492 research outputs found
Experimental Upper Bound on Superradiance Emission from Mn12 Acetate
We used a Josephson junction as a radiation detector to look for evidence of
the emission of electromagnetic radiation during magnetization avalanches in a
crystal assembly of Mn_12-Acetate. The crystal assembly exhibits avalanches at
several magnetic fields in the temperature range from 1.8 to 2.6 K with
durations of the order of 1 ms. Although a recent study shows evidence of
electromagnetic radiation bursts during these avalanches [J. Tejada, et al.,
Appl. Phys. Lett. {\bf 84}, 2373 (2004)], we were unable to detect any
significant radiation at well-defined frequencies. A control experiment with
external radiation pulses allows us to determine that the energy released as
radiation during an avalanche is less than 1 part in 10^4 of the total energy
released. In addition, our avalanche data indicates that the magnetization
reversal process does not occur uniformly throughout the sample.Comment: 4 RevTeX pages, 3 eps figure
6G Underlayer Network Concepts for Ultra Reliable and Low Latency Communication in Manufacturing
Underlayer networks in the context of 6G for manufacturing are crucial. They
address the evolving needs of highly interconnected and autonomous systems in
industry. The digitalization of manufacturing processes, driven by the Internet
of Things and increased data availability, enables more efficient and
demand-driven production. However, wireless connectivity, which offers
flexibility and easy integration of components, comes with challenges such as
signal interference or high latency. A new management system is needed to
coordinate and route traffic of multiple networks in a specific coverage area.
This paper proposes underlayer networks designed for manufacturing, providing
low latency, reliability, and security. These networks enable wireless
connectivity and integration of wireless technologies into the manufacturing
environment, enhancing flexibility and efficiency. The paper also discusses
network slicing, spectrum sharing, and the limitations of current wireless
networks in manufacturing. It introduces a network concept for underlayer
networks and evaluates its application in closed-loop communication for machine
tools. The study concludes with future research prospects in this area
The effect of finasteride on the prostate gland in men with elevated serum prostate-specific antigen levels.
Prostate cancer is a disease associated with androgens. It has been hypothesized that reducing the conversion of testosterone (T) to dihydrotestosterone (DHT) in the prostate by the use of the drug finasteride, a 5alpha-reductase inhibitor, will reduce the incidence of prostate cancer. We investigated the chemopreventive potential of finasteride by evaluating its effect on the prostate gland of men with elevated serum prostate-specific antigen (PSA). Fifty-two men with elevated PSA and prostate sextant biopsies negative for cancer were randomized to receive finasteride 5 mg day(-1) (27 patients) or no medication (25 patients) for 12 months and were rebiopsied at 12 months. The biopsies were evaluated for the presence of cancer, the proportion of glandular and hyperplastic tissue, and the presence of high-grade prostatic intraepithelial neoplasia (PIN). Epithelial proliferation was assessed in the prestudy and 12-month biopsies by immunohistochemistry using antibody to proliferating cell nuclear antigen (PCNA). Serum blood samples were drawn at baseline and after 1, 3, 6 and 12 months of study. In the control group, serum levels of PSA and T were unchanged throughout the 12 months. In the finasteride group, PSA decreased 48% (P < 0.001), DHT decreased 67% (P < 0.001) and T increased 21% (P < 0.001). Histological evaluation of prestudy and 12-month biopsy specimens revealed that the finasteride group had a 30% reduction in the percentage of hyperplastic epithelial tissue (P = 0.002), although this decrease was not statistically significantly different between the finasteride and control groups (P = 0.11). In patients with PIN on prestudy biopsy, no change occurred in the PIN lesions with finasteride treatment. Finasteride also had no effect on the proliferation index of prostatic epithelial cells. Of the 27 patients treated with finasteride, eight (30%) had adenocarcinoma of the prostate detected on the 12-month biopsy, compared with one (4%) of the control patients (P = 0.025). In the treatment group, six cancers occurred in the eight patients with PIN on the prestudy biopsy; in the observation group no cancers were detected in the five patients with PIN on the prestudy biopsy (P = 0.021). Two cancers occurred in the 19 men in the treatment group with no evidence of PIN on the prestudy biopsy, compared with one cancer in the 20 men in the observation group with no evidence of PIN on the prestudy biopsy (P = 0.60). This study, using a novel model for evaluating short-term efficacy of chemopreventive or therapeutic agents in men at high risk of prostate cancer, provides little evidence that finasteride is an effective chemopreventive agent for prostate cancer in men with elevated PSA
The perceived advantages of e-participation and its impact on citizens’ willingness to engage : findings from the Canton of Zurich
The aim of this study is to contribute to the growing literature on electronic participation (e-participation), by analysing various scenarios of participation. The main goal is to gain further insight into the role of perceived advantages concerning citizens’ willingness to engage in digital and non-digital participation. While several studies have identified advantages of e-participation compared to traditional, non-digital alternatives, little research has been conducted into how the perception of these advantages influences citizen willingness to engage in e-participation. This study examines three participation scenarios with different levels of citizen participation. We use a logistic regression model to analyse our data. The findings reveal new insights for both research and practice. First, the results show that simplicity, time savings, location independence, and cost reduction are generally considered to be advantages of e-participation. By comparison, data security and data protection are seen to be advantages of non-digital participation. However, only cost reduction and simplicity have a positive influence on citizens’ willingness to engage in all three scenarios. Additionally, when data security was perceived as an advantage of e-participation, the likelihood of preferring digital over non-digital participation was higher. This is true for the two scenarios with higher participation levels. These findings differ from those in previous studies and raise questions regarding the impact that the participation level has on the results. By studying this topic further, valuable insights can be gained into how governments can use and promote e-participation
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Economic Impact of Fuel Cell Deployment in Forklifts and for Backup Power under the American Recovery and Reinvestment Act
Parallel Magnetic Field Induced Transition in Transport in the Dilute Two-Dimensional Hole System in GaAs
A magnetic field applied parallel to the two-dimensional hole system in the
GaAs/AlGaAs heterostructure, which is metallic in the absence of an external
magnetic field, can drive the system into insulating at a finite field through
a well defined transition. The value of resistivity at the transition is found
to depend strongly on density
Next-generation ice-nucleating particle sampling on board aircraft: characterization of the High-volume flow aERosol particle filter sAmpler (HERA)
Atmospheric ice-nucleating particle (INP) concentration data from the free troposphere are sparse but urgently needed to understand vertical transport processes of INPs and their influence on cloud formation and properties. Here, we introduce the new High-volume flow aERosol particle filter sAmpler (HERA) which was specially developed for installation on research aircraft and subsequent offline INP analysis. HERA is a modular system consisting of a sampling unit and a powerful pump unit, and it has several features which were integrated specifically for INP sampling. Firstly, the pump unit enables sampling at flow rates exceeding 100 L min−1, which is well above typical flow rates of aircraft INP sampling systems described in the literature (∼ 10 L min−1). Consequently, required sampling times to capture rare, high-temperature INPs (≥ −15 ∘C) are reduced in comparison to other systems, and potential source regions of INPs can be confined more precisely. Secondly, the sampling unit is designed as a seven-way valve, enabling switching between six filter holders and a bypass with one filter being sampled at a time. In contrast to other aircraft INP sampling systems, the valve position is remote-controlled via software so that manual filter changes during flight are eliminated and the potential for sample contamination is decreased. This design is compatible with a high degree of automation, i.e., triggering filter changes depending on parameters like flight altitude, geographical location, temperature, or time. In addition to presenting the design and principle of operation of HERA, this paper describes laboratory characterization experiments with size-selected test substances, i.e., SNOMAX® and Arizona Test Dust. The particles were sampled on filters with HERA, varying either particle diameter (300 to 800 nm) or flow rate (10 to 100 L min−1) between experiments. The subsequent offline INP analysis showed good agreement with literature data and comparable sampling efficiencies for all investigated particle sizes and flow rates. Furthermore, the collection efficiency of atmospheric INPs in HERA was compared to a straightforward filter sampler and good agreement was found. Finally, results from the first campaign of HERA on the High Altitude and LOng range research aircraft (HALO) demonstrate the functionality of the new system in the context of aircraft application.</p
A Distribution of Tunnel Splittings in Mn-Acetate
In magnetic fields applied parallel to the anisotropy axis, the relaxation of
the magnetization of Mn measured for different sweep rates is shown to
collapse onto a single scaled curve. The form of the scaling implies that the
dominant symmetry-breaking process that gives rise to tunneling is a locally
varying second-order anisotropy, forbidden by tetragonal symmetry in the
perfect crystal, which gives rise to a broad distribution of tunnel splittings
in a real crystal of Mn-acetate. Different forms applied to even and
odd-numbered steps provide a distinction between even step resonances
(associated with crystal anisotropy) and odd resonances (which require a
transverse component of magnetic field).Comment: 4 pages, 5 figures. New title; text more clearly writte
Metal-insulator transition in a 2D electron gas: Equivalence of two approaches for determining the critical point
The critical electron density for the metal-insulator transition in a
two-dimensional electron gas can be determined by two distinct methods: (i) a
sign change of the temperature derivative of the resistance, and (ii) vanishing
activation energy and vanishing nonlinearity of current-voltage characteristics
as extrapolated from the insulating side. We find that in zero magnetic field
(but not in the presence of a parallel magnetic field), both methods give
equivalent results, adding support to the existence of a true zero-field
metal-insulator transition.Comment: As publishe
Classical versus Quantum Effects in the B=0 Conducting Phase in Two Dimensions
In the dilute two-dimensional electron system in silicon, we show that the
temperature below which Shubnikov-de Haas oscillations become apparent is
approximately the same as the temperature below which an exponential decrease
in resistance is seen in B=0, suggesting that the anomalous behavior in zero
field is observed only when the system is in a degenerate (quantum) state. The
temperature dependence of the resistance is found to be qualitatively similar
in B=0 and at integer Landau level filling factors.Comment: 3 pages, 3 figure
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