330 research outputs found
New Marker of Colon Cancer Risk Associated with Heme Intake: 1,4-Dihydroxynonane Mercapturic Acid
Background: Red meat consumption is associated with an increased risk of colon cancer. Animal studies show that heme, found in red meat, promotes preneoplastic lesions in the colon, probably due to the oxidative properties of this compound. End products of lipid peroxidation, such as 4-hydroxynonenal metabolites or 8-iso-prostaglandin-F2 (8-iso-PGF2), could reflect this oxidative process and could be used as biomarkers of colon cancer risk associated with heme intake.
Methods: We measured urinary excretion of 8-iso-PGF2 and 1,4-dihydroxynonane mercapturic acid (DHN-MA), the major urinary metabolite of 4-hydroxynonenal, in three studies. In a short-term and a carcinogenesis long-term animal study, we fed rats four different diets (control, chicken, beef, and blood sausage as a high heme diet). In a randomized crossover human study, four different diets were fed (a 60 g/d red meat baseline diet, 120 g/d red meat, baseline diet supplemented with heme iron, and baseline diet supplemented with non-heme iron).
Results: DHN-MA excretion increased dramatically in rats fed high heme diets, and the excretion paralleled the number of preneoplastic lesions in azoxymethane initiated rats (P < 0.0001). In the human study, the heme supplemented diet resulted in a 2-fold increase in DHN-MA (P < 0.001). Urinary 8-iso-PGF2 increased moderately in rats fed a high heme diet (P < 0.0001), but not in humans.
Conclusion: Urinary DHN-MA is a useful noninvasive biomarker for determining the risk of preneoplastic lesions associated with heme iron consumption and should be further investigated as a potential biomarker of colon cancer risk. (Cancer Epidemiol Biomarkers Prev 2006;15(11):2274–9
Electrical and thermal spin accumulation in germanium
In this letter, we first show electrical spin injection in the germanium
conduction band at room temperature and modulate the spin signal by applying a
gate voltage to the channel. The corresponding signal modulation agrees well
with the predictions of spin diffusion models. Then by setting a temperature
gradient between germanium and the ferromagnet, we create a thermal spin
accumulation in germanium without any tunnel charge current. We show that
temperature gradients yield larger spin accumulations than pure electrical spin
injection but, due to competing microscopic effects, the thermal spin
accumulation in germanium remains surprisingly almost unchanged under the
application of a gate voltage to the channel.Comment: 7 pages, 3 figure
Electrical spin injection and detection in Germanium using three terminal geometry
In this letter, we report on successful electrical spin injection and
detection in \textit{n}-type germanium-on-insulator (GOI) using a
Co/Py/AlO spin injector and 3-terminal non-local measurements. We
observe an enhanced spin accumulation signal of the order of 1 meV consistent
with the sequential tunneling process via interface states in the vicinity of
the AlO/Ge interface. This spin signal is further observable up to
220 K. Moreover, the presence of a strong \textit{inverted} Hanle effect points
at the influence of random fields arising from interface roughness on the
injected spins.Comment: 4 pages, 3 figure
Quantitative parameters for the examination of InGaN QW multilayers by low-loss EELS
We present a detailed examination of a multiple InxGa1-xN quantum well (QW) structure for optoelectronic applications. The characterization is carried out using scanning transmission electron microscopy (STEM), combining high-angle annular dark field (HAADF) imaging and electron energy loss spectroscopy (EELS). Fluctuations in the QW thickness and composition are observed in atomic resolution images. The impact of these small changes on the electronic properties of the semiconductor material is measured through spatially localized low-loss EELS, obtaining band gap and plasmon energy values. Because of the small size of the InGaN QW layers additional effects hinder the analysis. Hence, additional parameters were explored, which can be assessed using the same EELS data and give further information. For instance, plasmon width was studied using a model-based fit approach to the plasmon peak; observing a broadening of this peak can be related to the chemical and structural inhomogeneity in the InGaN QW layers. Additionally, Kramers-Kronig analysis (KKA) was used to calculate the complex dielectric function (CDF) from the EELS spectrum images (SIs). After this analysis, the electron effective mass and the sample absolute thickness were obtained, and an alternative method for the assessment of plasmon energy was demonstrated. Also after KKA, the normalization of the energy-loss spectrum allows us to analyze the Ga 3d transition, which provides additional chemical information at great spatial resolution. Each one of these methods is presented in this work together with a critical discussion of their advantages and drawbacks
Crossover from spin accumulation into interface states to spin injection in the germanium conduction band
Electrical spin injection into semiconductors paves the way for exploring new
phenomena in the area of spin physics and new generations of spintronic
devices. However the exact role of interface states in spin injection mechanism
from a magnetic tunnel junction into a semiconductor is still under debate. In
this letter, we demonstrate a clear transition from spin accumulation into
interface states to spin injection in the conduction band of -Ge. We observe
spin signal amplification at low temperature due to spin accumulation into
interface states followed by a clear transition towards spin injection in the
conduction band from 200 K up to room temperature. In this regime, the spin
signal is reduced down to a value compatible with spin diffusion model. More
interestingly, we demonstrate in this regime a significant modulation of the
spin signal by spin pumping generated by ferromagnetic resonance and also by
applying a back-gate voltage which are clear manifestations of spin current and
accumulation in the germanium conduction band.Comment: 5 pages, 4 figure
The Low Redshift survey at Calar Alto (LoRCA)
The Baryon Acoustic Oscillation (BAO) feature in the power spectrum of
galaxies provides a standard ruler to measure the accelerated expansion of the
Universe. To extract all available information about dark energy, it is
necessary to measure a standard ruler in the local, z<0.2, universe where dark
energy dominates most the energy density of the Universe. Though the volume
available in the local universe is limited, it is just big enough to measure
accurately the long 100 Mpc/h wave-mode of the BAO. Using cosmological N-body
simulations and approximate methods based on Lagrangian perturbation theory, we
construct a suite of a thousand light-cones to evaluate the precision at which
one can measure the BAO standard ruler in the local universe. We find that
using the most massive galaxies on the full sky (34,000 sq. deg.), i.e. a
K(2MASS)<14 magnitude-limited sample, one can measure the BAO scale up to a
precision of 4\% and 1.2\% using reconstruction). We also find that such a
survey would help to detect the dynamics of dark energy.Therefore, we propose a
3-year long observational project, named the Low Redshift survey at Calar Alto
(LoRCA), to observe spectroscopically about 200,000 galaxies in the northern
sky to contribute to the construction of aforementioned galaxy sample. The
suite of light-cones is made available to the public.Comment: 15 pages. Accepted in MNRAS. Please visit our website:
http://lorca-survey.ft.uam.es
The Low Redshift survey at Calar Alto (LoRCA)
The Baryon Acoustic Oscillation (BAO) feature in the power spectrum of
galaxies provides a standard ruler to measure the accelerated expansion of the
Universe. To extract all available information about dark energy, it is
necessary to measure a standard ruler in the local, z<0.2, universe where dark
energy dominates most the energy density of the Universe. Though the volume
available in the local universe is limited, it is just big enough to measure
accurately the long 100 Mpc/h wave-mode of the BAO. Using cosmological N-body
simulations and approximate methods based on Lagrangian perturbation theory, we
construct a suite of a thousand light-cones to evaluate the precision at which
one can measure the BAO standard ruler in the local universe. We find that
using the most massive galaxies on the full sky (34,000 sq. deg.), i.e. a
K(2MASS)<14 magnitude-limited sample, one can measure the BAO scale up to a
precision of 4\% and 1.2\% using reconstruction). We also find that such a
survey would help to detect the dynamics of dark energy.Therefore, we propose a
3-year long observational project, named the Low Redshift survey at Calar Alto
(LoRCA), to observe spectroscopically about 200,000 galaxies in the northern
sky to contribute to the construction of aforementioned galaxy sample. The
suite of light-cones is made available to the public.Comment: 15 pages. Accepted in MNRAS. Please visit our website:
http://lorca-survey.ft.uam.es
Recent activity and paleoseismicity of an intraplate extensional fault: the Calamocha fault (Jiloca graben, central Iberian Chain)
The Calamocha fault is an 18-km-long, NNW–SSE striking pure normal fault that moves down the northern sector of the Jiloca graben with respect to the Neogene infill of the Calatayud basin (central Iberian Chain). Its structure and kinematics are characterized by means of detailed geological mapping, morphotectonic analysis and data recording at the outcrop scale. The Calamocha fault represents the inversion of a previous contractional fault zone under the recent tensional stress field (WSW–ENE trending σ3 trajectories). The extensional activity started during the Late Pliocene (ca. 3.8 Ma), accumulating a maximum net slip of 190–230 m (long-term slip rate of 0.05–0.06 mm/a). The palaeoseismological study of three artificial exposures near Calamocha town evidenced recurrent slip during the Late Pleistocene, which proves its active character. Analysis of faulted clastic alluvial units, dated by means of optically stimulated luminescence (OSL), reveals at least eight slip events since 145.9 ± 9.1 ka, the last one being younger than 13.8 ± 0.9 ka. Only a few events represent visible accumulated displacement on the main synthetic rupture surfaces; this allows a rough estimate of the short-term slip rate (during the Late Pleistocene) of about 0.1 mm/a, faster than the long-term rate. The Calamocha fault could potentially produce a characteristic earthquake (in the sense of Schwartz and Coppersmith, J Geophys Res 89:5681–5698, 1984) with moment magnitude Mw ≈ 6.7 ± 0.3 (Mw ≈ 6.9 ± 0.3 in a scenario of activation of the whole Calamocha–Daroca fault zone), average coseismic displacement of 0.5–1.3 m and average recurrence period under 15 ka
Raman spectroscopy of wurtzite and zinc-blende GaAs nanowires: polarization dependence, selection rules and strain effects
Polarization dependent Raman scattering experiments realized on single GaAs
nanowires with different percentages of zinc-blende and wurtzite structure are
presented. The selection rules for the special case of nanowires are found and
discussed. In the case of zinc-blende, the transversal optical mode E1(TO) at
267 cm-1 exhibits the highest intensity when the incident and analyzed
polarization are parallel to the nanowire axis. This is a consequence of the
nanowire geometry and dielectric mismatch with the environment, and in quite
good agreement with the Raman selection rules. We also find a consistent
splitting of 1 cm-1 of the E1(TO). The transversal optical mode related to the
wurtzite structure, E2H, is measured between 254 and 256 cm-1, depending on the
wurtzite content. The azymutal dependence of E2H indicates that the mode is
excited with the highest efficiency when the incident and analyzed polarization
are perpendicular to the nanowire axis, in agreement with the selection rules.
The presence of strain between wurtzite and zinc-blende is analyzed by the
relative shift of the E1(TO) and E2H modes. Finally, the influence of the
surface roughness in the intensity of the longitudinal optical mode on {110}
facets is presented.Comment: 28 pages, 12 figures. to be published in Phys. Rev.
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