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

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

Simulating X-ray absorption spectra with CASSCF linear response methods

In this work, two approaches for simulating X-ray absorption (XA) spectra with the complete active space self-consistent field (CASSCF) linear response (LR) method are introduced. The first approach employs the well-known core-valence separation (CVS) approximation, which is predominantly used by many other electronic structure methods for simulating X-ray spectra. The second ansatz uses the harmonic Davidson algorithm (DA) for finding interior eigenvalues that lie close to a target excitation energy shift and virtually solves a shifted-and-inverted (S&I) generalized eigenvalue problem. Our implementations of these Davidson-type algorithms for core spectroscopies converge as rapidly as the standard DA for valence excitations. It is shown in a proof-of-principle application to the Manganese atom that the additional errors for excitations energies introduced by the CVS approximation compared to the exact S&I approach are negligible for K-edges, but become larger than the methodological error of the CASSCF LR method when computing M-edges. We could also demonstrate that, in case of large active-space K-edge calculations, the computational savings of the CVS approximation are huge as the configuration part of the response vectors is completely neglected. When simulating the oxygen K-edge XA spectrum of the permanganate ion, CASSCF LR showed a better agreement with the experimental spectrum than the CAS-CI and NEVPT2 methods, however, the order of the two close-together pre-edge peaks seems to be inverted