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BackgroundIn the face of the COVID-19 pandemic, the Defence Science and Technology Laboratory (Dstl) and Defence Pathology combined to form the Defence Clinical Lab (DCL), an accredited (ISO/IEC 17025:2017) high-throughput SARS-CoV-2 PCR screening capability for military personnel.Laboratory structure and resourceThe DCL was modular in organisation, with laboratory modules and supporting functions combining to provide the accredited SARS-CoV-2 (envelope (E)-gene) PCR assay. The DCL was resourced by Dstl scientists and military clinicians and biomedical scientists.Laboratory resultsOver 12 months of operation, the DCL was open on 289 days and tested over 72 000 samples. Six hundred military SARS-CoV-2-positive results were reported with a median E-gene quantitation cycle (Cq) value of 30.44. The lowest Cq value for a positive result observed was 11.20. Only 64 samples (0.09%) were voided due to assay inhibition after processing started.ConclusionsThrough a sustained effort and despite various operational issues, the collaboration between Dstl scientific expertise and Defence Pathology clinical expertise provided the UK military with an accredited high-throughput SARS-CoV-2 PCR test capability at the height of the COVID-19 pandemic. The DCL helped facilitate military training and operational deployments contributing to the maintenance of UK military capability. In offering a bespoke capability, including features such as testing samples in unit batches and oversight by military consultant microbiologists, the DCL provided additional benefits to the UK Ministry of Defence that were potentially not available from other SARS-CoV-2 PCR laboratories. The links between Dstl and Defence Pathology have also been strengthened, benefitting future research activities and operational responses.

In the era of precision cosmology, it is essential to determine the Hubble constant empirically with an accuracy of one per cent or better1. At present, the uncertainty on this constant is dominated by the uncertainty in the calibration of the Cepheid period–luminosity relationship2,3(also known as the Leavitt law). The Large Magellanic Cloud has traditionally served as the best galaxy with which to calibrate Cepheid period–luminosity relations, and as a result has become the best anchor point for the cosmic distance scale4,5. Eclipsing binary systems composed of late-type stars offer the most precise and accurate way to measure the distance to the Large Magellanic Cloud. Currently the limit of the precision attainable with this technique is about two per cent, and is set by the precision of the existing calibrations of the surface brightness–colour relation5,6. Here we report a calibration of the surface brightness–colour relation with a precision of 0.8 per cent. We use this calibration to determine a geometrical distance to the Large Magellanic Cloud that is precise to 1 per cent based on 20 eclipsing binary systems. The final distance is 49.59 ± 0.09 (statistical) ± 0.54 (systematic) kiloparsecs.

Background:: Obesity is a risk factor for incident prostate cancer (PC) as well as risk of disease progression and mortality. We hypothesized that men diagnosed with lower-risk PC and who elected active surveillance (AS) for their cancer management would likely initiate lifestyle changes that lead to weight loss. Methods:: Patients were enrolled in the Prostate Active Surveillance Study (PASS), a multicenter prospective biomarker discovery and validation study of men who have chosen AS for their PC. Data from 442 men diagnosed with PC within 1 year of study entry who completed a standard of care 12-month follow-up visit were analyzed. We examined the change in weight and body mass index (BMI) over the first year of study participation. Results:: After 1 year on AS, 7.5% (33/442) of patients had lost 5% or more of their on-study weight. The proportion of men who lost 5% or more weight was similar across categories of baseline BMI: normal/underweight (8%), overweight (6%) and obese (10%, ?2test P=0.44). The results were similar for patients enrolled in the study 1 year or 6 months after diagnosis. By contrast, after 1 year, 7.7% (34/442) of patients had gained >5% of their weight. Conclusions:: Only 7.5% of men with low-risk PC enrolled in AS lost a modest (?5%) amount of weight after diagnosis. Given that obesity is related to PC progression and mortality, targeted lifestyle interventions may be effective at this ‘teachable moment’, as men begin AS for low-risk PC.

We determine the metallicity distribution function (MDF) of the Galactic halo by means of a sample of 1638 metal-poor stars selected from the Hamburg/ESO objective-prism survey (HES). The sample was corrected for minor biases introduced by the strategy for spectroscopic follow-up observations of the metal-poor candidates, namely “best and brightest stars first”. Comparison of the metallicities [Fe/H] of the stars determined from moderate-resolution (i.e., $R\sim 2000$) follow-up spectra with results derived from abundance analyses based on high-resolution spectra (i.e., $R>20\,000$) shows that the [Fe/H] estimates used for the determination of the halo MDF are accurate to within 0.3 dex, once highly C-rich stars are eliminated. We determined the selection function of the HES, which must be taken into account for a proper comparison between the HES MDF with MDFs of other stellar populations or those predicted by models of Galactic chemical evolution. The latter show a reasonable agreement with the overall shape of the HES MDF for ${\rm [Fe/H]} > -3.6$, but only a model of Salvadori et al. (2007) with a critical metallicity for low-mass star formation of $Z_{\rm cr}=10^{-3.4}~Z_{\odot}$reproduces the sharp drop at ${\rm [Fe/H]} \sim -3.6$present in the HES MDF. Although currently about ten stars at ${\rm [Fe/H]} < -3.6$are known, the evidence for the existence of a tail of the halo MDF extending to ${\rm [Fe/H]} \sim -5.5$is weak from the sample considered in this paper, because it only includes two stars ${\rm [Fe/H]} < -3.6$. Therefore, a comparison with theoretical models has to await larger statistically complete and unbiased samples. A comparison of the MDF of Galactic globular clusters and of dSph satellites to the Galaxy shows qualitative agreement with the halo MDF, derived from the HES, once the selection function of the latter is included. However, statistical tests show that the differences between these are still highly significant.

Aims. Our aims are twofold. First we aim to evaluate the robustness and accuracy of stellar parameters and detailed elemental abundances that can be derived from high-resolution spectroscopic observations of microlensed dwarf and subgiant stars. We then aim to use microlensed dwarf and subgiant stars to investigate the abundance structure and chemical evolution of the Milky Way Bulge. Contrary to the cool giant stars, with their extremely crowded spectra, the dwarf stars are hotter, their spectra are cleaner, and the elemental abundances of the atmospheres of dwarf and subgiant stars are largely untouched by the internal nuclear processes of the star.

Background:: Expanding interest in and use of active surveillance for early state prostate cancer (PC) has increased need for prognostic biomarkers. Using a multi-institutional tissue microarray resource including over 1000 radical prostatectomy samples, we sought to correlate Ki67 expression captured by an automated image analysis system with clinicopathological features and validate its utility as a clinical grade test in predicting cancer-specific outcomes. Methods:: After immunostaining, the Ki67 proliferation index (PI) of tumor areas of each core (three cancer cores/case) was analyzed using a nuclear quantification algorithm (Aperio). We assessed whether Ki67 PI was associated with clinicopathological factors and recurrence-free survival (RFS) including biochemical recurrence, metastasis or PC death (7-year median follow-up). Results:: In 1004 PCs (∼4000 tissue cores) Ki67 PI showed significantly higher inter-tumor (0.68) than intra-tumor variation (0.39). Ki67 PI was associated with stage (P&lt;0.0001), seminal vesicle invasion (SVI, P=0.02), extracapsular extension (ECE, P&lt;0.0001) and Gleason score (GS, P&lt;0.0001). Ki67 PI as a continuous variable significantly correlated with recurrence-free, overall and disease-specific survival by multivariable Cox proportional hazard model (hazards ratio (HR)=1.04-1.1, P=0.02–0.0008). High Ki67 score (defined as ⩾5%) was significantly associated with worse RFS (HR=1.47, P=0.0007) and worse overall survival (HR=2.03, P=0.03). Conclusions:: In localized PC treated by radical prostatectomy, higher Ki67 PI assessed using a clinical grade automated algorithm is strongly associated with a higher GS, stage, SVI and ECE and greater probability of recurrence.

We present results of a photometric survey for variable stars in the field of the globular cluster ωCentauri. The observed region was centered roughly on the cluster core and covered 644 arcmin2. The cluster was monitored on 59 nights in 1999 and 2000. A total of 117 new variables were identified. Among them there are 17 RR Lyr-type stars, 35 SX Phe variables and 26 eclipsing binaries. A comprehensive catalog including all variable stars so far reported from the cluster field is presented. We list basic photometric properties and provide finding charts for a total of 392 objects. For 313 of them new $\it BV$light curves were obtained. The presented sample includes several interesting variables, such as SX Phe stars with extremely short periods of pulsation and several candidates for pulsating K giants. Optical counterparts to 9 X-ray sources detected by XMM and Chandra telescopes were identified: all of them are likely to be foreground variables not related to the cluster.

We report the identification of 36 new variable stars located in the central field of the globular cluster M 22. The sample includes 10 SX Phe stars, 7 RR Lyr stars and 17 candidate eclipsing binaries. A low-amplitude variable was detected among the extended horizontal branch stars.

We present CCD photometry of SX Phe variables in the field of the globular cluster M 55. We have discovered 27 variables, three of which are probable members of the Sagittarius dwarf galaxy. All of the SX Phe stars in M 55 lie in the blue straggler region of the cluster color-magnitude diagram. Using period ratio information we have identified the radial pulsation modes for one of the observed variables. Inspection of the period-luminosity distribution permits the probable identifications of the pulsation modes for most of the rest of the stars in the sample. We have determined the slope of the period-luminosity relation for SX Phe stars in M 55 pulsating in the fundamental mode. Using this relation and the HIPPARCOS data for SX Phe itself, we have estimated the apparent distance modulus to M 55 to be $(m-M)_V=13.86\pm0.25$mag.

We present V-band CCD photometry of 65 RR Lyr variables from the globular cluster M 5. We have estimated the basic physical parameters for 16 RRc stars and 26 RRab stars using a Fourier decomposition of the light curves of the variables. The mean values of mass, luminosity, effective temperature and relative helium abundance for the RRc stars are measured to be ${\cal M}=0.54~{\cal M}_\odot$, $\log (L/L_\odot)=1.69$, $T_{\rm eff}=7353$K and $Y=0.28$, respectively. For the RRab variables the derived mean values of absolute magnitude, metallicity and effective temperature are: MV=0.81, ${\rm [Fe/H]}=-1.23$and $T_{\rm eff}=6465$K. We find that the Vamplitude of an RRab star for a given period is a function of metal abundance rather than Oosterhoff type.
We find significant problems with the calibration of both the zero point and the scale of the luminosities measured with the Fourier technique. The apparent distance modulus derived from RRc stars is equal to $14.47\pm0.11$and it is in good agreement with recent determinations. On the other hand distance modulus obtained from the sample of RRab stars (calibrated by the Baade-Wesselink observations of field RR Lyr variables) is significantly smaller and equal to $14.27\pm0.04$

Trough photometric methods we have constructed the luminosity function for the southern open cluster NGC 2477 down to Mv≈12. We present $R-I$color-magnitude diagrams and near-infrared color-color diagrams, which allow us to separate statistically the cluster stars from the field ones, numerous because of the galactic latitude of the cluster. Our luminosity function (LF) reproduces some features obtained by other authors, namely, a dip at Mv≈7, and a probable maximum at Mv≈12. The method developed to separate cluster stars from field stars could be of interest to other astronomical problems.

Environmental factors, such as photoperiod and heat stress, can be manipulated during the dry period to influence health, productivity, and reproductive performance of dairy cows in their subsequent lactation. The impacts of photoperiod and heat stress on subsequent lactation are related to alterations in prolactin (PRL) signaling and may affect the expression of pregnancy-specific protein B (PSPB). Additionally, exposure of cows to heat stress during the dry period decreases gestation length; however, the mechanism involved in this process is unknown. The objective of these experiments was to evaluate the influence of environmental factors (i.e., heat stress and photoperiod) during late gestation (i.e., dry period) on PSPB concentrations in plasma of dairy cows. In Exp. 1, cows were dried off in the summer months approximately 46 d before expected calving and assigned randomly to heat stress (HT; n= 30) or cooling (CL; n= 30) treatment. Cooling cows were housed with sprinklers, fans, and shade, whereas HT cows were provided only shade. In Exp. 2, cows were dried off at approximately 60 d before expected calving in summer/fall months and randomly assigned to 3 treatments: long day photoperiod (LDPP: 16L:8D; n= 15), short day photoperiod (SDPP: 8L:16D; n= 14) and SDPP+PRL implant (12 mg/d of PRL at 28 d or 16 mg/d of PRL at 39 d; n= 11). In both experiments, plasma samples were collected at dry off and at −32, −18, −7, −3 and 0 d relative to calving. In Exp. 1, greater concentrations of PSPB were detected in plasma of CL versus HT cows (388.3 ± 24.7 vs. 287.4 ± 23.8 ng/mL; P< 0.01). Concentrations of PSPB did not differ between −46 to −18 d before calving (66.0 ng/mL). However, PSPB concentrations were greater (P< 0.01) for CL cows at d −7 (534.7 > 357.2 ng/mL), −3 (807.2 > 572.2 ng/mL) and 0 (800.8 > 563.5 ng/mL) relative to calving. Additionally, HT cows in Exp. 1 had increased PRL plasma concentrations compared with CL cows (21.01 ± 1.6 vs. 13.78 ± 1.6 ng/mL). In Exp. 2, no differences were detected in plasma concentrations of PSPB (ng/mL) among LDPP, SDPP, or SDPP+PRL groups on d −60 (41.5), −32 (51.7), −18 (58.5), −7 (532.9), −3 (838.2), and 0 (729.4) relative to parturition. Photoperiodic PRL concentrations were 10.81, 7.84, and 4.22 ng/mL for LDPP, SDPP+ PRL, and SDPP, respectively. Results indicate that HT alters PSPB concentrations in late pregnancy, suggesting that placental activity is altered in cows exposed to excessive elevated temperatures around the time of calving. However, the mechanism involved likely is not associated with changes in PRL secretion.

AbstractBecause of the importance of accurate data for fission chain yields (FCYs) for many applications, we present a rigorous “clean sheet” evaluation of all available data to provide an accurate set of pertinent FCYs. Because some nuclear data (e.g., half-lives, branching ratios, etc.) have been refined since the original analyses, where possible we update the data and their associated uncertainties. This evaluation is particularly topical since there are differences in the nuclear data used by radiochemists at different laboratories internationally and since some experiments from the 1970s have been recently reexamined with details published for the first time.The focus of this work is the production of a small set of fission products (95Zr, 99Mo, 144Ce, 147Nd) from plutonium irradiated by fission spectrum neutrons. Because 147Nd is a common isotope used at several laboratories, its production rate is examined critically. We find that most of the interlaboratory discrepancies can be explained by a dependence of its yield on the energy of the neutron causing fission, so we consider in detail the statistical significance of this claim. The potential for neutron energy dependence of 147Nd production from plutonium was first recognized in 1977 by Maeck and recently raised again as a possibility by Chadwick. The data for 95Zr, by contrast, demonstrate no statistically significant energy-dependence trends, but the data at the higher energies demonstrate significant scatter.With the relatively small number of data points, and recognizing that measurement methods and technologies have likely significantly improved in the nearly 30 years since the last measurement, additional measurements to refine the assessment and improve the uncertainties may be warranted.

Photoperiod, or the daily sequence of light and dark, has dramatic effects on many physiological systems across animal species. Light patterns alter melatonin secretion profiles and, subsequently, the release profiles and circulating concentrations of several hormones that influence a variety of physiological responses. Although the impact of photoperiod on reproductive processes is perhaps the most common example, it is often the seasonal aspects of ovulation and anestrus that are considered. However, in cattle, the final phase of reproduction, that is, lactation, is significantly influenced by photoperiod. In contrast to short days (SDPP; 8 h light:16 h dark), exposure to long days (LDPP) of 16 to 18 h of light and 6 to 8 h of darkness increases milk yield 2 to 3 kg/d, regardless of the stage of lactation. There is evidence that this LDPP effect is due to increased circulating IGF-I, independent of any effect on GH concentrations. Cows that are housed under SDPP during the dry period have increased mammary growth and produce 3 to 4 kg/d more milk in the subsequent lactation compared with cows on LDPP when dry. While cows are on SDPP, circulating prolactin (PRL) diminishes but expression of PRL receptor increases in mammary, liver, and immune cells. Moreover, PRL signaling pathways within those tissues are affected by photoperiod. Further, replacement of PRL to cows on SDPP partially reverses the effects of SDPP on production in the next lactation. Thus, effects on dry cows are mediated through a PRL-dependent pathway. Before maturity, LDPP improve mammary parenchymal accumulation and lean body growth, which lead to greater yields in the first lactation. The accumulated evidence supports the concept that photoperiod manipulation can be harnessed to improve the efficiency of production across the life cycle of the dairy cow.

In the present study, we performed quantitative reverse-transcription PCR (qPCR) to examine changes in gene expression of prolactin receptor (long form: l-PRLR; short form: s-PRLR) and 20α-hydroxysteroid dehydrogenase (20α-HSD; EC 1.1.1.149) in the bovine corpus luteum (CL) throughout the estrous cycle and pregnancy. Western blotting was used to determine protein abundance. Bovine CL were collected and luteal stages (n = 6/stage) were classified by macroscopic observation as early (d 1 to 4 after ovulation), mid (d 5 to 10), late (d 11 to 17), and regressing (d 18 to 20). A CL of pregnancy (n = 6) was determined by the presence of conceptus (d 28 to term). The mRNA for both forms of PRLRwere expressed at all the luteal stages. Expression of s-PRLRand l-PRLRmRNA was less (P< 0.01) during early and regressing luteal stages compared with mid and late stages. Expression of s-PRLRmRNA in CL of pregnancy was greater (P< 0.01) than early, mid, and regressing CL and did not differ from late luteal stage expression. A greater (P< 0.01) expression of l-PRLRmRNA was observed in pregnant vs. early and regressing CL. In addition, qPCR showed the presence of 20α-HSDmRNA during all luteal stages of the estrous cycle, with the greatest (P< 0.01) expression observed in the regressing luteal stage. Western blotting revealed protein abundance of both PRLR isoforms during all luteal stages and pregnancy, with a predominance of the s-PRLR protein. Densitometry analysis indicated that protein abundances of s-PRLR were greater (P< 0.05) than l-PRLR during early, mid, and late luteal stages and did not differ during the regressing luteal stage. Protein abundances of 20α-HSD were least (P< 0.05) during the early luteal stage. In conclusion, results of the current study suggest a possible involvement of PRLR, especially s-PRLR, in the regulation of progesterone secretion and metabolism during the bovine estrous cycle and pregnancy.

We report precipitable water vapor (PWV) measurements made at Las Campanas Observatory using optical spectra of H2O lines obtained with the Magellan echelle spectrograph, and calculated using a robust technique that is accurate to 5%-10%. Calibration of the relationship between our PWV measurements and opacity values at 225 GHz was made possible by simultaneous observations with a tipping radiometer. Based on this calibration, we present Las Campanas Observatory wintertime precipitable water vapor statistics, measured using the tipping radiometer, during a 1.5 month campaign. The median value of 2.8 ± 0.3 mm is consistent with that measured at the nearby La Silla Observatory during the VLT site survey. We conclude that in the Southern hemisphere winter months, we can expect good conditions for infrared observing (?1.5 mm) approximately 10% of the time at Las Campanas Observatory.

The experimental data of the 28Si(α, t)29P and 28Si(α, 3He)29Si reactions at 45 MeV have been analysed in terms of full finite-range coupled-channels calculations. In the calculations, the reaction paths, direct and two step via the inelastic states of the initial and final nuclei have been treated in terms of the finite-range transfer theory. The spectroscopic amplitudes connecting the deformed initial and final nuclei in both the reactions are obtained from Nilsson's model. The data of both the reactions, populating the 1/2+, 3/2+ and 5/2+ states in the Kπ = 1/2+ band and the 3/2+ and 5/2+ states in the Kπ = 3/2+ band, are best described by about 20% mixing of between the two bands. The effects of normal Woods–Saxon (WS), squared WS and molecular type of α-nucleus potentials are also discussed.

The experimental data of the ²⁸Si(α, t)²⁹P and ²⁸Si(α, ³He)²⁹Si reactions at 45 MeV have been analysed in terms of full finite-range coupled-channels calculations. In the calculations, the reaction paths, direct and two step via the inelastic states of the initial and final nuclei have been treated in terms of the finite-range transfer theory. The spectroscopic amplitudes connecting the deformed initial and final nuclei in both the reactions are obtained from Nilsson's model. The data of both the reactions, populating the 1/2⁺, 3/2⁺ and 5/2⁺ states in the K^π = 1/2⁺ band and the 3/2⁺ and 5/2⁺ states in the K^π = 3/2⁺ band, are best described by about 20% mixing of between the two bands. The effects of normal Woods–Saxon (WS), squared WS and molecular type of α-nucleus potentials are also discussed.

Operationally exhausted metal working fluids are chemically mixed, produced in large quantities (400 000 tonnes year in the U.K.), and potentially environmentally toxic. It is essential to develop more reliable and economical approaches for their disposal. We investigated the effectiveness of a defined bacterial consortium, constructed specifically for treating metal-working fluid (MWF), and contrasted its performance to that of undefined inocula from activated sludge. Construction of the consortium was based on knowledge of the diversity of bacterial communities that naturally colonize MWF and determination of their catabolic abilities and tolerance to the chemical constituents. Chemical analysis of the inoculated MWF bioreactor revealed that, after 100 h at 28 °C, the defined inoculum reduced the pollution load by over 80% from an initial chemical oxygen demand of approximately 48 000 mg L^-1. The inocula performance was approximately 50% more effective than that of the undefined microbial community from the activated sludge. Furthermore, the performance of the constructed consortium was more reproducible than that of an undefined community, an essential feature for bioaugmentation treatment of industrial wastes.

Abstract. Allogenic and alloplastic bone graft substitutes serve either as bioinert or bioactive osteoconductors. Bioglass is a bioactive osteoconductor and also shows osteoproductive effects due to its high level of bioactivity. However, the material lacks some cohesiveness when used in augmenting certain bony surfaces, i.e. large or pleomorphic defects. The addition of medium molecular weight dextran modifies the particulate to a putty consistency and improves the handling characteristics. The objective of this study is to evaluate the influence of dextran upon the bioactive properties of Bioglass. Standardized bony defects in the lateral femoral condyles in adult New Zealand white rabbits were filled with one of five material groups: (1) autogenous bone; (2) Bioglass particulate; (3) Bioglass particulate mixed with dextran to a putty-like consistency; (4) a mixture of Bioglass and autogenous bone; (5) a mixture of Bioglass putty with autogenous bone. Postoperative healing was observed after periods of 2 days, 1, 2, 3, 6 and 12 weeks. Results showed no evidence of toxicity in the dextran-containing materials, and defects in all test groups showed 100% bony ingrowth within 6 weeks. The addition of medium molecular weight dextran did not appear to alter the bioactive properties of Bioglass and had no adverse influence upon the ingrowth of bone into the defect sites. Copyright 2002 International Association of Oral and Maxillofacial Surgeons

We present $V$ -band CCD photometry of 65 RR Lyr variables from the globular cluster M 5. We have estimated the basic physical parameters for 16 RRc stars and 26 RRab stars using a Fourier decomposition of the light curves of the variables. The mean values of mass, luminosity, effective temperature and relative helium abundance for the RRc stars are measured to be ${\cal M}=0.54 {\cal M}_\odot$ , $og (L/L_\odot)=1.69$ , $T_{ m eff}=7353$ K and $Y=0.28$ , respectively. For the RRab variables the derived mean values of absolute magnitude, metallicity and effective temperature are: $M_V=0.81$ , ${ m [Fe/H]}=-1.23$ and $T_{ m eff}=6465$ K. We find that the $V$ amplitude of an RRab star for a given period is a function of metal abundance rather than Oosterhoff type. We find significant problems with the calibration of both the zero point and the scale of the luminosities measured with the Fourier technique. The apparent distance modulus derived from RRc stars is equal to $14.47\pm0.11$ and it is in good agreement with recent determinations. On the other hand distance modulus obtained from the sample of RRab stars (calibrated by the Baade-Wesselink observations of field RR Lyr variables) is significantly smaller and equal to $14.27\pm0.04$

Three bacterial species (one flocculent, one non-flocculent and one filamentous) were grown in pure culture under varying conditions of dissolved oxygen and nutritional balance. 60 hour growth samples were harvested and the extracellular polymer extracted. The analytical data from the fermentation and the extracted polymer were used to explain how the presence of the bacteria in activated sludge might affect the settlement of that sludge.

The thermodynamics of V-H2O and V-S-H2O systems at 298 K are summarized in the form of potential-pH and activity-pH diagrams calculated from recently published critically assessed standard Gibbs energies of formation. At pH 9, as used in Stretford Processes, V-H2O potential-pH diagrams predicted that the V(v)/V(iv) couple involves HV2O73-/V4O92- ions. However, in neutral and alkaline solutions there is difficulty in discriminating between kinetic intermediates and thermodynamically stable solution species, some with V(v)/V(iv) mixed oxidation states. Hence, V18O4212- ions may be the stable V(iv) species, depending on the concentration, though no thermodynamic data are available to enable them to be included in potential-pH calculations. Potential-pH diagrams for V-S-H2O systems predicted an area of stability for VS4 in the pH range ˜2–8 and over a restricted potential range; neither VS nor VS2 were predicted to be stable under any conditions considered. In cyclic voltammetric experiments at Hg, Au and vitreous carbon electrodes, reduction of vanadium (v) species (probably HV2O73- ions) was found to be irreversible on a variety of electrode surfaces and, at lower potentials, led predominantly to the formation of solid oxide films (V3O5, V2O3 and VO) rather than to V(iv) solution species, of which V18O4212- ions probably predominate at equilibrium. In the presence of the large excess of HS- ions required to form VS43- ions, the electrochemical behaviour of a gold electrode was dominated by the former species.

Stretford processes use air to oxidize H2S in process and natural gases to elemental sulphur, by absorption in aqueous solution at about pH 9 and reaction of the resulting HS- ions with dissolved oxygen, in the presence of anthraquinone disulphonates (AQDS) and vanadium (v) species, which act as catalysts. Kinetic measurements of the reactions (AQ27DS + HS- ions), (V(v) + HS- ions) and (AQ27DSH- + O2), primarily used stopped flow spectrophotometry, as reported here, following papers on the electrochemical behaviour of the individual redox couples in Stretford Processes. The course of reaction (AQ27DS + HS- ions) was also followed with a gold bead indicator electrode, the potential of which was determined essentially by the AQ27DS/AQ27DSH- couple as the former species were reduced to the latter. Attempts to use51V NMR to characterize aqueous vanadium-sulphur complexes were inconclusive. A possible mechanism for Stretford Processes is postulated, involving polysulphide (Sn2-) ions as intermediates, which are oxidized to elemental sulphur by another intermediate, H2O2, formed by reaction of AQ27DSH- ions and dissolved oxygen.

Electrochemical reduction of aqueous anthraquinone 2,7 disulphonate (AQ27DS) solutions at pH 9.3 were studied at Hg, Au and Pt electrodes. Cyclic voltammograms showed about 40 mV potential separation of the single pair of current peaks, precluding a simple one or two electron process. Charge measurements in controlled potential exhaustive reductions indicated a 2 mole- per mol AQ27DS process leading to quinolate anions, whereas the partially reduced solution showed an EPR spectrum, indicating the presence of radical species, which, if produced directly, would involve only a 1 mole- per mol AQ27DS process. U.v.-visible and EPR spectra of the deep red partially reduced AQ27DS solutions showed that both radical anions (AQ27DS ·-) and fully reduced anthraquinolate were present; AQ27DS ·-radicals predominated at low conversions, while complete conversion produced AQ27DSH- ions. The AQ27DS diffusion coefficient was determined as 3.73 × 10-10m2S-1 from steady-state voltammetry at a gold rotating disc electrode.

Electrochemical techniques were used to study the oxidation of HS- ions at pH 9.3. Voltammetry of gold electrodes in HS- -containing solutions showed that multilayers of sulphur and soluble oxidation products were formed. As a known HS- oxidation product, thiosulphate solutions were also studied voltammetrically, but found to be electro-inactive at mildly oxidising potentials. The voltammetric behaviour of polysulphide ions, Sn2-(n = 2 to 5), was similar to that of HS- solutions on oxidation, though they could be reduced to HS- ions at low potentials. Ring-disc electrode experiments, extending the HS- concentration range that had been studied previously, confirmed that polysulphide ions were produced on reduction of anodically deposited elemental sulphur. This was demonstrated in both cyclic Volammetry and potential step experiments. By comparison of the charges passed producing polysulphides from sulphur and reducing them to HS- ions, an average polysulphide chain length of 1.8 was calculated, indicating a mixture of species was produced. Ion chromatography confirmed that polysulphide solutions do contain a number of species, consistent with thermodynamic predictions.