The new ichnotaxon Bromleyia magnifica n. igen., n. isp., attributed to the feeding activity of bivalves, is proposed. This ichnotaxon consists of clusters of closely spaced curved ridges that form a fan-shaped structure oppositely distributed on both sides of a longitudinal axis or, more rarely, being present only on one side. Intergradation between Protovirgularia, Lockeia, and Bromleyia forms a compound trace fossil that records the activity of a cleft-foot protobranch bivalve while burrowing, moving through the sediment, and stopping to deposit feed. A specimen from the Carboniferous of Arkansas, previously regarded as Lophoctenium isp., is here included in Bromleyia magnifica. The spreite in Lophoctenium reflects complex behavioural patterns of horizontal strip-mining deposit feeders, including bundles of tubes bending to one side in a pectinate way or arranged on both sides in a highly systematic fashion, which contrasts with the coarse, horizontal fan-shaped, curved bundle of ridges from the Arkansas specimen. The trace fossil Hillichnus lobosensis records the activities of tellinacean deposit feeders and displays feather-like spreite structures reminiscent of Bromleyia. However, the spreite in Hillichnus is more organized, recording repetitive probing through the sediment in horizontal, oblique, and vertical directions of the tubular inhalant siphon. The resulting complex feeding structure, recorded in multiple preservational tiers, displays an alternate arrangement of ridges on either side of an axial basal structure. This configuration differs from the mostly horizontal, less-organized, coarse bundle of ridges with broadly opposite distribution to the sides of an axis present in Bromleyia. Moreover, contrary to Hillichnus, Bromleyia is commonly associated with Lockeia, indicating significant differences in burrowing strategy and mode of construction between these two ichnotaxa.

The early Miocene marine deposits in Tierra del Fuego bear a group of struthiolariid gastropods that stand out for their high morphological variability. since the end of the 19th century this variability was interpreted as reflecting (1) a highly diversified rapidly evolving group of species or (2) a single, plastic species characterized by ample intraspecific variability. The morphological study of more than 100 specimens of the Fuegian struthiolariid genus Perissodonta Martens collected in the Carmen Silva, Viamonte, and Irigoyen formations indicate that significant parameters, such as shell shape, spire length and number of spiral and axial sculptures (cords, threads, tubercles) vary continuously within an ample range of values, favoring a single, plastic species. Topotype specimens of Perissodonta ameghinoi (Ihering), collected from the early Miocene Monte León Formation in Patagonia, show similar plasticity of characters. Furthermore, recent topotype material of Perissodonta georgiana Strebel from Islas Georgias del Sur, a species considered very close or junior synonym of the genotype species P. mirabilis (Smith), indicates a similar degree of plasticity. Accordingly, the Fuegian struthiolariids previously assigned to Perissodonta ameghinoi; P. fueguina (Ihering); or P. densestriata (Ihering) are here referred to P. ameghinoi, a struthiolariid gastropod restricted to the early Miocene in Tierra del Fuego and Patagonia.

A new high-latitude record of the trace fossil Macaronichnus segregatis degiberti is documented from the lower Miocene Punta Basilica beds, Tierra del Fuego, which were previously considered to be deep-marine channel and levee deposits. Based on a combined ichnological and sedimentological study, however, these beds are herein re-interpreted as shallow-marine, delta-front clinoform deposits. Macaronichnus-bearing beds in the stratigraphically older clinoforms are characterized by: (1) sandstones with wave ripples and wave-ripple cross-lamination; (2) cross-stratified sandstones forming large compound dunes and tidal bars; and (3) intervening heterolithic mudstone-sandstone couplets with current and wave ripples. The sedimentary facies preserving M. s. degiberti were deposited during the onset of transgression, indicated by wave and tide reworking of underlying steeply dipping, delta-front clinoforms deposits. The master bedding surfaces of compound tidal bars are characterized by a dense, monospecific fabric of M. s. degiberti. Compared with other Macaronichnus ichnofabrics, reported elsewhere as characterizing short colonization windows on foresets of tidal dunes or bars, the Punta Basilica ichnofabric represents a longer colonization window, associated with episodic reworking and redeposition of loose, nutrient-rich sand grains just above the master bedding surfaces. The record of M. s. degiberti in Tierra del Fuego supports the previous interpretations that restrain its producer to high-latitude, shallow-marine cold waters.

There are two contrasting opinions on the stratigraphic and palaeogeographic distribution of the relatively rare trace fossil Ophiomorpha irregulaire: 1) the trace is mostly restricted to the Upper Cretaceous of the Western Interior Seaway, or 2) it has a post-Palaeozoic record and a worldwide geographic distribution. In this study we document the finding of O. irregulaire in Upper Cretaceous turbidites of the Alta Vista Formation, southern Patagonia, providing additional evidence on the morphology and composition of its pelletal masses, the ethology of its producer and the palaeogeographical and palaeoenvironmental distribution of the trace fossil. The burrow walls are lined with dark mud and their elongate, spiky pellets are formed by a sand core that is also lined with mud. The association with typical fodinichnia, such as Halopoa, Spirophyton, and Zoophycos and the common presence of O. irregulaire in sediments with abundant plant detritus, suggest that the producer was a deposit feeder. Crosscutting relationships and occurrences at several levels within thick-bedded turbidites, suggest a relatively deep tier emplacement of the trace. The finding of the trace in the Southern Hemisphere supports its envisaged worldwide palaeogeographic distribution

ABSTRACTTide-influenced deposits of the Pennsylvanian Rock Lake Shale Member, Stanton Formation, Missouri and Kansas (U.S.A.), contain well-preserved evidence of the burrowing activities of protobranch bivalves, including locomotion (Protovirgularia) and locomotion-resting (Protovirgularia-Lockeia) trace fossils. Protovirgularia shows three distinct morphotypes, the morphological variability of which was controlled by external factors such as substrate conditions, toponomy, and undertrack deficiency. Extreme morphological modifications of Protovirgularia and/or Lockeia, represented by irregular bilobate structures, probably result from erosion and subsequent partial passive filling of the original biogenic structures. In addition, very well-preserved trace fossils showing intergradation of a fan-shaped cluster of ridges with Protovirgularia-Lockeia structures are interpreted as a compound biogenic structure that represents locomotion, resting, and feeding activities of burrowing protobranch bivalves.

Fine-grained sandstones and siltstones of Late Cretaceous to Eocene age in Antarctica and Tierra del Fuego yield an association of well-known shallow-marine trace fossils. Among them stick out complex spreite burrows, which are formally described as Euflabella n. igen. and subdivided into five ichnospecies with different burrowing programs and occurrences. As shown by concentrations of diatoms, radiolarians, foraminifers, and calcispheres in particular backfill lamellae, the unknown trace makers lived on fresh detritus from the surface as well as the burrowed sediment. In some ichnospecies, vertical sections show that the spreite is three-dimensionally meandering in upward direction and that upper laminae tend to rework the upper backfill of the folds underneath. This could mean a second harvest, after cultivated bacteria had time to ferment refractory sediment components, which the metazoan trace maker had been unable to digest before.

The present work deals with the study of estradiol permeation in chitosan membranes. A fractional factorial design was built for the determination of the main factors affecting estradiol permeation. The independent factors analysed were: concentration of chitosan, concentration of cross-linking agent, cross-linking time and thermal treatment. It was found that concentration of chitosan and cross-linking time significantly affected the response. The effects of thermal treatment and concentration of cross-linking agent were not significant. An optimization process based on response surface methodology was carried out in order to develop a statistical model which describes the relationship between active independent variables and estradiol flux. This model can be used to find out a combination of factor levels during response optimization. Possible options for response optimization are to maximize, minimize or move towards a target value.

In the present study we evaluated the in vitro and in vivo degradation of an in situ forming biodegradable implant. For this purpose we used a poly(D,L-lactide-co-glycolide) (PLGA) polymer dissolved in biocompatible solvent dimethylsulfoxide (DMSO). The evolution of the morphology, mass loss, water gain, hollow fraction, and molecular weight of the implants degraded in both conditions was investigated and compared. Implants presented a porous morphology, being denser and having channels in vivo, as seen by scanning electron microscopy. Erosion in vivo of implants involved the appearance of new small pores, while an increase of the size of preexisting pores was seen in vitro. Mass loss and molecular weight –as a measure of erosion and degradation, respectively– decreased much faster in vivo than in vitro, suggesting the importance of environmental conditions on these processes of porous biodegradable matrices formed in situ.

Analytical solutions for the case of dispersed–drug controlled release from non–erodible planar matrices, based on Refined Integral Method, are presented. A new adjusting equation is used for the dissolved drug concentration profile in the depletion zone of the matrix. In order to illustrate the validity and usefulness of the model, comparisons with experimental profiles reported in the literature are presented. A close match between the model predictions and the experimental data is observed. In addition, a comparison with a model reported previously by others authors is also presented. The results show that our model has a better performance than the previously reported equations in the prediction of the experimental release profiles. As conclusion, the obtained results show that the model can be employed in a broad range of drug delivery systems.

Six mechanistic kinetic models of increasing complexity are analyzed to describe the RhCl(Ph3P)(3) catalyzed hydrogenation process ivermectin from avermectins B-1a and B-1b Global sensitivity analysis (GSA) usefulness, for selecting the simplest and the Most suitable model is shown. First-order and total effect sensitivity indices model T computed from GSA have been used for establishing those elementary reaction steps which were the most important in an extensive reaction framework. The prediction capability of the chosen model is corroborated by comparing its predictions with experimental data from both a lab-scale reactor and an industrial-scale reactor operating under isothermal and nonisothermal conditions, respectively. The best model is simple to use while resulting in a significant computational effort saving because there is no need to perform iterative algorithms for solving model equations. Another interesting feature is that ODEs for such a model have an analytical solution for isothermal hydrogenation processes. These features make modeling more amenable for cost-effective simulation and to include the selected model into computational frameworks for design of the hydrogenation process and control systems of the most usual catalytic method for producing ivermectin.

A mathematical modeling of controlled release of drug from one-layer and two-layer torus-shaped devices with external mass transfer resistance is presented.Analytical solutions based on the pseudosteady state approximation are derived.The validity of the equations is established in two stages.In the first stage, the validity of the models derived for more complex systems is determined by comparison with profiles predicted by the simplest model, in asymptotic cases.In the second stage, the reliability and usefulness of the models are ascertained by comparison of the simulation results with vaginal rings experimental release data reported in the literature.In order to measures quantitatively the fit of the theoretical models to the experimental data, the pair-wise procedure is used.A good agreement between the prediction of the models and the experimental data is observed.The models are applicable only to torusshaped systems in where the initial load of drug is higher than its solubility in the polymer.

Polymeric membranes with skin-mimetic permeability properties appear as attractive models for use in the development of transdermal drug delivery systems. These membranes can be placed in contact with the transdermal system and simulate the skin barrier. In the current work, statistical experimental design was implemented for preparation of the optimized chitosan membrane to mimic human epidermis. For this purpose, an optimization process based on response surface methodology was carried out in order to determine the best combination of independent factors for membrane preparation. The independent factors analyzed were concentration of chitosan, concentration of cross-linking agent, and cross-linking time. The optimized membrane successfully simulated the cumulative amount of estradiol released per unit time for human epidermis. In addition, the optimized membrane was evaluated for the development of an estradiol delivery system. This in vitro technology may offer an alternative methodology for the development of transdermal delivery systems.

Chitosan membranes were obtained by a casting/solvent evaporation method and cross-linking with sodium tripolyphosphate. The effect of cross-linking time was studied and the cross-linked membranes were characterized with respect to equilibrium water content, sodium content, IR spectroscopy and permeability to a model drug (Estradiol). Sodium content increased with increasing cross-linking time. Equilibrium water content was higher in the membrane with the lowest cross-linking time. This membrane also showed a higher flux of Estradiol compared with the other which exhibited an increment in equilibrium water content and flux of Estradiol with the increase in cross-linking duration. These dissimilar results could be explained by a significant correlation between the hydrophilicity of the membrane and the hydrophobicity of Estradiol.

The internal structure and growth direction of well-preserved Tasselia ordamensis specimens from the Upper Cretaceous–Cenozoic of Antarctica and Tierra del Fuego are not compatible with its current interpretation as a domichnion/equilibrichnium trace fossil. Accordingly, its functional morphology and the likely ethology of the producer are revised. Tasselia is a protrusive structure composed of a lined inner tube surrounded by vertically stacked sediment disks and ending in a basal chamber. Each disk has two domains of active burrow fills. The micritic, outer burrow fill domain consists of radial petaloid elements containing abundant radiolaria, calcispherules, diatoms and plant debris. This domain was formed by excavation due to deposit feeding; thereby non-ingested particles remained in the chamber and ingested particles passed through the gut to the sediment surface. Microfossil-rich material was collected at the sediment surface, placed in the feeding chamber, and rearranged within the petaloid elements probably after pulsed delivery of organic matter. The wineglass-shaped inner burrow fill domain is enriched in coarser particles and its petaloid elements crosscut the outer burrow fill domain. This domain probably functioned as “culturing compartment” for bacteria and its secondary reworking implies some form of ‘gardening’ and feeding on these bacterial populations at depth. The concentric striae on the organic-lined inner tube and the vertically stacked series of sediment-disks suggest maldanid polychaetes as the producers of T. ordamensis.

Analytical solutions for the case of controlled dispersed-drug release from planar non-erodible polymeric matrices, based on Refined Integral Method, are presented. A new adjusting equation is used for the dissolved drug concentration profile in the depletion zone. The set of equations match the available exact solution. In order to illustrate the usefulness of this model, comparisons with experimental profiles reported in the literature are presented. The obtained results show that the model can be employed in a broad range of applicability.

Analytical solutions based on the pseudo-steady state approximation (PSSA) were derived for the case of controlled dispersed-drug release from erodible and non-erodible planar matrices, through a membrane, and taking into account the existence of a diffusion boundary layer and a finite release medium. The solutions can be applied to a broad range of situations from drug release into finite or infinite medium, from erodible or non-erodible matrices, in the presence or absence of a membrane, and in the presence or absence of a stagnant liquid layer. The prediction is accurate for the cases in which the initial drug load is higher than the drug solubility in the polymer (e.g. A/Cs≥3) till the entire dispersed drug is dissolved. The dependence on the release kinetics with different parameters was simulated and provides a theoretical platform for the design of dispersed-drug release devices.

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A kinetic study of the homogeneous catalytic hydrogenation of avermectins is reported for a series of isosteric p-substituted arylphosphines as ligands. The activity of the rhodium complexes formed in situ from [RhCl(COD)](2) increased with increasing the electron-donor capacity of the P(p-XC6H4)(3): P(p-ClC6H4)(3) < P(C6H5)(3) < P(p-CH3C6H4)(3) < P(P-OCH3C6H4)(3). As expected, this trend was also observed when using preformed complexes thereof Linear correlations based on Hammett and Kabachnik treatments are provided as useful tools to guide the exploration work towards improved [RhCl(COD)](2)/P(p-XC6H4)(3) catalytic systems.

The kinetics of the hydrogenation and cis/trans isomerization of methyl oleate on a Ni/alpha-Al2O3 catalyst was studied in the absence of mass-transport limitation, at 398 K <= T <= 443 K and 370 kPa <= PH2 <= 650kPa. On the basis of the Horiuti-Polanyi mechanism, involving a sigma half-hydrogenated surface intermediate, a kinetic model was derived in the framework provided by the Langmuir-Hinshelwood-Hougen-Watson formalism, using the advanced concept of semi-competitive adsorption. The classical LHHW rate equations for competitive and non-competitive adsorption between the hydrogen and large organic species were matched as asymptotic cases. Statistical results clearly demonstrated the inadequacy of the model approaching non-competitive adsorption to describe the experimental data, but the residual sum of squares between experimental data and model predictions was insufficient to discriminate between the kinetic models based on competitive and semi-competitive adsorption. However, the model considering semi-competitive adsorption gave additional indication that the adsorbed molecules of cis- and trans-methyl oleate could cover up to eleven surface sites, which is in excellent agreement with a rough estimate from primary molecular modeling. This feature seems to be the most fascinating result, since it is factual and unattainable from the classical LHHW approaches. Results and distinctive features characterizing this advanced approach are highlighted. Some insights to improve parameter estimation and adsorption model discrimination are also pointed out. (c) 2008 Elsevier B.V. All rights reserved.