ATP-dependent chromatosome remodeling

Chromatin serves to package, protect and organize the complex eukaryotic genomes to assure their stable inheritance over many cell generations. At the same time, chromatin must be dynamic to allow continued use of DNA during a cell's lifetime. One important principle that endows chromatin with flexibility involves ATP-dependent `remodeling' factors, which alter DNA-histone interactions to form, disrupt or move nucleosomes. Remodeling is well documented at the nucleosomal level, but little is known about the action of remodeling factors in a more physiological chromatin environment. Recent findings suggest that some remodeling machines can reorganize even folded chromatin fibers containing the linker histone H1, extending the potential scope of remodeling reactions to the bulk of euchromatin

Advances on Matroid Secretary Problems: Free Order Model and Laminar Case

The most well-known conjecture in the context of matroid secretary problems claims the existence of a constant-factor approximation applicable to any matroid. Whereas this conjecture remains open, modified forms of it were shown to be true, when assuming that the assignment of weights to the secretaries is not adversarial but uniformly random (Soto [SODA 2011], Oveis Gharan and Vondr\'ak [ESA 2011]). However, so far, there was no variant of the matroid secretary problem with adversarial weight assignment for which a constant-factor approximation was found. We address this point by presenting a 9-approximation for the \emph{free order model}, a model suggested shortly after the introduction of the matroid secretary problem, and for which no constant-factor approximation was known so far. The free order model is a relaxed version of the original matroid secretary problem, with the only difference that one can choose the order in which secretaries are interviewed. Furthermore, we consider the classical matroid secretary problem for the special case of laminar matroids. Only recently, a constant-factor approximation has been found for this case, using a clever but rather involved method and analysis (Im and Wang, [SODA 2011]) that leads to a 16000/3-approximation. This is arguably the most involved special case of the matroid secretary problem for which a constant-factor approximation is known. We present a considerably simpler and stronger $3\sqrt{3}e\approx 14.12$-approximation, based on reducing the problem to a matroid secretary problem on a partition matroid

Absolute properties of the main-sequence eclipsing binary FM Leo

First spectroscopic and new photometric observations of the eclipsing binary FM Leo are presented. The main aims were to determine orbital and stellar parameters of two components and their evolutionary stage. First spectroscopic observations of the system were obtained with DDO and PST spectrographs. The results of the orbital solution from radial velocity curves are combined with those derived from the light-curve analysis (ASAS-3 photometry and supplementary observations of eclipses with 1 m and 0.35 m telescopes) to derive orbital and stellar parameters. JKTEBOP, Wilson-Devinney binary modelling codes and a two-dimensional cross-correlation (TODCOR) method were applied for the analysis. We find the masses to be M_1 = 1.318 $\pm$ 0.007 and M_2 = 1.287 $\pm$ 0.007 M_sun, the radii to be R_1 = 1.648 $\pm$ 0.043 and R_2 = 1.511 $\pm$ 0.049 R_sun for primary and secondary stars, respectively. The evolutionary stage of the system is briefly discussed by comparing physical parameters with current stellar evolution models. We find the components are located at the main sequence, with an age of about 3 Gyr.Comment: 5 pages, 4 figures, to appear in MNRA

The importance of submalleolar deformity in determining leg length discrepancy

Background and purposeThe association of leg length discrepancy (LLD) with a number of clinical disorders has made its determination a significant part of the physical examination. We believe that submalleolar causes of LLD may be under-acknowledged. The most common clinical method used to measure LLD is by tape from the anterior superior iliac spine (ASIS) to medial malleolus which disregards the potential for LLD arising from asymmetry in the foot distal to the tibiotalar joint.MethodsThe present pilot study involves a group of 5 volunteers (experimental group) and a group of 3 patients with flexible flat feet (clinical study). The differences in tibial tubercle height from the ground between full pronation and full supination were measured using the CODA MPX 30® system (Charnwood Dynamics Limited, Leicestershire, England). Correlations of the patterns within each group were produced.ResultsA significant relationship with leg lengths was found in the experimental group when they induced maximum pronation (R-squared = 0.62, p = 0.007) while an inverse relationship occurred with supination, although marginally significant (R-squared = 0.37, p = 0.064).ConclusionsWe have demonstrated that significant leg length discrepancy can occur in patients who do not have obvious deformity when non weight bearing. We recommend using the blocks method routinely. Appropriately measuring LLD is of vital importance to properly diagnosing and treating patients with unequal leg lengths or related symptoms

Revising the Metacognitive Awareness of Reading Strategies Inventory (MARSI) and testing for factorial invariance

In this study, we revised the Metacognitive Awareness of Reading Strategies Inventory (MARSI), a self-report instrument designed to assess students’ awareness of reading strategies when reading school-related materials. We collected evidence of structural, generalizability, and external aspects of validity for the revised inventory (MARSI-R). We first conducted a confirmatory factor analysis of the MARSI instrument, which resulted in the reduction of the number of strategy statements from 30 to 15. We then tested MARSI-R for factorial invariance across gender and ethnic groups and found that there is a uniformity in student interpretation of the reading strategy statements across these groups, thus allowing for their comparison on levels of metacognitive processing skills. We found evidence of the external validity aspect of MARSI-R data through correlations of such data with a measure of the students’ perceived reading ability. Given that this journal is oriented to second language learning and teaching, our article also includes comments on the Survey of Reading Strategies (SORS), which was based on the original MARSI and was designed to assess adolescents’ and adults’ metacognitive awareness and perceived use of ESL reading strategies. We provide a copy of the MARSI-R instrument and discuss the implications of the study’s findings in light of new and emerging insights relative to assessing students’ metacognitive awareness and perceived use of reading strategies

Revising the Metacognitive Awareness of Reading Strategies Inventory (MARSI) and Testing for Factorial Invariance

In this study, we revised the Metacognitive Awareness of Reading Strategies Inventory (MARSI), a self-report instrument designed to assess students’ awareness of reading strategies when reading school-related materials. We collected evidence of structural, generalizability, and external aspects of validity for the revised inventory (MARSI-R). We first conducted a confirmatory factor analysis of the MARSI instrument, which resulted in the reduction of the number of strategy statements from 30 to 15. We then tested MARSI-R for factorial invariance across gender and ethnic groups and found that there is a uniformity in student interpretation of the reading strategy statements across these groups, thus allowing for their comparison on levels of metacognitive processing skills. We found evidence of the external validity aspect of MARSI-R data through correlations of such data with a measure of the students’ perceived reading ability. Given that this journal is oriented to second language learning and teaching, our article also includes comments on the Survey of Reading Strategies (SORS), which was based on the original MARSI and was designed to assess adolescents’ and adults’ metacognitive awareness and perceived use of ESL reading strategies. We provide a copy of the MARSI-R instrument and discuss the implications of the study’s findings in light of new and emerging insights relative to assessing students’ metacognitive awareness and perceived use of reading strategies

Photometric and spectroscopic variability of the FUor star V582 Aurigae

We carried out BVRI CCD photometric observations in the field of V582 Aur from 2009 August to 2013 February. We acquired high-, medium-, and low-resolution spectroscopy of V582 Aur during this period. To study the pre-outburst variability of the target and construct its historical light curve, we searched for archival observations in photographic plate collections. Both CCD and photographic observations were analyzed using a sequence of 14 stars in the field of V582 Aur calibrated in BVRI. The pre-outburst photographic observations of V582 Aur show low-amplitude light variations typical of T Tauri stars. Archival photographic observations indicate that the increase in brightness began in late 1984 or early 1985 and the star reached the maximum level of brightness at 1986 January. The spectral type of V582 Aur can be defined as G0I with strong P Cyg profiles of H alpha and Na I D lines, which are typical of FU Orionis objects. Our BVRI photometric observations show large amplitude variations V~2.8 mag. during the 3.5 year period of observations. Most of the time, however, the star remains in a state close to the maximum brightness. The deepest drop in brightness was observed in the spring of 2012, when the brightness of the star fell to a level close to the pre-outburst. The multicolor photometric data show a color reversal during the minimum in brightness, which is typical of UX Ori variables. The corresponding spectral observations show strong variability in the profiles and intensities of the spectral lines (especially H alpha), which indicate significant changes in the accretion rate. On the basis of photometric monitoring performed over the past three years, the spectral properties of the maximal light, and the shape of the long-term light curve, we confirm the affiliation of V582 Aur to the group of FU Orionis objects.Comment: 9 pages, 8 figures, accepted for publication in A&

Multi-site, multi-year monitoring of the oscillating Algol-type eclipsing binary CT Her

We present the results of a multi-site photometric campaign carried out in 2004-2008 for the Algol-type eclipsing binary system CT Her, the primary component of which shows Delta Scuti-type oscillations. Our data consist of differential light curves collected in the filters B and V which have been analysed using the method of Wilson-Devinney (PHOEBE). After identification of an adequate binary model and removal of the best-matching light curve solution, we performed a Fourier analysis of the residual B and V light curves to investigate the pulsational behaviour. We confirm the presence of rapid pulsations with a main period of 27.2 min. Up to eight significant frequencies with semi-amplitudes in the range 3 to 1 mmag were detected, all of which surprisingly lie in the frequency range 43.5-53.5 c\d. This result is independent from the choice of the primary's effective temperature (8200 or 8700 K) since the light curve models for the binary are very similar in both cases. This is yet another case of a complex frequency spectrum observed for an accreting Delta Scuti-type star (after Y Cam). In addition, we demonstrate that the amplitudes of several of these pulsation frequencies show evidence of variability on time scales as short as 1-2 years, perhaps even less. Moreover, our analysis takes into account some recently acquired spectra, from which we obtained the corresponding radial velocities for the years 2007-2009. Investigation of the O-C diagram shows that further monitoring of the epochs of eclipse minima of CT Her will cast a new light on the evolution of its orbital period.Comment: 13 pages, 13 encapsulated Postscript figures. Tables~3, 4, 9 and 12 will be available in electronic form only. Astronomy and Astrophysics, in process (2011). Replaced the abstract with its final versio