3,494 research outputs found
EFFECTS OF HIGH AND LOW MANAGEMENT INTENSITY ON PROFITABILITY FOR THREE WATERMELON GENOTYPES
A replicated, small plot study on watermelon [Citrullus lanatus (Thunberg) Matsumura and Nakai] in 1997, 1999, and 2000 revealed that production management intensity affected yields and profitability of watermelon, in Oklahoma. Management intensity was based on a combination of cultural practices and levels of use of production methods. Low intensity management (LM) consisted of use of soil fertilization and weed control. High intensity management (HM) included the same weed control and fertilization as LM but also included use of plastic mulch, drip irrigation, insect pest control, and plant disease control. Cost and return analyses were based on the range of actual prices during the cropping season and the range of yields during the three years. Yields from the seedless triploid genotype 'Gem Dandy' consistently resulted in greater positive net revenue under HM than the diploid open pollinated 'Allsweet' or the hybrid diploid 'Sangria'. Under LM, yields from the seedless triploid also resulted in greater net revenues when conditions were favorable or lost less money than the open pollinated 'Allsweet' or the hybrid diploid 'Sangria' when conditions were unfavorable.Crop Production/Industries,
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Molecular containers in complex chemical systems.
Over the last decade molecular containers have been increasingly studied within the context of complex chemical systems. Herein we discuss selected examples from the literature concerning three aspects of this field: complex host-guest behaviour, adaptive transformations of molecular containers and reactivity modulation within them.The UK Engineering and Physical Sciences Research Council
(SZ, JRN), The European Research Council (DMW) and the
Gates Cambridge Trust (DAR) are acknowledged for financial
support.This is the accepted manuscript. The final version is available from RSC at http://pubs.rsc.org/en/Content/ArticleLanding/2015/CS/c4cs00165f#!divAbstract
Post-assembly Modification of Tetrazine-Edged Fe(II)4L6 Tetrahedra.
Post-assembly modification (PAM) is a powerful tool for the modular functionalization of self-assembled structures. We report a new family of tetrazine-edged Fe(II)4L6 tetrahedral cages, prepared using different aniline subcomponents, which undergo rapid and efficient PAM by inverse electron-demand Diels-Alder (IEDDA) reactions. Remarkably, the electron-donating or -withdrawing ability of the para-substituent on the aniline moiety influences the IEDDA reactivity of the tetrazine ring 11 bonds away. This effect manifests as a linear free energy relationship, quantified using the Hammett equation, between σ(para) and the rate of the IEDDA reaction. The rate of PAM can thus be adjusted by varying the aniline subcomponent.This work was supported by the UK Engineering and Physical Sciences Research Council (EPSRC). The au-thors thank Diamond Light Source (UK) for synchro-tron beamtime on I19 (MT8464), the Department of Chemistry NMR facility, University of Cambridge, and the EPSRC UK National Mass Spectrometry Facility at Swansea University. D.A.R. acknowledges the Gates Cambridge Trust for Ph.D. funding. B.S.P. acknowledges the Herchel Smith Research Fellowship from the University of Cambridge and the Fellowship from Corpus Christi College, Cambridge.This is the final version of the article. It first appeared from the American Chemical Society via http://dx.doi.org/10.1021/jacs.5b0508
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Stacking Interactions Drive Selective Self-Assembly and Self-Sorting of Pyrene-Based M(II)4L6 Architectures.
Subcomponent self-assembly of two isomeric bis(3-aminophenyl)pyrenes, 2-formylpyridine and the metal ions Fe(II), Co(II), and Zn(II) led to the formation of two previously unidentified structure types: a C2-symmetric M(II)4L6 assembly with meridionally coordinated metal centers, and a C3-symmetric self-included M(II)4L6 assembly with facially coordinated metal centers. In both structures the meta linkages within the ligands facilitate π-stacking between the pyrene panels of the ligands. A C2h-symmetric M(II)2L2 box was also obtained, which was observed to selectively bind electron-deficient aromatic guests between two parallel pyrene subunits. Similar donor-acceptor interactions drove the selective self-assembly of a singular M(II)4L4L'2 architecture incorporating both a pyrene-containing diamine and an electron-deficient NDI-based diamine. This heteroleptic architecture was shown to be thermodynamically favored over the corresponding homoleptic M(II)4L6 and M(II)4L'6 complexes, which were nonetheless stable in each others' absence. By contrast, an isomeric pyrene-based diamine was observed to undergo narcissistic self-sorting in the presence of the NDI-based diamine.This work was supported by the UK Engineering and Physical Sciences Research Council (EPSRC). D.A.R. acknowledges the Gates Cambridge Trust for Ph.D. funding (Gates Cambridge Scholarship). We thank the EPSRC Mass Spectrometry Service at Swansea for carrying out the high resolution mass spectrometry and Diamond Light Source (UK) for synchrotron beamtime on I19 (MT8464). We also thank the NMR service team at the Department of Chemistry, University of Cambridge for performing some NMR experiments.This is the final version of the article. It first appeared from the American Chemical Society via http://dx.doi.org/10.1021/jacs.5b0992
Electrically Driven Hyperbolic Nanophotonic Resonators as High Speed, Spectrally Selective Thermal Radiators
We introduce and experimentally demonstrate a new class of electrically
driven thermal emitter based on globally aligned carbon nanotube metamaterials
patterned as nanoscale ribbons. The metamaterial ribbons exhibit electronic and
photonic properties with extreme anisotropy, which enable low loss,
wavelength-compressed hyperbolic photonic modes along one axis and high
electrical resistivity and efficient Joule heating along the other axis.
Devices batch-fabricated on a single chip emit linearly polarized thermal
radiation with peak wavelengths dictated by their hyperbolic resonances, and
their low thermal mass yields infrared radiation modulation rates as high as
one megahertz. As a proof-of-concept demonstration, we show that two sets of
thermal emitters on a single chip, each operating with different spectral peak
positions and modulation rates, can be used to sense carbon dioxide with a
single detector. We anticipate that the combination of batch fabrication, wide
modulation bandwidth, and customized spectral tuning with hyperbolic chip-based
thermal emitters will enable new modalities in multiplexed infrared sources for
sensing, imaging, and metrology applications
Mitochondrial dysfunction and oxidative stress in patients with chronic kidney disease.
Mitochondria abnormalities in skeletal muscle may contribute to frailty and sarcopenia, commonly present in patients with chronic kidney disease (CKD). Dysfunctional mitochondria are also a major source of oxidative stress and may contribute to cardiovascular disease in CKD We tested the hypothesis that mitochondrial structure and function worsens with the severity of CKD Mitochondrial volume density, mitochondrial DNA (mtDNA) copy number, BNIP3, and PGC1α protein expression were evaluated in skeletal muscle biopsies obtained from 27 subjects (17 controls and 10 with CKD stage 5 on hemodialysis). We also measured mtDNA copy number in peripheral blood mononuclear cells (PBMCs), plasma isofurans, and plasma F2-isoprostanes in 208 subjects divided into three groups: non-CKD (eGFR>60 mL/min), CKD stage 3-4 (eGFR 60-15 mL/min), and CKD stage 5 (on hemodialysis). Muscle biopsies from patients with CKD stage 5 revealed lower mitochondrial volume density, lower mtDNA copy number, and higher BNIP3 content than controls. mtDNA copy number in PBMCs was decreased with increasing severity of CKD: non-CKD (6.48, 95% CI 4.49-8.46), CKD stage 3-4 (3.30, 95% CI 0.85-5.75, P = 0.048 vs. non-CKD), and CKD stage 5 (1.93, 95% CI 0.27-3.59, P = 0.001 vs. non-CKD). Isofurans were higher in patients with CKD stage 5 (median 59.21 pg/mL, IQR 41.76-95.36) compared to patients with non-CKD (median 49.95 pg/mL, IQR 27.88-83.46, P = 0.001), whereas F2-isoprostanes did not differ among groups. Severity of CKD is associated with mitochondrial dysfunction and markers of oxidative stress. Mitochondrial abnormalities, which are common in skeletal muscle from patients with CKD stage 5, may explain the muscle dysfunction associated with frailty and sarcopenia in CKD Further studies are required to evaluate mitochondrial function in vivo in patients with different CKD stages
Climate and atmospheric circulation during the Early and Mid-Holocene inferred from lake-carbonate oxygen-isotope records from western Ireland
The Early to Mid-Holocene experienced marked climate change over the northern hemisphere mid-latitudes in response to changing insolation and declining ice volume. Oxygen isotopes from lake sediments provide a valuable climate proxy, encoding information regarding temperature, hydroclimate and moisture source. We present oxygen-isotope records from two lakes in western Ireland that are strongly influenced by the North Atlantic. Excellent replication between the records suggests they reflect regional, not local, influences. Carbonate oxygen-isotope values peaked at the start of the Holocene, between 11.2 and 11.1 cal ka bp, and then decreased markedly until 6 cal ka bp at both sites. Palaeoecological evidence supports only modest change in temperature or hydroclimate during this interval and we therefore explain the decrease primarily by a reduction in the oxygen-isotope composition of precipitation (δ18Oppt). We show a similar decrease in δ18O values in a forward model of carbonate isotopes between 12–11 and 6–5 cal ka bp. However, the inferred reduction in δ18Oppt between the Early and Mid-Holocene in the model is mainly linked to a decrease in the δ18O of the ocean source water from ice sheet melting whereas the lake carbonate isotope records are more consistent with changes in the transport pathway of moisture associated with atmospheric circulation change as the dominant cause
Covalent Post-assembly Modification Triggers Multiple Structural Transformations of a Tetrazine-Edged Fe4L6 Tetrahedron
Covalent post-assembly modification (PAM) reactions are useful synthetic tools for functionalizing and stabilizing self-assembled metal-organic complexes. Recently, PAM reactions have also been explored as stimuli for triggering supramolecular structural transformations. Herein we demonstrate the use of inverse electron-demand Diels-Alder (IEDDA) PAM reactions to induce supramolecular structural transformations starting from a tetrazine-edged FeII4L6 tetrahedral precursor. Following PAM, this tetrahedron rearranged to form three different architectures depending on the addition of other stimuli: an electron-rich aniline or a templating anion. By tracing the stimulus-response relationships within the system, we deciphered a network of transformations that mapped different combinations of stimuli onto specific transformation products. Given the many functions being developed for self-assembled three-dimensional architectures, this newly established ability to control the interconversion between structures using combinations of different stimulus types may serve as the basis for switching the functions expressed within a system.D.A.R. acknowledges the Gates Cambridge Trust. B.S.P. acknowledges
the Royal Commission for the Exhibition of 1851 Fellowship and Corpus
Christi College, Cambridge. This work was supported by the UK
Engineering and Physical Sciences Research Council (EP/M01083X/1)
Methods of classification for women undergoing induction of labour: a systematic review and novel classification system
Background: The lack of reproducible methods for classifying women having an induction of labour (IOL) has led to controversies regarding the association of IOL and health outcomes for mother and baby. Objectives: To identify research papers that describe a methodology for classifying women having an IOL, and to evaluate the utility of these methods of classification for clinical, research and surveillance purposes. Search strategy: We conducted electronic searches in CINAHL, EMBASE and WEB of KNOWLEDGE from database inception until Oct 2013 and searched reference lists. Selection criteria: Two reviewers independently assessed eligibility. Studies had to describe a method for classifying women with an IOL using a minimum of two categories, regardless of whether or not this was the main purpose of the study. Data collection: Data were extracted on study characteristics, quality and results. Pre-specified criteria were used to evaluate the utility of these methods of classification for IOL. Main results: Seven studies met the inclusion criteria. All studies categorised women according to the presence or absence of a medical indication for IOL. Uncertainties and/or deficiencies were identified across all methods of classification related to the criteria of total inclusivity, reproducibility, clinical utility, implementability and data availability limiting their usefulness. Conclusion: Current methods of classifying women with an IOL are inadequate for clinical, research and surveillance purposes. Limitations with classification systems based on medical indications suggest that an alternative method of classification is required for women having IOL
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