As-molded shrinkage measurements on polystyrene injection molded products

An experimental study of shrinkage in injection molded products is presented in this paper and documented with all information needed for any further analysis. In particular, the effect of holding pressure, holding time and mold geometry on product shrinkage was investigated for amorphous polystyrene. It turned out with increasing holding pressure the in-plane shrinkages varied from 0.6% to 0.1%, while the product thickness increased from about 1% to 10%. The holding time only affected product shrinkage for settings less than gate freeze-off time. Shrinkage usually increases along the flow path unless back flow sets in at the end of the holding stage. It was also found that if a constraint prevents in-mold shrinkage to take place, final shrinkage may decrease if holding pressure and time are small. The effects of all the variables analyzed were described by a thermomechanical model recently proposed.     

Synthesis,Surface Properties,and Self-Aggregation Behavior of a Branched N,N-Dimethylalkylamine Oxide Surfactant

Amine-oxide surfactants have emerged as highly stable, nontoxic, and cost-effective constituents of detergent formulations, specifically as wetting agents and foam boosters. With the aim of enhancing their functional behavior, a new member of this family, N,N-dimethyl-2-propylheptan-1-amine oxide, bearing a branched alkyl tail (C₁₀DAO-branched) was synthesized and purified using a simple and easily scalable strategy starting from 2-propylheptan-1-ol. 2D-nuclear magnetic resonance (NMR) and mass spectrometry confirm the obtainment of the desired product in high yield and purity. The protonation behavior of the branched surfactant is not affected by alkyl tail branching, as shown by potentiometric titrations. In contrast, surface activity and aggregation behavior of C₁₀DAO-branched is dramatically different from that of the linear analog N,N-dimethyldecyl-1-amine oxide (C₁₀DAO-linear), in that it occupies a higher area at the solution interface and aggregates at much higher concentration, forming larger aggregates, as detected using tensiometry and dynamic light scattering (DLS), respectively. Aggregation behavior of C₁₀DAO-branched is less sensitive to pH variations. Foaming tests show that C₁₀DAO-branched is a more effective foam booster than its linear analog, in both acidic and basic solutions. The experimental results indicate that the branched surfactant can be used in applications that require enhanced and pH-independent surface activity and foamability.     

Extraction with Water-in-Carbon Dioxide Microemulsions: A Case Study on Steviol Glycosides

This work explores the use of water-in-supercritical carbon dioxide (scCO₂) microemulsions for the extraction of polar metabolites from plants. Stevia rebaudiana Bertoni leaves and polyethylene glycol trimethylnonyl ether (TMN) surfactants were selected for a case study. A CO₂-water-TMN 10 mixture at 35 °C and 30.0 MPa extracted 7 mg target analyte/g dry leaves. The extraction was proven to occur due to a water-surfactant liquid solution rather than a water-in-CO₂ microemulsion. Using a modified extraction setup, the microemulsion was created prior to extraction. TMN 6 was able to dissolve enough water in CO₂ to extract steviol glycosides, in detectable but very small amounts.     

Discovery of Inhibitors of Trypanosoma brucei by Phenotypic Screening of a Focused Protein Kinase Library

A screen of a focused kinase inhibitor library against Trypanosoma brucei rhodesiense led to the identification of seven series, totaling 121 compounds, which showed >50 % inhibition at 5 μm . Screening of these hits in a T. b. brucei proliferation assay highlighted three compounds with a 1H‐imidazo[4,5‐b]pyrazin‐2(3H)‐one scaffold that showed sub‐micromolar activity and excellent selectivity against the MRC5 cell line. Subsequent rounds of optimisation led to the identification of compounds that exhibited good in vitro drug metabolism and pharmacokinetics (DMPK) properties, although in general this series suffered from poor solubility. A scaffold‐hopping exercise led to the identification of a 1H‐pyrazolo[3,4‐b]pyridine scaffold, which retained potency. A number of examples were assessed in a T. b. brucei growth assay, which could differentiate static and cidal action. Compounds from the 1H‐imidazo[4,5‐b]pyrazin‐2(3H)‐one series were found to be either static or growth‐slowing and not cidal. Compounds with the 1H‐pyrazolo[3,4‐b]pyridine scaffold were found to be cidal and showed an unusual biphasic nature in this assay, suggesting they act by at least two mechanisms.     

Feasibility of using low pressure cold gas spray for the spraying of thick ceramic hydroxyapatite coatings

This article deals with the production of thick ceramic hydroxyapatite coatings obtained by Low Pressure Cold Gas Spray (LPCGS) system. Several factors such as powder microstructure, surface roughness and cold gas spray system are here discussed in the build-up process. The use of nanocrystalline powder composed by fine agglomerates and needle-like shape microstructure allows the realignment and compaction of individual crystallites to form thick deposits. In addition, the activation of the substrate surface results convenient for the first impinging particles anchored properly. Then, layer by layer, particles can remain attached leading to coating build-up. Additionally, the use of low shock pressure as well as constant feeding system provided by LPCGS system lead to homogeneous coatings in comparison with High Pressure Cold Gas Spray (HPCGS) system. The successful coating build-up has been achieved not only by the use of an agglomerated feedstock powder, but also by previous surface treatment and the use of the low pressure system. The obtaining of HA components by LPCGS is promising within biomedical field. An improvement of component strength is also suggested by means of thermomechanical analysis of the powder. The performance of a post heat-treatment leads to an increase in HA strength, as well as crystal size.     

Polymeric prodrugs containing neridronate and ferrocene: Synthesis,characterization, and antimalarial activity

Polyamidoamine prodrugs containing ferrocene derivatives and neridronate were successfully synthesized and characterized by NMR, FTIR, SEM, and EDX analyses. Appearance of characteristic peaks in ¹H and ³¹P NMR or EDX spectra were used to confirm the presence of neridronate or ferrocene in the conjugates and co-conjugates. In vitro evaluation of the new materials revealed improved antimalarial activity, especially for conjugate 5 and corresponding co-conjugate 8, when compared with chloroquine and quinine. Hemolysis studies revealed that synthesized prodrugs had no effect on the integrity of the host red blood cell membrane; a direct effect on the intra-erythrocytic parasite was, however, noted.     

Methylphenidate Ameliorates Depressive Comorbidity in ADHD Children without any Modification on Differences in Serum Melatonin Concentration between ADHD Subtypes

The vast majority of Attention-deficit/hyperactivity disorder (ADHD) patients have other associated pathologies, with depressive symptoms as one of the most prevalent. Among the mediators that may participate in ADHD, melatonin is thought to regulate circadian rhythms, neurological function and stress response. To determine (1) the serum baseline daily variations and nocturnal excretion of melatonin in ADHD subtypes and (2) the effect of chronic administration of methylphenidate, as well as the effects on symptomatology, 136 children with ADHD (Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision: DSM-IV-TR criteria) were divided into subgroups using the “Children’s Depression Inventory” (CDI). Blood samples were drawn at 20:00 and 09:00 h, and urine was collected between 21:00 and 09:00 h, at inclusion and after 4.61 ± 2.29 months of treatment. Melatonin and its urine metabolite were measured by radioimmunoassay RIA. Factorial analysis was performed using STATA 12.0. Melatonin was higher predominantly in hyperactive-impulsive/conduct disordered children (PHI/CD) of the ADHD subtype, without the influence of comorbid depressive symptoms. Methylphenidate ameliorated this comorbidity without induction of any changes in the serum melatonin profile, but treatment with it was associated with a decrease in 6-s-melatonin excretion in both ADHD subtypes. Conclusions: In untreated children, partial homeostatic restoration of disrupted neuroendocrine equilibrium most likely led to an increased serum melatonin in PHI/CD children. A differential cerebral melatonin metabolization after methylphenidate may underlie some of the clinical benefit.