Harnessing ultraconfined graphene plasmons to probe the electrodynamics of superconductors.

We show that the Higgs mode of a superconductor, which is usually challenging to observe by far-field optics, can be made clearly visible using near-field optics by harnessing ultraconfined graphene plasmons. As near-field sources we investigate two examples: graphene plasmons and quantum emitters. In both cases the coupling to the Higgs mode is clearly visible. In the case of the graphene plasmons, the coupling is signaled by a clear anticrossing stemming from the interaction of graphene plasmons with the Higgs mode of the superconductor. In the case of the quantum emitters, the Higgs mode is observable through the Purcell effect. When combining the superconductor, graphene, and the quantum emitters, a number of experimental knobs become available for unveiling and studying the electrodynamics of superconductors.

Lung abscess following ventilator-associated pneumonia during COVID-19: a retrospective multicenter cohort study.

BACKGROUND: Patients undergoing mechanical ventilation (MV) for COVID-19 exhibit an increased risk of ventilator-associated pneumonia (VAP). The occurrence of lung abscesses following VAP in these patients has been poorly studied. We aimed to describe the incidence, characteristics, risk factors and prognosis of lung abscesses complicating VAP after COVID-19. METHODS: We conducted an observational, retrospective study in three French intensive care units. Patients admitted for acute respiratory failure with a confirmed SARS-CoV-2 PCR and requiring MV for more than 48 h were included. RESULTS: Among the 507 patients included, 326 (64%) had a documented VAP. Of these, 23 (7%) developed a lung abscess. Enterobacterales (15/23, 65%) were the main documentation, followed by non-fermenting Gram-negative bacilli (10/23, 43%) and Gram-positive cocci (8/23, 35%). Lung abscesses were mainly plurimicrobial (15/23, 65%). In multivariate analysis, a plurimicrobial 1st VAP episode (OR (95% CI) 2.93 (1.16-7.51); p = 0.02) and the use of hydrocortisone (OR (95% CI) 4.86 (1.95-12.1); p = 0.001) were associated with lung abscess development. Intensive care unit (ICU) mortality of patients with lung abscesses reached 52%, but was not significantly higher than for patients with VAP but no lung abscess. Patients with lung abscesses had reduced ventilator-free days at day 60, a longer duration of MV and ICU stay than patients with VAP but no lung abscess (respectively, 0 (0-3) vs. 16 (0-42) days; p < 0.001, 49 (32-73) vs. 25 (11-41) days; p < 0.001, 52 (36-77) vs. 28 (16-47) days; p < 0.001). CONCLUSIONS: Lung abscessing pneumonia is not uncommon among COVID-19 patients developing VAP. A plurimicrobial first VAP episode and the use of hydrocortisone are independently associated with this complication. In COVID-19 patients with persistent VAP, a chest CT scan investigating the evolution toward lung abscess should be considered.

Potential Impact of Populations Drift on Botrytis Occurrence and Resistance to Multi- and Single-Site Fungicides in Florida Southern Highbush Blueberry Fields.

Incidence of blossom blight and Botrytis fruit rot (BFR), caused by Botrytis cinerea, on two southern highbush blueberry cultivars was evaluated in several blueberry fields grown in the vicinity (BB-Str(+)) or not (BB-Str(-)) of strawberry fields in central Florida. Blossom blight and BFR incidence were higher in BB-Str(+) fields in 2014 and significantly higher in 2015 compared to BB-Str(-) fields. In total, 613 B. cinerea isolates (i.e., 181 and 432 isolates from BB-Str(-) and BB-Str(+) fields, respectively) were collected. The isolates were evaluated for sensitivity to eight single-site and one multisite fungicides using a spore germination and a germ tube elongation assay. Overall, 5, 15, 24, 28, 54, and 93% of isolates collected from BB-Str(-) were resistant to penthiopyrad, cyprodinil, boscalid, fenhexamid, pyraclostrobin, and thiophanate-methyl, respectively. Respective resistance frequencies in BB-Str(+) isolates were 10, 30, 65, 66, 89, and 99%. Resistance frequencies for all fungicides were always higher in BB-Str(+) fields compared to BB-Str(-) fields. Isolates exhibiting resistance to six or five fungicides simultaneously were predominant (50 to 70%) in blueberry fields regardless if they were grown in the vicinity of strawberry fields or not. Among 308 and 305 B. cinerea isolates tested in 2014 and 2015, 41.8 and 47.1%, respectively, showed reduced sensitivity to the multisite fungicide captan. The lower label rate of captan applied preventively did not control isolates with reduced sensitivity on detached blueberry fruit. These findings suggest a potential population flow between strawberry and blueberry fields that may impact blossom blight and gray mold development in blueberry fields. The relatively lower fungicide input applied to blueberry fields compared with strawberry fields seems to be sufficient to select for resistance and multiple-resistant phenotypes in B. cinerea populations in blueberry.

Detection of Colletotrichum acutatum Sensu Lato on Strawberry by Loop-Mediated Isothermal Amplification.

Colletotrichum acutatum, one of the most economically damaging pathogens of strawberry, is the primary causal agent of anthracnose fruit rot (AFR). A key challenge in managing AFR is detecting the pathogen on asymptomatic plants. To meet this need, a loop-mediated isothermal amplification (LAMP) assay was developed that incorporated two sets of primers: LITSG1, targeted on the intergenic transcribed spacer (ITS) region of ribosomal DNA, and Ltub2, on the ß-tubulin 2 gene. In pure culture assays, Ltub2 was specific for detection of C. acutatum, whereas LITSG1 detected C. acutatum and two additional anthracnose pathogens, C. gloeosporioides and C. fragariae. LITSG1 had 10-fold lower detection threshold (20 pg of mycelial DNA) than Ltub2 (200 pg mycelial DNA) in detection of C. acutatum from pure culture. For detection on asymptomatic leaves, two protocols for dislodging C. acutatum for DNA extraction were compared: i) the sonicate-agitate (SA) method and ii) the freeze-incubate-sonicate-agitate (FISA) method, which initially freezes tissues, followed by 2 days of incubation at 26°C in darkness, and then, sonication and agitation. Both methods were used for greenhouse-grown plant leaves that had been spray inoculated with serial dilutions ranging from 1.5 × 106 to 1.5 conidia ml-1. The FISA method produced more repeatable results than the SA method. For the FISA method, detection limits (expressed as initial inoculum concentrations) using LITSG1 and Ltub2 were 1.5 × 101 and 1.5 × 102 conidia ml-1, respectively. For composite samples comprised of inoculated (1.5 × 106 conidia ml-1) and noninoculated leaves of greenhouse-grown strawberry, the two sets of LAMP primers were compared using the SA method. Primer set LITSG1 consistently detected the pathogen from a single inoculated leaf in bulk samples of 50 or fewer pathogen-free leaves, whereas Ltub2 consistently detected one inoculated leaf in 20 or fewer pathogen-free leaves. Using primer set LITSG1, FISA was more sensitive than SA for detecting C. acutatum on leaves of field-grown plants from Florida. In an Iowa field trial using the FISA method, both primer sets detected C. acutatum in samples of asymptomatic leaves 6 days before fruit symptoms appeared. The results indicate that the LAMP assay has potential to provide a simplified method for detection of C. acutatum on asymptomatic strawberry plants.

Genetic variation and gains in resistance of strawberry to Colletotrichum gloeosporioides.

Anthracnose crown rot is an important disease of strawberry primarily caused by Colletotrichum gloeosporioides in Florida and North Carolina. Information on the magnitude of additive and nonadditive genetic variation is required to define breeding strategies and to estimate potential genetic gains. However, little is known about the genetic control of resistance and its utility in breeding. Our objectives were to obtain estimates of heritabilities and of components of genetic variances, genotype-environment interactions, and gains for resistance, and to examine the effects of locations and transplant types on the estimates. An incomplete diallel mating design generated 42 full-sib families, which were propagated in plugs from seed (seedling tests) and as bare-root runner plants (clonal tests) of different genotypes of the same families. Both seedlings and clones were inoculated with C. gloeosporioides under field conditions in North Carolina and Florida during the 2010-11 season. Narrow-sense heritability (h(2)) and broad-sense heritability (H(2)) for both clones and seedlings were higher at the North Carolina location (h(2) = 0.34 to 0.62 and H(2) = 0.46 to 0.85) than at the Florida location (h(2) = 0.16 to 0.22 and H(2) = 0.37 to 0.46). Likewise, the seedling tests showed higher genetic control than the clonal tests at both locations. Estimates of dominance variance were approximately one-third of the additive variance at North Carolina and were even larger at Florida. Epistasis was negative at both locations and assumed zero for heritability (H(2)) calculations. Genotype-environment interactions were different by transplant type, suggesting rank changes across locations. 'Pelican' was the most resistant parent at both locations, followed by 'NCH09-68' at the NC location and 'Winter Dawn' at the Florida location. Selection and deployment of the most resistant clone within each of the five best families is estimated to produce average genetic gains of 53.0 and 73.7% at the North Carolina and Florida locations, respectively.

First Report on Resistance to Pyraclostrobin, Thiophanate-methyl, Fenhexamid and Boscalid in Botrytis cinerea from Eucalyptus Seedlings in Florida Greenhouses.

Botryotinia fuckeliana de Bary (anamorph Botrytis cinerea Pers.) is an ubiquitous plant pathogen causing gray mold disease on more than 200 crops grown in the field or in greenhouses. Eucalyptus seedlings originating from three different greenhouses showing stem lesions were submitted to the Gulf Coast Research and Education Center Disease Clinic in June 2012. Ten single spore isolates of B. cinerea were obtained and tested for sensitivity using spore germination and germ tube elongation assays described previously (4). Fungicides tested were pyraclostrobin at 100 µg/ml (Cabrio, BASF, Research Triangle Park, NC), thiophanate-methyl at 100 µg/ml (Topsin-M, UPI, King of Prussia, PA), fenhexamid at 1 and 50 µg/ml (Elevate, Arysta Life Sciences, Cary, NC), fludioxonil at 0.1 and 10 µg/ml (Medallion, Syngenta Crop Protection, Research Triangle Park, NC), and iprodione at 5 and 50 µg/ml (Rovral, Bayer CropScience, Greensboro, NC) on 1% malt extract agar (MEA, 10 g malt extract and 15 g agar), and to cyprodinil at 1 and 25 µg/ml (Vanguard, Syngenta Crop Protection) on 0.5% sucrose agar (4). Sensitivity to the succinate dehydrogenase inhibitors (SDHIs) boscalid at 5 µg/ml (Endura, BASF), penthiopyrad at 1 and 3 µg/ml (Fontelis, DuPont Crop Protection, Willington, DE), and fluopyram at 3 µg/ml (Luna Privilege, Bayer CropScience) was evaluated on yeast bacto acetate agar (YBA) (3). The discriminatory dose for boscalid was adapted from (2) whereas those used for penthiopyrad and fluopyram were developed in this study. Isolates were grown on malt yeast extract agar for 7 to 10 days and spore suspensions were prepared in sterile distilled water and diluted to 106 conidia/ml. Respective media in 9-cm petri dishes were seeded with 7-µl droplets from each isolate allowing testing for all isolates on one plate. Two plates were used for each fungicide and sensitivity tests were repeated twice. Germination and germ tube growth were assessed microscopically after 16 to 24 h incubation at 22°C. The frequency of isolates resistant to two, three, and four fungicides was 90, 60, and 10%, respectively. Nine isolates (90%) were resistant to thiophanate-methyl and pyraclostrobin, simultaneously, whereas six (60%) and two isolates (20%) were resistant to boscalid and fenhexamid, respectively. All boscalid-resistant isolates were also resistant to pyraclostrobin and thiophanate-methyl, but one fenhexamid-resistant isolate was sensitive to the other three fungicides. Eight isolates that germinated at 5 µg/ml iprodione but not at 50 µg/ml were considered sensitive. All isolates were sensitive to the SDHIs penthiopyrad and fluopyram as well as to cyprodinil and fludioxonil. To our knowledge, this is the first report of resistance to pyraclostrobin, thiophanate-methyl, fenhexamid, and boscalid in B. cinerea from eucalyptus seedlings in Florida. The absence of resistance to fludioxonil and iprodione is likely because these fungicides are not registered in nurseries as well as fluopyram and penthiopyrad which were developed only recently. Management practices should be developed to limit the selection and spread of additional resistant populations in eucalyptus nurseries as has occurred in Florida strawberries where multi-fungicide resistance is widespread (1). References: (1) A. Amiri et al. Plant Dis. 97:393, 2013. (2) M. Leroch et al. Appl. Environ. Microbiol. 79:159, 2013. (3) G. Stammler and J. Speakman. J. Phytopathol. 154:508, 2006. (4) R. W. S. Weber and M. Hahn. J. Plant Dis. Prot. 118:17, 2011.

Phenotypic Characterization of Multifungicide Resistance in Botrytis cinerea Isolates from Strawberry Fields in Florida.

Chemical control has always been essential for the management of gray mold, caused by Botrytis cinerea, to ensure sustainable strawberry production. However, lack of knowledge about actual resistance development may have disastrous consequences and lead to severe epidemics such as the one that affected several strawberry fields in 2012 in Florida. In this study, we tested 392 isolates collected from Florida strawberry fields between 2010 and 2012 for their sensitivity to boscalid (Bosc), a succinate dehydrogenase inhibitor (SdhI); pyraclostrobin, a quinone outside inhibitor (QoI); boscalid + pyraclostrobin (Pristine); fenhexamid, a hydroxyanilide (Hyd); pyrimethanil and cyprodinil, anilinopyrimidines; fludioxonil, a phenylpyrrole; and fludioxonil + cyprodinil (Switch). The respective resistance frequencies for boscalid, pyraclostrobin, Pristine, fenhexamid, cyprodinil, and pyrimethanil were 85.4, 86.5, 86.0, 44.4, 52.7, and 59.5%. Overall, 17.8 and 19.8% of isolates showed reduced sensitivity to fludioxonil and Switch, respectively. All fungicides sprayed preventively on detached strawberry fruit failed to control isolates with high levels of resistance to each fungicide except for fludioxonil and Switch. Four phenotypes with multifungicide resistance (MFR) were detected in B. cinerea populations from Florida. Isolates resistant to one fungicide (FR1), two (MFR2), three (MFR3), and four (MFR4) fungicides from different chemical groups represented 5.9, 28.6, 41.8, and 23.7% of the total resistant population, respectively. The MFR3 isolates were predominant and contained two subpopulations, the Bosc-QoI-APR isolates (56.5%) and the Bosc-QoI-HydR isolates (40.6%). In addition to reporting on very highly resistant populations to boscalid and QoI fungicides, we show evidence for a widespread multifungicide resistance to B. cinerea that warrants immediate implementation of novel management strategies to impede the development of more resistant populations.

Severe Outbreak of Downy Mildew Caused by Plasmopara obducens on Impatiens walleriana in Florida.

Impatiens, Impatiens walleriana Hook.f., are grown as an ornamental crop in greenhouse and shade house production in Florida and other regions of the United States. Downy mildew on impatiens was detected from numerous landscapes (Manatee, Hillsborough, Collier, Hendry, Broward, Palm Beach, and Miami-Dade counties) in the winter of 2012. Incidence reached nearly 100% on many affected landscape plantings. Symptoms initially appeared as yellowing on the lower leaves and were typically vein-delineated, although in some cases the entire leaf was affected. Diseased plants later wilted and infected leaves abscised from the stem. A white, downy growth was apparent on the abaxial leaf surface. Microscopic observation revealed coenocytic mycelium with sporangiophores that were hyaline, thin-walled, and had slightly swollen bases. Branches of sporangiophores were monopodial and formed right angles to the supporting branches. Sporangia were hyaline and obvoid with a single pore on the distal ends that was mostly flat. Sporangia measured 19 to 22.5 × 13 to 17 µm. Oospores were observed in stem and leaf tissue. Leaves of 10 potted impatiens plants, I. walleriana 'Super Elfin XP Coral' and 'Super Elfin XP White,' were inoculated with a suspension containing 1 × 105 sporangia/ml and sprayed till runoff (approximately 20 ml per plant) with a handheld pressurized Ulva sprayer. Plants were maintained outside in a shade house under 73% shade where the daytime temperatures averaged 24°C and RH averaged 74% and nighttime temperature averaged 18°C with an average of 91% RH. Ten non-inoculated impatiens plants served as controls. After 10 days, symptoms typical of downy mildew occurred on 100% of the inoculated impatiens plants and sporulation was confirmed microscopically. The non-inoculated control plants remained healthy. The 5' end of the large ribosomal subunit gene (762 bp) from two isolates, one collected in Hillsborough County and one from Miami-Dade County, was amplified by PCR (primers NL1-GCATATCAATAAGCGGAGGAAAAG and NL4-GGTCCGTGTTTCAAGACGG) and sequenced bi-directionally (1,2,3). The consensus sequence from both isolates was identical and it was deposited into GenBank (Accession No. JX217746). Sequence data matched (99% homology) with Plasmopara obducens reported on I. walleriana in Europe and Australia (1,2). To our knowledge, this is the first report of downy mildew on I. walleriana in Florida (4). The disease has made a major impact on impatiens in landscapes throughout Florida and will likely continue to affect future production. References: (1) A. Bulajic et. al. Plant Dis. 95:491, 2011. (2) J. H. Cunnington et. al. Plant Pathol. 57:371, 2008. (3) K. O'Donnell. Curr. Genet. 22:213, 1992. (4) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, 1989.

Influence of salivary acquired pellicle on colour changes and minerals content of dentine after application of silver diamine fluoride followed by potassium iodide.

PURPOSE: This study evaluated whether the presence of the salivary acquired pellicle (AP) had any effect on the dentin's darkening and on the caries arresting effect after the use of SDF + KI, in a cariogenic challenge. METHODS: Human dentin specimens were standardised, submitted to artificial caries lesion formation, and divided into five groups (n = 20): C: control group-no treatment, SDF: 38% SDF, APSDF: SDF 38% and AP, KISDF: 38% SDF and KI, and APKISDF: 38% SDF, KI and AP, that were submitted to pH cycling. Colour evaluation (CIE L*a*b* system) and surface hardness were performed before and after the treatments/pH cycling. RESULTS: SDF and APSDF groups showed no difference in colour. KISDF and APKISDF groups showed significantly different colours than the groups without KI. SDF, APSDF, and APKISDF groups had less mineral loss than C and KISDF. SDF, APSDF, and APKISDF revealed significantly greater mineral recovery, compared to KISDF and C. CONCLUSION: The AP did not influence the dentin´s colour after SDF + KI, but had a protective role in modulating the dentin´s mineral gain/loss. KI used after SDF decreased the dentin´s darkening, and did not interfere with the dentin de/remineralization process.

Use of Leaf Wetness and Temperature to Time Fungicide Applications to Control Botrytis Fruit Rot of Strawberry in Florida.

Botrytis fruit rot (BFR), caused by Botrytis cinerea, is a major disease of strawberry in Florida and is generally controlled by weekly fungicide applications. In this study, disease control programs using fungicides applied on a weekly basis were compared with applications based on three previously published models that correlated disease incidence with weather variables. Field trials were conducted for three seasons on two cultivars, 'Sweet Charlie' and 'Strawberry Festival'. Different thresholds for predicted BFR incidence were evaluated for triggering fungicide applications for the three models. BFR incidence in nontreated control plots of Sweet Charlie and Strawberry Festival was 12.4 and 3.5%, respectively, in 2006-07, 4.2 and 0.8% in 2007-08, and 1.3 and 0.5% in 2008-09. The model of Bulger and associates, with a threshold for disease flower incidence (INFBu) of 0.50, triggered half or fewer fungicide applications compared with a calendar-standard grower program, without significantly increasing BFR incidence or reducing yield. The model of Broome and associates, at a predicted fruit disease incidence threshold (INFBr) of 0.62, performed well but required more fungicide applications than the Bulger model (INFBu ≥ 0.50). The model of Xu and associates, based on field data to predict the incidence of diseased flowers, required more fungicide applications without improving disease control. Use of higher thresholds resulted in fewer applications but increased disease incidence in some cases. The Bulger model utilizing leaf wetness and temperature during the wetness period as input variables and a threshold of INFBu of 0.50 can be used effectively in a disease-forecasting system to time fungicide treatments, and greatly reduced the number of applications without loss of disease control or yield.

Use of Leaf Wetness and Temperature to Time Fungicide Applications to Control Anthracnose Fruit Rot of Strawberry in Florida.

Anthracnose fruit rot (AFR), caused by Colletotrichum acutatum, is a major disease of strawberry in Florida and is generally controlled by weekly fungicide applications. More than 20 applications may be made during the growing season, most commonly using captan and the quinone-outside inhibitors. Field experiments were conducted for three seasons on a susceptible and a partially resistant cultivar to evaluate the effectiveness of timing fungicide applications for managing AFR based on a previously published model by Wilson and associates that uses leaf wetness duration and temperature to predict fruit infection by C. acutatum under controlled conditions. For most treatments, rules were established where captan was applied when the predicted proportion of fruit infected (INF) from the model exceeded 0.15 and pyraclostrobin was applied when INF exceeded 0.5. For one model-timed treatment where captan and pyraclostrobin were applied before symptoms first appeared in the field, disease control was as good as the treatment where calendar weekly applications were made and the model-timed treatment utilized 47% fewer sprays. In treatments where fungicide application began after symptom appearance, the number of applications was reduced further but disease control was 40% less effective. Model-timed fungicide treatments that included pyraclostrobin gave better control than the treatments using captan alone. The model relating leaf wetness and temperature to predict AFR infection can be used effectively in a disease-forecasting system to time fungicide treatments and greatly reduce the number of applications without loss of disease control or yield.

First Report of Guignardia citricarpa Associated with Citrus Black Spot on Sweet Orange (Citrus sinensis) in North America.

In March 2010, citrus black spot symptoms were observed on sweet orange trees in a grove near Immokalee, FL. Symptoms observed on fruit included hard spot, cracked spot, and early virulent spot. Hard spot lesions were up to 5 mm, depressed with a chocolate margin and a necrotic, tan center, often with black pycnidia (140 to 200 µm) present. Cracked spot lesions were large (15 mm), dark brown, with diffuse margins and raised cracks. In some cases, hard spots formed in the center of lesions. Early virulent spot lesions were small (up to 7 mm long), bright red, irregular, indented, and often with many pycnidia. In addition, small (2 to 3 mm), elliptical, reddish brown leaf lesions with depressed tan centers were observed on some trees with symptomatic fruit. Chlorotic halos appeared as they aged. Most leaves had single lesions, occasionally up to four per leaf. Tissue pieces from hard spots and early virulent spots were placed aseptically on potato dextrose agar (PDA), oatmeal agar, or carrot agar and incubated with 12 h of light and dark at 24°C. Cultures that grew colonies within a week were discarded. Fourteen single-spore cultures were obtained from the isolates that grew slower than the Guignardia mangiferae reference cultures, although pycnidia formed more rapidly in the G. mangiferae cultures (1). No sexual structures were observed. Cultures on half-PDA were black and cordlike with irregular margins with numerous pycnidia, often bearing white cirrhi after 14 days. Conidia (7.1 to 7.8 × 10.3 to 11.8 µm) were hyaline, aseptate, multiguttulate, ovoid with a flattened base surrounded by a hyaline matrix (0.4 to 0.6 µm) and a hyaline appendage on the rounded apex, corresponding to published descriptions of G. citricarpa (anomorph Phyllosticta citricarpa) (1). A yellow pigment was seen in oatmeal agar surrounding G. citricarpa, but not G. mangiferae colonies as previously reported (1,2). DNA was extracted from lesions and cultures and amplified with species-specific primers (2). DNA was also extracted from G. mangiferae and healthy citrus fruit. The G. citricarpa-specific primers produced a 300-bp band from fruit lesions and pure cultures. G. mangiferae-specific primers produced 290-bp bands with DNA from G. mangiferae cultures. The internally transcribed spacer (ITS) of the rRNA gene, translation-elongation factor (TEF), and actin gene regions were sequenced from G. citricarpa isolates and deposited in GenBank. These sequences had 100% homology with G. citricarpa ITS sequences from South Africa and Brazil, 100% homology with TEF, and 99% homology with actin of a Brazilian isolate. Pathogenicity tests with G. citricarpa were not done because the organism infects immature fruit and has an incubation period of at least 6 months (3). In addition, quarantine restrictions limit work with the organism outside a contained facility. To our knowledge, this is the first report of black spot in North America. The initial infested area was ~57 km2. The disease is of great importance to the Florida citrus industry because it causes serious blemishes and significant yield reduction, especially on the most commonly grown 'Valencia' sweet orange. Also, the presence of the disease in Florida may affect market access because G. citricarpa is considered a quarantine pathogen by the United States and internationally. References: (1) R. P. Baayen et al. Phytopathology 92:464, 2002. (2) N. A. Peres et al. Plant Dis. 91:525, 2007 (3) R. F. Reis et al. Fitopath Bras. 31:29, 2006.

Wannier excitons confined in hexagonal boron nitride triangular quantum dots.

With the ever-growing interest in quantum computing, understanding the behavior of excitons in monolayer quantum dots has become a topic of great relevance. In this paper, we consider a Wannier exciton confined in a triangular quantum dot of hexagonal boron nitride. We begin by outlining the adequate basis functions to describe a particle in a triangular enclosure, analyzing their degeneracy and symmetries. Afterwards, we discuss the excitonic Hamiltonian inside the quantum dot and study the influence of the quantum dot dimensions on the excitonic states.

Laser induced enhanced coupling between photons and squeezed magnons in antiferromagnets.

In this paper we consider a honeycomb antiferromagnet subject to an external laser field. Obtaining a time-independent effective Hamiltonian, we find that the external laser renormalizes the exchange interaction between the in-plane components of the spin-operators, and induces a synthetic Dzyaloshinskii-Moria interaction (DMI) between second neighbors. The former allows the control of the magnon dispersion's bandwidth and the latter breaks time-reversal symmetry inducing non-reciprocity in momentum space. The eigen-excitations of the system correspond to squeezed magnons whose squeezing parameters depend on the properties of the laser. When studying how these spin excitations couple with cavity photons, we obtain a coupling strength which can be enhanced by an order of magnitude via careful tuning of the laser's intensity, when compared to the case where the laser is absent. The transmission plots through the cavity are presented, allowing the mapping of the magnons' dispersion relation.

Excitonic instability in transition metal dichalcogenides.

When transition-metal dichalcogenide monolayers lack inversion symmetry, their low-energy single particle spectrum near some high-symmetry points can, in some cases, be described by tilted massive Dirac Hamiltonians. The so-called Janus materials fall into that category. Inversion symmetry can also be broken by the application of out-of-plane electric fields, or by the mere presence of a substrate. Here we explore the properties of excitons in TMDC monolayers lacking inversion symmetry. We find that exciton binding energies can be larger than the electronic band gap, making such materials promising candidates to host the elusive exciton insulator phase. We also investigate the excitonic contribution to their optical conductivity and discuss the associated optical selection rules.

First Report of Acidovorax avenae subsp. avenae Causing Bacterial Leaf Stripe of Strelitzia nicolai.

White bird of paradise (Strelitzia nicolai Regel & K. Koch) is a commonly grown ornamental in central and south Florida. Each summer of 2004 to 2007, a reoccurring disease was observed at a commercial nursery in central Florida. Diseased plants had brown, necrotic stripes between the lateral leaf veins, which usually appeared along the midvein and spread toward the leaf edge. Lesions developed on the youngest leaves as they emerged from the central whorl. During 2004 and 2005, 20 symptomatic leaves were sampled. A white, nonfluorescent bacterium was consistently isolated from symptomatic tissue. It induced a hypersensitive response (HR) on tomato, grew at 41°C, and was identified as a Acidovorax sp. based on fatty acid analysis and as Acidovorax avenae subsp. avenae by Biolog metabolic phenotype analysis (similarity 0.76 to 0.86). A partial 16S rRNA gene sequence (1,455 bp) (Accession No. EF418616) was identical to four sequences in the NCBI (National Center for Biotechnology Information) database: one from A. avenae subsp. avenae and three from A. avenae of undetermined subspecies. To confirm pathogenicity, a bacterial suspension (O.D590 = 0.1) was applied to fill the central whorl (~0.5 to 1 ml) of potted S. nicolai. Plants were incubated for 7 to 10 days inside plastic bags at ambient temperature. Plants were inoculated individually with five strains of A. avenae subsp. avenae, four from S. nicolai, and one from corn (ATCC19860). Two to nine plants per strain were inoculated in each experiment. All strains were tested at least twice and noninoculated control plants were included. Symptoms were reproduced on the emerging leaf of 50 to 100% of inoculated plants with all five A. avenae subsp. avenae strains. No symptoms were observed on the controls. The bacteria recovered from symptomatic tissue were confirmed to be A. avenae subsp. avenae. Corn seedlings were inoculated as described above, except that entire seedlings were sprayed. Water-soaked lesions along the length of older leaf blades developed in 4 to 7 days. Only the corn strain was pathogenic (>80% of seedlings symptomatic), indicating host specificity. To our knowledge, this is the first report of A. avenae subsp. avenae infecting S. nicolai. In 1971, Wehlburg (2) described the same symptoms on orange bird of paradise (S. reginae) as being caused by a nonfluorescent Pseudomonas sp. This report likely describes the same disease since the published description is consistent with symptoms caused by A. avenae subsp. avenae. The pathogen reported by Wehlburg (2) had one polar flagellum, reduced nitrate, produced oxidase and a HR, and utilized arabinose, but not sucrose or arginine, characteristics consistent with those of A. avenae subsp. avenae (1). The only difference was A. avenae subsp. avenae has a delayed positive starch hydrolysis (1), whereas Welhburg's strain was negative. This disease occurs mainly on young leaves when plants receive daily overhead irrigation. Incidence can be as high as 40%, occasionally causing mortality, but even mild symptoms affect appearance and reduce marketability as an ornamental. References: (1) N. W. Schaad et al. Laboratory Guide for Identification of Plant Pathogenic Bacteria. 3rd ed. The American Phytopathological Society, St. Paul, MN, 2001. (2) C. Wehlburg. Plant Dis. Rep. 55:447, 1971.

Enhancing the hybridization of plasmons in graphene with 2D superconductor collective modes.

We explore ways in which the close proximity between graphene sheets and monolayers of 2D superconductors can lead to hybridization between their collective excitations. We consider heterostructures formed by combinations of graphene sheets and 2D superconductor monolayers. The broad range of energies in which the graphene plasmon can exist, together with its tunability, makes such heterostructures promising platforms for probing the many-body physics of superconductors. We show that the hybridization between the graphene plasmon and the Bardasis-Schrieffer mode of a 2D superconductor results in clear signatures on the near-field reflection coefficient of the heterostructure, which in principle can be observed in scanning near-field microscopy experiments.

Fungal and bacterial coinfections increase mortality of severely ill COVID-19 patients.

BACKGROUND: SARS-CoV-2 predisposes patients to secondary infections; however, a better understanding of the impact of coinfections on the outcome of hospitalized COVID-19 patients is still necessary. AIM: To analyse death risk due to coinfections in COVID-19 patients. METHODS: The odds of death of 212 severely ill COVID-19 patients were evaluated, with detailed focus on the risks for each pathogen, site of infection, comorbidities and length of hospitalization. FINDINGS: The mortality rate was 50.47%. Fungal and/or bacterial isolation occurred in 89 patients, of whom 83.14% died. Coinfected patients stayed hospitalized longer and had an increased odds of dying (odds ratio (OR): 13.45; R2 = 0.31). The risk of death was increased by bacterial (OR: 11.28) and fungal (OR: 5.97) coinfections, with increased levels of creatinine, leucocytes, urea and C-reactive protein. Coinfections increased the risk of death if patients suffered from cardiovascular disease (OR: 11.53), diabetes (OR: 6.00) or obesity (OR: 5.60) in comparison with patients with these comorbidities but without pathogen isolation. The increased risk of death was detected for coagulase-negative Staphylococcus (OR: 25.39), Candida non-albicans (OR: 11.12), S. aureus (OR: 10.72), Acinetobacter spp. (OR: 6.88), Pseudomonas spp. (OR: 4.77), and C. albicans (OR: 3.97). The high-risk sites of infection were blood, tracheal aspirate, and urine. Patients with coinfection undergoing invasive mechanical ventilation were 3.8 times more likely to die than those without positive cultures. CONCLUSION: Severe COVID-19 patients with secondary coinfections required longer hospitalization and had higher risk of death. The early diagnosis of coinfections is essential to identify high-risk patients and to determine the right interventions to reduce mortality.

Excitonic effects in the optical conductivity of gated graphene.

We study the effect of electron-electron interactions in the optical conductivity of graphene under an applied gate and derive a generalization of Elliott's formula, commonly used for semiconductors, for the optical intensity. We show that excitonic resonances are responsible for several features of the experimentally measured midinfrared response of graphene such as the increase of the conductivity beyond the universal value above the Fermi blocked regime, the broadening of the absorption at the threshold, and the decrease of the optical conductivity at higher frequencies.