Implications of tropical cyclones on damage and potential recovery and restoration of logged forests in Vietnam.

Many natural forests in Southeast Asia are degraded following decades of logging. Restoration of these forests is delayed by ongoing logging and tropical cyclones, but the implications for recovery are largely uncertain. We analysed meteorological, satellite and forest inventory plot data to assess the effect of Typhoon Doksuri, a major tropical cyclone, on the forest landscapes of central Vietnam consisting of natural forests and plantations. We estimated the return period for a cyclone of this intensity to be 40 years. Plantations were almost twice as likely to suffer cyclone damage compared to natural forests. Logged natural forests (9-12 years after cessation of government-licensed logging) were surveyed before and after the storm with 2 years between measurements and remained a small biomass carbon sink (0.1 ± 0.3 Mg C ha-1 yr-1) over this period. The cyclone reduced the carbon sink of recovering natural forests by an average of 0.85 Mg C ha-1 yr-1, less than the carbon loss due to ongoing unlicensed logging. Restoration of forest landscapes in Southeast Asia requires a reduction in unlicensed logging and prevention of further conversion of degraded natural forests to plantations, particularly in landscapes prone to tropical cyclones where natural forests provide a resilient carbon sink. This article is part of the theme issue 'Understanding forest landscape restoration: reinforcing scientific foundations for the UN Decade on Ecosystem Restoration'.

The role of thyronine in thyroid hormone metabolism.

Thryonine (T0) has been identified in human urine using gas chromatography-mass fragmentography (G.C.M.F.). In 22 normal individuals urinary T0 concentration was found to range between 8--25 nmol/24h. Assuming the mean normal thyroxine (T4) production rate to be approximately 100 nmol/24h, our findings indicate that less than 20% of this could be accounted for as urinary T0 excretion, thus supporting earlier findings that the peripheral metabolism of T4 is not limited solely to deiodination.

Measurement of haloacetic acids and their decomposition in wine by capillary gas chromatography.

A method has been developed for the analysis of haloacetic acids in wine involving solid-phase extraction followed by methylation and quantification by capillary gas chromatography with electron capture detection. Recoveries from spiked samples were greater than 85% for each of the acids and the limits of detection of the method were 100, 10 and 5 micrograms/litre for the chloroacetic, bromoacetic and iodoacetic acids, respectively. The haloacetic acids were not detected in a survey of over 30 retail samples. Separate stability studies showed that the concentration of chloroacetic acid added to wine was essentially unaffected by up to 90 days storage at 30 degrees C. Under the same conditions, however, less than 20% of bromoacetic acid and iodoacetic acid remained.

The determination of the flour improver potassium bromate in bread by gas chromatographic and ICP-MS methods.

The development and application of two methods for determining bromate in bread are described. A gas chromatographic (GC) method which relied on the formation of a volatile derivative of bromate gave a detection limit of 12 micrograms/kg. Duplicate analyses agreed well but recovery from breads spiked with bromate were low and averaged 30% for brown bread and 42% for white bread. Further studies indicated that this was caused by the derivatization reaction being suppressed by components of the sample and reagents used in their preparation. After taking both these factors into account, a recovery of 80% could be achieved. The GC method was used to carry out a survey of retail bread samples in 1989. Bromate was found in all six unwrapped breads analysed (median 35 micrograms/kg, range 17-317 micrograms/kg), whilst for 22 wrapped breads, seven were found to contain bromate (median < 12 micrograms/kg, range < 12-238 micrograms/kg). A second method of analysis employing inductively coupled plasma-mass spectrometry (ICP-MS) was developed which provided independent confirmation of the presence of bromate in these retail samples. The method gave a mean recovery of 71% from five spiked samples and a detection limit of 20 micrograms/kg. The GC and ICP-MS methods were compared by performing replicate analyses of a bread sample prepared with bromate-treated flour. Quantitative agreement between the two techniques was good. The precision of the ICP-MS technique (CV 12%) proved better than that found for the GC method (CV 18%). The Potassium Bromate (Prohibition as a Flour Improver) Regulation 1990 came into force on 1 April 1990 (Statutory Instrument 1990 Number 399).(ABSTRACT TRUNCATED AT 250 WORDS)

The contribution of azodicarbonamide to ethyl carbamate formation in bread and beer.

Data on ethyl carbamate concentrations in beers purchased and analysed between 1988 and 1990 are presented. The concentrations in draught beers were uniformly below the detection limit of 1 microgram/l. Canned beers contained rather more ethyl carbamate (up to 2.5 micrograms/l) which is considered to be due to their longer shelf-life and higher alcohol content (in some cases). Bottled beers contained even higher amounts of ethyl carbamate (up to 14.7 micrograms/l) and this was considered to be due to the use of azodicarbonamide as a blowing agent in the beer bottle cap liners. It is understood that modifications to the liner have led to reduced concentrations in bottled beers produced more recently. A survey of bread samples and related cereal products such as rusks, French toasts and pitta bread indicated typical ethyl carbamate concentrations between < 0.4 and 4.5 micrograms/kg. Toasting bread led to increases of between three- and eight-fold in ethyl carbamate concentrations ranging from 3.5 to 33.8 micrograms/kg on a wet weight basis. Analysis of the data indicated that commercial bread samples which indicated the use of azodicarbonamide as a flour improver showed statistically significant increases in ethyl carbamate concentrations. The mean increase for treated bread over untreated bread was 66%. When these breads were toasted, the mean increase for treated toast over untreated toast was 56%.

Mass spectral properties of volatile derivatives of thyronine (T0) and use of these in the study of thyronine excretion in eu-, hyper- and hypothyroidism.

The mass spectral properties of four classes of derivatives of thyronine are discussed ( oxazolidinone , O-methyl oxazolidinone , O-acetyl oxazolidinone and N,O- diheptafluorobutyryl methyl ester). An assay for thyronine in human urine is described based on the N,O- diheptafluorobutyryl methyl ester. Results of T0 excretion in euthyroid humans were compared with those obtained previously using an assay based on the O-acetyl oxazolidinone derivative. Patients with frank hyperthyroidism had significantly higher T0 excretion than euthyroid subjects (2 alpha less than 0.002) and hypothyroid patients lower T0 excretions than euthyroid subjects (2 alpha less than 0.002). Some overlap between the two pathological ranges and the normal euthyroid range was evident.