A Modified Indigo Method for the Determination of Ozone in Nonaqueous Solvents

The indigo method for the analysis of aqueous ozone was modified to allow analysis of dissolved ozone in nonaqueous liquid phases. The method was tested using the solvent decamethylcyclopentasiloxane 245 and a vegetable oil. The molar absorptivity at 600 nm of the indigo trisulphonate molecule was re-checked and found to be 20,069 ± 412 L mol^?1 cm^?1 which is in agreement with the generally accepted value. Linear correlation between liquid phase and gas phase ozone concentrations confirmed that ozone solubility in decamethylcyclopentasiloxane 245 obeyed Henry's law with a constant of 1.71 ± 0.09 mg L^?1 per mg L^?1 in the gas phase. Ozone solubility in the vegetable oil followed a power law model with k = 0.148 and n = 0.767 (liquid and gas phase concentrations in mg L^?1). The stoichiometry of the reaction between ozone in the nonaqueous phase and indigo trisulfonate in acidic solution was also confirmed as being about one. Moreover, the reaction products were confirmed by chromatographic analysis. This method was found effective to analyze ozone in nonaqueous solvents with a lower limit of detection of 2.6 μg L^?1 and upper limit of detection of 142.7 mg L^?1.     

Dyeing machine control using in-line colour measurement. Part 3: Online dyeing quality control

A system is described that controls the dyeing process so as to produce a package within a final unlevelness tolerance in the minimum time. This is achieved by incorporating into the control algorithm a mathematical model capable of predicting the unlevelness in a dyed package from the current state of the system. The use of such a general strategy allows production of dyeings of acceptable quality in minimum time and requires little intervention from the machine operator.     

The colour sensitivity of a colour matching recipe

The article examines the concepts of the following three quantities: partial colour sensitivity of a recipe to a particular colorant, colour balance of a recipe, and the overall colour sensitivity and the related property of colour robustness of a recipe. the way to calculate numerical estimates of the above quantities is extended from the case of CIE L *a*b* to the case CMC(l:c) colour difference formula. Results of a few numerical experiments are included for illustration and some possible practical consequences are discussed.     

Colour measurement by video camera

If video cameras could be used to measure colours directly, many technical and commercial possibilities would opened up. Christine Connolly, William Leung and Jim Nobbs describe how this is now close to being a reality.     

Nitrate and nitrite in fresh vegetables from queensland

Vegetables were collected near peak harvest from the main production regions in Queensland and were analysed for residues of nitrate and nitrite. A small sample of hydroponic produce was also included in the survey. Nitrite-N from 1 to 4 mg kg^-1 was found only in dwarf beans and in lettuces. Levels of nitrate in potatoes, cabbages and beets were higher than those reported in other surveys and exceeded threshold limits set in one other country. The median nitrate-N concentration measured in hydroponic lettuce (465 mg kg^-1 nitrate-N) was more than twice the median concentration for field-grown lettuce. Poor correlation between total N and nitrate in vegetables raises doubts about the use of total N alone as an indicator of N status.     

Interleukin 2 receptor regulation and IL-2 function in the human infant

IL-2 receptor is expressed at low levels on adult blood lymphocytes, and at lower levels on cord blood cells. IL-2 receptor alpha and beta chain expression increases gradually from 0-18 months of age. The level of soluble CD25 (IL-2 receptor alpha chain) has been reported to be elevated in cord blood. Quantitative RT-PCR showed that adult cells express 10 times as much CD25 mRNA as cord cells. Cord plasma showed only a marginal ability to strip CD25 from the membrane. To assess the functional consequences of low IL-2 receptor expression, cord and adult cells were activated in vitro. The response was stimulus-dependent, but cord cells upregulated CD25 readily. Cord and adult cells proliferated in an IL-2-dependent assay to a similar extent. Infants suffering acute infection showed marginally higher levels of membrane CD25 expression than infants without overt infection. Thus neonatal and infant lymphocytes express lower levels of IL-2 receptors than adult cells, reflecting lower mRNA concentrations at least for CD25; they are able to up-regulate receptors in response to in vitro stimulation and are able to respond in vitro to IL-2-dependent stimulation; however in vivo there may be a dampening down of the IL-2 system in infancy.     

A study of molecular orientation in drawn and shrunk poly(ethylene terephthalate) by means of birefringence,polarized fluorescence and X-ray diffraction measurements

Amorphous tapes of poly(ethylene terephthalate) (PET) containing the fluorescent additive 4,4′-(dibenzoxazolyl) stilbene, prepared by a method previously described, were drawn around a ‘pin’ at 80°C to draw ratios, λ, of 2.0, 2.5, 3.4₄, 3.5 and 4.2. Values of 〈P₂(cosθ)〉 were determined for samples from the tapes, either as-drawn or shrunk and crystallized in air under various conditions. P₂(cosθ) is the second order Legendre polynomial, θ is the angle between a chain axis and the draw direction and the angle brackets denote an average value. Measurements of refractive index and of the intensity of X-ray scattering were used to derive 〈P₂(cosθ)〉_opt and 〈P₂(cosθ)〉_c which refer, respectively, to the whole polymer and to the crystalline regions only. By making certain assumptions, values of 〈P₂(cosθ)〉_a for the amorphous regions only, were derived from measurements of the intensity of polarized fluorescence. The expected relationship between the three measures of orientation and the degree of crystallinity was verified, which justified the assumptions made in deriving 〈P₂(cosθ)〉_a. The PET samples appeared to behave as a rubber with 5.6 freely-jointed links between crosslink points when drawn and shrunk at 80°C for λ < 2.5. For higher λ, although the shrinkage was dramatically reduced, it was always associated with considerable disorientation of the amorphous regions, which suggests that this is the primary mechanism of shrinkage.     

A study of the orientations of fluorescent molecules incorporated in uniaxially oriented poly(ethylene terephthalate) tapes

The theory of the polarized fluorescence from fluorescent molecules incorporated in an oriented solid polymer is developed for a very general model of the optical behaviour of the molecules and it is concluded that any observed intensity can be expressed in terms of the components of a fourth rank tensor. Only twelve of these components are independent for samples of orthotropic symmetry and only six for samples of uniaxial symmetry. The effects of the birefringence of the polymer and the significant polarization-dependent absorption of the exciting light on the observed intensities are considered. The results of the analysis are presented for the uniaxial case in a form which allows values of $\text{cos}{}^2\text{θ}$ and $\text{cos}{}^4\text{θ}$ to be calculated from the experimental measurements of intensity. θ is the angle between the unique axis in the polymer and a unique axis in a fluorescent molecule and the bars denote the averages over the sample. The theory has been applied to molecules of a stilbene derivative (VPBO) incorporated at concentrations of 50–200 ppm in poly(ethylene terephthalate) (PET) of low crystallinity. It is concluded that the unique axes of the VPBO molecules are more highly oriented than the PET chains, but the two distributions of orientations appear to be uniquely related over the range of drawing temperatures (65–90°C) and draw ratios (1–5·85) used.