5,033 research outputs found
Axially linear slopes of composition for “delta” crystals
“Delta” crystals are solid solutions of miscible materials with large lattice parameter differences which contain high concentration gradients in one direction (parallel to a lattice plane strongly diffracting X-rays). The system GaSb-InSb has been chosen as suitable for study. By means of a “gradient projection method”, the growth of nearly linear composition profiles with relatively steep slopes of the lattice parameter (up to (Δa/ ) / Δz = 8.3% cm-1), adjustable by the temperature gradient, have been performed. However, the grown ingots were not monocrystalline due to the use of too high a growth rate
Internal-state thermometry by depletion spectroscopy in a cold guided beam of formaldehyde
We present measurements of the internal state distribution of
electrostatically guided formaldehyde. Upon excitation with continuous tunable
ultraviolet laser light the molecules dissociate, leading to a decrease in the
molecular flux. The population of individual guided states is measured by
addressing transitions originating from them. The measured populations of
selected states show good agreement with theoretical calculations for different
temperatures of the molecule source. The purity of the guided beam as deduced
from the entropy of the guided sample using a source temperature of 150K
corresponds to that of a thermal ensemble with a temperature of about 30 K
Sporopollenin, a natural copolymer, is robust under high hydrostatic pressure
Lycopodium sporopollenin, a natural copolymer, shows exceptional stability under high hydrostatic pressures (10 GPa) as determined by in situ high pressure synchrotron source FTIR spectroscopy. This stability is evaluated in terms of the component compounds of the sporopollenin: p-coumaric acid, phloretic acid, ferulic acid, and palmitic and sebacic acids, which represent the additional n-acid and ndiacid components. This high stability is attributed to interactions between these components, rather than the exceptional stability of any one molecular component. We propose a biomimetic solution for the creation of polymer materials that can withstand high pressures for a multitude of uses in aeronautics, vascular autografts, ballistics and light-weight protective materials
Geometric Mechanics of Curved Crease Origami
Folding a sheet of paper along a curve can lead to structures seen in
decorative art and utilitarian packing boxes. Here we present a theory for the
simplest such structure: an annular circular strip that is folded along a
central circular curve to form a three-dimensional buckled structure driven by
geometrical frustration. We quantify this shape in terms of the radius of the
circle, the dihedral angle of the fold and the mechanical properties of the
sheet of paper and the fold itself. When the sheet is isometrically deformed
everywhere except along the fold itself, stiff folds result in creases with
constant curvature and oscillatory torsion. However, relatively softer folds
inherit the broken symmetry of the buckled shape with oscillatory curvature and
torsion. Our asymptotic analysis of the isometrically deformed state is
corroborated by numerical simulations which allow us to generalize our analysis
to study multiply folded structures
Electrostatic extraction of cold molecules from a cryogenic reservoir
We present a method which delivers a continuous, high-density beam of slow
and internally cold polar molecules. In our source, warm molecules are first
cooled by collisions with a cryogenic helium buffer gas. Cold molecules are
then extracted by means of an electrostatic quadrupole guide. For ND the
source produces fluxes up to molecules/s with
peak densities up to molecules/cm. For
HCO the population of rovibrational states is monitored by depletion
spectroscopy, resulting in single-state populations up to .Comment: 4 pages, 4 figures, changes to the text, updated figures and
reference
Tuning the superconducting and magnetic properties in Fe_ySe_0.25Te_0.75 by varying the Fe-content
The superconducting and magnetic properties of FeSeTe
single crystals () were studied by means of x-ray
diffraction, SQUID magnetometry, muon spin rotation, and elastic neutron
diffraction. The samples with exhibit coexistence of bulk
superconductivity and incommensurate magnetism. The magnetic order remains
incommensurate for , but with increasing Fe content superconductivity
is suppressed and the magnetic correlation length increases. The results show
that the superconducting and the magnetic properties of the
FeSeTe can be tuned not only by varying the Se/Te ratio but
also by changing the Fe content
Clearance of meropenem during continuous renal replacement therapy in critically ill patients
Doing Occidentalism in Contemporary Japan: Nation Anthropomorphism and Sexualized Parody in Axis Power Hetalia,
Axis Powers Hetalia (2006–present), a Japanese gag comic and animation series, depicts relations between nations personified as cute boys against a background of World War I and World War II. The stereotypical rendering of national characteristics as well as the reduction of historically charged issues into amusing quarrels between nice-looking but incompetent boys was immensely popular, especially among female audiences in Japan and Asia, and among Euro-American manga, anime, and cosplay fans, but it also met with vehement criticism. Netizens from South Korea, for example, considered the Korean character insulting and in early 2009 mounted a protest campaign that was discussed in the Korean national assembly. Hetalia's controversial success relies to a great extent on the inventive conflation of male-oriented otaku fantasies about nations, weapons, and concepts represented as cute little girls, and of female-oriented yaoi parodies of male-male intimacy between powerful "white" characters and more passive Japanese ones. This investigation of the original Hetalia by male author Hidekaz Himaruya (b. 1985) and its many adaptations in female-oriented dōjinshi (fanzine) texts and conventions (between 2009 and 2011, Hetalia was by far the most adapted work) refers to notions of interrelationality, intersectionality, and positionality in order to address hegemonic representations of "the West," the orientalized "Rest" of the world, and "Japan" in the cross-gendered and sexually parodied mediascape of Japanese transnational subcultures
Attosecond control of electrons emitted from a nanoscale metal tip
Attosecond science is based on steering of electrons with the electric field
of well-controlled femtosecond laser pulses. It has led to, for example, the
generation of XUV light pulses with a duration in the sub-100-attosecond
regime, to the measurement of intra-molecular dynamics by diffraction of an
electron taken from the molecule under scrutiny, and to novel ultrafast
electron holography. All these effects have been observed with atoms or
molecules in the gas phase. Although predicted to occur, a strong light-phase
sensitivity of electrons liberated by few-cycle laser pulses from solids has
hitherto been elusive. Here we show a carrier-envelope (C-E) phase-dependent
current modulation of up to 100% recorded in spectra of electrons laser-emitted
from a nanometric tungsten tip. Controlled by the C-E phase, electrons
originate from either one or two sub-500as long instances within the 6-fs laser
pulse, leading to the presence or absence of spectral interference. We also
show that coherent elastic re-scattering of liberated electrons takes place at
the metal surface. Due to field enhancement at the tip, a simple laser
oscillator suffices to reach the required peak electric field strengths,
allowing attosecond science experiments to be performed at the 100-Megahertz
repetition rate level and rendering complex amplified laser systems
dispensable. Practically, this work represents a simple, exquisitely sensitive
C-E phase sensor device, which can be shrunk in volume down to ~ 1cm3. The
results indicate that the above-mentioned novel attosecond science techniques
developed with and for atoms and molecules can also be employed with solids. In
particular, we foresee sub-femtosecond (sub-) nanometre probing of (collective)
electron dynamics, such as plasmon polaritons, in solid-state systems ranging
in size from mesoscopic solids via clusters to single protruding atoms.Comment: Final manuscript version submitted to Natur
Estabelecimento de cultura in vitro de células embrionárias do carrapato Boophilus microplus.
bitstream/item/137709/1/PESQ-EM-ANDAMENTO-54.pdfCNPGC
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