The internal manifold geometry strongly influences the flow distribution inside an electrochemical reactor. The mass transport coefficient is a function of the flow pattern and is a key parameter in ...successful electrochemical reactor design and scale-up. In this work, a commercial computational flow dynamics (CFD) package was used to describe the flow pattern in the FM01-LC reactor at controlled volumetric flow rates (corresponding to mean linear flow velocities past the electrode surface between 0.024 and 0.11 m s
−1
). Numerical
Re
numbers were obtained for each local flow velocity at different positions in the reactor channel. From a known mass transport correlation (based on dimensionless groups, i.e.
Sh
,
Re
,
Sc
), numerical
k
m
values were obtained (in the range 200 <
Re
< 1,000) at different positions in the reactor channel. Computed
k
m
numbers are compared against experimental values. This computational approach could be useful in reactor design or selection since it facilitates a fast, preliminary reactor flow and mass transport characterisation without experimental electrochemical measurements.
The main objective of this study was to analyze what writing measures, or combination of measures, would be most appropriate for early detection of students at risk of presenting future difficulties ...in learning to write in Spanish, in terms of tasks, scoring indices (dependent, independent and accurate-precision) and duration. A sample of 231 first graders was scored through IPAE (Indicadores de Progreso de Aprendizaje en Escritura Indicators of Basic Early Writing Skills), a curriculum-based assessment, in fall, winter, and spring. The students were classified as at-risk or not at risk based on a standard instrument (EGWA, Early Grade Writing Assessment) administered to them in spring. The predictive usefulness of the IPAE measures and their diagnostic accuracy were analyzed using the ROC Curve and binary logistic regression. The results suggest that dictated arbitrary spelling, dictated rule-based spelling, and dictated nonsense words could be an effective single measure to be used as a universal screening in the first stage of a two-stage gated screening procedure. A combined measure that includes a combination of these tasks and allographs in 1 min and dictated sentences can be efficient in a second stage.
A new procedure for the fabrication of metal nanowires by template-assisted electrodeposition using porous polycarbonate templates is described. A thin sputtered film of silver (≤15nm) was deposited ...onto one side of the template. The silver seed layer was used to catalyse electroless copper deposition and a copper layer was grown on top (300–500nm) in less than 10min. The copper layer served to seal the pores of the template and to form an electrode of high electrical conductivity. The copper layer was easily removed with a chemical etchant to aid the release of the nanowires from the template mask after growth. To demonstrate the process, copper nanowires were prepared by controlled potential deposition and characterised by SEM and TEM. This new procedure has the ability to be applied to the preparation of a wide range of metallic nanostructures over a wide range of scales. It avoids the need for an extended vacuum deposition step and has the advantage of using low-cost metals in a combined short vacuum/wet chemical process so as to form the critical electrode layer for nanowire growth.
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•A new procedure for the fabrication of metal nanowires is described.•It uses low cost metals in a combined short vacuum/wet chemical process.•An electrode layer of high conductivity is deposited for uniform nanowire growth.
This paper describes the removal of methylene blue (MB) dye using Fe(II)-based gas diffusion electrodes (GDEs). GDEs were developed by rolling carbon black and polytetrafluoroethylene as a conductive ...layer for efficient oxygen reduction reaction, with an Fe(II) ink layer (
5
mg
cm
-
2
loading) to conduct Fenton chemistry. The GDEs demonstrated the ability to remove the colour and mineralize MB dye in an undivided, three-electrode cell. Colour removal achieved 99% in a
150
cm
3
solution containing 100 ppm of MB dye at constant potential of
-
1.0 V vs.
Hg/HgSO
4
in 240 min. The kinetics of the MB decolouration showed pseudo-first-order batch kinetics. The results demonstrated that a GDE containing immobilized Fe(II) ions appears to be a viable option for the environmental remediation of organic dyes in wastewater by an anodic Fenton oxidation.
Porous electrodes have shown high performance in industrial electrochemical processes and redox flow batteries for energy storage. These materials offer great advantages over planar electrodes in ...terms of larger surface area, superior space time yield and enhanced mass transport. In this work, a highly ordered porous stainless steel structure was manufactured by 3D-printing and coated with nickel from an acidic bath by electrodeposition in a divided rectangular channel flow cell. Following the electrodeposition, the volumetric mass transport coefficient of this electrode was determined by the electrochemical reduction of 1.0×10−3moldm−3 of ferricyanide ions by linear sweep voltammetry and chronoamperometry. The convection diffusion characteristics are compared with other geometries to demonstrate the novelty and the advantages of 3D-printed porous electrodes in electrochemical flow reactors. Robust porous electrodes with tailored surface area, composition, volumetric porosity and flow properties are possible.
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•3D-printed porous electrodes for electrochemical flow reactors are introduced.•A nickel-coated 3D-printed stainless steel electrode is characterized.•The mass transport coefficient is determined by the limiting current method.•The advantages of versatile, free-form, tailored porous electrodes are discussed.•Perspectives for applications of 3D-printed electrodes in flow cells are provided.
For over two decades, the high-temperature phase transition (HTPT) at around
T
p
= 180 °C on KH
2
PO
4
(KDP), which involves an ionic conductivity increase, constitutes a controversial subject; ...while most authors ratify a physical transformation (tetragonal → monoclinic phase transition), others defend the chemical transformation. A careful high-temperature phase behavior examination of this acid salt by means of modulated and conventional differential scanning calorimetry, thermogravimetric analysis, simultaneous thermogravimetric and differential scanning calorimetry, impedance spectroscopy, and temperature evolution of X-ray diffraction was performed to provide a possible solution to this long-standing issue. We found that the structural phase transition does not take place. Instead, a chemical transformation occurs at
T
p
. When KDP is heated through this temperature, the sample initially corresponding to a single phase (tetragonal) transforms to a sample composed of two solid phases: tetragonal KDP, located at its bulk, and monoclinic potassium metaphosphate (KPO
3
), located at its surface. Most of the water produced evaporates, but a small portion of liquid water bonds to KPO
3
. Because this is of polymeric nature, it takes the role of a host matrix that contains liquid water regions. Consequently, given that part of the water dissolves a portion of surface salt (providing protons), the surface sample system behaves in a similar manner to a polymer electrolyte membrane where the proton transport mechanism includes the vehicle type, using hydronium (H
3
O
+
) as a charge carrier. On further heating, the bulk tetragonal KDP phase reduced to its total decomposition. The metastability of the high-temperature phase below
T
p
is also explained.
لوصف أنماط البحث للحصول على معلومات حول الوقاية والعلاج من المخدر نفسي المفعول في المكسيك، سواء بالنسبة لعامة السكان أو للموظفين المتخصصين لمعرفة الوقاية والعلاج من هذا النوع من المواد في المكسيك.
تم ...إجراء دراسة استقصائية كمية مستعرضة باستخدام استبانة تم التحقق من صحتها عبر الإنترنت لجمع المعلومات الاجتماعية الديموغرافية والخلفية وأنماط البحث عبر الإنترنت المبلغ عنها ذاتيا حول الوقاية من استخدام المواد ذات المفعول النفسي، وتم حساب اختبار مربع كاي لتحديد الاختلافات بين المجموعات، وتم استخدام شجرة التصنيف لتحليل أنماط البحث. تم إدخال مجموعات معايير البحث مع موضوعات البحث في موقع مؤشرات غوغل.
المشاركون (عددهم 544 بالغا) كانوا في الغالب من النساء (65 ٪) الذين تتراوح أعمارهم بين 18 و 30 عاما، وحاملي درجة البكالوريوس (57 ٪)، والطلاب (32 ٪). الأفراد الذين بحثوا في الإنترنت عن الوقاية من تعاطي المخدرات أو العلاج (59٪) والمشاركون مهنيا في الوقاية من تعاطي المخدرات أو العلاج (12٪).
تم العثور على فروق ذات دلالة إحصائية بين عامة السكان والموظفين المتخصصين في خدمات ادمان المخدرات، وحددنا ستة أنماط بحث، حيث تم تصوير عملية صنع القرار للأشخاص الذين يسعون للحصول على معلومات حول الوقاية من المخدرات والعلاج على الإنترنت بشكل بياني باستخدام شجرة التصنيف، على الرغم من أن هذه الطريقة لم تسمح بالتمييز الواضح بين أنماط المجموعتين. تم التحقق من أنماط البحث بنجاح باستخدام موقع مؤشرات غوغل.
This study was aimed at describing the patterns of searches for information on the prevention and treatment of psychoactive drug use in Mexico, among both the general population and the personnel dedicated to the prevention and treatment of this type of substance use in Mexico.
An exploratory cross-sectional quantitative study was performed with a validated online questionnaire to collect sociodemographic information, background information and self-reported internet search patterns on psychoactive substance use prevention. A chi-square test was used to identify differences between groups, and a classification tree was used to analyze the search patterns. The combinations of the search criteria with the search topics were entered into Google Trends to validate the information.
The participants (n = 544 adults) were mostly women (65%), 18–30 years of age and bachelor's degree holders (57%). A total of 32% were students, 59% searched the Internet for drug use prevention or treatment, and 12% professionally engaged in drug use prevention or treatment.
Statistically significant differences were found between the general population and professionals dedicated to drug dependency services. We identified six search patterns used in the decision-making process by people seeking information on drug prevention and treatment on the Internet. These patterns were graphically visualized with a classification tree, although, this method did not allow clear differentiation of patterns between groups. The search patterns were successfully validated with Google trends.
Abstract
The behavior of composite beads of Zea mays rachis and sodium alginate (AL) for Pb (II) adsorption was studied. The Zea mays rachis–sodium alginate was prepared and characterized. The IR ...spectra showed interactions of the functional groups and the metal ions after adsorption. The kinetic data were fitted to the pseudo-first- and pseudo-second-order models, the maximum adsorption capacity was 60 mg/g for Pb (II), and the isotherm data were best adjusted to the Freundlich model, indicating that the adsorbent is heterogeneous. The thermodynamic study shows that the process is physisorption. The service time of columns increases as the height of columns increases, and this behavior was attributed to the active sites available in the columns. The initial concentration of Pb (II) had a significant effect on the breakthrough curves. As the concentration increases, the saturation time decreases. The material was regenerated four times (adsorption–desorption cycles), without a significant change in the removal efficiencies.
This study aimed to explore instructional practices used to teach words with irregular spelling patterns by Spanish-speaking teachers in 2nd and 3rd grade of elementary school. A sample of 320 ...teachers from Guatemala, Ecuador, and Spain answered an online survey, which included the Spelling Instructional Practices Scale. Item Response Theory and Confirmatory Factor Analysis were used to analyze the construct validity and reliability of the Spelling Instructional Practices Scale. Results pointed out adequate fit indexes of the proposed models. Spelling instructional practices used by teachers were finally grouped into three factors. Results indicated that Spanish-speaking teachers teach irregular spelling words using a combination of instructional practices. Differences in the informed use of spelling instructional practices according to the teachers' home countries were explored. Significant differences were found between Spanish and Latin-American teachers in the reported use of those instructional practices based on memorization and some materials to teach spelling. However, most teachers reported following a similar pattern when teaching irregular spelling to their students. Limitations and directions for future research are described.
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