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"Santiago, José S"
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Chemical and isotopic compositions of thermal springs, fumaroles and bubbling gases at Tacaná Volcano (Mexico–Guatemala): implications for volcanic surveillance
This study presents baseline data for future geochemical monitoring of the active Tacaná volcano–hydrothermal system (Mexico–Guatemala). Seven groups of thermal springs, related to a NW/SE-oriented fault scarp cutting the summit area (4,100m a.s.l.), discharge at the northwest foot of the volcano (1,500–2,000m a.s.l.); another one on the southern ends of Tacaná (La Calera). The near-neutral (pH from 5.8 to 6.9) thermal (
T
from 25.7°C to 63.0°C) HCO
3
–SO
4
waters are thought to have formed by the absorption of a H
2
S/SO
2
–CO
2
-enriched steam into a Cl-rich geothermal aquifer, afterwards mixed by Na/HCO
3
-enriched meteoric waters originating from the higher elevations of the volcano as stated by the isotopic composition (δD and δ
18
O) of meteoric and spring waters. Boiling temperature fumaroles (89°C at ~3,600m a.s.l. NW of the summit), formed after the May 1986 phreatic explosion, emit isotopically light vapour (δD and δ
18
O as low as −128 and −19.9‰, respectively) resulting from steam separation from the summit aquifer. Fumarolic as well as bubbling gases at five springs are CO
2
-dominated. The δ
13
C
CO2
for all gases show typical magmatic values of −3.6 ± 1.3‰ vs V-PDB. The large range in
3
He/
4
He ratios for bubbling, dissolved and fumarolic gases [from 1.3 to 6.9 atmospheric
3
He/
4
He ratio (
R
A
)] is ascribed to a different degree of near-surface boiling processes inside a heterogeneous aquifer at the contact between the volcanic edifice and the crystalline basement (
4
He source). Tacaná volcano offers a unique opportunity to give insight into shallow hydrothermal and deep magmatic processes affecting the CO
2
/
3
He ratio of gases: bubbling springs with lower gas/water ratios show higher
3
He/
4
He ratios and consequently lower CO
2
/
3
He ratios (e.g. Zarco spring). Typical Central American CO
2
/
3
He and
3
He/
4
He ratios are found for the fumarolic Agua Caliente and Zarco gases (3.1 ± 1.6 × 10
10
and 6.0 ± 0.9
R
A
, respectively). The
L
/
S
(5.9 ± 0.5) and (
L
+
S
)/
M
ratios (9.2 ± 0.7) for the same gases are almost identical to the ones calculated for gases in El Salvador, suggesting an enhanced slab contribution as far as the northern extreme of the Central American Volcanic Arc, Tacaná.
Journal Article
Genus one H-surfaces with k-ends in H2×R
We construct two different families of properly Alexandrov-immersed surfaces in H2×R with constant mean curvature 0
Journal Article
Genus one$H$ -surfaces with$k$ -ends in$\\mathbb{H}^{2}\\times\\mathbb{R}
We construct two different families of properly Alexandrov-immersed surfaces in H^2 R with constant mean curvature 0
Journal Article
Uniqueness of the Bonnet problem in Thurston geometries
We study the Bonnet problem in Bianchi--Cartan--Vrănceanu spaces and in \\(\\mathrm{Sol}_3\\). Our main contribution is to establish the uniqueness of Bonnet mates, which leads us to address the problem of determining when an isometric immersion can be continuously deformed through isometric immersions that preserve the principal curvatures -- a question originally posed in \\(\\mathbb{R}^3\\) by Chern~\\cite{Chern}. For Bianchi--Cartan--Vrănceanu spaces, we complete the local classification of Bonnet pairs by studying the uniqueness of the results obtained by Gálvez, Martínez and Mira~\\cite{GMM}, and we provide new examples of Bonnet mates that were not previously considered. In particular, we prove that the aforesaid continuous deformations only exist for minimal surfaces in the product spaces \\(\\mathbb{S}^2\\times\\mathbb{R}\\) and \\(\\mathbb{H}^2\\times\\mathbb{R}\\) and otherwise only for surfaces with constant principal curvatures. In the case of \\(\\mathrm{Sol}_3\\), we give a characterization of Bonnet mates via a system of two differential equations, addressing a problem proposed in~\\cite{GMM}. We conclude that the only surfaces admitting continuous isometric deformations that preserve the principal curvatures in \\(\\mathrm{Sol}_3\\) are those with constant left-invariant Gauss map.
Paper
Genus one \\(H\\)-surfaces with \\(k\\)-ends in \\(\\mathbb{H}^2\\times\\mathbb{R}\\)
We construct two different families of properly Alexandrov-immersed surfaces in \\(\\mathbb{H}^2\\times \\mathbb{R}\\) with constant mean curvature \\(0
Paper
Isometric immersions into three-dimensional unimodular metric Lie groups
We study isometric immersions of surfaces into simply connected 3-dimensional unimodular Lie groups endowed with either Riemannian or Lorentzian left-invariant metrics, assuming that Milnor's operator is diagonalizable in the Lorentzian case. We provide global models in coordinates for all these metric Lie groups that depend analytically on the structure constants and establish some fundamental theorems characterizing such immersions. In this sense, we study up to what extent we can recover the immersion from (a) the tangent projections of the natural left-invariant ambient frame, (b) the left-invariant Gauss map, and (c) the shape operator. As an application, we prove that an isometric immersion is determined by its left-invariant Gauss map up to certain well controlled angular companions. We also we classify totally geodesic surfaces and introduce four Lorentzian analogues of the Daniel correspondence within two families of Lorentzian homogeneous 3-manifolds with 4-dimensional isometry group. We also classify isometric immersions in \\(\\mathbb{R}^3\\) or \\(\\mathbb{S}^3\\) whose left-invariant Gauss maps differ by a direct isometry of \\(\\mathbb{S}^2\\). Finally, we show that Daniel's is the furthest extension of the classical Lawson correspondence for constant mean curvature surfaces within Riemannian unimodular metric Lie groups.
Paper
Genistein effect on cognition in prodromal Alzheimer’s disease patients. The GENIAL clinical trial
Background
Delaying the transition from minimal cognitive impairment to Alzheimer’s dementia is a major concern in Alzheimer’s disease (AD) therapeutics.
Pathological signs of AD occur years before the onset of clinical dementia. Thus, long-term therapeutic approaches, with safe, minimally invasive, and yet effective substances are recommended. There is a need to develop new drugs to delay Alzheimer’s dementia. We have taken a nutritional supplement approach with genistein, a chemically defined polyphenol that acts by multimodal specific mechanisms. Our group previously showed that genistein supplementation is effective to treat the double transgenic (APP/PS1) AD animal model.
Methods
In this double-blind, placebo-controlled, bicentric clinical trial, we evaluated the effect of daily oral supplementation with 120 mg of genistein for 12 months on 24 prodromal Alzheimer’s disease patients. The amyloid-beta deposition was analyzed using 18F-flutemetamol uptake. We used a battery of validated neurocognitive tests: Mini-Mental State Exam (MMSE), Memory Alteration Test (M@T), Clock Drawing Test, Complutense Verbal Learning Test (TAVEC), Barcelona Test-Revised (TBR), and Rey Complex Figure Test.
Results
We report that genistein treatment results in a significant improvement in two of the tests used (dichotomized direct TAVEC,
p
= 0.031; dichotomized delayed Centil REY copy
p
= 0.002 and a tendency to improve in all the rest of them.
The amyloid-beta deposition analysis showed that genistein-treated patients did not increase their uptake in the anterior cingulate gyrus after treatment (
p
= 0.878), while placebo-treated did increase it (
p
= 0.036). We did not observe significant changes in other brain areas studied.
Conclusions
This study shows that genistein may have a role in therapeutics to delay the onset of Alzheimer’s dementia in patients with prodromal Alzheimer’s disease. These encouraging results indicate that this should be followed up by a new study with more patients to further validate the conclusion that arises from this study.
Trial registration
NCT01982578, registered on November 13, 2013.
Journal Article
rock engraving made by Neanderthals in Gibraltar
Significance The production of purposely made painted or engraved designs on cave walls is recognized as a major cognitive step in human evolution, considered exclusive to modern humans. Here we present the first known example of an abstract pattern engraved by Neanderthals, from Gorham’s Cave in Gibraltar. It consists of a deeply impressed cross-hatching carved into the bedrock of the cave older than 39 cal kyr. The engraving was made before the accumulation of Mousterian layer IV. Most of the lines composing the design were made by repeatedly and carefully passing a pointed lithic tool into the grooves, excluding the possibility of an unintentional or utilitarian origin. This discovery demonstrates the Neanderthals’ capacity for abstract thought and expression.
Journal Article
Thermochemical Production of Hydrogen from Biomass: Pyrolysis and Gasification
Today, hydrogen is one of the best options for generating electrical energy, for both industrial and residential use. The greatest volume of hydrogen produced today derives from processes that utilize petroleum. Although hydrogen has numerous benefits, continuing to produce it by these means is undesirable. This document presents a review of the literature on biohydrogen production based on an analysis of over 15 types of terrestrial and marine biomasses. The fundamental components of different production systems are described, with a focus on the thermochemical processes of pyrolysis and gasification, which have been identified as two of the most effective, practical ways to produce hydrogen from biomass. It also discusses catalysts, solid residues, and residual water that are used in the thermochemical production of biohydrogen. The article ends with an analysis of hydrogen and its benefits as an energy option with great potential in the short term to participate in the transition from fossil fuels.
Journal Article
Occurrence and Ear Damage of Helicoverpa zea on Transgenic Bacillus thuringiensis Maize in the Field in Texas, U.S. and Its Susceptibility to Vip3A Protein
The corn earworm, Helicoverpa zea (Boddie), is a major pest of Bacillus thuringiensis (Bt) maize and cotton in the U.S. Reduced efficacy of Bt plants expressing Cry1 and Cry2 against H. zea has been reported in some areas of the U.S. In this study, we evaluated the occurrence and ear damage of H. zea on transgenic Bt maize expressing Cry proteins or a combination of Vip3A and Cry proteins in the field in Texas in 2018. We found that the occurrence of H. zea larvae and the viable kernel damage area on the ear were not different between non-Bt maize and Bt maize expressing Cry1A.105+Cry2Ab2 and Cry1Ab+Cry1F proteins. A total of 67.5% of the pyramided Bt maize expressing Cry1Ab+Cry1F+Vip3A was damaged by 2nd–4th instar larvae of H. zea. Diet bioassays showed that the resistance ratio against Vip3Aa51 for H. zea obtained from Cry1Ab+Cry1F+Vip3A maize was 20.4 compared to a field population collected from Cry1F+Cry1A.105+Cry2Ab2 maize. Leaf tissue bioassays showed that 7-day survivorship on WideStrike3 (Cry1F+Cry1Ac+Vip3A) cotton leaves was significantly higher for the H. zea population collected from Cry1Ab+Cry1F+Vip3A maize than for a Bt-susceptible laboratory population. The results generated from this study suggest that H. zea has evolved practical resistance to Cry1 and Cry2 proteins. Therefore, it is crucial to ensure the sustainable use of the Vip3A technology in Bt maize and cotton.
Journal Article