23 results on '"Molina, Veronica"'
Search Results
2. Method for potential assessment and adaptation for additive manufacturing of conventionally manufactured components.
- Author
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Siller, Nadja, Werner, Sebastian, Molina, Veronica, and Göhlich, Dietmar
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INDIVIDUATION (Philosophy) ,MACHINE learning ,MANUFACTURING processes ,VALUE proposition ,PROBLEM solving ,ELECTRON beam furnaces - Abstract
The novelty of additive manufacturing (AM) involves new requirements, restrictions and rules, that are considerably different to those of conventional manufacturing methods. Therefore, designers often lack experience and knowledge about identifying AM-suited components. However, to ensure profitability, it is essential to choose components, that are well suited for additive manufacturing. State-of-the-art user-support methods for identifying AM potential widely focus on either economic potential or manufacturability but fail to address both aspects. While machine learning solutions are considered highly efficient, the assessment outcome lacks process transparency, inhibiting troubleshooting, plausibility checks and problem-oriented considerations. This paper proposes a holistic, yet detailed and transparent approach to identify conventionally manufactured parts for AM from an existing product portfolio, enabling decision-making based on quantifiable results. It combines and advances state-of-the-art methods, considering manufacturability, economic profitability and socio-ecological aspects. Besides evaluating AM potential, the method additionally assesses the components' potential for re-design-based enhancement for AM suitability. Besides understanding product functions and present production processes, users are expected to have a basic understanding of company goals. The approach involves inquiries regarding company- and product-specific priorities, enabling a weighted assessment. The weights are determined based on individual company philosophies regarding AM value propositions such as differing stakeholder interests and priorities. Additionally, the approach allows users to investigate different development goals by weighting opportunistic and restrictive assessment. The method application is demonstrated via an assembly comprising 11 parts in a scenario focusing on serviceability, eventually determining suitability statements. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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3. Breakthrough dry seawater reverse osmosis elements.
- Author
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Perez Macia, Maria Angeles, Arias Peña, David, Al-Omar, Harith, García-Molina, Veronica, and Gilabert-Oriol, Guillem
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REVERSE osmosis ,SALINE water conversion ,GREENHOUSE gas mitigation ,WATER shortages ,SEAWATER ,DISRUPTIVE innovations - Abstract
Water scarcity is one key challenge mankind is facing. Seawater reverse osmosis desalination is a promising technology to solve it. However, further innovation which needs to go beyond product specifications is needed to decrease the total cost of water while at the same time, improving sustainability footprint. This paper describes a breakthrough step-change in innovation within the desalination industry: transitioning from wet-tested seawater reverse osmosis (SWRO) elements to dry-tested SWRO elements. This new concept has been achieved by DuPont thanks to a cumulation of significant breakthrough in reverse osmosis technology: continuous advancements in membrane chemistry, automated precision manufacturing, single source manufacturing, a robust quality control, and enhancements in testing methods. Dry SWRO elements offer significant advantages over wet elements, given the requirement to monitor and eventually replace preservation solutions for wet membranes. Dry membranes enable longer storage times, lower labor costs and easier longterm warehouse planning. Dry membranes are safer to install due to a 4 kg weight reduction and are easier to handle. From the sustainability point of view, the dry-test SW concept also brings plenty of benefits: (1) Reduces fresh-water consumption as no wet testing is required; (2) Eliminates wastewater generated during wet testing; (3) Significantly reduces energy consumption by skipping wet testing; and (4) the lower membrane weight will significantly decrease the environmental footprint of dry elements, reducing by up to 20% the CO
2 generation during transportation. In a large desalination installation supplied with dry SWRO elements, the greenhouse gas emissions reduction equals those generated by a passenger vehicle driving more than 500,000 km. Additionally, dry SWRO elements offer the same water productivity and permeate quality as wet elements. [ABSTRACT FROM AUTHOR]- Published
- 2022
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4. The importance of long term stable performance and durability of reverse osmosis elements.
- Author
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Gilabert-Oriol, Guillem, Salgado, Blanca, Garcia Molina, Veronica, Arias, David, and Warczok, Justyna
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REVERSE osmosis ,SALINE water conversion ,DURABILITY ,WATER shortages ,ARID regions ,HIGH temperatures - Abstract
Water scarcity is being recognized as one of the main threats that mankind is facing globally. Reverse osmosis membrane technology has developed as a promising technology to address this problem. This increase has been driven as materials are improved and costs dropped. This is especially relevant for Middle East countries (ME), where population is located in arid and semi-arid regions with limited rainfalls and a high degree of evaporation due to the high temperatures the region is exposed to. Therefore, getting a robust element that is able to offer a stable salt rejection even after multiple cleanings is of utmost importance to sustain the population and economic growth of the region. This paper aims at demonstrating the superior durability of FilmTec™ membranes compared to other manufacturers. This superior durability has been reported in a number of desalination plants where FilmTec™ membranes lifetime has exceeded more than 10 years, but a quantification and a reliable comparison of such superior durability compared to other manufacturers in a controlled environment has not been completed to date. In this paper, FilmTec™ SW30XLE elements are exposed together with equivalent commercially available membranes from other suppliers to a durability study to simulate long term operation and to determine the evolution of the membrane specifications over time. Particular focus is paid to the changes in salt rejection. Membrane durability plays a determining role in membrane replacement, which ultimately has a critical impact on the economics of any desalination plant. In this study, it was determined that after a number of cleanings, the salt passage increase over time of the membranes from other suppliers was close to 3.5 times larger than the value experienced by FilmTec™ membranes. More specifically, the salt passage increase experienced by FilmTec™ in the first study was 22%, while the membrane from another supplier showed a 73% increase; and in the second study, FilmTec™ had a salt passage increase of 43% while the membrane from the other manufacturer had a 140% salt passage increase. In a 100,000 m3/d desalination plant, this enhanced durability showed by FilmTec™ elements might represent a 5.5% cost of water decrease in the reverse osmosis stage, and total savings of 1.34 US ¢/m3 in the whole plant, which can be translated into savings of 488,000 USD/y. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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5. "I Had to Jump through a Lot of Hoops": How Working Mothers in Student Affairs Navigate Institutional Policies and Student Affairs Norms.
- Author
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McKinnon-Crowley, Saralyn, Bukoski, Beth, Black, Victoria, Burmicky, Jorge, Molina, Veronica, and Chacon, Krysta
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- 2022
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6. Ammonium release via dissolution and biological mineralization of food pellets used in salmon farming.
- Author
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Fernandez, Camila, Rain‐Franco, Angel, Rojas, Claudia, and Molina, Veronica
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BIOMINERALIZATION ,SALMON farming ,AQUACULTURE ,PELLETIZING ,BIOTIC communities ,WATER ,NUTRIENT cycles - Abstract
We studied the input of ammonium coming from the dissolution of food pellets commonly used in salmon farming as well as its potential for mineralization via ammonification and ammonium oxidation by natural bacterioplankton communities. Through experiments in central and southern Chile, we evaluated the potential for photo‐ and bio‐ammonification of food pellets in surface and subsurface waters (30 m depth) using irradiated (PAR + UV; IPS) and non‐irradiated dissolved‐pellet solutions (NIPS). Ammonium release was observed in both IPS and NIPS treatments and occurred at short time scales (<2 hr). Experiments in southern Chile during late winter showed high rates of pellet ammonium release in surface waters (up to 3.8 µmol L−1 min−1) compared with deeper samples (30 m depth). In contrast, in spring higher rates were observed at 30 m depth and reached up to 45 µmol L−1 min−1 while in surface waters they accounted for 9 µmol L−1 min−1. Ammonium oxidizing bacteria and archaea showed seasonal variability, but archaea were detected in all experiments reaching high potential activity, based in RT‐qPCR of functional genes expression copy numbers, in IPS treatments during the winter season in Chiloé. Overall, our results indicate that food pellets can be a source of ammonium, which can exceed by two orders of magnitude the average natural concentrations commonly found in the euphotic layer in coastal environments. The ammonium enrichment from dissolved pellet solutions was rapidly consumed by microbial communities including nitrifying assemblages. This has implications for the evaluation of aquaculture nutrient input and its recycling in the water column in areas highly impacted by climate change and aquaculture pressure. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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7. Adaptive Strategies in a Poly-Extreme Environment: Differentiation of Vegetative Cells in Serratia ureilytica and Resistance to Extreme Conditions.
- Author
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Filippidou, Sevasti, Junier, Thomas, Wunderlin, Tina, Kooli, Wafa M., Palmieri, Ilona, Al-Dourobi, Andrej, Molina, Veronica, Lienhard, Reto, Spangenberg, Jorge E., Johnson, Shannon L., Chain, Patrick S. G., Dorador, Cristina, and Junier, Pilar
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CELL differentiation ,SERRATIA ,BACTERIAL sporulation ,SCANNING electron microscopy ,ULTRAVIOLET radiation ,DORMANCY (Biology) ,MICROBIOLOGY of extreme environments - Abstract
Poly-extreme terrestrial habitats are often used as analogs to extra-terrestrial environments. Understanding the adaptive strategies allowing bacteria to thrive and survive under these conditions could help in our quest for extra-terrestrial planets suitable for life and understanding how life evolved in the harsh early earth conditions. A prime example of such a survival strategy is the modification of vegetative cells into resistant resting structures. These differentiated cells are often observed in response to harsh environmental conditions. The environmental strain (strain Lr5/4) belonging to Serratia ureilytica was isolated from a geothermal spring in Lirima, Atacama Desert, Chile. The Atacama Desert is the driest habitat on Earth and furthermore, due to its high altitude, it is exposed to an increased amount of UV radiation. The geothermal spring from which the strain was isolated is oligotrophic and the temperature of 54°C exceeds mesophilic conditions (15 to 45°C). Although the vegetative cells were tolerant to various environmental insults (desiccation, extreme pH, glycerol), a modified cell type was formed in response to nutrient deprivation, UV radiation and thermal shock. Scanning (SEM) and Transmission Electron Microscopy (TEM) analyses of vegetative cells and the modified cell structures were performed. In SEM, a change toward a circular shape with reduced size was observed. These circular cells possessed what appears as extra coating layers under TEM. The resistance of the modified cells was also investigated, they were resistant to wet heat, UV radiation and desiccation, while vegetative cells did not withstand any of those conditions. A phylogenomic analysis was undertaken to investigate the presence of known genes involved in dormancy in other bacterial clades. Genes related to spore-formation in Myxococcus and Firmicutes were found in S. ureilytica Lr5/4 genome; however, these genes were not enough for a full sporulation pathway that resembles either group. Although, the molecular pathway of cell differentiation in S. ureilytica Lr5/4 is not fully defined, the identified genes may contribute to the modified phenotype in the Serratia genus. Here, we show that a modified cell structure can occur as a response to extremity in a species that was previously not known to deploy this strategy. This strategy may be widely spread in bacteria, but only expressed under poly-extreme environmental conditions. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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8. Self-Care and the Social Worker: Taking Our Place in the Code.
- Author
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Willis, Nicole Gail and Molina, Veronica
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HEALTH self-care ,WELL-being ,CODES of ethics ,SOCIAL workers ,SECONDARY traumatic stress ,STRESS management ,SOCIAL worker & client ,HEALTH ,PSYCHOLOGICAL burnout ,PROFESSIONAL ethics of social workers ,PROFESSIONAL ethics ,SOCIAL services ,PSYCHOLOGICAL stress ,COMPASSION ,PROFESSIONAL practice - Abstract
The article discusses self-care and wellness in relation to the U.S. National Association of Social Workers' "Code of Ethics" which established the roles and responsibilities of social workers. Self-interest is addressed, along with the prevention and management of issues such as stress, burnout, and compassion fatigue in social workers. Secondary traumatization and social worker-client relations are assessed, as well as emotional and physical health.
- Published
- 2019
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9. Nitrogen excretion by copepods and its effect on ammonia‐oxidizing communities from a coastal upwelling zone.
- Author
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Valdés, Valentina, Fernandez, Camila, Molina, Veronica, and Escribano, Rubén
- Subjects
COPEPODA ,NITROGEN ,UPWELLING (Oceanography) ,ZOOPLANKTON ,OXIDATION of ammonia - Abstract
Abstract: The role of zooplankton in microbial nitrogen turnover in marine environments is poorly understood. Here, we present results from two experiments designed to determine the excretion rate of ammonium and dissolved organic nitrogen (DON) by dominant copepods,
Acartia tonsa andParacalanus cfindicus , fed with two natural sized‐fractioned diets (20–150 μm and < 20 μm), and its possible effects on the transcriptional activity of ammonia monooxygenase subunit A (amoA ), a functional marker for ammonia‐oxidizing archaea (AOA) and bacteria (AOB), as a response to the input of ammonium and DON by copepod excretion, during autumn and winter in central/southern Chile. Our results reveal that DON was the main excretion product, with rates up to 3.7 μmol L−1 h−1 . DON production increased in copepods fed with the small‐sized food. Ammonium was also excreted, with rates up to 0.08 μmol L−1 h−1 in autumn and 0.4 μmol L−1 h−1 in winter, and rapidly consumed by the microbial community, decreasing down to 0.07 μmol L−1 between the initial time to 4 h. Ammonium consumption coincided with increased AOB and AOAamoA transcript copies in copepods fed with the larger‐sized food, while a different microbial community, probably heterotrophic, reacted to nitrogen input via excretion by copepods fed with the smaller‐sized food in autumn. AOA‐A was transcriptionally active in winter with nearly zero ammonium concentration, suggesting that AOA outcompete AOB when ammonium becomes limited. We conclude that nitrogen excreted by copepods can be used directly by microbial communities, including nitrifying ones. Zooplankton excretion may thus provide significant remineralized nitrogen for new and regenerated production in the upper ocean. [ABSTRACT FROM AUTHOR]- Published
- 2018
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10. Nitrogen and phosphorus recycling mediated by copepods in Western Tropical South Pacific.
- Author
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Valdés, Valentina, Carlotti, François, Escribano, Ruben, Donoso, Katty, Pagano, Marc, Molina, Veronica, and Fernandez, Camila
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COPEPODA ,NITROGEN & the environment ,PHOSPHORUS & the environment ,FOREST regeneration ,MICROBIAL communities - Abstract
Zooplankton play a key role in the regeneration of nitrogen and phosphorus in the ocean through grazing and metabolism. This study investigates the role of the organic and inorganic nitrogen and phosphorus compounds released by copepods on biogeochemical processes and on the microbial community composition during the OUTPACE cruise (18 February-3 April 2015) at three long duration stations (LD). Two LD stations were located in the Melanesian Archipelago region (MA; LD A and LD B) and one in the South Pacific Gyre (SG; LD C), which represent oligotrophic and ultraoligotrophic regions respectively. At each station, microcosm onboard experiments were performed with locally sampled organisms, comprising a mix of epipelagic copepods fed with their natural food and then incubated along with wild microbial assemblages. In presence of copepods, ammonium and dissolved organic nitrogen showed a significant increase, compared to a control in two situations: in ammonium concentration (increasing rate: 0.29 μmol L
-1 h-1 after 4 h of incubation) in LD C and in dissolved organic nitrogen concentration (rate: 2.13 μmol L-1 h-1 after 0.5 h of incubation) in LD A. In addition, during the three experiments, an enhanced remineralization (ammonification and nitrification) was observed when adding copepods compared to the controls. A shift in the composition of active bacterial community was observed for the experiments in LD A and LD B mainly characterized by an increase in Alteromonadales and SAR11, respectively and linked with changes in nutrient concentrations. In the experiment performed in LD C, both groups increased but at different periods of incubation, Alteromonadales between 1 and 2 h after the beginning of the experiment, and SAR 11 at the end of incubation. Finally, our experimental results in near in situ conditions, show that copepods can be a source of organic and inorganic compounds for bacterial communities, which respond to excretion pulses at different scales, depending on the initial environmental conditions and on their community composition. These processes can contribute significantly to nutrient recycling in the epipelagic ecosystem of ultra and oligotrophic oceanic regions. [ABSTRACT FROM AUTHOR]- Published
- 2018
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11. Bridging Education and Practice With a Competency-Based Learning Contract.
- Author
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Molina, Veronica, Molina-Moore, Tammy, Smith, Misty G., and Pratt, Francine E.
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LEARNING contracts ,GATEKEEPING ,SOCIAL work education ,EDUCATION policy ,OUTCOME-based education - Abstract
Field work programs have a substantial responsibility for providing support and gatekeeping functions while ensuring an educational experience that allows students to master the nine holistic, multidimensional social work accreditation competencies. With additional emphasis on field as a “signature pedagogy,” field directors are tasked with finding placements that can support these explicit competencies. Through the utilization of a learning contract that combines the Council on Social Work Education Educational Policy and Accreditation Standards competencies (including component behaviors) students and supervisors can begin to discuss their joint progress on meeting each of these prior to the final evaluation. This process will ensure that students have demonstrated the necessary outcomes to become a generalist social work practitioner. [ABSTRACT FROM PUBLISHER]
- Published
- 2018
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12. Treatment of oil–water emulsions by adsorption onto resin and activated carbo.
- Author
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Àngels Tejero, Maria dels, Jové, Elbir, Carmona, Patricia, Gomez, Veronica, García-Molina, Veronica, Villa, Javier, and Das, Supriyo
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GRANULATED activated carbon (GAC) ,PETROLEUM waste ,BIOCHEMICAL oxygen demand ,OIL spill cleanup ,ADSORPTION (Chemistry) ,INDUSTRIAL wastes - Abstract
Water is essential in most of the industrial processes in order to guarantee proper production. Minimizing waste is one of the principles behind any circular economy initiative. Typically, industrial waste water contains oil and grease, BTEX (benzene, toluene, ethyl benzene and xylenes), high content in dissolved solids, suspended solids, heavy metals, biological oxygen demand (BOD) and chemical oxygen demand (COD). In order to be discharged or reused, waste water needs to be treated to meet the existing regulations. Emulsified oil in waste water constitutes a severe problem in the different treatment stages before being disposed of in a manner that does not violate environmental criteria. Several technologies are already in place to treat refinery wastewater. One commonly used technique for remediation of petroleum contaminated water is adsorption. The main objective of this study is to examine the removal of oil from oil-water emulsions by adsorption on a Dow resin and activated carbon. Experiments were performed at the Dow Water and Process Solutions (DW & PS) Global Water Technology Center (GWTC) in Tarragona, (Spain) in order to evaluate the removal of hydrocarbons from real oily water samples from a petrochemical company in Spain using DOWEX
TM OPTIPORETM L493 Polymeric Adsorbents and commercial granulated activated carbon. The results showed that the adsorbents were able to remove oil from water and that the adsorptive properties of the adsorbents are influenced by different factors such as contact time, flow rate, etc. Test data showed that OPTIPORE L493 could remove up to 99.7% of the oil-in-water contents consistently at flow rates where activated carbon efficiency had started to decline. The present paper includes the details of the results of this study. [ABSTRACT FROM AUTHOR]- Published
- 2017
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13. Method for distinguishing between abiotic organic and biological fouling of reverse osmosis elements used to treat wastewater.
- Author
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Massons-Gassol, Gerard, Gilabert-Oriol, Guillem, Gomez, Veronica, Garcia-Valls, Ricard, Garcia Molina, Veronica, and Arrowood, Tina
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FOULING ,SEWAGE ,REVERSE osmosis process (Sewage purification) ,REVERSE osmosis - Abstract
Fouling is one of the issues that is hindering the long-term performance of reverse osmosis systems. The aim of this study is to selectively quantify the extracellular polymeric substances (EPS) from the organic substances present in samples of autopsied elements. Samples were collected from elements used to treat wastewater, operated under two different fouling scenarios. In the first, fouling was mainly organic while in the second, biofouling was promoted by dosing nutrients. The overall percent)age of carbohydrates and proteins as organic foulants was quantified. In the first test, the percentage of the foulant consisting of EPS was only 19–34% vs. approximately 100% in the biofouling scenario. At the same time, the increase in the feed-concentrate pressure for the elements after the first test was only 50%, but more than 500% after the second test. This confirms that quantifying the EPS percentage on the foulant can be useful for determining the extent of biofouling versus abiotic organic fouling. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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14. Bacterial Survival under Extreme UV Radiation: A Comparative Proteomics Study of Rhodobacter sp., Isolated from High Altitude Wetlands in Chile.
- Author
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Pérez, Vilma, Hengst, Martha, Kurte, Lenka, Dorador, Cristina, Jeffrey, Wade H., Wattiez, Ruddy, Molina, Veronica, and Matallana-Surget, Sabine
- Subjects
EFFECT of ultraviolet radiation on bacteria ,PROTEOMICS ,RHODOBACTER - Abstract
Salar de Huasco, defined as a polyextreme environment, is a high altitude saline wetland in the Chilean Altiplano (3800 m.a.s.l.), permanently exposed to the highest solar radiation doses registered in the world. We present here the first comparative proteomics study of a photoheterotrophic bacterium, Rhodobacter sp., isolated from this remote and hostile habitat. We developed an innovative experimental approach using different sources of radiation (in situ sunlight and UVB lamps), cut-off filters (Mylar, Lee filters) and a high-throughput, label-free quantitative proteomics method to comprehensively analyze the effect of seven spectral bands on protein regulation. A hierarchical cluster analysis of 40 common proteins revealed that all conditions containing the most damaging UVB radiation induced similar pattern of protein regulation compared with UVA and visible light spectral bands. Moreover, it appeared that the cellular adaptation of Rhodobacter sp. to osmotic stress encountered in the hypersaline environment from which it was originally isolated, might further a higher resistance to damaging UV radiation. Indeed, proteins involved in the synthesis and transport of key osmoprotectants, such as glycine betaine and inositol, were found in very high abundance under UV radiation compared to the dark control, suggesting the function of osmolytes as efficient reactive oxygen scavengers. Our study also revealed a RecA-independent response and a tightly regulated network of protein quality control involving proteases and chaperones to selectively degrade misfolded and/or damaged proteins. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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15. A Combination of Extreme Environmental Conditions Favor the Prevalence of Endospore-Forming Firmicutes.
- Author
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Filippidou, Sevasti, Wunderlin, Tina, Junier, Thomas, Jeanneret, Nicole, Dorador, Cristina, Molina, Veronica, Johnson, David R., and Junier, Pilar
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BACTERIAL spores ,CLOSTRIDIUM ,CHEMOTAXIS - Abstract
Environmental conditions unsuitable for microbial growth are the rule rather than the exception in most habitats. In response to this, microorganisms have developed various strategies to withstand environmental conditions that limit active growth. Endosporeforming Firmicutes (EFF) deploy a myriad of survival strategies in order to resist adverse conditions. Like many bacterial groups, they can form biofilms and detect nutrient scarcity through chemotaxis. Moreover, within this paraphyletic group of Firmicutes, ecophysiological optima are diverse. Nonetheless, a response to adversity that delimits this group is the formation of wet-heat resistant spores. These strategies are energetically demanding and therefore might affect the biological success of EFF. Therefore, we hypothesize that abundance and diversity of EFF should be maximized in those environments in which the benefits of these survival strategies offsets the energetic cost. In order to address this hypothesis, geothermal and mineral springs and drillings were selected because in these environments of steep physicochemical gradients, diversified survival strategies may become a successful strategy.We collected 71 samples from geothermal and mineral environments characterized by none (null), single or multiple limiting environmental factors (temperature, pH, UV radiation, and specific mineral composition). To measure success, we quantified EFF gene copy numbers (GCN; spo0A gene) in relation to total bacterial GCN (16S rRNA gene), as well as the contribution of EFF to community composition. The quantification showed that relative GCN for EFF reached up to 20% at sites characterized by multiple limiting environmental factors, whereas it corresponded to less than 1% at sites with one or no limiting environmental factor. Pyrosequencing of the 16S rRNA gene supports a higher contribution of EFF at sites with multiple limiting factors. Community composition suggested a combination of phylotypes for which active growth could be expected, and phylotypes that are most likely in the state of endospores, in all the sites. In summary, our results suggest that diversified survival strategies, including sporulation and metabolic adaptations, explain the biological success of EFF in geothermal and natural springs, and that multiple extreme environmental factors favor the prevalence of EFF. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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16. Insights into electron leakage in the reaction cycle of cytochrome P450 BM3 revealed by kinetic modeling and mutagenesis.
- Author
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Lim, Joseph B., Barker, Kimberly A., Eller, Kristen A., Jiang, Linda, Molina, Veronica, Saifee, Jessica F., and Sikes, Hadley D.
- Abstract
As a single polypeptide, cytochrome P450 BM3 fuses oxidase and reductase domains and couples each domain's function to perform catalysis with exceptional activity upon binding of substrate for hydroxylation. Mutations introduced into the enzyme to change its substrate specificity often decrease coupling efficiency between the two domains, resulting in unproductive consumption of cofactors and formation of water and/or reactive species. This phenomenon can correlate with leakage, in which P450 BM3 uses electrons from NADPH to reduce oxygen to water and/or reactive species even without bound substrate. The physical basis for leakage is not yet well understood in this particular member of the cytochrome P450 family. To clarify the relationship between leakage and coupling, we used simulations to illustrate how different combinations of kinetic parameters related to substrate-free consumption of NADPH and substrate hydroxylation can lead to either minimal effects on coupling or a dramatic decrease in coupling as a result of leakage. We explored leakage in P450 BM3 by introducing leakage-enhancing mutations and combining these mutations to assess whether doing so increases leakage further. The variants in this study provide evidence that while a transition to high spin may be vital for coupled hydroxylation, it is not required for enhanced leakage; substrate binding and the consequent shift in spin state are not necessary as a redox switch for catalytic oxidation of NADPH. Additionally, the variants in this study suggest a tradeoff between leakage and stability and thus evolvability, as the mutations we investigated were far more deleterious than other mutations that have been used to change substrate specificity. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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17. Backwashing pressurized ultrafiltration using reverse osmosis brine in seawater desalination and its potential costs savings.
- Author
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Gilabert-Oriol, Guillem, Hassan, Mufeed, Dewisme, Javier, Garcia-Molina, Veronica, and Busch, Markus
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REVERSE osmosis (Water purification) ,ULTRAFILTRATION ,ARTIFICIAL membranes ,SALINE water conversion research ,WATER purification - Abstract
This paper discusses the feasibility of using reverse osmosis concentrate to backwash ultrafiltration membranes in the seawater reverse osmosis desalination space. Brine is produced through DOW FILMTEC™ reverse osmosis elements and it backwashed every 90 min to DOW™ ultrafiltration membranes. A side-by-side validation is done for 15 d using two parallel ultrafiltration and reverse osmosis integrated systems. One line uses brine for backwashing, while the other uses conventional filtrated water. The optimization is proven to have the same cleaning efficiency than the conventional backwashing methods and no precipitation is observed in the fibers. An additional validation period that uses reverse osmosis brine during backwashes and only two backwash steps is also carried out successfully. These steps are the previously identified backwash top with air scour and forward flush. Fibers also show an excellent integrity after the whole experimental period. A model is built in order to analyze the backwash efficiency of the optimized conditions and the transmembrane pressure increases during the filtration cycle. The results show the same fouling tendency for the line operating with brine and the line operating with filtrated water. The efficiency of the ultrafiltration process is improved from 88 to 98% thanks to this optimization together with the previous researches. This represents filtrating 96 min extra per day and a reduction of 100% in the filtrated water used during backwashes. The chemical equivalent concentration is also optimized from 0.28 to 0.06 mg/L NaClO thanks to the adjustment of the chemically enhanced backwash frequency. This accounts for a 7.1% savings in the ultrafiltration step and for a 1.2% savings in the whole desalination process. [ABSTRACT FROM PUBLISHER]
- Published
- 2015
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18. The transcriptional regulation of the glyoxylate cycle in SAR11 in response to iron fertilization in the Southern Ocean.
- Author
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Beier, Sara, Gálvez, María J., Molina, Veronica, Sarthou, Géraldine, Quéroué, Fabien, Blain, Stephane, and Obernosterer, Ingrid
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TRICARBOXYLIC acids ,ISOCITRATE lyase ,CHLOROPHYLL in water ,MARINE biology - Abstract
The tricarboxylic acid ( TCA) cycle is a central metabolic pathway that is present in all aerobic organisms and initiates the respiration of organic material. The glyoxylate cycle is a variation of the TCA cycle, where organic material is recycled for subsequent assimilation into cell material instead of being released as carbon dioxide. Despite the importance for the fate of organic matter, the environmental factors that induce the glyoxylate cycle in microbial communities remain poorly understood. In this study, we assessed the expression of isocitrate lyase, the enzyme that induces the switch to the glyoxylate cycle, of the ubiquitous SAR11 clade in response to natural iron fertilization in the Southern Ocean. The cell-specific transcriptional regulation of the glyoxylate cycle, as determined by the ratio between copy numbers of isocitrate lyase gene transcripts and isocitrate genes, was consistently lower in iron fertilized than in high-nutrient, low chlorophyll waters (by 2.4- to 16.5-fold). SAR11 cell-specific isocitrate lyase gene transcription was negatively correlated to chlorophyll a, and bulk bacterial heterotrophic metabolism. We conclude that the glyoxylate cycle is a metabolic strategy for SAR11 that is highly sensitive to the degree of iron and carbon limitation in the marine environment. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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19. Temporal and spatial variability of biological nitrogen fixation off the upwelling system of central Chile (35-38.5° S).
- Author
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Fernandez, Camila, González, Maria Lorena, Muñoz, Claudia, Molina, Veronica, and Farias, Laura
- Published
- 2015
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20. Optimal Inequalities, Contact d-Invariants and Their Applications.
- Author
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BANG-YEN CHEN and MARTIN-MOLINA, VERONICA
- Subjects
MATHEMATICAL inequalities ,CURVATURE ,IMMERSIONS (Mathematics) ,EMBEDDING theorems ,RIEMANNIAN manifolds - Abstract
Associated with a k-tuple (n
1 .,...,nk )∊y (2n+1) with n ≥ 1, we define a contact δ-invariant, δc (n1 ,....nk ), on an almost contact metric (2n+1)-manifold M. For an arbitrary isometric immersion of M into a Riemannian manifold, we establish an optimal inequality involving δc (n1 ,...,nk ) and the squared mean curvature of the immersion. Furthermore, we investigate isometric immersions of contact metric and K-contact manifolds into Riemannian space forms which verify the equality case of the inequality for some k-tuple [ABSTRACT FROM AUTHOR]- Published
- 2013
21. Optimizing seawater operating protocols for pressurized ultrafiltration based on advanced cleaning research.
- Author
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Oriol, Guillem Gilabert, Moosa, Nasir, Garcia-Valls, Ricard, Busch, Markus, and Garcia-Molina, Veronica
- Subjects
ULTRAFILTRATION ,SALINE water conversion research ,ARTIFICIAL membranes ,POLYVINYLIDENE fluoride ,FOULING - Abstract
This paper is part of a global research project conducted by Dow Water & Process Solutions to optimize the efficiency of ultrafiltration processes. After an initial identification of the backwash as the key opportunity to increase the efficiency of the process, a study based on its optimization is developed. Main emphasis is given to the sequence and subsequent number of steps involved in the backwash. The ultimate goal is thus to increase the availability and recovery of the process while still attaining a high cleaning effect during the backwash. This optimization is done through the realization of various experiments using DOW™ Ultrafiltration SFP-2660 outside-in polyvinylidene difluoride (PVDF) membranes following an exhaustively planned factorial design of experiments. The factors being assessed are the steps normally performed during a backwash. These are the air scour (AS/D), the draining (D), the backwash top (BWT) with or without air scour, the backwash bottom (BWB) and the forward flush (FF). The responses analyzed are the calculated efficiency of the process and the experimentally obtained transmembrane pressure, which represents the fouling rate of the membrane. The results are analyzed through a formal statistical study of the analysis of the variance and are validated through 25 days of stable operation. The results show that the backwash can be simplified from an original sequence of five steps to only two steps, which are the backwash top with air scour and the forward flush without impairing the effectiveness of the cleanings. This leads to an increase in efficiency higher than 5%, which represents a decrease of 50% in the filtration inefficiency. This is achieved thanks to the reduction of the time invested for the cleanings and the decrease in the amount of water consumed. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
22. Cost savings by novel seawater reverse osmosis elements and design concepts.
- Author
-
Molina, Veronica Garcia, Busch, Markus, and Sehn, Peter
- Subjects
SEAWATER ,REVERSE osmosis ,COST control ,WATER research ,WATER quality management - Abstract
Desalination market growth has triggered significant development in SWRO membrane and process development and the new extra high rejection and ultra low energy membranes from Dow, FILMTEC™ SW30XHR-400i and SW30ULE-400i, as well as the internally staged design concept, have been validated in extensive field testing and various commercial plants over the recent years and are now commercially available. These solutions from Dow can be used to increase membrane flux and system recovery and / or to reduce feed pressure. This yields capital cost and /or energy savings. These savings have been assessed in 4 different situations / geographies, using a thorough and validated cost model. These geographies are South Pacific (Australia), Persian Gulf (Saudi Arabia), with very different feed water qualities (in terms of feed salinity and temperature range) and product quality requirements (in terms of bromide, boron and salinity). Depending on the cost savings route chosen, there are strong differences in the consequences with regards to size of the RO stage (17-26% smaller), size of the pretreatment (9-12% smaller), and/or the feed pressure (2-6 bar lower). These cost savings are in the range of US cent 0.4-4.1/m³ water produced. This is equivalent to 0.7-6.5% water cost saving. Considering that these considerable cost savings are readily available since 2008 from Dow Water Solutions, the industry should start to significantly benefit from these in the coming years. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
23. CANARY ISLANDS TESTING GROUND FOR RO REVAMP.
- Author
-
Salgado, Blanca, Ortega, Juan Manuel, Blazheska, Jasna, Sanz, Joan, and Garcia-Molina, Veronica
- Published
- 2015
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