The Los Humeros volcanic complex, a 21×15km diameter caldera edifice nesting volcanic domes and a complex faulting structure, is located at the eastern edge of the Trans-mexican volcanic belt (TMVB). ...It is a young edifice (<0.5Ma) that hosts one of the five main geothermal fields of Mexico with still an important energy production (∼65kW installed capacity). Being one of the more studied producing fields, the geothermal system of the caldera is largely unknown at depths greater than ∼2.4km, which is the approximate penetration range of the available geothermal wells. Here we present the results of a geophysical survey in Los Humeros caldera and surroundings with the aim to provide further insight on the physical characteristics of the geothermal system at depths greater than 2.4km. The survey comprised 70 broadband magnetotelluric (MT) soundings distributed within and in the periphery of the caldera edifice of which we present here three EW profiles. We also accomplished a mesh of 718 accurately leveled gravity stations. These data sets were complemented with 13 TDEM soundings for static shift control, as well as with the aero-magnetic digital chart of the area (#E14-3, SGM, 2004). The MT data analysis yielded an average electric azimuth of N23W for the central profile where the field production is concentrated, which is quite consistent with the mapped NW-SE geological structure. However, at individual frequency ranges the strike follows the local faulting structures, most of which are apparently controlled by the deeper crater structure. At the production zone, the conductivity model reveals the existence of an eastward dipping resistive body, which follows the isotherms registered at the wells. The inclined conductivity interface above it seems to play an important role in controlling the heat and fluid flow towards shallow depths. Petrographic studies of well samples provide evidence of mineralogical assemblages that suggest magnetite-metasomatose hydrothermal alteration. The production zone coincides with maximum gravity and magnetic gradients, at the western edge of the well-defined circular crater anomaly. At this point the central MT section (profile 1) shows the shallower depth (2–3km) to the relatively high resistivity (∼400–500ohm-m) and magnetized intrusive-like body. The interpreted geophysical and surface geological data backed by well data support a reservoir and plume model structure consisting of a resistive propylitic core that feds the geothermal field through fractures and deep- seated faults. Surface conductors associated with stratified mineralization produced from lixiviation of geothermal fluids are well differentiated from deeper conductors. The better preserved northern sector of the Humeros caldera yields an anomalous deep conductor at depths of 6–7km below sea level (profile 5) as well as at the central production sector (profile 1) whereas the anomalous conductivity zone at the southern profile (profile 6) could be as shallow as 5km below sea level. These anomalous conductivity zones are expected to be associated to the primary energy source of the Los Humeros geothermal system in the form of partial fusion or hypercritical trapped fluids within the upper crust, conditions that have been concluded to prevail along cordilleras of the American continent (e.g. Hyndman, 2017).
SUMMARY
This study focuses in the analysis of the internal structure of the upper 3 km of Los Humeros (LH) caldera and the relation of electrical and hydrothermal anomalies. For this purpose, we ...measured, processed and interpreted 78 broad-band magnetotelluric (MT) soundings. We performed a 3-D inversion of the data set (ModEM) using all MT soundings, although only half of the available frequencies per sounding due to limited computed power. We also carried out the 2-D inversions (NLCG) of the invariant determinant along two orthogonal profiles (EW and NS) crossing the caldera structure; their comparison yields similar resistivity and structural models results. The resistivity modelling is complemented with the results of a joint 3-D inversion of an accurate gravity database of 720 stations, and total field aeromagnetic data (SGM) from the caldera crater. The combined results provide novel details about the structure of the shallow geothermal reservoir of the resurgence caldera complex hosting the active hydrothermal system. Density and resistivity models show the existence of a composed crater basin structure separated by an EW high-density structure; the northern basin is associated to the LH crater, whereas the southern basin associates to the emergent Los Potreros (LP) caldera basin. The magnetization model indicates that there is a common source for the magnetic volcanic products observed at the caldera surface, and that the LP fault is the more magnetized fault of the geothermal system. The propylic zoning under the geothermal field, which according to the MT model results has resistivities above ∼100 Ω-m, was extrapolated using this and additional criteria to obtain the distribution of other hypothetical propylitic zones of hydrothermal potential.
This study aimed to reinforce a polyvinyl acetate-D3 (PVAc-D3) adhesive to improve its mechanical and thermal properties. The goal was to reach a polyvinyl acetate-D4 (PVAc-D4) adhesive performance ...that could make PVAc-D3 more attractive and add value to wood products. PVAc-D3 was modified by adding 0.05% and 0.5% (wt.) of multi-walled carbon nanotube particles (MWCNTs) as well as 0.5% and 2.5% (wt.) of lignosulfonate (LIGNO) particles. Adhesive blends were compared to neat PVAc-D3 and PVAc-D4, evaluating their physical–chemical properties. Also, they were analyzed using Fourier transform infrared spectroscopy (FT-IR) and mechanical dynamic analysis (DMA) with a storage module (E′). The blends were used to fabricate laminated wood pieces, pressed at 60 and 120 min (min), to be tested at shear strength under dry, elevated temperature and vacuum-pressure conditions. Delamination and adhesive penetration were determined by microscopy. Incorporating fillers into PVAc resulted in a decrease in viscosity. FT-IR evidenced that the PVAc-D4 adhesive had a bigger cross-linked degree than the other adhesive samples. The DMA showed that LIGNO and MWCNT fillers help increase E′ at the bond line, reaching a higher stiffness level than neat PVAc-D3. In dry conditions, specimens glued with D3-LIGNO 0.5% at 120 min reached shear strengths that were 100%, 28%, and 3% higher than the standard requirement, PVAc-D4, and neat PVAc-D3, respectively. Also, those glued with D3-MWNTC 0.05% reached shear strengths that were 91%, 21%, and 3% higher than the standard requirement, D4, and neat D3, respectively. Only PVAc-D4 reached the standard requirement for elevated temperature and vacuum-pressure conditions. Delamination of ≤5% (standard requirement) was achieved by wood specimens glued with neat PVAc-D3, D3-MWNTC 0.5%, D3-LIGNO 0.5%, and PVAc D4 adhesive samples. In this study, it was found specific ranges of average penetration (AP) to ensure a glue line good quality. To conclude, LIGNO and MWCNT particles improved the PVAc-D3 adhesive’s performance in dry conditions, but they were not very relevant to the D3 adhesive’s behavior. At high temperatures, the LIGNO filler worked very well as a thermic stabilizer compared to the MWCNT filler. The solubility of the reinforcing agent can affect an adhesive’s blend quality and its cohesion properties. An adequate penetration depth procures a good quality bond between an adhesive and substrate with less possibilities of delamination. An extensive pressing time may cause a weak interphase and poor mechanical properties in an adhesive bond in the presence of humidity.
To compare peer-led dental education (PLDE) versus conventional dental instruction (CDI) in modifying children's oral self-care.
The intervention group (two schools) received PLDE and the control ...group (two schools) received CDI. The quality of oral self-care practice (OSC-P) and oral self-care skills (OSC-S) were indicated by dental plaque levels (%) and compared before and after dental education.
There were no baseline OSC-P differences between the control (55.8 ± 12.8%) and intervention (55.5 ± 14.6%) groups or OSC-S differences between the intervention (38.5 ± 13.2%) and control (38.1 ± 12.5%) groups. At the three-month follow-up we observed OSC-P deterioration in the control group (63.2 ± 15.0%) and OSC-P improvement in the intervention group (52.2 ± 15.6%). The OSC-P/OSC-S regression models found these predictors: baseline oral self-care, group affiliation, and mother's education (p<0.05).
The hypothesis was confirmed and significant predictors were baseline oral self-care levels, group affiliation, and mother's education.
La calidad de vida es un aspecto relevante en la vida de las personas, más aún cuando se presentan comorbilidades altas en población general, por lo que su medición de forma válida y confiable es ...necesaria. Objetivo: Determinar las propiedades psicométricas del Instrumento de Evaluación de Funcionalidad en el Tratamiento para Enfermedades Crónicas (FACT-GP) en población general mexicana. Método: Se empleó un diseño transversal, con un muestreo no probabilístico, por disponibilidad. Análisis estadístico: Se realizó un modelo factorial confirmatorio. Resultados: Se incluyeron 254 participantes con M = 23.5 años (21-32). Se identificaron 4 factores con 18 reactivos. La consistencia interna de la escala global fue .81, que explican el 58.93 % de la varianza. El análisis factorial confirmatorio presenta índices adecuados (CFI, RMR, RMSEA), que indican un ajuste equilibrado y parsimonioso de la estructura del modelo. Conclusión: El FACT-GP mostró una estructura similar a la versión original, con indicadores válidos y confiables para su uso en la atención clínica e investigación dirigida a población general mexicana.
The Los Humeros Volcanic Complex (LHVC) is a large silicic caldera complex in the Trans-Mexican Volcanic Belt (TMVB), hosting a geothermal field currently in exploitation by the Comisión Federal de ...Electricidad (CFE) of Mexico, with an installed capacity of ca. 95 MW of electric power. Understanding the structural architecture of LHVC is important to get insights into the interplay between the volcano-tectonic setting and the characteristics of the geothermal resources in the area. The analysis of volcanotectonic interplay in LHVC benefits from the availability of subsurface data obtained during the exploration of the geothermal reservoir that allows the achievement of a 3D structural view of the volcano system. The LHVC thus represents an important natural laboratory for the development of general models of volcano-tectonic interaction in calderas. In this study, we discuss a structural model of LHVC based on morphostructural and field analysis, integrated with well logs, focal mechanism solutions and magnetotelluric imaging. The structural analysis suggests that inherited regional tectonic structures recognized in the basement played an important role in the evolution of the magma feeding system, caldera collapses and post-caldera deformations. These inherited weak planes have been reactivated by resurgence faults and post-caldera magma-driven hydrofractures under a local radial stress field generated by the shallow LHVC magmatic/hydrothermal system. The local stress field induced caldera resurgence and volcanotectonic faulting. The results of this study are important to better constrain the structural architecture of large caldera complexes. Also, our study is useful to understand the structure of the Los Humeros geothermal field and support the exploration of deeper Super-Hot Geothermal Systems (SHGSs) and engineering of Enhanced Geothermal Systems (EGSs) for electric power production in the LHVC and other active resurgent calderas.
•Geomorphological, field, subsurface and geophysical information are integrated into a new 3D model of LHVC;•Magmatic radial stress field, overwhelming the regional stress field, induces caldera resurgence;•Volcanotectonic deformations and hydrofractures reactivated inherited tectonic weak planes;•Resurgence faults and volcanotectonic stress field control the location of structures producing geothermal fluids.
Advances in nanotechnology are producing an accelerated proliferation of new nanomaterial composites that are likely to become an important source of engineered health-related products. Nanoparticles ...with antifungal effects are of great interest in the formulation of microbicidal materials. Fungi are found as innocuous commensals and colonize various habitats in and on humans, especially the skin and mucosa. As growth on surfaces is a natural part of the Candida spp. lifestyle, one can expect that Candida organisms colonize prosthetic devices, such as dentures. Macromolecular systems, due to their properties, allow efficient use of these materials in various fields, including the creation of reinforced nanoparticle polymers with antimicrobial activity. This review briefly summarizes the results of studies conducted during the past decade and especially in the last few years focused on the toxicity of different antimicrobial polymers and factors influencing their activities, as well as the main applications of antimicrobial polymers in dentistry. The present study addresses aspects that are often overlooked in nanotoxicology studies, such as careful time-dependent characterization of agglomeration and ion release.
Land-use changes are one of the main causes of biodiversity loss. It would be expected that species with restricted habitats and distribution should experience the main negative effects of the ...modification of natural environments. To exemplify the potential effect of land transformation on restricted species, we focused on the potential habitat loss of six endemic and quasi-endemic species to Mexico (Ortalis poliocephala, Melanerpes chrysogenys, Trogon citreolus, Pheugopedius felix, Uropsila leucogastra, and Arremonops rufivirgatus) whose distributions include the state of Guerrero, in southern Mexico. Species distribution models were generated for each species, and potential habitat loss was evaluated using three temporal vegetation and land-use maps (1997, 2003, and 2013). These analyses were then repeated only for tropical dry forest, one of the most dominant ecosystem in the state of Guerrero and with the most severe transformation rates. The potential habitat of all species decreased considerably, particularly for the last periods; the habitats for M. chrysogenys and T. citreolus were reduced by 78% in 2013. The potential habitats of U. leucogastra and P. felix decreased to a lesser extent during the three periods. The reduction tendencies were higher for dry forest than for the remaining habitats, which were ranged from 88% to 93% for U. leucogastra and M. chrysogenys, respectively. These results suggest major negative potential effects of land transformation on the endemic species’ habitat.
The Los Humeros geothermal field is the third most important producer of geothermal electricity (70MW) in Mexico. Geothermal fluids are hosted in fractured andesitic lavas and mostly consist of high ...enthalpy steam with limited water content (vapor fraction>0.9). Despite the high reservoir temperature (~300–400°C), thermal manifestations at the surface are scarce and locally appear as steaming grounds, weak steam vents and advanced argillic alteration. Geothermal fluid upflow from the reservoir towards the surface is limited by welded ignimbrite deposits that act as a low-permeability barrier. In this study, we present the first measurements of CO2, CH4 and H2S degassing rates from the soil performed at Los Humeros. Flux measurements were complemented with δ13C composition of degassing CO2 and soil temperatures to discuss gas origin and thermal anomalies. We measured high soil degassing rates (up to 7530gm−2d−1 CO2, 33gm−2d−1 CH4 and 22gm−2d−1 H2S) in three localized areas (Humeros North – HN, Humeros South – HS and Xalapazco – XA) as well as high soil temperatures reaching the boiling temperature at the local altitude (90.6°C). The particular location of these three areas suggests that the steam-dominated reservoir degases to the surface through permeable faults crossing the ignimbritic deposits. The remaining surveyed areas are characterized by weak CO2 fluxes (≤44gm−2d−1), non-detectable CH4 and H2S fluxes, and lower soil temperatures (5–21°C). The compositions in δ13CCO2 from HN-HS-XA areas (δ13CCO2=−7.94 to −2.73‰) reflect a magmatic source with some possible contribution from the sedimentary basement, as well as fractionation induced by boiling and CO2 dissolution in shallow water bodies. We also discuss the processes causing the spread in CO2/CH4 flux ratios. Finally, we estimate the heat output from the three high degassing areas to a value of 16.4MWt.
•The location of high degassing areas at Los Humeros reveals the presence of permeable faults.•Carbon isotopic composition from gas efflux reflects a source dominantly magmatic and fractionation processes.•The spread in surface CO2/CH4 flux ratios reflects superficial processes and/or a deep characteristic of the reservoir.•A total heat output of 16.4 MWt is estimated for the three high degassing areas at Los Humeros.
Diabetes mellitus causes temperature alterations in the body. Proper treatment and follow-up can prevent serious complications. In this work, a case-control study was conducted with 16 children with ...diabetes mellitus type I and II and 25 healthy children attending a public hospital in San Luis Potosí, Mexico. Distal-to-proximal and bilateral temperature gradients were calculated from thermograms of each subject's arms, hands, and feet. A significant difference was found between the healthy groups and those with diabetes mellitus in the distal-to-proximal temperature gradient of the upper limbs on both the right side (p = 0.0011) and left side (p = 0.0005), as well as in the bilateral temperature gradient of the palms (p = 0.0084). Our results show a temperature difference in the upper extremities of children with diabetes but not in the lower extremities. Monitoring those temperature gradients could help evaluate the evolution of the disease, thus improving the clinical assessment of these patients.
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