59 research outputs found
Novel fabrication technique for planar glass waveguides
A novel technique has been developed for the deposition of low-loss planar glass waveguides by directly spin coating from the liquid, thus overcoming the problems of reproducing glass stoichiometry when depositing from the vapour
A 1.9µm thulium doped lead germanate waveguide laser
Tm3+ doped lead germanate glass has already been shown to be a promising source of 1.9µm radiation using the 3H4 to 3H6 transition in a fibre geometry. The maximum vibrational energy of these glasses lies between that of silica and heavy metal fluoride glasses. This increases the radiative lifetime of the upper laser level in comparison to silicates while increasing the multiphonon non-radiative decay from the 3F4 pumping level into the upper laser level in comparison to fluorides. Thus the 1.9µm Tm3+ laser performance is enhanced in these glasses bringing fibre laser thresholds easily within reach of diode pumping. Recent work has also shown that such glasses give very low propagation loss guides (0.15 dB/cm) when implanted with He ions. Here we report lasing in a planar ion-implanted waveguide in Tm-doped lead germanate. This is the first report of lasing for thulium in any planar waveguide system and this is also the longest wavelength so far reported for such systems. This is also the first report of lasing in a glass host using ion-implantation as the means of waveguide fabrication
Floristic variations in a woody plant community along a trail in a Semideciduous Seasonal Forest, Viçosa, Minas Gerais State, Brazil
The global burden of cancer attributable to risk factors, 2010–19: a systematic analysis for the Global Burden of Disease Study 2019
BACKGROUND: Understanding the magnitude of cancer burden attributable to potentially modifiable risk factors is crucial for development of effective prevention and mitigation strategies. We analysed results from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019 to inform cancer control planning efforts globally. METHODS: The GBD 2019 comparative risk assessment framework was used to estimate cancer burden attributable to behavioural, environmental and occupational, and metabolic risk factors. A total of 82 risk–outcome pairs were included on the basis of the World Cancer Research Fund criteria. Estimated cancer deaths and disability-adjusted life-years (DALYs) in 2019 and change in these measures between 2010 and 2019 are presented. FINDINGS: Globally, in 2019, the risk factors included in this analysis accounted for 4·45 million (95% uncertainty interval 4·01–4·94) deaths and 105 million (95·0–116) DALYs for both sexes combined, representing 44·4% (41·3–48·4) of all cancer deaths and 42·0% (39·1–45·6) of all DALYs. There were 2·88 million (2·60–3·18) risk-attributable cancer deaths in males (50·6% [47·8–54·1] of all male cancer deaths) and 1·58 million (1·36–1·84) risk-attributable cancer deaths in females (36·3% [32·5–41·3] of all female cancer deaths). The leading risk factors at the most detailed level globally for risk-attributable cancer deaths and DALYs in 2019 for both sexes combined were smoking, followed by alcohol use and high BMI. Risk-attributable cancer burden varied by world region and Socio-demographic Index (SDI), with smoking, unsafe sex, and alcohol use being the three leading risk factors for risk-attributable cancer DALYs in low SDI locations in 2019, whereas DALYs in high SDI locations mirrored the top three global risk factor rankings. From 2010 to 2019, global risk-attributable cancer deaths increased by 20·4% (12·6–28·4) and DALYs by 16·8% (8·8–25·0), with the greatest percentage increase in metabolic risks (34·7% [27·9–42·8] and 33·3% [25·8–42·0]). INTERPRETATION: The leading risk factors contributing to global cancer burden in 2019 were behavioural, whereas metabolic risk factors saw the largest increases between 2010 and 2019. Reducing exposure to these modifiable risk factors would decrease cancer mortality and DALY rates worldwide, and policies should be tailored appropriately to local cancer risk factor burden
A novel maize-infecting mastrevirus from La Réunion Island
Despite extensive sampling, only one virus
belonging to the genus Mastrevirus of the family Geminiviridae,
maize streak virus (MSV), has until now been
detected in maize with maize streak disease (MSD)
symptoms. Here, we report for the first time a second,
highly divergent, mastrevirus isolated from two maize
plants displaying characteristic MSD-like symptoms,
sampled on the South-west Indian Ocean Island, La
Re´union. The two isolates shared \57 % genome-wide
identity with all other known mastreviruses. We propose
calling the new species Maize streak Re´union virus. The genus Mastrevirus of the family Geminiviridae contains
species with circular single-stranded DNA (ssDNA)
genomes of approximately 2.7 kb. Mastreviruses infect a
wide variety of monocotyledonous and dicotyledonous
hosts and are transmitted by leafhopper vectors. Monocotinfecting
mastreviruses have previously been found
throughout Africa (including the South-west Indian Ocean
islands: SWIO), Europe, Japan, Southeast Asia, the island
of Vanuatu, and Australia. Mastreviruses previously found
on SWIO islands such as La Re´union and Mauritius
include various maize streak virus (MSV) strains, sugarcane
streak Re´union virus (SSRV) and sugarcane streak
virus (SSV) [13, 19, 25, 26].
Here, we report the genome sequences of two isolates
(PR50 and PR52) belonging to a divergent mastrevirus
species from La Re´union. Leaves were sampled in Saint
Pierre (21.6161 S, 55.45784 E and 21.3206 S, 55.48536 E)
from two maize plants displaying chlorotic streaks along
leaf veins similar to those seen in MSV infections of maize
Extensive recombination–induced disruption of genetic interactions is highly deleterious but can be partially reversed by small numbers of secondary-recombination events
Although homologous recombination can potentially provide viruses with vastly more evolutionary options than are available
through mutation alone, there are considerable limits on the adaptive potential of this important evolutionary process. Primary
among these is the disruption of favorable coevolved genetic interactions that can occur following the transfer of foreign genetic
material into a genome. Although the fitness costs of such disruptions can be severe, in some cases they can be rapidly recouped
by either compensatory mutations or secondary recombination events. Here, we used a maize streak virus (MSV) experimental
model to explore both the extremes of recombination-induced genetic disruption and the capacity of secondary recombination
to adaptively reverse almost lethal recombination events. Starting with two naturally occurring parental viruses, we synthesized
two of the most extreme conceivable MSV chimeras, each effectively carrying 182 recombination breakpoints and containing
thorough reciprocal mixtures of parental polymorphisms. Although both chimeras were severely defective and apparently noninfectious,
neither had individual movement-, encapsidation-, or replication-associated genome regions that were on their own
“lethally recombinant.” Surprisingly, mixed inoculations of the chimeras yielded symptomatic infections with viruses with secondary
recombination events. These recombinants had only 2 to 6 breakpoints, had predominantly inherited the least defective
of the chimeric parental genome fragments, and were obviously far more fit than their synthetic parents. It is clearly evident,
therefore, that even when recombinationally disrupted virus genomes have extremely low fitness and there are no easily accessible
routes to full recovery, small numbers of secondary recombination events can still yield tremendous fitness gains
Inducible resistance to Maize streak virus
Maize streak virus (MSV), which causes maize streak disease (MSD), is the major viral pathogenic constraint on maize production in Africa. Type member of the Mastrevirus genus in the family Geminiviridae, MSV has a 2.7 kb, single-stranded circular DNA genome encoding a coat protein, movement protein, and the two replication-associated proteins Rep and RepA. While we have previously developed MSV-resistant transgenic maize lines constitutively expressing “dominant negative mutant” versions of the MSV Rep, the only transgenes we could use were those that caused no developmental defects during the regeneration of plants in tissue culture. A better transgene expression system would be an inducible one, where resistance-conferring transgenes are expressed only in MSV-infected cells. However, most known inducible transgene expression systems are hampered by background or “leaky” expression in the absence of the inducer. Here we describe an adaptation of the recently developed INPACT system to express MSV-derived resistance genes in cell culture. Split gene cassette constructs (SGCs) were developed containing three different transgenes in combination with three different promoter sequences. In each SGC, the transgene was split such that it would be translatable only in the presence of an infecting MSV’s replication associated protein. We used a quantitative real-time PCR assay to show that one of these SGCs (pSPLITrepIII-Rb-Ubi) inducibly inhibits MSV replication as efficiently as does a constitutively expressed transgene that has previously proven effective in protecting transgenic maize from MSV. In addition, in our cell-culture based assay pSPLITrepIII-Rb-Ubi inhibited replication of diverse MSV strains, and even, albeit to a lesser extent, of a different mastrevirus species. The application of this new technology to MSV resistance in maize could allow a better, more acceptable produc
Evidence of pervasive biologically functional secondary-structures within the genomes of eukaryotic single-stranded DNA viruses
Single-stranded DNA (ssDNA) viruses have genomes that are potentially capable of forming complex secondary structures
through Watson-Crick base pairing between their constituent nucleotides. A few of the structural elements formed by such base
pairings are, in fact, known to have important functions during the replication of many ssDNA viruses. Unknown, however, are
(i) whether numerous additional ssDNA virus genomic structural elements predicted to exist by computational DNA folding
methods actually exist and (ii) whether those structures that do exist have any biological relevance. We therefore computationally
inferred lists of the most evolutionarily conserved structures within a diverse selection of animal- and plant-infecting ssDNA
viruses drawn from the families Circoviridae, Anelloviridae, Parvoviridae, Nanoviridae, and Geminiviridae and analyzed these
for evidence of natural selection favoring the maintenance of these structures. While we find evidence that is consistent with purifying
selection being stronger at nucleotide sites that are predicted to be base paired than at sites predicted to be unpaired, we
also find strong associations between sites that are predicted to pair with one another and site pairs that are apparently coevolving
in a complementary fashion. Collectively, these results indicate that natural selection actively preserves much of the pervasive
secondary structure that is evident within eukaryote-infecting ssDNA virus genomes and, therefore, that much of this structure
is biologically functional. Lastly, we provide examples of various highly conserved but completely uncharacterized
structural elements that likely have important functions within some of the ssDNA virus genomes analyzed here
Bromus catharticus striate mosaic virus: a new mastrevirus infecting Bromus catharticus from Australia.
Although monocotyledonous-plant-infecting mastreviruses (in the family Geminiviridae) are known to cause economically significant crop losses in certain areas of the world, in Australia, they pose no obvious threat to agriculture. Consequently, only a few Australian monocot-infecting mastreviruses have been described, and only two have had their genomes fully sequenced. Here, we present the third full-genome sequence of an Australian monocot-infecting mastrevirus from Bromus catharticus belonging to a distinct species, which we have tentatively named Bromus catharticus striate mosaic virus (BCSMV). Although the genome of this new virus shares only 57.7% sequence similarity with that of its nearest known relative, Digitaria didactyla striate mosaic virus (DDSMV; also from Australia), it has features typical of all other known mastrevirus genomes. Phylogenetic analysis showed that both the full genome and each of its probable expressed proteins group with the two other characterised Australian monocot-infecting mastreviruses. Besides the BCSMV genome sequence revealing that Australian monocot-infecting mastrevirus diversity rivals that seen in Africa, it has enabled us, for the first, to time detect evidence of recombination amongst the Australian viruses. Specifically, it appears that DDSMV possesses a short intergenic region sequence that has been recombinationally derived from either BCSMV or a close relative that has not yet been identified
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