Cole M.W.,Pennsylvania State University |
Crespi V.H.,University Park |
Dresselhaus M.S.,Massachusetts Institute of Technology |
Dresselhaus G.,Massachusetts Institute of Technology |
And 9 more authors.
Journal of Physics Condensed Matter | Year: 2010
This review addresses the field of nanoscience as viewed through the lens of the scientific career of Peter Eklund, thus with a special focus on nanocarbons and nanowires. Peter brought to his research an intense focus, imagination, tenacity, breadth and ingenuity rarely seen in modern science. His goal was to capture the essential physics of natural phenomena. This attitude also guides our writing: we focus on basic principles, without sacrificing accuracy, while hoping to convey an enthusiasm for the science commensurate with Peter's. The term 'colloquial review' is intended to capture this style of presentation. The diverse phenomena of condensed matter physics involve electrons, phonons and the structures within which excitations reside. The 'nano' regime presents particularly interesting and challenging science. Finite size effects play a key role, exemplified by the discrete electronic and phonon spectra of C60 and other fullerenes. The beauty of such molecules (as well as nanotubes and graphene) is reflected by the theoretical principles that govern their behavior. As to the challenge, 'nano' requires special care in materials preparation and treatment, since the surface-to-volume ratio is so high; they also often present difficulties of acquiring an experimental signal, since the samples can be quite small. All of the atoms participate in the various phenomena, without any genuinely 'bulk' properties. Peter was a master of overcoming such challenges. The primary activity of Eklund's research was to measure and understand the vibrations of atoms in carbon materials. Raman spectroscopy was very dear to Peter. He published several papers on the theory of phonons (Eklund 1995a Carbon 33 959-72, Eklund 1995b Thin Solid Films 257 211-32, Eklund 1992 J. Phys. Chem. Solids 53 1391-413, Dresselhaus and Eklund 2000 Adv. Phys. 49 705-814) and many more papers on measuring phonons (Pimenta 1998b Phys. Rev. B 58 16016-9, Rao 1991 a Nature 338 257-9, Rao 1997b Phys. Rev. B 55 4766-73, Rao 1997c Science 275 187-91, Rao 1998 Thin Solid Films 331 141-7). His careful sample treatment and detailed Raman analysis contributed greatly to the elucidation of photochemical polymerization of solid C 60 (Rao 1993b Science 259 955-7). He developed Raman spectroscopy as a standard tool for gauging the diameter of a single-walled carbon nanotube (Bandow 1998 Phys. Rev. Lett. 80 3779-82), distinguishing metallic versus semiconducting single-walled carbon nanotubes, (Pimenta 1998a J. Mater. Res. 13 2396-404) and measuring the number of graphene layers in a peeled flake of graphite (Gupta 2006 Nano Lett. 6 2667-73). For these and other ground breaking contributions to carbon science he received the Grqffin Lecture award from the American Carbon Society in 2005, and the Japan Carbon Prize in 2008. As a material, graphite has come full circle. The 1970s renaissance in the science of graphite intercalation compounds paved the way for a later explosion in nanocarbon research by illuminating many beautiful fundamental phenomena, subsequently rediscovered in other forms of nanocarbon. In 1985, Smalley, Kroto, Curl, Heath and O'Brien discovered carbon cage molecules called fullerenes in the soot ablated from a rotating graphite target (Kroto 1985 Nature 318 162-3). At that time, Peter's research was focused mainly on the oxide-based high-temperature superconductors. He switched to fullerene research soon after the discovery that an electric arc can prepare fullerenes in bulk quantities (Haufler 1990 J. Phys. Chem. 94 8634-6). Later fullerene research spawned nanotubes, and nanotubes spawned a newly exploding research effort on single-layer graphene. Graphene has hence evolved from an oversimplified model of graphite (Wallace 1947 Phys. Rev. 71 622-34) to a new member of the nanocarbon family exhibiting extraordinary electronic properties. Eklund's career spans this 35-year Odyssey. © 2010 IOP Publishing Ltd.
Nakazeko K.,Toho University |
Kajiwara H.,National Hospital Organization Tokyo Medical Center |
Watanabe H.,Showa University |
Kuwayama J.,Nihon Institute of Medical Science |
And 4 more authors.
Igaku butsuri : Nihon Igaku Butsuri Gakkai kikanshi = Japanese journal of medical physics : an official journal of Japan Society of Medical Physics | Year: 2012
We present a computer assisted learning (CAL) program to simulate head radiography. The program provides cone beam projections of a target volume, simulating three-dimensional computed tomography (CT) of a head phantom. The generated image is 512 x 512 x 512 pixels with each pixel 0.6 mm on a side. The imaging geometry, such as X-ray tube orientation and phantom orientation, can be varied. The graphical user interface (GUI) of the CAL program allows the study of the effects of varying the imaging geometry; each simulated projection image is shown quickly in an adjoining window. Simulated images with an assigned geometry were compared with the image obtained using the standard geometry in clinical use. The accuracy of the simulated image was verified through comparison with the image acquired using radiography of the head phantom, subsequently processed with a computed radiography system (CR image). Based on correlation coefficient analysis and visual assessment, it was concluded that the CAL program can satisfactorily simulate the CR image. Therefore, it should be useful for the training of head radiography.
Masumoto H.,University of Tsukuba |
Hashimoto T.,Yokohama Soei Junior College |
Matsui S.,University of Tsukuba
Journal of Magnetic Resonance | Year: 2010
The method of slice selection proposed for solid-state MRI by combining DANTE selective excitation with magic echo (ME) line narrowing requires a rephasing period ca. 0.6 times the DANTE excitation period. The added rephasing period results in a significant loss of sensitivity due to transverse relaxation. To solve the sensitivity problem, we make use of the self-refocusing effect of the 270° Gaussian-shaped soft pulse by introducing a 270° flipping Gaussian modulation to the ME DANTE method. This eliminates the rephasing period. The utility of the improved method is demonstrated by experiments performed on test samples of adamantane and polycarbonate. © 2010 Elsevier Inc. All rights reserved.
Sawaura T.,Yokohama City University |
Fujii D.,Yokohama City University |
Shen M.,Yokohama City University |
Yu Y.,Yokohama City University |
And 3 more authors.
Journal of Crystal Growth | Year: 2011
Dislocations in monoclinic hen egg-white lysozyme crystals were investigated by means of synchrotron monochromatic-beam X-ray topography. The loop and curved dislocations were observed to be predominant in the crystals. Almost all the dislocations lay in (1 0 1) crystallographic plane, which corresponds to that with smallest slicing energy estimated by macrobond approach. One of the Burgers vectors of the dislocations was determined to be [0 1 0], which corresponds to the smallest lattice translational vector on the (1 0 1) plane. It is suggested that the loop and curved dislocations are slip ones introduced by a stress concentration during or after the growth. © 2010 Elsevier B.V. All rights reserved.