This study was carried out to compare the results obtained using potential step voltammetry and linear sweep voltammetry with a rotating gold disc electrode (RDE), when models based on equivalent ...circuits (EC) were used. The results lead to an equivalent circuit model that allows us to interpret the electrochemical behavior of aqueous solutions containing Fe(CN)6−4 and Fe(CN)6−3. With this model, we determined the values of the electrical resistance of the medium (Rs) as well as its polarization resistance (Rp), and established correlations between these values and the kinetic parameters of the system. The proposal highlights the need to introduce a new component for modeling using EC, which we have called the electrochemical diode.
Potential step voltammetry is used to characterize the resistive and capacitive properties of electrochemical systems. Within those systems, electrochemical processes are modeled by means of ...equivalent circuits (ECs). In this study, we established and experimentally validated algebraic expressions describing the electrical response of those ECs. We then analyzed the features that allow significant differentiation between the ECs. Finally, we have proposed a method to graphically visualize and analyze the electrical response of the circuit to a potential step sequence. The application of this method to real electrochemical systems will allow us to not only identify the electrochemical processes taking place in an experiment but to also assess parameters such as the double layer capacitance, the solution resistance, and the polarization resistance of the redox process.
A two‐channel switchable nanoscopic hybrid system, able to modulate mass transport by photoresponsive appended organic groups and the presence of G1.5 PAMAM dendrimers as molecular caps, is reported. ...This new functional gatelike ensemble is chemically (by pH changes) and photochemically (using visible light) controlled in pure aqueous solution, as demonstrated by an experiment involving the controlled release of a dye (see figure).
A recently published article of this journal stated that informatics solutions can guide better public health decision-making during the COVID 19 (Coronavirus Disease 2019) pandemic. Honduras is a ...country facing the COVID-19 pandemic with a weak health surveillance system while also fighting a dengue epidemic and the aftermath of two hurricanes that struck its territory in November 2020. In response, we as academics started a COVID-19 and Dengue Observatory combining several technological platforms and developing multidisciplinary research to help the country navigate the crisis. Mapping the pandemic and the natural disasters showed us that technology can be applied toward epidemiology to benefit communities in a time of need by quickly building a basic digital health surveillance system for Honduras.
Artificial intelligence (AI) is an emerging technology that is revolutionizing the discovery of new materials. One key application of AI is virtual screening of chemical libraries, which enables the ...accelerated discovery of materials with desired properties. In this study, we developed computational models to predict the dispersancy efficiency of oil and lubricant additives, a critical property in their design that can be estimated through a quantity named blotter spot. We propose a comprehensive approach that combines machine learning techniques with visual analytics strategies in an interactive tool that supports domain experts' decision-making. We evaluated the proposed models quantitatively and illustrated their benefits through a case study. Specifically, we analyzed a series of virtual polyisobutylene succinimide (PIBSI) molecules derived from a known reference substrate. Our best-performing probabilistic model was Bayesian Additive Regression Trees (BART), which achieved a mean absolute error of 5.50±0.34 and a root mean square error of 7.56±0.47, as estimated through 5-fold cross-validation. To facilitate future research, we have made the dataset, including the potential dispersants used for modeling, publicly available. Our approach can help accelerate the discovery of new oil and lubricant additives, and our interactive tool can aid domain experts in making informed decisions based on blotter spot and other key properties.
In El Salvador, Guatemala, Honduras, Nicaragua, and Panama, we recruited 2466 female sex workers (FSWs) by probabilistic or comprehensive sampling and 1418 men who have sex with men (MSM) by ...convenience sampling to measure sociobehavioral risk and sexually transmitted infections. For MSM, HIV seroprevalence ranged from 7.6% in Nicaragua to 15.3% in El Salvador, and estimated HIV seroincidence per 100 person-years ranged from 2.7 in Panama to 14.4 in Nicaragua; 61% reported using condoms consistently with casual male partners, 29% reported exposure to behavioral interventions, and 22% reported recent sex with male and female partners. For FSWs, HIV seroprevalence ranged from 0.2% in Nicaragua and Panama to 9.6% in Honduras, where estimated HIV seroincidence was also highest (3.2 per 100 person-years); 77% and 72% of FSWs reported using condoms consistently with new and regular clients. Herpes simplex virus (HSV)-2 seroprevalence averaged 85.3% in FSWs and 48.2% in MSM, and syphilis seropositivity averaged 9.6% in FSWs and 8.3% in MSM. Chlamydia trachomatis and Neisseria gonorrhoeae prevalences in FSWs averaged 20.1% and 8.1%, and Trichomonas vaginalis and bacterial vaginosis prevalences averaged 11.0% and 54.8%. An ongoing HIV epidemic involves Central American MSM with potential bridging to women. In FSWs, HSV-2 infection was associated with HIV infection (odds ratio = 11.0, 95% confidence interval: 2.9 to 7.9). For these vulnerable populations, prevention must incorporate acceptable and effective sexual health services, including improved condom access and promotion.
Germline deletions at the 3′‐end of EPCAM have been involved in the etiology of Lynch syndrome (LS). The aim of this study was to characterize at the molecular level Spanish families harboring EPCAM ...deletions. Non‐commercial multiplex ligation‐dependent probe amplification (MLPA) probes and long‐range polymerase chain reaction (PCR) amplification were used to characterize each deletion. Haplotyping was performed by analyzing eight microsatellite markers and five MSH2single nucleotide polymorphisms (SNPs). Methylation of MSH2 was analyzed by methylation specific‐MLPA. Tumors diagnosed in seven Spanish families harboring EPCAM deletions were almost exclusively colorectal. Mosaicism in MSH2 methylation was observed in EPCAM deletion carrier samples, being average methylation levels higher in normal colon and colorectal tumors (27.6% and 31.1%), than in lymphocytes and oral mucosa (1.1% and 0.7%). Three families shared the deletion c.858 + 2568_*4596del, with a common haplotype comprising 9.9 Mb. In two families the novel EPCAM deletion c.858 + 2488_*7469del was identified. This study provides knowledge on the clinical and molecular characteristics of mosaic MSH2 epimutations. The identification of an EPCAM founder mutation has useful implications for the molecular diagnosis of LS in Spain.
Differences between the cell cross section and the electrodes’ area produce a heterogeneous distribution of the electric field that causes a non-linear relationship between electric resistance and ...distance for low values of electrode separation. Therefore, in actual structures, it is usually not correct to measure the resistivity of concrete by using the direct method because the electrodes’ area is smaller than the cross section of the concrete piece. In this experimental research the influence of the area and the distance between electrodes on the resistivity measurement is analyzed and a semi-empirical model is explained, in which the values of the electrical resistance with respect to distance are adjusted. Based on this model, two new non-destructive methods are proposed in order to measure the electrical resistivity of concrete when using electrodes with a smaller area than the cross section of the piece: one includes varying the distance between electrodes and the other uses electrodes with a different area, but maintains a fixed distance between them.
Tuning of the sensing abilities of certain chromogenic molecules is achieved by anchoring them to modified MCM‐41‐type solids. This approach allows chromogenic detection of primary aliphatic amines ...of a certain length in water. The Figure shows color changes of the functionalized solid (magenta–yellow) in the presence of n‐heptylamine, n‐octylamine, and n‐nonylamine. Longer or shorter aliphatic chains induced no significant color variation.
The temporal occurrence of slope movements, their contribution to relief evolution and human influence on those processes in two study areas of northern Spain are presented. The work is based on ...temporal analyses covering 100 ka in one study area and 43 years in the other. Temporal analysis has been the basis for quantitatively assessing the magnitude of human influence and developing landslide susceptibility and hazard models with known, independently-tested prediction capability.
The results obtained in one study area show a relationship between landsliding periods and increasing precipitation during upper Pleistocene and Holocene. Significant increases of landslide frequency and mobilisation rate were also found around 5500 and 200 years ago. Those moments coincide with two periods of intensified human presence and activities: Neolithic and industrial revolutions. The increase observed represents about one order of magnitude from pre-Neolithic to present.
A similar increase has been found between 1954 and 1997 in the other study area. The latter increase shows no relationship with changes in climate parameters or seismic activity. A fairly good correlation has been found between landslide frequency and socioeconomic indicators of human activity.
Sedimentation rates in two neighbouring estuaries were determined and significant increases, particularly in the second part of last century, were also found. Evidence obtained suggest that the increases observed in the frequency of slope instability events (and therefore hazard), denudation and sedimentation rates are due to a greater extent to indirect geomorphologic changes caused by human action rather than climate change.
Detailed analysis of landslide frequency during that 43-year period has also been used to produce and validate landslide susceptibility models and obtain landslide hazard maps with known prediction accuracy. Validation tests were carried out comparing susceptibility maps based on landslides that have occurred in the past with the ones occurring in several, later periods. Prediction capability of models could thus be determined. Validation of susceptibility maps using data derived from the temporal analysis of landslides was used to obtain hazard maps expressed as probability of new ruptures in a given time period, on the basis of past trends in terrain behaviour. Possible impacts of a growing influence of human activities on the terrain have been incorporated into the assessment of future hazards by considering different scenarios.
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