8,743 research outputs found
Noise and diffusion of particles obeying asymmetric exclusion processes
The relation between noise and Fick's diffusion coefficient in barrier
limited transport associated with hopping or tunneling mechanisms of particles
obeying the asymmetric simple exclusion processes (ASEP) is physically assessed
by Monte Carlo simulations. For a closed ring consisting of a large number of
barriers the diffusion coefficient is related explicitly to the current noise
thus revealing the existence of a generalized Nyquist-Einstein relation. Both
diffusion and noise are confirmed to decrease as the square root of the number
of barriers as a consequence of the correlation induced by ASEP. By contrast,
for an open linear chain of barriers the diffusion coefficient is found to be
no longer related to current noise. Here diffusion depends on particle
concentration but is independent of the number of barriers
Optimum frequency modulation receivers
Optimization of receivers for demodulating FM SIGNAL corrupted by Gaussian noise, and solution to maximum likelihood equatio
New Optimization Methods for Converging Perturbative Series with a Field Cutoff
We take advantage of the fact that in lambda phi ^4 problems a large field
cutoff phi_max makes perturbative series converge toward values exponentially
close to the exact values, to make optimal choices of phi_max. For perturbative
series terminated at even order, it is in principle possible to adjust phi_max
in order to obtain the exact result. For perturbative series terminated at odd
order, the error can only be minimized. It is however possible to introduce a
mass shift in order to obtain the exact result. We discuss weak and strong
coupling methods to determine the unknown parameters. The numerical
calculations in this article have been performed with a simple integral with
one variable. We give arguments indicating that the qualitative features
observed should extend to quantum mechanics and quantum field theory. We found
that optimization at even order is more efficient that at odd order. We compare
our methods with the linear delta-expansion (LDE) (combined with the principle
of minimal sensitivity) which provides an upper envelope of for the accuracy
curves of various Pade and Pade-Borel approximants. Our optimization method
performs better than the LDE at strong and intermediate coupling, but not at
weak coupling where it appears less robust and subject to further improvements.
We also show that it is possible to fix the arbitrary parameter appearing in
the LDE using the strong coupling expansion, in order to get accuracies
comparable to ours.Comment: 10 pages, 16 figures, uses revtex; minor typos corrected, refs. adde
Metastatic melanoma cells with BRAF G469A mutation: nab‑paclitaxel better than vemurafenib?
Purpose BRAF G469A is a missense mutation within
exon 11 of the BRAF gene resulting in a constitutively
activated enzyme frequently associated with MAP kinase
cascade signaling activation. No evidence currently exists
about its role in determining sensitivity/resistance to BRAF
inhibitors, utilized in the treatment of patients carrying
BRAF V600 mutations, and to chemotherapy. The newly
established metastatic melanoma (MM) cell line MO-1 was
characterized for its sensitivity to vemurafenib and nabpaclitaxel, both already utilized for the treatment of MM.
Methods All analyses were carried out by comparing
results with those found in MM cells wild type for BRAF
or mutated in V600. In addition, cellular effectors were
investigated by ELISA kits, western blotting and flow
cytometry.
Results The exposure to vemurafenib inhibited MO-1 cell
proliferation at concentrations similar to those obtained in
vemurafenib-resistant melanoma models, and an explanation of this sensitivity is the strong activation of Erk1/2 .
and the low expression of MITF. Nab-paclitaxel strongly
reduced proliferation of MO-1 cells perhaps for the very
low expression level of PMEL17, transcriptionally regulated by MITF and negatively involved in determining sensitivity to taxanes.
Conclusions Thus, the mutation BRAF G469A in MM
might be related to a weak effectiveness of therapy with
BRAF inhibitors and a promising therapeutic approach
may be with nab-paclitaxel
Commentary: Coding of serial order in verbal, visual and spatial working memory
Published: 21 November 201
GRB970228 and the class of GRBs with an initial spikelike emission: do they follow the Amati relation?
On the basis of the recent understanding of GRB050315 and GRB060218, we
return to GRB970228, the first Gamma-Ray Burst (GRB) with detected afterglow.
We proposed it as the prototype for a new class of GRBs with "an occasional
softer extended emission lasting tenths of seconds after an initial spikelike
emission". Detailed theoretical computation of the GRB970228 light curves in
selected energy bands for the prompt emission are presented and compared with
observational BeppoSAX data. From our analysis we conclude that GRB970228 and
likely the ones of the above mentioned new class of GRBs are "canonical GRBs"
have only one peculiarity: they exploded in a galactic environment, possibly
the halo, with a very low value of CBM density. Here we investigate how
GRB970228 unveils another peculiarity of this class of GRBs: they do not
fulfill the "Amati relation". We provide a theoretical explanation within the
fireshell model for the apparent absence of such correlation for the GRBs
belonging to this new class.Comment: 5 pages, 3 figures, in the Proceedings of the "4th Italian-Sino
Workshop on Relativistic Astrophysics", held in Pescara, Italy, July 20-28,
2007, C.L. Bianco, S.-S. Xue, Editor
Contraceptive use and sexual function: a comparison of Italian female medical students and women attending family planning services
Objectives: The aims of the study were to understand how education relates to contraceptive choice and how sexual function can vary in relation to the use of a contraceptive method. Methods: We surveyed female medical students and women attending a family planning service (FPS) in Italy. Participants completed an online questionnaire which asked for information on sociodemographics, lifestyle, sexuality and contraceptive use and also included items of the Female Sexual Function Index (FSFI). Results: The questionnaire was completed by 413 women (362 students and 51 women attending the FPS) between the ages of 18 and 30 years. FSFI scores revealed a lower risk of sexual dysfunction among women in the control group who did not use oral hormonal contraception. The differences in FSFI total scores between the two study groups, when subdivided by the primary contraceptive method used, was statistically significant (p < 0.005). Women using the vaginal ring had the lowest risk of sexual dysfunction, compared with all other women, and had a positive sexual function profile. In particular, the highest FSFI domain scores were lubrication, orgasm and satisfaction, also among the control group. Expensive contraception, such as long-acting reversible contraception, was not preferred by this young population, even though such methods are more contemporary and manageable. Compared with controls, students had lower compliance with contraception and a negative attitude towards voluntary termination of pregnancy. Conclusion: Despite their scientific knowledge, Italian female medical students were found to need sexual and contraceptive assistance. A woman's sexual function responds to her awareness of her body and varies in relation to how she is guided in her contraceptive choice. Contraceptive counselling is an excellent means to improve female sexuality
Autotrophic and Heterotrophic Growth Conditions Modify Biomolecole Production in the Microalga Galdieria sulphuraria (Cyanidiophyceae, Rhodophyta)
Algae have multiple similarities with fungi, with both belonging to the Thallophyte, a polyphyletic group of non-mobile organisms grouped together on the basis of similar characteristics, but not sharing a common ancestor. The main difference between algae and fungi is noted in their metabolism. In fact, although algae have chlorophyll-bearing thalloids and are autotrophic organisms, fungi lack chlorophyll and are heterotrophic, not able to synthesize their own nutrients. However, our studies have shown that the extremophilic microalga Galderia sulphuraria (GS) can also grow very well in heterotrophic conditions like fungi. This study was carried out using several approaches such as scanning electron microscope (SEM), gas chromatography/mass spectrometry (GC/MS), and infrared spectrophotometry (ATR-FTIR). Results showed that the GS, strain ACUF 064, cultured in autotrophic (AGS) and heterotrophic (HGS) conditions, produced different biomolecules. In particular, when grown in HGS, the algae (i) was 30% larger, with an increase in carbon mass that was 20% greater than AGS; (ii) produced higher quantities of stearic acid, oleic acid, monounsaturated fatty acids (MUFAs), and ergosterol; (iii) produced lower quantities of fatty acid methyl esters (FAMEs) such as methyl palmytate, and methyl linoleate, saturated fatty acids (SFAs), and poyliunsaturated fatty acids (PUFAs). ATR-FTIR and principal component analysis (PCA) statistical analysis confirmed that the macromolecular content of HGS was significantly different from AGS. The ability to produce different macromolecules by changing the trophic conditions may represent an interesting strategy to induce microalgae to produce different biomolecules that can find applications in several fields such as food, feed, nutraceutical, or energy production
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