Signal Extraction and Forecasting of the UK Tourism Income Time Series: A Singular Spectrum Analysis Approach

We present and apply singular spectrum analysis (SSA), a relatively new, non‐parametric and data‐driven method for signal extraction (trends, seasonal and business cycle components) and forecasting of UK tourism income. Our results show that SSA slightly outperforms SARIMA and time‐varying‐parameter state space models in terms of root mean square error, mean absolute error and mean absolute percentage error forecasting criteria. Copyright © 2011 John Wiley & Sons, Ltd.     

Formation of molecular gas in the tidal debris of violent galaxy-galaxy interactions

In many gravitational interactions between galaxies, gas and stars that have been torn from the precursor galaxies can collect in tidal 'tails'. Star formation begins anew in some of these regions, producing tidal dwarf galaxies. Observations of these new galaxies provides insight into processes relevant to galaxy formation more generally, because the timescale of the interaction is well defined. But tracking the star formation process has hitherto been difficult because the tidal dwarf galaxies with young stars showed no evidence of the molecular gas out of which those young stars formed. Here we report the discovery of molecular hydrogen (traced by carbon monoxide emission) in two tidal dwarf galaxies. In both cases, the concentration of molecular gas peaks at the same location as the maximum in atomic-hydrogen density, unlike the situation in most gas-rich galaxies. We infer from this that the molecular gas formed from the atomic hydrogen, rather than being torn in molecular form from the interacting galaxies. Star formation in the tidal dwarf galaxies therefore appears to mimic the process in normal spiral galaxies like our own.     

Phosphoglycerate dehydrogenase diverts glycolytic flux and contributes to oncogenesis

Most tumors exhibit increased glucose metabolism to lactate, however, the extent to which glucose-derived metabolic fluxes are used for alternative processes is poorly understood. Using a metabolomics approach with isotope labeling, we found that in some cancer cells a relatively large amount of glycolytic carbon is diverted into serine and glycine metabolism through phosphoglycerate dehydrogenase (PHGDH). An analysis of human cancers showed that PHGDH is recurrently amplified in a genomic region of focal copy number gain most commonly found in melanoma. Decreasing PHGDH expression impaired proliferation in amplified cell lines. Increased expression was also associated with breast cancer subtypes, and ectopic expression of PHGDH in mammary epithelial cells disrupted acinar morphogenesis and induced other phenotypic alterations that may predispose cells to transformation. Our findings show that the diversion of glycolytic flux into a specific alternate pathway can be selected during tumor development and may contribute to the pathogenesis of human cancer.     

Phenology of fruit and leaf production by ‘strangler’ figs on Barro Colorado Island,Panamá

Summary Fruit and leaf initiation by 26 trees representing five stranglerFicus species in the subgenusUrostigma were monitored for 5–8 years in a seasonal lowland forest of central Panamá. Individual trees of each species initiated fruit in synchronized crops. High variation in the number of crops, intervals between crops and dates of crop initiation indicate that these species, like species in the subgenusPharmacosycea, initiate fruit crops the year around. Nevertheless, mean crop initiation dates for four of five species fell within the four-month dry season. Similarly, all species produced new leaf flushes throughout the year, however, mean leaf flush dates of all species fell within the first three months of the dry season.     

A new hominid from the Upper Miocene of Chad,Central Africa

The search for the earliest fossil evidence of the human lineage has been concentrated in East Africa. Here we report the discovery of six hominid specimens from Chad, central Africa, 2,500 km from the East African Rift Valley. The fossils include a nearly complete cranium and fragmentary lower jaws. The associated fauna suggest the fossils are between 6 and 7 million years old. The fossils display a unique mosaic of primitive and derived characters, and constitute a new genus and species of hominid. The distance from the Rift Valley, and the great antiquity of the fossils, suggest that the earliest members of the hominid clade were more widely distributed than has been thought, and that the divergence between the human and chimpanzee lineages was earlier than indicated by most molecular studies.     

Poleward heat transport by the atmospheric heat engine

The atmospheric heat transport on Earth from the Equator to the poles is largely carried out by the mid-latitude storms. However, there is no satisfactory theory to describe this fundamental feature of the Earth's climate. Previous studies have characterized the poleward heat transport as a diffusion by eddies of specified horizontal length and velocity scales, but there is little agreement as to what those scales should be. Here we propose instead to regard the baroclinic zone--the zone of strong temperature gradients and active eddies--as a heat engine which generates eddy kinetic energy by transporting heat from a warmer to a colder region. This view leads to a new velocity scale, which we have tested along with previously proposed length and velocity scales, using numerical climate simulations in which the eddy properties have been varied by changing forcing and boundary conditions. The experiments show that the eddy velocity varies in accordance with the new scale, while the size of the eddies varies with the well-known Rhines beta-scale. Our results not only give new insight into atmospheric eddy heat transport, but also allow simple estimates of the intensities of mid-latitude storms, which have hitherto only been possible with expensive general circulation models.