Espinosa-Faller F.J.,Marista University |
Conradson D.R.,Los Alamos National Laboratory |
Riha S.C.,Colorado State University |
Martucci M.B.,Los Alamos National Laboratory |
And 5 more authors.
Journal of Physical Chemistry C | Year: 2014
A thorough structure determination has been performed on Cu2ZnSnS4 nanoparticles, a popular photovoltaic material, using neutron diffraction-to characterize the long-range average crystal structure-and X-ray absorption fine structure (XAFS) spectroscopy at the Cu, Zn, and Sn K-edges to elucidate the element-specific local structure. This is the first combined multiscale approach on nanoparticles of this material. The results indicate the presence of aperiodic disorder on the cation sites that is diminished by annealing. This disorder involves local lattice distortions around the crystallographic sites rather than the presence of interstitial atoms. It is most consistent with the known antisite substitutions that are integral to CZTS (referring to the ordering of the Cu, Zn, and Sn between planes). However, instead of being confined within single unit cells so as to maintain the crystallographic symmetry, periodicity, and homogeneity, the substitutional disorder appears to extend over larger regions consisting of multiple unit cells but still smaller than the physical dimensions of the nanoparticles. These results therefore imply the presence of nanoscale domains characterized by local fluctuations in composition that cause the individual domains to be enriched in certain metal ions and depleted in others. These will be mirrored by domains with the opposite fluctuations at other locations in the crystal so that the overall composition remains close to the stoichiometric Cu2ZnSnS4. This disorder is likely pronounced in these samples due to the relatively low temperature reaction (300 °C) and annealing (350 °C) conditions and can be expected to have a significant effect on the resulting physical properties of the material and its photovoltaic performance. © 2014 American Chemical Society.
Klanian M.G.,Marista University
Journal of Experimental Marine Biology and Ecology | Year: 2013
Dormancy is a state of reduced metabolic activity adopted by organisms during periods of environmental stress, including physiological and biochemical adaptations. In this study, the physiological and immunological statuses of two populations of Isostichopus badionotus with different times of dormancy (B12. =. 12. months and B24. =. 24. months) are compared with a physiologically active population (BC. =. control). The coelomic liquid (CL) of 18 organisms from each batch (B24, B12, and BC) was used to perform the biochemical analysis. The body volume of dormant I. badionotus decreased exponentially as time passed under stable conditions. The total protein of B24 (9.26. mg/ml) was lower than that of B12 (15.64. mg/ml) and BC (13.21. mg/ml). Carbohydrate content was similar in both groups (B24 and B12) of dormant I. badionotus but lower than that of the control (6.93. mg/ml). The cholesterol content of B12 (0.40. mg/ml) was significantly higher than the similar cholesterol levels of B24 and the control. Activities of superoxide dismutase (T-SOD), catalase (CAT), and glutathione peroxidase (GPx) were higher in B12 than in B24 and BC. Phenoloxidase was lower in dormant sea cucumbers than the control (37.3. U/ml). Dormancy for the B12 organisms appears to be a fairly light state, involving no physiological changes that cannot be rapidly reversed. In contrast, the B24 organisms showed deterioration of their antioxidant complex and low lipid and protein reserves after 48. months, suggesting that the return to an active state would be impossible. © 2013 Elsevier B.V.
Gullian M.,Marista University |
Aramburu C.,Marista University |
Sanders B.,Marista University |
Lope R.,Marista University
Aquaculture | Year: 2010
In the Gulf of Mexico constraints linked to the supply of post-larvae (PL) and legal pressures associated with the introduction of a non-native species have been the motives behind research on the aquaculture of the native shrimp. In the present study, the growth and survival of 25-day-post-larvae (PL-25) of the pink shrimp Farfantepenaeus duorarum in saline groundwaters were evaluated. During the experiment the shrimps were acclimated from 36 psu to 5 psu utilizing various acclimation times (T1 = 38 h, T2 = 42 h, and T3 = 45 h) with a variable rate of salinity reduction (T1 = 9.9% h- 1, T2 = 11.8% h- 1, and T3 = 11.4% h- 1). After a 1-day acclimation period there were no differences (P > 0.05) in survival between treatments (80.7 ± 3.5%). The salinity reduction rate of T1 (low acclimation time) was selected to acclimatize the PL for the nursery experiment due to the high survival rate recorded after the salinity stress test. During the nursery experiment, shrimp at a density of 80 PL m- 2 had the highest growth rate (20 mg week- 1) (F(2,9) = 10.73; P < 0.05) and survival rate (79%) (F(2,9) = 4.93; P < 0.05) in comparison to other densities (150 PL m- 2; 250 PL m- 2). The PL growth was adjusted to a non-linear regression function (0.030 * e (0.035 * d)). Shrimp at 80 PL m- 2 (t = 0.87) and 150 PL m- 2 (t = 1.54) showed isometric growth (Ho = b = 3). Temperature was the only environmental variable that explained the most consecutive additional variance (80.1%) in the PL weight. The temperature-growth response curve was fitted to a generalized additive model (GAM). Results from this research demonstrate that F. duorarum (PL-25) can be successfully acclimated to low-salinity (5 psu) conditions with a high percentage of survival and an acceptable growth rate in the nursery phase (45 days). In the future efforts should be made to improve survival at higher densities in order to make production profitable. Crown Copyright © 2010.
Torres-Acosta A.A.,Marista University
Concrete under Severe Conditions: Environment and Loading - Proceedings of the 6th International Conference on Concrete under Severe Conditions, CONSEC'10 | Year: 2010
This paper presents the result obtained from an experimental study that evaluated the efficacy of a controlled current system for accelerating corrosion of reinforced concrete elements. In the study, twenty four reinforced concrete beams (10 × 15 × 150 cm) were subjected to a nominal constant current density between 80 and 200 μA/cm 2 and was achieved using special circuitry. On the other hand, twenty eight reinforced concrete slabs (15 × 30 × 60 cm) were used for natural corrosion tests. All the specimens were cast with 3% chloride by weight of cement in either a localized or generalized region. The beams were placed in two different environments: constantly wet or dry. The slabs were placed in a constant dry laboratory environment only. Predicted metal loss using Faraday's Law in the accelerated specimens were compared against actual losses obtained by the gravimetric method. The correspondence between concrete crack propagation and/or pit depth and metal loss was also determined for both methods. Good correlation was obtained between Faradaic and gravimetric losses for both methods. No apparent difference between corrosion parameters (mass loss, crack opening and extension, pit depth) in accelerated and natural corrosion tests were observed, which support the use of such constant current accelerated method for remaining life forecasting. © 2010 Taylor & Francis Group, London.
Gullian M.,Marista University |
Espinosa-Faller F.J.,Marista University |
Nunez A.,Marista University |
Lopez-Barahona N.,Marista University
Aquaculture Research | Year: 2012
This research was carried out to study the effect of turbidity on the effectiveness of ultraviolet light (UVC) for removing heterotrophic bacteria (HB) from two commercial recirculating aquaculture systems (RAS). We developed a simple and straightforward UV disinfection model based on water turbidity to predict the cost-effectiveness of disinfection. The UVC from RAS1 (12.8m 3, 80Lmin -1, indoor system) was tested at 9.2, 9.9, 16.3, 17.2, 23.1 and 28.2 nephelometric turbidity units (NTU) after 24h of exposure. The RAS2 (140m 3, 1140Lmin -1, outdoor system) was tested at 8.0, 9.2, 11.0, 12.1, 16.0, 24.2, 27.0, 31.3 and 31.7NTU after 72h. An increase in turbidity in the water was achieved by rearing Oreochromis niloticus fish. The RAS1 achieved a maximum UV efficiency (89.8%≈1Log) at 9.2NTU after 24h and RAS2 at 8.0NTU (86.4%≈0.9Log) after 72h of exposure. For RAS1, the UVC removed 90% of HB in 24h when the turbidity was <9.9NTU. For RAS2, without restrictions on particle size and relatively high phytoplankton abundance, the UV was unlikely to be a cost-effective way of removing HB at turbidity above 11.0NTU. © 2011 Blackwell Publishing Ltd.
Gullian-Klania M.,Marista University
Journal of Aquatic Animal Health | Year: 2013
The effect of long-term freshwater acclimation on the blood and plasma ion composition of Red Drum Sciaenops ocellatus was investigated with the goal of elucidating the necessity of ion remediation. Four replicates (n = 50) of freshwater-acclimated (FW) fish (1.6 ± 0.2 g) were raised in 25-m3 tanks supported by 140,000 L of recirculating water. Four replicates (n = 50) of seawater (SW) fish groups were placed in 40-m3 offshore cages at 32-35 psu. Blood was collected from 100 fish (FW = 578 ± 50 g; SW = 686 ± 45 g) of each group (FW, SW) after 8 months of rearing. During the grow-out phase, the survival of FW and SW fish was 57.5% and 92.2%, respectively. The water ion composition (mainly the Ca2 + /K + [43%] and Ca2 + /Mg2 + ratios [1%]) explained 56.6% of the plasmatic ion variability in the fish groups. Freshwater exposure produced significant reductions in osmolality and in several plasma indicators (Na +, Cl-1, and Mg2 +); the K + levels from FW fish were the most compromised parameter. The water Ca2 + /Na + ratio had a greater influence (44%) on the plasma chemistry parameters, mainly glucose and creatinine. Freshwater-acclimated fish had a higher percentage of hematocrit, hemoglobin, and red blood cells than SW fish, but the water quality explained only 12.5% of the blood parameter variability between the FW and SW groups. The results support the conclusion that Red Drum tolerates salinity variations and can adopt a relatively stable condition for short periods; however, the data suggest that Red Drum have only a limited ability to withstand a hyposmotic environment for long periods due to their limited ability in maintaining K + concentrations without external supplementation. Freshwater environments with high Ca2 + /Na +, Ca2 + /K +, and Ca2 + /Mg2 + ratios appear to be a chronic stress factor that should be considered in future experiments.
Gullian-Klanian M.,Marista University |
Aramburu-Adame C.,Marista University
Latin American Journal of Aquatic Research | Year: 2013
The aim of this paper was evaluate the performance of Nile tilapia fingerlings (Oreochromis niloticus) raised at hyper intensive stocking density in a recirculating aquaculture system (RAS) with minimum water replacing. The experimental system was performed in a single-batch nursery system to obtain 50 g fish size in 60 days. Fish (2.07 ± 0.04 g) were stocked in triplicate at 400 (T1), 500 (T2) and 600 (T3) fish m-3 (0.84, 1.05, 1.22 kg m-3). RAS functioned with 12,000 L of recirculating water and 252 L day-1of water replacing (2.1% daily). The efficiency of the biofilter for removing the total ammonia nitrogen (TAN) was 48 ± 12.5 mg L-1. Stocking density did not affect significantly the survival (89.5 to 93.6%). The growth rate of T1 (0.96 g day-1; 5.01% day-1) and T2 (0.92 g day-1; 4.95% day-1) was significantly higher than T3 (0.83 g day-1; 4.80% day-1). The specific growth rate (SGR) of T1 was 41% influenced by temperature. For T2 and T3 the SGR were influenced by the variation of dissolved oxygen (DO) that explained 47 and 44% of the fish weight variation, respectively. The SGR from T3 was also affected by the concentration of ammonia nitrogen (31%). The high stocking density affected the overall size of fish and the size homogeneity, but had no negative effect on the length-weight relationship (L-W). Data support the conclusion that fingerling stocked at 400 and 500 fish m-3 shows high performance during 9-weeks when the biomass not exceed 37 kg m-3. At this time fish have reached the desired final nursery weight (50 g) for transfer to grow-out facilities.
Gullian Klanian M.,Marista University |
Geronimo Alonso M.,Marista University
Aquaculture Research | Year: 2015
This study compares sensory attributes, chemical composition, fatty acid profiles, and the taste of raw and cooked red drum Sciaenops ocellatus fillets, reared in seawater (SW) and in freshwater (FW) aquaculture systems. Significant nutritional differences were found in the raw fillets. The total lipid was higher (5.31%) in FW fish than the SW (2.60%). The ratio n-3/n-6 and EPA/DHA was higher in SW than FW fillets. The eicosenoic acid was only present in FW fillets. DHA was dominant in SW specimens, contrary to the arachidonic acid level, which was dominant in FW fillets. The assessors perceived a significant difference in the firmness and colour of raw fillets, but its odour intensity was not affected. Fillets from SW fish have higher acceptability (33.3%) than FW fillets (26.4%). Sensory differences in raw fillet were not correlated with consumer perceptions, as cooked fish was considered to have similar flavour, independent of its origin. © 2013 John Wiley & Sons Ltd.
Espinosa-Faller F.J.,Marista University |
Rendon-Rodriguez G.E.,Marista University
Journal of Applied Research and Technology | Year: 2012
A ZigBee wireless sensor network was developed for monitoring an experimental aquaculture recirculating system. Temperature, dissolved oxygen, water and air pressure as well as electric current sensors were included in the setup. The high fish densities required in these systems to become economically viable present a case where sensor networks can be applied to preserve a healthy livestock and to reduce the risk of failures that end up in the loss of production. Modules for reading and transmitting sensor values through a ZigBee wireless network were developed and tested. The modules were installed in an aquaculture recirculating system to transmit sensor values to the network coordinator. A monitoring program was created in order to display and store sensor values and to compare them with reference limits. An alert is emitted in case reference limits have been reached. E-mail and an SMS message alert can also be sent to the cellular phone of the system administrator, so immediate action can be taken. A web interface allows Internet access to the sensor values. The present work demonstrates the applicability of ZigBee wireless sensor network technology to aquaculture recirculating systems.
Seijo J.C.,Marista University |
Villanueva-Poot R.,Marista University |
Charles A.,Saint Mary's University, Halifax
Fisheries Research | Year: 2016
The impact of ocean acidification on fisheries is a relatively new issue facing decision-makers, and one for which very little empirical data is available to draw upon. This paper demonstrates how, despite the lack of knowledge, well-established methods of bioeconomic modelling and decision analysis can be applied to address the challenge. A decision support framework is developed, incorporating a dynamic age-structured bioeconomic model together with a set of decision tables applicable in the absence of known probabilities of future change. With such a model it is possible to trace ocean acidification as an additional stressor, specifically on fisheries targeting calcifier species, such as many high value mollusks. We do so by shifting growth and natural mortality parameters into time varying functions of ocean acidity (pH), as forecasted by climate scenarios reported by the Intergovernmental Panel on Climate Change (IPCC). Possible effects of ocean acidification on calcifier species with various life cycles were modeled beginning with initial biological parameters of the growth and mortality dynamic functions reflecting differences in individual growth, natural mortality and species longevity. The analysis illustrates how fishery outcomes depend on the extent of ocean acidification and the life cycle of calcifier species. Results also indicate that under uncertainty, there is value in taking precautionary management measures, such as reducing fishing intensity. © 2015 Elsevier B.V.