Meteoric Metal Chemistry in the Martian Atmosphere.

Recent measurements by the Imaging Ultraviolet Spectrograph (IUVS) instrument on NASA's Mars Atmosphere and Volatile EvolutioN mission show that a persistent layer of Mg+ ions occurs around 90 km in the Martian atmosphere but that neutral Mg atoms are not detectable. These observations can be satisfactorily modeled with a global meteoric ablation rate of 0.06 t sol-1, out of a cosmic dust input of 2.7 ± 1.6 t sol-1. The absence of detectable Mg at 90 km requires that at least 50% of the ablating Mg atoms ionize through hyperthermal collisions with CO2 molecules. Dissociative recombination of MgO+.(CO2)n cluster ions with electrons to produce MgCO3 directly, rather than MgO, also avoids a buildup of Mg to detectable levels. The meteoric injection rate of Mg, Fe, and other metals-constrained by the IUVS measurements-enables the production rate of metal carbonate molecules (principally MgCO3 and FeCO3) to be determined. These molecules have very large electric dipole moments (11.6 and 9.2 Debye, respectively) and thus form clusters with up to six H2O molecules at temperatures below 150 K. These clusters should then coagulate efficiently, building up metal carbonate-rich ice particles which can act as nucleating particles for the formation of CO2-ice clouds. Observable mesospheric clouds are predicted to occur between 65 and 80 km at temperatures below 95 K and above 85 km at temperatures about 5 K colder.

Regression models to predict the behavior of the coefficient of friction of AISI 316L on UHMWPE under ISO 14243-3 conditions.

Friction is the natural response of all tribosystems. In a total knee replacement (TKR) prosthetic device, its measurement is hindered by the complex geometry of its integrating parts and that of the testing simulation rig operating under the ISO 14243-3:2014 standard. To develop prediction models of the coefficient of friction (COF) between AISI 316L steel and ultra-high molecular weight polyethylene (UHMWPE) lubricated with fetal bovine serum dilutions, the arthrokinematics and loading conditions prescribed by the ISO 142433: 2014 standard were translated to a simpler geometrical setup, via Hertz contact theory. Tribological testing proceeded by loading a stainless steel AISI 316L ball against the surface of a UHMWPE disk, with the test fluid at 37 °C. The method has been applied to study the behavior of the COF during a whole walking cycle. On the other hand, the role of protein aggregation phenomena as a lubrication mechanism has been extensively studied in hip joint replacements but little explored for the operating conditions of a TKR. Lubricant testing fluids were prepared with fetal bovine serum (FBS) dilutions having protein mass concentrations of 5, 10, 20 and 36 g/L. The results were contrasted against deionized, sterilized water. The results indicate that even at protein concentration as low as 5 g/L, protein aggregation phenomena play an important role in the lubrication of the metal-on-polymer tribopair. The regression models of the COF developed herein are available for numerical simulations of the tribological behavior of the aforementioned tribosystem. In this case, surface stress rather than film thickness should be considered.

The coefficient of friction of UHMWPE along an entire walking cycle using a ball-on-disc tribometer under arthrokinematics and loading conditions prescribed by ISO 14243-3:2014.

The observation of tribological phenomena occurring in total knee replacement (TKR) simulators may be obscured by the intrinsic complexity of their operation: the dynamics and kinematics prescribed by the ISO 14243-3:2014 standard, and the geometry of the surfaces involved. On the other hand, evaluating the individual performance of the tribosystem elements may be carried out in simpler apparatuses. An experimental method is presented here, by means of which the arthrokinematics and loading conditions prescribed by the said standard are adapted to a ball-on-disc configuration in order to observe the behavior of the coefficient of friction along an entire walking cycle, using the contact point of an AISI 316L stainless steel ball rolling/sliding on an ultra-high molecular weight polyethylene (UHMWPE) disc, lubricated by a solution of fetal bovine serum, at 37°C. The method was tried on two different testing fluids prepared with protein concentrations of 20g/L, according to the said standard, and 36g/L, as received. The statistical model obtained for the behavior of the COF during the entire walking cycle may be used in numerical simulations of UHMWPE wear, under the conditions established by ISO 14243-3:2014.

A novel instrument to measure differential ablation of meteorite samples and proxies: The Meteoric Ablation Simulator (MASI).

On entering the Earth's atmosphere, micrometeoroids partially or completely ablate, leaving behind layers of metallic atoms and ions. The relative concentration of the various metal layers is not well explained by current models of ablation. Furthermore, estimates of the total flux of cosmic dust and meteoroids entering the Earth's atmosphere vary over two orders of magnitude. To better constrain these estimates and to better model the metal layers in the mesosphere, an experimental Meteoric Ablation Simulator (MASI) has been developed. Interplanetary Dust Particle (IDP) analogs are subjected to temperature profiles simulating realistic entry heating, to ascertain the differential ablation of relevant metal species. MASI is the first ablation experiment capable of simulating detailed mass, velocity, and entry angle-specific temperature profiles whilst simultaneously tracking the resulting gas-phase ablation products in a time resolved manner. This enables the determination of elemental atmospheric entry yields which consider the mass and size distribution of IDPs. The instrument has also enabled the first direct measurements of differential ablation in a laboratory setting.

Sources of cosmic dust in the Earth's atmosphere.

There are four known sources of dust in the inner solar system: Jupiter Family comets, asteroids, Halley Type comets, and Oort Cloud comets. Here we combine the mass, velocity, and radiant distributions of these cosmic dust populations from an astronomical model with a chemical ablation model to estimate the injection rates of Na and Fe into the Earth's upper atmosphere, as well as the flux of cosmic spherules to the surface. Comparing these parameters to lidar observations of the vertical Na and Fe fluxes above 87.5 km, and the measured cosmic spherule accretion rate at South Pole, shows that Jupiter Family Comets contribute (80 ± 17)% of the total input mass (43 ± 14 t d-1), in good accord with Cosmic Background Explorer and Planck observations of the zodiacal cloud.

On the size and velocity distribution of cosmic dust particles entering the atmosphere.

The size and velocity distribution of cosmic dust particles entering the Earth's atmosphere is uncertain. Here we show that the relative concentrations of metal atoms in the upper mesosphere, and the surface accretion rate of cosmic spherules, provide sensitive probes of this distribution. Three cosmic dust models are selected as case studies: two are astronomical models, the first constrained by infrared observations of the Zodiacal Dust Cloud and the second by radar observations of meteor head echoes; the third model is based on measurements made with a spaceborne dust detector. For each model, a Monte Carlo sampling method combined with a chemical ablation model is used to predict the ablation rates of Na, K, Fe, Mg, and Ca above 60 km and cosmic spherule production rate. It appears that a significant fraction of the cosmic dust consists of small (<5 µg) and slow (<15 km s-1) particles.

High temperature stability of anatase in titania-alumina semiconductors with enhanced photodegradation of 2, 4-dichlorophenoxyacetic acid.

The incorporation of aluminum acetylacetonate as alumina source during the gelation of titanium alkoxide reduces the nucleation sites for the formation of large rutile crystals on temperatures ranging from 400 to 800°C. As a result, the aggregation of anatase crystals is prevented at high temperature. A relationship among the specific surface area, pore size, energy band gap, crystalline structure and crystallite size as the most relevant parameters are evaluated and discussed. According to the results for the photocatalytic degradation of 2,4-dichlorophenoxyacetic acid, the specific surface area, pore size, Eg band gap are not determinant in the photocatalytic properties. It was found that the anatase crystallite size is the mores important parameter affecting the degradation efficiency.

Effect of estradiol and progesterone on metabolic biomarkers in healthy bitches.

The aim of this study was to evaluate the possible association between hormonal changes that occur during oestrus and biomarkers related with glucose metabolism (glucose and insulin), lipid metabolism (lipidic profile and BChE) and adipokines (adiponectin and ghrelin) in healthy bitches. For this purpose, we measured these analytes in serum of bitches, at two times: before (T1) and after (T2) the LH peak that were established according to progesterone concentrations. Increased levels of total cholesterol (p < 0.01), high density lipoprotein cholesterol (HDL-C) (p < 0.01), low density lipoprotein cholesterol (LDL-C) (p < 0.01), adiponectin (p < 0.01) and ghrelin (p < 0.05) were observed at T2 in comparison with T1. No statistically significant changes were observed in serum glucose, insulin, homoeostasis model assessment for insulin sensitivity (HOMA), triglycerides and BChE. When all data of T1 and T2 were pooled, serum adiponectin showed positive correlation with progesterone (r = 0.353; p = 0.022) and HDL-C (r = 0.307; p = 0.048), and negative with insulin (r = -0.429; p = 0.005), HOMA (r = -0.446; p = 0.003) and BChE (r = -0.522; p < 0.001). Ghrelin showed negative correlation with estradiol (r = -0.701; p = 0.004). BChE was negatively correlated with estradiol (r = -0.441; p = 0.018) and glucose (r = -0.343; p = 0.028), and positively with insulin (r = 0.460; p = 0.003) and HOMA (r = 0.505; p < 0.001). In conclusion, changes in metabolic biomarkers occur in bitches after LH peak, characterized by increased lipids (total cholesterol, HDL cholesterol and LDL cholesterol) without changes in BChE activity, and increased adiponectin and ghrelin concentrations, without significant changes in glucose and insulin.

Effects of orchidectomy in selective biochemical analytes in Beagle dogs.

The objective of this study was to evaluate the possible effects of orchidectomy and associate hormonal changes on circulating concentrations of acute-phase proteins (APPs) (CRP--C-reactive protein; Hp--haptoglobin; Cp--ceruloplasmin), adiponectin and IGF-1 in dogs. For this, a total of five adult Beagle dogs were subjected to orchidectomy. Blood samples were taken before neutering, during six consecutive days and on weeks 2, 4, 8 and 12 after surgery. Appropriate diet regime was maintained to keep stable body weight of the dogs. Concentrations of APPs significantly increased on days 2-3 for CRP and 2-7 for Hp and Cp. On days 3-4 after neutering, adiponectin levels were significantly lower than before surgery (p<0.05 and <0.01, respectively). After this initial change, adiponectin did not show any significant alteration during the 3 months. Serum IGF-1 concentrations were significantly decreased at days 2-5 after neutering. In addition, on weeks 8 and 12 serum IGF-1 levels were significantly lower (p<0.001 and <0.01 respectively) in comparison with those before surgery. In conclusion, orchidectomy induced a short-term inflammatory process that was associated with the increase in serum levels of APPs and decrease in IGF-1 and adiponectin levels. However, orchidectomy did not result in long-term changes of circulating concentrations of APPs or adiponectin. Although a decrease in IGF-1 levels was recorded 2 months after surgery, possibly as a consequence of associated decrease in androgen levels or food restriction.

Polymorphisms C677T and A1298C in the MTHFR gene in Mexican patients with rheumatoid arthritis treated with methotrexate: implication with elevation of transaminases.

Rheumatoid arthritis (RA) is the prototype of the rheumatic diseases worldwide. Methotrexate (MTX) is the drug of first choice in the treatment of this disease due to its immunosuppressant effect. However, side events are present in 30% of the patients. The C677T and A1298C polymorphisms of the methylenetetrahydrofolate reductase (MTHFR) gene are involved in the metabolism of MTX. Earlier studies reported an association between these polymorphisms and elevation of hepatic enzymes. We analyzed the frequencies of both polymorphisms and the presence of transaminasemia in 70 Mexican patients with rheumatic arthritis treated with MTX. The 19% (13/70) of patients had an increase in the serum level of transaminases. The A1298C polymorphism was associated with elevation of transaminases (P=0.024). The identification of MTHFR genotypes for C677T and A1298C polymorphisms could lead clinicians to identify patients in risk of elevation of transaminases, and give them an individualized treatment, as is a goal of pharmacogenetics.

Serologic survey of domestic animals for zoonotic arbovirus infections in the Lacandón Forest region of Chiapas, Mexico.

A serologic survey in domestic animals (birds and mammals) was conducted in four communities located in the Lacandón Forest region of northeastern Chiapas, Mexico, during June 29 to July 1, 2001, with the objective to identify zoonotic arboviruses circulating in this area. We collected 202 serum samples from healthy domestic chickens, geese, ducks, turkeys, horses and cattle. The samples were tested by plaque-reduction neutralization test for antibodies to selected mosquito-borne flaviviruses (family Flaviviridae), including St. Louis encephalitis (SLE), Rocio (ROC), Ilheus (ILH), Bussuquara (BSQ), and West Nile (WN) viruses, and selected alphaviruses (family Togaviridae), including Western equine encephalitis (WEE), Eastern equine encephalomyelitis (EEE), and Venezuelan equine encephalitis (VEE) viruses. Neutralizing antibodies to SLE virus were detected in two (8%) of 26 turkeys, 15 (23%) of 66 cattle, and three (60%) of five horses. Antibodies to VEE virus were detected in 29 (45%) of 65 cattle. Because some of these animals were as young as 2 months old, we demonstrated recent activity of these two viruses. Sub-typing of the VEE antibody responses indicated that the etiologic agents of these infections belonged to the IE variety of VEE, which has been reported from other regions of Chiapas. WN virus-neutralizing antibodies were detected in a single cattle specimen (PRNT(90) = 1:80) that also circulated SLE virus-neutralizing antibodies (PRNT(90) = 1:20), suggesting that WN virus may have been introduced into the region. We also detected weak neutralizing activity to BSQ virus in four cattle and a chicken specimen, suggesting the presence of this or a closely related virus in Mexico. There was no evidence for transmission of the other viruses (ROC, ILH, EEE, WEE) in the study area.

Pressurised metered-dose inhalers (MDIs) versus dry powder inhalers devices (DPIs) to rapid-acting inhaled b2-agonists for asthma in children.

OBJECTIVE: To compare the clinical effectiveness of pressurized metered-dose inhalers (MDIs) with that of dry powder inhalers (DPIs) in delivering short-acting b2-agonists in children with asthma. METHODS: Searches were performed in Medline (1997-March 2002), the Cochrane Library Database and the Embase reference lists of review articles and clinical trials. In addition, the international headquarters of b2-agonist manufacturers were contacted. We performed a review of randomized controlled trials. RESULTS: Ten randomized controlled trials were included. No differences in clinical effectiveness were found between MDIs and PDIs. Two studies reported that fewer adverse events occurred when the Turbuhaler was used. Two long-term studies in children found that children preferred the MDI to the Rotohaler. CONCLUSIONS: 1) In stable asthma, short-acting b2 bronchodilators in standard MDIs are as effective as dry powder inhalers. 2) Pooling of results was limited by the small number of studies and therefore no overall conclusions could be drawn. 3) From the limited data available, we found little or no evidence for an additional clinical benefit of DPI devices over standard MDIs in children with asthma.

Intramolecular Friedel-Crafts-type reactions involving N-acyliminium ions derived from glycine templates.

Enantiomerically pure 4-substituted 2-aralkyl-2,4-dihydro-1H-pyrazino[2,1-b]quinazoline-3,6-diones (1b-m) in which the alkyl chain is (CH(2))(n), n = 1-3, behave as glycine templates giving by treatment with [hydroxy(tosyloxy)iodo]benzene in ethyl acetate cis-1-tosyloxy derivatives. When these compounds contain electron-rich aryl substituents with n = 2, they spontaneously cyclize through intramolecular Friedel-Crafts-type diastereoselective reactions to give penta- or hexacyclic compounds. Otherwise, they give by solvolysis cis-1-alkoxy derivatives, which in a second step, may be cyclized in acid if n = 2, 3. All these reactions must occur through N-acyliminium species in S(N)1-like mechanisms. 1-Alkoxy-2-arylmethyl derivatives are reluctant to cyclize, giving trans-1-hydroxy compounds as the only isolated reaction products.

Positividad de la prueba del parche con fenitoína en un caso de síndromede Stevens-Johnson / Positive patch test with phenytoin in a case of Stevens-Johnson syndrome

El síndrome de Stevens-Johnson (SJS) o eritema multiforme mayor es una reacción de posible mecanismo inmunológico poco frecuente, con una incidencia media anual estimada de 1-2 casos por millón de habitantes. La fenitoína y otros anticonvulsivantes, tales como fenobarbital y carbamnacepina, se han asociado con casos de SJS. Se describe el caso de una mujer de 40 arios de edad, diagnosticada de un tumor cerebral (oligodendroglloma), que presentó un cuadro clínico compatible con SJS, 48 horcas después de administrarle metamizol magnésico y fenitoína, por vía intravenosa (la paciente había realizado previamente un ciclo de tratamiento con buena tolerancia a dichos fármacos). Se realizaron pruebas cutáncas (1prick test) con los preparados comerciales de fenitoína (50 mg/ml) y metamizol (400 mg/ml), que frieron negativas en ambos casos. Se llevaron a cabo pruebas epicutáneas con los preparados comerciales de los fármacos implicados que resultaron positivas a fenitoína, a las 48 y 96 horas con persistencia de la lesión resultante incluso una semana después, y negativas en el caso del metamizol. La provocación oral hasta alcanzar la dosis terapéutica con metamizol fue tolerada. La provocación con fenitoína no se realizó, por el riesgo de una reacción potencialmente grave. Este caso puede servir como ejemplo de la utilidad de las pruebas epicutáneas para llegas- a identificar al agente causal, en casos de SJS relacionados con la toma de varios medicamentos (AU)

[Bacteriological quality of human drinking water in high-margination zones in Chiapas]. / Calidad bacteriológica del agua para consumo humano en zonas de alta marginación de Chiapas.

OBJECTIVE: To analyze the bacteriological quality of drinking water (BQDW) and its association with diarrhoea and intestinal parasites in children 1 to 14 years old, in areas of high levels of poverty in Chiapas, Mexico. MATERIAL AND METHODS: From March to September 1998, drinking water was collected from a random sample of 99 households in the Border Region of Chiapas, Mexico; data on diarrhoeal disease (in the past 15 days) were collected and stool testing for intestinal parasites was performed in children 1 to 14 years old (n = 322). The BQDW was determined by the filtration membrane technique. Intestinal parasitic infections were determined by the Faust Method. The chi 2 statistic was used to analyse factors associated with BQDW. RESULTS: Only 31% of the water samples were adequate for human consumption. The BQDW and the presence of diarrhoea (informed by the mothers of the children) showed no association. Children living in households with inadequate BQDW had a higher prevalence of Entamoeba histolytica and a greater tendency to have intestinal parasites. CONCLUSIONS: It is necessary to develop programs that improve BQDW and to develop education efforts aimed at increasing the use of boiled water and the adequate management and care of community water storage sites.

Vagus nerve stimulation therapy for epilepsy in older adults.

The authors assessed the efficacy, safety, and tolerability of vagus nerve stimulation (VNS) for refractory epilepsy in 45 adults 50 years of age and older. They determined seizure frequency, adverse effects, and quality of life. At 3 months, 12 patients had a >50% decrease in seizure frequency; at 1 year, 21 of 31 studied individuals had a >50% seizure decrease. Side effects were mild and transient. Quality of life scores improved significantly with time.

Risperidone in the treatment of choreiform movements and aggressiveness in a child with "PANDAS".

The acronym 'PANDAS' (pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections) is used to describe neuropsychiatric symptoms putatively resulting from autoimmune responses to streptococcal infection in vulnerable children. A case of 'PANDAS' is presented to increase physician awareness of this disorder and to document effectiveness of risperidone in chorea and treatment-resistant disruptive behavior associated with this syndrome. To our knowledge, this is the first case report on risperidone in pediatric chorea, although studies on effectiveness of this agent in Tourette's disorders have been previously published.