The Oxidation of Azo Dyes and Its Relation to Light Fading

The action of light on dyed fibres in air appears in many cases to involve an oxidation of the dye. The present work has been a preliminary to the fuller investigation of the photochemistry of azo dyes several series of simple monoazo dyes have been examined. A study of thermal oxidation in solution by common oxidising agents was followed by comparison with a series of measurements of relative light fastness in an attempt to elucidate the mechanism of the light fading process. The work has confirmed that oxidation of azo dyes in aqueous media, with several common reagents, e.g., ceric sulphate, potassium dichromate or hydrogen peroxide, disrupts the azo group and leads to the formation of a diazo compound and a quinone. subsequently, these further decompose to give, respectively, a phenol and nitrogen (in acid media); and phthalic acid. The reaction thus appears to be common to many types of oxidising agent, since previous workers have observed similar effects with, e.g., sodium hypochlorite, lead dioxide and ozone. An acceptor has been used to combine with the quinone formed and thus enable it to be identified without danger of its further oxidation. By boiling the acid solution after oxidising the dye a quantitative yield of nitrogen from the azo group is obtained, except when free amino groups are also present. This procedure could be used in quantitative analysis. An hypothesis is put forward suggesting that the initial step in such chemical oxidation is one of hydrolytic attack on the -C= N- bond of the dye, when it is present as the hydrazone and not the azo tautomer. In order to confirm or disprove the postulated hypothesis, several dyes containing nitro, chloro, methyl, methoxy or sulphonic and carboxylic acid groups in various positions in the phenyl nucleus in the following parent dyes, were prepared. The rates of oxidation of the water-soluble dyes in presence of various oxidising agents, such as neutral and alkaline hydrogen peroxide, potassium persulphate and dilute nitric acid were studied quantitatively. In the case of the insoluble dyes the rate of nitrogen evolution was examined as a measure of ease of oxidation. To correlate the oxidation of azo dyes with their relative light fastness, the above dyes were exposed in graded depths on substrates of wool, cellulose (cotton and filter paper), unglazed tile, and anodised aluminium. The last two materials were chosen in the hope they might he inert substrates. Fading and oxidation data were plotted against Hammett sigma values to determine the effect of substituents in the phenyl nucleus. The results appear to show that fading on wool is caused by hydrogen peroxide, which it is suggested may be produced by photolysis of the fibre itself, whereas on other substrates some other disruption process of the dye molecule occurs, perhaps by attack of atmospheric oxygen. The results also signify that the initial step in fading is a simple reaction involving attack at one of the unsaturated centres of the dye molecule

Entry Dispersion Analysis for the Stardust Comet Sample Return Capsule

Stardust will be the first mission to return samples from beyond the Earth-Moon system. The sample return capsule, which is passively controlled during the fastest Earth entry ever, will land by parachute in Utah. The present study analyzes the entry, descent, and landing of the returning sample capsule. The effects of two aerodynamic instabilities are revealed (one in the high altitude free molecular regime and the other in the transonic/subsonic flow regime). These instabilities could lead to unacceptably large excursions in the angle-of-attack near peak heating and main parachute deployment, respectively. To reduce the excursions resulting from the high altitude instability, the entry spin rate of the capsule is increased. To stabilize the excursions from the transonic/subsonic instability, a drogue chute with deployment triggered by an accelerometer and timer is added prior to main parachute deployment. A Monte Carlo dispersion analysis of the modified entry (from which the impact of off-nominal conditions during the entry is ascertained) shows that the capsule attitude excursions near peak heating and drogue chute deployment are within Stardust program limits. Additionally, the size of the resulting 3-sigma landing ellipse is 83.5 km in downrange by 29.2 km in crossrange, which is within the Utah Test and Training Range boundaries

Statistical properties of eigenstate amplitudes in complex quantum systems

We study the eigenstates of quantum systems with large Hilbert spaces, via their distribution of wavefunction amplitudes in a real-space basis. For single-particle 'quantum billiards', these real-space amplitudes are known to have Gaussian distribution for chaotic systems. In this work, we formulate and address the corresponding question for many-body lattice quantum systems. For integrable many-body systems, we examine the deviation from Gaussianity and provide evidence that the distribution generically tends toward power-law behavior in the limit of large sizes. We relate the deviation from Gaussianity to the entanglement content of many-body eigenstates. For integrable billiards, we find several cases where the distribution has power-law tails.Comment: revised version, with appendices; 15 pages, 10 figure

Perinatal and infant outcome in prenatally diagnosed hyperechogenic kidneys

Objective: Hyperechogenic kidneys are a relatively rare antenatal finding, which can generate significant parental anxiety due to uncertain prognosis. We report on the perinatal and infant outcomes of a large cohort of fetuses with antenatally diagnosed hyperechogenic kidneys. Methods: This was a retrospective analysis of all cases diagnosed prenatally with hyperechogenic kidneys between 2002 and 2017 in a large tertiary fetal medicine unit. Hyperechogenicity was defined as kidney parenchyma with greater echogenicity than that of the liver. Pregnancy, pathological and postnatal outcomes were collected from hospital and general practitioner records up to 1 year of age. Abnormal renal outcome was defined as elevated creatinine beyond 6 months of age, hypertension requiring medication or major kidney surgery, such as nephrectomy. Severe abnormal renal outcome was defined as the need for dialysis or kidney transplant at any stage. Results: Three-hundred and sixteen fetuses with hyperechogenic kidneys were identified at a mean gestational age of 21 (range, 13–37) weeks. The majority of cases (97%) had bilateral hyperechogenic kidneys. In the 265 cases with available follow-up data, other associated renal tract abnormalities were identified prenatally in 36%, concomitant extrarenal structural abnormalities in 39% and abnormal karyotype in 15% of cases. Of the 316 included cases, 139 did not survive, including 105 terminations of pregnancy, five intrauterine deaths and 29 early neonatal deaths. Only 4.3% (6/139) of these fetuses had isolated hyperechogenic kidneys while 28.1% (39/139) had associated multiple renal tract abnormalities alongside hyperechogenic kidneys and over two-thirds (67.6%; 94/139) had concomitant extrarenal abnormalities. Of the 177 cases that survived beyond 1 month of age, outcome data were available in 126. Of these, based on the antenatal findings, 60 (47.6%) cases had isolated hyperechogenic kidneys, 56 (44.4%) had associated renal structural abnormalities and 10 (7.9%) had additional extrarenal abnormalities. Considering renal outcome alone, kidney function was abnormal in 13 (21.7%), 10 (17.9%) and 0 (0%) infants in these three groups, respectively, although concurrent pathology clearly affected global outcome in the more complex cases. Neonatal mortality of 1.6% was observed in the isolated renal hyperechogenicity group. The presence of oligohydramnios or abnormal renal volume was not associated significantly with abnormal renal function (odds ratio (OR), 2.32 (99% CI, 0.54–10.02) and OR, 0.74 (99% CI, 0.21–2.59), respectively) in this group. Conclusions: Hyperechogenic kidneys are often complicated by associated renal tract and extrarenal abnormalities, aberrant karyotype and genetic disease, and these factors have a greater effect on overall outcome than does kidney echogenicity. The renal outcome of fetuses with isolated hyperechogenic kidneys is good generally, with over 70% of cases having normal renal function postpartum. Importantly, for prognostic counseling, all of the fetuses in this non-selected series with isolated hyperechogenic kidneys and normal amniotic fluid levels had normal renal outcome in infancy. © 2020 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology

Diffractive Dissociation In The Interacting Gluon Model

We have extended the Interacting Gluon Model (IGM) to calculate diffractive mass spectra generated in hadronic collisions. We show that it is possible to treat both diffractive and non-diffractive events on the same footing, in terms of gluon-gluon collisions. A systematic analysis of available data is performed. The energy dependence of diffractive mass spectra is addressed. They show a moderate narrowing at increasing energies. Predictions for LHC energies are presented.Comment: 12 pages, latex, 14 figures (PostScript Files included); accepted for publication in Phys. Rev. D (Feb.97

Diagnosis of hyperthyroidism by external liver counting : correlation between external scintillation counting of the liver and plasma protein-bound iodine<SUP>131</SUP>

External liver counting clearly distinguishes between euthyroid and hyperthyroid patients (t = 10.2); hyperthyroid and nontoxic goitre patients (t = 11.9). Individual values for these patients show a good separation between the groups. Correlation coefficient between liver counts and PBI131 in euthyroid and hyperthyroid patients was found to be 0.84 and correlation coefficient for hyperthyroid and nontoxic goitre patients was 0.76. The advantages of external liver counting as an alternative method to plasma PBI131 estimations are: (a) simplicity of the techniques; (b) no additional well scintillation assembly needed, and (c) no errors in results due to contamination of glassware, chemicals, etc(a) simplicity of the techniques; (b) no additional well scintillation assembly needed, and (c) no errors in results due to contamination of glassware, chemicals, et

Interventions for hidradenitis suppurativa: a Cochrane systematic review incorporating GRADE assessment of evidence quality

Background More than 50 interventions have been used to treat hidradenitis suppurativa (HS) and so therapy decisions can be challenging. Objectives To summarise and appraise randomised controlled trial (RCT) evidence for HS interventions in adults. Materials and methods Searches were conducted in MEDLINE, EMBASE, CENTRAL, LILACS, five trials registers and abstracts from eight dermatology conferences until 13 August 2015. Two review authors independently assessed study eligibility, extracted data and assessed methodological quality. Primary outcomes were quality of life and adverse effects of the interventions. Results Twelve trials, from 1983 to 2015, investigating 15 different interventions met our inclusion criteria. Median trial duration was 16 weeks and the median number of participants was 27. Adalimumab 40mg weekly improved the Dermatology Life Quality Index by 4.0 points, which equates to the minimal clinically important difference for the scale, compared to placebo (95% confidence interval (CI) -6.5 to -1.5 points). Evidence quality was reduced to ‘moderate’ because results are based on only a single study. Adalimumab 40mg every other week was ineffective in a meta-analysis of two studies comprising 124 participants. Infliximab 5mg/kg improved DLQI score by 8.4 points after eight weeks in a moderate quality study completed by 33 of 38 participants. Etanercept 50mg twice weekly was ineffective. Inclusion of a gentamicin sponge prior to primary closure did not improve outcomes. Other interventions including topical and oral antibiotics, were investigated by relatively small studies, preventing treatment recommendations due to imprecision. Conclusions More, larger RCTs are required to investigate most HS interventions, particularly oral treatments and surgical therapy. Moderate quality evidence suggests that adalimumab given weekly and infliximab are effective whereas adalimumab every other week is ineffective