3,100 research outputs found
Core excitation in Ozone localized to one of two symmetry-equivalent chemical bonds - molecular alignment through vibronic coupling
Core excitation from terminal oxygen O in O is shown to be an
excitation from a localized core orbital to a localized valence orbital. The
valence orbital is localized to one of the two equivalent chemical bonds. We
experimentally demonstrate this with the Auger Doppler effect which is
observable when O is core-excited to the highly dissociative
O1s7a state. Auger electrons emitted from the atomic oxygen
fragment carry information about the molecular orientation relative to the
electromagnetic field vector at the moment of excitation. The data together
with analytical functions for the electron-peak profiles give clear evidence
that the preferred molecular orientation for excitation only depends on the
orientation of one bond, not on the total molecular orientation. The
localization of the valence orbital "7a" is caused by mixing of the valence
orbital "5b" through vibronic coupling of anti-symmetric stretching mode
with b-symmetry. To the best of our knowledge, it is the first discussion
of the localization of a core excitation of O. This result explains the
success of the widely used assumption of localized core excitation in
adsorbates and large molecules
Block copolymer self-assembly for nanophotonics
The ability to control and modulate the interaction of light with matter is crucial to achieve desired optical properties including reflection, transmission, and selective polarization. Photonic materials rely upon precise control over the composition and morphology to establish periodic interactions with light on the wavelength and sub-wavelength length scales. Supramolecular assembly provides a natural solution allowing the encoding of a desired 3D architecture into the chemical building blocks and assembly conditions. The compatibility with solution processing and low-overhead manufacturing is a significant advantage over more complex approaches such as lithography or colloidal assembly. Here we review recent advances on photonic architectures derived from block copolymers and highlight the influence and complexity of processing pathways. Notable examples that have emerged from this unique synthesis platform include Bragg reflectors, antireflective coatings, and chiral metamaterials. We further predict expanded photonic capabilities and limits of these approaches in light of future developments of the field
A formal definition and a new security mechanism of physical unclonable functions
The characteristic novelty of what is generally meant by a "physical
unclonable function" (PUF) is precisely defined, in order to supply a firm
basis for security evaluations and the proposal of new security mechanisms. A
PUF is defined as a hardware device which implements a physical function with
an output value that changes with its argument. A PUF can be clonable, but a
secure PUF must be unclonable. This proposed meaning of a PUF is cleanly
delineated from the closely related concepts of "conventional unclonable
function", "physically obfuscated key", "random-number generator", "controlled
PUF" and "strong PUF". The structure of a systematic security evaluation of a
PUF enabled by the proposed formal definition is outlined. Practically all
current and novel physical (but not conventional) unclonable physical functions
are PUFs by our definition. Thereby the proposed definition captures the
existing intuition about what is a PUF and remains flexible enough to encompass
further research. In a second part we quantitatively characterize two classes
of PUF security mechanisms, the standard one, based on a minimum secret
read-out time, and a novel one, based on challenge-dependent erasure of stored
information. The new mechanism is shown to allow in principle the construction
of a "quantum-PUF", that is absolutely secure while not requiring the storage
of an exponentially large secret. The construction of a PUF that is
mathematically and physically unclonable in principle does not contradict the
laws of physics.Comment: 13 pages, 1 figure, Conference Proceedings MMB & DFT 2012,
Kaiserslautern, German
Differences in Acoustic Measures of Vowels in Ventriloquial and Normal Speech
This study investigated and compared the acoustic properties of vowels in ventriloquial and normal speech. Voice recordings of a 51 year-old male participant producing 10 words containing target vowels, three times each were made in both normal and ventriloquial speech. Standard acoustic measures for frequency were gathered using Tiger Electronics Inc., Dr. Speech Science, Ver.2.0. Fundamental frequency, first, and second formant frequencies were analyzed as compared between the two types of speech. Although the results revealed no statistically significant differences in first and second formant frequencies, slight variations do exist. Statistically significant differences were found for two words in fundamental frequency. The results would seem to suggest that as long as vowel production is within a “range” of variability, vowels may be accurately perceived
Generation of bipartite spin entanglement via spin-independent scattering
We consider the bipartite spin entanglement between two identical fermions
generated in spin-independent scattering. We show how the spatial degrees of
freedom act as ancillas for the creation of entanglement to a degree that
depends on the scattering angle, . The number of Slater determinants
generated in the process is greater than 1, corresponding to genuine quantum
correlations between the identical fermions. The maximal entanglement
attainable of 1 ebit is reached at . We also analyze a simple
dependent Bell's inequality, which is violated for
. This phenomenon is unrelated to the symmetrization
postulate but does not appear for unequal particles.Comment: 5 pages and 3 figures. Accepted in PR
Gene rearrangements in bone marrow cells of patients with acute myelogenous leukemia
At diagnosis, clonal gene rearrangement probes {[}retinoic acid receptor (RAR)-alpha, major breakpoint cluster region (M-bcr), immunoglobulin (Ig)-JH, T cell receptor (TcR)-beta, myeloid lymphoid leukemia (MLL) or cytokine genes (GM-CSF, G-CSF, IL-3)] were detected in bone marrow samples from 71 of 153 patients with acute myelogenous leukemia (AML) (46%): in 41 patients with primary AML (pAML) (58%) and in 30 patients with secondary AML (42%). In all cases with promyelocytic leukemia (AML-M3) RAR-alpha gene rearrangements were detected (n = 9). Gene rearrangements in the Ig-JH or the TcR-beta or GM-CSF or IL-3 or MLL gene were detected in 12, 10, 16 and 12% of the cases, respectively, whereas only few cases showed gene rearrangements in the M-bcr (6%) or G-CSF gene (3%). Survival of pAML patients with TcR-beta gene rearrangements was longer and survival of pAML patients with IL-3 or GM-CSF gene rearrangement was shorter than in patients without those rearrangements. No worse survival outcome was seen in patients with rearrangements in the MLL, Ig-JH or M-bcr gene. In remission of AML (CR), clonal gene rearrangements were detected in 23 of 48 cases (48%) if samples were taken once in CR, in 23 of 26 cases (88%) if samples were taken twice in CR and in 23 of 23 cases (100%) if samples were studied three times in CR. All cases with gene rearrangements at diagnosis showed the same kind of rearrangement at relapse of the disease (n = 12). Our data show that (1) populations with clonal gene rearrangements can be regularly detected at diagnosis, in CR and at relapse of AML. (2) Certain gene rearrangements that are detectable at diagnosis have a prognostic significance for the patients' outcome. Our results point out the significance of gene rearrangement analyses at diagnosis of AML in order to identify `poor risk' patients - independently of the karyotype. Moreover, the persistence of clonal cells in the further course of AML can be studied by gene rearrangement analysis. Copyright (C) 2000 S. Karger AG, Basel
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