54 research outputs found
Analysis of acto-myosin network remodelling: towards a comprehensive understanding of tissue closure events
Land consolidation in the context of Lithuanian rural development and revitalization
This thesis investigates the actual situation in the rural areas of Lithuania, one of the Central and Eastern European countries which, after the collapse of the Soviet regime, started a programme of land reform and today faces problems such as land fragmentation, land abandonment, lack of infrastructure, land conflicts, etc. Such problems affecting sustainable rural development can be solved by applying a land management instrument – land consolidation that has worked successfully for hundreds of years in Western European countries. Since 2000, Lithuania with the support of international land consolidation experts, has dealt with this instrument and supplemented that legal framework in 2004. Unfortunately this instrument still doesn’t assure results compared with Western European countries. In order to identify aspects influencing comprehensive results, an investigation of the legal frameworks regulating land consolidation in six selected European countries was performed by analysing scientific papers, legal acts and interviewing land consolidation experts. Seeking to obtain a comprehensive Lithuanian land consolidation process picture, a case study analysis was applied and interviews with participating land owners and land surveyors as well as the online questionnaire for municipal specialists were performed. Moreover, based on European expert’s practice reflected in the online questionnaire, criteria showing the potential for comprehensive land consolidation in Lithuania (at municipal and project area scale) were developed and techniques based on Multi-Criteria Decision Analysis offered. The most significant part of this thesis is a developed framework for how to reach sustainable rural areas (re)development through land consolidation in Lithuanian and other Central and Eastern European countries. Developed criteria showing the potential for comprehensive land consolidation and framework provides the main original contribution to new knowledge by benefiting policy makers, land management authorities, land surveyors, the academic and professional community and rural communities on both a national and international scale
Decision support framework to rank and prioritise the potential land areas for comprehensive land consolidation
In Europe and often worldwide, national and local government authorities utilise different means to stimulate economic development and environmental protection of the land through the application of land consolidation. The direction of these efforts should take into consideration the fact that some administrative regions may have a higher potential for land consolidation than others. This is supported by the Food and Agriculture Organization of the United Nations (FAO) that advises on the identification of favourable regions for implementation of pilot land consolidation projects. In many European countries, especially those receiving European Union (EU) support for implementation land consolidation projects, the scrupulous allocation of funds to the best suitable regions is very important. The research in this paper identifies a key set of criteria and offers multiple-criteria analysis-based approach to rank and prioritise administrative regions for implementation of land consolidation. This methodology is applied in the case study identifying Klaipeda district as a municipality with the highest potential for land consolidations in the Western part of Lithuania. The proposed framework will enable national and local authorities to identify and prioritise regions for land consolidation in a transparent way ensuring efficient management of resources and fair allocation of financial support
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Stoichiometry of mercury-thiol complexes on bacterial cell envelopes
We have examined the speciation of Hg(II) complexed with intact cell suspensions (1013 cells L− 1) of Bacillus subtilis, a common gram-positive soil bacterium, Shewanella oneidensis MR-1, a facultative gram-negative aquatic organism, and Geobacter sulfurreducens, a gram-negative anaerobic bacterium capable of Hg-methylation at Hg(II) loadings spanning four orders of magnitude (120 nM to 350 μM) at pH 5.5 (± 0.2). The coordination environments of Hg on bacterial cells were analyzed using synchrotron based X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy at the Hg LIII edge. The abundance of thiols on intact cells was determined by a fluorescence-spectroscopy based method using a soluble bromobimane, monobromo(trimethylammonio)bimane (qBBr) to block thiol sites, and potentiometric titrations of biomass with and without qBBr treatment. The chemical forms of S on intact bacterial cells were determined using S k-edge XANES spectroscopy. Hg(II) was found to complex entirely with cell bound thiols at low Hg:biomass ratios. For Bacillus subtilis and Shewanella oneidensis MR-1 cells, the Hg—S stoichiometry changed from Hg—S₃ to Hg—S₂ and Hg—S (where ‘S’ represents a thiol site such as is present on cysteine) progressively as the Hg(II) loading increased on the cells. However, Geobacter sulfurreducens did not form Hg—S₃ complexes. Because the abundance of thiol was highest for Geobacter sulfurreducens (75 μM/g wet weight) followed by Shewanella oneidensis MR-1 (50 μM/g wet weight) and Bacillus subtilis (25 μM/g wet weight), the inability of Hg(II) to form Hg—S₃ complexes on Geobacter sulfurreducens suggests that the density and reactivity of S-amino acid containing cell membrane proteins on Geobacter sulfurreducens are different from those of Bacillus subtilis and Shewanella oneidensis MR-1. Upon saturation of the high affinity thiol sites at higher Hg:biomass ratios, Hg(II) was found to form a chelate with α-hydroxy carboxylate anion. The stoichiometry of cell envelope bound Hg-thiol complexes and the associated abundance of thiols on the cell envelopes provide important insights for understanding the differences in the rate and extent of uptake and redox transformations of Hg in the environment
Public Challenges, Private Solutions: Defining the Link between Private Military Companies and Democracies
In March of 2004, four armed Americans were killed during an ambush in\ud
Fallujah. Their bodies were dragged from their car, burned and strung up on a bridge over the Euphrates. The images of this horrific scene that were beamed around the world prompted the US invade the city four days later (Frontline 2005). However, these men\ud
were not soldiers, they were private military contractors working for the firm Blackwater\ud
USA. This gruesome event brought private military companies (PMCs) to the attention of the American public almost overnight. Private military companies are playing a larger role in war now than they ever have before. There are at least 50 different companies, employing over 30,000 employees that operate in Iraq (Elsea 2007, 3). While Iraq is\ud
perhaps one of the most visible cases, it is but one of many examples of PMCs providing military services for profit.\ud
Private military companies are one of the most important and yet least studied changes in international security studies in the last decade. The private military industry has seen tremendous growth in the last two decades. PMCs have now operated on every continent except for Antarctica (Singer 2003, 9). The industry has grown to be worth over\ud
$100 billion a year (War on Want 2006, 2). PMCs offer military services to governments,\ud
multinational corporations and international aid organizations. These services include military training and advice, arms procurement, security audits, site protection,\ud
intelligence analysis, maintenance and logistical support, among others. Some PMCs have openly conducted military operations on behalf of host governments, and even the US is increasingly using PMCs in roles that include a significant risk of combat. What accounts for this growth? There are a number of reasons are presented. Some argue that the structural changes after the Cold War are to blame. These changes include the massive troop demobilizations that occurred after Soviet Union fell, and the\ud
non-state and intrastate violence that filled the vacuum left by the Cold War's end. Other\ud
argues that PMCs allow leaders to use force without the political fallout associated with\ud
deploying uniformed troops. PMCs can act as proxies for troops when intervention is\ud
unpopular. Still others assert that the recent growth in the private military industry is\ud
merely the extension of the global phenomenon of outsourcing. More interesting of a question is why developed democracies represent the bulk of PMCs' clients? Some of the world's strong nations are the biggest consumers of private military services. Thus the\ud
question that this project endeavors to answer is: why do developed democracies with\ud
modern professional armies use PMCs? In this study I will analyze two competing explanations for why democratic states\ud
have turned to PMCs. The first argues that the extensive spread of neoliberal economics,\ud
outsourcing and privatization has resulted in states turning to PMCs to solve security challenges. The second explanation asserts that states will turn to PMCs when faced with economic, structural and political constraints on its military apparatus.\ud
To analyze these hypotheses I will examine three cases studies, the United States, United Kingdom and a group of European peer states. In each case I will evaluate the level of PMC use, pro-market sentiment and domestic constraints. From this data I intend\ud
to show that the level of domestic constraints that a state faces provides the best explanation of what motivate a state's political and military leaders to outsource military roles to the private sector. Before tackling the question at hand, it is important to note the history of privatized violence
Magnetic tweezers optimized to exert high forces over extended distances from the magnet in multicellular systems
Magnetic tweezers are mainly divided into two classes depending on the ability of applying torque or forces to the magnetic probe. We focused on the second category and designed a device composed by a single electromagnet equipped with a core having a special asymmetric profile to exert forces as large as 230 pN–2.8 μm Dynabeads at distances in excess of 100 μm from the magnetic tip. Compared to existing solutions our magnetic tweezers overcome important limitations, opening new experimental paths for the study of a wide range of materials in a variety of biophysical research settings. We discuss the benefits and drawbacks of different magnet core characteristics, which led us to design the current core profile. To demonstrate the usefulness of our magnetic tweezers, we determined the microrheological properties inside embryos of Drosophila melanogaster during the syncytial stage. Measurements in different locations along the dorsal-ventral axis of the embryos showed little variation, with a slight increase in cytoplasm viscosity at the periphery of the embryos. The mean cytoplasm viscosity we obtain by active force exertion inside the embryos is comparable to that determined passively using high-speed video microrheology
Force measurements of Myosin II waves at the yolk surface during Drosophila dorsal closure
The mechanical properties and the forces involved during tissue morphogenesis have been the focus of much research in the last years. Absolute values of forces during tissue closure events have not yet been measured. This is also true for a common force-producing mechanism involving Myosin II waves that results in pulsed cell surface contractions. Our patented magnetic tweezer, CAARMA, integrated into a spinning disk confocal microscope, provides a powerful explorative tool for quantitatively measuring forces during tissue morphogenesis. Here, we used this tool to quantify the in vivo force production of Myosin II waves that we observed at the dorsal surface of the yolk cell in stage 13 Drosophila melanogaster embryos. In addition to providing for the first time to our knowledge quantitative values on an active Myosin-driven force, we elucidated the dynamics of the Myosin II waves by measuring their periodicity in both absence and presence of external perturbations, and we characterized the mechanical properties of the dorsal yolk cell surface
Quantitative analysis of cytoskeletal reorganization during epithelial tissue sealing by large-volume electron tomography
The closure of epidermal openings is an essential biological process that causes major developmental problems such as spina bifida in humans if it goes awry. At present, the mechanism of closure remains elusive. Therefore, we reconstructed a model closure event, dorsal closure in fly embryos, by large-volume correlative electron tomography. We present a comprehensive, quantitative analysis of the cytoskeletal reorganization, enabling separated epidermal cells to seal the epithelium. After establishing contact through actin-driven exploratory filopodia, cells use a single lamella to generate ‘roof tile’-like overlaps. These shorten to produce the force, ‘zipping’ the tissue closed. The shortening overlaps lack detectable actin filament ensembles but are crowded with microtubules. Cortical accumulation of shrinking microtubule ends suggests a force generation mechanism in which cortical motors pull on microtubule ends as for mitotic spindle positioning. In addition, microtubules orient filopodia and lamellae before zipping. Our 4D electron microscopy picture describes an entire developmental process and provides fundamental insight into epidermal closure
Land Consolidation as an Instrument of Shaping the Agrarian Structure in Poland: A Case Study of the Wielkopolskie and Dolnośląskie Voivodeships
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