1,064 research outputs found
Development of diamond based KIDs
Kinetic Inductance Detectors (KIDs) have proven themselves as a very versatile cryogenic detector technology capable of applications in various fields due to their flexibility of design, sensibility and ease of production. We have recently proposed a polarization sensitive Lumped Elements KID as sensor for an innovative polarimetric diagnostics based on quantum cascade lasers (QCL) for application in the nuclear fusion. Each detector unit is composed by 4 pixels arranged at the vertices of a square, each pixels being sensible to only one polarization direction. The current system is based on niobium nitride (NbN) superconductor over High Resistivity Silicon (HRSi) substrate. Such material delivers good performances but its relatively high dielectric constant and loss tangent lead to increased substrate losses. Using a transparent substrate may improve this aspect and also the radiation resistance of such devices. Diamond is the substrate of choice, being a material already widely studied and used in the fusion environment as high power microwave window, due to its outstanding optical and mechanical performances. In this work we present the preliminary design study for a diamond based Kinetic Inductance Detector and subsequent characterization measurements of the first prototypes
Correlation of Dynamic PET and Gene Array Data in Patients with Gastrointestinal Stromal Tumors
Introduction. The results obtained with dynamic PET (dPET) were compared to gene expression data obtained in patients with gastrointestinal stromal tumors (GIST). The primary aim was to assess the association of the dPET results and gene expression data. Material and Methods. dPET was performed following the injection of F-18-fluorodeoxyglucose (FDG) in 22 patients with GIST. All patients were examined prior to surgery for staging purpose. Compartment and noncompartment models were used for the quantitative evaluation of the dPET examinations. Gene array data were based on tumor specimen obtained by surgery after the PET examinations. Results. The data analysis revealed significant correlations for the dPET parameters and the expression of zinc finger genes (znf43, znf85, znf91, znf189). Furthermore, the transport of FDG (k1) was associated with VEGF-A. The cell cycle gene cyclin-dependent kinase inhibitor 1C was correlated with the maximum tracer uptake (SUVmax) in the tumors. Conclusions. The data demonstrate a dependency of the tracer kinetics on genes associated with prognosis in GIST. Furthermore, angiogenesis and cell proliferation have an impact on the tracer uptake
Distal thoracic oesophageal perforation secondary to blunt trauma: Case report
BACKGROUND: Traumatic perforation of the distal oesophagus due to blunt trauma is a very rare condition and is still associated with a significant morbidity and mortality. This is further exacerbated by delayed diagnosis and management as symptoms and signs are often masked by or ascribed to more common blunt thoracic injuries. CASE REPORT: We present a case of a distal oesophageal perforation, secondary to a fall from a third storey window, which was masked by concomitant thoracic injuries and missed on both computed tomography imaging and laparotomy. The delay in his diagnosis significantly worsened the patient's recovery by allowing the development of an overwhelming chest sepsis that contributed to his death. CONCLUSION: Early identification of an intrathoracic oesophageal perforation requires deliberate consideration and is essential to ensure a favorable outcome. Treatment should be individualised taking into account the nature of the oesophageal defect, time elapsed from injury and the patient's general condition
The electronic structure of Amorphous Carbon Nanodots
We
have studied hydrogen-passivated amorphous carbon nanostructures
with semiempirical molecular orbital theory in order to provide an
understanding of the factors that affect their electronic properties.
Amorphous structures were first constructed using periodic calculations
in a melt/quench protocol. Pure periodic amorphous carbon structures
and their counterparts doped with nitrogen and/or oxygen feature large
electronic band gaps. Surprisingly, descriptors such as the elemental
composition and the number of sp<sup>3</sup>-atoms only influence
the electronic structure weakly. Instead, the exact topology of the
sp<sup>2</sup>-network in terms of effective conjugation defines the
band gap. Amorphous carbon nanodots of different structures and sizes
were cut out of the periodic structures. Our calculations predict
the occurrence of localized electronic surface states, which give
rise to interesting effects such as amphoteric reactivity and predicted
optical band gaps in the near-UV/visible range. Optical and electronic
gaps display a dependence on particle size similar to that of inorganic
colloidal quantum dots
Characterization of Boron-doped diamond and r-plane sapphire for plasma diagnostics in future nuclear fusion reactors -A survey of electrical and dielectric properties
p-Boron-doped polycrystalline CVD diamond samples were produced
and delivered by the German company Diamond Materials in Freiburg
(Germany). In a first step, main properties of this candidates for diagnostic
and/or heating windows in future nuclear fusion reactors were
investigated. By a special measurement technique, it was possible to
determine the Boron doping concentration in Diamond by measurement
of the resistive properties by using the van der Pauw method. So
prepared, an irradiation campaign with neutrons and/or heavy ions
on these samples will follow. The second material investigated, was
r-plane single crystalline sapphire. For the first characterization the
dielectric properties of a 3*-wafer in dependency of the frequency in
a FABRY-PEROT resonator setup was performed. Also, this is the
preparation for the next irradiation experiments in this project
Basic considerations for fracture toughness measurements of MPA CVD diamond to be used in nuclear fusion
In nuclear fusion, Microwave Plasma Assisted (MPA) Chemical Vapour Deposition (CVD) polycrystalline diamond is the only material allowing for transmission of high power microwave beams (1-2 MW) in long-pulse gyrotron operations. The reason lies in the combination of extraordinary thermal, mechanical and optical properties of diamond, which is used in the shape of disks having thickness of 1 to 2 mm for windows. Being diamond a brittle material, failure to fracture is the main failure mode. Accordingly, an appropriate mechanical characterization is required as diamond plays a major safety role in fusion machines. Due to limited body of work in literature, fracture toughness measurements have to be first carried out for this material and then a design criterion for structural integrity assessment has to be applied. In this work, the preliminary activities aiming to define the optimum experimental measurement method of fracture toughness for thin diamond samples are shown and discussed. An outlook to the next steps is also given
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