3,109 research outputs found
A banished Adam : Mark Twain and the father of the human race
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Title from title screen of research.pdf file (viewed on September 12, 2008)Thesis (M.A.) University of Missouri-Columbia 2008.While Mark Twain has long been viewed as irreligious, scholarship in recent years has underscored the fact that Christianity, the God of the Bible, and the Presbyterianism of his youth play an integral part in his work. Appearing with particular frequency is the story of Adam and his Fall; although Twain did not believe in the literal existence of Adam, the story of the Fall resonated deeply with him and appears again and again in his works. At times, Twain uses Adam for merely comic effects, but in his in depth treatments of the Fall, Twain uses Adam as a symbol for the entire human race, through whom he can celebrate, lament, and rage about the human condition, which he saw as subject to a controlling determinism. While Twain's Adamic works have long been overlooked and under appreciated, this neglect is unwarranted. In fact, these works, while failing to reach the artistic heights of some of his more well-known writings, can be viewed as the intersection of some of the questions Twain felt were most important. This work examines Twain's religious and philosophical development over the course of his life and how these two elements affect his extensive treatment of the story of the Fall of Man. Particularly, Twain's use of Adam reflects the influence of his childhood Calvinism, the deterministic ideas present in his treatise, What Is Man?, and his lifelong obsession with the question of human origins.Includes bibliographical reference
Laboratory Study Of Frequency Dependent Streaming Potentials
Frequency dependent streaming potentials were measured on a glass capillary, porous
filter, and a sample of Boise sandstone. The pore diameters for these three samples
range from 1 millimeter to 34 micrometers. The frequencies used in these experiments
range from 0-600 Hz with the critical frequencies being 6.8 Hz, 90 Hz, and 400 Hz
for the three specimens. The fluid was moved relative to the sample with the pressure
measured by hydrophones and the streaming potential measured using silver silverchloride
electrodes. Both Packard's (1953) and Pride's (1994) models satisfactorily
predict the streaming potential behavior for these frequencies, and the measured critical
frequencies are directly related to the sample pore diameters.United States. Air Force Office of Scientific Research (Grant F49620-95-1-0224)Massachusetts Institute of Technology. Borehole Acoustics and Logging ConsortiumMassachusetts Institute of Technology. Earth Resources Laboratory. Reservoir Delineation
Consortiu
The use of oscillatory signals in the study of genetic networks
The structure of a genetic network is uncovered by studying its response to
external stimuli (input signals). We present a theory of propagation of an
input signal through a linear stochastic genetic network. It is found that
there are important advantages in using oscillatory signals over step or
impulse signals, and that the system may enter into a pure fluctuation
resonance for a specific input frequency.Comment: 46 pages, 5 figures. Submitted to PNAS on May 27th 2004. The paper is
under consideratio
Comments on the optical lineshape function: Application to transient hole-burned spectra of bacterial reaction centers
Citation: Reppert, M., Kell, A., Pruitt, T., & Jankowiak, R. (2015). Comments on the optical lineshape function: Application to transient hole-burned spectra of bacterial reaction centers. Journal of Chemical Physics, 142(9), 7. doi:10.1063/1.4913685The vibrational spectral density is an important physical parameter needed to describe both linear and non-linear spectra of multi-chromophore systems such as photosynthetic complexes. Low-temperature techniques such as hole burning (HB) and fluorescence line narrowing are commonly used to extract the spectral density for a given electronic transition from experimental data. We report here that the lineshape function formula reported by Hayes et al. [J. Phys. Chem. 98, 7337 (1994)] in the mean-phonon approximation and frequently applied to analyzing HB data contains inconsistencies in notation, leading to essentially incorrect expressions in cases of moderate and strong electron-phonon (el-ph) coupling strengths. A corrected lineshape function L(omega) is given that retains the computational and intuitive advantages of the expression of Hayes et al. [J. Phys. Chem. 98, 7337 (1994)]. Although the corrected lineshape function could be used in modeling studies of various optical spectra, we suggest that it is better to calculate the lineshape function numerically, without introducing the mean-phonon approximation. New theoretical fits of the P870 and P960 absorption bands and frequency-dependent resonant HB spectra of Rb. sphaeroides and Rps. viridis reaction centers are provided as examples to demonstrate the importance of correct lineshape expressions. Comparison with the previously determined el-ph coupling parameters [Johnson et al., J. Phys. Chem. 94, 5849 (1990); Lyle et al., ibid. 97, 6924 (1993); Reddy et al., ibid. 97, 6934 (1993)] is also provided. The new fits lead to modified el-ph coupling strengths and different frequencies of the special pair marker mode, omega(sp), for Rb. sphaeroides that could be used in the future for more advanced calculations of absorption and HB spectra obtained for various bacterial reaction centers. (c) 2015 AIP Publishing LLC
Coherent two-dimensional infrared spectroscopy: Quantitative analysis of protein secondary structure in solution
We present a method to quantitatively determine the secondary structure composition of globular proteins using coherent two-dimensional infrared (2DIR) spectroscopy of backbone amide I vibrations (1550–1720 cm−1). Sixteen proteins with known crystal structures were used to construct a library of 2DIR spectra, and the fraction of residues in α-helix, β-sheet, and unassigned conformations was determined by singular value decomposition (SVD) of the measured two-dimensional spectra. The method was benchmarked by removing each individual protein from the set and comparing the composition extracted from 2DIR against the composition determined from the crystal structures. To highlight the increased structural content extracted from 2DIR spectra a similar analysis was also carried out using conventional infrared absorption of the proteins in the library.National Science Foundation (U.S.) (CHE-0616575)National Institutes of Health (U.S.) (CHE-0911107)Agilent Technologie
Circadian rhythm and cell population growth
Molecular circadian clocks, that are found in all nucleated cells of mammals,
are known to dictate rhythms of approximately 24 hours (circa diem) to many
physiological processes. This includes metabolism (e.g., temperature, hormonal
blood levels) and cell proliferation. It has been observed in tumor-bearing
laboratory rodents that a severe disruption of these physiological rhythms
results in accelerated tumor growth. The question of accurately representing
the control exerted by circadian clocks on healthy and tumour tissue
proliferation to explain this phenomenon has given rise to mathematical
developments, which we review. The main goal of these previous works was to
examine the influence of a periodic control on the cell division cycle in
physiologically structured cell populations, comparing the effects of periodic
control with no control, and of different periodic controls between them. We
state here a general convexity result that may give a theoretical justification
to the concept of cancer chronotherapeutics. Our result also leads us to
hypothesize that the above mentioned effect of disruption of circadian rhythms
on tumor growth enhancement is indirect, that, is this enhancement is likely to
result from the weakening of healthy tissue that are at work fighting tumor
growth
Modeling of fluorescence line-narrowed spectra in weakly coupled dimers in the presence of excitation energy transfer
This work describes simple analytical formulas to describe the fluorescence line-narrowed (FLN) spectra of weakly coupled chromophores in the presence of excitation energy transfer (EET). Modeling studies for dimer systems (assuming low fluence and weak coupling) show that the FLN spectra (including absorption and emission spectra) calculated for various dimers using our model are in good agreement with spectra calculated by: (i) the simple convolution method and (ii) the more rigorous treatment using the Redfield approach [T. Renger and R. A. Marcus, J. Chem. Phys.116, 9997 (2002)]. The calculated FLN spectra in the presence of EET of all three approaches are very similar. We argue that our approach provides a simplified and computationally more efficient description of FLN spectra in the presence of EET. This method also has been applied to FLN spectra obtained for the CP47 antenna complex of Photosystem II reported by Neupane et al. [J. Am. Chem. Soc.132, 4214 (2010)], which indicated the presence of uncorrelated EET between pigments contributing to the two lowest energy (overlapping) exciton states, each mostly localized on a single chromophore. Calculated and experimental FLN spectra for CP47 complex show very good qualitative agreement
The CP43 Proximal Antenna Complex of Higher Plant Photosystem II Revisited: Modeling and Hole Burning Study. I
The final version is available at:
http://pubs.acs.org/journal/jpcbfkThe CP43 core antenna complex of photosystem II is known to possess two quasi-degenerate “red”-trap states (Jankowiak, R. et al. J. Phys. Chem. B 2000, 104, 11805). It has been suggested recently ( Zazubovich, V.; Jankowiak, R. J. Lumin. 2007, 127, 245) that the site distribution functions of the red states (A and B) are uncorrelated and that narrow holes are burned in the subpopulations of chlorophylls (Chls) from states A and B that are the lowest-energy Chl in their complex and previously thought not to transfer energy. This model of uncorrelated excitation energy transfer (EET) between the quasidegenerate bands is expanded by taking into account both electron−phonon and vibrational coupling. The model is applied to fit simultaneously absorption, emission, zero-phonon action, and transient hole burned (HB) spectra obtained for the CP43 complex with minimized contribution from aggregation. It is demonstrated that the above listed spectra can be well-fitted using the uncorrelated EET model, providing strong evidence for the existence of efficient energy transfer between the two lowest energy states, A and B (either from A to B or from B to A), in CP43. Possible candidate Chls for the low-energy A and B states are discussed, providing a link between CP43 structure and spectroscopy. Finally, we propose that persistent holes originate from regular NPHB accompanied by the redistribution of oscillator strength due to excitonic interactions, rather than photoconversion involving Chl−protein hydrogen bonding, as suggested before (Hughes J. L. et al. Biochemistry 2006, 45, 12345). In the accompanying paper ( Reppert, M.; Zazubovich, V.; Dang, N. C.; Seibert, M.; Jankowiak, R. J. Phys. Chem. B 2008, 9934), it is demonstrated that the model discussed in this manuscript is consistent with excitonic calculations, which also provide very good fits to both transient and persistent HB spectra obtained under non-line-narrowing conditions.This work was supported by the start-up funding at the Department of Chemistry, Kansas State University (RJ, NCD, MR and BN), and in part by the U.S. Department of Energy (DOE) EPSCoR grant (RJ), Energy Biosciences Program, Basic Energy Sciences, DOE (MS and NCD) and BFU2005-07422-CO2-01; Spain (RP). VZ acknowledges support by NSERC.Peer reviewe
Zeta potential in intact natural sandstones at elevated temperatures
Supporting data are included in PDF and CSV files; any additional data may be obtained from the corresponding author (e-mail: [email protected]). TOTAL is thanked for partial support of Jackson's Chair in Geological Fluid Mechanics and for supporting the activities of the TOTAL Laboratory for Reservoir Physics at Imperial College London where these experiments were conducted. The Editor thanks Andre Revil and Paul Glover for their assistance in evaluating this paper.Peer reviewedPublisher PD
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