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1

A Characteristic Particle Length

It is argued that there are characteristic intervals associated with any particle that can be derived without reference to the speed of light $c$. Such intervals are inferred from zeros of wavefunctions which are solutions to the Schr\\"odinger equation. The characteristic length is $\\ell=\\beta^2\\hbar^2/(8Gm^3)$, where $\\beta=3.8\\dots$; this length might lead to observational effects on objects the size of a virus.

Mark D. Roberts

2014-06-14

2

Characteristic length of glass transition

NASA Astrophysics Data System (ADS)

The characteristic length of the glass transition (? _? ) is based on the concept of cooperatively rearranging regions (CRR's) by Adam & Gibbs (1965): ? _? is the diameter of one CRR. In the theoretical part of the talk a formula is derived how this length can be calculated from calorimetric data of the transformation interval. The approach is based on fluctuations in natural functional subsystems. The corresponding thermodynamics is represented e.g. in a book of the author (E. Donth, Relaxation and Thermodynamics in Polymers. Glass Transition, Akademie-Verlag, Berlin 1992). A typical value for this length is 3 nanometers. In the experimental part several examples are reported to enlarge the experimental evidence for such a length: Squeezing the glass transition in the amorphous layers of partially crystallized PET (C. Schick, Rostock), glass transition of small-molecule glass formers in a series of nanoscaled pores of porous glasses (F. Kremer, Leipzig), comparison with a concentration fluctuation model in homogeneous polymer mixtures (E.W. Fischer, Mainz), and, from our laboratory, backscaling to ? _? across the main transition from the entanglement spacing in several amorphous polymers such as PVAC, PS, NR, and some polymer networks. Rouse backscaling was possible in the ? ? splitting region of several poly(n alkyl methacrylates) resulting in small characteristic lengths of order 1 nanometer near the onset of ? cooperativity. In a speculative outlook a dynamic density pattern is presented, having a cellular structure with higher density and lower mobility of the cell walls. It will be explained, with the aid of different thermal expansion of wall and clusters, how the clusters within the cells maintain a certain mobility far below the glass temperature.

Donth, E.

1996-03-01

3

Characteristics of microjet methane diffusion flames

Characteristics of microjet methane diffusion flames stabilized on top of the vertically oriented, stainless-steel tubes with an inner diameter ranging from 186 to 778 ? m are investigated experimentally, theoretically and numerically. Of particular interest are the flame shape, flame length and quenching limit, as they may be related to the minimum size and power of the devices in which

T. S. Cheng; C.-P. Chen; C.-S. Chen; Y.-H. Li; C.-Y. Wu; Y.-C. Chao

2006-01-01

4

Diffusion lengths in amphoteric GaAs heteroface solar cells

NASA Technical Reports Server (NTRS)

Minority-carrier diffusion lengths in amphoteric GaAs:Si were investigated. Electron and hole diffusion lengths in p- and n-type, respectively, were determined to be 13 microns and 7 microns. Preliminary efficiency measurements on heteroface structures based on amphoteric GaAs:Si p-n junctions indicated that these devices should make excellent solar cells.

Ashley, K. L.; Beal, S. W.

1978-01-01

5

Long minority carrier diffusion lengths in bridged silicon nanowires.

Nanowires have large surface areas that create new challenges for their optoelectronic applications. Lithographic processes involved in device fabrication and substrate interfaces can lead to surface defects and substantially reduce charge carrier lifetimes and diffusion lengths. Here, we show that using a bridging method to suspend pristine nanowires allows for circumventing detrimental fabrication steps and interfacial effects associated with planar device architectures. We report electron diffusion lengths up to 2.7 ?m in bridged silicon nanowire devices, much longer than previously reported values for silicon nanowires with a diameter of 100 nm. Strikingly, electron diffusion lengths are reduced to only 45 nm in planar devices incorporating nanowires grown under the same conditions. The highly scalable silicon nanobridge devices with the demonstrated long diffusion lengths may find exciting applications in photovoltaics, sensing, and photodetectors. PMID:25541642

Triplett, M; Yang, Y; Léonard, F; Talin, A Alec; Islam, M Saif; Yu, D

2015-01-14

6

Study of minority carrier diffusion lengths in photoactive layers of multijunction solar cells

A technique for determining a minority carrier’s diffusion length in photoactive III–V layers of solar cells by approximating\\u000a their spectral characteristics is presented. Single-junction GaAs, Ge and multi-junction GaAs\\/Ge, GaInP\\/GaAs, and GaInP\\/GaInAs\\/Ge\\u000a solar cells fabricated by hydride metal-organic vapor-phase epitaxy (H-MOVPE) have been studied. The dependences of the minority\\u000a carrier diffusion length on the doping level of p-Ge and n-GaAs

S. A. Mintairov; V. M. Andreev; V. M. Emelyanov; N. A. Kalyuzhnyy; N. K. Timoshina; M. Z. Shvarts; V. M. Lantratov

2010-01-01

7

NASA Astrophysics Data System (ADS)

We demonstrate spectrally resolved photoluminescence quenching as a means to determine the exciton diffusion length of several archetype organic semiconductors used in thin film devices. We show that aggregation and crystal orientation influence the anisotropy of the diffusion length for vacuum-deposited polycrystalline films. The measurement of the singlet diffusion lengths is found to be in agreement with diffusion by Förster transfer, whereas triplet diffusion occurs primarily via Dexter transfer.

Lunt, Richard R.; Giebink, Noel C.; Belak, Anna A.; Benziger, Jay B.; Forrest, Stephen R.

2009-03-01

8

Performance Characteristics of Plane-Wall Two-Dimensional Diffusers

NASA Technical Reports Server (NTRS)

Experiments have been made at Stanford University to determine the performance characteristics of plane-wall, two-dimensional diffusers which were so proportioned as to insure reasonable approximation of two-dimensional flow. All of the diffusers had identical entrance cross sections and discharged directly into a large plenum chamber; the test program included wide variations of divergence angle and length. During all tests a dynamic pressure of 60 pounds per square foOt was maintained at the diffuser entrance and the boundary layer there was thin and fully turbulent. The most interesting flow characteristics observed were the occasional appearance of steady, unseparated, asymmetric flow - which was correlated with the boundary-layer coalescence - and the rapid deterioration of flow steadiness - which occurred as soon as the divergence angle for maximum static pressure recovery was exceeded. Pressure efficiency was found to be controlled almost exclusively by divergence angle, whereas static pressure recovery was markedly influenced by area ratio (or length) as well as divergence angle. Volumetric efficiency. diminished as area ratio increased, and at a greater rate with small lengths than with large ones. Large values of the static-pressure-recovery coefficient were attained only with long diffusers of large area ratio; under these conditions pressure efficiency was high and. volumetric efficiency low. Auxiliary tests with asymmetric diffusers demonstrated that longitudinal pressure gradient, rather than wall divergence angle, controlled flow separation. Others showed that the addition of even a short exit duct of uniform section augmented pressure recovery. Finally, it was found that the installation of a thin, central, longitudinal partition suppressed flow separation in short diffusers and thereby improved pressure recovery

Reid, Elliott G

1953-01-01

9

NASA Astrophysics Data System (ADS)

Ion dynamics in lithium bismuth borate conducting glasses have been reported in wide composition and temperature ranges. The activation energy for the dc conduction has been analysed using Anderson-Stuart model and a correlation between the dc conductivity and the doorway radius has been predicted. The characteristic length scales for ion dynamics, such as mean square displacement and spatial extent of sub-diffusive motion of lithium ions have been determined from the ac conductivity and dielectric spectra, respectively. A direct connection between the ion dynamics and the characteristic length scales and the network structural units have been established.

Shaw, A.; Ghosh, A.

2013-09-01

10

Ion dynamics in lithium bismuth borate conducting glasses have been reported in wide composition and temperature ranges. The activation energy for the dc conduction has been analysed using Anderson-Stuart model and a correlation between the dc conductivity and the doorway radius has been predicted. The characteristic length scales for ion dynamics, such as mean square displacement and spatial extent of sub-diffusive motion of lithium ions have been determined from the ac conductivity and dielectric spectra, respectively. A direct connection between the ion dynamics and the characteristic length scales and the network structural units have been established. PMID:24070293

Shaw, A; Ghosh, A

2013-09-21

11

Diffusion length in nanoporous TiO{sub 2} films under above-band-gap illumination

We determined the carrier diffusion lengths in TiO{sub 2} nanoporous layers of dye-sensitized solar cells by using scanning photocurrent microscopy using an ultraviolet laser. Here, we excited the carrier directly in the nanoporous layers where the diffusion lengths were found to 140 ?m as compared to that of visible illumination measured at 90 ?m. The diffusion length decreased with increasing laser modulation frequency, in which we determined the electron lifetimes and the diffusion coefficients for both visible and UV illuminations. The diffusion lengths have been studied in terms of the sintering temperatures for both cells with and without binding molecules. We found a strong correlation between the diffusion length and the overall light-to-current conversion efficiency, proving that improving the diffusion length and hence the interparticle connections, is key to improving cell efficiency.

Park, J. D.; Son, B. H.; Park, J. K.; Kim, Sang Yong; Park, Ji-Yong; Lee, Soonil; Ahn, Y. H., E-mail: ahny@ajou.ac.kr [Department of Physics and Division of Energy Systems Research, Ajou University, Suwon 443-749 (Korea, Republic of)

2014-06-15

12

Evidence of a characteristic ignition length of a flame

NASA Astrophysics Data System (ADS)

Ignition process of vegetation from a cylindrical flame radiation is examined using Koo and Pagni [1] model. The radiation flux is power-law decreasing with distance [2], while the ignition time increases exponentially. This last behavior yields a characteristic length of fuel ignition from a flame, inducing a percolation type phase transition.

Baara, Y.; Khalloufi, K.; Zekri, N.

2013-03-01

13

The Length and Characteristics of Women's Lifetime Work Experience.

ERIC Educational Resources Information Center

A study examined the length and characteristics of women's lifetime work experience. The principal data source for the survey was a set of detailed work, educational, marital, and fertility histories that were collected in the fall of 1979 from 314 couples in the Detroit metropolitan area. While prior researchers had relied upon measures of the…

Gwartney-Gibbs, Patricia A.

14

Changes in diffusion path length with old age in diffuse optical tomography

NASA Astrophysics Data System (ADS)

Diffuse, optical near infrared imaging is increasingly being used in various neurocognitive contexts where changes in optical signals are interpreted through activation maps. Statistical population comparison of different age or clinical groups rely on the relative homogeneous distribution of measurements across subjects in order to infer changes in brain function. In the context of an increasing use of diffuse optical imaging with older adult populations, changes in tissue properties and anatomy with age adds additional confounds. Few studies investigated these changes with age. Duncan et al. measured the so-called diffusion path length factor (DPF) in a large population but did not explore beyond the age of 51 after which physiological and anatomical changes are expected to occur [Pediatr. Res. 39(5), 889-894 (1996)]. With increasing interest in studying the geriatric population with optical imaging, we studied changes in tissue properties in young and old subjects using both magnetic resonance imaging (MRI)-guided Monte-Carlo simulations and time-domain diffuse optical imaging. Our results, measured in the frontal cortex, show changes in DPF that are smaller than previously measured by Duncan et al. in a younger population. The origin of these changes are studied using simulations and experimental measures.

Bonnéry, Clément; Leclerc, Paul-Olivier; Desjardins, Michèle; Hoge, Rick; Bherer, Louis; Pouliot, Philippe; Lesage, Frédéric

2012-05-01

15

Changes in diffusion path length with old age in diffuse optical tomography.

Diffuse, optical near infrared imaging is increasingly being used in various neurocognitive contexts where changes in optical signals are interpreted through activation maps. Statistical population comparison of different age or clinical groups rely on the relative homogeneous distribution of measurements across subjects in order to infer changes in brain function. In the context of an increasing use of diffuse optical imaging with older adult populations, changes in tissue properties and anatomy with age adds additional confounds. Few studies investigated these changes with age. Duncan et al. measured the so-called diffusion path length factor (DPF) in a large population but did not explore beyond the age of 51 after which physiological and anatomical changes are expected to occur [Pediatr. Res. 39(5), 889-894 (1996)]. With increasing interest in studying the geriatric population with optical imaging, we studied changes in tissue properties in young and old subjects using both magnetic resonance imaging (MRI)-guided Monte-Carlo simulations and time-domain diffuse optical imaging. Our results, measured in the frontal cortex, show changes in DPF that are smaller than previously measured by Duncan et al. in a younger population. The origin of these changes are studied using simulations and experimental measures. PMID:22612125

Bonnéry, Clément; Leclerc, Paul-Olivier; Desjardins, Michèle; Hoge, Rick; Bherer, Louis; Pouliot, Philippe; Lesage, Frédéric

2012-05-01

16

Characteristics of an adjacent pulse repetition interval length as a scale for length

NASA Astrophysics Data System (ADS)

This paper describes the characteristics of the adjacent pulse repetition interval length (APRIL), which is used as a scale for femtosecond optical frequency comb (FOFC)-based length measurements. This approach is based on the analogy between the phase refractive index and the group refractive index. Because the former influences the wavelength, which is the basic parameter used to describe monochromatic light in terms of length measurement, we investigated the latter to analyze the theoretical properties of the APRIL when used as a length standard. The results of theoretical analyses and numerical investigations show that when the air parameters change, the changes in the wavelength of a He-Ne laser and the APRIL of an FOFC laser are of the same order of magnitude. The difference between the effects of the phase refractive index on the wavelength and the group refractive index on the APRIL was also confirmed. The proposed concept and analysis pave the way for developing a length traceability system based on the APRIL via optical fibers.

Wei, Dong; Aketagawa, Masato

2014-05-01

17

Photoluminescence-based measurements of the energy gap and diffusion length of Zn3P2

Photoluminescence-based measurements of the energy gap and diffusion length of Zn3P2 Gregory M 2009; accepted 20 August 2009; published online 14 September 2009 The steady-state photoluminescence-resolved photoluminescence decay measurements, implying minority-carrier diffusion lengths of 7 m. Â© 2009 American Institute

Kimball, Gregory

18

Maximum length sequence and Bessel diffusers using active technologies

Active technologies can enable room acoustic diffusers to operate over a wider bandwidth than passive devices, by extending the bass response. Active impedance control can be used to generate surface impedance distributions which cause wavefront dispersion, as opposed to the more normal absorptive or pressure-cancelling target functions. This paper details the development of two new types of active diffusers which

Trevor J. Cox; Mark R. Avis; Lejun Xiao

2006-01-01

19

Diffusion Correction to Slow Invariant Manifolds in a Short Length Scale Limit

Diffusion Correction to Slow Invariant Manifolds in a Short Length Scale Limit Joshua D. Mengers Abstract-- Slow Invariant Manifolds (SIM) are calculated for isothermal closed reaction-diffusion systems as a model reduction technique. Diffusion effects are examined using a Galerkin projection that rigorously

20

Experimental Verification of Comparability between Spin-Orbit and Spin-Diffusion Lengths

NASA Astrophysics Data System (ADS)

We experimentally confirmed that the spin-orbit lengths of noble metals obtained from weak antilocalization measurements are comparable to the spin diffusion lengths determined from lateral spin valve ones. Even for metals with strong spin-orbit interactions such as Pt, we verified that the two methods gave comparable values which were much larger than those obtained from recent spin torque ferromagnetic resonance measurements. To give a further evidence for the comparability between the two length scales, we measured the disorder dependence of the spin-orbit length of copper by changing the thickness of the wire. The obtained spin-orbit length nicely follows a linear law as a function of the diffusion coefficient, clearly indicating that the Elliott-Yafet mechanism is dominant as in the case of the spin diffusion length.

Niimi, Yasuhiro; Wei, Dahai; Idzuchi, Hiroshi; Wakamura, Taro; Kato, Takeo; Otani, YoshiChika

2013-01-01

21

Effect of Orifice Length-Diameter Ratio on Spray Characteristics

NASA Technical Reports Server (NTRS)

The effect of variations of orifice length to diameter ratio on spray characteristics was determined for a 0.014-inch and a 0.040-inch orifice for ratio of 0.5 to 4.0. The nozzles containing the orifices were mounted in an injection valve and tested with a plan stem and with a helically grooved stem. The injection pressure was varied from 4000 to 8000 pounds per square inch. The air density into which the fuel was sprayed was varied from the density obtained with a pressure of 60 pounds per square inch to the density obtained with a pressure of 250 pounds per square inch at room temperature. The tests showed that increasing the orifice length to diameter ratio with a plain stem in the injection valve causes the spray tip penetration first to decrease, reaching a minimum between a ratio of 1.5 and 2.5, and then to increase, reaching a maximum at a ratio greater than 3.5. The spray cone angle showed little change with variation of the ratio. With a helically grooved stem and small ratio of orifice area to groove area, the penetration at first shows little tendency towards a minimum; but as the time of injection is increased to 0.004 second, the penetration becomes a minimum at a ratio between 0.5 and 2.0.

Gellales, A G

1930-01-01

22

Diffusion length damage coefficient and annealing studies in proton-irradiated InP

NASA Technical Reports Server (NTRS)

We report on the measurement of the diffusion length damage coefficient (K(sub L)) and the annealing characteristics of the minority carrier diffusion length (L(sub n)) in Czochralski-grown zinc-doped indium phosphide (InP), with a carrier concentration of 1 x 10(exp l8) cm(exp -3). In measuring K(sub L) irradiations were made with 0.5 MeV protons with fluences ranging from 1 x 10(exp 11) to 3 x 10(exp 13) cm(exp -2). Pre- and post-irradiation electron-beam induced current (EBIC) measurements allowed for the extraction of L(sub n) from which K(sub L) was determined. In studying the annealing characteristics of L(sub n) irradiations were made with 2 MeV protons with fluence of 5 x 10(exp 13) cm(exp -2). Post-irradiation studies of L(sub n) with time at room temperature, and with minority carrier photoinjection and forward-bias injection were carried out. The results showed that recovery under Air Mass Zero (AMO) photoinjection was complete. L(sub n) was also found to recover under forward-bias injection, where recovery was found to depend on the value of the injection current. However, no recovery of L(sub n) after proton irradiation was observed with time at room temperature, in contrast to the behavior of 1 MeV electron-irradiated InP solar cells reported previously.

Hakimzadeh, Roshanak; Vargas-Aburto, Carlos; Bailey, Sheila G.; Williams, Wendell

1993-01-01

23

Characterizing Tumor Response to Chemotherapy at Various Length Scales Using Temporal Diffusion

Characterizing Tumor Response to Chemotherapy at Various Length Scales Using Temporal Diffusion biomarkers for monitoring tumor response to treatment. However, conventional pulsed-gradient spin echo (PGSE) were significantly lower in treated tumors, consistent with increased intracellular restrictions

Xu, Junzhong

24

As was noted in the cover letter that accompanied the samples, the eleven bare silicon samples were from various manufacturers. Table I lists the codes for the samples and the manufacturer of each sample. It also notes if the sample was single or poly-crystalline. The samples had been polished on one side before being sent out for measurements, but no further processing was done. The participants of the study were asked to measure either the lifetime or diffusion length of each of the samples using their standard procedure. Table II shows the experimental conditions used by the groups who measured diffusion length. All the diffusion length measurements were performed using the Surface Photovoltage method (SPV). Table M shows the experimental conditions for the lifetime measurements. All the lifetime measurements were made using the Photoconductance Decay method (PCD) under low level injection. These tables show the diameter of the spot size used during the measurement (the effective sampling area), the locations where measurements were taken, and the number of measurements taken at each location. Table N shows the results of the measurements. The table is divided into diffusion length and lifetime measurements for each sample. The values listed are the average values reported by each group. One of the immediate artifacts seen in the data is the large variation in the lifetime measurements. The values from MIT and Mobil are generally close. However, the measurements from NCSU are typically an order of magnitude lower.

Cudzinovic, M.; Sopori, B. [comp.] [comp.

1995-11-01

25

NASA Astrophysics Data System (ADS)

Stable water isotope signals retrieved from polar ice core records are smoothed by diffusion in the firn stage. The total amount of diffusion a layer has experienced can be quantified in terms of the diffusion length, which is the average displacement of a molecule due to diffusion. This length is a function of the firn temperature and the accumulation rate which makes it a valuable proxy for past local temperatures (Johnsen et al, 2000, Simonsen et al, 2011). In principle this proxy can be derived from either of the individual isotope signals (Oxygen-18 or Deuterium), but it is much better constrained when the difference in diffusion length between the two isotopes is used. The individual diffusion lengths and the differential diffusion lengths are commonly calculated using the power spectral densities (PSD) of the isotope data. The Maximum Entropy Method (MEM) is often used for the calculation of the PSD, but other methods such as the fast fourier transform or ones based on the autocorrelation series of the isotope data can also be used. However, in all these methods a parameter has to be chosen, for example the auto regression order in the MEM. Additionally, it is necessary to define a cut off frequency in order to use only the red part of the power spectrum. These choices can significantly influence diffusion length obtained with these methods. We present a new method which circumvents these issues, based on the correlation between the Oxygen-18 and Deuterium records. The measured Deuterium record is numerically diffused, after which the correlation between this record and the measured Oxygen-18 record is calculated. The correlation reaches a maximum when the diffusion lengths of the two records are equal. This allows us to reconstruct the differential diffusion length. A large number of synthetic data sets were created to (1) test this correlation method and (2), for the MEM, find the optimum values for the parameters in this method. The values found by the correlation method need to be corrected for offsets resulting from the finite sampling resolution and measurement uncertainty. The two methods yield results with comparable precision. References: Johnsen, S. et al, 2000. Diffusion of stable isotopes in polar firn and ice: the isotope effect in diffusion. In: Physics of Ice Core Records, Ed: Hondoh, T., p.121-140, Hokkaido Press, Sapporo. Simonsen, S.B. et al, 2011. Past surface temperatures at the NorthGRIP drill site from the difference in firn diffusion of water isotopes. Climate of the Past 7, 1327-1335.

van der Wel, Gerko; Fischer, Hubertus; Meijer, Harro A. J.

2013-04-01

26

Diffusion length measurements using the scanning electron microscope. [in semiconductor devices

NASA Technical Reports Server (NTRS)

A measurement technique employing the scanning electron microscope is described in which values of the true bulk diffusion length are obtained. It is shown that surface recombination effects can be eliminated through the application of highly doped surface field layers. The influence of high injection level effects and low-high junction current generation on the resulting measurement was investigated. Close agreement is found between the diffusion lengths measured by this method and those obtained using a penetrating radiation technique.

Weizer, V. G.

1975-01-01

27

Characteristic lengths for evaporation suppression from patchy porous surfaces

NASA Astrophysics Data System (ADS)

For non-uniformly wet porous surfaces, evaporation rates vary nonlinearly with mean surface water content and with the areal fraction of wet patches. The nonlinearity stems from the complex vapor field forming over individual pores and patches that could enhance vapor fluxes from pores surrounded by dry area (relative to fluxes from the same area of free water surface). The resulting evaporation rates from such a surface are similar to free water surface evaporation despite considerably lower evaporating area (low surface water content). Theoretically, such flux compensation could be suppressed by lumping isolated pores into clusters with equal mean water content. The resulting arrangement in wet patches ensures nearly 1D conditions within the patch and some flux enhancement at the periphery. The interplay between patch water content, patch size, and mean surface water content within a prescribed air flow boundary layer was modeled analytically using single pore diffusion as a building block. Results show existence of a characteristic cluster size that yields the largest evaporation suppression for a given boundary layer thickness and spacing between patches. For patches larger than this size, the relative evaporation rate from patchy surface (relative to free water surface evaporation) reaches a predictable rate equal to the fractional area of clusters. Model predictions for the relation between pore cluster size and evaporation suppression were evaluated numerically and in a series of wind tunnel experiments using porous surfaces with different pore clusters. The findings could be used for the design of optimal porous covers for suppressing evaporation losses from water reservoirs, or for controlling evaporative drying from engineered porous surfaces.

Lehmann, Peter; Or, Dani

2014-05-01

28

Estimation of minority carrier diffusion lengths in InP/GaAs solar cells

NASA Technical Reports Server (NTRS)

Minority carrier diffusion length is one of the most important parameters affecting the solar cell performance. An attempt is made to estimate the minority carrier diffusion lengths is the emitter and base of InP/GaAs heteroepitaxial solar cells. The PC-1D computer model was used to simulate the experimental cell results measured at NASA Lewis under AMO (air mass zero) spectrum at 25 C. A 16 nm hole diffusion length in the emitter and a 0.42 micron electron diffusion length in the base gave very good agreement with the I-V curve. The effect of varying minority carrier diffusion lengths on cell short current, open circuit voltage, and efficiency was studied. It is also observed that the front surface recombination velocity has very little influence on the cell performance. The poor output of heteroepitaxial cells is caused primarily by the large number of dislocations generated at the interfaces that propagate through the bulk indium phosphide layers. Cell efficiency as a function of dislocation density was calculated and the effect of improved emitter bulk properties on cell efficiency is presented. It is found that cells with over 16 percent efficiencies should be possible, provided the dislocation density is below 10(exp 6)/sq cm.

Jain, R. K.; Flood, D. J.

1990-01-01

29

Determination of the Pt spin diffusion length by spin-pumping and spin Hall effect

The spin diffusion length of Pt at room temperature and at 8 K is experimentally determined via spin pumping and spin Hall effect in permalloy/Pt bilayers. Voltages generated during excitation of ferromagnetic resonance from the inverse spin Hall effect and anisotropic magnetoresistance effect were investigated with a broadband approach. Varying the Pt layer thickness gives rise to an evolution of the voltage line shape due to the superposition of the above two effects. By studying the ratio of the two voltage components with the Pt layer thickness, the spin diffusion length of Pt can be directly extracted. We obtain a spin diffusion length of ?1.2 nm at room temperature and ?1.6 nm at 8 K.

Zhang, Wei; Pearson, John E.; Hoffmann, Axel [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)] [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Vlaminck, Vincent [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States) [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Colegio de Ciencias e Ingenería, Universidad San Fransciso de Quito, Quito (Ecuador); Divan, Ralu [Center for Nanoscale Materials, Argonne National Laboratory, Illinois 60439 (United States)] [Center for Nanoscale Materials, Argonne National Laboratory, Illinois 60439 (United States); Bader, Samuel D. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States) [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Center for Nanoscale Materials, Argonne National Laboratory, Illinois 60439 (United States)

2013-12-09

30

Lifetime and diffusion length measurements on silicon material and solar cells

NASA Technical Reports Server (NTRS)

Experimental methods were evaluated for the determination of lifetime and diffusion length in silicon intentionally doped with potentially lifetime-degrading impurities found in metallurgical grade silicon, impurities which may be residual in low-cost silicon intended for use in terrestrial flat-plate arrays. Lifetime measurements were made using a steady-state photoconductivity method. Diffusion length determinations were made using short-circuit current measurements under penetrating illumination. Mutual consistency among all experimental methods was verified, but steady-state photoconductivity was found preferable to photoconductivity decay at short lifetimes and in the presence of traps. The effects of a number of impurities on lifetime in bulk material, and on diffusion length in cells fabricated from this material, were determined. Results are compared with those obtained using different techniques. General agreement was found in terms of the hierarchy of impurities which degrade the lifetime.

Othmer, S.; Chen, S. C.

1978-01-01

31

Probing sub-alveolar length scales with hyperpolarized-gas diffusion NMR

NASA Astrophysics Data System (ADS)

Diffusion MRI of the lung is a promising technique for detecting alterations of normal lung microstructure in diseases such as emphysema. The length scale being probed using this technique is related to the time scale over which the helium-3 or xenon-129 diffusion is observed. We have developed new MR pulse sequence methods for making diffusivity measurements at sub-millisecond diffusion times, allowing one to probe smaller length scales than previously possible in-vivo, and opening the possibility of making quantitative measurements of the ratio of surface area to volume (S/V) in the lung airspaces. The quantitative accuracy of simulated and experimental measurements in microstructure phantoms will be discussed, and preliminary in-vivo results will be presented.

Miller, Wilson; Carl, Michael; Mooney, Karen; Mugler, John; Cates, Gordon

2009-05-01

32

Diffuse and specular characteristics of leaf reflectance

NASA Technical Reports Server (NTRS)

In this paper, the evolution of current understanding of the mechanisms of leaf reflectance is reviewed. The use of measurements of polarized reflectance to separate leaf reflectance into diffuse and specular components is discussed. A section on the factors influencing leaf reflectance - leaf structure and physiological disturbances - is included along with discussion on the manner in which these influences are manifested.

Grant, Lois

1987-01-01

33

NASA Technical Reports Server (NTRS)

In scanning electron microscope (SEM) injection measurements of minority carrier diffusion lengths some uncertainties of interpretation exist when the response current is nonlinear with distance. This is significant in epitaxial layers where the layer thickness is not large in relation to the diffusion length, and where there are large surface recombination velocities on the incident and contact surfaces. An image method of analysis is presented for such specimens. A method of using the results to correct the observed response in a simple convenient way is presented. The technique is illustrated with reference to measurements in epitaxial layers of GaAs. Average beam penetration depth may also be estimated from the curve shape.

Flat, A.; Milnes, A. G.

1978-01-01

34

NASA Astrophysics Data System (ADS)

We have presented conductivity spectra at different temperatures for mixed network former silver borophosphate glasses. By mapping the conductivity spectra onto time dependence of the mean square displacement of mobile ions in the framework of linear response theory, we have obtained two characteristic lengths of ion dynamics viz characteristic mean square displacement at which crossover from diffusive to subdiffusive ion dynamics and spatial extent of localized motion of mobile silver ions occur. We have shown that the mixed network effect in these glasses is correlated to these characteristic lengths which are strongly influenced by the Coulomb repulsion between the mobile silver ions as well as the interaction between the mobile ions and the glass network.

Kabi, S.; Ghosh, A.

2012-10-01

35

Epitaxial silicon minority carrier diffusion length by photoluminescence D. H. Baek,1,a

Epitaxial silicon minority carrier diffusion length by photoluminescence D. H. Baek,1,a S. B. Kim,2 2008; published online 3 September 2008 Photoluminescence PL is a convenient contactless method. INTRODUCTION Photoluminescence PL has been largely the domain of III-V semiconductor characterization

Schroder, Dieter K.

36

The effect of bimodal side chain length distributions on pore morphology and solvent diffusion within hydrated amphiphilic polymeric membranes is predicted. Seven polymeric architectures are constructed from hydrophobic backbones from which at regular intervals side chains branch off that are alternatingly short (composed of p hydrophobic A fragments or beads) and long (q A fragments, q > p). The side chains are end-linked with a hydrophilic C fragment. Pore morphologies at a water volume fraction of 0.16 are calculated by dissipative particle dynamics (DPD). Water diffusion through the water containing pores is calculated by tracer diffusion calculations through 140 selected snapshots and from the water bead motions. Diffusion constants decrease with difference in side chain lengths, q - p. Overall, the distance between pores also decreases with q - p. The results are explained by counting for every architecture the average number of bonds ?Nbond? between an A and the nearest C fragment. These results are in line with a database that contains more than 60 architectures. Diffusion constants tend to increase linearly with ?Nbond?|C|(-1)|A|, where |C| and |A| are the C and A bead fractions within the architecture. ?Nbond? is therefore expected to be an interesting design parameter for obtaining low percolation thresholds for solvent and/or proton diffusion. PMID:25703230

Dorenbos, G

2015-03-25

37

Characteristic Length Scale of Bicontinuous Nanoporous Structure by Fast Fourier Transform

We propose a method derived from fast Fourier transform (FFT) process to measure the characteristic length scale of bicontinuous nanoporous structures. By rotationally averaging the FFT power spectrum of a nanoporous micrograph from scanning electron microscope (SEM) or transmission electron microscope (TEM), a significant peak in the power spectrum can be obtained, which reflects the characteristic length scale of the

Takeshi Fujita; Ming Wei Chen

2008-01-01

38

Length-dependent force characteristics of coiled coils.

Coiled-coil domains within and between proteins play important structural roles in biology. They consist of two or more alpha helices that form a superhelical structure due to packing of the hydrophobic residues that pattern each helix. A recent continuum model showed that the correspondence between the chirality of the pack to that of the underlying hydrophobic pattern comes about because of the internal deformation energy associated with each helix in forming the superhelix. We have developed a coarse-grained atomistic model for coiled coils that includes the competition between the hydrophobic energy that drives folding and the cost due to deforming each helix. The model exhibits a structural transition from a non-coiled-coil to coiled-coil state as the contribution from the deformation energy changes. Our model is able to reproduce naturally occurring coiled coils and essential features seen in unzipping experiments. We explore the force-extension properties of these model coiled coils as a function helix length and find that shorter coils unfold at lower force than longer ones with the required unfolding force eventually becoming length independent. PMID:20365192

Sadeghi, Sara; Emberly, Eldon

2009-12-01

39

NASA Astrophysics Data System (ADS)

The diffusion length, L, of electrons in Mg-doped p-GaN grown by metal-organic chemical vapor deposition was found to increase linearly from 0.55 to 2.0 ?m during 1500 s of electron beam irradiation. Similar trends were observed for p-type Mg-doped GaN and AlGaN/GaN superlattices grown by molecular-beam epitaxy. While the electron diffusion length in p-(Al)GaN depends on irradiation time, the diffusion length of holes in n-GaN remains unchanged, with L˜0.35 ?m. We attribute the observed diffusion length change in p-(Al)GaN to an increase in the minority carrier lifetime. This increase is likely due to electron beam-induced charging of the deep metastable centers associated with Mg doping. The concentration of these centers was estimated to be ˜1018cm-3. The minority carrier diffusion length increase in p-(Al)GaN, which occurs during electron injection, may lead to self-improvement of the bipolar transistor characteristics.

Chernyak, Leonid; Osinsky, Andrei; Fuflyigin, Vladimir; Schubert, E. F.

2000-08-01

40

Quantifying Characteristic Length Scales and Patterns in Topography

NASA Astrophysics Data System (ADS)

The geometry of mountain topography depends on climate, tectonic, and biologic processes that operate on different temporal and spatial scales. Quantitative measures of landscape geometry are of interest for a) identifying potential correlations with the different types of processes, and b) for comparing observed topography with calibrated landscape evolution models of different regions. Over the years, several of these geomorphic metrics have been developed and used. Most of these metrics are regional values, i.e. they are calculated over an area of specific extent. Usually a region's typical horizontal length scale, like the average ridge-to-valley-distance, is used for this. However, this value is often chosen arbitrarily from a visual assessment of the landscape. In this study we aim to develop a quantitative measure of landscape properties that identifies dominant trends in drainage spacing and orientation. This is done by taking into account variations in topographic relief on different wavelenghts. More specifically, we use an autocorrelation function that is evaluated for different directions, thereby identifying prevalent orientation of features. The area of interest is then subdivided into parts of the thus obtained size and the process repeated, so that higher order structures are revealed. The results not only provides a size for the area over which other geomorphic metrics can be calculated such as the mean slope or the hypsometric integral, but may also be used as an additional measure for the form of the landscape itself. The method is applied to three regions along the South American Pacific coastal areas between latitudes of 26°S and 40°S. The study areas have distinctly different climate and vegetation conditions, showing the effect of different landscape forms on the values obtained. Results indicate a systematic variation between the three investigated regions. In the northern drier part of the coast results indicate large variations in the obtained correlation lengths depending on orientation and distinct higher order features. This is in stark contrast to the southern most region where little variation in correlation length and only weak secondary structures can be seen.

Schmiddunser, Matthias; Ehlers, Todd A.

2014-05-01

41

Diffusion Characteristics of Upwind Schemes on Unstructured Triangulations

NASA Technical Reports Server (NTRS)

The diffusive characteristics of two upwind schemes, multi-dimensional fluctuation splitting and dimensionally-split finite volume, are compared for scalar advection-diffusion problems. Algorithms for the two schemes are developed for node-based data representation on median-dual meshes associated with unstructured triangulations in two spatial dimensions. Four model equations are considered: linear advection, non-linear advection, diffusion, and advection-diffusion. Modular coding is employed to isolate the effects of the two approaches for upwind flux evaluation, allowing for head-to-head accuracy and efficiency comparisons. Both the stability of compressive limiters and the amount of artificial diffusion generated by the schemes is found to be grid-orientation dependent, with the fluctuation splitting scheme producing less artificial diffusion than the dimensionally-split finite volume scheme. Convergence rates are compared for the combined advection-diffusion problem, with a speedup of 2-3 seen for fluctuation splitting versus finite volume when solved on the same mesh. However, accurate solutions to problems with small diffusion coefficients can be achieved on coarser meshes using fluctuation splitting rather than finite volume, so that when comparing convergence rates to reach a given accuracy, fluctuation splitting shows a 20-25 speedup over finite volume.

Wood, William A.; Kleb, William L.

1998-01-01

42

Characteristic length of an AdS/CFT superconductor

We investigate in more detail the holographic model of a superconductor recently found by Hartnoll, Herzog, and Horowitz [Phys. Rev. Lett. 101, 031601], which is constructed from a condensate of a charged scalar field in AdS_4-Schwarzschild background. By analytically studying the perturbation of the gravitational system near the critical temperature T_c, we obtain the superconducting coherence length proportional to 1/\\sqrt{1-T/T_c} via AdS/CFT correspondence. By adding a small external homogeneous magnetic field to the system, we find that a stationary diamagnetic current proportional to the square of the order parameter is induced by the magnetic field. These results agree with Ginzburg-Landau theory and strongly support the idea that a superconductor can be described by a charged scalar field on a black hole via AdS/CFT duality.

Kengo Maeda; Takashi Okamura

2008-10-30

43

Characteristic length of an AdS/CFT superconductor

We investigate in more detail the holographic model of a superconductor recently found by Hartnoll, Herzog, and Horowitz [Phys. Rev. Lett. 101, 031601 (2008)], which is constructed from a condensate of a charged scalar field in AdS{sub 4}-Schwarzschild background. By analytically studying the perturbation of the gravitational system near the critical temperature T{sub c}, we obtain the superconducting coherence length proportional to 1/{radical}(1-T/T{sub c}) via AdS/CFT (anti-de Sitter/conformal field theory) correspondence. By adding a small external homogeneous magnetic field to the system, we find that a stationary diamagnetic current proportional to the square of the order parameter is induced by the magnetic field. These results agree with Ginzburg-Landau theory and strongly support the idea that a superconductor can be described by a charged scalar field on a black hole via AdS/CFT duality.

Maeda, Kengo [Department of Engineering, Shibaura Institute of Technology, Saitama, 330-8570 (Japan); Okamura, Takashi [Department of Physics, Kwansei Gakuin University, Sanda, 669-1337 (Japan)

2008-11-15

44

NASA Astrophysics Data System (ADS)

Characteristic length scales are often present in topography, and they reflect the driving geomorphic processes. The wide availability of high resolution lidar Digital Terrain Models (DTMs) allows us to measure such characteristic scales, but new methods of topographic analysis are needed in order to do so. Here, we explore how transitions in probability distributions (pdfs) of topographic variables such as (log(area/slope)), defined as topoindex by Beven and Kirkby[1979], can be measured by Multi-Resolution Analysis (MRA) of lidar DTMs [Stark and Stark, 2001; Sangireddy et al.,2012] and used to infer dominant geomorphic processes such as non-linear diffusion and critical shear. We show this correlation between dominant geomorphic processes to characteristic length scales by comparing results from a landscape evolution model to natural landscapes. The landscape evolution model MARSSIM Howard[1994] includes components for modeling rock weathering, mass wasting by non-linear creep, detachment-limited channel erosion, and bedload sediment transport. We use MARSSIM to simulate steady state landscapes for a range of hillslope diffusivity and critical shear stresses. Using the MRA approach, we estimate modal values and inter-quartile ranges of slope, curvature, and topoindex as a function of resolution. We also construct pdfs at each resolution and identify and extract characteristic scale breaks. Following the approach of Tucker et al.,[2001], we measure the average length to channel from ridges, within the GeoNet framework developed by Passalacqua et al.,[2010] and compute pdfs for hillslope lengths at each scale defined in the MRA. We compare the hillslope diffusivity used in MARSSIM against inter-quartile ranges of topoindex and hillslope length scales, and observe power law relationships between the compared variables for simulated landscapes at steady state. We plot similar measures for natural landscapes and are able to qualitatively infer the dominant geomorphic processes. Also, we explore the variability in hillslope length scales as a function of hillslope diffusivity coefficients and critical shear stress in natural landscapes and show that we can infer signatures of dominant geomorphic processes by analyzing characteristic topographic length scales present in topography. References: Beven, K. and Kirkby, M. J.: A physically based variable contributing area model of basin hydrology, Hydrol. Sci. Bull., 24, 43-69, 1979 Howard, A. D. (1994). A detachment-limited model of drainage basin evolution.Water resources research, 30(7), 2261-2285. Passalacqua, P., Do Trung, T., Foufoula Georgiou, E., Sapiro, G., & Dietrich, W. E. (2010). A geometric framework for channel network extraction from lidar: Nonlinear diffusion and geodesic paths. Journal of Geophysical. Research: Earth Surface (2003-2012), 115(F1). Sangireddy, H., Passalacqua, P., Stark, C.P.(2012). Multi-resolution estimation of lidar-DTM surface flow metrics to identify characteristic topographic length scales, EP13C-0859: AGU Fall meeting 2012. Stark, C. P., & Stark, G. J. (2001). A channelization model of landscape evolution. American Journal of Science, 301(4-5), 486-512. Tucker, G. E., Catani, F., Rinaldo, A., & Bras, R. L. (2001). Statistical analysis of drainage density from digital terrain data. Geomorphology, 36(3), 187-202.

Sangireddy, H.; Passalacqua, P.; Stark, C. P.

2013-12-01

45

We derived new expressions for the diffusion length of singlet and triplet excitons by using the Föster and Dexter transfer mechanisms, respectively, and have found that the diffusion lengths of singlet and triplet excitons are comparable. By using the Langevin recombination theory, we derived the rate of recombination of dissociated free charges into their excitonic states. We found that in some organic polymers the probabilities of recombination of free charge carriers back into the singlet and triplet states are approximately 65.6 and 34.4?%, respectively, indicating that Langevin-type recombination into triplet excitons in organic semiconductors is less likely. This implies that the creation of triplet excitons may be advantageous in organic solar cells, because this may lead to dissociated free charge carriers that can be collected at their respective electrodes, which should result in better conversion efficiency. PMID:25735545

Ompong, David; Singh, Jai

2015-04-27

46

Characterization of nonideal silicon in terms of lifetime and diffusion length

NASA Technical Reports Server (NTRS)

Experimental methods have been evaluated for the determination of lifetime and diffusion length in silicon intentionally doped with potentially lifetime-degrading impurities which may be present in low-cost silicon intended for use in terrestrial flat-plate arrays. Results obtained with these methods have been compared for mutual consistency. The effects of a number of impurities on bulk lifetime were determined from steady-state photoconductivity, and solar cells fabricated from this material were characterized in terms of diffusion length using a penetrating light technique. Comparison was made with results obtained by others using photoconductivity decay. General agreement was found in terms of the hierachy of impurities to which the lifetime is sensitive. The utility of the steady-state photoconductivity method is established even in the presence of considerable trapping.

Othmer, S.; Chen, S. C.

1978-01-01

47

Path-length distributions of photons diffusely reflected from a semi-infinite atmosphere.

NASA Technical Reports Server (NTRS)

Knowledge of the probability distribution of photon path lengths for diffuse reflection in the continuum from a planetary atmosphere greatly simplifies computation of the shape and strength of absorption lines formed under conditions of multiple scattering. Graphs of this probability distribution are presented for diffuse reflection from a semiinfinite conservative atmosphere for both isotropic and forward-directed scattering, and for several angles of incidence and reflection. Graphs showing distributions for the case of absorption in the continuum are also discussed. The distributions are obtained from an analytic expression for the path-length distribution for nth-order scattering and a tabulation of nth-order intensities. It is found that te shape of the probability distribution depends markedly on the degree of forward scattering due to the phase function. The results are compared with those obtained by a Monte Carlo computation of the sort which might be used if tabulated nth-order intensities were not available.

Appleby, J. F.; Irvine, W. M.

1973-01-01

48

Improvement of carrier diffusion length in silicon nanowire arrays using atomic layer deposition

To achieve a high-efficiency silicon nanowire (SiNW) solar cell, surface passivation technique is very important because a SiNW array has a large surface area. We successfully prepared by atomic layer deposition (ALD) high-quality aluminum oxide (Al2O3) film for passivation on the whole surface of the SiNW arrays. The minority carrier lifetime of the Al2O3-depositedSiNW arrays with bulk silicon substrate was improved to 27 ?s at the optimum annealing condition. To remove the effect of bulk silicon, the effective diffusion length of minority carriers in the SiNW array was estimated by simple equations and a device simulator. As a result, it was revealed that the effective diffusion length in the SiNW arrays increased from 3.25 to 13.5 ?m by depositing Al2O3 and post-annealing at 400°C. This improvement of the diffusion length is very important for application to solar cells, and Al2O3 deposited by ALD is a promising passivation material for a structure with high aspect ratio such as SiNW arrays. PMID:23968156

2013-01-01

49

NASA Astrophysics Data System (ADS)

The acid-catalyzed deprotection of glassy poly(4-hydroxystyrene-co-tertbutyl acrylate) films was studied with infrared absorbance spectroscopy and stochastic simulations. Experimental data were interpreted with a simple description of subdiffusive acid transport coupled to second-order acid loss. This model predicts key attributes of observed deprotection rates, such as fast reaction at short times, slow reaction at long times, and a nonlinear dependence on acid loading. Fickian diffusion is approached by increasing the postexposure bake temperature or adding plasticizing agents to the polymer resin. These findings demonstrate that acid mobility and overall deprotection kinetics are coupled to glassy matrix dynamics. To complement the analysis of bulk kinetics, acid diffusion lengths were calculated from the anomalous transport model and compared with nanopattern line widths. The consistent scaling between experiments and simulations suggests that the anomalous diffusion model could be further developed into a predictive lithography tool.

Patil, Abhijit A.; Pandey, Yogendra Narayan; Doxastakis, Manolis; Stein, Gila E.

2014-10-01

50

A diffusion accelerated solution method for the nonlinear characteristic scheme

Recently the nonlinear characteristic scheme for spatially discretizing the discrete-ordinate equations was introduced. This scheme is accurate for both optically thin and optically thick spatial meshes and produces strictly positive angular and scalar fluxes. The nonlinear characteristic discrete-ordinate equations can be solved using the source iteration method; however, it is well known that the this method converges prohibitively slowly for optically thick problems with scattering ratios at or near unity. In this paper we describe a diffusion accelerated solution method for solving the nonlinear characteristic equations in slab geometry.

Wareing, T.A.; Walters, W.F.; Morel, J.E.

1995-02-01

51

Taylor-Couette Flow with Hourglass Geometry of Varying Lengths Simulated by Reaction-Diffusion

NASA Astrophysics Data System (ADS)

Previously, we have observed chaotic formation of Taylor-Vortex pairs in Modified Taylor- Couette Flow with Hourglass Geometry. In the experiment, the chaotic formation in a shorter system has been restricted to a narrow band about the waist of the hourglass. Such behavior has been modeled by The Reaction-Diffusion equation, which has been previously studied, by Riecke and Paap. Their calculation suggested that quadrupling length of the system would lead to spatial chaos in the vortex formation. We present a careful recreation of this result and consider an intermediate length. We demonstrate that doubling the length should be sufficient to observe spatially chaotic behavior. Richard J. Wiener et al, Phys. Rev. E 55, 5489 (1997). H. Riecke and H.-G. Paap, Europhys. Lett. 14, 1235 (1991).

Zhao, Yunjie; Halmstad, Andrew; Olsen, Thomas; Wiener, Richard

2008-11-01

52

Introduction This study aims to identify whether patient-level or provider-level characteristics are most influential on a patient’s length of stay in the acute care hospital. Materials and Methods A dataset containing a nationally representative sample of inpatient discharge abstracts was used. Multi-level linear regression models were used to evaluate the associations between patient- and provider-level characteristics on patients’ lengths of stay. Results The target population included 322,894 discharges with a primary procedure code for primary total knee arthroplasty and 193,553 discharges for total hip arthroplasty. The variables associated with the greatest increases in length of stay were a higher co-morbidity level among patient level attributes (+17.4%) and low surgeon volume among provider-level characteristics (+18.8%). Discussion Provider-level characteristics, particularly provider volume, had a greater impact on length of stay. PMID:21277159

Styron, Joseph F.; Koroukian, Siran; Klika, Alison; Barsoum, Wael K.

2010-01-01

53

Length-speed ratio (LSR) as a characteristic for moving elements real-time classification

In this article, the length-speed ratio (LSR) is proposed as a basic characteristic for the real-time detection of moving objects. We define the LSR of a uniform moving zone as the relation between its length in the direction of motion and the speed of this motion. For a given zone of the image with uniform gray level (or patch), the

Miguel A. Fern; A. Fern

54

NASA Technical Reports Server (NTRS)

Indium phosphide (InP) solar cells are more radiation resistant than gallium arsenide (GaAs) and silicon (Si) solar cells, and their growth by heteroepitaxy offers additional advantages leading to the development of light weight, mechanically strong, and cost-effective cells. Changes in heteroepitaxial InP cell efficiency under 0.5- and 3-MeV proton irradiations have been explained by the variation in the minority-carrier diffusion length. The base diffusion length versus proton fluence was calculated by simulating the cell performance. The diffusion length damage coefficient, K(sub L), was also plotted as a function of proton fluence.

Jain, Raj K.; Weinberg, Irving; Flood, Dennis J.

1993-01-01

55

Diffusion tensor characteristics of gyrencephaly using high resolution diffusion MRI in vivo at 7T.

Gyrification of the human cerebral cortex allows for the surface expansion that accommodates many more cortical neurons in comparison to other mammals. For neuroimaging, however, it forms a feature that complicates analysis. For example, it has long been established that cortical layers do not occupy the same depth in gyri and sulci. Recently, in vivo diffusion imaging has provided insights into the fibre architecture of the cortex, usually showing radial tensor orientations. This makes it relevant to investigate whether cortical diffusion tensor metrics depend on the gyral pattern. High-resolution (1mm isotropic) diffusion weighted MRI of the medial wall of the hemispheres was performed at 7T. Diffusion data were resampled to surfaces in the cortex and underlying white matter, where the cortical surfaces obeyed the equivolume principle for cortical laminae over the cortical curvature. Diffusion tensor metrics were averaged over bins of curvature to obtain maps of characteristic patterns in the gyrus. Diffusivity, anisotropy and radiality varied with curvature. Radiality was maximal in intermediate layers of the cortex next to the crown of the gyrus, not in white matter or on the crown. In the fundus, the deep cortical layers had tangential tensor orientations. In the white matter, tensor orientation changed from radial on the crown to tangential under the banks and fundus. White matter anisotropy gradually increased from the crown to the fundus. The characteristic pattern in the gyrus demonstrated here is in accordance with ex vivo diffusion MR microscopy and histological studies. The results indicate the necessity of taking into account the gyral pattern when cortical diffusion data is analysed. Additionally, the data suggest a confound for tractography approaches when reaching the gyrus, resulting in a possible bias towards the gyral crown. The implications for mechanisms that could drive cortical folding are discussed. PMID:25585019

Kleinnijenhuis, Michiel; van Mourik, Tim; Norris, David G; Ruiter, Dirk J; van Cappellen van Walsum, Anne-Marie; Barth, Markus

2015-04-01

56

Flow distribution characteristics and control in marine gas turbine diffusers

The object of this study was to investigate flow distribution characteristics and control in the marine gas turbine diffusers most suitable for waste heat recovery systems. The major technical problems associated with nonuniform flow distributions in heat-exchanger or flow-equipment systems were reviewed. Various means to alleviate or minimize these undesirable problems were evaluated. Four sets of candidate flow-distribution data were

M. K. Ellingsworth; Ho-Tine Shu; S. C. Kuo

1984-01-01

57

Nerve length and volume in synaptic vs diffusion neurotransmission: a model.

Non-synaptic diffusion neurotransmission (NDN) may be an important factor in brain space and energy conservation, especially within cell assemblies and for mass sustained functions. We have illustrated the extreme cases of total synaptic and total ND neurotransmission for the purpose of noting the differences between the two. For these modeling studies, in which we assume assemblies of 1000 to 100 000 cells supplied by at least one fiber and a single synapse from each of the other cells, each cell assembly would have approximately 200 m to 8000 km of nerve fibers more than when innervated by diffusion. For coeruleo-cortical synaptic innervation, linking each to a common origin (the locus coeruelus), the fiber lengths are 38 cm (1000 cells) to 170 m (100,000 cells). It is likely , however, that neuronal arrays include both 'wireless' (NDN) as well as synaptic intercellular communication systems. PMID:8856707

Bach-y-Rita, P; Aiello, G L

1996-06-17

58

Diffusion characteristics of ethylene glycol in skeletal muscle.

Part of the optical clearing study in biological tissues concerns the determination of the diffusion characteristics of water and optical clearing agents in the subject tissue. Such information is sufficient to characterize the time dependence of the optical clearing mechanisms—tissue dehydration and refractive index (RI) matching. We have used a simple method based on collimated optical transmittance measurements made from muscle samples under treatment with aqueous solutions containing different concentrations of ethylene glycol (EG), to determine the diffusion time values of water and EG in skeletal muscle. By representing the estimated mean diffusion time values from each treatment as a function of agent concentration in solution, we could identify the real diffusion times for water and agent. These values allowed for the calculation of the correspondent diffusion coefficients for those fluids. With these results, we have demonstrated that the dehydration mechanism is the one that dominates optical clearing in the first minute of treatment, while the RI matching takes over the optical clearing operations after that and remains for a longer time of treatment up to about 10 min, as we could see for EG and thin tissue samples of 0.5 mm. PMID:25525766

Oliveira, Luís M; Carvalho, Maria Inês; Nogueira, Elisabete M; Tuchin, Valery V

2015-05-01

59

. More gen- erally, the issue of carrier diffusion length in GaN NWs is poorly documented to date. Recent axis. The nanowires are grown by Plasma-assisted Molecu- lar Beam Epitaxy (MBE) on a 2-inch Si(111

Paris-Sud XI, UniversitÃ© de

60

Path-length-resolved dynamic light scattering in highly scattering random media: The transition to diffusing wave spectroscopy Kostadinka K. Bizheva, Andy M. Siegel, and David A. Boas Electro diffusive light. Our experimental analysis provides details on the transition from single scattering

61

Method and apparatus for determining minority carrier diffusion length in semiconductors

Method and apparatus are provided for determining the diffusion length of minority carriers in semiconductor material, particularly amorphous silicon, which has a significantly small minority carrier diffusion length using the constant magnitude surface-photovoltage (SPV) method. Steady or modulated illumination at several wavelengths provides the light excitation on the surface of the material to generate the SPV. A manually controlled or automatic servo system maintains a constant predetermined value of the SPB for each wavelength. A probe electrode immersed in an electrolyte solution containing redox couples (preferably quinhydrone) having an oxidation-reduction potential (E) in the order of +0.6 to -1.65 volts couples the SPV to a measurement system. The redox couple solution functions to create a liquid Schottky barrier at the surface of the material. The Schottky barrier is contacted by merely placing the probe in the solution. The redox solution is placed over and in contact with the material to be tested and light is passed through the solution to generate the SPV. To compensate for colored redox solutions a portion of the redox solution not over the material is also illuminated for determining the color compensated light intensity. Steady red light is also used as an optical bias to reduce deleterious space-charge effects that occur in amorphous silicon.

Moore, A.R.

1984-02-21

62

Method and apparatus for determining minority carrier diffusion length in semiconductors

Method and apparatus are provided for determining the diffusion length of minority carriers in semiconductor material, particularly amorphous silicon which has a significantly small minority carrier diffusion length using the constant magnitude surface-photovoltage (SPV) method. Steady or modulated illumination at several wavelengths provides the light excitation on the surface of the material to generate the SPV. A manually controlled or automatic servo system maintains a constant predetermined value of the SPV for each wavelength. A drop of a transparent electrolyte solution containing redox couples (preferably quinhydrone) having an oxidation-reduction potential (E) in the order of +0.6 to -1.65 volts couples the SPV to a measurement system. The drop of redox couple solution functions to create a liquid Schottky barrier at the surface of the material. Illumination light is passed through a transparent rod supported over the surface and through the drop of transparent electrolyte. The drop is held in the gap between the rod and the surface. Steady red light is also used as an optical bias to reduce deleterious space-charge effects that occur in amorphous silicon.

Moore, A.R.

1984-06-12

63

Method and apparatus for determining minority carrier diffusion length in semiconductors

Method and apparatus are provided for determining the diffusion length of minority carriers in semiconductor material, particularly amorphous silicon, which has a significantly small minority carrier diffusion length using the constant magnitude surface-photovoltage (SPV) method. Steady or modulated illumination at several wavelengths provides the light excitation on the surface of the material to generate the SPV. A manually controlled or automatic servo system maintains a constant predetermined value of the SPV for each wavelength. A probe electrode immersed in an electrolyte solution containing redox couples (preferably quinhydrone) having an oxidation-reduction potential (E) in the order of +0.6 to -1.65 volts couples the SPV to a measurement system. The redox couple solution functions to create a liquid Schottky barrier at the surface of the material. The Schottky barrier is contacted by merely placing the probe in the solution. The redox solution is placed over and in contact with the material to be tested and light is passed through the solution to generate the SPV. To compensate for colored redox solutions a portion of the redox solution not over the material is also illuminated for determining the color compensated light intensity. Steady red light is also used as an optical bias to reduce deleterious space-charge effects that occur in amorphous silicon.

Moore, Arnold R. (Princeton, NJ)

1984-02-21

64

Method and apparatus for determining minority carrier diffusion length in semiconductors

Method and apparatus are provided for determining the diffusion length of minority carriers in semiconductor material, particularly amorphous silicon which has a significantly small minority carrier diffusion length using the constant magnitude surface-photovoltage (SPV) method. Steady or modulated illumination at several wavelengths provides the light excitation on the surface of the material to generate the SPV. A manually controlled or automatic servo system maintains a constant predetermined value of the SPV for each wavelength. A drop of a transparent electrolyte solution containing redox couples (preferably quinhydrone) having an oxidation-reduction potential (E) in the order of +0.6 to -1.65 volts couples the SPV to a measurement system. The drop of redox couple solution functions to create a liquid Schottky barrier at the surface of the material. Illumination light is passed through a transparent rod supported over the surface and through the drop of transparent electrolyte. The drop is held in the gap between the rod and the surface. Steady red light is also used as an optical bias to reduce deleterious space-charge effects that occur in amorphous silicon.

Moore, Arnold R. (Princeton, NJ)

1984-01-01

65

Determination of spin diffusion length of gold utilizing lateral spin valves

NASA Astrophysics Data System (ADS)

Spin transport in lateral metallic structures is an intriguing, emerging area, which offers rich opportunities to explore complex spintronic devices. We demonstrate spin injection, diffusion, and detection in a series of lateral spin valves. A 220-nm wide and 20-nm thick gold wire is defined by e-beam lithography on a SiN substrate. Two permalloy (Py) electrodes, an injector and a detector, are subsequently overlaid on the Au wire. The charge current and spin current are separated by connecting current drain and voltage ground to opposite ends of the Au wire. A charge current that passes through the Py injector into the Au induces a spin accumulation, resulting in a split of the chemical potentials for the spin-up and spin-down electrons in the Au. The injected spins diffuse away on both sides of the injector, resulting in a spin current towards the detector even without a charge current. Depending on the relative orientations of the accumulated spin and the detector spin, a voltage contrast can be observed at the detector/Au interface. This separation of charge and spin currents results in a large percentage value of the spin signals, which rules out the possibilities of spurious effects such as AMR. By changing the injector-detector separation, we observe an exponential decay of the spin signals, and thus determine a spin diffusion length of 63 nm in Au at 10 K.

Ji, Yi

2005-03-01

66

Building on mode-coupling-theory calculations, we report a novel scenario for multiple glass transitions in a purely repulsive spherical potential: the square shoulder. The liquid-glass transition lines exhibit both melting by cooling and melting by compression as well as associated diffusion anomalies, similar to the ones observed in water. Differently from all previously investigated models, we find for small shoulder widths a glass-glass line that is disconnected from the liquid phase. Upon increasing the shoulder width such a glass-glass line merges with the liquid-glass transition lines, featuring two distinct end point singularities that give rise to logarithmic decays in the dynamics. We analytically explain these findings by considering the interplay of different repulsive length scales. PMID:20481944

Sperl, Matthias; Zaccarelli, Emanuela; Sciortino, Francesco; Kumar, Pradeep; Stanley, H Eugene

2010-04-01

67

Identifying local characteristic lengths governing sound wave properties in solid foams

science, in particular, for the design of porous media used as sound absorbers in building dominating the transport properties and sound absorbing behavior of polyurethane foam samples by performing#12;Identifying local characteristic lengths governing sound wave properties in solid foams Minh

Boyer, Edmond

68

We propose the use of “characteristic length,” based on radar cross section, as a metric for comparing the performance of orbital debris impactors of differing shapes, and the use of NASA's standard breakup model (SBM) “flake” shape as the representative particle for predicting orbital debris penetration effects. We also propose the use of a 26-view methodology for examining non-spherical particles

J. E. Williamsen; S. W. Evans

2006-01-01

69

Characteristic Length of Energy-containing Structures at the Base of a Coronal Hole

NASA Astrophysics Data System (ADS)

An essential parameter for models of coronal heating and fast solar wind acceleration that rely on the dissipation of MHD turbulence is the characteristic energy-containing length ? of the squared velocity and magnetic field fluctuations (u 2 and b 2) transverse to the mean magnetic field inside a coronal hole (CH) at the base of the corona. The characteristic length scale directly defines the heating rate. We use a time series analysis of solar granulation and magnetic field measurements inside two CHs obtained with the New Solar Telescope at Big Bear Solar Observatory. A data set for transverse magnetic fields obtained with the Solar Optical Telescope/Spectro-Polarimeter on board the Hinode spacecraft was utilized to analyze the squared transverse magnetic field fluctuations b_t^2. Local correlation tracking was applied to derive the squared transverse velocity fluctuations u 2. We find that for u 2 structures, the Batchelor integral scale ? varies in a range of 1800-2100 km, whereas the correlation length sigmav and the e-folding length L vary between 660 and 1460 km. Structures for b_t^2 yield ? ? 1600 km, sigmav ? 640 km, and L ? 620 km. An averaged (over ?, sigmav, and L) value of the characteristic length of u 2 fluctuations is 1260 ± 500 km, and that of b_t^2 is 950 ± 560 km. The characteristic length scale in the photosphere is approximately 1.5-50 times smaller than that adopted in previous models (3-30 × 103 km). Our results provide a critical input parameter for current models of coronal heating and should yield an improved understanding of fast solar wind acceleration.

Abramenko, V. I.; Zank, G. P.; Dosch, A.; Yurchyshyn, V. B.; Goode, P. R.; Ahn, K.; Cao, W.

2013-08-01

70

CHARACTERISTIC LENGTH OF ENERGY-CONTAINING STRUCTURES AT THE BASE OF A CORONAL HOLE

An essential parameter for models of coronal heating and fast solar wind acceleration that rely on the dissipation of MHD turbulence is the characteristic energy-containing length {lambda} of the squared velocity and magnetic field fluctuations (u{sup 2} and b{sup 2}) transverse to the mean magnetic field inside a coronal hole (CH) at the base of the corona. The characteristic length scale directly defines the heating rate. We use a time series analysis of solar granulation and magnetic field measurements inside two CHs obtained with the New Solar Telescope at Big Bear Solar Observatory. A data set for transverse magnetic fields obtained with the Solar Optical Telescope/Spectro-Polarimeter on board the Hinode spacecraft was utilized to analyze the squared transverse magnetic field fluctuations b{sub t}{sup 2}. Local correlation tracking was applied to derive the squared transverse velocity fluctuations u {sup 2}. We find that for u {sup 2} structures, the Batchelor integral scale {lambda} varies in a range of 1800-2100 km, whereas the correlation length sigmav and the e-folding length L vary between 660 and 1460 km. Structures for b{sub t}{sup 2} yield {lambda} Almost-Equal-To 1600 km, sigmav Almost-Equal-To 640 km, and L Almost-Equal-To 620 km. An averaged (over {lambda}, sigmav, and L) value of the characteristic length of u {sup 2} fluctuations is 1260 {+-} 500 km, and that of b{sub t}{sup 2} is 950 {+-} 560 km. The characteristic length scale in the photosphere is approximately 1.5-50 times smaller than that adopted in previous models (3-30 Multiplication-Sign 10{sup 3} km). Our results provide a critical input parameter for current models of coronal heating and should yield an improved understanding of fast solar wind acceleration.

Abramenko, V. I.; Yurchyshyn, V. B.; Goode, P. R.; Ahn, K.; Cao, W. [Big Bear Solar Observatory, 40386 N. Shore Lane, Big Bear City, CA 92314 (United States); Zank, G. P.; Dosch, A. [CSPAR, University of Alabama in Huntsville, Huntsville, AL (United States)

2013-08-20

71

NASA Astrophysics Data System (ADS)

A longitudinally excited CO2 laser pumped by a fast discharge emits a short laser pulse, similarly to TEA and Q-switched CO2 lasers. We investigated the relation between the discharge length and the laser pulse characteristics to develop a longitudinally excited CO2 laser producing a high spike laser pulse. We examined discharge lengths of 30, 45, and 60 cm, using the same mirrors and the same excitation circuit with the same input energy. A longer discharge length increased the discharge volume and improved the laser output energy. However, the longer discharge length caused a long discharge formation time (a slow fall time of the discharge voltage) due to the higher discharge impedance, which resulted in a long laser pulse tail. Therefore, the longitudinally excited CO2 laser had optimum conditions for obtaining a high spike laser pulse effectively.

Uno, Kazuyuki; Dobashi, Kazuma; Akitsu, Tetsuya; Jitsuno, Takahisa

2013-04-01

72

Characteristics of Gaseous Diffusion Flames with High Temperature Combustion Air in Microgravity

NASA Technical Reports Server (NTRS)

The characteristics of gaseous diffusion flames have been obtained using high temperature combustion air under microgravity conditions. The time resolved flame images under free fall microgravity conditions were obtained from the video images obtained. The tests results reported here were conducted using propane as the fuel and about 1000 C combustion air. The burner included a 0.686 mm diameter central fuel jet injected into the surrounding high temperature combustion air. The fuel jet exit Reynolds number was 63. Several measurements were taken at different air preheats and fuel jet exit Reynolds number. The resulting hybrid color flame was found to be blue at the base of the flame followed by a yellow color flame. The length and width of flame during the entire free fall conditions has been examined. Also the relative flame length and width for blue and yellow portion of the flame has been examined under microgravity conditions. The results show that the flame length decreases and width increases with high air preheats in microgravity condition. In microgravity conditions the flame length is larger with normal temperature combustion air than high temperature air.

Ghaderi, M.; Gupta, A. K.

2003-01-01

73

NASA Technical Reports Server (NTRS)

We report a systematic study of xenon gas diffusion NMR in simple model porous media, random packs of mono-sized glass beads, and focus on three specific areas peculiar to gas-phase diffusion. These topics are: (i) diffusion of spins on the order of the pore dimensions during the application of the diffusion encoding gradient pulses in a PGSE experiment (breakdown of the narrow pulse approximation and imperfect background gradient cancellation), (ii) the ability to derive long length scale structural information, and (iii) effects of finite sample size. We find that the time-dependent diffusion coefficient, D(t), of the imbibed xenon gas at short diffusion times in small beads is significantly affected by the gas pressure. In particular, as expected, we find smaller deviations between measured D(t) and theoretical predictions as the gas pressure is increased, resulting from reduced diffusion during the application of the gradient pulse. The deviations are then completely removed when water D(t) is observed in the same samples. The use of gas also allows us to probe D(t) over a wide range of length scales and observe the long time asymptotic limit which is proportional to the inverse tortuosity of the sample, as well as the diffusion distance where this limit takes effect (approximately 1-1.5 bead diameters). The Pade approximation can be used as a reference for expected xenon D(t) data between the short and the long time limits, allowing us to explore deviations from the expected behavior at intermediate times as a result of finite sample size effects. Finally, the application of the Pade interpolation between the long and the short time asymptotic limits yields a fitted length scale (the Pade length), which is found to be approximately 0.13b for all bead packs, where b is the bead diameter. c. 2002 Elsevier Sciences (USA).

Mair, R. W.; Sen, P. N.; Hurlimann, M. D.; Patz, S.; Cory, D. G.; Walsworth, R. L.

2002-01-01

74

Background To explore the characteristics of diffusion tensor imaging (DTI) and magnetic resonance (MR) imaging in healthy native kidneys. Methods Seventy-three patients without chronic kidney disease underwent DTI-MRI with spin echo-echo planar (SE-EPI) sequences accompanied by an array spatial sensitivity encoding technique (ASSET). Cortical and medullary mean, axial and radial diffusivity (MD, AD and RD), fractional anisotropy (FA) and primary, secondary and tertiary eigenvalues (?1, ?2, ?3) were analysed in both kidneys and in different genders. Results Cortical MD, ?2, ?3, and RD values were higher than corresponding medullary values. The cortical FA value was lower than the medullary FA value. Medullary ?1 and RD values in the left kidney were lower than in the right kidney. Medullary ?2, and ?3 values in women were higher than those in men. Medullary FA values in women were lower than those in men. Medullary FA (r?=?0.351, P?=?0.002) and ?1 (r?=?0.277, P?=?0.018) positively correlated with eGFR. Medullary FA (r?=??0.25, P?=?0.033) negatively correlated with age. Conclusions Renal water molecular diffusion differences exist in human kidneys and genders. Age and eGFR correlate with medullary FA and primary eigenvalue. PMID:25470776

Zheng, Zhenfeng; Shi, Huilan; Zhang, Jing; Zhang, Yunting

2014-01-01

75

Identifying local characteristic lengths governing sound wave properties in solid foams

NASA Astrophysics Data System (ADS)

Identifying microscopic geometric properties and fluid flow through opened-cell and partially closed-cell solid structures is a challenge for material science, in particular, for the design of porous media used as sound absorbers in building and transportation industries. We revisit recent literature data to identify the local characteristic lengths dominating the transport properties and sound absorbing behavior of polyurethane foam samples by performing numerical homogenization simulations. To determine the characteristic sizes of the model, we need porosity and permeability measurements in conjunction with ligament lengths estimates from available scanning electron microscope images. We demonstrate that this description of the porous material, consistent with the critical path picture following from the percolation arguments, is widely applicable. This is an important step towards tuning sound proofing properties of complex materials.

Tan Hoang, Minh; Perrot, Camille

2013-02-01

76

NASA Astrophysics Data System (ADS)

The role of native defect inhomogeneity on the minority-carrier properties in n-type GaAs LEC has been investigated. An array of Au/GaAs Schottky diodes has been evaporated along the wafer diameter; then the net donor concentration and the hole diffusion length were measured by C-V and SPV methods, respectively. The distribution of extended defects was measured by etch pit observations and electron beam induced current (EBIC) imaging. In order to correlate diffusion length and recombination centre radial distribution, a deep level transient spectroscopy (DLTS) investigation was carried out. A W-shaped distribution of etch pit density ranging from 2 × 10 4 to 1 × 10 5 cm -2 was found, while an M-shaped diffusion length within the interval (0.7-2.3) × 10 -4 cm was observed. The lifetime ? of the minority carriers has been directly measured by the photocurrent decay method and a value ranging in the interval (5-10) × 10 -9s was found. Some hypotheses on the dominant trap controlling the diffusion length and the lifetime and on its interaction with dislocations are discussed. The inhomogeneous distribution of the transport properties has been explained on the basis of different point-extended defects interaction in differently dislocated regions.

Castaldini, A.; Cavallini, A.; Gombia, E.; Mosca, R.; Tarricone, L.; Motta, A.; Bora, L.

1993-01-01

77

The surface photovoltage (SPV) technique is an attractive method for measuring the minority carrier diffusion length of solar cells. It has the advantage of not requiring permanent sample contacts. It does require, however, an accurate knowledge of the absorption coefficient-wavelength (?-?) relationship. This relationship is well known for single-crystal silicon and SPV plots are linear for such materials. However, for

I. G. Hwang; D. K. Schroder; J. H. Wohlgemuth

1993-01-01

78

with - XRF/ -XAS on several occasions to demonstrate the re- combination activity of iron4 and copper7, such as x-ray fluorescence microscopy -XRF and x-ray absorption microspectroscopy -XAS , yielding diffusion length of individual transition metal species in multicrystalline silicon. SR-XBIC, -XRF, and -XAS

79

A new method of determination of the minority carrier diffusion length (L) in the base region of an n[sup +]-p-p[sup +] silicon solar cell using the spectral response of the cell in a middle wavelength ([lambda]) range is presented. The minority carrier diffusion length (L) in the base region of an n[sup +]-p or n[sup +]-p-p[sup +] silicon solar cell has a profound effect on the solar cell performance. In this paper the authors report a new method of determination of diffusion length using the middle wavelength spectral response (MWSR) of the cell. It has been developed using a model of n[sup +]-p-p[sub +] silicon solar cells given by Singh and Jain and making some simplifying assumptions. It is equally applicable to cells with d/L > 2.5 and d/L < 2.5. In the following they give the theoretical basis of the method and present the result of the measurement of diffusion length of a few N[sup +]-p-p[sup +] silicon solar cells with d/L in the range 1.3--4.1 by using this method and the LWSR method.

Basu, P.K.; Singh, S.N.; Arora, N.K.; Chakravarty, B.C. (National Physical Lab., New Delhi (India))

1994-03-01

80

NASA Technical Reports Server (NTRS)

Carrier lifetimes and bulk diffusion length are qualitatively measured as a means for qualification of a P-N junction photovoltaic solar cell. High frequency (blue) monochromatic light pulses and low-frequency (red) monochromatic light pulses were alternately applied to the cell while it was irradiated by light from a solar simulator, and synchronously displaying the derivative of the output voltage of the cell on an oscilloscope. The output voltage is a measure of the lifetimes of the minority carriers (holes) in the diffused N layer and majority carriers (electrons) in the bulk P material, and of the diffusion length of the bulk silicon. By connecting a reference cell in this manner with a test cell to be tested in reverse parallel, the display of a test cell that matches the reference cell will be a substantially zero output.

Vonroos, O. H. (inventor)

1978-01-01

81

Flow development and turbulence length scales within an annular gas turbine exhaust diffuser

This paper presents the experimental investigation of a scaled down model of a PGT10 gas turbine diffuser by Nuovo Pignone S.p.A. The model was designed to operate in geometric and Reynolds number similarity with the GT diffuser, and 24 guide vanes are mounted at inlet to reproduce typical inlet conditions of an industrial gas turbine diffuser. The PGT10 diffuser has

Stefano Ubertini; Umberto Desideri

2000-01-01

82

NASA Astrophysics Data System (ADS)

Mass transfer characteristics of gas diffusion layer (GDL) are closely related to performance of polymer electrolyte fuel cells. Therefore, it is necessary to clarify the characteristics of water distribution relating to the microscopic conformation and oxygen diffusivity of GDL. A hybrid type carbon paper GDL with planar-distributed wettability is investigated for control of liquid water movement and distribution due to hydrophobic to hydrophilic areas that provide wettability differences in GDL and to achieve enhancement of both oxygen diffusion and moisture retention. Hybrid GDLs with different PTFE content were fabricated in an attempt to improve the oxygen diffusion characteristics. The effects of different PTFE contents on the oxygen diffusivity and water distribution were simultaneously measured and observed using galvanic cell oxygen absorber and X-ray radiography. The PTFE distribution was observed using scanning electron microscopy. The formation of oxygen diffusion paths was confirmed by X-ray radiography, where voids in the hybrid GDL were first formed in the hydrophobic regions and then spread to the untreated wetting region. Thus, the formation of oxygen diffusion paths enhanced the oxygen diffusion. In addition, the effects of local PTFE content in the hydrophobic region and the optimal amount of PTFE for hybrid GDL were elucidated.

Koresawa, Ryo; Utaka, Yoshio

2014-12-01

83

Characteristics of Cluster Implantation and Low Diffusion Annealing

NASA Astrophysics Data System (ADS)

Beyond 45 nm device fabrication, it is recognized that the ultra-shallow junction (USJ) formation is required, which is achieved by the ultra-low energy ion implantation and ultra-low diffusion annealing. For this purpose, Cluster ion implantation (CII) and the Flash lamp annealing (FLA) activation processes have been developed. In this paper, we introduce characteristics of activation using B18Hx+ implantation with FLA, which are applied to a source drain extension (SDE) for pMOSFET in Hgh-k/metal process. We will prove that the combined process of B18Hx+ and FLA can make the low sheet resistance and the fine crystal recovery for USJ formation such a SDE. Moreover, the combined process of C7Hx+ implantation and FLA can make the high stress region for nMOSFET by the high substitutional Carbon. If both of B18Hx+ implantation and C7Hx+ implantation with FLA are applied to High-k/metal process, it will give the highest performance. The combination of FLA and cluster ion implanter "CLARIS" which is developed for IC fabrication, will promise the most powerful performance beyond 45 nm node device.

Nagayama, Tsutomu; Hamamoto, Nariaki; Umisedo, Sei; Tanjyo, Masayasu; Ootsuka, Fumio; Aoyama, Takayuki

2008-11-01

84

We have studied the mixed network former effect on the dynamics of lithium ions in borotellurite glasses in wide composition and temperature ranges. The length scales of ion dynamics, such as characteristic mean square displacement and spatial extent of sub-diffusive motion of lithium ions have been determined from the ac conductivity and dielectric spectra, respectively, in the framework of linear response theory. The relative concentrations of different network structural units have been determined from the deconvolution of the FTIR spectra. A direct correlation between the ion dynamics and the characteristic length scales and the relative concentration of BO{sub 4} units has been established for different compositions of the borotellurite glasses.

Shaw, A.; Ghosh, A., E-mail: sspag@iacs.res.in [Department of Solid State Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India)

2014-10-28

85

We have studied the mixed network former effect on the dynamics of lithium ions in borotellurite glasses in wide composition and temperature ranges. The length scales of ion dynamics, such as characteristic mean square displacement and spatial extent of sub-diffusive motion of lithium ions have been determined from the ac conductivity and dielectric spectra, respectively, in the framework of linear response theory. The relative concentrations of different network structural units have been determined from the deconvolution of the FTIR spectra. A direct correlation between the ion dynamics and the characteristic length scales and the relative concentration of BO4 units has been established for different compositions of the borotellurite glasses. PMID:25362322

Shaw, A; Ghosh, A

2014-10-28

86

Venus' superrotation, mixing length theory and eddy diffusion - A parametric study

NASA Technical Reports Server (NTRS)

The concept of the Hadley mechanism is adopted to describe the axisymmetric circulation of the Venus atmosphere. It is shown that, for the atmosphere of a slowly rotating planet such as Venus, a form of the nonliner 'closure' (self-consistent solution) of the fluid dynamics system which constrains the magnitude of the eddy diffusion coefficients can be postulated. A nonlinear one-layer spectral model of the zonally symmetric circulation was then used to establish the relationship between the heat source, the meridional circulation, and the eddy diffusion coefficients, yielding large zonal velocities. Computer experiments indicated that proportional changes in the heat source and eddy diffusion coefficients do not significantly change the zonal velocities. It was also found that, for large eddy diffusion coefficients, the meridional velocity is virtually constant; below a threshold in the diffusion rate, the meridional velocity decreases; and, for large eddy diffusion and small heating rates, the zonal velocities decrease with decreasing planetary rotation rates.

Mayr, H. G.; Harris, I.; Schatten, K. H.; Stevens-Rayburn, D. R.; Chan, K. L.

1988-01-01

87

The appropriate spatial scale for a distributed energy balance model was investigated by: (a) determining the scale of variability associated with the remotely sensed and GIS-generated model input data; and (b) examining the effects of input data spatial aggregation on model response. The semi-variogram and the characteristic length calculated from the spatial autocorrelation were used to determine the scale of variability of the remotely sensed and GIS-generated model input data. The data were collected from two hillsides at Upper Sheep Creek, a sub-basin of the Reynolds Creek Experimental Watershed, in southwest Idaho. The data were analyzed in terms of the semivariance and the integral of the autocorrelation. The minimum characteristic length associated with the variability of the data used in the analysis was 15 m. Simulated and observed radiometric surface temperature fields at different spatial resolutions were compared. The correlation between agreement simulated and observed fields sharply declined after a 10×10 m2 modeling grid size. A modeling grid size of about 10×10 m2 was deemed to be the best compromise to achieve: (a) reduction of computation time and the size of the support data; and (b) a reproduction of the observed radiometric surface temperature.

Artan, Guleid A.; Neale, C. M. U.; Tarboton, D. G.

2000-01-01

88

NASA Astrophysics Data System (ADS)

Undoped- and Si-doped GaN epitaxial films were grown on sapphire substrates by metal-organic chemical vapor deposition. Variable angle spectroscopic ellipsometry (VASE) and surface photovoltage (SPV) spectroscopy were used to determine the minority carrier diffusion lengths in the films. Both the reflectivity (R) and absorption coefficient () could be calculated from the VASE measurements. In the SPV spectra at room temperature, a strong transition with a threshold at 3.42 eV was observed in both films, while an exciton-related absorption was observed only in the undoped GaN. The minority carrier diffusion lengths were measured to be about 200 nm for the undoped GaN and about 20 nm for the Si-doped GaN. Moreover, a large divergence in the range of 1/ in the undoped GaN was found and attributed to a high surface barrier energy.

Park, Seong-Eun; Kopanski, Joseph J.; Kang, Youn-Seon; Robins, Lawrence H.

2005-05-01

89

We present the experimental study of the spin Hall angle (SHA) and spin diffusion length of Pd with the spin pumping and microwave photoresistance effects. The Py/Pd bilayer stripes are excited with an out-of-plane microwave magnetic field. The pure spin current is thus pumped and transforms into charge current via the inverse spin Hall effect (ISHE) in Pd layer, yielding an ISHE voltage. The ISHE voltage can be distinguished from the unwanted signal caused by the anisotropic magnetoresistance according to their different symmetries. Together with Pd thickness dependent measurements of in and out-of-plane precessing angles and effective spin mixing conductance, the SHA and spin-diffusion length of Pd are quantified as 0.0056?±?0.0007 and 7.3?±?0.7?nm, respectively.

Tao, X. D.; Feng, Z.; Miao, B. F.; Sun, L.; You, B.; Wu, D.; Du, J.; Zhang, W.; Ding, H. F., E-mail: hfding@nju.edu.cn [Department of Physics, National Laboratory of Solid State Microstructures, Nanjing University, 22 Hankou Road, Nanjing 210093 (China)

2014-05-07

90

Moisture Diffusivity Characteristics of Rough Rice Under Infrared Radiation Heating

Technology Transfer Automated Retrieval System (TEKTRAN)

To design an efficient infrared (IR) dryer for rough rice, it is important to understand the drying behavior of rice grains under infrared heating. The objective of this study was to determine the moisture diffusivity and moisture diffusivity coefficient of rough rice under IR heating and cooling. ...

91

Effect on fan flow characteristics of length and axial location of a cascade thrust reverser

NASA Technical Reports Server (NTRS)

A series of static tests were conducted on a model fan with a diameter of 14.0 cm to determine the fan operating characteristics, the inlet static pressure contours, the fan-exit total and static pressure contours, and the fan-exit pressure distortion parameters associated with the installation of a partial-circumferential-emission cascade thrust reverser. The tests variables included the cascade axial length, the axial location of the reverser, and the type of fan inlet. It was shown that significant total and static pressure distortions were produced in the fan aft duct, and that some configurations induced a static pressure distortion at the fan face. The amount of flow passed by the fan and the level of the flow distortions were dependent upon all the variables tested.

Dietrich, D. A.

1975-01-01

92

On the characteristic length scales associated with plastic deformation in metallic glasses

Atomistic simulations revealed that the spatial correlations of plastic displacements in three metallic glasses, FeP, MgAl, and CuZr, follow an exponential law with a characteristic length scale l{sub c} that governs Poisson's ratio {nu}, shear band thickness t{sub SB}, and fracture mode in these materials. Among the three glasses, FeP exhibits smallest l{sub c}, thinnest t{sub SB}, lowest {nu}, and brittle fracture; CuZr exhibits largest l{sub c}, thickest t{sub SB}, highest {nu}, and ductile fracture, while properties of MgAl lie in between those of FeP and CuZr. These findings corroborate well with existing experimental observations and suggest l{sub c} as a fundamental measure of the shear transformation zone size in metallic glasses.

Murali, P.; Zhang, Y. W. [Institute of High Performance Computing, Singapore 138632 (Singapore); Gao, H. J. [School of Engineering, Brown University, Rhode Island 02912 (United States)

2012-05-14

93

Shortening or omitting the dry period (DP) has been proposed as a management strategy to improve energy balance of dairy cows in early lactation. Both shortening and complete omission of the DP reduces milk production in the subsequent lactation compared with a conventional DP length of 60d. Some cows have less milk production loss than other cows after applying no DP or a short DP. The aim of this study is to evaluate which cow characteristics are associated with the amount of milk production losses following no DP or a short DP (30d). Daily production information from the lactation before and after the DP was available from 161 dairy cows (54 cows with a 0-d DP, 51 cows with a 30-d DP, and 56 cows with a 60-d DP) from a research herd. Daily production (milk, fat, and protein) until 305d in milk was estimated for all cows. Subsequently, total fat- and protein-corrected milk yield from 60d before the expected calving date until 305d in the following lactation (FPCMtotal) was estimated. A statistical analysis was performed to evaluate which cow characteristics were associated with limited or no production losses following no DP or a short DP, compared with a conventional DP length of 60d. Average FPCMtotal was 9,341, 10,499, and 10,795kg for cows with no DP, a 30-d DP, and a 60-d DP, respectively. The cow characteristics parity, daily milk production at 12wk before the expected calving date, and reduction in daily milk production between 16 and 12wk before the expected calving date were associated with production loss due to a short (30d) or no DP. Compared with 60d DP, multiparous cows had less production loss (987kg) following no DP than primiparous cows (2,132kg). The difference in FPCMtotal between the 3DP groups was largest for cows with a low milk production (e.g., 10kg/d) at 12wk before the expected calving date. The greater the reduction in milk production between 16 and 12wk before the expected calving date, the larger the difference in FPCMtotal between the 3DP groups. The difference in FPCMtotal between cows with no DP and 60d DP at a reduction in milk production between 16 and 12wk of 10% was 665kg, whereas this difference was 1,138kg at a reduction of 70%. The cow characteristics found can be used to select cows for specific DP lengths in a decision-support model to support the farmer on the economic optimal DP length for each individual cow. Output of such a decision-support model can be, for instance, to advise a 30-d DP for multiparous cows with high milk production (e.g., 25kg/d) at 12wk before the expected calving date. PMID:24952774

Steeneveld, W; van Knegsel, A T M; Remmelink, G J; Kemp, B; Vernooij, J C M; Hogeveen, H

2014-08-01

94

NASA Technical Reports Server (NTRS)

We report values of minority carrier diffusion length in n-type 6H SiC measured using a planar Electron Beam Induced Current (EBIC) method. Values of hole diffusion length in defect free regions of n-type 6H SiC, with a doping concentration of 1.7El7 1/cu cm, ranged from 1.46 microns to 0.68 microns. We next introduce a novel variation of the planar method used above. This 'planar mapping' technique measured diffusion length along a linescan creating a map of diffusion length versus position. This map is then overlaid onto the EBIC image of the corresponding linescan, allowing direct visualization of the effect of defects on minority carrier diffusion length. Measurements of the above n-type 6H SiC resulted in values of hole diffusion length ranging from 1.2 micron in defect free regions to below 0.1 gm at the center of large defects. In addition, measurements on p-type 6H SiC resulted in electron diffusion lengths ranging from 1.42 micron to 0.8 micron.

Tabib-Azar, Massood

1997-01-01

95

The physicochemical properties of ionic liquids are strongly affected by the selective combination of the cations and anions comprising the ionic liquid. In particular, the length of the alkyl chains of ions has a clear influence on the ionic liquid's performance. In this paper, we study the self-diffusion of ions in a series of halogen-free boron-based ionic liquids (hf-BILs) containing bis(mandelato)borate anions and dialkylpyrrolidinium cations with long alkyl chains CnH2n+1 with n from 4 to 14 within a temperature range of 293-373 K. It was found that the hf-BILs with n = 4-7 have very similar diffusion coefficients, while hf-BILs with n = 10-14 exhibit two liquid sub-phases in almost the entire temperature range studied (293-353 K). Both liquid sub-phases differ in their diffusion coefficients, while values of the slower diffusion coefficients are close to those of hf-BILs with shorter alkyl chains. To explain the particular dependence of diffusion on the alkyl chain length, we examined the densities of the hf-BILs studied here. It was shown that the dependence of the density on the number of CH2 groups in long alkyl chains of cations can be accurately described using a "mosaic type" model, where regions of long alkyl chains of cations (named 'aliphatic' regions) and the residual chemical moieties in both cations and anions (named 'ionic' regions) give additive contributions. Changes in density due to an increase in temperature and the number of CH2 groups in the long alkyl chains of cations are determined predominantly by changes in the free volume of the 'ionic' regions, while 'aliphatic' regions are already highly compressed by van der Waals forces, which results in only infinitesimal changes in their free volumes with temperature. PMID:25372279

Filippov, Andrei; Taher, Mamoun; Shah, Faiz Ullah; Glavatskih, Sergei; Antzutkin, Oleg N

2014-12-28

96

NASA Technical Reports Server (NTRS)

Minority-Carrier diffusion lengths of n-type 6H-SiC were measured using the electron-beam induced current (EBIC) technique. Experimental values of primary beam current, EBIC, and beam voltage were obtained for a variety of SIC samples. This data was used to calculate experimental diode efficiency vs. beam voltage curves. These curves were fit to theoretically calculated efficiency curves, and the diffusion length and metal layer thickness were extracted. The hole diffusion length in n-6H SiC ranged from 0.93 +/- 0.15 microns.

Hubbard, S. M.; Tabib-Azar, M.; Balley, S.; Rybickid, G.; Neudeck, P.; Raffaelle, R.

2004-01-01

97

Wave Characteristics of Large-Diameter, High-Density Helicon Plasma with Short Axial Length II

NASA Astrophysics Data System (ADS)

We have demonstrated that a large-diameter, high-density (>= 10^12 cm-3) helicon plasma can be produced in a low aspect ratio (the ratio of the axial length L to the diameter R; in our case, R =73.8 cm and 5.5 cm <= L <= 35 cm) device using a flat spiral antenna (4-turn, 43 cm in diameter) installed just outside the quartz-glass window at one end of the device [1]. As a first step to understand the role of helicon waves in the discharge process, helicon wave characteristics in plasma has been investigated in detail [2]. It has been found that discrete axial eigenmodes, whose characteristics depend on the plasma density profile and the axial boundary conditions, exist in the excited helicon wave. The effects of the background magnetic field profile and the rf input power on the excited wave have also been examined in detail. [1] T. Motomura et al., J. Plasma Fusion Res. Ser., in press. [2] T. Motomura et al., Bull. Ameri. Phys. Soc. 53 (14), 175 (2008).

Motomura, Taisei; Shinohara, Shunjiro; Tanikawa, Takao; Shamrai, Konstantin P.

2009-11-01

98

—We present simulations of the decorrelation rate for a high and a low coherence light source in heterodyne light scattering geometry. Light scatters on an ensemble of particles of which the particle trajectories are calculated using a forced-diffusion model. The low coherence signal is constructed in the Fourier domain (as in Fourier-domain optical coherence tomography). I. INTRODUCTION The dynamics of

J. Kalkman; T. G. van Leeuwen; R. Sprik

2011-01-01

99

SIMULATION OF SOLIDIFICATION GRAIN STRUCTURES WITH A MULTIPLE DIFFUSION LENGTH SCALES MODEL

of the mushy zone. Diffusion in the solid and in the extradendritic liquid are modeled with analytical by the electromagnetic levitation (EML) of a volume of metallic alloy in the liquid and solid state. The melt can either, Welding and Advanced Solidification Processes, Vancouver & Alaska, June 7-13, 2009, S. Cockcroft, D

Paris-Sud XI, Université de

100

Planar, buried, ion-exchanged glass waveguides - Diffusion characteristics

NASA Astrophysics Data System (ADS)

A study of Ag(+)-Na(+) exchange in soda-lime silicate glasses in a molten bath containing a mixture of NaNO3 and Ag(+) is performed. Concentration profiles obtained using backscattered electrons in an SEM indicate that with no applied field the profile is given by the complementary error function. The estimated 0.133 sq micron/min self-diffusion coefficient value for low concentrations monotonically increases with surface concentration, C(0), until it saturates at about 0.3 sq microns/min for C(0) greater than 0.001 MF, though square root dependence of diffusion depth with time is independent of C(0). The effective depth of diffusion increases with an external field. Experimental results confirmed theoretical predictions, and a 15.55 sq micron/V mobility-of-Ag(+)-in-glass value was obtained. Finally, a two-step process is modified by performing a second diffusion in pure sodium nitrate to produce a buried symmetrical fiber-like profile.

Ramaswamy, R. V.; Najafi, S. I.

1986-06-01

101

Using the chromatographic technique (carrier-gas: N2; tracer-gases: He, Ar) the effective diffusivity in single-pellet string columns (SPSC) packed with porous slab particles was studied. Dispersion due to extra-column effects was eliminated via convolution of column responses for two lengths. The measurements were done for cordierite particles and for cordierite coated with alumina-based washcoat. The effective diffusion coefficients for two tracer–carrier

Tomáš Starý; Olga Šolcová; Petr Schneider; Miloš Marek

2006-01-01

102

We perform correlated studies of individual GaN nanowires in scanning electron microscopy combined to low temperature cathodoluminescence, microphotoluminescence, and scanning transmission electron microscopy. We show that some nanowires exhibit well localized regions emitting light at the energy of a stacking fault bound exciton (3.42?eV) and are able to observe the presence of a single stacking fault in these regions. Precise measurements of the cathodoluminescence signal in the vicinity of the stacking fault give access to the exciton diffusion length near this location.

Nogues, Gilles, E-mail: gilles.nogues@neel.cnrs.fr; Den Hertog, Martien [Inst. NEEL, Univ. Grenoble Alpes, F-38042 Grenoble (France); Inst. NEEL, CNRS, F-38042 Grenoble (France); Auzelle, Thomas; Gayral, Bruno; Daudin, Bruno [INAC, CEA, F-38054 Grenoble (France)

2014-03-10

103

NASA Astrophysics Data System (ADS)

Enhancement in power conversion efficiency is a persistent pursuit for solid-state dye-sensitized solar cells (DSSCs). We report an experimental strategy of synthesizing I-/I3- doped 3-hydroxypropionitrile/polyaniline (HPN/PANi) solid electrolytes, aiming at expanding I3- reduction reaction from electrolyte/counter electrode interface to solid electrolyte system and shortening the charge diffusion path length. The DSSC with HPN/1.0 wt% PANi shows an efficiency of 3.70% in comparison to 1.49% from the cell with pristine HPN.

Li, Pinjiang; Duan, Yanyan; Tang, Qunwei; He, Benlin; Li, Ru

2015-01-01

104

NASA Astrophysics Data System (ADS)

Previously, we have observed a period-doubling cascade to chaos in Modified Taylor-Couette Flow with Hourglass Geometry. Such behavior had been predicted by The Reaction-Diffusion model simulations. The chaotic formation of Taylor-Vortex pair formation was restricted to a very narrow band about the waist of the hourglass. It was suggested that with increasing lengths of systems, the chaotic region would expand. We present a battery of simulations to determine the variation of the size of the chaotic region with length, seeking the transition to spatio- temporal chaos. Richard J. Wiener et al, Phys. Rev. E 55, 5489 (1997). H. Riecke and H.-G. Paap, Europhys. Lett. 14, 1235 (1991).

Halmstad, Andrew; Olsen, Thomas; Wiener, Richard

2006-11-01

105

Time-reversal characteristics of quantum normal diffusion: time-continuous models

NASA Astrophysics Data System (ADS)

In quantum map systems exhibiting normal diffusion, time-reversal characteristics converge to a universal scaling behavior which implies a prototype of irreversible quantum process [H.S. Yamada, K.S. Ikeda, Eur. Phys. J. B 85, 41 (2012)]. In the present paper, we extend the investigation of time-reversal characteristic to time-continuous quantum systems which show normal diffusion. Typical four representative models are examined, which is either deterministic or stochastic, and either has or not has the classical counterpart. Extensive numerical examinations demonstrate that three of the four models have the time-reversal characteristics obeying the same universal limit as the quantum map systems. The only nontrivial counterexample is the critical Harper model, whose time-reversal characteristics significantly deviates from the universal curve. In the critical Harper model modulated by a weak noise that does not change the original diffusion constant, time-reversal characteristic recovers the universal behavior.

Yamada, H. S.; Ikeda, K. S.

2012-06-01

106

Conjecture on superrotation in planetary atmospheres - A diffusion model with mixing length theory

NASA Technical Reports Server (NTRS)

The component of rigid shell superrotation on Venus is discussed in the context of comparative planetary atmospheres. A simplified, heuristic analysis, utilizing mixed length theory to describe the small scale nonlinear advections of energy and angular momentum, thereby providing a closure of the dynamic system, is presented, on the basis of which a crude estimate of zonal velocity is made. The rigid shell (global average) component on Venus was calculated to be 105 m/sec.

Mayr, H. G.; Harris, I.; Hartle, R. E.; Schatten, K. H.; Chan, K. L.

1985-01-01

107

NASA Astrophysics Data System (ADS)

The characteristics of the voltage-induced metal insulator transition (MIT) of VO2 film devices are investigated as a function of ambient temperature and length. At the onset of voltage-induced MIT, an abrupt formation of a conduction channel is observed within the insulating phase. The carrier density of the device varies with ambient temperature (TA) and device length (L) across MIT. As the device length is reduced, a statistically random appearance of the conduction channel is observed. Our results suggest that the primary operation principles of the VO2 device can be chosen between Joule heating effect and the electric field effect.

Yoon, Joonseok; Lee, Giyong; Park, Changwoo; Mun, Bongjin Simon; Ju, Honglyoul

2014-08-01

108

Low-coherence enhanced backscattering (LEBS) is a technique that has recently shown promise for tissue characterization and the detection of early pre-cancer. Although several Monte Carlo models of LEBS have been described, these models have not been accurate enough to predict all of the experimentally observed LEBS features. We present an appropriate Monte Carlo model to simulate LEBS peak properties from polystyrene microsphere suspensions in water. Results show that the choice of the phase function greatly impacts the accuracy of the simulation when the transport mean free path (ls*) is much greater than the spatial coherence length (LSC). When ls* < LSC, a diffusion approximation based model of LEBS is sufficiently accurate. We also use the Monte Carlo model to validate that LEBS can be used to measure the radial scattering probability distribution (radial point spread function), p(r), at small length scales and demonstrate LEBS measurements of p(r) from biological tissue. In particular, we show that pre-cancerous and benign mucosal tissues have different small length scale light transport properties. PMID:21037980

Turzhitsky, Vladimir; Rogers, Jeremy D.; Mutyal, Nikhil N.; Roy, Hemant K.; Backman, Vadim

2009-01-01

109

An innovative multilayer growth of InAs quantum dots on GaAs(100) is demonstrated to lead to self-aggregation of correlated quantum dot chains over mesoscopic distances. The fundamental idea is that at critical growth conditions is possible to drive the dot nucleation only at precise locations corresponding to the local minima of the Indium chemical potential. Differently from the known dot multilayers, where nucleation of new dots on top of the buried ones is driven by the surface strain originating from the dots below, here the spatial correlations and nucleation of additional dots are mostly dictated by a self-engineering of the surface occurring during the growth, close to the critical conditions for dot formation under the fixed oblique direction of the incoming As flux, that drives the In surface diffusion.

Placidi, E., E-mail: ernesto.placidi@ism.cnr.it; Arciprete, F. [Istituto di Struttura della Materia, CNR, Via del Fosso del Cavaliere 100, 00133 Rome (Italy); Università di Roma “Tor Vergata”, Dipartimento di Fisica, via della Ricerca Scientifica 1, 00133 Rome (Italy); Latini, V.; Latini, S.; Patella, F. [Università di Roma “Tor Vergata”, Dipartimento di Fisica, via della Ricerca Scientifica 1, 00133 Rome (Italy); Magri, R. [Dipartimento di Scienze Fisiche, Informatiche e Matematiche (FIM), Università di Modena e Reggio Emilia, and Centro S3 CNR-Istituto Nanoscienze, Via Campi 213/A, 4100 Modena (Italy); Scuderi, M.; Nicotra, G. [CNR-IMM, Strada VIII, 5, 95121 Catania (Italy)

2014-09-15

110

NASA Astrophysics Data System (ADS)

The optical anisotropy and viscosity of micron interlayers, bounded by metallic substrates, of two n-alkane homologs — tridecane and heptadecane — have been measured. The thickness and characteristics of the orientational ordering of epitropic liquid-crystal layers formed on the substrates have been established. The structure parameters obtained are higher for heptadecane, which is attributable to the longer length of its alkyl chain.

Kiriyan, S. V.; Altoiz, B. A.; Shatagina, E. A.; Shatagina, A. A.

2012-03-01

111

ERIC Educational Resources Information Center

Effects of display characteristics on bias of estimates of whisker length of 2 types of box-and-whisker plots were studied in 2 studies involving 347 college students. Bias seems to be the product of a three-way interaction between spatial orientation, interquartile spread, and whisker/spread ratio. (SLD)

Wells, James B.; Layne, Ben H.

1996-01-01

112

The effects of operating temperature on an osmotic sucrose solution with a selected concentration pattern (30-50-70 °Brix) on mass transfer characteristics during the diffusion process in bilimbi fruits in a dehydration system were investigated. Half-ripe bilimbi fruits were used. In the pretreatment step, all fruits were blanched in boiling water for 1 min to soften the fruit for better diffusion.

Chairat SIRIPATANA

113

In this paper, we propose a characteristic tailored finite point method (CTFPM) for solving the convection-diffusion-reaction\\u000a equation with variable coefficients. We develop an algorithm to construct a streamline-aligned grid for the CTFPM. Our numerical\\u000a tests show for small diffusion coefficient the CTFPM solution resolves the internal and boundary layers regardless the mesh\\u000a size, and depicts that CTFPM method with a

Yintzer Shih; R. Bruce Kellogg; Yoyo Chang

2011-01-01

114

Response characteristics of partial discharge pulses according to the length of the signal lines

The signal transmission system from the sensor to the PD detector should be fully understood to avoid the measuring error due to the sensor resonance, the impedance and the length of communication cables and the connection status of terminals, etc. In this paper, the effect of the signal line length on PD pulse wave shape was investigated. For the purpose,

Jeongtae Kim; Jihong Kim

2010-01-01

115

Muscle length influences the contractile properties of muscle in that when muscle is lengthened the relaxation phase of the muscle twitch is prolonged and when muscle is shortened, the relaxation phase is shorter in duration. As a result, the force exerted by active motor units varies with muscle length during voluntary contractions. To determine if motoneuron spike trains were adjusted

D. W. Vander Linden; C. G. Kukulka; G. L. Soderberg

1991-01-01

116

Morphologic characteristics and immunohistochemical profile of diffuse intrinsic pontine gliomas

Tumors of the CNS are the second most common malignancy in children. In particular, diffuse intrinsic pontine gliomas (DIPGs) are aggressive tumors with poor prognosis and account for 10–25% of pediatric brain tumors. The majority of DIPGs are astrocytic, infiltrative and localized to the pons. Studies have shown median survival times of less than a year with 90% of children dying within 2 years. We built multi-tissue arrays with 24 post-mortem DIPG samples and analyzed the morphology and expression of several proteins (p53, EGFR, GFAP, MIB1, BMI1, B-catenin, p16, Nanog, Nestin, OCT4, OLIG2, Sox2) with the goal of identifying potential treatment targets and improving our understanding of the biology of these tumors. The majority of DIPGs were high-grade gliomas (22) with 18 cases having features of glioblastoma (WHO grade IV), and 4 cases with high-grade features consistent with anaplastic astrocytoma (WHO grade-III). One case was low grade (WHO grade II) and one case showed intermediate features between a grade II and grade III glioma (low mitotic rate, but increased cellularity and cell atypia), being difficult to grade precisely.. The majority of the tumors were positive for GFAP (24/24), MIB1 (23/24), OLIG2 (22/24), p16 (20/24), p53 (20/24), Sox2 (19/24), EGFR (16/24) and BMI1 (9/24). Our results suggest that dysregulation of EGFR and p53 may play an important role in the development of DIPGs. The majority of DIPGs express stem cell makers such as SOX2 and OLIG2, consistent with a role for tumor stem cells in the origin and maintenance of these tumors. Targeted therapies against these proteins could be beneficial in treatment. PMID:24076776

Ballester, Leomar Y.; Wang, Zengfeng; Shandilya, Shaefali; Miettinen, Markku; Burger, Peter C.; Eberhart, Charles G.; Rodriguez, Fausto J.; Raabe, Eric; Nazarian, Javad; Warren, Katherine; Quezado, Martha M.

2013-01-01

117

Wave Characteristics of Large-Diameter, High-Density Helicon Plasma with Short Axial Length

NASA Astrophysics Data System (ADS)

We have developed a large-diameter (73.8 cm) helicon device with an axial length of 486 cm that utilizes a flat spiral antenna at ISAS/JAXA [1]. It has been realized that a shorter axial length is desirable in certain applications. Therefore, the axial length has been shortened in a range of 12 to 123 cm by installing a movable termination plate. Even with very short axial length, the plasma density can exceed 10^12 cm-3 (pAr = 0.75 mTorr) with the input rf power of less than 4 kW, showing a rather high plasma production efficiency. When the axial length is relatively longer, the excitation of the higher order radial eigenmodes is found to be correlated with the magnetic field configuration and the radial density profile. When the axial length is further shortened, the axial wave structure tends to become standing wave like, where its wavelength depends on the plasma density and axial length as is expected. The details of the experimental results will be discussed in the presentation. [1] S. Shinohara and T. Tanikawa, Rev. Sci. Instrum. 75, 1941 (2004) & Phys. Plasmas 12, 044502 (2005).

Motomura, Taisei; Tanaka, Kenji; Murakami, Katsuhiko; Shinohara, Shunjiro; Tanikawa, Takao; Konstantin, Shamrai

2008-11-01

118

1. Relations between sarcomere length, tension and time course of isometric twitches at 20° C were determined for thirty-two sartorius muscles from Rana temporaria. 2. The maximum isometric twitch tension per unit cross-sectional area of muscle ranged from 0·56 to 2·2 kg/cm2 at 20° C and initial sarcomere length about 2·1 ?. This variation was not correlated with the corresponding measure of tetanic tension. 3. The maximum isometric twitch tension per unit cross-sectional area of muscle at 2·1 ? sarcomere length was directly correlated with twitch contraction time and inversely correlated with the cross-sectional area of the muscle. 4. The isometric twitch contraction was potentiated with increase in initial sarcomere length from about 2·1 to about 2·8 ? at 20° C, and the degree of potentiation was inversely correlated with the maximum isometric twitch tension per unit cross-sectional area of muscle at 2·1 ? sarcomere length. 5. The sarcomere length: twitch tension relation is labile and may be altered by changes in temperature and the after-effects of repetitive stimulation. 6. Variation in twitch contractions at different sarcomere lengths are discussed in connexion with excitation—contraction coupling and the degree of activation of muscle fibres during twitch contractions at 20° C. PMID:4536939

Close, R. I.

1972-01-01

119

NASA Astrophysics Data System (ADS)

The Reaction-Diffusion modelootnotetextH. Riecke and H.-G. Paap, Europhys. Lett. 14, 1235 (1991). has been applied to a wide variety of pattern forming systems. It correctly predicted a period doubling cascade to chaos in Taylor-Couette flow with hourglass geometryootnotetextRichard J. Wiener et al, Phys. Rev. E 55, 5489 (1997).. We have extended previous calculations to systems possessing a greater variety of lengths. We show that a modest doubling of length extends the region of phase slips (formation of Taylor Vortex pairs) from the length of one vortex pair to seven, while quadrupling only increases it to the length of eight.

Olsen, Thomas; Zhao, Yunjie; Halmstad, Andrew; Wiener, Richard

2007-11-01

120

The surface properties of a family of elastin-like polypeptides (ELPs), differing in molecular weight and sequence length, were investigated to understand how the nature of the polypeptide film might contribute to their thrombogenic profile. Physical adsorption of the ELPs onto Mylar increased surface wettability as the sequence length decreased while X-ray spectroscopy analysis showed an increasing amide content with sequence length. Chemical force microscopy analysis revealed that the ELP-coated surfaces displayed purely hydrophilic adhesion forces that increased as the ELP sequence length decreased. Adsorption isotherms performed using the quartz crystal microbalance with dissipation, showed that the surface coverage increased with ELP sequence length. The longer polypeptides (ELP2 and ELP4) also displayed higher specific dissipation values indicating that they established films with greater structural flexibility and associated water content than the shorter polypeptide, ELP1. Additionally, the stability of the ELP coating was lower with the shorter polypeptides. This study highlights the different surface properties of the ELP coatings as well as the dynamic nature of the ELP adsorbed layer wherein the conformational state may be an important factor contributing to their blood response. PMID:23053802

Srokowski, Elizabeth M; Woodhouse, Kimberly A

2013-01-01

121

Water management is an important issue in proton exchange membrane (PEM) fuel cell design and operation. The purpose of this work is to investigate the effects of the microstructure characteristics of the gas diffusion layer (GDL) and microporous layer (MPL), including pore size distribution, hydrophobic treatment, gas permeability, and other factors, on the water management and performance of a PEM

Chung-Jen Tseng; Shih-Kun Lo

2010-01-01

122

In the present paper, we propose a method for evaluating the bulk diffusion length of minority charge carriers in the photosensing layer of photovoltaic focal plane array (FPA) photodetectors. The method is based on scanning a strip-shaped illumination spot with one of the detector diodes at a low level of photocurrents j{sub ph} being registered; such scanning provides data for subsequent analysis of measured spot-scan profiles within a simple diffusion model. The asymptotic behavior of the effective (at j{sub ph}???0) charge-carrier diffusion length l{sub d} {sub eff} as a function of j{sub ph} for j{sub ph} ? 0 inferred from our experimental data proved to be consistent with the behavior of l{sub d} {sub eff} vs j{sub ph} as predicted by the model, while the obtained values of the bulk diffusion length of minority carriers (electrons) in the p-HgCdTe film of investigated HgCdTe n-on-p FPA photodetectors were found to be in a good agreement with the previously reported carrier diffusion-length values for HgCdTe.

Vishnyakov, A. V.; Stuchinsky, V. A., E-mail: stuchin@isp.nsc.ru; Brunev, D. V.; Zverev, A. V.; Dvoretsky, S. A. [Institute of Semiconductor Physics, Russian Academy of Science, Siberian Division, 13, Acad. Lavrent'ev Avenue, Novosibirsk 630090 (Russian Federation)

2014-03-03

123

We report a systematic study of xenon gas diffusion NMR in simple model porous media, random packs of mono-sized glass beads, and focus on three specific areas peculiar to gas-phase diffusion. These topics are: (i) diffusion of spins on the order of the pore dimensions during the application of the diffusion encoding gradient pulses in a PGSE experiment (breakdown of

R. W. Mair; P. N. Sen; M. D. Hürlimann; S. Patz; D. G. Cory; R. L. Walsworth

2002-01-01

124

Background An in-vitro setup was established in order to determine a) the diffusion activities of eight otic preparations (Aurizon®, Eas Otic®, Epi Otic®, Otifree®, Otomax®, Panolog®, Posatex®, Surolan®) through synthetic cerumen, and b) the ceruminolytic capacity and impregnation effects of these products. The main lipid classes of canine cerumen produced with moderate, non-purulent otitis externa were determined by thin layer chromatography and were subsequently used to produce a standardised synthetic cerumen (SCC). SCC was filled into capillary tubes, all of which were loaded with six commercially available multipurpose otic medications and two ear cleaners, each mixed with two markers in two experimental setups. These two marker compounds (Oil red O and marbofloxacin) were chosen, since they exhibit different physicochemical drug characteristics by which it is possible to determine and verify the diffusion activity of different types of liquids (i.e. the otic preparations). A synthetic cerumen described in the literature (JSL) was also used for comparison as its lipid composition was different to SCC. The diffusion activities of the otic preparations through both types of synthetic cerumen were studied over 24 hours. A second in-vitro experiment determined both the ceruminolytic activity and impregnation effect of the otic preparations by comparing the weight loss or weight gain after repeated incubation of JSL. Results Canine cerumen is mainly composed of triglycerides, sterol esters, fatty acid esters and squalene. The diffusion experiments showed a high diffusion efficacy along with a high impregnation effect for one test product. All the other products exhibited a lower diffusion activity with a mild to moderate impregnation effect. A mild ceruminolytic activity was observed for the two ear cleaners but not for any of the otic medications. Conclusions The present study demonstrates that there are significant differences in the diffusion characteristics and ceruminolytic properties of the eight tested otic preparations. PMID:23574753

2013-01-01

125

Channel characteristics analysis of diffuse indoor cellular optical wireless communication systems

NASA Astrophysics Data System (ADS)

In this paper, two models for diffuse indoor cellular optical wireless communication (OWC) systems with and without a holographic light shaping diffuser (LSD) are presented. For both models, the power distribution, the impulse response of the channels and root mean square (RMS) delay are described and analyzed. We perform a computer simulation to compare the channel characteristics of the typical indoor cellular OWC systems with that employing the holographic LSD. The results show that the system with the holographic LSD provides a more uniform power distribution and a less RMS delay spread for the same divergence angles.

Wu, D.; Ghassemlooy, Z.; Le-Minh, H.; Rajbhandari, S.; Chao, L.

2011-12-01

126

Electron-hole diffusion lengths > 175 ?m in solution-grown CH3NH3PbI3 single crystals

NASA Astrophysics Data System (ADS)

Long, balanced electron and hole diffusion lengths greater than 100 nanometers in the polycrystalline organolead trihalide compound CH3NH3PbI3 are critical for highly efficient perovskite solar cells. We found that the diffusion lengths in CH3NH3PbI3 single crystals grown by a solution-growth method can exceed 175 micrometers under 1 sun (100 mW cm?2) illumination and exceed 3 millimeters under weak light for both electrons and holes. The internal quantum efficiencies approach 100% in 3-millimeter-thick single-crystal perovskite solar cells under weak light. These long diffusion lengths result from greater carrier mobility, longer lifetime, and much smaller trap densities in the single crystals than in polycrystalline thin films. The long carrier diffusion lengths enabled the use of CH3NH3PbI3 in radiation sensing and energy harvesting through the gammavoltaic effect, with an efficiency of 3.9% measured with an intense cesium-137 source.

Dong, Qingfeng; Fang, Yanjun; Shao, Yuchuan; Mulligan, Padhraic; Qiu, Jie; Cao, Lei; Huang, Jinsong

2015-02-01

127

Solar cells. Electron-hole diffusion lengths > 175 ?m in solution-grown CH3NH3PbI3 single crystals.

Long, balanced electron and hole diffusion lengths greater than 100 nanometers in the polycrystalline organolead trihalide compound CH3NH3PbI3 are critical for highly efficient perovskite solar cells. We found that the diffusion lengths in CH3NH3PbI3 single crystals grown by a solution-growth method can exceed 175 micrometers under 1 sun (100 mW cm(-2)) illumination and exceed 3 millimeters under weak light for both electrons and holes. The internal quantum efficiencies approach 100% in 3-millimeter-thick single-crystal perovskite solar cells under weak light. These long diffusion lengths result from greater carrier mobility, longer lifetime, and much smaller trap densities in the single crystals than in polycrystalline thin films. The long carrier diffusion lengths enabled the use of CH3NH3PbI3 in radiation sensing and energy harvesting through the gammavoltaic effect, with an efficiency of 3.9% measured with an intense cesium-137 source. PMID:25636799

Dong, Qingfeng; Fang, Yanjun; Shao, Yuchuan; Mulligan, Padhraic; Qiu, Jie; Cao, Lei; Huang, Jinsong

2015-02-27

128

Arrested fluid-fluid phase separation in depletion systems: Implications of the characteristic, and the polymer-colloid size ratio is 0.37. For these systems, the transition to kinetically arrested states exhibit a wide range of disordered dynamically arrested states, including repulsive and attractive glasses

Schofield, Andrew

129

Diffusion characteristics and molecular size of DOM in plant and soil extracts

NASA Astrophysics Data System (ADS)

The main sources of dissolved organic matter (DOM) in soil are plant litter, root exudates, soil fauna, and the un-dissolved soil organic matter pool. A strong spatial heterogeneity of these sources, even on the microscale, is observed in soil. Consequently diffusion of DOM is an important transport process, which connects "hot-spots" of microbial activity and substrates. Therefore an experiment was conducted in order to measure diffusion constants of DOM and 2 inorganic nutrients. Furthermore, hydrodynamic diameters were calculated from these constants, which give an approximation of molecular size. The diffusion characteristics of several parameters in aqueous extracts of two soils and of barley were investigated. They were: Ammonium, nitrate, dissolved organic nitrogen (DON), dissolved inorganic carbon, dissolved organic carbon (DOC), and 3 different fluorophore groups associated with DOM. The fluorophore groups were identified and quantified from fluorescence excitation emission spectra with the PARAFAC model. Two of the groups resembled groups, which have been used to imply the presence of humic substances (HS). Our results give reason to believe these groups can be regarded as indicators of dissolved HS in aqueous extracts only with caution. The other group, enriched in the barley extract, was the "tryptophan" group. However, its diffusion constant differed markedly between the soil and barley extracts, indicating that compounds other than tryptophan contributed to this fluorophore in soil extracts. When the Stokes-Einstein equation was applied to the diffusion coefficients of DOC (in all extracts about 0.27 x 10-5 cm2 s-1 at 4 °C), a mean hydrodynamic diameter of 1.0 nm for the DOC was calculated. The diffusion constants for the other DOM parameters were also similar, regardless of source, with the exception of the "tryptophan" fluorophore group from barley, which diffused about 1.5 times faster than that from the soils and was in good agreement with the theoretical diffusion coefficient of tryptophan. There was no evidence of macromolecules in DOM. The diffusion of the inorganic nitrogen species was up to 4 times as rapid as that for DOC. Therefore, where in situ metabolism is fuelled by diffusion, diffusion rates of dissolved nitrogen are not likely to be the limiting factor.

Fuß, Roland; Zsolnay, Ádám.; Munch, Jean Charles

2010-05-01

130

Photovoltaic characteristics of diffused P/+N bulk GaAs solar cells

NASA Technical Reports Server (NTRS)

The photovoltaic characteristics of P(+)N junction solar cells fabricated on bulk GaAs by an open tube diffusion technique are described in this paper.Spectral response measurements were analyzed in detail and compared to a computer simulation in order to determine important material parameters. It is projected that proper optimization of the cell parameters can increase the efficiency of the cells from 12.2 percent to close to 20 percent.

Borrego, J. M.; Keeney, R. P.; Bhat, I. B.; Bhat, K. N.; Sundaram, L. G.; Ghandhi, S. K.

1982-01-01

131

OBJECTIVE: To determine the independent effect of hospitalist status upon inpatient length of stay after controlling for case mix, as\\u000a well as patient-level and provider-level variables such as age, years since physician medical school graduation, and volume\\u000a status of provider.\\u000a \\u000a \\u000a DESIGN: Observational retrospective cohort study employing a hierarchical random intercept logistic regression model.\\u000a \\u000a \\u000a \\u000a \\u000a SETTING: Tertiary-care teaching hospital.\\u000a \\u000a \\u000a \\u000a \\u000a PATIENTS: All admissions

William D. Rifkin; Eric Holmboe; Hannah Scherer; Hernan Sierra

2004-01-01

132

Freezing lines of colloidal Yukawa spheres. II. Local structure and characteristic lengths

Using the Rogers-Young (RY) integral equation scheme for the static pair correlation functions combined with the liquid-phase Hansen-Verlet freezing rule, we study the generic behavior of the radial distribution function and static structure factor of monodisperse charge-stabilized suspensions with Yukawa-type repulsive particle interactions at freezing. In a related article, labeled Paper I [J. Gapinski, G. Nägele, and A. Patkowski, J. Chem. Phys. 136, 024507 (2012)], this hybrid method was used to determine two-parameter freezing lines for experimentally controllable parameters, characteristic of suspensions of charged silica spheres in dimethylformamide. A universal scaling of the RY radial distribution function maximum is shown to apply to the liquid-bcc and liquid-fcc segments of the universal freezing line. A thorough analysis is made of the behavior of characteristic distances and wavenumbers, next-neighbor particle coordination numbers, osmotic compressibility factor, and the Ravaché-Mountain-Streett minimum-maximum radial distribution function ratio.

Gapinski, Jacek, E-mail: gapinski@amu.edu.pl; Patkowski, Adam [Molecular Biophysics Division, Faculty of Physics, A. Mickiewicz University, Umultowska 85, 61-614 Pozna? (Poland); NanoBioMedical Center, A. Mickiewicz University, Umultowska 85, 61-614 Pozna? (Poland); Nägele, Gerhard [Institute of Complex Systems (ICS-3), Forschungszentrum Jülich, D-52425 Jülich (Germany)

2014-09-28

133

NASA Astrophysics Data System (ADS)

A series of p-type 4H–SiC epilayers with aluminium concentration ranging from 2? × ?1016 to 8? × ?1019?cm?3 were investigated by time-resolved optical techniques in order to determine the effect of aluminium doping on high-injection carrier lifetime at room temperature and the diffusion coefficient at different injections (from ?3? × ?1018 to ?5? × ?1019?cm?3) and temperatures (from 78 to 730?K). We find that the defect limited carrier lifetime ?SRH decreases from 20?ns in the low-doped samples down to ?0.6?ns in the heavily doped epilayers. Accordingly, the ambipolar diffusion coefficient decreases from Da = 3.5?cm2?s?1 down to ?0.6?cm2?s?1, corresponding to the hole mobility of µh = 70?cm2?Vs?1 and 12?cm2?Vs?1, respectively. In the highly doped epilayers, the injection-induced decrease of the diffusion coefficient, due to the transition from the minority carrier diffusion to the ambipolar diffusion, provided the electron diffusion coefficient of De ? 3?cm2?s?1. The Al-doping resulted in the gradual decrease of the ambipolar diffusion length, from LD = 2.7?µm down to LD = 0.25?µm in the epilayers with the lowest and highest aluminium concentrations.

Liaugaudas, Gediminas; Dargis, Donatas; Kwasnicki, Pawel; Arvinte, Roxana; Zielinski, Marcin; Jaraši?nas, K?stutis

2015-01-01

134

Effects of Characteristic Length Scales on the Exciton Dynamics in Rubrene Single Crystals

As for its inorganic counterparts the future developments in organic electronics are driven by an advanced device miniaturization. Therefore, the opto-electronic behavior of up-to-date devices is progressively governed by the local structural environment. However, there is a lack of organic semiconductor materials providing access to the fundamental structure-functionality relation, either due to limitations by their inherent growth or their optical characteristics. In this work we present a systematic investigation of the optical states, so-called excitons, and their temporal evolution in the prototypical organic semiconductor rubrene by means of time and temperature dependent photoluminescence studies. This material offers the unique possibility of preparing well-defined morphologies with adjustable degree of confinement. By this approach we are able to confirm the direct influence on the temperature dependent optical processes with picosecond resolution already for a spatial localization of excitation on t...

Gieseking, Björn; Müller, Benjamin; Deibel, Carsten; Engels, Bernd; Dyakonov, Vladimir; Pflaum, Jens

2013-01-01

135

A microbial fuel cell (MFC) is a bio-electrochemical converter that can extract electricity from biomass by the catabolic reaction of microorganisms. This work demonstrates the impact of a small characteristic length in a Geobacteraceae-enriched, micro-scale microbial fuel cell (MFC) that achieved a high power density. The small characteristic length increased the surface-area-to-volume ratio (SAV) and the mass transfer coefficient. Together, these factors made it possible for the 100-µL MFC to achieve among the highest areal and volumetric power densities - 83 ?W/cm(2) and 3300 ?W/cm(3), respectively - among all micro-scale MFCs to date. Furthermore, the measured Coulombic efficiency (CE) was at least 79%, which is 2.5-fold greater than the previously reported maximum CE in micro-scale MFCs. The ability to improve these performance metrics may make micro-scale MFCs attractive for supplying power in sub-100 µW applications, especially in remote or hazardous conditions, where conventional powering units are hard to establish. PMID:24956566

Ren, Hao; Torres, César I; Parameswaran, Prathap; Rittmann, Bruce E; Chae, Junseok

2014-11-15

136

NASA Astrophysics Data System (ADS)

Minority carrier diffusion length in a p-type Mg-doped AlN /Al0.08Ga0.92N short period superlattice was shown to undergo a multifold and persistent (for at least 1week) increase under continuous irradiation by low-energy beam of a scanning electron microscope. Since neither the diffusion length itself nor the rate of its increase exhibited any measurable temperature dependence, it is concluded that this phenomenon is attributable to the increase in mobility of minority electrons in the two-dimensional electron gas, which in turn is limited by defect scattering. Cathodoluminescence spectroscopy revealed ˜40% growth of carrier lifetime under irradiation with an activation energy of 240meV.

Lopatiuk-Tirpak, O.; Chernyak, L.; Borisov, B. A.; Kuryatkov, V. V.; Nikishin, S. A.; Gartsman, K.

2007-10-01

137

A measurement method is described, which is used to determine the x-ray-; induced p-n transitions and diffusion length as well as the average energy ; requirements for formation of electron-cavity pairs. It is necessary for ; irradiation with monochromatic x radiation at two different wavelengths to ; measure the ratio of the striking radiation to the short-circuit current of the

Pfister

1963-01-01

138

NSDL National Science Digital Library

Diffusion is the net movement of particles from areas of high concentration (number of particles per unit area) to low concentration. In this activity, students use a molecular dynamics model to view the behavior of diffusion in gases and liquids.

2012-07-19

139

NASA Astrophysics Data System (ADS)

Previously, we have observed a period-doubling cascade to chaos in Modified Taylor-Couette Flow with Hourglass GeometryootnotetextRichard J. Wiener et al, Phys. Rev. E 55, 5489 (1997).. Such behavior has been modeled by The Reaction-Diffusion equationootnotetextH. Riecke and H.-G. Paap, Europhys. Lett. 14, 1235 (1991).. In the experiment, chaotic formation of Taylor-Vortex pair formation was restricted to a very narrow band about the waist of the hourglass. The calculations of Riecke and Paap suggested that a quadrupling of the length of the system would lead to spatial chaos in the vortex formation. We present a careful recreation of the previous calculation and consider an intermediate length. We demonstrate that doubling the length should be sufficient to observe spatially chaotic behavior.

Zhao, Yunjie; Halmstad, Andrew; Olsen, Thomas; Wiener, Richard

2007-11-01

140

Watershed Best Management Practices (BMPs) are often designed to reduce loading from particle-borne contaminants, but the temporal lag between BMP implementation and improvement in receiving water quality is difficult to assess because particles are only moved downstream episodically, resting for long periods in storage between transport events. A theory is developed that describes the downstream movement of suspended sediment particles accounting for the time particles spend in storage given sediment budget data (by grain size fraction) and information on particle transit times through storage reservoirs. The theory is used to define a suspended sediment transport length scale that describes how far particles are carried during transport events, and to estimate a downstream particle velocity that includes time spent in storage. At 5 upland watersheds of the mid-Atlantic region, transport length scales for silt-clay range from 4 to 60 km, while those for sand range from 0.4 to 113 km. Mean sediment velocities for silt-clay range from 0.0072 km/yr to 0.12 km/yr, while those for sand range from 0.0008 km/yr to 0.20 km/yr, 4–6 orders of magnitude slower than the velocity of water in the channel. These results suggest lag times of 100–1000 years between BMP implementation and effectiveness in receiving waters such as the Chesapeake Bay (where BMPs are located upstream of the characteristic transport length scale). Many particles likely travel much faster than these average values, so further research is needed to determine the complete distribution of suspended sediment velocities in real watersheds.

Pizzuto, James; Schenk, Edward R.; Hupp, Cliff R.; Gellis, Allen; Noe, Greg; Williamson, Elyse; Karwan, Diana L.; O'Neal, Michael; Marquard, Julia; Aalto, Rolf; Newbold, Denis

2014-01-01

141

Effects of phenotypic characteristics on the length of stay of dogs at two no kill animal shelters.

Adoption records from 2 no kill shelters in New York State were examined to determine how age, sex, size, breed group, and coat color influenced the length of stay (LOS) of dogs at these shelters. Young puppies had the shortest length of stay; LOS among dogs increased linearly as age increased. Neither coat color nor sex influenced LOS. Considering only size classifications, medium-size dogs had the greatest LOS, and extra small dogs and puppies remained in shelters for the least amount of time. Considering only breed groupings, dogs in the guard group had the greatest LOS and those in the giant group had the shortest LOS. The lack of effect of coat color was not expected, nor was the shorter LOS among "fighting" breeds compared with other breed groups. Coat color and breed may have only local effects on LOS that do not generalize to all shelters, including traditional shelters. Understanding the traits of dogs in a specific shelter and the characteristics of these nonhuman animals desired by adopters are critical to improving the welfare of animals served by that shelter. PMID:23282290

Brown, William P; Davidson, Janelle P; Zuefle, Marion E

2013-01-01

142

We show that the averaged characteristic polynomial and the averaged inverse characteristic polynomial, associated with Hermitian matrices whose elements perform a random walk in the space of complex numbers, satisfy certain partial differential, diffusion-like, equations. These equations are valid for matrices of arbitrary size. Their solutions can be given an integral representation that allows for a simple study of their asymptotic behaviors for a broad range of initial conditions.

Jean-Paul Blaizot; Jacek Grela; Maciej A. Nowak; Piotr Warcho?

2014-05-20

143

NASA Astrophysics Data System (ADS)

Previously, we have observed a period-doubling cascade to chaos in Modified Taylor-Couette Flow with Hourglass GeometryootnotetextRichard J. Wiener et al, Phys. Rev. E 55, 5489 (1997).. Such behavior has been modeled by The Reaction-Diffusion equation ootnotetextH. Riecke and H.-G. Paap, Europhys. Lett. 14, 1235 (1991).. In the experiment, chaotic formation of Taylor-Vortex pair formation was restricted to a very narrow band about the waist of the hourglass. We examine the dependence of the range of locations in which vortex pair formation occurs. We compare to previous calculations and consider intermediate length systems as well. We find doubling the length to be sufficient to generate spatially chaotic behavior.

Zhao, Yunjie; Halmstad, Andrew; Olsen, Thomas; Wiener, Richard

2008-05-01

144

NASA Astrophysics Data System (ADS)

High-speed directly modulated microlasers are potential light sources for on-chip optical interconnection and photonic integrated circuits. In this Letter, dynamic characteristics are studied for microring lasers by rate equation analysis considering radial carrier hole burning and diffusion and experimentally. The coupled modes with a wide radial field pattern and the injection current focused in the edge area of microring resonator can greatly improve the high speed response curve due to the less carrier hole burning. The small-signal response curves of a microring laser connected with an output waveguide exhibit a larger 3 dB bandwidth and smaller roll-off at low frequency than that of the microdisk laser with the same radius of 15 ?m, which accords with the simulation results.

Lv, Xiao-Meng; Huang, Yong-Zhen; Yang, Yue-De; Zou, Ling-Xiu; Long, Heng; Liu, Bo-Wen; Xiao, Jin-Long; Du, Yun

2014-04-01

145

Examined here were the accuracy and bias of estimates of whisker length based on box, line, and midgap plots. For each type of graph, a different sample of undergraduates viewed 48 single-plot graphs. For each plot, subjects were given the length of an interquartile spread and asked to estimate the length of a whisker. Plots varied in spatial orientation (horizontal

William A. Stock; John T. Behrens

1991-01-01

146

Microstructural Characteristics of HIP-bonded Monolithic Nuclear Fuels with a Diffusion Barrier

Due to the limitation of maximum uranium load achievable by dispersion fuel type, the Global Threat Reduction Initiative (GTRI) is developing an advanced monolithic fuel to convert US high performance research reactors to low-enriched uranium. Hot-isostatic-press bonding was the single process down-selected to bond monolithic U-Mo fuel meat to aluminum alloy cladding. A diffusion barrier was applied to the U–Mo fuel meat by roll-bonding process to prevent extensive interaction between fuel meat and aluminum-alloy cladding. Microstructural characterization was performed on fresh fuel plates fabricated at Idaho National Laboratory. Interfaces between fuel meat, cladding, and diffusion barrier, as well as U–10Mo fuel meat and Al–6061 cladding were characterized by scanning electron microscopy. Preliminary results indicate that the interfaces contain many different phases while decomposition, second phases, and chemical banding were also observed in the fuel meat. The important attributes of the HIP-bonded monolithic fuel are • A typical Zr diffusion barrier of thickness 25 µm • Transverse cross section that exhibits relatively equiaxed grains with an average grain diameter of 10 µm • Chemical banding, in some areas more than 100 µm in length, that is very pronounced in longitudinal (i.e., rolling) direction with Mo concentration varying from 7–13 wt% • Decomposed areas containing plate-shaped low-Mo phase • A typical Zr/cladding interaction layer of thickness 1-2 µm • A visible UZr2 bearing layer of thickness 1-2 µm • Mo-rich precipitates (mainly Mo2Zr, forming a layer in some areas) followed by a Mo-depleted sub-layer between the visible UZr2-bearing layer and the U–Mo matrix • No excessive interaction between cladding and the uncoated fuel edge • Cladding-to-cladding bonding that exhibits no cracks or porosity with second phases high in Mg, Si, and O decorating the bond line. • Some of these attributes might be critical to the irradiation performance of monolithic U-10Mo nuclear fuel. There are several issues or concerns that warrant more detailed study, such as precipitation along cladding-to-cladding bond line, chemical banding, uncovered fuel-zone edge, and interaction layer between U–Mo fuel meat and zirconium. Future post-irradiation examination results will focus, among other things, on identifying in-reactor failure mechanisms and, eventually, directing further fresh fuel characterization efforts.

Jan-Fong Jue; Dennis D. Keiser, Jr.; Cynthia R. Breckenridge; Glenn A. Moore; Mitchell K. Meyer

2014-05-01

147

Microstructural characteristics of HIP-bonded monolithic nuclear fuels with a diffusion barrier

NASA Astrophysics Data System (ADS)

Due to the limitation of maximum uranium load achievable by dispersion fuel type, the Global Threat Reduction Initiative is developing an advanced monolithic fuel to convert US high-performance research reactors to low-enriched uranium. Hot-isostatic-press (HIP) bonding was the single process down-selected to bond monolithic U-Mo fuel meat to aluminum alloy cladding. A diffusion barrier was applied to the U-Mo fuel meat by roll-bonding process to prevent extensive interaction between fuel meat and aluminum-alloy cladding. Microstructural characterization was performed on fresh fuel plates fabricated at Idaho National Laboratory. Interfaces between the fuel meat, the cladding, and the diffusion barrier, as well as between the U-10Mo fuel meat and the Al-6061 cladding, were characterized by scanning electron microscopy. Preliminary results indicate that the interfaces contain many different phases while decomposition, second phases, and chemical banding were also observed in the fuel meat. The important attributes of the HIP-bonded monolithic fuel are:

Jue, Jan-Fong; Keiser, Dennis D.; Breckenridge, Cynthia R.; Moore, Glenn A.; Meyer, Mitchell K.

2014-05-01

148

NSDL National Science Digital Library

Diffusion is the movement of particles from an area of high concentration to an area of low concentration. The molecules move until equilibrium is reached. If a perfume is sprayed on one side of the room, the perfume molecules will eventually spread out all over the room until there are equal concentrations of the molecules throughout the space.

Christopher Thomas (None; )

2006-11-09

149

The report gives results of Phase I of a laboratory assessment of the permeability and diffusion characteristics of Florida concretes. (NOTE: The ability of concrete to permit air flow under pressure (permeability) and the passage of radon gas without any pressure difference (dif...

150

151

ERIC Educational Resources Information Center

The accuracy and bias of estimates of whisker length based on box, line, and midgap plots were examined. For each type of graph, 20 different undergraduates (n=60) viewed 48 single-plot graphs. Whisker-length estimates for box and line plots were more accurate and less biased than those for midgap plots. (TJH)

Stock, William A.; Behrens, John T.

1991-01-01

152

NASA Astrophysics Data System (ADS)

This paper presents the geometric effects of a lateral asymmetric channel (LAC) structure for high-voltage (HV) MOSFETs. The LAC structure was adopted to enhance the device performance by modifying the potential distribution in the channel and reducing the parasitic transistor effect. The LAC structure was realized using a p-body doping region inside the channel for the HV device. The effects of the p-body length were examined. The experiments showed that the p-body length is a key parameter for device optimization considering circuit applications. The HV LAC device with a shorter p-body length showed transconductance (gm) improvement and on-resistance (RON) reduction. The maximized output resistance (rout) was obtained when the p-body length was approximately half of the channel length.

Baek, Ki-Ju; Na, Kee-Yeol; Lee, Young-Jun; Kim, Yeong-Seuk

2015-01-01

153

Characteristics of a highly efficient propeller type small wind turbine with a diffuser

We studied the improved effects a diffuser had on the output power of small wind turbine systems, aiming to introduce these systems to radio relay stations as an independent power supply system. A frustum-shaped diffuser was chosen from an economical standpoint and wind speed distribution. The effect the diffuser's shape had on the wind speed was analyzed by simulation and

Toshio Matsushima; Shinya Takagi; Seiichi Muroyama

2006-01-01

154

Recent experiments involving muscle force measurements over a range of muscle lengths show that effects of botulinum toxin (BTX) are complex e.g., force reduction varies as a function of muscle length. We hypothesized that altered conditions of sarcomeres within active parts of partially paralyzed muscle is responsible for this effect. Using finite element modeling, the aim was to test this hypothesis and to study principles of how partial activation as a consequence of BTX affects muscle mechanics. In order to model the paralyzing effect of BTX, only 50% of the fascicles (most proximal, or middle, or most distal) of the modeled muscle were activated. For all muscle lengths, a vast majority of sarcomeres of these BTX-cases were at higher lengths than identical sarcomeres of the BTX-free muscle. Due to such "longer sarcomere effect", activated muscle parts show an enhanced potential of active force exertion (up to 14.5%). Therefore, a muscle force reduction originating exclusively from the paralyzed muscle fiber populations, is compromised by the changes of active sarcomeres leading to a smaller net force reduction. Moreover, such "compromise to force reduction" varies as a function of muscle length and is a key determinant of muscle length dependence of force reduction caused by BTX. Due to longer sarcomere effect, muscle optimum length tends to shift to a lower muscle length. Muscle fiber-extracellular matrix interactions occurring via their mutual connections along full peripheral fiber lengths (i.e., myofascial force transmission) are central to these effects. Our results may help improving our understanding of mechanisms of how the toxin secondarily affects the muscle mechanically. PMID:24704169

Turkoglu, Ahu N; Huijing, Peter A; Yucesoy, Can A

2014-05-01

155

NSDL National Science Digital Library

Since the advent of the internet, a number of artists and related organizations have become interested in utilizing the web to promulgate new forms of artistic creation and their subsequent dissemination. Supported by the Arts Council of England, these Diffusion eBooks are essentially pdf files that readers can download, print out and make into booklets. As the site suggests, "the Diffusion format challenges conventions of interactivity-blending the physical and the virtual and breaking the dominance of mouse and screen as the primary forms of human computer interaction...the format's aim is to take the reader away from the screen and computer and engage them in the process of production." There are a number of creative booklets available here for visitors, complete with instruction on how to assemble them for the desired effect. For anyone with even a remote interest in the possibilities afforded by this rather curious new form of expression, this website is worth a look.

156

NASA Astrophysics Data System (ADS)

Heat diffusion characteristics of a spherical heat source dispersing magnetite nanoparticles (MNPs) in hydro-gel were investigated numerically and experimentally to evaluate the conditions required for magnetic fluid hyperthermia (MFH). Numerical estimation assumed one-dimensional spherical model and constant heat evolution. Experimental observation was carried out by exposing the magnetite-dispersed hydro-gel in an AC magnetic field with strength and frequency of 3.2 kA/m and 600 kHz, respectively. The temperature distribution observed along the radial axis of the spherical heat source agreed well with the theoretical estimation quantitatively and qualitatively. However, the minor difference existed between the theory and experiment was due to the variation in experimentally determined and actual particle size distributions. Thus, we could conclude that the proposed algorithm could be extended to be used in the estimation of the temperature distribution in intravital conditions with blood flow, metabolism etc., to arrive at biologically significant conclusions helpful for MFH cancer treatment.

Suto, Makoto; Kosukegawa, Hiroyuki; Maruta, Kaoru; Ohta, Makoto; Tohji, Kazuyuki; Jeyadevan, Balachandran

2009-10-01

157

The influencing factors of benzene diffusion fluxes from sand and black soil to atmosphere were investigated using a flux chamber (30.0 cm x 17.5 cm x 29.0 cm). In this study, the benzene diffusion fluxes were estimated by measuring the benzene concentrations both in the headspace of the chamber and in the soils of different layers. The results indicated that the soil water content played an important role in benzene diffusion fluxes. The diffusion flux showed positive correlation with the initial benzene concentration and the benzene dissolution concentration for both soil types. The changes of air flow rate from 300 to 900 mL x min(-1) and temperature from 20 degrees C to 40 degrees C resulted in increases of the benzene diffusion flux. Our study of benzene diffusion fluxes from contaminated soils will be beneficial for the predicting model, and emergency management and precautions. PMID:24640900

Du, Ping; Wang, Shi-Jie; Zhao, Huan-Huan; Wu, Bin; Han, Chun-Mei; Fang, Ji-Dun; Li, Hui-Ying; Hosomi, Masaaki; Li, Fa-Sheng

2013-12-01

158

Molecular dynamics (MD) simulations are used to investigate the diffusion characteristics in DDR, CHA, LTA, ITQ-29, and TSC zeolites that have cavities separated by 8-member ring windows of dimensions in the 3.4–4.6 Å range. These zeolites have potential usage for separation of a variety of mixtures, such as CO{sub 2}/CH{sub 4}, CO{sub 2}/H{sub 2}, H{sub 2}/CH{sub 4}, and propane/propene, relying on a combination of adsorption and diffusion selectivities. The magnitude of self-diffusivities, D{sub i,self}, of the CH{sub 4} is found to have a direct correlation with the size of the window opening, increasing by about two orders of magnitude for a 0.5 Å increase in the window aperture. The diffusion selectivities of CO{sub 2}/CH{sub 4}, and H{sub 2}/CH{sub 4} mixtures were also found to have direct, and strong, correlation, with the window aperture. This opens up the possibility of tuning diffusion selectivities by appropriate choice of the framework structure. Framework flexibility dynamics have also been investigated with the aid of two published force fields for all-silica zeolites. Due to the lattice vibrations there is a distribution of window sizes that varies with time. The diffusivity of CH4 for a flexible lattice was found to correlate with aperture size of the time-averaged window, in precisely the same manner as for fixed framework lattices. This leads to the conclusion that lattice flexibility, per se, has no influence on the magnitude of the diffusivity or diffusion selectivity.

Krishna, Rajamani; van Baten, Jasper M

2011-01-01

159

Effects of MRTI sampling characteristics on estimation of HIFU SAR and tissue thermal diffusivity

While the non-invasive and three-dimensional nature of magnetic-resonance temperature imaging (MRTI) makes it a valuable tool for high-intensity focused ultrasound (HIFU) treatments, random and systematic errors in MRTI measurements may propagate into temperature-based parameter estimates used for pretreatment planning. This study assesses the MRTI effects of zero-mean Gaussian noise (SD=0.0-2.0°C), temporal sampling (tacq=1.0-8.0 s), and spatial averaging (Res=0.5-2.0 mm isotropic) on HIFU temperature measurements and temperature-based estimates of the amplitude and full width half maximum (FWHM) of the HIFU specific absorption rate (SAR) and of tissue thermal diffusivity. The ultrasound beam used in simulations and ex vivo pork loin experiments has lateral and axial FWHM dimensions of 1.4 mm and 7.9 mm respectively. For spatial averaging simulations, beams with lateral FWHM varying from 1.2-2.2 mm are also assessed. Under noisy conditions, parameter estimates are improved by fitting to data from larger voxel regions. Varying the temporal sampling results in minimal changes in measured temperatures (<2% change) and parameter estimates (<5% change). For the HIFU beams studied, a spatial resolution of 1×1×3 mm3 or smaller is required to keep errors in temperature and all estimated parameters less than 10%. By quantifying the errors associated with these sampling characteristics, this work provides researchers with appropriate MRTI conditions for obtaining estimates of parameters essential to pretreatment modeling of HIFU thermal therapies. PMID:24077026

Dillon, C R; Todd, N; Payne, A; Parker, D L; Christensen, D A; Roemer, R B

2013-01-01

160

The primary objective of this paper is to compare the sorption characteristics of hydroxypropylmethylcellulose (HPMC) and hard gelatin (HG) capsules and their ability to protect capsule contents. Moisture sorption and desorption isotherms for empty HPMC and HG capsules have been investigated using dynamic vapour sorption (DVS) at 25°C. All sorption studies were analysed using the Young-Nelson model equations which distinguishes three moisture sorption types: monolayer adsorption moisture, condensation and absorption. Water vapour diffusion coefficients (D), solubility (S) and permeability (P) parameters of the capsule shells were calculated. ANOVA was performed with the Tukey comparison test to analyse the effect of %RH and capsule type on S, P, and D parameters. The moisture uptake of HG capsules were higher than HPMC capsules at all %RH conditions studied. It was found that values of D and P across HPMC capsules were greater than for HG capsules at 0-40 %RH; whereas over the same %RH range S values were higher for HG than for HPMC capsules. S values decreased gradually as the %RH was increased up to 60% RH. To probe the effect of moisture ingress, spray dried lactose was loaded into capsules. Phase evolution was characterised by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and differential scanning calorimetry (DSC). The capsules under investigation are not capable of protecting spray dried lactose from induced solid state changes as a result of moisture uptake. For somewhat less moisture sensitive formulations, HPMC would appear to be a better choice than HG in terms of protection of moisture induced deterioration. PMID:25526672

Barham, Ahmad S; Tewes, Frederic; Healy, Anne Marie

2015-01-30

161

Purpose To evaluate the role of diffusion-weighted imaging in differentiating between hepatic hemangiomas, both typical and atypical, and other hypervascular liver lesions. Methods Retrospective review of 182 hypervascular liver lesions in 117 patients was performed. Diffusion and contrast-enhanced magnetic resonance imaging were performed using a 1.5-T unit. Imaging protocol consisted of T2-weighted fast spin-echo images, breath-hold diffusion-weighted echo-planar images, and breath-hold unenhanced and contrast-enhanced T1-weighted 3-dimensional fat-suppressed spoiled gradient-echo images in the arterial phase (20 seconds) and portal venous phase (60 seconds). Signal intensity changes and apparent diffusion coefficient (ADC) values were evaluated for all lesions. Unpaired t test was used to compare the mean ADC values for different lesions, and statistical significance was set at P < 0.01. Receiver operating characteristic analysis was used to determine the accuracy of diffusion-weighted imaging in differentiating hemangiomas from other hypervascular liver lesions. Results Lesions included typical and atypical hemangioma (n = 38), hepatocellular carcinoma (HCC; n = 58), focal nodular hyperplasia (FNH; n = 22), and neuroendocrine tumor metastasis (NET; n = 64) with a mean tumor size of 5.3 cm. Mean ADC value for hemangioma, HCC, FNH, and NET was 2.29 × 10-3, 1.55 × 10-3, 1.65 × 10-3, and 1.43 × 10-3 mm2/s, respectively. There was a statistically significant difference in the ADC value of hemangioma compared with that of FNH (P < 0.001), HCC (P < 0.001), and NET (P < 0.001), respectively. The area under the receiver operating characteristic curve was 0.91. Conclusions Diffusion-weighted magnetic resonance imaging and ADC maps can provide rapid quantifiable information to differentiate typical and atypical hemangiomas from other hypervascular liver lesions. PMID:18830105

Vossen, Josephina A.; Buijs, Manon; Liapi, Eleni; Eng, John; Bluemke, David A.; Kamel, Ihab R.

2009-01-01

162

Chao-Hsiun Tang, PhD Background: Case payment has been implemented since the beginning of Taiwan's National Health Insurance Program in 1995. This study selected patients undergoing a vaginal delivery to explore the relationships between maternal length of stay (LOS) and hospital characteristics under the case-payment sys- tem in Taiwan. Methods: The National Health Insurance Research Database of 1999 from Taiwan's National

Herng-Ching Lin; Yu-Chi Tung; Chu-Chieh Chen

163

A study on the characteristics of the diffusion layer thickness and porosity of the PEMFC

In the preparation of electrodes for the proton exchange membrane (PEMFC), the effect of the fabrication method and the thickness of the gas diffusion layer and the impregnation method of Nafion solution on the cell performance was investigated, and unit cell tests were performed. The gas diffusion layer was prepared by rolling, spraying, and screen printing methods, and Nafion solution

Han-Kyu Lee; Jong-Ho Park; Do-Young Kim; Tae-Hee Lee

2004-01-01

164

Within an anonymousregion of honey bee DNA (locus227) diges ted with AluI, informative restriction fragment-length polymorphisms (RFLP) were found in Southern blots with a cloned honey bee DNA probe. The probe was subcloned, so that smaller sections of the locus could be analyzed with the polymerase chain reaction (PCR). Further screening of these ampliÞed sections revealed additional useful RFLPs with

Alonso Suazo; Myeong-lyeol Lee; H. Glenn Hall

2002-01-01

165

A retrospective study using maternal and birth statistics from an open, captive rhesus macaque colony was done to determine the effects of parity, exposure to simian retrovirus (SRV), housing, maternal parity, and maternal birth weight on infant birth weight, viability and gestation length. Retrospective colony statistics for a 23-y period indicated that birth weight, but not gestation length, differed between genders. Adjusted mean birth weights were higher in nonviable infants. Mothers positive for SRV had shorter gestations, but SRV exposure did not affect neonatal birth weights or viability. Infants born in cages had longer gestations than did those born in pens, but neither birth weight nor viability differed between these groups. Maternal birth weight did not correlate with infant birth weight but positively correlated with gestation length. Parity was correlated with birth weight and decreased viability. Increased parity of the mother was associated with higher birth weight of the infant. A transgenerational trend toward increasing birth weight was noted. The birth statistics of this colony were consistent with those of other macaque colonies. Unlike findings for humans, maternal birth weight had little predictive value for infant outcomes in rhesus macaques. Nonviable rhesus infants had higher birth weights, unlike their human counterparts, perhaps due to gestational diabetes occurring in a sedentary caged population. Similar to the situation for humans, multiparity had a protective effect on infant viability in rhesus macaques. PMID:19149417

Hopper, Kelly J; Capozzi, Denise K; Newsome, Joseph T

2008-01-01

166

Background Spasticity is an important complication after stroke, especially in the anti-gravity muscles, i.e. lower limb extensors. However the contribution of hyperexcitable muscle spindle reflex loops to gait impairments after stroke is often disputed. In this study a neuro-musculoskeletal model was developed to investigate the contribution of an increased length and velocity feedback and altered reflex modulation patterns to hemiparetic gait deficits. Methods A musculoskeletal model was extended with a muscle spindle model providing real-time length and velocity feedback of gastrocnemius, soleus, vasti and rectus femoris during a forward dynamic simulation (neural control model). By using a healthy subject’s base muscle excitations, in combination with increased feedback gains and altered reflex modulation patterns, the effect on kinematics was simulated. A foot-ground contact model was added to account for the interaction effect between the changed kinematics and the ground. The qualitative effect i.e. the directional effect and the specific gait phases where the effect is present, on the joint kinematics was then compared with hemiparetic gait deviations reported in the literature. Results Our results show that increased feedback in combination with altered reflex modulation patterns of soleus, vasti and rectus femoris muscle can contribute to excessive ankle plantarflexion/inadequate dorsiflexion, knee hyperextension/inadequate flexion and increased hip extension/inadequate flexion during dedicated gait cycle phases. Increased feedback of gastrocnemius can also contribute to excessive plantarflexion/inadequate dorsiflexion, however in combination with excessive knee and hip flexion. Increased length/velocity feedback can therefore contribute to two types of gait deviations, which are both in accordance with previously reported gait deviations in hemiparetic patients. Furthermore altered modulation patterns, in particular the reduced suppression of the muscle spindle feedback during swing, can contribute largely to an increased plantarflexion and knee extension during the swing phase and consequently to hampered toe clearance. Conclusions Our results support the idea that hyperexcitability of length and velocity feedback pathways, especially in combination with altered reflex modulation patterns, can contribute to deviations in hemiparetic gait. Surprisingly, our results showed only subtle temporal differences between length and velocity feedback. Therefore, we cannot attribute the effects seen in kinematics to one specific type of feedback. PMID:24885302

2014-01-01

167

Magnetic Resonance Diffusion Characteristics of Histologically Defined Prostate Cancer in Humans

The contrast provided by diffusion-sensitive magnetic resonance offers the promise of improved tumor localization in organ-confined human prostate cancer (PCa). Diffusion tensor imaging (DTI) measurements of PCa were performed in vivo, in patients undergoing radical prostatectomy, and later, ex vivo, in the same patients’ prostatectomy specimens. The imaging data were coregistered to histological sections of the prostatectomy specimens, thereby enabling unambiguous characterization of diffusion parameters in cancerous and benign tissues. Increased cellularity, and hence decreased luminal spaces, in peripheral zone PCa led to approximately 40% and 50% apparent diffusion policy (ADC) decrease compared with benign peripheral zone tissues in vivo and ex vivo, respectively. In contrast, no significant diffusion anisotropy differences were observed between the cancerous and noncancerous peripheral zone tissues. However, the dense fibromuscular tissues in prostate, such as stromal tissues in benign prostatic hyperplasia in central gland, exhibited high diffusion anisotropy. A tissue classification method is proposed to combine DTI and T2-weighted image contrasts that may provide improved specificity of PCa detection over T2-weighted imaging alone. PCa identified in volume rendered MR images qualitatively correlates well with histologically determined PCa foci. PMID:19215051

Xu, Junqian; Humphrey, Peter A.; Kibel, Adam S.; Snyder, Abraham Z.; Narra, Vamsidhar R.; Ackerman, Joseph J.H.; Song, Sheng-Kwei

2010-01-01

168

NASA Astrophysics Data System (ADS)

NbN films were prepared by radio frequency reactive magnetron sputtering and then employed as diffusion barriers between Cu and Si. The microstructure of the NbN films was an assembly of very small columnar crystallites with a cubic structure. To investigate the properties as diffusion barriers, we performed metallurgical reactions of Cu/NbN0.8/Si, Cu/Nb/Si and Cu/TaN0.7/Si for comparisons. The sheet resistance increased dramatically after annealing above 750°C for Cu/NbN0.80/Si, and above 500°C for both Cu/Nb/Si and Cu/TaN0.7/Si. The interfaces were deteriorated seriously and formation of Cu3Si was observed when the sheet resistance was significantly increased. The diffusion coefficient of Cu in NbN barrier films was estimated by using the change of resistance (? R s / R s %). Compared with TaN0.7, NbN0.8 films possess larger grain size and lower Cu diffusion coefficient. Our results suggest that the NbN film can be used as a diffusion barrier for Cu metallization as compared to the well-known TaN film.

Huang, Cheng-Lin; Lai, Chih-Huang; Tsai, Po-Hao; Huang, Hsing-An; Lin, Jing-Cheng; Lee, Chiapyng

2013-09-01

169

A study on the characteristics of the diffusion layer thickness and porosity of the PEMFC

NASA Astrophysics Data System (ADS)

In the preparation of electrodes for the proton exchange membrane (PEMFC), the effect of the fabrication method and the thickness of the gas diffusion layer and the impregnation method of Nafion solution on the cell performance was investigated, and unit cell tests were performed. The gas diffusion layer was prepared by rolling, spraying, and screen printing methods, and Nafion solution was impregnated using spraying and brushing methods. The diffusion layer in a PEMFC consists of a thin layer of carbon black mixed with polytetrafluoroethylene (PTFE) that is coated onto a sheet of macro-porous carbon backing cloth. The effects of different fabrication methods and thicknesses of gas diffusion layer are discussed in the light of porosimetry and I- V polarization curves and variables related to the electrode analyzed by numerical simulation. The spraying method proved to be more profitable for cell performance than the brushing method for the impregnation of Nafion solution because it reduced the charge transfer resistance and extended the three-phase region. The goals of this work are to find the optimum thickness of the gas diffusion layer and to undertake an analysis of the system.

Lee, Han-Kyu; Park, Jong-Ho; Kim, Do-Young; Lee, Tae-Hee

170

NASA Astrophysics Data System (ADS)

Based on the experimental observations using a liquid-gas coaxial injector with fairly dense liquid injection, an empirical calculation model of the breakup length of a liquid jet was derived. It is based on the one-dimensional momentum conservation equation for two-phase flow, as well as on the critical Eötvös number, which was derived experimentally by the author in a previous study. This model was applied to evaluate the local stripping rate of the liquid mass at the interaction surface between a liquid and a gas, and was applied to calculate the size of the formed droplets. Comparisons of the mean droplet size, distribution histogram of the size, and breakup length of the liquid jet were made with experimental data. This calculation model was also applied to evaluate the characteristics of the rocket injectors chosen as candidates for the LE-5, the liquid oxygen/hydrogen engine of the second stage of the Japanese H-1 launcher.

Yatsuyanagi, Nobuyuki

171

Materials evaluation of diffusion bonded steel bar and its impact characteristics

When we apply non-destructive test for evaluating the soundness of weld joints it is necessary to know the mechanical properties of the joints by destructive test. In this paper we tried to obtain the correlation between the data by ultrasonic C-scope method and the absorbed energy by Charpy impact test for diffusion bonded steel bars. The surface roughness of specimens

Mitsuaki Katoh; Kazumasa Nishio; Tomiko Yamaguchi

2002-01-01

172

Rapid growth in finding new applications for manufactured nanomaterials (MNM) has recently been accompanied by awareness about their related adverse toxicological and environmental impacts. Due to their intrinsic nature, measuring available concentrations of MNMs in the environment is a major challenge. This research is a launching point toward filling this gap, as it presents the potential of the well-established diffusive gradients in thin films (DGT) technique to determine MNMs concentrations in situ. Two binding layers commonly used in DGT devices were shown to be able to bind ZnO nanoparticles (ZnO NPs). The use of different types of diffusive layers demonstrated the critical role of their pore size for selective function of the DGT devices. The ZnO NPs can pass through the open pore diffusive layer used in standard DGT devices and be retained by the binding resin layer. However, the diffusion of ZnO NPs can be prevented when a 1000 MWCO (molecular weight cut off) dialysis membrane is placed in the front of the diffusive gel layer. A combination of two or more DGT devices with known diffusive layer properties should enable deduction of concentrations of available ZnO NPs in the environment. Unlike metal ions, determining diffusion coefficient values for ZnO NPs is challenging and greatly affected by shape, morphology, and solution-induced changes of the particles. Attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) demonstrated that retention of ZnO NPs by Chelex and Metsorb binding layers occurs through chemisorption. The superior uptake kinetic for Chelex indicates that it is a better candidate for further development of DGT devices to measure ZnO NPs. These initial results are promising and important for further developing the DGT technique to measure available concentrations of manufactured nanomaterials in the different environmental media (waters, soils, and sediments). Further experiments investigating the effects of pH, ionic strength, and solution chemistry on the performance of DGT for measuring MNM concentrations are needed. PMID:24831848

Pouran, Hamid M; Martin, Francis L; Zhang, Hao

2014-06-17

173

Anomalous diffusion in microchannel under magnetic field

NASA Astrophysics Data System (ADS)

We have performed experiments to characterize the diffusion of an aqueous ferrofluid in water submitted to a magnetic field. Experiments were carried out in a microfluidic device to take advantage of the low Reynolds number flow conditions at the microscale. We have measured the concentration profile across the microchannel, which defines a characteristic length of the diffusion zone. This characteristic length varies as the square-root of the distance from the entrance of the channel divided by the mean velocity, which evidences a diffusive regime. However the application of a magnetic field is shown to inhibit the diffusion, with an increasing efficiency as the field intensity increases. We propose an explanation of this effect based on the anisotr opy of the diffusion coefficient due to the magnetic field. This hypothesis is corroborated by numerical simulations.

Derec, Caroline; Smerlak, Matteo; Servais, Jacques; Bacri, Jean-Claude

174

Homocysteine level can lead to adverse effects on the brain white matter through endothelial dysfunction, microstructural inflammation, and neurotoxin effects. Despite previously observed associations between elevated homocysteine and macroscopic structural brain changes, it is still unknown whether microstructural associations of homocysteine on brain tissue properties can be observed in healthy subjects with routine MRI. To this end, we investigated potential relationships between homocysteine levels and microstructural measures computed with diffusion tensor imaging (DTI) in a cohort of 338 healthy participants. Significant positive correlations were observed between homocysteine levels and diffusivity measures in the bilateral temporal WM, the brainstem, and the bilateral cerebellar peduncle. This is the first study demonstrating that DTI is sufficiently sensitive to relate microstructural WM properties to homocysteine levels in healthy subjects. PMID:25693199

Hsu, Jung-Lung; Chen, Wei-Hung; Bai, Chyi-Huey; Leu, Jyu-Gang; Hsu, Chien-Yeh; Viergever, Max A.; Leemans, Alexander

2015-01-01

175

This study examined how content characteristics of antitobacco messages affect smokers’ selective exposure to and social sharing of those messages. Results from an experiment revealed that content features predicting smokers’ selection of antismoking messages are different from those predicting whether those messages are shared. Antismoking messages smokers tend to select are characterized by strong arguments (odds ratio = 2.02, P = .02) and positive sentiments (odds ratio = 3.08, P = .03). Once selected, the messages more likely to be retransmitted by smokers were those with novel arguments (B = .83, P = .002) and positive sentiments (B = 1.65, P = .005). This research adds to the literature about the content characteristics driving the social diffusion of antitobacco messages and contributes to our understanding of the role of persuasive messages about smoking cessation in the emerging public communication environment. PMID:24395989

2013-01-01

176

ObservationalcCharacteristics of a secondary magnetic island in an ion diffusion region

NASA Astrophysics Data System (ADS)

Numerical simulations have predicted that an extended current sheet may be unstable to secondary magnetic islands in the vicinity of the X line, and these islands can dramatically influence the reconnection rate. We present the first evidence of such a secondary island near the center of an ion diffusion region, which is consistent with the action of the secondary island instability occurring in the vicinity of the X line. In the island, the electron density peaks in the outer region while the dip is in the core region with a strong core magnetic field. A strong electron beam parallel to the magnetic field, as well as an obvious current antiparallel to the magnetic field with density up to ~ 40nA/m2 is observed in the outer region of the island. This suggests that the strong core magnetic field inside the island is generated by the electron beam and then the antiparallel current in the outer region of the island. The electron density dip in the core region is formed due to the existing strong core field which expels electrons out of the core region. The electron flat-top distributions are detected in the ion diffusion region except the core region of the island, and the shoulder energy range of the flat-top distributions is from 100eV to 4keV. An enhancement of the energetic electron flux up to 200keV is found in the ion diffusion region, and a further increase of energetic electron fluxes is observed inside the island. Waves at the lower hybrid frequency are intensified in the ion diffusion region, while the intensification is strong in the outer region of the island and becomes very weak in the core region. References: 1. Wang, R. S., Q. M. Lu, A. M. Du, and S. Wang, PRL, 104,175003, 2010. 2. Wang, R. S., Q. M. Lu, and X. Li et al., JGR, 2010, in press.

Lu, Q.; Wang, R.; Huang, C.; Wang, S.

2010-12-01

177

The new technique of diffusive gradients in thin films (DGT) has been used for the first time with a general cation exchange resin (AG50W-X8) as the binding agent. Its use for the measurement of Cs and Sr has been systematically investigated. Individual experiments showed that resin embedded in polyacrylamide gel efficiently removed Cs and Sr from solution. Cs and Sr

Ling-Yun Chang; William Davison; Hao Zhang; Mike Kelly

1998-01-01

178

Scale-Up of flat plate photobioreactors considering diffuse and direct light characteristics.

This study investigates the scaling of photobioreactor productivity based on the growth of Nannochloropsis salina incorporating the effects of direct and diffuse light. The scaling and optimization of photobioreactor geometry was analyzed by determining the growth response of a small-scale system designed to represent a core sample of a large-scale photobioreactor. The small-scale test apparatus was operated at a variety of light intensities on a batch time scale to generate a photosynthetic irradiance (PI) growth dataset, ultimately used to inform a PI growth model. The validation of the scalability of the PI growth model to predict productivity in large-scale systems was done by comparison with experimental growth data collected from two geometrically different large-scale photobioreactors operated at a variety of light intensities. For direct comparison, the small-scale and large-scale experimental systems presented were operated similarly and in such a way to incorporate cultivation relevant time scales, light intensities, mixing, and nutrient loads. Validation of the scalability of the PI growth model enables the critical evaluation of different photobioreactor geometries and design optimization incorporating growth effects from diffuse and direct light. Discussion focuses on the application of the PI growth model to assess the effect of diffuse light growth compared to direct light growth for the evaluation of photobioreactors followed by the use of the model for photobioreactor geometry optimization on the metric of areal productivity. PMID:21915850

Quinn, Jason C; Turner, Chris W; Bradley, Thomas H

2012-02-01

179

Abstract Traumatic brain injury (TBI) is a frequent and clinically highly heterogeneous neurological disorder with large socioeconomic consequences. TBI severity classification, based on the hospital admission Glasgow Coma Scale (GCS) score, ranges from mild (GCS 13–15) and moderate (GCS 9–12) to severe (GCS ? 8). The GCS reflects the risk of dying from TBI, which is low after mild (?1%), intermediate after moderate (up to 15%) and high (up to 40%) after severe TBI. Intracranial damage can be focal, such as epidural and subdural haematomas and parenchymal contusions, or diffuse, for example traumatic axonal injury and diffuse cerebral oedema, although this distinction is somewhat arbitrary. Study of the cellular and molecular post-traumatic processes is essential for the understanding of TBI pathophysiology but even more to find therapeutic targets for the development of neuroprotective drugs to be eventually used in human beings. To date, studies in vitro and in vivo, mainly in animals but also in human beings, are unravelling the pathological TBI mechanisms at high pace. Nevertheless, TBI pathophysiology is all but completely elucidated. Neuroprotective treatment studies in human beings have been disappointing thus far and have not resulted in commonly accepted drugs. This review presents an overview on the clinical aspects and the pathophysiology of focal and diffuse TBI, and it highlights several acknowledged important events that occur on molecular and cellular level after TBI. PMID:20738443

Andriessen, Teuntje M J C; Jacobs, Bram; Vos, Pieter E

2010-01-01

180

The generation of dendrimers based on poly(propylene imine) with CN end groups [DAB–dend–(CN)\\u000a x\\u000a ] and with palmitoyl end groups [DAB–dend–(C15)\\u000a x\\u000a ] was studied by methods of translational diffusion and viscometry. The volumes of the DAB–dend–(CN)\\u000a x\\u000a and DAB–dend–(C15)\\u000a x\\u000a dendrimers and the previously studied DAB–dend–(lacto)\\u000a x\\u000a dendrimer were compared to evaluate the volumes of the end groups in

G. M. Pavlov; E. V. Korneeva; E. W. Meijer

2002-01-01

181

NASA Astrophysics Data System (ADS)

We develop a technique for probing the harmonic measure of a diffusion-limited-aggregation (DLA) cluster surface with variable-size particles and generate 1000 clusters with 50×106 particles using an original off-lattice killing-free algorithm. Taking, in sequence, the limit of the vanishing size of the probing particles and then sending the growing cluster size to infinity, we achieve unprecedented accuracy in determining the fractal dimension D=1.7100(2) crucial to the characterization of the geometric properties of DLA clusters.

Menshutin, A. Yu.; Shchur, L. N.; Vinokur, V. M.

2007-01-01

182

Characteristics of diffusion-tensor imaging for healthy adult rhesus monkey brains

Diffusion-tensor imaging can be used to observe the microstructure of brain tissue. Fractional sotropy reflects the integrity of white matter fibers. Fractional anisotropy of a young adult brain is low in gray matter, high in white matter, and highest in the splenium of the corpus callosum. Thus, we selected the anterior and posterior limbs of the internal capsule, head of the caudate nucleus, semioval center, thalamus, and corpus callosum (splenium and genu) as regions of interest when using diffusion-tensor imaging to observe fractional anisotropy of major white matter fiber tracts and the deep gray matter of healthy rhesus monkeys aged 4–8 years. Results showed no laterality ferences in fractional anisotropy values. Fractional anisotropy values were low in the head of date nucleus and thalamus in gray matter. Fractional anisotropy values were highest in the splenium of corpus callosum in the white matter, followed by genu of the corpus callosum and the posterior limb of the internal capsule. Fractional anisotropy values were lowest in the semioval center and posterior limb of internal capsule. These results suggest that fractional anisotropy values in major white matter fibers and the deep gray matter of 4–8-year-old rhesus monkeys are similar to those of healthy young people. PMID:25206616

Zhao, Xinxiang; Pu, Jun; Fan, Yaodong; Niu, Xiaoqun; Yu, Danping; Zhang, Yanglin

2013-01-01

183

Interface characteristics in diffusion bonding of Fe3Al with Cr18-Ni8 stainless steel.

Fe3Al and Cr18-Ni8 stainless steel were diffusion-bonded in vacuum and a Fe3Al/Cr18-Ni8 interface with reaction layer was formed. Microstructure in the reaction layer at Fe3Al/Cr18-Ni8 interface was analyzed by means of scanning electron microscope (SEM) and electron probe micro-analyzer (EPMA). The growth of reaction layer with heating temperature (T) and holding time (t) was researched. The results indicate that FeAl, Fe3Al, Ni3Al, and alpha-Fe (Al) solid solution are formed in the reaction layer. These phases are favorable to promote the element diffusion and to accelerate the formation of the reaction layer at Fe3Al/Cr18-Ni8 interface. The growth of reaction layer obeys the parabolic law and its thickness (X) is expressed by X2 = 7.5 x 10(-4)exp(-83.59/RT)(t - t0). PMID:15797414

Wang, Juan; Li, Yajiang; Yin, Yansheng

2005-05-01

184

NASA Astrophysics Data System (ADS)

A single-wavelength Brillouin laser is demonstrated by using a 3-m-long erbium doped fiber (EDF) in a ring cavity. The EDF is used to provide both nonlinear and linear gains to generate a stimulated Brillouin scattering (SBS) and to amplify the generated SBS, respectively. The Brillouin erbium fiber laser (BEFL) operates at 1561.5 nm, where the operating wavelength is up-shifted by 0.08nm from the Brillouin pump. The operation wavelength is also tunable within 1560.6-1562.6 nm. The BEFL also shows a self-pulsing characteristic with repetition of 66.7 kHz when the BP is set around the threshold pump power of 13mW. Compared to the conventional Brillouin fiber laser with a long cavity length, the proposed BEFL exhibits a significantly lower amplitude of pulse. This laser has many potential applications, such as in optical communication and sensors.

Zarei, A.; Z. R. R. Rosdin, R.; M. Ali, N.; H., Ahmad; W. Harun, S.

2014-05-01

185

Diffuse mesenterial sclerosis: a characteristic feature of chronic small-bowel allograft rejection.

Chronic rejection is the major cause of late intestinal allograft dysfunction. The aim of this study was to analyze in detail the histopathological features of chronic rejection in the ACI-to-Lewis rat model of intestinal transplantation. Chronic rejection was achieved in orthotopic small-bowel allografts (ACI-Lewis) by limited immunosuppression with cyclosporin A (CyA). Isogeneic transplants (ACI-ACI) as well as native bowels (ACI) with and without immunosuppression served as controls. Bowels were removed together with the mesenteries 90 days postoperatively and analyzed using sections stained with hematoxylin and eosin as well as Masson's trichrome. The slides were coded, randomized and analyzed by grading of histological abnormalities. The most striking alterations of the allografts were noticed in the mesenteries exhibiting an extensive infiltration by mononuclear cells accompanied by a progressive diffuse fibrosis with shrinking of the mesenteries. These changes were most pronounced in the perivascular areas of the mesenteric arteriae and venae rectae. Three of five allografts showed vasculitis with myointimal proliferation of the arteriae rectae. Focally, there was spill-over of the inflammatory cells onto the intestinal muscularis propria. The mucosa of the allografts showed mild blunting, lymphocytic infiltration of the crypt epithelium and increased crypt cell apoptoses. The submucosa was unaffected, and there were no detectable abnormalities of the enteric ganglion cells. The present data support the view that chronic rejection of intestinal allografts is characterized by a diffuse sclerosing mesenteritis which may significantly contribute to late graft dysfunction. The present model may be useful to study the pathomechanisms of this inflammatory fibrosing process. PMID:12536314

Klaus, Alexander; Margreiter, Raimund; Pernthaler, Heinz; Klima, Günther; Offner, Felix A

2003-01-01

186

NASA Technical Reports Server (NTRS)

A study of the flow strength, creep resistance and diffusion welding characteristics of the titanium alloy Ti-6Al-2Nb-1Ta-0.8Mo was conducted. Two mill-processed forms of this alloy were examined. The forged material was essentially processed above the beta transus while the rolled form was subjected to considerable work below the beta transus. Between 1150 and 1250 K, the forged material was stronger and more creep resistant than the rolled alloy. Both forms exhibit superplastic characteristics in this temperature range. Strain measurements during diffusion welding experiments at 1200 K reveal that weld interfaces have no measurable effect on the overall creep deformation. Significant deformation appears to be necessary to produce a quality diffusion weld between superplastic materials. A 'soft' interlayer inserted between faying surfaces would seemingly allow manufacture of quality diffusion welds with little overall deformation.

Whittenberger, J. D.; Moore, T. J.

1977-01-01

187

NASA Astrophysics Data System (ADS)

The drain current vs gate voltage (ID-VG) and drain current vs drain voltage (ID-VD) characteristics of ferroelectric gate-all-around Si nanowire transistors are derived using the drift/diffusion transport theory. It is pointed out that the nonsaturated polarization in the ferroelectric film, which occurs near the drain region in the channel owing to the influence of the applied drain voltage, plays an important role in the calculation of the drain current as well as the polarization near the source region, and a graphical method using analytical expressions for the minor polarization hysteresis loops is presented to calculate the mobile charge density in the nanowire. By numerical analysis, the gate voltage range suitable for memory operation is determined in Si nanowire transistors with ferroelectric poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] gate films.

Ibata, Masakazu; Ohmi, Shun-ichiro; Ishiwara, Hiroshi

2012-03-01

188

We report the neuroimaging findings of a 26-year-old female patient with a biopsy-proven dysembryoplastic neuroepithelial tumor (DNET). DNETs are an uncommon, usually benign, glial-neural cortical neoplasm of children and young adults who typically present with intractable seizures. DNETs may occur in any region of the supratentorial cortex, but have a predilection for the temporal lobes. Accurate neuroimaging diagnosis is essential since patients with DNET benefit from complete resection. However, accurate differentiation from other cortical lesions may be challenging. Typical conventional Magnetic Resonance Imaging (MRI) features can help in the differentiation from other similar cortical tumors. Diffusion tensor imaging can also provide important additional diagnostic information regarding the degree of involvement of adjacent parenchyma and white matter tracts. In this case, tractography and fractional anisotropy maps demonstrated that fiber tracts surrounding the lesion were displaced, but fiber integrity was maintained, which is more suggestive of a DNET rather than a more aggressive neoplasm. Accurate identification of DNETs is essential for the purpose of rendering a timely diagnosis and start appropriate treatment. PMID:24421925

Paudel, Kalyan; Borofsky, Samuel; Jones, Robert V.; Levy, Lucien M.

2013-01-01

189

NASA Astrophysics Data System (ADS)

In seismology numerous observations indicate a relationship between pore pressure in the Earth's crust and the occurrence of earthquakes. In this paper we study aftershock sequences in the South Iceland Seismic Zone (SISZ), where poroelastic rebound has been observed in the post-seismic period of two M 6.5 earthquakes in 2000 June. We analyse characteristic features in the spatiotemporal distribution of aftershocks following the two M 6.5 2000 June 17 and 21 earthquakes and a M 4.5 earthquake on 1999 September 27. These features include an initial pre-power-law decay period characterized by an initially finite aftershock rate, a subsequent power-law decay interrupted by distinct and temporary rate increases and decreases as well as increased clustering of aftershocks with time in the main shock fault zones. Extending the analysis to a M 3.2 aftershock sequence in the same region confirms an increase in the duration of the initial pre-power-law decay period with increasing main shock magnitude. We find, from the return time of aftershock magnitudes to the long-term completeness level, that the initial pre-power-law decay period and its durational dependence on main shock magnitude may not only represent incompleteness artefacts but may also reflect the physics of the aftershock process in the SISZ. Based on pore pressure diffusion modelling, we interpret the origin of the observed SISZ aftershock features in terms of a spatially non-linear coseismic influence of the main shock on stresses in the surrounding crust and poroelastic adjustment of stresses and pore pressures during main shock initiated diffusion processes. In a discussion of alternative interpretations, we find that rate and state friction and dynamically propagating crack models, the statistical ETAS model, afterslip models, viscoelastic relaxation of the lower crust and upper mantle and a recently proposed dependence on the crustal state of stress all appear inconsistent with at least one of the characteristic spatiotemporal features of the studied SISZ aftershock sequences. We conclude that these features constitute strong evidence for pore pressure effects in aftershock triggering within the SISZ and recommend that poroelastic adjustment of stresses is taken into account in modelling of main shock initiated pore pressure diffusion.

Lindman, Mattias; Lund, Björn; Roberts, Roland

2010-12-01

190

A majority of traumatic brain injuries (TBI) in motor vehicle crashes and sporting environments are mild and caused by high-rate acceleration of the head. For injuries caused by rotational acceleration, both magnitude and duration of the acceleration pulse were shown to influence injury outcomes. This study incorporated a unique rodent model of rotational acceleration-induced mild TBI (mTBI) to quantify independent effects of magnitude and duration on behavioral and neuroimaging outcomes. Ninety-two Sprague-Dawley rats were exposed to head rotational acceleration at peak magnitudes of 214 or 350 krad/s(2) and acceleration pulse durations of 1.6 or 3.4 ms in a full factorial design. Rats underwent a series of behavioral tests including the Composite Neuroscore (CN), Elevated Plus Maze (EPM), and Morris Water Maze (MWM). Ex vivo diffusion tensor imaging (DTI) of the fixed brains was conducted to assess the effects of rotational injury on brain microstructure as revealed by the parameter fractional anisotropy (FA). While the injury did not cause significant locomotor or cognitive deficits measured with the CN and MWM, respectively, a main effect of duration was consistently observed for the EPM. Increased duration caused significantly greater activity and exploratory behaviors measured as open arm time and number of arm changes. DTI demonstrated significant effects of both magnitude and duration, with the FA of the amygdala related to both the magnitude and duration. Increased duration also caused FA changes at the interface of gray and white matter. Collectively, the findings demonstrate that the consequences of rotational acceleration mTBI were more closely associated with duration of the rotational acceleration impulse, which is often neglected as an independent factor, and highlight the need for animal models of TBI with strong biomechanical foundations to associate behavioral outcomes with brain microstructure. PMID:25344352

Stemper, Brian D; Shah, Alok S; Pintar, Frank A; McCrea, Michael; Kurpad, Shekar N; Glavaski-Joksimovic, Aleksandra; Olsen, Christopher; Budde, Matthew D

2014-10-25

191

Since the discovery of surfactant-templated silica by Mobil scientists in 1992, mesostructured silica has been synthesized in various forms including thin films, powders, particles, and fibers. In general, mesostructured silica has potential applications, such as in separation, catalysis, sensors, and fluidic microsystems. In respect to these potential applications, mesostructured silica in the form of thin films is perhaps one of the most promising candidates. The preparation of mesostructured silica films through preferential solvent evaporation-induced self-assembly (EISA) has recently received much attention in the laboratories. However, no amphiphile/silica films with reverse mesophases have ever been made through this EISA procedure. Furthermore, templates employed to date have been either surfactants or poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) triblock copolymers, such as pluronic P-123, both of which are water-soluble and alcohol-soluble. Due to their relatively low molecular weight, the templated silica films with mesoscopic order have been limited to relatively small characteristic length scales. In the present communication, the authors report a novel synthetic method to prepare mesostructured amphiphilic/silica films with regular and reverse mesophases of large characteristic length scales. This method involves evaporation-induced self-assembly (EISA) of amphiphilic polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymers. In the present study, the PS-b-PEO diblocks are denoted as, for example, PS(215)-b-PEO(100), showing that this particular sample contains 215 S repeat units and 100 EO repeat units. This PS(215)-b-PEO(100) diblock possesses high molecular weight and does not directly mix with water or alcohol. To the authors knowledge, no studies have reported the use of water-insoluble and alcohol-insoluble amphiphilic diblocks as structure-directing agents in the synthesis of mesostructured silica films through EISA. It is believed that the present system is the first to yield amphiphile/silica films with regular and reverse mesophases, as well as curved multi-bilayer mesostructures, through EISA. The ready formation of the diblock/silica films with multi-bilayer vesicular mesostructures is discussed.

YU,KUI; BRINKER,C. JEFFREY; HURD,ALAN J.; EISENBERG,ADI

2000-11-22

192

All adult BALB/c mice immunized with hen egg white lysozyme (HEL) or its dominant determinant, peptide (p)106–116, mount a T cell response using a “public” V?8.2J?1.5 T cell clone. Neonatal exposure to tolerance-inducing doses of antigen can drastically diminish responsiveness in the draining lymph nodes but not in the spleens of animals challenged as adults with the cognate antigen. To determine the role of T cell deletion or anergy within the mechanisms of observed neonatal “tolerance,” we treated neonatal BALB/c mice with HEL and directly followed the characteristic public clone using complementarity determining region 3 length T cell repertoire analysis. Our results confirm that despite intraperitoneal injection of neonates with a high dose of HEL emulsified in incomplete Freund's adjuvant, a strong splenic proliferative response to HEL was observed upon recall. However, the adult splenic T cell response of these neonatally treated mice lacked the usual V?8.2J?1.5 public clone characteristic of HEL-primed BALB/c mice. After challenge with HEL–complete Freund's adjuvant as adults, immunoglobulin (Ig)G2a isotype antibody was drastically reduced, and IgG1 was found to be the predominant anti-HEL IgG isotype expressed, indicating a deviation of cytokine response toward T helper type 2. 5-wk-old mice, nasally instilled with tolerogenic doses of HEL p106–116, also showed significant inhibition of this public T cell expansion. These results demonstrate that during neonatal and adult nasal tolerance induction, deletion/anergy removes the public clone, exposing a response of similar specificity but that is characterized by the T helper type 2 phenotype and a splenic residence. PMID:10684861

Maverakis, Emanual; Beech, Jonathan T.; Wilson, Stephen S.; Quinn, Anthony; Pedersen, Brian; Sercarz, Eli E.

2000-01-01

193

The amino- and carboxyl-terminal properties of the amyloid-beta (A beta) peptides deposited in diffuse plaques, one of the earliest forms of A beta deposition, were examined in the brains of patients with Down's syndrome and Alzheimer's disease and in aged individuals without dementia by immunocytochemistry. This was done using a panel of antibodies that specifically discriminate the terminal structures and modifications at the amino and carboxyl termini of A beta. Diffuse plaques found in the cerebral and cerebellar cortex, neostriatum, and hypothalamus of Down's syndrome, Alzheimer's disease, and nondemented brains were strongly immunoreactive for A beta N1(L-Asp), A beta N1(L-isoAsp), A beta N1(D-Asp), and A beta N3(pyroGlu) and weakly positive for A beta N11(pyroGlu) and A beta N17(Leu). Diffuse plaques also were positive for A beta 42(43) but negative for A beta 40, using carboxyl-terminal-specific anti-A beta antibodies. These results suggest that the amino termini of the A beta species that initially deposit in diffuse plaques begin with A beta N1(Asp) with or without structural modifications (isomerization and racemization), as well as with A beta N3(pyroGlu), and terminate preferentially at A beta 42(43) rather than A beta 40. Images Figure 2 Figure 3 PMID:8952519

Iwatsubo, T.; Saido, T. C.; Mann, D. M.; Lee, V. M.; Trojanowski, J. Q.

1996-01-01

194

NASA Technical Reports Server (NTRS)

An experimental investigation of the aerodynamic noise and flow field characteristics of internal-flow jet-augmented flap configurations (abbreviated by the term jet flap throughout the study) is presented. The first part is a parametric study of the influence of the Mach number (subsonic range only), the slot nozzle aspect ratio and the flap length on the overall radiated sound power and the spectral composition of the jet noise, as measured in a reverberation chamber. In the second part, mean and fluctuating velocity profiles, spectra of the fluctuating velocity and space correlograms were measured in the flow field of jet flaps by means of hot-wire anemometry. Using an expression derived by Lilley, an attempt was made to estimate the overall sound power radiated by the free mixing region that originates at the orifice of the slot nozzle (primary mixing region) relative to the overall sound power generated by the free mixing region that originates at the trailing edge of the flap (secondary mixing region). It is concluded that at least as much noise is generated in the secondary mixing region as in the primary mixing region. Furthermore, the noise generation of the primary mixing region appears to be unaffected by the presence of a flap.

Schrecker, G. O.; Maus, J. R.

1974-01-01

195

Standard Length versus Total Length

In an effort to determine the length measurement most representative of the bulk of the fish, the standard length and the total length were each compared with the weight of the fish. This comparison was made for four species of game fish, yellow perch (Perca flavescens), wall-eyed pike (Stizostedion v. vitreum), rock bass (Ambloplites rupestris), and lake trout (Cristivomer n.

William F. Royce

1942-01-01

196

The soil of several floodplain areas along large European rivers shows increased levels of heavy metals as a relict from past sedimentation of contaminants. These levels may pose risks of accumulation in food webs and toxicologic effects on flora and fauna. However, for floodplains, data on heavy-metal concentrations in vertebrates are scarce. Moreover, these environments are characterised by periodical flooding cycles influencing ecologic processes and patterns. To investigate whether the suggested differences in accumulation risks for insectivores and carnivores, omnivores, and herbivores are reflected in the actual heavy-metal concentrations in the species, we measured the current levels of Zn, Cu, Pb, and Cd in 199 specimens of 7 small mammal species (voles, mice, and shrews) and in their habitats in a diffusely polluted floodplain. The highest metal concentrations were found in the insectivorous and carnivorous shrew, Sorex araneus. Significant differences between the other shrew species, Crocidura russula, and the vole and mouse species was only found for Cd. The Cu concentration in Clethrionomys glareolus, however, was significantly higher than in several other vole and mouse species. To explain the metal concentrations found in the specimens, we related them to environmental variables at the trapping locations and to certain characteristics of the mammals. Variables taken into account were soil total and CaCl2-extractable metal concentrations at the trapping locations; whether locations were flooded or nonflooded; the trapping season; and the life stage; sex; and fresh weight of the specimens. Correlations between body and soil concentrations and location or specimen characteristics were weak. Therefore; we assumed that exposure of small mammals to heavy-metal contamination in floodplains is significantly influenced by exposure time, which is age related, as well as by dispersal and changes in foraging and feeding patterns under influence of periodic flooding. PMID:17387425

Leuven, R. S. E. W.; van der Velde, G.; Jungheim, G.; Koelemij, E. I.; de Vries, F. T.; Eijsackers, H. J. P.; Smits, A. J. M.

2007-01-01

197

The soil of several floodplain areas along large European rivers shows increased levels of heavy metals as a relict from past sedimentation of contaminants. These levels may pose risks of accumulation in food webs and toxicologic effects on flora and fauna. However, for floodplains, data on heavy-metal concentrations in vertebrates are scarce. Moreover, these environments are characterised by periodical flooding cycles influencing ecologic processes and patterns. To investigate whether the suggested differences in accumulation risks for insectivores and carnivores, omnivores, and herbivores are reflected in the actual heavy-metal concentrations in the species, we measured the current levels of Zn, Cu, Pb, and Cd in 199 specimens of 7 small mammal species (voles, mice, and shrews) and in their habitats in a diffusely polluted floodplain. The highest metal concentrations were found in the insectivorous and carnivorous shrew, Sorex araneus. Significant differences between the other shrew species, Crocidura russula, and the vole and mouse species was only found for Cd. The Cu concentration in Clethrionomys glareolus, however, was significantly higher than in several other vole and mouse species. To explain the metal concentrations found in the specimens, we related them to environmental variables at the trapping locations and to certain characteristics of the mammals. Variables taken into account were soil total and CaCl(2)-extractable metal concentrations at the trapping locations; whether locations were flooded or nonflooded; the trapping season; and the life stage; sex; and fresh weight of the specimens. Correlations between body and soil concentrations and location or specimen characteristics were weak. Therefore; we assumed that exposure of small mammals to heavy-metal contamination in floodplains is significantly influenced by exposure time, which is age related, as well as by dispersal and changes in foraging and feeding patterns under influence of periodic flooding. PMID:17387425

Wijnhoven, S; Leuven, R S E W; van der Velde, G; Jungheim, G; Koelemij, E I; de Vries, F T; Eijsackers, H J P; Smits, A J M

2007-05-01

198

NASA Astrophysics Data System (ADS)

Junctionless field-effect transistors (JL-FETs) with a 3 nm channel length are fabricated on silicon-on-insulator (SOI) substrates using simple process techniques. The anisotropic etching of Si crystals by alkaline solution is utilized to form V-grooves and to define nanometer-scale channel structures. Ultrathin channels created on the SOI have a 3 nm channel length that is determined by the edge of V-grooves. Dopants are introduced by ion implantation at the source and drain regions and diffused into the channel region at a high temperature and by long-period annealing. V-groove JL-FETs thus fabricated show superior performances by scaling the thickness of the SOI channel toward 1 nm and less. Through the measurement of many V-groove JL-FETs and a simulation study, it is clarified that the management of channel thickness with atomic-scale precision is indispensable for sub-10 nm FETs.

Migita, Shinji; Morita, Yukinori; Masahara, Meishoku; Ota, Hiroyuki

2013-04-01

199

Anomalous output characteristic shift of the n-type lateral diffused metal-oxide-semiconductor transistor with floating P-top layer is investigated. It shows that the linear drain current has obvious decrease when the output characteristic of fresh device is measured for two consecutive times. The charge pumping experiments demonstrate that the decrease is not from hot-carrier degradation. The reduction of cross section area for the current flowing, which results from the squeezing of the depletion region surrounding the P-top layer, is responsible for the shift. Consequently, the current capability of this special device should be evaluated by the second measured output characteristic.

Liu, Siyang; Zhang, Chunwei; Sun, Weifeng, E-mail: swffrog@seu.edu.cn [National ASIC System Engineering Research Center, Southeast University, Nanjing 210096 (China); Su, Wei; Wang, Shaorong; Ma, Shulang; Huang, Yu [CSMC Technologies Corporation, Wuxi 214061 (China)

2014-04-14

200

Characteristics of hydrogen–hydrocarbon composite fuel turbulent jet flames

The characteristics (flame length, pollutant emission, radiative heat loss fraction, and volumetric soot concentration) of hydrogen–hydrocarbon composite fuel turbulent jet diffusion flames are presented. A correlation of flame length with hydrogen concentration in the fuel mixture is shown. The reactivity of fuel mixture increases with the increase of hydrogen concentration, which ultimately shortens the combustion time, and thereby reduces the

Ahsan R. Choudhuri; S. R. Gollahalli

2003-01-01

201

Ballistic-Diffusive Heat-Conduction Equations

We present new heat-conduction equations, named ballistic-diffusive equations, which are derived from the Boltzmann equation. We show that the new equations are a better approximation than the Fourier law and the Cattaneo equation for heat conduction at the scales when the device characteristic length, such as film thickness, is comparable to the heat-carrier mean free path and\\/or the characteristic time,

Gang Chen; Gang

2001-01-01

202

NSDL National Science Digital Library

This lesson introduces students to the measurable attribute of length and provides practice in measuring length using non-standard units. The lesson is launched using the story Ladybug on the Move by Richard Fowler. Lesson objectives, teaching ideas, and handouts are included.

2012-01-01

203

NSDL National Science Digital Library

Practice measuring length. Play this fun game to work on length. Measure the teddy Next, practice measuring to the nearest 1/2 inch. Measure to 1/2 inches If your ready for a challenge, practice this next game: Measure to 1/4 inches Play the Fish Tales game! *Once you have played all the games, have an adult sign your planner that you practiced these games! You'll ...

Miss Lerdahl

2010-01-26

204

A large meteorological wind tunnel was used to simulate a suburban atmospheric boundary layer. The model-prototype scale was 1:300 and the roughness length was approximately 1.0 m full scale. The model boundary layer simulated full scale dispersion from ground-level and elevated ...

205

Boundary-layer analysis of subsonic inlet diffuser geometries for engines nacelles

NASA Technical Reports Server (NTRS)

Theoretical Mach number distributions and boundary-layer parameters are presented for subsonic nacelle inlet diffuser geometries with length to exit diameter ratios ranging from 0.4 to 1.6 and diffuser exit area to throat area ratios ranging from 1.1 to 2.0. The major portion of the study was done with a cubic diffuser contour with the inflection point at the midpoint of the diffuser, a diffuser throat Mach number of 0.6, and a free-stream Mach number of 0.12. Calculations were performed at both model (diffuser exit diameter, 30.5 cm) and full-scale (diffuser exit diameter, 183 cm) sizes. Separation limits were defined by establishing a separation boundary on plots of diffuser area ratio as a function of diffuser length to diameter ratio. The effects of diffuser contour, inlet lip geometry, and throat Mach number on the boundary-layer characteristics are illustrated. The major results of the study indicate that the separation boundary is shifted to greater area ratios by (1) increasing the diffuser length, (2) increasing the scale of the diffuser and, (3) moving the inflection point of the diffuser contour to or ahead of the midpoint of the diffuser.

Albers, J. A.; Felderman, E. J.

1974-01-01

206

NSDL National Science Digital Library

Although life experience plays a huge role in shaping who we are, the foundations of our personality begin in the womb. This Science Update describes a recent study that looks to finger length for signs of a man's pre-natal exposure to testosterone.

Science Update

2005-03-28

207

Diblock/silica films with multi-bilayer vesicular mesostructures of large characteristic length scales were synthesized through evaporation-induced self-assembly of PS-b-PEO. The present system is believed to be the first to yield diblock/silica films with multi-bilayer vesicular mesostructures through solvent evaporation-induced self-assembly (EISA). The ready formation in the present system is argued to be the polydispersity of polymer chains.

YU,KUI; BRINKER,C. JEFFREY; HURD,ALAN J.; EISENBERG,ADI

2000-11-22

208

The present study aims to elucidate the influence of the polyethylene glycol chain length on the miscibility of PEG/HPMC 2910 E5 polymer blends, the influence of polymer compatibility on the degree of molecular dispersion of itraconazole, and in vitro dissolution. PEG 2000, 6000, 10,000 and 20,000 were included in the study. Solid dispersions were prepared by spray drying and characterized with MDSC, XRPD and in vitro dissolution testing. The polymer miscibility increased with decreasing chain length due to a decrease in the Gibbs free energy of mixing. Recrystallization of itraconazole occurred as soon as a critical temperature of ca. 75 degrees C was reached for the glass transition that represents the ternary amorphous phase. Due to the lower miscibility degree between the longer PEG types and HPMC 2910 E5, the ternary amorphous phase was further separated, leading to a more rapid decrease of the ternary amorphous phase glass transition as a function of PEG and itraconazole weight percentage and hence, itraconazole recrystallization. In terms of release, an advantage of the shorter chain length PEG types (2000, 6000) over the longer chain length PEG types (10,000, 20,000) was observed for the polymer blends with 5% of PEG with respect to the binary itraconazole/HPMC 2910 E5 solid dispersion. Among the formulations with a 15/85 (w/w) PEG/HPMC 2910 E5 ratio on the other hand, there was no difference in the release profile. PMID:18656535

Janssens, Sandrien; Denivelle, Samgar; Rombaut, Patrick; Van den Mooter, Guy

2008-10-01

209

NSDL National Science Digital Library

This Science Update explores male agression patterns and their correlation to pre-natal testosterone exposure. Although life experience plays a huge role in shaping who we are, the foundations of our personality begin in the womb. One recent study looks to finger length for signs of a man's pre-natal exposure to testosterone.n women, the index and ring finger are roughly equal in length. But in most men, the ring finger is longer. That's a result of fetal exposure to testosterone. Psychologists Alison Bailey and Pete Hurd, of the University of Alberta in Canada, studied these finger ratios in male college students. And they found that men with more dramatic differences tended to be more aggressive. Additional links to resources are given for further inquiry.

American Association for the Advancement of Science (; )

2005-03-28

210

Analysis of EIS characteristics of CO 2 corrosion of well tube steels with corrosion scales

The electrochemical impedance spectroscopy (EIS) was used to study the characteristics of CO2 corrosion of N80 and 4Cr steels with corrosion scales. The results indicated that CO2 corrosion scale on tube steel could prevent the rate of mass transfer remarkably, corrosion rate was controlled by ions diffusion in corrosion scale, which led to finite length diffusion impedance occurred in electrochemical

Z. Q. Bai; C. F. Chen; M. X. Lu; J. B. Li

2006-01-01

211

Analysis of EIS characteristics of CO2 corrosion of well tube steels with corrosion scales

The electrochemical impedance spectroscopy (EIS) was used to study the characteristics of CO2 corrosion of N80 and 4Cr steels with corrosion scales. The results indicated that CO2 corrosion scale on tube steel could prevent the rate of mass transfer remarkably, corrosion rate was controlled by ions diffusion in corrosion scale, which led to finite length diffusion impedance occurred in electrochemical

Z. Q. Bai; C. F. Chen; M. X. Lu; J. B. Li

2006-01-01

212

NASA Technical Reports Server (NTRS)

Sideline noise and takeoff field length were varied for two types of Mach 2.32 cruise airplane to determine their effect on engine cycle selection. One of these airplanes was the NASA/Langley-LTV arrow wing while the other was a Boeing modified delta-plus-tail derived from the earlier 2707-300 concept. Advanced variable cycle engines were considered. A more conventional advanced low bypass turbofan engine was used as a baseline for comparison. Appropriate exhaust nozzle modifications were assumed, where needed, to allow all engines to receive either an inherent co-annular or annular jet noise suppression benefit. All the VCE's out-performed the baseline engine by substantial margins in a design range comparison, regardless of airplane choice or takeoff restrictions. The choice among the three VCE's considered, however, depends on the field length, noise level, and airplane selected.

Whitlow, J. B., Jr.

1976-01-01

213

The periodically fully developed laminar heat transfer and pressure drop of arrays with nonuniform plate length aligned at an angle (25 deg) to air direction have been investigated by numerical analysis in the Reynolds number range of 50--1700. The body-fitted coordinate system generated by the multisurface method was adopted to retain the corresponding periodic relation of the lines in physical and computational domains. The computations were carried out just in one cycle. Numerical results show that both the heat transfer and pressure drop increase with the increase in the length ratio of the long plate to the short place, and decrease with the decrease in the ratio of transverse pitch to the longitudinal pitch. The numerical results exhibit good agreement with available experimental data.

Wang, L.B.; Tao, W.Q. [Xi`an Jiaotong Univ. (China); Jiang, G.D. [Lanzhou Railway Inst. (China). Dept. of Mechanical Engineering; Ozoe, H. [Kyushu Univ. Kasuga (Japan). Inst. of Advanced Material Study

1998-11-01

214

Cellulose and chromaton-N-super as solid supports for direct determination of the immobilized nickel complexes with dimethylglyoxime and benzyldioxime by diffuse reflection spectroscopy were compared. The advantage of chromaton-N-super with use of benzyldioxime is shown. Detection limit is 0.02 microg/mL. The proposed method was applied for the analysis of soil. PMID:11225886

Ershova, N I; Ivanov, V M

2000-05-01

215

An improvement to the gas mixture used in diffuse glow discharge closing switches is disclosed which includes binary and ternary gas mixtures which are formulated to exhibit decreasing electron attachment with increasing temperature. This increases the efficiency of the conductance of the glow discharge and further inhibits the formation of an arc.

Christophorou, Loucas G. (Oak Ridge, TN); Hunter, Scott R. (Oak Ridge, TN)

1990-01-01

216

The report gives results of a study to: (1) establish the capability of measuring concrete's permeability and diffusivity, (2) measure these parameters in a small sampling of the typical types of Florida concrete, and (3) if possible, correlate the physical parameters of the conc...

217

An improvement to the gas mixture used in diffuse glow discharge closing switches is disclosed which includes binary and ternary gas mixtures which are formulated to exhibit decreasing electron attachment with increasing temperature. This increases the efficiency of the conductance of the glow discharge and further inhibits the formation of an arc. 11 figs.

Christophorou, L.G.; Hunter, S.R.

1990-06-26

218

Flow distribution problems have become increasingly important in the design of modern fluid flow and heat transfer systems. Flow distribution characteristics and control of marine gas turbine exhaust flow is studied. Major technical problems associated with nonuniform flow distribution are reviewed and various flow distribution control methods are evaluated. A two dimensional, turbulent flow model is developed for investigating flow

S. C. Kuo; H. T. Shu

1981-01-01

219

Previous investigations have shown that pulsed-held-gradient (PFG) NMR measurements can be used to measure a characteristic length scale in monodisperse porous media. In materials with broad distributions of length scales, those methods are not useful. It is shown that, in general, PFG NMR data can be used to calculate the probability that diffusing molecules will return to (or have not

P. P. Mitra; L. L. Latour; R. L. Kleinberg; C. H. Sotak

1995-01-01

220

NASA Technical Reports Server (NTRS)

The finite-element method has been applied to solve a combined radiative-conductive heat transfer problem for a large space telescope similar to those used in orbiting satellites. The derivation of the underlying matrices and associated solution algorithm for a 2-D triangular element is presented in detail. The resulting expressions for this triangular element typify such an analysis, which yields constitutive matrices when the heat equation is cast in the matrix form. The relevant matrices include those pertaining to thermal conductance, internal heat generation, radiative exchanges, and all possible external thermal loadings. Emphasis is placed on the treatment of non-linear radiative interchange between surfaces in an enclosure having mixed diffuse-specular surface characteristics. Essential differences in governing equations describing these distinctive surface characteristics are identified. Concluding remarks are drawn from an example simulating a Cassegrainian space telescope.

Lee, H.-P.; Jackson, C. E., Jr.

1975-01-01

221

Background Many households in sub-Saharan Africa utilize the private sector as a primary source of treatment for malaria episodes. Expanding access to effective treatment in private drug shops may help reduce incidence of severe disease and mortality. This research leveraged a longitudinal survey of stocking of subsidized artemisinin combination therapies (ACTs), an effective anti-malarial, in Accredited Drug Dispensing Outlets (ADDOs) in two regions of Tanzania. This provided a unique opportunity to explore shop and market level determinants of product diffusion in a developing country retail market. Methods 356 ADDOs in the Rukwa and Mtwara regions of Tanzania were surveyed at seven points between Feb 2011 and May 2012. Shop level audits were used to measure the availability of subsidized ACTs at each shop. Data on market and shop level factors were collected during the survey and also extracted from GIS layers. Regression and network based methodologies were used. Shops classified as early and late adopters, following Rogers’ model of product diffusion, were compared. The Bass model of product diffusion was applied to determine whether shops stocked ACTs out of a need to imitate market competitors or a desire to satisfy customer needs. Results Following the introduction of a subsidy for ACTs, stocking increased from 12% to nearly 80% over the seven survey rounds. Stocking was influenced by higher numbers of proximal shops and clinics, larger customer traffic and the presence of a licensed pharmacist. Early adopters were characterized by a larger percentage of customers seeking care for malaria, a larger catchment and sourcing from specific wholesalers/suppliers. The Bass model of product diffusion indicated that shops were adopting products in response to competitor behavior, rather than customer demand. Conclusions Decisions to stock new pharmaceutical products in Tanzanian ADDOs are influenced by a combination of factors related to both market competition and customer demand, but are particularly influenced by the behavior of competing shops. Efforts to expand access to new pharmaceutical products in developing country markets could benefit from initial targeting of high profile shops in competitive markets and wholesale suppliers to encourage faster product diffusion across all drug retailers. PMID:24350611

2013-01-01

222

A unique flower initiation of the wild Junebearing strawberry strain ‘CHI-24-1’ in Fragaria chiloensis occurs under 24 h DL and high temperature conditions. To introduce the floral initiation characteristics of ‘CHI-24-1’ into cultivated strawberries of F. × ananassa, a cross pollination was conducted between ‘CHI-24-1’ and the Japanese short-day type strawberry cultivar ‘Nyoho’. The floral initiation of ‘CHI-24-1’ was induced

Tomohiro Yanagi; Nobuaki Okuda; Takejiro Takamura

2005-01-01

223

Meat tenderness is known to be affected by sarcomere length (SL), proteolysis and collagen content (CC). Sixty lambs were slaughtered and the Longissimus muscle was sampled. Samples for shear force (SF), SL, proteolysis indicators (desmin degradation, particle size: PS) and CC were taken after the allotted ageing periods (1, 7, and 14days). PS explained a large part of the variation in shear force (approximately 34%) when modelled across ageing periods. Other factors (CC, SL) combined with proteolysis indicators (PS, desmin degradation) explained just under 40% of the variation in shear force. Within ageing periods SL explained a small, but significant, part of the variation in shear force after 14days of ageing (8%) and at day 1 of ageing desmin degradation explained 17% of the variation in shear force. Methods to improve the tenderness of lamb longissimus muscle should focus on increasing the extent of post-mortem proteolysis, when processing conditions are sufficient to prevent muscle fibre shortening. PMID:25768395

Starkey, Colin P; Geesink, Geert H; Oddy, V Hutton; Hopkins, David L

2015-07-01

224

The effect of diffusion induced lattice stress on the open-circuit voltage in silicon solar cells

NASA Technical Reports Server (NTRS)

It is demonstrated that diffusion induced stresses in low resistivity silicon solar cells can significantly reduce both the open-circuit voltage and collection efficiency. The degradation mechanism involves stress induced changes in both the minority carrier mobility and the diffusion length. Thermal recovery characteristics indicate that the stresses are relieved at higher temperatures by divacancy flow (silicon self diffusion). The level of residual stress in as-fabricated cells was found to be negligible in the cells tested.

Weizer, V. G.; Godlewski, M. P.

1984-01-01

225

Experimental study of vortex diffusers

This report documents experimental research performed on vortex diffusers used in ventilation and air-conditioning systems. The main objectives of the research were (1) to study the flow characteristics of isothermal jets issuing from vortex diffusers, (2) to compare the vortex diffuser`s performance with that of a conventional diffuser, and (3) to prepare a report that disseminates the results to the designers of ventilation and air-conditioning systems. The researchers considered three diffusers: a conventional round ceiling diffuser and two different styles of vortex diffusers. Overall, the vortex diffusers create slightly more induction of ambient air in comparison to the conventional diffuser.

Shakerin, S.; Miller, P.L. [National Renewable Energy Lab., Golden, CO (United States)

1995-11-01

226

NASA Astrophysics Data System (ADS)

This work addresses the combinatorial plating characteristics of dense Pd/Ni/porous stainless steel (PSS) composite membranes in comparison with Pd/PSS membranes. While Pd/PSS membranes were fabricated using 0.1 ?m nominal pore size PSS supports, Pd/Ni/PSS membranes were fabricated using 0.5 and 0.1 ?m nominal pore size PSS supports. Both Ni and Pd films were deposited using an identified novel electroless plating process that characterizes the optimal utilization of surfactant, sonication and reducing agent contacting pattern in Pd electroless plating baths. It was observed that the combinatorial plating characteristics for Pd/Ni/PSS membranes were significantly different and poorer in comparison with those obtained for the Pd/PSS membranes. In summary, it has been inferred that the introduction of nickel interdiffusion barrier was not fruitful to reduce the critical thickness of dense Pd film without jeopardizing upon the pore densification.

Pujari, Murali; Agarwal, Amrita; Uppaluri, Ramgopal; Verma, Anil

2014-06-01

227

Diffusion Geometry Diffusion Geometry

Diffusion Geometry Diffusion Geometry for High Dimensional Data Matthew J. Hirn July 3, 2013 #12;Diffusion Geometry Introduction Embedding of closed curve Figure: Left: A closed, non-self-intersecting curve in 3 dimensions. Right: Its embedding as a circle. #12;Diffusion Geometry Introduction Cartoon

Hirn, Matthew

228

NASA Technical Reports Server (NTRS)

A methodological evaluation for two-finite differencing schemes for computer-aided gas turbine design is presented. The two computational schemes include; a Bounded Skewed Finite Differencing Scheme (BSUDS); and a Quadratic Upwind Differencing Scheme (QSDS). In the evaluation, the derivations of the schemes were incorporated into two-dimensional and three-dimensional versions of the Teaching Axisymmetric Characteristics Heuristically (TEACH) computer code. Assessments were made according to performance criteria for the solution of problems of turbulent, laminar, and coannular turbulent flow. The specific performance criteria used in the evaluation were simplicity, accuracy, and computational economy. It is found that the BSUDS scheme performed better with respect to the criteria than the QUDS. Some of the reasons for the more successful performance BSUDS are discussed.

Syed, S. A.; Chiappetta, L. M.

1985-01-01

229

NASA Astrophysics Data System (ADS)

Radio-frequency (RF), atmospheric-pressure glow discharge (APGD) plasmas using bare metal electrodes have promising prospects in the fields of plasma-aided etching, deposition, surface treatment, disinfection, sterilization, etc. In this paper, the discharge characteristics, including the breakdown voltage and the discharge voltage for sustaining a stable and uniform ? mode discharge of the RF APGD plasmas are presented. The experiments are conducted by placing the home-made planar-type plasma generator in ambient and in a vacuum chamber, respectively, with helium as the primary plasma-forming gas. When the discharge processes occur in ambient, particularly for the lower plasma-working gas flow rates, the experimental measurements show that it is the back-diffusion effect of air in atmosphere, instead of the flow rate of the gas, that results in the obvious decrease in the breakdown voltage with increasing plasma-working gas flow rate. Further studies on the discharge characteristics, e.g. the luminous structures, the concentrations and distributions of chemically active species in plasmas, with different plasma-working gases or gas mixtures need to be conducted in future work.

Sun, Wen-Ting; Liang, Tian-Ran; Wang, Hua-Bo; Li, He-Ping; Bao, Cheng-Yu

2007-05-01

230

Estimation of Turbulent Diffusivity with Direct Numerical Simulation of Stellar Convection

NASA Astrophysics Data System (ADS)

We investigate the value of horizontal turbulent diffusivity ? by numerical calculation of thermal convection. In this study, we introduce a new method whereby the turbulent diffusivity is estimated by monitoring the time development of the passive scalar, which is initially distributed in a given Gaussian function with a spatial scale d 0. Our conclusions are as follows: (1) assuming the relation ? = L c v rms/3, where v rms is the root-mean-square (rms) velocity, the characteristic length L c is restricted by the shortest one among the pressure (density) scale height and the region depth. (2) The value of turbulent diffusivity becomes greater with the larger initial distribution scale d 0. (3) The approximation of turbulent diffusion holds better when the ratio of the initial distribution scale d 0 to the characteristic length L c is larger.

Hotta, H.; Iida, Y.; Yokoyama, T.

2012-05-01

231

NSDL National Science Digital Library

This is a description for a learning module from Maricopa Advanced Technology Education Center. This PDF describes the module; access may be purchased by visiting the MATEC website. In an orderly and comprehensive set of lectures, lessons, and laboratory activities, MATEC explicates for your learners the complex process of diffusion. Beginning with an overview of diffusion's purpose in altering a wafer's electrical characteristics, the module then drills down to specifics: process parameters, different techniques of diffusion, the use of a hot probe to evaluate diffusion, and wafer handling. Your learners demonstrate their new knowledge by diffusing selected dopants into a silicon wafer.

232

Inflatable penile prosthesis (IPP) remains the gold standard for the surgical treatment of refractory erectile dysfunction; however, current literature to aid surgeons on how best to counsel patients on their postoperative inflated penile length is lacking. The aim of this study was to identify preoperative parameters that could better predict postoperative penile length following insertion of an IPP. Twenty men were enrolled in a prospective study examining penile lengths before and after IPP surgery. Patients with Peyronie's disease were excluded from this analysis. Baseline preoperative characteristics, including body mass index, history of hypertension, diabetes, Sexual Health Inventory for Men scores and/or prior radical prostatectomy were recorded. All patients underwent implantation with a three-piece inflatable Coloplast penile prosthesis. We compared stretched penile length to pharmacologically induced erect lengths. Postoperatively, we measured inflated penile lengths at 6 weeks and assessed patients' perception of penile size at 12 weeks. The median (±interquartile range) stretched penile length and pharmacologically induced erect penile length was 15 (±3) and 14.25 (±2)?cm, respectively (P=0.5). Median post-prosthesis penile length (13.5±2.13?cm) was smaller than preoperative pharmacologically induced length (P=0.02) and preoperative stretched penile length (P=0.01). The majority of patients (70%) had a decrease in penile length (median loss 0.5±1.5?cm); however, this loss was perceptible by 43% of men. Stretched penile length and pharmacologically induced erect penile length were equally good predictors of postoperative inflated length (Spearman's correlation 0.8 and 0.9, respectively). Pharmacologically induced erect penile length and stretched penile lengths are equal predictors of post-prosthesis penile length. The majority of men will experience some decrease in penile length following prosthesis implantation; however <50% report a subjective loss of penile length. PMID:24430278

Osterberg, E C; Maganty, A; Ramasamy, R; Eid, J F

2014-01-01

233

A microscopic model of ballistic-diffusive crossover

NASA Astrophysics Data System (ADS)

Several low-dimensional systems show a crossover from diffusive to ballistic heat transport when system size is decreased. Although there is some phenomenological understanding of this crossover phenomenon at the coarse-grained level, a microscopic picture that consistently describes both the ballistic and the diffusive transport regimes has been lacking. In this work we derive a scaling form for the thermal current in a class of one dimensional systems attached to heat baths at boundaries and rigorously show that the crossover occurs when the characteristic length scale of the system competes with the system size.

Bagchi, Debarshee; Mohanty, P. K.

2014-11-01

234

Lateral diffusion in an archipelago. Dependence on tracer size.

In a pure fluid-phase lipid, the dependence of the lateral diffusion coefficient on the size of the diffusing particle may be obtained from the Saffman-Delbrück equation or the free-volume model. When diffusion is obstructed by immobile proteins or domains of gel-phase lipids, the obstacles yield an additional contribution to the size dependence. Here this contribution is examined using Monte Carlo calculations. For random point and hexagonal obstacles, the diffusion coefficient depends strongly on the size of the diffusing particle, but for fractal obstacles--cluster-cluster aggregates and multicenter diffusion-limited aggregates--the diffusion coefficient is independent of the size of the diffusing particle. The reason is that fractals have no characteristic length scale, so a tracer sees on average the same obstructions, regardless of its size. The fractal geometry of the excluded area for tracers of various sizes is examined. Percolation thresholds are evaluated for a variety of obstacles to determine how the threshold depends on tracer size and to compare the thresholds for compact and extended obstacles. Images FIGURE 3 PMID:8494970

Saxton, M J

1993-01-01

235

Accuracy of Reporting of Menstrual Cycle Length

There are many studies based on self-reported menstrual cycle length, yet little is known about the validity of this measure. The authors used data collected in 1990 from 352 women born in Chicago, Illinois, aged 37-39 years. Women reported their usual cycle length and behavioral and reproductive characteristics at study enrollment and then completed daily menstrual diaries for up to

Anne Marie; Zaura Jukic; Clarice R. Weinberg; Allen J. Wilcox; D. Robert McConnaughey; Paige Hornsby; Donna D. Baird

2008-01-01

236

A Multiscale Analysis of Diffusions on Rapidly Varying Surfaces

NASA Astrophysics Data System (ADS)

Lateral diffusion of molecules on surfaces plays a very important role in various biological processes, including lipid transport across the cell membrane, synaptic transmission, and other phenomena such as exo- and endocytosis, signal transduction, chemotaxis, and cell growth. In many cases, the surfaces can possess spatial inhomogeneities and/or be rapidly changing shape. Using a generalization of the model for a thermally excited Helfrich elastic membrane, we consider the problem of lateral diffusion on quasi-planar surfaces, possessing both spatial and temporal fluctuations. Using results from homogenization theory, we show that, under the assumption of scale separation between the characteristic length and timescales of the membrane fluctuations and the characteristic scale of the diffusing particle, the lateral diffusion process can be well approximated by a Brownian motion on the plane with constant diffusion tensor D that depends on a highly nonlinear way on the detailed properties of the surface. The effective diffusion tensor will depend on the relative scales of the spatial and temporal fluctuations, and for different scaling regimes, we prove the existence of a macroscopic limit in each case.

Duncan, A. B.; Elliott, C. M.; Pavliotis, G. A.; Stuart, A. M.

2015-02-01

237

A Multiscale Analysis of Diffusions on Rapidly Varying Surfaces

NASA Astrophysics Data System (ADS)

Lateral diffusion of molecules on surfaces plays a very important role in various biological processes, including lipid transport across the cell membrane, synaptic transmission, and other phenomena such as exo- and endocytosis, signal transduction, chemotaxis, and cell growth. In many cases, the surfaces can possess spatial inhomogeneities and/or be rapidly changing shape. Using a generalization of the model for a thermally excited Helfrich elastic membrane, we consider the problem of lateral diffusion on quasi-planar surfaces, possessing both spatial and temporal fluctuations. Using results from homogenization theory, we show that, under the assumption of scale separation between the characteristic length and timescales of the membrane fluctuations and the characteristic scale of the diffusing particle, the lateral diffusion process can be well approximated by a Brownian motion on the plane with constant diffusion tensor that depends on a highly nonlinear way on the detailed properties of the surface. The effective diffusion tensor will depend on the relative scales of the spatial and temporal fluctuations, and for different scaling regimes, we prove the existence of a macroscopic limit in each case.

Duncan, A. B.; Elliott, C. M.; Pavliotis, G. A.; Stuart, A. M.

2015-04-01

238

ERIC Educational Resources Information Center

Everyone with a thorough knowledge of single variable calculus knows that integration can be used to find the length of a curve on a given interval, called its arc length. Fortunately, if one endeavors to pose and solve more interesting problems than simply computing lengths of various curves, there are techniques available that do not require an…

Boudreaux, Gregory M.; Wells, M. Scott

2007-01-01

239

Measuring Thermodynamic Length

Thermodynamic length is a metric distance between equilibrium thermodynamic states. Among other interesting properties, this metric asymptotically bounds the dissipation induced by a finite time transformation of a thermodynamic system. It is also connected to the Jensen-Shannon divergence, Fisher information, and Rao's entropy differential metric. Therefore, thermodynamic length is of central interestin understanding matter out of equilibrium. In this Letter, we will consider how to denethermodynamic length for a small system described by equilibrium statistical mechanics and how to measure thermodynamic length within a computer simulation. Surprisingly, Bennett's classic acceptance ratio method for measuring free energy differences also measures thermodynamic length.

Crooks, Gavin E

2007-09-07

240

Combustion characteristics of hydrogen–hydrocarbon hybrid fuels

A comparative study of the flame structure and characteristics of diffusion flames of the mixture of hydrogen–hydrocarbon (natural gas and propane) hybrid fuel in a slow co-flowing stream of air is presented. The volumetric content of natural gas and propane in the mixture was varied from 0–35%. The burner exit Reynolds number was varied from 150–3000. Measurements include flame length,

Ahsan R Choudhuri; S. R Gollahalli

2000-01-01

241

Multi-port co-annular burners are widely used in practice to achieve low NOx and soot emissions from combustion devices. However, there is lack of fundamental studies on the structure and flame regime under different flow conditions. A conventional laminar axisymmetric coflow diffusion flame burner was modified by introducing a central air jet inside the fuel tube to investigate how the central

F. Liu; G. J. Smallwood

2011-01-01

242

Effects of Nanoparticle Geometry and Size Distribution on Diffusion Impedance of Battery Electrodes

The short diffusion lengths in insertion battery nanoparticles render the capacitive behavior of bounded diffusion, which is rarely observable with conventional larger particles, now accessible to impedance measurements. ...

Song, Juhyun

243

Welding arc length control system

NASA Technical Reports Server (NTRS)

The present invention is a welding arc length control system. The system includes, in its broadest aspects, a power source for providing welding current, a power amplification system, a motorized welding torch assembly connected to the power amplification system, a computer, and current pick up means. The computer is connected to the power amplification system for storing and processing arc weld current parameters and non-linear voltage-ampere characteristics. The current pick up means is connected to the power source and to the welding torch assembly for providing weld current data to the computer. Thus, the desired arc length is maintained as the welding current is varied during operation, maintaining consistent weld penetration.

Iceland, William F. (Inventor)

1993-01-01

244

The Late Pleistocene archaic humans from western Eurasia (the Neandertals) have been described for a century as exhibiting absolutely and relatively long clavicles. This aspect of their body proportions has been used to distinguish them from modern humans, invoked to account for other aspects of their anatomy and genetics, used in assessments of their phylogenetic polarities, and used as evidence for Late Pleistocene population relationships. However, it has been unclear whether the usual scaling of Neandertal clavicular lengths to their associated humeral lengths reflects long clavicles, short humeri, or both. Neandertal clavicle lengths, along with those of early modern humans and latitudinally diverse recent humans, were compared with both humeral lengths and estimated body masses (based on femoral head diameters). The Neandertal do have long clavicles relative their humeri, even though they fall within the ranges of variation of early and recent humans. However, when scaled to body masses, their humeral lengths are relatively short, and their clavicular lengths are indistinguishable from those of Late Pleistocene and recent modern humans. The few sufficiently complete Early Pleistocene Homo clavicles seem to have relative lengths also well within recent human variation. Therefore, appropriately scaled clavicular length seems to have varied little through the genus Homo, and it should not be used to account for other aspects of Neandertal biology or their phylogenetic status. PMID:24616525

Trinkaus, Erik; Holliday, Trenton W.; Auerbach, Benjamin M.

2014-01-01

245

The Late Pleistocene archaic humans from western Eurasia (the Neandertals) have been described for a century as exhibiting absolutely and relatively long clavicles. This aspect of their body proportions has been used to distinguish them from modern humans, invoked to account for other aspects of their anatomy and genetics, used in assessments of their phylogenetic polarities, and used as evidence for Late Pleistocene population relationships. However, it has been unclear whether the usual scaling of Neandertal clavicular lengths to their associated humeral lengths reflects long clavicles, short humeri, or both. Neandertal clavicle lengths, along with those of early modern humans and latitudinally diverse recent humans, were compared with both humeral lengths and estimated body masses (based on femoral head diameters). The Neandertal do have long clavicles relative their humeri, even though they fall within the ranges of variation of early and recent humans. However, when scaled to body masses, their humeral lengths are relatively short, and their clavicular lengths are indistinguishable from those of Late Pleistocene and recent modern humans. The few sufficiently complete Early Pleistocene Homo clavicles seem to have relative lengths also well within recent human variation. Therefore, appropriately scaled clavicular length seems to have varied little through the genus Homo, and it should not be used to account for other aspects of Neandertal biology or their phylogenetic status. PMID:24616525

Trinkaus, Erik; Holliday, Trenton W; Auerbach, Benjamin M

2014-03-25

246

NSDL National Science Digital Library

This project is use to review the concepts of diffusion and osmosis 1. Watch the tutorials on diffusion and osmosis. Take the online quiz at the end of each one. Diffusion Animation Osmosis Animation 2. Do the interactive lab on diffusion. Stop when you get to the calculating water potential section. Diffusion/Osmosis Interactive Demo 3. Play the Quia review games. Quia Games- matching/concetration Quia Jeopardy 4. Check out the Elodea leaf cells. Be able to ...

Jensen

2007-11-26

247

NASA Astrophysics Data System (ADS)

Among several different measurement techniques that have been already performed and presented in a radial impeller pump model including PIV, a directional pressure probe has been used to obtain mean velocity field and stagnation pressure between impeller outlet and the inlet vaned diffuser sections. These measurements are supposed to get more information not only about global pump head coefficient including vaned diffuser ones but also about impeller performances itself. Pressure probe information is affected by rotor-stator interactions and impeller rotation, and this paper presents a way to explain and correct pressure probe indications in order to achieve a better evaluation of overall impeller mean performances. The use of unsteady RANS calculation results is found to be a useful way to perform better data reduction analysis for this purpose.

Cherdieu, P.; Dupont, P.; Bayeul-Lainé, A. C.; Dazin, A.; Bois, G.

2013-12-01

248

Classical partial oxidation processes often suffer from low selectivities. Promising alternatives are electrochemical processes\\u000a where the oxidation takes place at a packed-bed anode while an oxygen-consuming gas–liquid membrane is used as cathode. As\\u000a a basis for the reliable design of such a process, the performance of oxygen-consuming gas-diffusion electrodes (GDE) is investigated\\u000a experimentally and is analysed based on a rigorous

Kai Sundmacher; Thorsten Schultz

2005-01-01

249

Optical and electrical investigation of a cylindrical diffuse-discharge chamber

NASA Astrophysics Data System (ADS)

More and more attention has been attached to atmospheric-pressure air diffuse plasma due to its enormous potential applications. In this paper, we designed a large-scale, cylindrical diffuse-plasma chamber using wire electrodes and a repetitive nanosecond pulse generator. The plasma chamber can be completely exposed in the open air without any barrier dielectric, and the length of cylindrical plasma chamber was extensible. Using optical and electrical measurements, we investigated the effects of electrode distance, electrode length, pulse repetition frequency, and electrode angle on the uniformity of discharge space. Four discharge regions were distinguished based on different spectral characteristics. Additionally, it was found that the discharge uniformity was improved as the electrode distance decreases, but remained almost constant with the variations of electrode length and pulse repetition frequency. Both of the plasma uniformity and the power density increased significantly as the electrode angle reduced.

Teng, Yun; Li, Lee; Cheng, Yong; Ma, Ning; Peng, Ming-yang; Liu, Ming-hai

2015-03-01

250

NASA Technical Reports Server (NTRS)

Force and pressure-recovery characteristics of a nacelle-type conical-spike inlet with a fixed-area bypass located in the top or bottom of the diffuser are presented for flight Mach numbers of 1.6, 1.8, and 2.0 for angles of attack from 0 degrees to 9 degrees. Top or bottom location of the bypass did not have significant effects on diffuser pressure-recovery, bypass mass-flow ratio, or drag coefficient over the range of angles of attack, flight Mach numbers, and stable engine mass-flow ratios investigated. A larger stable subcritical operating range was obtained with the bypass on the bottom at angles of attack from 3 degrees to 9 degrees at a flight Mach number of 2.0. At a flight Mach number of 2.0, the discharge of 14 percent of the critical mass flow of the inlet by means of a bypass increased the drag only one-fifth of the additive drag that would result for equivalent spillage behind an inlet normal shock without significant reductions in diffuser pressure recovery.

Allen, J L; Beke, Andrew

1953-01-01

251

Myofilament length dependent activation

The Frank-Starling law of the heart describes the interrelationship between end-diastolic volume and cardiac ejection volume, a regulatory system that operates on a beat-to-beat basis. The main cellular mechanism that underlies this phenomenon is an increase in the responsiveness of cardiac myofilaments to activating Ca{sup 2+} ions at a longer sarcomere length, commonly referred to as myofilament length-dependent activation. This review focuses on what molecular mechanisms may underlie myofilament length dependency. Specifically, the roles of inter-filament spacing, thick and thin filament based regulation, as well as sarcomeric regulatory proteins are discussed. Although the 'Frank-Starling law of the heart' constitutes a fundamental cardiac property that has been appreciated for well over a century, it is still not known in muscle how the contractile apparatus transduces the information concerning sarcomere length to modulate ventricular pressure development.

de Tombe, Pieter P.; Mateja, Ryan D.; Tachampa, Kittipong; Mou, Younss Ait; Farman, Gerrie P.; Irving, Thomas C. (IIT); (Loyola)

2010-05-25

252

ERIC Educational Resources Information Center

Describes a thought experiment using a general analysis approach with Lorentz transformations to show that the apparent self-contradictions of special relativity concerning the length-paradox are really non-existant. (GA)

Martins, Roberto de A.

1978-01-01

253

A study of signals originating near the lithium-diffused n+ contact of p-type point contact (PPC) high purity germanium detectors (HPGe) is presented. The transition region between the active germanium and the fully dead layer of the n+ contact is examined. Energy depositions in this transition region are shown to result in partial charge collection. This provides a mechanism for events with a well defined energy to contribute to the continuum of the energy spectrum at lower energies. A novel technique to quantify the contribution from this source of background is introduced. Experiments that operate germanium detectors with a very low energy threshold may benefit from the methods presented herein.

Aguayo, E. [Pacific Northwest National Laboratory (PNNL); Amman, M. [Lawrence Berkeley National Laboratory (LBNL); Avignone, F. T. [University of South Carolina/ORNL; Barabash, A.S. [Institute of Theoretical & Experimental Physics, Moscow, Russia; Barton, P. J. [Lawrence Berkeley National Laboratory (LBNL); Beene, James R [ORNL; Bertrand Jr, Fred E [ORNL; Boswell, M. [Los Alamos National Laboratory (LANL); Brudanin, V. [Joint Institute for Nuclear Research, Dubna, Russia; Busch, M. [Duke University; Chan, Y-D [Lawrence Berkeley National Laboratory (LBNL); Christofferson, C. D. [South Dakota School of Mines & Technology, Rapid City, SD; Collar, Juan I. [University of Chicago; Combs, D. C. [University of North Carolina / Triangle Universities Nuclear Lababoratory, Durham; Cooper, Reynold J [ORNL; Detwiler, J.A. [Lawrence Berkeley National Laboratory (LBNL); Doe, P. J. [University of Washington; Efremenko, Yuri [University of Tennessee (UTK) and Oak Ridge National Laboratory (ORNL); Egorov, V. [Joint Institute for Nuclear Research, Dubna, Russia; Ejiri, H. [Osaka University; Elliott, S. R. [Los Alamos National Laboratory (LANL); Esterline, J. [Duke University; Fast, J.E. [Pacific Northwest National Laboratory (PNNL); Fields, N. [University of Chicago; Finnerty, P. [University of North Carolina / Triangle Universities Nuclear Lababoratory, Durham; Fraenkle, F. M. [University of North Carolina / Triangle Universities Nuclear Lababoratory, Durham; Galindo-Uribarri, Alfredo {nmn} [ORNL; Gehman, V. M. [Los Alamos National Laboratory (LANL); Giovanetti, G. K. [Univ, of North Carolina & Triangle Universities Nucl. Lab - Durham, NC; Green, M. P. [University of North Carolina / Triangle Universities Nuclear Lababoratory, Durham; Guiseppe, V.E. [University of South Dakota; Gusey, K. [Joint Institute for Nuclear Research, Dubna, Russia; Hallin, A. L. [University of Alberta, Edmonton, Canada; Hazama, R. [Osaka University; Henning, R. [Univ, of North Carolina & Triangle Universities Nucl. Lab - Durham, NC; Hoppe, E.W. [Pacific Northwest National Laboratory (PNNL); Horton, M. [South Dakota School of Mines & Technology, Rapid City, SD; Howard, S. [South Dakota School of Mines and Technology; Howe, M. A. [University of North Carolina / Triangle Universities Nuclear Lababoratory, Durham; Johnson, R. A. [University of Washington, Seattle; Keeter, K.J. [Black Hills State University, Spearfish, SD; Kidd, M. F. [Los Alamos National Laboratory (LANL); Knecht, A. [University of Washington, Seattle; Kochetov, O. [Joint Institute for Nuclear Research, Dubna, Russia; Konovalov, S.I. [Institute of Theoretical & Experimental Physics, Moscow, Russia; Kouzes, R. T. [Pacific Northwest National Laboratory (PNNL); LaFerriere, B. D. [Pacific Northwest National Laboratory (PNNL); Leon, J. [University of Washington, Seattle; Leviner, L. E. [University of North Carolina / Triangle Universities Nuclear Lababoratory, Durham; Loach, J.C. [Lawrence Berkeley National Laboratory (LBNL); Looker, Q. [Lawrence Berkeley National Laboratory (LBNL); Luke, P.N. [Lawrence Berkeley National Laboratory (LBNL); MacMullin, S. [University of North Carolina / Triangle Universities Nuclear Lababoratory, Durham; Marino, M. G. [University of Washington, Seattle; Martin, R.D. [Lawrence Berkeley National Laboratory (LBNL); Merriman, J. H. [Pacific Northwest National Laboratory (PNNL); Miller, M. L. [University of Washington, Seattle; Mizouni, L. [PPNL/Univ. of South Carolina; Nomachi, M. [Osaka University; Orrell, John L. [Pacific Northwest National Laboratory (PNNL); Overman, N. R. [Pacific Northwest National Laboratory (PNNL); Perumpilly, G. [University of South Dakota; Phillips II, D. G. [University of North Carolina / Triangle Universities Nuclear Lababoratory, Durham; Poon, A.W.P. [Lawrence Berkeley National Laboratory (LBNL); et al.

2013-01-01

254

A study of signals originating near the lithium-diffused n+ contact of p-type point contact (PPC) high purity germanium detectors (HPGe) is presented. The transition region between the active germanium and the fully dead layer of the n+ contact is examined. Energy depositions in this transition region are shown to result in partial charge collection. This provides a mechanism for events with a well defined energy to contribute to the continuum of the energy spectrum at lower energies. A novel technique to quantify the contribution from this source of background is introduced. Experiments that operate germanium detectors with a very low energy threshold may benefit from the methods presented herein.

The MAJORANA Collaboration; E. Aguayo; M. Amman; F. T. Avignone III; A. S. Barabash; P. J. Barton; J. R. Beene; F. E. Bertrand; M. Boswell; V. Brudanin; M. Busch; Y-D. Chan; C. D. Christofferson; J. I. Collar; D. C. Combs; R. J. Cooper; J. A. Detwiler; P. J. Doe; Yu. Efremenko; V. Egorov; H. Ejiri; S. R. Elliott; J. Esterline; J. E. Fast; N. Fields; P. Finnerty; F. M. Fraenkle; A. Galindo-Uribarri; V. M. Gehman; G. K. Giovanetti; M. P. Green; V. E. Guiseppe; K. Gusey; A. L. Hallin; R. Hazama; R. Henning; E. W. Hoppe; M. Horton; S. Howard; M. A. Howe; R. A. Johnson; K. J. Keeter; M. F. Kidd; A. Knecht; O. Kochetov; S. I. Konovalov; R. T. Kouzes; B. D. LaFerriere; J. Leon; L. E. Leviner; J. C. Loach; Q. Looker; P. N. Luke; S. MacMullin; M. G. Marino; R. D. Martin; J. H. Merriman; M. L. Miller; L. Mizouni; M. Nomachi; J. L. Orrell; N. R. Overman; G. Perumpilly; D. G. Phillips II; A. W. P. Poon; D. C. Radford; K. Rielage; R. G. H. Robertson; M. C. Ronquest; A. G. Schubert; T. Shima; M. Shirchenko; K. J. Snavely; D. Steele; J. Strain; V. Timkin; W. Tornow; R. L. Varner; K. Vetter; K. Vorren; J. F. Wilkerson; E. Yakushev; H. Yaver; A. R. Young; C. -H. Yu; V. Yumatov

2012-07-28

255

On collisional diffusion in a stochastic magnetic field

NASA Astrophysics Data System (ADS)

The effect of particle collisions on the transport in a stochastic magnetic field in tokamaks is investigated. The model of resonant magnetic perturbations generated by external coils at the plasma edge is used for the stochastic magnetic field. The particle collisions are simulated by a random walk process along the magnetic field lines and the jumps across the field lines at the collision instants. The dependencies of the local diffusion coefficients on the mean free path ?mfp, the diffusion coefficients of field lines DFL, and the collisional diffusion coefficients, ?? are studied. Based on these numerical data and the heuristic arguments, the empirical formula, Dr=??+v||DFL/(1+Lc/?mfp), for the local diffusion coefficient is proposed, where Lc is the characteristic length of order of the connection length lc=?qR0, q is the safety factor, R0 is the major radius. The formula quite well describes the results of numerical simulations. In the limiting cases, the formula describes the Rechester-Rosenbluth and Laval scalings.

Abdullaev, S. S.

2013-08-01

256

On collisional diffusion in a stochastic magnetic field

The effect of particle collisions on the transport in a stochastic magnetic field in tokamaks is investigated. The model of resonant magnetic perturbations generated by external coils at the plasma edge is used for the stochastic magnetic field. The particle collisions are simulated by a random walk process along the magnetic field lines and the jumps across the field lines at the collision instants. The dependencies of the local diffusion coefficients on the mean free path ?{sub mfp}, the diffusion coefficients of field lines D{sub FL}, and the collisional diffusion coefficients, ?{sub ?} are studied. Based on these numerical data and the heuristic arguments, the empirical formula, D{sub r}=?{sub ?}+v{sub ||}D{sub FL}/(1+L{sub c}/?{sub mfp}), for the local diffusion coefficient is proposed, where L{sub c} is the characteristic length of order of the connection length l{sub c}=?qR{sub 0}, q is the safety factor, R{sub 0} is the major radius. The formula quite well describes the results of numerical simulations. In the limiting cases, the formula describes the Rechester-Rosenbluth and Laval scalings.

Abdullaev, S. S. [Forschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung - Plasmaphysik, EURATOM Association, 52425 Jülich (Germany)] [Forschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung - Plasmaphysik, EURATOM Association, 52425 Jülich (Germany)

2013-08-15

257

Technological changes have moved publishing to electronic-first publication where the print version has been relegated to simply another display mode. Distribution in HTML and EPUB formats, for example, changes the reading environment and reduces the need for strict pagination. Therefore, in an effort to streamline the calculation of length, the APS journals will no longer use the printed page as the determining factor for length. Instead the journals will now use word counts (or word equivalents for tables, figures, and equations) to establish length; for details please see http://publish.aps.org/authors/length-guide. The title, byline, abstract, acknowledgment, and references will not be included in these counts allowing authors the freedom to appropriately credit coworkers, funding sources, and the previous literature, bringing all relevant references to the attention of readers. This new method for determining length will be easier for authors to calculate in advance, and lead to fewer length-associated revisions in proof, yet still retain the quality of concise communication that is a virtue of short papers.

Sprouse, Gene D. [American Physical Society (United States)

2011-07-15

258

The dynamics of unsteady detonation with diffusion

Here we consider an unsteady detonation with diffusion included. This introduces an interaction between the reaction length scales and diffusion length scales. Detailed kinetics introduce multiple length scales as shown though the spatial eigenvalue analysis of hydrogen-oxygen system; the smallest length scale is {approx} 10{sup 7} m and the largest {approx} 10{sup -2} m; away from equilibrium, the breadth can be larger. In this paper, we consider a simpler set of model equations, similar to the inviscid reactive compressible fluid equations, but include diffusion (in the form of thermal/energy, momentum, and mass diffusion). We will seek to reveal how the complex dynamics already discovered in one-step systems in the inviscid limit changes with the addition of diffusion.

Aslam, Tariq Dennis [Los Alamos National Laboratory; Romick, Christopher [NOTRE DAME; Powers, Joseph [NOTRE DAME

2010-01-01

259

Anomalous Diffusion: In diffusion-weighted magnetic resonance imaging (MRI) of neural tissue modeled diffusion in neural tissue from the perspective of a continuous time random walk. Here, the characteristic diffusion decay is represented by the Mittag- Leffler function (see figure), which relaxes

McQuade, D. Tyler

260

Two-dimensional network simulation of diffusion driven coarsening of foam inside a porous medium

In order to use foams in subsurface applications, it is necessary to understand their stability in porous media. Diffusion driven coarsening of a stationary or nonflowing foam in a porous medium results in changing gas pressures and a coarsening of the foam texture. A two-dimensional network simulation has been created that predicts the behavior of foam in a porous medium by physically specifying the locations of all the lamellae in the system and by solving the complete set of Young-Laplace and diffusion equations. An hourglass approximates the shape of the pores, and the pore walls are considered to be highly water wet. A singularity arises in the system of differential algebraic equations due to the curvature of the pore walls. This singularity is a signal that the system must undergo oscillations or sudden lamellar rearrangements before the diffusion process can continue. Newton-Raphson iteration is used along with Keller`s method of arc-length continuation and a new jump resolution technique to locate and resolve bifurcations in the system of coupled lamellae. Gas bubbles in pore throats are regions of encapsulated pressure. As gas is released from these bubbles during diffusion, the pressure of the bubbles in the pore bodies increases. When the pressure increase is scaled by the characteristic Young-Laplace pressure, the equilibrium time for the diffusion process is scaled by the ratio of the square of the characteristic length to the gas diffusivity and two dimensionless groups. One describes the ease with which gas can diffuse through a lamella, the second represents the amount of gas encapsulated within the pore throats initially. Given this scaling, the resulting plots of pressure versus time and normalized lamellae positions versus time are universal for all system sizes and characteristics. This is true as long as the initial lamella distribution is the same in each case.

Cohen, D.; Patzek, T.W.; Radke, C.J.

1996-04-01

261

NSDL National Science Digital Library

This website includes an animation which illustrates the diffusion process. The two models that have been developed to explain the mechanism for the diffusion of dopants into silicon are the Vacancy model and the Interstitial model. It is the different bonding characteristics of the dopants with silicon that determine the diffusion mechanism. Although each model is based on these differences, they are not mutually exclusive. Objective: Explain the difference between the Vacancy and Interstitial diffusion models. You can find this animation under the heading "Process & Equipment III." This simulation is from Module 019 of the Process & Equipment III Cluster of the MATEC Module Library (MML). To view other clusters or for more information about the MML visit http://matec.org/ps/library3/process_I.shtmlKey

262

Relativistic Length Agony Continued

NASA Astrophysics Data System (ADS)

We made an attempt to remedy recent confusing treatments of some basic relativistic concepts and results. Following the argument presented in an earlier paper (Redzic 2008b), we discussed the misconceptions that are recurrent points in the literature devoted to teaching relativity such as: there is no change in the object in Special Relativity, illusory character of relativistic length contraction, stresses and strains induced by Lorentz contraction, and related issues. We gave several examples of the traps of everyday language that lurk in Special Relativity. To remove a possible conceptual and terminological muddle, we made a distinction between the relativistic length reduction and relativistic FitzGerald-Lorentz contraction, corresponding to a passive and an active aspect of length contraction, respectively; we pointed out that both aspects have fundamental dynamical contents. As an illustration of our considerations, we discussed briefly the Dewan-Beran-Bell spaceship paradox and the 'pole in a barn' paradox.

Redzic, D. V.

2014-06-01

263

NSDL National Science Digital Library

In this math lesson, learners explore the concept of using units to measure length. Learners first read "Ladybug on the Move" by Richard Fowler and measure the distance the ladybug travels on each page using yarn. Next, learners make their own "Go Ladybug Go!" books and use lima beans and a ladybug ruler to make and record measurements.

2012-09-18

264

NSDL National Science Digital Library

This lesson is designed to introduce students to the concepts of length, perimeter, and area. This lesson provides links to discussions and activities related to perimeter and area as well as suggested ways to integrate them into the lesson. Finally, the lesson provides links to follow-up lessons designed for use in succession with learning about perimeter and area.

2011-01-20

265

Power-law distributions are the main functional form for the distribution of repeat size and repeat copy number in the human genome. When the genome is broken into fragments for sequencing, the limited size of fragments and reads may prevent an unique alignment of repeat sequences to the reference sequence. Repeats in the human genome can be as long as 104 bases, or 105 ? 106 bases when allowing for mismatches between repeat units. Sequence reads from these regions are therefore unmappable when the read length is in the range of 103 bases. With a read length of 1000 bases, slightly more than 1% of the assembled genome, and slightly less than 1% of the 1 kb reads, are unmappable, excluding the unassembled portion of the human genome (8% in GRCh37/hg19). The slow decay (long tail) of the power-law function implies a diminishing return in converting unmappable regions/reads to become mappable with the increase of the read length, with the understanding that increasing read length will always move toward the direction of 100% mappability. PMID:25426137

Li, Wentian; Freudenberg, Jan

2014-01-01

266

NASA Astrophysics Data System (ADS)

A newly built static vacuum water vapor diffusion chamber was built to measure the concentration of ice nuclei (INs) at the top of Huangshan (the Yellow Mountains) in Southeast China. The experiments were conducted under temperatures between - 15 °C and - 23 °C and supersaturations with respect to ice between 4% and 25%. The results show that the average IN concentration was in the range of 0.27 to 7.02 L- 1, when the temperature was varied from - 15 °C to - 23 °C. The changes in IN concentrations with time were correlated with the change of number concentration of the aerosol particles of 0.5-20 ?m in diameter. The square correlation coefficients (R2) between IN and coarse aerosol particles (0.5-20 ?m in diameter) were all higher than 0.60, much higher than that (0.10) between IN and smaller particles (0.01-0.5 ?m). The concentration of ice nuclei at 14:00 LST was significantly higher than that at 08:00 LST, which is correlated with the diurnal variation of the concentration of aerosol particles. A parametric equation was developed based on measurements to represent the variations of IN concentration with temperature and supersaturation.

Jiang, Hui; Yin, Yan; Su, Hang; Shan, Yunpeng; Gao, Renjie

2015-02-01

267

NASA Technical Reports Server (NTRS)

The performance characteristics of InP-based In(x)Ga(1-x)As/In(0.52)Al(0.48)As (0.53 is less than or equal to x is less than or equal to 0.70) pseudomorphic modulation-doped field-effect transistors (MODFET's) as a function of strain in the channel, gate, length, and temperature were investigated analytically and experimentally. The strain in the channel was varied by varying the In composition x. The temperature was varied in the range of 40-300 K and the devices have gate lengths L(sub g) of 0.8 and 0.2 microns. Analysis of the device was done using a one-dimensional self consistent solution of the Poisson and Schroedinger equations in the channel, a two-dimensional Poisson solver to obtain the channel electric field, and a Monte Carlo simulation to estimate the carrier transit times in the channel. An increase in the value of the cutoff frequency is predicted for an increase in In composition, a decrease in temperature, and a decrease in gate length. The improvements seen with decreasing temperature, decreasing gate length, and increased In composition were smaller than those predicted by analysis. The experimental results on pseudomorphic InGaAs/InAlAs MODFET's showed that there is a 15-30 percent improvement in cutoff frequency in both the 0.8- and 0.2-micron gate length devices when the temperature is lowered from 300 to 40 K.

Lai, Richard; Bhattacharya, Pallab K.; Yang, David; Brock, Timothy L.; Alterovitz, Samuel A.; Downey, Alan N.

1993-01-01

268

NASA Astrophysics Data System (ADS)

This study tests whether Farsi vowels are contrastive with respective to length. Farsi has a six-vowel system with three lax vowels and three tense vowels. Both traditional grammarians and modern linguists believe that Farsi tense vowels are longer than lax vowels, and that there are no vowel pairs that contrast only in length. However, it has been suggested that Farsi exhibits compensatory lengthening, which is triggered by the deletion of glottal consonants in coda position in informal speech (Darzi, 1991). As a result, minimal pairs such as [tar] and [tarh] should contrast only with respect to vowel length. A corpus of 90 words of the form CVC, CVCG, CVGC, and CVCC (where V=a vowel and G=a glottal consonant) was recorded, and durations of vowels in different contexts were measured and compared. Preliminary results show that lax vowel durations fall into three groups with CVCC longer than CVCG/CVGC, and the latter longer than CVC. It remains to be seen whether CVCG/CVGC words show compensatory lengthening when the glottal consonant is deleted.

Shademan, Shabnam

2001-05-01

269

Lengthy Relationships: Foot Length, Stride, Leg Length, Height

NSDL National Science Digital Library

Paleontologists occasionally find ancient tracks and footprints preserved in the rocks. This lesson opens the door to analysing those footprints, and gleaning information about body size and activities of the extinct animals that made the tracks. Students will learn that patterns can reveal much about the past, in light of the present; and that bipedalism has appeared several times. Relationships will be found between foot length and leg length; foot length and height; leg length and height; stride length and leg length; and stride length and speed.

Jennifer Johnson

270

Inflatable penile prosthesis (IPP) remains the gold standard for the surgical treatment of refractory erectile dysfunction; however, current literature to aid surgeons on how best to counsel patients on their postoperative inflated penile length is lacking. The aim of this study was to identify preoperative parameters that could better predict postoperative penile length following insertion of an IPP. Twenty men were enrolled in a prospective study examining penile lengths before and after IPP surgery. Patients with Peyronie’s disease were excluded from this analysis. Baseline preoperative characteristics, including body mass index, history of hypertension, diabetes, Sexual Health Inventory for Men scores and/or prior radical prostatectomy were recorded. All patients underwent implantation with a three-piece inflatable Coloplast penile prosthesis. We compared stretched penile length to pharmacologically induced erect lengths. Postoperatively, we measured inflated penile lengths at 6 weeks and assessed patients’ perception of penile size at 12 weeks. The median (± interquartile range) stretched penile length and pharmacologically induced erect penile length was 15 (± 3) and 14.25 (± 2) cm, respectively (P = 0.5). Median post-prosthesis penile length (13.5 ± 2.13 cm) was smaller than preoperative pharmacologically induced length (P = 0.02) and preoperative stretched penile length (P = 0.01). The majority of patients (70%) had a decrease in penile length (median loss 0.5 ± 1.5 cm); however, this loss was perceptible by 43% of men. Stretched penile length and pharmacologically induced erect penile length were equally good predictors of postoperative inflated length (Spearman’s correlation 0.8 and 0.9, respectively). Pharmacologically induced erect penile length and stretched penile lengths are equal predictors of post-prosthesis penile length. The majority of men will experience some decrease in penile length following prosthesis implantation; however <50% report a subjective loss of penile length. PMID:24430278

Osterberg, EC; Maganty, A; Ramasamy, R; Eid, JF

2015-01-01

271

NSDL National Science Digital Library

This lab is designed to help students apply hillslope diffusion equations (derived in class prior to the lab) to understand real-world hillslopes. The major goal is a deeper understanding of hillslope processes and the equations used to describe hillslope diffusion by observing the same factors described in the equations on real-world hillslopes.

Jeni McDermott

272

A matched-asymptotics approach is proposed to show the occurrence of two distinct characteristic length scales in the carbonation process. The separation of these scales arises due to the strong competition between reaction and diffusion\\u000a effects. We show that for sufficiently large times ? the width of the carbonated region is proportional to \\u000a \\u000a , while the width of the reaction front

Adrian Muntean

2009-01-01

273

Fokker-Planck . . . Diffusion . . .

Fokker-Planck . . . Diffusion . . . Diffusion- . . . Application: . . . Summary and . . . First #12;Fokker-Planck . . . Diffusion . . . Diffusion- . . . Application: . . . Summary and . . . Topics: 1. Fokker-Planck transport equation 2. Diffusion approximation 3. Diffusion-convection transport

274

Introduction Diffusion Tensor Imaging

Introduction Diffusion Tensor Imaging Diffusion Kurtosis Imaging D-Eigenvalues and . . . Further ·Full Screen ·Close ·Quit Diffusion Tensor and Diffusion Kurtosis Tensor in Biomedical Engineering Diffusion Tensor Imaging Diffusion Kurtosis Imaging D-Eigenvalues and . . . Further Discussion Home Page

Zhang, Shuzhong

275

Approximate sample sizes required to estimate length distributions

The sample sizes required to estimate fish length were determined by bootstrapping from reference length distributions. Depending on population characteristics and species-specific maximum lengths, 1-cm length-frequency histograms required 375-1,200 fish to estimate within 10% with 80% confidence, 2.5-cm histograms required 150-425 fish, proportional stock density required 75-140 fish, and mean length required 75-160 fish. In general, smaller species, smaller populations, populations with higher mortality, and simpler length statistics required fewer samples. Indices that require low sample sizes may be suitable for monitoring population status, and when large changes in length are evident, additional sampling effort may be allocated to more precisely define length status with more informative estimators. ?? Copyright by the American Fisheries Society 2007.

Miranda, L.E.

2007-01-01

276

Protein self-diffusion in crowded solutions

Macromolecular crowding in biological media is an essential factor for cellular function. The interplay of intermolecular interactions at multiple time and length scales governs a fine-tuned system of reaction and transport processes, including particularly protein diffusion as a limiting or driving factor. Using quasielastic neutron backscattering, we probe the protein self-diffusion in crowded aqueous solutions of bovine serum albumin on nanosecond time and nanometer length scales employing the same protein as crowding agent. The measured diffusion coefficient D(?) strongly decreases with increasing protein volume fraction ? explored within 7% ? ? ? 30%. With an ellipsoidal protein model and an analytical framework involving colloid diffusion theory, we separate the rotational Dr(?) and translational Dt(?) contributions to D(?). The resulting Dt(?) is described by short-time self-diffusion of effective spheres. Protein self-diffusion at biological volume fractions is found to be slowed down to 20% of the dilute limit solely due to hydrodynamic interactions. PMID:21730176

Roosen-Runge, Felix; Hennig, Marcus; Zhang, Fajun; Jacobs, Robert M. J.; Sztucki, Michael; Schober, Helmut; Seydel, Tilo; Schreiber, Frank

2011-01-01

277

NSDL National Science Digital Library

In this activity, students measure the length of the day using the rotation of the Earth, and discover that the Sun is not exactly in the same place at the same clock time every day, understand that the changes are due to motions of the Earth, and lead to differences in solar, star, and sidereal time. This resource is from PUMAS - Practical Uses of Math and Science - a collection of brief examples created by scientists and engineers showing how math and science topics taught in K-12 classes have real world applications.

278

Dependence of Temporal Diffusion Spectra on Microstructural Properties of Biological Tissues

The apparent diffusion coefficient (ADC) measured using magnetic resonance imaging (MRI) methods provides information on micro-structural properties of biological tissues, and thus has found applications as a useful biomarker for assessing changes such as those that occur in ischemic stroke and cancer. Conventional pulsed gradient spin echo (PGSE) methods are in widespread use and provide information on, for example, variations in cell density. The oscillating gradient spin echo (OGSE) method has the additional ability to probe diffusion behaviors more readily at short diffusion times, and the temporal diffusion spectrum obtained by the OGSE method provides a unique tool for characterizing tissues over different length scales, including structural features of intra-cellular spaces. It has previously been reported that several tissue properties can affect ADC measurements significantly, and the precise biophysical mechanisms that account for ADC changes in different situations are still unclear. Those factors may vary in importance depending on the time and length scale over which measurements are made. In the present work, a comprehensive numerical simulation is used to investigate the dependence of the temporal diffusion spectra measured by OGSE methods on different micro-structural properties of biological tissues, including cell size, cell membrane permeability, intracellular volume fraction, intra-nucleus and intra-cytoplasm diffusion coefficients, nuclear size and T2 relaxation times. Some unique characteristics of the OGSE method at relatively high frequencies are revealed. The results presented in the paper offer a framework for better understanding possible causes of diffusion changes and may be useful to assist the interpretation of diffusion data from OGSE measurements. PMID:21129880

Xu, Junzhong; Does, Mark D.; Gore, John C.

2010-01-01

279

NASA Technical Reports Server (NTRS)

Payload customers for the Space Shuttle have recently expressed concerns about the possibility of their payloads at an adjacent pad being contaminated by plume effluents from a shuttle at an active pad as they await launch on an inactive pad. As part of a study to satisfy such concerns a ring of inexpensive dosimeters was deployed around the active pad at the inter-pad distance. However, following a launch, dosimeters cannot be read for several hours after the exposure. As a consequence factors such as different substrates, solvent systems, and possible volatilization of HCl from the badges were studied. This observation led to the length of stain (LOS) dosimeters of this invention. Commercial passive LOS dosimeters are sensitive only to the extent of being capable of sensing 2 ppm to 20 ppm if the exposure is 8 hours. To map and quantitate the HCl generated by Shuttle launches, and in the atmosphere within a radius of 1.5 miles from the active pad, a sensitivity of 2 ppm HCl in the atmospheric gases on an exposure of 5 minutes is required. A passive length of stain dosimeter has been developed having a sensitivity rendering it capable of detecting a gas in a concentration as low as 2 ppm on an exposure of five minutes.

Lueck, Dale E. (inventor)

1994-01-01

280

A diffusion-based cyclic particle extractor

A cyclic particle extractor based on particle diffusion is presented. The extraction realized by the device features simplicity,\\u000a programmability, and low cost. Although conventional particle separation based on diffusion can be spontaneously realized\\u000a without any active inputs, the extraction efficiency decreases as the size difference between particles decreases or if the\\u000a diffusion length is insufficient. In this article, a primary

Han-Sheng ChuangStephen; Stephen C. Jacobson; Steven T. Wereley

2010-01-01

281

NASA Technical Reports Server (NTRS)

The diffusion tube was designed to operate below about 0.25 percent of water supersaturation. It is simply a long tube lined on the inside with a damp chamois cloth, and heated isothermally to a few degrees centigrade above the incoming air. The diffusion coefficient for water vapor is slightly larger than that for heat, making it possible to supersaturate the airflow. This is the same principle by which transient supersaturations may occur in parallel plate cloud chambers. Only the diffusion of vapor and heat from the walls into the moving air are considered.

Leaitch, R.; Megaw, W. J.

1981-01-01

282

NASA Astrophysics Data System (ADS)

Parameterizations of the vertical eddy diffusivity over homogeneous terrain in neutral, stable and unstable conditions for the entire atmospheric boundary layer are proposed using the mixing length theory. The formulation utilizes the theoretically derived local mixing length scale that is composed of three component length scales. Proposed profiles of the eddy diffusivity in various stability conditions are compared to those reported in the literature. The proposed profiles of the eddy diffusivity are used in a generalized analytical model for dispersion of pollutants released from a continuous source in the atmospheric boundary layer. The dispersion model describing the crosswind integrated concentrations is briefly presented. By considering the proposed and other commonly applied parameterizations of eddy diffusivity, the dispersion model is evaluated with the tracer observations obtained from Copenhagen diffusion experiment in unstable conditions, Prairie Grass experiment in both unstable and stable conditions and Hanford experiment in stable conditions. The dispersion model with proposed parameterizations of the eddy diffusivity is performing reasonably well with the observations and demonstrates throughout a consistent and good performance in the concentration estimation for elevated and surface releases from a continuous point source in various stability conditions. Though the magnitudes of the various eddy diffusivities are different from the proposed one, the profiles of all parameterizations in terms of the shape have almost similar characteristics. The differences in the magnitudes of diffusion produced by various parameterizations cause minor but noticeable changes in the simulation of ground level concentrations from the dispersion model. In very stable conditions, the agreement of the model evaluations with measurements is less satisfactory and none of the parameterizations used here including proposed one is adequate to describe the atmospheric dispersion process in these conditions.

Kumar, Pramod; Sharan, Maithili

2012-03-01

283

The long and short of food-chain length

Food-chain length is a central characteristic of ecological communities that has attracted considerable attention for over 75 years because it strongly affects community structure, ecosystem processes and contaminant concentrations. Conventional wisdom holds that either resource availability or dynamical stability limit food-chain length; however, new studies and new techniques challenge the conventional wisdom and broaden the discourse on food-chain length. Recent

David M. Post

2002-01-01

284

NASA Astrophysics Data System (ADS)

The past decade has seen a significant increase in the availability of data on diffusion in accessory minerals obtained through direct characterization of laboratory-induced diffusive uptake profiles by SIMS, RBS or NRA. Recent studies of this type yield diffusion constants that are highly systematic, internally consistent, and time-independent over the range of conditions and durations accessible in the laboratory. Although satisfying to the experimentalists, this consistency does not always carry over to observations of natural rocks: in the real world, isotopic measurements sometimes point to open-system behavior in cases where experimental data preclude isotope mobility by lattice diffusion (the converse may be true in rare cases). The apparent discrepancies between lab and nature do not necessarily call into question the validity of information from either realm. In fact, the differences in viewpoint often arise simply because practitioners on the two sides -- rock analysts on the one hand and experimentalists on the other -- ask different questions. In simple terms, metamorphic petrologists and isotope geochemists ask "What happened to this specific sample?"; experimentalists ask "What would happen to a hypothetical sample, given certain idealized conditions?" The philosophical differences implicit in these two questions can be bridged by better communication, which may lead eventually to better understanding of natural systems. Experimentalists seek to constrain diffusion in an idealized, strain- and defect-free lattice, because this is the "baseline" transport process and the only one that is truly characteristic of a specific atomic structure. Even if a specific accessory mineral grain contains diffusion-enhancing defects, bulk diffusion in that grain is still controlled at some length scale by the properties of the normal lattice. Without knowledge of lattice diffusion from laboratory experiments, progress in understanding bulk diffusion in nature will be limited, as will reconciliation of apparent discrepancies in closure behavior. Recent results from the experimental lab are shedding light on the properties and systematics of intra-crystalline diffusive "fast paths."

Watson, B.

2004-05-01

285

Outburst Cycle Length Variations in Dwarf Novae

NASA Astrophysics Data System (ADS)

We have analysed variations of the cycle length for a group of Dwarf Novae. Results for certain stars are compared with that obtained for computer-simulated processs (random intervals between maxima, 2-order Markow chain). For EM Cyg, the observations of which are most numerous in our sample, the "seasonal" values of the cycle length were also obtained from a sine-like fit. All investigated stars showed significant changes of the cycle length from season to season. Existence of two groups of Cataclysmic Variables with "smooth" changes from "abruptly changing" observations by smoothing, e.g. by a "Runing Mean". THis phenomenon needs intensive investigation based on complex observations, as well as on theoretical modeling. The detailed study of the temporal behaviour of the individual time intervals showed apparent cyclicity with characteristic time of some years and similar to the solar-like activity (Bianchini, 1990) or may be "alternating" between two distinctly dufferent values (Andronov, Shakun, 1990)

Andronov, I. L.; Chinarova, L. L.; Mikhailik, V. A.

286

Sandstones of unexpectedly high diffusibility.

Measurements have been made of diffusion coefficients (D(i)=-mass flux/concentration gradient) using a double reservoir, steady-state method with two tracers, CaBr(2) and amino-G-acid, on intact samples of Triassic red-bed sandstone from northwest England. Diffusibility (D'=D(i)/diffusion coefficient in water) averages 0.124, ranging between 0.075 and 0.215 (porosity 0.1 to 0.24), very similar for the two tracers. Implied tortuosities (actual path length/straight line length) average 1.21 (range 1.06 to 1.47), with constrictivities close to 1. In comparison with limited red-bed sandstone data from elsewhere, these D' values are up to 4 times greater, and tortuosity correspondingly lower. Re-interpretation of formation factor data from previous studies on shallow sandstone samples also from northwest England confirms that diffusibility is significantly higher in these sandstones than others from similar palaeoenvironment/stratigraphic units. The lower tortuosities appear to result from the relatively high permeability, open fabric of the rock, properties likely to be present in shallow sandstone systems used for water supply. It is concluded that diffusion rates may, in some shallow freshwater-containing continental sandstone systems, be significantly greater than is implied by estimates of sandstone diffusibility current in the literature. PMID:21146250

Bashar, Khairul; Tellam, John H

2011-03-25

287

Lateral extent of oxidation-enhanced diffusion of phosphorus in <100> silicon

NASA Astrophysics Data System (ADS)

The lateral extent of oxidation-enhanced diffusion (OED) of phosphorus in (100) silicon oxidized in dry oxygen has been investigated. OED was observed near the Si/SiO2 interface under an oxidation mask composed of Si3N4/SiO2. It was found that under the mask OED decays nearly exponentially from the edge of the oxidized region. The characteristic decay length increases with square root of oxidation time and is exponentially dependent on temperature with activation energy of 2 eV. It is proposed that the OED observations can be explained on the basis of excess silicon self-interstitials diffusing away from the oxidized regions. Both diffusion and interface capture of self-interstitials play a role in their distribution in the silicon bulk.

Taniguchi, K.; Antoniadis, D. A.

1985-05-01

288

SELECTION FOR LENGTH OF LIFE IN THE HONEYBEE (APIS MELLIFERA)

SELECTION FOR LENGTH OF LIFE IN THE HONEYBEE (APIS MELLIFERA) Jovan M. KULIN Two-way selection in the honeybee for long and short length of life in laboratory cages was carried characteristics in honeybees has attracted the interest of several investigators of this beneficial insect. O. W

Paris-Sud XI, Université de

289

Scaling Behavior and Equilibrium Lengths of Knotted Polymers

Scaling Behavior and Equilibrium Lengths of Knotted Polymers Eric Rawdon Akos Dobay John C. Kern numerical simulations to investigate how the chain length and topology of freely fluctuating knotted polymer of a characteristic changes with the chain size and how this change depends on the topology of the modeled polymers

Bigelow, Stephen

290

Geometric Optimization of Relative Link Lengths for Biomimetic Robotic Fish

This paper focuses on the design of fishlike underwater robots using an optimization approach to choose relative link lengths. Considering both ichthyologic characteristics and mechatronic constraints, the optimal link-length ratios are numerically calculated by an improved constrained cyclic variable method. Comparative results, before and after the optimization, demonstrate the enhanced performance

Junzhi Yu; Long Wang; Min Tan

2007-01-01

291

NASA Technical Reports Server (NTRS)

A diffuse celestial radiation which is isotropic at least on a course scale were measured from the soft X-ray region to about 150 MeV, at which energy the intensity falls below that of the galactic emission for most galactic latitudes. The spectral shape, the intensity, and the established degree of isotropy of this diffuse radiation already place severe constraints on the possible explanations for this radiation. Among the extragalactic theories, the more promising explanations of the isotropic diffuse emission appear to be radiation from exceptional galaxies from matter antimatter annihilation at the boundaries of superclusters of galaxies of matter and antimatter in baryon symmetric big bang models. Other possible sources for extragalactic diffuse gamma radiation are discussed and include normal galaxies, clusters of galaxies, primordial cosmic rays interacting with intergalactic matter, primordial black holes, and cosmic ray leakage from galaxies.

1981-01-01

292

Three-dimensional analysis of MHD generators and diffusers

The three-dimensional flow and heat transfer phenomena in MHD channels and diffusers are analyzed by solving the governing partial differential equations for flow and electrical fields. The equation set consists of the mass continuity equation, the three momentum equations, the equations for enthalpy, turbulence kinetic energy and its dissipation rate, and the Maxwell equations. This set of coupled equations is solved by the use of a finite-difference calculation procedure. The turbulence is represented by a two-equation model of turbulence in which partial differential equations are solved for the turbulence kinetic energy and its dissipation rate. Calculations have been performed for Faraday and diagonally-connected channels. Specifically, the AEDC (Faraday) and the UTSI (diagonal) channels have been analyzed, and the results are compared with experimental data. The agreement is fairly good for all the measured quantities. The effects of channel loading on the three-dimensional flow characteristics of Faraday and diagonally-connected generators have been also analyzed. A simple argument is presented to show qualitatively the role of MHD body forces in generating axial vorticity and hence secondary flows in the cross-stream. Calculations have also been made to study the flow evolution in MHD diffusers. The calculations show that the velocity overshoots and secondary flows decay along the diffusers length. Plots of velocity, skin friction and pressure recovery are presented to illustrate the flow development in MHD diffusers.

Vanka, S P; Ahluwalia, R K; Doss, E D

1982-03-01

293

Reconstruction of brain neuronal pathways in brain from the diffusion tensor MRI data

NASA Astrophysics Data System (ADS)

MRI based fiber tracking is a diagnostic method based on the diffusion tensor MRI data, which allows to find pathways of neuronal bundles in brain in vivo. In this work we propose a method of neuronal pathways reconstruction using A-star algorithm, with the possibility to assess its the effectiveness. One of the criteria is the probabilistic search parameter G, defined by a set of diffusion coefficients in a given volume element. The parameter G obtained trajectory correlated to its length has the meaning of entropy and allows to assess reliability of the found path. The proposed method was tested on simulated data with the characteristic behavior of trajectories of the complex variations, different cases of intersection of the beams passing through the intersection without a common voxels, and obtained characteristics of the corresponding probability.

Nasretdinov, A. R.; Il'yasov, K. A.; Nedopekin, O. V.

2012-11-01

294

Objective To assess the effects of varying the number of diffusion gradient directions (NDGDs) on diffusion tensor fiber tracking (FT) in human brain white matter using tract characteristics. Materials and Methods Twelve normal volunteers underwent diffusion tensor imaging (DTI) scanning with NDGDs of 6, 11, 15, 21, and 31 orientations. Three fiber tract groups, including the splenium of the corpus callosum (CC), the entire CC, and the full brain tract, were reconstructed by deterministic DTI-FT. Tract architecture was first qualitatively evaluated by visual observation. Six quantitative tract characteristics, including the number of fibers (NF), average length (AL), fractional anisotropy (FA), relative anisotropy (RA), mean diffusivity (MD), and volume ratio (VR) were measured for the splenium of the CC at the tract branch level, for the entire CC at tract level, and for the full brain tract at the whole brain level. Visual results and those of NF, AL, FA, RA, MD, and VR were compared among the five different NDGDs. Results The DTI-FT with NDGD of 11, 15, 21, and 31 orientations gave better tracking results compared with NDGD of 6 after the visual evaluation. NF, FA, RA, MD, and VR values with NDGD of six were significantly greater (smallest p = 0.001 to largest p = 0.042) than those with four other NDGDs (11, 15, 21, or 31 orientations), whereas AL measured with NDGD of six was significantly smaller (smallest p = 0.001 to largest p = 0.041) than with four other NDGDs (11, 15, 21, or 31 orientations). No significant differences were observed in the results among the four NDGD groups of 11, 15, 21, and 31 directions (smallest p = 0.059 to largest p = 1.000). Conclusion The main fiber tracts were detected with NDGD of six orientations; however, the use of larger NDGD (? 11 orientations) could provide improved tract characteristics at the expense of longer scanning time. PMID:25741203

Yao, Xufeng; Yu, Tonggang; Liang, Beibei; Xia, Tian; Huang, Qinming

2015-01-01

295

Sequence length requirements Tandy Warnow

Sequence length requirements Tandy Warnow Department of Computer Science The University of Texas at Austin #12;Part 1: Absolute Fast Convergence #12;DNA Sequence Evolution AAGACTT TGGACTTAAGGCCT -3 mil yrs convergence (afc) #12;"Convergence rate" or sequence length requirement The sequence length (number of sites

Warnow,Tandy

296

NASA Technical Reports Server (NTRS)

Tests begun at Stennis Space Center's E Complex Sept. 13 evaluated a liquid oxygen lead for engine start performance, part of the A-3 Test Facility Subscale Diffuser Risk Mitigation Project at SSC's E-3 Test Facility. Phase 1 of the subscale diffuser project, completed Sept. 24, was a series of 18 hot-fire tests using a 1,000-pound liquid oxygen and gaseous hydrogen thruster to verify maximum duration and repeatability for steam generation supporting the A-3 Test Stand project. The thruster is a stand-in for NASA's developing J-2X engine, to validate a 6 percent scale version of A-3's exhaust diffuser. Testing the J-2X at altitude conditions requires an enormous diffuser. Engineers will generate nearly 4,600 pounds per second of steam to reduce pressure inside A-3's test cell to simulate altitude conditions. A-3's exhaust diffuser has to be able to withstand regulated pressure, temperatures and the safe discharge of the steam produced during those tests. Before the real thing is built, engineers hope to work out any issues on the miniature version. Phase 2 testing is scheduled to begin this month.

2007-01-01

297

NASA Astrophysics Data System (ADS)

The optical characteristics of absorption and scattering of irradiated tissue determine light spatial distribution and the subsequent biological effects, which could decide the dosimetry for laser medical applications. Studys have shown that the optical properties of bio-tissue could be determined through some fitting algorithms with spatially resolved diffuse reflectance theory based on the measurement of diffuse reflectance. The regression of reflectance data with by diffusion theory model was important for optical properties estimation. In the paper, the reflectance versus distance data acquired from Monte Carlo method was by fit to diffusion theory model by the nonliear least-squares fitting algorithm to study the produre and mothod of determination of optical properties. And attention was especially paid to the influence of the radial step width ?r, length of radial distance rL and start value of radial distance r0 on the regression results. Preliminary results indicated that the radial step width and length of radial distance rL both have little influence on the fitting. Nevertheless, the start value of radial distance r0 of reflectance data has great influence on the fitting. Fitting deviation would become little while the start value of radial distance r0 grow greater. and an appropriate r0 was important for data fitting. Study also showd a more accurate light diffuse reflectance theoretical model was need for estimate the optical parameters by fitting the diffuse reflectance data accurately. Our work maybe be helpful to the experiment measurement of light diffuse reflectance data for noninvasive optical properties determination.

Peng, Dong-qing; Li, Hui

2012-12-01

298

Lateral diffusion in an archipelago. Distance dependence of the diffusion coefficient.

An understanding of the distance dependence of the lateral diffusion coefficient is useful in comparing the results of diffusion measurements made over different length scales, and in analyzing the kinetics of mobile redox carriers in organelles. A distance-dependent, concentration-dependent diffusion coefficient is defined, and it is evaluated by Monte Carlo calculations of a random walk by mobile point tracers in the presence of immobile obstacles on a triangular lattice, representing the diffusion of a lipid or a small protein in the presence of immobile membrane proteins. This work confirms and extends the milling crowd model of Eisinger, J., J. Flores, and W. P. Petersen (1986. Biophys J. 49:987-1001). Similar calculations for diffusion of mobile particles interacting by a hard-core repulsion yield the distance dependence of the self-diffusion coefficient. An expression for the range of short-range diffusion is obtained, and the distance scales for various diffusion measurements are summarized. PMID:2790141

Saxton, M J

1989-01-01

299

We present our studies on the physicochemical properties of water confined in Dibutylimidazolium bis(trifluoromethanesulfonylimide) ([C4C4im][NTf2]) reverse micelles through the NMR relaxation measurements that provide us an understanding of microviscosity and pH in the confined condition. We present experimental results on phase behavior, diffusion, structural characteristics and pH in aqueous ionic liquid-confined media. The ternary phase diagram was constructed by the cloud point measurements and the microheterogeneous regions were detected by the measurement of bulk viscosity and diffusion coefficients of K4[Fe(CN)6] inside the homogeneous microemulsion systems through the cyclic voltammetric (CV) measurements. The size of the microemulsion systems was characterized by the dynamic light scattering (DLS) method. The (1)H NMR spectra of homogeneous microemulsion systems were taken which indicates the presence of bound and free water molecules inside the microemulsion system. The NMR spin-lattice relaxation time (T1) of water molecules in its homogeneous microemulsion systems were measured and the reorientational correlation time (?c) of water molecules obtained from it indicates that the fluidity of homogeneous confined media decreases with the decrease in the composition of water. Microviscosity of the aqueous confined media was calculated from the measured T1 relaxation time values by applying the Debye-Stokes equation and correlated with the bulk viscosity of the samples. It was observed that both the microviscosity and bulk viscosity show inverse relationship. The fraction of bound and free water molecules were calculated from the measured T1 values. NMR spin-spin relaxation time (T2) of water molecules in its homogeneous microemulsion systems were measured with the varying pH of the aqueous core. A change in the T2 relaxation time of the water proton was observed proposing an exchange of proton between the H2O and -OH group of the TX-100 molecules. Finally, methyl orange (MO) was used as a UV-vis spectrophotometric molecular probe and the measured ?max values of the probe were used for the detection of micropolarity of the homogeneous aqueous confined media and was found to be increase with the increase in the size of the confined media. PMID:25555212

Nanda, Raju; Kumar, Anil

2015-01-29

300

Critical Waves and the Length Problem of Biology

It is pointed out that the mystery of how biological systems measure their lengths vanishes away if one premises that they have discovered a way to generate linear waves analogous to compressional sound. These can be used to detect length at either large or small scales using echo timing and fringe counting. It is shown that suitable linear chemical potential waves can, in fact, be manufactured by tuning to criticality conventional reaction-diffusion with a small number substances. Min oscillations in E. coli are cited as precedent resonant length measurement using chemical potential waves analogous to laser detection. Mitotic structures in eucaryotes are identified as candidates for such an effect at higher frequency. The engineering principle is shown to be very general and functionally the same as that used by hearing organs. PNAS Significance Statement: This paper invokes physical principles to address the question of how living things might use reaction-diffusion to measure out and regulate the many thou...

Laughlin, R B

2015-01-01

301

NASA Technical Reports Server (NTRS)

We have extended the utility of NMR as a technique to probe porous media structure over length scales of approximately 100-2000 microm by using the spin 1/2 noble gas 129Xe imbibed into the system's pore space. Such length scales are much greater than can be probed with NMR diffusion studies of water-saturated porous media. We utilized Pulsed Gradient Spin Echo NMR measurements of the time-dependent diffusion coefficient, D(t), of the xenon gas filling the pore space to study further the measurements of both the pore surface-area-to-volume ratio, S/V(p), and the tortuosity (pore connectivity) of the medium. In uniform-size glass bead packs, we observed D(t) decreasing with increasing t, reaching an observed asymptote of approximately 0.62-0.65D(0), that could be measured over diffusion distances extending over multiple bead diameters. Measurements of D(t)/D(0) at differing gas pressures showed this tortuosity limit was not affected by changing the characteristic diffusion length of the spins during the diffusion encoding gradient pulse. This was not the case at the short time limit, where D(t)/D(0) was noticeably affected by the gas pressure in the sample. Increasing the gas pressure, and hence reducing D(0) and the diffusion during the gradient pulse served to reduce the previously observed deviation of D(t)/D(0) from the S/V(p) relation. The Pade approximation is used to interpolate between the long and short time limits in D(t). While the short time D(t) points lay above the interpolation line in the case of small beads, due to diffusion during the gradient pulse on the order of the pore size, it was also noted that the experimental D(t) data fell below the Pade line in the case of large beads, most likely due to finite size effects.

Mair, R. W.; Hurlimann, M. D.; Sen, P. N.; Schwartz, L. M.; Patz, S.; Walsworth, R. L.

2001-01-01

302

We have extended the utility of NMR as a technique to probe porous media structure over length scales of ~ 100 - 2000 micron by using the spin 1/2 noble gas 129Xe imbibed into the system's pore space. Such length scales are much greater than can be probed with NMR diffusion studies of water-saturated porous media. We utilized Pulsed Gradient Spin Echo NMR measurements of the time-dependent diffusion coefficient, D(t) of the xenon gas filling the pore space to study further the measurements of both the surface area-pore volume ratio, S/Vp, and the tortuosity (pore connectivity) of the medium. In uniform-size glass bead packs, we observed D(t) decreasing with increasing t, reaching an observed asymptote of ~ 0.62 - 0.65D0, that could be measured over diffusion distances extending over multiple bead diameters. Measurements of D(t)/D0 at differing gas pressures showed this tortuosity limit was not affected by changing the characteristic diffusion length of the spins during the diffusion encoding gradient pulse. This was not the case at the short time limit, where D(t)/D0 was noticeably affected by the gas pressure in the sample. Increasing the gas pressure, and hence reducing D0 and the diffusion during the gradient pulse served to reduce the previously observed deviation of D(t)/D0 from the S/Vp relation. The Pade approximation is used to interpolate between the long and short time limits in D(t). While the short time D(t) point lay above the interpolation line in the case of small beads, due to diffusion during the gradient pulse on the order of the pore size, it was also noted that the experimental D(t) data fell below the Pade line in the case of large beads, most likely due to finite size effects.

R. W. Mair; M. D. Hurlimann; P. N. Sen; L. M. Schwartz; S. Patz; R. L. Walsworth

2002-11-10

303

Exploratory laboratory study of lateral turbulent diffusion at the surface of an alluvial channel

In natural streams turbulent diffusion is one of the principal mechanisms by which liquid and suspended-particulate contaminants are dispersed in the flow. A knowledge of turbulence characteristics is therefore essential in predicting the dispersal rates of contaminants in streams. In this study the theory of diffusion by continuous movements for homogeneous turbulence is applied to lateral diffusion at the surface of an open channel in which there is uniform flow. An exploratory-laboratory investigation was conducted in which the lateral dispersion at the water surface of a sand-Led flume was studied by measuring the lateral spread from a point source of small floating polyethylene articles. The experiment was restricted to a single set of low and channel geometry conditions. The results of the study indicate that with certain restrictions lateral dispersion in alluvial channels may be successfully described by the theory of diffusion by continuous movements. The experiment demonstrates a means for evaluating the lateral diffusion coefficient and also methods for quantitatively estimating fundamental turbulence properties, such as the intensity and the Lagrangian integral scale of turbulence in an alluvial channel. The experimental results show that with increasing distance from the source the coefficient of lateral turbulent diffusion increases initially but tends toward a constant limiting value. This result is in accordance with turbulent diffusion theory. Indications are that the distance downstream from the source required for the diffusion coefficient to reach its limiting value is actually very small when compared to the length scale of most diffusion phenomena in natural streams which are of practical interest.

Sayre, William W.; Chamberlain, A.R.

1964-01-01

304

Anomalous diffusion due to obstacles: a Monte Carlo study.

In normal lateral diffusion, the mean-square displacement of the diffusing species is proportional to time. But in disordered systems anomalous diffusion may occur, in which the mean-square displacement is proportional to some other power of time. In the presence of moderate concentrations of obstacles, diffusion is anomalous over short distances and normal over long distances. Monte Carlo calculations are used to characterize anomalous diffusion for obstacle concentrations between zero and the percolation threshold. As the obstacle concentration approaches the percolation threshold, diffusion becomes more anomalous over longer distances; the anomalous diffusion exponent and the crossover length both increase. The crossover length and time show whether anomalous diffusion can be observed in a given experiment. PMID:8161693

Saxton, M J

1994-01-01

305

ERIC Educational Resources Information Center

Two demonstrations are described. Materials and instructions for demonstrating movement of molecules into cytoplasm using agar blocks, phenolphthalein, and sodium hydroxide are given. A simple method for demonstrating that the rate of diffusion of a gas is inversely proportional to its molecular weight is also presented. (AJ)

Foy, Barry G.

1977-01-01

306

ERIC Educational Resources Information Center

Diffusion has often been taught in science courses as one of the primary ways by which molecules travel, particularly within organisms. For years, classroom teachers have used the same common demonstrations to illustrate this concept (e.g., placing drops of food coloring in a beaker of water). Most of the time, the main contributor to the motion…

Dou, Remy; Hogan, DaNel; Kossover, Mark; Spuck, Timothy; Young, Sarah

2013-01-01

307

NSDL National Science Digital Library

Web-based intructional material describing the use of diffusion models in population ecology. This page is part of a set of on-line lectures on Quantitative Population Ecology produced by Alexei Sharov in the Department of Entomology at Virginia Tech.

Alexei Sharov

308

Relations between Some Characteristic Lengths in a Triangle

ERIC Educational Resources Information Center

The paper's aim is to note a remarkable (and apparently unknown) relation for right triangles, its generalisation to arbitrary triangles and the possibility to derive these and some related relations by elimination using Groebner basis computations with a modern computer algebra system. (Contains 9 figures.)

Koepf, Wolfram; Brede, Markus

2005-01-01

309

Relations between some characteristic lengths in a triangle

Keywords: Pythagorean Theorem, Altitude Theorem, Cathetus Theorems, Groebner basis, poly- nomial The Pythagorean group of theorems We start by noting the Pythagorean group of theorems. Assume a right triangle sections. Of course by construction the equation c p q= + is valid. The Pythagorean theorem is given

Koepf, Wolfram

310

NASA Technical Reports Server (NTRS)

Amorphous W-Zr and W-N alloys were investigated as diffusion barriers in silicon metallization schemes. Data were presented showing that amorphous W-Zr crystallizes at 900 C, which is 200 C higher than amorphous W-Ni films, and that both films react with metallic overlayers at temperatures far below the crystllization temperature. Also, W-N alloys (crystalline temperature of 600 C) were successfully incorporated as a diffusion barrier in contact structures with both Al and Ag overlayers. The thermal stability of the electrical characteristics of shallow n(+)p junctions significantly improved by incorporating W-N layers in the contact system. One important fact demonstated was the critical influence of the deposition parameters during formation of these carriers.

Kolawa, E.; So, F. C. T.; Nicolet, M-A.

1986-01-01

311

There is evidence for migration of tritiated water vapor through the tuff in the unsaturated zone from the buried disposal shafts located on a narrow mesa top at Area G, Los Alamos, NM. Field data are consistent with an effective in-situ vapor phase diffusion coefficient of 1.5x10{sup {minus}3} m{sup s}/s, or a factor of 60 greater than the binary diffusion coefficient for water vapor in air. A model is derived to explain this observation of anomolously large diffusion, which relates an effective vapor or gas phase diffusion coefficient in the fractured porous media to the subsurface propagation of atmospheric pressure fluctuations (barometric pumping). The near surface (unattenuated) diffusion coefficient is independent of mode period under the simplified assumptions of a complete {open_quote}mixing mechanism{close_quote} for the effective diffusion process. The unattenuated effective diffusion driven by this barometric pumping is proportional to an average media permeability times the sum of the square of pressure mode amplitudes, while the attenuation length is proportional to the squarer root of the product of permeability times mode period. There is evidence that the permeability needed to evaluate the pressure attenuation length is the in-situ value, approximately that of the matrix. The diffusion which results using Area G parameter values is negligible in the matrix but becomes large at the effective permeability of the fractured tuff matrix. The effective diffusion coefficient predicted by this model, due to pressure fluctuations and the observed fracture characteristics, is in good agreement with the observed in-situ diffusion coefficient for tritium field measurements. It is concluded that barometric pumping in combination with the enhanced permeability of the fractured media is a likely candidate to account for the observed in-field migration of vapor in the near surface unsaturated zone at Area G.

Vold, E.L.

1997-03-01

312

IMPEDANCE OF FINITE LENGTH RESISTOR

We determine the impedance of a cylindrical metal tube (resistor) of radius a, length g, and conductivity {sigma}, attached at each end to perfect conductors of semi-infinite length. Our main interest is in the asymptotic behavior of the impedance at high frequency, k >> 1/a. In the equilibrium regime, , the impedance per unit length is accurately described by the well-known result for an infinite length tube with conductivity {sigma}. In the transient regime, ka{sup 2} >> g, we derive analytic expressions for the impedance and wakefield.

KRINSKY, S.; PODOBEDOV, B.; GLUCKSTERN, R.L.

2005-05-15

313

Solute transport in clay-rich aquitards is characterized as molecular diffusion- or advection-dominated based on the Péclet number (P(e)). However, few field-based measurements of the coefficient of molecular diffusion (D(e)) exist, and none with a range of advection- or diffusion-dominated conditions in the same aquitard. In this long-term field experiment, standing water in a recovering well was spiked with deuterium ((2)H), then water-level recovery and ?(2)H values were monitored as the well returned to static conditions over 1054 days. After a second (2)H spike, water levels and ?(2)H values were monitored to day 1644 while under near static conditions. Modeling of the second spike was used to define the D(e) of (2)H as (3-4)× 10(-10)m(2)s(-1) for an accessible porosity of 0.31. Reservoir concentrations from the initial spike were modeled to define the transition from advection- to diffusion-dominated transport. This occurred after 200 days, consistent with a transition in P(e) from <1 to >1 when the length term is taken as the radial extent of the tracer plume (normalized concentration <0.05). This study verifies plume extent as the characteristic length term in the calculation of P(e) and demonstrates the transition from advection- to diffusion-dominated transport as the value of P(e) decreases below unity. PMID:22343012

Barbour, S Lee; Hendry, M Jim; Wassenaar, Leonard I

2012-04-01

314

Flux saturation length of sediment transport.

Sediment transport along the surface drives geophysical phenomena as diverse as wind erosion and dune formation. The main length scale controlling the dynamics of sediment erosion and deposition is the saturation length Ls, which characterizes the flux response to a change in transport conditions. Here we derive, for the first time, an expression predicting Ls as a function of the average sediment velocity under different physical environments. Our expression accounts for both the characteristics of sediment entrainment and the saturation of particle and fluid velocities, and has only two physical parameters which can be estimated directly from independent experiments. We show that our expression is consistent with measurements of Ls in both aeolian and subaqueous transport regimes over at least 5 orders of magnitude in the ratio of fluid and particle density, including on Mars. PMID:24313529

Pähtz, Thomas; Kok, Jasper F; Parteli, Eric J R; Herrmann, Hans J

2013-11-22

315

Cells control organelle size with great precision and accuracy to maintain optimal physiology, but the mechanisms by which they do so are largely unknown. Cilia and flagella are simple organelles in which a single measurement, length, can represent size. Maintenance of flagellar length requires an active transport process known as intraflagellar transport, and previous measurements suggest that a length-dependent feedback regulates intraflagellar transport. But the question remains: how is a length-dependent signal produced to regulate intraflagellar transport appropriately? Several conceptual models have been suggested, but testing these models quantitatively requires that they be cast in mathematical form. Here, we derive a set of mathematical models that represent the main broad classes of hypothetical size-control mechanisms currently under consideration. We use these models to predict the relation between length and intraflagellar transport, and then compare the predicted relations for each model with experimental data. We find that three models-an initial bolus formation model, an ion current model, and a diffusion-based model-show particularly good agreement with available experimental data. The initial bolus and ion current models give mathematically equivalent predictions for length control, but fluorescence recovery after photobleaching experiments rule out the initial bolus model, suggesting that either the ion current model or a diffusion-based model is more likely correct. The general biophysical principles of the ion current and diffusion-based models presented here to measure cilia and flagellar length can be generalized to measure any membrane-bound organelle volume, such as the nucleus and endoplasmic reticulum. PMID:25809250

Ludington, William B; Ishikawa, Hiroaki; Serebrenik, Yevgeniy V; Ritter, Alex; Hernandez-Lopez, Rogelio A; Gunzenhauser, Julia; Kannegaard, Elisa; Marshall, Wallace F

2015-03-24

316

Linear study of Rayleigh-Taylor instability in a diffusive quantum plasma

The linear Rayleigh-Taylor (RT) instability in an incompressible quantum plasma is investigated on the basis of quantum magnetohydrodynamic model. It is shown that the occurrence of RT instability depends on density-temperature inhomogeneity (characteristic lengths) on one hand, and the system layer size on the other. It is also observed that the combined effects of external magnetic field, diffusivity, and quantum pressure significantly modify the dispersion properties of system in both the parallel and perpendicular directions. For any case, the imaginary and real parts of dispersion relation are presented and the possibility and conditions for the instability growth rate are discussed.

Momeni, Mahdi [Faculty of Physics, Shahrood University, Shahrood (Iran, Islamic Republic of)] [Faculty of Physics, Shahrood University, Shahrood (Iran, Islamic Republic of)

2013-08-15

317

NSDL National Science Digital Library

This is Lesson 1 of a five lesson unit. "This lesson focuses students' attention on the attributes of length and develops their knowledge of and skill in using nonstandard units of measurement, their feet. It provides practice with and remediation of the measurable attributes of length." (from NCTM Illuminations)

Illuminations National Council of Teachers of Math

2009-01-28

318

Mapping the exciton diffusion in semiconductor nanocrystal solids.

Colloidal nanocrystal solids represent an emerging class of functional materials that hold strong promise for device applications. The macroscopic properties of these disordered assemblies are determined by complex trajectories of exciton diffusion processes, which are still poorly understood. Owing to the lack of theoretical insight, experimental strategies for probing the exciton dynamics in quantum dot solids are in great demand. Here, we develop an experimental technique for mapping the motion of excitons in semiconductor nanocrystal films with a subdiffraction spatial sensitivity and a picosecond temporal resolution. This was accomplished by doping PbS nanocrystal solids with metal nanoparticles that force the exciton dissociation at known distances from their birth. The optical signature of the exciton motion was then inferred from the changes in the emission lifetime, which was mapped to the location of exciton quenching sites. By correlating the metal-metal interparticle distance in the film with corresponding changes in the emission lifetime, we could obtain important transport characteristics, including the exciton diffusion length, the number of predissociation hops, the rate of interparticle energy transfer, and the exciton diffusivity. The benefits of this approach to device applications were demonstrated through the use of two representative film morphologies featuring weak and strong interparticle coupling. PMID:25682881

Kholmicheva, Natalia; Moroz, Pavel; Bastola, Ebin; Razgoniaeva, Natalia; Bocanegra, Jesus; Shaughnessy, Martin; Porach, Zack; Khon, Dmitriy; Zamkov, Mikhail

2015-03-24

319

Vortex/Flame Interactions in Microgravity Pulsed Jet Diffusion Flames

NASA Technical Reports Server (NTRS)

The problem of vortex/flame interaction is of fundamental importance to turbulent combustion. These interactions have been studied in normal gravity. It was found that due to the interactions between the imposed disturbances and buoyancy induced instabilities, several overall length scales dominated the flame. The problem of multiple scales does not exist in microgravity for a pulsed laminar flame, since there are no buoyancy induced instabilities. The absence of buoyant convection therefore provides an environment to study the role of vortices interacting with flames in a controlled manner. There are strong similarities between imposed and naturally occurring perturbations, since both can be described by the same spatial instability theory. Hence, imposing a harmonic disturbance on a microgravity laminar flame creates effects similar to those occurring naturally in transitional/turbulent diffusion flames observed in microgravity. In this study, controlled, large-scale, axisymmetric vortices are imposed on a microgravity laminar diffusion flame. The experimental results and predictions from a numerical model of transient jet diffusion flames are presented and the characteristics of pulsed flame are described.

Bahadori, M. Y.; Hegde, U.; Stocker, D. P.

1999-01-01

320

Slaved Diffusion in Phospholipid Bilayers

NASA Astrophysics Data System (ADS)

Dual-color fluorescence correlation spectroscopy (FCS) was employed to simultaneously investigate the translational diffusion of phospholipids in supported fluid bilayers and polymers which adsorb on these bilayers at incomplete surface coverage. It was found that the translational diffusion of phospholipids split into two populations due to polymer adsorption. A slow mode, whose magnitude was the same as that of adsorbed polymers, coexisted with a fast mode characteristic of naked lipid diffusion. Using 2-color fluorescence, cross-correlation between the diffusion of phospholipids and polymers suggested the plausible interpretation that polymer adsorption created nanodomains of lipid whose mobility was determined by the occluded area of the adsorbed polymer. That is, those lipids inside the nanodomains were enslaved by the adsorbed polymers and diffused collectively. Variations of the polymer molar mass showed that the slow mode of phospholipid diffusion varied inversely with molar mass of the adsorbate, as predicted by our notion of slaved diffusion. This work offers a new mechanism to explain how naonsized domains with reduced mobility arise in lipid membranes.

Zhang, Liangfang; Granick, Steve

2006-03-01

321

Dense gas flow in minimum length nozzles

Recently, dense gases have been investigated for many engineering applications such as for turbomachinery and wind tunnels. Supersonic nozzle design can be complicated by nonclassical dense-gas behavior in the transonic flow regime. In this paper, a method of characteristics (MOC) is developed for two-dimensional (planar) and axisymmetric flow of a van der Waals gas. A minimum length nozzle design code is developed that employs the MOC procedure to generate an inviscid wall contour. The van der Waals results are compared to perfect gas results to show the real-gas effects on the flow properties and inviscid wall contours.

Aldo, A.C.; Argrow, B.M. [Univ. of Colorado, Boulder, CO (United States). Dept. of Aerospace Engineering Sciences

1995-06-01

322

Strength versus gauge length in ceramic-matrix composites

The strength of ceramic-matrix composites as a function of sample gauge length is derived as a function of the composite constituent material properties. Within the context of a global load-sharing assumption for how load is transferred from broken to unbroken fibers, the analysis shows that, for samples shorter than 0.8[delta][sub c] (where [delta][sub c] is the characteristic slip length determining

William A. Curtin

1994-01-01

323

NASA Astrophysics Data System (ADS)

When magnetic forces are present in a partially ionized medium, the plasma drifts with respect to the neutrals. This plasma—neutral drift, which is known as ambipolar diffusion, occurs in all partially ionized astrophysical systems, including portions of the interstellar medium, protostellar accretion disks, and the chromosphere of the Sun and other cool stars. Ambipolar drift redistributes magnetic flux, which can trigger star formation. It affects short wavelength interstellar turbulence, the structure of interstellar shocks, flow driven instabilities, and the nature of magnetic reconnection. Energy dissipated by ion-neutral friction can be an important source of heat. This chapter reviews ambipolar drift as a process and discusses some of the implications.

Zweibel, Ellen G.

324

We consider a simple quantum system subjected to a classical random force. Under certain conditions it is shown that the noise-averaged Wigner function of the system follows an integro-differential stochastic Liouville equation. In the simple case of polynomial noise-couplings this equation reduces to a generalized Fokker-Planck form. With nonlinear noise injection new ``quantum diffusion`` terms rise that have no counterpart in the classical case. Two special examples that are not of a Fokker-Planck form are discussed: the first with a localized noise source and the other with a spatially modulated noise source.

Habib, S.

1994-10-01

325

An Experiment Investigation of Fully-Modulated, Turbulent Diffusion Flames in Reduced Gravity

NASA Technical Reports Server (NTRS)

Pulsed combustion appears to have the potential to provide for rapid fuel/air mixing, compact and economical combustors, and reduced exhaust emissions. The ultimate objective of this program is to increase the fundamental understanding of the fuel/air mixing and combustion behavior of pulsed, turbulent diffusion flames by conducting experiments in microgravity. In this research the fuel jet is fully-modulated (i.e., completely shut off between pulses) by an externally controlled valve system. This can give rise to drastic modification of the combustion and flow characteristics of flames, leading to enhanced fuel/air mixing mechanisms not operative for the case of acoustically excited or partially-modulated jets. In addition, the fully-modulated injection approach avoids the strong acoustic forcing present in pulsed combustion devices, significantly simplifying the mixing and combustion processes. Relatively little is known of the behavior of turbulent flames in reduced-gravity conditions, even in the absence of pulsing. The goal of this Flight-Definition experiment (PUFF, for PUlsed-Fully Flames) is to establish the behavior of fully-modulated, turbulent diffusion flames under microgravity conditions. Fundamental issues to be addressed in this experiment include the mechanisms responsible for the flame length decrease for fully-modulated, turbulent diffusion flames compared with steady flames, the impact of buoyancy on the mixing and combustion characteristics of these flames, and the characteristics of turbulent flame puffs under fully momentum-dominated conditions.

Hermanson, J. C.; Johari, H.; Usowicz, J. E.; Stocker, D. P.; Nagashima, T.; Obata, S.

1999-01-01

326

SLOW DIFFUSIVE GRAVITATIONAL INSTABILITY BEFORE DECOUPLING

Radiative diffusion damps acoustic modes at large comoving wavenumber (k) before decoupling ('Silk damping'). In a simple WKB analysis, neglecting moments of the temperature distribution beyond the quadrupole (the tight-coupling limit), damping appears in the acoustic mode as a term of order ik{sup 2}tau-dot{sup -1}, where tau-dot is the scattering rate per unit conformal time. Although the Jeans instability is stabilized on scales smaller than the adiabatic Jeans length, I show that the medium is linearly unstable to first order in tau-dot{sup -1} to a slow diffusive mode. At large comoving wavenumber, the characteristic growth rate becomes independent of spatial scale and constant: (t{sub KH} a){sup -1} approx (128piG/9kappa{sub T} c)(rho{sub m}/rho{sub b}), where a is the scale factor, rho{sub m} and rho{sub b} are the matter and baryon energy density, respectively, and kappa{sub T} is the Thomson opacity. This is the characteristic timescale for a fluid parcel to radiate away its total thermal energy content at the Eddington limit, analogous to the Kelvin-Helmholz (KH) timescale for a radiation pressure-dominated massive star or the Salpeter timescale for black hole growth. Although this mode grows at all times prior to decoupling and on scales smaller than roughly the horizon, the growth time is long, about 100 times the age of the universe at decoupling. Thus, it modifies the density and temperature perturbations on small scales only at the percent level. The physics of this mode in the tight-coupling limit is already accounted for in the popular codes CMBFAST and CAMB, but is typically neglected in analytic studies of the growth of primordial perturbations. The goal of this work is to clarify the physics of this diffusive instability in the epoch before decoupling, and to emphasize that the universe is formally unstable on scales below the horizon, even in the limit of very large tau-dot. Analogous instabilities that might operate at yet earlier epochs are also mentioned.

Thompson, Todd A., E-mail: thompson@astronomy.ohio-state.ed [Department of Astronomy and Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, OH 43210 (United States)

2010-02-01

327

Laminar Diffusion Flame Studies (Ground- and Space-Based Studies)

NASA Technical Reports Server (NTRS)

Laminar diffusion flames are of interest because they provide model flame systems that are far more tractable for analysis and experiments than more practical turbulent diffusion flames. Certainly, understanding flame processes within laminar diffusion flames must precede understanding these processes in more complex turbulent diffusion flames. In addition, many properties of laminar diffusion flames are directly relevant to turbulent diffusion flames using laminar flamelet concepts. Laminar jet diffusion flame shapes (luminous flame boundaries) have been of particular interest since the classical study of Burke and Schumann because they are a simple nonintrusive measurement that is convenient for evaluating flame structure predictions. Thus, consideration of laminar flame shapes is undertaken in the following, emphasizing conditions where effects of gravity are small, due to the importance of such conditions to practical applications. Another class of interesting properties of laminar diffusion flames are their laminar soot and smoke point properties (i.e., the flame length, fuel flow rate, characteristic residence time, etc., at the onset of soot appearance in the flame (the soot point) and the onset of soot emissions from the flame (the smoke point)). These are useful observable soot properties of nonpremixed flames because they provide a convenient means to rate several aspects of flame sooting properties: the relative propensity of various fuels to produce soot in flames; the relative effects of fuel structure, fuel dilution, flame temperature and ambient pressure on the soot appearance and emission properties of flames; the relative levels of continuum radiation from soot in flames; and effects of the intrusion of gravity (or buoyant motion) on emissions of soot from flames. An important motivation to define conditions for soot emissions is that observations of laminar jet diffusion flames in critical environments, e.g., space shuttle and space station facilities, cannot involve soot emitting flames in order to ensure that test chamber windows used for experimental observations are not blocked by soot deposits, thereby compromising unusually valuable experimental results. Another important motivation to define conditions where soot is present in diffusion flames is that flame chemistry, transport and radiation properties are vastly simplified when soot is absent, making such flames far more tractable for detailed numerical simulations than corresponding soot-containing flames. Motivated by these observations, the objectives of this phase of the investigation were as follows: (1) Observe flame-sheet shapes (the location of the reaction zone near phi=1) of nonluminous (soot free) laminar jet diffusion flames in both still and coflowing air and use these results to develop simplified models of flame-sheet shapes for these conditions; (2) Observe luminous flame boundaries of luminous (soot-containing) laminar jet diffusion flames in both still and coflowing air and use these results to develop simplified models of luminous flame boundaries for these conditions. In order to fix ideas here, maximum luminous flame boundaries at the laminar smoke point conditions were sought, i.e., luminous flame boundaries at the laminar smoke point; (3) Observe effects of coflow on laminar soot- and smoke-point conditions because coflow has been proposed as a means to control soot emissions and minimize the presence of soot in diffusion flames.

Dai, Z.; El-Leathy, A. M.; Lin, K.-C.; Sunderland, P. B.; Xu, F.; Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

2000-01-01

328

Optimal Patent Length and Breadth

In providing rewards to innovators, there is a tradeoff between patent length and breadth. This article provides conditions under which the optimal patent policy involves infinitely-lived patents, with patent breadth adjusting to provide the required reward for innovation.

Richard Gilbert; Carl Shapiro

1990-01-01

329

Bimanual and unimanual length perception.

From previous studies, it is unclear how bimanual length discrimination differs from unimanual length discrimination. To investigate the difference, we designed an experiment with four conditions. In the first two conditions, unimanual and bimanual discrimination thresholds are determined. In the third and fourth conditions, length is explored with the two index fingers like in the bimanual condition, but the reference is either internal, by clasping the hands together, or external, by grasping handles connected to the table. We find that thresholds for the unimanual condition (7.0%) and the clasping condition (9.2%) are both lower than for the bimanual condition (16%) and the grasping handles condition (15%). We conclude that when discriminating length unimanually and bimanually while clasping the hands together, the internal reference within the hand can be used and that explains the lower discrimination thresholds. PMID:24792507

Panday, Virjanand; Bergmann Tiest, Wouter M; Kappers, Astrid M L

2014-09-01

330

Generalized thermoelastic diffusive waves in heat conducting materials

Keeping in view the applications of diffusion processes in geophysics and electronics industry, the aim of the present paper is to give a detail account of the plane harmonic generalized thermoelastic diffusive waves in heat conducting solids. According to the characteristic equation, three longitudinal waves namely, elastodiffusive (ED), mass diffusion (MD-mode) and thermodiffusive (TD-mode), can propagate in such solids in

J. N. Sharma

2007-01-01

331

Strain-Rate-Free Diffusion Flames: Initiation, Properties, and Quenching

NASA Technical Reports Server (NTRS)

For about a half century, the stabilization of a steady planar deflagration on a heat-sink-type flat-flame burner has been of extraordinary service for the theoretical modeling and diagnostic probing of combusting gaseous mixtures. However, most engineering devices and most unwanted fire involve the burning of initially unmixed reactants. The most vigorous burning of initially separated gaseous fuel and oxidizer is the diffusion flame. In this useful idealization (limiting case), the reactants are converted to product at a mathematically thin interface, so no interpenetration of fuel and oxidizer occurs. This limit is of practical importance because it often characterizes the condition of optimal performance (and sometimes environmentally objectionable operation) of a combustor. A steady planar diffusion flame is most closely approached in the laboratory in the counterflow apparatus. The utility of this simple-strain-rate flow for the modeling and probing of diffusion flames was noted by Pandya and Weinberg 35 years ago, though only in the last decade or so has its use become internationally common place. However, typically, as the strain rate a is reduced below about 20 cm(exp -1), and the diffusion-flame limit (reaction rate much faster than the flow rate) is approached, the burning is observed to become unstable in earth gravity. The advantageous steady planar flow is not available in the diffusion-flame limit in earth gravity. This is unfortunate because the typical spatial scale in a counterflow is (k/a)(sup 1/2), where k denotes a characteristic diffusion coefficient; thus, the length scale becomes large, and the reacting flow is particularly amenable to diagnostic probing, as the diffusion-flame limit is approached. The disruption of planar symmetry is owing the fact that, as the strain rate a decreases, the residence time (l/a) of the throughput in the counterflow burner increases. Observationally, when the residence time exceeds about 50 msec, the inevitably present convective (Rayleigh-Benard) instabilities, associated with hot-under-cold (flame-under-fresh-reactant) stratification of fluid in a gravitational field, have time to grow to finite amplitude during transit of the burner.

Fendell, Francis; Rungaldier, Harald; Gokoglu, Suleyman; Schultz, Donald

1997-01-01

332

The influence of a voltage ramp on the measurement of I-V characteristics of a solar cell

NASA Technical Reports Server (NTRS)

For efficiency and convenience the voltage applied to a Si solar cell is often fairly rapidly driven from zero to the open circuit value typically at a common rate of 1 V per millisecond. During this time the values of current are determined as a function of the instantaneous voltage thus producing an I-V characteristic. The present paper shows that the customary expressions for the current as a function of cell parameters still remain valid provided that the diffusion length in the expression for the dark current is changed from its steady state value L to the effective diffusion length L1 given by L1 = L(1 + qV/kT.tau) to the -1/2, where V is the ramp rate considered constant and tau is the lifetime of minority carriers. This result is true to a very good approximation provided that low level injection prevails.

Von Roos, O.

1980-01-01

333

Structural and Environmental Characteristics of Stereotyped Behaviors.

ERIC Educational Resources Information Center

This study examined structural characteristics and environmental variables in the stereotypic behaviors of eight individuals with developmental disabilities. Findings indicated that structural characteristics (percentage of time, bout length, and bout length variability) were highly correlated. Also, stereotyped behaviors were more likely to occur…

Hall, Scott; Thorns, Tracy; Oliver, Chris

2003-01-01

334

Pairing versus quarteting coherence length

We systematically analyse the coherence length in even-even nuclei. The pairing coherence length in the spin-singlet channel for the effective density dependent delta (DDD) and Gaussian interaction is estimated. We consider in our calculations bound states as well as narrow resonances. It turns out that the pairing gaps given by the DDD interaction are similar to those of the Gaussian potential if one renormalizes the radial width to the nuclear radius. The correlations induced by the pairing interaction have in all considered cases a long range character inside the nucleus and decrease towards the surface. The mean coherence length is larger than the geometrical radius for light nuclei and approaches this value for heavy nuclei. The effect of the temperature and states in continuum is investigated. Strong shell effects are evidenced, especially for protons. We generalize this concept to quartets by considering similar relations, but between proton and neutron pairs. The quartet coherence length has a similar shape, but with larger values on the nuclear surface. We evidence the important role of proton-neutron correlations by estimating the so-called alpha coherence length, which takes into account the overlap with the proton-neutron part of the $\\alpha$-particle wave function. It turns out that it does not depend on the nuclear size and has a value comparable to the free $\\alpha$-particle radius. We have shown that pairing correlations are mainly concentrated inside the nucleus, while quarteting correlations are connected to the nuclear surface.

Doru S. Delion; Virgil V. Baran

2015-01-20

335

NONLINEAR DIFFUSION Erkut Erdem

NONLINEAR DIFFUSION Erkut Erdem Hacettepe University March 9th, 2013 CONTENTS 1 Perona-Malik Type Nonlinear Diffusion 1 2 Total Variation (TV) Regularization 5 3 Edge Enhancing Diffusion 8 References 11 1 PERONA-MALIK TYPE NONLINEAR DIFFUSION The main theory behind nonlinear diffusion models is to use

Erdem, Erkut

336

LINEAR DIFFUSION Erkut Erdem Hacettepe University February 24th, 2012 CONTENTS 1 Linear Diffusion 1 2 Appendix - The Calculus of Variations 5 References 6 1 LINEAR DIFFUSION The linear diffusion (heat (noisy) input image and u(x, t) be initialized with u(x, 0) = u0(x) = f (x). Then, the linear diffusion

Erdem, Erkut

337

AMBIPOLAR DIFFUSION HEATING IN TURBULENT SYSTEMS

The temperature of the gas in molecular clouds is a key determinant of the characteristic mass of star formation. Ambipolar diffusion (AD) is considered one of the most important heating mechanisms in weakly ionized molecular clouds. In this work, we study the AD heating rate using two-fluid turbulence simulations and compare it with the overall heating rate due to turbulent dissipation. We find that for observed molecular clouds, which typically have Alfven Mach numbers of {approx}1 and AD Reynolds numbers of {approx}20, about 70% of the total turbulent dissipation is in the form of AD heating. AD has an important effect on the length scale where energy is dissipated: when AD heating is strong, most of the energy in the cascade is removed by ion-neutral drift, with a comparatively small amount of energy making it down to small scales. We derive a relation for the AD heating rate that describes the results of our simulations to within a factor of two. Turbulent dissipation, including AD heating, is generally less important than cosmic-ray heating in molecular clouds, although there is substantial scatter in both.

Li, Pak Shing [Astronomy Department, University of California, Berkeley, CA 94720 (United States); Myers, Andrew [Physics Department, University of California, Berkeley, CA 94720 (United States); McKee, Christopher F., E-mail: psli@astron.berkeley.edu, E-mail: atmyers@berkeley.edu, E-mail: cmckee@berkeley.edu [Physics Department and Astronomy Department, University of California, Berkeley, CA 94720 (United States)

2012-11-20

338

IMF Length Scales and Predictability: The Two Length Scale Medium

NASA Technical Reports Server (NTRS)

We present preliminary results from a systematic study using simultaneous data from three spacecraft, Wind, IMP 8 (Interplanetary Monitoring Platform) and Geotail to examine interplanetary length scales and their implications on predictability for magnetic field parcels in the typical solar wind. Time periods were selected when the plane formed by the three spacecraft included the GSE (Ground Support Equipment) x-direction so that if the parcel fronts were strictly planar, the two adjacent spacecraft pairs would determine the same phase front angles. After correcting for the motion of the Earth relative to the interplanetary medium and deviations in the solar wind flow from radial, we used differences in the measured front angle between the two spacecraft pairs to determine structure radius of curvature. Results indicate that the typical radius of curvature for these IMF parcels is of the order of 100 R (Sub E). This implies that there are two important IMF (Interplanetary Magnetic Field) scale lengths relevant to predictability: (1) the well-established scale length over which correlations observed by two spacecraft decay along a given IMF parcel, of the order of a few tens of Earth radii and (2) the scale length over which two spacecraft are unlikely to even observe the same parcel because of its curvature, of the order of a hundred Earth radii.

Collier, Michael R.; Szabo, Adam; Slavin, James A.; Lepping, R. P.; Kokubun, S.

1999-01-01

339

Effective Cavity Length of Gyrotrons

NASA Astrophysics Data System (ADS)

Megawatt-class gyrotron oscillators for electron cyclotron heating and non-inductive current drive (ECH&CD) in magnetically confined thermonuclear fusion plasmas have relatively low cavity quality factors in the range of 1000 to 2000. The effective length of their cavities cannot be simply deduced from the cavity electric field profile, since this has by far not a Gaussian shape. The present paper presents a novel method to estimate the effective length of a gyrotron cavity just from the eigenvalue of the operating TEm,n mode, the cavity radius and the exact oscillation frequency which may be numerically computed or precisely measured. This effective cavity length then can be taken to calculate the Fresnel parameter in order to confirm that the cavity is not too short so that the transverse structure of any mode in the cavity is the same as that of the corresponding mode in a long circular waveguide with the same diameter.

Thumm, Manfred

2014-12-01

340

Screening length in plasma winds

We study the screening length L_s of a heavy quark-antiquark pair in strongly coupled gauge theory plasmas flowing at velocity v. Using the AdS/CFT correspondence we investigate, analytically, the screening length in the ultra-relativistic limit. We develop a procedure that allows us to find the scaling exponent for a large class of backgrounds. We find that for conformal theories the screening length is (boosted energy density)^{-1/d}. As examples of conformal backgrounds we study R-charged black holes and Schwarzschild-anti-deSitter black holes in (d+1)-dimensions. For non-conformal theories, we find that the exponent deviates from -1/d and as examples we study the non-extremal Klebanov-Tseytlin and Dp-brane geometries. We find an interesting relation between the deviation of the scaling exponent from the conformal value and the speed of sound.

Elena Caceres; Makoto Natsuume; Takashi Okamura

2007-06-04

341

Continuously variable focal length lens

A material preferably in crystal form having a low atomic number such as beryllium (Z=4) provides for the focusing of x-rays in a continuously variable manner. The material is provided with plural spaced curvilinear, optically matched slots and/or recesses through which an x-ray beam is directed. The focal length of the material may be decreased or increased by increasing or decreasing, respectively, the number of slots (or recesses) through which the x-ray beam is directed, while fine tuning of the focal length is accomplished by rotation of the material so as to change the path length of the x-ray beam through the aligned cylindrical slows. X-ray analysis of a fixed point in a solid material may be performed by scanning the energy of the x-ray beam while rotating the material to maintain the beam's focal point at a fixed point in the specimen undergoing analysis.

Adams, Bernhard W; Chollet, Matthieu C

2013-12-17

342

Modeling and characterization of short-channel double-diffused MOS transistors

NASA Astrophysics Data System (ADS)

The performance of short-channel double-diffused MOS transistors was examined through extensive modeling and characterization of DMOS and VMOS transistors. Two dimensional numerical simulations reveal several second-order effects which influence short-channel device performance. The effects include a shortening of the effective electrical channel length due to the nonuniform channel profile and horizontal electric fields and significant depletion and inversion of channel charge by large horizontal fields resulting in lower threshold voltages and higher output conductances. These effects are incorporated into an analytical model based on a two transistor equivalent circuit. The key feature of the model is the use of an exponential profile approximation and a geometrical partitioning of channel charge which allow the incorporation of nonuniform profile and two dimensional field effects. The analytical model is used to simulate DMOS and VMOS enhancement-depletion inverters and to compare their performance to conventional NMOS inverters. The results imply that the double-diffused technologies are superior to conventional NMOS for masked channel lengths greater than 3.0 microns. For shorter channel lengths, velocity saturation dominates the drain characteristics so that maximum driving currents and propagation delays converge for all three technologies.

Davanzo, D. C.

1980-12-01

343

Continuous lengths of oxide superconductors

A layered oxide superconductor prepared by depositing a superconductor precursor powder on a continuous length of a first substrate ribbon. A continuous length of a second substrate ribbon is overlaid on the first substrate ribbon. Sufficient pressure is applied to form a bound layered superconductor precursor powder between the first substrate ribbon and the second substrate ribbon. The layered superconductor precursor is then heat treated to establish the oxide superconducting phase. The layered oxide superconductor has a smooth interface between the substrate and the oxide superconductor.

Kroeger, Donald M. (Knoxville, TN); List, III, Frederick A. (Andersonville, TN)

2000-01-01

344

Normal and Anomalous Diffusion: A Tutorial

The purpose of this tutorial is to introduce the main concepts behind normal and anomalous diffusion. Starting from simple, but well known experiments, a series of mathematical modeling tools are introduced, and the relation between them is made clear. First, we show how Brownian motion can be understood in terms of a simple random walk model. Normal diffusion is then treated (i) through formalizing the random walk model and deriving a classical diffusion equation, (ii) by using Fick's law that leads again to the same diffusion equation, and (iii) by using a stochastic differential equation for the particle dynamics (the Langevin equation), which allows to determine the mean square displacement of particles. (iv) We discuss normal diffusion from the point of view of probability theory, applying the Central Limit Theorem to the random walk problem, and (v) we introduce the more general Fokker-Planck equation for diffusion that includes also advection. We turn then to anomalous diffusion, discussing first its formal characteristics, and proceeding to Continuous Time Random Walk (CTRW) as a model for anomalous diffusion. It is shown how CTRW can be treated formally, the importance of probability distributions of the Levy type is explained, and we discuss the relation of CTRW to fractional diffusion equations and show how the latter can be derived from the CTRW equations. Last, we demonstrate how a general diffusion equation can be derived for Hamiltonian systems, and we conclude this tutorial with a few recent applications of the above theories in laboratory and astrophysical plasmas.

Loukas Vlahos; Heinz Isliker; Yannis Kominis; Kyriakos Hizanidis

2008-05-05

345

Diffusion of Singlet Excitons in Tetracene Crystals

The diffusion length ls of singlet excitons in crystalline tetracene was measured in the temperature range 293 to 160 °K utilizing the quenching effect exerted on the crystal fluorescence by exciton traps located at the crystal surface. It is found that ls = 120 ± 10 Å at room temperature. It increases exponentially with decreasing temperature until it approaches a

G. Vaubel; H. Baessler

1970-01-01

346

Linear relationship statistics in diffusion limited aggregation

We show that various surface parameters in two-dimensional diffusion limited aggregation (DLA) grow linearly with the number of particles. We find the ratio of the average length of the perimeter and the accessible perimeter of a DLA cluster together with its external perimeters to the cluster size, and define a microscopic schematic procedure for attachment of an incident new particle

Abbas Ali Saberi

2009-01-01

347

Parallel flow diffusion battery

A parallel flow diffusion battery for determining the mass distribution of an aerosol has a plurality of diffusion cells mounted in parallel to an aerosol stream, each diffusion cell including a stack of mesh wire screens of different density.

Yeh, H.C.; Cheng, Y.S.

1984-01-01

348

Parallel flow diffusion battery

A parallel flow diffusion battery for determining the mass distribution of an aerosol has a plurality of diffusion cells mounted in parallel to an aerosol stream, each diffusion cell including a stack of mesh wire screens of different density.

Yeh, Hsu-Chi (Albuquerque, NM); Cheng, Yung-Sung (Albuquerque, NM)

1984-08-07

349

Scaling Behavior and Equilibrium Lengths of Knotted Polymers Eric Rawdon,

Scaling Behavior and Equilibrium Lengths of Knotted Polymers Eric Rawdon, Akos Dobay, John C. Kern fluctuating knotted polymer rings affect their various spatial characteristics such as the radius of the smallest sphere enclosing momentary configurations of simulated polymer chains. We describe how the average

Bigelow, Stephen

350

Cooperative Length Scale and Fragility of Polystyrene under Confinement

NASA Astrophysics Data System (ADS)

While thin films are an attractive model system to investigate the impact of confinement on glassy behavior, extending studies beyond thin films to geometries of higher dimensionalities is vital from both scientific and technological viewpoints. In this talk, we present the impact of confinement on the characteristic length at the glass transition as well as the fragility for confined polystyrene (PS) nanoparticles under isochoric conditions. We measure the glass transition temperature (Tg), fictive temperature (Tf) and isochoric heat capacity of silica-capped PS nanoparticles as a function of diameter via differential scanning calorimetry. From the measurement of Tf, we obtain the isochoric fragility, and via the fluctuation formula, the characteristic length at the glass transition. We illustrate that confinement under isochoric conditions for PS nanoparticles leads to a significant increase in the isochoric fragility while the characteristic length is reduced with size. At the minimum the results demonstrate a relationship between fragility and the characteristics length of isochorically-confined polymer that is not intuitive from the Adam-Gibbs theory.

Zhang, Chuan; Guo, Yunlong; Priestley, Rodney

2012-02-01

351

Calibration of the Mixing-length Theory for Convective White Dwarf Envelopes

NASA Astrophysics Data System (ADS)

A calibration of the mixing-length parameter in the local mixing-length theory (MLT) is presented for the lower part of the convection zone in pure-hydrogen-atmosphere white dwarfs. The parameterization is performed from a comparison of three-dimensional (3D) CO5BOLD simulations with a grid of one-dimensional (1D) envelopes with a varying mixing-length parameter. In many instances, the 3D simulations are restricted to the upper part of the convection zone. The hydrodynamical calculations suggest, in those cases, that the entropy of the upflows does not change significantly from the bottom of the convection zone to regions immediately below the photosphere. We rely on this asymptotic entropy value, characteristic of the deep and adiabatically stratified layers, to calibrate 1D envelopes. The calibration encompasses the convective hydrogen-line (DA) white dwarfs in the effective temperature range 6000 <= T eff (K) <=15, 000 and the surface gravity range 7.0 <= log g <= 9.0. It is established that the local MLT is unable to reproduce simultaneously the thermodynamical, flux, and dynamical properties of the 3D simulations. We therefore propose three different parameterizations for these quantities. The resulting calibration can be applied to structure and envelope calculations, in particular for pulsation, chemical diffusion, and convective mixing studies. On the other hand, convection has no effect on the white dwarf cooling rates until there is a convective coupling with the degenerate core below T eff ~ 5000 K. In this regime, the 1D structures are insensitive to the MLT parameterization and converge to the mean 3D results, hence they remain fully appropriate for age determinations.

Tremblay, P.-E.; Ludwig, H.-G.; Freytag, B.; Fontaine, G.; Steffen, M.; Brassard, P.

2015-02-01

352

Pairing versus quarteting coherence length

NASA Astrophysics Data System (ADS)

We systematically analyze the coherence length in even-even nuclei. The pairing coherence length in the spin-singlet channel for the effective density-dependent delta (DDD) and Gaussian interaction is estimated. We consider in our calculations bound states as well as narrow resonances. It turns out that the pairing gaps given by the DDD interaction are similar to those of the Gaussian potential if one renormalizes the radial width to the nuclear radius. The correlations induced by the pairing interaction have, in all considered cases, a long-range character inside the nucleus and a decrease towards the surface. The mean coherence length is larger than the geometrical radius for light nuclei and approaches this value for heavy nuclei. The effect of the temperature and states in the continuum is investigated. Strong shell effects are put in evidence, especially for protons. We generalize this concept to quartets by considering similar relations, but between proton and neutron pairs. The quartet coherence length has a similar shape, but with larger values on the nuclear surface. We provide evidence of the important role of proton-neutron correlations by estimating the so-called alpha coherence length, which takes into account the overlap with the proton-neutron part of the ? -particle wave function. It turns out that it does not depend on the nuclear size and has a value comparable to the free ? -particle radius. We have shown that pairing correlations are mainly concentrated inside the nucleus, while quarteting correlations are connected to the nuclear surface.

Delion, D. S.; Baran, V. V.

2015-02-01

353

Molecular Dynamics of Diffusive-Ballistic Heat Conduction in Single-Walled Carbon Nanotubes

effect gives rise to the long-time heat flux correlation.11) More recently, the length dependenceMolecular Dynamics of Diffusive-Ballistic Heat Conduction in Single-Walled Carbon Nanotubes-3-1 Hongo, Bunkyo-ku Tokyo 113-8656, Japan Diffusive-ballistic heat conduction of finite-length single

Maruyama, Shigeo

354

Characteristic Time Scales of Characteristic Magmatic Processes and Systems

NASA Astrophysics Data System (ADS)

Every specific magmatic process, regardless of spatial scale, has an associated characteristic time scale. Time scales associated with crystals alone are rates of growth, dissolution, settling, aggregation, annealing, and nucleation, among others. At the other extreme are the time scales associated with the dynamics of the entire magmatic system. These can be separated into two groups: those associated with system genetics (e.g., the production and transport of magma, establishment of the magmatic system) and those due to physical characteristics of the established system (e.g., wall rock failure, solidification front propagation and instability, porous flow). The detailed geometry of a specific magmatic system is particularly important to appreciate; although generic systems are useful, care must be taken to make model systems as absolutely realistic as possible. Fuzzy models produce fuzzy science. Knowledge of specific time scales is not necessarily useful or meaningful unless the hierarchical context of the time scales for a realistic magmatic system is appreciated. The age of a specific phenocryst or ensemble of phenocrysts, as determined from isotopic or CSD studies, is not meaningful unless something can be ascertained of the provenance of the crystals. For example, crystal size multiplied by growth rate gives a meaningful crystal age only if it is from a part of the system that has experienced semi-monotonic cooling prior to chilling; crystals entrained from a long-standing cumulate bed that were mechanically sorted in ascending magma may not reveal this history. Ragged old crystals rolling about in the system for untold numbers of flushing times record specious process times, telling more about the noise in the system than the life of typical, first generation crystallization processes. The most helpful process-related time scales are those that are known well and that bound or define the temporal style of the system. Perhaps the most valuable of these times comes from the observed durations and rates of volcanism. There can be little doubt that the temporal styles of volcanism are the same as those of magmatism in general. Volcano repose times, periodicity, eruptive fluxes, acoustic emission structures, lava volumes, longevity, etc. must also be characteristic of pluton-dominated systems. We must therefore give up some classical concepts (e.g., instantaneous injection of crystal-free magma as an initial condition) for any plutonic/chambered system and move towards an integrated concept of magmatism. Among the host of process-related time scales, probably the three most fundamental of any magmatic system are (1) the time scale associated with crystal nucleation (J) and growth (G) (tx}=C{1(G3 J)-{1}/4; Zieg & Marsh, J. Pet. 02') along with the associated scales for mean crystal size (L) and population (N), (2) the time scale associated with conductive cooling controlled by a local length scale (d) (tc}=C{2 d2/K; K is thermal diffusivity), and (3) the time scale associated with intra-crystal diffusion (td}=C{3 L2/D; D is chemical diffusivity). It is the subtle, clever, and insightful application of time scales, dovetailed with realistic system geometry and attention paid to the analogous time scales of volcanism, that promises to reveal the true dynamic integration of magmatic systems.

Marsh, B. D.

2004-05-01

355

Length dependence of carbon nanotube thermal conductivity and the "problem of long waves"

NASA Technical Reports Server (NTRS)

We present the first calculations of finite length carbon nanotube thermal conductivity that extend from the ballistic to the diffusive regime, throughout a very wide range of lengths and temperatures. The long standing problem of vanishing scattering of the "long wavelength phonf dramatically here, making the thermal conductivity diverge as the nanotube length increases. We show that the divergence disappears if 3-phonon scattering processes are considered to second or higher order. Nevertheless, for defect free nanotubes, the thermal conductivity keeps increasing up to very large lengths (10 gm at 300 K). Defects in the nanotube are also able to remove the long wavelength divergence.

Mingo, N.; Broido, D. A.

2005-01-01

356

To evaluate diffusion sampling as an alternative method to monitor volatile organic compound (VOC) concentrations in ground water, concentrations in samples collected by traditional pumped-sampling methods were compared to concentrations in samples collected by diffusion-sampling methods for 89 monitoring wells at or near the Massachusetts Military Reservation, Cape Cod. Samples were analyzed for 36 VOCs. There was no substantial difference between the utility of diffusion and pumped samples to detect the presence or absence of a VOC. In wells where VOCs were detected, diffusion-sample concentrations of tetrachloroethene (PCE) and trichloroethene (TCE) were significantly lower than pumped-sample concentrations. Because PCE and TCE concentrations detected in the wells dominated the calculation of many of the total VOC concentrations, when VOC concentrations were summed and compared by sampling method, visual inspection also showed a downward concentration bias in the diffusion-sample concentration. The degree to which pumped- and diffusion-sample concentrations agreed was not a result of variability inherent within the sampling methods or the diffusion process itself. A comparison of the degree of agreement in the results from the two methods to 13 quantifiable characteristics external to the sampling methods offered only well-screen length as being related to the degree of agreement between the methods; however, there is also evidence to indicate that the flushing rate of water through the well screen affected the agreement between the sampling methods. Despite poor agreement between the concentrations obtained by the two methods at some wells, the degree to which the concentrations agree at a given well is repeatable. A one-time, well-bywell comparison between diffusion- and pumped-sampling methods could determine which wells are good candidates for the use of diffusion samplers. For wells with good method agreement, the diffusion-sampling method is a time-saving and cost-effective alternative to pumped-sampling methods in a long-term monitoring program, such as at the Massachusetts Military Reservation.

Archfield, Stacey A.; LeBlanc, Denis R.

2005-01-01

357

Nanoparticle Diffusion in Polymer Nanocomposites

Large-scale molecular dynamics simulations show that nanoparticle (NP) diffusivity in weakly interacting mixtures of NPs and polymer melts has two very different classes of behavior depending on their size. NP relaxation times and their diffusivities are completely described by the local, Rouse dynamics of the polymer chains for NPs smaller than the polymer entanglement mesh size. The motion of larger NPs, which are comparable to the entanglement mesh size, is significantly slowed by chain entanglements, and is not describable by the Stokes-Einstein relationship. Our results are in essentially quantitative agreement with a force-level generalized Langevin equation theory for all the NP sizes and chain lengths explored, and imply that for these lightly entangled systems, activated NP hopping is not important.

Kalathi, Jagannathan [Columbia University, New York] [Columbia University, New York; Yamamoto, Umi [University of Illinois, Urbana-Champaign] [University of Illinois, Urbana-Champaign; Schweizer, Kenneth [University of Illinois] [University of Illinois; Grest, Gary S. [Sandia National Laboratories (SNL)] [Sandia National Laboratories (SNL); Kumar, Sanat [Columbia University, New York] [Columbia University, New York

2014-01-01

358

Imaging of diffuse liver disease.

Advances in imaging technology and development of liver-specific contrast agents have significantly increased the role of radiology in the detection and characterization of processes diffusely involving the liver. Tailored magnetic resonance imaging (MRI) sequences allow an accurate detection of many storage and metabolic diseases, such as iron overload disorders and steatosis (fatty liver). Faster scanning techniques available with both computed tomography (CT) and MRI provide, by assessing contrast dynamics, sufficient information for the characterization of diffuse neoplastic and vascular disorders. Characteristic changes in attenuation on CT, signal intensity on MRI, and enhancing features can be used to diagnose specific diffuse diseases such as candidiasis, diffuse/multifocal hepatocellular carcinoma, and schistosomiasis. Although an overlap in imaging findings still exists, familiarity with the imaging features of uncommon disorders such as Wilson's disease, amyloidosis, and sarcoidosis may be diagnostic in the proper clinical setting. This review focuses on the current role of imaging in the detection and characterization of diffuse liver disorders. Recent developments that have amplified the role of noninvasive diagnostic evaluation of these conditions are especially highlighted. PMID:11436572

Mortele, K J; Ros, P R

2001-05-01

359

Correlated diffusion of colloidal particles near a liquid-liquid interface.

Optical microscopy and multi-particle tracking are used to investigate the cross-correlated diffusion of quasi two-dimensional colloidal particles near an oil-water interface. The behaviors of the correlated diffusion along longitudinal and transverse direction are asymmetric. It is shown that the characteristic length for longitudinal and transverse correlated diffusion are particle diameter d and the distance z from particle center to the interface, respectively, for large particle separation z. The longitudinal and transverse correlated diffusion coefficient D||(r) and D[perpendicular](r) are independent of the colloidal area fraction n when n < 0.3, which indicates that the hydrodynamic interactions(HIs) among the particles are dominated by HIs through the surrounding fluid for small n. For high area fraction n > 0.4 the power law exponent for the spatial decay of [Formula: see text] begins to decrease, which suggests the HIs are more contributed from the 2D particle monolayer self for large n. PMID:24465498

Zhang, Wei; Chen, Song; Li, Na; Zhang, Jia Zheng; Chen, Wei

2014-01-01

360

Buoyancy Effects on Flow Transition in Hydrogen Gas Jet Diffusion Flames

NASA Technical Reports Server (NTRS)

Experiments were performed in earth-gravity to determine how buoyancy affected transition from laminar to turbulent flow in hydrogen gas jet diffusion flames. The jet exit Froude number characterizing buoyancy in the flame was varied from 1.65 x 10(exp 5) to 1.14 x 10(exp 8) by varying the operating pressure and/or burner inside diameter. Laminar fuel jet was discharged vertically into ambient air flowing through a combustion chamber. Flame characteristics were observed using rainbow schlieren deflectometry, a line-of-site optical diagnostic technique. Results show that the breakpoint length for a given jet exit Reynolds number increased with increasing Froude number. Data suggest that buoyant transitional flames might become laminar in the absence of gravity. The schlieren technique was shown as effective in quantifying the flame characteristics.

Albers, Burt W.; Agrawal, Ajay K.; Griffin, DeVon (Technical Monitor)

2000-01-01

361

Bunch Length Measurements using Coherent Radiation

The accelerating field that can be obtained in a beam-driven plasma wakefield accelerator depends on the current of the electron beam that excites the wake. In the E-167 experiment, a peak current above 10 kA will be delivered at a particle energy of 28 GeV. The bunch has a length of a few ten micrometers and several methods are used to measure its longitudinal profile. Among these, autocorrelation of coherent transition radiation (CTR) is employed. The beam passes a thin metallic foil, where it emits transition radiation. For wavelengths greater than the bunch length, this transition radiation is emitted coherently. This amplifies the long-wavelength part of the spectrum. A scanning Michelson interferometer is used to autocorrelate the CTR. However, this method requires the contribution of many bunches to build an autocorrelation trace. The measurement is influenced by the transmission characteristics of the vacuum window and beam splitter. We present here an analysis of materials, as well as possible layouts for a single shot CTR autocorrelator.

Ischebeck, Rasmus; Barnes, Christopher; Blumenfeld, Ian; Decker, Franz-Josef; Hogan, Mark; Iverson, Richard H.; Krejcik, Patrick; Siemann, Robert H.; Walz, Dieter; /SLAC; Kirby, Neil; /Stanford U., Phys. Dept.; Clayton, Chris; Huang, Chengkun; Johnson, Devon K.; Lu, Wei; Marsh, Ken; /UCLA; Deng, Suzhi; Oz, Erdem; /Southern California U.

2005-06-24

362

Diffusing Diffusivity: A Model for Anomalous, yet Brownian, Diffusion

NASA Astrophysics Data System (ADS)

Wang et al. [Proc. Natl. Acad. Sci. U.S.A. 106, 15160 (2009)] have found that in several systems the linear time dependence of the mean-square displacement (MSD) of diffusing colloidal particles, typical of normal diffusion, is accompanied by a non-Gaussian displacement distribution G(x ,t), with roughly exponential tails at short times, a situation they termed "anomalous yet Brownian" diffusion. The diversity of systems in which this is observed calls for a generic model. We present such a model where there is diffusivity memory but no direction memory in the particle trajectory, and we show that it leads to both a linear MSD and a non-Gaussian G(x ,t) at short times. In our model, the diffusivity is undergoing a (perhaps biased) random walk, hence the expression "diffusing diffusivity". G(x ,t) is predicted to be exactly exponential at short times if the distribution of diffusivities is itself exponential, but an exponential remains a good fit for a variety of diffusivity distributions. Moreover, our generic model can be modified to produce subdiffusion.

Chubynsky, Mykyta V.; Slater, Gary W.

2014-08-01

363

Variable focal length deformable mirror

A variable focal length deformable mirror has an inner ring and an outer ring that simply support and push axially on opposite sides of a mirror plate. The resulting variable clamping force deforms the mirror plate to provide a parabolic mirror shape. The rings are parallel planar sections of a single paraboloid and can provide an on-axis focus, if the rings are circular, or an off-axis focus, if the rings are elliptical. The focal length of the deformable mirror can be varied by changing the variable clamping force. The deformable mirror can generally be used in any application requiring the focusing or defocusing of light, including with both coherent and incoherent light sources.

Headley, Daniel (Albuquerque, NM); Ramsey, Marc (Albuquerque, NM); Schwarz, Jens (Albuquerque, NM)

2007-06-12

364

Diffusion, dimensionality and noise in transcriptional regulation

The precision of biochemical signaling is limited by randomness in the diffusive arrival of molecules at their targets. For proteins binding to the specific sites on the DNA and regulating transcription, the ability of the proteins to diffuse in one dimension by sliding along the length of the DNA, in addition to their diffusion in bulk solution, would seem to generate a larger target for DNA binding, consequently reducing the noise in the occupancy of the regulatory site. Here we show that this effect is largely cancelled by the enhanced temporal correlations in one dimensional diffusion. With realistic parameters, sliding along DNA has surprisingly little effect on the physical limits to the precision of transcriptional regulation.

Gasper Tkacik; William Bialek

2007-12-12

365

Numerical study of a macroscopic finite pulse model of the diffusion MRI signal

NASA Astrophysics Data System (ADS)

Diffusion magnetic resonance imaging (dMRI) is an imaging modality that probes the diffusion characteristics of a sample via the application of magnetic field gradient pulses. The dMRI signal from a heterogeneous sample includes the contribution of the water proton magnetization from all spatial positions in a voxel. If the voxel can be spatially divided into different Gaussian diffusion compartments with inter-compartment exchange governed by linear kinetics, then the dMRI signal can be approximated using the macroscopic Karger model, which is a system of coupled ordinary differential equations (ODEs), under the assumption that the duration of the diffusion-encoding gradient pulses is short compared to the diffusion time (the narrow pulse assumption). Recently, a new macroscopic model of the dMRI signal, without the narrow pulse restriction, was derived from the Bloch-Torrey partial differential equation (PDE) using periodic homogenization techniques. When restricted to narrow pulses, this new homogenized model has the same form as the Karger model. We conduct a numerical study of the new homogenized model for voxels that are made up of periodic copies of a representative volume that contains spherical and cylindrical cells of various sizes and orientations and show that the signal predicted by the new model approaches the reference signal obtained by solving the full Bloch-Torrey PDE in O (?2) , where ? is the ratio between the size of the representative volume and a measure of the diffusion length. When the narrow gradient pulse assumption is not satisfied, the new homogenized model offers a much better approximation of the full PDE signal than the Karger model. Finally, preliminary results of applying the new model to a voxel that is not made up of periodic copies of a representative volume are shown and discussed.

Li, Jing-Rebecca; Nguyen, Hang Tuan; Van Nguyen, Dang; Haddar, Houssem; Coatléven, Julien; Le Bihan, Denis

2014-11-01

366

Diffusion tensor MRI phantom exhibits anomalous diffusion.

This paper reports diffusion weighted MRI measurements of cyclohexane in a novel diffusion tensor MRI phantom composed of hollow coaxial electrospun fibers (average diameter 10.2 ?m). Recent studies of the phantom demonstrated its potential as a calibration standard at low b values (less than 1000 s/mm<;sup>2<;/sup>) for mean diffusivity and fractional anisotropy. In this paper, we extend the characterization of cyclohexane diffusion in this heterogeneous, anisotropic material to high b values (up to 5000 s/mm<;sup>2<;/sup>), where the apparent diffusive motion of the cyclohexane exhibits anomalous behavior (i.e., the molecular mean squared displacement increases with time raised to the fractional power 2?/?). Diffusion tensor MRI was performed at 9.4 T using an Agilent imaging scanner and the data fit to a fractional order Mittag-Leffler (generalized exponential) decay model. Diffusion along the fibers was found to be Gaussian (2?/?=l), while diffusion across the fibers was sub-diffusive (2?/?<;l). Fiber tract reconstruction of the data was consistent with scanning electron micrograph images of the material. These studies suggest that this phantom material may be used to calibrate MR systems in both the normal (Gaussian) and anomalous diffusion regimes. PMID:25570066

Ye, Allen Q; Hubbard Cristinacce, Penny L; Feng-Lei Zhou; Ziying Yin; Parker, Geoff J M; Magin, Richard L

2014-08-01

367

NASA Astrophysics Data System (ADS)

We compute the short-circuit diffusion current of excitons in an organic solar cell, with special emphasis on fluorescence losses. The exciton diffusion length is not uniform but varies with its position within the device, even with moderate fluorescence quantum efficiency. With large quantum efficiencies, the rate of fluorescence can be strongly reduced with proper choices of the geometrical and dielectric parameters. In this way, the diffusion length can be increased and the device performance significantly improved.

Kozyreff, G.; Urbanek, D. C.; Vuong, L. T.; Silleras, O. Nieto; Martorell, J.

2013-05-01

368

Preliminary experiments with diffusers for a supersonic flow CO-laser

Diffusers are used to minimize the pump systems required for the operation of supersonic CW CO lasers. After a review of the state of the art of diffuser technology, two different diffusers for the CO lasers are considered: (1) a short channel of 16.6 cm length and with constant cross section equal to that of the nozzle exit and attached

S. Krause

1976-01-01

369

An analysis of the effect of stress diffusion on the dynamics of creeping viscoelastic flow

of stress diffusivity is examined in both the Oldroyd-B and FENE- P models of a viscoelastic fluid on Wi, , and b, the maximum extensibility length. Key words: Viscoelastic Fluid Models, Stress Diffusion, Oldroyd-B, FENE-P 1. Introduction The inclusion of stress diffusivity is an important consideration in vis

Thomases, Becca

370

Applicability of Mixing Length Theory to a Turbulent Vortex System

NASA Technical Reports Server (NTRS)

The ability of mixing length theory to correlate vortex data is evaluated. Expressions are derived for eddy diffusivity by applying the techniques of von Karman and Prandtl which have been established for pipe flow. Total and static pressures were measured from the outer radius to the exhaust-nozzle radius of a vortex generator for a range of mass flows. These data are combined with Navier-Stokes solutions for this region of a compressible vortex to determine turbulent Reynolds numbers. The Reynolds number is related to Prandtl and Karman functions for various assumed boundary conditions, and the experimental data are used to determine the usefulness of these expressions. The following conclusions were reached: (1) Mixing length functions developed by applying von Karman's similarity hypothesis to vortex motion correlate the data better than do Prandtl functions obtained with the assumption that mixing length is proportional to radius. (2) Some of the expressions developed do not adequately represent the experimental data. (3) The data are correlated with acceptable scatter by evaluating the fluid radial inertia at the outer boundary and the shear stress at the inner boundary. The universal constant K was found to be 0.04 to 0.08, rather than the value of 0.4 which is accepted for rectilinear flow. (4) The data are best correlated by a modified Karman expression which includes an effect of radial inertia, as well as shear stress, on eddy diffusivity.

Ragsdale, Robert G.

1961-01-01

371

We present a method for texture synthesis based on the simulation of a process of local nonlinear interaction, called reaction-diffusion, which has been proposed as a model of biological pattern formation. We extend traditional reaction-diffusion systems by allowing anisotropic and spatially non-uniform diffusion, as well as multiple competing directions of diffusion. We adapt reaction-diffusion system to the needs of computer

Andrew P. Witkin; Michael Kass

1991-01-01

372

Strong gradients for spatially resolved diffusion measurements.

A new multilayer approach to gradient coil design, which allows the production of very strong gradient coils with reasonable resistance and consequent power dissipation, has been developed. Using this approach we have designed and built a strong z-gradient coil that will accommodate vertically mounted samples contained in 5-mm nuclear magnetic resonance tubes. The coil has an efficiency of 1.73 Tm-1A-1, an inductance of 49 microH, and a resistance of 1.8 omega, with a homogeneous volume consisting of a central cylinder of 4.5-mm length and diameter. This coil has been used to monitor the diffusion of water in Nylon 6.6 at room temperature, during desorption. This system is difficult to monitor via nuclear magnetic resonance (NMR), because the diffusion coefficients are typically less than 10(-13) m2s-1, while the T2 relaxation time is less than 1 ms even when the sample is fully saturated. The resulting measurements show a strong concentration dependence of the T2 relaxation time and self-diffusion coefficient of the absorbed water. The measured concentration profiles are consistent with a Fickian diffusion process with a concentration-dependent diffusion coefficient. The measured self-diffusion values are in reasonable agreement with those inferred from the variation of the concentration profiles as a function of time, using the one-dimensional Fickian diffusion equation. PMID:9803915

Snaar, J E; Robyr, P; Bowtell, R

1998-01-01

373

Restricted diffusion in annular geometrical pores

NASA Astrophysics Data System (ADS)

Nuclear magnetic resonance (NMR) diffusion (including diffusion MRI) experiments are only as powerful as the models used to analyse the NMR diffusion data. A major problem, especially with measurements on biological systems, is that the existing models are only very poor approximations of cellular shape. Here, diffusion propagators and pulsed gradient spin-echo attenuation equations are derived in the short gradient pulse limit for diffusion within the annular region of a concentric cylinder of finite length and, similarly, within the annular region of a concentric sphere. The models include the possibility of relaxation at the boundaries and, in the case of the concentric cylinder, having the cylinder arbitrarily oriented with respect to the direction of the applied field gradient. The two models are also of interest due to their direct analogy to optical double slit diffraction. Also expressions for the mean square displacements, which are very useful information for determining the diffusion coefficient within these complex geometries, are obtained as well as for the limiting cases of diffusion on cylindrical and spherical shells and in a ring.

Ghadirian, Bahman; Torres, Allan M.; Yadav, Nirbhay N.; Price, William S.

2013-03-01

374

Transmission electron diffraction (TED) and transmission electron microscope (TEM) studies have been made of organometallic vapor phase epitaxial Ga{sub x}In{sub 1{minus}x}P layers (x {approx} 0.5) grown at temperatures in the range 570--690 C to investigate ordering and ordered domain structures. TED and TEM examination shows that the size and morphology of ordered domains depend on the growth temperature. The ordered domains change from a fine rod-like shape to a plate-like shape as the growth temperature increases. The domains are of width 0.6--2 nm and of length 1{approximately}10 nm. Characteristic diffuse features observed in TED patterns are found to depend on the growth temperature. Extensive computer simulations show a direct correlation between the ordered domain structures and such diffuse features. A possible model is suggested to describe the temperature dependence of the ordered domain structure.

Yang, J.J.; Spirydon, R.; Seong, T.Y. [Kwangju Inst. of Science and Technology (Korea, Republic of). Dept. of Materials Science and Engineering; Lee, S.H.; Stringfellow, G.B. [Univ. of Utah, Salt Lake City, UT (United States). Dept. of Materials Science and Engineering

1998-10-01

375

NSDL National Science Digital Library

In this math lesson, learners explore the concept of using units to measure length. Learners first read "How Big is a Foot" by Rolf Myller and learn about units. Then, learners visit four measurement centers. In each center, learners will measure items with various kinds of units. Learners use non-standard units to measure their shoes, the distance between beanbags and a bull’s-eye target, their body parts (arms, legs, etc.), and some everyday objects. This lesson guide includes instructions on how to set up a "Shoe Store" dramatic play area that can be used to introduce learners to measurement prior to this activity.

Nichol Lyman

2012-09-26

376

An unresolved problem in physics is how the thermodynamic arrow of time arises from an underlying time reversible dynamics. We contribute to this issue by developing a measure of time-symmetry breaking, and by using the work fluctuation relations, we determine the time asymmetry of recent single molecule RNA unfolding experiments. We define time asymmetry as the Jensen-Shannon divergencebetween trajectory probability distributions of an experiment and its time-reversed conjugate. Among other interesting properties, the length of time's arrow bounds the average dissipation and determines the difficulty of accurately estimating free energy differences in nonequilibrium experiments.

Feng, Edward H.; Crooks, Gavin E.

2008-08-21

377

Interferometric measurements of a dendritic growth front solutal diffusion layer

NASA Technical Reports Server (NTRS)

An experimental study was undertaken to measure solutal distributions in the diffusion layer produced during the vertical directional solidification (VDS) of an ammonium chloride - water (NH4Cl-H2O) solution. Interferometry was used to obtain concentration measurements in the 1-2 millimeter region defining the diffusion layer. These measurements were fitted to an exponential form to extract the characteristic diffusion parameter for various times after the start of solidification. The diffusion parameters are within the limits predicted by steady state theory and suggest that the effective solutal diffusivity is increasing as solidification progresses.

Hopkins, John A.; Mccay, T. D.; Mccay, Mary H.

1991-01-01

378

Diffusion Confusion 8 4 Problem set #4: Fun with diffusion

Diffusion Confusion 8 4 Problem set #4: Fun with diffusion Today's thrill packed exercise will be to deal with diffusion and advection-diffusion in one dimension. All exercises here will be in Matlab-nicolson diffusion of a gaussian initial condition with dirichlet boundary conditions (Diffusion/diffusion cn

Spiegelman, Marc W.

379

Holographic diffuser by use of a silver halide sensitized gelatin process.

Diffusers play an important role in liquid crystal display (LCD) application as a beam-shaping device, a brightness homogenizer, a light-Scattering device, and an imaging screen. The transmittance and diffusing angle of the diffusers are the critical aspects for the applications to the LCD. The holographic diffusers by use of various processing methods have been investigated. The diffusing characteristics of different diffusing materials and processing methods have been evaluated and compared. The microstructures of holographic diffuse have been investigated by use of using scanning electron microscopy. The holographic diffusers by use of the silver halide sensitized gelatin (SHSG) method have the structural merits for the improvement of the quality of diffusers. The features of holographic diffuser were exceptional in terms of transmittance and diffusing angle. The replication method by use of the SHSG process can be directly used for the manufacturing of diffusers for the display application. PMID:12749559

Kim, Sun Il; Choi, Yoon Sun; Ham, Yong Nam; Park, Chong Yun; Kim, Jong Man

2003-05-10

380

Microfabricated diffusion source

A microfabricated diffusion source to provide for a controlled diffusion rate of a vapor comprises a porous reservoir formed in a substrate that can be filled with a liquid, a headspace cavity for evaporation of the vapor therein, a diffusion channel to provide a controlled diffusion of the vapor, and an outlet to release the vapor into a gas stream. The microfabricated diffusion source can provide a calibration standard for a microanalytical system. The microanalytical system with an integral diffusion source can be fabricated with microelectromechanical systems technologies.

Oborny, Michael C. (Albuquerque, NM); Frye-Mason, Gregory C. (Cedar Crest, NM); Manginell, Ronald P. (Albuquerque, NM)

2008-07-15

381

Factors affecting length at maturity and other important reproductive characteristics have not been investigated for Idaho redband trout Oncorhynchus mykiss gairdneri residing in desert streams. Prespawning redband trout were collected from nine streams, and estimates of length at sexual maturity, median age at maturity, sex ratio, and fecundity were developed along with models predicting length at maturity from physical stream

Daniel J. Schill; George W. LaBar; Elizabeth R. J. M. Mamer; Kevin A. Meyer

2010-01-01

382

Critical Waves and the Length Problem of Biology

It is pointed out that the mystery of how biological systems measure their lengths vanishes away if one premises that they have discovered a way to generate linear waves analogous to compressional sound. These can be used to detect length at either large or small scales using echo timing and fringe counting. It is shown that suitable linear chemical potential waves can, in fact, be manufactured by tuning to criticality conventional reaction-diffusion with a small number substances. Min oscillations in E. coli are cited as precedent resonant length measurement using chemical potential waves analogous to laser detection. Mitotic structures in eucaryotes are identified as candidates for such an effect at higher frequency. The engineering principle is shown to be very general and functionally the same as that used by hearing organs. PNAS Significance Statement: This paper invokes physical principles to address the question of how living things might use reaction-diffusion to measure out and regulate the many thousands of lengths required to make their body parts and internal organs. It argues that two ideas have been missing. One is that oscillation is necessary to achieve the necessary design stability and plasticity. The other is that the system must be tuned to criticality to stabilize the propagation velocity, thus enabling clocks to function as meter sticks. The broader significance is twofold: First, a fundamental piece of the machinery of life is probably invisible to present-day biochemical methods because they are too slow. Second, the simplicity of growth and form identified a century ago by D'Arcy Thompson is probably a symptom of biological engineering strategies, not primitive law.

R. B. Laughlin

2015-04-17

383

ERIC Educational Resources Information Center

Participants in a National Seminar on the Diffusion of New Instructional Materials and Practices included scientists and educators in the natural and social sciences and mathematics from universities, curriculum projects, and school districts throughout the United States. This document is the first of a series of working papers which were…

Social Science Education Consortium, Inc., Boulder, CO.

384

Measurement of Diffusion in Entangled Rod-Coil Triblock Copolymers

NASA Astrophysics Data System (ADS)

Although rod-coil block copolymers have attracted increasing attention for functional nanomaterials, their dynamics relevant to self-assembly and processing have not been widely investigated. Because the rod and coil blocks have different reptation behavior and persistence lengths, the mechanism by which block copolymers will diffuse is unclear. In order to understand the effect of the rigid block on reptation, tracer diffusion of a coil-rod-coil block copolymer through an entangled coil polymer matrix was experimentally measured. A monodisperse, high molecular weight coil-rod-coil triblock was synthesized using artificial protein engineering to prepare the helical rod and bioconjugaiton of poly(ethylene glycol) coils to produce the final triblock. Diffusion measurements were performed using Forced Rayleigh scattering (FRS), at varying ratios of the rod length to entanglement length, where genetic engineering is used to control the protein rod length and the polymer matrix concentration controls the entanglement length. As compared to PEO homopolymer tracers, the coil-rod-coil triblocks show markedly slower diffusion, suggesting that the mismatch between rod and coil reptation mechanisms results in hindered diffusion of these molecules in the entangled state.

Olsen, B. D.; Wang, M.

2012-02-01

385

Study on Bezier Curve Variable Step-length Algorithm

NASA Astrophysics Data System (ADS)

Bessel Curve also known as Bezier Curve, through which the general vector graphics software accurately draws curves, as the Bezier curve is relatively easy to calculate and its stable characteristic, in many areas it has been widely applied. However, for the deficiency of less efficiency exists in the common Bezier Curve Generation Algorithm, the selection of the parameter step-length significantly affects the accuracy and efficiency of the generated curve. This paper aims at the efficiency available in the existing Bezier Curve Generation Algorithm to propose the Variable Step-length Algorithm; by changing the parameter step-length of the curve generation algorithm, it can significantly reduce the calculations of a large number of duplicate points in the point-by-point generation algorithm; the algorithm not only maintains a higher accuracy, but also significantly improves the efficiency generated in the curve, with better application.

Xiao, Guorong; Xu, Xuemiao

386

Atomistic Simulation of Polymer Crystallization at Realistic Length Scales

Understanding the dynamics of polymer crystallization during the induction period prior to crystal growth is a key goal in polymer physics. Here we present the first study of primary crystallization of polymer melts via molecular dynamics simulations at physically realistic (about 46 nm) length scales. Our results show that the crystallization mechanism involves a spinodal decomposition microphase separation caused by an increase in the average length of rigid trans segments along the polymer backbone during the induction period. Further, the characteristic length of the growing dense domains during the induction period is longer than predicted by classical nucleation theory. These results indicate a new 'coexistence period' in the crystallization, where nucleation and growth mechanisms coexist with a phase separation mechanism. Our results provide an atomistic verification of the fringed micelle model.

Gee, R H; Fried, L E

2005-01-28

387

SOME GOOD ORTHOGONAL BIPOLAR SPREADING SEQUENCES OF LENGTHS 12 AND 20

SOME GOOD ORTHOGONAL BIPOLAR SPREADING SEQUENCES OF LENGTHS 12 AND 20 Jennifer Seberry, Beata J characteristics of the orthogonal bipolar spreading sequences of lengths 12 and 20. The orthogonal bipolar In [4], Lipski and Marek indicated that there is a common expectation that bipolar orthogonal (Hadamard

Seberry, Jennifer

388

The consequences of the relatively short lower limbs characteristic of AL 288-1 have been widely discussed, as have the causes and consequences of the short limbs of Neanderthals. Previous studies of the effect of limb length on the energetic cost of locomotion have reported no relationship; however, limb length could have accounted for as much as 19% of the variation

Karen L. Steudel-Numbers; Michael J. Tilkens

2004-01-01

389

Measurement of MODIS optics effective focal length, distortion, and modulation transfer function

NASA Astrophysics Data System (ADS)

A combination MODIS optics characteristics, short back focal length, and relatively distorting optics, has required major revisions in techniques used earlier to characterize effective focal length (EFL) and modulation transfer function (MTF) in the thematic mapper (TM) project. This paper compares measurement approaches used to characterize TM optics and revised methodology intended to characterize MODIS optics at an integration and assembly level.

Thurlow, Paul E.; Cline, Richard W.

1993-08-01

390

Most of the research on selecting foster parents has focused on matching children with specific behavioral characteristics to foster parents felt most likely to be successful with them. There has been no research which addresses the relationship of the length of care to the specific characteristics desired for a foster parent who will be most suited for a given length

CHARLES H AUERBACH

1985-01-01

391

Ligand chain length conveys thermochromism.

Thermochromic properties of a series of non-ionic copper compounds have been reported. Herein, we demonstrate that Cu(II) ion with straight-chain primary amine (A) and alpha-linolenic (fatty acid, AL) co-jointly exhibit thermochromic properties. In the current case, we determined that thermochromism becomes ligand chain length-dependent and at least one of the ligands (A or AL) must be long chain. Thermochromism is attributed to a balanced competition between the fatty acids and amines for the copper(II) centre. The structure-property relationship of the non-ionic copper compounds Cu(AL)2(A)2 has been substantiated by various physical measurements along with detailed theoretical studies based on time-dependent density functional theory. It is presumed from our results that the compound would be a useful material for temperature-sensor applications. PMID:24943491

Ganguly, Mainak; Panigrahi, Sudipa; Chandrakumar, K R S; Sasmal, Anup Kumar; Pal, Anjali; Pal, Tarasankar

2014-08-14

392

UPDATING APPLIED DIFFUSION MODELS

Most diffusion models currently used in air quality applications are substantially out of date with understanding of turbulence and diffusion in the planetary boundary layer. Under a Cooperative Agreement with the Environmental Protection Agency, the American Meteorological Socie...

393

Rumor diffusion in an interests-based dynamic social network.

To research rumor diffusion in social friend network, based on interests, a dynamic friend network is proposed, which has the characteristics of clustering and community, and a diffusion model is also proposed. With this friend network and rumor diffusion model, based on the zombie-city model, some simulation experiments to analyze the characteristics of rumor diffusion in social friend networks have been conducted. The results show some interesting observations: (1) positive information may evolve to become a rumor through the diffusion process that people may modify the information by word of mouth; (2) with the same average degree, a random social network has a smaller clustering coefficient and is more beneficial for rumor diffusion than the dynamic friend network; (3) a rumor is spread more widely in a social network with a smaller global clustering coefficient than in a social network with a larger global clustering coefficient; and (4) a network with a smaller clustering coefficient has a larger efficiency. PMID:24453911

Tang, Mingsheng; Mao, Xinjun; Guessoum, Zahia; Zhou, Huiping

2013-01-01

394

Rumor Diffusion in an Interests-Based Dynamic Social Network

To research rumor diffusion in social friend network, based on interests, a dynamic friend network is proposed, which has the characteristics of clustering and community, and a diffusion model is also proposed. With this friend network and rumor diffusion model, based on the zombie-city model, some simulation experiments to analyze the characteristics of rumor diffusion in social friend networks have been conducted. The results show some interesting observations: (1) positive information may evolve to become a rumor through the diffusion process that people may modify the information by word of mouth; (2) with the same average degree, a random social network has a smaller clustering coefficient and is more beneficial for rumor diffusion than the dynamic friend network; (3) a rumor is spread more widely in a social network with a smaller global clustering coefficient than in a social network with a larger global clustering coefficient; and (4) a network with a smaller clustering coefficient has a larger efficiency. PMID:24453911

Mao, Xinjun; Guessoum, Zahia; Zhou, Huiping

2013-01-01

395

Abstract-- Hybrid diffusion imaging (HYDI) is a new diffusion MRI method for characterizing complex diffusion. Diffusion-weighted measurements are obtained on multiple `shells' of constant diffusion weighting. This diffusion encoding approach is amenable to multiple types of diffusion imaging analysis. The inner shells

Bucci, David J.

396

Handbook on atmospheric diffusion

Basic meteorological concepts are covered as well as plume rise, source effects, and diffusion models. Chapters are included on cooling tower plumes and urban diffusion. Suggestions are given for calculating diffusion in special situations, such as for instantaneous releases over complex terrain, over long distances, and during times when chemical reactions or dry or wet deposition are important. (PSB)

Hanna, S.R.; Briggs, G.A.; Hosker, R.P. Jr.

1982-01-01

397

The Characteristics of Americana and Britannica

ERIC Educational Resources Information Center

In this study quantifiable characteristics of encyclopedia articles such as subjects treated, length, illustrations and bibliographies were examined. Random subsamples were analyzed and the findings are presented in twelve tables. (1 reference) (DH)

Cole, Dorothy Ethlyn

1973-01-01

398

Narrow groove welding gas diffuser assembly and welding torch

A diffuser assembly is provided for narrow groove welding using an automatic gas tungsten arc welding torch. The diffuser assembly includes a manifold adapted for adjustable mounting on the welding torch which is received in a central opening in the manifold. Laterally extending manifold sections communicate with a shield gas inlet such that shield gas supplied to the inlet passes to gas passages of the manifold sections. First and second tapered diffusers are respectively connected to the manifold sections in fluid communication with the gas passages thereof. The diffusers extend downwardly along the torch electrode on opposite sides thereof so as to release shield gas along the length of the electrode and at the distal tip of the electrode. The diffusers are of a transverse width which is on the order of the thickness of the electrode so that the diffusers can, in use, be inserted into a narrow welding groove before and after the electrode in the direction of the weld operation.

Rooney, Stephen J. (East Berne, NY)

2001-01-01

399

Narrow groove welding gas diffuser assembly and welding torch

A diffuser assembly is provided for narrow groove welding using an automatic gas tungsten arc welding torch. The diffuser assembly includes manifold adapted for adjustable mounting on the welding torch which is received in a central opening in the manifold. Laterally extending manifold sections communicate with a shield gas inlet such that shield gas supplied to the inlet passes to gas passages of the manifold sections. First and second tapered diffusers are respectively connected to the manifold sections in fluid communication with the gas passages thereof. The diffusers extend downwardly along the torch electrode on opposite sides thereof so as to release shield gas along the length of the electrode and at the distal tip of the electrode. The diffusers are of a transverse width which is on the order of the thickness of the electrode so that the diffusers can, in use, be inserted into a narrow welding groove before and after the electrode in the direction of the weld operation.

Rooney, Stephen J.

2000-02-04

400

Diffusion of surgical technology. An exploratory study.

The study presents an empirical analysis of the diffusion patterns of five surgical procedures. Roles of payer mix, regulatory policies, physician diffusion, competition among hospitals, and various hospital characteristics such as size and the spread of technologies are examined. The principal data base is a time series cross-section of 521 hospitals based on discharge abstracts sent to the Commission on Professional and Hospital Activities. Results on the whole are consistent with a framework used to study innovations in other contexts in which the decisions of whether to innovate and timing depend on anticipated streams of returns and cost. Innovation tends to be more likely to occur in markets in which the more generous payers predominate. But the marginal effects of payer mix are small compared to effects of location and hospital characteristics, such as size and teaching status. Hospital rate-setting sometimes retarded diffusion. Certificate of need programs did not. PMID:10317759

Sloan, F A; Valvona, J; Perrin, J M; Adamache, K W

1986-03-01

401

Diffusive limit of asymmetric simple exclusion

on ` and the dynamics and m(z; t) satisfies the dÂdimensional viscous Burgers equation. The diffusion matrix is given to the site x + e (e being a vector of length 1 on the lattice) provided that the site x + e is empty] for references) the inviscid Burgers equation @ t ae + ffi \\Delta r z [ae(1 \\Gamma ae)] = 0; (1.1) 2 #12;

402

Linear Relationship Statistics in Diffusion Limited Aggregation

We show that various surface parameters in two-dimensional diffusion limited\\u000aaggregation (DLA) grow linearly with the number of particles. We find the ratio\\u000aof the average length of the perimeter and the accessible perimeter of a DLA\\u000acluster together with its external perimeters to the cluster size, and define a\\u000amicroscopic schematic procedure for attachment of an incident new particle

A. A. Saberi

2009-01-01

403

Dinosaur Skull and Body Length Predictions

NSDL National Science Digital Library

In this activity (located on page 2 of PDF), learners will look for a relationship between skull size and body length among various dinosaurs. Starting from a list of dinosaur measurements, learners will compare dinosaur sizes to common objects and create a chart that plots body length against skull length to see if the data predicts other dinosaurs' length from skull size. Relates to the linked video, DragonflyTV GPS: Baby Dinosaurs.

Twin Cities Public Television, Inc.

2007-01-01

404

Largemouth Bass Fishery Responses to Length Limits

I compiled quantitative information from published and unpublished studies that evaluated large- mouth bass fishery responses to minimum-length and slot-length limits. My data set includes results from 91 evaluations conducted on 88 lakes located across the United States. Forty-nine evaluations were of minimum-length limits, and 42 were of slot-length limits. The most commonly evaluated regulations were 12- (n = 13)

Gene R. Wilde

1997-01-01

405

Length-dependent [Ca2+] sensitivity adds stiffness to muscle.

It is well documented that muscle fibers become more sensitive for [Ca2+] with increasing sarcomere length. In mechanical terms this length-dependent [Ca2+] sensitivity (LDCS) adds to the stiffness of muscle fibers, because muscle force, normalized for the force-length relationship at maximal stimulation, increases with contractile element (CE) length. Although LDCS is well-documented in the physiological literature, it is ignored in most motor control studies. The aim of the present study was to investigate the importance of LDCS as a contributor to the stiffness of a muscle. Comparison of experimental data with predictions derived from the model of activation dynamics proposed by Hatze (Myocybernetic Control Models of Skeletal Muscle, University of South Africa, Pretoria, 1981, pp. 31-42) indicated that this model captures the main characteristics of LDCS well. It was shown that LDCS accounts for the experimentally observed shifts in optimum length at sub-maximal stimulation levels. Furthermore, it was shown that in conditions with low-to-medium muscle stimulation, the contribution of LDCS to the total amount of stiffness provided by the muscle is substantial. It was concluded that LDCS is an important muscle property and should be taken into account in studies concerning motor control. PMID:16023468

Kistemaker, Dinant A; Van Soest, Arthur Knoek J; Bobbert, Maarten F

2005-09-01

406

Sexual harassment: Organizational context and diffuse status

Data from a large survey of federal employees is utilized to compare three broad competing perspectives that suggest effects on sexual harassment within organizations. Three different viewpoints stress power differentials, minority status, and diffuse master status characteristics. Results of the study indicate that intraorganizational theories emphasizing either power inequalities or work group compositional heterogeneities are unable to account for the

Terri C. Fain; Douglas L. Anderton

1987-01-01

407

Characteristics of the Martian atmosphere surface layer

NASA Technical Reports Server (NTRS)

Elements of various terrestrial boundary layer models are extended to Mars in order to estimate sensible heat, latent heat, and momentum fluxes within the Martian atmospheric surface ('constant flux') layer. The atmospheric surface layer consists of an interfacial sublayer immediately adjacent to the ground and an overlying fully turbulent surface sublayer where wind-shear production of turbulence dominates buoyancy production. Within the interfacial sublayer, sensible and latent heat are transported by non-steady molecular diffusion into small-scale eddies which intermittently burst through this zone. Both the thickness of the interfacial sublayer and the characteristics of the turbulent eddies penetrating through it depend on whether airflow is aerodynamically smooth or aerodynamically rough, as determined by the Roughness Reynold's number. Within the overlying surface sublayer, similarity theory can be used to express the mean vertical windspeed, temperature, and water vapor profiles in terms of a single parameter, the Monin-Obukhov stability parameter. To estimate the molecular viscosity and thermal conductivity of a CO2-H2O gas mixture under Martian conditions, parameterizations were developed using data from the TPRC Data Series and the first-order Chapman-Cowling expressions; the required collision integrals were approximated using the Lenard-Jones potential. Parameterizations for specific heat and binary diffusivity were also determined. The Brutsart model for sensible and latent heat transport within the interfacial sublayer for both aerodynamically smooth and rough airflow was experimentally tested under similar conditions, validating its application to Martian conditions. For the surface sublayer, the definition of the Monin-Obukhov length was modified to properly account for the buoyancy forces arising from water vapor gradients in the Martian atmospheric boundary layer. It was found that under most Martian conditions, the interfacial and surface sublayers offer roughly comparable resistance to sensible heat and water vapor transport and are thus both important in determining the associated fluxes.

Clow, G. D.; Haberle, R. M.

1990-01-01

408

Lexical Phonology and Sound Change: The Case of the Scottish Vowel Length Rule.

ERIC Educational Resources Information Center

Shows that the Scottish Vowel Length Rule supports Kiparsky's (1988) association of diffusing sound changes with lexical, and neogrammarian changes with postlexical rules, and to some extent, is a clearer illustration of Harris' (1989a: 55) notion of a phonological "life cycle" of changes and rules. (50 references) (GLR)

McMahon, April M. S.

1991-01-01

409

Compact noninvasive electron bunch-length monitor

A compact rf cavity was constructed that simultaneously resonates at many harmonic modes when excited by a repetitive bunched electron beam passing through its bore. The excitation of these modes provides a Fourier description of the temporal characteristics of the bunch train. The cavity was used to noninvasively characterize electron bunches produced from thin and thick GaAs photocathodes inside a DC high voltage photogun illuminated with 37 ps (full width half maximum, FWHM) laser pulses at repetition rates near 1500 MHz, at average beam current from 5 to 500????A , and at beam energy from 75 to 195 keV. The cavity bunch-length monitor could detect electron bunches as short as 57 ps (FWHM) when connected directly to a sampling oscilloscope, and could clearly distinguish bunches with varying degrees of space-charge induced growth and with different tail signatures. Efforts are under way to detect shorter bunches by designing cavities with increased bandwidth. This demonstration lends credibility to the idea that these cavities could also be used for other applications, including bunching and shaping, when driven with external rf.

Roberts, B.; Mammei, R. R.; Poelker, M.; McCarter, J. L.

2012-12-01

410

Scale length study in TFTR (Tokamak Fusion Test Reactor)

The scale lengths of the electron density (L/sub n//sub e/), temperature (L/sub T//sub e/), and pressure (L/sub p//sub e/) gradients were investigated during the 1985 operating period of the Tokamak Fusion Test Reactor (TFTR) for gas-fueled plasmas with neutral beam injection and movable limiter. Although the global energy confinement time degrades as the heating power increases or the plasma current decreases, the radial profiles of the scale lengths (L/sub T//sub e/ and L/sup p//sub e/) remain unchanged. Especially, the electron pressure profile is constrained not to change. This trend appears to hold over a fairly wide range of TFTR operational regimes. The radial profiles of L/sub n//sub e/ and /eta//sub e/ (= L/sub n//sub e//L/sub T//sub e/) also appear to remain unchanged, although the uncertainties of the experimental data for these quantities are greater than those for L/sub T//sub e/ and L/sub p//sub e/. The experimental parameters are used to evaluate theoretical predictions of the electron thermal diffusivity, and the results are compared with the empirical thermal diffusivity. 34 refs., 18 figs., 2 tabs.

Hiroe, S.; Goldston, R.J.; Bitter, M.; Bush, C.E.; Efthimion, P.C.; Grek, B.; Johnson, D.W.; Murakami, M.; Schivell, J.; Towner, H.H.

1988-12-01

411

Code of Federal Regulations, 2013 CFR

... 2013-07-01 2013-07-01 false Hair length. 551.4 Section 551.4 Judicial...MANAGEMENT MISCELLANEOUS Grooming § 551.4 Hair length. (a) The Warden may not restrict hair length if the inmate keeps it neat and...

2013-07-01

412

Code of Federal Regulations, 2012 CFR

... 2012-07-01 2012-07-01 false Hair length. 551.4 Section 551.4 Judicial...MANAGEMENT MISCELLANEOUS Grooming § 551.4 Hair length. (a) The Warden may not restrict hair length if the inmate keeps it neat and...

2012-07-01

413

Code of Federal Regulations, 2014 CFR

... 2014-07-01 2014-07-01 false Hair length. 551.4 Section 551.4 Judicial...MANAGEMENT MISCELLANEOUS Grooming § 551.4 Hair length. (a) The Warden may not restrict hair length if the inmate keeps it neat and...

2014-07-01

414

Code of Federal Regulations, 2010 CFR

... 2010-07-01 2010-07-01 false Hair length. 551.4 Section 551.4 Judicial...MANAGEMENT MISCELLANEOUS Grooming § 551.4 Hair length. (a) The Warden may not restrict hair length if the inmate keeps it neat and...

2010-07-01

415

Code of Federal Regulations, 2011 CFR

... 2011-07-01 2011-07-01 false Hair length. 551.4 Section 551.4 Judicial...MANAGEMENT MISCELLANEOUS Grooming § 551.4 Hair length. (a) The Warden may not restrict hair length if the inmate keeps it neat and...

2011-07-01

416

Word Length Analysis of Jane Austen's Letters

This paper deals with word length in twenty of Jane Austen's letters and is part of a research project performed in Göttingen. Word length in English has so far only been studied in the context of contemporary texts (Hasse & Weinbrenner, 1995; Riedemann, 1994) and in the English dictionary (Rothschild, 1986). It has been ascertained that word length in texts

Jutta Frischen

1996-01-01

417

NASA Astrophysics Data System (ADS)

Diffusion of Ti has been characterized in natural olivine and synthetic forsterite. Experiments on the natural olivines were run under buffered conditions (IW and NNO), and those on synthetic forsterite were run in air. Titanium diffusion appears relatively insensitive to crystallographic orientation and oxygen fugacity under the range of investigated conditions, and diffusivities are similar for Fe-bearing olivine and forsterite. For Ti diffusion in synthetic forsterite, we obtain the following Arrhenius relation for diffusion over the temperature range 900-1400 °C:

Cherniak, Daniele J.; Liang, Yan

2014-12-01

418

Diffusion of Asymmetric Swimmers

Particles moving along curved trajectories will diffuse if the curvature fluctuates sufficiently in either magnitude or orientation. We consider particles moving at a constant speed with either a fixed or with a Gaussian distributed curvature magnitude. At small speeds the diffusivity is independent of the speed. At larger particle speeds, the diffusivity depends on the speed through a novel exponent. We apply our results to intracellular transport of vesicles. In sharp contrast to thermal diffusion, the effective diffusivity increases with vesicle size and so may provide an effective means of intracellular transport.

Andrew D. Rutenberg; Andrew J. Richardson; Claire J. Montgomery

2003-02-19

419

Highly transparent sapphire micro-grating structures with large diffuse light scattering.

The highly transparent micro-grating structures (MGSs) of sapphire substrate with large diffuse light scattering were theoretically and experimentally studied. From the finite difference time domain simulation, it was found that the degree of diffuse light scattering is strongly dependent on the size of grating structures. For a highly transparent property, the sapphire MGSs were optimally designed by the theoretical calculations using the rigorous coupled wave analysis method. The order of taper, geometry (i.e., width and height), and pitch length of MGSs were optimized to maximize their average total transmittance over a wide wavelength range of 300-1800 nm. Additionally, the influence of the deposition of low-refractive index material such as SiO2 onto sapphire MGSs on the transmittance characteristics was investigated. To verify experimentally the feasibility, the sapphire MGSs were fabricated by the conventional lithography and dry etching processes. The SiO2 deposited sapphire MGS exhibited a further increase in the total transmittance due to its relatively more graded refractive index profile while maintaining a significantly enhanced diffuse light scattering. The experimental data were in a reasonable agreement with the theoretical results. PMID:21934920

Ko, Yeong Hwan; Yu, Jae Su

2011-08-01

420

Diffusion Enhancement in Core-softened fluid confined in nanotubes

We study the effect of confinement in the dynamical behavior of a core-softened fluid. The fluid is modeled as a two length scales potential. This potential in the bulk reproduces the anomalous behavior observed in the density and in the diffusion of liquid water. A series of $NpT$ Molecular Dynamics simulations for this two length scales fluid confined in a nanotube were performed. We obtain that the diffusion coefficient increases with the increase of the nanotube radius for wide channels as expected for normal fluids. However, for narrow channels, the confinement shows an enhancement in the diffusion coefficient when the nanotube radius decreases. This behavior, observed for water, is explained in the framework of the two length scales potential.

José R. Bordin; Alan B. de Oliveira; Alexandre Diehl; Marcia C. Barbosa

2012-08-05

421

NASA Astrophysics Data System (ADS)

The paper analyses particle diffusion from a thermodynamic standpoint. The main goal of the paper is to highlight the conceptual connection between particle diffusion, which belongs to non-equilibrium statistical physics, and mechanics, which deals with particle motion, at the level of third-year university courses. We start out from the fact that, near equilibrium, particle transport should occur down the gradient of the chemical potential. This yields Fick's law with two additional advantages. First, splitting the chemical potential into 'mechanical' and 'chemical' contributions shows how transport and mechanics are linked through the diffusivity-mobility relationship. Second, splitting the chemical potential into entropic and energetic contributions discloses the respective roles of entropy maximization and energy minimization in driving diffusion. The paper addresses first unary diffusion, where there is only one mobile species in an immobile medium, and next turns to binary diffusion, where two species are mobile with respect to each other in a fluid medium. The interrelationship between unary and binary diffusivities is brought out and it is shown how binary diffusion reduces to unary diffusion in the limit of high dilution of one species amidst the other one. Self- and mutual diffusion are considered and contrasted within the thermodynamic framework; self-diffusion is a time-dependent manifestation of the Gibbs paradox of mixing.

Bringuier, E.

2009-11-01

422

NASA Astrophysics Data System (ADS)

Imaging techniques based on the principle of nuclear magnetic resonance (NMR) rank with the most advanced methods for studying chemical and biological properties of substances. Their universality makes them particularly suitable for use in a wide range of scientific branches. NMR has found significant application in medicine. The diffusion effects of water molecules in tissues reduce the magnitude of spin echo in NMR measuring methods. Based on the amplitude change in the image, the diffusion coefficients and their distribution in the specimen being measured can be calculated. MR images of an object weighted by diffusion coefficients require a defined sequence of gradient pulses and accurate knowledge of their time behaviour. Methods for measuring the diffusion coefficients require knowledge of the minimum length of leading and trailing edges, the defined magnitude of the magnetic field gradient being excited and also the symmetry of positive and negative gradient pulses (the zero integral of pulses of the same magnitude with opposite polarity). To determine the above characteristics of the time behaviour of gradient pulses of both polarities a simple measuring method was developed and experimentally tested on a tomograph with 4.7 T induction of the basic magnetic field. This method is based on the principle of measuring the instantaneous frequency of the MR signal in the presence of a gradient pulse subsequent to exciting a thin defined layer of the specimen under examination outside the gradient field centre.

Bartusek, Karel; Gescheidtova, Eva

2006-08-01

423

NASA Astrophysics Data System (ADS)

The role of disorder in controlling diffusivity and mobility of charge-carriers in the hopping regime of transport within a potential landscape has become especially significant for organic semiconductors. The temperature and field dependence of diffusivity (D) and mobility (?) of injected charge-carriers have been simultaneously measured using electroluminescence transients for representative organic thin-films of tris(8-hydroxyquinoline) aluminum (III) (Alq3) and poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO). Significantly, the field dependence of diffusivity at different temperatures is similar except for a shift of a critical field beyond which it shows a sharp increase. The critical field is shown to be linearly decreasing with temperature ultimately vanishing at a characteristic limit T?, and the slope is a measure of the localization length. The normalization of diffusivity is used to demonstrate the role of field in controlling temperature dependence. The scheme has been used to neatly decouple contributions from energetic (diagonal) and positional (off-diagonal) disorder thus enabling independent experimental determination of all the parameters of standard and correlated versions of Gaussian disorder model. The results demonstrate the validity of Gaussian disorder model even for non-equilibrium carriers, and that the parameters can be obtained with appropriate scaling of the field in such cases.

Tripathi, Durgesh C.; Sinha, Dhirendra K.; Mohapatra, Y. N.

2013-10-01

424

High-power diffusing-tip fibers for interstitial photocoagulation

NASA Astrophysics Data System (ADS)

A line of optical fiber based diffusing tips has been designed, developed, and tested that are capable of distributing tens of watts of cw laser power over lengths ranging from two millimeters to over 10 cm. The result is a flexible non-stick diffuser capable of coagulating large volumes of tissue in reasonably short exposures of 3 - 5 minutes. Sub-millimeter diameter devices have a distinct effect on reducing the force needed to insert the applicator interstitially into tissue. Utilizing our design approach, we have produced diffusers based on 200 micrometer core fiber that has delivered over 35 watts of Nd:YAG energy over diffusion lengths as short as 4 mm. These applicators are being tested for applications in oncology, cardiology, electrophysiology, urology and gynecology.

Sinofsky, Edward L.; Farr, Norman; Baxter, Lincoln; Weiler, William

1997-05-01

425

Depth from Diffusion Changyin Zhou

in the diffusion angle a much less expensive proposition. We perform a detailed analysis of the image formation Optical Diffuser Figure 1. (a) A laser beam is diffused by a holographic diffuser. (b) The geometry diffusion angle, a small patch in a diffused image can be formulated as a convolution between a fo- cused

Nayar, Shree K.

426

Characterization of plant influent, effluent, and internal process streams provides plant operations personnel with the information they need to properly control treatment processes. To obtain that information, the operator should determine the characteristics of the raw wastewater and stream by collecting and analyzing representative samples throughout the plant. This paper gives a basic understanding of wastewater characteristics and sampling necessary

Samorn Muttamara

1996-01-01

427

Time and length scales within a fire and implications for numerical simulation

A partial non-dimensionalization of the Navier-Stokes equations is used to obtain order of magnitude estimates of the rate-controlling transport processes in the reacting portion of a fire plume as a function of length scale. Over continuum length scales, buoyant times scales vary as the square root of the length scale; advection time scales vary as the length scale, and diffusion time scales vary as the square of the length scale. Due to the variation with length scale, each process is dominant over a given range. The relationship of buoyancy and baroclinc vorticity generation is highlighted. For numerical simulation, first principles solution for fire problems is not possible with foreseeable computational hardware in the near future. Filtered transport equations with subgrid modeling will be required as two to three decades of length scale are captured by solution of discretized conservation equations. By whatever filtering process one employs, one must have humble expectations for the accuracy obtainable by numerical simulation for practical fire problems that contain important multi-physics/multi-length-scale coupling with up to 10 orders of magnitude in length scale.

TIESZEN,SHELDON R.

2000-02-02

428

Coarse grained model of diffusion in entangled bidisperse polymer melts

NASA Astrophysics Data System (ADS)

Chain diffusion is studied in mixtures of bidisperse linear polymers of same chemical identity by means of simulations. The two subpopulations are moderately to highly entangled, with the shorter chain length NS, fulfilling NS/Ne?5. To this end, a coarse grained model calibrated to reproduce both the structure and dynamics of chains in monodisperse entangled melts is used [A. Rakshit and R. C. Picu, J. Chem. Phys. 125, 164907 (2006)]. Its performance in reproducing chain dynamics in a polydisperse melt is tested by extensively comparing the results with those obtained from an equivalent fine scale representation of the same system (a bead-spring model). The coarse grained model is used further to investigate the scaling of the diffusion coefficient with the length of the two types of chains and its dependence on the respective fractions. The model reproduces many features observed experimentally. For example, the diffusion coefficient of one of the chain types decreases with increasing the length of the other type chains. It is shown that, in this model, this effect is not linked to constraint release. When the matrix chains become sufficiently long, their length does not influence the diffusion coefficient of the short chains anymore. The diffusion coefficient of the short chains scales with their weight fraction in a manner consistent with experimental observations. In mixtures, the dynamics of the short chains is slower and that of the long chains is marginally faster than in their respective monodisperse melts.

Picu, R. C.; Rakshit, A.

2007-10-01

429

Diffusion in confined geometries.

Diffusive transport of particles or, more generally, small objects, is a ubiquitous feature of physical and chemical reaction systems. In configurations containing confining walls or constrictions, transport is controlled both by the fluctuation statistics of the jittering objects and the phase space available to their dynamics. Consequently, the study of transport at the macro- and nanoscales must address both Brownian motion and entropic effects. Herein we report on recent advances in the theoretical and numerical investigation of stochastic transport occurring either in microsized geometries of varying cross sections or in narrow channels wherein the diffusing particles are hindered from passing each other (single-file diffusion). For particles undergoing biased diffusion in static suspension media enclosed by confining geometries, transport exhibits intriguing features such as 1) a decrease in nonlinear mobility with increasing temperature or also 2) a broad excess peak of the effective diffusion above the free diffusion limit. These paradoxical aspects can be understood in terms of entropic contributions resulting from the restricted dynamics in phase space. If, in addition, the suspension medium is subjected to external, time-dependent forcing, rectification or segregation of the diffusing Brownian particles becomes possible. Likewise, the diffusion in very narrow, spatially modulated channels is modified via contact particle-particle interactions, which induce anomalous sub-diffusion. The effective sub-diffusion constant for a driven single file also develops a resonance-like structure as a function of the confining coupling constant. PMID:19025741

Burada, P Sekhar; Hänggi, Peter; Marchesoni, Fabio; Schmid, Gerhard; Talkner, Peter

2009-01-12

430

NASA Astrophysics Data System (ADS)

Noninvasive measurements of microstructure in materials, cells, and in biological tissues, constitute a unique capability of gradient-assisted NMR. Diffusion-diffraction MR approaches pioneered by Callaghan demonstrated this ability; Oscillating-Gradient Spin-Echo (OGSE) methodologies tackle the demanding gradient amplitudes required for observing diffraction patterns by utilizing constant-frequency oscillating gradient pairs that probe the diffusion spectrum, D(?). Here we present a new class of diffusion MR experiments, termed Non-uniform Oscillating-Gradient Spin-Echo (NOGSE), which dynamically probe multiple frequencies of the diffusion spectral density at once, thus affording direct microstructural information on the compartment's dimension. The NOGSE methodology applies N constant-amplitude gradient oscillations; N - 1 of these oscillations are spaced by a characteristic time x, followed by a single gradient oscillation characterized by a time y, such that the diffusion dynamics is probed while keeping (N - 1)x + y ? TNOGSE constant. These constant-time, fixed-gradient-amplitude, multi-frequency attributes render NOGSE particularly useful for probing small compartment dimensions with relatively weak gradients - alleviating difficulties associated with probing D(?) frequency-by-frequency or with varying relaxation weightings, as in other diffusion-monitoring experiments. Analytical descriptions of the NOGSE signal are given, and the sequence's ability to extract small compartment sizes with a sensitivity towards length to the sixth power, is demonstrated using a microstructural phantom. Excellent agreement between theory and experiments was evidenced even upon applying weak gradient amplitudes. An MR imaging version of NOGSE was also implemented in ex vivo pig spinal cords and mouse brains, affording maps based on compartment sizes. The effects of size distributions on NOGSE are also briefly analyzed.

Shemesh, Noam; Álvarez, Gonzalo A.; Frydman, Lucio

2013-12-01

431

Oxygen diffusion in titanite: Lattice diffusion and fast-path diffusion in single crystals

Oxygen diffusion in titanite: Lattice diffusion and fast-path diffusion in single crystals X June 2006 Editor: P. Deines Abstract Oxygen diffusion in natural and synthetic single-crystal titanite be recognized as responsible for oxygen diffusion. The diffusion profiles showed two segments: a steep one close

Watson, E. Bruce

432

Inheritance of Telomere Length in a Bird

Telomere dynamics are intensively studied in human ageing research and epidemiology, with many correlations reported between telomere length and age-related diseases, cancer and death. While telomere length is influenced by environmental factors there is also good evidence for a strong heritable component. In human, the mode of telomere length inheritance appears to be paternal and telomere length differs between sexes, with females having longer telomeres than males. Genetic factors, e.g. sex chromosomal inactivation, and non-genetic factors, e.g. antioxidant properties of oestrogen, have been suggested as possible explanations for these sex-specific telomere inheritance and telomere length differences. To test the influence of sex chromosomes on telomere length, we investigated inheritance and sex-specificity of telomere length in a bird species, the kakapo (Strigops habroptilus), in which females are the heterogametic sex (ZW) and males are the homogametic (ZZ) sex. We found that, contrary to findings in humans, telomere length was maternally inherited and also longer in males. These results argue against an effect of sex hormones on telomere length and suggest that factors associated with heterogamy may play a role in telomere inheritance and sex-specific differences in telomere length. PMID:21364951

Horn, Thorsten; Robertson, Bruce C.; Will, Margaret; Eason, Daryl K.; Elliott, Graeme P.; Gemmell, Neil J.

2011-01-01

433

Low trap-state density and long carrier diffusion in organolead trihalide perovskite single crystals

NASA Astrophysics Data System (ADS)

The fundamental properties and ultimate performance limits of organolead trihalide MAPbX3 (MA = CH3NH3+; X = Br– or I–) perovskites remain obscured by extensive disorder in polycrystalline MAPbX3 films. We report an antisolvent vapor-assisted crystallization approach that enables us to create sizable crack-free MAPbX3 single crystals with volumes exceeding 100 cubic millimeters. These large single crystals enabled a detailed characterization of their optical and charge transport characteristics. We observed exceptionally low trap-state densities on the order of 109 to 1010 per cubic centimeter in MAPbX3 single crystals (comparable to the best photovoltaic-quality silicon) and charge carrier diffusion lengths exceeding 10 micrometers. These results were validated with density functional theory calculations.

Shi, Dong; Adinolfi, Valerio; Comin, Riccardo; Yuan, Mingjian; Alarousu, Erkki; Buin, Andrei; Chen, Yin; Hoogland, Sjoerd; Rothenberger, Alexander; Katsiev, Khabiboulakh; Losovyj, Yaroslav; Zhang, Xin; Dowben, Peter A.; Mohammed, Omar F.; Sargent, Edward H.; Bakr, Osman M.

2015-01-01

434

Diffusion tensor imaging in brainstem tuberculoma.

Integrity of descending white matter tracts can be evaluated by diffusion tensor imaging. In rim-enhancing intraparenchymal lesions, this technique can assist in the differentiation of demyelinating disease from tumor or abscess. Diffusion tensor imaging characteristics of tuberculoma have not been previously reported to our knowledge. A patient with headaches, dizziness, and mild left-sided weakness underwent MRI with diffusion tensor imaging. A large, rim-enhancing lesion within the pons was discovered, which subsequently was diagnosed as tuberculoma. Tractography maps prepared from diffusion tensor imaging data revealed predominantly displaced descending fiber tracts in the region of the rim-enhancing lesion. A few tracts adjacent to the lesion appeared truncated, and this abnormal finding correlated to the patient's clinical deficit. The tractography characteristics of diffusion tensor imaging in this patient potentially are distinct from those seen with demyelinating lesions, which may show more extensive tract truncation. Together with the consonance of exam findings and tract truncation seen in this patient, tractography may prove useful in the diagnosis of suspected tuberculoma. PMID:23707604

Lyons, Jennifer L; Neagu, Martha R; Norton, Isaiah H; Klein, Joshua P

2013-11-01

435

Anisotropic diffusion in a finite cylinder, with geochemical applications

NASA Astrophysics Data System (ADS)

Atomic diffusion in minerals may not be well represented by solutions to the diffusion equation for a sphere with a single-valued diffusivity, either because they have platy or elongated habits or because the energetics of diffusion is sensitive to crystallographic direction. In many cases, a cylinder having characteristic radial and axial diffusivities is arguably a better model, but rigorous solutions to the anisotropic diffusion equation for a finite cylinder have not been available. Here we develop general analytical solutions that capture both the internal distribution of diffusant as a function of time, C( r, z, t), and the fraction, F, of diffusant lost during a specified thermal history. These solutions are shown to conform with existing analytical expressions for limiting cases of diffusion in a slab or infinite cylinder. We present, in addition, a simple numerical (finite difference) approach that not only reproduces the results of our analytical expressions but also enables us to move beyond some of the limitations of the equations to simulate complex natural scenarios involving non-zero and time-dependent boundary conditions, arbitrary initial distribution of diffusant within the cylinder and simultaneous diffusion and radiogenic ingrowth. The complementary nature of the two approaches is emphasized and several illustrative applications to 'real-world' problems are described, including noble-gas thermochronometry and halogen-hydroxyl interdiffusion in apatite.

Watson, E. Bruce; Wanser, Keith H.; Farley, Kenneth A.

2010-01-01

436

Applicability of subpicosecond pulse lasers to determining thermal diffusivity of metals

The transient reflectivity change due to subpicosecond laser-pulse heating is measured for aluminum sheets and a gold film. While hot electron relaxation and\\/or diffusion seem to control the temperature relaxation in the gold film, the ordinary thermal diffusion seems to be responsible for that in the aluminum sheets. It is possible to determine the characteristic time of the thermal diffusion

T. Nagasaki; H. Ohno; Y. Arita; T. Matsui

2005-01-01

437

Diffusion magnetic resonance imaging (dmri) is a technique that can be used to examine the diffusion characteristics of water in the living brain. A recently developed application of this technique is tractography, in ...

Clayden, Jonathan D

2008-01-01

438

Island Diffusion and Coarsening on Metal (100) Surfaces

The diffusion and coarsening of two-dimensional homoepitaxial islands on Cu(100) and Ag(100) surfaces have been studied at room temperature with time-sequenced scanning tunneling microscopy. Quantitative analyses of the dependence of island diffusion coefficient D vs the island side length L , D{proportional_to}L{sup {minus}{alpha}} , yield noninteger scaling exponents which are consistent with island coalescence. Moreover, the near absence of island decay shows that the island diffusion occurs via mass transport along the island periphery. {copyright} {ital 1997} {ital The American Physical Society}

Pai, W.W.; Swan, A.K.; Zhang, Z.; Wendelken, J.F. [Solid State Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831 (United States)] [Solid State Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831 (United States)

1997-10-01

439

Germanium nanowire growth controlled by surface diffusion effects

Germanium nanowires (NWs) were grown onto Ge(111) substrates by the vapor-liquid-solid process using gold droplets. The growth was carried out in a molecular beam epitaxy chamber at substrate temperatures between 370 Degree-Sign C and 510 Degree-Sign C. The resulting nanowire growth rate turns out to be highly dependent on the substrate temperature exhibiting the maximum at T = 430 Degree-Sign C. The temperature dependence of growth rate can be attributed to surface diffusion both along the substrate and nanowire sidewalls. Analyzing the diffusive material transport yields a diffusion length of 126 nm at a substrate temperature of 430 Degree-Sign C.

Schmidtbauer, Jan; Bansen, Roman; Heimburger, Robert; Teubner, Thomas; Boeck, Torsten; Fornari, Roberto [Leibniz-Institut fuer Kristallzuechtung, Max-Born-Str. 2, 12489 Berlin (Germany)

2012-07-23

440

Topological Characteristics of the Dutch Road Infrastructure

Abstract—In this paper we study an example of a complex network, namely the road infrastructure of the Netherlands. In order to investigate the factors influencing the robustness of the complex network under consideration, we calculate a set of generic topological characteristics, related to the connectivity, degree, clustering and the shortest path length. Along with these widely considered topological characteristics, we

A. Jamakovic; H. Wang; P. Van Mieghem

2006-01-01