Abstract: The continued growth in demand for cement has raised concerns in the industry about environmental and sustainability issues. In addition, the worldwide generation of large quantities of solid waste threatens human health and on environmental quality. This paper proposes to assess the feasibility of using a residual powder derived from organic waste of vegetable or animal origin for replacing a part of Portland cement during concrete production. Specifically, the powder is derived from a living being such as the remains of food (meat, vegetables, fruits, eggshells), paper, wood, bones and seeds. His scientific contribution is a conscious change due to development of an alternative material for contribute with more sustainable processes in the construction industry. Three types of mixtures for cement content were studied: aggregate/cement (A/C) ratios of 15, 10, and 6. Concrete samples were then made by replacing the cement with organic waste powder in percentages of 5%, 10%, 15%, and 20%. These mixtures were evaluated for their physical and mechanical properties. The results showed that the reference concrete had higher compressive strength than the concrete with low cement content (A/C ratio of 15:1). However, samples made with a 5% of powder and an A/C ratio of 10:1 presented values at least 2.1% greater than compressive strength of reference concrete. Mixtures rich in cement (A/C ratio of 6:1) and the powder replacements of up to 10% showed in the best mechanical behavior in 13% in relation to the reference concrete. Therefore, waste powder can be used as filling material to replace a part of the cement, resulting in denser and more resistant concrete, as well as less specific absorption and voids.

Resumen: Actualmente, el crecimiento continuo en la demanda de cemento genera preocupaciones ambientales y de sostenibilidad en la industria cementera. Por otra parte, la generación de grandes cantidades de residuos sólidos urbanos a nivel mundial provoca daños en la salud humana y en la calidad del medio ambiente. Por lo anterior, esta investigación propone evaluar la sustitución parcial del cemento Portland por un polvo residual obtenido de la descomposición química de residuos orgánicos de origen vegetal o animal, tales como restos de alimentos (carne, vegetales, frutas, cáscara de huevo), papel, madera, huesos y semillas. De esta forma, una contribución científica podría generar un cambio consciente en el desarrollo de un producto como material alternativo que contribuya con procesos más sostenibles en la industria de la construcción. Se estudiaron tres tipos de mezcla, variando el contenido de cemento, seleccionando las proporciones agregados/cemento (a/c) de 15, 10 y 6. Se prepararon hormigones sustituyendo el cemento por el polvo de residuo orgánico, en peso, en porcentajes de 5, 10, 15 y 20%. Se evaluaron sus propiedades físicas y mecánicas. Los resultados mostraron que el hormigón de referencia presentó mayor resistencia a la compresión que el hormigón con bajo contenido de cemento (proporción a/c de 15:1). Sin embargo, las mezclas preparadas con un 5% de polvo y razón a/c de 10:1 presentaron valores de al menos 2,1% superiores a la resistencia a la compresión del hormigón de referencia. Las mezclas ricas en cemento (razón a/c de 6:1) con reemplazo de polvo de hasta un 10% mostraron un mejor desempeño mecánico, 13% superior, en relación al hormigón padrón. En consecuencia, se puede usar el polvo orgánico como material de relleno (filler) en el hormigón para sustituir parte del cemento puesto que se obtienen hormigones más resistentes y densos y con menor absorción específica e índice de vacíos.

In a farm with livestock production-agriculture integrated management, located in Cangrejeras, Artemisa province, the impact of agroecological methods was evaluated through the variation of the soil mesofauna. Three management systems were selected: pastureland area, designated as control area, which had been established for more than 20 years; forage area, planted in mosaic form, with small plots of perennial crops, and subject to an organic manure treatment; and polycrop area, with a rotation system of short-cycle crops and application of compost. The samplings were conducted six and eight years after making the transformations in the forage and crop areas, in both seasons. Five samples were taken in each system, at a depth of 0-10 cm, according to a completely randomized design. In general, in the forage and pastureland areas, regarding the Oribatida/Astigmata, Oribatida/Prostigmata and Astigmata/Mesostigmata ratios (in both seasons and years of transformation), the edaphic groups that constitute indicators of soil stability and fertility prevailed (Oribatida and Mesostigmata), as they are favored by the incorporation of organic matter and a higher soil cover, which stimulates the mesofauna to recover higher stability conditions. In the polycrop area the groups which are indicators of the soil instability and infertility (Astigmata and Prostigmata) prevailed, because the crop rotation and the management of the agroecological techniques did not guarantee yet the conditions that benefit the establishment of the other groups.

Se evaluó el impacto de los métodos agroecológicos a través de la variación de la mesofauna del suelo, en una finca con manejo integrado ganadería-agricultura (en Cangrejeras, provincia Artemisa). Se seleccionaron tres sistemas de manejo: área de pastizal, designada como área control, y con más de 20 años de establecida; área de forraje, sembrada en forma de mosaico, con pequeñas parcelas de cultivos perennes, y sometida a un tratamiento de abono orgánico; y área de policultivos, con un sistema de rotación de cultivos de ciclo corto y aplicación de compost. Los muestreos se efectuaron a los seis y ocho años de haber realizado las transformaciones en las áreas de forraje y cultivo, en ambas estaciones del año. Se tomaron cinco muestras en cada sistema, a una profundidad de 0-10 cm, según un diseño completamente aleatorizado. Por lo general en las áreas de forraje y pastizal, en cuanto a las relaciones oribátidos/astigmados, oribátidos/prostigmados y astigmados/mesostigmados (en ambas estaciones y años de transformación), dominaron los grupos edáficos que constituyen indicadores de estabilidad y fertilidad del suelo (oribátidos y mesostigmados), al estar favorecidos por la incorporación de la materia orgánica y una mayor cobertura del suelo, lo cual estimula que la mesofauna recobre condiciones de mayor estabilidad. En el área de policultivo predominaron los grupos indicadores de la inestabilidad e infertilidad del suelo (astigmados y prostigmados), ya que la rotación de cultivos y el manejo de las técnicas agroecológicas no garantizaron las condiciones que benefician el establecimiento de los otros grupos.

The present paper deals with the chemistry that is taught in schools from an epistemological and cognitive approach. We wonder about the meaning that can have the discipline for those who learn without identifying with the academic purposes because they are elementary school students working in a specific context (the school). From this reflection, we propose a chemistry course for initial training of elementary school teachers with a modeler orientation. From an epistemological point of view we are working with the notion of 'theoretical model', which is derived from current cognitive philosophy of science's perspective, which proposes a semantic concept of a scientific theory facilitating the approximation of the phenomena and the theory that explains them. The cognitive dimension leads us to identify the consistency between the experimental interventions of students, their abstract representations and the language they use to explain what they do, what happens and why happens when they intervene in chemical phenomena. We identify the modelling process with a progressive fit between the three dimensions of human cognition to acquire the Chemical Change Model that guides and gives coherence to the lessons. Narratives were used that kept the interest of students and they refined their explanations during the modelling process. Discourse analysis of students during the learning process enabled us to identify the relations students established between their representations and their experimental interventions and the language they used. All this brought a new perspective to assess means for students to progress and to establish comparisons between them.

Este artículo tiene que ver con la química que se enseña en las escuelas desde un enfoque epistemológico y cognitivo. Nos preguntamos el significado que puede tener la disciplina para quienes aprenden sin haber identificado el propósito académico, ya que son estudiantes de primaria que trabajan en un contexto específico (la escuela). Con este propósito planteamos un curso de química para el entrenamiento inicial de profesores con una orientación modelizadora.

In this article is presented a brief systematization about the evolution of the concept of blood circulation that considers the historical period between the conceptions of the Egyptians until century XVII, when Harvey consolidates a ''scientific model of Sanguineous Circulation'' in the human organism. Next, we applied the model of Toulmin to analyze blood flow, valves and cardiac frequency evolution concepts from pragmatic to a realistic perspective. Finally we raised some ideas that could serve as a guide for the education of this concept considering the historical aspects that we had analyzed.

En este artículo, se presenta una breve sistematización acerca de la evolución del concepto de sangre que considera el período histórico que transcurre entre las concepciones de los egipcios hasta el siglo XVII, cuando Harvey consolida un ''modelo científico'' de Circulación Sanguínea en el organismo humano. A continuación, aplicamos el modelo de Toulmin para analizar la evolución de los conceptos de movilidad sanguínea, septum y frecuencia cardiaca desde una perspectiva realista pragmática. Finalmente planteamos algunas ideas orientadoras que podrían servir de guía para la enseñanza de este concepto considerando los aspectos históricos que analizamos a través del consolidado de las ideas expuestas.

We studied the effects of infusion of nerve growth factor (NGF) into the hippocampus and entorhinal cortex of male Wistar rats (250-300 g, N = 11-13 per group) on inhibitory avoidance retention. In order to evaluate the modulation of entorhinal and hippocampal NGF in short- and long-term memory, animals were implanted with cannulae in the CA1 area of the dorsal hippocampus or entorhinal cortex and trained in one-trial step-down inhibitory avoidance (foot shock, 0.4 mA). Retention tests were carried out 1.5 h or 24 h after training to measure short- and long-term memory, respectively. Immediately after training, rats received 5 µl NGF (0.05, 0.5 or 5.0 ng) or saline per side into the CA1 area and entorhinal cortex. The correct position of the cannulae was confirmed by histological analysis. The highest dose of NGF (5.0 ng) into the hippocampus blocked short-term memory (P < 0.05), whereas the doses of 0.5 (P < 0.05) and 5.0 ng (P < 0.01) NGF enhanced long-term memory. NGF administration into the entorhinal cortex improved long-term memory at the dose of 5.0 ng (P < 0.05) and did not alter short-term memory. Taken as a whole, our results suggest a differential modulation by entorhinal and hippocampal NGF of short- and long-term memory.

Rats implanted bilaterally with cannulae in the CA1 region of the dorsal hippocampus or the entorhinal cortex were submitted to either a one-trial inhibitory avoidance task, or to 5 min of habituation to an open field. Immediately after training, they received intrahippocampal or intraentorhinal 0.5-µl infusions of saline, of a vehicle (2% dimethylsulfoxide in saline), of the glutamatergic N-methyl-D-aspartate (NMDA) receptor antagonist 2-amino-5-phosphono pentanoic acid (AP5), of the protein kinase A inhibitor Rp-cAMPs (0.5 µg/side), of the calcium-calmodulin protein kinase II inhibitor KN-62, of the dopaminergic D1 antagonist SCH23390, or of the mitogen-activated protein kinase kinase inhibitor PD098059. Animals were tested in each task 24 h after training. Intrahippocampal KN-62 was amnestic for habituation; none of the other treatments had any effect on the retention of this task. In contrast, all of them strongly affected memory of the avoidance task. Intrahippocampal Rp-cAMPs, KN-62 and AP5, and intraentorhinal Rp-cAMPs, KN-62, PD098059 and SCH23390 caused retrograde amnesia. In view of the known actions of the treatments used, the present findings point to important biochemical differences in memory consolidation processes of the two tasks.

This article is a transcription of an electronic symposium in which some active researchers were invited by the Brazilian Society for Neuroscience and Behavior (SBNeC) to discuss the last decade's advances in neurobiology of learning and memory. The way different parts of the brain are recruited during the storage of different kinds of memory (e.g., short-term vs long-term memory, declarative vs procedural memory) and even the property of these divisions were discussed. It was pointed out that the brain does not really store memories, but stores traces of information that are later used to create memories, not always expressing a completely veridical picture of the past experienced reality. To perform this process different parts of the brain act as important nodes of the neural network that encode, store and retrieve the information that will be used to create memories. Some of the brain regions are recognizably active during the activation of short-term working memory (e.g., prefrontal cortex), or the storage of information retrieved as long-term explicit memories (e.g., hippocampus and related cortical areas) or the modulation of the storage of memories related to emotional events (e.g., amygdala). This does not mean that there is a separate neural structure completely supporting the storage of each kind of memory but means that these memories critically depend on the functioning of these neural structures. The current view is that there is no sense in talking about hippocampus-based or amygdala-based memory since this implies that there is a one-to-one correspondence. The present question to be solved is how systems interact in memory. The pertinence of attributing a critical role to cellular processes like synaptic tagging and protein kinase A activation to explain the memory storage processes at the cellular level was also discussed.

Glutamate receptors have been implicated in memory formation. The aim of the present study was to determine the effect of inhibitory avoidance training on specific [3H]-glutamate binding to membranes obtained from the hippocampus or parietal cortex of rats. Adult male Wistar rats were trained (0.5-mA footshock) in a step-down inhibitory avoidance task and were sacrificed 0, 5, 15 or 60 min after training. Hippocampus and parietal cortex were dissected and membranes were prepared and incubated with 350 nM [3H]-glutamate (N = 4-6 per group). Inhibitory avoidance training induced a 29% increase in glutamate binding in hippocampal membranes obtained from rats sacrificed at 5 min (P<0.01), but not at 0, 15, or 60 min after training, and did not affect glutamate binding in membranes obtained from the parietal cortex. These results are consistent with previous evidence for the involvement of glutamatergic synaptic modification in the hippocampus in the early steps of memory formation.

Training in step-down inhibitory avoidance (0.3-mA footshock) is followed by biochemical changes in rat hippocampus that strongly suggest an involvement of quantitative changes in glutamate AMPA receptors, followed by changes in the dopamine D1 receptor/cAMP/protein kinase A (PKA)/CREB-P signalling pathway in memory consolidation. AMPA binding to its receptor and levels of the AMPA receptor-specific subunit GluR1 increase in the hippocampus within the first 3 h after training (20-70%). Binding of the specific D1 receptor ligand, SCH23390, and cAMP levels increase within 3 or 6 h after training (30-100%). PKA activity and CREB-P levels show two peaks: a 35-40% increase 0 h after training, and a second increase 3-6 h later (35-60%). The results correlate with pharmacological findings showing an early post-training involvement of AMPA receptors, and a late involvement of the D1/cAMP/PKA/CREB-P pathway in memory consolidation of this task

Male Wistar rats were trained in one-trial step-down inhibitory avoidance using a 0.4-mA footshock. At various times after training (0, 1.5, 3, 6 and 9 h for the animals implanted into the CA1 region of the hippocampus; 0 and 3 h for those implanted into the amygdala), these animals received microinfusions of SKF38393 (7.5 µg/side), SCH23390 (0.5 µg/side), norepinephrine (0.3 µg/side), timolol (0.3 µg/side), 8-OH-DPAT (2.5 µg/side), NAN-190 (2.5 µg/side), forskolin (0.5 µg/side), KT5720 (0.5 µg/side) or 8-Br-cAMP (1.25 µg/side). Rats were tested for retention 24 h after training. When given into the hippocampus 0 h post-training, norepinephrine enhanced memory whereas KT5720 was amnestic. When given 1.5 h after training, all treatments were ineffective. When given 3 or 6 h post-training, 8-Br-cAMP, forskolin, SKF38393, norepinephrine and NAN-190 caused memory facilitation, while KT5720, SCH23390, timolol and 8-OH-DPAT caused retrograde amnesia. Again, at 9 h after training, all treatments were ineffective. When given into the amygdala, norepinephrine caused retrograde facilitation at 0 h after training. The other drugs infused into the amygdala did not cause any significant effect. These data suggest that in the hippocampus, but not in the amygdala, a cAMP/protein kinase A pathway is involved in memory consolidation at 3 and 6 h after training, which is regulated by D1, ß, and 5HT1A receptors. This correlates with data on increased post-training cAMP levels and a dual peak of protein kinase A activity and CREB-P levels (at 0 and 3-6 h) in rat hippocampus after training in this task. These results suggest that the hippocampus, but not the amygdala, is involved in long-term storage of step-down inhibitory avoidance in the rat.

Lesions of the entorhinal cortex produce retrograde memory impairment in both animals and humans. Here we report the effects of bilateral entorhinal cortex lesions caused by the stereotaxic infusion of N-methyl-D-aspartate (NMDA) in rats at two different moments, before or after the training session, on memory of different tasks: two-way shuttle avoidance, inhibitory avoidance and habituation to an open field. Pre- or post-training entorhinal cortex lesions caused an impairment of performance in the shuttle avoidance task, which agrees with the previously described role of this area in the processing of memories acquired in successive sessions. In the inhibitory avoidance task, only the post-training lesions had an effect (amnesia). No effect was observed on the open field task. The findings suggest that the role of the entorhinal cortex in memory processing is task-dependent, perhaps related to the complexity of each task

A total of 182 young adult male Wistar rats were bilaterally implanted with cannulae into the CA1 region of the dorsal hippocampus and into the amygdaloid nucleus, the entorhinal cortex, and the posterior parietal cortex. After recovery, the animals were trained in a step-down inhibitory avoidance task. At various times after training (0, 30, 60 or 90 min) the animals received a 0.5-µl microinfusion of vehicle (saline) or 0.5 µg of muscimol dissolved in the vehicle. A retention test was carried out 24 h after training. Retention test performance was hindered by muscimol administered into both the hippocampus and amygdala at 0 but not at 30 min posttraining. The drug was amnestic when given into the entorhinal cortex 30, 60 or 90 min after training, or into the parietal cortex 60 or 90 min after training, but not before. These findings suggest a sequential entry operation, during the posttraining period, of the hippocampus and amygdala, the entorhinal cortex, and the posterior parietal cortex in memory processing

In rats pre-but not post-training ip administration of either flumazenil, a central benzodiazepine (BSD) receptor antagonist, or of n-butyl-B-carboline-carboxylate (BCCB), an inverse agonist, enhanced retention of inhibitory avoidance learning. Flumazenil vlocked the enhancing effect of BCCB, and the inhibitory effect of the BZD agonists clonazepam and diazepam also given pre-training. Post-training administration of these drugs had no effects. The peripheral BZD receptor agonist/chloride channel blocker Ro5-4864 had no effect on the inhibitory avoidance task when given ip prior to training, buth it caused enhancement when given immediately post-training either ip or icv. This effect was blocked by PK11195, a competitive antagonist of Ro5-4864. These results suggest that ther is an endogenous mechanism mediated by BZD agonists, which is sensitive to inverse agonists and that normally down-regulates the formation of memories through a mechanism involving GABA-A receptors and the corresponding chloride channels. The most likely agonists for the endogenous mechanism suggested are the diazepam-like BZDs found in brain whose origin is possibly alimentary. Levels of these BZDs in the cortex were found to sharply decrease after inhibitory acoidance training or mere exposure to the training apparatus.