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. 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)...

  14. 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)...

  15. 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....

  16. 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...

  17. 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...

  18. 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...

  19. 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...

  20. 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...

  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 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

  5. 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

  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 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

  7. 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

  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. 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

  11. 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

  12. 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

  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 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...

  18. 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...

  19. 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...

  20. 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...

  1. 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...

  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. 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.

  20. 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

  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. 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.

  9. 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.

  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. 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.

  17. 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

  18. 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.

  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. 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.

  11. 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.

  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. 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.

  6. 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.

  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. 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.

  8. 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

  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