bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Lower Boundary Conditions on the Stability of Radiative Shocks
Authors: Saxton Curtis J.
Published: September 2002

Thermal instabilities can cause a radiative shock to oscillate, thereby modulating the emission from the post-shock region. The mode frequencies are approximately quantised in analogy to those of a vibrating pipe. The stability properties depend on the cooling processes, the electron–ion energy exchange, and the boundary conditions. This paper considers the effects of the lower boundary condition on the post-shock flow, both ideally and for some specific physical models. Specific cases include constant perturbed velocity, pressure, density, flow rate, or temperature at the lower boundary, and the situation with nonzero stationary flow velocity at the lower boundary. It is found that for cases with zero terminal stationary velocity, the stability properties are insensitive to the perturbed hydrodynamic variables at the lower boundary. The luminosity responses are generally dependent on the lower boundary condition.
The Evolution of Shocks in Blazar Jets
Authors: Bicknell Geoffrey V. , Wagner Stefan J.
Published: September 2002

We consider the shock structures that can arise in blazar jets as a consequence of variations in the jet flow velocity. There are two possible cases: (1) a double shock system consisting of both a forward and reverse shock, and (2) a single shock (either forward or reverse) together with a rarefaction wave. These possibilities depend upon the relative velocity of the two different sections of jet. Using previously calculated spherical models for estimates of the magnetic field and electron number density of the emission region in the TeV blazar Mkn 501, we show that this region is in the form of a thin disk in the plasma rest frame. It is possible to reconcile spectral and pair opacity constraints for Mkn 501 for Doppler factors in the range of 10–20. This is easiest if the corrections for TeV absorption by the infrared background are not as large as implied by recent models.
Floral biology of dry rainforest in north Queensland and a comparison with adjacent savanna woodland
Authors: Hansman Dinah J.
Published: September 2002

In north Queensland, Australia, dry rainforest (deciduous and semi-evergreen
vine thicket) occurs as patches within a matrix of savanna woodland. With
floral morphology and pollen–ovule ratios as indicators of pollination
syndrome and breeding system, the floral biology of dry rainforest was
compared with that of adjacent savanna woodland and with rainforest elsewhere.
Contingency tables and analysis of variance were used to examine and compare
breeding system, flower diameter, floral display and putative pollination
syndrome for 156 dry rainforest and 33 savanna woodland taxa. Most (91 of 97)
dry rainforest species had pollen–ovule ratios indicating obligate
outbreeding. Similar levels of dioecy (21%) and patterns of flowering
phenology were observed to those reported for rainforests elsewhere. For dry
rainforest canopy trees, flower diameter and morphology indicated pollination
by small, generalist insects. Canopy trees tended to flower in the wet season
and have low ovule numbers. Taxa assigned to the wind-pollination syndrome had
the highest pollen–ovule ratios, suggesting less efficient pollen
transfer. Sclerophyll savanna taxa (and some emergent dry rainforest trees)
tended to flower in the dry season, have large flowers, high ovule numbers and
a high level of floral display.
Anatomical studies of shoot bud-forming roots of Brazilian tree species
Authors: Hayashi A. H. , Penha A. S. , Rodrigues R. R. , Appezzato-da-Glória B.
Published: September 2002

The present study is the first confirmation of the presence of shoot sprouts
on roots in tree species of the Brazilian tropical forest, as these
underground systems are usually only analysed by external gross morphological
observations. The shoot-bearing roots of seven species, collected in a forest
block frequently affected by fire, were sectioned and analysed for the number
of primary xylem ridges, stele type and reserve compounds. Starch was the
predominant reserve compound and occurred in different quantities among the
species. The epicormic shoot buds, which arise spontaneously on root cuttings
or plants subjected to fire, were analysed in two of the studied species.
These buds showed different sites of origin but were considered epicormic
(reparative) since they did not carry bud traces along the secondary xylem
during their early development. Shoot bud formation on root systems is
generally associated with disturbed environments, and confirmation that
sprouting from roots does occur may modify many aspects of our appreciation of
the community dynamics of forest species and models that define how we manage
and rehabilitate Brazilian forest fragments.
An investigation of long-distance dispersal based on species native to both Tasmania and New Zealand
Authors: Jordan Gregory J.
Published: September 2002

Some 200 species of plants are currently recognised as being native to both
Tasmania and New Zealand. It is argued that dispersal across the
1500–2000-km Tasman Sea has occurred in all of these species.
Almost all (187) are herbs and constitute over 20% of the herbaceous
flora of Tasmania. Common species, non-dioecious species, species with very
small seeds, species from aquatic, coastal or wet habitats and possibly
species with hooked fruit are all over-represented among the disjunct species
of herbs. The incidence of disjunct species also varies significantly among
families. In contrast, fleshy fruited species, or species with plumes or very
hairy disseminules, are not over-represented among the herbaceous disjunct
species. These data are used to model the probability that a species (past or
present) with given traits would show a within-species trans-Tasman
disjunction, and it is inferred that this can be used to give a crude
approximation of the rates of long-distance dispersal for different types of
species. The model can be tested by using molecular clock methods and could be
made more robust by incorporating equivalent data from other disjunct regions.
The history of Cunoniaceae in Australia from macrofossil evidence
Authors: Barnes Richard W. , Hill Robert S. , Bradford Jason C.
Published: September 2002

The macrofossil record of the plant family Cunoniaceae in Australia is
summarised and reviewed where necessary by using detailed studies of the
morphology of extant genera. Eleven of the 26 Cunoniaceae genera are
represented in the Australian macrofossil record and include leaves and leaf
fragments, foliar cuticle and reproductive structures, and range from Late
Paleocene to Quaternary in age. Macrofossils show that some genera had a
different or more widespread distribution in Australia during the Cenozoic,
with two genera (Weinmannia and
Codia) having become extinct from the continent. Changes
in climate, including increasing cold, frost, dryness, seasonality, or some
combination of these, or a reduction in vegetation disturbance regimes (e.g.
volcanism, uplifting, landslips), may be implicated in the regional or
continental extinctions demonstrated by the macrofossil record. Many extant
genera (Schizomeria, Vesselowskya,
Callicoma, Ceratopetalum,
Acsmithia, Codia) had evolved by
the Early Oligocene or earlier (Eucryphia, Late
Paleocene; Ceratopetalum, Middle Eocene), perhaps with
generic diversification more or less complete by the end of the Early Cenozoic
or earlier. A Cretaceous origin of the family is possible, and may account for
its widespread distribution on Southern Hemisphere landmasses, although
long-distance dispersal events are required to explain some modern geographic
disjunctions.
Succession after fire in alpine vegetation on Mount Wellington, Tasmania
Authors: Kirkpatrick J. B. , Bridle K. L. , Wild A. S.
Published: September 2002

The vegetation on either side of fire boundaries in the alpine zone of Mount
Wellington, Tasmania, was surveyed in 1978 and 1998. This combination of
spatial and temporal sampling gave data for 16, 31, 36 and 51 years since
burning. These data were used to test for convergence in vegetation
characteristics through time between the areas burned in 1947 and those burned
in 1962 and to determine whether lifeform is a reasonable predictor of the
successional dynamics of species. While convergence largely prevailed, some
lifeforms and species diverged and lifeform was generally a poor predictor of
species responses. For example, size class analyses of the larger shrub
species indicated a wide variety of successional responses to fire. The tall
shrubs on Mt Wellington have higher percentages of tolerators and species
relying on the soil seed store for postfire regeneration than physiognomically
similar vegetation in more fire-prone environments. Fifty-one years after
fire, there is evidence of continuing floristic and structural change in the
alpine vegetation that may be partly related to recent climatic warming.
Estimates of Heterozostera tasmanica, Zostera muelleri and Ruppia megacarpa distribution and biomass in the Hopkins Estuary, western Victoria, by GIS
Authors: Ierodiaconou Daniel A. , Laurenson Laurie J. B.
Published: September 2002

Knowledge of the spatial arrangement of the seagrass distribution and biomass
within the Hopkins Estuary is an essential step towards gaining an
understanding of the functioning of the estuarine ecosystem. This study marks
the first attempt to map seagrass distribution and model seagrass biomass and
epiphyte biomass along depth gradients by the use of global positioning system
(GPS) and geographical information system (GIS) technologies in the estuary.
For mapping seagrass in small estuaries, ground-surveying the entire system is
feasible. Three species of seagrasses,
Heterozostera tasmanica (Martens ex Aschers),
Zostera muelleri (Irmisch ex Aschers) and
Ruppia megacarpa (Mason), were identified in the Hopkins
Estuary. All beds investigated contained a mixed species relationship. Three
harvest techniques were trialed in a pilot study, with the 25 × 25-cm
quadrat statistically most appropriate. Biomass of seagrasses and epiphytes
was found to vary significantly with depth, but not between sites. The average
estimate of biomass for total seagrasses and their epiphytes in the estuary in
January 2000 was 222.7 g m–2 (dry weight). Of the
total biomass, 50.6% or 112.7 g m–2 (dry
weight) was contributed by seagrasses and 49.4% of the biomass (110.0 g
m–2) were epiphytes. Of the 50.6% of the
total biomass represented by seagrasses, 39.3% (87.5 g
m–2) were leaves and 11.3% (25.2 g
m–2) were rhizomes. The total area of seagrasses
present in the Hopkins Estuary was estimated to be 0.4 ± 0.005
km2, with the total area of the estuary estimated to be
1.6 ± 0.02 km2 (25% cover). The total
standing crop of seagrasses and epiphytes in the Hopkins Estuary in January
2000 was estimated to be 102.3 ± 57 t in dry weight, 56% (56.9
± 17 t, dry weight) seagrasses and 44% (45.4 ± 19 t, dry
weight) epiphytes. Of the seagrass biomass, 39% (39.7 ± 13 t,
dry weight) was contributed by leaves and 17% (17.3 ± 7 t, dry
weight) by rhizomes.
Effects of heat and smoke on germination of soil-stored seed in a south-eastern Australian sand heathland
Authors: Wills Timothy J. , Read Jennifer
Published: September 2002

Various fire-related agents, including heat, smoke, ash and charred wood, have
been shown to break dormancy and promote germination of soil-stored seed in a
broad range of species in mediterranean-type systems. However, relatively
little work has been conducted in south-eastern Australian heathlands. This
study examined the effects of heat and smoked water on germination of the soil
seed bank in a mature sand heathland within the Gippsland Lakes Coastal Park,
in south-eastern Australia. Heat was clearly the most successful treatment for
promoting seed germination, followed by smoked water, then controls, with
55% of species present in the germinable soil seed bank requiring a
heat or smoke stimulus to promote seed germination. Mean species richness of
the germinable soil seed bank was found to be significantly higher in
heat-treated soil than in smoke and control treatments. Seedling density of
heat-treated soil was almost 10 times that of controls, while smoke-treated
soil was almost five times that of controls. Seedling emergence was fastest in
heat-treated soil, followed by smoke and control soils. Of the species found
in the soil seed bank, 25% were absent from the extant vegetation,
suggesting the existence of post-fire colonisers in the soil seed bank. The
results have implications for the design of soil seed bank experiments and the
use of fire as a tool in vegetation management.
An assessment of historic human impact on south-eastern Australian environmental systems, using late Holocene rates of environmental change
Authors: Dodson John R. , Mooney Stuart D.
Published: September 2002

The late Holocene of south-eastern Australia was typified by stable climate, vegetation and sedimentary regimes, in relative equilibrium with Aboriginal land use and fire management. The arrival of Europeans, with the associated vegetation clearance, introduction of exotic plants and animals, notably for grazing and agriculture and a change in fire regimes, resulted in changes in vegetation and sedimentary patterns. Impacts varied in type and magnitude through the region and evidence of impacts that is preserved varies with sedimentary setting. Here we take a number of proxy measures of vegetation change, fire history, erosion and weathering from six sediment sections across south-eastern Australia and use an index to measure overall rate of change. This shows that the vegetation and environmental systems of south-eastern Australia have been very sensitive to human impact following European settlement.
Seasonal patterns of xylem sap pH, xylem abscisic acid concentration, leaf water potential and stomatal conductance of six evergreen and deciduous Australian savanna tree species
Authors: Thomas Dane S. , Eamus Derek
Published: September 2002

Deciduous trees of Australia’s northern savannas typically have
less-negative leaf water potentials than evergreen species and their stomata
are more sensitive to soil drought than those of evergreen species. This paper
presents the first investigation of the role of xylem sap pH and abscisic acid
content in explaining stomatal behaviour of Australian trees in the field. We
measured stomatal conductance, leaf-to-air vapour pressure difference
(D) and leaf water potential, xylem abscisic acid (ABA)
concentration and xylem sap pH of evergreen, semideciduous and fully deciduous
tree species in the field over a 15-month period. Measurements were made
during both the wet and the dry seasons. Stomata closed in response to
increasing D in both evergreen and deciduous species and
were equally sensitive to increasing D or declining leaf
water potential. Xylem ABA concentration increased with declining leaf water
potential in evergreen and semi-deciduous species, but not deciduous species.
Similarly, there was an inverse correlation between stomatal conductance and
xylem ABA concentration. Xylem sap pH increased as leaf water potential
declined from wet to dry season for evergreen and semi-deciduous species but
not for deciduous species. Deciduous species had less-negative water
potentials and lower xylem ABA concentrations than evergreen species or
semi-deciduous species. We conclude that changes in xylem sap pH and ABA
content do occur seasonally in the wet–dry tropics of Australia and that
these changes influence stomatal conductance, but only in evergreen and
semi-deciduous species. Deciduous species do not appear to modulate either of
these chemical signals.
Growth dynamics and leaf quality of the stinging trees Dendrocnide moroides and Dendrocnide cordifolia (Family Urticaceae) in Australian tropical rainforest: implications for herbivores
Authors: Hurley M.
Published: September 2002

Leaf growth dynamics and leaf quality of
Dendrocnide moroides (Wedd.) and
Dendrocnide cordifolia (L.S.Sm.) Jackes and Hurley
varied widely with age, season, plant height and habitat. Althoughleaves were
produced continuously, growth rates varied seasonally. Leaf moisture and
nitrogen content increased in spring and summer and decreased with age, while
toughness increased with age. All leaf growth attributes varied with height,
with the majority of activity occurring on mid-sized plants. Leafgrowth rates
and proportions of different leaf age classes were similar for both species.
Leaves were larger and lived longer in shade. Size and longevity responded
rapidly to changing light conditions, reflecting their ability to survive in
small rainforest gaps. Leaves of all ages were highly nutritious and the
exceptionally nutritious young leaves were abundant throughout the year making
them susceptible to herbivore attack. However, immature stinging tree leaves
were densely covered with painful stinging hairs and hair density decreased
with age. Further to causing pain, stinging hairs of
D. moroides and D. cordifolia are
shed continuously and may deter mammalian herbivores by causing allergic
reactions. However, the leaves of stinging trees appeared better suited to the
rapid colonisation of rainforest gaps, than in fending off or avoiding
herbivore damage.
Relationships between site factors and distribution of Phytophthora cinnamomi in the Eastern Otway Ranges, Victoria
Authors: Wilson B. A. , Aberton J. , Cahill D. M.
Published: September 2002

The Eastern Otway Ranges, Victoria is an area recognised for its significant
flora and fauna communities. An area of about 7000 ha, the Anglesea heathlands
has been listed on the register of the National Estate. Although symptoms of
the plant pathogen Phytophthora cinnamomi have been
recorded in the area since the 1970s, the extent of infestation and its
effects have not been documented. The aims of this study were to assess the
distribution of infestation, identify the relationship of plant infection to
site variables and to identify evidence of spread of the pathogen. The
presence of P. cinnamomi was assessed at 50 study sites
by a visual evaluation of the vegetation, using species such as
Xanthorrhoea australis (Austral grass tree) and
Isopogon ceratophyllus (horny cone bush) as indicator
species. Soil and plant tissues were assayed for the presence of the pathogen
by cotyledon baiting and immunoassay methods.
Phytophthora cinnamomi was isolated at 76% of the
study sites from the floristic communities identified: heathy open forest;
heathy woodland I and II; Bald Hills heathland; riparian open forest. There
were significantly more diseased sites at lower altitudes. The pathogen is
widely spread and causing disease throughout the area, but at present often
only in small patches. There is an urgent need for disease management to
protect the significant communities. These findings suggest that management
actions such as mapping current infestations, closing tracks and implementing
vehicle wash-down points are required.
Patterns of mating in Persoonia mollis (Proteaceae) revealed by an analysis of paternity using AFLP: implications for conservation
Authors: Krauss Siegfried L.
Published: September 2002

A detailed characterisation of mating in natural populations is desirable for
the better conservation of rare or threatened taxa. The PCR-based
DNA-fingerprinting technique amplified fragment length polymorphism (AFLP) is
a powerful new genetic marker for mating system analysis because it enables
the unambiguous assignment of paternity to progeny. Mating patterns following
natural pollination were characterised by paternity assignment using AFLP in a
natural population of Persoonia mollis subsp.
nectens (Proteaceae). This study serves as a comparison
for future studies of the mating system of the threatened close relative
P. mollis subsp. maxima. Twelve
seeds from each of 21 plants (252 seeds in total) were analysed for paternity.
Of these, 199 were assigned paternity unambiguously to one of the known
potential sires. The remaining 53 seeds were sired by plants outside the known
population. Three seeds were presumably selfed as they possessed only maternal
alleles, giving a population outcrossing rate of 98.8%. Realised pollen
flow distances showed a leptokurtic distribution, with a mean of 24.7 m (s.e.
= 2.0; range = 0–137 m). Mean realised pollen dispersal
distance to and from each plant varied markedly from 0 to 57.4 m, and was
largely influenced by the immediate density of plants. The seeds of all plants
had multiple sires, with an average of 5.3 sires for 10 seeds (s.e. =
0.3; range = 2–8). Individual paternal success varied from one to
24 seeds sired (mean = 9.1; s.e. = 1.2). Individual maternal
success varied from a percentage fruit set of 5.2 to 37.9 (mean = 18.3;
s.e. = 2.1). Male and female reproductive success, measured as the
number of seeds sired and percentage fruit set, respectively, was positively
correlated. Mean genetic dissimilarity among all seeds (29.1% of 151
loci polymorphic; s.e. = 0.05; n = 30 876)
was not significantly different from the mean genetic dissimilarity among all
adults (29.5%; s.e. = 0.5; n =
300), and indicates an overall absence of inbreeding. The active management
and conservation implications of these more sensitive data include the
avoidance of inbreeding in established and new populations and in
ex situ collections, as well as the sensitive detection
of changes in mating in disturbed populations which may indicate future
genetic decline.
Seed production in woodland and isolated trees of Eucalyptus melliodora (yellow box, Myrtaceae) in the South Western Slopes of New South Wales
Authors: Burrows G. E.
Published: September 2002

Seed production in woodland and isolated
Eucalyptus melliodora Cunn. ex Schauer trees was
investigated. Measurement of physical parameters such as mean capsule weight,
mean seed weight and mean ratio of the weight of the capsule contents to the
weight of the empty capsule showed no significant differences between woodland
and isolated trees. In contrast, reproductive output as measured by mean
number of seeds per capsule, mean number of seeds per 10 g of capsule contents
and mean seed weight as a percentage of the weight of the capsule contents,
was significantly lower (45–48% less) in isolated trees than in
woodland trees. Mean percentage seed germination was also significantly lower
(14% less) in the isolated trees and the mean number of viable seeds
per 10 g of capsule contents was only 38% of the woodland trees. These
results indicate that E. melliodora, like many
eucalypts, has a mixed mating breeding system with preferential outcrossing
but is also capable of self pollination leading to a reduction in seed yield
and viability. The woodland and isolated trees produced a mean of 4.6 and 2.1
seeds per capsule, respectively. It would be relatively easy to collect large
numbers of seeds from isolated trees of E. melliodora
and subsequently propagate potentially genetically inferior plants.
Alleviation of salinity and dark-enforced dormancy in Allenrolfea occidentalis seeds under various thermoperiods
Authors: Gul Bilquees , Khan M. Ajmal , Weber Darrell J.
Published: September 2002

The effect of germination-regulating chemicals on the alleviation of
salinity-enforced germination inhibition of
Allenrolfea occidentalis (S.Wats.) Kuntze at various
thermoperiods in complete darkness was investigated. There was poor
germination at cool temperatures and germination-regulating chemicals were
ineffective in alleviating this effect. Germination in the dark increased
progressively with increase in temperature and maximum germination was
obtained at 25–35˚C thermoperiod. Ethephon and fusicoccin (FC)
substantially reverted dark-induced inhibition at moderate thermoperiods. All
other germination-regulating chemicals were more effective at moderate
temperature, while germination was not specifically different from control at
higher temperature. Salinity-enforced germination inhibition was partially
alleviated by all growth regulators at the higher temperature regime
(25–35˚C). Best reversal was obtained with the application of
ethephon and FC. Our results suggest that temperature is the most critical
factor influencing the germination of Allenrolfea seeds.
Allenrolfea occidentalis seeds germinated better at
higher than at lower temperatures in the dark and all of the growth-promoting
compounds showed their maximum reversal effect at higher temperatures.
Synthesis of (±)-Cathaformine.
Authors: Nimgirawath Surachai , Podoy Phansuang
Published: September 2002

The structure previously assigned to the
N-(methoxycarbonyl)aporphine alkaloid
(±)cathaformine has been confirmed by a total synthesis of the racemic
substance in which the key step involved formation of ring C by a
radical-initiated cyclization.
Antifungal Thiosulfonates: Potency with Some Selectivity
Authors: Baerlocher Felix Jakob , Baerlocher Mark Otto , Chaulk Crystal Lee , Langler Richard Francis , MacQuarrie Stephanie Lee
Published: September 2002

A series of thiosulfonates have been prepared and tested against
Aspergillus niger and
Aspergillus flavus. In general, the thiosulfonates are
moderate antifungal agents—more potent than corresponding inactive
disulfides and less potent than corresponding very active fungitoxic
disulfides. Apair of thiosulfonates show high selectivity, each killing only
one kind of fungus.
2-Hydroxyvirensic Acid, a New Depsidone from the Lichen Sulcaria sulcata.
Authors: Elix John A. , Wardlaw Judith H. , Obermayer Walter
Published: September 2002

The new depsidone 2-hydroxyvirensic acid
(4-formyl-2,3,8-trihydroxy-1,6,9-trimethyl-11-oxo-11H-dibenzo[b,e][1,4]dioxepin-7-carboxylic
acid) (6) has been isolated from a chemical race of the lichen
Sulcaria sulcataand the structure (6) deduced from a
combination of spectroscopic data.
Angucyclinones Related to Ochromycinone. IV. The Structures and Reactions of Unusual Diels-Alder Adducts Formed from Maleic Anhydride and Racemic 5,5-Dimethyl-3-vinylcyclohex-2-en-1-ol
Authors: Brinkworth Craig , Rozek Tomas , Bowie John H. , Skelton Brian W. , White Allan H.
Published: September 2002

The Diels–Alder reaction between maleic anhydride and racemic
5,5-dimethyl-3-vinylcyclohex-2-en-1-ol gives two racemic diastereomers, the
major product
(2a,S,3R,8aS,8bR)-7,7-dimethyl-2-oxo-2a,3,4,6,7,8,8a,8b-octahydro-2H-benzo[cd]isobenzofuran-3-carboxylic
acid (63% yield), and the minor product
(2aR,3S,8aS,8bS)-7,7-dimethyl-2-oxo-2a,3,4,6,7,8,8a,8b-octahydro-2H-benzo[cd]isobenzofuran-3-carboxylic
acid (9%). Epoxidation of the major product gives racemic
(1aS,3R,3aS,5aR,8aS,8bR)-7,7-dimethyl-4
oxoperhydro-benzo[cd]oxireno[2,3-e]isobenzofuran-3-carboxylic
acid in 81% yield, while opening of the epoxide ring gave the trans
diol
(2aS,3R,5S,5aR,8aR,8bR)-5,5a-dihydroxy-7,7-dimethyl-2-oxoperhydrobenzo[cd]isobenzofuran-3-carboxylic
acid in 58% yield. Treatment of the major Diels–Alder product
with osmium tetraoxide gave the cis diol
(2aS,3R,5S,5aR,8aS,8bR)-5,5a-dihydroxy-7,7-dimethyl-2-oxoperhydrobenzo[cd]isobenzofuran-3-carboxylic
acid in 86% yield. The structures of four products were confirmed by
X-ray and n.m.r. methods. None of the products exhibit anticancer activity.
Ionization of Water in Concentrated Potassium Halide Media
Authors: Samani Faradj K. , Capewell Stephen G. , Sipos Pal M. , May Peter M. , Hefter Glenn
Published: September 2002

The ionic product of water, pKw
=
–log[H+][OH–],
has been determined as a function of ionic strength (I )
in concentrated aqueous solutions of KCl, KBr and KI at 25˚C by
high-precision glass electrode potentiometric titrations. The
pKw values obtained are in
excellent agreement with, but generally more precise than, literature data. At
I > 1 M the
pKw values increase smoothly and
show systematic differences in the order KCl < KBr < KI, consistent with
the decreasing H+-acceptor ability of the medium
anions. Analogous behaviour is observed in MCl solutions, with
pKw values varying in the order
NaCl < KCl < CsCl. Formation constants of MOH0 ion
pairs derived from these data are consistent with literature values.
Intramolecular Rearrangements of But-3-enoic Esters
Authors: Tsaconas Michael , Prager Rolf H. , Millan David S.
Published: September 2002

Support for the proposal by Khalafy and Prager1 of a
cheletropic rearrangement of a 6-methylidenecyclohexa-2,4-diene-1-carboxylate
under flash vacuum pyrolysis (f.v.p.) conditions has been obtained by a study
of the f.v.p. products obtained from methyl
1-methyl-6-methylidenecyclohexa-2,4-diene-1-carboxylate and methyl
2,2-dimethylbut-3-enoate. A significant product in each case arises from a
reaction involving decarbonylation and transfer of a methoxy group to C 4
(but-3-enoate numbering).
Epoxide Sesquiterpenes and Steroids from Cremanthodium discoideum
Authors: Zhu Ying , Zhu Qi Xiu , Jia Zhong Jian
Published: September 2002

Two new epoxide bisabolane sesquiterpenes and a new steroid were isolated from
the whole plants of Cremanthodium discoideum Maxim. Their structures have been
established by spectroscopic methods including two-dimensional n.m.r.
(1H–1H COSY,
1H–1H NOESY, HMBC, HMQC)
techniques. Six known steroids were also isolated and characterized. Compound
(1) has antibacterial activity against
Bacillus aeruginosus and
B. subtilis. Two sesquiterpenes showed significant
activity against two tumour cell lines: human promyelocytic leukemia cell
HL-60 and human hapatoma cell SMMC-7721.
Subpsoromic Acid, a New Depsidone from the Lichen Ocellularia praestans
Authors: Elix John A. , Wardlaw Judith H. , Kalb Klaus
Published: September 2002

The new depsidone subpsoromic acid
(4-formyl-3-hydroxy-8-methoxy-1-methyl-11-oxo-11H-dibenzo[b,e]-[1,4]dioxepin-6-carboxylic
acid) (6) has been isolated from the lichen
Ocellularia praestans and the structure (6) deduced from
a combination of spectroscopic data.
Structural Variety in Solvated Lanthanoid(III ) Halide Complexes
Authors: Deacon Glen B. , Feng Tiecheng , Junk Peter C. , Meyer Gerd , Scott Natalie M. , Skelton Brian W. , White Allan H.
Published: September 2002

Treatment of lanthanum metal with
CH2Br2 or
CH2I2 in tetrahydrofuran (thf)
under ultrasound conditions yields the corresponding
[LaX3(thf)4] (X =
Br, I) complexes in good yield. Recrystallization of
[LaBr3(thf)4] from
1,2-dimethoxyethane (dme) or bis(2-methoxyethyl) ether (diglyme) generates
[LaBr2(µ-Br)(dme)2]2
and
[LaBr2(dig-lyme)2][LaBr4(diglyme)].
Treatment of lanthanoid metals with hexachloroethane in dme yields
[LnCl3(dme)2] (Ln
= La, Nd, Er or Yb) and in acetonitrile
[YbCl2(MeCN)5]2[YbCl3(MeCN)(-Cl)2YbCl3(MeCN)].
The reaction of Yb metal pieces with 1,2-dibromoethane in thf and dme gave
single crystals of
[YbBr3(thf)3] and
[YbBr3(dme)2],
respectively. The X-ray determined structure of
[LaBr3(thf)4] shows a
seven-coordinate monomer with pentagonal-bipyramidal stereochemistry and
apical bromide ligands. For
[YbBr3(thf)3], a
monomeric structure with mer-octa-hedral stereochemistry
is observed. In
[LaBr2(µ-Br)(dme)2]2,
two eight-coordinate La centres are linked by two bridging bromides. The dme
ligands have a trans relationship to each other, and
cis terminal bromides are transoid
to the bridging bromides with dodecahedral stereochemistry for La. By
contrast, the 1: 1.5 diglyme adduct is found to be ionic
[LaBr2(diglyme)2][LaBr4(diglyme)],
with an eight-coordinate bicapped trigonal-prismatic lanthanum cation and a
seven-coordinate pentagonal-bipyramidal lanthanum anion. In the cation, the
bromide ligands are cis to each other, and in the anion,
two bromides are equatorial and two are axial. In
[YbBr3(dme)2],
[YbCl3(dme)2] and
[ErCl3(dme)2], a
seven-coordinate pentagonal-bipyramidal arrangement exists with apical halogen
ligands. Far-infrared data, and in particular the absence of absorptions
attributable to Ì(La–Clter), suggest that
[LaCl3(dme)] is polymeric with six bridging
chlorides per lanthanum. For
[YbCl2(MeCN)5]2[YbCl3(MeCN)(-Cl)2YbCl3-(MeCN)],
a remarkable ionic structure, with pentagonal-bipyramidal
[YbCl2(MeCN)5]+
cations and octahedral di-nuclear
[YbCl3(MeCN)(-Cl)2YbCl3(MeCN)]2–
counter ions, is observed. In the former, chloride ligands are apical, while
the MeCN ligands of the latter are transoid.
Structural Systematics of Rare Earth Complexes. XXII. ('Maximally') Hydrated Rare Earth Iodides
Authors: Lim Kevin C. , Skelton Brian W. , White Allan H.
Published: September 2002

Low-temperature (c. 153 K) single-crystal X-ray
structure determinations, carried out on trivalent rare earth iodides
crystallized from aqueous solution at room temperature, have defined two
series of hydrates,
LnI3.nH2O.
For Ln = La–Ho, a nonahydrate phase (n
= 9) is defined, orthorhombic Pmmn,
a ~ 11.5, b ~ 8.0,
c ~ 8.8 Å, Z = 2, the
second phase (n = 10), monoclinic
P21/c,
Z = 4 being defined for Ln = Er–Lu,
a ~ 8.2, b ~ 12.8,
c ~ 17.1 Å, β ~ 103.7˚. Neither of these
phases is isomorphous with any of those pertinent to the previously studied
chloride or bromide (hydrated) arrays, nor, unlike those, does the halide
(iodide) in any case enter the coordination sphere of the lanthanoid. The
n = 9 phase takes the form
[Ln(OH2)9]I3,
the nine-coordinate lanthanoid environment stereochemistry being tricapped
trigonal-prismatic, while the n = 10 phase is
[Ln(OH2)8]I3.2H2O,
the eight-coordinate lanthanoid environment being square-antiprismatic.
Photolysis of Fused Cyclobutatriazolines: An Adventitious Route to 3,6-Di(2-pyridyl)pyridazonorbornadiene
Authors: Margetic Davor , Butler Douglas N. , Warrener Ronald N.
Published: September 2002

Ultraviolet irradiation of the triazolines (18a,b) formed by the high-pressure
addition of benzyl azide to dimethyl
3,6-di(2-pyridyl)-4,5-diazatetracyclo[6.4.1.0 2,3
.0 9,12
]trideca-3,5,7,10-tetraene-10,12-dicarboxylate (16a) and the related
monoester (16b), forms 13–17% of the expected aziridine (19a,b),
together with cyclobutane-cleavage products that include the hitherto unknown
pyridazinonorbornadiene (2), its di-π-methane rearrangement product (21)
and the corresponding triazoles (20a,b). Mechanistic pathways are discussed.
Short Communication: The 1 :1 Co-Crystal of 2-Amino-5-nitro-1,3-thiazole with 4-Aminobenzoic Acid
Authors: Lynch Daniel E.
Published: September 2002

The basic structural unit of the 1:1 co-crystal of
2-amino-5-nitro-1,3-thiazole with 4-aminobenzoic acid,
[(2-antz)(4-aba)], comprises two constituent molecules associated by
a hydrogen-bonded R2 2(8) graph
set dimer through the carboxylic group across the N/N site of the thiazole
[O–H···N, 2.614(3) Å;
N–H···O, 2.991(3) Å]. Additional
hydrogen-bonding associations from the three remaining amino hydrogen atoms
construct a non-centrosymmetric packing lattice (space group:
P21). The bulk ungraded powder
exhibits a second harmonic signal of
I/Iurea=
5.7.
Manuscript received: 16 July 2001.
Final version: 9 November 2001.
Current Chemistry: Nanostructured Biomaterials: a Novel Approach to Artificial Bone Implants
Authors: Lutton Cameron , Read Jonathon , Trau Matt
Published: September 2002

Manuscript received: 14 September 2001.
Final version: 3 December 2001.
Current Chemistry: Transition Metal Coordination Complexes of Verdazyl Radicals: New Building Blocks for Molecule-Based Magnets
Authors: Hicks Robin G.
Published: September 2002

Manuscript received: 1 October 2001.
Final version: 6 November 2001.
Current Chemistry: Strategies for Supramolecular Assembly
Authors: Dinev Zoran , Lambert John N.
Published: September 2002

Manuscript received: 10 October 2001.
Final version: 17 December 2001.
Review: The Materials Chemistry of Inorganic Catalysts
Authors: Thomas John Meurig , Raja Robert
Published: September 2002

The factors that govern the materials chemistry of a variety of new catalysts
are identified and illustrated. Prominence is given mainly to nanoporous (and
some nanoparticle) catalysts, which are of high relevance in
‘clean’ technology and ‘green’ chemistry. In
particular, molecular sieve catalysts for the regioselective
oxyfunctionalization of alkanes, clay catalysts for Brønsted-acid
catalysed ester formation, titanium ion-centred epoxidation catalysts,
enantioselective catalysts based on organometallic moieties heterogenized
within mesoporous silicas, and Fischer–Tropsch catalysts for both the
production of fuel and desirable chemical commodities are described. A
single-step, solvent-free nanoporous, bifunctional catalyst for the benign
ammoximation of cyclohexanone (leading to caproclactam) is also outlined, as
is the lure and limitations of combinatorial chemistry for the design of new
catalysts.
Manuscript received: 15 October 2001.
Final version: 2 November 2001.
Multifunctional Properties of (Z)-β-(N-Hexadecyl-4-quinolinium)-α-cyano-4-styryldicyanomethanide: a Molecular Rectifier, Optically Non-Linear Dye, and Ammonia Sensor
Authors: Ashwell G. J. , Paxton G. A. N.
Published: September 2002

The zwitterionic dye, Z-β-(N-hexadecyl-4-quinolinium)-α-cyano-4-styryldicyanomethanide (C16H33-Q3CNQ), forms dimeric solution aggregates, which are probably centric, but adopt a non-centrosymmetric arrangement at the air/water interface. When spread from dilute solution, e.g. 3 × 10-5 M in CH2Cl2, the resultant Langmuir-Blodgett (LB) films are purple, λmax 563 ± 3 nm. They have an optimum effective second-order non-linear optical susceptibility of 75 pm V-1 at 1.064 μm and, when sandwiched between gold electrodes, exhibit asymmetric current-voltage curves, characteristic of molecular rectification. In contrast, when spread at slightly higher concentrations (e.g. 10-4 M), the resultant LB films are polymorphic and have absorption maxima at 563 and 670 nm, the latter being characteristic of the benzyl analogue (φ-CH2-Q3CNQ). Its films are turquoise, λmax 668 ± 3 nm, and both molecular rectification and second-harmonic generation are inhibited. Thus, the red-shifted charge-transfer band probably reflects an altered alignment whereby the molecules adopt a centric antiparallel arrangement within the monolayer. The zwitterionic films readily protonate, with bleaching, and may be used to sense ammonia at concentrations of ca. 1 ppm by monitoring changes in the surface plasmon resonance.
Structure of the Lipopolysaccharide Core Region of the Bacteria of the Genus Proteus
Authors: Vinogradov E. , Sidorczyk Z. , Knirel Y. A.
Published: September 2002

The lipopolysaccharide (LPS) core structure was studied in seven rough strains of Proteus and 26 smooth strains belonging to various Proteus O-serogroups. All LPSs share a common heptasaccharide fragment, which includes two Kdo, three Hep, one Glc, and one GalA residue. Core structures differ between strains and within each strain in the presence of a variety of additional monosaccharides and non-sugar substituents. In many strains, the LPS includes a cyclic acetal of GalNAc in the open-chain form, which builds up a new type of linkage between monosaccharides. The covalent linkage of aliphatic polyamines, e.g. putrescine and spermidine, to the LPS was confirmed for the first time and the location of the amines at the carboxyl group of a GalA residue established. Analyses revealed peculiar features of the core structure, which are characteristic of P. mirabilis on one hand and P. vulgaris and P. penneri on the other hand.
Rhodomyrtone, an antibotic from Rhodomyrtus tomentosa
Authors: Salni Dachriyanus , Sargent M. V. , Skelton B. W. , Soediro I. , Sutisna M. , White A. H. , Yulinah E.
Published: September 2002

The ethyl acetate extract of the leaves of Rhodomyrtus tomentosa (Ait.) Hassk. yielded rhodomyrtone (5) [6,8-dihydroxy-2,2,4,4-tetramethyl-7-(3-methyl-1-oxobutyl)-9-(2-methylpropyl)-4,9-dihydro-1H-xanthene-1,3(2H)-di-one] which had significant activity against Escherichia coli and Staphylococcus aureus. The structural elucidation followed from spectroscopic evidence and from a single-crystal X-ray structural determination.
Novel Secondary Dopants for Camphorsulfonic Acid Doped Polyaniline Emeraldine Salts
Authors: Norris I. D. , Kane-Maguire L. A. , Wallace G. G. , Dai L. , Zhang F. , Mau A. W. H.
Published: September 2002

The doping of emeraldine base with (±)-10-camphorsulfonic acid (HCSA) or (+)-HCSA in molten thymol (60°C) or liquid carvacrol (5-isopropyl-2-methylphenol) as solvents provides emeraldine polyaniline (PAn)�HCSA salts (1) with 'expanded coil'-type conformations for their polyaniline chains. Conversion of both racemic PAn�(±)-HCSA (1a) and optically active PAn�(+)-HCSA (1b) films from a 'compact coil' into a partial 'expanded coil' conformation is also facilitated by exposure of the films to either thymol or carvacrol vapours. These conformational changes are supported by modifications to their ultraviolet-visible-near-infrared and circular dichroism spectra and by the marked increase in the electrical conductivity of the films. In the case of carvacrol vapour, treated films of (1a) and (1b) exhibited conductivities of ≥ 130 S/cm, similar to conductivities previously generated by m-cresol. In view of the much lower toxicity of carvacrol compared with m-cresol, it would appear to have considerable promise as an effective 'secondary dopant' for emeraldine salts leading to materials with enhanced electrical conductivity.
A New Catalyst for the Reductive Elimination of Acylated Glycosyl Bromides to Form Glycals
Authors: Stick R. V. , Stubbs K. A. , Tilbrook D. M. G. , Watts A. G.
Published: September 2002

Ethylene-N,N-bis(salicylideneiminato)oxovanadium(IV) {VO(salen)} has been developed as a useful catalyst for the reductive elimination of acylated glycosyl bromides to form glycals, both in the pyranose and furanose series, using zinc/ammonium chloride/methanol or zinc/acetic acid/acetonitrile.
C-Glycosides by Aqueous Condensation of β-Dicarbonyl Compounds with Unprotected Sugars
Authors: Riemann I. , Fessner W.-D. , Papadopoulos M. A. , Knorst M.
Published: September 2002

Condensation of 1,3-diketones with unprotected aldoses in water, under mildly alkaline conditions, provides a�convenient and effective route to C-glycosidic ketones in high yields. Reactions usually proceed with high β`anomeric' stereoselectivity because product composition is determined by thermodynamic control. Mechanistically, the condensation follows a typical Knoevenagel scheme, after which an intramolecular oxa-Michael cyclization determines C-glycoside configuration by following an exo- or endo-trig pathway. With open-chain 1,3-diketones, an ensuing retro-Claisen fragmentation occurs to furnish simple glycosyl monoketones. The C-glycosides then slowly further dehydrate under the reaction conditions to give 2,5-disubstituted furans.
Pigments of Fungi. LXIX. Total Synthesis of (R)-Ochratoxin α and the Formal Total Synthesis of Ochratoxin
Authors: Donner C. , Gill M.
Published: September 2002

(R)-Ochratoxin α, the monochiral carboxylic acid component of the biologically active dipeptide ochratoxin A, is synthesized for the first time over nine steps from (R)-propylene oxide. The method constitutes a versatile and general route to functionalized dihydroisocoumarins.
Trifluoroacetamido Substituted Sialyl Donors for the Preparation of Sialyl Galactosides
Authors: De Meo C. , Demchenko A. V. , Boons G.-J.
Published: September 2002

Glycosidations of sialyl donor (1a), bearing a trifluoroacetamido group at C5, with partially protected D-galactosyl derivatives afforded (2,3)-linked disaccharides in high yields and excellent stereoselectivities, even when sterically hindered alcohols were used as glycosyl acceptors. Good yields but modest stereoselectivities were obtained when (1a) was glycosidated with the C6 hydroxyl of D-galactosides.
Editorial: The World Chemistry Congress 2001 and the Young Scientist Awards
Authors: Green Alison
Published: September 2002

Manuscript received: 2 January 2002.
Final version: 4 February 2002.
A Polyfunctional Lewis Acid with Antifacial µ3-N,N-Dimethylformamide Ligands in [(o-HgC6F4)3(dmf)2]
Authors: Baldamus J. , Deacon G. B. , Hey-Hawkins E. , Junk P. C. , Martin C.
Published: September 2002

In [(o-HgC6F4)3(dmf)2], the cyclotrimeric tetrafluoro-o-phenylenemercury(II) molecule is ligated by two m3-dmf-O molecules above (Hg-O 2.837(7), 2.895(5), 3.036(5) �) and below (Hg-O 2.820(5), 2.863(6), 2.927(6) �) the Hg3 plane with the two oxygens and the three mercury atoms in a trigonal bipyramidal arrangement about the centroid of the Hg3 plane.
Model Compounds Related to Saquayamycin. Attempts to Oxygenate the A/B Ring Junction
Authors: Apponyi M. A. , Bowie J. H. , Skelton B. W. , White A. H.
Published: September 2002

The aim of this project was to attempt to find a method for introducing the cis-dihydroxyl substitution at the A/B-ring junction of model compounds related to the saquayamycins. The Diels-Alder reactions of maleic anhydride and bromomaleic anhydride with 5,5-dimethyl-3-vinylcyclohexa-1,2-dienyl acetate gave the two required endo-adducts in good yield, namely (octahydrobenzo[e]isobenzofuran-9-yl acetate (6) and (octahydrobenzo[e]isobenzofuran-9-yl acetate (9). Each of these was converted into the B-ring mono-epoxide, namely (H-benzo[e]oxireno-2,3-furan-1-yl acetate (7) and a mixture of two racemic diastereoisomers of 9a-bromo-3,3-dimethyl-7,9-dioxoperhydrobenzo[e]oxi- reno[2,3-f]isobenzofuran-1-yl acetate (12), respectively. It was then hoped to deprotonate both (7) and (12) at the 9a position in order to effect migration of the 8,9 double bond to the 9,9a position. Reaction of (7) with a mild base (pyridine) did not effect any reaction. Similar treatment of (12) did remove the 9a proton, but it also effected ring opening of the epoxide, followed by dehydration and dehydrobromination to give an excellent (but unwanted) yield of the aromatized system (±)-7,7-dimethyl-1,3-dioxo-1,3,5,7-tetrahydrobenzo (e]isobenzofuran-9-yl acetate. Dehydrobromination of (9), and deprotonation of the 9a position, similarly formed the aromatic system (e]isobenzofuran-9-yl acetate (11) in good yield.
New Aspects of an AGEing Chemistry — Recent Developments Concerning the Maillard Reaction
Authors: Gerrard J. A.
Published: September 2002

The chemistry and consequences of the Maillard reaction network-initiated by the condensation of an amine with a carbonyl group, often from a reducing sugar—are reviewed. This chemistry has consequences that pervade the two disparate literatures of food science and medicine. The Maillard reaction is responsible for many aspects of the colour, flavour and texture of processed foods. It is also a key player in the ageing process, especially amongst diabetics. Recent developments have led to detailed characterization of some of the many Maillard reaction products and a sufficient understanding of their mechanisms of formation to pique the interest of mainstream chemists. Much remains to be elucidated, but the potential rewards of understanding, and ultimately controlling, this chemistry are enormous.