Synthesis and characterization of poly(2-methylaziridine)

Summary The cationic polymerization of 2-methylaziridine using boron trifluoride etherate as initiator at different monomer/initiator ratios, temperatures, solvents, and times of polymerization was carried out. The effect of these variables on the polymerization yield and viscosity of the polymers was studied. All the polymers were characterized by elemental analysis, FT-IR, ¹H-NMR, ¹³C-NMR spectroscopy, thermogravimetric analyses and differential scanning calorimetry.     

Immobilization of Myceliophthora thermophila laccase on poly(glycidyl methacrylate) microspheres enhances the degradation of azinphos-methyl

Laccase enzymes are multicopper oxidases capable of oxidizing different compounds. However, to be able to use this biocatalyst for industrial applications, their immobilization is needed. The present work investigates the immobilization of Myceliophthora thermophila laccase (MtL) on monodisperse microspheres of poly(glycidyl methacrylate) (PGMA) to be used in azinphos-methyl degradation. The immobilization was optimized to achieve the highest activity of the immobilized enzyme. As result, the protein load obtained was 2.5 mg protein g⁻¹ carrier (35 U g⁻¹ of carrier). The immobilized enzymes showed a broadened pH and temperature range of optimum activity and significantly improved the storage and operational stability. Finally, the complete degradation of azinphos-methyl using immobilized laccase was achieved after 1 h of reaction. The collected data indicate that the immobilization of MtL on PGMA microspheres is an excellent alternative to improve biochemical properties in the enzyme and to allow their efficient use in pesticides degradation. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47417.     

Effect on compressive and flexural strength of agave fiber reinforced adobes

Adobe bricks, formed from raw clay, are used as construction materials since ancient times. Their main drawback is a low flexural and compressive strength. Agave bagasse is a waste material from the Mezcal production process. Angustifolia haw agave bagasse fiber was added to improve the properties of adobes. Adobe bricks were made with agave fibers ranging from 10 to 25 mm length and 0.25 to 1% concentration. At 1% concentration of agave, 25 mm long, the compressive and flexural strength are improved by 33% and 7.01%, fulfilling the requirements of Mexican construction regulation norm N-CMT-2-01-001/02 class C.     

Water‐soluble polymers: Optimization of arsenate species retention by ultrafiltration

The liquid‐phase polymer‐based retention (LPR) technique was employed to study the retention of arsenate species by poly(vinylbenzyl trimethylammonium chloride), P(ClVBTA), and poly[2‐(acryloyloxy)ethyltrimethylammonium chloride], P(ClAETA). The effect of parameters such as polymer concentration, time exposure, competition of sulfate and phosphate anions, and the use of natural systems as drinking water on the retention of As(V) species was analyzed. The mole ratios of polymer : As(V) of (31 : 1), (20 : 1), (10 : 1), (6 : 1), and (3 : 1) by using the washing method at pH 8 and 6 were assayed. The retention capacity was a function of polymer concentration and pH. The optimum mole ratio of polymer : As(V) was (20 : 1) for all pHs studied and all polymeric structures. The polymer's activity recovery assays were performed by washing at pH 2 and 3. A 95% As(V) elimination was achieved from polymers. A study of competition in the presence of other anions was performed at the same polymer : As(V) ratio (20 : 1). At pH 8 and at the same concentration of arsenate anions, sulfate, and phosphate anions, no important competition on arsenic retention was observed. Assays for P(ClVBTA) at pH 8 and mole ratio of polymer : As(V) (20 : 1), (40 : 1), and (60 : 1) using drinking water showed that the efficiency was higher under these conditions for the three As(V) retention cases. An unbuffered system with drinking water was tested for washing and enrichment methods by determining the maximum saturation capacity of the P(ClVBTA) polymer. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Studies on the motility of smooth muscles of the teats in lactating cows

Rhythmic motility of teats in lactating cows in vivo was studied by an improved plethysmographic technique. Oxytocin was infused intravenously and drugs were injected into the artery of the filled udder. The beta-adrenergic agent, isoprenaline, induced relaxation of the teats whereas the alpha-adrenergic agents phenylephrine and noradrenaline, elicited contraction. In one animal however, noradrenaline always exerted a biphasic effect. Pre-treatment with propranolol, a beta-adrenergic blocking agent, changed the biphasic effect into a purely activating response. Adrenaline, which exhibits both alpha and beta effects, induced relaxation, but after propranolol treatment relaxation was abolished and even converted into contraction of the teat. It seems clear that both alpha and beta adrenoceptors are present in longitudinal smooth muscles of the teats. Milk losses as intermittent spurts were observed in several cows. Spurts occurred synchronously with rhythmical teat motility in the filled udder during oxytocin infusion. The intensity of milk leakage was increased by isoprenaline and inhibited by noradrenaline, indicating the presence of alpha and beta receptors in teat sphincter muscles. Starting and stopping of milk spurts in correlation with rhythmical teat contractions were studied by audiovisual synchronization of video recording tape. The most common type of spurt began near the middle of the teat's relaxation phase and ended either just before or exactly at the beginning of the contraction phase. Interruption of the spurt is primarily due to closure of the streak canal.     

Synthesis and behaviour of two copolymers of poly[acrylamide-co-(N-(hydroxymethyl)acrylamide)] in ultrafiltration experiments

Summary Water absorbing materials on the basis of acrylamide copolymers have been investigated. The cross-linking of polymer chains strongly effects the degree of water absorption. The influence of starting composition of polyacrylamide : sodium hydroxide, duration of hydrolysis and irradiation conditions on cross-linking have been determined and optimized technological parameters have been derived. Water super absorbents with the ability to absorb up to 900g water by one gram material have been prepared. Received: 20 December 1999/Revised version: 19 June 2000/Accepted: 17 July 2000     

Resource finding in store-and-forward networks

We present a model of searching for a resource in a distributed system whose nodes are connected through a store-and-forward network. Based on this model, we show a lower bound on the number of messages needed to find a resource when nothing is known about the nodes that have the current location of the resource. The model also helps us to establish results about the time complexity of determining a message optimal resource finding algorithm when the probability distribution for the location of the resource in the network is known. We show that the optimization problem is NP-hard for general networks. Finally we show that optimal resource finding algorithms can be determined in polynomial time for a class of tree networks and bidirectional rings. The polynomial algorithms can be used as a basis of heuristic algorithms for general networks.This work was supported in part by NSF grants CCR-8806358 and NCR-8604850     

Functional water‐soluble polymers: polymer–metal ion removal and biocide properties

Water‐soluble polymers have attracted much interest due to their potential applications in environmental protection engineering to remove harmful pollutants and in biomedicine in the areas of tissue engineering, within‐body implants or other medical devices, artificial organ prostheses, ophthalmology, dentistry, bone repair, and so on. In this review, particular emphasis is given to the ability of water‐soluble polymers with amine, amide, carboxylic acid, hydroxyl and sulfonic acid functional groups to remove metal ions by means of the liquid‐phase polymer‐based retention (LPR) technique that combines the use of water‐soluble polymers and ultrafiltration membranes. The second part is dedicated to showing the potential application of functional water‐soluble polymers and their polymer–metal complexes as biocides for various bacteria. These polymers and polymer–metal complexes show an efficient bactericide activity, especially to Gram‐negative bacteria, Staphylococcus aureus reaching concentrations lower than 4 µg mL^?1. This activity depends on polymer size, type of metal ion, contact time and concentration of polymer and metal ion. The discussion reveals that in the case of the LPR process the efficiency of metal ion removal depends strongly on the type of polymer functional group and the feed pH value. In general, two mechanisms of ion entrapment are suggested: complex formation and electrostatic interaction. In the case of the medical use of water‐soluble polymers and their complexes with metal ions, the review documents the unique bactericide properties of the investigated species. The polymer‐metal ion complexes show a reduced genotoxic activity compared with free metal ions. Copyright © 2009 Society of Chemical Industry