Laplace-transformed multi-reference second-order perturbation theories in the atomic and active molecular orbital basis

In the present article, we show how to formulate the partially contracted n-electron valence second order perturbation theory (NEVPT2) energies in the atomic and active molecular orbital basis by employing the Laplace transformation of orbital-energy denominators (OED). As atomic-orbital (AO) basis functions are inherently localized and the number of active orbitals is comparatively small, our formulation is particularly suited for a linearly-scaling NEVPT2 implementation. Some of the NEVPT2 energy contributions can be formulated completely in the AO basis as single-reference second-order M{\o}ller-Plesset perturbation theory and benefit from sparse active-pseudo density matrices - particularly if the active molecular orbitals are localized only in parts of a molecule. Furthermore, we show that for multi-reference perturbation theories it is particularly challenging to find optimal parameters of the numerical Laplace transformation as the fit range may vary among the 8 different OEDs by many orders of magnitude. Selecting the number of quadrature points for each OED separately according to an accuracy-based criterion allows us to control the errors in the NEVPT2 energies reliably

Relativistic Cholesky-decomposed density matrix MP2

In the present article, we introduce the relativistic Cholesky-decomposed density (CDD) matrix second-order M{\o}ller-Plesset perturbation theory (MP2) energies. The working equations are formulated in terms of the usual intermediates of MP2 when employing the resolution-of-the-identity approximation (RI) for two-electron integrals. Those intermediates are obtained by substituting the occupied and virtual quaternion pseudo-density matrices of our previously proposed two-component atomic orbital-based MP2 (J. Chem. Phys. 145, 014107 (2016)) by the corresponding pivoted quaternion Cholesky factors. While working within the Kramers-restricted formalism, we obtain a formal spin-orbit overhead of 16 and 28 for the Coulomb and exchange contribution to the 2C MP2 correlation energy, respectively, compared to a non-relativistic (NR) spin-free CDD-MP2 implementation. This compact quaternion formulation could also be easily explored in any other algorithm to compute the 2C MP2 energy. The quaternion Cholesky factors become sparse for large molecules and, with a block-wise screening, block sparse-matrix multiplication algorithm, we observed an effective quadratic scaling of the total wall time for heavy-element containing linear molecules with increasing system size. The total run time for both 1C and 2C calculations was dominated by the contraction to the exchange energy. We have also investigated a bulky Te-containing supramolecular complex. For such bulky, three-dimensionally extended molecules the present screening scheme has a much larger prefactor and is less effective

Brain oxygenation patterns during the execution of tool use demonstration, tool use pantomime, and body-part-as-object tool use

© 2015 Elsevier B.V. Divergent findings exist whether left and right hemispheric pre- and postcentral cortices contribute to the production of tool use related hand movements. In order to clarify the neural substrates of tool use demonstrations with tool in hand, tool use pantomimes without tool in hand, and body-part-as-object presentations of tool use (BPO) in a naturalistic mode of execution, we applied functional Near InfraRed Spectroscopy (fNIRS) in twenty-three right-handed participants. Functional NIRS techniques allow for the investigation of brain oxygenation during the execution of complex hand movements with an unlimited movement range. Brain oxygenation patterns were retrieved from 16 channels of measurement above pre- and postcentral cortices of each hemisphere. The results showed that tool use demonstration with tool in hand leads to increased oxygenation as compared to tool use pantomimes in the left hemispheric somatosensory gyrus. Left hand executions of the demonstration of tool use, pantomime of tool use, and BPO of tool use led to increased oxygenation in the premotor and somatosensory cortices of the left hemisphere as compared to right hand executions of either condition. The results indicate that the premotor and somatosensory cortices of the left hemisphere constitute relevant brain structures for tool related hand movement production when using the left hand, whereas the somatosensory cortex of the left hemisphere seems to provide specific mental representations when performing tool use demonstrations with the tool in hand

Patterning Worry in Narrative, Gender and the Domestic Sphere in Mark Haddon's A Spot of Bother and The Red House

This thesis argues for the significance of worry in Mark Haddon’s A Spot of Bother (2006) and The Red House (2012). All of Haddon’s novels can be said to be a study of the human consciousness, containing a variety of worried characters, but it is notable that worry is most predominantly present in the two novels that centre around complex family dynamics. For this reason, these two novels will be the focus of the analysis. The thesis contains a background chapter which traces the etymology of worry, locates the incipience of worry in literature during the Modernist period, and places worry in the framework of gender theory. The text analysis starts with a focus on worry in relation to possibility through a methodological examination of the novels using Mieke Bal’s narratological theory. Next, the worry that is present in the text is contextualised in a gendered framework, in which it is argued that a correlation exists between the represented worry in the novels to the boundaries of gender and the family as a gendered construction. The findings of the thesis are that the way a narrative is constructed is influential in the way worry is both present and represented in a literary text. The contextualisation of worry with a gender perspective explores the idea that the object of worry and the way characters respond to worry is largely determined by notions of femininity and masculinity, both in an individual sense and through the expectations of the way mothers, fathers, sons and daughters are expected to behave

Multi-component porphyrin self-assembly

The self-assembly of organic molecules offers an attractive bottom-up approach to create nano-meter sized objects. By usage of chromophoric building blocks in a multi-component environment, supramolecular assemblies become highly interesting for numerous applications in the fields of sensing, catalysis and light harvesting. Regarding the development of functional supramolecular materials and mimicking natural systems, it is highly important to understand self-assembly processes in detail and the ability to control them; particularly the control over the arrangement and number of molecules in an aggregate. However, due to the presence of multiple interacting components in a dynamic assembly, these systems are inherently complex, which requires in-depth analyses in multi-component self-assembly. Rather than the description of their functional properties, the focus in this thesis is on insights into multi-component self-assembly of porphyrin monomers into non-discrete helical architectures. By the employment of modeling tools, the thermodynamic aspects of different interacting moieties via orthogonal supramolecular interactions are addressed, which allows one to predict the behavior of several systems comprising of Zn-porphyrins and different axial ligands. In these analyses, the role of cooperativity is closely examined, which strongly enhances the stimuli-responsiveness of the system. The supramolecular chirality has been applied as an additional probe to study the multi-component porphyrin self-assembly. In addition, chiral amplification experiments reveal that the supramolecular chirality provides a level of control over the mixing of different porphyrin monomers in an aggregate. Lastly, besides thermodynamic assessments, the kinetic properties of multi-component porphyrin assemblies have been studied. Here, different dynamic processes such as the exchange of monomers in an aggregate, aggregate interconversions and the imprint of helical conformations have been investigated. In Chapter 1, a literature overview is presented on the formation of porphyrin-based assemblies, in which different non-covalent interactions are used to construct well-defined architectures. The versatility of the porphyrin building block allows for a diversity of supramolecular motifs, which self-assemble by different mechanisms. Functional properties arise in multi-component mixtures, in which strategies are presented to control the mutual chromophore arrangement in discrete and non-discrete assemblies. Besides stoichiometric and positional control, a special focus in on cooperativity and the stimuli-responsiveness of porphyrin-based aggregates in multi-component systems. A library of metallo-porphyrin derivatives is developed in Chapter 2, in which the effect of metal center, amide linker and side-chain chirality on the one-component self-assembly is investigated. A hydrogen bond-assisted and highly cooperative self-assembly process is deduced for all amide-functionalized metallo-porphyrins. Their cofacial arrangement results into extended, helical, 1-dimensional H-type aggregates, which are fully analyzed for self-assembled S-chiral zinc-porphyrin "S-Zn" in methylcyclohexane (MCH). Temperature- and concentration-dependent UV-vis and CD measurements have been performed to obtain a thermodynamic description for the cooperative self-assembly. The resulting thermodynamic parameters for S-Zn have been deduced and applied in multiple equilibrium models that describe the self-assembly of S-Zn in the presence of different axial ligands in Chapter 3/4/5. In Chapter 3, the self-assembly of S-Zn is studied in the presence of pyridine, which depolymerizes the porphyrin stacks in a bimodal fashion into hydrogen-bonded, pyridine-capped dimers. As a result of cooperativity, a monomer-driven depolymerization mechanism is validated by fitting spectroscopy data of the pyridine titration to a corresponding thermodynamic model. Simulations on this depolymerization model are used to assess the competition between hydrogen bonding and metal-ligand association in a coupled system, which reveals a dilution-induced self-assembly of the porphyrin stacks. A slow interconversion between dimers and stacks is observed upon the addition of MCH and this kinetic property is used to control the distribution between both aggregate types by diffusive mass transfer in a microfluidic H-cell. Using the design rules for a strong pyridine-responsiveness between stacks and dimers established in Chapter 3, the photo-induced alteration of the binding constant of phenylazopyridines is explored to photo-regulate the self-assembly of S-Zn in Chapter 4. In the absence of hydrogen bonding, the thermodynamic properties of the photo-induced (de)complexation have been deduced by titration and irradiation studies, which have subsequently been introduced in a modified depolymerization model. High conversion ratios and a large difference in binding constant between both isomers induce a strong photo-switch-ability, which is predicted between 2% and 90% of stacked S-Zn monomers. Regardless the experimental deviations from the model, a reversible photo-induced (de)polymerization of the porphyrin stacks between 1% and 81% is achieved based on CD spectroscopy. Corroborating the spectroscopic measurements, the irradiation of the auxiliary causes a change in solution viscosity. In Chapter 5, the self-assembly of S-Zn is studied in the presence of the bidentate axial ligand DABCO. In the absence of hydrogen bonding, the thermodynamic properties of the Zn-porphyrin:DABCO 2:1 sandwich complexation have been deduced by UV-vis and 1H-NMR titrations, which reveal that coordination of the second nitrogen of DABCO is less favorable than the first. This negative cooperativity has subsequently been introduced in a modified depolymerization model, which describes the DABCO-induced formation of an alternating supramolecular block copolymer comprising of DABCO units and hydrogen bonded, Zn-porphyrin dimers. Using multiple analytical techniques, DABCO titration experiments reveal the formation of chiral, elongated structures at a 2:1 stoichiometry of S-Zn and DABCO, respectively. The unexpected stability of the alternating copolymer towards excessive amounts of DABCO is analyzed by the model, which demonstrates that stability is provided by positive cooperativity. Unlike their stability towards excessive amounts of DABCO, preliminary chain-stopping experiments indicate that the alternating copolymers readily depolymerize upon the addition of monotopic Mn(III)-porphyrins, which reveal energy transfer upon chain stopping. In Chapter 6, the coaggregation of porphyrin monomers with different chirality is studied by chiral amplification experiments. Efficient coaggregation has been observed between achiral and chiral porphyrins, as evidenced by a strong Sergeant-and-Soldiers effect. On the other hand, no chiral amplification is observed in the Majority-Rules experiment as a consequence of narcissistic self-sorting. The distinctive behavior in chiral amplification is quantified by modeling studies that reveal a combination of high helix reversal and high mismatch penalties. The latter penalty is also operative at the end of the stack as evidenced by the induction of the supramolecular chirality upon the addition of a chiral chain stopper. For mixed-metal Sergeants-and-Soldiers and Majority-Rules studies, the same trends in chiral amplification are also observed by fluorescence quenching between Zn and Cu-porphyrins. Within the same library, the limits of coaggregation are explored by a Diluted-Majority-Rules experiment, which demonstrate that opposite enantiomers only coaggregate when achiral comonomers are added to the system. The dynamic properties of mixed-metal porphyrin assemblies are investigated by the selective removal of Zn-porphyrin comonomers by axial ligation with quinuclidine. The extraction process proceeds at different time scales depending on the coaggregated state; slow extraction kinetics are found for the Sergeant-and-Soldiers and Diluted-Majority-Rules systems, while an instant extraction process has been deduced for the self-sorted Majority-Rules system. By simultaneously monitoring the supramolecular chirality during extraction, a chiral memory effect is observed for both systems that showed slow extraction kinetics. For the Sergeant-and-Soldiers system, the remaining supramolecular backbone comprises of achiral Cu-porphyrins only, which give rise to a long-lasting chiral memory with slow, entropy-driven atropisomerization. The stability of the chiral memory is analyzed by time- and temperature-dependent CD studies; for the latter, the memory can be erased and partially restored upon heating and cooling of the solutions. In case of the Diluted-Majority-Rules experiment, the remaining supramolecular backbone comprises of a mixture of achiral and chiral Cu-porphyrins. Being present in an aggregate with the unpreferred helicity, the remaining chiral Cu-porphyrins induce a short chiral memory with enthalpy-driven atropisomerization. The final Chapter is an outlook towards porphyrin-based polymeric systems, in which non-symmetrical porphyrins are covalently linked to polymeric backbones. Preliminary feasibility studies have been performed to investigate if porphyrin-functionalized polymers offer a suitable platform to convey the stimuli-responsiveness deduced in solution to the macroscopic level

Improved understanding of boron-oxygen-related carrier lifetime degradation and regeneration in crystalline silicon solar cells

This thesis examines carrier lifetime instabilities in oxygen-rich boron-doped p-type Czochralski-grown silicon (Cz-Si) with the focus on the permanent deactivation of the boron-oxygen (BO)-related defect center leading to a regeneration in lifetime. In order to resolve contradictory statements reported previously in the literature concerning the mechanism of regeneration in this thesis, passivated emitter and rear solar cells (PERCs) fabricated on boron-doped p-type Cz-Si wafers are regenerated in darkness by carrier injection via application of a forward-bias voltage V_appl at elevated temperatures. The regeneration kinetics is analyzed under regeneration conditions by measuring the total recombination current of the solar cell at the actual regeneration temperature at varying applied voltages Vappl. In parallel, we measure the electroluminescence signal emitted by the solar cell at different time steps during regeneration to directly determine the injected excess carrier concentration Delta{n} at each applied forward-bias voltage V_appl. The deactivation rate constant R_de of the BO defect is determined from the measured time-dependent cell current. The experimental results show unambiguously for the first time that R_de increases proportionally with Delta{n} during the regeneration process, solving the inconsistencies reported in the literature under actual regeneration conditions. To identify the impact of hydrogen on the BO-related lifetime degradation and regeneration kinetics, different amounts of hydrogen are introduced into the silicon bulk by rapid thermal annealing (RTA) treatment in an infrared conveyor-belt furnace quantified by measurements of the silicon resistivity increase. The silicon resistivity increases under dark-annealing due to hydrogen passivation of boron dopant atoms. The hydrogen source in our experiments are hydrogen-rich silicon nitride (SiN_x:H) layers deposited on the silicon wafer surfaces. Varying the peak-temperature of the RTA step indicates that there exists a temperature-dependent maximum in the hydrogen content introduced into the silicon bulk. The exact position of this maximum depends on the composition of the SiN_x:H layers. The highest total hydrogen content, exceeding 10^15 cm^{-3}, is introduced into the silicon bulk from silicon-rich SiN_x layers with a refractive index of n =2.3 (at a wavelength of lamda = 633 nm) at an RTA peak temperature of 800°C. Adding a 20 nm thick Al_2O_3 interlayer in-between the silicon wafer surfaces and the SiN_x:H layers, reduces the in-diffused hydrogen content up to a factor of four, demonstrating that Al_2O_3 acts as a highly effective hydrogen diffusion barrier. By varying the Al_2O_3 thickness, the hydrogen bulk content is varied over more than one order of magnitude. In order to examine the impact of hydrogen on the degradation kinetics, all samples are illuminated at a light intensity of 0.1 suns near room temperature. No influence of the in-diffused hydrogen content on the degradation rate constant is measured, confirming that hydrogen is not involved in the BO degradation mechanism. The regeneration experiments at a light intensity of 1 suns at elevated temperatures, however, show a clear dependence on the hydrogen content with a linear increase of the regeneration rate constant with increasing bulk hydrogen concentration. An extrapolation of this correlation towards a zero in-diffused hydrogen content shows that the regeneration is still working even without any in-diffused hydrogen. Hence, our experiments clearly reveal for the first time that two distinct regeneration processes are taking place, one involving hydrogen, the other not. These results confirm a previous theoretical model, which had not been experimentally verified so far. In another series of experiments, we examine the long-term stability of the carrier lifetime in boron-doped Cz-Si materials with different boron and oxygen concentrations after regeneration in an industrial belt furnace. After firing and subsequent regeneration in the conveyor-belt furnace, the silicon samples are exposed to longterm illumination at an intensity of 0.1 suns and a sample temperature of about 30°C for more than two years. After regeneration, the lifetime samples re-degrade (30-72% reduced compared to the degradation observed without regeneration step). This re-degradation is attributed to an incomplete regeneration within the belt furnace due to the short regeneration period. All in all, the industrial process consisting of firing with subsequent regeneration in the same belt-furnace unit seems to be very effective for industrially relevant silicon materials. Typical industrial silicon wafers with a resistivity of (1.75+-0.03) Ohmcm and an interstitial oxygen concentration of (6.9+-0.3) x 10^{17} cm^{-3} show lifetimes larger than 2 ms after regeneration and two years of light exposure

Searching for the familiar

Master's Project (M.A.) University of Alaska Fairbanks, 2016This paper describes my implementation of the Language Experience Approach, a method of developing language skills, in my elementary classroom. Through the Language Experience Approach the teacher is able to tap into the rich resources of the students' home lives and start to bring that knowledge into the school. This is done by the students creating a language piece with the help of the teacher that is not only at an appropriate reading level but also is a high interest reading piece because it is comes from the students themselves. This project includes my rationale, lesson plan, and supporting materials

What’s in a mood?:looking for dynamic predictors of individual improvement in depression

Many people are affected by depression at some point in their lives, but it is unfortunately not yet well understood who will experience improvement or recurrence of symptoms, and what predicts such symptom change. Both short-lived variations in emotions and sudden shifts in symptoms appear to be relevant in predicting a better prognosis for people’s depressive complaints, on average. However, it is unclear how these findings translate to the individual. Therefore, in this dissertation I investigated the way depression changes over time in individual patients, with a specific focus on the moment-to-moment fluctuations in mood that precede the recovery of symptoms during psychological treatment. We measured people intensively throughout the day, asking them repeatedly how they were feeling at a given moment. By collecting so many measurements per person we could study the changes in emotions these people experienced over the day, as well as map the trajectory of their symptoms over time. The studies in this dissertation show that the path to recovery from depression rarely follows a simple straight line. The odds of responding to treatment were higher for people who experienced sudden symptom improvements within their overall improvement trajectory, and stronger negative emotions in the week before treatment started. We also investigated whether we could detect any early warning signals before changes in symptoms (such as improvements during psychological treatment, or a recurrence of depressive symptoms). Some people showed such early warning signals, but these signals were not detected often enough to be useful for the clinical practice yet