Connection between Mechanical Relaxation and Equilibration Kinetics in a High-Entropy Metallic Glass.

The slow transition from an out-of-equilibrium glass towards a supercooled liquid is a complex relaxation phenomenon. In this Letter, we study the correlation between mechanical relaxation and equilibration kinetics in a Pd_{20}Pt_{20}Cu_{20}Ni_{20}P_{20} high-entropy metallic glass. The evolution of stress relaxation with aging time was obtained with an unprecedented detail, allowing us to pinpoint new interesting features. The long structural relaxation towards equilibrium contains a wide distribution of activation energies, instead of being just associated to the ß relaxation as commonly accepted. The stress relaxation time can be correlated with the equilibration rate and we observe a decrease of microstructural heterogeneity which contrasts with an increase of dynamic heterogeneity. These results significantly enhance our insight of the interplay between relaxation dynamics and thermodynamics in metallic glasses.

Influence of nanosecond laser surface patterning on dental 3Y-TZP: Effects on the topography, hydrothermal degradation and cell response.

OBJECTIVES: Laser surface micropatterning of dental-grade zirconia (3Y-TZP) was explored with the objective of providing defined linear patterns capable of guiding bone-cell response. METHODS: A nanosecond (ns-) laser was employed to fabricate microgrooves on the surface of 3Y-TZP discs, yielding three different groove periodicities (i.e., 30, 50 and 100 µm). The resulting topography and surface damage were characterized by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). X-Ray diffraction (XRD) and Raman spectroscopy techniques were employed to assess the hydrothermal degradation resistance of the modified topographies. Preliminary biological studies were conducted to evaluate adhesion (6 h) of human mesenchymal stem cells (hMSC) to the patterns in terms of cell number and morphology. Finally, Staphylococcus aureus adhesion (4 h) to the microgrooves was investigated. RESULTS: The surface analysis showed grooves of approximately 1.8 µm height that exhibited surface damage in the form of pile-up at the edge of the microgrooves, microcracks and cavities. Accelerated aging tests revealed a slight decrease of the hydrothermal degradation resistance after laser patterning, and the Raman mapping showed the presence of monoclinic phase heterogeneously distributed along the patterned surfaces. An increase of the hMSC area was identified on all the microgrooved surfaces, although only the 50 µm periodicity, which is closer to the cell size, significantly favored cell elongation and alignment along the grooves. A decrease in Staphylococcus aureus adhesion was observed on the investigated micropatterns. SIGNIFICANCE: The study suggests that linear microgrooves of 50 µm periodicity may help in promoting hMSC adhesion and alignment, while reducing bacterial cell attachment.

Mechanical reliability of dental grade zirconia after laser patterning.

The aim of this work is to test the mechanical properties of dental zirconia surfaces patterned with Nd:YAG laser interference (λ = 532 nm and 10 ns pulse). The laser treatment produces an alteration of the topography, engraving a periodic striped pattern. Laser-material interaction results mainly in thermal effects producing microcracking, phase transformation and texturization. The role of such microstructural modifications and collateral damage on the integrity and mechanical performances has been assessed. Laser patterned discs of zirconia doped with 3% mol yttria (3Y-TZP) have been tested before and after a thermal treatment to anneal residual stresses and revert phase transformation. Both groups of samples behave in a similar manner, excluding residual stresses and phase transformation from the origin of properties modification. Result show that laser patterning induces a minor decrease in mechanical properties and surface integrity of 3Y-TZP surfaces. The biaxial strength decreases as a consequence of the damage induced by laser patterning. Fractographic observations identify preexisting defects enlarged by local laser interaction as the fracture origins. The Hardness and Young modulus of treated surfaces tested with nanoindentation also decrease slightly after laser treatment and this may be attributed to laser-induced microcracking.

Contact fatigue of veneer feldspathic porcelain on dental zirconia.

OBJECTIVES: To understand the resistance to cyclic and static contact loading of feldspathic porcelain on dental zirconia (3Y-TZP), in order to understand the partial failure of porcelain (chipping or cracking). METHODS: Hertzian contact techniques were used to evaluate the appearance of damage as a ring crack in terms of applied load and number of cycles in air and simulated saliva. RESULTS: Static contact loading showed the presence of stress corrosion cracking in the porcelain; the environmental crack growth in air was determined from the results of time to damage under static load. There was also a contribution of fatigue effects due to the interactions of the crack with the microstructure. From the obtained results, a time to failure was estimated depending on the material counterpart. Cracking can occur on porcelain coatings if the contact counterpart is teeth or porcelain in a time interval of a few years, consistent with clinical studies. SIGNIFICANCE: Contact loading, particularly against teeth or other ceramic materials can be a significant cause of failure and chipping of feldspathic porcelain on zirconia, especially if the patient suffers from bruxism. Protection, by e.g. a guard, against repetitive contact against the porcelain can increase the lifetime of the veneer.

Ecotoxicological impact of MSW landfills: assessment of teratogenic effects by means of an adapted FETAX assay.

The introduction of chemical products into the environment can cause long-term effects on the ecosystems. Increasing efforts are being made to determine the extent of contamination in particularly affected areas using diverse methods to assess the ecotoxicological impact. We used a modified Frog Embrio Toxicity Assay-Xenopus method to determine the extent of toxicological load in different sample soils obtained near three municipal solid waste landfills in Catalonia (Spain). The results show that the Garraf landfill facility produces more embryotoxic damage to the surroundings, than the others ones: Can Mata landfill and Montferrer-Castellbó landfill. The aim of this work is to demonstrate how different management of complex sources of contamination as the controlled dumping sites can modulate the presence of toxics in the environment and their effects and through this, help determine the safer way to treat these wastes. To this effect some conceptual modifications have been made on the established American Society for Testing and Materials protocol. The validity of the new model, both as to model of calculation as to protocol, has been demonstrated in three different sites with complex sources of contamination.

Assessment of developmental delay in the zebrafish embryo teratogenicity assay.

In this study we analyzed some aspects of the assessment of developmental delay in the zebrafish embryotoxicity/teratogenicity test and explored the suitability of acetylcholinesterase (AChE) activity as a biochemical marker and as a higher throughput alternative to morphological endpoints such as head-trunk angle, tail length and morphological score. Embryos were exposed from 4 to 52 h post-fertilization (hpf) to a selection of known embryotoxic/teratogen compounds (valproic acid, retinoic acid, caffeine, sodium salicylate, glucose, hydroxyurea, methoxyacetic acid, boric acid and paraoxon-methyl) over a concentration range. They were evaluated for AChE activity, head-trunk angle, tail length and several qualitative parameters integrated in a morphological score. In general, the different patterns of the concentration-response curves allowed distinguishing between chemicals that produced growth retardation (valproic and methoxyacetic acid) and chemicals that produced non-growth-delay related malformations. An acceptable correlation between the morphological score, AChE activity and head-trunk angle as markers of developmental delay was observed, being AChE activity particularly sensitive to detect delay in the absence of malformations.

Persistent organochlorine residues in livers of six species of Ciconiiformes (aves) from Spain.

Liver samples of 42 birds belonging to 6 species of Ciconiiformes (grey heron (n = 17), little egret (n = 12), cattle egret (n = 1), glossy ibis (n = 1), little bittern (n = 1), and white stork (n = 10)), collected from two different zones of Spain (Ebro Delta and Madrid) in 1992-1997, were analyzed for organochlorine pesticides and PCBs. SigmaPCBs (sum of concentrations of individual congeners), p,p'-DDE, HCB, gamma-HCH, and heptachlor epoxide were the most prevalent residues detected in all samples (occurrence > 95%). There were no statistically significant differences in organochlorine levels between grey herons and little egrets, while levels of SigmaPCBs, p,p'-DDE, HCB, gamma-HCH, and heptachlor were significantly lower for white storks. These results could be explained by the different habitat of these species, aquatic in the Ebro Delta (grey herons, little egrets) and dry in Madrid (white stork), and their diverse feeding habits.

Lung cancer susceptibility in relation to combined polymorphisms of microsomal epoxide hydrolase and glutathione S-transferase P1.

Human microsomal epoxide hydrolase (mEH) catalyzes a key step in the biotransformation of benzo[a]pyrene that yields the highly mutagenic (+)-anti-7,8-diol-9,10 epoxide (BPDE). Two polymorphisms have been described in the coding region of the mEH gene (EPHX1) that produce two protein variants: 113Tyr-->113His (exon 3) and 139His-->139Arg (exon 4). We performed a case-control study among Northwestern Mediterranean Caucasians to investigate a possible association between these EPHX1 variants and lung cancer risk. Both EPHX1 polymorphisms were analyzed in a group of lung cancer patients (n=176) and in a control group of healthy smokers (n=187). The results showed a significantly decreased risk for the rare homozygous 113His/113His (adjusted odds ratio (OR): 0.44, 95% confidence interval (CI): 0.27-0.71) and 139Arg/139Arg (adjusted OR: 0.55, 95% CI: 0.33-0.91) compared with the major wild-types 113Tyr/113Tyr and 139His/139His, respectively, as the references. Thereafter, we analyzed the EPHX1 variants in combination with three glutathione S-transferase polymorphic genes (GSTM1, GSTT1, and GSTP1) and we found a significant overepresentation of cancer patients with a combination of exon 3 113Tyr/113Tyr EPHX1 and exon 5 105Ile/105Ile GSTP1 (adjusted OR: 2.34, 95% CI: 1.21-4.52). The polymorphic site within the exon 5 of GSTP1 results in a Ile-->Val substitution, and the isoleucine GSTpi isoform has been found in vitro to be less active than the valine isoform towards the conjugation of BPDE. The 113 Tyr/Tyr EPHX1 encodes for a high-activity mEH. Our results agree with these observations in vitro and suggest that a genetically determined combination of a high-activity mEH and a low-activity GSTpi may increase lung cancer risk among smokers.

The Bubi population of Equatorial Guinea characterised by HUMTH01, HUMVWA31A, HUMCSF1PO, HUMTPOX, D3S1358, D8S1179, D18S51 and D19S253 STR polymorphisms.

Allele frequencies for eight STR loci (HUMTH01, HUMVWA31A, HUMCSF1PO, HUMTPOX, D3S1358, D8S1179, D18S51, D19S253) have been analysed in the Bubi population of Bioko Island, Equatorial Guinea. For all loci, no deviation from Hardy-Weinberg equilibrium was found. Data obtained were compared with that of Caucasian and African populations. Significant differences were found for all systems between all the black populations compared and the Caucasoid population. Similarities were observed between the Bubi and Zimbabweans, and also with African American populations. Also, more affinities were observed between Zimbabweans and Ugandans and Ovambos than between these groups and the Bubi population. From these comparisons it is suggested that in Africa, as in other continents, there is a certain genetic heterogeneity.

Population study of Aymara Amerindians for the PCR-DNA polymorphisms HUMTH01, HUMVWA31A, D3S1358, D8S1179, D18S51, D19S253, YNZ22 and HLA-DQalpha.

Allele and genotype frequencies for eight DNA polymorphisms (HUMTH01, HUMVWA31A, D3S1358, D8S1179, D18S51, D19S253, YNZ22 and HLA-DQalpha) were determined in a population sample of Aymara Indians from Bolivia using PCR. No deviations of the observed allelic frequencies from Hardy-Weinberg equilibrium were found for all the systems studied. Significant differences in the allele frequencies were found between the Aymara and Quechua populations only for HUMVWA31A, which suggests a certain degree of genetic differentiation between the two populations.

Haplotype frequencies of eight Y-chromosome STR loci in Barcelona (North-East Spain).

Haplotype frequencies for eight Y-chromosomal short tandem repeat (STR) loci were determined in paragraph signa population sample from Barcelona (NE Spain). After PCR amplification and denaturing PAGE electrophoresis, DYS19, DYS388, DYS389 I/II, DYS390, DYS391, DYS392 and DYS393 loci were typed. Complete eight paragraph signY-chromosomal STRs haplotypes could be formed for 223 subjects, among which 137 different haplotypes were observed. The most common haplotype was shared by 13% of the sample, while 108 haplotypes were unique. The discrimination capacity was 61.5% and the gene diversity was 0.978. From the forensic point of view the combined polymorphisms provide a high diagnostic efficiency.

An outbreak of tinea gladiatorum in Lanzarote.

Canary Islands wrestling is a variant of the sport played exclusively in that region, and is associated with close participant contact. An outbreak of a fungal infection, so-called tinea gladiatorum, amongst such wrestlers in Lanzarote, one island in the archipelago is now described. 102 wrestlers from the eight teams on the island were examined; some of the clubs are 50 km apart; 45 wrestlers (44.1% of those examined) were noted to be affected. To our knowledge, this is the largest reported series of patients with tinea gladiatorum and the only one to demonstrate such infection in a variety of geographical locations.

Genetic polymorphism of glutathione S-transferase P1 gene and lung cancer risk.

OBJECTIVES: The human GSTTP1 gene is polymorphic with an A-->G transition in exon 5 causing a replacement 105 Ile-->Val in the GSTP1 protein. The two isoforms, encoded by the alleles GSTP1*A and GSTP1*B, respectively, show different catalytic efficiencies towards some carcinogenic epoxides. In this study we have addressed the possible role of the Ile105Val GSTP1 polymorphism in lung cancer susceptibility. METHODS: The polymorphic site was genotyped by RFLP in a group of lung cancer patients (n = 164) and in two control groups (healthy smokers, n = 132; general population, n = 200). All patients and controls were Northwestern Mediterranean Caucasians of the same ethnic origin. RESULTS AND CONCLUSIONS: The cancer patients showed frequencies of GSTP1*A/A; GSTP1*A/B and GSTP1*B/B (50%, 38%, 11%, respectively) very similar to those of both control groups (healthy smokers: 48%, 41%, 11%). After adjusting for age, sex and smoking status, no association was found between the GSTP1*B allele and lung cancer risk (OR: 1.18; 95% CI: 0.67-2.07). The Ile105val GSTP1 polymorphism was also analysed in combination with the GSTM1 and GSTT1 genes. The results showed that allelism at GSTP1 did not increase the risk associated with the GSTM1 or GSTT1 deletions.

Quechua Amerindian population characterized by HLA-DQ alpha, YNZ22, 3'APO B, HUMTH01, and HUMVWA31A polymorphisms.

Allele and genotype frequencies of DNA polymorphisms were determined in a population sample of Quechua (n = 113) using the polymerase chain reaction (PCR). We report data on the frequencies of HLA-DQ alpha, YNZ22, 3'ApoB, HUMTH01 and HUMVWA31A alleles and the distribution of the different genotypes. No significant deviations between observed and expected numbers were found, thus assuming the Hardy-Weinberg equilibrium.

Catalonian population study of the tetranucleotide repeat loci D3S1358, D8S1179, D18S51 and D19S253.

Allele frequencies for four short tandem repeat loci were determined in a population sample from Catalonia (NE Spain). After denaturing PAGE electrophoresis, 8 alleles were identified for D3S1358 (n=201), 10 alleles for D8S1179 (n=198), 13 alleles for D18S51 (n=197) and 11 alleles for D19S253 (n=201). No deviation from Hardy-Weinberg equilibrium was found. Complete and relative uniformity in Caucasoid populations has been observed for D18S51 and D8S1179 respectively. Pronounced differences were found between different ethnic groups for both systems. Catalonia and Portugal do not differ for D3S1358 locus. Multiplex PCR amplifications of three loci (D3S1358, D18S51 and D19S253) without overlapping fragment size ranges could be interesting for monochrome automated laser fluorescence devices.