Disposable electrochemical platform based on solid-binding peptides and carbon nanomaterials: an alternative device for leishmaniasis detection.

Neglected tropical diseases are those caused by infectious agents or parasites and are considered endemic in low-income populations. These diseases also have unacceptable indicators and low investment in research, drug production, and control. Tropical diseases such as leishmaniasis are some of the main causes of morbidity and mortality around the globe. Electrochemical immunosensors are promising tools for diagnostics against these diseases. One such benefit is the possibility of assisting diagnosis in isolated regions, where laboratory infrastructure is lacking. In this work, different peptides were investigated to detect antibodies against Leishmania in human and canine serum samples. The peptides evaluated (395-KKG and 395-G) have the same recognition site but differ on their solid-binding domains, which ensure affinity to spontaneously bind to either graphene oxide (GO) or graphene quantum dots (GQD). Cyclic voltammetry and differential pulse voltammetry were employed to investigate the electrochemical behavior of each assembly step and the role of each solid-binding domain coupled to its anchoring material. The graphene affinity peptide (395-G) showed better reproducibility and selectivity when coupled to GQD. Under the optimized set of experimental conditions, negative and positive human serum samples responses were distinguished based on a cut-off value of 82.5% at a 95% confidence level. The immunosensor showed selective behavior to antibodies against Mycobacterium leprae and Mycobacterium tuberculosis, which are similar antibodies and potentially sources of false positive tests. Therefore, the use of the graphene affinity peptide as a recognition site achieved outstanding performance for the detection of Leishmania antibodies.

Sodium and lithium exert differential effects on the central carbon metabolism of Debaryomyces hansenii through the glyoxylate shunt regulation.

Debaryomyces hansenii is a halotolerant/halophilic yeast usually found in salty environments. The yeast accumulated sodium at high concentrations, which improved growth in salty media. In contrast, lithium was toxic even at low concentrations and its presence prevented cell proliferation. To analyse the responses to both cations, metabolite levels, enzymatic activities and gene expression were determined, showing that NaCl and LiCl trigger different cellular responses. At high concentrations of NaCl (0.5 or 1.5 M) cells accumulated higher amounts of the intermediate metabolites glyoxylate and malate and, at the same time, the levels of intracellular oxoglutarate decreased. Additionally, 0.5 M NaCl increased the activity of the enzymes isocitrate lyase and malate synthase involved in the synthesis of glyoxylate and malate respectively and decreased the activity of isocitrate dehydrogenase. Moreover, transcription of the genes coding for isocitrate lyase and malate synthase was activated by NaCl. Also, cells accumulated phosphate upon NaCl exposure. None of these effects was provoked when LiCl (0.1 or 0.3 M) was used instead of NaCl. Lithium induced accumulation of higher amounts of oxoglutarate and decreased the concentrations of glyoxylate and malate to non-detectable levels. Cells incubated with lithium also showed higher activity of the isocitrate dehydrogenase and neither increased isocitrate lyase and malate synthase activities nor the transcription of the corresponding genes. In summary, we show that sodium, but not lithium, up regulates the shunt of the glyoxylic acid in D. hansenii and we propose that this is an important metabolic adaptation to thrive in salty environments.

Microfluidic electrochemical device for real-time culturing and interference-free detection of Escherichia coli.

Bacterial contamination and infection is a major health concern today leading to the significance of its detection. Being lab-based bacterial culturing processes, the present approaches are time consuming and require trained skillset. An economical, and miniaturized lab-on-chip device, capable of simultaneous detection of bacterial growth, could be a benchmarking tool for monitoring the bacterial contamination. Herein, the microfluidic-based electrochemical device for a fast, susceptible, detection of Escherichia coli was developed. The device could aid incubator free bacteria culturing in the ambient atmosphere and simultaneously monitor and detect the growth electrochemically. A three-electrode system, integrated with a reservoir and a portable thermostat temperature controller was fabricated and assembled. To achieve this, three-electrodes were embedded on the microfluidic device by screen-printing carbon paste, and the working electrode was enhanced by graphitized mesoporous carbon. Cyclic voltammetry response was noted as the function of concentration and growth of Escherichia Coli in the reservoir. The device gave a linear bacterial concentration range of 0.336 × 1012 to 40 × 1012 CFU mL-1, detection limit of 0.35 CFU mL-1 and the quantification limit of 1.05 CFU mL-1 which was less than the maximum allowable limit. The developed platform was further used to detect and continuously monitor the bacterial growth in the real sample (mango juice) for a period of 36 h. Finally, the interference from other common bacteria on the electrode selectivity was also investigated. Such approach in being further modified for specific sensing of bacteria in patients suffering from different diseases such as corneal ulcers, Diarrhea, tuberculosis, leprosy, and syphilis.

Nitrogen plasma modification boosts up the hemocompatibility of new PVDF-carbon nanohorns composite materials with potential cardiological and circulatory system implants application.

To design new material for blood-related applications one needs to consider various factors such as cytotoxicity, platelet adhesion, or anti-thrombogenic properties. The aim of this work is the design of new, highly effective materials possessing high blood compatibility. To do this, the new composites based on the poly(vinylidene fluoride) (PVDF) support covered with a single-walled carbon nanohorns (CNHs) layer were prepared. The PVDF-CNHs composites were subsequently used for the first time in the hemocompatibility studies. To raise the hemocompatibility a new, never applied before for CNHs, plasma-surface modifications in air, nitrogen and ammonia were implemented. This relatively cheap, facile and easy method allows generating the new hybrid materials with high effectiveness and significant differences in surface properties (water contact angle, surface ζ-potential, and surface functional groups composition). Changing those properties made it possible to select the most promising samples for blood-related applications. This was done in a fully controlled way by applying Taguchi's "orthogonal array" procedure. It is shown for the first time that nitrogen plasma treatment of new surfaces is the best tool for hemocompatibility rise and leads to very low blood platelet adhesion, no cytotoxicity, and excellent performance in thromboelastometry and hemolysis tests. We propose a possible mechanism explaining this behavior. The optimisation results are coherent with biological characterisation and are supported with Hansen Solubility Parameters. New surfaces can find potential applications in cardiological and circulatory system implants as well as other blood-related biomaterials.

Biosurfactant production by halophilic yeasts isolated from extreme environments in Botswana.

Nine morphologically distinct halophilic yeasts were isolated from Makgadikgadi and Sua pans, as pristine and extreme environments in Botswana. Screening for biosurfactant production showed that Rhodotorula mucilaginosa SP6 and Debaryomyces hansenii MK9 exhibited the highest biosurfactant activity using Xanthocercis zambesiaca seed powder as a novel and alternative inexpensive carbon substrate. Chemical characterization of the purified biosurfactants by Fourier Transform Infra-Red spectroscopy suggested that the biosurfactant from R. mucilaginosa SP6 was a rhamnolipid-type whereas the biosurfactant from D. hansenii MK9 was a sophorolipid-type. The two biosurfactants exhibited antimicrobial activities against eight pathogenic bacteria and fungal strains (Proteus vulgaris, Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Micrococcus luteus, Cryptococcus neoformans, Candida albicans and Aspergilus niger). The sophorolopid-type biosurfactant was found to be the most potent among the antimicrobial drug resistant strains tested. The findings open up prospects for the development of environmentally friendly antimicrobial drugs that use an inexpensive source of carbon to reduce the costs associated with the production of biosurfactants.

Ratiometric dual-emission of Rhodamine-B grafted carbon dots for full-range solvent components detection.

Quick and visual detection of component contents, such as water, in a mixed solvent is important for many practical applications, and a full range detection is especially preferred. In this work, a carbon dots based ratiometric fluorescent sensor was synthesized by grafting fluorescent group (Rhodamine B, RhB) on carbon dots, and the dual emission peaks exhibited a linear ratiometric response with the change of polarity and hydrogen bond of Solvent Hansen solubility parameters. This responsive behavior is attributed to surface state photoluminescence mechanisms, and has been used for the quantitative detection of water content in ethanol with an excellent linear relationship (R2 = 0.996), a low detection limit (0.2%), and a full detection range (0-100%). Furthermore, a paper-based ratiometric fluorescence sensing strip is also demonstrated, which exhibits good storage stability and sensitivity. This study suggests that RhB grafted carbon dots could be feasibly and effectively used as ratiometric fluorescent sensors for solvent content detection.

Threshold effects of capital investments on carbon emissions in G20 economies.

Investment in capitals is sacrosanct to launch a country to a greater path of sustainable development. Notwithstanding, its deleterious impacts on environment are equally incontestable. In light of this stark reality, this paper examines the threshold effects of capital investments on carbon emissions in G20 economies over the period, 1992-2014, for which data are available. The study uses both exogenously determined and endogenously determined thresholds to uncover the relationship. While the former relies on median approach to determining the threshold on the one hand, the latter uses both the fixed effects panel threshold model proposed by (Hansen J Econ 93:345-368, 1999) and the bootstrap method by (Hansen Econometrica 68:575-603, 2000) to assess the statistical relevance of the threshold effects on the other hand. The results of the exogenously determined thresholds show higher statistical significant environmental impacts of capital investments at a median threshold of above 3.068 than when it is lesser. The findings of the latter approach indicate the relationship between capital investments and carbon emissions to be non-linear for the G20 countries. More specifically, this study establishes a single-threshold level of capital investment on carbon emissions for the group of countries. The threshold estimator of 3.434 is established at the 95% confidence interval. Beyond this point, the environmental impacts of capital investments are imaginable. On the policy front, keeping to the limit set by threshold effects would go a long way to stemming environmental pollution and mitigating climatic change impacts.

Effect of pH Buffer and Carbon Metabolism on the Yield and Mechanical Properties of Bacterial Cellulose Produced by Komagataeibacter hansenii ATCC 53582.

Bacterial cellulose (BC) is widely used in the food industry for products such as nata de coco. The mechanical properties of BC hydrogels, including stiffness and viscoelasticity, are determined by the hydrated fibril network. Generally, Komagataeibacter bacteria produce gluconic acids in a glucose medium, which may affect the pH, structure and mechanical properties of BC. In this work, the effect of pH buffer on the yields of Komagataeibacter hansenii strain ATCC 53582 was studied. The bacterium in a phosphate and phthalate buffer with low ionic strength produced a good BC yield (5.16 and 4.63 g/l respectively), but there was a substantial reduction in pH due to the accumulation of gluconic acid. However, the addition of gluconic acid enhanced the polymer density and mechanical properties of BC hydrogels. The effect was similar to that of the bacteria using glycerol in another carbon metabolism circuit, which provided good pH stability and a higher conversion rate of carbon. This study may broaden the understanding of how carbon sources affect BC biosynthesis.

A physiological characterization in controlled bioreactors reveals a novel survival strategy for Debaryomyces hansenii at high salinity.

Debaryomyces hansenii is traditionally described as a halotolerant non-conventional yeast and has served as a model organism for the study of osmotolerance and salt tolerance mechanisms in eukaryotic systems for the past 30 years. However, unraveling of D. hansenii's biotechnological potential has always been difficult due to the persistent limitations in the availability of efficient molecular tools described for this yeast. Additionally, there is a lack of consensus and contradictory information along the recent years that limits a comprehensive understanding of its central carbon metabolism, mainly due to a lack of physiological studies in controlled and monitored environments. Moreover, there is little consistency in the culture conditions (media composition, temperature, and pH among others) used by different groups, which makes it complicated when trying to get prevalent conclusions on behavioral patterns. In this work, we present for the first time a characterization of D. hansenii in batch cultivations using highly controlled lab-scale bioreactors. Our findings contribute to a more complete picture of the central carbon metabolism and the external pH influence on the yeast's ability to tolerate high Na+ and K+ concentrations, pointing to a differential effect of both salts, as well as a positive effect in cell performance when low environmental pH values are combined with a high sodium concentration in the media. Finally, a novel survival strategy at very high salinity (2 M) is proposed for this yeast, as well as potential outcomes for its use in industrial biotechnology applications. TAKE AWAY: High salt concentrations stimulate respiration in Debaryomyces hansenii. Sodium exerts a stronger positive impact on cell performance than potassium. µmax is higher at a combination of low pH, high salt, and high temperature. Concentrations of 2 M salt result in slower growth but increased biomass yield. The positive effect of salts is enhanced at low glucose concentration.

Intracellular Mycobacterium leprae Utilizes Host Glucose as a Carbon Source in Schwann Cells.

New approaches are needed to control leprosy, but understanding of the biology of the causative agent Mycobacterium leprae remains rudimentary, principally because the pathogen cannot be grown in axenic culture. Here, we applied 13C isotopomer analysis to measure carbon metabolism of M. leprae in its primary host cell, the Schwann cell. We compared the results of this analysis with those of a related pathogen, Mycobacterium tuberculosis, growing in its primary host cell, the macrophage. Using 13C isotopomer analysis with glucose as the tracer, we show that whereas M. tuberculosis imports most of its amino acids directly from the host macrophage, M. leprae utilizes host glucose pools as the carbon source to biosynthesize the majority of its amino acids. Our analysis highlights the anaplerotic enzyme phosphoenolpyruvate carboxylase required for this intracellular diet of M. leprae, identifying this enzyme as a potential antileprosy drug target.IMPORTANCE Leprosy remains a major problem in the world today, particularly affecting the poorest and most disadvantaged sections of society in the least developed countries of the world. The long-term aim of research is to develop new treatments and vaccines, and these aims are currently hampered by our inability to grow the pathogen in axenic culture. In this study, we probed the metabolism of M. leprae while it is surviving and replicating inside its primary host cell, the Schwann cell, and compared it to a related pathogen, M. tuberculosis, replicating in macrophages. Our analysis revealed that unlike M. tuberculosis, M. leprae utilized host glucose as a carbon source and that it biosynthesized its own amino acids, rather than importing them from its host cell. We demonstrated that the enzyme phosphoenolpyruvate carboxylase plays a crucial role in glucose catabolism in M. leprae Our findings provide the first metabolic signature of M. leprae in the host Schwann cell and identify novel avenues for the development of antileprosy drugs.

Response to Comment on "Tropical forests are a net carbon source based on aboveground measurements of gain and loss".

The Hansen et al critique centers on the lack of spatial agreement between two very different datasets. Nonetheless, properly constructed comparisons designed to reconcile the two datasets yield up to 90% agreement (e.g., in South America).

Cellulose synthesis by Komagataeibacter rhaeticus strain P 1463 isolated from Kombucha.

Isolate B17 from Kombucha was estimated to be an efficient producer of bacterial cellulose (BC). The isolate was deposited under the number P 1463 and identified as Komagataeibacter rhaeticus by comparing a generated amplified fragment length polymorphism (AFLP™) DNA fingerprint against a reference database. Static cultivation of the K. rhaeticus strain P 1463 in Hestrin and Schramm (HS) medium resulted in 4.40 ± 0.22 g/L BC being produced, corresponding to a BC yield from glucose of 25.30 ± 1.78 %, when the inoculum was made with a modified HS medium containing 10 g/L glucose. Fermentations for 5 days using media containing apple juice with analogous carbon source concentrations resulted in 4.77 ± 0.24 g/L BC being synthesised, corresponding to a yield from the consumed sugars (glucose, fructose and sucrose) of 37.00 ± 2.61 %. The capacity of K. rhaeticus strain P 1463 to synthesise BC was found to be much higher than that of two reference strains for cellulose production, Komagataeibacter xylinus DSM 46604 and Komagataeibacter hansenii DSM 5602T, and was also considerably higher than that of K. hansenii strain B22, isolated from another Kombucha sample. The BC synthesised by K. rhaeticus strain P 1463 after 40 days of cultivation in HS medium with additional glucose supplemented to the cell culture during cultivation was shown to have a degree of polymerization of 3300.0 ± 122.1 glucose units, a tensile strength of 65.50 ± 3.27 MPa and a length at break of 16.50 ± 0.83 km. For the other strains, these properties did not exceed 25.60 ± 1.28 MPa and 15.20 ± 0.76 km.

Haemophilus ducreyi Seeks Alternative Carbon Sources and Adapts to Nutrient Stress and Anaerobiosis during Experimental Infection of Human Volunteers.

Haemophilus ducreyi causes the sexually transmitted disease chancroid in adults and cutaneous ulcers in children. In humans, H. ducreyi resides in an abscess and must adapt to a variety of stresses. Previous studies (D. Gangaiah, M. Labandeira-Rey, X. Zhang, K. R. Fortney, S. Ellinger, B. Zwickl, B. Baker, Y. Liu, D. M. Janowicz, B. P. Katz, C. A. Brautigam, R. S. MunsonJr, E. J. Hansen, and S. M. Spinola, mBio 5:e01081-13, 2014, http://dx.doi.org/10.1128/mBio.01081-13) suggested that H. ducreyi encounters growth conditions in human lesions resembling those found in stationary phase. However, how H. ducreyi transcriptionally responds to stress during human infection is unknown. Here, we determined the H. ducreyi transcriptome in biopsy specimens of human lesions and compared it to the transcriptomes of bacteria grown to mid-log, transition, and stationary phases. Multidimensional scaling showed that the in vivo transcriptome is distinct from those of in vitro growth. Compared to the inoculum (mid-log-phase bacteria), H. ducreyi harvested from pustules differentially expressed ∼93 genes, of which 62 were upregulated. The upregulated genes encode homologs of proteins involved in nutrient transport, alternative carbon pathways (l-ascorbate utilization and metabolism), growth arrest response, heat shock response, DNA recombination, and anaerobiosis. H. ducreyi upregulated few genes (hgbA, flp-tad, and lspB-lspA2) encoding virulence determinants required for human infection. Most genes regulated by CpxRA, RpoE, Hfq, (p)ppGpp, and DksA, which control the expression of virulence determinants and adaptation to a variety of stresses, were not differentially expressed in vivo, suggesting that these systems are cycling on and off during infection. Taken together, these data suggest that the in vivo transcriptome is distinct from those of in vitro growth and that adaptation to nutrient stress and anaerobiosis is crucial for H. ducreyi survival in humans.

Phenol degradation by halophilic fungal isolate JS4 and evaluation of its tolerance of heavy metals.

Phenol is one of the most common pollutants in many kinds of industrial wastewater, some of which are in high salinity, resulting in more difficulties of biodegradation. In this work, a halophilic strain capable of utilizing phenol as sole source of carbon and energy in both hypersaline and no-salt media was isolated and identified as genus Debaryomyces. The optimization of environmental parameters including phenol concentration, pH, dissolved oxygen as well as salinity was carried out and tolerance of heavy metals by the strain was evaluated. The strain Debaryomyces sp. was able to grow in culture when initial phenol concentration, pH, agitation and salinity were at wide ranges (0-1200 mg L(-1), 4.0-10.0, 50-200 rpm, 0 %-15 %, respectively). High removal efficiency was hardly affected in the presence of 5 mM of Zn (II) and Mn (II). Under optimal conditions (pH 6.0, 200 rpm, 1 % of salinity without heavy metals), 500 mg L(-1) of phenol could be completely degraded within 32 h. The high removal efficiency of phenol by the strain with significant variations of process parameters might contribute to the bioremediation of phenol-polluted environments under hypersaline or no-salt conditions.

The Essential Role of Cholesterol Metabolism in the Intracellular Survival of Mycobacterium leprae Is Not Coupled to Central Carbon Metabolism and Energy Production.

UNLABELLED: Mycobacterium leprae induces the formation of lipid droplets, which are recruited to pathogen-containing phagosomes in infected macrophages and Schwann cells. Cholesterol is among the lipids with increased abundance in M. leprae-infected cells, and intracellular survival relies on cholesterol accumulation. The present study investigated the capacity of M. leprae to acquire and metabolize cholesterol. In silico analyses showed that oxidation of cholesterol to cholest-4-en-3-one (cholestenone), the first step of cholesterol degradation catalyzed by the enzyme 3ß-hydroxysteroid dehydrogenase (3ß-HSD), is apparently the only portion of the cholesterol catabolic pathway seen in Mycobacterium tuberculosis preserved by M. leprae. Incubation of bacteria with radiolabeled cholesterol confirmed the in silico predictions. Radiorespirometry and lipid analyses performed after incubating M. leprae with [4-(14)C]cholesterol or [26-(14)C]cholesterol showed the inability of this pathogen to metabolize the sterol rings or the side chain of cholesterol as a source of energy and carbon. However, the bacteria avidly incorporated cholesterol and, as expected, converted it to cholestenone both in vitro and in vivo. Our data indicate that M. leprae has lost the capacity to degrade and utilize cholesterol as a nutritional source but retains the enzyme responsible for its oxidation to cholestenone. Thus, the essential role of cholesterol metabolism in the intracellular survival of M. leprae is uncoupled from central carbon metabolism and energy production. Further elucidation of cholesterol metabolism in the host cell during M. leprae infection will establish the mechanism by which this lipid supports M. leprae intracellular survival and will open new avenues for novel leprosy therapies. IMPORTANCE: Our study focused on the obligate intracellular pathogen Mycobacterium leprae and its capacity to metabolize cholesterol. The data make an important contribution for those interested in understanding the mechanisms of mycobacterial pathogenesis, since they indicate that the essential role of cholesterol for M. leprae intracellular survival does not rely on its utilization as a nutritional source. Our findings reinforce the complexity of cholesterol's role in sustaining M. leprae infection. Further elucidation of cholesterol metabolism in the host cell during M. leprae infection will establish the mechanism by which this lipid supports M. leprae intracellular survival and will open new avenues for novel leprosy therapies.

Non-stabilized nucleophiles in Cu-catalysed dynamic kinetic asymmetric allylic alkylation.

The development of new reactions forming asymmetric carbon-carbon bonds has enabled chemists to synthesize a broad range of important carbon-containing molecules, including pharmaceutical agents, fragrances and polymers. Most strategies to obtain enantiomerically enriched molecules rely on either generating new stereogenic centres from prochiral substrates or resolving racemic mixtures of enantiomers. An alternative strategy--dynamic kinetic asymmetric transformation--involves the transformation of a racemic starting material into a single enantiomer product, with greater than 50 per cent maximum yield. The use of stabilized nucleophiles (pKa < 25, where Ka is the acid dissociation constant) in palladium-catalysed asymmetric allylic alkylation reactions has proved to be extremely versatile in these processes. Conversely, the use of non-stabilized nucleophiles in such reactions is difficult and remains a key challenge. Here we report a copper-catalysed dynamic kinetic asymmetric transformation using racemic substrates and alkyl nucleophiles. These nucleophiles have a pKa of ≥50, more than 25 orders of magnitude more basic than the nucleophiles that are typically used in such transformations. Organometallic reagents are generated in situ from alkenes by hydrometallation and give highly enantioenriched products under mild reaction conditions. The method is used to synthesize natural products that possess activity against tuberculosis and leprosy, and an inhibitor of para-aminobenzoate biosynthesis. Mechanistic studies indicate that the reaction proceeds through a rapidly isomerizing intermediate. We anticipate that this approach will be a valuable complement to existing asymmetric catalytic methods.

Statistical optimization of medium composition for bacterial cellulose production by Gluconacetobacter hansenii UAC09 using coffee cherry husk extract--an agro-industry waste.

During the production of grape wine, the formation of thick leathery pellicle/bacterial cellulose (BC) at the airliquid interface was due to the bacterium, which was isolated and identified as Gluconacetobacter hansenii UAC09. Cultural conditions for bacterial cellulose production from G. hansenii UAC09 were optimized by central composite rotatable experimental design. To economize the BC production, coffee cherry husk (CCH) extract and corn steep liquor (CSL) were used as less expensive sources of carbon and nitrogen, respectively. CCH and CSL are byproducts from the coffee processing and starch processing industry, respectively. The interactions between pH (4.5- 8.5), CSL (2-10%), alcohol (0.5-2%), acetic acid (0.5- 2%), and water dilution rate to CCH ratio (1:1 to 1:5) were studied using response surface methodology. The optimum conditions for maximum BC production were pH (6.64), CSL (10%), alcohol (0.5%), acetic acid (1.13%), and water to CCH ratio (1:1). After 2 weeks of fermentation, the amount of BC produced was 6.24 g/l. This yield was comparable to the predicted value of 6.09 g/l. This is the first report on the optimization of the fermentation medium by RSM using CCH extract as the carbon source for BC production by G. hansenii UAC09.

Dose response of alanine detectors irradiated with carbon ion beams.

PURPOSE: The dose response of the alanine detector shows a dependence on particle energy and type when irradiated with ion beams. The purpose of this study is to investigate the response behavior of the alanine detector in clinical carbon ion beams and compare the results to model predictions. METHODS: Alanine detectors have been irradiated with carbon ions with an energy range of 89-400 MeV/u. The relative effectiveness of alanine has been measured in this regime. Pristine and spread out Bragg peak depth-dose curves have been measured with alanine dosimeters. The track structure based alanine response model developed by Hansen and Olsen has been implemented in the Monte Carlo code FLUKA and calculations were compared to experimental results. RESULTS: Calculations of the relative effectiveness deviate less than 5% from the measured values for monoenergetic beams. Measured depth-dose curves deviate from predictions in the peak region, most pronounced at the distal edge of the peak. CONCLUSIONS: The used model and its implementation show a good overall agreement for quasi-monoenergetic measurements. Deviations in depth-dose measurements are mainly attributed to uncertainties of the detector geometry implemented in the Monte Carlo simulations.

Characterization of vinasses from five certified brands of origin (CBO) and use as economic nutrient for the xylitol production by Debaryomyces hansenii.

Vinasses coming from the five CBOs of Galicia, north-western Spain, were characterized, and successfully employed as economic nutritional supplements for xylitol production by Debaryomyces hansenii. All fermentations can be modelled showing kinetic patterns fairly described by the mathematical models. No negative effect of the phenolic compounds in the liquid phase on the initial volumetric rate of product formation (r(P)(0)) was observed. Multiple linear regression analysis was used to describe the effect of metals and initial xylose acting on P(max) and Y(P/S). Zn was the most influential variable. Besides, partial least-squares regression models show a clear separation, based on the first two principal components, between the whole vinasses and the liquid fractions, which provided the higher P(max), with the exception of CBO 4, where P(max)=40.4 g/L, was achieved using the solid and liquid fraction.

Intercomparison of measurement techniques for black or elemental carbon under urban background conditions in wintertime: influence of biomass combustion.

A generally accepted method to measure black carbon (BC) or elemental carbon (EC) still does not exist. An earlier study in the Vienna area comparing practically all measurement methods in use in Europe gave comparable BC and EC concentrations under summer conditions (Hitzenberger et al., 2006a). Under summer conditions, Diesel traffic is the major source for EC or BC in Vienna. Under winter conditions, space heating (also with biomass as fuel) is another important source (Caseiro et al., 2007). The present study compares the response of thermal methods (a modified Cachier method, Cachier et al., 1989; a thermal-optical method, Schmid et al., 2001; and two thermal-optical (TOT) methods using Sunset instruments, Birch and Cary, 1996 and Schauer et al., 2003) and optical methods (a light transmission method, Hansen et al., 1984; the integrating sphere method, Hitzenberger et al., 1996; and the multiangle absorption photometer MAAP, Petzold and Schönlinner, 2004). Significant differences were found between the TOT methods on the one hand and all other methods on the other. The TOT methods yielded EC concentrations that were lower by 44 and 17% than the average of all measured concentrations (including the TOT data). The largest discrepancy was found when the contribution of brown carbon (measured with the integrating sphere method) was largest.