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Selected AbstractsOptical techniques to determine thermal effects on proteinsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 11 2008Teepakorn Kongraksawech Summary Optical rotation (OR) and transmitted light (TL) measurements were conducted on 1%, 2.5% and 5% (w/v) bovine serum albumin (BSA) in 0.01 m phosphate buffer at pH 7 and ionic strength 0.08. Denaturation temperatures (Td) obtained from OR measurements were consistent with reported differential scanning calorimetry values. Protein concentration did not affect Td in agreement with most reports. Changes in TL reflecting gel formation and protein aggregation were influenced by BSA concentration. Sugar concentration in the range used in this study (0,5%) did not affect the thermal stability of BSA. The lack of difference in sucrose, trehalose and sorbitol effects on the thermal stability of BSA was consistent with some but not all reports. The optical system used to study protein denaturation had acceptable accuracy (consistency with published Td values) and precision (coefficient of variation under 3.5%) levels. [source] Aspects of the population biology of Cephalopholis fulva from the central coast of BrazilJOURNAL OF APPLIED ICHTHYOLOGY, Issue 3 2009J. N. Araújo Summary Age and size composition samples of Cephalopholis fulva from the central coast of Brazil were collected from research surveys and from line fishery landings between 1997 and 1999. The samples suggest that the submarine banks located further offshore are characterized by having fish larger than those caught in the continental shelf area. Although the oldest specimens were caught in the continental shelf area, only 34.6% of the specimens were older than 10 years as compared to 51.4% in the submarine banks. The observed size and age differences seem to be related to the lower fishing pressure on the submarine banks, although size composition bias resulting from different sampling procedures and different catchability between sites cannot be excluded. A resampling scheme was used to overcome the influences of size composition bias and to generate a three-dimensional plot of parameters as a means to compare the growth between the submarine banks and the continental shelf area; this plot showed no overlap between growth patterns of the two sites. The natural mortality (M) estimate based on the oldest specimen observed was 0.17 year,1. Total mortality (Z) estimated from catch-curve analyses using samples from both areas varied from 0.24 to 0.34 year,1, depending on the age range used. With this level of mortality, the C. fulva stock in the central coast area of Brazil was close to or already at the level of overexploitation in the late 1990s. [source] Comparison of temperate and tropical rainforest tree species: growth responses to temperatureJOURNAL OF BIOGEOGRAPHY, Issue 1 2003S. Cunningham Abstract Aim, To investigate whether the latitudinal distribution of rainforest trees in Australia can be explained by their growth responses to temperature. Methods, The rainforest canopy trees Acmena smithii (Poir.) Merrill & Perry, Alstonia scholaris (L.) R. Br., Castanospermum australe Cunn. & C. Fraser ex Hook., Eucryphia lucida (Labill.) Baill., Heritiera trifoliolata (F. Muell.) Kosterm., Nothofagus cunninghamii (Hook.) Oerst., Sloanea woollsii F. Muell. and Tristaniopsis laurina (Sm.) Wilson & Waterhouse were selected to cover the latitudinal range of rainforests in eastern Australia. Seedlings of these species were grown under a range of day/night temperature regimes (14/6, 19/11, 22/14, 25/17, and 30/22 °C) in controlled-environment cabinets. These seedlings were harvested after 16 weeks to determine differences in growth rate and biomass allocation among species and temperature regimes. Results, The temperate species showed maximum growth at lower temperatures than the tropical species. However, there was considerable overlap in the growth rates of the temperate and tropical rainforest types across the temperature range used. Maximum growth of the tropical rainforest types was associated with changes in biomass allocation whereas the temperate rainforest types showed no significant changes in biomass allocation across the temperature range. Main conclusions, All species showed temperatures for maximum growth that were considerably higher than those previously shown for maximum net photosynthesis. The growth responses to temperature of the rainforest species under these experimental conditions provided limited evidence for their restriction to certain latitudes. These growth responses to temperature showed that the physiological assumptions used in various types of vegetation-climate models may not be true of Australian rainforest trees. [source] Study of the production of hydrogen bubbles at low current densities for electroflotation processesJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 10 2010Carlos Jiménez Abstract BACKGROUND: Flotation processes are widely used in waste-water treatment and it is quite important to have a tool to determine and optimize the size distribution of the bubbles produced. In this work, the electrochemical production of bubbles to enhance the performance of electrocoagulation processes by flotation is studied. To do this, a current density range characteristic of electrocoagulation processes is used to produce microbubbles (<5 mA cm,2), instead of the higher values used in other studies to characterize electroflotation in non-combined processes. RESULTS: Current density and pH were found to influence the process significantly. In the range used, higher current densities allow a larger number of small size bubbles to be obtained, appropriate for use in electroflotation processes. However, at the boundaries of the range, the size of the bubbles was increased advising against use. Neutral pH values also favour the formation of small bubbles, and the presence of possible competing reactions have to be considered because they diminish the gas flow and affect the number of bubbles and their size. The roughness of the surface of the electrode material also has an important influence. CONCLUSIONS: The image acquisition and analysis system developed allows measurement of the size distribution of hydrogen bubbles in the range of current densities studied. Current density and pH seem to be the main parameters affecting the mean diameter of bubbles and the amount of gas produced, and the electrode material may also influence hydrogen production significantly. Copyright © 2010 Society of Chemical Industry [source] Cones perform a non-linear transformation on natural stimuliTHE JOURNAL OF PHYSIOLOGY, Issue 3 2010D. Endeman Visual information in natural scenes is distributed over a broad range of intensities and contrasts. This distribution has to be compressed in the retina to match the dynamic range of retinal neurons. In this study we examined how cones perform this compression and investigated which physiological processes contribute to this operation. M- and L-cones of the goldfish were stimulated with a natural time series of intensities (NTSI) and their responses were recorded. The NTSI displays an intensity distribution which is skewed towards the lower intensities and has a long tail into the high intensity region. Cones transform this skewed distribution into a more symmetrical one. The voltage responses of the goldfish cones were compared to those of a linear filter and a non-linear biophysical model of the photoreceptor. The results show that the linear filter under-represents contrasts at low intensities compared to the actual cone whereas the non-linear biophysical model performs well over the whole intensity range used. Quantitative analysis of the two approaches indicates that the non-linear biophysical model can capture 91 ± 5% of the coherence rate (a biased measure of information rate) of the actual cone, where the linear filter only reaches 48 ± 8%. These results demonstrate that cone photoreceptors transform an NTSI in a non-linear fashion. The comparison between current clamp and voltage clamp recordings and analysis of the behaviour of the biophysical model indicates that both the calcium feedback loop in the outer segment and the hydrolysis of cGMP are the major components that introduce the specific non-linear response properties found in the goldfish cones. [source] The dielectric properties of cancerous tissues in a nude mouse xenograft modelBIOELECTROMAGNETICS, Issue 7 2004Done-Sik Yoo Abstract The dielectric properties of various cancers, namely brain tumor, breast cancer, gastric carcinoma, and colon cancer, were measured in the frequency range of 500 MHz to 5 GHz. Cancers were cultivated applying the xenograft model of growing human cancerous tissues using the specific pathogen free, homo inbred mouse (a nude mouse). The complex permittivity was measured using an open-ended coaxial probe (HP85070B) and a computer controlled network analyzer (HP8510C). For the measurement of the dielectric properties, a total of 58 xenografted specimens was used. The results showed that measured values of complex permittivity for all four cancerous tissues were similar, with little variations over the frequency range used. It might be agreed that components and characteristics of different cancerous tissues would be similar despite their different occurrences in the human body. It is necessary to investigate this result further. Bioelectromagnetics 25:492,497, 2004. © 2004 Wiley-Liss, Inc. [source] Diatomaceous Lessons in Nanotechnology and Advanced MaterialsADVANCED MATERIALS, Issue 29 2009Dusan Losic Abstract Silicon, in its various forms, finds widespread use in electronic, optical, and structural materials. Research on uses of silicon and silica has been intense for decades, raising the question of how much diversity is left for innovation with this element. Shape variation is particularly well examined. Here, we review the principles revealed by diatom frustules, the porous silica shells of diatoms, microscopic, unicellular algae. The frustules have nanometer-scale detail, and the almost 100,000 species with unique frustule morphologies suggest nuanced structural and optical functions well beyond the current ranges used in advanced materials. The unique frustule morphologies have arisen through tens of millions of years of evolutionary selection, and so are likely to reflect optimized design and function. Performing the structural and optical equivalent of data mining, and understanding and adopting these designs, affords a new paradigm in materials science, an alternative to combinatorial materials synthesis approaches in spurring the development of new material and more nuanced materials. [source] The effect of elevated oocyte triiodothyronine content on development of rainbow trout embryos and expression of mRNA encoding for thyroid hormone receptorsJOURNAL OF FISH BIOLOGY, Issue 1 2004J. C. Raine The ability of developing rainbow trout Oncorhynchus mykiss embryos to compensate for elevated oocyte triiodothyronine (T3) content and whether elevation of oocyte T3 content within a physiologically meaningful range affects growth rates of the embryo or the expression of genes encoding for thyroid hormone receptors ,(TR,) and ,(TR,) were examined. Oocytes were immersed in ovarian fluid alone (control) or T3 -enriched ovarian fluid prior to fertilization and water hardening, to induce a dose-dependant increase in oocyte T3 content of c. 3 (control), c. 30 (LT3) or c. 110 ng egg,1(HT3). To examine the interaction of embryo somatic growth with altered thyroid state more effectively, the embryos were reared at two ambient temperatures (8·5 and 5·5°C ) to induce different growth rates. A significant decline in whole embryo T3 content was measured in the T3 -treatment groups reared at both water temperatures by 3 weeks post-fertilization (dpf), and may have reflected the action of outer ring monodeiodinase, which was present in microsomes prepared from embryos 23 dpf. Whole embryo T3 levels in the HT3 group, however, remained higher than controls until phase 2 of development [the onset of endogenous thyroid hormone (TH) release]. This suggested that the embryos exerted some control over their response to exogenous TH, but that there was a limit to the level of control exerted by the embryonic tissues. Reverse transcriptase-polymerase chain reaction (RT-PCR) revealed the presence of mRNA encoding for the two TR isoforms as early as 26 dpf, and quantitative real-time RT-PCR (qPCR) was used to examine the effect of elevated oocyte T3 content on the expression of these TR genes in embryos raised at 8·5 and 5·5° C, and sampled at similar developmental stages prior to the onset of embryonic TH synthesis, to ensure that the oocyte T3 was the only source of TH exposure to the embryo. There was a suppression of the TR, gene expression in the control 5·5° C group relative to the control 8·5° C group. In addition, both TR, and TR, mRNA accumulation was lower, relative to the controls, in the LT3 treatment group reared at 8·5° C suggesting a suppressive effect of the lower level of T3 treatment on the TR gene expression. Conversely, there were no differences from controls in the HT3 treatment group, possibly indicating that this level of exposure overrides the down-regulating capacity of the embryo. Similar patterns were seen for TR, and TR, mRNA accumulation in embryos reared at 5·5° C, but because of the temperature suppressed level of TR, mRNA in the controls, significant affects of the LT3 treatment were only found for TR,. There were no measurable effects of T3 treatment on oocyte fertility or embryo somatic growth for either temperature treatment group, nor was somatic growth hormone content (measured only in the 8·5° C treatment group) apparently related to in ovo T3 levels. The results suggest that altered in ovo T3 levels, within the ranges used here, do not induce marked affects on embryo development, probably because of the ability of the embryo to maintain the integrity of its TH milieu. [source] Imaging pharmaceutical tablets with optical coherence tomographyJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 1 2010Jakob M.A. Mauritz Abstract Optical coherence tomography (OCT) is a recently developed optical technique that produces depth profiles of three-dimensional objects. It is a nondestructive interferometric method responding to refractive index variation in the sample under study and can reach a penetration depth of a few millimetres. OCT employs near-infrared (NIR) light and therefore provides a link between NIR spectroscopy and Terahertz (THz) measurements that are often used to characterise tablets. In this article we assess the potential of OCT as a reliable and practical tool in the analysis of pharmaceutical tablets and coatings. A variety of tablets were tested with different shapes, formulations and coatings. We consider the origins of contrast in the obtained images and demonstrate that it correlates strongly with the expected tablet structure. The influence of absorption and scattering are considered for the wavelength ranges used. The results show that OCT is a promising diagnostic tool with an important role to play in the tablet and coating technologies. The high measurement speed of OCT and its relative ease of implementation make it also an attractive candidate technology for in-line quality control during manufacturing. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:385,391, 2010 [source] Reproducibility and variability of activated clotting time measurements in the cardiac catheterization laboratoryCATHETERIZATION AND CARDIOVASCULAR INTERVENTIONS, Issue 3 2005Terence M. Doherty Abstract The objective of this study was to characterize the reproducibility and variability in the measurement to the activated clotting time (ACT) when performed on two different types of instruments, the HemoTec ACT (Medtronic) and the Hemochron 801 (International Technidyne). The ACT has evolved into the most common point-of-care test used in the cardiac catheterization lab to manage patient heparinization. Since the test has not been standardized, different systems frequently produce different results under the same clinical conditions. Duplicate paired ACT tests (n = 885) from 359 patients were performed on both instruments. Prothrombin times (PT) and activated partial thromboplastin times (aPTT) were also determined on subsets of these same samples (PT = 533; aPTT = 487). The performance and relationships between the two tests were determined using a variety of statistical analytical techniques. The average difference between the ACT devices was only 8 sec, yet more than 60% of the measurements varied by more than 10%. Over one-fourth of measurements varied by more than 20%. The reproducibility to the HemoTec instrument was superior to the Hemochron instrument across the entire range of ACTs measured (mean coefficient of variation 2.4% 54± 3.1% vs. 7.2% 54± 6.1% for HemoTec and Hemochron, respectively; P < 0.00001; range = 65,555 sec). The relationship between the two ACTs was nonlinear. In therapeutic ranges used for interventional procedures (200,350 sec), HemoTec and Hemochron ACTs are not comparable to one another. Statistical comparative analysis indicated that the HemoTec ACT has better overall performance. © 2005 Wiley-Liss, Inc. [source] | ||||||||||||||||