Showing papers by "Australian National University published in 2000"

Multiple view geometry in computer vision

Abstract: From the Publisher: A basic problem in computer vision is to understand the structure of a real world scene given several images of it. Recent major developments in the theory and practice of scene reconstruction are described in detail in a unified framework. The book covers the geometric principles and how to represent objects algebraically so they can be computed and applied. The authors provide comprehensive background material and explain how to apply the methods and implement the algorithms directly.

New Support Vector Algorithms

Abstract: We propose a new class of support vector algorithms for regression and classification. In these algorithms, a parameter ν lets one effectively control the number of support vectors. While this can be useful in its own right, the parameterization has the additional benefit of enabling us to eliminate one of the other free parameters of the algorithm: the accuracy parameter epsilon in the regression case, and the regularization constant C in the classification case. We describe the algorithms, give some theoretical results concerning the meaning and the choice of ν, and report experimental results.

Conservation of the sequence and temporal expression of let-7 heterochronic regulatory RNA

Abstract: Two small RNAs regulate the timing of Caenorhabditis elegans development. Transition from the first to the second larval stage fates requires the 22-nucleotide lin-4 RNA and transition from late larval to adult cell fates requires the 21-nucleotide let-7 RNA. The lin-4 and let-7 RNA genes are not homologous to each other, but are each complementary to sequences in the 3' untranslated regions of a set of protein-coding target genes that are normally negatively regulated by the RNAs. Here we have detected let-7 RNAs of ~21 nucleotides in samples from a wide range of animal species, including vertebrate, ascidian, hemichordate, mollusc, annelid and arthropod, but not in RNAs from several cnidarian and poriferan species, Saccharomyces cerevisiae, Escherichia coli or Arabidopsis. We did not detect lin-4 RNA in these species. We found that let-7 temporal regulation is also conserved: let-7 RNA expression is first detected at late larval stages in C. elegans and Drosophila , at 48 hours after fertilization in zebrafish, and in adult stages of annelids and molluscs. The let-7 regulatory RNA may control late temporal transitions during development across animal phylogeny.

Final Results from the Hubble Space Telescope Key Project to Measure the Hubble Constant

Abstract: We present here the final results of the Hubble Space Telescope Key Project to measure the Hubble constant. We summarize our method, the results and the uncertainties, tabulate our revised distances, and give the implications of these results for cosmology. The analysis presented here benefits from a number of recent improvements and refinements, including (1) a larger LMC Cepheid sample to define the fiducial period-luminosity (PL) relations, (2) a more recent HST Wide Field and Planetary Camera 2 (WFPC2) photometric calibration, (3) a correction for Cepheid metallicity, and (4) a correction for incompleteness bias in the observed Cepheid PL samples. New, revised distances are given for the 18 spiral galaxies for which Cepheids have been discovered as part of the Key Project, as well as for 13 additional galaxies with published Cepheid data. The new calibration results in a Cepheid distance to NGC 4258 in better agreement with the maser distance to this galaxy. Based on these revised Cepheid distances, we find values (in km/sec/Mpc) of H0 = 71 +/- 2 (random) +/- 6 (systematic) (type Ia supernovae), 71 +/- 2 +/- 7 (Tully-Fisher relation), 70 +/- 5 +/- 6 (surface brightness fluctuations), 72 +/- 9 +/- 7 (type II supernovae), and 82 +/- 6 +/- 9 (fundamental plane). We combine these results for the different methods with 3 different weighting schemes, and find good agreement and consistency with H0 = 72 +/- 8. Finally, we compare these results with other, global methods for measuring the Hubble constant.

Mental health literacy. Public knowledge and beliefs about mental disorders.

Abstract: Background Although the benefits of public knowledge of physical diseases are widely accepted, knowledge about mental disorders (mental health literacy) has been comparatively neglected. Aims To introduce the concept of mental health literacy to a wider audience, to bring together diverse research relevant to the topic and to identify gaps in the area. Method A narrative review within a conceptual framework. Results Many members of the public cannot recognise specific disorders or different types of psychological distress. They differ from mental health experts in their beliefs about the causes of mental disorders and the most effective treatments. Attitudes which hinder recognition and appropriate help-seeking are common. Much of the mental health information most readily available to the public is misleading. However, there is some evidence that mental health literacy can be improved. Conclusions If the public's mental health literacy is not improved, this may hinder public acceptance of evidence-based mental health care. Also, many people with common mental disorders may be denied effective self-help and may not receive appropriate support from others in the community.

'Accountability': an ever-expanding concept?

Abstract: The scope and meaning of ‘accountability’ has been extended in a number of directions well beyond its core sense of being called to account for one’s actions. It has been applied to internal aspects of official behaviour, beyond the external focus implied by being called to account; to institutions that control official behaviour other than through calling officials to account; to means of making officials responsive to public wishes other than through calling them to account; and to democratic dialogue between citizens where no one is being called to account. In each case the extension is readily intelligible because it is into an area of activity closely relevant to the practice of core accountability. However, in each case the extension of meaning may be challenged as weakening the importance of external scrutiny

Global Business Regulation

Abstract: Across an amazing sweep of the critical areas of business regulation - from contract, intellectual property and corporations law, to trade, telecommunications, labour standards, drugs, food, transport and environment - this book confronts the question of how the regulation of business has shifted from national to global institutions. Based on interviews with 500 international leaders in business and government, this book examines the role played by global institutions such as the WTO, the OECD, IMF, Moody's and the World Bank, as well as various NGOs and significant individuals. The authors argue that effective and decent global regulation depends on the determination of individuals to engage with powerful agendas and decision-making bodies that would otherwise be dominated by concentrated economic interests. This book will become a standard reference for readers in business, law, politics and international relations.

Temporary Jobs: Stepping Stones or Dead Ends?

Abstract: In Britain about 7% of male employees and 10% of female employees are in temporary jobs. In contrast to much of continental Europe, this proportion has been relatively stable over the 1990s. Using data from the British Household Panel Survey, we find that temporary workers report lower levels of job satisfaction, receive less work-related training, and are less well-paid than their counterparts in permanent employment. However, there is evidence that fixed-term contracts are a stepping stone to permanent work. Women (but not men) who start in fixed-term employment and move to permanent jobs fully catch up to those who start in permanent jobs.

A model of inductive bias learning

Abstract: A major problem in machine learning is that of inductive bias: how to choose a learner's hypothesis space so that it is large enough to contain a solution to the problem being learnt, yet small enough to ensure reliable generalization from reasonably-sized training sets. Typically such bias is supplied by hand through the skill and insights of experts. In this paper a model for automatically learning bias is investigated. The central assumption of the model is that the learner is embedded within an environment of related learning tasks. Within such an environment the learner can sample from multiple tasks, and hence it can search for a hypothesis space that contains good solutions to many of the problems in the environment. Under certain restrictions on the set of all hypothesis spaces available to the learner, we show that a hypothesis space that performs well on a sufficiently large number of training tasks will also perform well when learning novel tasks in the same environment. Explicit bounds are also derived demonstrating that learning multiple tasks within an environment of related tasks can potentially give much better generalization than learning a single task.

Sister-scanning: a Monte Carlo procedure for assessing signals in recombinant sequences.

Abstract: Motivation: To devise a method that, unlike available methods, directly measures variations in phylogenetic signals in gene sequences that result from recombination, tests the significance of the signal variations and distinguishes misleading signals. Results: We have developed a method, that we call ‘sisterscanning’, for assessing phylogenetic and compositional signals in the various patterns of identity that occur between four nucleotide sequences. A Monte Carlo randomization is done for all columns (positions) within a window and Z -scores are obtained for four real sequences or three real sequences with an outlier that is also randomized. The usefulness of the approach is demonstrated using tobamovirus and luteovirus sequences. Contradictory phylogenetic signals were distinguished in both datasets, as were regions of sequence that contained no clear signal or potentially misleading signals related to compositional similarities. In the tobamovirus dataset, contradictory phylogenetic signals were separated by coding sequences up to a kilobase long that contained no clear signal. Our re-analysis of this dataset using sister-scanning also yielded the first evidence known to us of an interspecies recombination site within a viral RNA-dependent RNA polymerase gene together with evidence of an unusual pattern of conservation in the three codon positions. Availability: A program package, SiScan, for use under MS-DOS can be downloaded from http:// life.anu.edu.au/ with test data and instructions.

The MACHO Project: Microlensing Results from 5.7 Years of Large Magellanic Cloud Observations

Abstract: We report on our search for microlensing toward the Large Magellanic Cloud (LMC). Analysis of 5.7 yr of photometry on 11.9 million stars in the LMC reveals 13-17 microlensing events. A detailed treatment of our detection efficiency shows that this is significantly more than the ~2-4 events expected from lensing by known stellar populations. The timescales () of the events range from 34 to 230 days. We estimate the microlensing optical depth toward the LMC from events with 2 < < 400 days to be τ = 1.2 × 10-7, with an additional 20% to 30% of systematic error. The spatial distribution of events is mildly inconsistent with LMC/LMC disk self-lensing, but is consistent with an extended lens distribution such as a Milky Way or LMC halo. Interpreted in the context of a Galactic dark matter halo, consisting partially of compact objects, a maximum-likelihood analysis gives a MACHO halo fraction of 20% for a typical halo model with a 95% confidence interval of 8%-50%. A 100% MACHO halo is ruled out at the 95% confidence level for all except our most extreme halo model. Interpreted as a Galactic halo population, the most likely MACHO mass is between 0.15 and 0.9 M☉, depending on the halo model, and the total mass in MACHOs out to 50 kpc is found to be 9 × 1010 M☉, independent of the halo model. These results are marginally consistent with our previous results, but are lower by about a factor of 2. This is mostly due to Poisson noise, because with 3.4 times more exposure and increased sensitivity to long-timescale events, we did not find the expected factor of ~4 more events. In addition to a larger data set, this work also includes an improved efficiency determination, improved likelihood analysis, and more thorough testing of systematic errors, especially with respect to the treatment of potential backgrounds to microlensing. We note that an important source of background are supernovae (SNe) in galaxies behind the LMC.

Timing of the Last Glacial Maximum from observed sea-level minima

Abstract: During the Last Glacial Maximum, ice sheets covered large areas in northern latitudes, and global temperatures were significantly lower than today. But few direct estimates exist of the volume of the ice sheets, or the timing and rates of change during their advance and retreat. Here we analyze four distinct sediment facies in the shallow, tectonically stable Bonaparte Gulf, Australia - each of which is characteristic of a distinct range in sea level - to estimate the maximum volume of land-based ice during the last glaciation and the timing of the initial melting phase. We use faunal assemblages and preservation status of the sediments to distinguish open marine, shallow marine, marginal marine and brackish conditions, and estimate the timing and the mass of the ice sheets using radiocarbon dating and glacio-hydroisostatic modelling. Our results indicate that from at least 22,000 to 19,000 (calendar) years before present, land-based ice volume was at its maximum, exceeding today's grounded ice sheets by 52.5 x 10 exp 6 cu km. A rapid decrease in ice volume by about 10 percent within a few hundred years terminated the Last Glacial Maximum at 19,000 +/- 250 years.

Gender equity in theories of fertility transition

Abstract: Recent theoretical discussion has postulated that low fertility in advanced countries is attributable to low levels of gender equity. Low gender equity is evidenced in the lack of support for women to combine paid employment and childrearing; tax-transfer systems that remain based on the male-breadwinner model of the family; and the retention of gender-oriented roles within the family. Hence, it is argued that an increase in gender equity is a precondition of a rise in fertility from very low levels. At the same time, theorists argue that, in less developed countries, higher levels of gender equity are a necessary condition for achieving lower fertility. The article addresses this apparent contradiction by distinguishing two types of gender equity: gender equity in individual-oriented institutions and gender equity in family-oriented institutions. The argument is made that the transition from very high fertility to replacement-level fertility has been associated with a gradual increase in gender equity primarily within the family itself. In contrast, the further movement to very low fertility is associated with a rapid shift toward high levels of gender equity in individual institutions such as education and market employment, in combination with persistent low levels of gender equity within the family and in family-oriented institutions.

Indicators of biodiversity for ecologically sustainable forest management

Abstract: The conservation of biological diversity has become one of the important goals of managing for- ests in an ecologically sustainable way. Ecologists and forest resource managers need measures to judge the success or failure of management regimes designed to sustain biological diversity. The relationships between potential indicator species and total biodiversity are not well established. Carefully designed studies are re- quired to test relationships between the presence and abundance of potential indicator species and other taxa and the maintenance of critical ecosystem processes in forests. Other indicators of biological diversity in forests, in addition or as alternatives to indicator species, include what we call structure-based indicators. These are stand-level and landscape-level (spatial) features of forests such as stand structural complexity and plant species composition, connectivity, and heterogeneity. Although the adoption of practices to sustain (or recreate) key characteristics of forest ecosystems appear intuitively sensible and broadly consistent with cur- rent knowledge, information is lacking to determine whether such stand- and landscape-level features of for- ests will serve as successful indices of (and help conserve) biodiversity. Given our limited knowledge of both indicator species and structure-based indicators, we advocate the following four approaches to enhance biodiversity conservation in forests: (1) establish biodiversity priority areas (e.g., reserves) managed prima- rily for the conservation of biological diversity; (2) within production forests, apply structure-based indica- tors including structural complexity, connectivity, and heterogeneity; (3) using multiple conservation strate- gies at multiple spatial scales, spread out risk in wood production forests; and (4) adopt an adaptive management approach to test the validity of structure-based indices of biological diversity by treating man- agement practices as experiments. These approaches would aim to provide new knowledge to managers and improve the effectiveness of current management strategies.

Pgh1 modulates sensitivity and resistance to multiple antimalarials in Plasmodium falciparum.

Abstract: Throughout the latter half of this century, the development and spread of resistance to most front-line antimalarial compounds used in the prevention and treatment of the most severe form of human malaria has given cause for grave clinical concern. Polymorphisms in pfmdr1, the gene encoding the P-glycoprotein homologue 1 (Pgh1) protein of Plasmodium falciparum, have been linked to chloroquine resistance1; Pgh1 has also been implicated in resistance to mefloquine and halofantrine2,3,4,5. However, conclusive evidence of a direct causal association between pfmdr1 and resistance to these antimalarials has remained elusive, and a single genetic cross has suggested that Pgh1 is not involved in resistance to chloroquine and mefloquine6. Here we provide direct proof that mutations in Pgh1 can confer resistance to mefloquine, quinine and halofantrine. The same mutations influence parasite resistance towards chloroquine in a strain-specific manner and the level of sensitivity to the structurally unrelated compound, artemisinin. This has important implications for the development and efficacy of future antimalarial agents.

Varroa jacobsoni (Acari: Varroidae) is more than one species

Abstract: Varroa jacobsoni was first described as a natural ectoparasitic mite of the Eastern honeybee (Apis cerana) throughout Asia. It later switched host to the Western honeybee (A. mellifera) and has now become a serious pest of that bee worldwide. The studies reported here on genotypic, phenotypic and reproductive variation among V. jacobsoni infesting A. cerana throughout Asia demonstrate that V. jacobsoni is a complex of at least two different species. In a new classification V. jacobsoni is here redefined as encompassing nine haplotypes (mites with distinct mtDNA CO-I gene sequences) that infest A. cerana in the Malaysia–Indonesia region. Included is a Java haplotype, specimens of which were used to first describe V. jacobsoni at the beginning of this century. A new name, V. destructor n. sp., is given to six haplotypes that infest A. cerana on mainland Asia. Adult females of V. destructor are significantly larger and less spherical in shape than females of V. jacobsoni and they are also reproductively isolated from females of V. jacobsoni. The taxonomic positions of a further three unique haplotypes that infest A. cerana in the Philippines is uncertain and requires further study. Other studies reported here also show that only two of the 18 different haplotypes concealed within the complex of mites infesting A. cerana have become pests of A. mellifera worldwide. Both belong to V. destructor, and they are not V. jacobsoni. The most common is a Korea haplotype, so-called because it was also found parasitizing A. cerana in South Korea. It was identified on A. mellifera in Europe, the Middle East, Africa, Asia, and the Americas. Less common is a Japan/Thailand haplotype, so-called because it was also found parasitizing A. cerana in Japan and Thailand. It was identified on A. mellifera in Japan, Thailand and the Americas. Our results imply that the findings of past research on V. jacobsoni are applicable mostly to V. destructor. Our results will also influence quarantine protocols for bee mites, and may present new strategies for mite control.

Diversity and dynamics of dendritic signaling.

Abstract: Communication between neurons in the brain occurs primarily through synapses made onto elaborate treelike structures called dendrites. New electrical and optical recording techniques have led to tremendous advances in our understanding of how dendrites contribute to neuronal computation in the mammalian brain. The varied morphology and electrical and chemical properties of dendrites enable a spectrum of local and long-range signaling, defining the input-output relationship of neurons and the rules for induction of synaptic plasticity. In this way, diversity in dendritic signaling allows individual neurons to carry out specialized functions within their respective networks.

Rare earth element chemistry of zircon and its use as a provenance indicator

Abstract: Sedimentary mineral assemblages commonly contain detrital zircon crystals as part of the heavy-mineral fraction. Age spectra determined by U-Pb isotopic analysis of single zircon crystals within a sample may directly image the age composition—but not the chemical composition—of the source region. Rare earth element (REE) abundances have been measured for zircons from a range of common crustal igneous rock types from different tectonic environments, as well as kimberlite, carbonatite, and high-grade metamorphic rocks, to assess the potential of using zircon REE characteristics to infer the rock types present in sediment source regions. Except for zircon with probable mantle affinities, zircon REE abundances and normalized patterns show little intersample and intrasample variation. To evaluate the actual variation in detrital zircon REE composition in a true sediment of known mixed provenance, zircons from a sandstone sample from the Statfjord Formation (North Sea) were analyzed. Despite a provenance including high-grade metasediment and granitoids and a range in zircon age of 2.82 b.y., the zircon REEs exhibit a narrow abundance range with no systematic differences in pattern shape. These evidences show zircon REE patterns and abundances are generally not useful as indicators of provenance.

On the LASSO and its dual

Abstract: Proposed by Tibshirani, the least absolute shrinkage and selection operator (LASSO) estimates a vector of regression coefficients by minimizing the residual sum of squares subject to a constraint on the l 1-norm of the coefficient vector. The LASSO estimator typically has one or more zero elements and thus shares characteristics of both shrinkage estimation and variable selection. In this article we treat the LASSO as a convex programming problem and derive its dual. Consideration of the primal and dual problems together leads to important new insights into the characteristics of the LASSO estimator and to an improved method for estimating its covariance matrix. Using these results we also develop an efficient algorithm for computing LASSO estimates which is usable even in cases where the number of regressors exceeds the number of observations. An S-Plus library based on this algorithm is available from StatLib.

Gender equity, social institutions and the future of fertility

Abstract: Sustained very low levels of fertility in advanced countries can be explained by incoherence between the levels of gender equity applying in different social institutions. In countries with very low levels of fertility, high levels of gender equity are postulated in institutions that deal with people as individuals, while low levels of gender equity apply in institutions that deal with people as members of families.

Does old age reduce the risk of anxiety and depression? A review of epidemiological studies across the adult life span.

Abstract: Background. There is considerable disagreement about what happens to the risk of anxiety and depression disorders and symptoms as people get older.Methods. A search was made for studies that examine the occurrence of anxiety, depression or general distress across the adult life span. To be included, a study had to involve a general population sample ranging in age from at least the 30s to 65 and over and use the same assessment method at each age.Results. There was no consistent pattern across studies for age differences in the occurrence of anxiety, depression or distress. The most common trend found was for an initial rise across age groups, followed by a drop. Two major factors producing this variability in results were age biases in assessment of anxiety and depression and the masking effect of other risk factors that vary with age. When other risk factors were statistically controlled, a more consistent pattern emerged, with most studies finding a decrease in anxiety, depression and distress across age groups. This decrease cannot be accounted for by exclusion of elderly people in institutional care from epidemiological surveys or by selective mortality of people with anxiety or depression.Conclusion. There is some evidence that ageing is associated with an intrinsic reduction in susceptibility to anxiety and depression. However, longitudinal studies covering the adult life span are needed to distinguish ageing from cohort effects. More attention needs to be given to understanding the mechanism behind any ageing-related reduction in risk for anxiety and depression with age. Possible factors are decreased emotional responsiveness with age, increased emotional control and psychological immunization to stressful experiences.

The Hubble Space Telescope Key Project on the Extragalactic Distance Scale. XXVIII. Combining the Constraints on the Hubble Constant

Abstract: Since the launch of Hubble Space Telescope (HST) 9 yr ago, Cepheid distances to 25 galaxies have been determined for the purpose of calibrating secondary distance indicators. Eighteen of these have been measured by the HST Key Project team, six by the Supernova Calibration Project, and one independently by Tanvir. Collectively, this work sets out an array of survey markers over the region within 25 Mpc of the Milky Way. A variety of secondary distance indicators can now be calibrated, and the accompanying four papers employ the full set of 25 galaxies to consider the Tully-Fisher relation, the fundamental plane of elliptical galaxies, Type Ia supernovae, and surface brightness fluctuations. When calibrated with Cepheid distances, each of these methods yields a measurement of the Hubble constant and a corresponding measurement uncertainty. We combine these measurements in this paper, together with a model of the velocity field, to yield the best available estimate of the value of H0 within the range of these secondary distance indicators and its uncertainty. The uncertainty in the result is modeled in an extensive simulation we call the "virtual Key Project." The velocity-field model includes the influence of the Virgo cluster, the Great Attractor, and the Shapley supercluster, but does not play a significant part in determining the result. The result is H0 = 71 ± 6 km s-1 Mpc-1. The largest contributor to the uncertainty of this 67% confidence level result is the distance of the Large Magellanic Cloud, which has been assumed to be 50 ± 3 kpc. This takes up the first 6.5% of our 9% error budget. Other contributors are the photometric calibration of the WFPC2 instrument, which takes up 4.5%, deviations from uniform Hubble flow in the volume sampled (2%), the composition sensitivity of the Cepheid period-luminosity relation (4%), and departures from a universal reddening law (~1%). These are the major components that , when combined in quadrature, make up the 9% total uncertainty. If the LMC distance modulus were systematically smaller by 1 σ than that adopted here, the derived value of the Hubble constant would increase by 4 km s-1 Mpc-1. Most of the significant systematic errors are capable of amelioration in future work. These include the uncertainty in the photometric calibration of WFPC2, the LMC distance, and the reddening correction. A NICMOS study is in its preliminary reduction phase, addressing the last of these concerns. Various empirical analyses have suggested that Cepheid distance moduli are affected by metallicity differences. If we adopted the composition sensitivity obtained in the Key Project's study of M101, and employed the oxygen abundances measured spectroscopically in each of the Cepheid fields we have studied, the value of the Hubble constant would be reduced by 4% ± 2% to 68 ± 6 km s-1 Mpc-1.

Single clinopyroxene thermobarometry for garnet peridotites. Part I. Calibration and testing of a Cr-in-Cpx barometer and an enstatite-in-Cpx thermometer

Abstract: Experimental clinopyroxenes synthesized at 850–1500 °C and 0–60 kbar in the CMS and CMAS-Cr systems and in more complex lherzolitic systems have been used to calibrate a Cr-in-Cpx barometer and an enstatite-in-Cpx thermometer for Cr-diopsides derived from garnet peridotites. The experiments cover a wide range of possible natural peridotitic compositions, from fertile pyrolite to refractory, high-Cr lherzolite. The barometer is based on the Cr exchange between clinopyroxene and garnet. Pressure is formulated as a function of temperature and clinopyroxene composition:

Crystal structure of a nucleosome core particle containing the variant histone H2A.Z

Abstract: Activation of transcription within chromatin has been correlated with the incorporation of the essential histone variant H2A.Z into nucleosomes. H2A.Z and other histone variants may establish structurally distinct chromosomal domains; however, the molecular mechanism by which they function is largely unknown. Here we report the 2.6 A crystal structure of a nucleosome core particle containing the histone variant H2A.Z. The overall structure is similar to that of the previously reported 2.8 A nucleosome structure containing major histone proteins. However, distinct localized changes result in the subtle destabilization of the interaction between the (H2A.Z-H2B) dimer and the (H3-H4)(2) tetramer. Moreover, H2A.Z nucleosomes have an altered surface that includes a metal ion. This altered surface may lead to changes in higher order structure, and/or could result in the association of specific nuclear proteins with H2A.Z. Finally, incorporation of H2A.Z and H2A within the same nucleosome is unlikely, due to significant changes in the interface between the two H2A.Z-H2B dimers.

Nuclear targeting signal recognition: a key control point in nuclear transport?

Abstract: Recent progress indicates that there are multiple pathways of nucleocytoplasmic transport which involve specific targeting sequences, such as nuclear localization sequences (NLSs), and cytosolic receptor molecules of the importin/karyopherin superfamily which recognise and dock the NLS-containing proteins at the nuclear pore. This first step of nuclear import/export is of central importance, with the affinity of the importin-targeting sequence interaction a critical parameter in determining transport efficiency. Different importins possess distinct NLS-binding specificities, which allows the system to be modulated through differential expression of the importins themselves, as well as through competition between different importins for the same protein, and between different proteins for the same importin. The targeting sequence-importin interaction can also be influenced directly by phosphorylation increasing the affinity of the interaction with importins or by targeting sequence masking through phosphorylation or specific protein binding. Targeting sequence recognition thus appears to represent a key control point in the regulation of nuclear transport. BioEssays 22:532-544, 2000.

The Rush Hour: The Character of Leisure Time and Gender Equity

Abstract: The distribution of leisure time between the genders is contested. Becker's theory of specialization suggests that there is an underlying gender equity in leisure, while the competing view suggests that women are now bearing a "dual burden" as both family providers and family carers. Using indicators of the quantity and quality of leisure drawn from the Multinational Time Budget Data Archive and the Australian Time Use Survey, we find some support for both views. Although men and women have similar quantities of free time; when the character of leisure is considered the gap between genders reemerges.