86,935 research outputs found
Asymptotically Schwarzschild solutions in f (R) extension of general relativity
No full textWe address the question of how to build a class of f(R) extensions of General Relativity which are compatible with solar system experiments, without making any preliminary assumption on the properties of f. The aim is reached by perturbatively solving the modified Einstein equations around a Schwarzschild background and retrieving a posteriori the corresponding f(R). This turns out to be non analytical in R=0 and should be intended as the leading correction to the Einstein-Hilbert action in the low curvature limit. The parameters characterizing the f(R) class are then set by constraining the corrections to four different local tests with the observations. The result is a class of f(R) theories built up from a purely bottom-up approach and compatible with the local tests. At a more general level, this result can help constraining exact f(R) models working in Cosmology, since it provides the correct local limit. Further developments and possible extensions of the approach to Cosmology are also discussed
Which are important targets in development of S.aureus mastitis vaccine?
No full textStaphylococcus aureus represents one of the leading causes of mastitis in dairy cows worldwide. S. aureus IMI have variable outcomes due to virulence of the strain involved, immune defenses of the host, and by antibiotic resistance. The difficulty in eradication and the increasing concerns on antibiotics usages underscore the interest in developing new tools to control S. aureus mastitis. Vaccination represents one of the most studied of these tools but, so far, no vaccine seems to provide reliable protection. This review summarizes current knowledge on the major vaccine targets, including surface proteins, capsular polysaccharides, biofilm, and toxins. Finally, the present status of vaccination against S. aureus and the future of vaccines design were discussed,includi ng how differences among in vivo models may influence vaccines development.Fil: Scali, F.. Universita Degli Studi Di Milano; ItaliaFil: Camussone, Cecilia María. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Santa Fe. Estación Experimental Agropecuaria Rafaela; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Calvinho, L. F.. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Santa Fe. Estación Experimental Agropecuaria Rafaela; ArgentinaFil: Cipolla, M.. Universita Degli Studi Di Milano; ItaliaFil: Zecconi, A.. Universita Degli Studi Di Milano; Itali
Rana di Lataste. In: F. Bernini, L. Bonini, V. Ferri, A. Gentilli, E. Razzetti, S. Scali (Editors), Atlante degli Anfibi e dei Rettili della Lombardia
No full textgli scali ferroviari di Milano, oggi prima di domani
No full textDocumentazione dello stato degli scali ferroviari di milano dopo la dismissione degli anni 80 e la trasformazione delle aree limitrofe prima degli interventi di recupero urbano.
Luogo: Casa dell' energia, Fondazione AEM, Milano
14 giugno - 28 dicembre 201
Control of Systems with Recycle by means of Compensators
No full textThe paper analyses the effects of the presence of recycle streams on the performance of the control system of chemical processes and the possibility of success of compensators. Control schemes based on a regulator designed for the process without recycle and augmented by a recycle compensator are compared with specific controllers designed for the global process; potential benefits, in terms of superiority of performance and simpler design, are clearly illustrated for a SISO reference case. Application to two multivariable processes proposed in literature, the two reactors in series (Ray, 1981) and the two reactors plus three distillation columns (Luyben and Luyben, 1995) shows that also in these more realistic cases main advantages of the compensator are retained
Chromosomal evidence of hemiclonal and all-paternal offspring production in Bacillus rossius-grandii benazzii (Insecta Phasmatodea)
No full textThe stick insects Bacillus rossius-grandii benazzii and B. rossius-grandii grandii naturally reproduce by hybridogenesis and androgenesis. The hybrid karyotype of the former (2 n=35, XX female; 34, X0 male) clearly sums up a B. rossius haploset (r) with n=18 and a B. grandii benazzii one (gb) with n=17. The two sets keep the parental features for C-heterochromatin amount (much larger in the gb complement) and satellites/NORs (nuclear organizer regions) (more numerous and variably located in the r set); hybridogenetically produced males always show severely impaired gametogenesis and are therefore sterile, whereas hybridogenetic females are fertile. Reproductive, karyological and cytogenetical properties of the hybridogenetic system have been exploited to obtain the chromosomal evidence of whole haploset exchanges. In progenies obtained by crossing B. rossiusgrandii benazzii females to B. rossius males with either standard or repatterned (with Robertsonian fusions) karyotypes, there has always been complete agreement between electrophoretically genotyped and karyologically analyzed hybridogenetic offspring: the unassorted maternal r haploset (rm) is transmitted and the gbm haploset replaced by that of the fathering male (rp), thus evidencing the hemiclonal reproduction and the new rm-rp chromosomal constitution. New karyotype traits of the offspring relate to chromosome number (2 n=36, female; 35, male), C-heterochromatin pattern (the heterochromatin-rich gb haploset completely disappears) and satellite/NOR features (corresponding to rm plus rp locations). The same crosses also produce genetically and chromosomally all-paternal descendants (androgenetics), of both sexes and fully fertile, with an rprp structure. These androgenetic progeny show segregation for alleles and chromosomes at which fathering males are heterozygous: it was therefore possible to demonstrate that androgenetics can derive from syngamy of two sperm nuclei, of the several present in the polyspermic hybridogenetic egg. The production of androgenetics from field fertilized females of B. rossius-grandii benazzii, B. rossius-grandii grandii and parthenogenetic Bacillus whitei (=B. rossius/grandii grandii) suggests the occurrence of unsuspected relationships between hybrids and their parental species, so that the hybrids cannot be simply considered as 'sexual parasites'. Furthermore, there is a suggestion of evolution of parthenogenetic clonal species from selection of initially hybridogenetic strains. The ability to produce uniparental progeny naturally from the spermatic genome may open a new field of investigation on genomic imprinting. © 1993 Springer-Verlag
C-banding, ag-nor localization and chromosomal repatterning in sardinian bacillus atticus (Insecta, phasmatodea)
No full textAll demcs of Sardinian Bacillus atticus share a 2n = 33 karyotype which is fully comparable to the standard one (2n = 34), except for a Robertsonian fusion of the two chromosomes of pair 11. Furthermore, the San Vito population shows a cytotype with 34 elements, derived from the common 33-chromosomes with the addition of an unusual, all-heterochromatic large acrocentric one. C-banding and silver staining have revealed a rather constant heterocromatin and NOR localizations in all samples; this suggests a most likely derivation of all Sardinian demes from common founder(s). The cytogenetic degree of differentiation of Sardinian B. atticus from other conspecific Italian demes, and from the bisexual B. grandii, is discussed. No cytogenetic evidence supporting the repeatedly stated hybrid structure of B. atticus is revealed from karyological studies, and the hybrid origin of B. atticus can be maintained on genetical grounds only. It is also suggested that the odd chromosome in the San Vito cytotype derives from a fission of a large satellite with the gain of a centromeric function. Since a paleointrogression of B. atticus genes into syntopic B. rossius had been evidenced in the Sardinian B. atticus range, the role of the 11–11 Robertsonian fusion in the hybrid zone is taken into account. © 1991, Taylor & Francis Group, LLC
Allozymic and cytological evidence for hemiclonal, all‐paternal, and mosaic offspring of the hybridogenetic stick insect Bacillus rossius‐grandii grandii
No full textBacillus hybridogens represent the first example of hemiclonal reproduction among invertebrates and they were analyzed in the present study for comparison with vertebrate hybridogenetic complexes (Poeciliopsis and Rana). Experimental crosses of southeastern hybridogenetic B. rossius‐grandii grandii females with both the parental species and hybrid males were carried out to test the reproductive potential of hybridogens. Allozyme and chromosome markers indicated that hemiclonal females actually reproduced in a variety of ways. Hybridogenesis was the most common and the rossius unassorted haploset was passed to the progeny while the grandii haploset was discarded during meiosis and replaced by that of the fathering male. Andro‐genesis, which was much rarer, led to the production of two types of all‐paternal offspring: unipa‐rental progeny of both sexes and all‐male progeny with the same allozyme and chromosome structure as their father. Mosaics of two kinds were also produced: the “h + h” type, with two different hybridogenetic cell lines; and the “h + a” type, with one hybridogenetic and one androgenetic cell line. Mosaics evolved into intersexes when their cell lines were sexually discordant. Among the evolutionary outcomes of this wide array of reproductive ways seems to be a shift from hemiclonality to clonality. This possibility is supported by the well‐established parthenogen B. whitei and the occasional production of rare invariant specimens from the northwestern hybridogenetic form B. rossius‐grandii benazzii. Bacillus and other unisexuals provide evidence of numerous reproductive interactions between hybrids and their bisexual relatives: the occurrence of such interactions may play an important role in the persistence, diversification and evolution of unisexuals. © 1995 Wiley‐Liss, Inc. Copyright © 1995 Wiley‐Liss, Inc., A Wiley Compan
Satellite DNA variation in parental and derived unisexual hybrids of Bacillus stick insects (Phasmatodea)
No full textThe Bag320 sequence family of satellite DNA (satDNA) has been found in some stick insect taxa- the bisexual Bacillus grandii, the related parthenogen B. atticus and their hybrids with B. rossius. However, under the same experimental conditions, the Bag320 sequences were not found in B. rossius. Bag320 sequences of the clonal hybrid B. whitei (= B. rossius/grandii grandii) intermingled with those of B. grandii in all plotted dendrograms. On the whole, satDNA features (restriction pattern, sequence variation, fluorescent in situ hybridization (FISH)), allozymes and karyology support a relatively recent origin of B. whitei. Our investigations on unisexual hybrids of Bacillus also suggested that their origin and clonal reproduction allow the occurrence of different sequence subsets of limited variability in isolated populations stemming from the hybridization focus
Rapid assessment of maturation stage and reproductive mode in centrolecytic eggs of stick insects (Phasmatodea) using DAPI stain
No full textA rapid three-step DAPI technique is proposed for detecting meiotic stages and sperm head evolution in yolky, fertilized stick insect eggs, which were difficult to analyze with other methods. Fixed eggs were freed from chorionic envelopes and stained directly in DAPI/PBS solution. After rinsing, eggs were singly squashed in a drop of mounting buffer and examined under a microscope with incident fluorescent illumination. The method was almost uniformly successful, and direct observation of nuclear structures, coupled with fluorometry, allowed easy recognition of bivalents, diads, pronuclei and their DNA content. The DAPI method proposed here appears particularly helpful for investigating unusual reproductive modes in eggs with large amounts of yolk. © 1992 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted
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