Di-n-Butyl-, Tri-n-Butyl- and Triphenyltin dl-Terebates: Synthesis, Characterization and In Vitro Antitumour Activity

Di-n-butyltin, tri-n-butyltin and triphenyltin terebates were screened against several human tumour cell lines and found comparably or more active than carboplatin, cis-platin, 5-fluorouracil, methotrexate and doxorubicin, some reference compounds used clinically.     

Architected Polymer Foams via Direct Bubble Writing

Polymer foams are cellular solids composed of solid and gas phases, whose mechanical, thermal, and acoustic properties are determined by the composition, volume fraction, and connectivity of both phases. A new high‐throughput additive manufacturing method, referred to as direct bubble writing, for creating polymer foams with locally programmed bubble size, volume fraction, and connectivity is reported. Direct bubble writing relies on rapid generation and patterning of liquid shell–gas core droplets produced using a core–shell nozzle. The printed polymer foams are able to retain their overall shape, since the outer shell of these bubble droplets consist of a low‐viscosity monomer that is rapidly polymerized during the printing process. The transition between open‐ and closed‐cell foams is independently controlled by the gas used, while the foam can be tailored on‐the‐fly by adjusting the gas pressure used to produce the bubble droplets. As exemplars, homogeneous and graded polymer foams in several motifs, including 3D lattices, shells, and out‐of‐plane pillars are fabricated. Conductive composite foams with controlled stiffness for use as soft pressure sensors are also produced.     

Advanced water treatment with manganese oxide for the removal of 17alpha-ethynylestradiol (EE2)

Municipal wastewater is supposed to be one of the most important sources of endocrine-disrupting compounds (EDCs) in water. Therefore, advanced treatments and cost-efficient techniques should be developed to prevent the spread of this type of pollution into the environment. In this view, experiments were conducted in which the removal of 17alpha-ethynylestradiol (EE2), a synthetic and persistent estrogen, from water was monitored in three upstream bioreactors (UBRs), filled with, respectively, sand, granulated activated carbon (GAC) and MnO(2) granules. Tap water, spiked with 15,000ngEE2/L was filtered through the reactors with a hydraulic retention time of approximately 1h. The removal of EE2 in the sand, GAC and MnO(2) reactors was, respectively, 17.3%,>99.8% and 81.7%. The removal in the GAC reactor was mainly due to adsorption. The MnO(2) reactor, however, removed significantly more EE2 than could be predicted from its adsorption capacity, probably thanks to its catalytic properties. These catalytic properties could make it a cost-efficient technique for the removal of EE2, but further research at more environmentally relevant concentrations is needed.     

Anaerobic treatment of wastes containing methanol and higher alcohols

Experiments have been performed to ascertain the feasibility of anaerobic digestion for the treatment of an alcoholic waste (i.e. fusel oil), consisting of approx. 50% methanol and 50% higher alcohols. Batch experiments as well as continuous experiments have been conducted. The continuous experiments have been carried out using the “Upflow Anaerobic Sludge Blanket” (UASB-) process. As inoculum a sugar beet waste grown and highly settleable and active anaerobic sludge (SBA-sludge) has been used. The SBA-sludge was shown to be superior to digested sewage sludge as seed material for an anaerobic treatment process, because—although it in fact is adapted to the fermentation of volatile fatty acids (VFA)—it does not have any significant difficulty with respect to the methanogenesis of the alcohols present in the fusel oil waste. The breakdown of higher alcohols starts immediately and that of methanol within a few days, depending on the initial load applied. In the UASB-experiments sludge loads up to 0.6 kg COD·kg VSS⁻¹·day⁻¹ could already be well accommodated within 1 week, so that within this period a space load could be handled as high as 20 kg COD·m⁻³·day⁻¹, simply by supplying the reactor with approx. 30 kg SBA-VSS·m⁻³ averaged over the total reactor volume.Contrary to recent findings of Smith & Mah (Appl. envir. Microbial. 36, 870–879, 1978), which were obtained with a pure culture of Methanosarcina barkeri, the sludge is capable of fermenting VFA and methanol rapidly and simultaneously, provided the conditions for VFA and methanol fermentation are favourable. However, as in previous experiments with aqueous solutions of methanol (Lettinga et al., Water Res. 13, 725–737, 1979), we observed that the digestion process can easily become upset, especially with respect to the degradation of VFA. Once again indications have been obtained that one or more trace elements are of eminent importance with respect to the stability of the process. At present the operation of a stable anaerobic treatment process for methanolic wastes cannot be guaranteed.     

Boston harbor outfall tunnel: An environmental imperative

In February 1989, the Massachusetts Water Resource Authority (MWRA) began the design and construction of a 15.3-km subsea tunnel and ocean riser system to discharge effluent in conjunction with the design and construction of a large secondary treatment plant. The court-mandated schedule required the tunnel and risers to be completed in July 1995. The paper discusses the project from the viewpoints of management, concept design and construction methods, including the ocean riser system. Key to th success of the project is the accuracy of the location of the risers. The design calls for a final tunnel alignment to be driven within 10 m of the riser shafts, beginning at a distance of 13.1 km from shore.     

Thermal optimization in transient thermoelasticity using response surface approximations

Response surface methodology is used to construct approximations to temperature and stress in transient thermoelastic analysis of non-linear systems. The analysis forms the core component of a heating/cooling rate maximization problem in which the ordinates of the ambient temperature at equally spaced time intervals are chosen as the design variables. Polynomials or cubic splines are fitted through the ordinates to describe the ambient temperature profile required for the convective heat transfer analysis. An experimental design method based on D-optimality and a genetic algorithm was used to select the design points used to create the approximations. Linear response surfaces were found to be sufficiently accurate, thereby minimizing the number of finite element analyses. Two examples of which one is a thick-walled pressure vessel are used to illustrate the methodology. © 1998 John Wiley & Sons, Ltd.     

Engineering yeast for efficient cellulose degradation

Saccharomyces cerevisiae produces several β-1,3-glucanases, but lacks the multicomponent cellulase complexes that hydrolyse the β-1,4-linked glucose polymers present in cellulose-rich biomass as well as in haze-forming glucans in certain wines and beers. We have introduced into S. cerevisiae a functional cellulase complex for efficient cellulose degradation by cloning the Endomyces fibuliger cellobiase (BGL1) gene and co-expressing it with the Butyrivibrio fibrisolvens endo-β-1,4-glucanase (END1), the Phanerochaete chrysosporium cellobiohydrolase (CBH1) and the Ruminococcus flavefaciens cellodextrinase (CEL1) gene constructs in this yeast. The END1, CBH1 and CEL1 genes were inserted into yeast expression/secretion cassettes. Expression of END1, CBH1 and CEL1 was directed by the promoter sequences derived from the alcohol dehydrogenase II (ADH2), the phosphoglycerate kinase I (PKG1) and the alcohol dehydrogenase I (ADH1) genes, respectively. In contrast, BGL1 was expressed under the control of its native promoter. Secretion of End1p and Cel1p was directed by the signal sequence of the yeast mating pheromone α-factor (MFα1), whereas Cbh1p and Bgl1p were secreted using their authentic leader peptides. The construction of a fur1 ura3 S. cerevisiae strain allowed for the autoselection of this multicopy URA3-based plasmid in rich medium. S. cerevisiae transformants secreting biologically active endo-β-1,4-glucanase, cellobiohydrolase, cellodextrinase and cellobiase were able to degrade various substrates including carboxymethylcellulose, hydroxyethylcellulose, laminarin, barley glucan, cellobiose, polypectate, birchwood xylan and methyl-β-d-glucopyranoside. This study could lead to the development of industrial strains of S. cerevisiae capable of converting cellulose in a one-step process into commercially important commodities. © 1998 John Wiley & Sons, Ltd.     

Measuring free metal ion concentrations in situ in natural waters using the Donnan Membrane Technique

Metal toxicity is not related to the total but rather to the free or labile metal ion concentration. One of the techniques that can be used to measure several free metal ion concentrations simultaneously is the Donnan Membrane Technique (DMT) in combination with the inductively coupled plasma-mass spectrometer (ICP-MS). However, free metal ion concentrations in natural waters are commonly below the detection limit of ICP-MS. We decreased the detection limit by making use of a ligand, and we developed a field DMT cell that can be applied in situ in natural waters. A kinetic approach can be used to calculate free metal ion concentrations when the equilibrium time becomes too large. The field DMT measured in situ in natural waters a free metal ion concentration ranging from 0.015% (Cu) to 13% (Zn) of a total metal concentration ranging from 0.06 nM (Cd) to 237 nM (Zn). The free metal ion concentrations were difficult to predict using an equilibrium speciation model, probably due to the uncertainty in the nature of the dissolved organic matter or the presence of other reactive colloids. It is shown that DMT can follow changes in the free metal ion concentration on times scales less than a day under certain conditions.