Ultrafast Vibrational Dynamics of Biomimetic Catalysts

Ultrafast two-dimensional infrared (2D-IR) spectroscopy is used in this work to study the vibrational dynamics of a series of biomimetic catalysts. We set out to investigate the vibrational dynamics of catalytic compounds in systems directly relevant to molecular reactivity, specifically reactive oxidation states, catalytically relevant self-isomerizations, dendritically-induced nano-confinement, and excitonic coherence transfer. For most of the work performed for this thesis we used diiron hexacarbonyl small-molecule mimics of the [FeFe]-hydrogenase enzyme’s active site. The vibrational dynamics of [(1,1’-bis(diphenylphosphino)ferrocene)chromium-(CO)4] (DPPFCr) in its neutral, closed-shell state were compared to the vibrational dynamics of DPPFCr as a cation radical. This comparison is possible because molecular oxidation does not significantly change the vibrational displacements of the carbonyl modes, which are studied here. Molecular oxidation induces an acceleration of the vibrational relaxation of the carbonyl modes but does not significantly affect the spectral diffusion dynamics of the carbonyl groups. We attribute this to an idiosyncrasy of the non-interacting solvent used for the experiment, CH2Cl2, which was chosen specifically for the weak nature of its solvent-solute interactions. Unexpectedly pronounced and slow spectral diffusion in the carbonyl modes of (µ-pdt)[Fe(CO)3]2 (pdt = 1,3-propanedithiolate) was observed in alkane solvents. The contribution of solvent-solute interactions in alkane solvents to spectral diffusion is expected to be minimal, and we related the spectral diffusion to fluctuations of the carbonyl potential induced by a catalytically-relevant mode of molecular fluxionality in (µ-pdt)[Fe(CO)3]2. Comparison with a different diiron hexacarbonyl compound, (µ-edt)[Fe(CO)3]2 (edt = 1,2-ethanedithiolate), effectively ruled out isomerization of the bridging organic disulfide group, and a Boltzmann distribution of states derived from electronic structure calculations supported our hypothesis by suggesting that a significant distribution of molecular conformations were present in at room temperature. Other fluxional organometallic complexes M3(CO)12 (M=Ru, Os) displayed similar spectral diffusion. This is the first use of spectral diffusion to study molecular conformational flexibility. We also observed an unexpected dependence of the rate of intracarbonyl IVR on the chain length of the alkane solvent. Nano-confinement has been reported on several occasions to favorably modulate the reactivity of diiron hexacarbonyl compounds, and dendritic assemblies with diiron hexacarbonyl cores were synthesized and the vibrational dynamics of the carbonyl groups were compared to the vibrational dynamics of carbonyls on similar diiron hexacarbonyl compounds without dendritic groups. Slower IVR and an additional timescale of spectral diffusion were observed in dendritic assemblies, which are hypothesized to reflect nano-modulation of the carbonyl group’s first solvation shell by the dendritic groups. Three diiron hexacarbonyl compounds with differing bridging disulfide groups (edt, pdt, and o-xylyldithiolate) are found to display unusual modulations of cross peak intensity which have previously been identified as spectral signatures of vibrational coherence transfer. Specific modulations of cross peak amplitude are observed in all three compounds, suggesting that certain coherence transfer events are common in diiron hexacarbonyl compounds, and an oscillatory frequency resulting from coherence transfer between bright and dark vibrational modes is identified.PHDChemistryUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/145788/1/zpeckert_1.pd

Traditional used Plants against Cognitive Decline and Alzheimer Disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized clinically by progressive memory deficits, impaired cognitive function, and altered and inappropriate behavior. Aging represents the most important risk factor for AD and the global trend in the phenomenon of population aging has dramatic consequences for public health, healthcare financing, and delivery systems in the word and, especially in developing countries. Mounting evidence obtained in in vitro and in vivo studies, suggests that various traditionally used plants in Asia, India, and Europe significantly affect key metabolic alterations culminating in AD-typical neurodegeneration. The present article aims to bring the reader up-to-date on the most recent studies and advances describing the direct and indirect activities of traditional used plants and its constituents possibly relieving features of AD. A variety of traditional used plants and its extracts exerted activities on AD related drug targets including AChE activity, antioxidative activity, modulation of Aβ-producing secretase activities, Aβ-degradation, heavy metal chelating, induction of neurotrophic factors, and cell death mechanisms. Although pre-clinical investigations identified promising drug candidates for AD, clinical evidences are still pending

Optimal entanglement criterion for mixed quantum states

We develop a strong and computationally simple entanglement criterion. The criterion is based on an elementary positive map Phi which operates on state spaces with even dimension N >= 4. It is shown that Phi detects many entangled states with positive partial transposition (PPT) and that it leads to a class of optimal entanglement witnesses. This implies that there are no other witnesses which can detect more entangled PPT states. The map Phi yields a systematic method for the explicit construction of high-dimensional manifolds of bound entangled states.Comment: 4 pages, no figures, replaced by published version (minor changes), Journal-reference adde

Large-Scale Mechanical Buckle Fold Development and the Initiation of Tensile Fractures

Tensile failure associated with buckle folding is commonly associated to the distribution of outer arc extension but has also been observed on fold limbs. This study investigates whether tensile stresses and associated failure can be explained by the process of buckling under realistic in situ stress conditions. A 2-D plane strain finite element modeling approach is used to study single-layer buckle folds with a Maxwell viscoelastic rheology. A variety of material parameters are considered and their influence on the initiation of tensile stresses during the various stages of deformation is analyzed. It is concluded that the buckling process determines the strain distribution within the fold layer but is not solely responsible for the initiation of tensile stresses. The modeling results show that tensile stresses are most dependent on the permeability, viscosity, and overburden thickness. Low permeability (\u3c10-19 m2), high viscosity (≥1021 Pa s), and low overburden pressure can explain tensile failure at the fold hinge. Tensile stresses in the limb of the fold cannot (in general) be explained by buckling. Rather, it develops due to a combination of compression and erosional unloading. The modeling results show that erosion of high permeability rocks can explain the generation of tensile stresses at significant depths (∼2 km) both at the hinge of the fold and throughout the limb of the fold. This study shows that tensile stresses and associated failure within buckle folds is directly dependent on the distribution of material parameters but moreover to the strain history of the geologic system

Prognostic significance of DNA cytometry in cutaneous malignant lymphomas.

The current classification of cutaneous malignant lymphomas (ML) into low-grade and high-grade lymphomas was found to be of limited reproducibility and permitted only a rough prediction about outcome. With this in mind, the relationship between nuclear DNA content and both prognosis and histologic grading according to the Kiel classification was evaluated on Feulgen-stained imprint specimens. In all, 49 cases of malignant non-Hodgkin's lymphoma, primary of the skin or with an involvement of the skin as one of the first symptoms, were studied using a computerized high-resolution image analysis system. The 2c deviation index (2cDI), which reflects the variation of the nuclear DNA values around the normal diploid peak, was found to be the best prognostically relevant criterion. Using the 2cDI, a significant discrimination (P less than 0.001 in the U test) between low-grade and high-grade ML was achieved. The prognostic benefit of the 2cDI was well documented by a significant inverse correlation between the 2cDI and the period of time until the patients progressed at least into one higher stage or died of lymphoma (r equals -0.63, P less than 0.05). In addition, the 2cDI enabled prognosis of the course of disease. In the group with low 2cDI values (2cDI, less than 0.5), no progression of the disease was observed after 1 year. In the groups presenting with a 2cDI between 0.5 and 1.0 and higher than 1.0, a progression was found in 57% and 64% of the cases studied, respectively. In conclusion, these measurements indicate that the determination of DNA distribution patterns in imprint specimens allows a precise and objective prognostic evaluation of cutaneous ML

Towards Agility: Definition, Benchmark and Design Considerations for Small, Quadrupedal Robots

Agile quadrupedal locomotion in animals and robots is yet to be fully understood, quantified or achieved. An intuitive notion of agility exists, but neither a concise definition nor a common benchmark can be found. Further, it is unclear, what minimal level of mechatronic complexity is needed for this particular aspect of locomotion. In this thesis we address and partially answer two primary questions: (Q1) What is agile legged locomotion (agility) and how can wemeasure it? (Q2) How can wemake agile legged locomotion with a robot a reality? To answer our first question, we define agility for robot and animal alike, building a common ground for this particular component of locomotion and introduce quantitative measures to enhance robot evaluation and comparison. The definition is based on and inspired by features of agility observed in nature, sports, and suggested in robotics related publications. Using the results of this observational and literature review, we build a novel and extendable benchmark of thirteen different tasks that implement our vision of quantitatively classifying agility. All scores are calculated from simple measures, such as time, distance, angles and characteristic geometric values for robot scaling. We normalize all unit-less scores to reach comparability between different systems. An initial implementation with available robots and real agility-dogs as baseline finalize our effort of answering the first question. Bio-inspired designs introducing and benefiting from morphological aspects present in nature allowed the generation of fast, robust and energy efficient locomotion. We use engineering tools and interdisciplinary knowledge transferred from biology to build low-cost robots able to achieve a certain level of agility and as a result of this addressing our second question. This iterative process led to a series of robots from Lynx over Cheetah-Cub-S, Cheetah-Cub-AL, and Oncilla to Serval, a compliant robot with actuated spine, high range of motion in all joints. Serval presents a high level of mobility at medium speeds. With many successfully implemented skills, using a basic kinematics-duplication from dogs (copying the foot-trajectories of real animals and replaying themotion on the robot using a mathematical interpretation), we found strengths to emphasize, weaknesses to correct and made Serval ready for future attempts to achieve even more agile locomotion. We calculated Servalâs agility scores with the result of it performing better than any of its predecessors. Our small, safe and low-cost robot is able to execute up to 6 agility tasks out of 13 with the potential to reachmore after extended development. Concluding, we like to mention that Serval is able to cope with step-downs, smooth, bumpy terrain and falling orthogonally to the ground

Vitamin C and Its Radicals: Tautomerism, Electronic Structure and Properties

The biological importance and activity of ascorbic acid and its radicals are briefly reviewed. The quantum mechanical calculations performed on these remarkable compounds are presented in some detail. Particular attention is devoted to structural and electronic features offered by the semiempirical MINDO/3 and MNDO schemes. By making use of the self-consistent charge (SCC-MO) method, the ESCA spectra of the ascorbic acid tautomers are predicted. It is found that the radical anion is more stable than each of the four AA tautomers. This is of importance because the unusual biological protective property of ascorbate against free radical damage is most likely related to the stability of its radical, Ortgins of the enhanced stability of the radical anion are analyzed by the energy partitioning technique

Adaptive foot design for small quadruped robots

Biologically inspired robots that are used for research of the animal and the technological realm become more and more refined. Control schemes for sensor-less and sensorized robots were developed, are able to handle torque control and sometimes even adapt to a changing task set. Further mechanics and electronics have evolved and take part in more reliable and robust bio-inspired robots. Robots reproduce animal structures or use bio-mechanical principles to excel in a specific task. Never the less, during this evolution of robots the feet were often oversimplified compared to their animal counterparts. Our current work centers around the foot as a bio-mechanically complex but extremely important end-effector

Gas-to-aqueous Phase Transfer for Three Paint Solvents Injected into an Abiotic, Industrial Biotrickling Filter Measured with a Flame Ionization Detector

This is a knowledge contribution to the unsatisfactory biodegradation problem, when biotrickling filters are purifying mixed paint solvents. A biotrickling filter manufacturer reported low biodegradation rates during the purification of a hydrocarbon pollutant mix from an industrial paint spraying floor. From a gas chromatograph/mass spectrometer analysis both hydrophilic and hydrophobic solvents were found in the polluted air. It is known that biodegradation is retarded, if the pollutant does not transfer from gas to liquid into the biofilm and it was therefore suspected that hydrophobic pollutants do not sufficiently migrate into the water/biofilm. To test this hypothesis, pure, rather than mixed pollutants, were injected into the abiotic biotrickling filter. When hydrophobic paint solvent (xylene) was sprayed into the biotrickling filter, the solvent load at the outlet of the filter was almost as high as at the inlet. But when pure, hydrophilic paint solvent (PGME) was sprayed into the abiotic biotrickling filter, the solvent load measured at the outlet of the filter was zero, indicating complete dissolution into the circulation water. Carbon/solvent loads at the filter outlet and inlet were measured with a portable flame ionization detector instrument. The experiment confirms that the hydrophobic solvent does not migrate into the liquid phase. This poor mass transfer of hydrophobic solvents is likely to be the reason for the low biodegradation rate. The result is highly relevant to the paint spraying industry and manufacturers of exhaust gas treatment equipment alike, who spend millions in non-sustainable incineration of exhaust gases