920 resultados para surface structure


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Heparan sulfate proteoglycans and their corresponding binding sites have been suggested to play an important role during the initial attachment of blastocysts to uterine epithelium and human trophoblastic cell lines to uterine epithelial cell lines. Previous studies on RL95 cells, a human uterine epithelial cell line, characterized a single class of cell surface heparin/heparan sulfate (HP/HS)-binding sites. Three major HP/HS-binding peptide fragments were isolated from RL95 cell surfaces by tryptic digestion and partial amino-terminal amino acid sequence from each peptide fragment was obtained. In the current study, using the approaches of reverse transcription-polymerase chain reaction and cDNA library screening, a novel cell surface $\rm\underline{H}$P/HS $\rm\underline{i}$nteracting $\rm\underline{p}$rotein (HIP) has been isolated from RL95 cells. The full-length cDNA of HIP encodes a protein of 259 amino acids with a calculated molecular weight of 17,754 Da and pI of 11.75. Transfection of HIP cDNA into NIH-3T3 cells demonstrated cell surface expression and a size similar to that of HIP expressed by human cells. Predicted amino acid sequence indicates that HIP lacks a membrane spanning region and has no consensus sites for glycosylation. Northern blot analysis detected a single transcript of 1.3 kb in both total RNA and poly(A$\sp+$) RNA. Examination of human cell lines and normal tissues using both Northern blot and Western blot analysis revealed that HIP is differentially expressed in a variety of human cell lines and normal tissues, but absent in some cell lines examined. HIP has about 80% homology, at the level of both mRNA and protein, to a rodent protein, designated as ribosomal protein L29. Thus, members of the L29 family may be displayed on cell surfaces where they participate in HP/HS binding events. Studies on a synthetic peptide derived from HIP demonstrate that HIP peptide binds HS/HP with high selectivity and has high affinity (Kd = 10 nM) for a subset of polysaccharides found in commercial HIP preparations. Moreover, HIP peptide also binds certain forms of cell surface, but not secreted or intracellular. HS expressed by RL95 and JAR cells. This peptide supports the attachment of several human trophoblastic cell lines and a variety of mammalian adherent cell lines in a HS-dependent fashion. Furthermore, studies on the subset of HP specifically recognized by HIP peptide indicate that this high-affinity HP (HA-HP) has a larger median MW and a greater negative charge density than bulk HP. The minimum size of oligosaccharide required to bind to HIP peptide with high affinity is a septa- or octasaccharide. HA-HP also quantitatively binds to antithrombin-III (AT-III) with high affinity, indicating that HIP peptide and AT-III may recognize the same or similar oligosaccharide structure(s). Furthermore, HIP peptide antagonizes HP action and promotes blood coagulation in both factor Xa- and thrombin-dependent assays. Finally, HA-HP recognized by HP peptide is highly enriched with anticoagulant activity relative to bulk HP. Collectively, these results demonstrate that HIP may play a role in the HP/HS-involved cell-cell and cell-matrix interactions and recognizes a motif in HP similar or identical to that recognized by AT-III and therefore, may modulate blood coagulation. ^

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BACKGROUND Nebulized surfactant therapy has been proposed as an alternative method of surfactant administration. The use of a perforated vibrating membrane nebulizer provides a variety of advantages over conventional nebulizers. We investigated the molecular structure and integrity of poractant alfa pre- and post-nebulization. METHOD Curosurf® was nebulized using an Investigational eFlow® Nebulizer System. Non-nebulized surfactant ("NN"), recollected surfactant droplets from nebulization through an endotracheal tube ("NT") and nebulization of surfactant directly onto a surface ("ND") were investigated by transmission electron microscopy. Biophysical characteristics were assessed by the Langmuir-Wilhelmy balance and the Captive Bubble Surfactometer. RESULTS Volume densities of lamellar body-like forms (LBL) and multi-lamellar forms (ML) were high for "NN" and "NT" samples (38.8% vs. 47.7% for LBL and 58.2% vs. 47.8% for ML). In the "ND" sample, we found virtually no LBL's, ML's (72.6%) as well as uni-lamellar forms (16.4%) and a new structure, the "garland-like" forms (9.4%). Surface tension for "NN" and "NT" was 23.33 ± 0.29 and 25.77 ± 1.12 mN/m, respectively. Dynamic compression-expansion cycling minimum surface tensions were between 0.91 and 1.77 mN/m. CONCLUSION The similarity of surfactant characteristics of nebulized surfactant via a tube and the non-nebulized surfactant suggests that vibrating membrane nebulizers are suitable for surfactant nebulization. Alterations in surfactant morphology and characteristics after nebulization were transient. A new structural subtype of surfactant was identified. Pediatr Pulmonol. 2014; 49:348-356. © 2013 Wiley Periodicals, Inc.

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Six years of daily satellite data are used to quantify and map intraseasonal variability of chlorophyll and sea surface temperature (SST) in the California Current. We define intraseasonal variability as temporal variation remaining after removal of interannual variability and stationary seasonal cycles. Semivariograms are used to quantify the temporal structure of residual time series. Empirical orthogonal function (EOF) analyses of semivariograms calculated across the region isolate dominant scales and corresponding spatial patterns of intraseasonal variability. The mode 1 EOFs for both chlorophyll and SST semivariograms indicate a dominant timescale of similar to 60 days. Spatial amplitudes and patterns of intraseasonal variance derived from mode 1 suggest dominant forcing of intraseasonal variability through distortion of large scale chlorophyll and SST gradients by mesoscale circulation. Intraseasonal SST variance is greatest off southern Baja and along southern Oregon and northern California. Chlorophyll variance is greatest over the shelf and slope, with elevated values closely confined to the Baja shelf and extending farthest from shore off California and the Pacific Northwest. Intraseasonal contributions to total SST variability are strongest near upwelling centers off southern Oregon and northern California, where seasonal contributions are weak. Intraseasonal variability accounts for the majority of total chlorophyll variance in most inshore areas save for southern Baja, where seasonal cycles dominate. Contributions of higher EOF modes to semivariogram structure indicate the degree to which intraseasonal variability is shifted to shorter timescales in certain areas. Comparisons of satellite-derived SST semivariograms to those calculated from co-located and concurrent buoy SST time series show similar features.

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The generation of collimated electron beams from metal double-gate nanotip arrays excited by near infrared laser pulses is studied. Using electromagnetic and particle tracking simulations, we showed that electron pulses with small rms transverse velocities are efficiently produced from nanotip arrays by laser-induced field emission with the laser wavelength tuned to surface plasmon polariton resonance of the stacked double-gate structure. The result indicates the possibility of realizing a metal nanotip array cathode that outperforms state-of-the-art photocathodes.

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The liquid–vapor interface is difficult to access experimentally but is of interest from a theoretical and applied point of view and has particular importance in atmospheric aerosol chemistry. Here we examine the liquid–vapor interface for mixtures of water, sodium chloride, and formic acid, an abundant chemical in the atmosphere. We compare the results of surface tension and X-ray photoelectron spectroscopy (XPS) measurements over a wide range of formic acid concentrations. Surface tension measurements provide a macroscopic characterization of solutions ranging from 0 to 3 M sodium chloride and from 0 to over 0.5 mole fraction formic acid. Sodium chloride was found to be a weak salting out agent for formic acid with surface excess depending only slightly on salt concentration. In situ XPS provides a complementary molecular level description about the liquid–vapor interface. XPS measurements over an experimental probe depth of 51 Å gave the C 1s to O 1s ratio for both total oxygen and oxygen from water. XPS also provides detailed electronic structure information that is inaccessible by surface tension. Density functional theory calculations were performed to understand the observed shift in C 1s binding energies to lower values with increasing formic acid concentration. Part of the experimental −0.2 eV shift can be assigned to the solution composition changing from predominantly monomers of formic acid to a combination of monomers and dimers; however, the lack of an appropriate reference to calibrate the absolute BE scale at high formic acid mole fraction complicates the interpretation. Our data are consistent with surface tension measurements yielding a significantly more surface sensitive measurement than XPS due to the relatively weak propensity of formic acid for the interface. A simple model allowed us to replicate the XPS results under the assumption that the surface excess was contained in the top four angstroms of solution.

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An axisymmetric, elastic pipe is filled with an incompressible fluid and is immersed in a second, coaxial rigid pipe which contains the same fluid. A pressure pulse in the outer fluid annulus deforms the elastic pipe which invokes a fluid motion in the fluid core. It is the aim of this study to investigate streaming phenomena in the core which may originate from such a fluid-structure interaction. This work presents a numerical solver for such a configuration. It was developed in the OpenFOAM software environment and is based on the Arbitrary Lagrangian Eulerian (ALE) approach for moving meshes. The solver features a monolithic integration of the one-dimensional, coupled system between the elastic structure and the outer fluid annulus into a dynamic boundary condition for the moving surface of the fluid core. Results indicate that our configuration may serve as a mechanical model of the Tullio Phenomenon (sound-induced vertigo).

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Amawaka ([ɑmɨ̃ˈwɐkɑ]) is a highly endangered and underdocumented tonal language of the Headwaters (Fleck 2011) subgroup of the Panoan family in the Southwest Amazon Basin, spoken by approximately 200 people. Undocumented phonetic and phonological phenomena of Amawaka include its tonal structure, both in terms of surface realizations and the patterns underlying these realizations. Original audiovisual data from the author’s fieldwork in various Amawaka communities at the Peru-Brazil border will illuminate the as-yet obscure tonal systematicity of the language. Unlike other elements, monosyllabic bimoraic phonological nominal words with long vowels display variation in their surface realization. All the words with the open back unrounded /ɑ/, like /ˈkɑ̀:/ (patarashca, a traditional Amazonian dish), /ˈnɑ̀:/ “mestizo” etc. [with the exception of /ˈtɑ:/ “reed”, which surfaces with either a H or L tone] bear a low tone in isolation. This realization contrasts with all the encountered nominal monosyllables with vowels from the close and close-mid front and central spectrum /i, ɘ, ɨ, ɨ̃/, which clearly surface as high tone words in isolation, for example /ˈmɨ̃́:/ (a clay-lick for animals), /ˈwí:/ “Anopheles, spp. mosquito”. Monosyllables with close-mid back rounded /o/ have a less restrictive pitch that varies among speakers from low to high realizations, and sometimes even across the speech tokens from an individual speaker, e.g. /wó:/ or /wō:/ “hair”, /ɧō:/ or /ɧò:/ (a type of tarantula). Phrasal tonal phonology is more complex, when these three kinds of monosyllables appear in larger noun phrases. Some retain the same surface tones as their isolation form, while others seem to vary freely in their surface realization, e.g. /ˈtɘ́:.nɑ̀:/ or /ˈtɘ́:.nɑ́:/ ‘one mestizo’. Yet other monosyllables, e.g. /mɑ̀:/, exhibit a falling tone when preceded by a H syllable, suggesting probably latent tone sandhi phenomena, e.g /ˈtɘ́:.mɑ̂:/ (one clay-lick for parrots). In disyllabic, trisyllabic and quadrisyllabic nouns, tonal and stress patterns generally seem to be more consistent and tend to be retained both in isolation and in larger intonational phrases. Disyllabic nouns, for instance, surface as L-H or L-L when a glottal stop is in coda position. The association of L with a glottal stop is a feature that occurs in other Panoan languages as well, like Capanahua (Loos 1969), and more generally it is an areal feature, found in other parts of Amazonia (Hyman 2010). So, tone has significant interactions with the glottal stop and glottalization, which generally co-occurs with L. The data above suggest that the underlying tonal system of Amawaka is much more complex than the privative one-tone analysis (/H/ vs. Ø, i.e. lack of tone) that was proposed by Russell and Russell (1959). Evidence from field data suggests either an equipollent (Hyman 2010) two-tone opposition between /H/ and /L/, or a hybrid system, with both equipollent and privative features; that is, /H/ vs. /L/ vs. either Ø or /M/. This first systematic description of Amawaka tone, in conjunction with ongoing research, is poised to address broader questions concerning interrelationships between surface/underlying tone and other suprasegmental features, such as nasality, metrical stress, and intonation. References Fleck, David W. 2011. Panoan languages and linguistics. In Javier Ruedas and David W. Fleck (Eds.), Panoan Histories and Interethnic Identities, To appear. Hyman, Larry. 2010. Amazonia and the typology of tone systems. Presented at the conference Amazonicas III: The structure of the Amazonian languages. Bogotá. Loos, Eugene E. 1969. The phonology of Capanahua and its grammatical basis. Norman: SIL and U. Oklahoma. Russell, Robert & Dolores. 1959. Syntactotonemics in Amahuaca (Pano). Série Lingüistica Especial, 128-167. Publicaçoes do Museu Nacional, Rio de Janeiro, Brasil.

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Recently, sub-wavelength-pitch stacked double-gate metal nanotip arrays have been proposed to realize high current, high brightness electron bunches for ultrabright cathodes for x-ray free-electron laser applications. With the proposed device structure, ultrafast field emission of photoexcited electrons is efficiently driven by vertical incident near infrared laser pulses, via near field coupling of the surface plasmon polariton resonance of the gate electrodes with the nanotip apex. In this work, in order to gain insight in the underlying physical processes, the authors report detailed numerical studies of the proposed device. The results indicate the importance of the interaction of the double-layer surface plasmon polariton, the position of the nanotip, as well as the incident angle of the near infrared laser pulses.

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The surfaces of many objects in the Solar System comprise substantial quantities of water ice sometimes mixed with minerals and/or organic molecules. The sublimation of the ice changes the structural and optical properties of these objects. We present laboratory data on the evolution of the structure and the visible and near-infrared spectral reflectance of icy surface analogues of cometary ices, made of water ice, complex organic matter (tholins) and silicates, as they undergo sublimation under low temperature (<-70°C) and pressure (10-⁵mbar) conditions inside the SCITEAS simulation chamber. As the water ice sublimated, we observed in situ the formation of a porous sublimation lag deposit, or sublimation mantle, at the top of the ice. This mantle is a network of filaments made of the non-volatile particles. Organics or phyllosilicates grains, able to interact via stronger inter-particulate forces than olivine grains, can form a foam-like structure having internal cohesiveness, holding olivine grains together. As this mantle builds-up, the band depths of the sub-surface water ice are attenuated until complete extinction under only few millimeters of mantle. Optically thick sublimation mantles are mainly featureless in the near infrared. The absorption bands of the minerals present in the mantle are weak, or even totally absent if minerals are mixed with organics which largely dominate the VIS–NIR reflectance spectrum. During sublimation, ejections of large fragments of mantle, triggered by the gas flow, expose ice particles to the surface. The contrast of brightness between mantled and ice-exposed areas depends on the wavelength range and the dust/ice ratio considered. We describe how the chemical nature of the non-volatiles, the size of their particles, the way they are mixed with the ice and the dust/ice mass ratio influence the texture, activity and spectro-photometric properties of the sublimation mantles. These data provide useful references for interpreting remote-sensing observations of comets and also icy satellites or trans-neptunian objects.

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Images from the OSIRIS scientific imaging system onboard Rosetta show that the nucleus of 67P/Churyumov-Gerasimenko consists of two lobes connected by a short neck. The nucleus has a bulk density less than half that of water. Activity at a distance from the Sun of >3 astronomical units is predominantly from the neck, where jets have been seen consistently. The nucleus rotates about the principal axis of momentum. The surface morphology suggests that the removal of larger volumes of material, possibly via explosive release of subsurface pressure or via creation of overhangs by sublimation, may be a major mass loss process. The shape raises the question of whether the two lobes represent a contact binary formed 4.5 billion years ago, or a single body where a gap has evolved via mass loss.

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Using miniature thermistors with integrated data loggers, the decrease in summer lake surface water temperature (LSWT) with increasing altitude a.s.l. was investigated in 10 Swiss Alpine lakes located between 613 m a.s.l. and 2339 m a.s.l. The LSWTs exhibit essentially the same short-term structure as regional air temperature, but are about 3 to 5°C higher than the air temperature at the altitude of the lake. LSWTs decrease approximately linearly with increasing altitude at a rate slightly greater than the surface air temperature lapse rate. Diel variations in LSWT are large, implying that single water temperature measurements are un- likely to be representative of the mean. Local factors will affect LSWT more than they affect air temperature, possibly resulting in severe distortion of the empirical relationship between the two. Several implications for paleoclimate reconstruction studies result. (1) Paleolimnologically reconstructed LSWTs are likely to be higher than the air temperatures prevailing at the altitude of the lake. (2) Lakes used for paleoclimate reconstruction should be selected to minimize local effects on LSWT. (3) The calibration of organism-specific quantitative paleotemperature inference models should not be based on single water temperature measurements. (4) Consideration should be given to calibrating such models directly against air temperature rather than water temperature. (5) The primary climate effect on the aquatic biota of high-altitude lakes may be mediated by the timing of the ice cover.

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Coagulase-negative staphylococci (CNS) are recognized as important pathogens and are particularly associated with foreign body infections. S. epidermidis accounts for approximately 75% of the infections caused by CNS. Three genes, sdrF, sdrG, and sdrH, were identified by screening a S. epidermidis genomic library with a probe encompassing the serine-aspartate dipeptide repeat-encoding region (region R) of clfA from S. aureus. SdrG has significant amino acid identity to ClfA, ClfB and other surface proteins of S. aureus. SdrG is also similar to a protein (Fbe) recently described by Nilsson, et al. (Infection and Immunity, 1998, 66:2666–73) from S. epidermidis. The N-terminal domain (A region) of SdrG was expressed as a his-tag fusion protein in E. coli. In an ELISA, this protein, rSdrG(50-597) was shown to bind specifically to fibrinogen (Fg). Western ligand blot analysis showed that SdrG binds the Bβ chain of Fg. To further characterize the rSdrG(50-597)-Fg interaction, truncates of the Fg Bβ chain were made and expressed as recombinant proteins in E. coli. SdrG was shown to bind the full-length Bβ chain (1462), as well as the N-terminal three-quarters (1-341), the N-terminal one-half (1-220) and the N-terminal one-quarter (1-95) Bβ chain constructs. rSdrG(50-597) failed to bind to the recombinant truncates that lacked the N-terminal 25 amino acid residues of this polypeptide suggesting that SdrG recognizes a site within this region of the Bβ chain. Inhibition ELISAs have shown that peptide mimetics, including β1–25, and β6–20, encompassing this 25 residue region can inhibit binding of rSdrG(50-597) to Fg coated wells. Using fluorescence polarization we were able to determine an equilibrium constant (KD) for the interaction of rSdrG(50-597) with the Fg Bβ chain peptide β1–25. The labeled peptide was shown to bind to rSdrG(50-597) with a KD of 0.14 ± 0.01μM. Because rSdrG(50-597) recognizes a site in the Fg Bβ chain close to the thrombin cleavage site, we investigated the possibility of the rSdrG(50-597) site either overlapping or lying close to this cleavage site. An ELISA showed that rSdrG(50-597) binding to thrombin-treated Fg was significantly reduced. In a clot inhibition assay rSdrG(50-597) was able to inhibit fibrin clot formation in a concentration dependent manner. Furthermore, rSdrG(50-597) was able to inhibit clot formation by preventing the release of fibrinopeptide B as determined by HPLC. To further define the interaction between rSdrG(50-597) and peptide β6–20, we utilized an alanine amino acid replacement strategy. The residues in β6–20 that appear to be important in rSdrG(50-597) binding to Fg, were confirmed by the rSdrG(273-597)-β6–20 co-crystal structure that was recently solved by our collaborators at University of Alabama-Birmingham. Additionally, rSdrG(50-597) was not able to bind to Fg from different animal species, rather it bound specifically to human Fg in an ELISA. This suggests that the sequence variation between Fg Bβ chains of different species, specifically with in the N-terminal 25 residues, affects the ability of rSdrG(50-597) binding to Fg, and this may explain why S. epidermidis is primarily a human pathogen. ^

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Much advancement has been made in recent years in field data assimilation, remote sensing and ecosystem modeling, yet our global view of phytoplankton biogeography beyond chlorophyll biomass is still a cursory taxonomic picture with vast areas of the open ocean requiring field validations. High performance liquid chromatography (HPLC) pigment data combined with inverse methods offer an advantage over many other phytoplankton quantification measures by way of providing an immediate perspective of the whole phytoplankton community in a sample as a function of chlorophyll biomass. Historically, such chemotaxonomic analysis has been conducted mainly at local spatial and temporal scales in the ocean. Here, we apply a widely tested inverse approach, CHEMTAX, to a global climatology of pigment observations from HPLC. This study marks the first systematic and objective global application of CHEMTAX, yielding a seasonal climatology comprised of ~1500 1°x1° global grid points of the major phytoplankton pigment types in the ocean characterizing cyanobacteria, haptophytes, chlorophytes, cryptophytes, dinoflagellates, and diatoms, with results validated against prior regional studies where possible. Key findings from this new global view of specific phytoplankton abundances from pigments are a) the large global proportion of marine haptophytes (comprising 32 ± 5% of total chlorophyll), whose biogeochemical functional roles are relatively unknown, and b) the contrasting spatial scales of complexity in global community structure that can be explained in part by regional oceanographic conditions. These publicly accessible results will guide future parameterizations of marine ecosystem models exploring the link between phytoplankton community structure and marine biogeochemical cycles.

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A prominent control on the flow over subaqueous dunes is the slope of the downstream leeside. While previous work has focused on steep (~30°), asymmetric dunes with permanent flow separation, little is known about dunes with lower lee-slope angles for which flow separation is absent or intermittent. Here, we present a laboratory investigation where we systematically varied the dune lee-slope, holding other geometric parameters and flow hydraulics constant, to explore effects on the turbulent flow field and flow resistance. Three sets of fixed dunes (lee-slopes of 10°, 20° and 30°) were separately installed in a 15 m long and 1 m wide flume and subjected to 0.20 m deep flow. Measurements consisted of high-frequency, vertical profiles collected with a Laser Doppler Velocimeter (LDV). We show that the temporal and spatial occurrence of flow separation decreases with dune lee-slope. Velocity gradients in the dune leeside depict a free shear layer downstream of the 30° dunes and a weaker shear layer closer to the bed for the 20° and 10° dunes. The decrease in velocity gradients leads to lower magnitude of turbulence production for gentle lee-slopes. Aperiodic, strong ejection events dominate the shear layer, but decrease in strength and frequency for low-angle dunes. Flow resistance of dunes decreases with lee-slope; the transition being non-linear. Over the 10°, 20° and 30° dunes, shear stress is 8%, 33% and 90 % greater than a flat bed, respectively. Our results demonstrate that dune lee-slope plays an important, but often ignored role in flow resistance.

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The development of the ecosystem approach and models for the management of ocean marine resources requires easy access to standard validated datasets of historical catch data for the main exploited species. They are used to measure the impact of biomass removal by fisheries and to evaluate the models skills, while the use of standard dataset facilitates models inter-comparison. North Atlantic albacore tuna is exploited all year round by longline and in summer and autumn by surface fisheries and fishery statistics compiled by the International Commission for the Conservation of Atlantic Tunas (ICCAT). Catch and effort with geographical coordinates at monthly spatial resolution of 1° or 5° squares were extracted for this species with a careful definition of fisheries and data screening. In total, thirteen fisheries were defined for the period 1956-2010, with fishing gears longline, troll, mid-water trawl and bait fishing. However, the spatialized catch effort data available in ICCAT database represent a fraction of the entire total catch. Length frequencies of catch were also extracted according to the definition of fisheries above for the period 1956-2010 with a quarterly temporal resolution and spatial resolutions varying from 1°x 1° to 10°x 20°. The resolution used to measure the fish also varies with size-bins of 1, 2 or 5 cm (Fork Length). The screening of data allowed detecting inconsistencies with a relatively large number of samples larger than 150 cm while all studies on the growth of albacore suggest that fish rarely grow up over 130 cm. Therefore, a threshold value of 130 cm has been arbitrarily fixed and all length frequency data above this value removed from the original data set.