212 research outputs found
An Emergence Trap for Aquatic Insects
Excerpt: The identification of organisms is a prerequisite to developing water quality criteria for aquatic life. Identification is necessary because differences in water quality requirements are specific and may be different for closely allied species. The taxonomy of various species, particularly those associated with the aquatic environment, is much more detailed and better known for adults than for immature instars. To facilitate correlation of adult and larval forms, a trap was needed to collect the emerging adults from the various streams
Ligand selectivity in stabilising tandem parallel folded G-quadruplex motifs in human telomeric DNA sequences
Biophysical studies of ligand interactions with three human telomeric repeat sequences (d(AGGG(TTAGGG)n, n = 3, 7 and 11)) show that an oxazole-based ‘click’ ligand, which induces parallel folded quadruplexes, preferentially stabilises longer telomeric repeats providing evidence for selectivity in binding at the interface between tandem quadruplex motifs
Utilization of solar collector for treatment of plant growth substrates.
Solar collectors were tested for the control of Meloidogyne arenaria, Sclerotium rolfsii, Verticillium sp. and nut sedge (Cyperus rotundus). Verticillium isolate multiplied on popcorn, soil infested with M. arenaria, sclerodia of S. rofsii and nodules of nut sedge were mixed with soil and treated for different times in solar collectors. The recovered popcorn seeds and sclerodia were desinfected and transferred to Petri dishes for the evaluation of the pathogen survival. The sedge nodules recovered from treated soil were planted in pots for the evaluation of emergence. Tomato (Lycopersicon esculentum var. cerasiforme) seedlings were planted in soil infested with M. arenaria and the effect of soil exposure was evaluated by weighting the intact plants, by counting the number of nodules on the root system, and by determining the nematode population before and after the treatment. The results showed that depending upon the climatic conditions, two days are required for the desinfestation of soil infested with M. arenaria and Verticillium sp. whereas only one day is required for S. rolfsii and nut sedge, since under the condition of complete solar radiation the substrate reaches temperatures up to 85 .C
The North American and Pelican Nebulae I. IRAC Observations
We present a 9 deg^2 map of the North American and Pelican Nebulae regions
obtained in all four IRAC channels with the Spitzer Space Telescope. The
resulting photometry is merged with that at JHKs from 2MASS and a more
spatially limited survey from previous ground-based work. We use a
mixture of color- color diagrams to select a minimally contaminated set of more
than 1600 objects that we claim are young stellar objects (YSOs) associated
with the star forming region. Because our selection technique uses IR excess as
a requirement, our sample is strongly biased against inclusion of Class III
YSOs. The distribution of IRAC spectral slopes for our YSOs indicates that most
of these objects are Class II, with a peak towards steeper spectral slopes but
a substantial contribution from a tail of flat spectrum and Class I type
objects. By studying the small fraction of the sample that is optically
visible, we infer a typical age of a few Myr for the low mass population. The
young stars are clustered, with about a third of them located in eight clusters
that are located within or near the LDN 935 dark cloud. Half of the YSOs are
located in regions with surface densities higher than 1000 YSOs / deg^2. The
Class I objects are more clustered than the Class II stars.Comment: 16 pages, 12 figures, ApJ In pres
The VISCACHA survey -- V. Rejuvenating three faint SMC clusters
We present the analysis of three faint clusters of the Small Magellanic Cloud
RZ82, HW42 and RZ158. We employed the SOAR telescope instrument SAM with
adaptive optics, allowing us to reach to V~23-24 mag, unprecedentedly, a depth
sufficient to measure ages of up to about 10-12Gyr. All three clusters are
resolved to their centres, and the resulting colour-magnitude diagrams (CMDs)
allow us to derive ages of 3.9, 2.6, and 4.8Gyr respectively. These results are
significantly younger than previous determinations (7.1, 5.0, and 8.3Gyr,
respectively), based on integrated photometry or shallower CMDs. We rule out
older ages for these clusters based on deep photometry and statistical
isochrone fitting. We also estimate metallicities for the three clusters of
[Fe/H]=-0.68, -0.57 and -0.90, respectively. These updated ages and
metallicities are in good agreement with the age-metallicity relation for the
bulk of SMC clusters. Total cluster masses ranging from ~7-11x10^3Mo were
estimated from integrated flux, consistent with masses estimated for other SMC
clusters of similar ages. These results reduce the number of SMC clusters known
to be older than about 5 Gyr and highlight the need of deep and spatially
resolved photometry to determine accurate ages for older, low-luminosity SMC
star clusters.Comment: Accepted for publication as MNRAS letter, 5 pages, 5 figure
The VISCACHA survey -- VII. Assembly history of the Magellanic Bridge and SMC Wing from star clusters
The formation scenario of the Magellanic Bridge during an encounter between
the Large and Small Magellanic Clouds Myr ago, as proposed by
-body models, would be imprinted in the chemical enrichment and kinematics
of its stars, and sites of ongoing star formation along its extension. We
present an analysis of 33 Bridge star clusters using photometry obtained with
the SOAR 4-m telescope equipped with adaptive optics for the VISCACHA survey.
We performed a membership selection and derived self-consistent ages,
metallicities, distances and reddening values via statistical isochrone
fitting, as well as tidal radii and integrated masses from structure analysis.
Two groups are clearly detected: 13 well-studied clusters older than the
Bridge, with Gyr and dex; and 15 clusters with
dex, probably formed in-situ. The old
clusters follow the overall age and metallicity gradients of the SMC, whereas
the younger ones are uniformly distributed along the Bridge. The main results
are as follows: we derive ages and metallicities for the first time for 9
and 18 clusters, respectively; we detect two metallicity dips in the
age-metallicity relation of the Bridge at Myr and Gyr ago
for the first time, possibly chemical signatures of the formation of the Bridge
and Magellanic Stream; we estimate a minimum stellar mass for the
Bridge of ; we confirm that all the young
Bridge clusters at are metal-rich dex.Comment: 15 pages, 13 figures + appendix. Accepted for publication in MNRA
Capturing protest in urban environments:The ‘police kettle’ as a territorial strategy
‘Kettling’ has emerged in recent decades as an established, if controversial, tactic of public order policing. Departing from a historical emphasis on dispersal, kettling instead acts to contain protesters within a police cordon for sustained periods of time. This article elaborates upon the spatial and temporal logics of kettling by investigating the conditions of is historical emergence. We argue that kettling should be understood as a territorial strategy that co-evolved in relation to forms of disruptive protest. Whereas techniques of crowd dispersal serve to diffuse a unified collective, ‘kettling’ aims to capture the volatile intensities of public dissent and exhaust its political energies. Drawing on police manuals, media coverage, accounts from activists and expert interviews, we show how the ‘kettle’ re-territorializes protest by acting on its spatio-temporal and affective constitution. By fabricating an inner outside of the urban milieu, freezing the time of collective mobilization and inducing debilitating affects such as fear and boredom, kettling intervenes into the scene of political subjectification that each congregation of protesting bodies seeks to fashion
Formation of a G-quadruplex at the BCL2 major breakpoint region of the t(14;18) translocation in follicular lymphoma
The t(14;18) translocation in follicular lymphoma is one of the most common chromosomal translocations. Most breaks on chromosome 18 are located at the 3′-UTR of the BCL2 gene and are mainly clustered in the major breakpoint region (MBR). Recently, we found that the BCL2 MBR has a non-B DNA character in genomic DNA. Here, we show that single-stranded DNA modeled from the template strand of the BCL2 MBR, forms secondary structures that migrate faster on native PAGE in the presence of potassium, due to the formation of intramolecular G-quadruplexes. Circular dichroism shows evidence for a parallel orientation for G-quadruplex structures in the template strand of the BCL2 MBR. Mutagenesis and the DMS modification assay confirm the presence of three guanine tetrads in the structure. 1H nuclear magnetic resonance studies further confirm the formation of an intramolecular G-quadruplex and a representative model has been built based on all of the experimental evidence. We also provide data consistent with the possible formation of a G-quadruplex structure at the BCL2 MBR within mammalian cells. In summary, these important features could contribute to the single-stranded character at the BCL2 MBR, thereby contributing to chromosomal fragility
Filament Depolymerization Can Explain Chromosome Pulling during Bacterial Mitosis
Chromosome segregation is fundamental to all cells, but the force-generating mechanisms underlying chromosome translocation in bacteria remain mysterious. Caulobacter crescentus utilizes a depolymerization-driven process in which a ParA protein structure elongates from the new cell pole, binds to a ParB-decorated chromosome, and then retracts via disassembly, pulling the chromosome across the cell. This poses the question of how a depolymerizing structure can robustly pull the chromosome that disassembles it. We perform Brownian dynamics simulations with a simple, physically consistent model of the ParABS system. The simulations suggest that the mechanism of translocation is “self-diffusiophoretic”: by disassembling ParA, ParB generates a ParA concentration gradient so that the ParA concentration is higher in front of the chromosome than behind it. Since the chromosome is attracted to ParA via ParB, it moves up the ParA gradient and across the cell. We find that translocation is most robust when ParB binds side-on to ParA filaments. In this case, robust translocation occurs over a wide parameter range and is controlled by a single dimensionless quantity: the product of the rate of ParA disassembly and a characteristic relaxation time of the chromosome. This time scale measures the time it takes for the chromosome to recover its average shape after it is has been pulled. Our results suggest explanations for observed phenomena such as segregation failure, filament-length-dependent translocation velocity, and chromosomal compaction
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