Search Results - (Author, Cooperation:L. Colombo)

2012-10-13

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

2013-10-26

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

2015-01-03

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

1089-7550

AIP Digital Archive

Physics

The dependence of majority carrier mobility on carrier concentration at 77 K in Hg0.78Cd0.22Te has been studied by Hall measurements on about 190 n-type and 360 p-type liquid phase epitaxial films. The n-type films were indium doped with the carrier concentration varying from 1×1014 to 2×1016 cm−3. The measured electron mobility changed from 2×105 to 8×104 cm2/V s. The p-type films were undoped (Hg vacancy) with the carrier concentration varying from 2×1015 to 3×1017 cm−3. The measured hole mobility changed from 600 to 200 cm2/V s. By comparing calculated mobility curves with the experimental data, we found that the major scattering mechanisms for electron mobility in n-type materials were polar optical phonon, ionized impurity, and alloy disorder scatterings. These three scattering mechanisms also dominate the hole mobility in p-type materials at 77 K. It was also found that a model with Hg vacancy as doubly ionized shallow acceptors fitted very well the hole mobility versus carrier concentration data.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

In the framework of a central force-constant model and a surface Green function matching technique we calculate the dynamical effects of biaxial strain in a short period Cu/Ni(111) superlattice. We show that sizeable changes in the spectral features are predicted, so that a spectroscopic characterization of these systems is stimulated. An important reason to investigate the vibrational features of such a system is that it has been studied in detail as a prototype of fcc-modulated alloys, i.e., artificially grown structures, which edisplay a huge stiffening of the bulk modulus.〈l 〉

Electronic Resource

1089-7550

AIP Digital Archive

Physics

The recombination mechanisms of the minority-carrier lifetime in n-type indium-doped Hg0.78Cd0.22Te liquid-phase-epitaxial films have been studied. Its temperature dependence was measured from 78 to 200 K using standard photoconductivity decay method. The dependence on doping concentration from 1×1014 to 2×1015 cm−3 was measured using a contactless microwave reflection method at 77 K. From best fits to the experimental temperature dependence data, it was found that lifetimes at temperatures higher than 130 K were dominated by Auger recombination with a value of 0.15 for the overlap integral of Bloch functions. For most films with a doping concentration below 1×1015 cm−3, Shockley–Read–Hall recombination via an acceptor-like deep level at about 40 meV below the conduction band affected lifetimes below 120 K. It was also found that the recombination parameters determined from fitting the lifetime versus temperature curves were adequate to analyze and understand the lifetime versus doping concentration curve, which comprised data from over 100 films.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

We measured room-temperature reflectivity in the far-infrared region (100–700 cm−1) of In1−xGaxAsyP1−y films grown by metalorganic phase epitaxy on InP substrate. The actual As content of the quaternary alloy (ranging from y=0.29 to y=1) was derived by combining photoluminescence and high-resolution x-ray diffraction results. Over the whole compositional range four different vibrational branches, corresponding to InAs-like, GaAs-like, InP-like, and GaP-like mode, have been observed, thus confirming the attribution of "four-mode behavior'' to the quaternary alloy. The frequency position of the four main peaks has been calculated within a valence-force-field model. The frequency shift of these peaks in the alloy with respect to the bulk values has been explained taking into account anharmonicity and strain effects by means of a simplified elastic model.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

The measured switched polarization properties of integrated Pb(Zr,Ti)O3 (PZT) capacitors arrays have been found to show a small dependence on individual capacitor size in the range from 0.17 and 100 μm2. These thin (90 nm) PZT capacitors have low voltage switching properties with polarization saturation of 〈1.8 V with switched polarization for the smallest capacitors (0.17 μm2) still larger than 25 μC/cm2. The capacitor stack consisted of TiAlN hardmask/Ir/IrOx/PZT/Ir/TiAlN on either SiO2 dielectric or W plugs. The capacitor was patterned using 248 nm lithography and etched using only one mask. For wafers without W plugs, the Ir bottom electrode was not etched. For wafers with W plugs, the entire capacitor stack was etched and electrical connection to the bottom electrode was through the W plugs. The capacitors were integrated using SiO2 dielectrics and one level of Al metallization. These data suggest that high-density, ferroelectric capacitor-based memories may be feasible. © 2001 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Physical and electrical properties of HfSiON that make this material desirable as the gate dielectric in a standard metal–oxide–semiconductor flow are reported. Sputtering was used to deposit films with minimal low dielectric constant interface layers, equivalent oxide thicknesses below 13 Å, and leakage current density at least two orders of magnitude lower than SiO2. The presence of nitrogen in the film enhances the thermal stability relative to HfSiO, and no crystallization was observed for anneals up to 1100 °C. © 2002 American Institute of Physics.

Electronic Resource

1749-6632

Blackwell Publishing Journal Backfiles 1879-2005

Natural Sciences in General

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

We present a study of the thermodynamical properties of C60 in the microcanonical ensemble. Solidlike and metastable liquidlike form can be identified in the low energy and in the high energy range, respectively. The transition between the two phases is characterized by a finite energy range, in agreement with general theories of cluster melting. In particular, we have observed that the melting is preceded by a highly isomerized transition region where a sizeable atomic mobility is achieved via hopping between different isomer structures. © 1995 American Institute of Physics.

Electronic Resource

1365-2303

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Fine needle aspiration cytology of primary lymphoma of the thyroid: a report of 17 cases Between 1980 and 1998, 4272 thyroid surgical specimens with a preoperative fine needle aspirate were sent to our Anatomical Pathology Department. Among these cases there were 17 primary thyroid lymphomas, which constituted 0.3% of all the thyroid lesions and 2.3% of the thyroid malignancies. Seven cases were diffuse large B-cell (DLBC) lymphomas and 10 were MALT lymphomas. Of the DLBC lymphomas six were correctly diagnosed by fine needle aspiration cytology (FNAC) and one was diagnosed as positive for malignancy, and among MALT lymphomas four were diagnosed as lymphoma, four as suspicious for lymphoma, and three as Hashimoto’s thyroiditis (HT). Our data indicate that the diagnosis of primary thyroid lymphoma of high grade is easy, and immunocytochemistry (ICC) can confirm suspicious cases. The diagnosis of MALT lymphoma is more difficult; ICC can confirm suspicious cases, and false-negative results seem to be caused by sampling error, because HT usually coexists with MALT lymphoma.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

Among the hypothetical forms of fully covalent carbon lattices with either graphite-like sp2 or mixed sp2/sp3 bonding we investigated the possibility of monocrystals with a hollow structure. We have calculated the structural, elastic and electronic properties of two prototypical face–centered cubic lattices C20 and C22, respectively, making also a critical comparison to diamond and graphite. The first of these lattices belongs to a new class of sp2–bonded periodic solids which we call hollow graphites. We give a topological classification of such solids along with the algorithm to generate them. Both crystals, having a nanoporous lattice made of periodic sequence of adjacent cavities, rather than the tubular structure of schwarzites, are characterized by a large internal specific area and should be suitable to form reversible high capacity lithium insertion compounds. © 1997 American Institute of Physics.

Electronic Resource

1365-3091

Blackwell Publishing Journal Backfiles 1879-2005

Geosciences

Ten samples from a Late Messinian section measured at Capo Rossello, a few hundred metres laterally from and stratigraphically immediately below the Miocene/ Pliocene boundary stratotype, have been investigated by various techniques: carbonate content, grain-size analysis, loss on ignition, clay mineral composition, frequency of euryhaline ostracods. Two lithological sub-units. with different palaeoenvironmental implications, are recognized. Both sub-units were deposited after the termination of evaporitic conditions, and immediately after deposition of an ash fall tuff. The lower unit is the Congeria marl which yields the ‘lago-mare’faunal assemblage, the autochthony of which is supported by biometrical analysis of Cyprides agrigentina, indicating brackish, shallow-water conditions with Paratethyan affinities, and the upper, the Arenazzolo, a thin sandy unit indicating a higher energy environment whose duration is estimated at some thousand years. Marine faunas yielded by the Arenazzolo are interpreted as allochthonous. Sedimentary structures suggest a littoral setting at the edge of the lake, or a delta lobe.The main environmental change occurs at the base of the immediately overlying Trubi Formation, where open marine conditions indicative of oceanic depths mark the termination of the Messinian salinity crisis.

Electronic Resource

1439-0426

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Three experiments of spawning induction in shi drum, Umbrina cirrosa L., were performed in six different commercial Italian hatcheries from May to August (water temperatures: 19–29 °C; salinity: 21–37 p.p.t.). In the first experiment, 119 females (1–4.7 kg), subdivided into 29 lots, were injected with a single dose (2, 5, 8, 10, 15 and 20 μg kg−1 body weight) of short-acting gonadotropin- releasing hormone agonist (GnRHa-S), des-Gly10,[D-Ala6]-LH-RH ethylamide. In the other two experiments, 85 females (0.7–5.8 kg), subdivided into 22 and four lots, were treated with one (40 or 80 μg kg−1) or three doses (40 μg kg−1) of long-acting GnRHa (GnRHa-L), respectively. GnRHa-S stimulated spawning in 69% of the 29 treated lots; the number of eggs laid reached a maximum of 130 000 and a weighted mean of 29 200 total eggs kg−1. GnRHa-L elicited a spawning response in 95% of the 22 one-dose treated lots; the number of laid eggs was higher than with GnRHa-S, reaching a maximum of 213 100 and a weighted mean of 59 400 total eggs kg−1. The yield of developing embryos in 67% of the single GnRHa-L treatments was higher (sometimes up to three times) than with GnRHa-S. Triple treatments of the four lots of females with GnRHa-L always resulted in spawning responses; the best result corresponded to a number of total laid eggs of 358 900 eggs kg−1 with a yield of 177 300 developing embryos.

Electronic Resource

1439-0426

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

The European sea bass, Dicentrarchus labrax L., was successfully subjected to chromosome manipulation. Triploidy was induced by cold-shocking eggs at 0–2°C for 20 min starting 5 min after fertilization in order to prevent the extrusion of the second polar body. Meiogynogenesis was also obtained by fertilizing eggs with UV-irradiated sperm (3300 and 6600 erg m−2) and subsequently doubling the chromosome set by meiotic block as above. The commercial advantages of culturing triploid and gynogenetic sea bass are discussed.

Electronic Resource

1365-2761

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Medicine

A polymerase chain reaction (PCR)-based assay to detect nervous necrosis virus (NNV) in fish was developed by using two sets of primers designed on a highly conserved region of the coat protein gene encoded by RNA2 of NNV. The first pair of primers amplified a fragment of 605 bp by one-step reverse-transcription (RT)-PCR, while the second pair amplified an internal segment of 255 bp by nested PCR. Addition of nested PCR increased the assay sensitivity 100-fold when carried out in a separate tube (two-step assay) and 10-fold when performed in the same tube (one-step assay). The sensitivity of the two-step assay was 104 times higher than that of virus cultivation. Nested PCR served also to confirm the specificity of the first amplification, as verified also by Southern hybridization analysis and direct sequencing. In species known to be susceptible to infection, such as European sea bass, Dicentrarchus labrax, and gilthead seabream, Sparus aurata, NNV was often detectable in brain tissue by RT-PCR alone but only by the two-step assay in blood, sperm, ovarian tissue or larvae. The same was true for sperm and ovarian tissue of shi drum, Umbrina cirrosa. NNV was also detected in the brains of Japanese red seabream, Pagrus major and brown meagre, Sciaena umbra, suggesting that these species can also be infected. No NNV was detected in samples of Artemia salina nauplii and rotifers obtained from a fish farm with an NNV outbreak. The inclusion of nested PCR in the assay appears to be necessary to screen out NNV-positive broodfish by blood sampling and testing of their larval progeny.

Electronic Resource

0006-291X

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Chemistry and Pharmacology

Physics

Electronic Resource

0924-2031

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Chemistry and Pharmacology

Physics

Electronic Resource

0016-6480

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Medicine

Electronic Resource