1,450 research outputs found
Effects of Magnetic Field on Josephson Current in SNS System
The effect of a magnetic field on Josephson current has been studied for a
superconductor/normal-metal/superconductor (SNS) system, where N is a
two-dimensional electron gas in a confining potential. It is found that the
dependence of Josephson currents on the magnetic field are sensitive to the
width of the normal metal. If the normal metal is wide and contains many
channels (subbands), the current on a weak magnetic field shows a dependence
similar to a Fraunhofer-pattern in SIS system and, as the field gets strong, it
shows another type of oscillatory dependence on the field resulting from the
Aharonov-Bohm interference between the edge states. As the number of channels
decreases (i.e. normal metal gets narrower), however, the dependence in the
region of the weak field deviates from a clear Fraunhofer pattern and the
amplitude of the oscillatory dependence in the region of the strong field is
reduced.Comment: 14 pages, 9 figure
Prognostic value of clinical and MRI features in the screening of lipomatous lesions
BACKGROUND AND OBJECTIVES: Differentiation of lipomatous tumors mostly requires diagnostic biopsy but is essential to decide for the most adequate therapy. This study aims to investigate the prognostic value of available clinical and radiological features with regard to malignancy of the lesion, recurrence and survival.
METHODS: In this retrospective cohort study, 104 patients with a biopsy-proven lipomatous tumor between 2010 and 2015 and a minimum clinical follow-up of two years were enrolled. Next to clinical features (age, gender, location of the lesion, histopathologic diagnosis, stage of disease, time to recurrence and death), MRI parameters were recorded retrospectively and blinded to the histological diagnosis.
RESULTS: Malignant lipomatous tumors were associated with location in the lower extremities and MRI features like thick septation (>2 mm), presence of a non-adipose mass, foci of high T2/STIR signal and contrast agent enhancement. A non-adipose mass was a predictor for recurrence and inferior overall survival, while lesions with high T2/STIR signal showed higher risk of recurrence only. In combination, clinical and radiological features (lower extremities, septation > 2 mm, existence of non-adipose mass, contrast enhancement, and foci of high T2/STIR signal) predicted a malignant lipomatous tumor with an accuracy of 0.941 (95% CI of 0.899-0.983; 87% sensitivity, 86% specificity).
CONCLUSION: Localization and characteristic MR features predict malignancy in most lipomatous lesions. Non-adipose masses are a poor prognostic factor, being associated with tumor recurrence and disease-related death
Articular degeneration after subchondral cementation for giant cell tumors at the knee
PURPOSE
To quantify joint degeneration and the clinical outcome after curettage and cementation in subchondral giant cell tumors of the bone (GCTB) at the knee.
METHODS
We conducted a retrospective analysis of 14 consecutive patients (seven female, seven male) with a mean age of 34 years (range 19-51) who underwent curettage and subchondral cementation for a biopsy-confirmed GCTB at the distal femur or the proximal tibia between August 2001 and August 2017, with a mean follow-up period of 54.6 months (range 16.1-156 months). The Whole-Organ Magnetic Resonance Imaging Score (WORMS), Kellgren-Lawrence (KL) classification, and Musculo-Skeletal Tumor Society (MSTS) score were assessed.
RESULTS
Radiological degeneration progressed from preoperative to the latest follow-up, with a median WORMS from 2.0 to 4.0 (p = 0.006); meanwhile, the median KL score remained at 0 (p = 0.102). Progressive degeneration (WORMS) tended to be associated with the proximity of the tumor to the articular cartilage (mean 1.57 mm; range 0-12 mm) (p = 0.085). The most common degenerative findings were cartilage lesions (n = 11), synovitis (n = 5), and osteophytes (n = 4). Mean MSTS score increased from 23.1 (preoperatively) to 28.3 at the latest follow-up (p < 0.01). Seven patients (50%) were treated for a local recurrence, with six revision surgeries performed. Removal of the cement spacer and filling of the cavity with a cancellous autograft was performed in seven patients. Conversion to a total knee arthroplasty was performed in one patient for local tumor control.
CONCLUSIONS
Cementation following the curettage of GCTB around the knee is associated with slight degeneration at medium-term follow-up and leads to a significant reduction in pain. Removal of the cement and reconstruction with an autograft may be beneficial in the long term
Electron focusing, mode spectroscopy and mass enhancement in small GaAs/AlGaAs rings
A new electron focusing effect has been discovered in small single and
coupled GaAs/AlGaAs rings. The focusing in the single ring is attributed solely
to internal orbits. The focusing effect allows the ring to be used as a small
mass spectrometer. The focusing causes peaks in the magnetoresistance at low
fields, and the peak positions were used to study the dispersion relation of
the one-dimensional magnetoelectric subbands. The electron effective mass
increases with the applied magnetic field by a factor of , at a magnetic
field of . This is the first time this increase has been measured
directly. General agreement obtains between the experiment and the subband
calculations for straight channels.Comment: 13 pages figures are available by reques
Assessment of ractopamine in meat and bone meal through LC-MS/MS using solid phase extraction (SPE).
Ractopamine (RCT) used as feed additive acts metabolically to decrease fat content contributing to a lean carcass. However, RCT is not broadly accepted worldwide but limited to stringent rules imposed by some countries. To assure human consumption safety, governments are encouraging research institutions to develop sensitive methods to accurately detect and quantify RCT. Yet, little is known about RCT concentration in raw materials such as meat and bone meal (MBM). The effectiveness of a previously developed method for RCT analysis was tested to determine sources of RCT contamination in MBM and discern from potential overestimation in feed
The spin-orbit interaction as a source of new spectral and transport properties in quasi-one-dimensional systems
We present an exact theoretical study of the effect of the spin-orbit (SO)
interaction on the band structure and low temperature transport in long
quasi-one-dimensional electron systems patterned in two-dimensional electron
gases in zero and weak magnetic fields. We reveal the manifestations of the SO
interaction which cannot in principle be observed in higher dimensional
systems.Comment: 5 pages including 5 figures; RevTeX; to appear in Phys.Rev.B (Rapid
Communications
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