| 1. |
- Schimel, D, et al.
(author)
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Contribution of increasing CO2 and climate to carbon storage by ecosystems in the United States
- 2000
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In: Science. - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 287:5460, s. 2004-2006
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Journal article (peer-reviewed)abstract
- The effects of increasing carbon dioxide (CO2) and climate on net carbon storage in terrestrial ecosystems of the conterminous United States for the period 1895-1993 were modeled with new, detailed historical climate information. For the period 1980-1993, results from an ensemble of three models agree within 25%, simulating a land carbon sink from CO2 and climate effects of 0.08 gigaton of carbon per year. The best estimates of the total sink from inventory data are about three times larger, suggesting that processes such as regrowth on abandoned agricultural land or in forests harvested before 1980 have effects as large as or larger than the direct effects of CO2 and climate. The modeled sink varies by about 100% from year to year as a result of climate variability.
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| 2. |
- Antzutkin, Oleg, et al.
(author)
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Multiple quantum solid-state NMR indicates a parallel, not antiparallel, organization of β-sheets in Alzheimer's β-amyloid fibrils
- 2000
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In: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 97:24, s. 13045-13050
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Journal article (peer-reviewed)abstract
- Senile plaques associated with Alzheimer's disease contain deposits of fibrils formed by 39- to 43-residue β-amyloid peptides with possible neurotoxic effects. X-ray diffraction measurements on oriented fibril bundles have indicated an extended β-sheet structure for Alzheimer's β-amyloid fibrils and other amyloid fibrils, but the supramolecular organization of the β-sheets and other structural details are not well established because of the intrinsically noncrystalline, insoluble nature of amyloid fibrils. Here we report solid-state NMR measurements, using a multiple quantum (MQ) 13C NMR technique, that probe the β-sheet organization in fibrils formed by the full-length, 40-residue β-amyloid peptide (Aβ1-40). Although an antiparallel β-sheet organization often is assumed and is invoked in recent structural models for full-length β-amyloid fibrils, the MQNMR data indicate an in-register, parallel organization. This work provides site-specific, atomic-level structural constraints on full-length β-amyloid fibrils and applies MQNMR to a significant problem in structural biology.
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| 3. |
- Badelek, B, et al.
(author)
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The photon collider at TESLA
- 2004
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In: International Journal of Modern Physics A. - 0217-751X. ; 19:30, s. 5097-5186
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Research review (peer-reviewed)abstract
- High energy photon colliders (gammagamma,gammae) are based on e(-)e(-) linear colliders where high energy photons are produced using Compton scattering of laser light on high energy electrons just before the interaction point. This paper is a part of the Technical Design Report of the linear collider TESLA.(1) Physics program, possible parameters and some technical aspects of the photon collider at TESLA are discussed.
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| 4. |
- Balbach, John J., et al.
(author)
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Amyloid Fibril Formation by Aβ16-22, a Seven-Residue Fragment of the Alzheimer's β-Amyloid Peptide, and Structural Characterization by Solid State NMR
- 2000
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In: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 39:45, s. 13748-13759
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Journal article (peer-reviewed)abstract
- The seven-residue peptide N-acetyl-Lys-Leu-Val-Phe-Phe-Ala-Glu-NH2, called Aβ16-22 and representing residues 16-22 of the full-length β-amyloid peptide associated with Alzheimer's disease, is shown by electron microscopy to form highly ordered fibrils upon incubation of aqueous solutions. X-ray powder diffraction and optical birefringence measurements confirm that these are amyloid fibrils. The peptide conformation and supramolecular organization in Aβ16-22 fibrils are investigated by solid state 13C NMR measurements. Two-dimensional magic-angle spinning (2D MAS) exchange and constant-time double-quantum-filtered dipolar recoupling (CTDQFD) measurements indicate a β-strand conformation of the peptide backbone at the central phenylalanine. One-dimensional and two-dimensional spectra of selectively and uniformly labeled samples exhibit 13C NMR line widths of <2 ppm, demonstrating that the peptide, including amino acid side chains, has a well-ordered conformation in the fibrils. Two-dimensional 13C-13C chemical shift correlation spectroscopy permits a nearly complete assignment of backbone and side chain 13C NMR signals and indicates that the β-strand conformation extends across the entire hydrophobic segment from Leu17 through Ala21. 13C multiple-quantum (MQ) NMR and 13C/15N rotational echo double-resonance (REDOR) measurements indicate an antiparallel organization of β-sheets in the Aβ16-22 fibrils. These results suggest that the degree of structural order at the molecular level in amyloid fibrils can approach that in peptide or protein crystals, suggest how the supramolecular organization of β-sheets in amyloid fibrils can be dependent on the peptide sequence, and illustrate the utility of solid state NMR measurements as probes of the molecular structure of amyloid fibrils. Aβ16-22 is among the shortest fibril-forming fragments of full-length β-amyloid reported to date, and hence serves as a useful model system for physical studies of amyloid fibril formation.
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| 5. |
- Coriani, S, et al.
(author)
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On the electric field gradient induced birefringence and electric quadrupole moment of CO, N2O, and OCS.
- 2003
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In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606. ; 118:16, s. 7329-7339
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Journal article (peer-reviewed)abstract
- An ab initio coupled cluster investigation of the electric field gradient induced birefringence of three dipolar linear molecules—CO, N2O, and OCS—is presented. Special emphasis is given to the effect of triple excitations in the cluster operator on the so-called effective quadrupole center as well as to the accurate determination of the molecular electric quadrupole moment relative to this origin. Triple excitations are found to be essential in the case of CO, with reference in particular to the existing disagreement between two semiclassical theories for the interpretation of the experimentally observed birefringence. The present results favor the older theory due to Buckingham and Longuet-Higgins.©2003 American Institute of Physics.
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| 6. |
- Jonsson, D., et al.
(author)
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The Cotton-Mouton effect of gaseous CO2, N2O, OCS, and CS2. A cubic response multiconfigurational self-consistent field study
- 2001
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In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 114:19, s. 8372-8381
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Journal article (peer-reviewed)abstract
- The hypermagnetizability and the hypermagnetizability anisotropy of CO2, N2O, OCS, and CS2 are computed at a wavelength of 632.8 nm using cubic response theory with multiconfigurational self-consistent field wave functions. The anisotropies of the electric dipole polarizability and of the magnetizability are also obtained. This allows us to study the temperature dependence of the Cotton-Mouton constant for all four molecules and thus to compare to the results of the experimental study by Kling and Huttner [Chem. Phys. Lett. 90, 207 (1984)]. We also assess the importance of pure and zero-point vibrational effects on the relevant molecular properties. In particular, we show that for CO2, OCS, and CS2, the pure vibrational effects to the hypermagnetizability anisotropy can be even more important than the electronic contribution.
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| 7. |
- Rizzo, A., et al.
(author)
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Density-functional and electron correlated study of five linear birefringences - Kerr, Cotton-Mouton, Buckingham, Jones, and magnetoelectric - in gaseous benzene
- 2004
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In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 121:18, s. 8814-8830
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Research review (peer-reviewed)abstract
- We present the results of an extended study of five birefringences-Kerr, Cotton-Mouton, Buckingham, Jones, and Magnetoelectric-on benzene in the gas phase. The relevant molecular quantities-first-order properties, linear, quadratic, and cubic response functions-are computed employing the density-functional theory (DFT) response theory, with a choice of functionals. In some cases, different functionals are employed for the wave-function computational step and for the subsequent analytical response calculation to determine the combination yielding at the same time the optimal energy and energy derivative results. Augmented correlation consistent basis sets of double and triple zeta quality are used. The DFT results are compared to those obtained at the Hartree-Fock level and in some cases within a coupled cluster singles and doubles electronic structure model. The study tries to assess the ability of the DFT response theory to describe a wide range of properties in a system of rather large size and high complexity. The relative strength of the five birefringences for plausible experimental conditions is determined and, when possible, comparison is made with the results of the measurements.
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