352 research outputs found
Metabolic control of stemness and differentiation
Prove crescenti evidenziano un ruolo fondamentale per il metabolismo nella fisiologia delle cellule staminali e nella specifica del lignaggio [1, 2]. Il metabolismo, infatti, non è più considerato solo una fonte di energia né un endpoint della regolazione genica. Invece, i metaboliti e l'ambiente nutritivo sono attori attivi nel determinare la segnalazione intracellulare e le attività enzimatiche e di conseguenza modulatori del destino delle cellule staminali. Inoltre, gli intermedi metabolici del metabolismo cellulare regolano i meccanismi epigenetici, comprese le modificazioni degli istoni, la metilazione del DNA e gli RNA non codificanti, modulando in tal modo il paesaggio e lo staminali dell'epigenoma globale [3].
Questo numero speciale riunisce 9 documenti per evidenziare i recenti sviluppi nel campo.Increasing evidence highlights a pivotal role for metabolism in stem cell physiology and lineage specification [1, 2]. Metabolism, indeed, is no longer considered merely an energy source nor an endpoint of gene regulation. Instead, metabolites and the nutrient environment are active players in determining intracellular signaling and enzymatic activities and consequently modulators of stem cell fate. Moreover, metabolic intermediates of cellular metabolism regulate epigenetic mechanisms, including histone modifications, DNA methylation, and noncoding RNAs, thereby modulating the global epigenome landscape and stemness [3].
This special issue brings together 9 papers to highlight recent developments in the field
Geological solutions concluded by petroleum geochemical data in Western Greece
Τα προηγούμενα χρόνια έχει πραγματοποιηθεί μια λεπτομερής γεωχημική μελέτη πετρελαίου στη Δυτική Ελλάδα. Εντοπίστηκαν αρκετοί ορίζοντες πιθανών μητρικών πετρωμάτων πετρελαίου, προσδιορίστηκε το παράθυρο πετρελαίου στις πιο σημαντικές υπολεκάνες, ενώ από τη μελέτη συσχετισμού πετρελαίων προσδιορίστηκαν οι διαφορετικές ομάδες πετρελαίου της περιοχής, που έχουν παραχθεί από τα διαφορετικά μητρικά πετρώματα υδρογονανθράκων. Τα αποτελέσματα αυτά είναι πολύ σημαντικά και απαραίτητα για την έρευνα πετρελαίου στην περιοχή. Όμως, εκτός από αυτά τα δεδομένα, κάποιες επιπλέον γεωχημικές παρατηρήσεις μπορεί να αποβούν εξίσου σημαντικές στην επίλυση ορισμένων γεωλογικών προβλημάτων της Δυτικής Ελλάδας.- Ένα πολύ σημαντικό πρόβλημα είναι η απόθεση και διατήρηση του οργανικού υλικού στις λεκάνες της Δυτικής Ελλάδας.- Η δολομιτίωση σε συνάρτηση με τη γένεση πετρελαίου είναι ένα πρόβλημα.- Ένα άλλο θέμα είναι ο υπολογισμός του πάχους που διαβρώθηκε από τους υπερκείμενους σχηματισμούς.- Ο προσδιορισμός της παλαιογεωθερμικής βαθμίδας είναι επίσης πολύ σημαντικός.Οι δύο τελευταίοι παράμετροι είναι απόλυτα απαραίτητοι για τον προσδιορισμό της ωριμότητας του οργανικού υλικού.Η μελέτη όλων των παραπάνω παραμέτρων συμπληρώνει τη γεωχημική μελέτη της Δυτικής Ελλάδας, και σε συνδυασμό με άλλες γεωλογικές μελέτες μπορεί να δώσει λύσεις σε προβλήματα που σχετίζονται με την έρευνα υδρογονανθράκων στην περιοχή.A detailed petroleum geochemical study has been performed in the previous years in the Western Greece. Several source rock horizons have been identified, the oil window has been calculated for the most significant sub-basins and the oil correlation study has distinguished the different oil groups of the area, generated from different hydrocarbon sources. These results are very significant and useful for the oil exploration. But, further to these, some more geochemical observations can also be very important on solving some geological problems of the area.- A major problem is the deposition and preservation of the organic matter in the Western Greece.- The dolomitization in relation with the oil generation is also an issue.- Another issue is the calculation of the eroded overburden formations thickness.- The Paleogeothermal gradient determination is also very important.The last two parameters are absolutely necessary for organic matter maturity calculations.The study of all the above parameters completes the geochemical study of the Western Greece, and in relation with other geological studies can provide solutions in the petroleum exploration of the area
Bi-local baryon interpolating fields with two flavours
We construct bi-local interpolating field operators for baryons consisting of
three quarks with two flavors, assuming good isospin symmetry. We use the
restrictions following from the Pauli principle to derive relations/identities
among the baryon operators with identical quantum numbers. Such relations that
follow from the combined spatial, Dirac, color, and isospin Fierz
transformations may be called the (total/complete) Fierz identities. These
relations reduce the number of independent baryon operators with any given spin
and isospin. We also study the Abelian and non-Abelian chiral transformation
properties of these fields and place them into baryon chiral multiplets. Thus
we derive the independent baryon interpolating fields with given values of spin
(Lorentz group representation), chiral symmetry ( group
representation) and isospin appropriate for the first angular excited states of
the nucleon.Comment: 15 pages, 4 tables, accepted by EPJ
Wide-angle elastic scattering and color randomization
Baryon-baryon elastic scattering is considered in the independent scattering
(Landshoff) mechanism. It is suggested that for scattering at moderate
energies, direct and interchange quark channels contribute with equal color
coefficients because the quark color is randomized by soft gluon exchange
during the hadronization stage. With this assumption, it is shown that the
ratio of cross sections at CM angle
decreases from a high energy value of R_{\pbar p / pp} \approx 1/2.7, down to
R_{\pbar p / pp} \approx 1/28, compatible with experimental data at moderate
energies. This sizable fall in the ratio seems to be characteristic of the
Landshoff mechanism, in which changes at the quark level have a strong effect
precisely because the hadronic process occurs via multiple quark scatterings.
The effect of color randomization on the angular distribution of proton-proton
elastic scattering and the cross section ratio is also discussed.Comment: 18 pages, latex2e, 4 uuencoded figures, include
Boron excess imbalances root/shoot allometry, photosynthetic and chlorophyll fluorescence parameters and sugar metabolism in apple plants
Boron (B) excess frequently impair plant performances and their productivity; in particular in arid and semi‐arid environments. In the present experiment; hydroponically‐grown ‘Granny Smith’ apple plants grafted on M9 rootstock were treated with optimal (25 μΜ) or excess (400 μΜ) B for 116 days to evaluate allometric responses of plants to B toxicity and to highlight physiological (photosynthesis and chlorophyll fluorescence) and biochemical (pigment content and sugar metabolism) responses of apple plants to B excess. Boron accumulated principally in top > middle > basal stems and leaves of high‐B‐stressed plants. Notably, the stem dramatically accumulated a higher level of B, as an attempt to preserve leaves, especially the youngest from further B accumulation. B accumulation seriously affected photosynthesis of younger leaves and caused both stomata (reduced stomatal conductance) and biochemical (reduction of apparent CO2 use efficiency and pigment content) limitations and altered the photochemistry and energy partitioning in photosystem II. Boron excess altered leaf sugar proportion; increasing the accumulation of non‐translocating sugars such as glucose and fructose. Our dataset adds knowledge on the effect of B excess in apple tree and poses serious concerns about the possible effect of B in altering sugar metabolism; which, in turn, can strongly affect fruit production of this worldwide‐cropped species
The KLN Theorem and Soft Radiation in Gauge Theories: Abelian Case
We present a covariant formulation of the Kinoshita, Lee, Nauenberg (KLN)
theorem for processes involving the radiation of soft particles. The role of
the disconnected diagrams is explored and a rearrangement of the perturbation
theory is performed such that the purely disconnected diagrams are factored
out. The remaining effect of the disconnected diagrams results in a simple
modification of the usual Feynman rules for the S-matrix elements. As an
application, we show that when combined with the Low theorem, this leads to a
proof of the absense of the corrections to inclusive processes (like the
Drell-Yan process). In this paper the abelian case is discussed to all orders
in the coupling.Comment: 27 pages, LaTeX, 14 figure
NNLO corrections to the total cross section for Higgs boson production in hadron-hadron collisions
We present the next-to-next-to-leading order (NNLO) corrections to the total
cross section for (pseudo-) scalar Higgs boson production using an alternative
method than those used in previous calculations. All QCD partonic subprocesses
have been included and the computation is carried out in the effective
Lagrangian approach which emerges from the standard model by taking the limit
where denotes the mass of the top quark. Our results
agree with those published earlier in the literature. We estimate the
theoretical uncertainties by comparing the -factors and the variation with
respect to the mass factorization/renormalization scales with the results
obtained by lower order calculations. We also investigate the dependence of the
cross section on several parton density sets provided by different groups.
Further we study which part of the coefficient functions dominates the cross
section. This is of interest for the resummation of large corrections which
occur near the boundary of phase space. It turns out that depending on the
definition of the total cross section the latter is dominated by the the
soft-plus-virtual gluon corrections represented by and
terms. PACS numbers: 12.38.-t, 12.38.Bx, 13.85.-t,
14.80.Gt.Comment: 61 pages, LaTeX, 15 postscript figures. With respect to the previous
version a more thorough comparison is made between two definitions of the
soft plus virtual gluon approximation. Misprints are corrected and references
are changed. Figs. 8a, 9a are changed into Figs. 8,9 respectively and Figs.
8b, 9b are droppe
New anomalous trajectory in Regge theory
We show that a new Regge trajectory with \alpha_{f_1} (0) \approx 1 and slope
\alpha_{f_1}'(0) \approx 0 explains the features of hadron-hadron scattering
and photoproduction of the rho and phi mesons at large energy and momentum
transfer. This trajectory with quantum numbers P = C = +1 and odd signature can
be considered as a natural partner of the Pomeron which has even signature. The
odd signature of the new exchange leads to contributions to the spin-dependent
cross sections, which do not vanish at large energy. The links between the
anomalous properties of this trajectory, the axial anomaly and the flavor
singlet axial vector f_1 (1285) meson are discussed.Comment: 20 pages, REVTeX, 8 figures (9 eps files), version to appear in Phys.
Rev.
Acoustic Response of a Layer of Spherical Inclusions with a Random or Periodic Arrangement
Starting with the classic work of Ying and Truell [1], the scattering of a plane elastic wave by an isolated elastic sphere embedded in an unbounded medium has been studied in great detail. Similarly, the propagation of an effective elastic wave in an elastic matrix containing a random or periodic distribution of inclusions has received considerable attention. By comparison, an intermediate level of microstructure — a single layer of inclusions in an elastic matrix — has received very little attention. Apart from the fact that this problem is worth studying in its own right because of its inherent value as a canonical problem in elastodynamics of materials with a microstructure, it has applications in geophysics and quantitative nondestructive evaluation
Liver transplantation as last-resort treatment for patients with bile duct injuries following cholecystectomy: A multicenter analysis
Background Liver transplantation (LT) has been used as a last resort in patients with end-stage liver disease due to bile duct injuries (BDI) following cholecystectomy. Our study aimed to identify and evaluate factors that cause or contribute to an extended liver disease that requires LT as ultimate solution, after BDI during cholecystectomy. Methods Data from 8 high-volume LT centers relating to patients who underwent LT after suffering BDI during cholecystectomy were prospectively collected and retrospectively analyzed. Results Thirty-four patients (16 men, 18 women) with a median age of 45 (range 22-69) years were included in this study. Thirty of them (88.2%) underwent LT because of liver failure, most commonly as a result of secondary biliary cirrhosis. The median time interval between BDI and LT was 63 (range 0-336) months. There were 23 cases (67.6%) of postoperative morbidity, 6 cases (17.6%) of post-transplant 30-day mortality, and 10 deaths (29.4%) in total after LT. There was a higher probability that patients with concomitant vascular injury (hazard ratio 10.69, P=0.039) would be referred sooner for LT. Overall survival following LT at 1, 3, 5 and 10 years was 82.4%, 76.5%, 73.5% and 70.6%, respectively. Conclusion LT for selected patients with otherwise unmanageable BDI following cholecystectomy yields acceptable long-term outcomes
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