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  • Open access
  • 291 Reads
Soil structure and carbon sequestration as ecosystem services under different land uses in the ecuadorian amazon region

The identification of the factors that cause changes in agroecosystems and the services they provide is essential to design management that minimizes negative impacts on the environment. In this sense, the objective of this research was to characterize some structural indices and the carbon sequestration potential under different land uses in the Ecuadorian Amazon region. In each selected land use, we collected disturbed an undisturbed soil samples within depths from 0-10 and 10-30 cm. From these samples were evaluated some structural indexes such as the bulk density (BD), saturated hydraulic conductivity (Ksat), total porosity. (Tp), aeration porosity (Ap), retention porosity (Rp) and total organic carbon (TOC). The results showed significant differences by treatment and depth, obtaining the best physical condition in the Forest and in some uses of grass with trees. Regardless of land use, the structural conditions evaluated through the structural indexes exhibited better results in the surface horizon, which is strongly associated with the content of organic matter. It is shown that the reduction of greenhouse gas emissions (CO2) is associated with the increase and protection of organic matter with agroforestry systems.

  • Open access
  • 108 Reads
Application of molecular topology to the prediction and optimization of mosquito repellent activity of N-acyl-piperidine derivatives

 A topological-mathematical model has been developed based on Multilinear Regression Analysis in order to search new active molecules with mosquito repellent activity. The molecular characterization was performed using topo­logical indexes and a 5-variable model was chosen for prediction of protection times (R2 = 0.8457 and Q2 = 0.7486). The model was validated by an internal leave-one-out type cross-validation and a randomization test. The results confirmed the predictive power for the property under study. Finally, after carrying out a virtual screening, new compounds have been proposed with expected higher potency as mosquito repellents.

  • Open access
  • 87 Reads
Patterns of scuba diver behaviour to assess environmental impact on marine benthic communities: a suitable tool for management of recreational diving on Benidorm island (Western Mediterranean sea).

Scuba diving is one of the tourist activities with the greatest growth over the last few years. Nevertheless, few studies have analyzed the SCUBA divers’ behaviour in the Mediterranean Sea and none of them involved marine unprotected areas. Generally speaking  the damage done by individuals is quite low, but the, accumulative effects of these disturbances can cause significant localised destruction of benthic marine organisms. The present study was carried out during the year 2005 on a diving site called La Llosa, on Benidorm Island (Alicante: Western Mediterranean Sea) with more than 7,000 dives per year. Two hundred and seventeen (217) divers were monitored randomly. Each subject was observed underwater for 10 minutes (according to the methods proposed by Rouphael & Inglis, 2001). The diver’s actions as well as  how often each diver made direct physical contact with the substratum were noted.

Samples were randomly collected during the high diving season (June-October). Divers were not aware of this surveillance so as not to interfere with their normal patterns of behaviour. The results showed that 95% of divers came into physical contact with benthic substrata during the 10-min observation period. Fin contact rates were significantly different depending on the diving certification level (Man-Whitney test, p<0.003) detecting the greatest number of contacts within higher diving certification levels (Bonferroni correction). Divers using an underwater light device came intocontact with the substratum significantly more frequently than non-light users (2, p<0.022). However, contact rate did not show significant variance across divers using a camera and those who did not (p<0.366). No difference was found between contact rates of divers who were given a briefing and those who were not. Environmental briefing before diving had no effect on the divers’ hand contact rates (2, p< 0.194), which shows a low marine environmental sensitivity level of divers. We concluded that the decrease in scuba divers contact rate would take place given an improvement of environmental awareness, specially among professional  divers.

  • Open access
  • 101 Reads
Comunidad de poliquetos de los fondos blandos de la playa de Canet d’en Berenguer (Valencia-Spain).

Se analizó la estructura, composición y distribución de la comunidad de poliquetos asociada a la desembocadura de un emisario submarino situado en la zona infralitoral costera de una playa de arena con suave pendiente. Los análisis físico-químicos de la columna de agua y del sedimento, revelaron la presencia de una masa de agua homogénea, en la zona de estudio a excepción de las cercanías al efluente del emisario, donde se obtuvieron datos característicos de aguas residuales urbanas y los valores más bajos de riqueza específica y abundancia de toda la zona de muestreo.

Se identificaron un total de 85 especies pertenecientes a 30 familias de poliquetos, siendo las especies Nephtys hombergii y Onuphis eremita las más frecuentes en toda la zona de estudio. El análisis de los grupos tróficos pertenecientes a la fauna anelidiana mostró mayor abundancia de los carnívoros y omnívoros, seguido de los detritívoros superficiales y detritívoros sub-superficiales. El análisis de afinidad de las estaciones en función del contenido en materia orgánica y tamaño de grano del sedimento agrupó las estaciones en rangos batimétricos claramente diferenciados, permitiendo distinguir entre la Comunidad de Arenas Finas Superficiales y la Comunidad de Arenas Finas Bien Calibradas. Tanto el contenido en materia orgánica como los valores de abundancia y riqueza específica de la comunidad anelidiana, mostraron concordancia con la dirección de la corriente predominante en la zona de estudio (NE-SW).

  • Open access
  • 120 Reads
Thermoalkaline pretreatment influence on anaerobic biodegradability of filter cake for methane production

Currently millions of tons of solid waste are produced worldwide, receiving only a small part of some kind of treatment, the rest are used indiscriminately pollute the environment. Complexity of these wastes requires the study of alternative methods to help improve the efficiency of the stabilization process. Thermoalkaline pretreatment study was carried out taking into account the nature of filter cake from sugar manufacturing process. Sodium hydroxide NaOH was used as chemical agent and temperature conditions of 75 0C evaluated for different times. This research was conducted in order to determine the effect of pretreatment of filter cake to increase the yield of methane. The physical-chemical characterization of filter cake from “Melanio Hernández” Sugar Mill (Sancti Spiritus, Cuba), it was carried out through analysis of total solids (ST), volatile solids (SV) and pH. Methane yield parameter for anaerobic digestion in mesophilic conditions (37 ± 1 C) was determined. It was demonstrated that filter cake is a solid residue of sugar industry in this sector with high energy potential due to its organic content for the production of methane. Pretreatment at 1 hour had greatest increase in methane potential with respect to the untreated filter cake. These results demonstrate the relevance of the thermoalkaline pretreatment severity in terms of time and sodium loading to obtain the optimum anaerobic biodegradability of this biomass.

  • Open access
  • 117 Reads
In Vitro Antifungal Effect of Isoeugenol Against Penicillium citrinum Strains

Human mycoses have controversial treatment, since the available antifungal drugs besides favoring the appearance of resistant isolates, can present great toxicity to the human organism. This fact has driven the search for more efficient, safe and natural therapeutic alternatives with the objective of reversing this scenario of resistance presented by pathogenic fungi, for this, new natural and effective alternatives, such as the use of plant extracts, natural compounds and semi-synthetic, have been extensively investigated for the development of new drugs. In view of this scenario, this study aims to evaluate the antifungal activity of isoeugenol in vitro against strains of Penicillium citrinum. For this, the broth microdilution technique was used to determine the Minimum Inhibitory Concentration (MIC) and Minimum Fungicide Concentration (MFC) of isoeugenol and voriconazole. The concentrations by which the strains were submitted, 1024 μg/mL to 0.5 μg/mL, were obtained by means of serial dilution at a ratio of two, so that in the first row of the plate is the highest concentration and in the last , the lowest concentration. Finally, 10 μL of the fungal inoculum of each isolate was added to the wells, where each strain was placed on a plate column. MIC was defined as the lowest concentration capable of inhibiting fungal growth visually verified by maintaining the original coloration of the medium. After reading the MIC, aliquots of 20 μL of the supernatant from the wells where complete inhibition of fungal growth in the microdilution plates were observed were plated on Sabouraud dextrose agar plates. Plates were incubated, and MFC was considered the lowest concentration at which growth was less than 3 colonies. The assays were performed in triplicate and the geometric mean was calculated. The CIM of isoeugenol varied between 256 and 32 μg/mL, being the highest MIC value for the LM-21 strain and the lowest value for the LM-02, LM-03, LM-08, LM-155, LM- 157 and LM-161. The MIC range of voriconazole was 0.5 to 256 μg/mL. The MFC of isoeugenol varied between 64-512 μg/mL and for voriconazole it was 2 μg/mL and above 1024 μg/mL. In this way, we can conclude that isoeugenol presented an antifungal effect, which enables it as a potential antifungal drug, requiring complementary tests that clarify the mechanism of action involved in its antimicrobial activity.

  • Open access
  • 122 Reads
Variation of concentration of soluble solids and agricultural yield with organic fertilization in three varieties of sugar cane (Saccharum sp. hybrid) for the production of panela in the conditions of the ecuadorian amazon.

The cultivation of sugarcane is an agricultural activity of great socio-economic importance in Ecuadorian Amazon. The study was carried out in the sugarcane production area of the municipality of Simon Bolivar, Pastaza province, Ecuadorian Amazon Region.We used a factorial design in random blocks with three replicates for a total of 27 experimental plots.The study factors were the varieties of sugarcane identified as: POJ 27-14, Crystalline and POJ 93 and two types of organic fertilizers: pollinaza and sugarcane bagasse at a dose of 9060 kgha-1 compared with an absolute control without application of fertilizer.The analysis of combined variance and the Tukey's mean test with a significance level of 5% was performed to detect differences in mean between treatments.The results suggest that the concentration of sugars expressed in brix degrees did not show significant differences between the varieties, but it did show differences between the types of fertilization, being higher with the application of pollinaza with values of 15.9 degrees brix.The agricultural yield was affected according to the variety, registering higher values with variety POJ 27-14 with a yield of 107 t ha-1 in comparison with the other two varieties, which showed statistically similar yields.

  • Open access
  • 84 Reads
An analysis of the multiple choice test evaluation

We evaluate the approach which usually justifies how much has to be subtracted for every incorrect answer in a multiple choice test. We have developed a calculation which takes into account the possibility of blank answer some questions, which is not possible with the usual approach. We show that when the number of questions tends to infinity, both approaches are asymptotically equivalent.

  • Open access
  • 84 Reads
Evaluation of the Interference of Solvents Used in the Evaluation of Antimicrobial Activity of Liposoluble Natural Compounds

Because it is an activity already consolidated throughout the ages, the use of compounds from plants has been well studied and tested for definition or proof of its antibacterial activity. Despite the difficulties encountered as the solubility of essential oils, there are compounds that help in experiments, they are called solvents and emulsifiers and the most used in phytotherapeutic tests are: ethyl acetate, acetone, ethyl alcohol, methyl alcohol, neutral detergent (phosphates free), dimethylsulfoxide (DMSO), triton X-I00 and polysorbate 80 (tween 80). In view of this fact, the present work seeks to identify concentrations of polysorbate 80 (Tween 80) and dimethylsulfoxide (DMSO) capable of performing an antibacterial activity, due to its wide use in the scientific environment, against the following bacterial strains: Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa ATCC 27853, Proteus mirabilis ATCC 25922 and Enterococcus faecalis ATCC 29212. The evaluation of the activity of the compounds was performed by the diffusion disc method. This method is the one recommended by the Clinical and Laboratory Standards Institute and is based on the diffusion through the agar of a reagent impregnated in a disc of filter paper and the diffusion of the same leads to the formation of a halo of inhibition of growth of the micro- organisms whose diameter is inversely proportional to the minimum inhibitory concentration. This method is qualitative, that is, it allows to classify the bacterial sample as susceptible, intermediate or resistant to antimicrobial. The tests were carried out with different concentrations of the reagents to determine the antimicrobial effect of the studied solvents. The experiments were run in triplicate at all concentrations using the compounds in combination (DMSO + Tween). The incubation was done in a greenhouse at 35 ± 2 ° C, for a period of 24 hours. The tests were performed and the results expressed in mm by the arithmetic mean of the diameter of the inhibition halos, formed around the discs. As results, no values ​​were determined that determined antimicrobial activity, and it is not possible to determine MIC when the formed halo is equal to or less than 6 mm or when there is no formation thereof. In view of the results, it can be observed that the compounds may not present activities against the microorganisms tested or, due to their physico-chemical characteristics, suffer some interference, such as the diffusion difficulty in the agar, its insolubility in water and chemical complexity.

  • Open access
  • 138 Reads
Antibacterial Potential Of The Alpha-pinene Positive Enantiomer Against The Strain Proteus mirabilis

Essential oils are complex mixtures of volatile aromatic compounds derived from the secondary metabolism of plants, and which have several chemical components responsible for their therapeutic and organoleptic properties, among them, the class of terpenes, specifically alpha-pinene, a compound organic, which acts as an antibacterial agent. Among the multiresistant strains, the gram-negative species Proteus mirabilis is responsible for causing urinary tract infections. Thus, the present study aims to evaluate the antibacterial potential of (+) - alpha-pinene against the ATTC (American Type Culture Collection) standard strain of Proteus mirabilis ATCC 25933. Knowing the sensitivity of the bacterial strain, after the test of microdilution in broth, we intend to evaluate the antibacterial potential, ie the time by which the compound was able to act to eliminate the bacterial strain. For this, the present work used the methodology of Time Killing (Bacterial). In this sense, the strain was initially peeled into Mueller Hinton Agar (AMH) 24 hours prior to the test. For the analysis of the death curve in the time intervals 0, 2, 4, 8 and 24 hours of the MIC and MICx2 of the α-pinene, MIC of the amikacin and negative control, that is, the culture medium plus the bacterial inoculum. A 10 μL aliquot of the well contents and diluted in a 0.9% physiological solution was withdrawn, thereby forming a suspension, and an aliquot of 10 μL of this new dilution was then withdrawn and plated on plates containing Mueller Hinton agar with the aid of a Drigalski handle. This procedure was repeated at times t0, t2, t4, t8 and t24. The plates were then incubated at 35 ± 2 ° C for 24 hours and the number of colony forming units (CFU) counted, adjusting with the dilution factor used in each procedure. It is worth noting that this work is a pioneer in the evaluation of the antibacterial activity of the positive enantiomer of α-pinene, considering that there are no reports in the literature of studies against this bacterial. The MIC of amikacin was shown to be able to totally inhibit the growth of the strain within the first two hours, and the alpha-pinene MIC inhibited the growth of P. mirabilis after 24 hours. Inhibition occurred progressively at times 2, 4 and 8 hours until its total inhibition at 24 hours. However, the MICx2 of the alpha-pinene was also able to inhibit the total growth of the strain, but in a less time, requiring 8 hours for its total effect. It is therefore observed that the test substance, (+) - alpha-pinene has therapeutic potential to treat infections resulting from this bacterial strain. It is hoped that this study may support the development of future research to better elucidate the mechanism of action, the clinical safety of the substance as well as the toxicity of the compound. Thus, it may be a naturally occurring compound used as a new therapeutic option in opportunistic infections caused by Proteus mirabilis.