128 research outputs found
Fish egg predation by Baltic sprat and herring: do species characteristics and development stage matter?
Predation of eggs by clupeids has been identified as a major factor contributing to early life stage mortality of Baltic cod. We used data from ichthyoplankton sampling and clupeid stomach analyses to investigate whether eggs of other fish species are to a similar extent subject to predation, and how predation pressure differs between egg development stages. Cod, sprat and rockling eggs dominated in the ichthyoplankton fraction in herring and sprat diet, whereas flounder and dab eggs occurred only occasionally. In spring, cod eggs at advanced development stages were positively and sprat eggs generally negatively selected by both predators, while fish eggs were non-selectively consumed in summer. Predation is suggested to account for a large fraction of mortality of cod eggs at older stages, i.e. those eggs, which have survived the often detrimentally low oxygen concentration in and below the permanent halocline. The consumption rates of sprat eggs at all development stages relative to production rates were considerably lower compared to cod, suggesting that egg predation is of lesser importance for sprat recruitment.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
Single-bit Feedback and Quantum Dynamical Decoupling
Synthesizing an effective identity evolution in a target system subjected to
unwanted unitary or non-unitary dynamics is a fundamental task for both quantum
control and quantum information processing applications. Here, we investigate
how single-bit, discrete-time feedback capabilities may be exploited to enact
or to enhance quantum procedures for effectively suppressing unwanted dynamics
in a finite-dimensional open quantum system. An explicit characterization of
the joint unitary propagators correctable by a single-bit feedback strategy for
arbitrary evolution time is obtained. For a two-dimensional target system, we
show how by appropriately combining quantum feedback with dynamical decoupling
methods, concatenated feedback-decoupling schemes may be built, which can
operate under relaxed control assumptions and can outperform purely closed-loop
and open-loop protocols.Comment: 12 pages, 2 figure
Control of Decoherence: Dynamical Decoupling versus Quantum Zeno Effect - a case study for trapped ions
The control of thermal decoherence via dynamical decoupling and via the
quantum Zeno effect (Zeno control) is investigated for a model of trapped ion,
where the dynamics of two low lying hyperfine states undergoes decoherence due
to the thermal interaction with an excited state. Dynamical decoupling is a
procedure that consists in periodically driving the excited state, while the
Zeno control consists in frequently measuring it. When the control frequency is
high enough, decoherence is shown to be suppressed. Otherwise, both controls
may accelerate decoherence.Comment: 24 pages, 8 figure
The distribution of quantum fidelities
When applied to different input states, an imperfect quantum operation yields
output states with varying fidelities, defined as the absolute square of their
overlap with the desired states. We present an expression for the distribution
of fidelities for a class of operations applied to a general qubit state, and
we present general expressions for the variance and input-space averaged
fidelities of arbitrary linear maps on finite dimensional Hilbert spaces.Comment: 5 pages, 1 figur
Experimental investigation of the effect of transpiration cooling on second mode instabilities in a hypersonic boundary layer
The influence of localized nitrogen transpiration on second mode instabilities in a hypersonic boundary layer is experimentally investigated. The study is conducted using a 7deg half-angle cone with a length of 1100 mm and small nose bluntness at 0deg angle of attack. Transpiration is realized through a porous Carbon/Carbon patch of 44×82 mm located near the expected boundary layer transition onset location. Transpiration mass flow rates in the range of 0.05–1% of the equivalent boundary layer edge mass flow rate were used. Experiments were conducted in the High Enthalpy Shock Tunnel Göttingen (HEG) at total enthalpies around 3 MJ/kg and unit Reynolds numbers in the range of 1.4e6 to 6.4e6 1/m. Measurements were conducted by means of coaxial thermocouples, Atomic Layer Thermopiles (ALTP), pressure transducers and high-speed schlieren. The present study shows that the most amplified second mode frequencies were shifted to lower values as nitrogen is transpired into the boundary layer. In some cases the instability amplitudes were found to be significantly reduced. The observed frequency reduction was verified to correlate with the change of the relative sonic line height in the boundary layer. The amplitude damping was observed to occur only until the most amplified frequencies were reduced to around 50% of their undisturbed values. When transpiration within this limit was performed shortly upstream of the natural boundary layer transition onset, a transition delay of approximately 17% could be observed
Fidelity of quantum operations
We present a derivation and numerous applications of a compact explicit
formula for the average fidelity of a quantum operation on a finite dimensional
quantum system. The formula can be applied to averages over particularly
relevant subspaces; it is easily generalized to multi-component systems, and as
a special result, we show that when the same completely positive
trace-preserving map is applied to a large number of qubits with one-bit
fidelity F close to unity, the average fidelity of the operation on the full
K-bit register scales as .Comment: 5 pages, no figures. The text has been modified to acknowledge that
our Eq.(1) has appeared already in quant-ph/0503243 and quant-ph/051221
General entanglement
The paper contains a brief review of an approach to quantum entanglement
based on analysis of dynamic symmetry of systems and quantum uncertainties,
accompanying the measurement of mean value of certain basic observables. The
latter are defined in terms of the orthogonal basis of Lie algebra,
corresponding to the dynamic symmetry group. We discuss the relativity of
entanglement with respect to the choice of basic observables and a way of
stabilization of robust entanglement in physical systems.Comment: 7 pages, 1 figure,1 tabe, will be published in special issue of
Journal of Physics (Conference Series) with Proceedings of CEWQO-200
Externally driven mortality of cod early life stages in the central Baltic: hydrography vs. predation
Increased incidence of vertebral fractures in German adults from 2009 to 2019 and the analysis of secondary diagnoses, treatment, costs, and in-hospital mortality
The aim of this cross-sectional study was to present the nationwide rates of hospitalized patients with vertebral fractures over one decade and to comprehensively analyze the treatment characteristics and direct costs incurred in 2019. Therefore, the trends in the incidence rate were quantified based on annual ICD-10 diagnosis codes from all German medical facilities between 2009 and 2019, provided by the Federal Statistical Office (Destatis). The ICD-10 Codes “S12.0-2; S22.0-; S32.0-, and S32.1-2” were evaluated. The relative change from 2009 through 2019 was determined. Using data from the Institute for Hospital Remuneration Systems (InEK) for 2019 the secondary diagnoses, OPS-codes, intensive care unit (ICU) treatment, in-hospital mortality, the proportion of G-DRGs and cumulative costs were evaluated. The documented number of vertebral fractures increased by 45.6% between 2009 and 2019 to an incidence of 150.7 per 100,000 inhabitants. The lumbar spine was most commonly affected with an incidence of 70.5/100,000 inhabitants in 2019 (46.8% of all vertebral fractures). The highest increases were seen in the numbers of subaxial cervical fractures (+ 121.2%) and sacral fractures (+ 306.6%). Of all vertebral fractures in 2019, 63.7% were diagnosed in women and 69.0% in patients aged 70 years or older. Osteoporosis was documented in 17.9% of cases as a concomitant diagnosis. In 10.1% of all cases, an ICU treatment was documented. The in-hospital mortality was 2.0% in 2019. I68D was the most frequently used G-DRG code, accounting for 33.3% of cases. The total direct costs for inpatient treatment in 2019 amounted to €589,205,715. The evaluation of 955,091 vertebral fractures showed a sharp increase in the nation-wide incidence rate. The presented age and sex distribution, the comorbidity profile and the in-hospital mortality rate indicate the importance of comprehensive geriatric assessment and emphasize the need for spinal care centers to be established
Quantum damping of position due to energy measurements
Quantum theory for measurements of energy is introduced and its consequences
for the average position of monitored dynamical systems are analyzed. It turns
out that energy measurements lead to a localization of the expectation values
of other observables. This is manifested, in the case of position, as a damping
of the motion without classical analogue. Quantum damping of position for an
atom bouncing on a reflecting surface in presence of a homogeneous
gravitational field is dealt in detail and the connection with an experiment
already performed in the classical regime is studied. We show that quantum
damping is testable provided that the same measurement strength obtained in the
experimental verification of the quantum Zeno effect in atomic spectroscopy [W.
M. Itano et al., Phys. Rev. A {\bf 41}, 2295 (1990)] is made available.Comment: 19 pages + 4 figures available upon request; Plain REVTeX; To be
published in Phys. Rev.
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