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Biomedical subjects

G Ghiringhelli

Publications and source records attributed to G Ghiringhelli.

At least 19 recordsLinked to original sources
PubMed2005

Femtosecond dynamics in ferromagnetic metals investigated with soft x-ray resonant emission.

We present measurements of the magnetic circular dichroism in x-ray resonant emission in the perpendicular geometry (circularly polarized x rays at normal incidence to the magnetization) for L(2,3) the absorption region in Fe, Co, and Ni metal. The results show that spin-dependent screening of the core hole takes place within the scattering time scale, which is supported by the absence of the effect in ionic systems. This allows an assessment of the time scale for the screening process (up to a few femtoseconds). The process is almost complete within the scattering time for Fe and Co, but this is not the case for the narrow band metal Ni which shows a much slower dynamics.

Journal Article↗
PubMed2005

Localized electronic excitations in NiO studied with resonant inelastic X-Ray scattering at the Ni M threshold: evidence of spin flip.

We studied the neutral electronic excitations of NiO localized at the Ni sites by measuring the resonant inelastic x-ray scattering (RIXS) spectra at the Ni M2,3 edges. The good energy resolution allows an unambiguous identification of several spectral features due to excitations. The dependence of the RIXS spectra on the excitation energy gives evidence of local spin flip and yields a value of 125 +/- 15 meV for the antiferromagnetic exchange interaction. Accurate crystal field parameters are also obtained.

Journal Article↗
PubMed2005

Experimental observation and theoretical description of the pure Fano effect in the valence-band photoemission of ferromagnets.

The pure Fano effect in angle-integrated valence-band photoemission of ferromagnets has been observed for the first time. A contribution of the intrinsic spin polarization to the spin polarization of the photoelectrons has been avoided by an appropriate choice of the experimental parameters. The theoretical description of the resulting spectra reveals a complete analogy to the Fano effect observed before for paramagnetic transition metals. While the theoretical photocurrent and spin-difference spectra are found in good quantitative agreement with experiment in the case of Fe and Co, only a qualitative agreement could be achieved in the case of Ni by calculations on the basis of plain local spin-density approximation. Agreement with experimental data could be improved in this case in a very substantial way by a treatment of correlation effects on the basis of dynamical mean field theory.

Journal Article↗
PubMed2005

Determination of the orbital moment and crystal-field splitting in LaTiO3.

Utilizing a sum rule in a spin-resolved photoelectron spectroscopic experiment with circularly polarized light, we show that the orbital moment in LaTiO3 is strongly reduced from its ionic value, both below and above the Ne el temperature. Using Ti L2,3 x-ray absorption spectroscopy as a local probe, we found that the crystal-field splitting in the t2g subshell is about 0.12-0.30 eV. This large splitting does not facilitate the formation of an orbital liquid.

Journal Article↗
PubMed2004

Low energy electronic excitations in the layered cuprates studied by copper L3 resonant inelastic x-ray scattering.

We have measured the resonant inelastic x-ray scattering (RIXS) spectra at the Cu L3 edge in a variety of cuprates. Exploiting a considerably improved energy resolution (0.8 eV) we recorded significant dependencies on the sample composition and orientation, on the scattering geometry, and on the incident photon polarization. The RIXS final states correspond to two families of electronic excitations, having local (dd excitations) and nonlocal (charge-transfer) character. The dd energy splitting can be estimated with a simple crystal field model. The RIXS at the L3 edge demonstrates here a great potential, thanks to the resonance strength and to the large 2p spin-orbit splitting.

Journal Article↗
PubMed2003

Crossing the gap from p- to n-type doping: nature of the states near the chemical potential in La(2)-(x)Sr(x)CuO(4) and Nd(2-x)Ce(x)CuO(4-delta).

We report on an x-ray absorption and resonant photoemission study on single crystals of the high-T(c) cuprates La2-xSrxCuO4 and Nd(2-x)Ce(x)CuO(4-delta). Using an intrinsic energy reference, we find that the chemical potential of La2-xSrxCuO4 lies near the top of the La2CuO4 valence band whereas in Nd(2-x)Ce(x)CuO(4-delta) it is situated near the bottom of the Nd2CuO4 conduction band. The data clearly establish that the introduction of Ce in Nd2CuO4 results in electrons being doped into the CuO2 planes. We infer that the states closest to the chemical potential have a Cu 3d(10) singlet origin in Nd(2-x)Ce(x)CuO(4-delta) and a 3d(9)L singlet origin in La2-xSrxCuO4.

Journal Article↗
PubMed2003

Sum rules in x-ray resonant Raman scattering: recovering the Co ground state information in CoFe2O4 as a test case.

We present an approach to x-ray resonant Raman scattering suitable for sum-rule analysis. In magnetic systems it gives ground state information as represented by an expansion in coupled multipoles of orbital and spin moments. The experiment is based on the angular dependence of the integrated peak intensities. In 3d transition elements one obtains information up to order 4 from the channel 2p(6)3d(n)-->2p(5)3d(n+1)-->2p(6)3s(1)3d(n+1). By combining these results with L(2,3) absorption dichroism, we show quantitatively the atomiclike properties of cobalt in CoFe2O4 up to high-order multipoles.

Journal Article↗
PubMed2002

Exchange splitting and charge carrier spin polarization in EuO.

High quality thin films of the ferromagnetic semiconductor EuO have been prepared and were studied using a new form of spin-resolved spectroscopy. We observed large changes in the electronic structure across the Curie and metal-insulator transition temperature. We found that these are caused by the exchange splitting of the conduction band in the ferromagnetic state, which is as large as 0.6 eV. We also present strong evidence that the bottom of the conduction band consists mainly of majority spins. This implies that doped charge carriers in EuO are practically fully spin polarized.

Journal Article↗
PubMed2001

Detection of Zhang-Rice singlets using spin-polarized photoemission.

From a spin-resolved photoemission study on the Bi(2)Sr(2)CaCu(2)O(8+delta) superconductor, we show experimentally that the first ionization state is of nearly pure singlet character. This is true both above and below the superconducting transition and in the presence of doping and band formation. This provides direct support for the existence and stability of Zhang-Rice singlets in high-temperature superconductors, justifying the ansatz of single-band models. Moreover, we establish this technique as an important probe for a wide range of cuprates and strongly correlated materials.

Journal Article↗
PubMed2001

Spin-orbit coupling in the Mott insulator Ca(2)RuO(4).

O 1s x-ray absorption study of the Mott insulator Ca(2)RuO(4) shows that the orbital population of the 4d t(2g) band dramatically changes with temperature. In addition, spin-resolved circularly polarized photoemission study of Ca(2)RuO(4) shows that a substantial orbital angular momentum is induced in the Ru 4d t(2g) band. Based on the experimental results and model Hartree-Fock calculations, we argue that the cooperation between the strong spin-orbit coupling in the Ru 4d t(2g) band and the small distortion of the RuO(6) octahedra causes the interesting changeover of the spin and orbital anisotropy as a function of temperature.

Journal Article↗
PubMed2001

Element-selective nanosecond magnetization dynamics in magnetic heterostructures.

We have developed a new original technique to study the magnetization reversal dynamics of thin films with element selectivity in the nanosecond time scale. X-ray magnetic circular dichroism measurements in pump-probe mode are carried out taking advantage of the time structure of synchrotron radiation. The dynamics of the magnetization reversal of each of the layers of complex heterostructures (like spin valves or tunnel junctions) can be probed independently. The interlayer coupling in the studied systems has been shown to play a key role in the determination of the magnetization reversal of each individual layer.

Journal Article↗
PubMed1998

Bone mineral density and bone size in men with primary osteoporosis and vertebral fractures.

The bone mineral density (BMD) at the lumbar spine, proximal femur, and total skeleton was evaluated in 38 men with primary osteoporosis and vertebral fractures. BMD of the patients was significantly reduced over all skeletal areas compared with controls. The Z-score of the lumbar spine (-2.8 +/- 0.9) was less than that of the other areas (P < 0.001) except the legs (-2.5 +/- 1.1) (p.n.s.) showing that bone loss had a tendency to be greater over the axial skeleton. Vertebral dimensions compared with age-matched controls were as follows: projected L2-L4 area (cm 2): 45.7 +/- 5.6 versus 53.7 +/- 3. 6 (P < 0.001); vertebral width (cm): 4.37 +/- 0.44 versus 4.90 +/- 0. 36 (P < 0.001). Serum biochemical parameters and testosterone levels were similar between osteoporotic and control men. We conclude that men with vertebral osteoporotic fractures have reduced vertebral BMD and vertebral dimensions compared with age-matched controls. Thus, these findings indicate that the achievement of a reduced bone size at the end of the growth period or a failure of periosteal increase during adult life is likely to contribute to the pathogenesis of the vertebral fractures observed in older men.

Adult↗
PubMed1997

[Clinical, humoral and scintigraphic assessment of a bisphosphonate as potential treatment of diaphyseal dysplasia: Ribbing and Cammurati-Engelmann diseases].

Cammurati-Engelmann's Disease or Progressive Diaphyseal Dysplasia (PDD), is a rare autosomal dominant disorder, sometimes non hereditable, which begins in childhood, and is characterized by symmetrical excess of osseous apposition in diaphysis and metaphysis of long bones. In severe cases skull and vertebrae could be involved. Clinically, patients refer limb pain, muscular weakness and atrophy, easy fatigability and waddling gait. Later on S. Ribbing described an illness that he thought was a separate entity with sclerosis and enlargement of diaphysis of femora and tibiae, which begins after puberty, is less extensive, not always symmetric and without gait or neurological involvement. Some authors think it may be an adult form of the PDD. As no specific treatments are available we report one case of each entity, treated with the bisphosphonate pamidronate, by the oral route. A white female, 69 years old, with clinic and radiology of Ribbing's Disease, had positive scintigraphy in the affected areas and elevated bone biochemical markers: Serum alkaline phosphatase (SAP): 57 UKA. Total urinary hydroxyproline (THP): 60 mg/24 h. Bone Gla protein (BGP): 40 ng/ml. Considering the high bone turnover treatment with oral pamidronate, 400 mg/day plus Calcium 1g/day was started, dose was then progressively reduced. After two months pain almost disappeared, and THP became normal: 14 mg/24 h; with normalization of BGP values: 8 ng/ml, and a decrease of SAP: 21 UKA, 99mTc MDP uptake by affected bones decreased after 1 year of treatment. Because of these results we decided to begin treatment in a white female 17 years old, 32 kg weight, 1.47 m height with PDD characteristics and also a high bone turnover (THP: 95 mg/24 h. SAP: 32 UKA). After six months of Calcium 1 g/day, given with meals, and oral pamidronate 100 mg/day, she became painless with normal strength and gait, almost normalization of THP (48 mg/24 h). Although a small decrease of SAP, and no charges in scintigraphy. These results obtained with pamidronate suggest that it may be useful to treat dysplasias with high bone turnover.

Adolescent↗
PubMed1996

Hormone replacement therapy increases trabecular and cortical bone density in osteoporotic women.

Twenty five postmenopausal Caucasian women with established osteoporosis or severe osteopenia were treated with continuous combined estrogen/progesterone (2 mg 17 beta estradiol and 5 mg medroxiprogesterone) and 1000 mg of calcium daily. The mean age of the patients was 57 +/- 6 years (range 44 to 69 years), and the average postmenopausal interval was of 10.7 +/- 4.2 years. The bone mineral density (BMD) of the lumbar spine and proximal femur was determined using DXA densitometer at baseline, 12 and 24 months of treatment. Serum and urine measurements were done at baseline and 12 months. After 24 months of treatment bone mineral density increased at the trochanter 10.2% p < 0.001, lumbar spine 9.6% p < 0.001, Ward's triangle 8.6% p < 0.005 and femoral neck 5.7% p < 0.001 in comparison to basal levels. In the first year of treatment serum alkaline phosphatase and urinary hydroxiproline diminished significantly in comparison to basal levels (p < 0.001, for both). In conclusion, this study indicates that continuous combined estrogen progesterone therapy decreases bone turnover and increases BMD of the spine, femoral neck and trochanter in established osteoporosis.

Adult↗
PubMed1990

Bone diminution of osteoporotic females at different skeletal sites.

The bone mineral density (BMD) of the radius and spine was determined by photo absorptiometry in a large number of controls (radius: n = 111; spine: n = 85; age range: 50-79 years) and osteoporotic women (radius: n = 98; spine n = 140; age range: 50-79 years) with at least one "atraumatic" vertebral compression fracture. Compared to age-matched controls, the BMD of the osteoporotic women showed the following diminutions: sixth decade: radius: -9.1%; spine: -25%; femur: -33%; seventh decade: radius: -16%; spine: -19%; femur: -23%; eighth decade: radius: -21%; spine: -20%; femur: -24%. The BMD was significantly diminished at all sites in all decades but in contrast to the radius, the difference from controls was bigger in the spine and femur in the sixth decade than in the seventh and eighth decade. In the osteoporotic women there was a significant correlation between radius BMD and age (r = -0.56; P less than 0.01) but not between spine or femoral BMD and age. The femoral neck BMD was also determined in a subset group of female controls (n = 68), patients with crush fractures of the spine without a fracture of the hip (n = 46), and in patients with fractures of the proximal femur (n = 21). There was no difference among these groups in mean age (64 +/- 7, range: 50-79 years). Patients with hip fracture and spine fracture showed bone diminution in all three regions that was significantly below controls (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1990

[Bone mineral density of the lumbar spine and proximal femur of normal females in Buenos Aires].

The bone mineral density (BMD) of the lumbar spine and proximal femur was determined in 170 and 131 respectively normal females from 20 to 79 years of age. The BMD was determined by dual photon absorptiometry with a Lunar DP3 equipment. The results per decade of age are shown on table 2. The percentage fall between the 3rd and 8th decades of age at different skeletal sites is summarized on table 3. Meanwhile the bone loss at the lumbar spine and mid-radius from a previous study was approximately 3% before the menopause, the BMD of proximal femur diminished approximately 14% over the neck and 19% at the Ward's triangle during the same period. From age 50 to 80 the average bone loss was similar at the spine and femoral neck (approximately 15%) but it was more severe at the Ward's triangle (approximately 24%). The results obtained in the Buenos Aires females were compared to the values observed in studies performed in United States and Australia using the same equipment. No differences were found among the three populations using the Bonferroni's analysis for multiple comparisons. The BMD appears to be similar in different caucasian populations when the same type of equipment is used, but the values cannot be compared with the results obtained with other equipment. A sustained diminution of the proximal femur BMD was observed from age 20 to 80, whereas over the spine a distinct difference before and after the menopause was found.

Absorptiometry, Photon↗
PubMed1989

Acute effect of the intranasal administration of salmon calcitonin in osteoporotic women.

Eleven women with primary osteoporosis (mean age, 63.1 years; range, 57-78) received in a random schema: placebo, 200 and 400 IU of salmon calcitonin nasal spray (sCT-NS) during 3 successive days. Total and ionized calcium and phosphate in serum were determined before and 5 h after calcitonin. Total hydroxyproline (THP) and creatinine excretion were measured in urine in three periods of 8 h each after calcitonin administration. The THP excretion after placebo administration showed a circadian rhythm with peak excretion during the night. This rhythm was not altered by sCT-NS administration at 8 a.m. but a sustained diminution of the THP/creatinine excretion was observed. The average decrease after 400 IU of sCT-NS was 9, 16 and 6% during the first, second and third periods of urine collection. Although the average effect of the 200 and 400 IU doses was similar, only the diminution induced by the latter dose on the 24-h period was statistically significant: placebo, 24.8 +/- 2.9; 200 IU, 20.8 +/- 2.9 (P n.s.); 400 IU, 20.1 +/- 2.2 mg/24 h (P less than 0.01). No significant changes were observed on serum except a fall provoked by the 400 IU dose upon ionized calcium (4.44 +/- 0.08 to 4.37 +/- 0.06 mg/dl; P less than 0.05). The administration of 200 or 400 IU of sCT-NS provoked a sustained but moderate decrease of bone resorption on osteoporotic females of a lesser degree than the one observed in a previous study after the parenteral administration of 100 IU.

Administration, Intranasal↗