Weather regimes in the South American sector and neighbouring oceans during winter Solman, Silvina Alicia; Menendez, Claudio Guillermo We classified 34 years of winter daily 500 hPa geopotential height patterns over the eastern South Pacific-South America-South Atlantic region using the K-means clustering method. We found a significant classification into five weather regimes (WRs) defined as the most frequent large-scale circulation anomalies: WR1 (trough centred downstream of the Drake Passage), WR2 (trough over the SW Pacific and ridge downstream), WR3 (ridge over the SE Pacific and NW–SE trough downstream), WR4 (trough over the SE Pacific and NW–SE ridge downstream) and WR5 (weak ridge to the west of southern South America). We also analysed their persistence and temporal evolution, including transitions between them and development around onsets and breaks of each regime. The preferred transitions, WR1→WR3→WR2→WR4→WR1 and also WR1→WR3→WR2→WR1, suggest the progression of a Rossby wave-like pattern in which each of the regimes resemble the Pacific-South America modes. Significant influence of the WRs on local climate over Argentina was found. The preferred transitions WR1→WR3 and WR3→WR2 induce sustained cold conditions over Patagonia and over northern Argentina, respectively. The most significant change in precipitation frequency is found for WR3, with wetter conditions over all the analysed regions. Finally, the interannual to interdecadal significant variations in the occurrence of these regimes were discussed. WR1 and WR3 are more frequent and WR2 is less frequent during El Niño, and WR2 and WR5 are more frequent and WR1 is less frequent during La Niña. A significant decrease in WR2 and increase of WR4 and WR5 during the 1970s and early 1980s were found.

Post-mortem analysis of formic acid disposition in acute methanol intoxication Ferrari, Luis Alberto; Arado, Miriam G.; Nardo, Cesar A.; Giannuzzi, Leda Fifteen cases of fatal massive methanol intoxication have been investigated. Victims received either no treatment or ethanol therapeutic treatment. Methanol poisoning cases were classified in three groups according to survival time: more than 3 days (group 1), up to 3 days (group 2) and few hours (group 3). Body distribution of methanol and formic acid, as the main metabolite, was analyzed in blood and in different organs (brain, kidney, lung and liver). Relationships between formic acid concentration in the different tissues, survival time and type of treatment applied to victims were studied. Formic acid in blood and tissues was analyzed by head space gas chromatography (head space-GC) with FID detector, previous transformation in methyl formate, essentially as described by Abolin. Formic acid concentration was between 0.03 and 1.10g/l in the samples under study. A good correlation between blood and brain, but poor between blood and the remaining tissues was found. Obtained data suggested that the use of blood and brain could help to improve the analysis of formic acid intoxication. The best correlation among organs was found between lung and kidney for all groups (r2=0.91, 0.84 and 0.87, corresponding to groups 1, 2 and 3, respectively). Lethality index was defined as LI = (concentration of formic acid in blood in (g/l)/0.5) × 100, taking into account that 0.5g/l is the concentration reported by Mahieu in severe methanol poisoning. LI parameter was used to estimate formic acid incidence on the lethality of methanol poisoning cases. LI showed a good correlation with total formic acid concentration of the different tissues analyzed (r2=0.80). Furthermore, LI allowed us to discriminate between individuals that received therapeutic treatment and survived different periods. LI>100 indicated a severe intoxication and short survival time if the victim was assisted with ethanol therapy and hemodialysis was not applied. With regard to victims who received no therapeutic treatment and died in few hours, LI was in the range 40-100. LI was below 40 for individuals that survived more than 3 days and hemodyalisis was not performed. Results showed the importance of performing formic acid analysis to diagnose severe methanol intoxication in post-mortem cases.

Predictive Functional Control based on Fuzzy Model: Comparison with linear predictive functional control and PID control Lepetic, Marko; Skrjanc, Igor; Chiacchiarini, Hector Gerardo; Matko, Drago The implementation of the fuzzy predictive functional control (FPFC) on the magnetic suspension system is presented in the paper. The magnetic suspension system was in our case the pilot plant for magnetic bearing and is an open-loop unstable process, therefore a lead compensator was used to stabilize it. The high quality control requirements were a-periodical step response and zero steady-state error. Adding the integrator to a feedback causes overshoot. The solution to the problem was cascade control with fuzzy predictive functional controller in the outer loop. To cope with the unknown model parameters and the nonlinear nature of the magnetic system, a fuzzy identification based on FNARX model was used. After successful validation the obtained fuzzy model was used for controller design. The FPFC is compared with a cascade linear predictive functional control (PFC) and PID control. The results we obtained with the FPFC are very promising and hardly comparable with conventional control techniques.

Isotropic and anisotropic components of the neutron emissions at the FN-II and PACO dense plasma focus devices Castillo, F.; Herrera, J. J. E.; Rangel, J.; Milanese, Maria Magdalena; Moroso, Roberto Luis; Pouzo, Jorge Osvaldo; Golzarri, J. I.; Espinosa, G. The average angular distribution of neutron emissions has been measured in the Fuego Nuevo II (FN-II) dense plasma focus device (5 kJ) by means of CR-39 plastic nuclear track detectors. When pure deuterium is used as the filling gas, the data can be adjusted to a Gaussian function, related to anisotropic emission, superposed on a constant pedestal, related to isotropic emission. When deuterium–argon admixtures are used, the anisotropic contribution is best represented by a parabola. The same analysis is applied to previously reported results, for fewer shots, in pure deuterium from the PACO device, which is similar in size to the FN-II. In both devices the anisotropic component is smaller than the isotropic one, but with different features. In PACO the anisotropic component is concentrated on a large narrow beam around the axis, but its contribution to the total neutron yield is significantly smaller than in the FN-II, where the anisotropic component spreads over a wider range. The neutron flux per shot is monitored in both devices with calibrated silver activation detectors, at 20˚ and at 90˚ from the axis. The average values of the neutron flux at these two angles are used, along with the angular distributions obtained form the track detectors, in order to estimate the absolute neutron yield of both the isotropic and the anisotropic contributions. From examining different groups of shots, it is found that the shape of the angular distribution is important in the estimation of anisotropy, and that the value usually reported, as the ratio of neutron counts head-on and side-on, as measured by activation counters, may be misleading.

Theory of braided Hopf crossed products Guccione, Jorge Alberto; Guccione, Juan Jose We define a type of crossed product over braided Hopf algebras, which generalizes the ones introduced by Blattner, Cohen and Montgomery and Doi and Takeuchi, and we study some of its properties. For instance, we prove a Maschke´s Theorem for these new crossed products and under suitable hypothesis we construct a natural Morita context which extends the one obtained by Cohen, Fischman and Montgomery.

On the composition of the integral and derivative operators of functional order Hartzstein, Silvia Inés; Viviani, Beatriz Eleonora In this work we show that the composition of the integral and derivative operators of order phi, T_phi = D_phi◦I_phi, is a singular integral operator.This result in addition with the results obtained in [HV2] of boundedness of I_phi and D_phi or the T1-theorems proved in [HV1] yield the fact that T_phi is a Calderón-Zygmund operator bounded on the generalized Besov and Triebel-Lizorkin spaces of functional order.

Bulk hydrosilylation reaction of poly(dimethylsiloxane) chains catalyzed by a platinum salt: Effect of the initial concentration of reactive groups on the final extent of reaction Roth, Leandro E.; Vallés, Enrique M.; Villar, Marcelo Armando Model silicone networks obtained by curing linear poly(dimethylsiloxane) (PDMS) chains with end-vinyl groups, (B2), with a polyfunctional silane-terminated crosslinker of functionality f, (Af), through a hydrosilylation reaction have been widely used. In these networks, the principal characteristics of their ultimate molecular structure are strongly affected by the final extent of reaction reached during the crosslinking reaction. This work analyzes the effect of the initial concentration of the reactive end groups on the maximum attainable extent of reaction under normal bulk crosslinking conditions. This was accomplished by examining the reaction between linear B2 PDMS chains with difunctional and trifunctional silanes. The experimental results were fitted by an exponential equation to have an empirical equation able to predict the maximum extent of reaction to be obtained as a function of the initial concentration of reactive groups. Molecular parameters relevant to this study, such as the degree of polymerization, the weight-average molecular weight for the A2 + B2 system, or the weight fraction of solubles for the A3 + B2 system, were calculated with a mean field theory (recursive approach).

Intestinal passive absorption of hydrosoluble compounds by sparrows: effect of molecular size and luminal nutrients Chediack, Juan Gabriel; Caviedes Vidal, Enrique Juan Raul; Fasulo, Sara Veronica; Yamin, L. J.; Karasov, William We tested predictions that: (1) absorption of water-soluble probes decreases with increasing molecular size, consistent with movement through effective pores in epithelia, and (2) absorption of probes is enhanced when measured in the presence of luminal nutrients, as predicted for paracellular solvent drag. Probes (L-arabinose, L-rhamnose, perseitol, lactulose; MW 150.1–342.3 Da) were gavaged in nonanesthetized House sparrows (Passer domesticus), or injected into the pectoralis, and serially measured in plasma. Bioavailability was calculated as F=AUC by gavage/AUC by injection, where AUC is the area under the curve of plasma probe concentration vs. time. Consistent with predictions, F declined with probe size by 75% from the smallest to the largest probe, and absorption of probes increased by 40% in the presence of luminal glucose or food compared to a mannitol control. Absorption of water-soluble probes by sparrows is much higher than in humans, which is much higher than in rats. These differences seem mainly attributable to differences in paracellular solvent flux and less to differences in effective paracellular pore size.

The two isoforms of the cAMP-dependent protein kinase catalytic subunit are involved in the control of dimorphism in the human fungal pathogen Candida albicans Cloutier, Monikca; Castilla Lozano, Maria del Rocio; Bolduc, Nathalie; Zelada, Alicia Mercedes; Martineau, Philippe; Bouillon, Marlène; Magee, Beatrice B.; Di Bernardo, Maria Susana; Giasson, Luc; Cantore, Maria Leonor We have cloned the Candida albicans TPK2 gene encoding a cAMP-dependent protein kinase (PKA) catalytic subunit and generated a tpk2 homozygous null mutant to assess its ability to germinate in liquid media. N-acetylglucosamine (GlcNAc)-induced germ-tube formation was attenuated in the tpk2 strain and enhanced by compounds that are known to increase the PKA activity in situ. Germination was completely blocked in the presence of the myristoylated derivative of the heat-stable PKA inhibitor (MyrPKI). These results indicate that TPK1 acts positively in regulating the morphogenetic transition in C. albicans in the absence of the TPK2 gene. We were able to identify an mRNA from this second form of PKA in both wild-type and tpk2 null mutant cells. We found that PKA activity measured in the mutant lacking the TPK2 gene was about 10% of that displayed by the wild-type. The finding that the germinative response of tpk2 null mutant to serum was severely diminished at low serum concentrations indicates that the level of PKA is an important determinant of filamentous growth at low serum concentrations. The extent of germination attained at higher serum concentrations (5%) was similar in the wild-type and in the tpk2 null mutant strains suggesting that under these conditions germination was triggered through a PKA-independent pathway.

Imaging study of NGC 3372, the Carina nebula -I. UBVRIJHK photometry of Tr 14, Tr 15, Tr 16 and Car I Tapia, Mauricio Andres; Roth, Miguel; Vazquez, Ruben Angel; Feinstein, Alejandro We present the results of a large-scale imaging photometric study of the stellar population in the northern part of NGC 3372 in the UBVRIJHK bands with a wavelength coverage from 0.33 to 2.5 μm. The observations were made at Las Campanas Observatory. The optical CCD mosaics cover an area approximately of 32 × 22 arcmin2 centred between the Tr 14 and Tr 16 clusters. The survey was extended to cover 12 × 12 arcmin2 at the location of Tr 15. Near-infrared NICMOS3 mosaics covering the areas occupied by these clusters were obtained in the JHK photometric bands. By means of star counts in V, the centres and sizes of each cluster were redetermined yielding: Tr 14 (r = 264 arcsec), Tr 15 (r = 320 arcsec) and Tr 16 (r = 320 arcsec). It was confirmed that Cr 232 is not a true cluster. Multicolour optical photometry was obtained for 4152 stars. Two colour and colour-magnitude diagrams are presented and analysed for each individual cluster and compared to those of the field. We confirm the widespread variations in the dust density and also in the dust size distribution leading to widely different values of AV and reddening laws towards Tr 14 and Tr 16. No spatial patterns were found for these variations. Spectroscopic parallaxes were computed and the results are consistent with all three clusters being at a similar distance from the Sun (〈d〉 = 2.7 kpc) but the data have shown very large scatter in both AV and d. Analyses of the extinction-corrected colour-magnitude diagrams suggest ages between 3 and 60 million years for the stars in Tr 15 and between less than 1 and 6 million years for Tr 14 and Tr 16. A small number of infrared-excess stars were found in Tr 16 and Tr 14 but not in Tr 15. The distribution of stars in Tr 14 seen in the near-infrared suggests that this cluster is partially embedded in a molecular cloud. This molecular cloud extends towards the west reaching its highest density, marked by a CO peak emission, some three arcmin to the south-west of the nucleus of Tr 14. The rich ultraviolet field created by the Tr 14 stars ionizes most of the visible H II region in its vicinity and most of the radio H II region Car I. Evidence is found of ionization fronts leading into the molecular cloud, which appears to be 'wrapping' the Tr 14 cluster. Deep JHK images of the Car I region reveal the presence of an embedded stellar population illuminating a large infrared reflection nebula. It includes at least one O9-B0 star associated with an ultracompact H II region. Nebulous 2.2 μm emission from three of the mid-infrared sources in the Tr 14 region is also found.

Fouling behaviour of polyethersulfone UF membranes made with different PVP Marchese, Jose; Ponce, Mariela Leticia; Ochoa, Nelio Ariel; Prádanos, Pedro; Palacio, Laura; Hernández, Antonio Several polyethersulfone (PES) ultrafiltration membranes have been made with small quantities of polyvinyl-pyrrolidone (PVP) of different molecular weights to increase the permeability without a significant reduction in selectivity. The corresponding fouling mechanism and subsequent structural modifications have been analyzed when in contact with bovine serum albumin (BSA) and DL-histidine (DLH). It has been shown that according to the relative sizes of solute and pores of the membranes: BSA fouls the three membranes externally whereas DLH fouls them internally. Moreover, BSA fouls the non-PVP membranes faster than DLH fouls them slower, according to the action of hydrophobic and electrostatic forces acting at the working pH (4.9). The changes in structure, remaining after water rinsing, is quite similar for the three membranes and both the solutes, as obtained by a r etention test of adequate polyethylene glycols (PEGs).

Transtegumental diffusion of benzimidazole anthelmintics into Moniezia benedeni: correlation with their octanol–water partition coefficients Mottier, Maria de Lourdes; Alvarez, Luis Ignacio; Pis, Ma. Alejandra; Lanusse, Carlos Edmundo The experiments described here report on the correlation between the ex vivo diffusion of different benzimidazole (BZD) anthelmintics into the cestode parasite Moniezia benedeni, and their octanol–water partition coefficients (P.C.). The characterisation of the drug diffusion process into target parasites is relevant to understand the mechanism of drug penetration and the pharmacological activity of anthelmintic drugs. Specimens of the tapeworm M. benedeni, used as a helminth parasite model, were obtained from untreated cattle killed at the local abattoir. The collected parasites were incubated (5–210 min) with either fenbendazole (FBZ),albendazole (ABZ), ricobendazole (RBZ), oxfendazole (OFZ), mebendazole (MBZ), oxibendazole (OBZ), or thiabendazole (TBZ), in a Kreb’s Ringer Tris buffer medium at a final concentration of 5 nmol/ml. After the incubation time elapsed, samples of parasite material were chemically extracted and prepared for high performance liquid chromatography (HPLC) analysis to measure drug/metabolite concentrations. Additionally, the octanol–water P.C. for each molecule was estimated as an indicator of drug lipophilicity,using reversed phase HPLC analysis. All the incubated drugs were recovered from the tapeworms as early as 5 min post incubation. There was a high correlation (r ¼ 0:87) between drug lipophilicity, expressed as octanol–water P.C. (Log P), and drug availability within the parasite. The most lipophilic BZD compounds (FBZ, ABZ, and MBZ), with P.C. values higher than 3.7, were measured at significative higher concentrations within the tapeworm compared to those drugs with the lowest P.C. values. Considering the results from the current and previous studies, it is clear that passive diffusion is a major mechanism of BZD penetration into cestode parasites, where lipid solubility is a determinant factor influencing the diffusion of these anthelmintic molecules through the parasite tegument.

Simulation of an Industrial Packed Column for Reactive Absorption of CO2 Gómez, C.; Borio, Daniel Oscar; Schbib, Noemi Susana − The steady-state simulation of a reactive absorption column is presented. The absorber is used in a large-scale ammonia plant to remove CO2 from the process gas stream. To enhance the absorption process, high pressures and low temperatures are commonly used (T = 45-80 °C, P = 30-40 bar). At the outlet of the absorber, the CO2 content in the process gas must be reduced to less than 500 ppm (dry basis) to avoid an excessive temperature rise in the methanation reactor (downstream of the absorption section). To represent the gas-liquid system, a rigorous mathematical model based on the two-film theory is considered. The heat effects are taken into account. The behaviour of different process variables for a reference operating condition is analyzed. The influence of changes in some operating variables is evaluated.

On-line complexation/cloud point preconcentration for the sensitive determination of dysprosium in urine by flow injection inductively coupled plasma-optical emission spectrometry Ortega, Claudia Alicia; Cerutti, Estela Soledad; Olsina, Roberto Antonio; Silva, María Fernanda; Martinez, Luis Dante An on-line dysprosium preconcentration and determination system based on the hyphenation of cloud point extraction (CPE) to flow injection analysis (FIA) associated with ICP-OES was studied. For the preconcentration of dysprosium, a Dy(III)-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol complex was formed on-line at pH 9.22 in the presence of nonionic micelles of PONPE-7.5. The micellar system containing the complex was thermostated at 30°C in order to promote phase separation, and the surfactant-rich phase was retained in a microcolumn packed with cotton at pH 9.2. The surfactant-rich phase was eluted with 4 mol L-1 nitric acid at a flow rate of 1.5 mL min -1, directly in the nebulizer of the plasma. An enhancement factor of 50 was obtained for the preconcentration of 50 mL of sample solution. The detection limit value for the preconcentration of 50 mL of aqueous solution of Dy was 0.03 μg L-1. The precision for 10 replicate determinations at the 2.0 μg L-1 Dy level was 2.2% relative standard deviation (RSD), calculated from the peak heights obtained. The calibration graph using the preconcentration system for dysprosium was linear with a correlation coefficient of 0.9994 at levels near the detection limits up to at least 100 μg L-1. The method was successfully applied to the determination of dysprosium in urine.

Cohomology of split algebras and of trivial extensions Cibils, Claude; Marcos, Eduardo; Redondo, Maria Julia; Solotar, Andrea Leonor We consider associative algebras λ over a field provided with a direct sum decomposition of a two-sided ideal M and a sub-algebra A - examples are provided by trivial extensions or triangular type matrix algebras. In this relative and split setting we describe a long exact sequence computing the Hochschild cohomology of λ. We study the connecting homomorphism using the cup-product and we infer several results, in particular the first Hochschild cohomology group of a trivial extension never vanishes.

Report on the 1st International Workshop of the IUGS Lower Cretaceous Ammonite Working Group, the 'Kilian Group' (Lyon, 11 July 2002) Hoedemaeker, Philip J.; Reboulet, Stéphane; Aguirre-Urreta, Maria Beatriz; Alsen, Peter; Aoutem, Mohamed; Atrops, François; Barragan, Ricardo; González Arreola, Celestina; Klein, Jaap; Lukeneder, Alexander; Ploch, Isabela; Raisossadat, Seyed Naser; Rawson, Peter F.; Ropolo, Pierre; Vasícek, Zdenek; Vermeulen, Jean; Wippich, Max G. E. The Lower Cretaceous Ammonite Working Group forms part of the IUGS Subcommission on Cretaceous Stratigraphy (Peter Rawson, chair) and is the successor of the Lower Cretaceous Cephalopod Team that formed part of IGCP Projects 262 and 362 respectively. The latter team had organized five Workshops (Klein & Hoedemaeker, 1999;Hoedemaeker & Rawson, 2000) and this is the first workshop under the new IUGS umbrella, which was organized by Stéphane Reboulet (Université de Lyon 1) directly after the 3rd French Symposium on Stratigraphy (Lyon, 8–10 July 2002). The workshop was attended by 18 members from 13 countries. The attendants agreed to call the group the ‘Kilian Group' after the famous French palaeontologist W. Kilian.

A prothrombin activator from Bothrops erythromelas (jararaca-da-seca) snake venom: characterization and molecular cloning Silva, Márcia B.; Schattner, Mirta Ana; Ramos, Celso R. R.; Junqueira de Azevedo, Inácio L. M.; Guarnieri, Míriam C.; Lazzari, María Ángela; Sampaio, Claudio A. M.; Pozner, Roberto Gabriel; Ventura, Janaina S.; Ho, Paulo L.; Chudzinski Tavassi, Ana M. A novel prothrombin activator enzyme, which we have named 'berythractivase', was isolated from Bothrops erythromelas (jararaca-da-seca) snake venom. Berythractivase was purified by a single cation-exchange-chromatography step on a Resource S (Amersham Biosciences) column. The overall purification (31-fold) indicates that berythractivase comprises about 5% of the crude venom. It is a single-chain protein with a molecular mass of 78 kDa. SDS/PAGE of prothrombin after activation by berythractivase showed fragment patterns similar to those generated by group A prothrombin activators, which convert prothrombin into meizothrombin, independent of the prothrombinase complex. Chelating agents, such as EDTA and o-phenanthroline, rapidly inhibited the enzymic activity of berythractivase, like a typical metalloproteinase. Human fibrinogen Aα-chain was slowly digested only after longer incubation with berythractivase, and no effect on the β- or γ-chains was observed. Berythractivase was also capable of triggering endothelial proinfiammatory and procoagulant cell responses, von Willebrand factor was released, and the surface expression of both intracellular adhesion molecule-1 and E-selectin was up-regulated by berythractivase in cultured human umbilical-vein endothelial cells. The complete berythractivase cDNA was cloned from a B. erythromelas venom-gland cDNA library. The cDNA sequence possesses 2330 bp and encodes a preproprotein with significant sequence similarity to many other mature metalloproteinases reported from snake venoms. Berythractivase contains metalloproteinase, desintegrin-like and cysteine-rich domains. However, berythractivase did not elicit any haemorrhagic response. These results show that, although the primary structure of berythractivase is related to that of snake-venom haemorrhagic metalloproteinases and functionally similar to group A prothrombin activators, it is a prothrombin activator devoid of haemorrhagic activity. This is a feature not observed for most of the snake venom metalloproteinases, including the group A prothrombin activators.

Propagator matrices as matrices of power's series. II. It's relationship with HF's stability problem and alternative solutions Gómez, Carlos Anselmo; Provasi, Patricio Federico; Aucar, Gustavo Adolfo Some non-singlet quasi-instabilities (QIs) cases that arise in the calculation of NMR-Jparameters are analyzed within response theory. The relationship between ‘very close to zero’ eigenvalues of the principal propagator and the rate of convergency for specific coupling pathways is shown by a power series implemented to calculate the principal propagator matrix. A natural criterion for the analysis of the stability problem emerges from that series. This is more general and accurate compared with previous proposals. Its relationship with π-type molecular orbitals is given. We present an alternative scheme to minimize the effects of non-singlet QIs in such a way that the NMR-J parameters become close to the best theoretical calculations for H2CX (X=CH2, NH and O).

Arginine metabolic pathways involved in the modulation of tumor‐induced angiogenesis by macrophages Davel, Lilia Elena; Jasnis, Maria Adela; de la Torre, Eulalia; Gotoh, Tomomi; Diament, Miriam; Magenta, Gabriela Viviana; Sacerdote de Lustig, Eugenia; Sales, María Elena Neovascularization, an essential step for tumor progression and metastasis development, can be modulated by the presence of macrophages (Mps) in the tumor microenvironment. The ability of Mps to regulate the angiogenicity of the LMM3 tumor cell line was studied. Peritoneal Mps from LMM3 tumor‐bearing mice (TMps) potentiate in vivo LMM3 angiogenicity. These results were confirmed by CD31 immunoblotting assays. The activity of TMps depended on nitric oxide synthase (NOS) and arginase (A) activity. By immunoblotting we evidenced that AI and AII isoforms were up‐regulated in TMps while the inducible and neuronal NOS isoforms were highly expressed in normal Mps. TMps might positively modulate tumor growth by stimulating angiogenic cascade mainly through polyamine synthesis.

Body mass and habitat correlates of song structure in a primitive group of birds Bertelli, Sara Beatriz; Tubaro, Pablo Luis We assessed relationships between acoustic frequency, body mass, and habitat in tinamous. This monophyletic group of primitive birds comprises 47 ground dwelling species whose habitats range from dense humid forest to open grasslands.The relationship between frequency and body mass was found to be negative, while the songs of open habitat species exhibited higher frequencies and a wider bandwidth than the closed-habitat ones. Residual variation in song frequency, after controlling for the effect of body mass and phylogeny, tends to differ among habitats. However, a statistical test of this pattern was not possible because of the existence of only five pairs of sister species differing in habitat. In spite of this, positive contrasts of bandwidth were associated with positive contrasts of habitat, confirming that songs of open-habitat species have a wider bandwidth than those of their more closed habitat relatives.