238 research outputs found
Large phonon-drag enhancement induced by narrow quantum confinement at the LaAlO3/SrTiO3 interface
The thermoelectric power of the two-dimensional electron system (2DES) at the
LaAlO3/SrTiO3 interface is explored below room temperature, in comparison with
that of Nb-doped SrTiO3 single crystals. For the interface we find a region
below T =50 K where thermopower is dominated by phonon-drag, whose amplitude is
hugely amplified with respect to the corresponding bulk value, reaching values
~mV/K and above. The phonon-drag enhancement at the interface is traced back to
the tight carrier confinement of the 2DES, and represents a sharp signature of
strong electron-acoustic phonon coupling at the interface
Shear effects in lateral piezoresponse force microscopy at 180 ferroelectric domain walls
In studies using piezoresponse force microscopy, we observe a non-zero
lateral piezoresponse at 180 domain walls in out-of-plane polarized,
c-axis-oriented tetragonal ferroelectric Pb(ZrTi)O
epitaxial thin films. We attribute these observations to a shear strain effect
linked to the sign change of the piezoelectric coefficient through the
domain wall, in agreement with theoretical predictions. We show that in
monoclinically distorted tetragonal BiFeO films, this effect is
superimposed on the lateral piezoresponse due to actual in-plane polarization,
and has to be taken into account in order to correctly interpret the
ferroelectric domain configuration.Comment: 4 pages, 3 figure
Down-regulation of transforming growth factor-β type II receptor (TGF-βRII) protein and mRNA expression in cervical cancer
<p>Abstract</p> <p>Background</p> <p>Cervical carcinogenesis is a multistep process initiated by "high risk" human papillomaviruses (HR-HPV), most commonly HPV16. The infection <it>per se </it>is, however, not sufficient to induce malignant conversion. Transforming Growth Factor β (TGF-β) inhibits epithelial proliferation and altered expression of TGF-β or its receptors may be important in carcinogenesis. One cofactor candidate to initiate neoplasia in cervical cancer is the prolonged exposure to sex hormones. Interestingly, previous studies demonstrated that estrogens suppress TGF-β induced gene expression. To examine the expression of TGF-β2, TGF-βRII, p15 and c-myc we used <it>in situ </it>RT-PCR, real-time PCR and immunohistochemistry in transgenic mice expressing the oncogene E7 of HPV16 under control of the human Keratin-14 promoter (K14-E7 transgenic mice) and nontransgenic control mice treated for 6 months with slow release pellets of 17β-estradiol.</p> <p>Results</p> <p>Estrogen-induced carcinogenesis was accompanied by an increase in the incidence and distribution of proliferating cells solely within the cervical and vaginal squamous epithelium of K14-E7 mice. TGF-β2 mRNA and protein levels increased in K14-E7 transgenic mice as compared with nontransgenic mice and further increased after hormone-treatment in both nontransgenic and transgenic mice. In contrast, TGF-βRII mRNA and protein levels were decreased in K14-E7 transgenic mice compared to nontransgenic mice and these levels were further decreased after hormone treatment in transgenic mice. We also observed that c-myc mRNA levels were high in K14-E7 mice irrespective of estrogen treatment and were increased in estrogen-treated nontransgenic mice. Finally we found that p15 mRNA levels were not increased in K14-E7 mice.</p> <p>Conclusion</p> <p>These results suggest that the synergy between estrogen and E7 in inducing cervical cancer may in part reflect the ability of both factors to modulate TGF-β signal transduction.</p
Giant Oscillating Thermopower at Oxide Interfaces
Understanding the nature of charge carriers at the LaAlO3/SrTiO3 interface is
one of the major open issues in the full comprehension of the charge
confinement phenomenon in oxide heterostructures. Here, we investigate
thermopower to study the electronic structure in LaAlO3/SrTiO3 at low
temperature as a function of gate field. In particular, under large negative
gate voltage, corresponding to the strongly depleted charge density regime,
thermopower displays record-high negative values of the order of 10^4 - 10^5
microV/K, oscillating at regular intervals as a function of the gate voltage.
The huge thermopower magnitude can be attributed to the phonon-drag
contribution, while the oscillations map the progressive depletion and the
Fermi level descent across a dense array of localized states lying at the
bottom of the Ti 3d conduction band. This study is the first direct evidence of
a localized Anderson tail in the two-dimensional (2D) electron liquid at the
LaAlO3/SrTiO3 interface.Comment: Main text: 28 pages and 3 figures; Supplementary information: 29
pages, 5 figures and 1 tabl
Seebeck effect in the conducting LaAlO_{3}/SrTiO_{3} interface
The observation of metallic behavior at the interface between insulating
oxides has triggered worldwide efforts to shed light on the physics of these
systems and clarify some still open issues, among which the dimensional
character of the conducting system. In order to address this issue, we measure
electrical transport (Seebeck effect, Hall effect and conductivity) in
LaAlO_{3}/SrTiO_{3} interfaces and, for comparison, in a doped SrTiO_{3} bulk
single crystal. In these experiments, the carrier concentration is tuned, using
the field effect in a back gate geometry. The combined analysis of all
experimental data at 77 K indicates that the thickness of the conducting layer
is ~7 nm and that the Seebeck effect data are well described by a
two-dimensional (2D) density of states. We find that the back gate voltage is
effective in varying not only the charge density, but also the thickness of the
conducting layer, which is found to change by a factor of ~2, using an electric
field between -4 and +4MV/m at 77K. No enhancement of the Seebeck effect due to
the electronic confinement and no evidence for two-dimensional quantization
steps are observed at the interfaces.Comment: 15 pages, 5 figure
Two-dimensional quantum oscillations of the conductance at LaAlO3/SrTiO3 interfaces
We report on a study of magnetotransport in LaAlO3/SrTiO3 interfaces
characterized by mobilities of the order of several thousands cm/Vs. We
observe Shubnikov-de Haas oscillations that indicate a two-dimensional
character of the Fermi surface. The frequency of the oscillations signals a
multiple sub-bands occupation in the quantum well or a multiple valley
configuration. From the temperature dependence of the oscillation amplitude we
extract an effective carrier mass \,. An electric field
applied in the back-gate geometry increases the mobility, the carrier density
and the oscillation frequency.Comment: 4 pages, 4 figure
Evaluation of carcass and meat traits of Muscovy duck fed with black soldier fly partially defatted meal
The aim of this study was to evaluate the carcass characteristics and breast meat quality in Muscovy duck (Cairina moschata domestica) fed different inclusion levels of a partially defatted black soldier fly larva (BSF) meal. A total of 256 Muscovy ducklings (average live weight, LW: 71.32\ub12.70 g) were reared from day 3 to day 48 and randomly allotted in 32 pens (8 replicates/treatment). Four different diets were formulated with increasing substitution level of corn gluten meal with BSF larva meal (0, 3, 6 and 9%; BSF0, BSF3, BSF6 and BSF9, respectively) and divided in 3 feeding phases: starter (1-14 days), grower (14-35 days) and finisher (35-48 days). At day 48, 2 animals/replicate were slaughtered and dissected to determine their carcass yields. The weights of spleen, bursa of Fabricius, liver, heart and abdominal fat were recorded. Breast and thigh muscles were then excised from 16 ducks/treatment and weighted. Ultimate pH (pHu) and L*, a*, b* colour values were then measured on breast muscle. The collected data were tested by means of oneway ANOVA evaluating the effect of dietary BSF inclusion level by polynomial contrasts. Significance was declared
at P<0.05. The inclusion of BSF did not affect final LW (2,515.68\ub192.42 g on average). Hot and cold carcass weights showed a quadratic response (P<0.05) to increasing BSF larva meal, with a minimum corresponding to BSF6; however, refrigeration losses were not affected by treatments. Weight of spleen, bursa of Fabricius, liver and heart did not differ among treatments. The weight of abdominal fat showed a quadratic response to increasing BSF meal with a minimum corresponding to BSF6 group (P<0.05). Breast and thigh yields, pHu and L*, a*, b* colour values did not differ among
groups. With the exception of BSF6, the inclusion of BSF meal did not affect meat traits and carcass characteristics, confirming the potential use of BSF meal in Muscovy duck diets
Apparent digestibility of insect protein meals for rainbow trout
Insect meals are considered to be promising future ingredients for aquaculture feeds. In past feeding trials in rainbow trout, insect meals were included in diets only on the basis of their nutrients content and energy density without taking into account their biological availability due to the lack of their digestible values. Apparent digestibility (ADC) provides good indication of the bioavailability of nutrients and energy thus providing rational basis for the correct inclusion of feedstuffs. The aim of this research was to assess, in an in vivo trial on rainbow trout, the ADC of five full fat insect meals: one Tenebrio molitor (TM), two Hermetia illucens obtained through two different process (HI1 and HI2), one Musca domestica (MD), and one Alphitobius diaperinus (AD). Fish were fed a high-quality reference diet (R) and test diets obtained mixing the R diet with each of the test ingredients at a ratio of 70:30. Diets contained 1% celite as inert marker. Fish were fed to visual satiety twice a day and faecal samples collected using a continuous automatic device. Faeces were freeze dried and frozen (-20 \ub0C) until analyses. The ADC of dry matter, crude protein and ether extract of each insect meal diet were calculated. ADC for dry matter varied between 70.07 (HI1) and 80.85 (TM). ADC for protein was above 84% in all treatments and resulted the highest in MD, TM and AD treatments. Ether extract apparent digestibility significantly differed among diets with the highest value reported for TM treatment. All treatments reported values higher than 96%. Observed differences could be due to the insect species and meal treatment but in general, tested insect meals were highly digestible for rainbow trout. The results from this research could be useful to optimize the diet formulation
Origin of interface magnetism in BiMnO3/SrTiO3 and LaAlO3/SrTiO3 heterostructures
Possible ferromagnetism induced in otherwise non-magnetic materials has been
motivating intense research in complex oxide heterostructures. Here we show
that a confined magnetism is realized at the interface between SrTiO3 and two
insulating polar oxides, BiMnO3 and LaAlO3. By using polarization dependent
x-ray absorption spectroscopy, we find that in both cases the magnetic order is
stabilized by a negative exchange interaction between the electrons transferred
to the interface and local magnetic moments. These local magnetic moments are
associated to Ti3+ ions at the interface itself for LaAlO3/SrTiO3 and to Mn3+
ions in the overlayer for BiMnO3/SrTiO3. In LaAlO3/SrTiO3 the induced magnetic
moments are quenched by annealing in oxygen, suggesting a decisive role of
oxygen vacancies in the stabilization of interfacial magnetism.Comment: 5 pages, 4 figure
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