Reflection and transmission coefficients of a single layer in poroelastic media

Wave propagation in poroelastic media is a subject that finds applications in many fields of research, from geophysics of the solid Earth to material science. In geophysics, seismic methods are based on the reflection and transmission of waves at interfaces or layers. It is a relevant canonical problem, which has not been solved in explicit form, i.e., the wave response of a single layer, involving three dissimilar media, where the properties of the media are described by Biot's theory. The displacement fields are recast in terms of potentials and the boundary conditions at the two interfaces impose continuity of the solid and fluid displacements, normal and shear stresses, and fluid pressure. The existence of critical angles is discussed. The results are verified by taking proper limits—zero and 100% porosity—by comparison to the canonical solutions corresponding to single-phase solid (elastic) media and fluid media, respectively, and the case where the layer thickness is zero, representing an interface separating two poroelastic half-spaces. As examples, it was calculated the reflection and transmission coefficients for plane wave incident at a highly permeable and compliant fluid-saturated porous layer, and the case where the media are saturated with the same fluid.Facultad de IngenieríaFacultad de Ciencias Astronómicas y Geofísica

Reflection and transmission coefficients of a single layer in poroelastic media

Wave propagation in poroelastic media is a subject that finds applications in many fields of research, from geophysics of the solid Earth to material science. In geophysics, seismic methods are based on the reflection and transmission of waves at interfaces or layers. It is a relevant canonical problem, which has not been solved in explicit form, i.e., the wave response of a single layer, involving three dissimilar media, where the properties of the media are described by Biot's theory. The displacement fields are recast in terms of potentials and the boundary conditions at the two interfaces impose continuity of the solid and fluid displacements, normal and shear stresses, and fluid pressure. The existence of critical angles is discussed. The results are verified by taking proper limits—zero and 100% porosity—by comparison to the canonical solutions corresponding to single-phase solid (elastic) media and fluid media, respectively, and the case where the layer thickness is zero, representing an interface separating two poroelastic half-spaces. As examples, it was calculated the reflection and transmission coefficients for plane wave incident at a highly permeable and compliant fluid-saturated porous layer, and the case where the media are saturated with the same fluid.Facultad de IngenieríaFacultad de Ciencias Astronómicas y Geofísica

Enantiopure Indolo[2,3-a]quinolizidines: Synthesis and Evaluation as NMDA Receptor Antagonists

Enantiopure tryptophanol is easily obtained from the reduction of its parent natural amino acid trypthophan (available from the chiral pool), and can be used as chiral auxiliary/inductor to control the stereochemical course of a diastereoselective reaction. Furthermore, enantiopure tryptophanol is useful for the syntheses of natural products or biological active molecules containing the aminoalcohol functionality. In this communication, we report the development of a small library of indolo[2,3-a]quinolizidines and evaluation of their activity as N-Methyl D-Aspartate (NMDA) receptor antagonists. The indolo[2,3-a]quinolizidine scaffold was obtained using the following key steps: (i) a stereoselective cyclocondensation of (S)- or (R)-tryptophanol with appropriate racemic -oxoesters; (ii) a stereocontrolled cyclization on the indole nucleus. The synthesized enantiopure indolo[2,3-a]quinolizidines were evaluated as NMDA receptor antagonists and one compound was identified to be 2.9-fold more potent as NMDA receptor blocker than amantadine (used in the clinic for Parkinson's disease). This compound represents a hit compound for the development of novel NMDA receptor antagonists with potential applications in neurodegenerative disorders associated with overactivation of NMDA receptors

Tryptophanol-derived oxazolopiperidone lactams: identification of a hit compound as NMDA receptor antagonist

N-Methyl-D-Aspartate (NMDA) receptors are neuronal ionotropic channels that play an important role in memory and learning processes. Their exacerbated activation leads to neuron death by necrosis or apoptosis in a phenomenon called excitotoxicity. Compounds like memantine or amantadine act as antagonists of these receptors and are currently used for the treatment of Alzheimer's or Parkinson's diseases. We herein present the development of a series of new NMDA receptor antagonists using enantiopure tryptophanol and racemic δ-oxo-esters as synthetic precursors in only one synthetic step and good yields. The most active hit exhibited an IC50 of 63.4 µM in cultured rat cerebellar granule neurons thus being 1.5 fold more active than the positive control used, amantadine (IC50 = 92 µM). The versatility of our synthetic approach together with the well-defined absolute stereoutcome of the tryptophanol-derived oxazolopiperidones is currently being explored to produce valuable structure activity relationships for the development of new potent NMDAR antagonists

Synthesis of phenylalaninol-derived oxazolopyrrolidone lactams and evaluation as NMDA receptor antagonists

N-Methyl-D-aspartate (NMDA) receptor antagonists are known to rescue neuronal cell death caused by excessive activation of glutamate receptors. This phenomenon, known as excitotoxicity, is implicated in the pathogenesis of several neurodegenerative disorders including ischemia, Alzheimer's disease, Parkinson's disease, and Huntington's disease. Unfortunately, some NMDA receptor antagonists have shown discouraging results when tested in clinical trials. However, recent advances in the physiology and pharmacology of the NMDA receptor have kept interest alive in modulating NMDA receptors for therapeutic intervention. We present here the synthesis of a small library of phenylalaninol-derived oxazolopyrrolidone lactams and their evaluation as NMDA receptor antagonists. The compounds were easily synthesized in yields up to 92 %. In addition, one of the compounds has a 50 % inhibitory concentration (IC 50) of 62 μM and offers potential to develop more potent NMDA receptor antagonists

A rapid, non invasive and simple molecular method for sex determination in pygoscelis penguins

En los pingüinos Adelia (Pygoscelis adeliae) y pingüinos papua (Pygoscelis papua), no existe un dimorfismo sexual conspicuo y a menudo resulta difícil determinar el sexo en base a la morfología externa. La información sobre el sexo es importante en muchos estudios de ecología y conservación. En este artículo se evaluó el uso de un par de cebadores (2550F/2718R) para identificar el sexo en aves sexualmente monomórficas. Para ambas especies de pingüinos la amplificación produjo dos bandas discretas, CHD1Z y CHD1W, que permitieron la identificación sexual. Se trata de un sistema sencillo, rápido y económico para el sexaje molecular de los pingüinos papua y Adelia.In Adélie penguins (Pygoscelis adeliae) and gentoo penguins (Pygoscelis papua), the conspicuous sexual dimorphism often makes it difficult to determine sex on the basis of external morphology. The information about sex is important in many ecology and conservation studies. In this paper we evaluated the use of an established primer pair (2550F/2718R) to identify sex in sexually monomorphic birds. In both penguin species, it resulted in two distinct CHD1Z and CHD1W PCR bands, allowing sex identification. This is a simple, rapid and cheap system for molecular sexing of gentoo and Adélie penguins.Instituto Multidisciplinario de Biología CelularFacultad de Ciencias Naturales y MuseoConsejo Nacional de Investigaciones Científicas y Técnica

Spermatozoa recovery and post-thawing quality of brown bear ejaculates is affected for centrifugation regimes

P. 77–84Sperm cryopreservation protocols for brown bear (Ursus arctos) require the centrifugation of semen samples to increase sperm concentration and to clean urine in contaminated samples. We evaluated the effect of centrifugation regimes (time and relative centrifugal force—RCF) on the quantity of sperm recovered and the quality of post-thawed sperm. Thirteen brown bears were electroejaculated. The ejaculates were diluted 1:1 in Tris–citric acid–glucose (TCG) extender and centrifuged with different RCF/time combinations: 600×g, 1,200×g and 2,400×g, for 3, 6 or 12 min. After centrifugation, spermatozoa were diluted in TES–Tris–fructose extender with egg yolk and glycerol (final glycerol concentration of 8%) and frozen in 0.25-mL straws. In the post-thawed semen, motility was assessed by CASA, and acrosomal status (PNA-FITC), viability (SYBR-14 with propidium iodide) and chromatin status (SCSA) were determined by flow cytometry. The longest centrifugation time (12 min) significantly decreased some motility parameters. Sperm recovery significantly decreased in brown bear at 600×g. Our results suggest that brown bear spermatozoa are more sensitive to long centrifugation times than to high RCF. Centrifugation regimes showed no effects on the post-thawing chromatin status. We recommend preparing the brown bear semen for freezing by centrifugation 1,200×g or 2,400×g for 6 min, after electroejaculation and dilution 1:1 in TCG extender, since these procedures increase the spermatozoa recovery without harmful effects on the post-thawed quality of brown bear spermatozoa.S

An SEIR Epidemic Model of Fractional Order to Analyze the Evolution of the Covid-19 Epidemic in Argentina

A pandemic caused by a new coronavirus (Covid-19) has spread worldwide, inducing an epidemic still active in Argentina. In this chapter, we present a case study using an SEIR (Susceptible-Exposed-Infected-Recovered) diffusion model of fractional order in time to analyze the evolution of the epidemic in Buenos Aires and neighboring areas (Region Metropolitana de Buenos Aires, (RMBA)) comprising about 15 million inhabitants. In the SEIR model, individuals are divided into four classes, namely, susceptible (S), exposed (E), infected (I) and recovered (R). The SEIR model of fractional order allows for the incorporation of memory, with hereditary properties of the system, being a generalization of the classic SEIR first-order system, where such effects are ignored. Furthermore, the fractional model provides one additional parameter to obtain a better fit of the data. The parameters of the model are calibrated by using as data the number of casualties officially reported. Since infinite solutions honour the data, we show a set of cases with different values of the lockdown parameters, fatality rate, and incubation and infectious periods. The different reproduction ratios $R_0$ and infection fatality rates (IFR) so obtained indicate the results may differ from recent reported values, constituting possible alternative solutions. A comparison with results obtained with the classic SEIR model is also included. The analysis allows us to study how isolation and social distancing measures affect the time evolution of the epidemic.Facultad de Ciencias Astronómicas y Geofísica

Elastin-like recombinamers with acquired functionalities for gene-delivery applications

Producción CientíficaIn this work, well-defined elastin-like recombinamers (ELRs) were studied as a choice to the existing nonviral vectors due to their biocompatibility and ease of scale-up. Functional motifs, namely penetratin and LAEL fusogenic peptides were incorporated into a basic ELR sequence, and imidazole groups were subsequently covalently bound obtaining ELRs with new functionalities. Stable polyplexes composed of plasmid DNA and ELRs were formed. A particle size around 200 nm and a zeta potential up to nearly +24 mV made them suitable for gene delivery purposes. Additionally, viability and transfection assays with C6 rat glioma cell line showed an increase in the cellular uptake and transfection levels for the construction containing the LAEL motif. This study highlights the importance of controlling the polymer functionality using recombinant techniques and establishes the utility of ELRs as biocompatible nonviral systems for gene-therapy applications.ERDF Funding from the EU and MINECO; contract grant number: MAT2010-15982FCCI Subprogram: Modality ACI-COLABORA Spain-India 2010-2012; contract grant numbers: MAT2010-15310, PRIPIBAR- 2011-1403, MAT2012-38043, and MAT2013-41723-RJCyL; contract grant numbers: VA049A11, VA152A12, and VA155A12CIBER-BBN, JCyL, and the Instituto de Salud Carlos III under the “Network Center of Regenerative Medicine and Cellular Therapy of Castilla and Leon” and DST (Indo-Spanish), (New Delhi

Effects on brown bear (Ursus arctos) spermatozoa freezability of different extender and dilution ratios used for pre-freezing centrifugation

P. 259–266The objective of this study was to determine how the extender and dilution ratio used during centrifugation affect bear spermatozoa quality before and after freezing–thawing. Semen was collected from 15 brown bears by electroejaculation. In experiment 1, semen was divided into five aliquots and diluted using one of the following extenders: Tris-citric-glucose (TCG), Tris-citric-glucose-3% BSA, Tris-citric-glucose-1% egg yolk or CaninePro. In experiment 2, semen was divided into five aliquots and diluted 1:1, 1:4, 1:8 or 1:16 (semen:extender) with Tris-citric-glucose. In both experiments, one aliquot was left undiluted and it was used as a control. All the aliquots were centrifuged at 600×g for 6 min and frozen. Samples were analysed by post-thawing for motility (CASA) and, by flow cytometry, for viability (YO-PRO-1), acrosomal status (PNA-FITC/PI) and mitochondrial status (JC-1). CaninePro rendered the highest motility with respect to the undiluted control (total motility, 53.1% vs. 38.5%, P < 0.001), and CaninePro and TCG significantly increased the percentage of viable and acrosome-intact spermatozoa (43.2 and 43.4, respectively, vs. 39.4, P < 0.05). In experiment 2, dilution 1:4 yielded the highest value of total motility (78.8 vs. 67.2, P < 0.05) and proportion of spermatozoa with intact membrane and acrosome (64.5 vs. 54.4, P < 0.01). In general, diluting 1:4 or 1:8 brown bear semen prior to centrifugation improved the motility and acrosome status of the thawed spermatozoa