1,411 research outputs found
Frontiers of parasitology research in the People's Republic of China : infection, diagnosis, protection and surveillance
ABSTRACT: Control and eventual elimination of human parasitic diseases in the People's Republic of China (P.R. China) requires novel approaches, particularly in the areas of diagnostics, mathematical modelling, monitoring, evaluation, surveillance and public health response. A comprehensive effort, involving the collaboration of 188 scientists (<85% from P.R. China) from 48 different institutions and universities (80% from P.R. China), covers this collection of 29 articles published in Parasites & Vectors. The research mainly stems from a research project entitled 'Surveillance and diagnostic tools for major parasitic diseases in P.R. China' (grant no. 2008ZX10004-011) and highlights the frontiers of research in parasitology. The majority of articles in this thematic series deals with the most important parasitic diseases in P.R. China, emphasizing Schistosoma japonicum, Plasmodium vivax and Clonorchis sinensis plus some parasites of emerging importance such as Angiostrongylus cantonensis. Significant achievements have been made through the collaborative research programme in the following three fields: (i) development of control strategies for the national control programme; (ii) updating the surveillance data of parasitic infections both in human and animals; and (iii) improvement of existing, and development of novel, diagnostic tools to detect parasitic infections. The progress is considerable and warrants broad validation efforts. Combined with the development of improved tools for diagnosis and surveillance, integrated and multi-pronged control strategies now pave the way for elimination of parasitic diseases in P.R. China. Experiences and lessons learned can stimulate control and elimination efforts of parasitic diseases in other parts of the world
Sub-dekahertz ultraviolet spectroscopy of 199Hg+
Using a laser that is frequency-locked to a Fabry-Perot etalon of high
finesse and stability, we probe the 5d10 6s 2S_1/2 (F=0) - 5d9 6s 2D_5/2 (F=2)
Delta-m_F = 0 electric-quadrupole transition of a single laser-cooled 199Hg+
ion stored in a cryogenic radio-frequency ion trap. We observe
Fourier-transform limited linewidths as narrow as 6.7 Hz at 282 nm (1.06 X
10^15 Hz), yielding a line Q = 1.6 X 10^14. We perform a preliminary
measurement of the 5d9 6s2 2D_5/2 electric-quadrupole shift due to interaction
with the static fields of the trap, and discuss the implications for future
trapped-ion optical frequency standards.Comment: 4 pages, 4 figures, submitted for publicatio
SEPARATION OF MITOCHONDRIAL MEMBRANES OF NEUROSPORA CRASSA : II. Submitochondrial Localization of the Isoleucine-Valine Biosynthetic Pathway
Separation of Neurospora mitochondrial outer membranes from the inner membrane/matrix fraction was effected by digitonin treatment and discontinuous density gradient centrifugation. The solubilization of four isoleucine-valine biosynthetic enzymes was studied as a function of digitonin concentration and time of incubation in the detergent. The kinetics of the appearance of valine biosynthetic function in fractions outside of the inner membrane/matrix fraction, coupled with enzyme solubilization patterns similar to that for the matrix marker, mitochondrial malate dehydrogenase, indicate that the four isoleucine-valine pathway enzymes are localized in the mitochondrial matrix
The Potential and Limitations of 2D Seismic Experiments for 3D Tomography
The Liguro-Provençal Basin is located in a complex tectonic area, at the junction of the Western Alps and Northern Apennines. Despite its central location within Europe, much about the basin, including the character of the crust, and the continuation of the Alpine orogen offshore, remain ambiguous.
The basin began opening in the late Oligocene as a back-arc basin related to the retreat of the Apennine subduction zone. Opening continued into the early Miocene with the counter-clockwise rotation of the Corsica-Sardinia block to its current position. In the southern part of the basin where this rotation opened the widest, seismic tomography has shown evidence of oceanic crust, however, the extent of this spreading zone northward into the Ligurian Sea is poorly mapped. The nature of the crust in the basin, whether atypical oceanic crust or partially serpentinized mantle overlain by sediments or highly thinned continental crust is still a matter of debate.
At a larger scale there are still open questions as to the continuation of the alpine orogen offshore, and the change in polarity between the Alp and Apennine subduction zones. As well, present day seismicity with thrust-faulting focal mechanisms have been observed in the basin, indicating that the stress field is now compressive. This could potentially reactivate rift-structures in the basin, which are difficult to map due to thick sediment cover including a layer of Messinian salt with variable thickness.
These open questions, and the accessibility of the basin in the heart of Europe, have led to the collection of at least 18 active seismic profiles, and even more multi-channel seismic lines. Each of these studies have contributed to understanding the tectonics of the area through 2D tomography along the profile, but these are small snapshots of a complex setting. The amount of data that has been collected provides a unique opportunity to combine data sets and examine the possibility of gaining new information in the form of 3D tomography from existing 2D data sets.
In this project we use active seismic data from the LOBSTER-AlpArray Experiment, the GROSMarin Experiment, and the SARDINIA Experiment, as well as passive seismic data from the AlpArray Experiment and the ISC Bulletin. We explore the potential and limitations of these data sets for use in 3D tomography using two new methods. We first use off-profile stations along a 2D seismic line combined with passive seismicity to provide back-shots for the stations, then in the Gulf of Lion we use two parallel seismic profiles where stations recorded shots from both profiles. This project is part of the DFG Priority Program “Mountain Building Processes in Four Dimensions (4DMB)”
Laser frequency stabilization to a single ion
A fundamental limit to the stability of a single-ion optical frequency
standard is set by quantum noise in the measurement of the internal state of
the ion. We discuss how the interrogation sequence and the processing of the
atomic resonance signal can be optimized in order to obtain the highest
possible stability under realistic experimental conditions. A servo algorithm
is presented that stabilizes a laser frequency to the single-ion signal and
that eliminates errors due to laser frequency drift. Numerical simulations of
the servo characteristics are compared to experimental data from a frequency
comparison of two single-ion standards based on a transition at 688 THz in
171Yb+. Experimentally, an instability sigma_y(100 s)=9*10^{-16} is obtained in
the frequency difference between both standards.Comment: 15 pages, 5 figures, submitted to J. Phys.
Coherent optical phase transfer over a 32-km fiber with 1-s instability at
The phase coherence of an ultrastable optical frequency reference is fully
maintained over actively stabilized fiber networks of lengths exceeding 30 km.
For a 7-km link installed in an urban environment, the transfer instability is
at 1-s. The excess phase noise of 0.15 rad, integrated from
8 mHz to 25 MHz, yields a total timing jitter of 0.085 fs. A 32-km link
achieves similar performance. Using frequency combs at each end of the
coherent-transfer fiber link, a heterodyne beat between two independent
ultrastable lasers, separated by 3.5 km and 163 THz, achieves a 1-Hz linewidth.Comment: 4 pages, 4 figure
Complementation of Subquandles
Saki and Kiani proved that the subrack lattice of a rack is necessarily
complemented if is finite but not necessarily complemented if is
infinite. In this paper, we investigate further avenues related to the
complementation of subquandles. Saki and Kiani's example of an infinite rack
without complements is a quandle, which is neither ind-finite nor profinite. We
provide an example of an ind-finite quandle whose subobject lattice is not
complemented, and conjecture that profinite quandles have complemented
subobject lattices. Additionally, we provide a complete classification of
subquandles whose set-theoretic complement is also a subquandle, which we call
\textit{strongly complemented}, and provide a partial transitivity criterion
for the complementation in chains of strongly complemented subquandles. One
technical lemma used in establishing this is of independent interest: the inner
automorphism group of a subquandle is always a subquotient of the inner
automorphism group of the ambient quandle
Quantum state engineering on an optical transition and decoherence in a Paul trap
A single Ca+ ion in a Paul trap has been cooled to the ground state of
vibration with up to 99.9% probability. Starting from this Fock state |n=0> we
have demonstrated coherent quantum state manipulation on an optical transition.
Up to 30 Rabi oscillations within 1.4 ms have been observed. We find a similar
number of Rabi oscillations after preparation of the ion in the |n=1> Fock
state. The coherence of optical state manipulation is only limited by laser and
ambient magnetic field fluctuations. Motional heating has been measured to be
as low as one vibrational quantum in 190 ms.Comment: 4 pages, 5 figure
Observation of the 1S0 - 3P0 clock transition in 27Al+
We report for the first time, laser spectroscopy of the 1S0 - 3P0 clock
transition in 27Al+. A single aluminum ion and a single beryllium ion are
simultaneously confined in a linear Paul trap, coupled by their mutual Coulomb
repulsion. This coupling allows the beryllium ion to sympathetically cool the
aluminum ion, and also enables transfer of the aluminum's electronic state to
the beryllium's hyperfine state, which can be measured with high fidelity.
These techniques are applied to a measurement of the clock transition
frequency, \nu = 1 121 015 393 207 851(8) Hz. They are also used to measure the
lifetime of the metastable clock state, \tau = 20.6 +/- 1.4 s, the ground state
1S0 g-factor, g_S = -0.00079248(14), and the excited state 3P0 g-factor, g_P =
-0.00197686(21), in units of the Bohr magneton.Comment: 4 pages, 2 figures; updated author lis
- …