5,209 research outputs found
A warm mode of gas accretion on forming galaxies
We present results from high--resolution cosmological hydrodynamical
simulations of a Milky--Way-sized halo, aimed at studying the effect of
feedback on the nature of gas accretion. Simulations include a model of
inter-stellar medium and star formation, in which SN explosions provide
effective thermal feedback. We distinguish between gas accretion onto the halo,
which occurs when gas particles cross the halo virial radius, and gas accretion
onto the central galaxy, which takes place when gas particles cross the inner
one-tenth of the virial radius. Gas particles can be accreted through three
different channels, depending on the maximum temperature value, ,
reached during the particles' past evolution: a cold channel for K, and a warm one for
intermediate values of . We find that the warm channel is at least
as important as the cold one for gas accretion onto the central galaxy. This
result is at variance with previous findings that the cold mode dominates gas
accretion at high redshift. We ascribe this difference to the different
supernova feedback scheme implemented in our simulations. While results
presented so far in the literature are based on uneffective SN thermal feedback
schemes and/or the presence of a kinetic feedback, our simulations include only
effective thermal feedback. We argue that observational detections of a warm
accretion mode in the high--redshift circum-galactic medium would provide
useful constraints on the nature of the feedback that regulates star formation
in galaxies.Comment: 6 pages, 3 figures, accepted for publication in ApJ
The density of badger setts in a natural river corridor (NE Italy)
The European badger Meles meles (Linnaeus, 1758) is a common semifossorial mustelid species widely distributed throughout Europe. It also shows a high degree of plasticity, adapting its spatial and temporal behaviour to live in highly disturbed environments. Badgers live in social groups occupying underground systems called setts, which could be classified as “main” (i.e., the complex systems with a great number of entrances), and as “outliers”, “annexes” and “subsidiary” (i.e., the other burrows with a low number of entrances). An extensive scientific literature occurs on the ecology and biology of this species, and some information is available also for setts density in Europe and in Italy, too. However, since badgers may inhabit a wide variety of habitats, the setts density varies significantly both locally and on a large scale. We aimed to provide setts density in a river basin in the North-East of Italy. From January to March 2022, a sett survey was conducted in the eastern plain of Friuli Venezia Giulia Region (NE Italy), along the floodplains of the lowest reaches of Isonzo/Soca river basin, from Pavia di Udine (Torre river) to the Isonzo river mouth, a natural corridor surrounded by a highly human-modified matrix. Transects to collect setts information were made in the entire area of 27.82 km2 by two or three operators. For each sett, we recorded the geo-referenced location, the type (main, subsidiary and outliers), the habitat, and the number of entrances. To estimate the density, we only considered active main setts, dividing their number by the area. A total of 22 main setts were identified within the floodplains, corresponding to a density of 0.79 setts/km2. The mean number of entrances was 13.67 (min: 5, max: 28) and they were mainly recorded in forested patches (riverine forests and transitional woodlands-shrublands). We founded other 14 subsidiaries and 13 outliers setts. The density estimated in our study area is remarkably high compared to those estimated in similar environmental conditions (e.g., Po plain area, NW Italy), but considerably lower than those reported for natural habitats (e.g., Alpine area). Even if we did not specifically analyse habitat selection of the badger for the location of setts, our results confirm the importance of the forested area and specifically riverine forests for the badgers in agricultural matrices. Furthermore, it is known that several mammals use the complex burrow system of the European badger as shelter or as a reproductive site. In a highly fragmented and disturbed area, the high density of badger setts could favour the expansion and the survival of other species, some of which are of conservation interest (e.g., European wildcat Felis silvestris and golden jackal Canis aureus) and some other invasive species (e.g., the raccoon dog Nyctereutes procyonoides)
An irreducibility criterion for group representations, with arithmetic applications
We prove a criterion for the irreducibility of an integral group representation p over the fraction field of a noetherian domain R in terms of suitably defined reductions of p at prime ideals of R. As applications, we give irreducibility results for universal deformations of residual representations, with a special attention to universal deformations of residual Galois representations associated with modular forms of weight at least 2
A pH-sensitive stearoyl-PEG-poly(methacryloyl sulfadimethoxine)-decorated liposome system for protein delivery: an application for bladder cancer treatment
Stealth pH-responsive liposomes for the delivery of therapeutic proteins to the bladder epithelium were prepared using methoxy-poly(ethylene glycol)5kDa-1,2-distearoyl-sn-glycero-3-phosphoethanolamine (mPEG5kDa-DSPE) and stearoyl-poly(ethylene glycol)-poly(methacryloyl sulfadimethoxine) copolymer (stearoyl-PEG-polySDM), which possesses an apparent pKa of 7.2. Liposomes of 0.2:0.6:100, 0.5:1.5:100 and 1:3:100 mPEG5kDa-DSPE/stearoyl-PEG-polySDM/(soybean phosphatidylcholine + cholesterol) molar ratios were loaded with bovine serum albumin (BSA) as a protein model. The loading capacity was 1.3% w/w BSA/lipid. At pH 7.4, all liposome formulations displayed a negative zeta-potential and were stable for several days. By pH decrease or addition to mouse urine, the zeta potential strongly decreased, and the liposomes underwent a rapid size increase and aggregation. Photon correlation spectroscopy (PCS) and transmission electron microscopy (TEM) analyses showed that the extent of the aggregation depended on the stearoyl-PEG-polySDM/lipid molar ratio. Cytofluorimetric analysis and confocal microscopy showed that at pH 6.5, the incubation of MB49 mouse bladder cancer cells and macrophages with fluorescein isothiocyanate-labelled-BSA (FITC-BSA) loaded and N-(Lissamine Rhodamine B sulfonyl)-1, 2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine triethylammonium salt (rhodamine-DHPE) labelled 1:3:100 mPEG5kDa-DSPE/stearoyl-PEG-polySDM/lipid molar ratio liposomes resulted in a time-dependent liposome association with the cells. At pH 7.4, the association of BSA-loaded liposomes with the MB49 cells and macrophages was remarkably lower than at pH 6.5. Confocal images of bladder sections revealed that 2 h after the instillation, liposomes at pH 7.4 and control non-responsive liposomes at pH 7.4 or 6.5 did not associate nor delivered FITC-BSA to the bladder epithelium. On the contrary, the pH-responsive liposome formulation set at pH 6.5 and soon administered to mice by bladder instillation showed that, 2 h after administration, the pH-responsive liposomes efficiently delivered the loaded FITC-BSA to the bladder epitheliu
Heat-shock pretreatment inhibits sorbitol-induced apoptosis in K562, U937 and HeLa cells.
The aim of this study was to determine whether heat-shock pretreatment
exerted a protective effect against sorbitol-induced apoptotic
cell death in K562, U937 and HeLa cell lines and whether
such protection was associated with a decreased cytochrome c
release from mithocondria and a decreased activation of caspase-9
and -3. Following heat-shock pretreatment (42 6 0.3C for 1 hr),
these cell lines were exposed to sorbitol for 1 hr. Apoptosis was evaluated
by DNA fragmentation, whereas caspase-9,-3 activation, cytochrome
c release and heat-shock protein70 (HSP70) were assayed
by Western Blot. Sorbitol exposure-induced apoptosis in these different
cell lines with a marked activation of caspase-9 and caspase-
3, whereas heat-shock pretreatment before sorbitol exposure,
induced expression of HSP70 and inhibited sorbitol-mediated cytochrome
c release and subsequent activation of caspase-9 and caspase-
3. Similarly, overexpression of HSP70 in the three cell lines
studied prevented caspase-9 cleavage and activation as well as cell
death. Furthermore, we showed that the mRNA expression of iNOS
decreased during both the heat-shock treatment and heat-shock
pretreatment before sorbitol exposure. By contrast, the expression
of Cu-Zn superoxide dismutase (SOD) and Mn-SOD proteins
increased during heat-shock pretreatment before sorbitol exposure.
We conclude that, heat-shock pretreatment protects different cell
lines against sorbitol-induced apoptosis through a mechanism that
is likely to involve SOD family members
Effects of vibration direction and pressing force on finger vibrotactile perception and force control
This paper reports about the effects of vibration direction and finger-pressing force on vibrotactile perception, with the goal of improving the effectiveness of haptic feedback on interactive surfaces. An experiment was conducted to assess the sensitivity to normal or tangential vibration at 250 Hz of a finger exerting constant pressing forces of 0.5 or 4.9 N. Results show that perception thresholds for normal vibration depend on the applied pressing force, significantly decreasing for the stronger force level. Conversely, perception thresholds for tangential vibrations are independent of the applied force, and approximately equal the lowest thresholds measured for normal vibration
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