scholarly journals Characterization and Long-Term Stability of Historical PMMA: Impact of Additives and Acrylic Sheet Industrial Production Processes

Polymers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2198
Author(s):  
Sara Babo ◽  
Joana Lia Ferreira ◽  
Ana Maria Ramos ◽  
Anna Micheluz ◽  
Marisa Pamplona ◽  
...  
Keyword(s):  
Size Exclusion ◽  
Organic Additives ◽  
Total Period ◽  
Long Term Stability ◽  
Production Processes ◽  
Exclusion Chromatography ◽  
Acrylic Sheet ◽  
The 1960S ◽  
Long Term Behavior

This work aims at understanding the influence of the production processes and materials in the properties and long term behavior of acrylic sheet, i.e., poly(methyl methacrylate) (PMMA), a material generally considered very stable in museum collections. A comparative study was conducted in samples from cast acrylic sheets produced in the early 2000s, from which manufacturing details were known, and samples provided by the artist Lourdes Castro from acrylic sheets she had bought in the 1960s. Transparent and red opaque cast acrylic samples, containing cadmium red pigment, were used. All samples were artificially aged in a solarbox with irradiation λ > 300 nm for a total period of 8000 h, and alterations were followed by a multi-analytical approach which included Raman, infrared (FTIR-ATR) and UV-Vis spectroscopies; gravimetry; size exclusion chromatography (SEC); thermogravimetry (TGA); micro-indentation; colorimetry; and optical microscopy. Not all cast PMMA sheets presented similar stabilities. We have concluded that the production processes (which may include the polymerization conditions, the organic additives and the origin of the monomer) play a more important role in the properties and long-term behavior of these acrylic sheets than the presence of cadmium red and/or the age of the material.

scholarly journals Correction: Babo et al. Characterization and Long-Term Stability of Historical PMMA: Impact of Additives and Acrylic Sheet Industrial Production Processes. Polymers 2020, 12, 2198

Polymers ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 4105
Author(s):  
Sara Babo ◽  
Joana Lia Ferreira ◽  
Ana Maria Ramos ◽  
Anna Micheluz ◽  
Marisa Pamplona ◽  
...  
Keyword(s):  
Industrial Production ◽  
Term Stability ◽  
Long Term Stability ◽  
Production Processes ◽  
Acrylic Sheet ◽  
Published Paper

The authors wish to make a change to the published paper [...]

The End of Family Business? The Mittelstand and German Capitalism in Transition, 1949–2000

2006 ◽  
Vol 80 (2) ◽  
pp. 263-295 ◽  
Author(s):  
Hartmut Berghoff
Keyword(s):  
Family Business ◽  
Family Firms ◽  
German Economy ◽  
Term Stability ◽  
Long Term Stability ◽  
Sociocultural Environment ◽  
The Past ◽  
The 1960S ◽  
Modern Form

TheMittelstandsector of the German economy, which is made up of small and medium-sized family firms, is generally not mentioned in debates about German capitalism. This article makes the case that the focus of research on the German economy should shift from large corporate structures to these smaller firms. The classic Mittelstand model, which dominated the economy until about 1970, was characterized by identity of ownership and management, strong emotional investment by owners and staff, and an emphasis on continuity, paternalism, and independence. Beginning in the 1960s, this model was undermined by fundamental changes in the country's economic and sociocultural environment. In response, the firms abandoned a number of their traditional attributes, a process that led to the demise of some businesses and the regeneration of others. Although the modern form adopted by the surviving Mittelstand firms allows them to be less dependent on individual families, to enjoy more access to external capital, and to display more openness and international orientation, they can no longer rely on the prospect of long-term stability, as they did in the past.

scholarly journals Coupling Multi-Angle Light Scattering to Reverse-Phase Ultra-High-Pressure Chromatography (RP-UPLC-MALS) for the characterization monoclonal antibodies

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Lorenzo Gentiluomo ◽  
Vanessa Schneider ◽  
Dierk Roessner ◽  
Wolfgang Frieß
Keyword(s):  
High Pressure ◽  
Light Scattering ◽  
Physical Stability ◽  
Exchange Chromatography ◽  
Protein Characterization ◽  
Size Exclusion ◽  
Reverse Phase ◽  
Long Term Stability ◽  
Ultra High Pressure ◽  
Exclusion Chromatography

Abstract Multi-angle light scattering coupled with size-exclusion chromatography (SEC-MALS) is a standard approach for protein characterization. Recently MALS detection has been coupled with ion-exchange chromatography (IEX) which demonstrated the feasibility and high value of MALS in combination with non-sized-based fractionation methods. In this study we coupled reverse-phase ultra-high pressure liquid chromatography (RP-UPLC) with a low-dispersion MALS detector for the characterization of intact monoclonal antibody (mAbs) and their fragments. We confirmed a constant refractive index increment value for mAbs in RP gradients, in good agreement with the values in literature for other classes of proteins. We showed that the impurities eluting from a RP column can often be related to aggregated species and we confirmed that in most cases those oligomers are present also in SEC-MALS. Yet, in few cases small aggregates fractions in RP-UPLC are an artifact. In fact, proteins presenting thermal and physical stability not suitable for the harsh condition applied during the RP separation of mAbs (i.e. organic solvents at high temperature) can aggregate. Further, we applied RP-UPLC-MALS during a long term stability studies. The different principle of separation used in RP-UPLC- MALS provides an additional critical level of protein characterization compared to SEC-MALS and IEX-MALS.

The End of Family Business? The Mittelstand and German Capitalism in Transition, 1949–2000

2006 ◽  
Vol 80 (2) ◽  
pp. 263-295 ◽  
Author(s):  
Hartmut Berghoff
Keyword(s):  
Family Business ◽  
Family Firms ◽  
German Economy ◽  
Term Stability ◽  
Long Term Stability ◽  
Sociocultural Environment ◽  
The Past ◽  
The 1960S ◽  
Modern Form

TheMittelstandsector of the German economy, which is made up of small and medium-sized family firms, is generally not mentioned in debates about German capitalism. This article makes the case that the focus of research on the German economy should shift from large corporate structures to these smaller firms. The classic Mittelstand model, which dominated the economy until about 1970, was characterized by identity of ownership and management, strong emotional investment by owners and staff, and an emphasis on continuity, paternalism, and independence. Beginning in the 1960s, this model was undermined by fundamental changes in the country's economic and sociocultural environment. In response, the firms abandoned a number of their traditional attributes, a process that led to the demise of some businesses and the regeneration of others. Although the modern form adopted by the surviving Mittelstand firms allows them to be less dependent on individual families, to enjoy more access to external capital, and to display more openness and international orientation, they can no longer rely on the prospect of long-term stability, as they did in the past.

scholarly journals Comparison of the Efficacy of Two Novel Antitubercular Agents in Free and Liposome-Encapsulated Formulations

2021 ◽  
Vol 22 (5) ◽  
pp. 2457
Author(s):  
Nikoletta Kósa ◽  
Ádám Zolcsák ◽  
István Voszka ◽  
Gabriella Csík ◽  
Kata Horváti ◽  
...  
Keyword(s):  
Cellular Uptake ◽  
Drug Carrier ◽  
Antimycobacterial Activity ◽  
Size Exclusion ◽  
In Silico Docking ◽  
Term Stability ◽  
Long Term Stability

Tuberculosis is one of the top ten causes of death worldwide, and due to the appearance of drug-resistant strains, the development of new antituberculotic agents is a pressing challenge. Employing an in silico docking method, two coumaran (2,3-dihydrobenzofuran) derivatives—TB501 and TB515—were determined, with promising in vitro antimycobacterial activity. To enhance their effectiveness and reduce their cytotoxicity, we used liposomal drug carrier systems. Two types of small unilamellar vesicles (SUV) were prepared: multicomponent pH-sensitive stealth liposome (SUVmixed) and monocomponent conventional liposome. The long-term stability of our vesicles was obtained by the examination of particle size distribution with dynamic light scattering. Encapsulation efficiency (EE) of the two drugs was determined from absorption spectra before and after size exclusion chromatography. Cellular uptake and cytotoxicity were determined on human MonoMac-6 cells by flow cytometry. The antitubercular effect was characterized by the enumeration of colony-forming units on Mycobacterium tuberculosis H37Rv infected MonoMac-6 cultures. We found that SUVmixed + TB515 has the best long-term stability. TB515 has much higher EE in both types of SUVs. Cellular uptake for native TB501 is extremely low, but if it is encapsulated in SUVmixed it appreciably increases; in the case of TB515, quasi total uptake is accessible. It is concluded that SUVmixed + TB501 seems to be the most efficacious antitubercular formulation given the presented experiments; to find the most promising antituberculotic formulation for therapy further in vivo investigations are needed.

scholarly journals Mucin Degradation Mechanisms by Distinct Pseudomonas aeruginosa Isolates In Vitro

2003 ◽  
Vol 71 (10) ◽  
pp. 5565-5575 ◽  
Author(s):  
Lina Panayiota Aristoteli ◽  
Mark D. P. Willcox
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Culture Supernatant ◽  
Tear Film ◽  
Size Exclusion ◽  
Bacterial Keratitis ◽  
Degradation Mechanisms ◽  
Exclusion Chromatography ◽  
Agarose Electrophoresis

ABSTRACT Pseudomonas aeruginosa has emerged as an important causative agent of bacterial keratitis, a rapidly progressive ocular condition that may result in blindness. Secretory mucin forms the main constituent of the precorneal tear film, a three-layer film on the ocular surface protecting the underlying corneal epithelium from potential pathogens. The purpose of the present study was to compare mucin degradation mechanisms between ocular P. aeruginosa strains. Mucin degradation was assessed by agarose electrophoresis, lectin blotting, and size exclusion chromatography. The results indicate that certain P. aeruginosa strains (Paer12, ATCC 15442, 6294, and Paer25) had depleted mucin from the culture supernatant and that this was contingent on the inherent ability of these isolates to produce proteases. Non-protease-producing strains (Paer1 and Paer3) did not appreciably degrade mucin. Further, galactosidase, N-acetylglucosaminidase, and N-acetylgalactosaminidase activities were detected in some strains, suggesting the operation of further mechanisms of mucin degradation by P. aeruginosa. Mucin degradation by P. aeruginosa also seemed to be for the acquisition of nutrients, as a growth advantage was observed in mucin-depleting strains over nondepleting strains in the long term. It is postulated that the degradation of mucin serves to collapse the mucin barrier and its associated network containing antibacterial tear components and to provide energy for sustained bacterial growth.

scholarly journals Preparation and Biological Evaluation of 67Gallium- Labeled Iranian Hemiscorpius Lepturus Scorpion Venom

2020 ◽  
Vol 13 (2) ◽  
pp. 99-106 ◽  
Author(s):  
Amir Jalali ◽  
Mona Haddad Zahmatkesh ◽  
Amir Reza Jalilian ◽  
Amir Taheri Borujeni ◽  
Behrouz Alirezapour
Keyword(s):  
Radiochemical Purity ◽  
Biological Evaluation ◽  
Scorpion Venom ◽  
Size Exclusion ◽  
Clinical Effects ◽  
Molar Activity ◽  
Exclusion Chromatography ◽  
Delayed Toxicity ◽  
Hemiscorpius Lepturus

Background: The Hemiscorpius lepturus (H. lepturus) is a deadly scorpion species living in the southern Iran. Objective: H. lepturus induces delayed toxicity symptoms and understanding the long term biodistribution/ biokinetic of the venom is of great interest in toxicology. Methods: A Ga-67 labeled venom was prepared using a DOTA -conjugated venom followed by radiolabeling using 67GaCl3 at 40°C for 90 min. The purification of the radiolabeled venom was performed using size exclusion-chromatography (radiochemical purity 71%). The radiolabeled venom was stable in the final solution in the presence of human serum at 37°C for 72 hours. The tissue distribution was studied in blood, heart, liver, spleen, muscle, brain, kidney, intestine and skin tissues at the intervals of 1, 4, 24, 48 and 72 hours using tissue counting and SPECT imaging. Results: The radiolabeled venom mixture obtained with an estimated molar activity of 0.52 MBq/μg. The main accumulation tissues during the first 72 hours were kidneys, blood, liver, intestines, stomach and skin, respectively. Therefore, it is likely that H. lepturus’ clinical effects and renal toxicity are primary and caused by direct effects of the H. lepturus venom. Conclusion: The results have largely shown the direct clinical effects on the studied tissues during the 72-hour period and antivenom administration can strongly alleviate the toxicity effects as early as 72 hours in the management of the patients.

scholarly journals Influence of different Ni coatings on the long-term behavior of ultrasonic welded EN AW 1370 cable/EN CW 004A arrestor dissimilar joints

2020 ◽  
Author(s):  
Tobias Köhler ◽  
Michael Grätzel ◽  
Jean Pierre Bergmann
Keyword(s):  
Power Systems ◽  
Stress Tests ◽  
Dissimilar Joints ◽  
Long Term Stability ◽  
Nickel Coatings ◽  
Standards And Regulations ◽  
Increasing Demand ◽  
The One ◽  
Long Term Behavior

AbstractThe increasing demand for energy-efficient vehicles requires suitable methods for cost and weight reduction. This can be achieved by the replacement of copper by aluminum, in particular for the on-board power systems. However, the complete substitution is restricted by the mechanical and physical material properties of aluminum as well as challenges in the aluminum copper interface. The challenges concern the corrosion vulnerability and the occurrence of brittle intermetallic compounds (IMC) which can negatively influence the mechanical properties and the electrical conductivity. Therefore, current investigations focus on the one hand on the realization of dissimilar aluminum copper joints by suitable joining technologies, like ultrasonic welding, and on the other hand on the assurance of a sufficient prevention against harmful corrosion effects. In cases where the joint cannot be protected against corrosion by sealing, nickel coatings can be used to protect the joint. In the present study, the influence of electroless, electroplated, and sulfamate nickel coatings was investigated regarding the long-term stability. The joints were performed as industry-related arrester connections, consisting of EN AW 1370 cables and EN CW 004A terminals. The samples were exposed to corrosive as well as electrical, thermal, and mechanical stress tests according to current standards and regulations.

Sign in / Sign up

Export Citation Format

Share Document