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The aim of the paper is to examine the performance of bootstrap and asymptotic parametric inference methods in structural VAR analysis. The results obtained through a Monte Carlo experiment suggest that the two approaches are largely equivalent in most, but not all, cases. While the asymptotic method turns out to be surprisingly robust with respect to the distribution of the errors, the bootstrap does deliver results superior in terms of both length of the confidence interval and coverage when highly non-linear statistics (such as the components of the variance of the forecast error) are considered. 相似文献
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Anna Maria Frassanito Laura Barsanti Vincenzo Passarelli Valtere Evangelista Paolo Gualtieri 《Cellular and molecular life sciences : CMLS》2010,67(6):965-971
Here, we report the DNA sequence of the rhodopsin gene in the alga Cyanophora paradoxa (Glaucophyta). The primers were designed according to the conserved regions of prokaryotic and eukaryotic rhodopsin-like
proteins deposited in the GenBank. The sequence consists of 1,272 bp comprised of 5 introns. The correspondent protein, named
Cyanophopsin, showed high identity to rhodopsin-like proteins of Archea, Bacteria, Fungi, and Algae. At the N-terminal, the
protein is characterized by a region with no transmembrane α-helices (80 aa), followed by a region with 7α-helices (219 aa)
and a shorter 35-aa C-terminal region. The DNA sequence of the N-terminal region was expressed in E. coli and the recombinant purified peptide was used as antigen in hens to obtain polyclonal antibodies. Indirect immunofluorescence
in C. paradoxa cells showed a marked labeling of the muroplast (aka cyanelle) membrane. 相似文献
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Elisa Bisicchia Valerio Chiurchiù Maria Teresa Viscomi Laura Latini Filomena Fezza Luca Battistini Mauro Maccarrone Marco Molinari 《Cellular and molecular life sciences : CMLS》2013,70(12):2191-2204
Endocannabinoids (eCBs) and glucocorticoids (GCs) are two distinct classes of signaling lipids that exert both neuroprotective and immunosuppressive effects; however, the possibility of an actual interaction of their receptors [i.e., type-2 cannabinoid (CB2) and glucocorticoid receptor α (GRα), respectively] remains unexplored. Here, we demonstrate that the concomitant activation of CB2 and GRα abolishes the neuroprotective effects induced by each receptor on central neurons and on glial cells in animal models of remote cell death. We also show that the ability of eCBs and GCs, used individually, to inhibit tumour necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) production from activated human T lymphocytes is lost when CB2 and GRα are activated simultaneously. In addition, signal transduction pathways triggered by concomitant activation of both receptors led to increased levels of GRβ, heat-shock proteins-70 and -90, and p-JNK, as well as to reduced levels of p-STAT6. These effects were reversed only by selectively antagonizing CB2, but not GRα. Overall, our study demonstrates for the first time the existence of a CB2-driven negative cross-talk between eCB and GC signaling in both rats and humans, thus paving the way to the possible therapeutic exploitation of CB2 as a new target for chronic inflammatory and neurodegenerative diseases. 相似文献
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When two or more (groups of) researchers independently investigating the same domain arrive at the same result, a multiple discovery occurs. The pervasiveness of multiple discoveries in science suggests the intuition that they are in some sense inevitable—that one should view them as results that force themselves upon us, so to speak. We argue that, despite the intuitive force of such an “inevitabilist insight,” one should reject it. More specifically, we distinguish two facets of the insight and argue that: (a) the profusion of multiple discoveries in scientific practice does not support the inevitabilist side of the inevitability/contingency of science controversy; and (b) the crucial role of background knowledge in scientific inquiry complicates the attempt to interpret the pervasiveness of multiple discoveries in realist terms. 相似文献
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Silvia Ravera Marina Podestà Federica Sabatini Chiara Fresia Marta Columbaro Silvia Bruno Ezio Fulcheri Luca Antonio Ramenghi Francesco Frassoni 《Cellular and molecular life sciences : CMLS》2018,75(5):889-903
We evaluated the energy metabolism of human mesenchymal stem cells (MSC) isolated from umbilical cord (UC) of preterm (< 37 weeks of gestational age) and term (≥ 37 weeks of gestational age) newborns, using MSC from adult bone marrow as control. A metabolic switch has been observed around the 34th week of gestational age from a prevalently anaerobic glycolysis to the oxidative phosphorylation. This metabolic change is associated with the organization of mitochondria reticulum: preterm MSCs presented a scarcely organized mitochondrial reticulum and low expression of proteins involved in the mitochondrial fission/fusion, compared to term MSCs. These changes seem governed by the expression of CLUH, a cytosolic messenger RNA-binding protein involved in the mitochondria biogenesis and distribution inside the cell; in fact, CLUH silencing in term MSC determined a metabolic fingerprint similar to that of preterm MSC. Our study discloses novel information on the production of energy and mitochondrial organization and function, during the passage from fetal to adult life, providing useful information for the management of preterm birth. 相似文献
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Theory predicts and observations confirm that low-mass stars (like the Sun) in their early life grow by accreting gas from the surrounding material. But for stars approximately 10 times more massive than the Sun (approximately 10M(o)), the powerful stellar radiation is expected to inhibit accretion and thus limit the growth of their mass. Clearly, stars with masses >10M(o) exist, so there must be a way for them to form. The problem may be solved by non-spherical accretion, which allows some of the stellar photons to escape along the symmetry axis where the density is lower. The recent detection of rotating disks and toroids around very young massive stars has lent support to the idea that high-mass ( > 8M(o)) stars could form in this way. Here we report observations of an ammonia line towards a high-mass star forming region. We conclude that the gas is falling inwards towards a very young star of approximately 20M(o), in line with theoretical predictions of non-spherical accretion. 相似文献
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Caffau E Bonifacio P François P Sbordone L Monaco L Spite M Spite F Ludwig HG Cayrel R Zaggia S Hammer F Randich S Molaro P Hill V 《Nature》2011,477(7362):67-69
The early Universe had a chemical composition consisting of hydrogen, helium and traces of lithium; almost all other elements were subsequently created in stars and supernovae. The mass fraction of elements more massive than helium, Z, is known as 'metallicity'. A number of very metal-poor stars has been found, some of which have a low iron abundance but are rich in carbon, nitrogen and oxygen. For theoretical reasons and because of an observed absence of stars with Z?1.5?×?10(-5), it has been suggested that low-mass stars cannot form from the primitive interstellar medium until it has been enriched above a critical value of Z, estimated to lie in the range 1.5?×?10(-8) to 1.5?×?10(-6) (ref. 8), although competing theories claiming the contrary do exist. (We use 'low-mass' here to mean a stellar mass of less than 0.8 solar masses, the stars that survive to the present day.) Here we report the chemical composition of a star in the Galactic halo with a very low Z (≤?6.9?×?10(-7), which is 4.5?×?10(-5) times that of the Sun) and a chemical pattern typical of classical extremely metal-poor stars--that is, without enrichment of carbon, nitrogen and oxygen. This shows that low-mass stars can be formed at very low metallicity, that is, below the critical value of Z. Lithium is not detected, suggesting a low-metallicity extension of the previously observed trend in lithium depletion. Such lithium depletion implies that the stellar material must have experienced temperatures above two million kelvin in its history, given that this is necessary to destroy lithium. 相似文献
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