Starburst clusters in the Galactic center

The central region of the Galaxy is the most active site of star formation in the Milky Way, where massive stars have formed very recently and are still forming today. The rich population of massive stars in the Galactic center provide a unique opportunity to study massive stars in their birth environment and probe their initial mass function, which is the spectrum of stellar masses at their birth. The Arches cluster is the youngest among the three massive clusters in the Galactic center, providing a collection of high-mass stars and a very dense core which makes this cluster an excellent site to address questions about massive star formation, the stellar mass function and the dynamical evolution of massive clusters in the Galactic center. In this thesis, I perform an observational study of the Arches cluster using Ks-band imaging obtained with NAOS/CONICA at the VLT combined with Subaru/Cisco J-band data to gain a full understanding of the cluster mass distribution out to its tidal radius for the first time. Since the light from the Galactic center reaches us through the Galactic disc, the extinction correction is crucial when studying this region. I use a Bayesian method to construct a realistic extinction map of the cluster. It is shown in this study that the determination of the mass of the most massive star in the Arches cluster, which had been used in previous studies to establish an upper mass limit for the star formation process in the Milky Way, strongly depends on the assumed slope of the extinction law. Assuming the two regimes of widely used infrared extinction laws, I show that the difference can reach up to 30% for individually derived stellar masses and ∆AKs ∼ 1 magnitude in acquired Ks-band extinction, while the present-day mass function slope changes by ∼ 0.17 dex. The present-day mass function slope derived assuming the more recent extinction law, which suggests a steeper wavelength dependence for the infrared extinction law, reveals an overpopulation of massive stars in the core (r Nishi = −2.21 ± 0.27 in the intermediate annulus (0.2 Nishi = −3.21 ± 0.30 in the outer annulus (0.4 Recently, more than 100 Wolf-Rayet and OB stars were identified in the Galactic center. About a third of these sources are not spatially associated with any of the known star clusters in this region. As the comparison of our observational study to N-body models of the cluster revealed, the clusters in the Galactic center region are dynamically evolved at younger ages due to their high cluster mass and the special Galactic center environment. Therefore, I probed the contribution of drifted sources from numerical models of the massive clusters in the Galactic center to the observed distribution of isolated massive sources in this region. This study shows that stars as massive as 100 M⊙ drift away from the center of each cluster by up to ∼ 60 pc using the cluster models. The best analyzed model reproduces ∼ 60% of the known isolated massive stars out to 80 pc from the center of the Arches cluster. This number increases to 70 − 80% when we only consider the region that is ∼ 20 pc from the Arches cluster. Our finding shows that most of the apparently isolated high-mass stars might originate from the known star clusters. This result, together with the fact that no top-heavy mass function is required to explain the spatial variation of the mass function in the Arches cluster, implies that no evidence is seen for a deviating (top-heavy) initial mass function in the wider environment of the Galactic center

Recircula challenge 2021

FinalistaObjectius de Desenvolupament Sostenible::9 - Indústria, Innovació i InfraestructuraPostprint (published version

Antibiotic resistance properties of uropathogenic Escherichia coli isolated from pregnant women with history of recurrent urinary tract infections

Purpose: To investigate the antibiotic resistance pattern of uropathogenic Escherichia coli (UPEC) strains isolated from pregnant women with history of recurrent urinary tract infections (RUTIs) and healthy pregnant women.Methods: A total of 485 high vaginal swab specimens were collected from pregnant women with history of RUTIs and healthy ones. Samples were cultured and those that were E. coli positive were analyzed by polymerase chain reaction (PCR) and disk diffusion tests.Results: Twenty eight out of 445 (6.29 %) samples were positive for E. coli. Prevalence of E. coli in pregnant women with history of RUTIs and healthy ones were 9 and 4.08 %, respectively. Women older than 40 years were the most commonly infected. UPEC strains showed the highest levels of resistance against ampicillin (96.42 %), tetracycline (85.71 %), amikacin (71.42 %), ciprofloxacin (67.85 %) and gentamycin (58.71 %).Conclusion: RUTIs and pregnancy in old age are two important risk factors for transmission of UPEC strains from the urinary tract into the vagina. Primary treatment of infected pregnant women with imipenem, mezlocillin and nitrofurantoin would be effective for the prevention and management of vaginal infections in pregnant women.Keywords: Uropathogenic Escherichia coli, Recurrent urinary tract infections, Antibiotic resistance, Pregnant wome

Modeling Users' Information Needs in a Document Recommender for Meetings

People are surrounded by an unprecedented wealth of information. Access to it depends on the availability of suitable search engines, but even when these are available, people often do not initiate a search, because their current activity does not allow them, or they are not aware of the existence of this information. Just-in-time retrieval brings a radical change to the process of query-based retrieval, by proactively retrieving documents relevant to users' current activities, in an easily accessible and non-intrusive manner. This thesis presents a novel set of methods intended to improve the relevance of a just-in-time retrieval system, specifically a document recommender system designed for conversations, in terms of precision and diversity of results. Additionally, we designed an evaluation protocol to compare the proposed methods in the thesis with other ones using crowdsourcing. In contrast to previous systems, which model users' information needs by extracting keywords from clean and well-structured texts, this system models them from the conversation transcripts, which contain noise from automatic speech recognition (ASR) and have a free structure, often switching between several topics. To deal with these issues, we first propose a novel keyword extraction method which preserves both the relevance and the diversity of topics of the conversation, to properly capture possible users' needs with minimum ASR noise. Implicit queries are then built from these keywords. However, the presence of multiple unrelated topics in one query introduces significant noise into the retrieval results. To reduce this effect, we separate users' needs by topically clustering keyword sets into several subsets or implicit queries. We introduce a merging method which combines the results of multiple queries which are prepared from users' conversation to generate a concise, diverse and relevant list of documents. This method ensures that the system does not distract its users from their current conversation by frequently recommending them a large number of documents. Moreover, we address the problem of explicit queries that may be asked by users during a conversation. We introduce a query refinement method which leverages the conversation context to answer the users' information needs without asking for additional clarifications and therefore, again, avoiding to distract users during their conversation. Finally, we implemented the end-to-end document recommender system by integrating the ideas proposed in this thesis and then proposed an evaluation scenario with human users in a brainstorming meeting

The Galactic Centre source G2 was unlikely born in any of the known massive binaries

The source G2 has already completed its pericentre passage around Sgr A*, the super-massive black hole in the centre of our Galaxy. Although it has been monitored for 15 years, its astrophysical nature and origin still remain unknown. In this work, we aim to test the hypothesis of G2 being the result of a stellar wind collision. To do so, we study the motion and final fate of gas clumps formed as a result of collisions of stellar winds in massive binaries. Our approach is based on a test-particle model in order to describe the trajectories of such clumps. The model takes into account the gravitational field of Sgr A*, the interaction of the clumps with the interstellar medium as well as their finite lifetimes. Our analysis allows us to reject the hypothesis based on four arguments: i) if G2 has followed a purely Keplerian orbit since its formation, it cannot have been produced in any of the known massive binaries since their motions are not consistent; ii) in general, gas clumps are evaporated through thermal conduction on very short timescale (< 100yr) before getting close enough to Sgr A*; iii) IRS 16SW, the best candidate for the origin of G2, cannot generate clumps as massive as G2; and iv) clumps ejected from IRS 16SW describe trajectories significantly different to the observed motion of G2.Comment: 14 pages, 10 figures. Accepted for publication in MNRA

Pola Asuh Orang Tua dan Lingkungan Sosial dalam Menumbuhkan Akidah pada Anak Usia Dini

As the main burden of family education, growing the creed from an early age must be closely monitored by parents. Aqidah education given to children by the family can be used as a step to keep them from deviant behavior and free them from moral depravity. In order for high moral children to realize this, as parents, one must instill a high creed. Therefore, along with the higher trust in children, the pattern of parental guidance is very important in doing it early on. The formulation of the problem is how the pattern of parental guidance and the social environment that develops beliefs or beliefs to early childhood and the factors that affect it. The purpose of this study is to find out the parenting and social environment in cultivating early childhood faith and the factors that affect the process of early childhood faith growth.&nbsp; This research is a library research technique (library research) data collection technique in this study is to read and record the information contained in the data.The results of this study suggest that parental parenting and social environments can increase trust in early childhood. In increasing early childhood confidence there are various methods that can be lived by parents is to educate habituation, example, advice and praise or reprimand. While in growing the faith in children precisely in the social environment that can be done by getting used to good things in children and paying attention to the child's social association. If the parenting of parents and the social environment in growing the creed in children is good, it will affect the character of the child

Artifacts in Optical Coherence Tomography Angiography

We performed a comprehensive search of the published literature in PubMed and Google Scholar to identify types, prevalence, etiology, clinical impact, and current methods for correction of various artifacts in optical coherence tomography angiography (OCTA) images. We found that the prevalence of OCTA image artifacts is fairly high. Artifacts associated with eye motion, misidentification of retinal layers, projections, and low optical coherence tomography signal are the most prevalent types. Artifacts in OCTA images are the major limitations of this diagnostic modality in clinical practice and identification of these artifacts and measures to mitigate them are essential for correct diagnosis and follow-up of patients