Formation damage is a common problem in petroleum reservoirs and happens in different stages of reservoir development from drilling to production. The causes of formation damage include particle invasion, formation fines migration, chemical precipitation, and pore deformation or collapse. Formation damage adversely affects productivity of wells by reducing the permeability of near wellbore region. Furthermore, formation damage also affects well logging results. Therefore, understanding the mechanism of formation damage is vital to predict the extent and severity of formation damage and to control it. This thesis is focused on the study of formation damage caused by external particle invasion. A simplified numerical method based on a commercial code PFC (Particle Flow Code) is proposed to simulate the particle invasion process. The fluid-particle interaction is simplified as hydrodynamic drag forces acted on particles by fluids; the particle-grain interaction is modeled as two rigid balls on contact. Furthermore, an pore network flow model is developed in this study to estimate permeability of damaged formations, which contain two well-separated particle sizes. The effects of the particle size and the initial formation porosity on formation damage are studied in detail. Our study shows that big particles tend to occupy the formation face, while small particles invade deep into the formation. Moreover, particles which are smaller than pore throats (entrances) impair permeability more than those bigger than pore throats. Our study also indicates that a higher initial formation porosity results in more particle invasion and permeability impairment. It is suggested that, in order to reduce formation damage, mud particle size distributions should be carefully selected according to given formation properties. Although our model has some limitations, it may serve as a tool to predict formation damage according to given parameters, and to understand the mechanism of formation damage from a micro-scopic point of view. / text

This dissertation presents four microbial microcosm-based experimental studies addressing questions related to the causes and consequences of biodiversity. All four studies adopted an approach that integrates ecology and evolutionary biology. Two studies explored the utility of knowledge on species phylogenetic relationships for understanding community assembly (chapter 1) and invasibility (chapter 3). The other two studies investigated the impacts of important ecological factors, including competition (chapter 2) and temporal niches (chapter 4), on adaptive radiation, using the rapidly diversifying bacterium Pseudomonas fluorescens SBW25 as the model organism. The first study, described in Chapter 1, examined how phylogenetic relatedness between competing species affected the strength of priority effects and ecosystem functioning during community assembly. Strong priority effects emerged only when competing bacterial species were phylogenetically most closely related, resulting in multiple community states associated with different assembly histories. In addition, the phylogenetic diversity of bacterial communities effectively predicted bacterial production and decomposition. The second study, described in Chapter 2, explored the role of competition in the adaptive radiation of P. fluorescens. The adaptive radiation was generally suppressed by competition, but its effect was strongly modulated by the phylogenetic relatedness between the diversifying and competing species and their immigration history. The inhibitive effect of competition on adaptive radiation was strongest when phylogenetic relatedness was high and when competitors were introduced earlier. The third study, described in Chapter 3, evaluated the relative importance of phylogenetic relatedness between resident and invading species and phylogenetic diversity of resident communities for invasibility. Laboratory bacterial communities containing a constant number of resident species with varying phylogenetic diversity and relatedness to invaders were challenged by nonresident bacterial species. Whereas invader abundance decreased as phylogenetic relatedness increased as predicted by Darwin's naturalization hypothesis, it was unaffected by phylogenetic diversity. The final study, described in Chapter 4, presented the first experimental demonstration of the maintenance of biodiversity that emerged from adaptive radiation in the presence of temporal niches. Only when provided with temporal niche opportunities were multiple derived phenotypes of P. fluorescens able to coexist as a result of negative frequency-dependent selection. When temporal niche was absent, the specialized phenotypes either did not emerge or were predominated by one superior phenotype.

No description available.

Der Anteil an nicht-einheimischen Pflanzenarten (Neophyten), die durch menschlichen Einfluss in neue Gebiete eingebracht worden sind, hat in den letzten zwei Jahrhunderten deutlich zugenommen. Weltweit gefährdet die Invasion von Neophyten beträchtlich die einheimische Biodiversität und Ökosystemfunktionen. Verschiedene biologische Eigenschaften (z.B. hohe Zuwachsrate und schnelle Vermehrung) führen zu einer besseren Konkurrenzfähigkeit von invasiven Arten und verursachen Veränderungen in der natürlichen Artzusammensetzung. Eine genauere Erfassung der Eigenschaften, die Neophyten zu starken Konkurrenten machen, könnte dabei helfen pflanzliche Invasionen besser zu verstehen und zukünftig effektiver zu steuern. Topfversuche ermöglichen die Untersuchung von Pflanzeninteraktionen unter kontrollierten Bedingungen ohne den schwer kalkulierbaren Einfluss heterogener Umweltfaktoren. Allerdings führen die Langlebigkeit und die größeren Dimensionen von Baumindividuen zu mehr Problemen in Topfversuchen im Vergleich zur Untersuchung krautiger Pflanzen. Aus diesem Grund wurde im Rahmen eines Reviews Literatur ausgewertet, um einen Überblick über die praktische Durchführung von Topfversuchen, die sich ausschließlich mit Baumarten beschäftigen, zu geben. Es ist offensichtlich, dass der Vorteil von Topfversuchen zugleich auch einen Nachteil darstellt: Aufgrund der kontrollierten Bedingungen sind Topfversuche in ihrer Eignung natürliche Gegebenheiten zu imitieren immer eingeschränkt. Die Zuverlässigkeit von Topfversuchen bei der Vorhersage des Baumwachstums unter natürlichen Bedingungen ist daher problematisch. Eine Möglichkeit um die Übertragbarkeit von Topfversuchen zu verbessern, könnte die Durchführung zusätzlicher Felduntersuchungen sein. In einem Topfversuch wurden die, durch Unterschiede in der Wuchsrate, Biomasseproduktion und Biomasseverteilung bedingten, Konkurrenzmechanismen von zwei einheimischen (Quercus robur L., Carpinus betulus L.) und zwei nicht-einheimischen Baumarten untersucht (Prunus serotina Ehrh., Robinia pseudoacacia L.). Einjährige Jungpflanzen wurden verschiedenen intra- und interspezifischen Konkurrenzbedingungen ausgesetzt, mit oder ohne den Einfluss von Wurzelkonkurrenz. Um die Konkurrenzmechanismen genauer zu bestimmen, wurde zwischen Wurzel- und Sprosskonkurrenz unterschieden, indem entweder ober- oder unterirdische Plastiktrennwände in die Töpfe integriert wurden. Es wurde angenommen, dass die Gesamtbiomasseproduktion der Neophyten im Vergleich zur Biomasseproduktion der einheimischen Baumarten signifikant höher ist und dies zu einer Verringerung der Biomasse von Q. robur und C. betulus führt. Des Weiteren wurde der Einfluss der unterirdischen Konkurrenz auf das Wachstum und die Biomasseverteilung der einheimischen Arten gemäß der ‚balanced-growth hypothesis‘ untersucht. Unsere Ergebnisse bestätigen die Annahmen, dass die Biomasseproduktion der beiden Neophyten P. serotina und R. pseudoacacia signifikant höher ist und dies zu einem großen Konkurrenzvorteil und zu einer Biomassereduktion der beigemischten konkurrenzschwächeren einheimischen Arten führt. Der Konkurrenzdruck auf Q. robur und C. betulus wurde vor allem durch die Wurzelkonkurrenz der nicht-einheimischen Arten verursacht. Die Ausschaltung von unterirdischen Pflanzeninteraktionen durch Trennwände führte somit zu einem Anstieg der Biomasseproduktion der beiden einheimischen Arten. Demzufolge scheint sogar ein begrenztes Wurzelvolumen bessere Wachstumsbedingungen zu bieten als direkter Wurzelkontakt mit invasiven Konkurrenten. In Übereinstimmung mit der ‚balanced-growth hypothesis‘ reagieren Q. robur und C. betulus auf die starke unterirdische Konkurrenz durch die Neophyten, indem sie mehr Biomasse in Richtung der Wurzeln transportieren. Die verstärkte Investition der Pflanzen in die Wurzeln geht vor allem zu Lasten von Blatt- und Astbiomasse. Außerdem hat sich gezeigt, dass Artenmischungen aus einheimischen und nicht-einheimischen Bäumen mehr Biomasse produzieren, als man anhand des Wachstums dieser Arten in Monokulturen erwartet hätte. Im Vergleich zu Monokulturen oder Mischungen beider Neophyten war der Konkurrenzdruck für P. serotina und R. pseudoacacia in Mischungen mit den weniger produktiven einheimischen Baumarten geringer. Bei Betrachtung der beiden nicht-einheimischen Arten wird deutlich, dass P. serotina signifikant mehr Biomasse produziert. Trotzdem hat R. pseudoacacia aufgrund der starken Wurzelkonkurrenz einen negativen Einfluss auf die Biomasseproduktion von P. serotina. Wachsen die beiden konkurrenzstarken Neophyten zusammen in einem Topf, produzieren sie weniger Biomasse als in den entsprechenden Monokulturen. Es gibt Anzeichen dafür, dass die starke Konkurrenzfähigkeit der invasiven Neophyten oftmals zu Lasten ihrer Stresstoleranz geht. Damit einhergehend zeigten die beiden nicht-einheimischen Arten im Topfversuch eine höhere Mortalitätsrate: Vor allem P. serotina scheint zudem empfindlich gegenüber Schatten, Trockenheit und Überflutung zu sein. Möglicherweise könnte diese Schwachstelle der Neophyten genutzt werden, um eine weitere Ausbreitung einzudämmen.

Ovarian cancer is a fatal disease because of the lack of symptoms and markers for early detection. Most ovarian neoplasms resemble and are classified according to the complex characteristics of Mullerian duct epithelia. We tested the hypothesis that Mullerian epithelial characteristics influence early ovarian neoplastic progression. The most common type of ovarian cancer is the serous carcinoma which resembles Mullerian-derived oviductal epithelium. We discovered that oviduct-specific glycoprotein (OVGP1), a tubal differentiation marker, was present in inclusion cysts, which are the preferential sites for malignant transformation, and in most low grade serous tumors, but absent in ovarian surface epithelium and most high grade carcinomas. OVGP1 was almost entirely limited to ovarian neoplasms with the notable exception of endometrial hyperplasia and carcinoma. A new antibody against OVGP1 detected elevated serum levels from most women with low grade ovarian cancers compared to normal controls. OVGP1 also identified a subset of patients with high grade serous carcinomas who had a more favorable outcome. To examine whether the differentiated phenotype of early ovarian neoplasms alters invasiveness, we established the first permanent cell line for serous borderline ovarian tumors (SBOT), which are differentiated but noninvasive. The results revealed a striking phenotypic similarity between two lines regardless of their cytogenetic diversity. They retained Mullerian epithelial characteristics in vitro, as demonstrated by their morphologic appearance and the differentiation markers keratin, E-cadherin, CA125 and OVGP1. Neither disruption of the growth pattern nor manipulations of the cadherin profile induced invasivenesss. Induction of invasiveness by SV40 early genes was associated with a loss in morphologic differentiation and of differentiation markers but increased motility. MMP secretion was independent of the invasion status. Our findings indicate that OVGP1 is an indicator of early ovarian epithelial neoplasia. It can be detected in the sera from women with early ovarian cancer, and thus, may be a new promising diagnostic marker for the early detection of ovarian cancer. In addition, the results show that Mullerian differentiation does not directly prevent invasiveness, but it diminishes in parallel with invasion caused by other factors. The lack of invasiveness by SBOT cells may depend on factors that regulate motility.

Magistro darbe tiriami tauriųjų elnių auginimo aptvaruose ypatumai Lietuvos sąlygomis. Darbo objektas - S.Petraičio privatus elnininkystės ūkis, esantis Joniškio rajone. Darbo tikslas - išaiškinti aptvaruose auginamų tauriųjų elnių augimo ir veisimosi ypatumus. Darbo uždaviniai – nustatyti tauriųjų elnių veisimosi, kūno ir ragų augimo ypatumus, užsikrėtimą ligomis bei parazitais. Išaiškinti ar šėrimo racionas tenkina tauriųjų elnių poreikius. Darbo metodai – vizualinis tauriųjų elnių stebėjimas visais metų laikais, nustatant elgsenos ypatumus. Helmintų tyrimas (helmintoovoskopija) – laboratorijoje tiriami sviežiai surinkti tauriųjų elnių ekskrementai. Šėrimo raciono išaiškinimas, pagal maisto medžiagų kiekius skirtingose pašaro rūšyse ir elnių poreikius nustatomas jo pakankamumas. Rujos, jauniklių vedimo bei įvairių kitų darbų ir operacijų stebėjimas tiesiogiai dalyvaujant jose (haremų tvarkymas, vakcinavimas, ženklinimas (numeravimas), ir kt.). Kūno morfometrijos duomenys surinkti iš jau sumedžiotų elnių. Numestų ragų matavimas pagal CIC sistemą. Darbo rezultatai – intensyviai ūkininkaujant ir esant labai dideliam tauriųjų elnių tankumui susiduriama su labai daug problemų. Joniškio rajone esančiame elnininkystės ūkyje paskutiniais duomenimis yra 800 tauriųjų elnių, kurie gyvena 150 ha senų obelų sodų ir natūralių pievų, t.y. 5,3 individo kiekviename hektare. Esant tokiam žvėrių tankiui ir nevykdant dehelmintizacijos absoliučiai visi jauni elniai, o ypač iki vienerių metų... [toliau žr. visą tekstą] / In the Master’s Thesis the peculiarities of breeding the red deers in enclosures under the conditions of Lithuania are investigated. Work object – private deers’ farm of S.Petraitis in Joniškis region. Work aim – to reveal the peculiarities of growing and breeding of red deers in the enclosures. Work objectives – to ascertain the peculiarities of breeding the red deers, body and antlers, infection with diseases and parasites. To find out whether the feeding ration is suitable for the needs of the red deers. Work methods – visual observation of the red deers during all seasons, when determining the behaviour peculiarities. Analysis of helminths (helminthovoscopy) – the freshly collected excrements of the red deers are analysed in the laboratory. The exploration of feeding ration – its sufficiency is estimated according to the nourishing quantities in the types of feed and the needs of deers. The observation of rut, calving and various works and operations is performed by taking part directly in them (arranging of harems, vaccination, marking (numbering), etc.). The body morphometry data are collected from the bagged deers. Metering of dropped antlers according to CIC system. Work results – when performing the intensive farming and when the big density of the red deers is estimated, a lot of problems arise. According to the recent data, in the farm of deers in Joniškis region 800 red deers live in the garden of old apple-trees and natural meadows of 150 ha, i.e. 5.3... [to full text]

Parasites may express proteins that mimic host proteins such that the host immune system cannot discriminate between host and parasite. An immune response to host proteins results in autoimmunity, and therefore, mechanisms to avert autoimmunity also limit the capacity of the immune system to respond to parasites that are mimics. In failing to elicit an immune response, parasites that are mimics appear to have a selective advantage and so it is unclear why all parasites do not evolve to be mimics. In this thesis, I demonstrate that next-generation methods can be used to perform an evolutionary invasion analysis. Subsequently, I use this method to identify evolutionarily stable strategies and to investigate three hypotheses for why all parasites are not mimics. These are: (1) that mimicry increases the risk of inducing autoimmunity and that hosts with autoimmunity are less likely to transmit the parasite; (2) that proteins which mimic host proteins have a reduced ability to perform the vital functions necessary for parasite replication; and (3) that owing to a feedback between the types of parasites that infect a host and the host's immune response, when parasites are likely to re-infect the same hosts, mimics are more likely to elicit an immune response. I show that each of these hypotheses explain why all parasites are not mimics. The key data needed to assess the applicability of these results is to quantify the number of secondary infections generated by hosts infected with parasites that are molecular mimics. This thesis motivates a new question in evolutionary epidemiology, furthers the field of evolutionary medicine and contributes novel methodologies for host-parasite multi-scale modelling in mathematical biology. / Thesis (Ph.D, Mathematics & Statistics) -- Queen's University, 2011-04-05 10:27:20.49

Invaziniai augalai – tai sparčiai plintantys augalai. Jie įsikuria įvairiose buveinėse, jas smarkiai pakeičia arba net visai sunaikina. Vienas iš aplinkai pavojingų augalų laikomas gausialapis lubinas. Jis yra įtrauktas į Lietuvos augalų sąrašą, kuriuos reikia išnaikinti. Todėl šito augalo populiacijų tyrimai yra labai svarbus. Darbo tikslas – nustatyti gausialapio lubino (Lupinus polyphyllus) populiacijų demografinę sudėtį ir ištirti dauginimąsi skirtingomis ekologinėmis sąlygomis. Tyrimai atlikti 2008 ir 2010 metais. Kiekvienoje populiacijoje tyrimams 2008 metais buvo parinkta po du laukus. Tyrimams buvo rinkti gausialapio lubino individų šaknys ir įvertinti jų antžeminių dalių rodikliai. Laboratorijoje buvo atlikti šaknų kaklelio herbochronologiniai tyrimai. Tyrimams 2010 metais gausialapio lubino populiacijos buvo pasirinktos dvi vietos iš tų kurios buvo tirtos 2008 metais. Kiekvienoje populiacijoje buvo pasirinkta po 30 gausialapio lubino kerų, iš to kero pasirinkta po vieną žydinti stiebą. Tyrimo metu buvo įvertinti kiekvieno žiedyno parametrai. Tyrimo metu nustatyta, kad visos tirtos gausialapio lubino populiacijos nėra labai tankios. Pagal amžiaus grupes visos tirtos populiacijos turėjo ir generatyvinių, ir vegetatyvinių gausialapio lubino individų ir jų skaičius skirtingose populiacijose buvo įvairus. Pagal daugumą morfologinių generatyvinių ir vegetatyvinių individų požymių visos keturios populiacijos skiriasi nedaug. Pagal amžių tirtos populiacijos yra skirtingos... [toliau žr. visą tekstą] / Invasion plants are widely spread plants. They grow in different places, they are changed very much or even annihilated entirely. One of the most dangerous plants for environment is washington lupin. It is included in Lithuania plants list, which should be annihilated. Therefore investigations of this plant populiations are very important. The aim of the work is to determine demographic composition of populiations of washington lupin (Lupinus polyphyllus) and to investigate its reproduction in different ecological conditions. Investigations were made in 2008 and 2010 years. For each populiation of 2008 year investigations two fields were chosen. For investigations individuals roots of washington lupin were chosen and their overground parts readings were taken. Roots necks herbochronological investigations were made in laboratory. For 2010 year investigations of washington lupin populations, two places frons earlier investigated in 2008 year places, were chosen. In each population 30 bushes of washington lupin were chosen, from this bush one blooming stem was chosen. While investigating each floscule parameters were taken. While investigating it was ascertained that all investigated washington lupin populations were not very thick. As far as age group is concerned, all investigated populations ha generative and vegetative washington lupin individuals and their quantity in different populations were different. By majority of morphological generative and vegetative individuals... [to full text]

The responses of invasive exotic plant species (IES) to silvicultural treatments one growing season after timber harvesting were examined in the Cumberland Plateau region of Southeastern Kentucky. Treatments included a commercial deferment harvest and unharvested control applied to five watersheds within University of Kentucky’s Robinson Forest. The effects of harvesting were compared between treatments and between preharvest and postharvest samplings. The spatial distribution and abundance of targeted IES throughout forest sites and trail systems were calculated from several sampling schemes. Additional analyses were performed to quantify forest disturbances derived from harvest activities to determine the relationships between soil, light levels, and other environmental characteristics and IES cover. Logistic and multivariate analysis techniques were used to analyze differences in IES distribution between pre-harvest and post-harvest units to relate post-harvest IES to microsite conditions. Microsite conditions within the forest and along the trail system proved important for explaining the presence and distribution of IES. Timber harvesting caused a significant increase in both Ailanthus altissima and Microstegium vimineum within harvested areas. However, many other identified IES did not initially respond to disturbances. Throughout the treatment units, species were influenced by disturbance type and intensity, as well as proximity to reclaimed surface mined land.

The objective of this study was to determine the effect of nutrient density and housing on E. coli populations in beef and dairy production systems. In the first trial, sixty second trimester beef cows were housed in two different overwintering environments and provided dry hay which was either bale grazed or placed in a feed bunk. Selected pens had supplemented with dried distiller’s grain with soluble (DDGS; 2.5 kg/cow/every third day) or rolled barley (1 kg/cow/day). In the second trial, six rumen and caecal-cannulated, non-lactating, multiparous Holstein cows received one of the following diets: i) 70% forage ii) grain pellet or iii) alfalfa pellet. The latter two diets were formulated to induce subacute ruminal acidosis (SARA). All animals were randomly sorted to pens and treatments. Fecal samples were collected and cultured on selective media. E. coli were enumerated and three isolates were chosen for PCR to detect the presence of 18 selected genes encoding a range of virulence factors. These same isolates were tested for their ability to invade the human adenocarcinoma epithelial cell line HT-29. Diet did not significantly affect E. coli abundance but did influence the prevalence of virulence genes involved in adhesion of bacteria to epithelial surfaces. When the diet contained grain, cows shed isolates which were more invasive than those from cows in the other treatments. The data suggest that diet may affect the abundance of E. coli shed in the feces and increase the presence of E. coli harbouring particular virulence genes that mediate adhesion and invasion of epithelial surfaces.