record set in 2005 and substantially below the long-term average. This image shows the Arctic as observed by the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) aboard NASA's Aqua satellite on September 16, 2007. In this image, blue indicates open water, white indicates high sea ice concentration, and turquoise indicates loosely packed sea ice. The black circle at the North Pole results from an absence of data as the satellite does not make observations that far north. Three contour lines appear on this image. The red line is the 2007 minimum, as of September 15, about the same time the record low was reached, and it almost exactly fits the sea ice observed by AMSR-E. The green line indicates the 2005 minimum, the previous record low. The yellow line indicates the median minimum from 1979 to 2000.

  1. Crystal-Size Effects on Carbon Dioxide Capture of a Covalently Alkylamine-Tethered Metal-Organic Framework Constructed by a One-Step Self-Assembly

    PubMed Central

    Kim, Yun Kyeong; Hyun, Sung-min; Lee, Jae Hwa; Kim, Tae Kyung; Moon, Dohyun; Moon, Hoi Ri

    2016-01-01

    To enhance the carbon dioxide (CO2) uptake of metal-organic frameworks (MOFs), amine functionalization of their pore surfaces has been studied extensively. In general, amine-functionalized MOFs have been synthesized via post-synthetic modifications. Herein, we introduce a one-step construction of a MOF ([(NiLethylamine)(BPDC)] = MOFNH2; [NiLethylamine]2+ = [Ni(C12H32N8)]2+; BPDC2− = 4,4‘-biphenyldicarboxylate) possessing covalently tethered alkylamine groups without post-synthetic modification. Two-amine groups per metal centre were introduced by this method. MOFNH2 showed enhanced CO2 uptake at elevated temperatures, attributed to active chemical interactions between the amine groups and the CO2 molecules. Due to the narrow channels of MOFNH2, the accessibility to the channel of CO2 is the limiting factor in its sorption behaviour. In this context, only crystal size reduction of MOFNH2 led to much faster and greater CO2 uptake at low pressures. PMID:26757890

  2. Crystal-Size Effects on Carbon Dioxide Capture of a Covalently Alkylamine-Tethered Metal-Organic Framework Constructed by a One-Step Self-Assembly

    NASA Astrophysics Data System (ADS)

    Kim, Yun Kyeong; Hyun, Sung-Min; Lee, Jae Hwa; Kim, Tae Kyung; Moon, Dohyun; Moon, Hoi Ri

    2016-01-01

    To enhance the carbon dioxide (CO2) uptake of metal-organic frameworks (MOFs), amine functionalization of their pore surfaces has been studied extensively. In general, amine-functionalized MOFs have been synthesized via post-synthetic modifications. Herein, we introduce a one-step construction of a MOF ([(NiLethylamine)(BPDC)] = MOFNH2 [NiLethylamine]2+ = [Ni(C12H32N8)]2+ BPDC2- = 4,4‘-biphenyldicarboxylate) possessing covalently tethered alkylamine groups without post-synthetic modification. Two-amine groups per metal centre were introduced by this method. MOFNH2 showed enhanced CO2 uptake at elevated temperatures, attributed to active chemical interactions between the amine groups and the CO2 molecules. Due to the narrow channels of MOFNH2, the accessibility to the channel of CO2 is the limiting factor in its sorption behaviour. In this context, only crystal size reduction of MOFNH2 led to much faster and greater CO2 uptake at low pressures.

  3. Minimum variance geographic sampling

    NASA Technical Reports Server (NTRS)

    Terrell, G. R. (Principal Investigator)

    1980-01-01

    Resource inventories require samples with geographical scatter, sometimes not as widely spaced as would be hoped. A simple model of correlation over distances is used to create a minimum variance unbiased estimate population means. The fitting procedure is illustrated from data used to estimate Missouri corn acreage.

  4. Minimum Critical Values Study

    SciTech Connect

    Fox, P.B.

    2005-07-11

    This report provides minimum critical values for various 30-cm water-reflected uranium and plutonium oxide and nitrate aqueous mixtures as calculated by the SCALE CSAS1X sequence using the 238-group ENDF/B-V neutron cross-section library. The minimum values were determined through parametric searches in one-dimensional geometry. The calculations have been performed to obtain the minimum values: critical volume and mass for spheres, critical radius for cylinders, critical thickness for slabs, and minimum critical concentration (infinite geometry) for the following homogeneous mixtures: (1) UO{sub 2}-H{sub 2}O for 3, 4, 5, 20, and 100 wt % {sup 235}U; (2) UNH for 3, 4, 5, 20, and 100 wt % {sup 235}U; (3) PuO{sub 2}-H{sub 2}O for 100/0/0, 95/5/0, 90/5/5, 80/10/10, and 71/17/11/1 wt % of {sup 239}Pu/{sup 240}Pu/{sup 241}Pu(/{sup 242}Pu); and (4) PuNH for 100/0/0, 95/5/0, 90/5/5, 80/10/10, and 71/17/11/1 wt % of {sup 239}Pu/{sup 240}Pu/{sup 241}Pu(/{sup 242}Pu). All bounding surfaces were fully reflected by 30 cm of H{sub 2}O.

  5. Design and synthesis of new type I bicontinuous cubic lyotropic liquid crystal monomers based on the gemini framework for molecular-size separation applications

    NASA Astrophysics Data System (ADS)

    Wiesenauer, Brian R.

    The overall objective of this thesis research was the design and synthesis of new type I bicontinuous cubic (QI) phase-forming, gemini-shaped lyotropic liquid crystal (LLC) monomers for the preparation of nanoporous polymer membrane materials. These new QI-phase LLC monomers were designed to overcome several shortcomings of previously developed QI-phase LLC monomers in the Gin research group that include expensive and difficult synthesis, poor film processibility, and limited blendability with additives. The first method for obtaining this objective was the synthesis of six homologues of a new gemini ammonium LLC monomer, two of which exhibit a QI phase with water. Both of these LLCs form a robust Q I phase such that a gel of these materials can be fully infused into a microporous support membrane and then cross-linked to maintain the LLC phase structure. The resulting QI-phase polymer film showed a uniform pore size of 0.86 nm in water nanofiltration and desalination experiments. This QI monomer platform is less costly and less rigorous to synthesize than previously synthesized phosphonium-based gemini QI LLC monomers. These new LLC monomers also have the ability to blend with the hydrophobic, commercially available cross-linkable elastomer vinyl-EPDM (v-EPDM) to form breathable composite barrier materials. In the appropriate composition, melt-infused gemini ammonium monomer/v-EPDM polymer membranes exhibit extremely high pure water vapor fluxes, and high rejection of toxic industrial chemical vapors. A new cross-linkable gemini LLC monomer based on charged imidazolium units was also developed that forms a QI phase with glycerol. This new LLC monomer can be solution-cast from MeOH and UV-irradiated to form cross-linked thin-film composite QI membranes with slightly larger effective pore size (0.96 nm) than the previous systems. A related goal of this thesis research was to develop methods for systematically tuning the effective pore size of nanoporous QI polymer

  6. Crystallization during emplacement of lava flows

    NASA Technical Reports Server (NTRS)

    Crisp, J.

    1991-01-01

    Thermal models of lava flows provide a way of estimating emplacement durations and eruption rates of planetary lava flows, which can help constrain magma ascent, rheology and composition. Most of the models that have been developed consider only the effects of cooling by radiation. However, heating due to crystallization can be a large component of the overall heat budget of a flow. Little is known about the amount of crystallization and latent heating during flow advance. Crystal size distribution (CSD) measurements were made to quantify and study the effects of crystallization in the 1984 Mauna Loa flow. For flows on Mars, we must assume that the amount of crystallization is similar to that in terrestrial flows and place minimum and maximum bounds on the latent heat effect. Unfortunately, as examples given here show, there can be anywhere from 0 to 60 percent crystallization during flow advance. To improve constraints for Martian flows, we need to search for correlations in terrestrial flows between flow morphology and the amount of crystallization during emplacement.

  7. Menu Plans: Maximum Nutrition for Minimum Cost.

    ERIC Educational Resources Information Center

    Texas Child Care, 1995

    1995-01-01

    Suggests that menu planning is the key to getting maximum nutrition in day care meals and snacks for minimum cost. Explores United States Department of Agriculture food pyramid guidelines for children and tips for planning menus and grocery shopping. Includes suggested meal patterns and portion sizes. (HTH)

  8. Rising above the Minimum Wage.

    ERIC Educational Resources Information Center

    Even, William; Macpherson, David

    An in-depth analysis was made of how quickly most people move up the wage scale from minimum wage, what factors influence their progress, and how minimum wage increases affect wage growth above the minimum. Very few workers remain at the minimum wage over the long run, according to this study of data drawn from the 1977-78 May Current Population…

  9. Bulk size crystal growth, spectroscopic, dielectric and surface studies of 4-N,N-dimethylamino-4-N'-methylstilbazolium m-nitrobenzenesulfonate (DSMNS): A potential THz crystal of stilbazolium family.

    PubMed

    Antony Raj, A; John Sundaram, S; Gunaseelan, R; Sagayaraj, P

    2015-10-01

    The synthesis and growth of a potentially useful and efficient nonlinear optical organic single crystal of 4-N,N-dimethylamino-4-N'-methylstilbazolium m-nitrobenzenesulfonate (DSMNS) is reported. The growth experiment involved the slope nucleation method coupled with slow cooling as well as slow solvent evaporation techniques. Single crystal X-ray diffraction (XRD), Fourier transform infrared (FT-IR), FT-Raman and nuclear magnetic resonance (NMR) techniques have been employed to ascertain the structure and composition of the crystal. Second harmonic generation (SHG) efficiency of the sample has been examined by Kurtz and Perry powder test. Thermogravimetry (TG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC) techniques are employed to investigate the thermal behavior of the grown crystal. The frequency/temperature dependent dielectric properties of the organic crystal of DSMNS are studied. The surface features of the grown crystal are investigated by chemical etching study and atomic force microscopy (AFM). PMID:26010563

  10. 7 CFR 51.1216 - Size requirements.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Standards for Grades of Peaches Size § 51.1216 Size requirements. (a) The numerical count or a count-size based on equivalent tray pack size designations or the minimum diameter of the peaches packed in a... count, of peaches in any lot may be below the specified minimum size and not more than 15 percent may...

  11. 7 CFR 51.1216 - Size requirements.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Standards for Grades of Peaches Size § 51.1216 Size requirements. (a) The numerical count or a count-size based on equivalent tray pack size designations or the minimum diameter of the peaches packed in a... count, of peaches in any lot may be below the specified minimum size and not more than 15 percent may...

  12. 7 CFR 51.1216 - Size requirements.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Standards for Grades of Peaches Size § 51.1216 Size requirements. (a) The numerical count or a count-size based on equivalent tray pack size designations or the minimum diameter of the peaches packed in a... count, of peaches in any lot may be below the specified minimum size and not more than 15 percent may...

  13. Influence of particle size and shape on the backscattering linear depolarisation ratio of small ice crystals - cloud chamber measurements in the context of contrail and cirrus microphysics

    NASA Astrophysics Data System (ADS)

    Schnaiter, M.; Büttner, S.; Möhler, O.; Skrotzki, J.; Vragel, M.; Wagner, R.

    2012-06-01

    The article presents the laser scattering and depolarisation instrument SIMONE that is installed at the large aerosol and cloud chamber facility AIDA of the Karlsruhe Institute of Technology. SIMONE uses a 488 nm cw laser to probe simulated atmospheric clouds by measuring the scattered light from the 1.8° and 178.2° directions. At 178.2°, the scattered light is analysed for the linear polarisation state to deduce the linear depolarisation ratio δl which is a common measurement parameter of atmospheric LIDAR applications. The optical setup and the mathematical formalism of the depolarisation detection concept are given. SIMONE depolarisation measurements in spheroidal hematite aerosol and supercooled liquid clouds are used to validate the instrument. SIMONE data from a series of AIDA ice nucleation experiments at temperatures between 195 and 225 K were analysed in terms of the impact of the ice particle microphysics on δl. We found strong depolarisation values of up to 0.4 in case of small growing and sublimating ice particles with volume equivalent diameters of only a few micrometers. Modelling runs with the T-matrix method showed that the measured depolarisation ratios can be accurately reproduced assuming spheroidal and cylindrical particles with a size distribution that has been constrained by IR extinction spectroscopy. Based on the T-matrix modelling runs, we demonstrate that in case of small ice crystals the SIMONE depolarisation results are representative for the LIDAR depolarisation ratio which is measured at exact backscattering direction of 180°. The relevance of our results for the interpretation of recent LIDAR observations in cirrus and contrails is discussed. In view of our results, the high depolarisation ratios observed by the spaceborne LIDAR CALIOP in the tropical upper troposphere might be a hint for the presence of small (sublimating) ice particles in the outflows of deep convective systems.

  14. Influence of particle size and shape on the backscattering linear depolarisation ratio of small ice crystals - cloud chamber measurements in the context of contrail and cirrus microphysics

    NASA Astrophysics Data System (ADS)

    Schnaiter, M.; Büttner, S.; Möhler, O.; Skrotzki, J.; Vragel, M.; Wagner, R.

    2012-11-01

    The article presents the laser scattering and depolarisation instrument SIMONE that is installed at the large aerosol and cloud chamber facility AIDA of the Karlsruhe Institute of Technology. SIMONE uses a 488 nm cw laser to probe simulated atmospheric clouds by measuring the scattered light from the 1.8° and 178.2° directions. At 178.2°, the scattered light is analysed for the linear polarisation state to deduce the particle linear depolarisation ratio δp which is a common measurement parameter of atmospheric lidar applications. The optical setup and the mathematical formalism of the depolarisation detection concept are given. SIMONE depolarisation measurements in spheroidal hematite aerosol and supercooled liquid clouds are used to validate the instrument. SIMONE data from a series of AIDA ice nucleation experiments at temperatures between 195 and 225 K were analysed in terms of the impact of the ice particle microphysics on δp. We found strong depolarisation values of up to 0.4 in case of small growing and sublimating ice particles with volume equivalent diameters of only a few micrometers. Modelling runs with the T-matrix method showed that the measured depolarisation ratios can be accurately reproduced assuming spheroidal and cylindrical particles with a size distribution that has been constrained by IR extinction spectroscopy. Based on the T-matrix modelling runs, we demonstrate that in case of small ice crystals the SIMONE depolarisation results are representative for the lidar depolarisation ratio which is measured at exact backscattering direction of 180°. The relevance of our results for the interpretation of recent lidar observations in cirrus and contrails is discussed. In view of our results, the high depolarisation ratios observed by the spaceborne lidar CALIOP in the tropical upper troposphere might be a hint for the presence of small (sublimating) ice particles in the outflows of deep convective systems.

  15. Structure of self - assembled two-dimensional spherical crystals

    NASA Astrophysics Data System (ADS)

    Bausch, Andreas R.

    2004-03-01

    Dense spherical particles on a flat surface usually pack into a simple triangular lattice, similar to billiard balls at the start of a game. The minimum energy configuration for interacting particles on the curved surface of a sphere, however, presents special difficulties, as recognized already by J.J. Thomson. We describe experimental investigations of the structure of two-dimensional spherical crystals. The crystals, formed by beads self-assembled on water droplets in oil, serve as model systems for exploring very general theories about the minimum energy configurations of particles with arbitrary repulsive interactions on curved surfaces. Above a critical system size we find that crystals develop distinctive high-angle grain boundaries or "scars" not found in planar crystals. The number of excess defects in a scar is shown to grow linearly with the dimensionless system size. First experiments where the melting of the crystal structure was observable will be discussed. Dynamic triangulation methods allow the analysis of the dynamics of the defects. Possible modifications towards mechanically stabilized self assembly structures result in so called Colloidosomes, which are promising for many different encapsulation purposes.

  16. Controlling morphology and crystallite size of Cu(In{sub 0.7}Ga{sub 0.3})Se{sub 2} nano-crystals synthesized using a heating-up method

    SciTech Connect

    Hsu, Wei-Hsiang; Hsiang, Hsing-I; Chia, Chih-Ta; Yen, Fu-Su

    2013-12-15

    CuIn{sub 0.7}Ga{sub 0.3}Se{sub 2}(CIGS) nano-crystals were successfully synthesized via a heating-up process. The non-coordinating solvent (1-octadecene) and selenium/cations ratio effects on the crystalline phase and crystallite size of CIGS nano-crystallites were investigated. It was observed that the CIGS nano-crystallite morphology changed from sheet into spherical shape as the amount of 1-octadecene addition was increased. CIGS nano-crystals were obtained in 9–20 nm sizes as the selenium/cations ratio increased. These results suggest that the monomer reactivity in the solution can be adjusted by changing the solvent type and selenium/cations ratio, hence affecting the crystallite size and distribution. - Graphical abstract: CuIn{sub 0.7}Ga{sub 0.3}Se{sub 2}(CIGS) nano-crystals were successfully synthesized via a heating-up process in this study. The super-saturation in the solution can be adjusted by changing the OLA/ODE ratio and selenium/cation ratio.

  17. Minimum Competency in Secondary Education.

    ERIC Educational Resources Information Center

    De Landsheere, Viviane

    1987-01-01

    Discusses issues related to the movement toward minimum competency in secondary education. Addresses the problem of defining minimum competency and the dangers of imposed standardization. Identifies three conceptualizations of minimum competency as: (1) the narrowly educational standpoint, (2) the concern with functional literacy, and (3) a more…

  18. Artistic Crystal Creations

    ERIC Educational Resources Information Center

    Lange, Catherine

    2008-01-01

    In this inquiry-based, integrative art and science activity, Grade 5-8 students use multicolored Epsom salt (magnesium sulfate) crystallizing solutions to reveal beautiful, cylindrical, 3-dimensional, needle-shaped structures. Through observations of the crystal art, students analyze factors that contribute to crystal size and formation, compare…

  19. 7 CFR 51.1545 - Size.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Size. 51.1545 Section 51.1545 Agriculture Regulations... Standards for Grades of Potatoes 1 Size § 51.1545 Size. (a) The minimum size, or minimum and maximum sizes... Inches Ounces Creamer 3/4 (3) 15/8 (3) Chef 23/4 8 41/2 28 Size A2 17/8 (3) (3) (3) Size B 11/2 (3)...

  20. Design for Minimum Risk

    NASA Technical Reports Server (NTRS)

    Wetherholt, Jon; Heimann, Timothy J.

    2010-01-01

    Design for Minimum Risk (DFMR) is a term used by NASA programs as an expansion of the general hazard reduction process where if an identified hazard cannot be eliminated, the design is modified to reduce the associated mishap risk to an acceptable level. DFMR is a set of specific requirements to minimize risk. DFMR is not well understood and there are many misconceptions concerning the meaning and use. This paper will provide insight into the use of DFMR for space applications; it s comparison to other hazard mitigation strategies and examples of how the approach has been used in the past. It will also highlight documents used by NASA on various programs to determine DFMR.

  1. Analysing the effect of crystal size and structure in highly efficient CH3NH3PbI3 perovskite solar cells by spatially resolved photo- and electroluminescence imaging

    NASA Astrophysics Data System (ADS)

    Mastroianni, S.; Heinz, F. D.; Im, J.-H.; Veurman, W.; Padilla, M.; Schubert, M. C.; Würfel, U.; Grätzel, M.; Park, N.-G.; Hinsch, A.

    2015-11-01

    CH3NH3PbI3 perovskite solar cells with a mesoporous TiO2 layer and spiro-MeOTAD as a hole transport layer (HTL) with three different CH3NH3I concentrations (0.032 M, 0.044 M and 0.063 M) were investigated. Strong variations in crystal size and morphology resulting in diversified cell efficiencies (9.2%, 16.9% and 12.3%, respectively) were observed. The physical origin of this behaviour was analysed by detailed characterization combining current-voltage curves with photo- and electroluminescence (PL and EL) imaging as well as light beam induced current measurements (LBIC). It was found that the most efficient cell shows the highest luminescence and the least efficient cell is most strongly limited by non-radiative recombination. Crystal size, morphology and distribution in the capping layer and in the porous scaffold strongly affect the non-radiative recombination. Moreover, the very non-uniform crystal structure with multiple facets, as evidenced by SEM images of the 0.032 M device, suggests the creation of a large number of grain boundaries and crystal dislocations. These defects give rise to increased trap-assisted non-radiative recombination as is confirmed by high-resolution μ-PL images. The different imaging techniques used in this study prove to be well-suited to spatially investigate and thus correlate the crystal morphology of the perovskite layer with the electrical and radiative properties of the solar cells and thus with their performance.CH3NH3PbI3 perovskite solar cells with a mesoporous TiO2 layer and spiro-MeOTAD as a hole transport layer (HTL) with three different CH3NH3I concentrations (0.032 M, 0.044 M and 0.063 M) were investigated. Strong variations in crystal size and morphology resulting in diversified cell efficiencies (9.2%, 16.9% and 12.3%, respectively) were observed. The physical origin of this behaviour was analysed by detailed characterization combining current-voltage curves with photo- and electroluminescence (PL and EL) imaging as

  2. 7 CFR 51.344 - Size.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Standards for Grades of Apples for Processing Size § 51.344 Size. (a) The minimum and maximum sizes or range... the apples determined by the smallest opening through which it will pass. Application of Standards...

  3. 7 CFR 51.344 - Size.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Standards for Grades of Apples for Processing Size § 51.344 Size. (a) The minimum and maximum sizes or range... the apples determined by the smallest opening through which it will pass. Application of Standards...

  4. 7 CFR 51.344 - Size.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Standards for Grades of Apples for Processing Size § 51.344 Size. (a) The minimum and maximum sizes or range... the apples determined by the smallest opening through which it will pass. Application of Standards...

  5. Switchable liquid-crystal phase-shift mask for super-resolution photolithography based on Pancharatnam-Berry phase

    NASA Astrophysics Data System (ADS)

    Glazar, Nikolaus; Culbreath, Christopher; Li, Yannian; Yokoyama, Hiroshi

    2015-11-01

    We present a novel liquid-crystal-based phase-shift mask that utilizes the Pancharatnam-Berry phase for super-resolution photolithography. Using an automated maskless photoalignment technique, we pattern an azobenzene alignment layer in a nematic liquid-crystal cell to fabricate the mask. Since the image is formed by phase cancellation, the minimum feature size is not restricted by the diffraction limit; here, we obtain submicron features. The liquid-crystal properties of the cell allow the mask to be switched on and off by applying a voltage. The cost effectiveness and flexibility of this technique make it a promising new technology for photolithography.

  6. A molecular-sized tunnel-porous crystal with a ratchet gear structure and its one-way guest-molecule transportation property

    NASA Astrophysics Data System (ADS)

    Kataoka, Keisuke; Yasumoto, Tetsuaki; Manabe, Yousuke; Sato, Hiroyasu; Yamano, Akihito; Katagiri, Toshimasa

    2013-01-01

    An anisotropic tunnel microporous crystal was prepared. Active transportation of anthracene as a guest molecule in the anisotropic tunnels was observed. The direction of anthracene movement implies that the anisotropic tunnel did not work as a flap-check valve. The direction of the movement was consistent with that caused by a Brownian ratchet.An anisotropic tunnel microporous crystal was prepared. Active transportation of anthracene as a guest molecule in the anisotropic tunnels was observed. The direction of anthracene movement implies that the anisotropic tunnel did not work as a flap-check valve. The direction of the movement was consistent with that caused by a Brownian ratchet. Electronic supplementary information (ESI) available. CCDC reference numbers 837539 and 837540. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c2nr30880k

  7. The Role of ZnO Particle Size, Shape and Concentration on Liquid Crystal Order and Current-Voltage Properties for Potential Photovoltaic Applications

    NASA Astrophysics Data System (ADS)

    Martinez-Miranda, Luz J.; Branch, Janelle; Thompson, Robert; Taylor, Jefferson W.; Salamanca-Riba, Lourdes

    2012-02-01

    We investigate the role order plays in the transfer of charges in ZnO nanoparticle - octylcyanobiphenyl (8CB) liquid crystal system for photovoltaic applications as well as the role the nominally 7x5x5nm^3 or 20x5x5nm^3 ZnO nanoparticles play in improving that order. Our results for the 5nm nanoparticles show an improvement in the alignment of the liquid crystal with increasing weight percentage of ZnO nanoparticles^1. Our results for the 7x5x5 nm^3 sample show that the current is larger than the current obtained for the 5 nm samples. We find that order is improved for concentrations close to 35% wt ZnO for both the 7x5x5 nm^3 and 20x5x5 nm^3. We have analyzed the X-ray scans for both the 7x5x5 and the 20x5x5 nm^3 samples. The signal corresponding to the liquid crystal aligned parallel to the substrate is much smaller than the peak corresponding to the liquid crystal aligned approximately at 70 with respect to the substrate for the 7x5x5 nm^3 sample whereas this same peak is comparable or more intense for the 20x5x5 nm^3 sample. 1. L. J. Mart'inez-Miranda, Kaitlin M. Traister, Iriselies Mel'endez-Rodr'iguez, and Lourdes Salamanca-Riba, Appl. Phys. Letts, 97, 223301 (2010).

  8. 50 CFR 622.492 - Minimum size limit.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... ADMINISTRATION, DEPARTMENT OF COMMERCE FISHERIES OF THE CARIBBEAN, GULF OF MEXICO, AND SOUTH ATLANTIC Queen Conch... limit for Caribbean queen conch is 9 inches (22.9 cm) in length, that is, from the tip of the spire to the distal end of the shell, and 3/8 inch (9.5 mm) in lip width at its widest point. A queen...

  9. 50 CFR 648.104 - Summer flounder minimum fish sizes.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE FISHERIES OF THE NORTHEASTERN UNITED STATES Management... possession, e.g., fillets, except that party and charter vessels possessing valid state permits...

  10. 50 CFR 622.492 - Minimum size limit.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... limit for Caribbean queen conch is 9 inches (22.9 cm) in length, that is, from the tip of the spire to the distal end of the shell, and 3/8 inch (9.5 mm) in lip width at its widest point. A queen...

  11. Minimum Sample Size Requirements for Mokken Scale Analysis

    ERIC Educational Resources Information Center

    Straat, J. Hendrik; van der Ark, L. Andries; Sijtsma, Klaas

    2014-01-01

    An automated item selection procedure in Mokken scale analysis partitions a set of items into one or more Mokken scales, if the data allow. Two algorithms are available that pursue the same goal of selecting Mokken scales of maximum length: Mokken's original automated item selection procedure (AISP) and a genetic algorithm (GA). Minimum…

  12. Equivalence to the Minimum Qualifications

    ERIC Educational Resources Information Center

    Academic Senate for California Community Colleges, 2006

    2006-01-01

    In 1988 the Community College Reform Act (AB 1725) began a phase out of credentials in favor of a process for establishing minimum qualifications and the determination of equivalencies that are at least equal to the state-adopted minimum qualifications for a particular discipline. According to Education Code sections 87359 and 87360, someone…

  13. Parameterization of ion channeling half-angles and minimum yields

    NASA Astrophysics Data System (ADS)

    Doyle, Barney L.

    2016-03-01

    A MS Excel program has been written that calculates ion channeling half-angles and minimum yields in cubic bcc, fcc and diamond lattice crystals. All of the tables and graphs in the three Ion Beam Analysis Handbooks that previously had to be manually looked up and read from were programed into Excel in handy lookup tables, or parameterized, for the case of the graphs, using rather simple exponential functions with different power functions of the arguments. The program then offers an extremely convenient way to calculate axial and planar half-angles, minimum yields, effects on half-angles and minimum yields of amorphous overlayers. The program can calculate these half-angles and minimum yields for axes and [h k l] planes up to (5 5 5). The program is open source and available at

  14. Growth of dopamine crystals

    NASA Astrophysics Data System (ADS)

    Patil, Vidya; Patki, Mugdha

    2016-05-01

    Many nonlinear optical (NLO) crystals have been identified as potential candidates in optical and electro-optical devices. Use of NLO organic crystals is expected in photonic applications. Hence organic nonlinear optical materials have been intensely investigated due to their potentially high nonlinearities, and rapid response in electro-optic effect compared to inorganic NLO materials. There are many methods to grow organic crystals such as vapor growth method, melt growth method and solution growth method. Out of these methods, solution growth method is useful in providing constraint free crystal. Single crystals of Dopamine have been grown by evaporating the solvents from aqueous solution. Crystals obtained were of the size of orders of mm. The crystal structure of dopamine was determined using XRD technique. Images of crystals were obtained using FEG SEM Quanta Series under high vacuum and low KV.

  15. Autocorrelation of rainfall and streamflow minimums

    USGS Publications Warehouse

    Matalas, N.C.

    1963-01-01

    Hydrologic time series of annual minimum mean monthly rainfall and annual minimum 1-day and 7-day discharge, considered as drought indices, were used to study the distribution of droughts with respect to time. The rainfall data were found to be nearly random. The discharge data, however, were found to be nonrandomly distributed in time and generated by a first-order Markov process. The expected value of the variance for a time series generated by a first-order Markov process was compared with the expected value of the variance for a random time series. This comparison showed that the expected value of the variance for a nonrandom time series converged to the population variance with an increase in sample size at a slower rate than for a random time series.

  16. Nucleation and crystal growth in a suspension of charged colloidal silica spheres with bi-modal size distribution studied by time-resolved ultra-small-angle X-ray scattering.

    PubMed

    Hornfeck, Wolfgang; Menke, Dirk; Forthaus, Martin; Subatzus, Sebastian; Franke, Markus; Schöpe, Hans-Joachim; Palberg, Thomas; Perlich, Jan; Herlach, Dieter

    2014-12-01

    A suspension of charged colloidal silica spheres exhibiting a bi-modal size distribution of particles, thereby mimicking a binary mixture, was studied using time-resolved ultra-small-angle synchrotron X-ray scattering (USAXS). The sample, consisting of particles of diameters d(A) = (104.7 ± 9.0) nm and d(B) = (88.1 ± 7.8) nm (d(A)/d(B) ≈ 1.2), and with an estimated composition A(0.6(1))B(0.4(1)), was studied with respect to its phase behaviour in dependance of particle number density and interaction, of which the latter was modulated by varying amounts of added base (NaOH). Moreover, its short-range order in the fluid state and its eventual solidification into a long-range ordered colloidal crystal were observed in situ, allowing the measurement of the associated kinetics of nucleation and crystal growth. Key parameters of the nucleation kinetics such as crystallinity, crystallite number density, and nucleation rate density were extracted from the time-resolved scattering curves. By this means an estimate on the interfacial energy for the interface between the icosahedral short-range ordered fluid and a body-centered cubic colloidal crystal was obtained, comparable to previously determined values for single-component colloidal systems. PMID:25481168

  17. Synthesis, X-ray crystal structures and thermal analyses of some new antimicrobial zinc complexes: New configurations and nano-size structures.

    PubMed

    Masoudiasl, A; Montazerozohori, M; Naghiha, R; Assoud, A; McArdle, P; Safi Shalamzari, M

    2016-04-01

    Some new five coordinated ZnLX2 complexes, where L is N3-Schiff base ligand obtained by condensation reaction between diethylenetriamine and (E)-3-(2-nitrophenyl)acrylaldehyde and X (Cl(-), Br(-), I(-), N3(-) and NCS(-)), were synthesized and characterized by FT-IR, (1)H and (13)CNMR, UV-visible, ESI-mass spectra and molar conductivity measurements. The structures of zinc iodide and thiocyanate complexes were determined by X-ray crystallographic analysis. The X-ray results showed that the Zn (II) center in these complexes is five-coordinated in a distorted trigonal-bipyramidal configuration. Zinc iodide and thiocyanate complexes crystallize in the monoclinic and triclinic systems with space groups of C2/c and P1- with eight and two molecules per unit cell respectively. The crystal packing of the complexes consists of intermolecular interactions such as C-H(…)O and C-H(…)I, C-H(···)S, N(…)O, together with π-π stacking and some other unexpected interactions. The mentioned interactions cause three-dimensional supramolecular structure in the solid state. Zinc complexes were also prepared in nano-structure by sonochemical method confirmed by XRD, SEM and TEM analyses. Moreover, ZnO nanoparticles were synthesized by direct thermolysis of zinc iodide complex. Furthermore, antimicrobial and thermal properties of the compounds were completely investigated. PMID:26838912

  18. Large-Size CH3NH3PbBr3 Single Crystal: Growth and In Situ Characterization of the Photophysics Properties.

    PubMed

    Zhao, Pengjun; Xu, Jinbao; Dong, Xiaoyu; Wang, Lei; Ren, Wei; Bian, Liang; Chang, Aimin

    2015-07-01

    We reported a facile single-solution fabrication method to grow large-scale CH3NH3PbBr3 hybrid perovskite single crystal at room temperature. The obtained single crystal in this experiment was 14 × 14 mm. The sample's in situ photophysics properties under dark and illumination, including the surface morphology, work function, surface current distribution, microcosmic I-V curves, as well as the polarization behavior, were in situ characterized by integrated utilization of a scanning probe microscopy, respectively. Piezoresponse force microscopy (PFM) phase angles indicated the existence of "polarization" in CH3NH3PbBr3 lattice. Interestingly, the "polarization effect" was enhanced by the plus light source. Moreover, a surface potential shift as large as 200 mV was observed under the condition of the illumination on and off. This research is proposed to provide an opportunity to take a fresh look at the architectural design and photovoltaic performance origin of the hybrid perovskite solar cells. PMID:26266744

  19. Venus ionopause during solar minimum

    NASA Technical Reports Server (NTRS)

    Mahajan, K. K.; Mayr, H. G.

    1989-01-01

    Pioneer Venus ion composition measurements are used to study the Venus ionosphere during solar minimum. It is suggested that the topside electron density profile at Venus during solar minimum has two distinct regimes. One beween 140 and 180 km is dominated by O2(+) ions which are in photochemical equilibrium. The other regime is above 180 km and is dominated by O(+) ions which are disturbed by the solar wind induced plasma transport. For Pioneer Venus, Mariner 10, and Venera 9 and 10 data, it is found that Venus exhibits a photodynamical type of ionopause during solar minimum.

  20. Ozone Minimums, 1979 to 2013

    NASA Video Gallery

    Minimum concentration of ozone in the southern hemisphere for each year from 1979-2013 (there is no data from 1995). Each image is the day of the year with the lowest concentration of ozone. A grap...

  1. Safe Minimum Internal Temperature Chart

    MedlinePlus

    ... JSR 286) Actions ${title} Loading... Safe Minimum Internal Temperature Chart Safe steps in food handling, cooking, and ... from other foods. Cook —Cook to the right temperature. Chill —Refrigerate food promptly. Cook all food to ...

  2. 2013 Arctic Sea Ice Minimum

    NASA Video Gallery

    After an unusually cold summer in the northernmost latitudes, Arctic sea ice appears to have reached its annual minimum summer extent for 2013 on Sept. 13, the NASA-supported National Snow and Ice ...

  3. Arctic Sea Ice Minimum, 2015

    NASA Video Gallery

    This animation shows the evolution of the Arctic sea ice cover from its wintertime maximum extent, which was reached on Feb. 25, 2015, and was the lowest on record, to its apparent yearly minimum, ...

  4. Decrease in thermal conductivity in polymeric P3HT nanowires by size-reduction induced by crystal orientation: new approaches towards thermal transport engineering of organic materials.

    PubMed

    Rojo, Miguel Muñoz; Martín, Jaime; Grauby, Stéphane; Borca-Tasciuc, Theodorian; Dilhaire, Stefan; Martin-Gonzalez, Marisol

    2014-07-21

    To date, there is no experimental characterization of thermal conductivity of semiconductor polymeric individual nanowires embedded in a matrix. This work reports on scanning thermal microscopy measurements in a 3ω configuration to determine how the thermal conductivity of individual nanowires made of a model conjugated polymer (P3HT) is modified when decreasing their diameters. We observe a reduction of thermal conductivity, from λNW = 2.29 ± 0.15 W K(-1) m(-1) to λNW = 0.5 ± 0.24 W K(-1) m(-1), when the diameter of nanowires is reduced from 350 nm to 120 nm, which correlates with the polymer crystal orientation measured by WAXS. Through this work, the foundations for future polymer thermal transport engineering are presented. PMID:24933655

  5. Minimum Principles in Motor Control.

    PubMed

    Engelbrecht, Sascha E.

    2001-06-01

    Minimum (or minimal) principles are mathematical laws that were first used in physics: Hamilton's principle and Fermat's principle of least time are two famous example. In the past decade, a number of motor control theories have been proposed that are formally of the same kind as the minimum principles of physics, and some of these have been quite successful at predicting motor performance in a variety of tasks. The present paper provides a comprehensive review of this work. Particular attention is given to the relation between minimum theories in motor control and those used in other disciplines. Other issues around which the review is organized include: (1) the relation between minimum principles and structural models of motor planning and motor control, (2) the empirically-driven development of minimum principles and the danger of circular theorizing, and (3) the design of critical tests for minimum theories. Some perspectives for future research are discussed in the concluding section of the paper. Copyright 2001 Academic Press. PMID:11401453

  6. Effect of grain size of polycrystalline diamond on its heat spreading properties

    NASA Astrophysics Data System (ADS)

    Simon, Roland B.; Anaya, Julian; Faili, Firooz; Balmer, Richard; Williams, Gruffudd T.; Twitchen, Daniel J.; Kuball, Martin

    2016-06-01

    The exceptionally high thermal conductivity of polycrystalline diamond (>2000 W m‑1 K‑1) makes it a very attractive material for optimizing the thermal management of high-power devices. In this paper, the thermal conductivity of a diamond sample capturing grain size evolution from nucleation towards the growth surface is studied using an optimized 3ω technique. The thermal conductivity is found to decrease with decreasing grain size, which is in good agreement with theory. These results clearly reveal the minimum film thickness and polishing thickness from nucleation needed to achieve single-crystal diamond performance, and thus enable production of an optimal polycrystalline diamond for heat-spreading applications.

  7. Solar Cycle Predictions Near Sunspot Minimum

    NASA Technical Reports Server (NTRS)

    Hathaway, David H.

    1997-01-01

    Observations of solar magnetic activity and the dynamics of the solar convection zone have produced severe constraints on models of the Sun's magnetic dynamo. These constraints are so severe that, at present, we do not have numerical models that can accept the current conditions and then march forward in time to predict future activity. Given this state of solar dynamo theory we are forced to examine previous behavior to discover patterns and trends that afford us some measure of predictability. Here we examine the behavior of several indicators of solar activity near solar minimum that are well correlated with the amplitude of the following solar maximum to predict the level of solar activity over cycle 23. Sunspot numbers, areas, and positions are useful for characterizing solar cycle behavior due to the extent of the data (12 cycles or more). These data exhibit several patterns that relate future activity to past behavior. With the Odd-Even effect the odd numbered cycles have been larger than their even numbered predecessors for each of the last six cycle pairs. With the Amplitude-Period effect short period cycles have been followed by large amplitude cycles and long period cycles have been followed by small amplitude cycles for 10 of the last 13 cycles. With the Maximum-Minimum effect the sunspot number at minimum is directly correlated with the sunspot number at maximum for a given cycle. The geomagnetic indices aa and Ap are also related to solar activity by the connections between disturbances in the solar wind and variations in the Earth's magnetic field. Like the Maximum-Minimum effect for sunspots, the size of the aa and Ap indices at minimum are directly related to the amplitude of the following maximum. The number of geomagnetically disturbed days (days with Ap >= 25) over the course of a cycle is another indicator for the size of the next cycle. The aa and Ap indices can each be separated into a component in phase with the current sunspot cycle and an

  8. 7 CFR 51.2836 - Size classifications.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Size classifications. 51.2836 Section 51.2836...) Size Classifications § 51.2836 Size classifications. The size of onions may be specified in accordance with one of the following classifications. Size designation Minimum diameter Inches Millimeters...

  9. High-resolution dielectric study reveals pore-size-dependent orientational order of a discotic liquid crystal confined in tubular nanopores.

    PubMed

    Całus, Sylwia; Kityk, Andriy V; Borowik, Lech; Lefort, Ronan; Morineau, Denis; Krause, Christina; Schönhals, Andreas; Busch, Mark; Huber, Patrick

    2015-07-01

    We report a high-resolution dielectric study on a pyrene-based discotic liquid crystal (DLC) in the bulk state and confined in parallel tubular nanopores of monolithic silica and alumina membranes. The positive dielectric anisotropy of the DLC molecule at low frequencies (in the quasistatic case) allows us to explore the thermotropic collective orientational order. A face-on arrangement of the molecular discs on the pore walls and a corresponding radial arrangement of the molecules is found. In contrast to the bulk, the isotropic-to-columnar transition of the confined DLC is continuous, shifts with decreasing pore diameter to lower temperatures, and exhibits a pronounced hysteresis between cooling and heating. These findings corroborate conclusions from previous neutron and x-ray-scattering experiments as well as optical birefringence measurements. Our study also indicates that the relative simple dielectric technique presented here is a quite efficient method in order to study the thermotropic orientational order of DLC-based nanocomposites. PMID:26274191

  10. Ice crystal c-axis orientation and mean grain size measurements from the Dome Summit South ice core, Law Dome, East Antarctica

    NASA Astrophysics Data System (ADS)

    Treverrow, Adam; Jun, Li; Jacka, Tim H.

    2016-06-01

    We present measurements of crystal c-axis orientations and mean grain area from the Dome Summit South (DSS) ice core drilled on Law Dome, East Antarctica. All measurements were made on location at the borehole site during drilling operations. The data are from 185 individual thin sections obtained between a depth of 117 m below the surface and the bottom of the DSS core at a depth of 1196 m. The median number of c-axis orientations recorded in each thin section was 100, with values ranging from 5 through to 111 orientations. The data from all 185 thin sections are provided in a single comma-separated value (csv) formatted file which contains the c-axis orientations in polar coordinates, depth information for each core section from which the data were obtained, the mean grain area calculated for each thin section and other data related to the drilling site. The data set is also available as a MATLAB™ structure array. Additionally, the c-axis orientation data from each of the 185 thin sections are summarized graphically in figures containing a Schmidt diagram, histogram of c-axis colatitudes and rose plot of c-axis azimuths. All these data are referenced by doi:10.4225/15/5669050CC1B3B and are available free of charge at https://data.antarctica.gov.au.<

  11. ACSB: A minimum performance assessment

    NASA Technical Reports Server (NTRS)

    Jones, Lloyd Thomas; Kissick, William A.

    1988-01-01

    Amplitude companded sideband (ACSB) is a new modulation technique which uses a much smaller channel width than does conventional frequency modulation (FM). Among the requirements of a mobile communications system is adequate speech intelligibility. This paper explores this aspect of minimum required performance. First, the basic principles of ACSB are described, with emphasis on those features that affect speech quality. Second, the appropriate performance measures for ACSB are reviewed. Third, a subjective voice quality scoring method is used to determine the values of the performance measures that equate to the minimum level of intelligibility. It is assumed that the intelligibility of an FM system operating at 12 dB SINAD represents that minimum. It was determined that ACSB operating at 12 dB SINAD with an audio-to-pilot ratio of 10 dB provides approximately the same intelligibility as FM operating at 12 dB SINAD.

  12. The Maunder minimum: a revision

    NASA Astrophysics Data System (ADS)

    Zolotova, Nadezhda; Ponyavin, Dmitri

    2015-08-01

    One of the most enigmatic features of the solar history in the past was the Maunder minimum (1645-1715). We estimated the daily nominal sunspot counts of each observer individually from 1610 to 1720. Simultaneous comparison of textual reports, tables, and sunspot drawings reveals a significant difference between them. Some observers (among whom were Jean Picard and Giovanni Domenico Cassini, both from the Royal Observatory in Paris) systematically made gaps in reports when others noticed sunspots. Philippe de La Hire announced only fewer sunspot groups compared with the other observers. We argue that different points of view of observers of the seventeenth-century on the origin of sunspots resulted in strong underestimation of sunspot groups. Our findings suggest that the Maunder minimum was an ordinary secular minimum with reduced but non-stopped solar cyclicity.

  13. Analysis of Crystallization Kinetics

    NASA Technical Reports Server (NTRS)

    Kelton, Kenneth F.

    1997-01-01

    A realistic computer model for polymorphic crystallization (i.e., initial and final phases with identical compositions), which includes time-dependent nucleation and cluster-size-dependent growth rates, is developed and tested by fits to experimental data. Model calculations are used to assess the validity of two of the more common approaches for the analysis of crystallization data. The effects of particle size on transformation kinetics, important for the crystallization of many systems of limited dimension including thin films, fine powders, and nanoparticles, are examined.

  14. Crystallization kinetics of ammonium perchlorate in MSMPR crystallizer

    NASA Astrophysics Data System (ADS)

    Tanrıkulu, S. Ü.; Eroğlu, İ.; Bulutcu, A. N.; Özkar, S.

    2000-01-01

    The effects of supersaturation level, sodium chloride (NaCl) as impurity, and the suspension density of the crystallizer content on the crystallization kinetics of ammonium perchlorate (AP) were studied in a mixed-suspension mixed-product removal crystallizer. The product crystals have a plate-like morphology. The crystal size distribution is not affected by the supersaturation level. There was a deviation from the ideal population density where the growth rate of pure AP crystallization was size dependent with the order of 0.4 according to Abegg, Stevens and Larson (ASL) model. However, the ASL model was not found to be suitable to express the growth rate of the crystals in NaCl containing AP solution. Also when suspension density of the crystallizer increased, secondary nucleation was observed.

  15. On the Minimum Vocabulary Problem.

    ERIC Educational Resources Information Center

    Chandrasekharan, N.; And Others

    1987-01-01

    Demonstrates the use of a directed graph model as a tool for finding desirable minimum vocabularies to be used in indexing and information retrieval. The basic algorithm is outlined, possible enhancements to the model are discussed, and further research questions are suggested. (Author/CLB)

  16. 76 FR 11668 - Minimum Capital

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-03

    ... Enterprises' future, FHFA is monitoring the activities of the Enterprises to: (a) Limit their risk and... 12 U.S.C. 4612(d). The 60-day comment period closed on April 9, 2010. See Federal Register 75 FR 6151... amended. See 74 FR 5597 (January 30, 2009). As a result, the definition of ``minimum capital level''...

  17. Tennessee Minimum School Bus Standards.

    ERIC Educational Resources Information Center

    Tennessee State Board of Education, 2004

    2004-01-01

    The School Bus Specifications and Procedures adopted by the 2000 National Conference on School Transportation and the Federal Motor Vehicle Safety Standards (FMVSS) were used as guides by the Tennessee State Board of Education Pupil Transportation Advisory Committee in developing the revised minimum specifications for school bus chassis and school…

  18. Equivalence to the Minimum Qualifications.

    ERIC Educational Resources Information Center

    California Community Colleges, Sacramento. Academic Senate.

    Assembly Bill (AB) 1725 provides for the hiring of faculty who do not meet the precise letter of the minimum qualifications, provided that the governing board of an institution determines that an applicant possesses qualifications that are at least equivalent. In order to make these determinations, each district must have and use an equivalency…

  19. Solar Effects on Climate and the Maunder Minimum: Minimum Certainty

    NASA Technical Reports Server (NTRS)

    Rind, David

    2003-01-01

    The current state of our understanding of solar effects on climate is reviewed. As an example of the relevant issues, the climate during the Maunder Minimum is compared with current conditions in GCM simulations that include a full stratosphere and parameterized ozone response to solar spectral irradiance variability and trace gas changes. The GISS Global Climate/Middle Atmosphere Model coupled to a q-flux/mixed layer model is used for the simulations, which begin in 1500 and extend to the present. Experiments were made to investigate the effect of total versus spectrally-varying solar irradiance changes; spectrally-varying solar irradiance changes on the stratospheric ozone/climate response with both pre-industrial and present trace gases; and the impact on climate and stratospheric ozone of the preindustrial trace gases and aerosols by themselves. The results showed that: (1) the Maunder Minimum cooling relative to today was primarily associated with reduced anthropogenic radiative forcing, although the solar reduction added 40% to the overall cooling. There is no obvious distinguishing surface climate pattern between the two forcings. (2)The global and tropical response was greater than 1 C, in a model with a sensitivity of 1.2 C per W m-2. To reproduce recent low-end estimates would require a sensitivity 1/4 as large. (3) The global surface temperature change was similar when using the total and spectral irradiance prescriptions, although the tropical response was somewhat greater with the former, and the stratospheric response greater with the latter. (4) Most experiments produce a relative negative phase of the NAO/AO during the Maunder Minimum, with both solar and anthropogenic forcing equally capable, associated with the tropical cooling and relative poleward EP flux refraction. (5) A full stratosphere appeared to be necessary for the negative AO/NAO phase, as was the case with this model for global warming experiments, unless the cooling was very large

  20. 42 CFR 84.124 - Facepiece tests; minimum requirements.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... § 84.124 Facepiece tests; minimum requirements. (a) The complete gas mask will be fitted to the faces... or sizes for the gas mask, together with the approximate measurements of faces they are designed to fit, the Institute will insure that test subjects suit such facial measurements. (c) Any gas...

  1. 42 CFR 84.124 - Facepiece tests; minimum requirements.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... § 84.124 Facepiece tests; minimum requirements. (a) The complete gas mask will be fitted to the faces... or sizes for the gas mask, together with the approximate measurements of faces they are designed to fit, the Institute will insure that test subjects suit such facial measurements. (c) Any gas...

  2. 42 CFR 84.124 - Facepiece tests; minimum requirements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... § 84.124 Facepiece tests; minimum requirements. (a) The complete gas mask will be fitted to the faces... or sizes for the gas mask, together with the approximate measurements of faces they are designed to fit, the Institute will insure that test subjects suit such facial measurements. (c) Any gas...

  3. 42 CFR 84.124 - Facepiece tests; minimum requirements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... § 84.124 Facepiece tests; minimum requirements. (a) The complete gas mask will be fitted to the faces... or sizes for the gas mask, together with the approximate measurements of faces they are designed to fit, the Institute will insure that test subjects suit such facial measurements. (c) Any gas...

  4. Maximum Likelihood and Minimum Distance Applied to Univariate Mixture Distributions.

    ERIC Educational Resources Information Center

    Wang, Yuh-Yin Wu; Schafer, William D.

    This Monte-Carlo study compared modified Newton (NW), expectation-maximization algorithm (EM), and minimum Cramer-von Mises distance (MD), used to estimate parameters of univariate mixtures of two components. Data sets were fixed at size 160 and manipulated by mean separation, variance ratio, component proportion, and non-normality. Results…

  5. Minimum-Impact Camping in the Front Woods.

    ERIC Educational Resources Information Center

    Schatz, Curt

    1994-01-01

    Minimum-impact camping techniques that can be applied to resident camp programs include controlling group size and behavior, designing camp sites, moving groups frequently, proper use of fires, proper disposal of food and human wastes, use of biodegradable soaps, and encouraging staff and camper awareness of impacts on the environment. (LP)

  6. 5 CFR 630.206 - Minimum charge.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 5 Administrative Personnel 1 2010-01-01 2010-01-01 false Minimum charge. 630.206 Section 630.206... and General Provisions for Annual and Sick Leave § 630.206 Minimum charge. (a) Unless an agency establishes a minimum charge of less than one hour, or establishes a different minimum charge...

  7. 5 CFR 630.206 - Minimum charge.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 5 Administrative Personnel 1 2011-01-01 2011-01-01 false Minimum charge. 630.206 Section 630.206... and General Provisions for Annual and Sick Leave § 630.206 Minimum charge. (a) Unless an agency establishes a minimum charge of less than one hour, or establishes a different minimum charge...

  8. Genetic Algorithms with Local Minimum Escaping Technique

    NASA Astrophysics Data System (ADS)

    Tamura, Hiroki; Sakata, Kenichiro; Tang, Zheng; Ishii, Masahiro

    In this paper, we propose a genetic algorithm(GA) with local minimum escaping technique. This proposed method uses the local minimum escaping techique. It can escape from the local minimum by correcting parameters when genetic algorithm falls into a local minimum. Simulations are performed to scheduling problem without buffer capacity using this proposed method, and its validity is shown.

  9. 5 CFR 551.301 - Minimum wage.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 5 Administrative Personnel 1 2014-01-01 2014-01-01 false Minimum wage. 551.301 Section 551.301... FAIR LABOR STANDARDS ACT Minimum Wage Provisions Basic Provision § 551.301 Minimum wage. (a)(1) Except... employees wages at rates not less than the minimum wage specified in section 6(a)(1) of the Act for...

  10. 5 CFR 551.301 - Minimum wage.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 5 Administrative Personnel 1 2011-01-01 2011-01-01 false Minimum wage. 551.301 Section 551.301... FAIR LABOR STANDARDS ACT Minimum Wage Provisions Basic Provision § 551.301 Minimum wage. (a)(1) Except... employees wages at rates not less than the minimum wage specified in section 6(a)(1) of the Act for...

  11. 5 CFR 551.301 - Minimum wage.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Minimum wage. 551.301 Section 551.301... FAIR LABOR STANDARDS ACT Minimum Wage Provisions Basic Provision § 551.301 Minimum wage. (a)(1) Except... employees wages at rates not less than the minimum wage specified in section 6(a)(1) of the Act for...

  12. 5 CFR 551.301 - Minimum wage.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 5 Administrative Personnel 1 2010-01-01 2010-01-01 false Minimum wage. 551.301 Section 551.301... FAIR LABOR STANDARDS ACT Minimum Wage Provisions Basic Provision § 551.301 Minimum wage. (a)(1) Except... employees wages at rates not less than the minimum wage specified in section 6(a)(1) of the Act for...

  13. 5 CFR 551.301 - Minimum wage.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 5 Administrative Personnel 1 2013-01-01 2013-01-01 false Minimum wage. 551.301 Section 551.301... FAIR LABOR STANDARDS ACT Minimum Wage Provisions Basic Provision § 551.301 Minimum wage. (a)(1) Except... employees wages at rates not less than the minimum wage specified in section 6(a)(1) of the Act for...

  14. Understanding the Minimum Wage: Issues and Answers.

    ERIC Educational Resources Information Center

    Employment Policies Inst. Foundation, Washington, DC.

    This booklet, which is designed to clarify facts regarding the minimum wage's impact on marketplace economics, contains a total of 31 questions and answers pertaining to the following topics: relationship between minimum wages and poverty; impacts of changes in the minimum wage on welfare reform; and possible effects of changes in the minimum wage…

  15. On the Importance of Cycle Minimum in Sunspot Cycle Prediction

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.; Hathaway, David H.; Reichmann, Edwin J.

    1996-01-01

    The characteristics of the minima between sunspot cycles are found to provide important information for predicting the amplitude and timing of the following cycle. For example, the time of the occurrence of sunspot minimum sets the length of the previous cycle, which is correlated by the amplitude-period effect to the amplitude of the next cycle, with cycles of shorter (longer) than average length usually being followed by cycles of larger (smaller) than average size (true for 16 of 21 sunspot cycles). Likewise, the size of the minimum at cycle onset is correlated with the size of the cycle's maximum amplitude, with cycles of larger (smaller) than average size minima usually being associated with larger (smaller) than average size maxima (true for 16 of 22 sunspot cycles). Also, it was found that the size of the previous cycle's minimum and maximum relates to the size of the following cycle's minimum and maximum with an even-odd cycle number dependency. The latter effect suggests that cycle 23 will have a minimum and maximum amplitude probably larger than average in size (in particular, minimum smoothed sunspot number Rm = 12.3 +/- 7.5 and maximum smoothed sunspot number RM = 198.8 +/- 36.5, at the 95-percent level of confidence), further suggesting (by the Waldmeier effect) that it will have a faster than average rise to maximum (fast-rising cycles have ascent durations of about 41 +/- 7 months). Thus, if, as expected, onset for cycle 23 will be December 1996 +/- 3 months, based on smoothed sunspot number, then the length of cycle 22 will be about 123 +/- 3 months, inferring that it is a short-period cycle and that cycle 23 maximum amplitude probably will be larger than average in size (from the amplitude-period effect), having an RM of about 133 +/- 39 (based on the usual +/- 30 percent spread that has been seen between observed and predicted values), with maximum amplitude occurrence likely sometime between July 1999 and October 2000.

  16. GMTI radar minimum detectable velocity.

    SciTech Connect

    Richards, John Alfred

    2011-04-01

    Minimum detectable velocity (MDV) is a fundamental consideration for the design, implementation, and exploitation of ground moving-target indication (GMTI) radar imaging modes. All single-phase-center air-to-ground radars are characterized by an MDV, or a minimum radial velocity below which motion of a discrete nonstationary target is indistinguishable from the relative motion between the platform and the ground. Targets with radial velocities less than MDV are typically overwhelmed by endoclutter ground returns, and are thus not generally detectable. Targets with radial velocities greater than MDV typically produce distinct returns falling outside of the endoclutter ground returns, and are thus generally discernible using straightforward detection algorithms. This document provides a straightforward derivation of MDV for an air-to-ground single-phase-center GMTI radar operating in an arbitrary geometry.

  17. Crystal Creations.

    ERIC Educational Resources Information Center

    Whipple, Nona; Whitmore, Sherry

    1989-01-01

    Presents a many-faceted learning approach to the study of crystals. Provides instructions for performing activities including crystal growth and patterns, creating miniature simulations of crystal-containing rock formations, charcoal and sponge gardens, and snowflakes. (RT)

  18. Centrosymmetry vs noncentrosymmetry in La2Ga0.33SbS5 and Ce4GaSbS9 based on the interesting size effects of lanthanides: Syntheses, crystal structures, and optical properties

    NASA Astrophysics Data System (ADS)

    Zhao, Hua-Jun

    2016-05-01

    Two new quaternary sulfides La2Ga0.33SbS5 and Ce4GaSbS9 have been prepared from stoichiometric elements at 1223 K in an evacuated silica tube. Interestingly, La2Ga0.33SbS5 crystallizes in the centrosymmetric structure, while Ce4GaSbS9 crystallizes in the noncentrosymmetric structure, which show obvious size effects of lanthanides on the crystal structures of these two compounds. Ce4GaSbS9 belongs to RE4GaSbS9 (RE=Pr, Nd, Sm, Gd-Ho) structure type with a=13.8834(9) Å, b=14.3004(11) Å, c=14.4102(13) Å, V=2861.0(4) Å3. The structure features infinite chains of [Ga2Sb2S1110-]∞ propagating along a direction separated by Ce3+ cations and S2- anions. La2Ga0.33SbS5 adopts the family of La4FeSb2S10-related structure with a=7.5193(6) Å, c=13.4126(17) Å, V=758.35(13) Å3. Its structure is built up from the alternate stacking of La/Sb/S and La/Ga/S 2D building blocks. The La/Sb/S slabs consist of teeter-totter chains of Sb1S4 seesaws, which are connected via sharing the apexes of μ4-S1. Moreover, La1 is positionally disordered with Sb1 and stabilized in a bicapped trigonal prismatic coordination sphere. Between these La/Sb/S slabs, La2S8 square antiprisms are connected via edge-sharing into 2D building blocks, creating tetrahedral sites partially occupied by the Ga1 atoms. UV/Vis diffuse reflectance spectroscopy study shows that the optical gap of La2Ga0.33SbS5 is about 1.76 eV.

  19. Magma Pulsing and Internal Structure of the Torres del Paine Laccolith (Patagonia) Constrained by High Precision Zircon U-Pb Dating, and Thermal and Crystal Size Modeling of its Contact Aureole.

    NASA Astrophysics Data System (ADS)

    Baumgartner, L. P.; Bodner, R.; Leuthold, J.; Muntener, O.; Putlitz, B.

    2014-12-01

    The shallow Torres del Paine Intrusive Complex (TPIC) belongs to a trench-parallel belt of igneous bodies in Southern Chile and Argentina. It is located in a transitional position between the Patagonia Batholith in the West, and the alkaline Cenozoic plateau lavas in the East. Volumetrically small amounts of magmatism started around 28 my ago in the Torres del Paine area. A second period occurred between 17-16 Ma, and igneous activity peaked with the TPIC 12.59-12.43 Ma ago. Finally, very minor magmatism occurred less than a million year ago. Intrusion depth, estimated based on contact metamorphic assemblages, decreased from ca. 10-12km at 17 Ma to ca. 3km at 12.5 Ma, the latter depth corresponding well with hornblende thermobarometry in mafic rocks and the water saturated granite solidus compositions observed. The TPIC is composed of a granitic laccolith emplaced over 90ka (1) in 3 several 100m thick sheets, forming an overall thickness of nearly 2 km. The granitic laccolith is under-plated by a ca. 400m thick mafic laccolith, built up over 50ka (2), constructed bottom up. Each sheet is itself composed of a multitude (>10) of metric to decametric pulses with mostly ductile contacts, resulting in outcrop patterns resembling braided stream sediments. Thermal modeling of the contact metamorphism, including heat of crystallization and the enthalpy of metamorphic reactions constrains the granite intrusion temperature to ca. 1000°C. Peak metamorphic temperatures suggest that intrusion of magma had to occur in a rapid succession of pulses, preferentially along the granite-host rock contact. Enthalpy released due to hydration of the biotite and feldspar of the immature sediments in the outer aureole contributed significantly to the far-field temperatures in the host-rock. Numerical crystal growth models matching the crystal size distribution indicate significant overstepping during onset of the contact metamorphic reactions. Nevertheless, sharp isogrades are predicted by

  20. Advanced distortion-invariant minimum average correlation energy (MACE) filters.

    PubMed

    Casasent, D; Ravichandran, G

    1992-03-10

    The original minimum average correlation energy (MACE) filter is addressed by using a new database (strategic relocatable objects, missile launchers) and including noise performance, depression angle, and resolution effects on the number of training set images that are required. Major attention is given to our new MACE filter algorithms for distortion-invariant pattern recognition: shifted-MACE filters (to suppress large false correlation peaks), minimum variance-MACE filters (for improved noise performance), multiple symbolic encoded filters (to reduce the effect of false correlation peaks), and Gaussian-MACE filters (to improve noise performance and intraclass recognition and reduce the training set size). PMID:20720728

  1. Advanced distortion-invariant minimum average correlation energy (MACE) filters

    NASA Astrophysics Data System (ADS)

    Casasent, David; Ravichandran, Gopalan

    1992-03-01

    The original minimum average correlation energy (MACE) filter is addressed by using a new database (strategic relocatable objects and missile launchers) and including noise performance, depression angle, and resolution effects on the number of training set images that are required. Major attention is given to new MACE filter algorithms for distortion-invariant pattern recognition: shifted-MACE filters to suppress large false correlation peaks, minimum variance-MACE filters for improved noise performance, multiple symbolic encoded filters to reduce the effect of false correlation peaks, and Gaussian-MACE filters to improve noise performance and intraclass recognition and reduce the training set size.

  2. Macromolecular Crystal Quality

    NASA Technical Reports Server (NTRS)

    Snell, Edward H.; Borgstahl, Gloria E. O.; Bellamy, Henry D.; Curreri, Peter A. (Technical Monitor)

    2001-01-01

    There are many ways of judging a good crystal. Which we use depends on the qualities we seek. For gemstones size, clarity and impurity levels (color) are paramount. For the semiconductor industry purity is probably the most important quality. For the structural crystallographer the primary desideratum is the somewhat more subtle concept of internal order. In this chapter we discuss the effect of internal order (or the lack of it) on the crystal's diffraction properties.

  3. Polymer Crystallization under Confinement

    NASA Astrophysics Data System (ADS)

    Floudas, George

    Recent efforts indicated that polymer crystallization under confinement can be substantially different from the bulk. This can have important technological applications for the design of polymeric nanofibers with tunable mechanical strength, processability and optical clarity. However, the question of how, why and when polymers crystallize under confinement is not fully answered. Important studies of polymer crystallization confined to droplets and within the spherical nanodomains of block copolymers emphasized the interplay between heterogeneous and homogeneous nucleation. Herein we report on recent studies1-5 of polymer crystallization under hard confinement provided by model self-ordered AAO nanopores. Important open questions here are on the type of nucleation (homogeneous vs. heterogeneous), the size of critical nucleus, the crystal orientation and the possibility to control the overall crystallinity. Providing answers to these questions is of technological relevance for the understanding of nanocomposites containing semicrystalline polymers. In collaboration with Y. Suzuki, H. Duran, M. Steinhart, H.-J. Butt.

  4. Minimum Bayes risk image correlation

    NASA Technical Reports Server (NTRS)

    Minter, T. C., Jr.

    1980-01-01

    In this paper, the problem of designing a matched filter for image correlation will be treated as a statistical pattern recognition problem. It is shown that, by minimizing a suitable criterion, a matched filter can be estimated which approximates the optimum Bayes discriminant function in a least-squares sense. It is well known that the use of the Bayes discriminant function in target classification minimizes the Bayes risk, which in turn directly minimizes the probability of a false fix. A fast Fourier implementation of the minimum Bayes risk correlation procedure is described.

  5. Ceramic veneers with minimum preparation

    PubMed Central

    da Cunha, Leonardo Fernandes; Reis, Rachelle; Santana, Lino; Romanini, Jose Carlos; Carvalho, Ricardo Marins; Furuse, Adilson Yoshio

    2013-01-01

    The aim of this article is to describe the possibility of improving dental esthetics with low-thickness glass ceramics without major tooth preparation for patients with small to moderate anterior dental wear and little discoloration. For this purpose, a carefully defined treatment planning and a good communication between the clinician and the dental technician helped to maximize enamel preservation, and offered a good treatment option. Moreover, besides restoring esthetics, the restorative treatment also improved the function of the anterior guidance. It can be concluded that the conservative use of minimum thickness ceramic laminate veneers may provide satisfactory esthetic outcomes while preserving the dental structure. PMID:24932126

  6. Resistance minimum and heavy fermions.

    PubMed

    Jun, Kondo

    2006-12-01

    The phenomenon of the resistance minimum in dilute magnetic alloys is explained in terms of the s-d interaction which takes account of scattering of the conduction electron off the magnetic impurities in metals. Some of the intermetallic compounds which involve rare earth elements or uranium show a very large electronic specific heat and remain non-magnetic even though they show a Curie-like susceptibility at higher temperatures. These phenomena are also explained based on the s-d interaction model. PMID:25792794

  7. Resistance minimum and heavy fermions

    PubMed Central

    Jun, Kondo

    2006-01-01

    The phenomenon of the resistance minimum in dilute magnetic alloys is explained in terms of the s-d interaction which takes account of scattering of the conduction electron off the magnetic impurities in metals. Some of the intermetallic compounds which involve rare earth elements or uranium show a very large electronic specific heat and remain non-magnetic even though they show a Curie-like susceptibility at higher temperatures. These phenomena are also explained based on the s-d interaction model. PMID:25792794

  8. Solid phase stability of a double-minimum interaction potential system

    SciTech Connect

    Suematsu, Ayumi; Yoshimori, Akira Saiki, Masafumi; Matsui, Jun; Odagaki, Takashi

    2014-06-28

    We study phase stability of a system with double-minimum interaction potential in a wide range of parameters by a thermodynamic perturbation theory. The present double-minimum potential is the Lennard-Jones-Gauss potential, which has a Gaussian pocket as well as a standard Lennard-Jones minimum. As a function of the depth and position of the Gaussian pocket in the potential, we determine the coexistence pressure of crystals (fcc and bcc). We show that the fcc crystallizes even at zero pressure when the position of the Gaussian pocket is coincident with the first or third nearest neighbor site of the fcc crystal. The bcc crystal is more stable than the fcc crystal when the position of the Gaussian pocket is coincident with the second nearest neighbor sites of the bcc crystal. The stable crystal structure is determined by the position of the Gaussian pocket. These results show that we can control the stability of the solid phase by tuning the potential function.

  9. Protein Crystals Grown in Space

    NASA Technical Reports Server (NTRS)

    2000-01-01

    A collage of protein and virus crystals, many of which were grown on the U.S. Space Shuttle or Russian Space Station, Mir. The crystals include the proteins canavalin; mouse monoclonal antibody; a sweet protein, thaumatin; and a fungal protease. Viruses are represented here by crystals of turnip yellow mosaic virus and satellite tobacco mosaic virus. The crystals are photographed under polarized light (thus causing the colors) and range in size from a few hundred microns in edge length up to more than a millimeter. All the crystals are grown from aqueous solutions and are useful for X-ray diffraction analysis. Credit: Dr. Alex McPherson, University of California, Irvine.

  10. Mechanical Properties Of Large Sodium Iodide Crystals

    NASA Technical Reports Server (NTRS)

    Lee, Henry M.

    1988-01-01

    Report presents data on mechanical properties of large crystals of thallium-doped sodium iodide. Five specimens in shape of circular flat plates subjected to mechanical tests. Presents test results for each specimen as plots of differential pressure versus center displacement and differential pressure versus stress at center. Also tabulates raw data. Test program also developed procedure for screening candidate crystals for gamma-ray sensor. Procedure eliminates potentially weak crystals before installed and ensures material yielding kept to minimum.

  11. Optimizing Crystal Volume for Neutron Diffraction Studies

    NASA Technical Reports Server (NTRS)

    Snell, E. H.

    2003-01-01

    For structural studies with neutron diffraction more intense neutron sources, improved sensitivity detector and larger volume crystals are all means by which the science is being advanced to enable studies on a wider range of samples. We have chosen a simplistic approach using a well understood crystallization method, with minimal amounts of sample and using design of experiment techniques to maximize the crystal volume all for minimum effort. Examples of the application are given.

  12. The minimum mantle viscosity of an accreting earth

    NASA Technical Reports Server (NTRS)

    Cooperman, S. A.

    1983-01-01

    The minimum mantle viscosity in an earth accreting from planetesimals is estimated. A plausible distribution of planetesimal sizes deposits enough energy to melt the outer nine-tenths of earth's mass; however, vigorous convection keeps temperatures near the solidus. Viscosity is significantly lower than prevails now. The temperature-dependent viscosity provides self-regulation so there is a continuing balance between accretional energy input and heat transfer out. This allows calculation of the minimum viscosity necessary to transfer out heat by a Nu/Ra-number relation. Typical viscosities are 0.1 to a million sq m/sec, lowest at mid-accretion when the mass growth rate is largest. Terrestrial planets are compared, and minimum iron descent times to central lithospheres are calculated.

  13. Computational strain gradient crystal plasticity

    NASA Astrophysics Data System (ADS)

    Niordson, Christian F.; Kysar, Jeffrey W.

    2014-01-01

    A numerical method for viscous strain gradient crystal plasticity theory is presented, which incorporates both energetic and dissipative gradient effects. The underlying minimum principles are discussed as well as convergence properties of the proposed finite element procedure. Three problems of plane crystal plasticity are studied: pure shear of a single crystal between rigid platens as well as plastic deformation around cylindrical voids in hexagonal close packed and face centered cubic crystals. Effective in-plane constitutive slip parameters for plane strain deformation of specifically oriented face centered cubic crystals are developed in terms of the crystallographic slip parameters. The effect on geometrically necessary dislocation structures introduced by plastic deformation is investigated as a function of the ratio of void radius to plasticity length scale.

  14. Does the Minimum Wage Affect Welfare Caseloads?

    ERIC Educational Resources Information Center

    Page, Marianne E.; Spetz, Joanne; Millar, Jane

    2005-01-01

    Although minimum wages are advocated as a policy that will help the poor, few studies have examined their effect on poor families. This paper uses variation in minimum wages across states and over time to estimate the impact of minimum wage legislation on welfare caseloads. We find that the elasticity of the welfare caseload with respect to the…

  15. Do Some Workers Have Minimum Wage Careers?

    ERIC Educational Resources Information Center

    Carrington, William J.; Fallick, Bruce C.

    2001-01-01

    Most workers who begin their careers in minimum-wage jobs eventually gain more experience and move on to higher paying jobs. However, more than 8% of workers spend at least half of their first 10 working years in minimum wage jobs. Those more likely to have minimum wage careers are less educated, minorities, women with young children, and those…

  16. 43 CFR 3923.10 - Minimum bid.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Minimum bid. 3923.10 Section 3923.10 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR RANGE MANAGEMENT (4000) OIL SHALE LEASING Minimum Bid § 3923.10 Minimum bid....

  17. 43 CFR 3923.10 - Minimum bid.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false Minimum bid. 3923.10 Section 3923.10 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE INTERIOR MINERALS MANAGEMENT (3000) OIL SHALE LEASING Minimum Bid § 3923.10 Minimum...

  18. 77 FR 32444 - Minimum Internal Control Standards

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-01

    ... Minimum Internal Control Standards. 64 FR 590. The rule added a new part to the Commission's regulations... National Indian Gaming Commission 25 CFR Part 543 RIN 3141-AA27 Minimum Internal Control Standards AGENCY... (NIGC) proposes to amend its minimum internal control standards for Class II gaming under the...

  19. 78 FR 63873 - Minimum Internal Control Standards

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-25

    ... NIGC published a final rule in the Federal Register called Minimum Internal Control Standards. 64 FR... National Indian Gaming Commission 25 CFR Part 543 RIN 3141-AA27 Minimum Internal Control Standards AGENCY... Commission (NIGC) amends its minimum internal control standards for Class II gaming under the Indian...

  20. 30 CFR 202.53 - Minimum royalty.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 2 2010-07-01 2010-07-01 false Minimum royalty. 202.53 Section 202.53 Mineral Resources MINERALS MANAGEMENT SERVICE, DEPARTMENT OF THE INTERIOR MINERALS REVENUE MANAGEMENT ROYALTIES Oil, Gas, and OCS Sulfur, General § 202.53 Minimum royalty. For leases that provide for minimum...

  1. Exploratory Factor Analysis with Small Sample Sizes

    ERIC Educational Resources Information Center

    de Winter, J. C. F.; Dodou, D.; Wieringa, P. A.

    2009-01-01

    Exploratory factor analysis (EFA) is generally regarded as a technique for large sample sizes ("N"), with N = 50 as a reasonable absolute minimum. This study offers a comprehensive overview of the conditions in which EFA can yield good quality results for "N" below 50. Simulations were carried out to estimate the minimum required "N" for different…

  2. Protein crystal growth

    NASA Technical Reports Server (NTRS)

    Bugg, Charles E.

    1993-01-01

    Proteins account for 50% or more of the dry weight of most living systems and play a crucial role in virtually all biological processes. Since the specific functions of essentially all biological molecules are determined by their three-dimensional structures, it is obvious that a detailed understanding of the structural makeup of a protein is essential to any systematic research pertaining to it. At the present time, protein crystallography has no substitute, it is the only technique available for elucidating the atomic arrangements within complicated biological molecules. Most macromolecules are extremely difficult to crystallize, and many otherwise exciting and promising projects have terminated at the crystal growth stage. There is a pressing need to better understand protein crystal growth, and to develop new techniques that can be used to enhance the size and quality of protein crystals. There are several aspects of microgravity that might be exploited to enhance protein crystal growth. The major factor that might be expected to alter crystal growth processes in space is the elimination of density-driven convective flow. Another factor that can be readily controlled in the absence of gravity is the sedimentation of growing crystal in a gravitational field. Another potential advantage of microgravity for protein crystal growth is the option of doing containerless crystal growth. One can readily understand why the microgravity environment established by Earth-orbiting vehicles is perceived to offer unique opportunities for the protein crystallographer. The near term objectives of the Protein Crystal Growth in a Microgravity Environment (PCG/ME) project is to continue to improve the techniques, procedures, and hardware systems used to grow protein crystals in Earth orbit.

  3. Adhesion of single crystals on modified surfaces in crystallization fouling

    NASA Astrophysics Data System (ADS)

    Mayer, Moriz; Augustin, Wolfgang; Scholl, Stephan

    2012-12-01

    In crystallization fouling it has been observed that during a certain initial phase the fouling is formed by a non-uniform layer consisting of a population of single crystals. These single crystals are frequently formed by inverse soluble salts such as CaCO3. During heterogeneous nucleation and heterogeneous growth an interfacial area between the crystal and the heat transfer surface occurs. The development of this interfacial area is the reason for the adhesion of each single crystal and of all individual crystals, once a uniform layer has been built up. The emerging interfacial area is intrinsic to the heterogeneous nucleation of crystals and can be explained by the thermodynamic principle of the minimum of the Gibbs free energy. In this study CaCO3 crystals were grown heterogeneously on untreated and on modified surfaces inside a flow channel. An untreated stainless steel (AISI 304) surface was used as a reference. Following surface modifications were investigated: enameled and electropolished stainless steel as well as diamond-like-carbon based coatings on stainless steel substrate. The adhesion was measured through a novel measurement technique using a micromanipulator to shear off single crystals from the substrate which was fixed to a spring table inside a SEM.

  4. Scanning electron microscope view of iron crystal growing on pyroxene crystal

    NASA Technical Reports Server (NTRS)

    1972-01-01

    A scanning electron microscope photograph of a four-micron size iron crystal growing on a pyroxene crystal (calcium-magnesium-iron silicate) from the Apollo 15 Hadley-Apennino lunar landing site. The well developed crystal faces indicate that the crystal was formed from a hot vapor as the rock was cooling.

  5. Minimum variance beamformer weights revisited.

    PubMed

    Moiseev, Alexander; Doesburg, Sam M; Grunau, Ruth E; Ribary, Urs

    2015-10-15

    Adaptive minimum variance beamformers are widely used analysis tools in MEG and EEG. When the target brain activity presents in the form of spatially localized responses, the procedure usually involves two steps. First, positions and orientations of the sources of interest are determined. Second, the filter weights are calculated and source time courses reconstructed. This last step is the object of the current study. Despite different approaches utilized at the source localization stage, basic expressions for the weights have the same form, dictated by the minimum variance condition. These classic expressions involve covariance matrix of the measured field, which includes contributions from both the sources of interest and the noise background. We show analytically that the same weights can alternatively be obtained, if the full field covariance is replaced with that of the noise, provided the beamformer points to the true sources precisely. In practice, however, a certain mismatch is always inevitable. We show that such mismatch results in partial suppression of the true sources if the traditional weights are used. To avoid this effect, the "alternative" weights based on properly estimated noise covariance should be applied at the second, source time course reconstruction step. We demonstrate mathematically and using simulated and real data that in many situations the alternative weights provide significantly better time course reconstruction quality than the traditional ones. In particular, they a) improve source-level SNR and yield more accurately reconstructed waveforms; b) provide more accurate estimates of inter-source correlations; and c) reduce the adverse influence of the source correlations on the performance of single-source beamformers, which are used most often. Importantly, the alternative weights come at no additional computational cost, as the structure of the expressions remains the same. PMID:26143207

  6. 50 CFR 622.56 - Size limits.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ..., DEPARTMENT OF COMMERCE FISHERIES OF THE CARIBBEAN, GULF OF MEXICO, AND SOUTH ATLANTIC Shrimp Fishery of the Gulf of Mexico § 622.56 Size limits. Shrimp not in compliance with the applicable size limit as... shrimp harvested in the Gulf EEZ are subject to the minimum-size landing and possession limits...

  7. 50 CFR 622.37 - Size limits.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ..., DEPARTMENT OF COMMERCE FISHERIES OF THE CARIBBEAN, GULF OF MEXICO, AND SOUTH ATLANTIC Reef Fish Resources of the Gulf of Mexico § 622.37 Size limits. All size limits in this section are minimum size limits... for Gulf reef fish and commercial quantities of Gulf reef fish, i.e., Gulf reef fish in excess......

  8. 50 CFR 622.37 - Size limits.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ..., DEPARTMENT OF COMMERCE FISHERIES OF THE CARIBBEAN, GULF OF MEXICO, AND SOUTH ATLANTIC Reef Fish Resources of the Gulf of Mexico § 622.37 Size limits. All size limits in this section are minimum size limits... for Gulf reef fish and commercial quantities of Gulf reef fish, i.e., Gulf reef fish in excess......

  9. 50 CFR 622.56 - Size limits.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ..., DEPARTMENT OF COMMERCE FISHERIES OF THE CARIBBEAN, GULF OF MEXICO, AND SOUTH ATLANTIC Shrimp Fishery of the Gulf of Mexico § 622.56 Size limits. Shrimp not in compliance with the applicable size limit as... shrimp harvested in the Gulf EEZ are subject to the minimum-size landing and possession limits...

  10. Struvite precipitation from urine - Influencing factors on particle size.

    PubMed

    Ronteltap, Mariska; Maurer, Max; Hausherr, Rainer; Gujer, Willi

    2010-03-01

    Struvite crystallisation is a fast and reliable phosphorus removal and recovery process for concentrated waste streams - such as hydrolysed human urine. In order to optimise P-elimination efficiency, it is beneficial to obtain larger particle sizes: they are easier to separate and less prone to wash-out than smaller particles. This paper presents the results of a study on the effect of process parameters on particle size in a single step struvite precipitation. Crystals formed in batch experiments with real hydrolysed urine were shown to have an average size of >90 microm at pH 9 and 20 degrees C. This is reduced to 45 microm when changing stirrer type. Particle size increases with lower supersaturation. The results showed that under otherwise constant conditions, particle size decreases with lower temperature and has a minimum between pH 9 and 10. Deviating trends are observed at pH <8. Struvite formation in a CSTR (continuously stirred tank reactor) process was shown to be a reliable stable process that does not require any pH control. A method based on conductivity measurement is presented to estimate ionic strength, which is needed for equilibrium calculations. PMID:20116825

  11. Minimum distance classification in remote sensing

    NASA Technical Reports Server (NTRS)

    Wacker, A. G.; Landgrebe, D. A.

    1972-01-01

    The utilization of minimum distance classification methods in remote sensing problems, such as crop species identification, is considered. Literature concerning both minimum distance classification problems and distance measures is reviewed. Experimental results are presented for several examples. The objective of these examples is to: (a) compare the sample classification accuracy of a minimum distance classifier, with the vector classification accuracy of a maximum likelihood classifier, and (b) compare the accuracy of a parametric minimum distance classifier with that of a nonparametric one. Results show the minimum distance classifier performance is 5% to 10% better than that of the maximum likelihood classifier. The nonparametric classifier is only slightly better than the parametric version.

  12. Crystal growth and annealing method and apparatus

    DOEpatents

    Gianoulakis, Steven E.; Sparrow, Robert

    2001-01-01

    A method and apparatus for producing crystals that minimizes birefringence even at large crystal sizes, and is suitable for production of CaF.sub.2 crystals. The method of the present invention comprises annealing a crystal by maintaining a minimal temperature gradient in the crystal while slowly reducing the bulk temperature of the crystal. An apparatus according to the present invention includes a thermal control system added to a crystal growth and annealing apparatus, wherein the thermal control system allows a temperature gradient during crystal growth but minimizes the temperature gradient during crystal annealing. An embodiment of the present invention comprises a secondary heater incorporated into a conventional crystal growth and annealing apparatus. The secondary heater supplies heat to minimize the temperature gradients in the crystal during the annealing process. The secondary heater can mount near the bottom of the crucible to effectively maintain appropriate temperature gradients.

  13. Class Size.

    ERIC Educational Resources Information Center

    Underwood, Siobhan; Lumsden, Linda S.

    1994-01-01

    The items featured in this annotated bibliography touch on several aspects of the multifaceted class-size debate. Allen Odden reviews the literature and contends that class-size reduction should be used "sparingly and strategically." C. M. Achilles and colleagues examines two different class-size situations and find student test performance in the…

  14. Class Size.

    ERIC Educational Resources Information Center

    Johnston, Holly R.

    Exploring the class-size issue, this paper focuses on the primary grades and asks questions such as "does a reduction in class size promote an increase in academic achievement?" and "how substantial does the reduction in numbers have to be in order for a significant increase to occur?" The paper surveys debates on class size and the social factors…

  15. Structural contribution to the roughness of supersmooth crystal surface

    SciTech Connect

    Butashin, A. V.; Muslimov, A. E. Kanevsky, V. M.; Deryabin, A. N.; Pavlov, V. A.; Asadchikov, V. E.

    2013-05-15

    Technological advances in processing crystals (Si, sapphire {alpha}-Al{sub 2}O{sub 3}, SiC, GaN, LiNbO{sub 3}, SrTiO{sub 3}, etc.) of substrate materials and X-ray optics elements make it possible to obtain supersmooth surfaces with a periodicity characteristic of the crystal structure. These periodic structures are formed by atomically smooth terraces and steps of nano- and subnanometer sizes, respectively. A model surface with such nanostructures is proposed, and the relations between its roughness parameters and the height of atomic steps are determined. The roughness parameters calculated from these relations almost coincide with the experimental atomic force microscopy (AFM) data obtained from 1 Multiplication-Sign 1 and 10 Multiplication-Sign 10 {mu}m areas on the surface of sapphire plates with steps. The minimum roughness parameters for vicinal crystal surfaces, which are due to the structural contribution, are calculated based on the approach proposed. A comparative analysis of the relief and roughness parameters of sapphire plate surfaces with different degrees of polishing is performed. A size effect is established: the relief height distribution changes from stochastic to regular with a decrease in the surface roughness.

  16. Exact Models for the k-Connected Minimum Energy Problem

    NASA Astrophysics Data System (ADS)

    Burt, Christina; Chan, Yao-Ban; Sonenberg, Nikki

    We consider the minimum energy problem for a mobile ad hoc network, where any node in the network may communicate with any other via intermediate nodes. To provide quality of service, the network must be connected, even if one or more nodes drop out. This motivates the notion of k-connectivity. The minimum energy problem aims to optimise the total energy that all nodes spend for transmission. Previous work in the literature includes exact mixed-integer programming formulations for a 1-connected network. We extend these models for when the network is k-connected, and compare the models for various network sizes. As expected, the combinatorial nature of the problem limits the size of the networks that we can solve to optimality in a timely manner. However, these exact models may be used for the future design of mobile ad hoc networks and provide useful benchmarks for heuristics in larger networks.

  17. Crystal Systems.

    ERIC Educational Resources Information Center

    Schomaker, Verner; Lingafelter, E. C.

    1985-01-01

    Discusses characteristics of crystal systems, comparing (in table format) crystal systems with lattice types, number of restrictions, nature of the restrictions, and other lattices that can accidently show the same metrical symmetry. (JN)

  18. Minimum cost criteria for SPS transportation to GEO

    NASA Technical Reports Server (NTRS)

    Koelle, D. E.

    1980-01-01

    The application of cost optimization to vehicle design is discussed relative to establishing ground rules for a minimum cost heavy cargo launch vehicle to transport the Satellite Power System to geosynchronous orbit. Criteria defined include: fully reusable; unmanned; technical simplicity; and operations simplicity. Graphs are presented depicting (1) the launch vehicle concept schematic, (2) the cost comparison, (3) the launch vehicle sizing, and (4) the specific transportation cost.

  19. Refinement of thermal imager minimum resolvable temperature difference calculating method

    NASA Astrophysics Data System (ADS)

    Kolobrodov, V. G.; Mykytenko, V. I.

    2015-11-01

    Calculating methods, which accurately predict minimum resolvable temperature difference (MRTD), are of significant interest for many years. The article deals with improvement the accuracy of determining the thermal imaging system MRTD by elaboration the visual perception model. We suggest MRTD calculating algorithm, which is based on a reliable approximation of the human visual system modulation transfer function (MTF) proposed by N. Nill. There was obtained a new expression for the bandwidth evaluation, which is independent of angular size of the Foucault bar target.

  20. Manipulating crystallization with molecular additives.

    PubMed

    Shtukenberg, Alexander G; Lee, Stephanie S; Kahr, Bart; Ward, Michael D

    2014-01-01

    Given the importance of organic crystals in a wide range of industrial applications, the chemistry, biology, materials science, and chemical engineering communities have focused considerable attention on developing methods to control crystal structure, size, shape, and orientation. Tailored additives have been used to control crystallization to great effect, presumably by selectively binding to particular crystallographic surfaces and sites. However, substantial knowledge gaps still exist in the fundamental mechanisms that govern the formation and growth of organic crystals in both the absence and presence of additives. In this review, we highlight research discoveries that reveal the role of additives, either introduced by design or present adventitiously, on various stages of formation and growth of organic crystals, including nucleation, dislocation spiral growth mechanisms, growth inhibition, and nonclassical crystal morphologies. The insights from these investigations and others of their kind are likely to guide the development of innovative methods to manipulate crystallization for a wide range of materials and applications. PMID:24579880

  1. Confined Crystals of the Smallest Phase-Change Material

    PubMed Central

    2013-01-01

    The demand for high-density memory in tandem with limitations imposed by the minimum feature size of current storage devices has created a need for new materials that can store information in smaller volumes than currently possible. Successfully employed in commercial optical data storage products, phase-change materials, that can reversibly and rapidly change from an amorphous phase to a crystalline phase when subject to heating or cooling have been identified for the development of the next generation electronic memories. There are limitations to the miniaturization of these devices due to current synthesis and theoretical considerations that place a lower limit of 2 nm on the minimum bit size, below which the material does not transform in the structural phase. We show here that by using carbon nanotubes of less than 2 nm diameter as templates phase-change nanowires confined to their smallest conceivable scale are obtained. Contrary to previous experimental evidence and theoretical expectations, the nanowires are found to crystallize at this scale and display amorphous-to-crystalline phase changes, fulfilling an important prerequisite of a memory element. We show evidence for the smallest phase-change material, extending thus the size limit to explore phase-change memory devices at extreme scales. PMID:23984706

  2. Structure, microstructure, and size dependent catalytic properties of nanostructured ruthenium dioxide

    SciTech Connect

    Nowakowski, Pawel; Dallas, Jean-Pierre; Villain, Sylvie; Kopia, Agnieszka; Gavarri, Jean-Raymond

    2008-05-15

    Nanostructured powders of ruthenium dioxide RuO{sub 2} were synthesized via a sol gel route involving acidic solutions with pH varying between 0.4 and 4.5. The RuO{sub 2} nanopowders were characterized by X-ray diffraction, scanning and transmission electron microscopy (SEM and TEM). Rietveld refinement of mean crystal structure was performed on RuO{sub 2} nanopowders and crystallized standard RuO{sub 2} sample. Crystallite sizes measured from X-ray diffraction profiles and TEM analysis varied in the range of 4-10 nm, with a minimum of crystallite dimension for pH=1.5. A good agreement between crystallite sizes calculated from Williamson Hall approach of X-ray data and from direct TEM observations was obtained. The tetragonal crystal cell parameter (a) and cell volumes of nanostructured samples were characterized by values greater than the values of standard RuO{sub 2} sample. In addition, the [Ru-O{sub 6}] oxygen octahedrons of rutile structure also depended on crystal size. Catalytic conversion of methane by these RuO{sub 2} nanostructured catalysts was studied as a function of pH, catalytic interaction time, air methane composition, and catalysis temperature, by the way of Fourier transform infrared (FTIR) spectroscopy coupled to homemade catalytic cell. The catalytic efficiency defined as FTIR absorption band intensities I(CO{sub 2}) was maximum for sample prepared at pH=1.5, and mainly correlated to crystallite dimensions. No significant catalytic effect was observed from sintered RuO{sub 2} samples. - Graphical abstract: Nanosized crystals of RuO{sub 2} prepared by sol gel route, at pH=0.4 and 1.5. Mean size values , respectively, 10 and 8 nm.

  3. Ice crystal terminal velocities.

    NASA Technical Reports Server (NTRS)

    Heymsfield, A.

    1972-01-01

    Terminal velocities of different ice crystal forms were calculated, using the most recent ice crystal drag coefficients, aspect ratios, and densities. The equations derived were primarily for use in calculating precipitation rates by sampling particles with an aircraft in cirrus clouds, and determining particle size in cirrus clouds by Doppler radar. However, the equations are sufficiently general for determining particle terminal velocity at any altitude, and almost any crystal type. Two sets of equations were derived. The 'general' equations provide a good estimate of terminal velocities at any altitude. The 'specific' equations are a set of equations for ice crystal terminal velocities at 1000 mb. The calculations are in good agreement with terminal velocity measurements. The results from the present study were also compared to prior calculations by others and seem to give more reasonable results, particularly at higher altitudes.

  4. Role of Solvents in Improvement of Dissolution Rate of Drugs: Crystal Habit and Crystal Agglomeration

    PubMed Central

    Maghsoodi, Maryam

    2015-01-01

    Crystallization is often used for manufacturing drug substances. Advances of crystallization have achieved control over drug identity and purity, but control over the physical form remains poor. This review discusses the influence of solvents used in crystallization process on crystal habit and agglomeration of crystals with potential implication for dissolution. According to literature it has been known that habit modification of crystals by use of proper solvents may enhance the dissolution properties by changing the size, number and the nature of crystal faces exposed to the dissolution medium. Also, the faster dissolution rate of drug from the agglomerates of crystals compared with the single crystals may be related to porous structure of the agglomerates and consequently their better wettability. It is concluded from this review that in-depth understanding of role of the solvents in crystallization process can be applied to engineering of crystal habit or crystal agglomeration, and predictably dissolution improvement in poorly soluble drugs. PMID:25789214

  5. Monomial Crystals and Partition Crystals

    NASA Astrophysics Data System (ADS)

    Tingley, Peter

    2010-04-01

    Recently Fayers introduced a large family of combinatorial realizations of the fundamental crystal B(Λ0) for ^sln, where the vertices are indexed by certain partitions. He showed that special cases of this construction agree with the Misra-Miwa realization and with Berg's ladder crystal. Here we show that another special case is naturally isomorphic to a realization using Nakajima's monomial crystal.

  6. Improved initial guess for minimum energy path calculations.

    PubMed

    Smidstrup, Søren; Pedersen, Andreas; Stokbro, Kurt; Jónsson, Hannes

    2014-06-01

    A method is presented for generating a good initial guess of a transition path between given initial and final states of a system without evaluation of the energy. An objective function surface is constructed using an interpolation of pairwise distances at each discretization point along the path and the nudged elastic band method then used to find an optimal path on this image dependent pair potential (IDPP) surface. This provides an initial path for the more computationally intensive calculations of a minimum energy path on an energy surface obtained, for example, by ab initio or density functional theory. The optimal path on the IDPP surface is significantly closer to a minimum energy path than a linear interpolation of the Cartesian coordinates and, therefore, reduces the number of iterations needed to reach convergence and averts divergence in the electronic structure calculations when atoms are brought too close to each other in the initial path. The method is illustrated with three examples: (1) rotation of a methyl group in an ethane molecule, (2) an exchange of atoms in an island on a crystal surface, and (3) an exchange of two Si-atoms in amorphous silicon. In all three cases, the computational effort in finding the minimum energy path with DFT was reduced by a factor ranging from 50% to an order of magnitude by using an IDPP path as the initial path. The time required for parallel computations was reduced even more because of load imbalance when linear interpolation of Cartesian coordinates was used. PMID:24907989

  7. Improved initial guess for minimum energy path calculations

    SciTech Connect

    Smidstrup, Søren; Pedersen, Andreas; Stokbro, Kurt

    2014-06-07

    A method is presented for generating a good initial guess of a transition path between given initial and final states of a system without evaluation of the energy. An objective function surface is constructed using an interpolation of pairwise distances at each discretization point along the path and the nudged elastic band method then used to find an optimal path on this image dependent pair potential (IDPP) surface. This provides an initial path for the more computationally intensive calculations of a minimum energy path on an energy surface obtained, for example, by ab initio or density functional theory. The optimal path on the IDPP surface is significantly closer to a minimum energy path than a linear interpolation of the Cartesian coordinates and, therefore, reduces the number of iterations needed to reach convergence and averts divergence in the electronic structure calculations when atoms are brought too close to each other in the initial path. The method is illustrated with three examples: (1) rotation of a methyl group in an ethane molecule, (2) an exchange of atoms in an island on a crystal surface, and (3) an exchange of two Si-atoms in amorphous silicon. In all three cases, the computational effort in finding the minimum energy path with DFT was reduced by a factor ranging from 50% to an order of magnitude by using an IDPP path as the initial path. The time required for parallel computations was reduced even more because of load imbalance when linear interpolation of Cartesian coordinates was used.

  8. Surface crystallization of a fluoride glass

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Doremus, Robert H.

    1983-01-01

    Growth of crystals on the surface of a Zr-Ba-La fluoride glass was observed by optical and scanning electron microscopy. Small, dark crystal nucleated rapidly and grew to a size of about 10 microns; then they stopped growing, and wrinkled regions emerged, covering the entire crystal surface.

  9. Economic analysis of crystal growth in space

    NASA Technical Reports Server (NTRS)

    Ulrich, D. R.; Chung, A. M.; Yan, C. S.; Mccreight, L. R.

    1972-01-01

    Many advanced electronic technologies and devices for the 1980's are based on sophisticated compound single crystals, i.e. ceramic oxides and compound semiconductors. Space processing of these electronic crystals with maximum perfection, purity, and size is suggested. No ecomonic or technical justification was found for the growth of silicon single crystals for solid state electronic devices in space.

  10. Determining the Molecular Growth Mechanisms of Protein Crystal Faces by Atomic Force Microscopy

    NASA Technical Reports Server (NTRS)

    Nadarajah, Arunan; Li, Huayu; Pusey, Marc L.

    1999-01-01

    A high resolution atomic force microscopy (AFM) study had shown that the molecular packing on the tetragonal lysozyme (110) face corresponded to only one of two possible packing arrangements, suggesting that growth layers on this face were of bimolecular height. Theoretical analyses of the packing also indicated that growth of this face should proceed by the addition of growth units of at least tetramer size corresponding to the 43 helices in the crystal. In this study an AFM linescan technique was devised to measure the dimensions of individual growth units on protein crystal faces as they were being incorporated into the lattice. Images of individual growth events on the (110) face of tetragonal lysozyme crystals were observed, shown by jump discontinuities in the growth step in the linescan images as shown in the figure. The growth unit dimension in the scanned direction was obtained from these images. A large number of scans in two directions on the (110) face were performed and the distribution of lysozyme growth unit sizes were obtained. A variety of unit sizes corresponding to 43 helices, were shown to participate in the growth process, with the 43 tetramer being the minimum observed size. This technique represents a new application for AFM allowing time resolved studies of molecular process to be carried out.

  11. Lysozyme Crystal

    NASA Technical Reports Server (NTRS)

    2004-01-01

    To the crystallographer, this may not be a diamond but it is just as priceless. A Lysozyme crystal grown in orbit looks great under a microscope, but the real test is X-ray crystallography. The colors are caused by polarizing filters. Proteins can form crystals generated by rows and columns of molecules that form up like soldiers on a parade ground. Shining X-rays through a crystal will produce a pattern of dots that can be decoded to reveal the arrangement of the atoms in the molecules making up the crystal. Like the troops in formation, uniformity and order are everything in X-ray crystallography. X-rays have much shorter wavelengths than visible light, so the best looking crystals under the microscope won't necessarily pass muster under the X-rays. In order to have crystals to use for X-ray diffraction studies, crystals need to be fairly large and well ordered. Scientists also need lots of crystals since exposure to air, the process of X-raying them, and other factors destroy them. Growing protein crystals in space has yielded striking results. Lysozyme's structure is well known and it has become a standard in many crystallization studies on Earth and in space.

  12. Sample Sizes when Using Multiple Linear Regression for Prediction

    ERIC Educational Resources Information Center

    Knofczynski, Gregory T.; Mundfrom, Daniel

    2008-01-01

    When using multiple regression for prediction purposes, the issue of minimum required sample size often needs to be addressed. Using a Monte Carlo simulation, models with varying numbers of independent variables were examined and minimum sample sizes were determined for multiple scenarios at each number of independent variables. The scenarios…

  13. A search for minimum volume of Breed and Burn cores

    SciTech Connect

    Di Sanzo, C.; Greenspan, E.

    2012-07-01

    The objective of the present study is to quantify the minimum volume a Breed and Burn (B and B) core can be designed to have and the corresponding burnup required for sustaining the breed-and-burn mode of operation based on neutronics; radiation damage constraints are ignored. The minimum radius for an idealized spherical B and B reactor is 136 cm or 110 cm for, respectively, 40% or 28% coolant volume fraction. The peak required burnup is about 25%. The minimum volume of a more realistic cylindrical B and B core is estimated to be only {approx}15% larger than that of the idealized spherical core but is only 43% of the volume of the medium-size B and B core previously designed to fit within the S-Prism reactor vessel. Thus it appears that SMR s can, in principle, be designed to have a B and B core. It was also found that the minimum volume B and B core does not necessarily coincide with the maximum permissible leakage from a core that can sustain the B and B mode of operation. (authors)

  14. Minimum wafer thickness by rotated ingot ID wafering. [Inner Diameter

    NASA Technical Reports Server (NTRS)

    Chen, C. P.; Leipold, M. H.

    1984-01-01

    The efficient utilization of materials is critical to certain device applications such as silicon for photovoltaics or diodes and gallium-gadolinium-garnet for memories. A variety of slicing techniques has been investigated to minimize wafer thickness and wafer kerf. This paper presents the results of analyses of ID wafering of rotated ingots based on predicted fracture behavior of the wafer as a result of forces during wafering and the properties of the device material. The analytical model indicated that the minimum wafer thickness is controlled by the depth of surface damage and the applied cantilever force. Both of these factors should be minimized. For silicon, a minimum thickness was found to be approximately 200 x 10 - 6th m for conventional sizes of rotated ingot wafering. Fractures through the thickness of the wafer rather than through the center supporting column were found to limit the minimum wafer thickness. The model suggested that the use of a vacuum chuck on the wafer surface to enhance cleavage fracture of the center supporting core and, with silicon, by using 111-line-type ingots could have potential for reducing minimum wafer thickness.

  15. Does the Current Minimum Validate (or Invalidate) Cycle Prediction Methods?

    NASA Technical Reports Server (NTRS)

    Hathaway, David H.

    2010-01-01

    This deep, extended solar minimum and the slow start to Cycle 24 strongly suggest that Cycle 24 will be a small cycle. A wide array of solar cycle prediction techniques have been applied to predicting the amplitude of Cycle 24 with widely different results. Current conditions and new observations indicate that some highly regarded techniques now appear to have doubtful utility. Geomagnetic precursors have been reliable in the past and can be tested with 12 cycles of data. Of the three primary geomagnetic precursors only one (the minimum level of geomagnetic activity) suggests a small cycle. The Sun's polar field strength has also been used to successfully predict the last three cycles. The current weak polar fields are indicative of a small cycle. For the first time, dynamo models have been used to predict the size of a solar cycle but with opposite predictions depending on the model and the data assimilation. However, new measurements of the surface meridional flow indicate that the flow was substantially faster on the approach to Cycle 24 minimum than at Cycle 23 minimum. In both dynamo predictions a faster meridional flow should have given a shorter cycle 23 with stronger polar fields. This suggests that these dynamo models are not yet ready for solar cycle prediction.

  16. Gypsum crystals formed on decomposing calcium citrate

    NASA Astrophysics Data System (ADS)

    Söhnel, O.; Křivánková, I.; Krčmář, S.; Jurčová, M.

    1991-06-01

    Particle size and the specific surface area of gypsum crystals formed on decomposing an aqueous suspension of solid calcium citrate tetrahydrate by diluted 50% sulphuric acid at 25, 40, 60, 80 and 100°C was studied. The size of the gypsum crystals increases with increasing temperature of decomposition. At a constant temperature within the range of 25 to 100°C the median of gypsum crystal size distribution (PSD) increases for approximately 4 h after commencing decomposition and then reaches a virtually constant value. The specific surface area of gypsum crystals decreases after commencement of the reaction for approximately 6 h before reaching a constant value. Gypsum crystal growth by solute deposition from the liquid is responsible for PSD changes for approximately one hour at the commencement of reaction. Then the growth of larger crystals at the expense of smaller crystals, i.e. ripening, is apparently responsible for further changes in the PSD.

  17. Unifying the crystallization behavior of hexagonal and square crystals with the phase-field-crystal model

    NASA Astrophysics Data System (ADS)

    Tao, Yang; Zheng, Chen; Jing, Zhang; Yongxin, Wang; Yanli, Lu

    2016-03-01

    By employing the phase-field-crystal models, the atomic crystallization process of hexagonal and square crystals is investigated with the emphasis on the growth mechanism and morphological change. A unified regime describing the crystallization behavior of both crystals is obtained with the thermodynamic driving force varying. By increasing the driving force, both crystals (in the steady-state) transform from a faceted polygon to an apex-bulged polygon, and then into a symmetric dendrite. For the faceted polygon, the interface advances by a layer-by-layer (LL) mode while for the apex-bulged polygonal and the dendritic crystals, it first adopts the LL mode and then transits into the multi-layer (ML) mode in the later stage. In particular, a shift of the nucleation sites from the face center to the area around the crystal tips is detected in the early growth stage of both crystals and is rationalized in terms of the relation between the crystal size and the driving force distribution. Finally, a parameter characterizing the complex shape change of square crystal is introduced. Project supported by the National Natural Science Foundation of China (Grant Nos. 54175378, 51474176, and 51274167), the Natural Science Foundation of Shaanxi Province, China (Grant No. 2014JM7261), and the Doctoral Foundation Program of Ministry of China (Grant No. 20136102120021).

  18. Crystal growth and annealing for minimized residual stress

    DOEpatents

    Gianoulakis, Steven E.

    2002-01-01

    A method and apparatus for producing crystals that minimizes birefringence even at large crystal sizes, and is suitable for production of CaF.sub.2 crystals. The method of the present invention comprises annealing a crystal by maintaining a minimal temperature gradient in the crystal while slowly reducing the bulk temperature of the crystal. An apparatus according to the present invention includes a thermal control system added to a crystal growth and annealing apparatus, wherein the thermal control system allows a temperature gradient during crystal growth but minimizes the temperature gradient during crystal annealing.

  19. RNA Crystallization

    NASA Technical Reports Server (NTRS)

    Golden, Barbara L.; Kundrot, Craig E.

    2003-01-01

    RNA molecules may be crystallized using variations of the methods developed for protein crystallography. As the technology has become available to syntheisize and purify RNA molecules in the quantities and with the quality that is required for crystallography, the field of RNA structure has exploded. The first consideration when crystallizing an RNA is the sequence, which may be varied in a rational way to enhance crystallizability or prevent formation of alternate structures. Once a sequence has been designed, the RNA may be synthesized chemically by solid-state synthesis, or it may be produced enzymatically using RNA polymerase and an appropriate DNA template. Purification of milligram quantities of RNA can be accomplished by HPLC or gel electrophoresis. As with proteins, crystallization of RNA is usually accomplished by vapor diffusion techniques. There are several considerations that are either unique to RNA crystallization or more important for RNA crystallization. Techniques for design, synthesis, purification, and crystallization of RNAs will be reviewed here.

  20. 30 CFR 1202.53 - Minimum royalty.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Minimum royalty. 1202.53 Section 1202.53 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR Natural Resources Revenue ROYALTIES Oil, Gas, and OCS Sulfur, General § 1202.53 Minimum royalty. For leases...

  1. 30 CFR 1202.352 - Minimum royalty.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Minimum royalty. 1202.352 Section 1202.352 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR Natural Resources Revenue ROYALTIES Geothermal Resources § 1202.352 Minimum royalty. In no event shall the...

  2. 49 CFR 639.27 - Minimum criteria.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 7 2010-10-01 2010-10-01 false Minimum criteria. 639.27 Section 639.27 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL TRANSIT ADMINISTRATION, DEPARTMENT OF TRANSPORTATION CAPITAL LEASES Cost-Effectiveness § 639.27 Minimum criteria. In making...

  3. 14 CFR 205.5 - Minimum coverage.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 4 2011-01-01 2011-01-01 false Minimum coverage. 205.5 Section 205.5... REGULATIONS AIRCRAFT ACCIDENT LIABILITY INSURANCE § 205.5 Minimum coverage. (a) Insurance contracts and self... maintain the following coverage: (1) Third-party aircraft accident liability coverage for bodily injury...

  4. 14 CFR 205.5 - Minimum coverage.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 4 2013-01-01 2013-01-01 false Minimum coverage. 205.5 Section 205.5... REGULATIONS AIRCRAFT ACCIDENT LIABILITY INSURANCE § 205.5 Minimum coverage. (a) Insurance contracts and self... maintain the following coverage: (1) Third-party aircraft accident liability coverage for bodily injury...

  5. 14 CFR 205.5 - Minimum coverage.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 4 2012-01-01 2012-01-01 false Minimum coverage. 205.5 Section 205.5... REGULATIONS AIRCRAFT ACCIDENT LIABILITY INSURANCE § 205.5 Minimum coverage. (a) Insurance contracts and self... maintain the following coverage: (1) Third-party aircraft accident liability coverage for bodily injury...

  6. The minimum flux corona; theory or concept

    NASA Technical Reports Server (NTRS)

    Underwood, J. H.; Antiochos, S. K.

    1980-01-01

    The reply to the criticisms of the minimum flux theory is discussed. These criticisms are correct in substance, as well as in detail. Counter arguments that the minimum flux corona theory is untenable, because of errors in its formulation, are presented.

  7. 30 CFR 202.352 - Minimum royalty.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 2 2010-07-01 2010-07-01 false Minimum royalty. 202.352 Section 202.352 Mineral Resources MINERALS MANAGEMENT SERVICE, DEPARTMENT OF THE INTERIOR MINERALS REVENUE MANAGEMENT ROYALTIES Geothermal Resources § 202.352 Minimum royalty. In no event shall the lessee's annual...

  8. Minimum Foundation Program: 2003-2004 Handbook

    ERIC Educational Resources Information Center

    Louisiana State Department of Education, 2004

    2004-01-01

    This handbook was created to provide the user with an informative reference of the various elements contained in the Louisiana Minimum Foundation Program formula. The MFP formula adopted by the State Board of Elementary and Secondary Education and approved by the Legislature determines the cost of a minimum foundation program of education in all…

  9. 14 CFR 205.5 - Minimum coverage.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 4 2014-01-01 2014-01-01 false Minimum coverage. 205.5 Section 205.5 Aeronautics and Space OFFICE OF THE SECRETARY, DEPARTMENT OF TRANSPORTATION (AVIATION PROCEEDINGS) ECONOMIC REGULATIONS AIRCRAFT ACCIDENT LIABILITY INSURANCE § 205.5 Minimum coverage. (a) Insurance contracts and self-insurance plans shall provide...

  10. 30 CFR 1202.352 - Minimum royalty.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 3 2014-07-01 2014-07-01 false Minimum royalty. 1202.352 Section 1202.352 Mineral Resources OFFICE OF NATURAL RESOURCES REVENUE, DEPARTMENT OF THE INTERIOR NATURAL RESOURCES REVENUE ROYALTIES Geothermal Resources § 1202.352 Minimum royalty. In no event shall the lessee's...

  11. 30 CFR 1202.352 - Minimum royalty.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 3 2012-07-01 2012-07-01 false Minimum royalty. 1202.352 Section 1202.352 Mineral Resources OFFICE OF NATURAL RESOURCES REVENUE, DEPARTMENT OF THE INTERIOR NATURAL RESOURCES REVENUE ROYALTIES Geothermal Resources § 1202.352 Minimum royalty. In no event shall the lessee's...

  12. 30 CFR 1202.352 - Minimum royalty.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 3 2013-07-01 2013-07-01 false Minimum royalty. 1202.352 Section 1202.352 Mineral Resources OFFICE OF NATURAL RESOURCES REVENUE, DEPARTMENT OF THE INTERIOR NATURAL RESOURCES REVENUE ROYALTIES Geothermal Resources § 1202.352 Minimum royalty. In no event shall the lessee's...

  13. New Minimum Wage Research: A Symposium.

    ERIC Educational Resources Information Center

    Ehrenberg, Ronald G.; And Others

    1992-01-01

    Includes "Introduction" (Ehrenberg); "Effect of the Minimum Wage [MW] on the Fast-Food Industry" (Katz, Krueger); "Using Regional Variation in Wages to Measure Effects of the Federal MW" (Card); "Do MWs Reduce Employment?" (Card); "Employment Effects of Minimum and Subminimum Wages" (Neumark, Wascher); and "Wage Mobility of MW Workers" (Smith,…

  14. Minimum Wage Effects in the Longer Run

    ERIC Educational Resources Information Center

    Neumark, David; Nizalova, Olena

    2007-01-01

    Exposure to minimum wages at young ages could lead to adverse longer-run effects via decreased labor market experience and tenure, and diminished education and training, while beneficial longer-run effects could arise if minimum wages increase skill acquisition. Evidence suggests that as individuals reach their late 20s, they earn less the longer…

  15. Minimum Competency Program, Citizenship: Suggestions for Implementation.

    ERIC Educational Resources Information Center

    Virginia State Dept. of Education, Richmond.

    This monograph explains the need for graduating high school seniors to demonstrate minimum competence in citizenship and suggests performance-related assessment tasks to help school authorities determine whether these competency requirements have been met. Minimum citizenship competencies are interpreted to include essential skills and concepts…

  16. 78 FR 11793 - Minimum Internal Control Standards

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-20

    ... Internal Control Standards. 64 FR 590. The rule added a new part to the Commission's regulations... National Indian Gaming Commission 25 CFR Part 543 RIN 3141-AA27 Minimum Internal Control Standards AGENCY... (NIGC) proposes to amend its minimum internal control standards for Class II gaming under the...

  17. 77 FR 58707 - Minimum Internal Control Standards

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-21

    ... Minimum Internal Control Standards. 64 FR 590. The rule added a new part to the Commission's regulations... published a notice to reinstate that control number on April 25, 2012. 77 FR 24731. There is no change to... Minimum Internal Control Standards; Final Rule #0;#0;Federal Register / Vol. 77 , No. 184 /...

  18. 30 CFR 281.30 - Minimum royalty.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 2 2010-07-01 2010-07-01 false Minimum royalty. 281.30 Section 281.30 Mineral Resources MINERALS MANAGEMENT SERVICE, DEPARTMENT OF THE INTERIOR OFFSHORE LEASING OF MINERALS OTHER THAN OIL, GAS, AND SULPHUR IN THE OUTER CONTINENTAL SHELF Financial Considerations § 281.30 Minimum...

  19. Small-scale batch crystallization of proteins revisited: an underutilized way to grow large protein crystals.

    PubMed

    Rayment, Ivan

    2002-02-01

    Growth of high-quality crystals is a major obstacle in many structural investigations. In recent years, the techniques for screening crystals have improved dramatically, whereas the methods for obtaining large crystals have progressed more slowly. This is an important issue since, although many structures can be solved from small crystals with synchrotron radiation, it is far easier to solve and refine structures when strong data is recorded from large crystals. In an effort to improve the size of crystals, a strategy for a small-scale batch method has been developed that in many cases yields far larger crystals than attainable by vapor diffusion. PMID:11839300

  20. Approaching the Minimum Thermal Conductivity in Rhenium-Substituted Higher Manganese Silicides

    SciTech Connect

    Chen, Xi; Girard, S. N.; Meng, F.; Lara-Curzio, Edgar; Jin, S; Goodenough, J. B.; Zhou, J. S.; Shi, L

    2014-01-01

    Higher manganese silicides (HMS) made of earth-abundant and non-toxic elements are regarded as promising p-type thermoelectric materials because their complex crystal structure results in low lattice thermal conductivity. It is shown here that the already low thermal conductivity of HMS can be reduced further to approach the minimum thermal conductivity via partial substitu- tion of Mn with heavier rhenium (Re) to increase point defect scattering. The solubility limit of Re in the obtained RexMn1 xSi1.8 is determined to be about x = 0.18. Elemental inhomogeneity and the formation of ReSi1.75 inclusions with 50 200 nm size are found within the HMS matrix. It is found that the power factor does not change markedly at low Re content of x 0.04 before it drops considerably at higher Re contents. Compared to pure HMS, the reduced lattice thermal conductivity in RexMn1 xSi1.8 results in a 25% increase of the peak figure of merit ZT to reach 0.57 0.08 at 800 K for x = 0.04. The suppressed thermal conductivity in the pure RexMn1 xSi1.8 can enable further investigations of the ZT limit of this system by exploring different impurity doping strategies to optimize the carrier concentration and power factor.