224 research outputs found
Chilled to the Pill: The Japanese Judiciary’s Cool Reception of the Poison Pill and Potential Repercussions
While the 1990s is frequently referred to as Japan’s “lost decade” because of the nation’s economic underperformance and weak structures for corporate governance, the past few years have shown a business environment that is in the midst of significant transition. Most importantly, Japan is experiencing a boom in mergers and acquisitions (M&A), with the first half of 2005 alone accounting for an aggregate value of 108.9 billion in Japanese M&A transactions (greater than the 108.5 billion of deal value accumulated in all of 2004). Among the major factors contributing to this trend are the improved cash positions of many companies, a record level of foreign share ownership that has helped strengthen shareholder activism, and, perhaps most significantly, the gradual unwinding of stable cross-shareholding relationships that were previously a staple of Japanese corporate strategy and stability.\u
Knudsen Diffusion in Silicon Nanochannels
Measurements on helium and argon gas flow through an array of parallel,
linear channels of 12 nm diameter and 200 micrometer length in a single
crystalline silicon membrane reveal a Knudsen diffusion type transport from
10^2 to 10^7 in Knudsen number Kn. The classic scaling prediction for the
transport diffusion coefficient on temperature and mass of diffusing
species,D_He ~ sqrt(T), is confirmed over a T range from 40 K to 300 K for He
and for the ratio of D_He/D_Ar ~ sqrt(m_Ar/m_He). Deviations of the channels
from a cylindrical form, resolved with transmission electron microscopy down to
subnanometer scales, quantitatively account for a reduced diffusivity as
compared to Knudsen diffusion in ideal tubular channels. The membrane
permeation experiments are described over 10 orders of magnitude in Kn,
encompassing the transition flow regime, by the unified flow model of Beskok
and Karniadakis.Comment: 4 pages, 3 figure
Infrared study of the phonon modes in PrMnO and CaMnO
The infrared (IR) reflectivity spectra of orthorhombic manganese perovskites
PrMnO and CaMnO are studied in the frequency range of optical phonon
modes at temperatures varying from 300 to 4 K. The IR phonon spectra of these
two materials are analyzed by a fitting procedure based on a Lorentz model, and
assigned to definite vibrational modes of structures by comparison with
the results of lattice dynamical calculations. The calculations have been
performed in the framework of a shell model using short range
Born-Mayer-Buckingham and long range Coulomb potentials, whose parameters have
been optimized in order that the calculated Raman and IR active phonon
frequencies, and lattice parameters match with their experimental values. We
find a close correspondence between the values of the IR phonon frequencies of
PrMnO and CaMnO, which shows that the substitution of the Pr
ions with Ca results in a reduction of the frequency of medium- and
high-energy IR phonons, and an increase of the frequency of those of
low-energy. Nevertheless, the experimentally obtained IR phonon amplitudes of
the two materials appear to be unrelated. A comparative study of the
vibrational patterns of these modes reveals that most of them correspond to
complex atomic vibrations significantly different from PrMnO to CaMnO
which cannot be assigned only to a given type of vibration (external, bending,
or stretching modes). In particular, these results confirm that the structure
of CaMnO is quite far from the ideal (cubic) perovskite structure.Comment: 10 pages, 6 figure
Observation of charge-density-wave excitations in manganites
In the optical conductivity of four different manganites with commensurate
charge order (CO), strong peaks appear in the meV range below the ordering
temperature T_{CO}. They are similar to those reported for one-dimensional
charge density waves (CDW) and are assigned to pinned phasons. The peaks and
their overtones allow one to obtain, for La{1-n/8}Ca{n/8}$MnO{3} with n = 5, 6,
the electron-phonon coupling, the effective mass of the CO system, and its
contribution to the dielectric constant. These results support a description of
the CO in La-Ca manganites in terms of moderately weak-coupling and of the CDW
theory.Comment: To be published on Phys. Rev. Let
The E5 protein of the human papillomavirus type 16 down-regulates HLA-I surface expression in calnexin-expressing but not in calnexin-deficient cells
The human papillomavirus type 16 E5 protein (HPV16 E5) down-regulates surface expression of HLA-I molecules. The molecular mechanisms underlying this effect are so far unknown. Here we show that HPV16 E5 down-regulates HLA-I surface expression in calnexin-containing but not in calnexin-deficient cells. Immunoprecipitation experiments reveal that calnexin and HPV16E5 can be co-precipitated and that this association depends on the presence of a wild-type first hydrophobic region of E5. When an E5 mutant (M1) in which the first putative transmembrane helix had been disrupted was used for the transfections calnexin-E5 co-precipitation was strongly impaired. In addition, we show that the M1 mutant is only able to marginally down-regulate HLA-I surface expression compared to the wild-type protein. Besides, we demonstrate that E5 forms a ternary complex with calnexin and the heavy chain of HLA-I, which is mediated by the first hydrophobic region of the E5 protein. On the basis of our results we conclude that formation of this complex is responsible for retention of HLA-I molecules in the ER of the cells
NASA Desert RATS 2010: Preliminary Results for Science Operations Conducted in the San Francisco Volcanic Field, Arizona
The National Aeronautics and Space Administration (NASA) is working with international partners to develop the space architectures and mission plans necessary for human spaceflight beyond earth orbit. These mission plans include the exploration of planetary surfaces with significant gravity fields. The Apollo missions to the Moon demonstrated conclusively that surface mobility is a key asset that improves the efficiency of human explorers on a planetary surface. NASA's Desert Research and Technology Studies (Desert RATS) is a multi-year series tests of hardware and operations carried out annually in the high desert of Arizona. Conducted since 1998, these activities are designed to exercise planetary surface hardware and operations in relatively harsh climatic conditions where long-distance, multi-day roving is achievabl
Probabilistic Plane Fitting in 3D and an Application to Robotic Mapping
This paper presents a method for probabilistic plane fitting and an application to robotic 3D mapping. The plane is fitted in an orthogonal least-square sense and the output complies with the conventions of the Symmetries and Perturbation model (SPmodel). In the second part of the paper, the presented plane fitting method is used within a 3D mapping application. It is shown that by using probabilistic information, high precision 3D maps can be generate
Pseudogap and charge density waves in two dimensions
An interaction between electrons and lattice vibrations (phonons) results in
two fundamental quantum phenomena in solids: in three dimensions it can turn a
metal into a superconductor whereas in one dimension it can turn a metal into
an insulator. In two dimensions (2D) both superconductivity and charge-density
waves (CDW) are believed to be anomalous. In superconducting cuprates, critical
transition temperatures are unusually high and the energy gap may stay unclosed
even above these temperatures (pseudogap). In CDW-bearing dichalcogenides the
resistivity below the transition can decrease with temperature even faster than
in the normal phase and a basic prerequisite for the CDW, the favourable
nesting conditions (when some sections of the Fermi surface appear shifted by
the same vector), seems to be absent. Notwithstanding the existence of
alternatives to conventional theories, both phenomena in 2D still remain the
most fascinating puzzles in condensed matter physics. Using the latest
developments in high-resolution angle-resolved photoemission spectroscopy
(ARPES) here we show that the normal-state pseudogap also exists in one of the
most studied 2D examples, dichalcogenide 2H-TaSe2, and the formation of CDW is
driven by a conventional nesting instability, which is masked by the pseudogap.
Our findings reconcile and explain a number of unusual, as previously believed,
experimental responses as well as disprove many alternative theoretical
approaches. The magnitude, character and anisotropy of the 2D-CDW pseudogap are
intriguingly similar to those seen in superconducting cuprates.Comment: 14 pages including figures and supplementary informatio
A Compact Approximate Solution to the Friedel-Anderson Impuriy Problem
An approximate groundstate of the Anderson-Friedel impurity problem is
presented in a very compact form. It requires solely the optimization of two
localized electron states and consists of four Slater states (Slater
determinants). The resulting singlet ground state energy lies far below the
Anderson mean field solution and agrees well with the numerical results by
Gunnarsson and Schoenhammer, who used an extensive 1/N_{f}-expansion for a spin
1/2 impurity with double occupancy of the impurity level.
PACS: 85.20.Hr, 72.15.R
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