First RAFT polymerization of captodative 2-acetamidoacrylic acid (AAA) monomer: An experimental and theoretical study

A capto-dative monomer, 2-acetamidoacrylic acid (AAA), was homopolymerized through RAFT polymerization method using 2-(2-cyanopropanyl dithiobenzoate) (CPDB) as a chain transfer agent and AIBN free radical initiator in DMF at 70 °C. DFT calculations were performed in the selection of the CTA for this unique monomer as well as to elucidate the influence of cd-stabilized growing radical on the kinetic parameters in comparison to methacrylic acid (MAA) and N-(prop-1-en-2-yl)acetamide (NPAA), which represent the captive and dative groups of AAA, respectively. K_eq for these three monomers is in the order of AAA < MAA < NPAA. While k_β > k_−add for NPAA and MAA, for AAA k_−add is about four orders of magnitude larger than k_β. This is the major disadvantage in the RAFT process of AAA using CPDB. Yet, poly(AAA) could be achieved with PDI as low as 1.49. Molecular weight of the polymer can be tuned by the monomer/AIBN ratio. First block copolymers of AAA with MAA and MMA using poly(AAA) as a macro-CTA were also synthesized, indicating the presence of active chain ends.     

Isothermal crystallization kinetics and mechanical properties of polycaprolactone composites with zinc oxide,oleic acid,and glycerol monooleate

The isothermal crystallization and mechanical behavior of polycaprolactone (PCL) with zinc oxide (ZnO) with oleic acid and glycerol monooleate (GMO) were studied. Theoretical melting points calculated by the Flory–Huggins and Thompson–Gibbs models were thoroughly compared with differential scanning calorimetry experimental observations. The isothermal crystallization kinetic parameters by Avrami analysis showed that crystallization was controlled by nucleation, crystal growth was spherical, and the nucleation type changed between thermal and athermal nucleation. X‐ray diffraction showed that when the additives were used together both the crystal thickness and the degree of crystallinity increased. A multiple‐response regression analysis was made with the ZnO, oleic acid, and GMO concentrations as variables and the crystallinity as output. Interaction parameters by the Pukanzky model were calculated from the tensile strength at the yield point and indicated that the addition of oleic acid or GMO improved the interface between the ZnO particles and PCL. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1259‐1275, 2013     

A water-soluble Irgacure 2959-based diallylammonium salt system for antibacterial coatings

A water-soluble mixture of a novel diallylammonium salt photoinitiator based on 2-hydroxy-1-[4-(2-hydroxyethoxy) phenyl]-2-methyl-1-propanone (Irgacure 2959 or I2959) and diallylammonium tosylate has been prepared. It shows excellent water-solubility of 6.8 wt% in water, much greater than the solubility of I2959 (<2 wt%). It has a strong absorbance at 269 nm (ε ~ 15731) in methanol. It exhibits 15.6 times higher migration stability than I2959 due to its monomeric nature. Its photoinitiating efficiency of 2-hydroxyethylmethacrylate (HEMA) and poly(ethylene glycol) diacrylate (PEGDA, M_n = 575 D) was found to be similar to I2959. PEGDA hydrogels prepared using the synthesized photoinitiator (PI) were found to have highly porous structures (15.44 μm) compared with those using I2959. PEGDA film prepared using this PI has demonstrated antibacterial properties against gram-negative Pseudomonas aeruginosa (ATCC 15442) and gram-positive Staphylococcus aureus (ATCC 23235) bacterial species.     

Comparative evaluation of push-out bond strength of Neo MTA Plus with Biodentine and white ProRoot MTA

Objective: The aim of this in vitro study was to evaluate the bond strength of a new calcium silicate cement, Neo MTA Plus (Avalon Biomed Inc. Bradenton, FL, U.S.A) by comparing ProRoot MTA and Biodentine.

Material and Methods: Sixty dentin slices were instrumented to achieve a diameter of 1.3 mm. Group 1: white ProRoot MTA, group 2: Biodentine, group 3: Neo MTA Plus – G (powder mixed with gel), group 4: Neo MTA Plus – W (powder mixed with distilled water) were loaded into cavities. The push-out bond strength values were measured. Data were analyzed using Welch ANOVA with Bonferroni correction p = 0.05. Failure modes (adhesive, cohesive, and mixture) were analyzed.

Results: The highest bond strength value was recorded in Neo MTA Plus mixed with gel (5.23 ± 1.78 MPa), whereas white ProRoot MTA (2.57 ± 0.66 MPa) had the lowest. Bond strength values of Neo MTA Plus mixed either with gel or with distilled water were statistically different from both white ProRoot MTA and Biodentine (2.61 ± 0.70 MPa) (p < 0.05). Adhesive failure was predominantly observed in all groups.

Conclusion: Neo MTA Plus could be considered as alternatives to the ProRoot MTA and Biodentine due to its better performance in bonding to root dentin.     

Utilization of multiple graphene layers in fuel cells. 1. An improved technique for the exfoliation of graphene-based nanosheets from graphite

An improved, safer and mild method was proposed for the exfoliation of graphene like sheets from graphite to be used in fuel cells. The major aim in the proposed method is to reduce the number of layers in the graphite material and to produce large quantities of graphene bundles to be used as catalyst support in polymer electrolyte membrane fuel cells. Graphite oxide was prepared using potassium dichromate/sulfuric acid as oxidant and acetic anhydride as intercalating agent. The oxidation process seemed to create expanded and leafy structures of graphite oxide layers. Heat treatment of samples led to the thermal decomposition of acetic anhydride into carbondioxide and water vapor which further swelled the layered graphitic structure. Sonication of graphite oxide samples created more separated structures. Morphology of the sonicated graphite oxide samples exhibited expanded the layer structures and formed some tulle-like translucent and crumpled graphite oxide sheets. The mild procedure applied was capable of reducing the average number of graphene sheets from 86 in the raw graphite to nine in graphene-based nanosheets. Raman spectroscopy analysis showed the significant reduction in size of the in-plane sp² domains of graphene nanosheets obtained after the reduction of graphite oxide.     

Changes in vibrational entropy during the early stages of chemical unmixing in fcc Cu–6% Fe

A nanocrystalline face-centered cubic (fcc) solid solution of 6% Fe in Cu was prepared by high-energy ball milling, and annealed at temperatures from 200 to 360 °C to induce chemical unmixing. The chemical state of the material was characterized by three-dimensional atom probe microscopy, Mössbauer spectrometry and X-ray powder diffractometry. The unmixing was heterogeneous, with iron atoms forming iron-rich zones that thicken with further annealing. The phonon partial density of states (pDOS) of ⁵⁷Fe was measured by nuclear resonant inelastic X-ray scattering, showing the pDOS of the as-prepared material to be that of an fcc crystal. The features of this pDOS became broader in the early stages of unmixing, but only small changes in average phonon frequencies occurred until the body-centered cubic (bcc) phase began to form. The vibrational entropy calculated from the pDOS underwent little change during the early stage of annealing, but decreased rapidly when the bcc phase formed in the material.     

Fibre products of Kummer covers and curves with many points

We study the general fibre product of any two Kummer covers of the projective line over finite fields. Under some assumptions, we obtain an involved condition for the existence of rational points in the fibre product over a rational point of the projective line so that we determine the exact number of the rational points. Using this, we construct explicit examples of such fibre products with many rational points. In particular we obtain a record and a new entry for the table (http://www.science.uva.nl/^~geer/tables-mathcomp15.ps).      

Technological Assessment of Radio Frequency Identification Technology for Indoor Localization

Indoor localization is needed for guiding people who are not familiar with a facility. This need is more critical when guidance is needed to locate people or objects that need immediate attention. For example, an inexperienced facility worker might need to locate a building component (e.g., leaking pipe) for repair to prevent any damage to a facility or its residents. In such situations, an approach that can help the user to reach his/her destination point (i.e., a component of interest or a specific location in a facility) based on his/her current location is desired. To provide such guidance, the location of a person needs to be determined at a given point in time. This process is known as localization. The objective of this research study is to determine the technological viability of using radio frequency identification (RFID) to support localization. To assess the capability of RFID for localization, the writers conducted multiple field tests under real operating conditions within a facility at Carnegie Mellon University. Hypothesis tests and K-nearest neighborhood algorithm were used to determine the technological feasibility of RFID to support localization. The results showed that it is possible to identify the location of a user using this approach; however, some improvements in accuracy are needed.     

Effectiveness of combined sewer overflow treatment for dissolved oxygen improvement in the Chicago waterways.

An Use Attainability Analysis (UAA) has been initiated to evaluate what water-quality standards can be achieved in the Chicago Waterway System (CWS). There are nearly 200 combined sewer overflow (CSO) locations discharging to the CWS by gravity. Three CSO pumping stations also drain approximately 140 km2. Because of the dynamic nature of the CWS the DUFLOW model that is capable of simulating hydraulics and water-quality processes under unsteady-flow conditions was used to evaluate the effectiveness of water-quality improvement techniques identified by the UAA including CSO treatment. Several CSO treatment levels were applied at gravity flow CSOs to evaluate improvement in dissolved oxygen (DO). The results show that pollutant removal at CSOs improves DO to a certain degree, but it still was not sufficient to bring DO concentrations to 5 mg/L or higher for 90% of the time during wet weather at most locations on the CWS. Flow from the pumping stations results in substantial stress on DO since a huge amount of un-treated water with a high pollution load is discharged into the CWS in a short period of time at a certain location. The simulation results indicate that CSO treatment does not effectively improve DO during wet-weather periods on the CWS.     

Renovation of a Safety-Inspection Methodology for River Bridges

River bridges and related infrastructural elements need to be monitored and inspected periodically for deterioration and loss of function due to aging, adverse hydraulic conditions, and chemical attacks. Necessary protective works and related actions should then be implemented to increase safety. Types of items to be inspected would be categorized as structural, geotechnical, hydraulic, and structural material conditions. Requirements for periodic inspections and the ways of handling these activities were discussed within the framework of the aforementioned aspects. Since each bridge authority has its own inspection grading system according to variations in local conditions and the socioeconomic status of the country, a common core methodology should be implemented such that comparisons with different case studies are meaningful. The aim of this study is the renovation of the current inspection system in Turkey, in order to implement it primarily for saving human life, as well as promoting Turkey’s economy, labor, and manpower. An algorithm, based on evaluating components of the main body, earth-retaining facilities, and serviceability, as well as hydraulic aspects, is proposed. This renovation enables the identification of rank-based prioritization of events. The evaluation and interpretation steps were displayed with the help of a case study.