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222 results on '"Brum, J. A."'

1. Generic Rotation Sets in Hyperbolic Surfaces

Author

Alonso, J., Brum, J., and Passeggi, A.

Subjects
Mathematics - Dynamical Systems
Abstract

We show that for generic homeomorphisms homotopic to the identity in a closed and oriented surface of genus $g>1$, the rotation set is given by a union of at most $2^{5g-3}$ convex sets. Examples showing the sharpness for this asymptotic order are provided.

Published
2020

2. On the geometry of positive cones in finitely generated groups

Author

Alonso, J., Antolín, Y., Brum, J., and Rivas, C.

Subjects
Mathematics - Group Theory, Mathematics - Metric Geometry, 20F60, 20E08, 20F67
Abstract

We study the geometry of positive cones of left-invariant total orders (left-order, for short) in finitely generated groups. We introduce the \textit{Hucha property} and the \texit{Prieto property} for left-orderable groups. The first one means that in any left-order the corresponding positive cone is not coarsely connected, and the second one that in any left-order the corresponding positive cone is coarsely connected. We show that all left-orderable free products have the Hucha property, and that the Hucha property is stable under certain free products with amalgamatation over Prieto subgroups. As an application we show that non-abelian limit groups in the sense of Z. Sela (e.g. free groups, fundamental group of hyperbolic surfaces, doubles of free groups and others) and non-abelian finitely generated subgroups of free $\mathbb{Q}$-groups in the sense of G. Baumslag have the Hucha property. In particular, this implies that these groups have empty BNS-invariant $\Sigma^1$ and that they don't have finitely generated positive cones., Comment: 32 pages

Published
2020

3. Drastic slowdown of shear waves in unjammed granular suspensions

Author

Brum, J., Gennisson, J. -L., Fink, M., Tourin, A., and Jia, X.

Subjects
Condensed Matter - Soft Condensed Matter
Abstract

We present an experimental investigation of shear elastic wave propagation along the surface of a dense granular suspension. Using an ultrafast ultrasound scanner, we monitor the softening of the shear wave velocity inside the optically opaque medium as the driving amplitude increases. For such nonlinear behavior two regimes are found: in the first regime, we observe a significant shear modulus weakening, but without visible grain rearrangements. In the second regime, there is a clear grain rearrangement accompanied by a modulus decrease up to 88%. A friction model is proposed to describe the interplay between nonlinear elasticity and plasticity, which highlights the crucial effect of contact slipping before contact breaking. Investigation of these nonlinear shear waves may bridge the gap between two disjoint approaches for describing the dynamics near unjamming: linear elastic soft modes and nonlinear collisional shock., Comment: 20 pages and 7 figures, including the supplemental material (5 pages, 3 figures)

Published
2018
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4. Optically controlled spin-polarization memory effect on Mn delta-doped heterostrucutres

Author

Balanta, M. A. G., Brasil, M. J. S. P., Iikawa, F., Mendes, Udson C., Brum, J. A., Danilov, Yu. A., Dorokhin, M. V., Vikhrova, O. V., and Zvonkov, B. N.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

We investigated the dynamics of the interaction between spin-polarized photo-created carriers and Mn ions on InGaAs/GaAs:Mn structures. The carriers are confined in an InGaAs quantum well and the Mn ions come from a Mn delta-layer grown at the GaAs barrier close to the well. Even though the carriers and the Mn ions are spatially separated, the interaction between them is demonstrated by time-resolved spin-polarized photoluminescence measurements. Using a pre-pulse laser excitation with an opposite circular-polarization clearly reduces the polarization degree of the quantum-well emission for samples where a strong magnetic interaction is observed. The results demonstrate that the Mn ions act as a spin-memory that can be optically controlled by the polarization of the photocreated carriers. On the other hand, the spin-polarized Mn ions also affect the spin-polarization of the subsequently created carriers as observed by their spin relaxation time. These effects fade away with increasing time delays between the pulses as well as with increasing temperatures., Comment: 12 pages, 5 figures

Published
2015
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5. Theory of Magnetic Anisotropy in III_{1-x}Mn_{x}V Ferromagnets

Author

Abolfath, M., Jungwirth, T., Brum, J., and MacDonald, A. H.

Subjects
Condensed Matter - Materials Science
Abstract

We present a theory of magnetic anisotropy in ${\rm III}_{1-x}{\rm Mn}_{x}{\rm V}$ diluted magnetic semiconductors with carrier-induced ferromagnetism. The theory is based on four and six band envelope functions models for the valence band holes and a mean-field treatment of their exchange interactions with ${\rm Mn}^{++}$ ions. We find that easy-axis reorientations can occur as a function of temperature, carrier density $p$, and strain. The magnetic anisotropy in strain-free samples is predicted to have a $p^{5/3}$ hole-density dependence at small $p$, a $p^{-1}$ dependence at large $p$, and remarkably large values at intermediate densities. An explicit expression, valid at small $p$, is given for the uniaxial contribution to the magnetic anisotropy due to unrelaxed epitaxial growth lattice-matching strains. Results of our numerical simulations are in agreement with magnetic anisotropy measurements on samples with both compressive and tensile strains. We predict that decreasing the hole density in current samples will lower the ferromagnetic transition temperature, but will increase the magnetic anisotropy energy and the coercivity., Comment: 15 pages, 15 figures

Published
2000
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8. Environmental characteristics of Agulhas rings affect interocean plankton transport

Author

Tara Oceans Coordinators, Villar, E., Farrant, G. K., Follows, M., Garczarek, L., Speich, S., Audic, S., Bittner, L., Blanke, B., Brum, J. R., Brunet, C., Casotti, R., Chase, A., Dolan, J. R., d'Ortenzio, F., Gattuso, J.-P., Grima, N., Guidi, L., Hill, C. N., Jahn, O., Jamet, J.-L., Le Goff, H., Lepoivre, C., Malviya, S., Pelletier, E., Romagnan, J.-B., Roux, S., Santini, S., Scalco, E., Schwenck, S. M., Tanaka, A., Testor, P., Vannier, T., Vincent, F., Zingone, A., Dimier, C., Picheral, M., Searson, S., Kandels-Lewis, S., Acinas, S. G., Bork, P., Boss, E., de Vargas, C., Gorsky, G., Ogata, H., Pesant, S., Sullivan, M. B., Sunagawa, S., Wincker, P., Karsenti, E., Bowler, C., Not, F., Hingamp, P., and Iudicone, D.

Published
2015

9. Patterns and ecological drivers of ocean viral communities

Author

Tara Oceans Coordinators, Brum, J. R., Ignacio-Espinoza, J. C., Doulcier, S. Roux G., Acinas, S. G., Alberti, A., Chaffron, S., Cruaud, C., de Vargas, C., Gasol, J. M., Gorsky, G., Gregory, A. C., Guidi, L., Hingamp, P., Iudicone, D., Not, F., Ogata, H., Pesant, S., Poulos, B. T., Schwenck, S. M., Speich, S., Dimier, C., Kandels-Lewis, S., Picheral, M., Searson, S., Bork, P., Bowler, C., Sunagawa, S., Wincker, P., Karsenti, E., and Sullivan, M. B.

Published
2015

10. Medición de Diámetros Arteriales Utilizando Ultrasonido de Alta Resolución: Validación in vitro

Author

Brum, J., Bia, D., Benech, N., Balay, G., Armentano, R., Negreira, C., Folgueras Méndez, José, editor, Aznielle Rodríguez, Tania Y., editor, Calderón Marín, Carlos F., editor, Llanusa Ruiz, Susana Beatriz, editor, Castro Medina, Jorge, editor, Vega Vázquez, Haddid, editor, Carballo Barreda, Maylen, editor, and Rodríguez Rojas, Rafael, editor

Published
2013
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17. Environmental characteristics of Agulhas rings affect interocean plankton transport

Author

Villar, E., Farrant, G. K., Follows, M., Garczarek, L., Speich, S., Audic, S., Bittner, L., Blanke, B., Brum, J. R., Brunet, C., Casotti, R., Chase, A., Dolan, J. R., dʼOrtenzio, F., Gattuso, J.-P., Grima, N., Guidi, L., Hill, C. N., Jahn, O., Jamet, J.-L., Le Goff, H., Lepoivre, C., Malviya, S., Pelletier, E., Romagnan, J.-B., Roux, S., Santini, S., Scalco, E., Schwenck, S. M., Tanaka, A., Testor, P., Vannier, T., Vincent, F., Zingone, A., Dimier, C., Picheral, M., Searson, S., Kandels-Lewis, S., Oceans Coordinators, Tara, Acinas, S. G., Bork, P., Boss, E., de Vargas, C., Gorsky, G., Ogata, H., Pesant, S., Sullivan, M. B., Sunagawa, S., Wincker, P., Karsenti, E., Bowler, C., Not, F., Hingamp, P., and Iudicone, D.

Published
2015

18. Patterns and ecological drivers of ocean viral communities

Author

Brum, J. R., Ignacio-Espinoza, J. C., Roux, S., Doulcier, G., Acinas, S. G., Alberti, A., Chaffron, S., Cruaud, C., de Vargas, C., Gasol, J. M., Gorsky, G., Gregory, A. C., Guidi, L., Hingamp, P., Iudicone, D., Not, F., Ogata, H., Pesant, S., Poulos, B. T., Schwenck, S. M., Speich, S., Dimier, C., Kandels-Lewis, S., Picheral, M., Searson, S., Oceans Coordinators, Tara, Bork, P., Bowler, C., Sunagawa, S., Wincker, P., Karsenti, E., and Sullivan, M. B.

Published
2015

19. A genomic catalog of Earth’s microbiomes

Author

Nayfach, S., Roux, S., Seshadri, R., Udwary, D., Varghese, N., Schulz, F., Wu, D., Paez-Espino, D., Chen, I., Huntemann, M., Palaniappan, K., Ladau, J., Mukherjee, S., Reddy, T., Nielsen, T., Kirton, E., Faria, J., Edirisinghe, J., Henry, C., Jungbluth, S., Chivian, D., Dehal, P., Wood-Charlson, E., Arkin, A., Tringe, S., Visel, A., Abreu, H., Acinas, S., Allen, E., Allen, M., Alteio, L., Andersen, G., Anesio, A., Attwood, G., Avila-Magaña, V., Badis, Y., Bailey, J., Baker, B., Baldrian, P., Barton, H., Beck, D., Becraft, E., Beller, H., Beman, J., Bernier-Latmani, R., Berry, T., Bertagnolli, A., Bertilsson, S., Bhatnagar, J., Bird, J., Blanchard, J., Blumer-Schuette, S., Bohannan, B., Borton, M., Brady, A., Brawley, S., Brodie, J., Brown, S., Brum, J., Brune, A., Bryant, D., Buchan, A., Buckley, D., Buongiorno, J., Cadillo-Quiroz, H., Caffrey, S., Campbell, A., Campbell, B., Carr, S., Carroll, J., Cary, S., Cates, A., Cattolico, R., Cavicchioli, R., Chistoserdova, L., Coleman, M., Constant, P., Conway, J., Mac Cormack, W., Crowe, S., Crump, B., Currie, C., Daly, R., DeAngelis, K., Denef, V., Denman, S., Desta, A., Dionisi, H., Dodsworth, J., Dombrowski, N., Donohue, T., Dopson, M., Driscoll, T., Dunfield, P., Dupont, C., Dynarski, K., Edgcomb, V., Edwards, E., Elshahed, M., Figueroa, I., Flood, B., Fortney, N., Fortunato, C., Francis, C., Gachon, C., Garcia, S., Gazitua, M., Gentry, T., Gerwick, L., Gharechahi, J., Girguis, P., Gladden, J., Gradoville, M., Grasby, S., Gravuer, K., Grettenberger, C., Gruninger, R., Guo, J., Habteselassie, M., Hallam, S., Hatzenpichler, R., Hausmann, B., Hazen, T., Hedlund, B., Henny, C., Herfort, L., Hernandez, M., Hershey, O., Hess, M., Hollister, E., Hug, L., Hunt, D., Jansson, J., Jarett, J., Kadnikov, V., Kelly, C., Kelly, R., Kelly, W., Kerfeld, C., Kimbrel, J., Klassen, J., Konstantinidis, K., Lee, L., Li, W., Loder, A., Loy, A., Lozada, M., MacGregor, B., Magnabosco, C., Maria da Silva, A., McKay, R., McMahon, K., McSweeney, C., Medina, M., Meredith, L., Mizzi, J., Mock, T., Momper, L., Moran, M., Morgan-Lang, C., Moser, D., Muyzer, G., Myrold, D., Nash, M., Nesbø, C., Neumann, A., Neumann, R., Noguera, D., Northen, T., Norton, J., Nowinski, B., Nüsslein, K., O’Malley, M., Oliveira, R., Maia de Oliveira, V., Onstott, T., Osvatic, J., Ouyang, Y., Pachiadaki, M., Parnell, J., Partida-Martinez, L., Peay, K., Pelletier, D., Peng, X., Pester, M., Pett-Ridge, J., Peura, S., Pjevac, P., Plominsky, A., Poehlein, A., Pope, P., Ravin, N., Redmond, M., Reiss, R., Rich, V., Rinke, C., Rodrigues, J., Rodriguez-Reillo, W., Rossmassler, K., Sackett, J., Salekdeh, G., Saleska, S., Scarborough, M., Schachtman, D., Schadt, C., Schrenk, M., Sczyrba, A., Sengupta, A., Setubal, J., Shade, A., Sharp, C., Sherman, D., Shubenkova, O., Sierra-Garcia, I., Simister, R., Simon, H., Sjöling, S., Slonczewski, J., Correa de Souza, R., Spear, J., Stegen, J., Stepanauskas, R., Stewart, F., Suen, G., Sullivan, M., Sumner, D., Swan, B., Swingley, W., Tarn, J., Taylor, G., Teeling, H., Tekere, M., Teske, A., Thomas, T., Thrash, C., Tiedje, J., Ting, C., Tully, B., Tyson, G., Ulloa, O., Valentine, D., Van Goethem, M., VanderGheynst, J., Verbeke, T., Vollmers, J., Vuillemin, A., Waldo, N., Walsh, D., Weimer, B., Whitman, T., van der Wielen, P., Wilkins, M., Williams, T., Woodcroft, B., Woolet, J., Wrighton, K., Ye, J., Young, E., Youssef, N., Yu, F., Zemskaya, T., Ziels, R., Woyke, T., Mouncey, N., Ivanova, N., Kyrpides, N., Eloe-Fadrosh, E., Consortium, I., and Agencia Estatal de Investigación (España)

Subjects
Resource, Life sciences, biology, Biomedical Engineering, FILOGENIA, Bioengineering, Genomics, Biology, Microbiology, Applied Microbiology and Biotechnology, Genome, purl.org/becyt/ford/1 [https], 03 medical and health sciences, ddc:570, EARTH MICROBIOME PROJECT, Microbiome, purl.org/becyt/ford/1.6 [https], 030304 developmental biology, 2. Zero hunger, 0303 health sciences, 030306 microbiology, Phylum, 15. Life on land, biology.organism_classification, Computational biology and bioinformatics, Phylogenetic diversity, Evolutionary biology, Earth Microbiome Project, Molecular Medicine, Evolutionary ecology, MAGS, GENOMICS, Biotechnology, Archaea, MICROBIAL DIVERSITY
Abstract

13 pages, 5 figures, supplementary information https://doi.org/10.1038/s41587-020-0718-6.-- Data availability: All available metagenomic data, bins and annotations are available through the IMG/M portal (https://img.jgi.doe.gov/). Bulk download for the 52,515 MAGs is available at https://genome.jgi.doe.gov/GEMs and https://portal.nersc.gov/GEM. Genome-scale metabolic models for the nonredundant, high-quality GEMs are summarized at https://doi.org/10.25982/53247.64/1670777 and available in KBase (https://narrative.kbase.us/#org/jgimags). IMG/M identifiers of all metagenomes binned, including detailed information for each metagenome, are available in Supplementary Table 1.-- The pipeline used to generate the metagenome bins is available at https://bitbucket.org/berkeleylab/metabat/src/master/, Publisher Correction: A genomic catalog of Earth’s microbiomes; Nature Biotechnology 39: 520 (2021); https://doi.org/10.1038/s41587-020-00769-4, The reconstruction of bacterial and archaeal genomes from shotgun metagenomes has enabled insights into the ecology and evolution of environmental and host-associated microbiomes. Here we applied this approach to >10,000 metagenomes collected from diverse habitats covering all of Earth’s continents and oceans, including metagenomes from human and animal hosts, engineered environments, and natural and agricultural soils, to capture extant microbial, metabolic and functional potential. This comprehensive catalog includes 52,515 metagenome-assembled genomes representing 12,556 novel candidate species-level operational taxonomic units spanning 135 phyla. The catalog expands the known phylogenetic diversity of bacteria and archaea by 44% and is broadly available for streamlined comparative analyses, interactive exploration, metabolic modeling and bulk download. We demonstrate the utility of this collection for understanding secondary-metabolite biosynthetic potential and for resolving thousands of new host linkages to uncultivated viruses. This resource underscores the value of genome-centric approaches for revealing genomic properties of uncultivated microorganisms that affect ecosystem processes, This work was conducted by the US DOE Joint Genome Institute, a DOE Office of Science User Facility (contract no. DE-AC02–05CH11231), and used resources of the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the US DOE (contract no. DE-AC02–05CH11231). This work was also supported as part of the Genomic Sciences Program DOE Systems Biology KBase (award nos. DE-AC02-05CH11231, DE-AC02-06CH11357, DE-AC05-00OR22725, and DE-AC02-98CH10886).-- With the funding support of the ‘Severo Ochoa Centre of Excelle

Published
2020

26. Enhancement of carrier lifetimes in type-II quantum dot/quantum well hybrid structures.

Author

Couto Jr., O. D. D., de Almeida, P. T., dos Santos, G. E., Balanta, M. A. G., Andriolo, H. F., Brum, J. A., Brasil, M. J. S. P., Iikawa, F., Liang, B. L., and Huffaker, D. L.

Subjects
QUANTUM dots, QUANTUM wells, ELECTRONS, PHOTOLUMINESCENCE, EXCITON theory, SOLAR cells
Abstract

We investigate optical transitions and carrier dynamics in hybrid structures containing type-I GaAs/AlGaAs quantum wells (QWs) and type-II GaSb/AlGaAs quantum dots (QDs). We show that the optical recombination of photocreated electrons confined in the QWs with holes in the QDs and wetting layer can be modified according to the QW/QD spatial separation. In particular, for low spacer thicknesses, the QW optical emission can be suppressed due to the transference of holes from the QW to the GaSb layer, favoring the optical recombination of spatially separated carriers, which can be useful for optical memory and solar cell applications. Time-resolved photoluminescence (PL) measurements reveal non-exponential recombination dynamics. We demonstrate that the PL transients can only be quantitatively described by considering both linear and quadratic terms of the carrier density in the bimolecular recombination approximation for type-II semiconductor nanostructures. We extract long exciton lifetimes from 700 ns to 5 μs for QDs depending on the spacer layer thickness. [ABSTRACT FROM AUTHOR]

Published
2016
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29. Effects of a nearby Mn delta layer on the optical properties of an InGaAs/GaAs quantum well.

Author

Balanta, M. A. G., Brasil, M. J. S. P., Iikawa, F., Brum, J. A., Mendes, Udson C., Danilov, Yu. A., Dorokhin, M. V., Vikhrova, Olga V., and Zvonkov, Boris N.

Subjects
OPTICAL properties, ELECTRO-optical effects, QUANTUM dots, POTENTIAL theory (Physics), CAVITY polaritons
Abstract

We investigated the effects of nearby Mn ions on the confined states of a InGaAs/GaAs quantum well through circularly polarized and magneto-optical measurements. The addition of a Mn delta-doping layer at the barrier close to the well gives rise to surprisingly narrow absorption peaks in the photoluminescence excitation spectra. The peaks become increasingly stronger for decreasing spacer-layer thicknesses between the quantum well and the Mn layer. Most of the peaks were identified based on self-consistent calculations; however, we observed additional peaks that cannot be identified with quantum well transitions, which origin we attribute to an enhanced exciton-phonon coupling. Finally, we discuss possible effects related to the exciton magneto-polaron complex in the reinforcement of the photoluminescence excitation peaks. [ABSTRACT FROM AUTHOR]

Published
2014
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33. Quantum-State Spectroscopy in Quantum Wires and Quantum Dots

Author

Smith, T. P., primary, Arnot, H., additional, Brum, J. A., additional, Chang, L. L., additional, Esaki, L., additional, Fowler, A. B., additional, Hansen, W., additional, Hong, J. M., additional, Kern, D. P., additional, Knoedler, C. M., additional, Laux, S. E., additional, and Lee, K. Y., additional

Published
1990
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37. Optical studies of impurity trapping at the GaAlAs/GaAs interface in quantum well structures.

Author

Meynadier, M. H., Brum, J. A., Delalande, C., Voos, M., Alexandre, F., and Liévin, J. L.

Subjects
*PHOTOLUMINESCENCE, *GALLIUM arsenide, *QUANTUM wells
Abstract

Presents low-temperature photoluminescence studies of nominally undoped gallium arsenide quantum wells in which weak acceptor-related emissions can be observed. Experimental details; Determination of the impurity profile; Conclusion.

Published
1985
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41. Nem tudo o que parece ser, é lesão: aspectos anatômicos, não lesões, artefatos, lesões sem significado clínico e alterações post mortem encontrados na necropsia de suínos domésticos e selvagens (Sus scrofa)

Author

RECH, R. R., SILVA, M. C. da, LANGOHR, I. M., MARQUES, M. G., PESCADOR, C. A., SILVA, G. S., DUTRA, M. C., BRUM, J. S., KRAMER, B., BORDIN, L. C., SILVA, V. S., RAQUEL RUBIA RECH, CNPSA, MARCIA C. DA SILVA, CEDISA, INGEBORG M. LANGOHR, Lousiana State University, MARIANA GROKE MARQUES, CNPSA, CAROLINE A. PESCADOR, UFMT, GUSTAVO S. SILVA, UFMT, MAURÍCIO C. DUTRA, USP, JULIANA S. BRUM, UFSM, BEATRIS KRAMER, CNPSA, LUIZ CARLOS BORDIN, CNPSA, and VIRGINIA SANTIAGO SILVA, CNPSA.

Subjects
Lesão, Lesion(animal), Javali, Swine, Sus scrofa, Autópsia, Necropsy, Suíno
Published
2013

43. State coupling effects in GaAs/InGaAs/AlGaAs modulation doped quantum wells.

Author

Abbade, M. L. F., Iikawa, F., Brum, J. A., Tröster, Th., Bernussi, A. A., Pereira, R. G., and Borghs, G.

Subjects
PHOTOLUMINESCENCE, ARSENIC compounds, QUANTUM wells
Abstract

Presents a study which utilized photoluminescence and magneto-luminescence techniques to evaluate the optical properties of pseudomorphic arsenides modulation doped single quantum wells. Analysis of the data using self-consistent calculations; Relation of coupling effects on transitions in the emission spectra.

Published
1996
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46. Ballistic transport in semiconductor quantum wires in the presence of defects

Author

Rocha, A. R. and Brum, J. A.

Subjects
Condensed Matter::Mesoscopic Systems and Quantum Hall Effect
Abstract

We present calculations of the conductance in semiconductor quasi-one-dimensional systems using the Landauer formalism. We consider the effects on the transport properties inside semiconductor quantum waveguides of different shapes when a defect is located either in the wire region or in the quasi-two-dimensional region. We observe changes on the plateau's threshold when the defect is placed inside the wire and lowering of the conductance plateaus themselves below the conductance quantum G0 =2e² /h when the defect is outside the wire.

Published
2002

47. Effect of collection, transport, processing and storage of blood specimens on the activity of lysomal enzimes in plasma and leukocytes

Author

Burin, Maira Graeff, Dutra Filho, Carlos Severo, Brum, J., Mauricio, T., Amorim, M., and Giugliani, Roberto

Subjects
Bioquímica, Lysosomal enzymes, Storage of blood samples, Sample handling, Lysosomal storage diseases, Inborn errors of metabolism, Reference laboratories
Abstract

This study was designed to evaluate the effect of different conditions of collection, transport and storage on the quality of blood samples from normal individuals in terms of the activity of the enzymes ß- glucuronidase, total hexosaminidase, hexosaminidase A, arylsulfatase A and ß-galactosidase. The enzyme activities were not affected by the different materials used for collection (plastic syringes or vacuum glass tubes). In the evaluation of different heparin concentrations (10% heparin, 5% heparin, and heparinized syringe) in the syringes, it was observed that higher doses resulted in an increase of at least 1-fold in the activities of ß-galactosidase, total hexosaminidase and hexosaminidase A in leukocytes, and ß-glucuronidase in plasma. When the effects of time and means of transportation were studied, samples that had been kept at room temperature showed higher deterioration with time (72 and 96 h) before processing, and in this case it was impossible to isolate leukocytes from most samples. Comparison of heparin and acid citrate-dextrose (ACD) as anticoagulants revealed that ß-glucuronidase and hexosaminidase activities in plasma reached levels near the lower normal limits when ACD was used. In conclusion, we observed that heparin should be used as the preferable anticoagulant when measuring these lysosomal enzyme activities, and we recommend that, when transport time is more than 24 h, samples should be shipped by air in a styrofoam box containing wet ice.

Published
2000

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