Papers by Valentin I Popa
Structure and Function, 2 Volume Set, 2013
CRC Press eBooks, Jan 17, 2013
CRC Press eBooks, Jan 17, 2013
ABSTRACT doi:10.1201/b13758-8
CRC Press eBooks, Jan 17, 2013
CRC Press eBooks, Jan 17, 2013
CRC Press eBooks, Jan 17, 2013
CRC Press eBooks, Jan 17, 2013
CRC Press eBooks, Jan 17, 2013
Polymeric Biomaterials, 2013
Annals of Internal Medicine, 1982
Following your need to always fulfil the inspiration to obtain everybody is now simple. Connectin... more Following your need to always fulfil the inspiration to obtain everybody is now simple. Connecting to the internet is one of the short cuts to do. There are so many sources that offer and connect us to other world condition. As one of the products to see in internet, this website becomes a very available place to look for countless drug treatment of respiratory disease sources. Yeah, sources about the books from countries in the world are provided. With this condition, when you need a book hurriedly, never be worried. Just find and visit this site and get the book quickly. Now, when the drug treatment of respiratory disease is what you seek for now, you can get this book directly in this page. By visiting the link that we offer, you can start to get this book. It is very simple, you may not need to go offline and visit the library or book stores.
Cellulose Chemistry and Technology, 2000
A possible maximization of the biosynthesis process of cellulases involves the establishment of s... more A possible maximization of the biosynthesis process of cellulases involves the establishment of some peculiar conditions of cultivation, so that the biological potential of the microorganism should be most propitiously utilized. The experiments carried out using two fungal strains, Phanerochaete chrysosporium and Chaetomium elatum have shown a different behaviour to the variation of some factors of influence, such as: the cellulosic inducer, the biological material for inoculation, the type of medium, the hydrodynamic conditions, pH and temperature of cultivation. The enzymatic activities, the extracellular protein content, the pH variation and the behaviour of biosynthetized cellulasic complex in hydrolysis reactions have been also analyzed in order to establish the optimum conditions for which the whole complex or only one of its components may be produced.
of PhD thesis defended by Roxana Elena Ghitescu at the “Gheorghe Asachi” Technical University of ... more of PhD thesis defended by Roxana Elena Ghitescu at the “Gheorghe Asachi” Technical University of Iasi, Romania The thesis focuses on the extraction and immobilization possibility of the phenolic compounds from spruce wood bark and is divided into two parts with a total of 5 chapters. The first part, Chapter I, Polyphenols important biologically active compounds presents the newest information regarding the classification of the phenolic compounds, chemical, biochemical and biological properties, the extraction and characterization of the phenolic compounds, the electrosppinning method and possibile applications of the polyphenols in the immobilized forms. The second part, Chapter II entitled Extraction of polyphenolic compounds from spruce wood bark, discusses the extraction of the phenolic compounds by using ultrasound and microwave assisted extraction, allowing the optimization of the processes. In this context, the main parameters that influence the extraction process were evalua...
Wochenblatt Fur Papierfabrikation, 1999
CDM (colloidal dissolved material) control has become increasingly important in view of ever-incr... more CDM (colloidal dissolved material) control has become increasingly important in view of ever-increasing recycled fiber inputs and circuit closures. In fhe first part of the paper, the authors demonstrate how the wet end characteristics are affected in a papermaking system which uses 100% OCC and recycles 80% of its whitewater. When the recirculation of white water was simulated on a DDJ apparatus, filtrate analyses performed after each cycle showed that fines and CDM accumulate and reach a relative equilibrium after 16-18 cycles. The negative zeta potential (microelectrophoresis) of the filtrate decreases slowly as the conductivity increases, and is finally stabilized. On the other hand, the cationic demand (colloidal titration) increases with each cycle whilst the drainage rate of stock is considerably reduced owing to accumulating fines and CDM. The second part of the study focuses on several options to limit the accumulation of CDM in papermaking systems. Specifically, two soluti...
Bulletin of University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca. Agriculture, 2016
The plant kingdom is an inexhaustible source of bioactive compounds with antioxidant character. I... more The plant kingdom is an inexhaustible source of bioactive compounds with antioxidant character. It is known that, natural polyphenols are essential compounds in stimulating plant growth and development. The aim of this study was to identify the internal structure changes in maize (Zea mays L.) seedlings, under the influence of hemp shives polyphenolic extract. Hemp shives polyphenolic extract was characterized in terms of the total content of polyphenols and individual content by HPLC. Germination tests were carried out going through a standard procedure. In order to perform the histo-anatomical characterization, the vegetal material was fixed and preserved in alcohol 70%, following to be cut by hand microtome. The sections obtained were stained using double staining reagents: green - iodine and ruthenium red. It was observed, compared with the control, that hemp shives polyphenolic extract determines a good development of the root hairs and increase leading bundles number and centr...
Cellulose Chemistry and Technology, 2019
Shells resulting from food processing and agricultural activities, such as hard shells of apricot... more Shells resulting from food processing and agricultural activities, such as hard shells of apricot, are considered as wastes and are generally used as fuel. However, this residue shows promise as lignocellulosic feedstock for biorefineries, for its conversion to liquid fuel or bio-products. This study is dedicated to the characterization and isolation of lignin, cellulose and hemicelluloses from apricot shells (AS). The chemical composition and thermal stability of AS after chemical treatment with solvents (ethanol-toluene), cellulose, hemicelluloses and lignin were analyzed by standard methods, i.e. Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Further, almost 50.2 wt% of a water-insoluble extract was obtained after the bleaching process, which showed the removal of lignin, and the final percentages for this extraction were 50.2 ± 0.34%, 26.5 ± 0.83%, 23.7 ± 0.29% and 35 ± 1% for holocellulose, cellulose, hemicelluloses and lignin, respectively. FTIR spectroscopy evidenced the structure of lignin, cellulose and hemicelluloses. Thermal analysis and the kinetic study suggested that cellulose had higher thermal stability than the other components, with the activation energy of 289.62 kJ/mol. Thus, our results indicated the high potential of AS to be used as an environmentally friendly material in a biorefinery, as well as in the modern polymer and chemical industries.
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Papers by Valentin I Popa
High-Tech Applications
Series: De Gruyter STEM
Edited by: Valentin I. Popa, De Gruyter 2020
OVERVIEW
This book presents the aspects of cellulose obtained in correlation with its integration into the new concept of biorefining. The authors detail the individual steps of pulp manufacture as well as properties and fiber characterization techniques for paper, cellulose derivatives and processing by-products. This book is of interest to scientists and advanced students working in the fields of renewable resources and biorefining.
• The authors consider pulp production and processing from the perspective of not only chemical engineering, but also chemistry and physics.
• Addresses the process products as well as by-products, giving both their properties and potential applications.
AUTHOR INFORMATION
Prof. em. Valentin I. Popa, Technical University of Iasi "Gheorghe Asachi", Romania.
Valentin I. Popa (editor) Pulp Production and Processing; high-tech applications, 2nd edition, De Gruyter, 2020, ISBN 978-3-11-06588305, 404 p.
Cartea prezintă oportunitățile oferite de industria de celuloză și hârtie pentru implementarea biorafinării pentru a obține alături de produsele de bază și altele cu performanțe ridicate aplicabile în domenii diferite. Această situație este posibilă din următoarele motive: în primul rând, alături de lemn ca materie primă, se pot include deșeurile de lemn și din exploarea forestieră si agricultură, maculatura și plantațiile energetice. În al doilea rând, industria dispune de infrastructura necesară aprovizionării, depozitării și livrării produselor fabricate. În al treilea rând, fabricile au o infrastructură administrativă și resurse umane suficiente pentru a gestiona sistemul de biorafinare și extindere a producției fără costuri suplimentare. În al patrulea rând, fabricile de celuloză și hârtie au rețea de utilități (apă, electricitate, abur, tratarea deșeurilor și protecție a mediului) care poate asigura umbrela sub care să se desfășoare operațiile incluse în biorafinare fără costuri suplimentare. In al cincilea rând fabricile care produc celuloză chimică pot avea acces la tehnologiile de obținere a hârtiei și cartoanelor, a fibrelor și pot dezvolta bioproduse, derivați de celuloză, aditivi, biocombustibili etc. Cartea care reprezintă contribuția unor autori recunoscuți la nivel mondial poate constitui un instrument util atât pentru cercetători cât și pentru studenții care abordează aspecte din domeniul bioresurselor.
Prof.emerit dr.ing. Valentin I. Popa, Universitatea Tehnică, Iași, membru corespondent ASTR