The effect of polymer adsorption on the wetting properties of partially hydrophobized magnetite.

Upon reverse flotation of iron ore, the surface of the iron ore concentrate may become partially hydrophobized due to adsorption of flotation collector, which is facilitated by the calcium ions present in the process water. Hydrophobic areas on the concentrate surface may introduce problems in subsequent pelletization of the concentrate. A possible way to restore the wettability of the surface could be by modifying the surface with a hydrophilic polymer. The effect of hydrophilic polymers of different types, viz. cationic, anionic, and non-ionic, on the wettability of the magnetite surface after adsorption of a surfactant was investigated. Although all the polymers could adsorb on magnetite at pH 8.5, the contact angle measurements revealed that only anionic ammonium polyacrylate could decrease the contact angle of synthetic magnetite after surfactant adsorption to a level close to that of as-synthesized magnetite. Such effect was probably achieved due to shielding of the hydrophobic surfactant chains from the aqueous phase by hydrophilic polyacrylate molecules. The fact that polyacrylate adsorption on magnetite occurred via calcium ions makes polyacrylate suitable for application in calcium-rich process water. The results presented in this work illustrate that ammonium polyacrylate could be successfully used to improve the wettability of magnetite after adsorption of surfactants.

Low-CO(2) electricity and hydrogen: a help or hindrance for electric and hydrogen vehicles?

The title question was addressed using an energy model that accounts for projected global energy use in all sectors (transportation, heat, and power) of the global economy. Global CO(2) emissions were constrained to achieve stabilization at 400-550 ppm by 2100 at the lowest total system cost (equivalent to perfect CO(2) cap-and-trade regime). For future scenarios where vehicle technology costs were sufficiently competitive to advantage either hydrogen or electric vehicles, increased availability of low-cost, low-CO(2) electricity/hydrogen delayed (but did not prevent) the use of electric/hydrogen-powered vehicles in the model. This occurs when low-CO(2) electricity/hydrogen provides more cost-effective CO(2) mitigation opportunities in the heat and power energy sectors than in transportation. Connections between the sectors leading to this counterintuitive result need consideration in policy and technology planning.

The effect of calcium ions and sodium silicate on the adsorption of a model anionic flotation collector on magnetite studied by ATR-FTIR spectroscopy.

Previous studies have shown that agglomeration of the magnetite concentrate after reverse flotation of apatite is negatively affected by the collector species adsorbed on the surface of magnetite. In this work, the effect of ionic strength, calcium ions and sodium silicate on the unwanted adsorption of a model anionic flotation collector on synthetic magnetite was studied in situ using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). The amount of collector adsorbed was found to increase with increasing ionic strength at pH 8.5 providing evidence to the contribution of electrostatic forces to the adsorption of the collector. Adding sodium silicate to the system resulted in a threefold decrease in the amount of collector adsorbed compared to when no sodium silicate was added, confirming the depressing activity of sodium silicate on magnetite. Calcium ions were shown to increase the adsorption of both the collector and sodium silicate on magnetite. The depressing effect of sodium silicate on collector adsorption was completely suppressed in the presence of calcium ions under the conditions studied. Furthermore, the amount of collector adsorbed on magnetite from the silicate-collector solution increased 14 times upon addition of calcium ions suggesting that calcium ions in the process water may increase undesired adsorption of the collector on the iron oxide.

Fuel and vehicle technology choices for passenger vehicles in achieving stringent CO2 targets: connections between transportation and other energy sectors.

The regionalized Global Energy Transition (GET-R 6.0) model has been modified to include a detailed description of light-duty vehicle options and used to investigate the potential impact of carbon capture and storage (CCS) and concentrating solar power (CSP) on cost-effective fuel/vehicle technologies in a carbon-constrained world. Total CO2 emissions were constrained to achieve stabilization at 400-550 ppm, by 2100, at lowesttotal system cost The dominantfuel/vehicle technologies varied significantly depending on CO2 constraint future cost of vehicle technologies, and availability of CCS and CSP. For many cases, no one technology dominated on a global scale. CCS provides relatively inexpensive low-CO2 electricity and heatwhich prolongs the use of traditional ICEVs. CSP displaces fossil fuel derived electricity, prolongs the use of traditional ICEVs, and promotes electrification of passenger vehicles. In all cases considered, CCS and CSP availability had a major impact on the lowest cost fuel/vehicle technologies, and alternative fuels are needed in response to expected dwindling oil and natural gas supply potential by the end of the century.

Socioeconomic differences in smoking trends among pregnant women at first antenatal visit in Sweden 1982-2001: increasing importance of educational level for the total burden of smoking.

BACKGROUND: There was a decrease in smoking during early pregnancy in Swedish women between 1982 and 2001. We sought to determine whether there was a parallel decrease in socioeconomic inequality in smoking. METHODS: Registry data indicating educational level and smoking status at first antenatal visit in all 2,022,469 pregnancies in Sweden 1982-2001 were analysed. Prevalence differences, odds ratios based on prevalences and total attributable fractions were compared for five-year intervals. RESULTS: The prevalence differences of smoking showed a greater decrease at the lowest and middle educational level compared with the highest educational level (14.5%, 15.7% and 10.2%, respectively) indicating reduced inequality in absolute terms. However, odds ratios regarding low educational attainment versus high, increased from 5.6 to 14.2, signifying increased inequality in relative terms. Moreover, the total attributable fraction of low and intermediate educational level regarding smoking at first antenatal visit increased from 61% to 76% during the period studied. CONCLUSIONS: Smoking at first antenatal visit in Sweden between 1982 to 2001 decreased in a way that conclusions regarding trends in inequalities in smoking at first antenatal visit depend on the type of measure applied. However, using the measure of total attributable fraction, which takes into consideration the impact of the exposure on the individual as well as the effect of the varying size of the group of exposed, the growing importance of educational level for the behaviour in the population was demonstrated.

Biocompatible materials developments for new medical implants.

Recent work on modifying silicone rubber to improve water permeability and biocompatibility is described. In addition, modifications to the interface between an active implanted device and the body are reported, which have led to reduced power consumption and improved device performance.

Influence of genetic dissimilarity in the reproductive success and mate choice of brown trout - females fishing for optimal MHC dissimilarity.

We examined the reproductive success of 48 adult brown trout (Salmo trutta L.) which were allowed to reproduce in a stream that was controlled for the absence of other trout. Parentage analyses based on 11 microsatellites permitted us to infer reproductive success and mate choice preferences in situ. We found that pairs with intermediate major histocompatibility complex (MHC) dissimilarity mated more often than expected by chance. It appears that female choice was the driving force behind this observation because, compared with other individuals, males with intermediate MHC dissimilarity produced a larger proportion of offspring, whereas female reproductive output did not show this pattern. Hence, rather than seeking mates with maximal MHC dissimilarity, as found in several species, brown trout seemed to prefer mates of intermediate MHC difference, thus supporting an optimality-based model for MHC-dependent mate choice.

Major histocompatibility complex variation and mate choice in a lekking bird, the great snipe (Gallinago media).

Genes of the major histocompatibility complex (MHC) play a major part in the activation of the vertebrate immune system. In addition, they also appear to function as cues for mate choice. In mammals especially, several kinds of MHC-dependent mate choice have been hypothesized and observed. These include choice of mates that share no or few alleles with the choosing individual, choice of mates with alleles that differ as much as possible from the choosing individual, choice of heterozygous mates, choice of certain genotypes and choice of rare alleles. We investigated these different aspects of mate choice in relation to MHC in a lekking bird species, the great snipe (Gallinago media). We found no evidence for MHC disassortative mating, no preference for males with many MHC alleles and no preference for rare alleles. However, we did find that some allelic lineages were more often found in males with mating success than in males without mating success. Females do not seem to use themselves as references for the MHC-dependent mate choice, rather they seem to prefer males with certain allele types. We speculate that these alleles may be linked to resistance to common parasites.

Fibrin glue in the management of anal fistulae.

OBJECTIVE: Fibrin glue has been used as a sphincter sparing approach for the treatment of anal fistulae for two decades. However, there is uncertainty about its short and long-term efficacy. The objective of this review was to ascertain the role of fibrin glue in the management of anal fistulae, including assessment of recurrence rates, continence disturbance and other complications. METHODS: We searched Medline (January 1966 to February 2004), the Cochrane database, and EMBASE using the terms anal fistulae, fistula-in-ano, and fibrin glue. Relevant papers from the reference lists of these articles and from the authors' personal collections were also reviewed. A systematic review of all articles relating to the use of fibrin glue in the treatment of anal fistulae was performed. This included 19 studies. Reviewers performed data extraction independently. Outcomes evaluated included recurrence rates, continence disturbance, septic complications, adverse drug reactions, and duration of follow-up. Heterogeneity of the clinical trials made direct comparisons difficult and meta-analysis impossible. RESULTS: The success rates reported in published studies range from 0% to 100%. Differences in patient selection (including fistula aetiology and type), treatment protocols, and follow-up duration may contribute to such diverse results. CONCLUSIONS: Fibrin glue is simple to use, has a minimal morbidity and should not affect later treatment options in the event of its failure. It is therefore theoretically attractive as a first line treatment in the management of those types of anal fistula in which it has been shown to work. However, further research into 'biological' glues is merited and these subject to randomised controlled study.

Influence of MHC on sibling discrimination in Arctic char, Salvelinus alpinus (L.).

The preference of juvenile Arctic char [Salvelinus alpinus (L.)] for odors from siblings and nonsiblings with different major histocompability complex class II (MHC) genotypes was studied in two-choice fluviarium tests. In the first part of the study, test fish demonstrated no preference for water scented by a sibling with a MHC genotype different from its own versus water scented by a MHC identical nonsibling. When both donors were siblings with different MHC genotypes, however, the test fish chose the water scented by the fish with the same MHC type as the test fish. The results suggest that odors with information about kinship are dependent on MHC but also on other, unknown factors. In the second part of the study, we observed that fish isolated since fertilization did not show any behavioral discrimination towards siblings, based on MHC genotype. One reasonable explanation for this result is that Arctic char learn to discriminate between odors from individuals of different MHC types.

Association between major histocompatibility complex class IIB alleles and resistance to Aeromonas salmonicida in Atlantic salmon.

We have tested the importance of genetic variation in the major histocompatibility complex (MHC) class IIB in Atlantic salmon (Salmo salar) for survival after challenge with a highly virulent bacterial pathogen. Forty juvenile full siblings from each of 120 families were infected with the bacterium Aeromonas salmonicida, which causes high mortality in salmon due to furunculosis. Fishes from high-resistance (HR, < 35% mortality) and low-resistance (L,R, > 80% mortality) families were screened for their MHC class IIB genotypes using the denaturing gradient gel electrophoresis (DGGE) technique. The exon 2 sequences, encoding the major part of the peptide-binding region, were established for each DGGE fragment. One allele, e, containing a missense single base substitution was significantly more prevalent in HR families than in LR families. An odds-ratio test showed that broods carrying this allele had a 12-fold higher chance of being HR than broods without the e allele. A second allele, i, showed significantly higher frequencies in uninfected and surviving individuals than in infected dead individuals. A third allele, j, tended to more prevalent both in LR families and in individuals that had died of the infection. There was no correlation between MHC heterozygosity and resistance to A. salmonicida. Our results support the hypothesis that MHC polymorphism is maintained through pathogen-driven selection acting by means of frequency-dependent selection rather than heterozygous advantage.

A rapid spectrophotometric assay for tetracycline in gingival crevicular fluid.

AIM: The aim of this study was to investigate a rapid spectrophotometric assay for its potential to measure tetracycline levels in gingival crevicular fluid (GCF). MATERIALS AND METHODS: The technique involves complexation of tetracycline with molybdenum in order to shift the absorbance spectrum away from that region where interference with plasma proteins is a problem. The sensitivity of the assay and reproducibility of elution were examined together with an assessment of the effect of plasma proteins. The assay was also tested in a small pilot clinical project, measuring tetracycline levels in GCF following placement of a test gel formulation in 25 periodontal pockets in 5 patients. RESULTS: The in vitro results showed good sensitivity of the assay over the concentration range tested (0.5-200 microg tetracycline) and with little effect of plasma proteins. Elution from the paper strips was reproducible with a good linear correlation between direct and filter absorbed assays (r=0.9989, p<0.01). The pilot clinical study indicated a mean half-time of tetracycline in GCF of 28 min with confidence intervals of 21 to 34 min, although wide variation between the drug levels of individual periodontal pockets was seen. CONCLUSIONS: The results indicate good sensitivity for this assay to measure tetracycline hydrochloride in vivo. The potential for rapidly processing large numbers of samples contrasts with the assay time and limited sample throughput of other methods such as high pressure liquid chromatography (HPLC) and suggests that the technique may be a useful addition to current techniques for measuring tetracycline hydrochloride in vivo.

Significantly increased lesion size by using the near-infrared photosensitizer 5,10,15,20-tetrakis (m-hydroxyphenyl)bacteriochlorin in interstitial photodynamic therapy of normal rat liver tissue.

BACKGROUND AND OBJECTIVE: Penetration of tissues by activating light ultimately limits the size of the lesions achievable in interstitial photodynamic therapy. Measurements of the wavelength-dependence of tissue optical properties suggest that substantial improvements may be possible, particularly in pigmented organs such as the liver, by using drugs absorbing at near infrared wavelengths. STUDY DESIGN/MATERIALS AND METHODS: In this study, the extent of light induced necrosis with the photosensitive agents Photofrin (activated at 632 nm), meta-tetra(hydroxyphenyl)chlorin (mTHPC) (activated at 652 nm) and 5,10,15,20-tetrakis(m-hydroxyphenyl)bacteriochlorin (mTHPBC) (activated at 740 nm) are compared in normal rat liver. Interstitial irradiation of mTHPBC-sensitized liver tissue resulted in significantly larger necrotic areas than irradiation of Photofrin and mTHPC-sensitised livers. CONCLUSION: The results illustrate the advantage of near-infrared photosensitizer activation and point to a specific role for mTHPBC in the interstitial treatment of liver tumours.

In vivo photodynamic characteristics of the near-infrared photosensitizer 5,10,15,20-tetrakis(M-hydroxyphenyl) bacteriochlorin.

This paper describes the photodynamic characteristics of the new near-infrared photosensitizer 5,10,15,20-tetrakis(m-hydroxyphenyl)bacteriochlorin (mTHPBC or SQN400) in normal rat and mouse tissues. A rat liver model of photodynamic tissue necrosis was used to determine the in vivo action spectrum and the dose-response relationships of tissue destruction with drug and light doses. The effect of varying the light irradiance and the time interval between drug administration and light irradiation on the biological response was also measured in the rat liver model. Photobleaching of mTHPBC was measured and compared with that of its chlorine analog (mTHPC) in normal mouse skin and an implanted mouse colorectal tumor. The optimum wavelength for biological activation of mTHPBC in rat liver was 739 nm. mTHPBC was found to have a marked drug-dose threshold of around 0.6 mg kg-1 when liver tissue was irradiated 48 h after drug administration. Below this administered drug dose, irradiation, even at very high light doses, did not cause liver necrosis. At administered doses above the photodynamic threshold the effect of mTHPBC-PDT was directly proportional to the product of the drug and light doses. No difference in the extent of liver necrosis produced by mTHPBC was found on varying the light irradiance from 10 to 100 mW cm-2. The extent of liver necrosis was greatest when tissue was irradiated shortly after mTHPBC administration and necrosis was absent when irradiation was performed 72 h or later after drug administration, suggesting that the drug was rapidly cleared from the liver. In vivo photobleaching experiments in mice showed that the rate of bleaching of mTHPBC was approximately 20 times greater than that of mTHPC. It is argued that this greater rate of bleaching accounts for the higher photodynamic threshold and this could be exploited to enhance selective destruction of tissues which accumulate the photosensitizer.

Screening of Mhc variation in Atlantic salmon (Salmo salar): a comparison of restriction fragment length polymorphism (RFLP), denaturing gradient gel electrophoresis (DGGE) and sequencing.

We compared three different molecular methods currently used for screening of Mhc variation in population studies of Atlantic salmon. Restriction fragment length polymorphism (RFLP) of the entire class II gene detected 22 haplotypes. Seventeen exon 2 sequences were obtained from individuals carrying the 22 haplotypes, two of which had not been detected by RFLP. The six alleles (27%) detected by RFLP and not by exon 2 sequencing probably resulted from sequence variation outside exon 2. Within exon 2, RFLP differentiated 88% of the sequences. Alternatively, denaturing gradient gel electrophoresis (DGGE) performed under two run conditions detected 94% of the sequence variation. Both RFLP using different probes, and the two PCR-based methods using three different primer pairs, suggest that there is only a single Mhc class II B gene in the Baltic populations of Atlantic salmon.

Biodistribution and bioactivity of tetra-pegylated meta-tetra(hydroxyphenyl)chlorin compared to native meta-tetra(hydroxyphenyl)chlorin in a rat liver tumor model.

It has been proposed that the construction of a photosensitizer-polymer conjugate would lead to an increased selective retention of the drug in tumor tissue resulting in an enhancement of selective tumor destruction by light in photodynamic therapy. In this study the kinetics of a tetra-pegylated derivative of meta-tetra(hydroxyphenyl)chlorin (mTHPC-PEG) were compared with those of native meta-tetra(hydroxyphenyl)chlorin (mTHPC) in a rat liver tumor model. In addition, the time course of bioactivity of both drugs was studied in normal liver tissue. Pegylation of mTHPC resulted in a two-fold increase in the plasma half-life time, a five-fold decrease in liver uptake and an increase in the tumor selectivity at early time intervals after drug administration. However, although mTHPC concentrations in liver decrease rapidly with time, mTHPC-PEG liver concentrations increased as a function of time. This led to a loss of tumor selectivity at all but the earliest time points, whereas with mTHPC tumor selectivity increased with time. For both drugs the time course of bioactivity in the liver parallels drug concentration levels with extensive necrosis after irradiation of mTHPC-PEG-sensitized liver tissue up to drug-light intervals of 120 h. It is concluded that on balance mTHPC-PEG does not appear to show any benefits over native mTHPC for the treatment of liver tumors, as normal liver tissue accumulates the compound. However, pegylation is a potentially promising strategy with an increase in tumor selectivity and reduced liver uptake if accumulation in the liver can be prevented.

Dietary conjugated linoleic acids alter serum IGF-I and IGF binding protein concentrations and reduce bone formation in rats fed (n-6) or (n-3) fatty acids.

A study was designed to examine the effects of dietary conjugated linoleic acid (CLA) on serum concentrations of insulin-like growth factor-I (IGF-I) and IGF binding proteins (IGFBP) and the relationship of these factors to bone metabolism. Weanling male rats were fed AIN-93G diet containing 70 g/kg of added fat for 42 days. Treatments included 0 g/kg or 10 g/kg of CLA and soybean oil (SBO) or menhaden oil + safflower oil (MSO) following a 2 x 2 factorial design. Serum IGFBP was influenced by dietary polyunsaturated fatty acid (PUFA) type ((n-6) and (n-3)) and CLA (p = 0.01 for 38-43 kDa bands corresponding to IGFBP-3). CLA increased IGFBP level in rats fed SBO (p = 0.05) but reduced it in those fed MSO (p = 0.01). Rats fed MSO had the highest serum IGFBP-3 level. Both (n-3) fatty acids and CLA lowered ex vivo prostaglandin E2 production in bone organ culture. In tibia, rats given CLA had reduced mineral apposition rate (3.69 vs. 2.79 microm/day) and bone formation rate (BFR) (0.96 vs. 0.65 microm3/microm2/day); however, the BFR tended to be higher with MSO. Dietary lipid treatments did not affect serum intact osteocalcin or bone mineral content. These results showed that dietary PUFA type and CLA modulate local factors that regulate bone metabolism.

Good genes, oxidative stress and condition-dependent sexual signals.

The immune and the detoxication systems of animals are characterized by allelic polymorphisms, which underlie individual differences in ability to combat assaults from pathogens and toxic compounds. Previous studies have shown that females may improve offspring survival by selecting mates on the basis of sexual ornaments and signals that honestly reveal health. In many cases the expression of these ornaments appears to be particularly sensitive to oxidative stress. Activated immune and detoxication systems often generate oxidative stress by an extensive production of reactive metabolites and free radicals. Given that tolerance or resistance to toxic compounds and pathogens can be inherited, female choice should promote the evolution of male ornaments that reliably reveal the status of the bearers' level of oxidative stress. Hence, oxidative stress may be one important agent linking the expression of sexual ornaments to genetic variation in fitness-related traits, thus promoting the evolution of female mate choice and male sexual ornamentation, a controversial issue in evolutionary biology ever since Darwin.

mTHPC Polymer Conjugates: The In Vivo Photodynamic Activity of Four Candidate Compounds.

The in vivo photodynamic activities of four poly(ethylene glycol) (PEG) conjugates of the photosensitiser 5,10,15,20-tetrakis-(m-hydroxyphenyl)chlorin (mTHPC, temoporfin, Foscan(®)) were compared with that of mTHPC over a range of drug-light intervals using acute tumour necrosis and skeletal muscles swelling in a mouse model in order to ascertain the influence of linking group stability and PEG chain length on the photodynamic activity. The four compounds examined contained either PEG 2000 or PEG 5000 attached by carbonate or triazine linkages at the phenol hydroxyl groups of the mTHPC.All compounds tested caused tumour necrosis at drug-light intervals of between one and four days. mTHPC produced tumour necrosis of over 5 mm at drug-light intervals of 1 and 2 days with limited muscle damage at early drug-light intervals. The relatively labile carbonate-linked conjugates gave tumour necrosis similar to mTHPC but produced severe muscle and systemic phototoxicity on irradiation at 4-24 h after injection. The more stable triazine-linked conjugates produced no significant muscle damage at any of the drug-light intervals tested, but gave only limited tumour necrosis under the conditions tested. PEG chain length had relatively little effect on the patterns of bioactivity.It is concluded that both classes of mTHPC PEG conjugates may be suitable for photodynamic therapy if the problems of stability and early photosensitivity in the case of the carbonates and reduced potency in the case of the triazines can be overcome through improved formulations and PDT treatment regimens.

MHC and kin discrimination in juvenile Arctic charr, Salvelinus alpinus (L.).

Kin recognition and discrimination are thought to occur in several species of various taxonomic groups. In salmonid fish, juveniles can discriminate between odours of siblings and nonsiblings from the same population even if the odour donors and the test fish have been reared separately since fertilization. This indicates that some genetic factor is important in the recognition process. The mechanisms behind kin recognition and discrimination have not yet been described. In the present study, we performed fluviarium tests to examine whether kin recognition and discrimination in juvenile Arctic charr are influenced by the major histocompatibility complex (MHC). Prior to the fluviarium tests, exon 2 of an MHC class II B gene in charr was analysed with denaturing gradient gel electrophoresis (DGGE) and individual genotypes were determined. In the fluviarium, when fish had the choice between water scented by an MHC identical sibling and a sibling with a different MHC genotype they preferred water from identical siblings. Moreover, water scented by an MHC different sibling was preferred to water from an MHC different nonsibling. However, we observed no discrimination when the test fish shared one allele with the nonsibling donor but no alleles with the sibling donor. Our results indicate that the MHC has a significant influence on the odours used for kin recognition and discrimination in juvenile Arctic charr.Copyright 1998 The Association for the Study of Animal Behaviour