Chemical weed control in Dracaena fragans cv. massangeana in Alajuela, Costa Rica

En dos localidades del Valle Central Occidental, de Costa Rica: en Buenos Aires y Zaragoza de Palmares, Alajuela, ubicadas a 1000 msnm, precipitación anual de 1142 mm y temperatura de 23ºC, se realizaron dos experimentos con herbicidas preemergentes en Dracaena fragans cv. massangeana. El primer experimento se realizó en Buenos Aires, en los meses de agosto a noviembre de 1987, en una plantación de un año de edad, sembrada a 1 x 0,75 m. Los tratamientos evaluados fueron: oxifluorfén + terbutilazina (0,5 + 1,5 kg/ha); oxifluorfén + terbutrina (0,5 + 1,5 kg/ha); oxifluorfén + metribuzina (0,5 + 0,4 kg/ha); oxifluorfén + atrazina (0,5 + 1,5 kg/ha); alaclor + metribuzina (1,5 + 0,4 kg/ha); alaclor + terbutrina (1,5 + 1,5 kg/ha); alaclor + ametrina (1,5 + 1,5 kg/ha); y diurón (1,0 kg/ha). El segundo experimento se realizó en Zaragoza, en los meses de setiembre a noviembre de 1988, en una plantación de 1,5 años, sembrada a 1 x 0,75 m. Los tratamientos fueron: oxifluorfén (0,6kg/ha); oxifluorfén + terbutilazina (0,6 + 1,75 kg/ha); alaclor + terbutilazina (1,75 + 1,75 kg/ha); alaclor + atrazina (1,75 + 1,75 kg/ha); alaclor + oxifluorfén (1,75 + 0,6 kg/ha) y diurón + atrazina (1,5 + 1,75 kg/ha). Se incluyeron, en ambos experimentos, dos testigos, uno de libre competencia y otro con una deshierba mecánica cada 30 días después de la aplicación. Con ningún tratamiento ocurrió fitotoxicidad en el cultivo. El mejor control de malezas gramíneas se obtuvo cuando las mezclas contenían oxifluorfén. Se logró comprobar que las prácticas culturales y la morfología de las plantas en conjución con la densidad de siembra, disminuyen la densidad y agresividad de las malezas, a medida que el follaje del cultivo crece y forma un microclima desfavorable, para aquellas malezas que crecen bajo su copa.Two trials were conducted with pre-emergent herbicides in Dracaena fragans cv. massangeana, at two localities of the Western Central Plateau, located at 1000 m.a.s.l., with an annual rainfal of 1142 mm and a temperature of 23ºC. The first test was conducted from August to November of 1987 in a year old plantation, with a planting distance of 1 x 0.75 m. The evaluated treatments were: oxyflurofen + terbutylazine at (0.5 + 1.5 kg/ha), oxyfluorfen + terbutryn at (0.5 + 1.5 kg/ha), oxyfluorfen + metribuzin at (0.5 + 0.4 kg/ha), oxyfluorfen + atrazine at (0.5 + 1.5 kg/ha), alachlor + metribuzin at (1.5 + 0.4 kg/ha), alaclor + terbutryn at (1.5 + 1.5 kg/ha), alaclor + ametryn at (1.5 + 1.5 kg/ha) and diuron at (1.0 kg/ha). The second trial was conducted in Zaragoza, from September to November, 1988, in a one and one-half year's old plantation, with the same planting distance. The treatments were: oxyfluorfen at (0.6 kg/ha), oxyfluorfen + terbutylazine at (0.6 + 1.75 kg/ha), alachlor + terbutylazine at (1.75 + 1.75 kg/ha), alaclor + atrazine at (1.75 + 1.75 kg/ha), alachlor + oxyfluorfen at (1.75 + 0.6 kg/ha) and diuron + atrazine al (1.50 + 1.75 kg/ha). Two controls were included in both experiments, one unweeded and the other one was mechanically weeded every 30 days after the application. No phytotoxicity symptoms were observed in any of the treatments. The best gramineous control was obtained when oxyfluorfen was included in the mixture. It was proved that the cultural practices and the plant morphology, joined to the plant density, reduced the population and aggresiveness of the weeds. As the crop's foliage grows, it produces an unfavorable microclimate for those weeds growing under its shade.UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Estación Experimental Agrícola Fabio Baudrit Moreno (EEAFBM

Towards disentangling photodesorption and photodissociation in astronomical ice analogues

Laboratory astrophysics and astrochemistr

Quantification of O2formation During UV Photolysis of Water Ice: H2O and H2O:CO2ices

Context. The Rosetta and Giotto missions investigated the composition of the cometary comae of 67P/Churyumov-Gerasimenko and 1P/Halley, respectively. In both cases, a surprisingly large amount of molecular oxygen (O2) was detected and was well correlated with the observed abundances of H2O. Laboratory experiments simulating chemical processing for various astronomical environments already showed that formation of solid state O2 is linked to water. However, a quantitative study of O2 formation upon UV photolysis of pure H2O and H2O dominated interstellar ice analogues is still missing. Aims. The goal of this work is to investigate whether the UV irradiation of H2O-rich ice produced at the earliest stages of star formation is efficient enough to explain the observed abundance of cometary O2. Methods. The photochemistry of pure H216O (H218O) as well as mixed H2O:CO2 (ratio of 100:11, 100:22, 100:44) and H2O:CO2:O2 (100:22:2) ices was quantified during UV photolysis. Laser desorption post-ionisation time of flight mass spectrometry (LDPI TOF MS) was used to probe molecular abundances in the ice as a function of UV fluence. Results. Upon UV photolysis of pure amorphous H2O ice, deposited at 20 K, formation of O2 and H2O2 is observed at abundances of, respectively, (0.9 ± 0.2)% (O2/H2O) and (1.3 ± 0.3)% (H2O2/H2O). To the best of our knowledge, this is the first quantitative characterisation of the kinetics of this process. During the UV photolysis of mixed H2O:CO2 ices, the formation of the relative amount of O2 compared to H2O increases to a level of (1.6 ± 0.4)% (for H2O:CO2 ratio of 100:22), while the (H2O2/H2O) yield remains similar to experiments with pure water. In an ice enriched with O2 (2%), the O2 level increases up to 7% with regard to H2O, at low UV fluence, which is higher than expected on the basis of the enrichment alone. The resulting O2/H2O values derived for the H2O and H2O:CO2 ices may account for a (substantial) part of the high oxygen amounts found in the comae of 67P and 1P. © ESO 2022.Acknowledgements. The authors would like to acknowledge T. Hama for his thorough referee report which improved the quality of this article. M.B. and H.L. acknowledge the European Union (EU) and Horizon 2020 funding awarded under the Marie Skłodowska-Curie action to the EUROPAH consortium (grant number 722346) as well as NOVA 5 funding. Recent support through INTERCAT is acknowledged as well. Additional funding has been realized through a NWO-VICI grant. G.F. also acknowledges financial support from the Russian Ministry of Science and Higher Education via the State Assignment Contract FEUZ-2020-0038. J.T.v.S. is supported by the Dutch Astrochemistry II

Guidelines for Genome-Scale Analysis of Biological Rhythms

Genome biology approaches have made enormous contributions to our understanding of biological rhythms, particularly in identifying outputs of the clock, including RNAs, proteins, and metabolites, whose abundance oscillates throughout the day. These methods hold significant promise for future discovery, particularly when combined with computational modeling. However, genome-scale experiments are costly and laborious, yielding “big data” that are conceptually and statistically difficult to analyze. There is no obvious consensus regarding design or analysis. Here we discuss the relevant technical considerations to generate reproducible, statistically sound, and broadly useful genome-scale data. Rather than suggest a set of rigid rules, we aim to codify principles by which investigators, reviewers, and readers of the primary literature can evaluate the suitability of different experimental designs for measuring different aspects of biological rhythms. We introduce CircaInSilico, a web-based application for generating synthetic genome biology data to benchmark statistical methods for studying biological rhythms. Finally, we discuss several unmet analytical needs, including applications to clinical medicine, and suggest productive avenues to address them

Guidelines for Genome-Scale Analysis of Biological Rhythms

Genome biology approaches have made enormous contributions to our understanding of biological rhythms, particularly in identifying outputs of the clock, including RNAs, proteins, and metabolites, whose abundance oscillates throughout the day. These methods hold significant promise for future discovery, particularly when combined with computational modeling. However, genome-scale experiments are costly and laborious, yielding ‘big data’ that is conceptually and statistically difficult to analyze. There is no obvious consensus regarding design or analysis. Here we discuss the relevant technical considerations to generate reproducible, statistically sound, and broadly useful genome scale data. Rather than suggest a set of rigid rules, we aim to codify principles by which investigators, reviewers, and readers of the primary literature can evaluate the suitability of different experimental designs for measuring different aspects of biological rhythms. We introduce CircaInSilico, a web-based application for generating synthetic genome biology data to benchmark statistical methods for studying biological rhythms. Finally, we discuss several unmet analytical needs, including applications to clinical medicine, and suggest productive avenues to address them

Gas-phase infrared spectroscopy of the rubicene cation (C_26H_14^+). A case study for interstellar pentagons

Laboratory astrophysics and astrochemistr

Probing mixed valence in a new tppz-bridged diruthenium(III,II) complex{(mu-tppz)[Ru(bik)Cl]2}(3+) (tppz=2,3,5,6-tetrakis(2-pyridyl)pyrazine, bik=2,3,5,6-tetrakis(2-pyridyl)pyrazine, bik=2,2'-bis(1-methylimidazolyl)ketone): EPR silence, intervalence absorption, and v(CO) line broadening

The complex dication of the diruthenium(II) compound {(mu-tppz)[Ru(bik)Cl](2)}(ClO4)(2) can be oxidized and reduced in two one-electron steps each. In CH3CN/0.1 M Bu4NPF6, the odd-electron intermediates{(mu-tppz)[Ru(bik)Cl](2)}(n+), n = 1 and 3, have comproportionation constants of 7 x 10(8) and 1 x 10(5), respectively. Both exhibit near-infrared absorptions, in the case of n = 3 the 1640 nm band (epsilon = 1200 M-1 cm(-1), Delta nu(1/2) = 1560 cm(-1)) is attributed to an intervalence charge-transfer transition. While the mixed-valent intermediate (n = 3) is EPR silent even at 4 K, the n = 1 form shows g(II) 2.005 and g(perpendicular to) 1.994 at that temperature, signifying a diruthenium(II) complex of the tppz(center dot-) radical anion. The variation of energy and intensity of nu(CO) and of the ring vibration band around 1590 cm(-1) has been monitored not only for {(mu-tppz)[Ru(bik)Cl](2)}(n+), n = 0-4, but also for the mononuclear {(tppz)Ru(bik)Cl}(n+), n = 0-2. In the dinuclear complex the carbonyl stretching bands of the spectator ligand bik are shifted by about 15 cm(-1) on each one-electron-transfer step, increasing with the positive charge. The mixed-valent {(mu-tppz)[Ru(bik)Cl](2)}(3+) shows a perceptibly broader nu(CO) band, suggesting incomplete valence averaging (partial localization)

Effect of molecular structure on the infrared signatures of astronomically relevant PAHs

Emission bands from polycyclic aromatic hydrocarbons (PAHs) dominate the mid-infrared spectra of a wide variety of astronomical sources, encompassing nearly all stages of stellar evolution. Despite their similarities, details in band positions and shapes have allowed a classification of PAH emission to be developed. It has been suggested that this classification is in turn associated with the degree of photoprocessing of PAHs. Over the past decade, a more complete picture of the PAH interstellar life-cycle has emerged, in which a wide range of PAH species are formed during the later stages of stellar evolution. After this they are photoprocessed, increasing the relative abundance of the more stable (typically larger and compact) PAHs. For this work we have tested the effect of the symmetry, size, and structure of PAHs on their fragmentation pattern and infrared spectra by combining experiments at the free electron laser for infrared experiments (FELIX) and quantum chemical computations. Applying this approach to the cations of four molecular species, perylene (C20H12), peropyrene (C26H14), ovalene (C32H14) and isoviolanthrene (C34H18), we find that a reduction of molecular symmetry causes the activation of vibrational modes in the 7–9 μm range. We show that the IR characteristics of less symmetric PAHs can help explain the broad band observed in the class D spectra, which are typically associated with a low degree of photoprocessing. Such large, nonsymmetrical irregular PAHs are currently largely missing from the NASA Ames PAH database. The band positions and shapes of the largest more symmetric PAH measured here, show the best resemblance with class A and B sources, representative of regions with high radiation fields and thus heavier photoprocessing. Furthermore, the dissociation patterns observed in the mass spectra hint to an enhanced stability of the carbon skeleton in more symmetric PAHs with respect to the irregular and less symmetric species, which tend to loose carbon containing units. Although not a direct proof, these findings are fully in line with the grandPAH hypothesis, which claims that symmetric large PAHs can survive as the radiation field increases, while their less symmetric counterparts are destroyed or converted to symmetric PAHs

Quantification of O

Context. The Rosetta and Giotto missions investigated the composition of the cometary comae of 67P/Churyumov-Gerasimenko and 1P/Halley, respectively. In both cases, a surprisingly large amount of molecular oxygen (O2) was detected and was well correlated with the observed abundances of H2O. Laboratory experiments simulating chemical processing for various astronomical environments already showed that formation of solid state O2 is linked to water. However, a quantitative study of O2 formation upon UV photolysis of pure H2O and H2O dominated interstellar ice analogues is still missing. Aims. The goal of this work is to investigate whether the UV irradiation of H2O-rich ice produced at the earliest stages of star formation is efficient enough to explain the observed abundance of cometary O2. Methods. The photochemistry of pure H216O (H218O) as well as mixed H2O:CO2 (ratio of 100:11, 100:22, 100:44) and H2O:CO2:O2 (100:22:2) ices was quantified during UV photolysis. Laser desorption post-ionisation time of flight mass spectrometry (LDPI TOF MS) was used to probe molecular abundances in the ice as a function of UV fluence. Results. Upon UV photolysis of pure amorphous H2O ice, deposited at 20 K, formation of O2 and H2O2 is observed at abundances of, respectively, (0.9 ± 0.2)% (O2/H2O) and (1.3 ± 0.3)% (H2O2/H2O). To the best of our knowledge, this is the first quantitative characterisation of the kinetics of this process. During the UV photolysis of mixed H2O:CO2 ices, the formation of the relative amount of O2 compared to H2O increases to a level of (1.6 ± 0.4)% (for H2O:CO2 ratio of 100:22), while the (H2O2/H2O) yield remains similar to experiments with pure water. In an ice enriched with O2 (2%), the O2 level increases up to 7% with regard to H2O, at low UV fluence, which is higher than expected on the basis of the enrichment alone. The resulting O2/H2O values derived for the H2O and H2O:CO2 ices may account for a (substantial) part of the high oxygen amounts found in the comae of 67P and 1P