1,107 research outputs found
Giant Relaxation Oscillations in a Very Strongly Hysteretic SQUID ring-Tank Circuit System
In this paper we show that the radio frequency (rf) dynamical characteristics
of a very strongly hysteretic SQUID ring, coupled to an rf tank circuit
resonator, display relaxation oscillations. We demonstrate that the the overall
form of these characteristics, together with the relaxation oscillations, can
be modelled accurately by solving the quasi-classical non-linear equations of
motion for the system. We suggest that in these very strongly hysteretic
regimes SQUID ring-resonator systems may find application in novel logic and
memory devices.Comment: 7 pages, 5 figures. Uploaded as implementing a policy of arXiving old
paper
Pinch Resonances in a Radio Frequency Driven SQUID Ring-Resonator System
In this paper we present experimental data on the frequency domain response
of a SQUID ring (a Josephson weak link enclosed by a thick superconducting
ring) coupled to a radio frequency (rf) tank circuit resonator. We show that
with the ring weakly hysteretic the resonance lineshape of this coupled system
can display opposed fold bifurcations that appear to touch (pinch off). We
demonstrate that for appropriate circuit parameters these pinch off lineshapes
exist as solutions of the non-linear equations of motion for the system.Comment: 9 pages, 8 figures, Uploaded as implementing a policy of arXiving old
paper
Pollutant dispersion in a developing valley cold-air pool
Pollutants are trapped and accumulate within cold-air pools, thereby affecting air quality. A numerical model is used to quantify the role of cold-air-pooling processes in the dispersion of air pollution in a developing cold-air pool within an alpine valley under decoupled stable conditions. Results indicate that the negatively buoyant downslope flows transport and mix pollutants into the valley to depths that depend on the temperature deficit of the flow and the ambient temperature structure inside the valley. Along the slopes, pollutants are generally entrained above the cold-air pool and detrained within the cold-air pool, largely above the ground-based inversion layer. The ability of the cold-air pool to dilute pollutants is quantified. The analysis shows that the downslope flows fill the valley with air from above, which is then largely trapped within the cold-air pool, and that dilution depends on where the pollutants are emitted with respect to the positions of the top of the ground-based inversion layer and cold-air pool, and on the slope wind speeds. Over the lower part of the slopes, the cold-air-pool-averaged concentrations are proportional to the slope wind speeds where the pollutants are emitted, and diminish as the cold-air pool deepens. Pollutants emitted within the ground-based inversion layer are largely trapped there. Pollutants emitted farther up the slopes detrain within the cold-air pool above the ground-based inversion layer, although some fraction, increasing with distance from the top of the slopes, penetrates into the ground-based inversion layer.Peer reviewe
A Fully Quantum Mechanical Model of a SQUID Ring Coupled to an Electromagnetic Field
A quantum system comprising of a monochromatic electromagnetic field coupled
to a SQUID ring with sinusoidal non-linearity, is studied. A magnetostatic flux
is also threading the SQUID ring, and is used to control the
coupling between the two systems. It is shown that for special values of
the system is strongly coupled. The time evolution of the system is
studied. It is shown that exchange of energy takes place between the two modes
and that the system becomes entangled. A second quasi-classical model that
treats the electromagnetic field classically is also studied. A comparison
between the fully quantum mechanical model with the electromagnetic field
initially in a coherent state and the quasi-classical model, is made.Comment: 7 pages, 9 figures. Uploaded as implementing a policy of arXiving old
paper
Cloud Screening and Quality Control Algorithm for Star Photometer Data: Assessment with Lidar Measurements and with All-sky Images
This paper presents the development and set up of a cloud screening and data quality control algorithm for a star photometer based on CCD camera as detector. These algorithms are necessary for passive remote sensing techniques to retrieve the columnar aerosol optical depth, delta Ae(lambda), and precipitable water vapor content, W, at nighttime. This cloud screening procedure consists of calculating moving averages of delta Ae() and W under different time-windows combined with a procedure for detecting outliers. Additionally, to avoid undesirable Ae(lambda) and W fluctuations caused by the atmospheric turbulence, the data are averaged on 30 min. The algorithm is applied to the star photometer deployed in the city of Granada (37.16 N, 3.60 W, 680 ma.s.l.; South-East of Spain) for the measurements acquired between March 2007 and September 2009. The algorithm is evaluated with correlative measurements registered by a lidar system and also with all-sky images obtained at the sunset and sunrise of the previous and following days. Promising results are obtained detecting cloud-affected data. Additionally, the cloud screening algorithm has been evaluated under different aerosol conditions including Saharan dust intrusion, biomass burning and pollution events
Energy Down Conversion between Classical Electromagnetic Fields via a Quantum Mechanical SQUID Ring
We consider the interaction of a quantum mechanical SQUID ring with a
classical resonator (a parallel tank circuit). In our model we assume that
the evolution of the ring maintains its quantum mechanical nature, even though
the circuit to which it is coupled is treated classically. We show that when
the SQUID ring is driven by a classical monochromatic microwave source, energy
can be transferred between this input and the tank circuit, even when the
frequency ratio between them is very large. Essentially, these calculations
deal with the coupling between a single macroscopic quantum object (the SQUID
ring) and a classical circuit measurement device where due account is taken of
the non-perturbative behaviour of the ring and the concomitant non-linear
interaction of the ring with this device.Comment: 7 pages, 6 figure
Complications of Common Gynecologic Surgeries among HIV-Infected Women in the United States
Objective. To compare frequencies of complications among HIV-infected and-uninfected women undergoing common gynecological surgical procedures in inpatient settings. Methods. We used 1994–2007 data from the Nationwide Inpatient Sample of the Healthcare Cost and Utilization Project, a nationally representative sample of inpatient hospitalizations. Our analysis included discharge records of women aged ≥15 undergoing hysterectomy, oophorectomy, salpingectomy for ectopic pregnancy, bilateral tubal sterilization, or dilation and curettage. Associations between HIV infection status and surgical complications were evaluated in multivariable logistic regression models, adjusting for key covariates. Results. For each surgery, HIV infection was associated with experiencing ≥1 complication. Adjusted ORs ranged from 2.0 (95% confidence interval (CI): 1.7, 2.2) for hysterectomy with oophorectomy to 3.1 (95% CI: 2.4, 4.0) for bilateral tubal sterilization with no comorbidity present. HIV infection was positively associated with extended length of stay and infectious complications of all of the surgeries examined. For some surgeries, it was positively associated with transfusion and anemia due to acute blood loss. Among HIV-infected women, the odds of infectious and other complications did not decrease between 1994–2000 and 2001–2007. Conclusion. HIV infection was associated with elevated frequencies of complications of gynecologic surgeries in the US, even in the era of HAART
Non-linear Multi-level Dynamics of a SQUID Ring-resonator System in the Hysteretic Regime
We consider the dynamical behavior of a strongly hysteretic SQUID ring coupled to a radio frequency resonator. By experiment we show that this system can display novel multiple level structures in its rf voltage-current characteristics which are solutions of the nonlinear equations of motion describing the system
Site-specific occurrence of nonmelanoma skin cancers in patients with cutaneous melanoma
In a registry-based case–control study, we compared the site-specific occurrence of nonmelanoma (keratinocytic) skin cancers among patients with cutaneous melanoma cases (cases, n=3774) and solid tumours (controls, n=349 923), respectively. Overall, patients with melanoma were almost five-fold more likely to develop keratinocytic cancers compared with solid tumour controls (adjusted OR 4.7, 95% CI 4.1–5.3), but the risks varied depending upon the site of melanoma. Whereas patients with melanoma of the head and neck had similarly increased risks of keratinocytic cancers across all body sites, patients with melanoma of the trunk were significantly more likely to develop keratinocyte cancer diagnosed on the trunk (adjusted OR 12.5, 95% CI 7.2–20.2) than on the head and neck (adjusted OR 3.0, 95% CI 2.2–4.3). Similar colocalisation of skin tumours was observed for patients with melanomas of the lower limb. These findings provide support for the hypothesis that skin cancers at different anatomical sites may arise through different causal pathways
Quantum Statistics and Entanglement of Two Electromagnetic Field Modes Coupled via a Mesoscopic SQUID Ring
In this paper we investigate the behaviour of a fully quantum mechanical
system consisting of a mesoscopic SQUID ring coupled to one or two
electromagnetic field modes. We show that we can use a static magnetic flux
threading the SQUID ring to control the transfer of energy, the entanglement
and the statistical properties of the fields coupled to the ring. We also
demonstrate that at, and around, certain values of static flux the effective
coupling between the components of the system is large. The position of these
regions in static flux is dependent on the energy level structure of the ring
and the relative field mode frequencies, In these regions we find that the
entanglement of states in the coupled system, and the energy transfer between
its components, is strong.Comment: 15 pages, 19 figures, Uploaded as implementing a policy of arXiving
old paper
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