7,855 research outputs found
Cutting-Edge Life Sciences in Swiss Gymnasia – Success is not a Secret
What can be done to achieve a high-quality education in Life Sciences at gymnasia level that arouses the interest of most students and motivates them to accomplish high performances? The recipe for success is simple: Employ excellent natural scientists who combine the passion for their
subject with strong pedagogic skills as teachers to your school. The challenge is to create an environment that makes teaching attractive for scientists and that has a positive and lasting effect on the motivation of the teachers. We consider the following criteria especially significant:
The social structure/arrangement is likely to be the key aspect. Ideally it consists of a constructive relation between the teachers, the school administrators, the staff and most importantly the students. The work must be challenging, but the workload should be in a good proportion to the
resources of the teachers. To communicate a realistic impression of Life Sciences an adequate infrastructure and facilities are necessary that allow an education based on experiments and practica. The curriculum should consider the interests of the students and should contain topics which
are relevant for society. Finally it should grant enough educational latitude for the teachers so they can use their specialized skills. Contacts to other gymnasia, universities and industry are important for orientation, the exchange of knowledge and to enable extracurricular projects
TriMinimal Parametrization of the Neutrino Mixing Matrix
Current experimental data on neutrino mixing are very well described by
TriBiMaximal mixing. Accordingly, any phenomenological parametrization of the
MNSP matrix must build upon TriBiMaximal mixing. We propose one particularly
natural parametrization, which we call "TriMinimal". The three small deviations
of the PDG angles from their TriBiMaximal values, and the PDG phase,
parametrize the TriMinimal mixing matrix. As an important example of the
utility of this new parametrization, we present the simple resulting
expressions for the flavor-mixing probabilities of atmospheric and
astrophysical neutrinos. As no foreseeable experiment will be sensitive to more
than second order in the small parameters, we expand these flavor probabilities
to second order.Comment: Typos corrected, references added, title changed; matches version
appearing in PRL 100, 111801 (2008)
Coherent probing of excited quantum dot states in an interferometer
Measurements of elastic and inelastic cotunneling currents are presented on a
two-terminal Aharonov--Bohm interferometer with a Coulomb blockaded quantum dot
embedded in each arm. Coherent current contributions, even in magnetic field,
are found in the nonlinear regime of inelastic cotunneling at finite bias
voltage. The phase of the Aharonov--Bohm oscillations in the current exhibits
phase jumps of at the onsets of inelastic processes. We suggest that
additional coherent elastic processes occur via the excited state. Our
measurement technique allows the detection of such processes on a background of
other inelastic current contributions and contains information about the
excited state occupation probability and the inelastic relaxation rates
EC 11481-2303 - A Peculiar Subdwarf OB Star Revisited
EC 11481-2303 is a peculiar, hot, high-gravity pre-white dwarf. Previous
optical spectroscopy revealed that it is a sdOB star with an effective
temperature (Teff) of 41790 K, a surface gravity log(g)= 5.84, and He/H = 0.014
by number. We present an on-going spectral analysis by means of non-LTE
model-atmosphere techniques based on high-resolution, high-S/N optical
(VLT-UVES) and ultraviolet (FUSE, IUE) observations. We are able to reproduce
the optical and UV observations simultaneously with a chemically homogeneous
NLTE model atmosphere with a significantly higher effective temperature and
lower He abundance (Teff = 55000 K, log (g) = 5.8, and He / H = 0.0025 by
number). While C, N, and O appear less than 0.15 times solar, the iron-group
abundance is strongly enhanced by at least a factor of ten.Comment: 8 pages, 11 figure
Characterization of bimetallic interface in Cu-Al and Ni-Cu rods cold-welded by ECAP
While cold welding by equal channel angular pressing has already been confirmed to be a viable alternative to join materials that commonly tend to exhibit unwanted brittleness and other heat-induced properties, the exact processes taking place at the interface as well as their effects have not been well studied. Herein, the exact chemical composition along the bimetal interface is analyzed by multiple energy-dispersive X-ray spectroscopy line scans. Furthermore, microhardness maps are drawn up based on Vickers microindentations in the same area. Based on these findings, the presence and distribution of intermetallics, as signs of successful welding, are determined, as well as their influence on the mechanical properties of the weld.Peer ReviewedPostprint (author's final draft
Evidence for shape coexistence in Mo
A angular correlation experiment has been performed to
investigate the low-energy states of the nucleus Mo. The new data,
including spin assignments, multipole mixing ratios and lifetimes reveal
evidence for shape coexistence and mixing in Mo, arising from a proton
intruder configuration. This result is reproduced by a theoretical calculation
within the proton-neutron interacting boson model with configuration mixing,
based on microscopic energy density functional theory. The microscopic
calculation indicates the importance of the proton particle-hole excitation
across the Z=40 sub-shell closure and the subsequent mixing between spherical
vibrational and the -soft equilibrium shapes in Mo.Comment: 6 pages, 5 figures, 3 tables; published in Phys. Rev.
The Orbiter Stability Experiment on STS-40
The Orbiter Stability Experiment (OSE) was developed to evaluate the steadiness of the STS Orbiter as a potential platform for instrumentation that would image the Sun in its extreme ultraviolet and soft X-ray radiations. We were interested in any high frequency motions of the Orbiter's orientation due to normal operations and manned activities. Preliminary results are presented of the observations. Other than the expected slow motion of the Orbiter within the specified angular deadband of 0.1 degrees during the observations, it was found that high frequency (above 1 Hz) angular motions (jitter) were not detectable at the 0.25 arc sec detection limit of the most sensitive detector, for most of the period of observation. No high frequency motions were recorded during intervals that were identified with vernier thruster firings. However, one short interval with detectable spectral power to a frequency of 10 Hz has been found to date. It has not yet been correlated with a particular activity going on at the time. The results of the observations may also be of value in assessing perturbations to the Orbiter's micro-gravity environment produced by normal operations
Probing Spin-Polarized Currents in the Quantum Hall Regime
An experiment to probe spin-polarized currents in the quantum Hall regime is
suggested that takes advantage of the large Zeeman-splitting in the
paramagnetic diluted magnetic semiconductor zinc manganese selenide
(ZnMnSe). In the proposed experiment spin-polarized electrons are
injected by ZnMnSe-contacts into a gallium arsenide (GaAs) two-dimensional
electron gas (2DEG) arranged in a Hall bar geometry. We calculated the
resulting Hall resistance for this experimental setup within the framework of
the Landauer-B\"uttiker formalism. These calculations predict for 100%
spininjection through the ZnMnSe-contacts a Hall resistance twice as high as in
the case of no spin-polarized injection of charge carriers into a 2DEG for
filling factor . We also investigated the influence of the equilibration
of the spin-polarized electrons within the 2DEG on the Hall resistance. In
addition, in our model we expect no coupling between the contact and the 2DEG
for odd filling factors of the 2DEG for 100% spininjection, because of the
opposite sign of the g-factors of ZnMnSe and GaAs.Comment: 7 pages, 5 figure
Systematic screening of polyphosphate (poly P) levels in yeast mutant cells reveals strong interdependence with primary metabolism
BACKGROUND: Inorganic polyphosphate (poly P) occurs universally in all organisms from bacteria to man. It functions, for example, as a phosphate and energy store, and is involved in the activation and regulation of proteins. Despite its ubiquitous occurrence and important functions, it is unclear how poly P is synthesized or how poly P metabolism is regulated in higher eukaryotes. This work describes a systematic analysis of poly P levels in yeast knockout strains mutated in almost every non-essential gene. RESULTS: After three consecutive screens, 255 genes (almost 4% of the yeast genome) were found to be involved in the maintenance of normal poly P content. Many of these genes encoded proteins functioning in the cytoplasm, the vacuole or in transport and transcription. Besides reduced poly P content, many strains also exhibited reduced total phosphate content, showed altered ATP and glycogen levels and were disturbed in the secretion of acid phosphatase. CONCLUSION: Cellular energy and phosphate homeostasis is suggested to result from the equilibrium between poly P, ATP and free phosphate within the cell. Poly P serves as a buffer for both ATP and free phosphate levels and is, therefore, the least essential and consequently most variable component in this network. However, strains with reduced poly P levels are not only affected in their ATP and phosphate content, but also in other components that depend on ATP or free phosphate content, such as glycogen or secreted phosphatase activity
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