Microbial fuel cells (MFCs) have been used for several years as biosensors for measuring environmental parameters such as biochemical oxygen demand and water toxicity. The present study is focused on ...the detection of toxic matter using a novel silicon-based MFC. Like other existing toxicity sensors based on MFCs, this device is capable of detecting the variation on the current produced by the cell when toxic compounds are present in the medium. The MFC approach presented in this work aims to obtain a simple, compact and planar device for its further application as a biosensor in the design and fabrication of equipment for toxicity monitoring. It consists on a proton exchange membrane placed between two microfabricated silicon plates that act as current collectors. An array of square 80
μm
×
80
μm vertical channels, 300
μm deep, have been defined trough the plates over an area of 6
mm
×
6
mm. The final testing assembly incorporates two perspex pieces positioned onto the plates as reservoirs with a working volume of 144
μL per compartment.
The operation of the microdevice as a direct electron transfer MFC has been validated by comparing its performance against a larger scale MFC, run under the same conditions. The device has been tested as a toxicity sensor by setting it at a fixed current while monitoring changes in the output power. A drop in the power production is observed when a toxic compound is added to the anode compartment. The compact design of the device makes it suitable for its incorporation into measurement equipment either as an individual device or as an array of sensors for high throughput processing.
Models of disease spread in networks typically focus on exploring various measures to reduce the spread of disease across individuals within a network. However, the topology of the underlying network ...plays an important role in determining the best time to implement mitigation measures to achieve better results. In this article we show the behavior of the well-known SIR (susceptible-infected-removed) and SIS (susceptible-infected-susceptible) models over networks with both scale-free and dense structure with power-law topology
P
(
k
)
∼
k
-
ζ
with
1
<
ζ
<
∞
. Focusing on the maximum number of infected individuals (
I
max
) and the number of days before it emerges, i.e., the speed at which infected individuals increase. We show that as the network structure becomes dense, i.e., the number of connections among the individuals within the network increases and
ζ
approaches one,
I
max
tends to be higher and it emerges rapidly. In those cases, implementing quick mitigation measures is very important. In this sense, we found that mitigation measures like social distancing can help to reduce the amount of infected individuals, specially when
ζ
≥
3
. Moreover, for
ζ
bellow three, social distancing loses its effectiveness as mitigation measure.
Graphic abstract
In left, the scheme of the Susceptible-Infected-Removed and Susceptible-Infected-Susceptible models are illustrated. In right, the solution of the classical SIR and SIS models is showed, denotting graphically the maximum number of infected individuals (
I
max
) and the number of days before it is reached
Members of the Miridae (Lygus lineolaris Palisot de Beauvois and Pseudatomoscelis seriatus Reuter) and Pentatomidae (Acrosternum hilare Say, Euschistus servus (Say), Euschistus tristigmus (Say), ...Euschistus quadrator Rolston, Oebalus pugnax (F.), Piezodorus guildinii (Westwood), and Thyanta custator accerra McAtee) comprise a piercing—sucking insect complex that continues to plague multiple crops, including cotton. All these species have been associated with pathogen transmission. Breaching of boll carpel walls facilitates introduction of pathogens, and it is unknown whether stylets of these pests can fully penetrate carpel walls. Thus, stylet penetration estimates are needed and have been the focus of the present work. Stylet penetration estimates for L. lineolaris were significantly deeper than P. seriatus. Among the Pentatomidae, highest mean penetrationwas estimated for E. servus followed by A. hilare, yet A. hilare possessed a longer rostrum. Similarly, O. pugnax showed deeper penetration estimates than P. guildinii yet P. guildinii possessed a longer rostrum. Thus, rostrum length should not be equated to penetration potential. Pseudatomoscelis seriatus and L. lineolaris both infest early-season cotton, and the ranges of observed penetration indicate these insects, as well as the Pentatomidae, can breach the walls of critical pinhead squares and smaller bolls. The insects addressed herein affect a myriad of crops globally, and penetration estimates allow identification of growth stages susceptible to feeding and disease transmission.
•New knowledge about the substitution of OPC by fly ash(FA) and limestone filler(LF).•Appropriate combinations of FA + LF counteracts the setting delays in FA concretes.•Appropriate combinations of ...FA+LF improve resistivity and volume stability.
Self-compacting concrete (SCC) has become a preferred option for many projects that should satisfy strict fresh stage properties that are of major concern in quality assurance. To ensure stable and robust fresh stage properties, typically a significant amount of fine materials is incorporated, but this often increases shrinkage. For this purpose, fly ash (FA) has been used, but because it can induce delays in times of setting, it is not extensively used. Under this scenario, micro limestone powders (L) have been effectively used to counteract the delays in the times of setting of concrete with high volumes of fly ash.
For a fixed water/powder ratio equivalent to a water-to-cement ratio of 0.40 in a 100% cement mixture, a total of thirteen mortars were produced to evaluate the synergetic effects of twelve portland cement substitutions by FA + L on times of setting, compressive strength, shrinkage and electrical resistivity. Results indicate appropriate FA + L combinations to counteract delays in times of setting and to significantly improve electrical resistivity and volume stability.
In the paper Geometric Algebra
G
6
,
3
(Zamora-Esquivel in Adv Appl Clifford Algebras 24:493–514, 2014) a generalization of CGA was introduced. Now
G
6
,
3
is called Quadric Geometric Algebra (QGA), ...and in which the use of axis aligned quadrics and their intersections were presented. In this paper the rotation of
G
6
,
3
geometric entities is described, introducing new concepts like vanishing vectors, also the polar representation of quadric geometric entities is being used.
Nanocrystalline Al-xV (x = 0, 0.5, 2, 5, 10 and 20 at. %) alloys were produced by high-energy ball milling (HEBM) followed by consolidation at room temperature under uniaxial pressure of 3 GPa. Grain ...size, dispersion of the alloying element (V) and formation of solid solution were studied using X-ray diffraction (XRD) analysis and scanning electron microscope (SEM) coupled with energy dispersive X-ray spectroscopy (EDXS). High-energy ball milling imparted nanocrystalline structure and high solid solubility of V in Al - several orders of magnitude higher than the thermodynamically predicted value. Hardness of Al-xV alloys, which increased with increasing the V content, was higher than the commercial Al alloys. High hardness of the Al-xV alloys was attributed to the solid solution strengthening caused by high solid solubility of V and grain refinement <100 nm.
•Synthesis of nanocrystalline Al-V alloys by high-energy ball milling.•Influence of V content on the grain size and hardness of Al-V alloys.•Influence of V content on the solid solubility of V in Al.•Superior hardness of high-energy ball milled Al-V alloys.
This study aimed to compare the survival experience of adult inpatients with laboratory-confirmed COVID-19 during the first three waves (wild type, Delta, and Omicron) of the pandemic in Mexico.
A ...retrospective and nationwide study was conducted.
Data from 229,311 participants were analyzed using the Kaplan–Meier method, and estimates per each pandemic wave were obtained. A multivariate Cox proportional hazard regression model was fitted, and hazard ratios (HRs) and 95% confidence intervals (CIs) were computed.
The overall mortality rate was 49.1 per 1000 person-days. Heterogeneous survival rates were observed during the analyzed emergences (log-rank test, P < 0.001), and the lowest survival functions were computed during the Omicron variant dominance. In multiple analyses and after adjusting by host characteristics and COVID-19 vaccination status, cases occurring during the Delta (vs wild type: HR = 1.03, 95% CI 1.01–1.05) and Omicron emergence were at increased risk for a fatal in-hospital outcome (HR = 1.17, 95% CI 1.13–1.22).
Our results suggest variant-related differences in the survival rates of hospitalized patients with laboratory-positive COVID-19. When compared with the wild-type virus, lower rates were observed during the Delta and Omicron emergence.
Dielectric Properties and Relaxation of Bi2Ti2O7 Turner, Christopher G.; Esquivel-Elizondo, J. Roberto; Nino, Juan C.
Journal of the American Ceramic Society,
June 2014, Letnik:
97, Številka:
6
Journal Article
Recenzirano
The dielectric properties of Bi2Ti2O7 were explored as a function of temperature and frequency. A comparison between the dielectric response of the well‐known Bi1.5Zn0.92Nb1.5O6.92 (BZN) pyrochlore ...and the recently available Bi2Ti2O7 sintered ceramic revealed considerable differences, which indicate that chemical disorder, and not atomic displacement on its own, is chiefly responsible for the dielectric relaxation in bismuth pyrochlores. A low‐frequency (<10 kHz) and relatively high‐temperature (~125 K) dielectric relaxation was observed in Bi2Ti2O7. An Arrhenius function was used to model the relaxation behavior and yielded an activation energy of 0.162 eV and an attempt jump frequency of ~1 MHz. This response is consistent with space charge polarization and not the result of dipolar or ionic disorder.
•Slurry-phase hydrocracking kinetics of a heavy oil in a batch reactor was determined.•High residue conversion was attained, even at low reaction time.•High selectivity toward Naphtha was ...obtained.•Slurry catalyst resists coke formation.
The kinetics of slurry phase heavy oil hydrocracking with nickel nanoparticles dispersed in PEG300 as the slurry phase catalyst was investigated. Colloidal metal nanoparticles were synthesized using a chemical reduction method. Catalytic evaluations were performed in a batch reactor with 7.0 MPa H2 and varying temperatures (310–370 °C) and reaction times (4–72 h). A five-lump kinetic model was used to obtain kinetic parameters using the R software with the Levenberg-Marquardt nonlinear least-squares algorithm. The order of the residue hydrocracking reaction rate equation was 2.5. The activation energies were determined, and the calculated product compositions were in agreement with the experimental values (<5%). The residue exhibited high selectivity towards naphtha. High residue conversion was accomplished, even at low reaction times.
Invasive alien species and climate change are two of the main current threats to conservation of biodiversity worldwide. Their effects have been extensively studied individually, but we know less ...about their combined effect. This study analyzes the population changes in the plant community of the high mountain legume shrub habitat of Tenerife over 10 years (between 2009 and 2018), using alien herbivore exclusion plots distributed over two sectors with different patterns of climate. Our outcomes show contrasting effects of herbivory and climate in plant communities, with significant shifts in community composition. The dominant species, Teide broom (Spartocytisus supranubius), is negatively affected by both climate and alien herbivores, leading to a regression of its abundance. In contrast, a formerly rare species, Pterocephalus lasiospermus, is benefiting from warmer temperatures and from herbivore presence owing to its low palatability. Simultaneously, some thermal native species from the neighboring pine forest are invading the alpine ecosystem. We conclude that the alpine habitat is changing very quickly and differently according to whether it is in warmer or colder sectors of the summit of Tenerife. This work reveals the need to simultaneously consider multiple drivers to understand the response of mountain ecosystems to global change.
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