This work comprises two main parts. The first part outlines our efforts to expand on the recent work of Gütlich et.al. by synthesizing Co(II) based spin crossover systems within a dendritic framework. We wanted to investigate the possibility of synthesizing different first generation, triazole containing dendrimers using “click” type reactions and their coordination ability with Co(II) ions. To this end we have had limited success mainly due to the numerous challenges in synthesizing a pure dendrimer product. The second part details our efforts in the synthesis of a mononuclear Co(II) based single molecule magnet. This comes as an extension to recent reports by Chang and Long where they have successfully obtained mononuclear Fe(II) single molecule magnets by inducing structural distortions within the complexes to amplify the spin-orbit coupling. We postulated that the use of Co(II) in conjunction with a bulky ligand framework would lead to desirable magnetic properties. We chose the known bis(imino)pyridine ligand scaffold due to its rich chemistry and its interesting and unexpected coordination behaviour, as we have seen in previous research efforts by our lab. To this end we were successful in isolating and characterizing 4 compounds, and we have carried out detailed magnetic measurements on the two most magnetically interesting species.

Ultracold Fermi gas is an exciting field benefiting from atomic physics, optical physics and condensed matter physics. It covers many aspects of quantum mechanics. Here I introduce some of my work during my graduate study. We proposed an optical spectroscopic method based on electromagnetically-induced transparency (EIT) as a generic probing tool that provides valuable insights into the nature of Fermi paring in ultracold Fermi gases of two hyperfine states. This technique has the capability of allowing spectroscopic response to be determined in a nearly non-destructive manner and the whole spectrum may be obtained by scanning the probe laser frequency faster than the lifetime of the sample without re-preparing the atomic sample repeatedly. Both quasiparticle picture and pseudogap picture are constructed to facilitate the physical explanation of the pairing signature in the EIT spectra. Motivated by the prospect of realizing a Fermi gas of 40 K atoms with a synthetic non-Abelian gauge field, we investigated theoretically BEC-HCS crossover physics in the presence of a Rashba spin-orbit coupling in a system of two-component Fermi gas with and without a Zeeman field that breaks the population balance. A new bound state (Rashba pair) emerges because of the spin-orbit interaction. We studied the properties of Rashba pairs using a standard pair fluctuation theory. As the two-fold spin degeneracy is lifted by spin-orbit interaction, bound pairs with mixed singlet and triplet pairings (referred to as rashbons) emerge, leading to an anisotropic superfluid. We discussed in detail the experimental signatures for observing the condensation of Rashba pairs by calculating various physical observables which characterize the properties of the system and can be measured in experiment. The role of impurities as experimental probes in the detection of quantum material properties is well appreciated. Here we studied the effect of a single classical impurity in trapped ultracold Fermi superfluids. Although a non-magnetic impurity does not change macroscopic properties of s-wave Fermi superfluids, depending on its shape and strength, a magnetic impurity can induce single or multiple mid-gap bound states. The multiple mid-gap states could coincide with the development of a Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase within the superfluid. As an analog of the Scanning Tunneling Microscope, we proposed a modified radio frequency spectroscopic method to measure the focal density of states which can be employed to detect these states and other quantum phases of cold atoms. A key result of our self consistent Bogoliubov-de Gennes calculations is that a magnetic impurity can controllably induce an FFLO state at currently accessible experimental parameters.

Cycling of the relative humidity (RH) levels in the reactant streams of polymer electrolyte membrane (PEM) fuel cells has been reported to decay fuel cell performance. This study focuses on the accelerated durability testing to examine different modes of membrane failure via RH cycling. A single PEM fuel cell with an active area of 42.25 cm2 was tested. A Greenlight G50 test station was used to establish baseline cell (Run 1) performance with 840 hours of degradation under high-humidity idle conditions at a constant current density of 10 mA cm-2. Under the same conditions, two other experiments were conducted by varying the RH. For the H2-air RH cycling test (Run 2), anode and cathode inlet gases were provided as dry and humidified gases. Another RH cycling experiment was the H2 RH cycling test (Run 3): the anode inlet gas was cycled whereas keeping the other side constantly at full humidification. These two RH cycling experiments were alternated in dry and 100% humidified conditions every 10 and 40 minutes, respectively. In the experiments, the fuel cells contained a GoreTM 57 catalyst coated membrane (CCM) and 35 BC SGL gas diffusion layers (GDLs). The fuel cell test station had been performed under idle conditions at a constant current density of 10 mA cm-2. Under the idle conditions, operating at very low current density, a low chemical degradation rate and minimal electrical load stress were anticipated. However, the membrane was expected to degrade due to additional stress from the membrane swelling/contraction cycle controlled by the RH. In this work the performance of the 100% RH humidified cell (Run 1) was compared with that of RH cycling cells (Run 2 and Run 3). Chemical and mechanical degradation of the membrane were investigated using in-situ and ex-situ diagnostic methods. The results of each measurement during and after fuel cell operation are consistent. They clearly show that changing in RH lead to an overall PEM fuel cell degradation due to the increase in membrane degradation rate from membrane resistance, fluoride ion release concentration, hydrogen crossover current, membrane thinning, and hot-spot/pin-hole formation.

Femtosecond electron diffraction experiments were performed on solid state iron(II) tris(2,2'-bipyridine) bis(hexafluorophosphate). The cation is known to undergo a spin crossover process when solvated in water and irradiated with 400 nm coherent light which results in a transition from a low spin to high spin state within a picosecond which is accompanied by a uniform 0.2 Å Fe-N bond elongation. A femtosecond diffraction experiment was performed on the solid sample and was unable to find evidence of a fast spin crossover transition. Suspecting this may be due to limitations of the apparatus, an ultrafast transient absorption experiment was performed. Emulating the liquid study by Gawelda et al, the pump probe experiment found evidence of spin crossover in the solid state sample. This result awaits verification by an improved transient absorption apparatus and has inspired efforts to perform an improved femtosecond electron diffraction experiment.

Femtosecond electron diffraction experiments were performed on solid state iron(II) tris(2,2'-bipyridine) bis(hexafluorophosphate). The cation is known to undergo a spin crossover process when solvated in water and irradiated with 400 nm coherent light which results in a transition from a low spin to high spin state within a picosecond which is accompanied by a uniform 0.2 Å Fe-N bond elongation. A femtosecond diffraction experiment was performed on the solid sample and was unable to find evidence of a fast spin crossover transition. Suspecting this may be due to limitations of the apparatus, an ultrafast transient absorption experiment was performed. Emulating the liquid study by Gawelda et al, the pump probe experiment found evidence of spin crossover in the solid state sample. This result awaits verification by an improved transient absorption apparatus and has inspired efforts to perform an improved femtosecond electron diffraction experiment.

Cycling of the relative humidity (RH) levels in the reactant streams of polymer electrolyte membrane (PEM) fuel cells has been reported to decay fuel cell performance. This study focuses on the accelerated durability testing to examine different modes of membrane failure via RH cycling. A single PEM fuel cell with an active area of 42.25 cm2 was tested. A Greenlight G50 test station was used to establish baseline cell (Run 1) performance with 840 hours of degradation under high-humidity idle conditions at a constant current density of 10 mA cm-2. Under the same conditions, two other experiments were conducted by varying the RH. For the H2-air RH cycling test (Run 2), anode and cathode inlet gases were provided as dry and humidified gases. Another RH cycling experiment was the H2 RH cycling test (Run 3): the anode inlet gas was cycled whereas keeping the other side constantly at full humidification. These two RH cycling experiments were alternated in dry and 100% humidified conditions every 10 and 40 minutes, respectively. In the experiments, the fuel cells contained a GoreTM 57 catalyst coated membrane (CCM) and 35 BC SGL gas diffusion layers (GDLs). The fuel cell test station had been performed under idle conditions at a constant current density of 10 mA cm-2. Under the idle conditions, operating at very low current density, a low chemical degradation rate and minimal electrical load stress were anticipated. However, the membrane was expected to degrade due to additional stress from the membrane swelling/contraction cycle controlled by the RH. In this work the performance of the 100% RH humidified cell (Run 1) was compared with that of RH cycling cells (Run 2 and Run 3). Chemical and mechanical degradation of the membrane were investigated using in-situ and ex-situ diagnostic methods. The results of each measurement during and after fuel cell operation are consistent. They clearly show that changing in RH lead to an overall PEM fuel cell degradation due to the increase in membrane degradation rate from membrane resistance, fluoride ion release concentration, hydrogen crossover current, membrane thinning, and hot-spot/pin-hole formation.

Bioequivalence determines if two drugs are alike. The three kinds of bioequivalence are Average, Population, and Individual Bioequivalence. These Bioequivalence criteria can be evaluated using aggregate and disaggregate methods. Considerable work assessing bioequivalence in a frequentist method exists, but the advantages of Bayesian methods for Bioequivalence have been recently explored. Variance parameters are essential to any of theses existing Bayesian Bioequivalence metrics. Usually, the prior distributions for model parameters use either informative priors or vague priors. The Bioequivalence inference may be sensitive to the prior distribution on the variances. Recently, there have been questions about the routine use of inverse gamma priors for variance parameters. In this paper we examine the effect that changing the prior distribution of the variance parameters has on Bayesian models for assessing Bioequivalence and the carry-over effect. We explore our method with some real data sets from the FDA.

Tiriamajame darbe nagrinėjama techninės analizės metodų pelningumas bei patikimumas, jų praktinė nauda ir veikimo principai mažesnėse akcijų biržose (Vilniaus, Rygos, Talino). Gautų rezultatų palyginimui į tyrimą įtraukiama S&P500 akcijų indeksas. Pagrindinis tyrimo tikslas išnagrinėti du techninės analizės metodus - Santykinio stiprumo indeksą ir Slankiųjų vidurkių metodą, praktiškai juos panaudojant aukščiau paminėtose akcijų biržose, ištirti generuojamų pirkimo – pardavimo signalų patikimumą. Fundamentalios analizės atveju yra nagrinėjama Lietuvos komercinių bankų teikiamų konkrečių įmonių akcijų apžvalgų-rekomendacijų, patikimumas bei praktinė nauda. Pirmoje darbo dalyje aprašoma efektyvios rinkos teorijos prasmė (pamatinė techninės ir fundamentalios analizės teorija), kartu paliečiant pagrindinius fundamentalios ir techninės analizės principus. Plačiau nagrinėjami pasaulyje atlikti techninės analizės tyrimai, gauti jų rezultatai. Antroje darbo dalyje pateikiama metodologija kaip buvo atliktas techninės analizės tyrimas su Baltijos šalių ir JAV akcijų indeksais, nubrėžiamos pagrindinės tyrimo ribos. Trečioje tyrimo dalyje pateikiami rezultatai. Didžiausias metinis pelningumas buvo gautas remiantis Slankiųjų vidurkių metodu (50/200 su OMXV akcijų indeksu) – 24,44 proc., kai tuo tarpu „pirk ir laikyk“ strategijos gautas pelningumas – 22,68 proc. po mokesčių. RSI indekso metodas geriausiai pasiteisino su S&P500 akcijų indeksu. Šio metodo metinė grąža siekė 2,15 proc., o... [toliau žr. visą tekstą] / The profitability and reliability of technical analysis methods is the main theme of this work. The practical value of these methods and main rules of operation are analyzed in smaller markets (Vilnius, Ryga and Tallin) and also in comparison with S&P 500 index. The main purpose of this study is to practically test couple of technical analysis methods (Relative Strength Index – RSI and Dual Moving Average Crossover - DMAC) by applying them in markets mentioned above, explore the signals for buying and selling. The fundamental analysis is evaluated while analyzing the reliability and practical benefits of recommendations provided by the commercial banks of Lithuania. The meaning of efficient market theory (it’s the most basic theory for technical and fundamental analysis) is described in literature analysis part. Also, the main rules of fundamental and technical analysis are described there. All the methodology of the research with Baltic and USA indexes is provided in the second part of the work. The third part is filled with results of the research. The best annual after tax gain providing method was DMAC (Dual Moving Average Crossover) (50/200 with OMXV share index) with 22,44% gain for the shareholder, while “buy and keep” strategy provided only 22,68%. RSI (Relative Strength Index) worked best with S&P500 index. The annual odd of this method was 2,15%, while “buy and keep” strategy was only 0,087. DMAC (20/100) also worked best while analyzing the truthfulness of... [to full text]

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Cette thèse présente la conception et l'implémentation d'une nouvelle génération de puces à atomes, ouvrant de nouvelles perspectives expérimentales dans des micropièges magnétiques très anisotropes. Les propriétés thermiques des puces en nitrure d'aluminium sont étudiées en détail. Le dispositif a été optimisé pour piéger de plus grands nombres d'atomes et améliorer la qualité de l'imagerie, notamment en fabriquant un miroir de planéité sub-λ/10 à la surface de la puce.Nous étudions des gaz quasi-1D grâce à des images in situ de profils fluctuants et des méthodes précises de calibration et d'analyse statistique. Nous mesurons des fluctuations non-gaussiennes, ce qui permet de tester sensiblement la thermodynamique du gaz et donne une mesure de corrélations à trois corps. Nous étudions précisément la transition de quasicondensation et mesurons pour la première fois sa loi d'échelle. En régime 3D, c'est une condensation transverse qui déclenche la quasicondensation longitudinale, tandis qu'en régime 1D, la formation d'un quasicondensat est gouvernée par les interactions répulsives et non par la dégénérescence quantique.Obtenant des températures record pour des gaz 1D, nous observons des fluctuations subpoissoniennes lorsque les corrélations atomiques sont déterminées, au moins localement, par les fluctuations quantiques qui dominent les fluctuations thermiques. Nous discutons également la thermalisation étonnamment rapide mesurée en régime 1D profond qui suggère que des collisions effectives à 3 corps brisent l'intégrabilité du système.