620 research outputs found
Modeling Scientists as Agents. How Scientists Cope with the Challenges of the New Public Management of Science
The paper at hand applies agent-based modeling and simulations (ABMS) as a tool to reconstruct and to analyze how the science system works. A Luhmannian systems perspective is combined with a model of decision making of individual actors. Additionally, changes in the socio-political context of science, such as the introduction of „new public management\", are considered as factors affecting the functionality of the system as well as the decisions of individual scientists (e.g. where to publish their papers). Computer simulation helps to understand the complex interplay of developments at the macro (system) and the micro (actor) level.Systems Theory, Theory of Action and Decision Making, Academic Publication System, Science System, New Public Management, Agent-Based Modeling and Simulation
Entanglement-enhanced optical gyroscope
Fiber optic gyroscopes (FOG) based on the Sagnac effect are a valuable tool
in sensing and navigation and enable accurate measurements in applications
ranging from spacecraft and aircraft to self-driving vehicles such as
autonomous cars. As with any classical optical sensors, the ultimate
performance of these devices is bounded by the standard quantum limit (SQL).
Quantum-enhanced interferometry allows us to overcome this limit using
non-classical states of light. Here, we report on an entangled-photon gyroscope
that uses path-entangled NOON-states (N=2) to provide phase supersensitivity
beyond the standard-quantum-limit
Twisted Light Transmission over 143 kilometers
Spatial modes of light can potentially carry a vast amount of information,
making them promising candidates for both classical and quantum communication.
However, the distribution of such modes over large distances remains difficult.
Intermodal coupling complicates their use with common fibers, while free-space
transmission is thought to be strongly influenced by atmospheric turbulence.
Here we show the transmission of orbital angular momentum modes of light over a
distance of 143 kilometers between two Canary Islands, which is 50 times
greater than the maximum distance achieved previously. As a demonstration of
the transmission quality, we use superpositions of these modes to encode a
short message. At the receiver, an artificial neural network is used for
distinguishing between the different twisted light superpositions. The
algorithm is able to identify different mode superpositions with an accuracy of
more than 80% up to the third mode order, and decode the transmitted message
with an error rate of 8.33%. Using our data, we estimate that the distribution
of orbital angular momentum entanglement over more than 100 kilometers of free
space is feasible. Moreover, the quality of our free-space link can be further
improved by the use of state-of-the-art adaptive optics systems.Comment: 12 pages, 4 figure
Microwave quantum illumination using a digital receiver
Quantum illumination is a powerful sensing technique that employs entangled signal-idler photon pairs to boost the detection efficiency of low-reflectivity objects in environments with bright thermal noise. The promised advantage over classical strategies is particularly evident at low signal powers, a feature which could make the protocol an ideal prototype for non-invasive biomedical scanning or low-power short-range radar. In this work we experimentally investigate the concept of quantum illumination at microwave frequencies. We generate entangled fields using a Josephson parametric converter to illuminate a room-temperature object at a distance of 1 meter in a free-space detection setup. We implement a digital phase conjugate receiver based on linear quadrature measurements that outperforms a symmetric classical noise radar in the same conditions despite the entanglement-breaking signal path. Starting from experimental data, we also simulate the case of perfect idler photon number detection, which results in a quantum advantage compared to the relative classical benchmark. Our results highlight the opportunities and challenges on the way towards a first room-temperature application of microwave quantum circuits
Linear and nonlinear capacitive coupling of electro-opto-mechanical photonic crystal cavities
We fabricate and characterize a microscale silicon electro-opto-mechanical
system whose mechanical motion is coupled capacitively to an electrical circuit
and optically via radiation pressure to a photonic crystal cavity. To achieve
large electromechanical interaction strength, we implement an inverse shadow
mask fabrication scheme which obtains capacitor gaps as small as 30 nm while
maintaining a silicon surface quality necessary for minimizing optical loss.
Using the sensitive optical read-out of the photonic crystal cavity, we
characterize the linear and nonlinear capacitive coupling to the fundamental 63
MHz in-plane flexural motion of the structure, showing that the large
electromechanical coupling in such devices may be suitable for realizing
efficient microwave-to-optical signal conversion.Comment: 8 papers, 4 figure
Response to Induced Relaxation During Pregnancy: Comparison of Women with High Versus Low Levels of Anxiety
Relaxation exercises have become a standard intervention for individuals with anxiety disorders but little is known about their potential for anxiety relief during pregnancy. The purpose of this study was to examine psychoendocrine (i) baseline differences and (ii) changes after a standardized relaxation period in pregnant women with high versus low levels of anxiety. Thirty-nine third-trimester high and low anxious pregnant women performed active or passive relaxation while levels of anxiety, hypothalamic-pituitary-adrenal (HPA) axis and sympathetic-adrenal-medullary (SAM) system activity were assessed before and after the relaxation period. In women with high levels of trait anxiety, state anxiety (F(1,36)=8.3, p=.007) and negative affect (F(1,36)=7.99, p=.008) as well as ACTH (F(1,35)=9.24, p=.002) remained elevated over the entire course of the experimental procedure, the last indicating increased HPA axis activity. In addition, norepinephrine showed a constricted decrease of relaxation reflecting lower response of the SAM-system (F(1,37)=4.41, p=.043). Although relaxation exercises have become a standard intervention for individuals with anxiety, pregnant women with high levels of trait anxiety benefited less than women with low levels from a single standardized relaxation perio
Identification of antenatal depression in obstetric care
Purpose: Detection rates of depression in obstetric care are generally low, and many women remain undiagnosed and do not receive adequate support. In many obstetric settings, screening tools for depression are not applied routinely and there is a great need to sensitize health care professionals for the patient at risk for enhanced levels of depression. The present study aimed at identifying commonly assessed patient characteristics that are associated with antenatal depression. Methods: One hundred and thirty seven women were screened using the Edinburgh Postnatal Depression Scale (EPDS) at the beginning of the second trimester at the outpatient department of a Tertiary University Hospital. Women were identified as at high risk for depression if scores were above a cut-off score of twelve. Obstetric history and outcome were extracted from patient files after delivery. Results: Twenty one percent of the sample screened as depression positive. Logistic regression with backwards elimination showed that the triad of nausea during pregnancy, reports of (premature) contractions and consumption of analgesics during pregnancy significantly predicted high depression scores with a positive predictive value of 84.3%. The relative risk for a depressed pregnant woman to regularly take analgesics during pregnancy was fourfold higher than for non-depressed women. Conclusions: If depression screening is not part of routine prenatal care, systematic assessment of depression should be targeted for patients presenting with the markers identified in this stud
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