• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 4
  • 1
  • Tagged with
  • 7
  • 4
  • 4
  • 3
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The role of B1 in the dual nature of ARS in Saccharomyces cerevisiae

Chisamore-Robert, Patricia 16 February 2012 (has links)
In Saccharomyces cerevisiae, DNA replication initiates at distinct origins termed Autonomously Replicating Sequences (ARSs). A key element in ARS is the ACS/B1 sequence, which binds the Origin Recognition Complex (ORC). During early G1 phase, the pre-replication complex is assembled by ORC. These ARSs are termed replicators. In yeast, ORC is also involved in gene silencing. These loci also contain an ACS/B1 element; however at these positions ORC recruits the silencing SIR complex. ARSs found here are termed silencers. Therefore, ARSs have a dual function. Research has also shown that origin ARSs can be substituted for silencing ARSs and vice versa. Since a mutation in ACS abolishes replication activity, studies have turned to the B1 element to account for the functional duality, but results have been mixed. I hypothesize that the B1 element plays a key role in the dual nature of ARS. To test this hypothesis, silencer and replicator ARSs were subjected to site directed mutagenesis around the WTW motif of the B1 element. Their efficiency was then tested using routine silencing and replication assays. Results reveal that the silencing ability of silencer ARSs is unaffected by these mutations; however mutations within and around the WTW motif reduce silencing efficiency of replicator ARSs. Sequence alignments have also shown that silencer ARSs have a broader WTW consensus than replicator ARSs. Preliminary replication assays are consistent with the above results and other research, contributing to a conclusion that the B1 element is not the sole determining factor in the dual nature of ARS. / NSERC
2

The standardization of major Well-to-Wheel models : measuring uncertainty on a macro level

El-Houjeiri, Hassan M. January 2011 (has links)
This project concentrated upon the development of the Standardization Transport Model (STM) by assembling the largest possible assessment platform. It combines data from all of the major Well-to-Wheel (WtW) models in the field. The STM was developed for each chain under study by formulating the data in the major databases so that the Well-to-Tank processes covered Feedstock Production, Feedstock Transport, Fuel Production and Fuel Distribution. With the addition of Tank-to-Wheel data, a comprehensive STM was obtained for each chain. For each stage there is a range of values that was characterized by a probability distribution and through the use of Monte Carlo simulation the distribution was sampled and overall values for the total energy consumption, in MJ/km, and total GHG emissions in grams of carbon dioxide equivalent per kilometre (gCO2eq/km) were generated. By statistical means these distributions were compared to assess the risk of debt as well as the likelihood of major savings if they were to be implemented. The scope of the analysis was limited to passenger cars transport and does not include other forms of road transport. Major classic WtW models may account for subjective uncertainty in the input parameters of the model but with a default set of inputs which represents only one database and one set of modelling assumptions and choices. This individualism and determinism in the WtW modelling nowadays explains the significant discrepancies that arise across the results from different models. The level of variation presented poses a major problem in the context of policy making and strategic planning. The generation of the STM rests upon the convection that a synthesis which generates a statistically relevant aggregate of the different WtW results from the different models of the major expert groups would eliminate the present inconsistencies and deliver the reliability required for making robust strategic decisions. Advantage was taken of the richness of the STM outputs to assess the sensitivity of the results and identify the major factors of disagreement within the expert systems. Here the STM presents the largest platform of comparison and the most comprehensive evaluation of the different WtW models in the field. The provision of such a sensitivity analysis was not possible without allowing for variation in the elements of the model as done using the STM. Secondly, the key outputs of the model were compared under the criterion of sustainability from both energy and environmental perspectives. This was done by the synthesis of a first-of-its-kind distribution of the difference between the conventional system and the alternative system for each option under study. The output reflects as complete a population as possible of what may occur in reality in terms of direct impact on sustainability. This method of comparison was not possible without synthesizing an aggregate of possibilities as done using the STM. Thirdly, synergies with the power sector were studied to identify which strategies delay the global reduction in GHG emissions and which are to be preferred from an overall perspective. Here the author lead the transport research community in looking on the global benefits of alternative transport systems, rather than only looking through the window of the transport sector, by redrawing the boundary for the analysis of prospective transport systems. Last and not least, the outcomes of the comparative analyses of the STM results were aggregated into a proposed strategic framework for carbon and energy reduction in passenger cars transport. The strategic framework is placed into perspective by building a set of future scenarios and scaling the effect for the progressive implementation of these scenarios and making a comparison with the business-as-usual forecast. The creation of an energy economy based on hydrogen fuel was found to be a highly questionable objective because electrically driven vehicles are superior with regard to systems that are either nuclear resourced or based on non-biomass renewables. For hydrogen, only the option from waste wood via gasification was found to be very attractive. However because only a minor role for hydrogen is foreseen, it is envisaged that the development of a hydrogen infrastructure would not be feasible. Therefore the use of hydrogen will be constrained to decentral systems or central systems with liquid hydrogen distribution. With regard to cultivated biomass, the sugar ethanol options are the best in terms of land use with sugarcane having the advantage of being economic and available for short-term penetration. The safe implementation of sugar ethanol, which includes avoidance of CO₂ emissions from indirect land use change and low fertilizers use, guarantees significant savings and have a good potential for large CO₂ emissions savings. Generally due to land use limitation cultivated biomass based options cannot be sustained on the long term. Last and not least, the CO2 emissions savings from clean coal technology is questionable without CCS technology and even though with the implementation of CCS no significant savings are certain. On the other hand, besides the transport sector the power sector is another major sector of energy resource consumption and careful consideration of any synergies between the sectors is essential for the completeness of the analysis. The strategy in which the use of alternatives such as NG, nuclear and renewables is not diversified but fed only into the power sector is to be preferred as this avoids possible CO₂ emissions from indirect resource use change, and it also isolates the power market to maintain upstream energy security. Finally, the answer to whether it is still possible to save the World from the disastrous consequences of Global Warming is a preliminary "yes" but requires the development and implementation of a complete technology package including nuclear power which is widely debated at the present.
3

ABC County’s Welfare-to-Work (WTW) Program Participation Rate

Banuelos, Alberto 01 January 2020 (has links)
Welfare-to-work (WTW) programs are an essential part of societal assistance made available to families in need. In ABC County, CA, problems have been found with the implementation and success rates of their WTW program: Temporary Assistance to Needy Families (TANF). Even with funds allotted for the program, ABC County has not been able to design a WTW program that meets the TANF program work participation requirement of 50% of active TANF recipients in a WTW activity. The purpose of this study was to address this need as it related to the TANF program specifically. A qualitative, exploratory, single case study was used to explore how TANF personnel interacted with TANF recipients and how that interaction influenced recipients’ decision to participate in this WTW program. Data was collected from 12 TANF workers using semi-structured interviews, observation sessions, and document reviews. The results of this study indicated that the most relevant strategies TANF eligibility staff could use when interacting with TANF recipients were: cultural sensitivity, motivating, providing information, and empathizing. Shortcomings that were identified and that still need to be addressed and improved upon were communication skills, a general lack of encouragement, judgmental behavior, and personal insecurities. In terms of TANF staff perceptions regarding their influence on client decisions to participate in the program, there were mixed results. Seven study participants believed that they had an influence on client participation in this WTW program while the rest of the participants disagreed with this statement for various reasons. As a result of this research, potential social implications include the improvement of the TANF program overall and an increase in the participation rate of the beneficiaries within the program.
4

Energy consumption and GHG emissions evaluation of conventional and battery-electric refuse collection trucks

Derakhshan, Rojin 09 December 2019 (has links)
The notorious fuel consumption and environmental impact of conventional diesel refuse collection trucks (D-RCTs) encourage collection fleets to adopt alternative technologies with higher efficiency and lower emissions/noise impacts into their fleets. Due to the nature of refuse trucks’ duty cycles with low driving speeds, frequent braking and high idling time, a battery-electric refuse collection truck (BE-RCT) seems a promising alternative, taking advantage of energy-saving potentials along with zero tailpipe emissions. However, whether or not this newly-introduced technology can be commercially feasible for a collection fleet and/or additionally mitigate GHG emissions should be examined over its lifetime explicitly for the specific fleet. This study evaluates the performance of a D-RCT and BE-RCT in a collection fleet to assess the potential of BE-RCT in reducing diesel fuel consumption and the total GHG emissions. A refuse truck duty cycle (RTDC) was generated representing the driving nature and vocational operation of the refuse truck, including the speed, mass, and hydraulic cycles along with the extracted route grade profile. As a case study, the in-use data of a collection fleet, operating in the municipality of Saanich, British Columbia (BC), Canada, are applied to develop the representative duty cycle. Using the ADVISOR simulator, the D-RCT and BE-RCT are modeled and energy consumption of the trucks are estimated over the representative duty cycle. Fuel-based Well-to-Wheel (WTW) GHG emissions of the trucks are estimated considering the fuel (diesel/electricity) upstream and downstream GHG emissions over the 100-year horizon impact factor for greenhouse gases. The results showed that the BE-RCT reduces energy use by 77.7% and WTW GHG emissions by 98% compared to the D-RCT, taking advantage of the clean grid power in BC. Also, it was indicated that minimum battery capacity of 220 kWh is required for the BE-RCT to meet the duty cycle requirements for the examined fleet. A sensitivity analysis has been done to investigate the impact of key parameters on energy use and corresponding GHG emissions of the trucks. Further, the lifetime total cost of ownership (TCO) for both trucks was estimated to assess the financial competitiveness of the BE-RCT over the D-RCT. The TCO indicated that the BE-RCT deployment is not financially viable for the examined fleet unless there are considerable incentives towards the purchase cost of the BE-RCT and/or sufficient increase in carbon tax/diesel fuel price. From the energy useevaluation, this study estimates the required battery capacity of the BE-RCT for the studied fleet, and the TCO outputs can assist them in future planning for the adoption of battery-electric refuse trucks into their collection fleet where the cost parameters evolve. / Graduate
5

Modeling sustainability in complex urban transportation systems

Azevedo, Kyle Kellogg 30 August 2010 (has links)
This thesis proposes a framework to design and analyze sustainability within complex urban transportation systems. Urban transit systems have large variability in temporal and spatial resolution, and are common in lifecycle analyses and sustainability studies. Unlike analyses with smaller scope or broader resolution, these systems are composed of numerous interacting layers, each intricate enough to be a complete system on its own. In addition, detailed interaction with the system environment is often not accounted for in lifecycle studies, despite its strong potential effects on the problem domain. To manage such complexity, this thesis suggests a methodology that focuses on integrating existing modeling constructs in a transparent manner, and capturing structural and functional relationships for efficient model reuse. The Systems Modeling Language (OMG SysML ) is used to formally implement the modeling framework. To demonstrate the method, it is applied to a large scale multi-modal transportation network. Analysis of key network parameters such as emissions output, well-to-wheel energy use, and system capacity are presented in a case study of the Atlanta, Georgia metropolitan area. Results of the case study highlight several areas that differ from more traditional lifecycle analysis research. External influences such as regional electricity generation are found to have extremely large effects on environmental impact of a regional mobility system. The model is used to evaluate various future scenarios and finds that existing policy measures for curbing energy use and emissions are insufficient for reducing impact in a growing urban region.
6

Konsekvenser av vätgasproduktion för fordonsdrift : klimatpåverkan och energieffektivitet för olika produktionsvägar för vätgas jämfört med fordonsgas och vindkraftsel producerat av energibolag i Östergötland / Consequenses for hydrogen production for vehicles : climate influence and energy efficiency for different hydrogen production pathways compared with biogas and electricity from windmills produced by an energy company in Östergötland

Lilja, Dennis January 2019 (has links)
Sedan 2016 har flera politiska incitament genomförts för att undersöka möjligheten för att få den nordiska vätgasmarknaden att växa. Vätgas är en energibärare med potential att användas som ett miljövänligt drivmedelsalternativ för transportflottan eftersom utsläppen vid användning med bränslecell är rent vatten och bränslecellsbilar har en hög energieffektivitet i jämförelse med bilar med traditionella förbränningsmotorer. De enda utsläppen som förknippas med vätgas är de som sker i samband med produktionen av gasen. Det finns flera olika sätt att producera vätgas ur olika substrat. Idag produceras den mesta vätgasen från naturgas på raffinaderier för användning i bensin- och dieselproduktion. Det planeras en expansion av tankstationer för vätgas i Sverige, men då det finns få producenter så finns det ett intresse för Tekniska verken i Linköping AB att undersöka vad olika produktionsvägar för vätgas har för fördelar och nackdelar i jämförelse med andra biodrivmedel som fordonsgas och elektricitet. Studiens syfte var att undersöka tekniskt lämpliga produktionsvägar för vätgas som är kompatibla med biogasproduktion eller vindkraftsel, och jämföra de olika produktionsvägarna med biogas och vindkraftsel i relation till klimatpåverkan och energieffektivitet då drivmedel för 100 km körsträcka produceras. Efter en teknisk screening av vätgasproduktion, biogasproduktion och elektricitet från vindkraft konstanterades att vätgasproduktion viaångreformering av biogas, tvåstegsrötning av organiskt avfall och PEM-elektrolys är de produktionsvägar som har bäst potential för miljövänlig vätgasproduktion hos Tekniska verken i Linköping AB. Vidare kartlades viktiga parametrar för modellering och simulering av klimatpåverkan i programvaran simaPro. För jämförelse av produktionsvägarna för vätgas från rötning av matavfall användes WTW-metodik. För jämförelsen mellan elektricitet och elektrolys användes modifierad LCA-metodik med klimatpåverkan för hela livscykeln för vindkraftverket men för resterande processteg användes endast klimatpåverkan för driften för produktionen. Resultaten för jämförelsen mellan produktion av biogas, ångreformering och tvåstegsrötning visar ingen tydlig skillnad i varken klimatpåverkan eller energieffektivitet. Studien påvisar däremot att ångreformering av fordonsgas behöver mindre mängd matavfall för produktion av drivmedel för 100 km körsträcka (38 kg/100km) i jämförelse med tvåstegsrötning (44 kg/100km) och biogas (54 kg/100 km). För jämförelsen mellan produktion av vätgas via elektrolys och vindkraftsel visades systemet för vindkraftsel (23,6 kWh/100 km) vara dubbelt så energieffektivt jämfört med systemet för elektrolys (50,9 kWh/100 km), medan systemens klimatpåverkan förhöll sig till en liknande ratio med 0,154 kg CO2-eq utsläpp/100 km i jämförelse med 0,343 kg CO2-eq utsläpp/100 km. Studien visar att vid analys av energieffektivitet och klimatpåverkan för närbesläktade produktionssystem så spelar energieffektiviteten i använd bil stor roll för resultatet. Studiens resultat är framförallt intressant för svenska energibolag som vill veta mer om vätgasproduktion och hur dess klimatnytta och energiproduktion förhåller sig till andra fossilfria drivmedel.
7

Electricity carbon intensity in European Member States: Impacts on GHG emissions of electric vehicles

Moro, Alberto, Lonza, Laura 21 December 2020 (has links)
The Well-To-Wheels (WTW) methodology is widely used for policy making in the transportation sector. In this paper updated WTW calculations are provided, relying on 2013 statistic data, for the carbon intensity (CI) of the European electricity mix; detail is provided for electricity consumed in each EU Member State (MS). An interesting aspect presented is the calculation of the GHG content of electricity traded between Countries, affecting the carbon intensity of the electricity consumed at national level. The amount and CI of imported electricity is a key aspect: a Country importing electricity from another Country with a lower CI of electricity will lower, after the trade, its electricity CI, while importing electricity from a Country with a higher CI will raise the CI of the importing Country. In average, the CI of electricity used in EU at low voltage in 2013 was 447 gCO2eq/kWh, which is the 17% less compared to 2009. Then, some examples of calculation of GHG emissions from the use of electric vehicles (EVs) compared to internal combustion engine vehicles are provided. The use of EVs instead of gasoline vehicles can save (about 60% of) GHG in all or in most of the EU MSs, depending on the estimated consumption of EVs. Compared with diesel, EVs show average GHG savings of around 50% and not savings at all in some EU MS.

Page generated in 0.0443 seconds