928 research outputs found
Growth and physiological responses of lettuce grown under pre-dawn or end-of-day sole-source light-quality treatments
The objective of this study was to evaluate growth and physiological responses of ‘Cherokee’ and ‘Waldmann’s Green’ lettuce (Lactuca sativa) exposed to small changes in light quality and intensity within a 24-h period. Three pre-dawn (PD; 0600 to 0700) and three end-of-day (EOD; 2100 to 2200) treatments were evaluated in the study, each providing 50 ± 2 μmol·m−2·s−1 of either blue, red, or broadband white light from light-emitting diodes (LEDs). To account for the main daily light integral (DLI), broadband white LEDs provided 210 ± 2 μmol·m−2·s−1 from 0700 to 2200 or from 0600 to 2100 for the PD or EOD treatments, respectively. A control treatment was included which provided 200 ± 2 μmol·m−2·s−1 of white light from 0600 to 2200. All treatments provided a DLI of 11.5 mol·m−2·day−1 over a 16-h photoperiod. Regardless of cultivar, no treatment difference was measured for hypocotyl length or leaf number. However, plants grown under EOD-blue or PD-white had up to 26% larger leaves than those grown under PD-red and 20% larger leaves than control. In addition, plants grown under EOD-blue produced up to 18% more shoot fresh mass compared to those grown under control, EOD-red, or PD-red. Contrasts for gas-exchange data collected during the main photoperiod showed that light quality was not significant within PD or EOD for any of the parameters evaluated. However, regardless of light quality, stomatal conductance (gs) and transpiration (E) were up to 34% and 42% higher, respectively, for EOD-grown plants compared to control. Our results suggest that 1 h of low intensity EOD-blue light has the potential to promote lettuce growth by increasing leaf area and shoot fresh mass when the main DLI from sole-source lighting is provided by broadband white LEDs
Synthesis of Propargylamines by Cross-Dehydrogenative Coupling
Propargylamines are versatile compounds for heterocyclic synthesis, some of which are current drugs prescribed to treat patients with Parkinson’s disease. There are different methods to synthesize propargylamines, however, modern chemistry has moved progressively to rely on new strategies that meet the principles of Green Chemistry. In this context, propargylamines are readily accessible by the cross-dehydrogenative coupling (CDC) of two C-H bonds (i.e., NCsp3-H and Csp-H bonds); surely, CDC can be considered the most atom-economic and efficient manner to form C-C bonds. The aim of this review is to provide a comprehensive survey on the synthesis of propargylamines by the CDC of amines and terminal alkynes from three fronts: (a) transition-metal homogeneous catalysis, (b) transition-metal heterogeneous catalysis and (c) photoredox catalysis. A section dealing with the asymmetric synthesis of chiral propargylamines is also included. Special attention is also devoted to the proposed reaction mechanisms.This work was generously supported by the Spanish Ministerio de Ciencia, Innovación y Universidades (MICIU; grant no. CTQ2017-88171-P), the Generalitat Valenciana (GV; grant no. AICO/2017/007) and the Instituto de SÃntesis Orgánica (ISO). I.B. is also grateful to the Spanish MICIU for a Juan de la Cierva-incorporación grant (no. IJCI-2017-33706)
Deflection and Rotation of CMEs from Active Region 11158
Between the 13 and 16 of February 2011 a series of coronal mass ejections
(CMEs) erupted from multiple polarity inversion lines within active region
11158. For seven of these CMEs we use the Graduated Cylindrical Shell (GCS)
flux rope model to determine the CME trajectory using both Solar Terrestrial
Relations Observatory (STEREO) extreme ultraviolet (EUV) and coronagraph
images. We then use the Forecasting a CME's Altered Trajectory (ForeCAT) model
for nonradial CME dynamics driven by magnetic forces, to simulate the
deflection and rotation of the seven CMEs. We find good agreement between the
ForeCAT results and the reconstructed CME positions and orientations. The CME
deflections range in magnitude between 10 degrees and 30 degrees. All CMEs
deflect to the north but we find variations in the direction of the
longitudinal deflection. The rotations range between 5\mydeg and 50\mydeg with
both clockwise and counterclockwise rotations occurring. Three of the CMEs
begin with initial positions within 2 degrees of one another. These three CMEs
all deflect primarily northward, with some minor eastward deflection, and
rotate counterclockwise. Their final positions and orientations, however,
respectively differ by 20 degrees and 30 degrees. This variation in deflection
and rotation results from differences in the CME expansion and radial
propagation close to the Sun, as well as the CME mass. Ultimately, only one of
these seven CMEs yielded discernible in situ signatures near Earth, despite the
active region facing near Earth throughout the eruptions. We suggest that the
differences in the deflection and rotation of the CMEs can explain whether each
CME impacted or missed the Earth.Comment: 18 pages, 6 figures, accepted in Solar Physic
Measuring the Purpose Strength
In the preceding chapters, a new logic for the twenty-first-century organization was proposed—the logic of leading based on a shared and common business purpose, one that captures the mind, captivates the heart, and guides the
day-to-day routines of every individual in the organization. In view of this
new logic, though, the question becomes, how are leaders to assess whether or not the purpose of the business is truly common and deeply shared
The LHC Logging Service : Handling terabytes of on-line data
Based on previous experience with LEP, a long-term data logging service for the LHC was developed and put in place in 2003, several years before beam operation. The scope of the logging service covers the evolution over time of data acquisitions on accelerator equipment and beam related parameters. The intention is to keep all this time-series data on-line for the lifetime of LHC, allowing easy data comparisons with previous years. The LHC hardware commissioning has used this service extensively prior to the first beams in 2008 and even more so in 2009. Current data writing rates exceed 15TB/year and continue to increase. The high data volumes and throughput rates, in writing as well as in reading, require special arrangements on data organization and data access methods
Whistler Waves Driven by Anisotropic Strahl Velocity Distributions: Cluster Observations
Observed properties of the strahl using high resolution 3D electron velocity distribution data obtained from the Cluster/PEACE experiment are used to investigate its linear stability. An automated method to isolate the strahl is used to allow its moments to be computed independent of the solar wind core+halo. Results show that the strahl can have a high temperature anisotropy (T(perpindicular)/T(parallell) approximately > 2). This anisotropy is shown to be an important free energy source for the excitation of high frequency whistler waves. The analysis suggests that the resultant whistler waves are strong enough to regulate the electron velocity distributions in the solar wind through pitch-angle scatterin
Topical Issue in Solar Physics: Flux-rope Structure of Coronal Mass Ejections Preface
This Topical Issue of Solar Physics, devoted to the study of flux-rope
structure in coronal mass ejections (CMEs), is based on two Coordinated Data
Analysis Workshops (CDAWs) held in 2010 (20 - 23 September in Dan Diego,
California, USA) and 2011 (September 5-9 in Alcala, Spain). The primary purpose
of the CDAWs was to address the question: Do all CMEs have flux rope structure?
There are 18 papers om this topical issue, including this preface.Comment: 4 page
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