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41.
42.
Markus Neuenschwander Ulrich Lienhard Hans-Peter Fahrni Beat Hurni 《Helvetica chimica acta》1978,61(7):2428-2436
Amide Synthesis by Means of ‘Push-Pull’-Acetylenes ‘Push-Pull’-acetylenes react easily with carbon acids, Addition of amines to the crude reaction mixture gives amides in an excellent yield by a simple one-pot procedure. Because of the high selectivity of the acetylenes 1 towards carboxylic functions and of the high selectivity of the enol esters 4 towards amine functions, ‘push-pull’-acetylenes could be excellent reagents for peptide synthesis. 相似文献
43.
Bushev P Wilson A Eschner J Raab C Schmidt-Kaler F Becher C Blatt R 《Physical review letters》2004,92(22):223602
An excited-state atom whose emitted light is backreflected by a distant mirror can experience trapping forces, because the presence of the mirror modifies both the electromagnetic vacuum field and the atom's own radiation reaction field. We demonstrate this mechanical action using a single trapped barium ion. We observe the trapping conditions to be notably altered when the distant mirror is translated across an optical wavelength. The well-localized barium ion enables the spatial dependence of the forces to be measured explicitly. The experiment has implications for quantum information processing and may be regarded as the most elementary optical tweezers. 相似文献
44.
A.B. Mundt A. Kreuter C. Russo C. Becher D. Leibfried J. Eschner F. Schmidt-Kaler R. Blatt 《Applied physics. B, Lasers and optics》2003,76(2):117-124
We demonstrate coherent coupling of the quadrupole S1/2D5/2 optical transition of a single trapped 40Ca+ ion to the standing wave field of a high-finesse cavity. The dependence of the coupling on temporal dynamics and spatial
variations of the intracavity field is investigated in detail. By precisely controlling the position of the ion in the cavity
standing wave field and by selectively exciting vibrational state-changing transitions the ion’s quantized vibration in the
trap is deterministically coupled to the cavity mode. We confirm coherent interaction of ion and cavity field by exciting
Rabi oscillations with short resonant laser pulses injected into the cavity, which is frequency-stabilized to the atomic transition.
Received: 23 August 2002 / Published online: 8 January 2003
RID="*"
ID="*"Corresponding author. E-mail: christoph.becher@uibk.ac.at
RID="**"
ID="**"Present address: Time and Frequency Division, National Institute of Standards and Technology, Boulder, CO 80305, USA 相似文献
45.
Blatt RJ 《Community genetics》2000,3(4):204-211
While DNA databases may offer the opportunity to (1) assess population-based prevalence of specific genes and variants, (2) simplify the search for molecular markers, (3) improve targeted drug discovery and development for disease management, (4) refine strategies for disease prevention, and (5) provide the data necessary for evidence-based decision-making, serious scientific and social questions remain. Whether samples are identified, coded, or anonymous, biological banking raises profound ethical and legal issues pertaining to access, informed consent, privacy and confidentiality of genomic information, civil liberties, patenting, and proprietary rights. This paper provides an overview of key policy issues and questions pertaining to biological banking, with a focus on developments in specimen collection, transnational distribution, and public health and academic-industry research alliances. It highlights the challenges posed by the commercialization of genomics, and proposes the need for harmonization of biological banking policies. 相似文献
46.
47.
In this article we study the regularity of stationary points of the knot energies E (α) introduced by O’Hara (Topology 30(2):241–247, 1991; Topol Appl 48(2):147–161, 1992; Topol Appl 56(1):45–61, 1994) in the range ${\alpha\in(2,3)}$ . In a first step we prove that E (α) is C 1 on the set of all regular embedded curves belonging to ${{H^{(\alpha+1)/2,2}(\mathbb {R}{/}\mathbb {Z}, \mathbb {R}^n)}}$ and calculate its derivative. After that we use the structure of the Euler-Lagrange equation to study the regularity of stationary points of E (α) plus a positive multiple of the length. We show that stationary points of finite energy are of class C ∞—so especially all local minimizers of E (α) among curves with fixed length are smooth. 相似文献
48.
Letw be a suitable weight function,B
n,p denote the polynomial of best approximation to a functionf inL
w
p
[–1, 1],v
n
be the measure that associates a mass of 1/(n+1) with each of then+1 zeros ofB
n+1,p–B
n,p and be the arcsine measure defined by
. We estimate the rate at which the sequencev
n
converges to in the weak-* topology. In particular, our theorem applies to the zeros of monic polynomials of minimalL
w
p
norm.This author gratefully acknowledges partial support from NSA contract #A4235802 during 1992, AFSOR Grant 226113 during 1993 and The Alexander von Humboldt Foundation during both of these years. 相似文献
49.
50.