Structure of Mesoporous Aerogels

MRS Bulletin ◽  
1994 ◽  
Vol 19 (4) ◽  
pp. 49-53 ◽  
Author(s):  
Dale W. Schaefer
Keyword(s):  
Mesoporous Materials ◽  
Pore Formation ◽  
High Performance ◽  
Classification Scheme ◽  
Structural Data ◽  
Ceramic Materials ◽  
Fine Scale ◽  
Manufacturing Methods ◽  
The Relationship ◽  
New Strategies

Several emerging technologies depend on the development of porous materials with pore dimensions in the nanometer range (1 nm = 10 Å). Based on the canonical classification scheme, such materials are defined as “mesoporous materials.” Specialty uses, such as separation applications, require porosities engineered to meet stringent pore-size requirements, particularly for separating high-boiling-temperature or-ganics. In addition, commodity products, such as high-performance thermal insulation, await credible manufacturing methods to produce fine-scale pores. Finally, information discovered during the development of mesoporous materials could be helpful in finding new strategies to generate void-free ceramic materials by reverse engineering.Although several methods exist to generate nanometer porosity, our ability to tailor porosity for specific applications is still primitive. Because we lack adequate structural data and models for pore formation, the relationship between synthetic protocol and pore structure remains enigmatic.

scholarly journals Determination of ballistic resistance of cementitious composites

2021 ◽  
Vol 1205 (1) ◽  
pp. 012013
Author(s):  
J Vojtisek ◽  
E Bystrianska ◽  
O Koutny ◽  
J Kratochvil ◽  
M Drdlova
Keyword(s):  
High Performance ◽  
Ceramic Materials ◽  
Cementitious Composites ◽  
Cement Composites ◽  
Penetration Test ◽  
Depth Of Penetration ◽  
Ballistic Resistance ◽  
Differential Efficiency ◽  
The Relationship

Abstract The paper describes the possibility of using the DOP test, standardly used to evaluate the ballistic resistance of ceramics, to determine the ballistic resistance of cement composites. DOP - Depth of penetration test - is based on measurement of residual penetration of projectile in witness system after the sample perforation; this parameter is used to determine differential efficiency factor (DEF), characterizing the ballistic resistance of the particular material. To verify the method for non-ceramic materials, four variants of cementitious composites with compressive strengths in the range of 30–150 MPa have been tested. The obtained results confirm the method’s suitability for determining the ballistic resistance of cement composites in terms of ease of implementation, sensitivity, and accuracy of the obtained results for both composites of common strengths and high-performance variants. The paper also discusses some aspects of the relationship between the mechanical parameters of cement composites under static loading and their ballistic resistance.

Spaces of Consumption in American Literary Realism

2019 ◽  
pp. 391-410
Author(s):  
Gary Totten
Keyword(s):  
Consumer Culture ◽  
Social Space ◽  
Natural World ◽  
Power Dynamics ◽  
Literary Realism ◽  
Natural Environments ◽  
Production And Consumption ◽  
The Social ◽  
The Relationship ◽  
New Strategies

This chapter discusses how consumer culture affects the depiction and meaning of the natural world in the work of American realist writers. These writers illuminate the relationship between natural environments and the social expectations of consumer culture and reveal how such expectations transform natural space into what Henri Lefebvre terms “social space” implicated in the processes and power dynamics of production and consumption. The representation of nature as social space in realist works demonstrates the range of consequences such space holds for characters. Such space can both empower and oppress individuals, and rejecting or embracing it can deepen moral resolve, prompt a crisis of self, or result in one’s death. Characters’ attempts to escape social space and consumer culture also provide readers with new strategies for coping with their effects.

scholarly journals The Relationship between Learning Styles and Academic Performance: Consistency among Multiple Assessment Methods in Psychology and Education Students

2021 ◽  
Vol 13 (6) ◽  
pp. 3341
Author(s):  
Jesús Maya ◽  
Juan F. Luesia ◽  
Javier Pérez-Padilla
Keyword(s):  
Early Childhood ◽  
Academic Performance ◽  
Learning Styles ◽  
Primary Education ◽  
High Performance ◽  
Multiple Choice ◽  
Assessment Methods ◽  
Theory And Practice ◽  
Education Students ◽  
The Relationship

Universities strive to ensure quality education focused on the diversity of the student body. According to experiential learning theory, students display different learning preferences. This study has a three-fold objective: to compare learning styles based on personal and educational variables, to analyze the association between learning styles, the level of academic performance, and consistency of performance in four assessment methods, and to examine the influence of learning dimensions in students with medium-high performance in the assessment methods. An interdisciplinary approach was designed involving 289 psychology, early childhood education and primary education students at two universities in Spain. The Learning Style Inventory was used to assess learning styles and dimensions. The assessment methods used in the developmental psychology course included the following question formats: multiple-choice, short answer, creation-elaboration and an elaboration question on the relationship between theory and practice. Univariate analysis, multivariate analysis, and binomial logistic models were computed. The results reveal Psychology students to be more assimilative (theoretical and abstract), while early childhood and primary education students were evenly distributed among styles and were more divergent and convergent (practical) in absolute terms. In addition, high scores in perception (abstract conceptualization) were associated with a high level of performance on the multiple-choice tests and the elaboration question on the relationship between theory and practice. Abstract conceptualization was also associated with medium-high performance in all assessment methods and this variable predicted consistent high performance, independent of the assessment method. This study highlights the importance of promoting abstract conceptualization. Recommendations for enhancing this learning dimension are presented.

scholarly journals Relationship between Plasma Trimethylamine N-Oxide Levels and Renal Dysfunction in Patients with Hypertension

2021 ◽  
pp. 1-12
Author(s):  
Jia Zhou ◽  
Dingkun Wang ◽  
Bingong Li ◽  
Xuelian Li ◽  
Xingjun Lai ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Kidney Disease ◽  
Renal Dysfunction ◽  
High Performance ◽  
Characteristic Curve ◽  
Area Under The Curve ◽  
Hypertensive Patients ◽  
Ckd Stage ◽  
Liquid Chromatography Tandem Mass ◽  
The Relationship

<b><i>Introduction:</i></b> Trimethylamine N-oxide (TMAO) is a metabolite produced by gut bacteria. Although increased TMAO levels have been linked to hypertension (HTN) and chronic kidney disease (CKD) with poor prognosis, no clinical studies have directly addressed the relationship between them. In this study, we investigated the relationship between TMAO and renal dysfunction in hypertensive patients. <b><i>Methods:</i></b> We included healthy controls (<i>n</i> = 50), hypertensive patients (<i>n</i> = 46), and hypertensive patients with renal dysfunction (<i>n</i> = 143). Their blood pressure values were taken as the highest measured blood pressure. Renal function was evaluated using the estimated glomerular filtration rate. Plasma TMAO levels were measured using high-performance liquid chromatography tandem mass spectrometry. <b><i>Results:</i></b> We found significant differences in plasma TMAO levels among the 3 groups (<i>p</i> &#x3c; 0.01). The plasma TMAO of patients with HTN was significantly higher than that of healthy people, and the plasma TMAO of patients with HTN complicated by renal dysfunction was significantly higher than either of the other groups. Patients in the highest TMAO quartile were at a higher risk of developing CKD stage 5 than those in the lowest quartile. In the receiver operating characteristic curve, the area under the curve of TMAO combined with β 2-macroglobulin for predicting renal dysfunction in patients with HTN was 0.85 (95% confidence interval 0.80–0.90). <b><i>Conclusion:</i></b> An elevated TMAO level reflects higher levels of HTN and more severe renal dysfunction. TMAO, combined with β 2-macroglobulin levels, may assist in diagnosing CKD in hypertensive patients. Plasma TMAO has predictive value for early kidney disease in hypertensive patients.

scholarly journals Changes in Optical Properties upon Dye–Clay Interaction: Experimental Evaluation and Applications

Nanomaterials ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 197
Author(s):  
Giorgia Giovannini ◽  
René M. Rossi ◽  
Luciano F. Boesel
Keyword(s):  
Optical Properties ◽  
Hybrid Materials ◽  
High Performance ◽  
Fluorescent Properties ◽  
Chemical Mechanisms ◽  
Strong Electrostatic Interaction ◽  
Potential Applications ◽  
Photochemical Properties ◽  
Physical And Chemical ◽  
The Relationship

The development of hybrid materials with unique optical properties has been a challenge for the creation of high-performance composites. The improved photophysical and photochemical properties observed when fluorophores interact with clay minerals, as well as the accessibility and easy handling of such natural materials, make these nanocomposites attractive for designing novel optical hybrid materials. Here, we present a method of promoting this interaction by conjugating dyes with chitosan. The fluorescent properties of conjugated dye–montmorillonite (MMT) hybrids were similar to those of free dye–MMT hybrids. Moreover, we analyzed the relationship between the changes in optical properties of the dye interacting with clay and its structure and defined the physical and chemical mechanisms that take place upon dye–MMT interactions leading to the optical changes. Conjugation to chitosan additionally ensures stable adsorption on clay nanoplatelets due to the strong electrostatic interaction between chitosan and clay. This work thus provides a method to facilitate the design of solid-state hybrid nanomaterials relevant for potential applications in bioimaging, sensing and optical purposes.

Polyimide-Silica Hybrid Aerogels with High Mechanical Strength for Thermal Insulation Applications

2011 ◽  
Vol 1306 ◽  
Author(s):  
Wenting Dong ◽  
Wendell Rhine ◽  
Shannon White
Keyword(s):  
Thermal Conductivity ◽  
High Performance ◽  
Ambient Conditions ◽  
Separation Membranes ◽  
Low Dielectric ◽  
Aging Conditions ◽  
Hybrid Aerogels ◽  
Mechanical Strengths ◽  
The Relationship ◽  
Silica Hybrid

ABSTRACTHigh performance polyimides have been widely investigated as materials with excellent thermal, mechanical, and electronic properties due to their highly rigid structures. Aspen has developed an approach to prepare polyimide aerogels which have applications as low dielectric constant materials, separation membranes, catalyst supports and insulation materials. In this paper, we will discuss the preparation of polyimide-silica hybrid aerogel materials with good mechanical strengths and low thermal conductivities. The polyimide-silica hybrid aerogels were made by a two-step process and the materials were characterized to determine thermal conductivity and compressive strength. Results show that compressive moduli of the polyimide-silica hybrid aerogels increase dramatically with density (power law relationship). Thermal conductivity of the aerogels is dependent on the aging conditions and density, with the lowest value achieved so far being ~12 mW/m-K at ambient conditions. The relationship between aerogel density and surface area, thermal stability, porosity and morphology of the nanostructure of the polyimide-silica hybrid aerogels are also described in this paper.

“It's the work climate that keeps me here”: the interplay between the HRM process and emergent factors in the construction of employee experiences

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Maarit Laiho ◽  
Essi Saru ◽  
Hannele Seeck
Keyword(s):  
High Performance ◽  
Design Methodology ◽  
Qualitative Interview ◽  
Employee Perceptions ◽  
Content Type ◽  
Systematic Data ◽  
High Performance Work System ◽  
Employee Experience ◽  
The Relationship ◽  
Shed Light

PurposeThe purpose of this paper is to explore the interplay between human resource management (HRM) and emergent factors in constructing a strong HRM climate. Specifically, the paper aims to shed light on how employee perceptions of the HRM process and emergent factors together construct a strong HRM climate, i.e. employees' shared perceptions of HRM.Design/methodology/approachThe paper uses qualitative interview data (managers and employees) from two organisations operating in Finland. The data are analysed based on a systematic data analysis and gives an illustration of the interplay between high-performance work system and the emergent factors.FindingsThe findings illustrate the three types of interplay between HPWS and emergent factors – supplementation, substitution and suffocation – that construct employee experience.Originality/valueThe paper extends earlier discussions on the relationship between HRM and employee experience by empirically examining how the HRM process – together with emergent factors – constructs a strong HRM climate. The present study contributes to further theorising and increasing our understanding of the creation of employee experience.

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