Ceramic Dental Molds for the Precision Casting of Titanium and Titanium Alloys: I, Relationship between Particle-Size Distribution of Aggregates and Mold Expansion

A new ceramic dental mold can cast excellent Ti restoratives by controlling expansion due to the oxidation of additive metal particles. The packing structure of the metal and aggregate particles in the mold can be considered a function of the size distribution of the aggregate grains. An investigation of the expansion mechanism reveals three different relationships of void fraction versus linear thermal expansion for the molds at the high temperature under which oxidation of the metal particles occurs. Room-temperature casting, favorable for making high-quality Ti restoratives, can also be achieved by precisely controlling both the amount of additive metal powder and the compositional distribution of aggregate grain sizes in the mold.     

Growth characteristics of agrowaste‐immobilised lactobacilli in soymilk during refrigerated storage

We aimed at evaluating agricultural wastes as solid supports for the immobilisation of lactobacilli in a liquid media, namely soymilk. Lactobacillus acidophilus FTDC 1331, L. acidophilus FTDC 2631, L. acidophilus FTDC 2333, L. acidophilus FTDC 1733 and L. bulgaricus FTCC 0411 were immobilised on solid supports produced from durian (Durio zibethinus), cempedak (Artocarpus champeden) and mangosteen (Garcinia mangostana). The immobilised cells were inoculated into soymilk and stored at 4 °C over 168 h. Soymilk inoculated with non‐immobilised cells was used as the control. Immobilised cells showed higher survivability over 168 h compared to the control, accompanied by higher reduction of simple sugars and oligosaccharides in soymilk. Higher growth and higher utilisation of substrates also led to the higher production of lactic and acetic acids, which lowered the pH in soymilk compared to the control. Our results illustrated that agrowastes could be used as immobilisers to enhance the growth of lactobacilli in a liquid medium.     

Communication, symbolic communication, and language: Reply to Seidenberg and Pettito.

Seidenberg and Petitto's (1987) assertion that Kanzi and Mulika's lexigram usage is not representational is evaluated by contrasting their abilities with Nim's. Kanzi and Mulika's data indicate that they (a) comprehend spoken English words; (b) can identify lexigram symbols when they hear these words; (c) can comprehend lexigram usage; (d) can use lexigrams when referents are absent and can, if asked, lead someone to the referent; and (e) that all these skills were acquired through observation, not conditioning. Nim evidenced no comprehension of signs and could not use signs when referents were absent. He was forced to sign and encouraged to imitate his teachers. Seidenberg and Petitto's negative experiences with Nim apparently led them to overgeneralize to all other apes, regardless of species, modality, or training history. Consequently, they unjustifiably disregard important components of Kanzi and Mulika's comprehension data which demonstrate that their lexical knowledge could not have been acquired in an instrumental fashion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Determination of Mark-Houwink-Sakurada equation for phenolic resins containing alkylenediamine in the main chain and estimation of their molecular conformation in tetrahydrofuran solution

Summary Phenolic resins containing alkylenediamine in the main chain could be prepared by the co-condensation reaction of phenol, formaldehyde and alkylenediamines such as ethylenediamine and hexamethylenediamine. The molecular structures were determined by¹H-NMR spectra, IR spectra and nitrogen content. The molecular conformation of these resins in THF solution were studied from the viscosity measurements, and it became clear that the molecules were considerably compact compared with linear vinyl polymers. To clarify the reason of this phenomenon, the resins whose degrees of branching were different from each other and the resins whose phenolic hydroxyl groups were acetylated were prepared. From viscosity data, it was pointed out that the intramolecular hydrogen bonding contributes to the compaction of the phenolic resins containing alkylenediamine in the main chain more strongly than the branching does.     

Italian multicentre study on microbial environmental contamination in dental clinics: a pilot study

The dental practice is associated with a high risk of infections, both for patients and healthcare operators, and the environment may play an important role in the transmission of infectious diseases. A microbiological environmental investigation was carried out in six dental clinics as a pilot study for a larger multicentre study that will be performed by the Italian SItI (Society of Hygiene, Preventive Medicine and Public Health) working group "Hygiene in Dentistry". Microbial contamination of water, air and surfaces was assessed in each clinic during the five working days of the week, before and during treatments. Air and surfaces were also examined at the end of the daily activity. A wide variation was found in microbial environmental contamination, both within the participating clinics and relative to the different sampling times. Microbial water contamination in Dental Unit Water Systems (DUWS) reached values of up to 26 × 10⁴ cfu/mL (colony forming units per millilitre). P. aeruginosa was found in 33% of the sampled DUWS and Legionella spp. in 50%. A significant decrease in the Total Viable Count (TVC) was recorded during the activity. Microbial air contamination showed the highest levels during dental treatments and tended to decrease at the end of the working activity (p < 0.05). Microbial buildup on surfaces increased significantly during the working hours. As these findings point out, research on microbial environmental contamination and the related risk factors in dental clinics should be expanded and should also be based on larger collections of data, in order to provide the essential knowledge aimed at targeted preventive interventions.     

Differential Effects of Indole and Aliphatic Glucosinolates on Lepidopteran Herbivores

Glucosinolates are a diverse group of defensive secondary metabolites that is characteristic of the Brassicales. Arabidopsis thaliana (L.) Heynh. (Brassicaceae) lines with mutations that greatly reduce abundance of indole glucosinolates (cyp79B2 cyp79B3), aliphatic glucosinolates (myb28 myb29), or both (cyp79B2 cyp79B3 myb28 myb29) make it possible to test the in vivo defensive function of these two major glucosinolate classes. In experiments with Lepidoptera that are not crucifer-feeding specialists, aliphatic and indole glucosinolates had an additive effect on Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) larval growth, whereas Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae) and Manduca sexta (L.) (Lepidoptera: Sphingidae) were affected only by the absence of aliphatic glucosinolates. In the case of two crucifer-feeding specialists, Pieris rapae (L.) (Lepidoptera: Pieridae) and Plutella xylostella (L.) (Lepidoptera: Plutellidae), there were no major changes in larval performance due to decreased aliphatic and/or indole glucosinolate content. Nevertheless, choice tests show that aliphatic and indole glucosinolates act in an additive manner to promote larval feeding of both species and P. rapae oviposition. Together, these results support the hypothesis that a diversity of glucosinolates is required to limit the growth of multiple insect herbivores.     

Partially cured epoxy/SWCNT thin films for the reinforcement of vacuum-assisted resin-transfer-molded composites

An approach to strategically introduce carbon nanotubes (CNTs) into epoxy to prepare epoxy/CNT composites has been developed. CNTs can be placed at locations of interest inside a vacuum-assisted resin-transfer-molded composite, thus allowing for optimized composite reinforcement at lower cost. Moreover, it helps avoid viscosity related processing issues due to the addition of CNTs to epoxy.     

Laboratory studies into how glass-reinforced plastic (GRP) vat surfaces can be repaired without causing migration of styrene into foodstuffs

Glass–fiber-reinforced plastic (GRP) vats are used widely for the storage of foodstuffs and potable water. As the inner surfaces deteriorate during decades of use, they need to be repaired. The unsaturated polyester resins that are used for recoating are crosslinked with styrene which can cause taint and odor problems. This article describes some coating parameters that affect the content of residual styrene and its subsequent migration. The influences of cure temperature and duration, along with the effect of washing with warm detergent solution, were investigated. Cured specimens were tested for their residual styrene content and for styrene migration into the food simulants, distilled water, 3% acetic acid, and 15% ethanol. The dominant factor in reducing the amount of residual styrene is the temperature. The resin self-heats as it cures, typically up to 50°C. Thus, any further lowering of the styrene content requires a higher cure temperature than this. A 3-h cure at 80°C reduced both the residual content and the migration levels by about 100-fold. At lower cure temperatures, the heating effect of washing at 60°C is more important than the washing effect of the detergent. When less catalyst was used the residual styrene levels rose dramatically, from 70 to 360 to 1300 mg/kg for the normal dose, half and quarter the normal dose, respectively. There was a linear relationship between residual content in the GRP and the migration levels. This correlation could be used for monitoring the quality of vats repaired in situ, using styrene-based coating resins.     

Cover Image,Volume 97, Issue 11

The cover image, by Hannah C Wells et al., is based on the Research Article Deer leather: analysis of the microstructure affecting pebble, DOI: 10.1002/jsfa.8199 .