A nationwide epidemiological study of myasthenia gravis in Latvia.

BACKGROUND AND PURPOSE: Myasthenia gravis (MG) is an autoimmune disorder characterized by fatigable muscle weakness due to antibody-mediated impairment of neuromuscular transmission. The aim of this study was to investigate the incidence and prevalence of MG in Latvia, and to characterize this population by well-established clinical parameters such as age at onset, presence of associated antibodies and thymus pathology. METHODS: All prevalent cases on 1 January 2015 and cases of patients newly presenting with MG symptoms from 1 January 2010 to 31 December 2014 were selected from the database of the Neuromuscular Disease Clinic of Pauls Stradins Clinical University Hospital and Children's Clinical University Hospital. Crude rates were calculated based on population data. These were directly age-standardized to the European and World Health Organization world standard populations. The analysis of clinical characteristics was carried out in a cohort of patients who had undergone a complete set of electrophysiological, serological and radiological investigations (n = 153; 68%). RESULTS: During the study period 99 incident and 226 prevalent cases were identified. The total crude MG incidence was 9.7 per million person-years. The prevalence of MG on 1 January 2015 was 113.8 per million. 54.2% of patients tested positive for acetylcholine receptor antibodies, 7.8% for muscle specific kinase antibodies and 1.3% for lipoprotein related protein 4 antibodies. CONCLUSIONS: This is the first study of MG in Latvia and the second population-based study of MG in Eastern Europe. Our epidemiological results are similar to those in some other European and Northern American countries, and show high prevalence and increasing incidence of late-onset MG.

Aromatic profile of aqueous banana essence and banana fruit by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry (GC-O).

Gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry (GC-O) were used to determine the aromatic composition and aroma active components of commercial banana essence and fresh banana fruit paste. Totals of 43 and 26 compounds were quantified in commercial banana essence and fresh banana fruit paste, respectively. Five new components in commercial banana essence were identified as methyl butyrate, 2,3-butanediol diacetate, 2-hydroxy-3-methylethylbutyrate, 1-methylbutyl isobutyrate, and ethyl 3-hydroxyhexanoate. A total of 42 components appear to contribute to the aromatic profile in banana. Isoamyl acetate, 2-pentanol acetate, 2-methyl-1-propanol, 3-methyl-1-butanol, 3-methylbutanal, acetal, isobutyl acetate, hexanal, ethyl butyrate, 2-heptanol, and butyl butyrate had high concentrations and were most detected by GC-O panelists in the commercial banana essence. Volatile components found only in fresh banana fruit paste that were detected by aroma panelists include E-2-hexenal, limonene, and eugenol.

Formation cross-sections of singlet and triplet excitons in pi-conjugated polymers.

Electroluminescence in organic light-emitting diodes arises from a charge-transfer reaction between the injected positive and negative charges by which they combine to form singlet excitons that subsequently decay radiatively. The quantum yield of this process (the number of photons generated per electron or hole injected) is often thought to have a statistical upper limit of 25 per cent. This is based on the assumption that the formation cross-section of singlet excitons, sigmaS, is approximately the same as that of any one of the three equivalent non-radiative triplet exciton states, sigmaT; that is, sigmaS/sigmaT approximately 1. However, recent experimental and theoretical work suggests that sigmaS/sigmaT may be greater than 1. Here we report direct measurements of sigmaS/sigmaT for a large number of pi-conjugated polymers and oligomers. We have found that there exists a strong systematic, but not monotonic, dependence of sigmaS/sigmaT on the optical gap of the organic materials. We present a detailed physical picture of the charge-transfer reaction for correlated pi-electrons, and quantify this process using exact valence bond calculations. The calculated sigmaS/sigmaT reproduces the experimentally observed trend. The calculations also show that the strong dependence of sigmaS/sigmaT on the optical gap is a signature of the discrete excitonic energy spectrum, in which higher energy excitonic levels participate in the charge recombination process.

Studies on metallochromic indicators-III Hematoxylin and hematein.

The use of hematoxylin and hematein as metallochromic indicators in direct EDTA titration of Zr(4+), Th(4+), Bi(3+), VO(+), Ga(3+), In(3+), Al(3+), Pb(+), Zn(2+), Mn(2+), Cd(2+), Cu(2+), Ni(2+), Co(2+), Mg(2+), and a few rare earths is described. Aluminium is titrated directly in presence of acetate buffer, lactic or glycoliic acid being used as auxiliary complexing agent. Mixtures of two metal ions can be titrated if one is Bi(3+) and the other Al(3+), Pb(2+), Zn(2+), Cu(2+), Cd(2+), La(3+), Ce(3+), Pr(3+), Nd(3+), Sm(3+), Gd(3+) or Er(3+). Aluminium alloys can be analysed via EDTA titrations, with these indicators.

Studies on metallochromic indicators--II. Zincon and its mercury and zinc complexes as indicators in EDTA titrations.

Zincon has been found to be an excellent indicator in the titration of mercury(II) with EDTA at pH 5.5-7. Moreover the mercury(II)-Zincon and zinc-Zincon systems have been found to be suitable indicators in the direct EDTA titrations of Pb(2+), Cd(1+) and Ca(2+). Interference studies of a number of cations and anions have been made. Chloride and bromide can be tolerated in the titration of mercury(II), up to equivalent concentrations.

Studies on metallochromic indicators--I. Pyrocatecholphthalein as metallochromic indicator.

Pyrocatecholphthalein has been used as a metallochromic indicator for the direct complexometric titrations of a number of metal ions with EDTA, both in acidic and in alkaline medium. Th, Bi(III), Ba, Sr, Ca, Mg, Mn(II), Pb(II), Cu(II), Cd, Ni, Co(II) and Zn have been successfully titrated. In comparison with Pyrocatechol Violet, this dyestuff gives sharper end-points when the titrations are done at high pH.

Adsorption indicators in the titrations of hexacyanoferrate(II) and oxalate with thorium ions.

Alizarin Red S, Pyrocatechol Violet and Xylenol Orange are shown to be effective adsorption indicators for the titrations of hexacyanoferrate(II) and oxalate with Thorium(IV) solution. The action of the indicators can be explained by the theory of surface compound formation.

Complexometric determination of mercury(II) using Congo Red as indicator.

Congo Red is suggested as an indicator for the direct titration of mercury(II) ions with EDTA or with potassium thiocyanate. An interference study of a number of cations has been made. The titration with thiocyanate is more advantageous than that with EDTA.