PubMed Health⌕ Search

Biomedical subjects

E Busetto

Publications and source records attributed to E Busetto.

8 recordsLinked to original sources
PubMed2005

Pressure-induced structural phase transformations in silicon nanowires.

High-pressure structural behavior of silicon nanowires is investigated up to approximately 22 GPa using angle dispersive X-ray diffraction measurements. Silicon nanowires transform from the cubic to the beta-tin phase at 7.5-10.5 GPa, to the Imma phase at approximately 14 GPa, and to the primitive hexagonal structure at approximately 16.2 GPa. On complete release of pressure, it transforms to the metastable R8 phase. The observed sequence of phase transitions is the same as that of bulk silicon. Though the X-ray diffraction experiments do not reveal any size effect, the pressure dependence of Raman modes shows that the behavior of nanowires is in between that of the bulk crystal and porous Si.

Crystallization↗
PubMed2002

X-ray absorption holography.

The transmission of monochromatic x rays through a CoO single crystal was measured for different orientations of the sample. The small variations in the linear absorption coefficient were considered as a hologram and the real-space image of the local atomic environment was successfully reconstructed. The holographic signal constituted about 1% of the detected intensity. Besides other benefits, the use of the absorption holography can increase the signal-to-background ratio by more than 1 order compared with the fluorescence holography.

Journal Article↗
PubMed2000

X-ray diffraction on Si single crystal with a W-shaped longitudinal groove.

The measurement of the sagittal deviation of an X-ray beam diffracted on the inclined surface of an Si(111) single crystal was performed on beamline BM5 at the ESRF, with lambda = 0.1 nm and an inclination angle, beta, of 70 degrees . The measured value agrees with the theory developed in previous papers. The topographic picture of the longitudinal edge shows a structure that can be explained in terms of the properties of inclined diffraction.

Journal Article↗
PubMed1999

Determination of the site of incorporation of cobalt in CoZnPO-CZP by multiple-wavelength anomalous-dispersion crystallography.

Data were collected from a crystal of CoZnPO-CZP {sodium cobalt-zinc phosphate hydrate, Na(6)[Co(0.2)Zn(0.8)PO(4)](6).6H(2)O} using synchrotron radiation at ELETTRA at the inflection point and 'white line' for both the cobalt and zinc K edges, and at 1.45 Å, a wavelength remote from the K edges of both metals. The data were processed using the programs DENZO and SCALEPACK. The CCP4 program suite was used for the scaling of data sets and the subsequent calculation of dispersive difference Fourier maps. Optimal scaling was achieved by using a subset of reflections with little or no contribution from the metal atoms (i.e. which were essentially wavelength independent in their intensities) and using weights based on the sigma's to obtain an overall scale factor in each case. Phases were calculated with SHELXL97 based on the refined structure using a much higher resolution and complete Cu Kalpha data set. An occupancy of 100% by zinc at the two metal-atom sites was assumed. The dispersive difference Fourier map calculated for zinc gave two peaks above the background of similar heights at the expected metal-atom sites. The peak height at the Zn1 site was a little higher than at the Zn2 site. The dispersive difference Fourier map calculated for cobalt gave just one peak above the background, at the Zn1 site, and only a small peak at the Zn2 site, thus indicating that incorporation of cobalt takes place mainly at one site. Refinement of the zinc occupancies using MLPHARE reinforces this conclusion. The chemical environment of each site is discussed.

Journal Article↗
PubMed1998

Rotated-inclined double-crystal monochromator for synchrotron radiation: aberration and its compensation.

A rotated-inclined double-crystal X-ray monochromator was designed for high-power undulator beamlines for SPring-8 to reduce the impinging radiation power density. Recently, it has been shown that an inclined double-crystal monochromator suffers from a certain type of geometrical aberration that may be relatively easily compensated. In this paper, it is shown that a similar aberration exists also in the case of rotated-inclined monochromators and that as in the inclined case the aberration may also be compensated.

Journal Article↗
PubMed1995

Compensation of Aberration of Inclined X-ray Monochromators.

Inclined double-crystal monochromator for synchrotron radiation suffer from aberration that is connected with the horizontal divergence of the synchrotron radiation beam. Two different methods are proposed to compensate for this aberration. The first method introduces slightly different angles of inclination for the first and the second monochromator crystals. The condition for the difference of the angles of inclination is Bragg angle dependent and also depends on the projection of the distance of both crystals onto the direction of the normal to the diffracting planes. The second method uses an additional inclined double-crystal monochromator cut such that the aberration introduced by the first pair of crystals is nearly completely compensated by the second pair of crystals. This method is independent of wavelength. Both methods are illustrated by ray tracing.

Journal Article↗
PubMed1984

Nonparallel patterns of calcitonin and carcinoembryonic antigen levels in the follow-up of medullary thyroid carcinoma.

Serum levels of calcitonin (CT) and carcinoembryonic antigen (CEA) were evaluated in a group of 41 patients with histologically proven medullary thyroid carcinoma (MCT) before and sequentially after treatment for a period up to 7 years. Before thyroidectomy, CT levels were high in all patients, and significantly more elevated when metastases were present. On the other hand, CEA levels were high in most but not all the patients, and they also were found more frequently to be elevated in patients with metastases. After treatment, most of the patients without metastases showed persistently normal basal and pentagastrin stimulated CT and CEA levels. In some patients either without or with local metastases, postoperative CT levels, although considerably reduced, remained persistently above normal limits, whereas CEA levels became completely normal. This pattern may be due to the persistence of minute occult foci of the tumor, not sufficient to produce measurable amounts of CEA, which is not synthesized by all tumor cells. Most of the patients with metastases at diagnosis, showed still elevated CT and CEA levels after treatment. In the nonprogressive cases both markers decreased after adjunctive treatment or remained unchanged. In patients with progressive disease, an increase of CEA levels in the absence of a parallel increase of CT levels, which even decreased, was often observed. In one patient with progressive disease high CEA levels were seen for the first time when liver metastases had occurred. These data seem to suggest that, even though CEA production is not recognizable in all patients with MCT, in the CEA positive cases CEA levels may follow a nonparallel pattern and may have a distinct diagnostic meaning with respect to CT levels. In some cases, particularly in advanced disease, CEA may be a more useful marker of poor prognosis.

Adolescent↗