Analytical procedure results as substantive evidence

https://egrove.olemiss.edu/dl_proceedings/1085/thumbnail.jp

Cooperative DNA-binding by Bicoid provides a mechanism for threshold-dependent gene activation in the Drosophila embryo

The Bicoid morphogen directs pattern formation along the anterior-posterior (A-P) axis of the Drosophila embryo. Bicoid is distributed in a concentration gradient that decreases exponentially from the anterior pole, however, it transcribes target genes such as hunchback in a step-function-like pattern; the expression domain is uniform and has a sharply defined posterior boundary. A 'gradient-affinity' model proposed to explain Bicoid action states that (i) cooperative gene activation by Bicoid generates the sharp on/off switch for target gene transcription and (ii) target genes with different affinities for Bicoid are expressed at different positions along the A-P axis. Using an in vivo yeast assay and in vitro methods, we show that Bicoid binds DNA with pairwise cooperativity; Bicoid bound to a strong site helps Bicoid bind to a weak site. These results support the first aspect of the model, providing a mechanism by which Bicoid generates sharp boundaries of gene expression. However, contrary to the second aspect of the model, we find no significant difference between the affinity of Bicoid for the anterior gene hunchback and the posterior gene knirps, We propose, instead, that the arrangement of Bicoids bound to the target gene presents a unique signature to the transcription machinery that, in combination with overall affinity, regulates the extent of gene transcription along the A-P axis

Colloids in light fields: particle dynamics in random and periodic energy landscapes

The dynamics of colloidal particles in potential energy landscapes have mainly been investigated theoretically. In contrast, here we discuss the experimental realization of potential energy landscapes with the help of light fields and the observation of the particle dynamics by video microscopy. The experimentally observed dynamics in periodic and random potentials are compared to simulation and theoretical results in terms of, e.g. the mean-squared displacement, the time-dependent diffusion coefficient or the non-Gaussian parameter. The dynamics are initially diffusive followed by intermediate subdiffusive behaviour which again becomes diffusive at long times. How pronounced and extended the different regimes are, depends on the specific conditions, in particular the shape of the potential as well as its roughness or amplitude but also the particle concentration. Here we focus on dilute systems, but the dynamics of interacting systems in external potentials, and thus the interplay between particle-particle and particle-potential interactions, is also mentioned briefly. Furthermore, the observed dynamics of dilute systems resemble the dynamics of concentrated systems close to their glass transition, with which it is compared. The effect of certain potential energy landscapes on the dynamics of individual particles appears similar to the effect of interparticle interactions in the absence of an external potential

Substructure in the Andromeda Galaxy Globular Cluster System

In the most prominent current scenario of galaxy formation, galaxies form hierarchically through the merger of smaller systems. Such mergers could leave behind dynamical signatures which may linger long after the event. In particular, the globular cluster system (GCS) of a merging satellite galaxy may remain as a distinct sub-population within the GCS of a massive galaxy. Using the latest available globular cluster velocities and metallicities, we present the results of a search for grouping in the GCS of our nearest large spiral galaxy neighbor, M31. A modified friends-of-friends algorithm is used to identify a number of possible merger remnants in projected position, radial velocity and [Fe/H] parameter space. Numerical simulations are used to check that such merger remnants are indeed plausible over the timescales of interest. The identification of stellar streams associated with these groups is required in order to confirm that they represent merger remnants.Comment: 19 pages, 3 figures, accepted for publication in the Ap

A New Evolutionary Path to Type Ia Supernovae: Helium-Rich Super-Soft X-Ray Source Channel

We have found a new evolutionary path to Type Ia supernovae (SNe Ia) which has been overlooked in previous work. In this scenario, a carbon-oxygen white dwarf (C+O WD) is originated, not from an asymptotic giant branch star with a C+O core, but from a red-giant star with a helium core of $\sim 0.8-2.0 M_\odot$. The helium star, which is formed after the first common envelope evolution, evolves to form a C+O WD of $\sim 0.8-1.1 M_\odot$ with transferring a part of the helium envelope onto the secondary main-sequence star. This new evolutionary path, together with the optically thick wind from mass-accreting white dwarf, provides a much wider channel to SNe Ia than previous scenarios. A part of the progenitor systems are identified as the luminous supersoft X-ray sources or the recurrent novae like U Sco, which are characterized by the accretion of helium-rich matter. The white dwarf accretes hydrogen-rich, helium-enhanced matter from a lobe-filling, slightly evolved companion at a critical rate and blows excess matter in the wind. The white dwarf grows in mass to the Chandrasekhar mass limit and explodes as an SN Ia. A theoretical estimate indicates that this channel contributes a considerable part of the inferred rate of SNe Ia in our Galaxy, i.e., the rate is about ten times larger than the previous theoretical estimates for white dwarfs with slightly evolved companions.Comment: 19 pages including 12 figures, to be published in ApJ, 519, No.

Major hepatic resections – the progress of a new HBP surgical-centre

Spitalul Clinic “Dr. Ion Cantacuzino”, București, România, Al XIII-lea Congres al Asociației Chirurgilor „Nicolae Anestiadi” și al III-lea Congres al Societății de Endoscopie, Chirurgie miniminvazivă și Ultrasonografie ”V.M.Guțu” din Republica MoldovaIntroducere: In mod istoric, rezecțiile hepatice au fost insoțite de morbitate si morbitate majore, reprezentând un tip prohibitiv de chirurgie până în ultimii ani. Odata cu evoluția tehnologiei și imbunătățirea tehnicilor imagistice, cât și a dezvoltării unui management perioperator specific ficatului, rezectiile hepatice au ajuns sa fie efectuate în centre de volum mare cu o rată a mortalitații de < 5%. Material si metode: În ultimii 5 ani, Spitalul Clinic “Dr. Ion Cantacuzino” s-a dezvoltat ca un nou centru de chirurgie hepato-biliopancreatică, o varietate largă de rezecții hepatice fiind practicate de rutină. Rezultate: Experiența acestei clinici în ceea ce privește rezecțiile hepatice majore a progresat până la 15 cazuri, la ora actuală, cu un singur deces postoperator. Concluzii: Din perspectiva unui centru în creștere a devenit aparent faptul ca se pot realiza rezecții hepatice majore în siguranță și cu rezultate postoperatorii bune, atât timp cât se aplica o selecție riguroasă a pacienților și sunt urmarite protocoale standardizate.Background: Historically major hepatic resections have been associated with high morbidity and mortality, being a prohibitive type surgery until recent years. With the advancement of technology and better imaging techniques, as well as liver-specific perioperative care, hepatic resections are performed in high-volume centres with a mortality of less than 5 %. Method and materials: The “Dr. Ion Cantacuzino” Hospital in Bucharest has developed as a new hepato-biliary-pancreatic surgical centre in the past 5 years, with a wide variety of hepatic resections performed on a regular basis. Results: The experience of this clinic, as far as major hepatic resections is concerned, has progressed, to date, to 15 such cases, with just one postoperative death. Conclusion: From the perspective of a growing centre it has become apparent that major hepatic resections can be safely performed and with good postoperative outcomes, with a thorough selection of patients and if standardised protocols are followed

hernia repair – is there a place for one-day surgery?

Spitalul Clinic “Dr. Ion Cantacuzino”, București, România, Al XIII-lea Congres al Asociației Chirurgilor „Nicolae Anestiadi” și al III-lea Congres al Societății de Endoscopie, Chirurgie miniminvazivă și Ultrasonografie ”V.M.Guțu” din Republica MoldovaIntroducere: Tratamentul chirurgical al herniilor inghinale este una dintre cele mai frecvente intervenții chirurgicale care se practică pe plan mondial, în ciuda faptului că persistă o lipsă de conses în ceea ce privește “cel mai bun” procedeu; unii autori susținând avantajele procedeelor deschise, în principiu operația Lichtenstein, în timp ce alții beneficiile abordarilor laparoscopice, TAPP sau TEP. Material și metode: Am realizat un studiu retrospectiv în cadrul Spitalului Clinic “Dr. Ion Cantacuzino”, pe o perioadă de 5 ani, pe 517 pacienți la care s-au practicat diferite intervenții chirurgicale pentru tratamentul herniilor inghinale. Pacienții au fost imparțiți în 2 grupuri, unii beneficiind de un procedeu deschis, în timp ce alții de laparoscopie. Variabile introduse în studiu au fost vârsta, sexul, perioada medie de spitalizare, media zilelor de spitalizare postoperatorie, timpul operatorie si costurile aferente spitalizării. Rezultate: Procedee laparoscopice s-au efectuat la 304/517 (59,37%), cu o mică prevalență TEP vs TAPP. Perioada de spitalizare, cheltuielile și timpii operatori au fost semnificativ mai mici pentru grupul TEP, majoritatea pacientilor fiind externați în prima zi postoperator. Concluzii: Rezultatele studiului nostru sprijină ideea ca procedeul TEP se poate practica într-un regim de “one-day surgery” într-un spital public astfel crescând confortul pacientului și scazând cheltuielile de spitalizare.Background: Hernia surgery is one of the most frequent operation performed world-wide, although there still seems to be a lack of consensus as to “the best” technique, with some authors still advocating for open, mainly Lichtenstein repair, while others supporting laparoscopic techniques, TAPP or TEP. Methods and materials: A retrospective study was performed in a public county hospital, over a period of 5 years, on 517 patients who benefitted from a surgical procedure for inguinal hernia treatment. Patients were divided into 2 groups, one with open surgical repair and, the other, laparoscopic. Variables taken into account were age, sex, mean hospital stay, mean postoperative hospital stay, hospital expenses, and operative time. Results: Laparoscopic repair was performed for 304/517 (59,37%), with a slight prevalence of TEP over TAPP; Hospital stay, expenses and operative time were significantly lower for the TEP group, most of the patients being discharged the following day. Conclusion: The results of our study seems to support the idea that TEP hernia repair could be performed on a “one-day surgery” basis in a public hospital, thus increasing patient comfort and decreasing hospital expenses

Chandra Observation of Diffuse Gas and LMXBs in the Elliptical Galaxy NGC 4649 (M60)

We present a Chandra X-ray observation of the X-ray bright E2 elliptical galaxy NGC4649. In addition to bright diffuse emission, we resolve 165 discrete sources, most of which are presumably low-mass X-ray binaries (LMXBs). As found in previous studies, the luminosity function of the resolved sources is well-fit by a broken power-law. In NGC4697 and NGC1553, the break luminosity was comparable to the Eddington luminosity of a $1.4 M_{\odot}$ neutron star. One possible interpretation of this result is that those sources with luminosities above the break are accreting black holes and those below are mainly accreting neutron stars. The total X-ray spectrum of the resolved sources is well-fit by a hard power-law, while the diffuse spectrum requires a hard and a soft component, presumably due to the relatively soft diffuse gas and the harder unresolved sources. We also find evidence for structure in the diffuse emission near the center of NGC4649. Specifically, there appear to be bright "fingers" of emission extending from the center of the galaxy and a 5 arcsec long bar at the center of the galaxy. The fingers are morphologically similar to radial features seen in two-dimensional hydrodynamic simulations of cooling flows in elliptical galaxies, and although their other properties do not match the predictions of the particular simulations used we conclude that the radial fingers might be due to convective motions of hot outflowing gas and cooler inflowing gas. The bar is coincident with the central extended radio source; we conclude that the bar may be caused by weak shocks in the diffuse gas from an undetected low-luminosity active galactic nucleus (AGN).Comment: 26 pages, 11 figures. Accepted for publication in the Astrophysical Journa

A Wide Symbiotic Channel to Type Ia Supernovae

As a promising channel to Type Ia supernovae (SNe Ia), we have proposed a symbiotic binary system consisting of a white dwarf (WD) and a low mass red-giant (RG), where strong winds from the accreting WD play a key role to increase the WD mass to the Chandrasekhar mass limit. Here we propose two new evolutionary processes which make the symbiotic channel to SNe Ia much wider. (1) We first show that the WD + RG close binary can form from a wide binary even with such a large initial separation as $a_i \lesssim 40000 R_\odot$. Such a binary consists of an AGB star and a low mass main-sequence (MS) star, where the AGB star is undergoing superwind before becoming a WD. If the superwind at the end of AGB evolution is as fast as or slower than the orbital velocity, the wind outflowing from the system takes away the orbital angular momentum effectively. As a result the wide binary shrinks greatly to become a close binary. Therefore, the WD + RG binary can form from much wider binaries than our earlier estimate. (2) When the RG fills its inner critical Roche lobe, the WD undergoes rapid mass accretion and blows a strong optically thick wind. Our earlier analysis has shown that the mass transfer is stabilized by this wind only when the mass ratio of RG/WD is smaller than 1.15. Our new finding is that the WD wind can strip mass from the RG envelope, which could be efficient enough to stabilize the mass transfer even if the RG/WD mass ratio exceeds 1.15. With the above two new effects (1) and (2), the symbiotic channel can account for the inferred rate of SNe Ia in our Galaxy.Comment: 29 pages including 14 firgures, to be published in ApJ, 521, No.