Analysis of spectroscopic measurements of leaf water content at terahertz frequencies using linear transforms

We provide a unified framework for a range of linear transforms that can be used for the analysis of terahertz spectroscopic data, with particular emphasis on their application to the measurement of leaf water content. The use of linear transforms for filtering, regression, and classification is discussed. For illustration, a classification problem involving leaves at three stages of drought and a prediction problem involving simulated spectra are presented. Issues resulting from scaling the data set are discussed. Using Lagrange multipliers, we arrive at the transform that yields the maximum separation between the spectra and show that this optimal transform is equivalent to computing the Euclidean distance between the samples. The optimal linear transform is compared with the average for all the spectra as well as with the Karhunen–Loève transform to discriminate a wet leaf from a dry leaf. We show that taking several principal components into account is equivalent to defining new axes in which data are to be analyzed. The procedure shows that the coefficients of the Karhunen–Loève transform are well suited to the process of classification of spectra. This is in line with expectations, as these coefficients are built from the statistical properties of the data set analyzed.

Measurements of leaf water content using terahertz radiation

A novel technique for the noninvasive continuous measurement of leaf water content is presented. The technique is based on transmission measurements of terahertz radiation with a null-balance quasi-optical transmissometer operating at 94 GHz. A model for the propagation of terahertz radiation through leaves is presented. This, in conjunction with leaf thickness information determined separately, may be used to quantitatively relate transmittance measurements to leaf water content. Measurements using a dispersive Fourier transform spectrometer in the range of 100 GHz-500 GHz using Phormium tenax and Fatsia japonica leaves are also reported.

Parametrizing the horizontal inhomogeneity of ice water content using CloudSat data products

In order to calculate unbiased microphysical and radiative quantities in the presence of a cloud, it is necessary to know not only the mean water content but also the distribution of this water content. This article describes a study of the in-cloud horizontal inhomogeneity of ice water content, based on CloudSat data. In particular, by focusing on the relations with variables that are already available in general circulation models (GCMs), a parametrization of inhomogeneity that is suitable for inclusion in GCM simulations is developed. Inhomogeneity is defined in terms of the fractional standard deviation (FSD), which is given by the standard deviation divided by the mean. The FSD of ice water content is found to increase with the horizontal scale over which it is calculated and also with the thickness of the layer. The connection to cloud fraction is more complicated; for small cloud fractions FSD increases as cloud fraction increases while FSD decreases sharply for overcast scenes. The relations to horizontal scale, layer thickness and cloud fraction are parametrized in a relatively simple equation. The performance of this parametrization is tested on an independent set of CloudSat data. The parametrization is shown to be a significant improvement on the assumption of a single-valued global FSD

A regime-dependent parametrization of subgrid-scale cloud water content variability

The subgrid-scale spatial variability in cloud water content can be described by a parameter f called the fractional standard deviation. This is equal to the standard deviation of the cloud water content divided by the mean. This parameter is an input to schemes that calculate the impact of subgrid-scale cloud inhomogeneity on gridbox-mean radiative fluxes and microphysical process rates. A new regime-dependent parametrization of the spatial variability of cloud water content is derived from CloudSat observations of ice clouds. In addition to the dependencies on horizontal and vertical resolution and cloud fraction included in previous parametrizations, the new parametrization includes an explicit dependence on cloud type. The new parametrization is then implemented in the Global Atmosphere 6 (GA6) configuration of the Met Office Unified Model and used to model the effects of subgrid variability of both ice and liquid water content on radiative fluxes and autoconversion and accretion rates in three 20-year atmosphere-only climate simulations. These simulations show the impact of the new regime-dependent parametrization on diagnostic radiation calculations, interactive radiation calculations and both interactive radiation calculations and in a new warm microphysics scheme. The control simulation uses a globally constant f value of 0.75 to model the effect of cloud water content variability on radiative fluxes. The use of the new regime-dependent parametrization in the model results in a global mean which is higher than the control's fixed value and a global distribution of f which is closer to CloudSat observations. When the new regime-dependent parametrization is used in radiative transfer calculations only, the magnitudes of short-wave and long-wave top of atmosphere cloud radiative forcing are reduced, increasing the existing global mean biases in the control. When also applied in a new warm microphysics scheme, the short-wave global mean bias is reduced.

Stalagmite water content as a proxy for drip water supply in tropical and subtropical areas

In this pilot study water was extracted from samples of two Holocene stalagmites from Socotra Island, Yemen, and one Eemian stalagmite from southern continental Yemen. The amount of water extracted per unit mass of stalagmite rock, termed "water yield" hereafter, serves as a measure of its total water content. Based on direct correlation plots of water yields and δ18Ocalcite and on regime shift analyses, we demonstrate that for the studied stalagmites the water yield records vary systematically with the corresponding oxygen isotopic compositions of the calcite (δ18Ocalcite). Within each stalagmite lower δ18Ocalcite values are accompanied by lower water yields and vice versa. The δ18Ocalcite records of the studied stalagmites have previously been interpreted to predominantly reflect the amount of rainfall in the area; thus, water yields can be linked to drip water supply. Higher, and therefore more continuous drip water supply caused by higher rainfall rates, supports homogeneous deposition of calcite with low porosity and therefore a small fraction of water-filled inclusions, resulting in low water yields of the respective samples. A reduction of drip water supply fosters irregular growth of calcite with higher porosity, leading to an increase of the fraction of water-filled inclusions and thus higher water yields. The results are consistent with the literature on stalagmite growth and supported by optical inspection of thin sections of our samples. We propose that for a stalagmite from a dry tropical or subtropical area, its water yield record represents a novel paleo-climate proxy recording changes in drip water supply, which can in turn be interpreted in terms of associated rainfall rates.

Specific leaf areas of the tank bromeliad Guzmania monostachia perform distinct functions in response to water shortage

Leaves comprise most of the vegetative body of tank bromeliads and are usually subjected to strong longitudinal gradients. For instance, while the leaf base is in contact with the water accumulated in the tank, the more light-exposed middle and upper leaf sections have no direct access to this water reservoir. Therefore, the present study attempted to investigate whether different leaf portions of Guzmania monostachia, a tank-forming C(3)-CAM bromeliad, play distinct physiological roles in response to water shortage, which is a major abiotic constraint in the epiphytic habitat. Internal and external morphological features, relative water content, pigment composition and the degree of CAM expression were evaluated in basal, middle and apical leaf portions in order to allow the establishment of correlations between the structure and the functional importance of each leaf region. Results indicated that besides marked structural differences, a high level of functional specialization is also present along the leaves of this bromeliad. When the tank water was depleted, the abundant hydrenchyma of basal leaf portions was the main reservoir for maintaining a stable water status in the photosynthetic tissues of the apical region. In contrast, the CAM pathway was intensified specifically in the upper leaf section, which is in agreement with the presence of features more suitable for the occurrence of photosynthesis at this portion. Gas exchange data indicated that internal recycling of respiratory CO(2) accounted for virtually all nighttime acid accumulation, characterizing a typical CAM-idling pathway in the drought-exposed plants. Altogether, these data reveal a remarkable physiological complexity along the leaves of G. monostachia, which might be a key adaptation to the intermittent water supply of the epiphytic niche. (C) 2009 Elsevier GmbH. All rights reserved.

Vanadium oxide-porphyrin nanocomposites as gas sensor interfaces for probing low water content in ethanol

Vanadium pentoxide xerogels (VXG) incorporating meso(3- and 4-pyridyl)porphyrin cobalt(III) species coordinated to four [Ru(bipy)(2)Cl](+) complexes were employed as gas sensing materials capable of detecting small amounts of water in commercial ethanol and fuel supplies. According to their X-ray diffraction data, the original VXG lamellar framework was maintained in the nanocomposite material, but the interlamellar distance increased from 11.7 to 15.2 angstrom, reflecting the intercalation of the porphyrin species into the vanadium pentoxide matrix. The films generated by direct deposition of the nanocomposite aqueous suspensions exhibited good electrical and electrochemical performance for application in resistive sensors. The analysis of water in ethanol and fuels was carried out successfully using an especially designed electric setup incorporating a laminar gas flow chamber and interdigitated gold electrodes coated with the nanocomposites. (C) 2010 Elsevier B.V. All rights reserved.

Spatial variability of soil water content and mechanical resistance of Brazilian ferralsol

The spatial variability of mechanical resistance to penetration (PR) and gravimetric moisture (GM) was studied at a depth of 0-0.40 m, in a ferralsol cropped with corn, and under conventional tillage in llha Solteira, Brazil (latitude 20 degrees 17'S, and longitude 52 degrees 25'W). The purpose of this study was to analyse and to try explaining the spatial variability of the mentioned soil physical properties using geostatistics. Soil data was collected at points arranged on the nodes of a mesh with 97 points. Geostatistics was used to analyse the spatial variability of PR and GM at four depths: 0-0. 1, 0.1-0.2, 0.2-0.3 and 0.3-0.4 m. PR showed a higher variability of data, with coefficients of variation of 52.39, 30.54, 16.91, and 15.18%, from the surface layers to the deepest layers. The values of the coefficients of variation for GM were lower: 9.99, 5.13, 5.59, and 5.69%. Correlation between GM and PR for the same soil layers was low. Penetration resistance showed spatial structure only in the 0.30-0.40 m layer, while gravimetric moisture showed spatial structure at all depths except for 0-0. 10 m. All the models of fitted semivariograms were spherical and exponential, with ranges of 10-80 m. Data for the variable 'GM' in the 0.20-0.30 and 0.30-0.40 m layers revealed a trend in data attributed to the occurrence of subsurface water flow. (C) 2005 Elsevier B.V. All rights reserved.

Photosynthetic limitations caused by different rates of water-deficit induction in Glycine max and Vigna unguiculata

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Water content and GA(3)-induced embryonic cell expansion explain Euterpe edulis seed germination, rather than seed reserve mobilisation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Thermophysical Properties of Lemon Juice as Affected by Temperature and Water Content

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Physiological parameters in sugarcane cultivars submitted to water deficit

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Temperature and water content influence on thermophysical properties of coffee extract

Specific heat, thermal conductivity, thermal diffusivity, and density of coffee extract were experimentally determined in the range of 0.49 to 0.90 (wet basis) water content and at temperatures varying from 30 to 82 degreesC. Thermal conductivity and specific heat were measured by means of the same apparatus- a cell constituted of two concentric cylinders - operating at steady and unsteady state, respectively. The thermal diffusivity was measured by the well-known Dickerson's method and density was determined by picnometry. The results obtained were used to derive mathematical models for predicting these properties as a function of concentration and temperature.

The influence of the caruncle on the germination of castor seed under high salinity or low soil water content

The caruncle is a structure present in the micropylar region of Euphorbiaceae seeds. This structure has the ecological function of promoting seed dispersal by ants (myrmecochory), but it is debated whether it also has an agronomical importance influencing seed germination. The influence of the caruncle on castor (Ricinus communis) seed germination was evaluated under low soil water content and high soil salinity. Seeds were germinated at soil water storage capacities varying from 22 to 50% and salinities (NaCl) varying from 0 to 10 dS m(-1) The germination (%) increased following the increments in soil moisture. hut the caruncle had no influence on this process at any moisture level. In one genotype. more root dry mass was produced when caruncle was excised. Increasing salinity reduced the percentage and speed of germination of castor seeds, but no influence of caruncle was detected. No evidence of caruncle influencing castor seed germination was found under low soil water content and high salinity.

Thermophysical Properties of Brazilian Orange Juice as Affected by Temperature and Water Content

The specific heat, thermal conductivity, thermal diffusivity and density of Brazilian orange juice were determined between 0.34 and 0.73 (w/w) water content and with temperatures from 0.5 to 62°C. The experimental data were fitted as functions of temperature and water content and all properties showed a linear dependency with these variables. In the tested range, the water content exhibited a greater influence on the analyzed properties than temperature. © 1998 Elsevier Science Limited. All rights reserved.