Advances in catalytic routes for the production of carboxylic acids from biomass: a step forward for sustainable polymers.

Polymers are ubiquitously present in our daily life because they can meet a wide range of needs and fields of applications. This success, based on an irresponsible linear consumption of plastics and the access to cheap oil, is creating serious environmental problems. Two lines of actions are needed to cope with them: to adopt a circular consumption of plastics and to produce renewable carbon-neutral monomers. This review analyses the recent advances in the chemocatalytic processes for producing biomass-derived carboxylic acids. These renewable carboxylic acids are involved in the synthesis of relevant general purpose and specialty polyesters and polyamides; some of them are currently derived from oil, while others can become surrogates of petrochemical polymers due to their excellent performance properties. Polyesters and polyamides are very suitable to be depolymerised to other valuable chemicals or to their constituent monomers, what facilitates the circular reutilisation of these monomers. Different types of carboxylic acids have been included in this review: monocarboxylic acids (like glycolic, lactic, hydroxypropanoic, methyl vinyl glycolic, methyl-4-methoxy-2-hydroxybutanoic, 2,5-dihydroxypent-3-enoic, 2,5,6-trihydroxyhex-3-enoic acids, diphenolic, acrylic and δ-amino levulinic acids), dicarboxylic acids (2,5-furandicarboxylic, maleic, succinic, adipic and terephthalic acids) and sugar acids (like gluconic and glucaric acids). The review evaluates the technology status and the advantages and drawbacks of each route in terms of feedstock, reaction pathways, catalysts and economic and environmental evaluation. The prospects and the new research that should be undertaken to overcome the main problems threatening their economic viability or the weaknesses that prevent their commercial implementation have also been underlined.

Molecular characterization of human immunodeficiency virus type 1-infected individuals from bolivia reveals the presence of two distinct genetic subtypes B and F.

Thirty HIV-1-positive samples from Bolivia were genetically characterized on the basis of HMA and DNA sequencing, revealing the presence of B and F subtypes, in accordance with the molecular epidemiology pattern already described for other South American countries such as Brazil and Argentina. The interpatient divergence of subtype B Bolivian specimens was on average 14.2% (4.3-19.8%) at the nucleotide level, whereas the two unlinked subtype F samples (BO23 and BO29) were only 8.2% divergent, suggesting a more recent introduction of this subtype in the country. In our study group, which represents 13% of the HIV/AIDS cases already described in Bolivia as of May 1996, the transmission occurred more frequently through heterosexual exposures (46.7%), followed by homosexual (23.3%), bisexual (10%), intravenous drug use (3.3%), and vertical (3.3%); in one case the potential exposure category could not be defined (3.3%). No association could be established between exposure categories, gender, or clinical classification and subtype distribution in the Bolivian HIV/AIDS patients.

The utilization of cnidarian nematocysts by aeolid nudibranchs: nematocyst maintenance and release in Spurilla.

Some nudibranchs that feed on cnidarians are known to store nematocysts within cnidophage cells and use them for their own defense. Most of the nematocysts are in direct contact with the cytoplasm of the cnidophage. Nematocysts are not subjected to lysosomal enzymes because any phagocytic membrane that surrounded the nematocyst after engulfment does not persist. Cnidophage organelles are restricted to regions surrounding the nematocysts and may aid in the maintenance and development of the nematocysts. The release of cnidophages is initiated by a contraction of a dense muscle complex surrounding the cnidosac. Nematocysts do not discharge if the cnidophage membrane does not rupture upon release. A comparison of nematocysts maintenance in Spurilla neapolitana and nematocyst retention in other organisms is presented.

Ultrastructure of nematocyst discharge in catch tentacles of the sea anemone Haliplanella luciae (Cnidaria: Anthozoa).

The mature nematocyst lies just beneath the cnidodyte plasma membrane. A microtubule array surrounds the nematocyst capsule just beneath the capsule tip. We propose that the array helps to hold the capsule at the cnidocyte cell surface until discharge. The undischarged capsule tip is sealed by three apical flaps, joined together along complex radial seams. The seams are filled with subunits that appear to bind the flaps together. Upon discharge, the flaps separate along the radial seams to permit thread eversion. The everted thread is lined on both sides by subunits that are stained by antimonate, indicating that they bind calcium. We suggest that, together, the subunits hold the uneverted thread in its folded and coiled configuration. Thread eversion would follow subunit uncoupling. The capsule and thread interiors of partially discharged nematocysts are stained by antimonate. In contrast, the capsule and thread interiors of fully discharged nematocysts are not stained by antimonate. Thus, nematocyst calcium might be injected into the target tissue where it is presumed to act in conjunction with nematocyst venom to promote cell death.

Comparative ultrastructure of catch tentacles and feeding tentacles in the sea anemone Haliplanella.

TEM observations of catch tentacles revealed that the tentacle tip epidermis is filled with two size classes of mature holotrich nematocysts and a gland cell filled with electron-dense vesicles. Vesicle production is restricted to upper-middle and tentacle tip regions, whereas holotrich development occurs in the lower-middle and tentacle base regions. Thus, catch tentacles have a maturity gradient along their length, with mature tissues concentrated at the tentacle tip. Occasional feeding tentacle cnidae (microbasic p-mastigophores and basitrichs) and mucus gland cells occur in proximal portions of catch tentacles, but are phagocytized by amoeboid granulocytes and transported to the gastrodermis for further degradation. No feeding tentacle cnidae or mucus cells occur distally in catch tentacles. Unlike catch tentacles, feeding tentacles are homogeneous in structure along their length with enidocytes containing mature spirocysts, microbasic p-mastigophore or basitrich nematocysts distributed along the epithelial surface. Cnidoblasts are recessed beneath cnidocytes, occurring along the nerve plexus. Mucus gland cells and gland cells filled with electron-dense vesicles are present in feeding tentacles, distributed at the epithelial surface. Granular phagocytes are rare in the feeding tentacle tip, but common in the tentacle base.

[Fuenlabrada study: lipid and lipoprotein levels in children and adolescents associated with ischemic cardiopathy prevalence among their relatives]. / Estudio de Fuenlabrada: asociación entre los niveles de lípidos y lipoproteínas en niños y adolescentes con la prevalencia de cardiopatía isquémica en sus familiares.

The prevalence of coronary heart disease (CHD) was studied in parents and grandparents of 2,419 children surveyed for lipid levels. Children and their families were divided into 3 groups depending on the level of each lipid and lipoprotein studied in children: high greater than or equal to 95 percentile (p), medium 5-95 p, and low less than 5 p. Total cholesterol (Chol) and triglycerides (TG) were determined by enzymatic techniques in autoanalyzer. C-HDL was determined by precipitation method. C-LDL and C-VLDL were obtained by Friedewald-Fredrickson's equation. The prevalence of CHD in parents and grandparents was ascertained from clinical history. Fathers of children in the high groups of Chol, TG, C-LDL/C-HDL, and low group of C-HDL had increased prevalence of CHD compared with those of the low groups of Chol, TG, C-LDL, C-LDL/C-HDL and high group of C-HDL. The strongest association was with C-HDL. Maternal and paternal grandfathers of children in the high groups of Chol had also increased prevalence of CHD compared with those of low group of Chol. There was no association with any other variable. The association was not significant neither in mothers nor in maternal and paternal grandmothers. Childhood lipid and lipoprotein levels could identify families at elevated risk for CHD.

[The Fuenlabrada's study: tobacco as cardiovascular risk factor in children and adolescents]. / Estudio de Fuenlabrada: el tabaco como factor de riesgo cardiovascular en niños y adolescentes.

Smoking habits were studied in 1,274 healthy adolescents of both sexes, aged 10 to 18 years, of Fuenlabrada, Madrid. It was known by personal interview. 30% of the population were smokers. Smoking habits increased with age up to 18 years when 63% of males and 53% of females were smokers. Smoking prevalence was significantly higher among males than in females. Males and females smokers had significantly lower levels of C-HDL and higher levels of C-LDL/C-HDL ratio than non smokers. No differences were observed for anthropometric variables, body mass index, blood pressure, skin-fold thickness, total cholesterol, glucemia and uric acid. The implications of these findings are of concern in light of the apparently protective role of C-HDL in coronary heart disease. These findings provide valuable information to the promotion of antismoking campaigns in adolescent age.

[The Fuenlabrada study: relationship between anthropometric variables and cardiovascular risk factors]. / Estudio de Fuenlabrada: relación de las variables antropométricas con los factores de riesgo cardiovascular.

Anthropometric variables were studied in 2,153 healthy children, 1,115 males and 1,038 females, aged 0 to 18 years, of the Fuenlabrada population, Madrid. Height was measured by an anthropometer and weight by a weighting scale. Tricipital and subscapular skinfold thickness were measured by Holtain caliper. Body mass index (kg/m2) and ponderal index (kg/m3) were calculated from weight and height. In the total population skinfold thickness had the highest correlation with total body fat. But, when only obese children (greater than 95 p) were analyzed, other variables like body mass index and ponderal index had also high correlation. Different fatness trends were observed between sexes, although females always were the fattest. In our population the correlation of skinfold thickness, body mass index and ponderal index with lipids, blood pressure, glycemia and uric acid were significant. Obese children and adolescents had nearly a twofold increase in relative risk of arterial hypertension, hypertriglyceridemia, hyperuricemia and low C-HDL.

[The Fuenlabrada study: lipids and lipoproteins in children and adolescents]. / Estudio de Fuenlabrada: lípidos y lipoproteínas en niños y adolescentes.

Lipids and lipoproteins were studied in 2,153 healthy children, of both sexes, aged 0 to 18 years old, of Fuenlabrada, Madrid, population. We determined: Total Cholesterol (TC) and Triglycerides (TG) by automatized enzymatic techniques. C-HDL by precipitation method. C-LDL and C-VLDL were calculated by Friedewald-Fredrickson equation. Our laboratory have previously standardized the techniques of obtention of TC, TG and C-HDL using serums of reference. Mean values were: TC = 166 +/- 36 mg/dl, TG = 63 +/- 39 mg/dl, C-HDL = 53 +/- 13 mg/dl, C-LDL = 102 +/- 34 mg/dl, C-VLDL = 13 +/- 6 mg/dl. In our population 14% had TC greater than or equal to 200 mg/dl, 2.6% TG greater than or equal to 140 mg/dl and 15% C-HDL less than or equal to 40 mg/dl. During adolescence a significant change in the lipid and lipoprotein pattern in both sexes was observed. At the end of the adolescence, males had C-HDL lower and TG, C-LDL and C-VLDL higher than females. Correlations and associations of lipids and lipoproteins were similar in our population than in adult population. The mean finding of this study is the actual high level of TC in our children population.

[Cardiovascular risk factors in children and adolescents in Fuenlabrada: objectives, features of the population, design, participation, equipment, laboratory technics, and quality control]. / Estudio de los factores de riesgo cardiovascular en niños y adolescentes de Fuenlabrada: objetivos, características de la población, diseño, participación, equipo, técnicas de laboratorio y controles de calidad.

Fuenlabrada is at the present time the most industrialized town placed at the south are of Madrid. This population has some peculiar attractive characteristics from the epidemiologic point of view. Perhaps the most important is that the majority of its inhabitants are immigrant from other depressed rural areas of the country, with a low socio-economic and cultural level. The new conditions of life could have changed the life expectation and the causes of morbidity and mortality of this population. Between 1981 and 1984 we have studied the prevalence of cardiovascular risk factors in children and adolescents of its population, the relationships with cardiovascular risk factors and cardiovascular disease of the family and type of lactancy of the newborn. The variables studied were: height, weight, skin fold, blood pressure, lipids, lipoproteins, glycemia, uric acid and tobacco habit. The laboratory technics were standardized with serums of reference. The index of participation in the study of the required population was approximately of 80%.

Cyclopentyl methyl ether: a green co-solvent for the selective dehydration of lignocellulosic pentoses to furfural.

The effects of cyclopentyl methyl ether (CPME) addition during the aqueous xylose dehydration reaction to furfural are reported here. These investigations were conducted by using pure xylose and Cynara cardunculus (cardoon) lignocellulose as sugar source and H(2)SO(4) as catalyst. The research was also applied to aqueous solutions containing NaCl, since it has been previously demonstrated that NaCl incorporation to these reaction mixtures remarkably increases the furfural formation rate. It has been found that CPME incorporation inhibits the formation of undesired products (resins, condensation products and humins). Thus, cardoon lignocellulosic pentoses were selectively transformed into furfural (near 100%) at the following reaction conditions: 1 wt.% H(2)SO(4), 4 wt.% biomass referred to aqueous solution, 30 min reaction, 443 K, CPME/aqueous phase mass ratio equals to 2.33, and NaCl/aqueous solution mass ratio of 0.4. In contrast, no effect was observed for cellulosic glucose transformation into hydroxymethylfurfural and levulinic acid at identical reaction conditions.

TXRF analysis of aged three way catalysts.

A methodology for the quantitative analysis of the elements present in car exhaust catalysts by TXRF is described. Some of the most relevant catalytic components (Zr, Rh, Pd) and contaminant elements (P, Pb, Zn, Pt, Ca and Ni) on car Three Way Catalysts were quantified during vehicle aging. The study was conducted along the main axis of a Ford Focus 1.6i catalytic cartridge, aiming to obtain the axial profile of the elements retained or eliminated after more than 59,000 km. The analysis of a fresh Three Way Catalysts (0 km) was also conducted for comparative purposes. The existence of a strong differences for elemental concentration in the interphase between the two blocks of the catalytic cartridge has been quantitatively measured for first time. In addition, the behaviour of the contaminant absorption capacity of both catalytic blocks has been obtained. Finally, the loss of the contaminant elements Pb and Zn to the environment has been proven.

The form and function of cnidarian spirocysts. 2. Ultrastructure of the capsule tip and wall and mechanism of discharge.

The electron-dense capsule tip (apical cap) of sea anemone and coral spirocysts is of a different structure than the capsule wall. The capsule wall is composed of a double layer of fiber-like materials which cross each other at roughly right angles. The innermost layer is characterized by numerous serrations, the tips of which project into the lumen of the capsule. Within each serration, a band of finely cross-striated material encircles the capsule at right angles to its longitudinal axis. The membrane lining the lumen of the capsule appears to be continuous with the wall of the undischarged thread. The outer capsule wall layer consists of closely spaced microfilaments (cnidofilaments) which are oriented in the longitudinal axis of the capsule. The cnidofilaments appear to merge with the apical cap material. Contrary to some previous reports in the literature, it has been found that spirocysts normally discharge by eversion, as do nematocysts. The relationship of the capsule wall sub-structure to the spirocyst discharge process is discussed.

Dentistry and the hemophiliac: a review of current literature, Part I.

This article, the first of two parts, discusses the history and etiology of hemophilia. The authors describe several disorders related to hemophilia. They further discuss the medical management of the hemophilia patient and, more specifically, dental treatment.

The form and function of cnidarian spirocysts. 1. Ultrastructure of the capsule exterior and relationship to the tentacle sensory surface.

The commonest intracellular organelle characteristic of the Phylum Cnidaria or Coelenterata (Subclass Zoantharia) is the spirocyst. Based on scanning and transmission electron microscopy of the tentacles of sea anemones and corals, it appears that the tip of the spirocyst is either exposed to the environment or covered by a thin plasma membrane and often has a pebbled or knobby appearance. Surrounding the spirocyst tip is a ring-like structure which seems to be formed by the junction of the enclosing cell (the spirocyte) and the tip of the spirocyst. The spirocyst thread is continuous with the capsule wall and emerges from within the apical ring during discharge. No ciliary structures appear to be associated with spirocysts. Instead, two different types of microvilli have been found: short microvilli on the spirocyte itself and long microvilli furnished by the cell or cells surrounding the spirocyte. The significance of these findings is discussed in relation to the reception of stimuli for spirocyst discharge.

The form and function of cnidarian spirocysts. 3. Ultrastructure of the thread and the function of spirocysts.

Unlike most nematocysts, undischarged spirocyst threads bear hollow tubules rather than spines. The undischarged tubules are interconnected in hexagonal arrays and appear to be arranged in bundles along the length of the thread. Although the wall of the thread is folded in length and width, the tubules are not. Upon discharge and contact with sea water, the tubules solubilize and adhere to various substrates and prey. Traction between such objects and the everting thread causes the tubules to spin out into a web or meshwork of fine microfibrillae. Lack of contact of the everting thread with objects results in the tubules forming small droplets of partially solubilized material, some of which appear to be arranged in a helical pattern around the thread. The web or meshwork formed by the solubilized tubules in contact with various substrates probably serves to increase significantly the surface area and adhesive properties of the everted spirocyst thread.

Chemical analysis of used three-way catalysts by total reflection X-ray fluorescence.

The methodology developed for evaluating, by total reflection X-ray fluorescence, the main elements in used three-way catalysts for cars after more than 59 000 km is described. The analytical method does not require chemical manipulation of the samples, is quick (30 min for sample preparation and 10 min for analysis), precise (between 1% and 10% of variation coefficient), and simple. The two catalytic monoliths contained in the cartridge of a car with more than 59,000 km have been analyzed. The mass relationships between the detected elements and Si, a component of the cordierite ceramic substrate, have been used to follow the axial and radial profiles of the elements. Information concerning the loss of active elements and the retention of contaminating elements as a consequence of the working conditions was attained by comparison between the results obtained for the used catalyst (59 000 km) with those of a fresh catalyst (0 km). The interface effect between the first and the second catalytic bricks was also studied.