1,475 research outputs found

    II. On the structure and biology of archotermopsis, together with descriptions of new species of intestinal protozoa, and general observations on the isoptera

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    The following paper is intended as a contribution towards a knowledge of the structure and biology of Archotermopsis wroughtoni, Desn., one of the most primitive of living Termites. Included herewith are also observations and deductions bearing upon some of the more important general biological problems which are associated with the Isoptera. Archotermopsis wroughtoni was described 12 years ago by Desneux from examples taken by Wroughton in June, 1903. They were discovered in old stumps of trees, chiefly Pinus excelsa, in the Kashmir Valley. Since its discovery, this species has remained a great rarity, and practically nothing had been ascertained concerning its biology. In June, 1910, I first came across this insect in a decaying fallen trunk of Pinus excelsa, in a forest area situated between the Kuari Pass and Ramni, at an altitude of about 8,500 feet, in the Himalayas of British Garwhal. In the same month during 1912 I had the good fortune to meet with it in great abundance in a dead fallen trunk of Pinus longifolia near Dharmoti, in the Ranikhet District. This locality is situated at an altitude of about 4,000 feet in the Kumaon Himalaya. Being aware of the biological and phylogenetic interest likely to be afforded by a study of this species, I made a prolonged search in many other likely localities in the North Western Himalayas during the years 1912-13. It was subsequently found plentifully at Bhowali, near Naini Tal, at an elevation of 5,800 feet, near Nadh in the Ohakrata District of Jaunsar, and I have also been able to procure examples from near Gulmerg in Kashmir. It seems probable, therefore, that it will eventually be found to be generally distributed in the lower-level coniferous forests of the North Western Himalayas, up to an elevation of about 9,000 feet

    Are you a researcher as well as a medical illustrator?

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    When we list the areas of practice for medical illustrators we always include research, but how involved in research are we? The aim of this activity is to encourage your professional development not just as a medical illustrator but your involvement with research whether that is undertaking your own research, undertaking evidence based practice (1) , working as part of a research team, advising researchers on the value of medical illustration or supporting a student undertaking a research project for their degree or post-graduate qualification

    Kinetochore-localized PP1-Sds22 couples chromosome segregation to polar relaxation

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    Cell division requires the precise coordination of chromosome segregation and cytokinesis. This coordination is achieved by the recruitment of an actomyosin regulator, Ect2, to overlapping microtubules at the centre of the elongating anaphase spindle. Ect2 then signals to the overlying cortex to promote the assembly and constriction of an actomyosin ring between segregating chromosomes. Here, by studying division in proliferating Drosophila and human cells, we demonstrate the existence of a second, parallel signalling pathway, which triggers the relaxation of the polar cell cortex at mid anaphase. This is independent of furrow formation, centrosomes and microtubules and, instead, depends on PP1 phosphatase and its regulatory subunit Sds22 (refs 2, 3). As separating chromosomes move towards the polar cortex at mid anaphase, kinetochore-localized PP1-Sds22 helps to break cortical symmetry by inducing the dephosphorylation and inactivation of ezrin/radixin/moesin proteins at cell poles. This promotes local softening of the cortex, facilitating anaphase elongation and orderly cell division. In summary, this identifies a conserved kinetochore-based phosphatase signal and substrate, which function together to link anaphase chromosome movements to cortical polarization, thereby coupling chromosome segregation to cell division

    Donut: measuring optical aberrations from a single extra-focal image

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    We propose a practical method to calculate Zernike aberrations from analysis of a single long-exposure defocused stellar image. It consists in fitting the aberration coefficients and seeing blur directly to a realistic image binned into detector pixels. This "donut" method is different from curvature sensing in that it does not make the usual approximation of linearity. We calculate the sensitivity of this technique to detector and photon noise and determine optimal parameters for some representative cases. Aliasing of high-order un-modeled aberrations is evaluated and shown to be similar to a low-order Shack-Hartmann sensor. The method has been tested with real data from the SOAR and Blanco 4m telescopes.Comment: 13 pages, 9 figures. Accepted at PAS

    Dynamical effects of interactions and the Tully-Fisher relation for Hickson compact groups

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    We investigate the properties of the B-band Tully-Fisher (T-F) relation for 25 compact group galaxies, using Vmax derived from 2-D velocity maps. Our main result is that the majority of the Hickson Compact Group galaxies lie on the T-F relation. However, about 20% of the galaxies, including the lowest-mass systems, have higher B luminosities for a given mass, or alternatively, a mass which is too low for their luminosities. We favour a scenario in which outliers have been brightened due to either enhanced star formation or merging. Alternatively, the T-F outliers may have undergone truncation of their dark halo due to interactions. It is possible that in some cases, both effects contribute. The fact that the B-band T-F relation is similar for compact group and field galaxies tells us that these galaxies show common mass-to-size relations and that the halos of compact group galaxies have not been significantly stripped inside R25. We find that 75% of the compact group galaxies studied (22 out of 29) have highly peculiar velocity fields. Nevertheless, a careful choice of inclination, position angle and center, obtained from the velocity field, and an average of the velocities over a large sector of the galaxy enabled the determination of fairly well-behaved rotation curves for the galaxies. However, two of the compact group galaxies which are the most massive members in M51--like pairs, HCG 91a and HCG 96a, have very asymmetric rotation curves, with one arm rising and the other one falling, indicating, most probably, a recent perturbation by the small close companions.Comment: 15 pages, 4 figures, accepted for publication in the Astronomical Journa

    European Men-Who-Have-Sex-With-Men Internet Survey (EMIS-2017): Design and Methods

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    AbstractMen-who-have-sex-with-men (MSM) carry a disproportionate burden of sexually transmitted infections across Europe. Health planners require sexual health needs assessment data to respond appropriately. In addition, surveillance of risk and precaution behaviours in this population enables evaluative judgements of policy responses. The European MSM Internet Survey (EMIS-2017) aimed to repeat the pan-European online survey on male homosexual behaviour conducted in 2010, both to update information required to plan and monitor health promotion interventions and consolidate harmonisation of existing behavioural surveillance approaches. Our study team collaborated with more than 200 partners from academia, public health and civil society across 50 countries. Starting from our previous EMIS-2010 questionnaire, partners engaged in three rounds of iterative survey development and piloting until the final content was agreed. Transfer to an online survey application was followed by further pre-testing before translation into 32 additional languages, final testing and sign-off. The survey was available to complete online in 33 languages simultaneously from 18 October 2017 to 31 January 2018. Ten international MSM dating mobile apps were paid to send short promotional messages, and national partners promoted the survey via at least another 272 websites and social media accounts. Real-time monitoring of responses facilitated targeted advertising by country and recruitment source. Ultimately 144,305 cases were submitted of which 137,358 (95.2%) were eligible for inclusion. EMIS-2017 demonstrated the feasibility of multi-country online MSM surveying with public funding. Meaningful involvement of a large number of collaborators in the survey design and its execution ensured successful recruitment. Careful design, piloting and presentation ensured the survey was acceptable and had authority and perceived community benefit. Partners in 38 countries have already been supplied with a national database of 100 or more respondents for national analysis, while the study team has focussed on international comparisons among 137,358 respondents in 50 countries.</jats:p

    The Properties of Poor Groups of Galaxies: III. The Galaxy Luminosity Function

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    We obtain R-band photometry for galaxies in six nearby poor groups for which we have spectroscopic data, including 328 new galaxy velocities. For the five groups with luminous X-ray halos, the composite group galaxy luminosity function (GLF) is fit adequately by a Schechter function with Mstar = -21.6 +/- 0.4 + 5log h and alpha = -1.3 +/- 0.1. We also find that (1) the ratio of dwarfs to giants is significantly larger for the five groups with luminous X-ray halos than for the one marginally X-ray detected group, (2) the composite GLF for the luminous X-ray groups is consistent in shape with that for rich clusters, (3) the composite group GLF rises more steeply at the faint end than that of the field, (4) the shape difference between the field and composite group GLF's results mostly from the population of non-emission line galaxies, whose dwarf-to-giant ratio is larger in the denser group environment than in the field, and (5) the non-emission line dwarfs are more concentrated about the group center than the non-emission line giants. This last result indicates that the dwarfs and giants occupy different orbits (i.e., have not mixed completely) and suggests that the populations formed at a different times. Our results show that the shape of the GLF varies with environment and that this variation is due primarily to an increase in the dwarf-to-giant ratio of quiescent galaxies in higher density regions, at least up to the densities characteristic of X-ray luminous poor groups. This behavior suggests that, in some environments, dwarfs are more biased than giants with respect to dark matter. This trend conflicts with the prediction of standard biased galaxy formation models. (Abridged)Comment: 36 pages, AASLaTeX with 8 figures. Table 1 also available at http://atropos.as.arizona.edu/aiz/papers/all_grp_lf_ascii.dat.final . To appear in Ap
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