Existence of Nearest Neighbor and Variable Range Hopping in Pr2_2ZnMnO6_6

A joint investigation of X-ray diffraction (XRD) pattern and Raman spectrum authenticate the double phase monoclinic P21/n and cubic Fd-3m structures of polycrystalline Pr2ZnMnO6 (PZM). The existence of two different conduction mechanisms (Nearest neighbor hopping and Motts variable range hopping) is observed using a combined study of conductivity, dielectric relaxation and impedance spectra in PZM. This investigation point towards a transition from nearest neighbor hoping to Motts variable range hopping mechanism due to lowering activation energy around 580 K. The charge carriers hopping between the localized acceptor states at the grain boundaries (GBs), which dominants conduction mechanism below 580 K. The ac conductivity, dielectric relaxation, Nyquist plot, and electric modulus highlight the blended effect of grains (Gs) and GBs leads to the charge carrier dynamics in PZM. The dielectric relaxation and modulus formalism are analyzed on the basis of empirical Cole-Cole model. The conduction mechanism is found to be highly correlated with the relaxation mechanism and impedance spectroscopy.Comment: 15 page

How to Survive the Western Democratising Pressure?

Competitive Authoritarianism: Hybrid Regimes After the Cold War by Steven Levitsky and Lucan A. Way, 2010, New York, NY: Cambridge University Press

Syphilis serology in HIV-positive and HIV-negative Nigerians: The public health significance

Syphilis has acquired new potential for morbidity and mortality through association with increased risk for HIV infection. Case-control survey was conducted using Rapid Plasma Reagin test and confirmatory Immunochromatographic test among HIV-positive (cases) and HIV-negative (control) Nigerians. A total of 35(14.0%) of 250 HIV-positive and 5(2.0%) of 250 HIV-negative individuals studied were seropositive for syphilis, the difference was statistically significant (P<0.05). The prevalence was higher among females than males of HIV-positive (15.0% versus 12.7%) and of the HIV-negative (2.1% versus 1.9%) individuals. Syphilis seroprevalence was highest among HIV-positive individuals aged 21-30 years (20.5%) and 41-50 years old HIV-negative individuals (4.5%). Sex education, promotion of safer sexual behaviour, prompt diagnosis of STDs and provision of effective, accessible treatment are recommende

Järvede produktiivsuse ja toitainete peetuse sesoonsus, aastatevahelised erinevused ning sõltuvus järvede morfomeetriast

Despite the considerable percentage of inland waters in the temperate zone land cover, their role in the global carbon balance is not clear and the existing data suggest large type specific differences. Respiratory CO2 release from inland waters is a major process in the global carbon cycle, retaining more than half of the carbon flux from terrestrial sources that otherwise would reach the sea. The strongly lake-type-specific balance between primary production and respiration determines whether a lake acts regionally as a net sink or source of CO2. In the global change context even small changes in photosynthesis and respiration rates and/or in the loadings of organic matter or nutrients (e.g. phosphorus) may change the metabolic type of the lake and turn it from autotrophic to heterotrophic system or vice versa. Todays in situ sondes fitted with sensitive and accurate optical oxygen probes have become a useful tool for estimating lake ecosystem metabolism through high frequency continuous measurements. The sonde method provides an alternative to more traditional methods of measuring metabolism that only use discrete samples. Continuous sampling by sondes overcomes many of the limitations of discrete samples and makes it possible to measure metabolism in a wide variety of systems. Long-term observations across many years define the range of natural variability of ecological systems and provide a baseline from which to assess whether a system has changed significantly. Regular hydrological data on large and shallow (area 270 km2; mean depth 2.8 m) Lake Võrtsjärv have been collected for more than 80 years. Regular measurements of nutrients and ecosystem components started in 1960s. Lake Võrtsjärv was intensively studied for more than 50 years before the first monitoring buoy was deployed for high frequency measurements of physical and chemical parameters. Phytoplankton primary production in situ measurements with monthly frequency started in Võrtsjärv already in 1982 but the dataset has many gaps. Present thesis summarizes for Lake Võrtsjärv: the first data on seasonal changes of the ecosystem metabolism based on high frequency measurements; the reconstruction of long term series of phytoplankton primary production by bio-optical modelling; the incoming and outgoing fluxes of carbon, nitrogen, phosphorus, and silicon; and gives an overview of phosphorus retention in Lake Võrtsjärv compared with 54 lakes and reservoirs in different climate regions around the world.Hoolimata siseveekogude rohkusest parasvöötmes, mis on limnoloogiliselt enim uuritud piirkond Maal, ei ole meil senini selget ülevaadet nende veekogude rollist globaalses süsinikubilansis. Elusorganismide elutegevuse käigus toodetav süsihappegaas (CO2) vabaneb meid ümbritsevasse keskkonda. Magevetes hingamisel vabaneva CO2 kogus omab olulist rolli globaalses süsinikuringes. Tänu mageveekogudes toimuvale fotosünteesile tarbitakse esmatootjate (primaarprodutsentide) poolt ära rohkem kui pool kogu maismaal toodetavast süsihappegaasist, mis vastasel juhul jõuaks meid ümbritsevasse keskkonda. Veekogudes toimuva primaarproduktsiooni ja hingamise alusel saab järved jagada kahte erinevasse ainevahetuse tüüpi: CO2 tootvateks (heterotroofseteks) ja CO2 talletavateks (autotroofseteks). Globaalses kontekstis võib ka väikene nihe nii primaarproduktsiooni kui hingamise tasakaalus, põhjustatuna näiteks orgaanilise aine või toiteainete (näiteks fosforiühendite) sissevoolu muutustest, muuta järve kui terviku ainevahetuse tüüpi. Oma varasematele uurimistele ja teadmistele tuginedes oletasime, et Võrtsjärv võib vahetada oma metabolismi tüüpi jää tuleku ja minekuga. Jää- ja lumekatte all väheneb oluliselt vette jõudev valguse hulk, mis on üks kõige olulisem mõjur fotosünteesi käivitamisel ja läbiviimisel. Valguse ööpäevane ja aastaajaline muutlikkus ongi üheks peamiseks põhjuseks veekogude metabolismitüübi kujundamisel. Muutused erinevate tegurite osas, mis mõjutavad primaarproduktsiooni või hingamisprotsesse, võivad toimuda ajaliselt üsna kiiresti (tundide ja päevade jooksul), mistõttu oli neid seni kord kuus toimunud vaatluste abil väga raske jälgida. Võrtsjärve on regulaarseire raames uuritud juba rohkem kui 80 aastat. Primaarproduktsiooni mõõtmistega tehti algust 1982. aastal, kuid kogutud andmeridades esineb kahjuks mitmeid "auke". 2008. aastal alustati süsinikubilansi koostamiseks vajalikke uuringuid ka Võrtsjärve suurematest sissevooludes ning väljavoolus. Tänu Euroopa Liidu toetusfondidele ja riiklikult sihtfinantseeritavale teadusteemale soetati 2009. ja 2010. aastal mitmeid uurimisplatvorme ning ka järvepoi, millede abil said Võrtsjärvel alguse pidevmõõtmised. Käesolev töö: määratleb Võrtjärve kui suure ja madala eutroofse parasvöötme järve metabolismitüübi ja rolli nii regionaalses kui globaalses süsinikuringes; koondab Võrtsjärve primaarproduktsiooni (PP) pikaajalised muutused ning täidab PP andmestikus olevad lüngad modelleerimise abil; annab ülevaate Võrtsjärve sisse- ja väljavoolude süsinikuühendite ja toiteainete hulkadest; ning hindab fosfori kinnipidamist 54. erinevas maailma järves.The doctoral studies and the publication of the current thesis were supported by the Doctoral School of Ecology and Environmental Sciences created under the auspice of European Union Social Fund

Computational composition strategies in audiovisual laptop performance

We live in a cultural environment in which computer based musical performances have become ubiquitous. Particularly the use of laptops as instruments is a thriving practice in many genres and subcultures. The opportunity to command the most intricate level of control on the smallest of time scales in music composition and computer graphics introduces a number of complexities and dilemmas for the performer working with algorithms. Writing computer code to create audiovisuals offers abundant opportunities for discovering new ways of expression in live performance while simultaneously introducing challenges and presenting the user with difficult choices. There are a host of computational strategies that can be employed in live situations to assist the performer, including artificially intelligent performance agents who operate according to predefined algorithmic rules. This thesis describes four software systems for real time multimodal improvisation and composition in which a number of computational strategies for audiovisual laptop performances is explored and which were used in creation of a portfolio of accompanying audiovisual compositions

"I hear nothing, I say nothing" : constructions of impotence and ignorance in the work of Samuel Beckett

This thesis examines the themes of impotence and ignorance across four novels by Samuel Beckett: Watt, Molloy, Malone Dies and The Unnamable. Continuities and discontinuities are discussed, along with the relationship of impotence and ignorance to Beckett's project of indicating a type of existence beyond meaningful language and conventional reality. The thesis suggests that Beckett's work is unusually open to multiple interpretations due to its lack of tellability, which is a result of the epistemological collapse of its protagonists. Impotence and ignorance figure as elements in a critique of the three orders of Cartesian rationalism, empirical knowledge, and religious belief, all of which find their limits in the doubts and failures of Beckett's characters. Impotence and ignorance are sometimes chosen states, and sometimes the result of an unchosen process of becoming-other, or a situation in which the protagonist finds himself. Impotence is often figured in terms of physical incapacity, old age, and an asymptotic decay towards death, while ignorance is associated with the gap between real objects and beings, and their representation in language. Beckett's characters undergo a collapse of representational categorisation which is the source of their impotence and ignorance, and which is often connected to a desire to retreat to the inner life. This process also causes the collapse of subjectivity and the ability to narrate, yet it coexists with an inexplicable compulsion to “go on” (speaking, writing, or living) which keeps Beckett's characters always on the edge of death, silence, or disappearance. This process of near-disappearance is of a variety which creates a type of textual production which frustrates any possible interpretation, pointing as it does to a domain beyond language, which is variously figured as chaos, becoming, darkness, and death

Sünteetiliste molekulaarretseptorite disainiprintsiibid anioon-selektiivsetele elektroodidele

Väitekirja elektrooniline versioon ei sisalda publikatsiooneIoonide määramiseks kasutatavaid portatiivseid sensorsüsteeme on laiatarbeliselt kättesaadavad vaid üksikud, näiteks Na+/K+ elektroodid, pH meetrid ja NO3- elektroodid. Anioonselektiivseid elektroodid on vajalikud meditsiinis, toiduainetööstuses, põllumajanduses. Nendes valdkondades on üheks huvipakkuvaks aineklassiks karboksüülhapete anioonid ehk karboksülaadid, mille selektiivseks määramiseks toimub arendustegevus elektrokeemiliste sensorite valmistamises. Selle uurimissuuna üheks strateegiaks on molekulaarretseptorite kasutamine ioonselektiivsetes elektroodides. Taoliste retseptorite arendamisega tegeleb just supramolekulaarkeemia ning ajapikku on loodud palju erinevaid retseptormolekulide valimeid. Kahjuks ei jõua sellised ained arendustegevuses kaugemale aineomaduste määramisest. Tulemusliku lõpuni arendatakse sensorsüsteemide prototüüpe üksikutel juhtudel. Käesoleva dissertatsiooni eesmärgiks on nimetatud kahe uurimisvaldkonna ühendamine ja uute anioonselektiivsete elektroodide arendamisel tekkivate väljakutsete uurimine. Sellega kaasnevad mitmed fundamentaalteaduslikud probleemid, mille lahendamiseks uuritakse töös mõjutegureid nagu seondumisvõime, lipofiilsus, kahefaasilised seondumiskeskkonnad jt.Commercially available portative sensor systems for ion recognition are available for only a few select applications. Some examples include Na+/K+ electrodes, pH meters and NO3- electrodes. Anion-selective electrodes are required in several fields, such as medicine, food industry, agriculture etc. One desired class of analytes are ions of carboxylic acids, i.e., carboxylates. One strategy for the selective recognition of these anions is to use molecular receptors in ion-selective electrodes. In supramolecular chemistry, which deals with designing new receptor molecules, mountains of receptor candidates are available for this possible application. However, these compounds do not reach the electrochemical research field, where molecular receptors could be used as input for sensor prototypes. This dissertation aims to connect these two research fields and demonstrate the challenges of creating new ion-selective electrodes for carboxylate sensing. This process is accompanied by several scientific challenges at the fundamental level of supramolecular chemistry. To address these problems, influencing factors are explored, such as improving binding, lipophilicity, biphasic binding environments etc

Book Review: How to Survive the Western Democratising Pressure?

Competitive Authoritarianism: Hybrid Regimes After the Cold War by Steven Levitsky and Lucan A. Way, 2010, New York, NY: Cambridge University Press