A chemical mutagenesis approach to insert post-translational modifications in aggregation-prone proteins

Neurodegenerative diseases are a class of disorders linked to the formation in the nervous system of fibrillar protein aggregates called amyloids. This aggregation process is affected by a variety of post-translational modifications, whose specific mechanisms are not fully understood yet. Emerging chemical mutagenesis technology is currently striving to address the challenge of introducing protein post-translational modifications, while maintaining the stability and solubility of the proteins during the modification reaction. Several amyloidogenic proteins are highly aggregation-prone, and current modification procedures can lead to unexpected precipitation of these proteins, affecting their yield and downstream characterization. Here, we present a method for maintaining amyloidogenic protein solubility during chemical mutagenesis. As proof-of-principle, we applied our method to mimic the phosphorylation of serine-26 and the acetylation of lysine-28 of the 40-residue long variant of amyloid-β peptide, whose aggregation is linked to Alzheimer’s disease

Estimating Photometric Redshifts for X-ray sources in the X-ATLAS field, using machine-learning techniques

We present photometric redshifts for 1,031 X-ray sources in the X-ATLAS field, using the machine learning technique TPZ (Carrasco Kind & Brunner 2013). X-ATLAS covers 7.1 deg2 observed with the XMM-Newton within the Science Demonstration Phase (SDP) of the H-ATLAS field, making it one of the largest contiguous areas of the sky with both XMMNewton and Herschel coverage. All of the sources have available SDSS photometry while 810 have additionally mid-IR and/or near-IR photometry. A spectroscopic sample of 5,157 sources primarily in the XMM/XXL field, but also from several X-ray surveys and the SDSS DR13 redshift catalogue, is used for the training of the algorithm. Our analysis reveals that the algorithm performs best when the sources are split, based on their optical morphology, into point-like and extended sources. Optical photometry alone is not enough for the estimation of accurate photometric redshifts, but the results greatly improve when, at least, mid-IR photometry is added in the training process. In particular, our measurements show that the estimated photometric redshifts for the X-ray sources of the training sample, have a normalized absolute median deviation, n_mad=0.06, and the percentage of outliers, eta=10-14 percent, depending on whether the sources are extended or point-like. Our final catalogue contains photometric redshifts for 933 out of the 1,031 X-ray sources with a median redshift of 0.9.Comment: 10 pages, 13 figures, A&A accepte

Phonological short-term memory contributions to vocabulary acquisition.

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN029879 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Ηλεκτρονικές αγορές & προιόντα τεχνολογίας - μια σύγχρονη έρευνα.

Το θέμα της διπλωματικής εργασίας αφορά τις ηλεκτρονικές αγορές και τα προϊόντα τεχνολογίας, και αναλύεται ως εξής: Στο 1ο κεφάλαιο η: «αγοραστική συμπεριφορά καταναλωτών» καταγράφονται γενικά στοιχεία του θέματος, οι κύριοι παράγοντες που επηρεάζουν τη συμπεριφορά των καταναλωτών, τα στάδια της διαδικασίας αγοράς καταναλωτών, οι τύποι αγοραστών, οι τύποι αγοραστικής συμπεριφοράς καταναλωτών και οι κατηγορίες που επηρεάζουν τη διαδικασία απόφασης αγοράς καταναλωτών (προσωπικοί παράγοντες, ψυχολογικοί παράγοντες, κοινωνικοί παράγοντες). Στο 2ο κεφάλαιο: «οι πτυχές του ηλεκτρονικού εμπορίου» αναφέρονται γενικά στοιχεία, η συσχέτιση με το παραδοσιακό εμπόριο, οι κρίσιμες πτυχές της οικοδόμησης παρουσίας ηλεκτρονικού εμπορίου, η προστασία προσωπικών δεδομένων, η ασφάλεια, και η θέση των επιχειρήσεων ηλεκτρονικού εμπορίου. Στο 3ο κεφάλαιο με τίτλο: «βιβλιογραφική επισκόπηση του θέματος» επισημαίνονται σύγχρονες έρευνες για το θεματικό πεδίο των ηλεκτρονικών αγορών και των προϊόντων τεχνολογίας. Στο 4ο κεφάλαιο: «μεθοδολογία έρευνας» παρουσιάζονται εισαγωγικά στοιχεία για τις ερευνητικές μεθόδους αλλά και η ακολουθούμενη μεθοδολογία, η γενική κατηγορία – το θεματικό πεδίο έρευνας, το ερευνητικό εργαλείο, το δείγμα έρευνας, ο τρόπος ανάλυσης των στοιχείων και τέλος οι περιορισμοί της έρευνας. Στο 5ο κεφάλαιο η: «ανάλυση έρευνας» στοιχειοθετούνται τα κοινωνικό - δημογραφικά στοιχεία της έρευνας, η συμπεριφορά των καταναλωτών ως προς το ηλεκτρονικό εμπόριο και την επιλογή προϊόντος λόγω πανδημίας και ως προς τα προϊόντα τεχνολογίας, πίνακες διασταύρωσης (crosstabs) και τεστ χ2 διαφόρων μεταβλητών. Στο 6ο και τελευταίο κεφάλαιο τα: «συμπεράσματα - συζήτηση» παρουσιάζονται με περιεκτικό τρόπο τα γενικά αποτελέσματα της διπλωματικής καθώς και τα προβλήματα και ανασταλτικοί παράγοντες κατά την εκπόνησή της αλλά και προτάσεις για περαιτέρω έρευνα.The topic of the dissertation concerns e-purchases and technology products, and is analyzed as follows: Chapter 1: «Consumer buying behavior» lists general elements of the topic, the main factors influencing consumer behavior, the stages of the buying process consumers, types of buyers, types of consumers buying behavior and the categories that influence the consumer decision-making process (personal factors, psychological factors, social factors). Chapter 2: «Aspects of e-commerce» provides general information, the relationship with traditional commerce, the critical aspects of building an e-commerce presence, personal data protection, security, and the position of e-commerce businesses. Chapter 3, entitled: «bibliographic overview of the subject», highlights current research on the subject area of electronic markets and technology products. Chapter 4: «research methodology» presents introductory data on research methods and the methodology followed, the general category - the research topic, the research tool, the research sample, the way the data are analyzed and finally the limitations of the research. Chapter 5: «research analysis» documents the socio-demographic data of research, consumer behavior towards e-commerce and product selection due to pandemic and technology products, cross-tabulations and x2 tests of various variables. In the 6th and last chapter: «conclusions – discussion» are presented in a comprehensive way the general results of the diplomacy as well as the problems and inhibiting factors during its elaboration as well as suggestions for further research

Disentangling the AGN and Star-Formation connection using XMM-Newton

There is growing evidence supporting the coeval growth of galaxies and their resident SMBH. Most studies also claim a correlation between the activity of the SMBH and the star-formation of the host galaxy. It is unclear, though, whether this correlation extends to all redz and LX. In this work, we use data from the X-ATLAS and XMM-XXL North fields and compile the largest X-ray sample up to date, to investigate how X-ray AGN affect the star-formation of their host galaxies in a wide redz and luminosity baseline, i.e., 0.03<z<3 and log LX (2-10 keV)= (41-45.5) ergs-1. Our sample consists of 3336 AGN. 1872 X-ray objects have spectroscopic redz. For the remaining sources we calculate photometric redz using TPZ, a machine-learning algorithm. We estimate stellar masses (M*) and Star Formation Rates (SFRs) by applying SED fitting through the CIGALE code, using optical, near-IR and mid-IR photometry. 608 of our sources also have far-IR photometry (Herschel). We use these sources to calibrate the SFR calculations of the rest of our X-ray sample. Our results show a correlation between the LX and the SFR, at all redz and LX spanned by our sample. We also find a dependence of the specific SFR (sSFR) on redz, while there are indications that LX enhances the sSFR even at low redz. We then disentangle the effects of M* and redz on the SFR and study again its dependence on the LX. Towards this end, we use the Schreiber et al. formula to estimate the SFR of main sequence galaxies that have the same stellar mass and redshift as our X-ray AGN. Our analysis reveals that the AGN enhances the star-formation of its host galaxy, when the galaxy lies below the main sequence and quenches the star-formation of the galaxy it lives in, when the host lies above the main sequence. Therefore, the effect of AGN on the SFR of the host galaxy, depends on the location of the galaxy relative to the main sequence.Comment: A&A Accepted 10 pages, 8 figures, 2 table

Cognitive Mechanisms of Monolingual and Bilingual Children in Monoliterate Educational Settings: Evidence From Sentence Repetition.

Sentence repetition (SR) tasks have been extensively employed to assess bilingual children's linguistic and cognitive resources. The present study examined whether monoliterate bilingual children differ from their monolingual (and monoliterate) peers in SR accuracy and cognitive tasks, and investigated links between vocabulary, updating, verbal and visuospatial working memory and SR performance in the same children. Participants were two groups of 35 children, 8-12 years of age: one group consisted of Albanian-Greek monoliterate bilingual children and the other of Greek monolingual children attending a monolingual-Greek educational setting. The findings demonstrate that the two groups performed similarly in the grammaticality scores of the SR. However, monolinguals outperformed the monoliterate bilinguals in SR accuracy, as well as in the visuospatial working memory and updating tasks. The findings did not indicate any bilingual advantage in cognitive performance. The results also demonstrate that updating and visuospatial working memory significantly predicted monolingual children's SR accuracy scores, whereas Greek vocabulary predicted the performance of our monoliterate bilingual children in the same task. We attribute this outcome to the fact that monoliterate bilingual children do not rely on their fluid cognitive resources to perform the task, but instead rely on language proficiency (indicated by expressive vocabulary) while performing the SR

Why computational models are better than verbal theories: the case of nonword repetition

Tests of nonword repetition (NWR) have often been used to examine children’s phonological knowledge and word learning abilities. However, theories of NWR primarily explain performance either in terms of phonological working memory or long-term knowledge, with little consideration of how these processes interact. One theoretical account that focuses specifically on the interaction between short-term and long-term memory is the chunking hypothesis. Chunking occurs because of repeated exposure to meaningful stimulus items, resulting in the items becoming grouped (or chunked); once chunked, the items can be represented in short-term memory using one chunk rather than one chunk per item. We tested several predictions of the chunking hypothesis by presenting 5-6 year-old children with three tests of NWR that were either high, medium, or low in wordlikeness. The results did not show strong support for the chunking hypothesis, suggesting that chunking fails to fully explain children’s NWR behavior. However, simulations using a computational implementation of chunking (namely CLASSIC, or Chunking Lexical And Sublexical Sequences In Children) show that, when the linguistic input to 5-6 year old children is estimated in a reasonable way, the children’s data is matched across all three NWR tests. These results have three implications for the field: (a) a chunking account can explain key NWR phenomena in 5-6 year old children; (b) tests of chunking accounts require a detailed specification both of the chunking mechanism itself and of the input on which the chunking mechanism operates; and (c) verbal theories emphasizing the role of long-term knowledge (such as chunking) are not precise enough to make detailed predictions about experimental data, but computational implementations of the theories can bridge the gap

Linking working memory and long-term memory: A computational model of the learning of new words

The nonword repetition (NWR) test has been shown to be a good predictor of children’s vocabulary size. NWR performance has been explained using phonological working memory, which is seen as a critical component in the learning of new words. However, no detailed specification of the link between phonological working memory and long-term memory (LTM) has been proposed. In this paper, we present a computational model of children’s vocabulary acquisition (EPAM-VOC) that specifies how phonological working memory and LTM interact. The model learns phoneme sequences, which are stored in LTM and mediate how much information can be held in working memory. The model’s behaviour is compared with that of children in a new study of NWR, conducted in order to ensure the same nonword stimuli and methodology across ages. EPAM-VOC shows a pattern of results similar to that of children: performance is better for shorter nonwords and for wordlike nonwords, and performance improves with age. EPAM-VOC also simulates the superior performance for single consonant nonwords over clustered consonant nonwords found in previous NWR studies. EPAM-VOC provides a simple and elegant computational account of some of the key processes involved in the learning of new words: it specifies how phonological working memory and LTM interact; makes testable predictions; and suggests that developmental changes in NWR performance may reflect differences in the amount of information that has been encoded in LTM rather than developmental changes in working memory capacity. Keywords: EPAM, working memory, long-term memory, nonword repetition, vocabulary acquisition, developmental change

Star-forming early-type galaxies and quiescent late-type galaxies in the local Universe

Aims: The general consensus is that late-type galaxies undergo intense star-formation, activity while early-type galaxies are mostly inactive. We question this general rule and investigate the existence of star-forming early-type and quiescent late-type galaxies in the local Universe. By computing the physical properties of these galaxies and by using information on their structural properties as well as the density of their local environment, we seek to understand the differences from their `typical' counterparts. Methods: We made use of the multi-wavelength photometric data (from the ultraviolet to the sub-millimetre), for 2209 morphologically classified galaxies in the Galaxy And Mass Assembly survey. Furthermore, we separated the galaxies into subsets of star-forming and quiescent based on their dominant ionising process, making use of established criteria based on the WHα width and the [NII/Hα] ratio. Taking advantage of the spectral energy distribution fitting code CIGALE, we derived galaxy properties, such as the stellar mass, dust mass, and star-formation rate, and we also estimated the unattenuated and the dust-absorbed stellar emission, for both the young (≤200 Myr) and old (> 200 Myr) stellar populations. Results: We find that about 47% of E/S0 galaxies in our sample show ongoing star-formation activity and 8% of late-type galaxies are quiescent. The star-forming elliptical galaxies, together with the little blue spheroids, constitute a population that follows the star-forming main sequence of spiral galaxies very well. The fraction of the luminosity originating from young stars in the star-forming early-type galaxies is quite substantial (∼25%) and similar to that of the star-forming late-type galaxies. The stellar luminosity absorbed by the dust (and used to heat the dust grains) is highest in star-forming E/S0 galaxies (an average of 35%) followed by star-forming Sa-Scd galaxies (27%) with this fraction becoming significantly smaller for their quiescent analogues (6% and 16%, for E/S0 and Sa-Scd, respectively). Star-forming and quiescent E/S0 galaxies donate quite different fractions of their young stellar luminosities to heat up the dust grains (74% and 36%, respectively), while these fractions are very similar for star-forming and quiescent Sa-Scd galaxies (59% and 60%, respectively). Investigating possible differences between star-forming and quiescent galaxies, we find that the intrinsic (unattenuated) shape of the SED of the star-forming galaxies is, on average, very similar for all morphological types. Concerning their structural parameters, quiescent galaxies tend to show larger values of the r-band Sérsic index and larger effective radii (compared to star-forming galaxies). Finally, we find that star-forming galaxies preferably reside in lower density environments compared to the quiescent ones, which exhibit a higher percentage of sources being members of groups