5,116 research outputs found
The chemical structure of the very young starless core L1521E
L1521E is a dense starless core in Taurus that was found to have relatively
low molecular depletion by earlier studies, thus suggesting a recent formation.
We aim to characterize the chemical structure of L1521E and compare it to the
more evolved L1544 pre-stellar core. We have obtained 2.52.5
arcminute maps toward L1521E using the IRAM-30m telescope in transitions of
various species. We derived abundances for the species and compared them to
those obtained toward L1544. We estimated CO depletion factors. Similarly to
L1544, -CH and CHOH peak at different positions. Most species
peak toward the -CH peak. The CO depletion factor derived toward the
dust peak is 4.31.6, which is about a factor of three lower
than that toward L1544. The abundances of sulfur-bearing molecules are higher
toward L1521E than toward L1544 by factors of 2-20. The abundance of
methanol is similar toward the two cores. The higher abundances of
sulfur-bearing species toward L1521E than toward L1544 suggest that significant
sulfur depletion takes place during the dynamical evolution of dense cores,
from the starless to pre-stellar stage. The CO depletion factor measured toward
L1521E suggests that CO is more depleted than previously found. Similar
CHOH abundances between L1521E and L1544 hint that methanol is forming at
specific physical conditions in Taurus, characterized by densities of a few
10 cm and (H)10 cm, when CO
starts to catastrophically freeze-out, while water can still be significantly
photodissociated, so that the surfaces of dust grains become rich in solid CO
and CHOH, as already found toward L1544. Methanol can thus provide
selective crucial information about the transition region between dense cores
and the surrounding parent cloud.Comment: Accepted for publication in A&A, abstract abridge
First sample of nitrogen isotopic ratio measurements in low-mass protostars
Context. The nitrogen isotopic ratio is considered an important diagnostic
tool of the star formation process, and is particularly important
because it is directly linked to molecular nitrogen . However, theoretical
models still lack to provide an exhaustive explanation for the observed
values.
Aims. Recent theoretical works suggest that the behaviour is
dominated by two competing reactions that destroy : dissociative
recombination and reaction with CO. When CO is depleted from the gas phase, if
recombination rate is lower with respect to the one, the
rarer isotopologue is destroyed faster. This implies that the isotopic
ratio in protostars should be lower than the one in prestellar cores, and
consistent with the elemental value of ~440. We aim to test this hypothesis,
producing the first sample of measurements in low mass
protostars.
Methods. We observe the and lowest rotational
transition towards six young stellar objects in Perseus and Taurus molecular
clouds. We model the spectra with a custom python code using a constant
approach to fit the observations. We discuss in appendix the validity
of this hypothesis. The derived column densities are used to compute the
nitrogen isotopic ratio.
Results. Our analysis yields an average of in the protostellar sample. This is consistent with the protosolar
value of 440, and significantly lower than the average value previously
obtained in a sample of prestellar objects. Conclusions. Our results are in
agreement with the hypothesis that, when CO is depleted from the gas-phase,
dissociative recombinations with free electrons destroy faster
than , leading to high isotopic ratios in prestellar cores, where CO is
frozen on dust grains.Comment: Accepted on A&A on 09 Oct 202
Analysis of water vapor LIDAR measurements during the MAP campaign: evidence of sub-structures of stratospheric intrusions
This paper presents two case studies of transport of dry air in the free troposphere measured by a ground based Raman LIDAR in the Northern-Italy, during the Mesoscale Alpine Programme (MAP). Two observations characterized by the presence of anomalously dry layers, below 6 km height, were analyzed using Lagrangian techniques. These events are related to upper-tropospheric, high Potential Vorticity (PV) streamers crossing the Alpine region. These are interpreted as small-scale features of stratospheric intrusions associated with the PV ridge during its phase of dissipation. One of the measurements also shows the presence of two distinct dehydrated structures associated with the same event. The water vapor concentration also suggests dilution processes of dry stratospheric air in the troposphere. Lagrangian simulations allowed to successfully reproduce the observed water vapor distribution and the air parcel histories confirmed the stratospheric origin of the dry layers
Control of field quality for the production of the main LHC dipoles
We review the warm magnetic measurements of the first four main dipole prototypes (8 apertures) and their agreement with nominal design. We then estimate the order of magnitude of the corrections that may be needed to re-center the low-order normal harmonics around the nominal values for the forthcoming series production. Correction strategies that provide the minumum impact on production schedule and costs are analysed. For the case of b3 and b5 two possibilities are considered: a variation of the shims to optimize the azimuthal length of the two coil layers, and a variation of the copper wedges of the inner layer, leaving unchanged the azimuthal coil size. For optimizing b2 and b4, we consider modifications of the shape of the ferromagnetic insert, that is placed between the collars and the yoke. Comparison between measurements and simulations of the implemented insert modifications are given and a final design is proposed. Intrinsic limits to the control of field quality during the production are discussed
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Lab-on-Chip for Testing Myelotoxic Effect of Drugs and Chemicals
This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.In the last twenty years, one of the main goals in the drug discovery field has been the development
of reliable in vitro models. In particular, in 2006 the European Centre for the Validation of Alternative
Methods (ECVAM) has approved the Colony forming Unit-Granulocytes-Macrophages (CFU-GM) test,
which is the first and currently unique test applied to evaluate the myelotoxicity of xenobiotics in vitro. The
present work aimed at miniaturizing this in vitro assay by developing and validating a Lab-on-Chip (LoC)
platform consisting of a high number of bioreactor chambers with screening capabilities in a high-throughput
regime
High-throughput microfluidic platform for adherent single cells non-viral gene delivery
The widespread use of gene therapy as a therapeutic tool relies on the development of DNA-carrying vehicles devoid of any safety concerns. In contrast to viral vectors, non-viral gene carriers show promise in this perspective, although their low transfection efficiency leads to the necessity to carry out further optimizations. In order to overcome the limitations of traditional macroscale approaches, which mainly consist of time-consuming and simplified models, a microfluidic strategy has been developed to carry out transfection studies on single cells in a high-throughput and deterministic fashion. A single cell trapping mechanism has been implemented, based on the dynamic variation of fluidic resistances. For this purpose, we designed a round-shaped culture chamber integrated with a bottom trapping junction, which modulates the hydraulic resistance. Several layouts of the chamber were designed and computationally validated for optimization of the single cell trapping efficacy. The optimized chamber layout was integrated in a polydimethylsiloxane (PDMS) microfluidic platform presenting two main functionalities: (i) 288 chambers for trapping single cells, and (ii) a serial dilution generator with chaotic mixing properties, able to deliver to the chambers both soluble factors and non-diffusive particles (i.e., polymer/DNA complexes, polyplexes) under spatio-temporally controlled chemical patterns. The devices were experimentally validated and allowed the trapping of individual human glioblastoma–astrocytoma epithelial-like cells (U87-MG) with a trapping efficacy of about 40%. The cells were cultured within the device and underwent preliminary transfection experiments using 25 kDa linear polyethylenimine (lPEI)-based polyplexes, confirming the potentiality of the proposed platform for the future high-throughput screening of gene delivery vectors and for the optimization of transfection protocols
Avaliação da mortalidade através do contato de machos de Grapholita molesta (Lepidoptera, Tortricidae) com o produto Splat Cida Grafo Bona.
Este trabalho teve como objetivo avaliar a mortalidade de machos de Grapholita molesta por contato com o Splat Cida Grafo Bona
High-Throughput Microfluidic Platform for 3D Cultures of Mesenchymal Stem Cells, Towards Engineering Developmental Processes
The development of in vitro models to screen the effect of different concentrations, combinations and temporal sequences of morpho-regulatory factors on stem/progenitor cells is crucial to investigate and possibly recapitulate developmental processes with adult cells. Here, we designed and validated a microfluidic platform to (i) allow cellular condensation, (ii) culture 3D micromasses of human bone marrow-derived mesenchymal stromal cells (hBM-MSCs) under continuous flow perfusion, and (ii) deliver defined concentrations of morphogens to specific culture units. Condensation of hBM-MSCs was obtained within 3 hours, generating micromasses in uniform sizes (56.2 ± 3.9 μm). As compared to traditional macromass pellet cultures, exposure to morphogens involved in the first phases of embryonic limb development (i.e. Wnt and FGF pathways) yielded more uniform cell response throughout the 3D structures of perfused micromasses (PMMs), and a 34-fold higher percentage of proliferating cells at day 7. The use of a logarithmic serial dilution generator allowed to identify an unexpected concentration of TGFβ3 (0.1 ng/ml) permissive to hBM-MSCs proliferation and inductive to chondrogenesis. This proof-of-principle study supports the described microfluidic system as a tool to investigate processes involved in mesenchymal progenitor cells differentiation, towards a ‘developmental engineering’ approach for skeletal tissue regeneration
Avaliação do raio de ação de armadilha Delta iscada com o feromônio sexual sintético de Grapholita molesta (Lepidoptera, Tortricidae), em pomares de pessegueiro.
Neste trabalho foi determinado o raio de ação do atrativo sexual de G. molesta (Iscalure Grapholita® ISCA Tecnologias) em armadilhas Delta, em pomares de pessegueiro
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