Ciencia

Tabla de Contenido

2021-11-10T15:26:40+00:00

Physicochemical and microbial characterization of an oil pit from Zulia state, Venezuela

2021-11-10T16:07:57+00:00

Oil pits are poorly designed soil excavations used to store hazardous wastes, which can leak into the environment causing serious damage to the ecosystem. They are considered a hostile environment for life due to the toxic compounds they possess, but there are microbial communities that adapt to this environment and can be used for their recovery. In this work, samples of water, sediment and oil from an oil well in the state of Zulia, Venezuela, were characterized physicochemically and microbiologically using standardized laboratory techniques. The water presented the following physicochemical characteristics: temperature: (30 ± 2)ºC, pH: 5.10-5.90, total alkalinity: 8.00 mg CaCO3 / L, Salinity: 0 UPS, BOD5.20: <0.10 mg/L, COD: 184.6-215.4 mg/L, dissolved oxygen: 8.00-8.97 mg/L, SST: 61-235 mg/L, SSV: 35-47 mg/L, nitrites: <0.0020, nitrates: <0.025 mg/L, NTK: 2.78-5.57 mg/L, orthophosphates: <0.15 mg/L, total phosphorus: 0.47-0.74 mg/L, HTP: 673.4- 821.7 mg/L, saturated: 86.73%, aromatics, resins and asphaltenes: <4.5%, Ni and V: <0.02 mg/L. The sediment presented organic matter: (4.09 ± 0.95)%, NTK: 728.33 ± 45.25 mg/Kg, total phosphorus: 40.37 ± 11.80 mg/Kg, crude in sediment: 13.05 ± 0.75%, saturated: 48.5%, aromatic: 33.5%, resins: 6.5% and asphaltenes: 11.5%. In crude oil, the following were determined: saturated: 48.1%, aromatic: 23.6%, resins: 19.4%, and asphaltenes: 8.9%. Microbial populations were quantified obtaining: (4.15 ± 1.43) x 106 org/mL of photosynthetic microorganisms (microalgae and cyanobacteria), (2.71 ± 0.49) x 107 CFU/mL of fungi in petrolized water and (2.25 ± 0.24) x 106 CFU/g in sediment, (2.09 ± 1.50) x 101 org/mL of rotifers in water and a bacterial population of (2.45 ± 0.34) x 105 CFU/mL in petrolized water and (2.83 ± 0.26) x 105 CFU/g in sediment. It is concluded that despite the fact that physicochemical conditions such as acidic pH in the water, low concentration of nutrients and organic matter, and high concentration of hydrocarbons were present in the oil well, microbial populations adapted to these conditions were found that could be used as biocatalysts for the bioremediation of the oil well.

Illegal wildlife trafficking on the main highways in north-western of Venezuela

2021-11-10T16:48:20+00:00

Illegal wildlife trafficking is one of the greatest threats to biodiversity in Venezuela. Our research aims were: (i) to register the trafficked species on four of the country’s north-western regional highways; (ii) to identify type of use and prices of the commercialised products, and (iii) to assess the conservation status of the species observed. Surveys were conducted following the convenience protocol between 2008 and 2010 on the following road routes: (a) Falcón-Zulia, (b) Pan-American Highway, (c) San Francisco-Machiques-Colon (Main road 6), and (d) Troncal del Caribe-Castilletes main road. We conducted aleatory convenience samplings, direct observation, and interviews (informal and semi-structured). Reptiles were the taxonomic group with most trafficked species (32.14%, n= 9), then mammals (25%, n= 7), birds (21.42%, n= 6); fish (14.3%, n= 4), and invertebrates (7.14%, n= 2). According to their conservation status, 50% (n= 14) of the species documented during this research are categorized as threatened by the International Union for Conservation of Nature (IUCN), and the main identified use was direct consumption (75%, n= 21). The interviewees affirmed that
the main reasons to carry out this illegal activity are (i) lack of alternative economic sources, and (ii) little or no monitoring by environmental authorities. Effective strategies to surveillance and control to minimize this threat towards biodiversity are urgently needed.

ZENDEROZ: Public transport route planner for Maracaibo (Venezuela)

2021-11-10T17:03:54+00:00

Geographic Information Systems are now as ubiquitous as social networks or the use of the Internet. Its impact from urban planning to crisis management is undeniable. This research presents the application of GIS in commute planning with public transport routes in Maracaibo. Throughout the phases of the software development cycle, a preliminary analysis was carried out of a base tool that uses graphs to represent the road and public transport networks in Maracaibo and the Dijkstra algorithm to efficiently calculate shortest routes; a module was built for tracking and estimating arrival times of public transport units; an adaptive web interface was developed for the integration of the various functionalities; and functional tests were carried out on the resulting system. The final product complies with GIS quality standards and its performance is computationally optimal.

Preliminary study on the 1-hexene hydromethoxycarbonylation with nickel catalytic systems containing mono- and diphosphines

2021-11-10T19:27:39+00:00

In this work, it was evaluated the catalytic activity of nickel systems formed in situ by addition of mono- (PPh3) and diphosphines (dppe, dppp and dppb) to NiCl2.6H2O for the homogeneous ydrometoxycarbonylation of 1-hexene in the presence of carbon monoxide and of an acid. The system Ni/4PPh3 in the presence of ten equivalents of p-toluensulphonic acid showed the highest activity, under mild reaction conditions (140 ºC, 50 atm de CO), obtaining the esters methyl heptanoate and methyl 2-methylhexanoate (n/i < 1). The systems Ni/diphosphine showed activities lower than Ni/4PPh3, where the tendency was dppe > dppp ~ dppb. The experimental results showed that the hydrometoxycarbonylation reaction proceeds through an intermediate containing one triphenylphosphine ligand, possibly [NiH(CO)2(PPh3)]+.

DFT study of non-linear optical properties of derivatives of diphosphaferrocene

2021-11-10T18:50:38+00:00

In this work, a preliminary study of the non-linear optical properties (NLO) of diphosphaferrocene derivatives was carried out at the DFT level. These properties were determined with the BLYP method and the DNP base set, implementing the finite field formalism based on the Kurtz equations. In general, the results obtained show that the effects of substituents on the phospholyl ring of diphosphaferrocene generate favorable increases in optical properties. Likewise, by generating a push-pull effect in a phospholyl ring of diphosphaferrocene, a high increase in NLO properties is observed. On the other hand, when the -NO2 group is introduced to the 2-styryl-diphosphaferrocene complex to form the push-pull system: (E)-2-(4-nitrophenyl)-2-ethenyl-diphosphaferrocene, it is observed that the properties are increase considerably, being the complex with the highest optical responses, which can be attributed to the strong attractor character of the nitro group, since the intramolecular charge transfer coincides with the orientation of the dipole moment, as has been reported in p -nitroaniline. Finally, diphosphaferrocene derivatives could be considered as molecular candidates for the design and creation of new materials in NLO.

Kinetic study of the N-deacetylation of chitin extracted from crustaceans’ exoskeletons employing ion chromatography

2021-11-10T19:21:37+00:00

The chitin N-deacetylation kinetics from crustaceans’ exoskeletons was established in this work, following the acetate ion concentration as a reaction product. A single-stage deacetylation reactions was conducted at 100 °C in a NaOH at 50% m/v in m:v ratios of 5:10, 10:150, 15:150 and 20:150 mg:mL. The acetate ion concentration was determined using ionic chromatography each 10 min until 5 hours. Deacetylation degree (DD) influence, insoluble matter percentage, and ash content against variation of chitin quantities exposed in an alkali define volume was also studied. The increase of deacetylation degree was observed at higher ratios of m:v, in the same manner as insoluble matter and the ash content. These studies showed that single-stage deacetylation reaction has pseudo-first-order kinetics because the reaction rate correlated with the acetate group. Furthermore, it was established that from apart 150 min that all chitin:alkali ratios showed high deacetylation degrees. Multistep reactions lead to higher DD than those found for single-stage reactions.