3,584 research outputs found
Variation around a Pyramid theme: optical recombination and optimal use of photons
We propose a new type of Wave Front Sensor (WFS) derived from the Pyramid WFS
(PWFS). This new WFS, called the Flattened Pyramid-WFS (FPWFS), has a reduced
Pyramid angle in order to optically overlap the four pupil images into an
unique intensity. This map is then used to derive the phase information. In
this letter this new WFS is compared to three existing WFSs, namely the PWFS,
the Modulated PWFS (MPWFS) and the Zernike WFS (ZWFS) following tests about
sensitivity, linearity range and low photon flux behavior. The FPWFS turns out
to be more linear than a modulated pyramid for the high-spatial order
aberrations but it provides an improved sensitivity compared to the
non-modulated pyramid. The noise propagation may even be as low as the ZWFS for
some given radial orders. Furthermore, the pixel arrangement being more
efficient than for the PWFS, the FPWFS seems particularly well suited for
high-contrast applications.Comment: 4 pages, 4 figures, accepted for publication in Optics Letters -
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Fast image reconstruction for near-field terahertz imaging with multistatic non-uniform sparse arrays
Conference paper presented at Radar Sensor Technology XXVII, Orlando, FL, USA, 30 April - 5 May, 2023.In this paper, first, the structure of a linear sparse periodic array for two-dimensional scanning is described. Then, based on its characteristics, an algorithm is presented for fast image reconstruction of the scene in a near-field (NF) multistatic terahertz imaging scenario. Although the basis of this algorithm is developed in the Fourier domain, it is compatible with the non-uniform structure of the array and also takes into account the phase deviations caused by multistatic imaging in NF. The performance of the proposed approach is evaluated with numerical data obtained from electromagnetic simulations in FEKO as well as experimental data. The results are discussed in terms of computational time on the central processing unit and graphics processing unit as well as the quality of the reconstructed image.Leverhulme Trust under Research Leadership Award RL-2019-019. The work of Shaoqing Hu is funded by Brunel University London under Research Development Fund LBG194 and 2022/2023 Brunel Research Initiative and Enterprise Fund 12455
Prevenzione e management odontoiatrico dei pazienti oncologici a rischio di osteonecrosi delle ossa mascellari da farmaci
non disponibil
L\u2019odontoiatria a misura del paziente con patologia osteometabolica a rischio di osteonecrosi delle ossa mascellari da farmaci.
L\u2019osteonecrosi delle ossa mascellari
(ONJ) da farmaci \ue8 una severa patologia
odontoiatrica, recentemente defi nita
come \uabuna reazione avversa farmacocorrelata,
caratterizzata dalla progressiva
distruzione e necrosi dell\u2019osso
mandibolare e/o mascellare di soggetti
esposti al trattamento con farmaci per
cui sia accertato un aumentato rischio
di malattia, in assenza di un pregresso
trattamento radiante\ubb1-3. I pazienti
osteometabolici a rischio di sviluppare
l\u2019ONJ sono quelli sottoposti a terapia
con bisfosfonati (in particolare aminobisfosfonati
o Nitrogen-containing
BisPhosphonate/NBP) e, pi\uf9 recentemente,
con denosumab (anticorpo monoclonale
anti-RANKL)4. Tali farmaci
antiriassorbitivi caratterizzati da una
prevalente azione inibitoria sul metabolismo
dell\u2019osso, sono ampiamente
prescritti per la cura di patologie osteometaboliche,
prevalentemente osteoporosi
primaria o secondaria, oltre che
per la prevenzione e il trattamento di
lesioni scheletriche in pazienti con patologia
onco-ematologica1,5-7
Shape of the Galactic Orbits in the CNOC1 Clusters
We present an analysis of the orbital properties in 9 intermediate-redshifts
cluster of the CNOC1 survey and we compare them to a control sample of 12
nearby clusters. Similar to the nearby elliptical galaxies, the bulge-dominated
galaxies in clusters at redshifts ~0.1-0.4 present orbits that are more
eccentric than those for disk-dominated galaxies. However, the orbital
segregation is less significant than that found for elliptical and spiral
galaxies in nearby cluster. When galaxies are separated by colors - red
galaxies with colors in the rest frame (U-V)_o > 1.4, and blue galaxies with
(U-V)_o =< 1.4 - the strongest orbital segregation is found. Therefore, the
segregation we found seems to modify more efficiently the star formation
activity than the internal shape of the galaxies. When we compare the orbits of
early-type galaxies at intermediate-redshift with those for z=0, they seem to
develop significant changes getting much more eccentric. A different behavior
is observed in the late-type galaxies, which present no-significant evolution
in their orbit shapes.Comment: Accepted for publication in ApJ, April 2000. Latex with aaspp4.sty,
20 pages, 4 tables, 6 eps figure
A microscopic 2D lattice model of dimer granular compaction with friction
We study by Monte Carlo simulation the compaction dynamics of hard dimers in
2D under the action of gravity, subjected to vertical and horizontal shaking,
considering also the case in which a friction force acts for horizontal
displacements of the dimers. These forces are modeled by introducing effective
probabilities for all kinds of moves of the particles. We analyze the dynamics
for different values of the time during which the shaking is applied to
the system and for different intensities of the forces. It turns out that the
density evolution in time follows a stretched exponential behavior if is
not very large, while a power law tail develops for larger values of .
Moreover, in the absence of friction, a critical value exists which
signals the crossover between two different regimes: for the
asymptotic density scales with a power law of , while for
it reaches logarithmically a maximal saturation value. Such behavior smears out
when a finite friction force is present. In this situation the dynamics is
slower and lower asymptotic densities are attained. In particular, for
significant friction forces, the final density decreases linearly with the
friction coefficient. We also compare the frictionless single tap dynamics to
the sequential tapping dynamics, observing in the latter case an inverse
logarithmic behavior of the density evolution, as found in the experiments.Comment: 10 pages, 15 figures, to be published in Phys. Rev.
Galaxy Clusters in the Swift/BAT era II: 10 more Clusters detected above 15 keV
We report on the discovery of 10 additional galaxy clusters detected in the
ongoing Swift/BAT all-sky survey. Among the newly BAT-discovered clusters there
are: Bullet, Abell 85, Norma, and PKS 0745-19. Norma is the only cluster, among
those presented here, which is resolved by BAT. For all the clusters we perform
a detailed spectral analysis using XMM-Newton and Swift/BAT data to investigate
the presence of a hard (non-thermal) X-ray excess. We find that in most cases
the clusters' emission in the 0.3-200keV band can be explained by a
multi-temperature thermal model confirming our previous results. For two
clusters (Bullet and Abell 3667) we find evidence for the presence of a hard
X-ray excess. In the case of the Bullet cluster, our analysis confirms the
presence of a non-thermal, power-law like, component with a 20-100 keV flux of
3.4 \times 10-12 erg cm-2 s-1 as detected in previous studies. For Abell 3667
the excess emission can be successfully modeled as a hot component (kT=~13keV).
We thus conclude that the hard X-ray emission from galaxy clusters (except the
Bullet) has most likely thermal origin.Comment: Accepted for publication by Ap
Valorization of cigarette butts for synthesis of levulinic acid as top value-added chemicals
Unprecedented in the literature, levulinic acid (LA), one of the top value-added intermediates of chemical industry, is obtained from cigarette butts as cellulose feedstock by means of a one-pot hydrothermal process carried out at 200 °C for 2 h and catalysed by phosphoric acid. The protocol avoids the use of more aggressive and toxic H2SO4 and HCl, that are generally employed on several cellulose sources (e.g. sludge paper), thus minimizing corrosion phenomena of plants. Neither chemical pre-treatment of butts nor specific purification procedure of LA are required. Notably, by simply modifying acid catalyst (e.g. using CH3COOH), another top value-added fine chemical such as 5-hydroxymethylfuraldehyde (HMF) is obtained, thus widening the scope of the method. Being cigarette filters a waste available in quantities of megatonnes per year, they represent an unlimited at no cost source of cellulose, thus enabling the up-scale to an industrial level of LA production
Role of PET/CT in the detection of liver metastases from colorectal cancer
The aim of this study was to compare the diagnostic accuracy of 2-[fluorine-18] fluoro-2-deoxy-D-glucose positron emission tomography (F-18-FDG-PET) and computed tomography (CT) with PET/CT in the detection of liver metastases during tumour staging in patients suffering from colorectal carcinoma for the purposes of correct surgical planning and follow-up. A total of 467 patients underwent a PET/CT scan using an iodinated contrast medium. We compared images obtained by the single PET scan, the single CT scan and by the fusion of the two procedures (PET/CT). The final diagnosis was obtained by histological examination and/or by the follow-up of all patients, including those who did not undergo surgery or biopsy. The PET scan had 94.05% sensitivity, 91.60% specificity and 93.36% accuracy; the CT scan had 91.07% sensitivity, 95.42% specificity and 92.29% accuracy. The combined procedures (PET/CT) had the following values: sensitivity 97.92%, specificity 97.71% and accuracy 97.86%. This study indicates that PET/CT is very useful in staging and restaging patients suffering from colorectal cancer. It was particularly useful when recurrences could not be visualised either clinically or by imaging despite increasing tumour markers, as it guaranteed an earlier diagnosis. PET/CT not only provides high diagnostic performance in terms of sensitivity and specificity, enabling modification of patient treatment, but it is also a unique, high-profile procedure that can produce cost savings
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