4,176 research outputs found
The evolution of the number density of compact galaxies
We compare the number density of compact (small size) massive galaxies at low
and high redshift using our Padova Millennium Galaxy and Group Catalogue
(PM2GC) at z=0.03-0.11 and the CANDELS results from Barro et al. (2013) at
z=1-2. The number density of local compact galaxies with luminosity weighted
(LW) ages compatible with being already passive at high redshift is compared
with the density of compact passive galaxies observed at high-z. Our results
place an upper limit of a factor ~2 to the evolution of the number density and
are inconsistent with a significant size evolution for most of the compact
galaxies observed at high-z. The evolution may be instead significant (up to a
factor 5) for the most extreme, ultracompact galaxies. Considering all compact
galaxies, regardless of LW age and star formation activity, a minority of local
compact galaxies (<=1/3) might have formed at z<1. Finally, we show that the
secular decrease of the galaxy stellar mass due to simple stellar evolution may
in some cases be a non-negligible factor in the context of the evolution of the
mass-size relation, and we caution that passive evolution in mass should be
taken into account when comparing samples at different redshifts.Comment: ApJ in pres
Bright galaxies at Hubble's redshift detection frontier: Preliminary results and design from the redshift z~9-10 BoRG pure-parallel HST survey
We present the first results and design from the redshift z~9-10 Brightest of
the Reionizing Galaxies {\it Hubble Space Telescope} survey BoRG[z9-10], aimed
at searching for intrinsically luminous unlensed galaxies during the first 700
Myr after the Big Bang. BoRG[z9-10] is the continuation of a multi-year
pure-parallel near-IR and optical imaging campaign with the Wide Field Camera
3. The ongoing survey uses five filters, optimized for detecting the most
distant objects and offering continuous wavelength coverage from
{\lambda}=0.35{\mu}m to {\lambda}=1.7{\mu}m. We analyze the initial ~130
arcmin of area over 28 independent lines of sight (~25% of the total
planned) to search for z>7 galaxies using a combination of Lyman break and
photometric redshift selections. From an effective comoving volume of (5-25)
Mpc for magnitudes brighter than in the
-band respectively, we find five galaxy candidates at z~8.3-10
detected at high confidence (S/N>8), including a source at z~8.4 with mAB=24.5
(S/N~22), which, if confirmed, would be the brightest galaxy identified at such
early times (z>8). In addition, BoRG[z9-10] data yield four galaxies with . These new Lyman break galaxies with m are
ideal targets for follow-up observations from ground and space based
observatories to help investigate the complex interplay between dark matter
growth, galaxy assembly, and reionization.Comment: Accepted for publication on ApJ. 21 pages, 11 figures, 4 table
Mappe di rischio sismico a scala nazionale con dati aggiornati sulla pericolosità sismica di base e locale
Le mappe di rischio sismico nazionale rappresentano un importante strumento per la sua mitigazione e possono essere utilizzate nella valutazione delle priorità di intervento per la messa in sicurezza degli edifici. La realizzazione di queste mappe è
possibile valutando la pericolosità sismica, la vulnerabilità per le diverse classi di edifici presenti sul territorio italiano e l’esposizione. In questo articolo, oltre a presentare le nuove mappe di rischio sismico per l’Italia si vuole analizzare l’influenza del fattore di amplificazione litostratigrafica sui risultati ottenuti,
mettendo a confronto le mappe di rischio che
sono state sviluppate utilizzando sia i fattori di amplificazione litostratigrafica previsti dall’OPCM n°3274 che quelli previsti dalle NTC08. Inoltre, in modo innovativo rispetto agli studi condotti in Italia negli ultimi 10 anni, vengono considerate curve analitiche di vulnerabilità e valori di pericolosità
sismica basati sugli spettri di accelerazione
Effects of relaxed lockdown on pediatric er visits during sars-cov-2 pandemic in Italy
Previously, we demonstrated an 81% reduction in pediatric Emergency Room (ER) visits in Italy during the strict lockdown due to the SARS-CoV-2 pandemic. Since May 2020, lockdown measures were relaxed until 6 November 2020, when a strict lockdown was patchily reintroduced. Our aim was to evaluate the impact of the relaxed lockdown on pediatric ER visits in Italy. We performed a retrospective multicenter study involving 14 Italian pediatric ERs. We compared total ER visits from 24 September 2020 to 6 November 2020 with those during the corresponding timeframe in 2019. We evaluated 17 ER specific diagnoses grouped in air communicable and non-air communicable diseases. We recognized four different triage categories: white, green, yellow and red. In 2020 total ER visits were reduced by 51% compared to 2019 (16,088 vs. 32,568, respectively). The decrease in air communicable diseases was significantly higher if compared to non-air communicable diseases (−64% vs. −42%, respectively). ER visits in each triage category decreased in 2020 compared to 2019, but in percentage, white and red codes remained stable, while yellow codes slightly increased and green codes slightly decreased. Our results suggest that preventive measures drastically reduced the circulation of air communicable diseases even during the reopening of social activities but to a lesser extent with regard to the strict lockdown period (March–May 2020)
Measurement of the W-pair Production Cross-section and W Branching Ratios at =205 and 207 GeV
The cross-section for the process e+e-->W+W- was measured with the data sample collected by DELPHI at centre-of-mass energies up to 209 GeV and corresponding to a total integrated luminosity of about 209 pb^-1. The branching ratios of the W decay were also measured; from them the value of |Vcs| was extracted. The results are compared with the most recent calculations in the frame of the Standard Model
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FlyBase 2.0: the next generation.
FlyBase (flybase.org) is a knowledge base that supports the community of researchers that use the fruit fly, Drosophila melanogaster, as a model organism. The FlyBase team curates and organizes a diverse array of genetic, molecular, genomic, and developmental information about Drosophila. At the beginning of 2018, 'FlyBase 2.0' was released with a significantly improved user interface and new tools. Among these important changes are a new organization of search results into interactive lists or tables (hitlists), enhanced reference lists, and new protein domain graphics. An important new data class called 'experimental tools' consolidates information on useful fly strains and other resources related to a specific gene, which significantly enhances the ability of the Drosophila researcher to design and carry out experiments. With the release of FlyBase 2.0, there has also been a restructuring of backend architecture and a continued development of application programming interfaces (APIs) for programmatic access to FlyBase data. In this review, we describe these major new features and functionalities of the FlyBase 2.0 site and how they support the use of Drosophila as a model organism for biological discovery and translational research
The Research on SMEs Relation Financing
中小企业融资难是一个国际难题。从20世纪90年代以来,一种建立在意会信息基础上的关系型融资成为政府和学术界关注的热点。理论研究和部分国家的实践表明,关系型融资有助于减少银企之间的信息不对称,降低金融交易成本,能有效缓解中小企业的融资约束。 由于我国正处于经济转轨时期,市场经济体制尚未完全建立,金融市场还不完善,各种市场主体也未完全步入成熟,社会信用体系相当薄弱,不管是证券市场还是银行信贷市场,信息不对称问题都非常突出。因此,选择关系型融资作为研究对象,并在研究其本身的理论前沿与国内外实践进展的基础上,研究构建什么模式的关系型融资体系,以适应我国经济转轨时期中小企业的融资需求,具有十分重要的理...The development of SMEs(small and medium-sized enterprises) faces financing puzzle all over the world. Relation financing, as a brand-new financing way which based on tacit information, becomes an important point and a concerned front problem of government and economists since 1990s.This way can help reduce the information asymmetry and cut the transaction cost so as to solve the financing “bottle...学位:经济学硕士院系专业:经济学院经济系_政治经济学学号:20040906
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