627 research outputs found
Unveiling the germination requirements for Cereus hildmannianus (Cactaceae), a potential new crop from southern and southeastern Brazil
Cereus hildmannianus K. Schum is a columnar cactus native to South and Southeast Brazil. The cultivation of this species seems justifiable for several reasons: its fruits are spineless and edible; it is not threatened with extinction; it naturally occurs in Pampa and Atlantic Forest under non-xeric conditions that may be unsuitable for the cultivation of other tropical cacti; and the plants are pollinator-dependent and so should benefit from native pollinators. This study aimed to test seed germination of C. hildmannianus with samples collected at three different localities in southern Brazil, as a necessary step preceding any attempts of management and domestication. Seeds were exposed to temperatures of 20° C, 25° C, 30° C and room temperature. The germinability, average germination time and synchronization index were calculated. All samples showed higher germinability at 20° C and 25° C. Seeds from Caçapava do Sul and Santiago showed significant variation in the synchronization index at 25° C and 30° C, respectively. Seeds from Porto Alegre had maximum germinability, indicating greater vigor. Our results show that the seeds of C. hildmannianus germinate well and thrive within a wide range of temperatures and that cultivation of the species from seed-raised plants should not be problematic
Diversity of gut microflora is required for the generation of B cell with regulatory properties in a skin graft model
B cells have been reported to promote graft rejection through alloantibody production. However, there is growing evidence that B cells can contribute to the maintenance of tolerance. Here, we used a mouse model of MHC-class I mismatched skin transplantation to investigate the contribution of B cells to graft survival. We demonstrate that adoptive transfer of B cells prolongs skin graft survival but only when the B cells were isolated from mice housed in low sterility "conventional" (CV) facilities and not from mice housed in pathogen free facilities (SPF). However, prolongation of skin graft survival was lost when B cells were isolated from IL-10 deficient mice housed in CV facilities. The suppressive function of B cells isolated from mice housed in CV facilities correlated with an anti-inflammatory environment and with the presence of a different gut microflora compared to mice maintained in SPF facilities. Treatment of mice in the CV facility with antibiotics abrogated the regulatory capacity of B cells. Finally, we identified transitional B cells isolated from CV facilities as possessing the regulatory function. These findings demonstrate that B cells, and in particular transitional B cells, can promote prolongation of graft survival, a function dependent on licensing by gut microflora
Approximation algorithms for maximally balanced connected graph partition
Given a simple connected graph , we seek to partition the vertex
set into non-empty parts such that the subgraph induced by each part is
connected, and the partition is maximally balanced in the way that the maximum
cardinality of these parts is minimized. We refer this problem to as {\em
min-max balanced connected graph partition} into parts and denote it as
{\sc -BGP}. The general vertex-weighted version of this problem on trees has
been studied since about four decades ago, which admits a linear time exact
algorithm; the vertex-weighted {\sc -BGP} and {\sc -BGP} admit a
-approximation and a -approximation, respectively; but no
approximability result exists for {\sc -BGP} when , except a
trivial -approximation. In this paper, we present another
-approximation for our cardinality {\sc -BGP} and then extend it to
become a -approximation for {\sc -BGP}, for any constant .
Furthermore, for {\sc -BGP}, we propose an improved -approximation.
To these purposes, we have designed several local improvement operations, which
could be useful for related graph partition problems.Comment: 23 pages, 7 figures, accepted for presentation at COCOA 2019 (Xiamen,
China
Rapid Evolution in the Most Luminous Galaxies During the First 900 Million Years
The first 900 million years (Myr) to redshift z~6 (the first seven per cent
of the age of the Universe) remains largely unexplored for the formation of
galaxies. Large samples of galaxies have been found at z~6, but detections at
earlier times are uncertain and unreliable. It is not at all clear how galaxies
built up from the first stars when the Universe was ~300 Myr old (z~12-15) to
z~6, just 600 Myr later. Here we report the results of a search for galaxies at
z~7-8, about 700 Myr after the Big Bang, using the deepest near-infrared and
optical images ever taken. Under conservative selection criteria we find only
one candidate galaxy at z~7-8, where ten would be expected if there were no
evolution in the galaxy population between z~7-8 and z~6. Using less
conservative criteria, there are four candidates, where 17 would be expected
with no evolution. This demonstrates that very luminous galaxies are quite rare
700 Myr after the Big Bang. The simplest explanation is that the Universe is
just too young to have built up many luminous galaxies at z~7-8 by the
hierarchical merging of small galaxies.Comment: Accepted for publication in Nature, 20 pages, 5 figures, 2 tables
(includes Supplementary Information), replaced to match version in pres
Deconstructing the lesbian, gay, bisexual, transgender victim of sex trafficking: Harm, exceptionality and religion–sexuality tensions
Contrary to widespread belief, sex trafficking also targets lesbian, gay, bisexual, transgender (LGBT) communities. Contemporary social and political constructions of victimhood lie at the heart of regulatory policies on sex trafficking. Led by the US Department of State, knowledge about LGBT victims of trafficking constitutes the newest frontier in the expansion of criminalization measures. These measures represent a crucial shift. From a burgeoning range of preemptive measures enacted to protect an amorphous class of ‘all potential victims’, now policies are heavily premised on the risk posed by traffickers to ‘victims of special interest’. These constructed identities, however, are at odds with established structures. Drawing on a range of literatures, the core task of this article is to confront some of the complexities and tensions surrounding constructions of LGBT trafficking victims. Specifically, the article argues that discourses of ‘exceptional vulnerability’ and the polarized notions of ‘innocence’ and ‘guilt’ inform hierarchies of victimhood. Based on these insights, the article argues for the need to move beyond monolithic understandings of victims, by reframing the politics of harm accordingly
Current trends in the surgical management of Dupuytren’s disease in Europe: an analysis of patient charts
Introduction: Dupuytren's disease (DD) causes progressive digital flexion contracture and is more common in men of European descent. Methods: Orthopaedic and plastic surgeons in 12 European countries (the Czech Republic, Denmark, Finland, France, Germany, Hungary, Italy, The Netherlands, Poland, Spain, Sweden and the UK) with >3 and <30 years experience reviewed the medical charts of five consecutive patients they had treated surgically for DD in 2008. Descriptive statistics are reported. Results: In total, 3,357 patient charts were reviewed. Mean (standard deviation) patient age was 61.9 (10.2) years; 81% were men. At the time of the procedure, 11% of patients were at Tubiana stage Ia (0-20° total flexion); 30%, stage Ib (21-45°); 34%, stage II (46-90°); 17%, stage III (91-135°); and 5%, stage IV (&135°). Percutaneous needle fasciotomy was performed in 10%, fasciotomy in 13%, fasciectomy in 69% and dermofasciectomy (DF) in 6% of patients. After surgery, fingers improved a mean of 1.9 Tubiana stages, and 54% of patients had no nodules or contracture. The rate of reported complications during the procedure was 4% overall (11% in patients undergoing DF). The most common postoperative complications reported were haematoma (8%), wound healing complications (6%) and pain (6%). No postoperative complications were reported in 77% of patients. Conclusions: In this European study of more than 3,000 patients with DD, most patients were diagnosed at Tubiana stage I or II, the majority received fasciectomy and more than half had no nodules or contracture remaining after surgery
Transit Timing and Duration Variations for the Discovery and Characterization of Exoplanets
Transiting exoplanets in multi-planet systems have non-Keplerian orbits which
can cause the times and durations of transits to vary. The theory and
observations of transit timing variations (TTV) and transit duration variations
(TDV) are reviewed. Since the last review, the Kepler spacecraft has detected
several hundred perturbed planets. In a few cases, these data have been used to
discover additional planets, similar to the historical discovery of Neptune in
our own Solar System. However, the more impactful aspect of TTV and TDV studies
has been characterization of planetary systems in which multiple planets
transit. After addressing the equations of motion and parameter scalings, the
main dynamical mechanisms for TTV and TDV are described, with citations to the
observational literature for real examples. We describe parameter constraints,
particularly the origin of the mass/eccentricity degeneracy and how it is
overcome by the high-frequency component of the signal. On the observational
side, derivation of timing precision and introduction to the timing diagram are
given. Science results are reviewed, with an emphasis on mass measurements of
transiting sub-Neptunes and super-Earths, from which bulk compositions may be
inferred.Comment: Revised version. Invited review submitted to 'Handbook of
Exoplanets,' Exoplanet Discovery Methods section, Springer Reference Works,
Juan Antonio Belmonte and Hans Deeg, Eds. TeX and figures may be found at
https://github.com/ericagol/TTV_revie
Hydropower plans in eastern and southern Africa increase risk of concurrent climate-related electricity supply disruption
Hydropower comprises a significant and rapidly expanding proportion of electricity production in eastern and southern Africa. In both regions, hydropower is exposed to high levels of climate variability and regional climate linkages are strong, yet an understanding of spatial interdependences is lacking. Here we consider river basin configuration and define regions of coherent rainfall variability using cluster analysis to illustrate exposure to the risk of hydropower supply disruption of current (2015) and planned (2030) hydropower sites. Assuming completion of the dams planned, hydropower will become increasingly concentrated in the Nile (from 62% to 82% of total regional capacity) and Zambezi (from 73% to 85%) basins. By 2030, 70% and 59% of total hydropower capacity will be located in one cluster of rainfall variability in eastern and southern Africa, respectively, increasing the risk of concurrent climate-related electricity supply disruption in each region. Linking of nascent regional electricity sharing mechanisms could mitigate intraregional risk, although these mechanisms face considerable political and infrastructural challenges
The Rossiter-McLaughlin effect in Exoplanet Research
The Rossiter-McLaughlin effect occurs during a planet's transit. It provides
the main means of measuring the sky-projected spin-orbit angle between a
planet's orbital plane, and its host star's equatorial plane. Observing the
Rossiter-McLaughlin effect is now a near routine procedure. It is an important
element in the orbital characterisation of transiting exoplanets. Measurements
of the spin-orbit angle have revealed a surprising diversity, far from the
placid, Kantian and Laplacian ideals, whereby planets form, and remain, on
orbital planes coincident with their star's equator. This chapter will review a
short history of the Rossiter-McLaughlin effect, how it is modelled, and will
summarise the current state of the field before describing other uses for a
spectroscopic transit, and alternative methods of measuring the spin-orbit
angle.Comment: Review to appear as a chapter in the "Handbook of Exoplanets", ed. H.
Deeg & J.A. Belmont
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