The adsorption and sensing capabilities of CO and NO on pristine and metal-decorated (8,0) SWCNT were analyzed by DFT. Both gases cause a slight deformation of the nanotube curvature in the direction ...of molecular adsorption. The molecule's adsorption and sensing performance are enhanced with the transition metal (Sc, Cr, Fe, and Ni) decoration on SWCNT. Decorated nanotubes are suitable for high-temperature sensors. According to relative energies for NO, the operational range is 900–1200 K. For CO/Cr- and Sc-SWCNT between 100 and 200 K and close to 550 K in the cases of decoration with Fe and Ni. From the recovery time analysis, the metal-decorated materials exhibit better performance at high temperatures and low pressures for NO compared to CO. Changes in magnetic moment suggest that Cr-decorated SWCNT could serve as a magnetic sensor for both molecules.
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•The pristine CNT is more reactive to NO than CO.•The transition metal (TM) doping enhances the adsorption energy and sensing performance for NO and CO.•TM-doped SWCNTs are better for sensing NO at high temperature and low pressure.•Recovery time shows that the best sensors for NO are Cr and Ni decorated CNT.•At room temperature, TM-SWCNTs could be effective for absorbing material to clean both gases.
In situ measurements of alternative respiratory pathway activity are needed to provide insight into the energy efficiency of plant metabolism under various conditions in the field. The only reliable ...method at present to measure alternative oxidase (AOX) activity is through measurement of changes in $\delta {}^{18}\text{O}(\text{O}_{2})$, which to date has only been used in laboratory environments. We have developed a cuvette system to measure partitioning of electrons to AOX that is suitable for off-line use and for field experiments. Plant samples are enclosed in airtight cuvettes and O2 consumption is monitored. Gas samples from the cuvette are stored in evacuated gas containers until measurement of $\delta {}^{18}\text{O}(\text{O}_{2})$. We have validated this method using differing plant material to assess AOX activity. Fractionation factors were calculated from $\delta {}^{18}\text{O}(\text{O}_{2})$ measurements, which could be measured with an accuracy and precision to 0.1‰ and 0.3‰, respectively. Potential sources of error are discussed and quantified. Our method provides results similar to those obtained with laboratory incubations on-line to a mass spectrometer but greatly increases the potential for adoption of the stable isotope method.
The growth‐promoting effects of gibberellins (GAs) on plants are well documented, but a complete growth analysis at the whole plant level on plants with an altered GA biosynthesis has never been ...reported. In the present work, the relative growth rate (RGR), biomass partitioning and morphological parameters of wildtype (Wt) tomato (Solanum lycopersicum L. cv. Moneymaker) plants were compared with those of isogenic (gib) mutants with a reduced biosynthesis of gibberellins. GA deficiency reduced RGR and specific leaf area (SLA, leaf area per unit leaf mass) and increased the net assimilation rate (NAR, the rate of biomass increment per unit leaf area). Despite the free access to nitrogen in the rooting medium, the low‐GA mutants had a much higher root mass ratio (RMR, the root mass per unit plant biomass) than the Wt, suggesting that the mutants were disturbed in their growth response to nitrate supply. The experiment was repeated at a low exponential nitrate supply, which forced all plants to grow at the same low RGR. The persistence of the differences in RMR at low N‐supply indicated that the high RMR of the mutants was a direct effect of low GA, which was independent of nitrate supply. Because the low N‐supply increased the RMRs of all genotypes to the same extent, the response of RMR to N‐supply does not seem to depend on GA. Although many of the traits of the slow growing GA mutants were very similar to those of inherently slow growing plant species from unproductive habitats, gibberellins are unlikely to be a main determinant of a plant's potential RGR.
We investigated how the differences in growth and morphology, between fast‐growing wildtype (Wt) tomato (Solanum lycopersicum L.) plants and slow‐growing gibberellin (GA) deficient W335 mutants, were ...reflected in cell numbers and cell sizes. We also studied whether the differences between the Wt and the low‐GA mutant would persist at a growth‐limiting supply of nitrate. Both a low endogenous GA concentration and a low supply of nitrate reduced the number and size of leaf cells, whereas they increased the size and number of root cortex cells. The effects of low N‐supply on the size and number of leaf and root cells did not depend on endogenous GA concentrations. The mutant's higher allocation to roots seemed to be the result of the strongly reduced growth of the shoot.
In this paper we firstly show some general responses of biomass partitioning upon nitrogen deprivation. Secondly, these responses are explained in terms of allocation of carbon and nitrogen, ...photosynthesis and respiration, using a simulation model. Thirdly, we present a hypothesis for the regulation of biomass partitioning to shoots and roots. Shortly after nitrogen deprivation, the relative growth rate (RGR) of the roots generally increases and thereafter decreases, whereas that of the shoot decreases immediately. The increased RGR of the root and decreased RGR of the shoot shortly after a reduction in the nitrogen supply, cause the root weight ratio (root weight per unit plant weight) to increase rapidly. We showed previously that allocation of carbon and nitrogen to shoots and roots can satisfactorily be described as a function of the internal organic plant nitrogen concentration. Using these functions in a simulation model, we analyzed why the relative growth rate of the roots increases shortly after a reduction in nitrogen supply. The model predicts that upon nitrogen deprivation, the plant nitrogen concentration and the rate of photosynthesis per unit plant weight rapidly decrease, and the allocation of recently assimilated carbon and nitrogen to roots rapidly increases. Simulations show that the increased relative growth rate of the root upon nitrogen deprivation is explained by decreased use of carbon for root respiration, due to decreased carbon costs for nitrogen uptake. The stimulation of the relative growth rate of the root is further amplified by the increased allocation of carbon and nitrogen to roots. Using the simple relation between the plant nitrogen concentration and allocation, the model describes plant responses quite realistically. Based on information in the literature and on our own experiments we hypothesize that allocation of carbon is mediated by sucrose and cytokinins. We propose that nitrogen deprivation leads to a reduced cytokinin production, a decreased rate of cytokinin export from the roots to the shoot, and decreased cytokinin concentrations. A reduced cytokinin concentration in the shoot represses cell division in leaves, whereas a low cytokinin concentration in roots neutralizes the inhibitory effect of cytokinins on cell division. A reduced rate of cell division in the leaves leads to a reduced unloading of sucrose from the phloem into the expanding cells. Consequently, the sucrose concentration in the phloem nearby the expanding cells increases, leading to an increase in turgor pressure in the phloem nearby the leaf's division zone. In the roots, cell division continues and no accumulation of sugars occurs in dividing cells, leading to only marginal changes in osmotic potential and turgor pressure in the phloem nearby the root's cell division zone. These changes in turgor pressure in the phloem of roots and sink leaves affect the turgor pressure gradients between source leaf - sink leaf and source leaf - root in such a way that relatively more carbohydrates are exported to the roots. As a consequence RWR increases after nitrogen deprivation. This hypothesis also explains the strong relationship between allocation and the plant nitrogen status.
The electronic properties of the
Mg
2
NiH
4
monoclinic phase are calculated using a density functional approach calculation. The crystalline parameters and interatomic distances calculated are close ...to the experimental values within a 3% error. We also evaluate the density of states (DOS) and character of the chemical bonding for the hydrogen's located in their equilibrium positions. While the Ni–Mg interaction is dominant in the pure alloy, in the hydride the hydrogen atoms present a bonding much more developed with Ni than with Mg. The principal bonding interaction is Ni sp–H s. Moreover, a small bonding between Ni
d
eg
and H 1s is observed. Up the Fermi level, the Ni–H interaction is slightly antibonding. The Mg–Ni bonding interactions are weaker in the hydride phase when compared with the pure
Mg
2
Ni
alloy. The present study is potentially useful because the alloys Mg–Ni are good materials for hydrogen storage.
In situ measurements of alternative respiratory pathway activity are needed to provide insight into the energy efficiency of plant metabolism under various conditions in the field. The only reliable ...method at present to measure alternative oxidase (AOX) activity is through measurement of changes in δ
18
O(O
2
), which to date has only been used in laboratory environments. We have developed a cuvette system to measure partitioning of electrons to AOX that is suitable for off-line use and for field experiments. Plant samples are enclosed in airtight cuvettes and O
2
consumption is monitored. Gas samples from the cuvette are stored in evacuated gas containers until measurement of δ
18
O(O
2
). We have validated this method using differing plant material to assess AOX activity. Fractionation factors were calculated from δ
18
O(O
2
) measurements, which could be measured with an accuracy and precision to 0.1‰ and 0.3‰, respectively. Potential sources of error are discussed and quantified. Our method provides results similar to those obtained with laboratory incubations on-line to a mass spectrometer but greatly increases the potential for adoption of the stable isotope method.
In situ measurements of alternative respiratory pathway activity are needed to provide insight into the energy efficiency of plant metabolism under various conditions in the field. The only reliable ...method at present to measure alternative oxidase (AOX) activity is through measurement of changes in delta(18)O(O(2)), which to date has only been used in laboratory environments. We have developed a cuvette system to measure partitioning of electrons to AOX that is suitable for off-line use and for field experiments. Plant samples are enclosed in airtight cuvettes and O(2) consumption is monitored. Gas samples from the cuvette are stored in evacuated gas containers until measurement of delta(18)O(O(2)). We have validated this method using differing plant material to assess AOX activity. Fractionation factors were calculated from delta(18)O(O(2)) measurements, which could be measured with an accuracy and precision to 0.1 per thousand and 0.3 per thousand, respectively. Potential sources of error are discussed and quantified. Our method provides results similar to those obtained with laboratory incubations on-line to a mass spectrometer but greatly increases the potential for adoption of the stable isotope method.
A spin-independent whole theoretical treatment of nuclear quadrupole resonance echoes of half-integer spin systems with zero asymmetry parameter is presented. It is shown that the expression of both ...Hahn and Solid echoes are identical up to the second order for all half-integer spins, also that the separate measurement of homonuclear and quadrupole–heteronuclear broadening is possible by means of mixed echoes techniques.
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