322 research outputs found
The Levels of DAHP Synthase, the First Enzyme of the Shikimate Pathway, Are Related to Free Aromatic Amino Acids and Glutamine Content in Nicotiana plumbaginifolia Cell Cultures
Aromatic amino acid homeostasis was investigated in cell suspension cultures of Nicotiana plumbaginifolia and was related to the activity of the first enzyme in aromatic biosynthesis, 3-deoxy-D-arabino-heptulosonate-7-phosphate (DAHP) synthase. An inverse relationship was found between the intracellular content of free phenylalanine, tyrosine and tryptophan and enzyme specific activity levels, suggesting the occurrence of end-product control mechanisms. Two DAHP synthase isogenes are present in wild tobacco that showed a different expression pattern during the culture growth cycle. Intracellular levels of aromatic amino acids were increased or decreased by adding the culture medium with phenylalanine, tyrosine and tryptophan, or with sublethal doses of the shikimate pathway inhibitor glyphosate, respectively. As a consequence, enzyme levels varied in the opposite direction. The concomitant exogenous supply of glutamine further reduced enzyme activity in mid-log cells, suggesting induction by both aromatic amino acid depletion and nitrogen starvation
On the transient behavior of frictional melt during seismic slip
In a recent work on the problem of sliding surfaces under the presence
of frictional melt (applying in particular to earthquake fault dynamics),
we derived from first principles an expression for the steady state
friction compatible with experimental observations. Building on the
expressions of heat and mass balance obtained in the above study for
this particular case of Stefan problem (phase transition with a migrating
boundary) we propose here an extension providing the full time-dependent
solution (including the weakening transient after pervasive melting
has started, the effect of eventual steps in velocity and the final
decelerating phase). A system of coupled equations is derived and
solved numerically. The resulting transient friction and wear evolution
yield a satisfactory fit (1) with experiments performed under variable
sliding velocities (0.9-2 m/s) and different normal stresses (0.5-20
MPa) for various rock types and (2) with estimates of slip weakening
obtained from observations on ancient seismogenic faults that host
pseudotachylite (solidified melt). The model allows to extrapolate
the experimentally observed frictional behavior to large normal stresses
representative of the seismogenic Earth crust (up to 200 MPa), high
slip rates (up to 9 m/s) and cases where melt extrusion is negligible.
Though weakening distance and peak stress vary widely, the net breakdown
energy appears to be essentially independent of either slip velocity
and normal stress. In addition, the response to earthquake-like slip
can be simulated, showing a rapid friction recovery when slip rate
drops. We discuss the properties of energy dissipation, transient
duration, velocity weakening, restrengthening in the decelerating
final slip phase and the implications for earthquake source dynamics
Clinical validation results of an innovative non-invasive device for colorectal cancer preventive screening through fecal exhalation analysis
Screening is recommended to reduce both incidence and mortality of colorectal cancer.
Currently, many countries employ fecal occult blood test (FOBT). In Emilia-Romagna (Italy), since
2005, FOBT immunochemical version (FIT) is performed every two years on people aged between 50
and 69 years. A colonoscopy is then carried out on those who are FIT positive. However, FIT shows
approximately 65% false positives (non-tumoral bleedings), leading to many negative colonoscopies.
The use of an economic and easy-to-use method to check FOBT-positives will improve screening
effectiveness, reducing costs to the national health service. This work illustrates the results of a
three-year clinical validation protocol (started in 2016) of a patented device composed of a core of
nanostructured gas sensors. This device was designed to identify CRC presence by fecal volatile
compounds, with a non-invasive, in vitro and low-cost analysis. Feces are, in fact, affected by
tumor-volatile biomarkers, produced by cellular peroxidation and metabolic alterations. The protocol
consisted in the analysis of fecal samples of FIT-positive subjects, using colonoscopy as a gold standard.
A total of 398 samples were analyzed with machine learning techniques, leading to a sensitivity and
specificity of 84.1% and 82.4%, respectively, and a positive predictive value of 72% (25–35% for FIT)
Devices for Screening and Monitoring of Tumors Based on Chemoresistive Sensors
Abstract In this work two devices are presented, named SCENT A1 (A1) and SCENT B1 (B1), composed of chemoresistive sensors. Such devices are capable of discriminating the different compositions of gas mixtures emitted by stools, for colorectal cancer screening (A1), and by blood, for tumors monitoring (B1), according to defined sampling protocols. Results have been acquired by a LabView® software and statistically treated (e.g. quadratic discriminant analysis, QDA) and show to be encouraging with an error of 5% for SCENT A1. Preliminary results of SCENT B1 proved to be promising. Further studies will be carried out for clinically validating the two devices
Wavelet analysis on paleomagnetic (and computer simulated) VGP time series
We present Continuous Wavelet Transform (CWT) data analysis of Virtual Geomagnetic Pole (VGP) latitude
time series. The analyzed time series are sedimentary paleomagnetic and geodynamo simulated data. Two mother
wavelets (the Morlet function and the first derivative of a Gaussian function) are used in order to detect features
related to the spectral content as well as polarity excursions and reversals. By means of the Morlet wavelet,
we estimate both the global spectrum and the time evolution of the spectral content of the paleomagnetic data
series. Some peaks corresponding to the orbital components are revealed by the spectra and the local analysis
helped disclose their statistical significance. Even if this feature could be an indication of orbital influence on
geodynamo, other interpretations are possible. In particular, we note a correspondence of local spectral peaks
with the appearance of the excursions in the series. The comparison among the paleomagnetic and simulated
spectra shows a similarity in the high frequency region indicating that their degree of regularity is analogous. By
means of Gaussian first derivative wavelet, reversals and excursions of polarity were sought. The analysis was
performed first on the simulated data, to have a guide in understanding the features present in the more complex
paleomagnetic data. Various excursions and reversals have been identified, despite of the prevalent normality of
the series and its inherent noise. The found relative chronology of the paleomagnetic data reversals was compared
with a coeval global polarity time scale (Channel et al., 1995). The relative lengths of polarity stability intervals
are found similar, but a general shift appears between the two scales, that could be due to the datation uncertainties
of the Hauterivian/Barremian boundary
Chemoresistive Gas Sensor based on SiC Thick Film: Possible Distinctive Sensing Properties Between H2S and SO2☆
Commercially available nanosized powder of silicon carbide (named SiC), was thermally, morphologically and structurally characterized. After that, it was screen-printed onto alumina substrates in order to obtain thick films to be tested as functional material for conductometric gas sensors. Samples were exposed to SO2 and H2S, gases with high importance in many application fields, with the aim of verifying its capability of distinguishing between them. The characterization highlighted that this semiconductor type is selective for sulphur dioxide (SO2), in concentrations within the ppm range. This interesting result was found at high temperatures (600-800°C), useful for harsh environmental, and the measurements proved to be completely free from humidity interference. Applications of such a sensor could span many fields, since SO2 plays an important role in air pollution, industrial processes and wine making monitoring
Introduction : translingual work.
This issue both reflects and builds on the efforts prompted by the 2011 College English essay “Language Difference in Writing: Toward a Translingual Approach,” by Bruce Horner, Min-Zhan Lu, Jacqueline Jones Royster, and John Trimbur. Contributions to this symposium contextualize the emergence of a translingual approach, explore the tension and interconnections between a translingual approach and a variety of fields, and explore the viability of a translingual approach in light of existing academic structures
AS-773-13 Resolution of Commendation for Margaret Camuso
Commends Margaret Camuso for her service to the Academic Senate
The Steady State Fluctuation Relation for the Dissipation Function
We give a proof of transient fluctuation relations for the entropy production
(dissipation function) in nonequilibrium systems, which is valid for most time
reversible dynamics. We then consider the conditions under which a transient
fluctuation relation yields a steady state fluctuation relation for driven
nonequilibrium systems whose transients relax, producing a unique
nonequilibrium steady state. Although the necessary and sufficient conditions
for the production of a unique nonequilibrium steady state are unknown, if such
a steady state exists, the generation of the steady state fluctuation relation
from the transient relation is shown to be very general. It is essentially a
consequence of time reversibility and of a form of decay of correlations in the
dissipation, which is needed also for, e.g., the existence of transport
coefficients. Because of this generality the resulting steady state fluctuation
relation has the same degree of robustness as do equilibrium thermodynamic
equalities. The steady state fluctuation relation for the dissipation stands in
contrast with the one for the phase space compression factor, whose convergence
is problematic, for systems close to equilibrium. We examine some model
dynamics that have been considered previously, and show how they are described
in the context of this work.Comment: 30 pages, 1 figur
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