Seven forest soils, Cambisols under pinus, located at Galicia (NW Spain) and affected by forest wildfires were collected to determine the loss of organic matter due to the effect of burning, using calorimetric methods. The enthalpy of combustion, ΔH, of the organic matter of the burnt and the corresponding unburnt soils was calculated from the thermograms obtained with a differential scanning calorimeter (DSC-7, Perkin-Elmer). From these data, the loss of organic matter during the fires was calculated. On the other hand, the organic matter content for each burnt and unburnt soil studied was determined by thermogravimetry (TG) and, in the same way, the loss of organic matter was obtained. High linear, significant correlations were found between the enthalpy of combustion of the soil organic matter (SOM) and the organic matter content measured by thermogravimetry. Consequently, comparison of the loss of organic matter obtained by both methods indicated that the quantitative results are similar. Both techniques allow to determine the degradation level of the soils affected by forest wildfires, taking the loss of organic matter during the fire as a degradation index. 相似文献
Manipulators with free links are called underactuated manipulators, and in these systems, the number of actuators is less
than the degree of freedom of the manipulator. Motivations of the study on the underactuated manipulators are, for example,
to construct back-up strategies in case of actuator failure in extreme missions such as space robots and to realize cost reduction
by employing fewer actuators. In this paper, we investigate the reachable area of the tip of a two-link underactuated manipulator
whose first link (active link) is equipped through an actuator to a base rotated with a constant angular velocity. We produce
pitchfork bifurcations in the free link (second link) by motion with a high-frequency component of the active link and actuate
perturbations of the pitchfork bifurcations by changing the configuration of the active link with respect to the direction
of the centrifugal force. We investigate the reachable area of the tip of the manipulator under the control by analytical
approach and experimentally discuss the validity of the theoretical prediction. 相似文献
We study the existence and stability of persistent states in large networks of quadratic integrate-and-fire neurons. The networks consist of two populations, one excitatory and one inhibitory. The stability of the asynchronous state is studied analytically. Our study demonstrates the role of recurrent inhibition and inhibitory-inhibitory interactions in stable persistent activity in large neuronal networks. 相似文献
In a majority of environments, microbes live as interacting communities. Microbial communities are composed of a mix of microbes with often unknown functions. Polymicrobial diseases represent the clinical and pathological manifestations induced by the presence of multiple infectious agents. These diseases are difficult to diagnose and treat and usually are more severe than monomicrobial infections. The interaction relationship between Enterococcus faecalis and Escherichia coli was researched using a Calvet calorimeter. Three mixtures of both bacteria were prepared in the following proportions: 20 + 80 % (0.2 mL E. faecalis + 0.8 mL E. coli), 50 + 50 % (0.5 mL E. faecalis + 0.5 mL E. coli) and 80 + 20 % (0.8 mL E. faecalis + 0.2 mL E. coli). Experiments were carried out at concentration of 106 CFU mL?1 and a constant temperature of 309.65 K. The differences in shape of graph of E. faecalis, E. coli and their mixtures were compared. Also, the thermokinetic parameters such as detection time (td), growth constant (k), generation time (G) and the amount of heat released (Q) were calculated. 相似文献
Excess molar enthalpies, HE,
for the binary mixtures {p-xylene+(1–x) octane}, {xp-xylene+(1–x)
diethyl carbonate}, {x octane+(1–x) diethyl carbonate} and the corresponding ternary
system {x1p-xylene+x2
octane+(1–x1–x2) diethyl carbonate} have
been measured by using a Calvet microcalorimeter at 298.15 K under atmospheric
pressure. The experimental HE
values are all positive for the binary and ternary mixtures over the entire
composition range. 相似文献
We solve the dynamics of the strongly diluted version of a model recently proposed by Herz et al. to store sequences of patterns with spatio-temporal retrieval properties. We analyze the spurious sequence solutions and we find the region in the (,T) plane where the only relevant attractors are the learnt cycles. 相似文献
Excess molar enthalpies
of the ternary system {x1p-xylene+x2decane+(1–x1–x2)diethyl
carbonate} and the involved binary mixtures {p-xylene+(1–x)decane}, {xp-xylene+(1–x)diethyl carbonate} and {xdecane+(1–x)diethyl carbonate} have been determined at the
temperature of 298.15 K and atmospheric pressure, over the whole composition
range, using a Calvet microcalorimeter. The experimental excess molar enthalpies HmE
are positive for all the binary systems studied over the whole composition
range. Excess molar enthalpy for the ternary system is positive as well, showing
maximum values at x1=0, x2=0.4920, x3=0.5080, Hm,123E=1524
J mol–1. 相似文献
A Cu‐based organic–inorganic perovskite framework exhibits high‐temperature ferroelectricity with strong magnetoelectric effects. Both electric field control of magnetization and magnetic field control of polarization are realized. Theoretical calculations suggest that a new mechanism of hybrid improper ferroelectricity arising from the Jahn–Teller distortions of magnetic metal ions and tilting of the organic cations are responsible for the peculiar multiferroic behaviors.