Oxidations of thio ketones by singlet and triplet oxygen

Oxidation of di-tert-butyl thioketone (1) and 2,2,4,4-tetramethylcyclobutylth ioketone (2) by singlet oxygen yields the corresponding sulfine and ketone; in the case of 1 the sulfine is the major product, whereas in 2 it is the ketone. 1,2,3-Dioxathietane has been suggested as the precursor for the ketones, and the zwitterionic/diradid peroxide is believed to be a common primary intermediate for both sulfine and ketone. Steric influence is felt both during primary interaction between singlet oxygen and thioketone and during the partitioning of the peroxide intermediate. Steric interaction is suggested as the reason for variations in the product distribution between 1 and 2. Singlet oxygen is also generated through energy transfer from the triplet state of thioketones. These excited states also directly react with oxygen to yield ketone.

Self-assembly of a Pd-II neutral molecular rectangle via a new organometallic Pd-2(II) molecular clip and oxygen donor linker

Two components self-assembly of a Pd-4 neutral molecular rectangle driven by Pd-O bond coordination has been achieved and this pi-electron rich rectangle shows fluorescence quenching in presence of nitroaromatics, which are the chemical signatures of many explosives.

Chlorination of silver dosed with potassium and barium in presence of oxygen: An X-ray photoelectron spectroscopy study

XPS studies show that the presence of chemisorbed chlorine stabilizes and also enhances molecular dioxygen species on Ag surfaces dosed with either K or Ba. The surface atomic oxygen is found to become depleted on chlorination. The variation in the nature of surface species with respect to temperature shows chlorine-induced diffusion of atomic oxygen into the subsurface region at 300 K. For coverages of potassium up to 8 × 1014 atoms/cm2, preferential chloridation of Ag occurs while at higher potassium coverages, KCl formation is distinctly observed on the surface. In the case of barium, two types of adsorbed chlorine species, Cl(α) and Cl(β), associated with Ag and Ba, respectively, are clearly seen even at low barium coverages. This is believed to be due to the higher valence occupation of barium compared to potassium. The Cl(α) species associated with Ag is found to occupy a preferred site on both K- and Ba-dosed surfaces, involving chemisorptive replacement of O(α) to the subsurface region.

Influence of harvesting strategy on nutrient supply and production of dairy cows consuming diets based on grass and red clover silage

The main objective of this thesis was to elucidate the effects of regrowth grass silage and red clover silage on nutrient supply and milk production of dairy cows as compared with primary growth grass silages. In the first experiment (publication I), two primary growth and four regrowth grass silages were harvested at two stages of growth. These six silages were fed to 24 lactating dairy cows with two levels of concentrate allowance. Silage intake and energy corrected milk yield (ECM) responses, and the range in these response variables between the diets, were smaller when regrowth silages rather than primary growth silages were fed. Milk production of dairy cows reflected the intake of metabolizable energy (ME), and no differences in the ME utilization were found between the diets based on silages harvested from primary growth and regrowth. The ECM response to increased concentrate allowance was, on average, greater when regrowth rather than primary growth silages were fed. In the second experiment (publication II), two silages from primary growth and two from regrowth used in I were fed to rumen cannulated lactating dairy cows. Cows consumed less feed dry matter (DM), energy and protein, and produced less milk, when fed diets based on regrowth silages rather than primary growth silages. Lower milk production responses of regrowth grass silage diets were mainly due to the lower silage DM intake, and could not be accounted for by differences in energy or protein utilization. Regrowth grass silage intake was not limited due to neutral detergent fibre (NDF) digestion or rumen fill or passage kinetics. However, lower intake may be at least partly attributable to plant diseases such as leaf spot infections, dead deteriorating material or abundance of weeds, which are all higher in regrowth compared with primary growth, and increase with advancing regrowth. In the third experiment (publications III and IV), red clover silages and grass silages harvested at two stages of growth, and a mixed diet of red clover and grass silages, were fed to five rumen cannulated lactating dairy cows. In spite of the lower average ME intake for red clover diets, the ECM production remained unchanged suggesting more efficient utilisation of ME for red clover diets compared with grass diets. Intake of N, and omasal canal flows of total non-ammonia N (NAN), microbial and non-microbial NAN were higher for red clover than for grass silage diets, but were not affected by forage maturity. Delaying the harvest tended to decrease DM intake of grass silage and increase that of red clover silage. The digestion rate of potentially digestible NDF was faster for red clover diets than for grass silage diets. Delaying the harvest decreased the digestion rate for grass but increased it for red clover silage diets. The low intake of early-cut red clover silage could not be explained by silage digestibility, fermentation quality, or rumen fill but was most likely related to the nutritionally suboptimal diet composition because inclusion of moderate quality grass silage in mixed diet increased silage DM intake. Despite the higher total amino acid supply of cows fed red clover versus grass silage diets, further milk production responses on red clover diets were possibly compromised by an inadequate supply of methionine as evidenced by lower methionine concentration in the amino acid profile of omasal digesta and plasma. Increasing the maturity of ensiled red clover does not seem to affect silage DM intake as consistently as that of grasses. The efficiency of N utilization for milk protein synthesis was lower for red clover diets than for grass diets. It was negatively related to diet crude protein concentration similarly to grass silage diets.

Simian Virus 40 Small T Antigen Activates AMPK and Triggers Autophagy To Protect Cancer Cells from Nutrient Deprivation

As tumors grow larger, they often experience an insufficient supply of oxygen and nutrients. Hence, cancer cells must develop mechanisms to overcome these stresses. Using an in vitro transformation model where the presence of the simian virus 40 (SV40) small T (ST) antigen has been shown to be critical for tumorigenic transformation, we investigated whether the ST antigen has a role to play in regulating the energy homeostasis of cancer cells. We find that cells expressing the SV40 ST antigen (+ST cells) are more resistant to glucose deprivation-induced cell death than cells lacking the SV40 ST antigen (-ST cells). Mechanistically, we find that the ST antigen mediates this effect by activating a nutrient-sensing kinase, AMP-activated protein kinase (AMPK). The basal level of active, phosphorylated AMPK was higher in +ST cells than in -ST cells, and these levels increased further in response to glucose deprivation. Additionally, inhibition of AMPK in +ST cells increased the rate of cell death, while activation of AMPK in -ST cells decreased the rate of cell death, under conditions of glucose deprivation. We further show that AMPK mediates its effects, at least in part, by inhibiting mTOR (mammalian target of rapamycin), thereby shutting down protein translation. Finally, we show that +ST cells exhibit a higher percentage of autophagy than -ST cells upon glucose deprivation. Thus, we demonstrate a novel role for the SV40 ST antigen in cancers, where it functions to maintain energy homeostasis during glucose deprivation by activating AMPK, inhibiting mTOR, and inducing autophagy as an alternate energy source.

Regulating supply chains to protect road transport workers: An early assessment of the road safety remuneration tribunal

The Road Safety Remuneration Act 2012 (Cth) (the Act) explicitly enables the Road Safety Remuneration Tribunal to make orders that can impose binding requirements on all the participants in the road transport supply chain, including consignors and consignees at the apex the chain, for the pay and safety of both employee and independent contractor drivers. The tribunal is also specifically empowered to make enforceable orders to reduce or remove remuneration related incentives and pressures that contribute to unsafe work practices in the road transport industry. Recently the tribunal handed down its first order. The article considers whether, and the degree to which, the tribunal has been willing to exercise its explicit power to impose enforceable obligations on consignors and consignees — such as large supermarket chains — at the apex of road transport supply chains. It examines the substance and extent of the obligations imposed by the tribunal, including whether the tribunal has exercised the full range of powers vested in it by the Act. We contend that the tribunal’s first order primarily imposes obligations on direct work providers and drivers without making large, powerful consignors and consignees substantively responsible for driver pay and safety. We argue that the tribunal’s first order could have more comprehensively fulfilled the objectives of the Act by more directly addressing the root causes of low pay and poor safety in the road transport industry.

Influence of oxygen content of the certain types of biodiesels on particulate oxidative potential

Oxidative potential (OP) is related to the organic phase, specifically to its oxygenated organic fraction (OOA). Furthermore, the oxygen content of fuel molecules has significant influence on particulate OP. Thus, this study aimed to explore the actual dependency of the OOA and ROS to the oxygen content of the fuel. In order to reach the goal, different biodiesels blends, with various ranges of oxygen content; have been employed. The compact time of flight aerosol mass spectrometer (c-ToF AMS) enabled better identification of OOA. ROS monitored by using two assays: DTT and BPEA-nit. Despite emitting lower mass, both assays agreed that oxygen content of a biodiesel is directly correlated with its OOA, and highly related to its OP. Hence, the more oxygen included in the considered biodiesels, the higher the OP of PM emissions. This highlights the importance of taking oxygen content into account while assessing emissions from new fuel types, which is relevant from a health effects standpoint.

Molecularly adsorbed oxygen on metals: electron spectroscopic studies

Oxygen is shown to adsorb molecularly on gold as well as on Ag and Pt. UV and X-ray photoelectron spectroscopy and Auger electron spectroscopy have been employed to investigate electron states of molecularly adsorbed oxygen.

Rates of oxidation of thioketones by singlet oxygen

Rate constants for the quenching of singlet oxygen by a series of thioketones were measured by monitoring the inhibition of the self-sensitized photooxidation of rubrene. A correlation of the quenching rate with the nature of the substituents on the aromatic rings for the diarylthioketones and arylalkylthioketones was found, whereas correlation with the n orbital ionization potential was observed for the dialkylthioketones.

An alternative approach to selective sea water oxidation for hydrogen production

Sea water electrolysis is one of the promising ways to produce hydrogen since it is available in plentiful supply on the earth. However, in sea water electrolysis toxic chlorine evolution is the preferred reaction over oxygen evolution at the anode. In this work, research has been focused on the development of electrode materials with a high selectivity for oxygen evolution over chlorine evolution. Selective oxidation in sea water electrolysis has been demonstrated by using a cation-selective polymer. We have used a perm-selective membrane (Nafion®), which electrostatically repels chloride ions (Cl−) to the electrode surface and thereby enhances oxygen evolution at the anode. The efficiency and behaviour of the electrode have been characterized by means of anode current efficiency and polarization studies. The surface morphology of the electrode has been characterized by using a scanning electron microscope (SEM). The results suggest that nearly 100% oxygen evolution efficiency could be achieved when using an IrO2/Ti electrode surface-modified by a perm-selective polymer.

Polymerization of Ethene and Branched α-olefins with Group IV Metal Complexes Bearing Nitrogen- and Oxygen-Based Ligands

The commodity plastics that are used in our everyday lives are based on polyolefin resins and they find wide variety of applications in several areas. Most of the production is carried out in catalyzed low pressure processes. As a consequence polymerization of ethene and α-olefins has been one of the focus areas for catalyst research both in industry and academia. Enormous amount of effort have been dedicated to fine tune the processes and to obtain better control of the polymerization and to produce tailored polymer structures The literature review of the thesis concentrates on the use of Group IV metal complexes as catalysts for polymerization of ethene and branched α-olefins. More precisely the review is focused on the use of complexes bearing [O,O] and [O,N] type ligands which have gained considerable interest. Effects of the ligand framework as well as mechanical and fluxional behaviour of the complexes are discussed. The experimental part consists mainly of development of new Group IV metal complexes bearing [O,O] and [O,N] ligands and their use as catalysts precursors in ethene polymerization. Part of the experimental work deals with usage of high-throughput techniques in tailoring properties of new polymer materials which are synthesized using Group IV complexes as catalysts. It is known that the by changing the steric and electronic properties of the ligand framework it is possible to fine tune the catalyst and to gain control over the polymerization reaction. This is why in this thesis the complex structures were designed so that the ligand frameworks could be fairly easily modified. All together 14 complexes were synthesised and used as catalysts in ethene polymerizations. It was found that the ligand framework did have an impact within the studied catalyst families. The activities of the catalysts were affected by the changes in complex structure and also effects on the produced polymers were observed: molecular weights and molecular weight distributions were depended on the used catalyst structure. Some catalysts also produced bi- or multi-modal polymers. During last decade high-throughput techniques developed in pharmaceutical industries have been adopted into polyolefin research in order to speed-up and optimize the catalyst candidates. These methods can now be regarded as established method suitable for both academia and industry alike. These high-throughput techniques were used in tailoring poly(4-methyl-1-pentene) polymers which were synthesized using Group IV metal complexes as catalysts. This work done in this thesis represents the first successful example where the high-throughput synthesis techniques are combined with high-throughput mechanical testing techniques to speed-up the discovery process for new polymer materials.

Polymer supported metal complexes as catalysts for oxidation of thiosalts by molecular oxygen IV. Quaternised poly(4-vinyl pyridine) complexes with Cu2+ as template

Copper(II) complexes of quaternised poly(4-vinylpyridine) (PVP) of different degrees of quaternisation and copper content have been prepared by crosslinking the polymer with 1,2-dibromoethane in the presence of Cu2+ ion as template. The stability constant of the PVP---Cu(II) complexes is found to increase with the degree of crosslinking quaternisation of the resin, but the rate at which Cu2+ is adsorbed by the resin decreases. An optimum combination of both stability and rate can be achieved with a moderate degree (31%) of crosslinking. A kinetic study reveals that quaternisation increases significantly the catalytic activity of the complex for the oxidation of S2O2−3 by O2 compared with PVP----Cu(II) without quaternisation, but it deactivates the complex for the oxidation of both S3O2−6 and S4O2−6. The batch reactor oxidation kinetics at pH 2.16, where the rate is observed to be maximum, is well explained by the Langmuir—Hinshelwood model assuming the coordination of both O2 and thioanion to Cu(II) as a precursor to the oxidation reaction.

Oxidation of Thioketens by Singlet Oxygen and Ozone

Di-t-butylthioketen (1) readily reacts with SINGLET-OXYGaEdNdi tion to heterocumulenes is of current singlet oxygen to yield unexpected products (based on interest1 and products derived from the interaction of the behaviour of other heterocumulenes) and reacts with singlet oxygen with the carbon-carbon double bond have ozone to give, quantitatively, the corresponding sul- been characterised. Investigations of the oxidation of phoxide (2). thioketens using di-t-butylthioketen (1) as a model have