Competing correlated states around the zero-field Wigner crystallization transition of electrons in two dimensions.

The competition between kinetic energy and Coulomb interactions in electronic systems leads to complex many-body ground states with competing orders. Here we present zinc oxide-based two-dimensional electron systems as a high-mobility system to study the low-temperature phases of strongly interacting electrons. An analysis of the electronic transport provides evidence for competing correlated metallic and insulating states with varying degrees of spin polarization. Some features bear quantitative resemblance to quantum Monte Carlo simulation results, including the transition point from the paramagnetic Fermi liquid to Wigner crystal and the absence of a Stoner transition. At very low temperatures, we resolve a non-monotonic spin polarizability of electrons across the phase transition, pointing towards a low spin phase of electrons, and a two-order-of-magnitude positive magnetoresistance that is challenging to understand within traditional metallic transport paradigms. This work establishes zinc oxide as a platform for studying strongly correlated electrons in two dimensions.

Rapid microbial methanogenesis during CO2 storage in hydrocarbon reservoirs.

Carbon capture and storage (CCS) is a key technology to mitigate the environmental impact of carbon dioxide (CO2) emissions. An understanding of the potential trapping and storage mechanisms is required to provide confidence in safe and secure CO2 geological sequestration1,2. Depleted hydrocarbon reservoirs have substantial CO2 storage potential1,3, and numerous hydrocarbon reservoirs have undergone CO2 injection as a means of enhanced oil recovery (CO2-EOR), providing an opportunity to evaluate the (bio)geochemical behaviour of injected carbon. Here we present noble gas, stable isotope, clumped isotope and gene-sequencing analyses from a CO2-EOR project in the Olla Field (Louisiana, USA). We show that microbial methanogenesis converted as much as 13-19% of the injected CO2 to methane (CH4) and up to an additional 74% of CO2 was dissolved in the groundwater. We calculate an in situ microbial methanogenesis rate from within a natural system of 73-109 millimoles of CH4 per cubic metre (standard temperature and pressure) per year for the Olla Field. Similar geochemical trends in both injected and natural CO2 fields suggest that microbial methanogenesis may be an important subsurface sink of CO2 globally. For CO2 sequestration sites within the environmental window for microbial methanogenesis, conversion to CH4 should be considered in site selection.

Expression profiles of host immune response-related genes against HEV genotype 3 and genotype 1 infections in rhesus macaques.

Hepatitis E virus (HEV) genotype (gt) 3 infection is food-borne causing sporadic infections in older individuals and gt1 infection is waterborne, often causing epidemics affecting primarily young adults. Although HEV infection causes self-limited disease, gt3 induces chronic infection in immunocompromised individuals. Hepatic host gene expression against gt3 infection remains unknown. Host gene expression profiles for HEV gt1 (n = 3) and gt3 (n = 7) infections were analysed in the livers of experimentally infected rhesus macaques. HEV RNA was detected from 2 to 24 days after inoculation (DAI) in stool and serum, elevated alanine aminotransferase (ALT) activity was detected from 7 to 31 DAI, and anti-HEV antibody became detectable between 12 and 42 DAI. All 10 animals cleared the infection between 34 and 68 DAI. We found that 24%, 48% and 41% of hepatic immune response genes against gt3 infection were upregulated during the early, peak and decline phases of HEV RNA replication. For gt1 infection, 25% of hepatic immune response-related genes were downregulated during early viremia, but 6%, 34% and 37% of genes were upregulated at the early, peak and during decline of HEV RNA replication, respectively. Our study demonstrated distinct differences in the expression profiles of host immune response-related genes of HEV gt3 and gt1 infections in experimentally infected rhesus macaques.

Live animal assessments of rump fat and muscle score in Angus cows and steers using 3-dimensional imaging.

The objective of this study was to develop a proof of concept for using off-the-shelf Red Green Blue-Depth (RGB-D) Microsoft Kinect cameras to objectively assess P8 rump fat (P8 fat; mm) and muscle score (MS) traits in Angus cows and steers. Data from low and high muscled cattle (156 cows and 79 steers) were collected at multiple locations and time points. The following steps were required for the 3-dimensional (3D) image data and subsequent machine learning techniques to learn the traits: 1) reduce the high dimensionality of the point cloud data by extracting features from the input signals to produce a compact and representative feature vector, 2) perform global optimization of the signatures using machine learning algorithms and a parallel genetic algorithm, and 3) train a sensor model using regression-supervised learning techniques on the ultrasound P8 fat and the classified learning techniques for the assessed MS for each animal in the data set. The correlation of estimating hip height (cm) between visually measured and assessed 3D data from RGB-D cameras on cows and steers was 0.75 and 0.90, respectively. The supervised machine learning and global optimization approach correctly classified MS (mean [SD]) 80 (4.7) and 83% [6.6%] for cows and steers, respectively. Kappa tests of MS were 0.74 and 0.79 in cows and steers, respectively, indicating substantial agreement between visual assessment and the learning approaches of RGB-D camera images. A stratified 10-fold cross-validation for P8 fat did not find any differences in the mean bias ( = 0.62 and = 0.42 for cows and steers, respectively). The root mean square error of P8 fat was 1.54 and 1.00 mm for cows and steers, respectively. Additional data is required to strengthen the capacity of machine learning to estimate measured P8 fat and assessed MS. Data sets for and continental cattle are also required to broaden the use of 3D cameras to assess cattle. The results demonstrate the importance of capturing curvature as a form of representing body shape. A data-driven model from shape to trait has established a proof of concept using optimized machine learning techniques to assess P8 fat and MS in Angus cows and steers.

Intrachromosomal rearrangements in avian genome evolution: evidence for regions prone to breakpoints.

It is generally believed that the organization of avian genomes remains highly conserved in evolution as chromosome number is constant and comparative chromosome painting demonstrated there to be very few interchromosomal rearrangements. The recent sequencing of the zebra finch (Taeniopygia guttata) genome allowed an assessment of the number of intrachromosomal rearrangements between it and the chicken (Gallus gallus) genome, revealing a surprisingly high number of intrachromosomal rearrangements. With the publication of the turkey (Meleagris gallopavo) genome it has become possible to describe intrachromosomal rearrangements between these three important avian species, gain insight into the direction of evolutionary change and assess whether breakpoint regions are reused in birds. To this end, we aligned entire chromosomes between chicken, turkey and zebra finch, identifying syntenic blocks of at least 250 kb. Potential optimal pathways of rearrangements between each of the three genomes were determined, as was a potential Galliform ancestral organization. From this, our data suggest that around one-third of chromosomal breakpoint regions may recur during avian evolution, with 10% of breakpoints apparently recurring in different lineages. This agrees with our previous hypothesis that mechanisms of genome evolution are driven by hotspots of non-allelic homologous recombination.

An appraisal of nuclear organisation in interphase embryonic fibroblasts of chicken, turkey and duck.

Determining the nuclear 'addresses' of chromosome territories is a well-documented means of assaying for nuclear organisation in many cell types and species. Data in avian species are however limited at best, despite the pivotal role played by birds (particularly chickens) in agriculture, and as model organisms in developmental biology. That is, studies have hitherto focussed mostly on mammals (especially humans) and have demonstrated the importance of chromosome territory positioning in embryology, disease and evolution. Thus a detailed study of nuclear organisation in many species, many cell types and many developmental stages in birds is warranted, however, before this is achieved, 'baseline' needs to be established to determine precisely the relative locations of chromosome territories in at least 1 cell type of at least 1 bird. With this in mind we hybridised FISH probes from chicken chromosomes 1-28 to embryonic fibroblast nuclei, determining nuclear addresses using a newly developed plug-in to the image analysis package ImageJ. In our experience, evenly spaced representative BAC clones yielded more consistent results than hybridisation of chromosome paints. Results suggested that chromosome territory distribution best fitted a chromosome size-based (rather than gene density-based) pattern. Identical BAC clones were then hybridised to turkey and duck in a comparative genomic strategy. Observations were consistent with those seen in chicken (although, less well-defined in duck), providing preliminary evidence of conservation throughout evolution.

Increased health costs from mandated Therapeutic Substitution of proton pump inhibitors in British Columbia.

BACKGROUND: In 2003, British Columbia's PharmaCare programme implemented a drug reimbursement policy called Therapeutic Substitution, which required patients with acid-related diseases, primarily gastro-oesophageal reflux disease (GERD), to make a medically unnecessary switch from their prescribed proton pump inhibitor (PPI) to the cheapest available brand name PPI (Pariet, rabeprazole sodium), comprising a different (nongeneric) chemical. AIM: To evaluate the independent effects of PPI Therapeutic Substitution on individual healthcare utilization among those complying with the policy. METHODS: We used the BC Ministry of Health Services' individual-level linked data, allowing isolation of healthcare utilization for the entire population of PPI consumers from 2002 to 2005. RESULTS: After controlling for individual case variation in age, gender and a proxy for pre-existing health status, regression analysis revealed statistically significant greater overall use of PPIs, physician services and hospital services independently associated with patients who complied with Therapeutic Substitution. Over the 3-year period 2003-2005, this represented net healthcare expenditures totalling approximately C$43.51 million (C$9.11 million in total PPI drug expenditures, C$24.65 million for physician services and C$9.75 million for hospital services). CONCLUSION: Medically unnecessary drug switching caused by compliance with Therapeutic Substitution policy appears to be independently associated with higher overall healthcare utilization.

Classification of EEG signals using a genetic-based machine learning classifier.

This paper investigates the efficacy of the genetic-based learning classifier system XCS, for the classification of noisy, artefact-inclusive human electroencephalogram (EEG) signals represented using large condition strings (108bits). EEG signals from three participants were recorded while they performed four mental tasks designed to elicit hemispheric responses. Autoregressive (AR) models and Fast Fourier Transform (FFT) methods were used to form feature vectors with which mental tasks can be discriminated. XCS achieved a maximum classification accuracy of 99.3% and a best average of 88.9%. The relative classification performance of XCS was then compared against four non-evolutionary classifier systems originating from different learning techniques. The experimental results will be used as part of our larger research effort investigating the feasibility of using EEG signals as an interface to allow paralysed persons to control a powered wheelchair or other devices.

Practicable approaches to facilitate rapid and accurate molecular cytogenetic mapping in birds and mammals.

Molecular cytogenetic mapping by FISH is a common feature of most genome projects as it provides a global, low-resolution overview of the genome and facilitates comparative genomics. An essential prerequisite for cytogenetic mapping is the ability to identify accurately the chromosome on which the clone (e.g. BAC) resides. This is not usually a barrier to human mapping as knowledge of the human karyotype is commonplace. For other species however accurate assignment can be problematic either because, as in birds, the karyotype is too complex to analyze by standard means or because of the paucity of individuals skilled to perform the karyotyping. Using chicken as a model we have developed a reproducible approach for accurate cytogenetic mapping that involves: a single colour FISH, measurement of the ratio of the size of the signal bearing chromosome to that of chromosome 8, and final assignment through a small series of dual colour experiments. Reference values for size ratios were established using base pair estimate information from the Ensembl browser. By this method cytogenetic mapping to highly complex karyotypes can be achieved in a small number of simple steps. We have also developed and tested a karyotyping tutorial programme adapted from one previously reported in this journal. That is, we have used pig as an example of a model species with a relatively tractable karyotype and demonstrated that scientists and students, even after only one hour using our tutorial, can readily identify pig chromosomes and thus make appropriate assignments using FISH. Simple, practicable means often provide preferable solutions than complex alternatives (e.g. m-FISH) to the solution of scientific problems. Such is the case for the approaches described here.

The evolution of the avian genome as revealed by comparative molecular cytogenetics.

Birds are characterised by feathers, flight, a small genome and a very distinctive karyotype. Despite the large numbers of chromosomes, the diploid count of 2n approximately 80 has remained remarkably constant with 63% of birds where 2n = 74-86, 24% with 2n = 66-74 and extremes of 2n = 40 and 2n = 142. Of these, the most studied is the chicken (2n = 78), and molecular cytogenetic probes generated from this species have been used to further understand the evolution of the avian genome. The ancestral karyotype is, it appears, very similar to that of the chicken, with chicken chromosomes 1, 2, 3, 4q, 5, 6, 7, 8, 9, 4p and Z representing the ancestral avian chromosomes 1-10 + Z; chromosome 4 being the most ancient. Avian evolution occurred primarily in three stages: the divergence of the group represented by extant ratites (emu, ostrich etc.) from the rest; divergence of the Galloanserae (chicken, turkey, duck, goose etc.)--the most studied group; and divergence of the 'land' and 'water' higher birds. Other than sex chromosome differentiation in the first divergence there are no specific changes associated with any of these evolutionary milestones although certain families and orders have undergone multiple fusions (and some fissions), which has reduced their chromosome number; the Falconiformes are the best described. Most changes, overall, seem to involve chromosomes 1, 2, 4, 10 and Z where the Z changes are intrachromosomal; there are also some recurring (convergent) events. Of these, the most puzzling involves chromosomes 4 and 10, which appear to have undergone multiple fissions and/or fusions throughout evolution - three possible hypotheses are presented to explain the findings. We conclude by speculating as to the reasons for the strange behaviour of these chromosomes as well as the role of telomeres and nuclear organisation in avian evolution.

Seleção por conseqüências / Selection by consequences

A seleção por conseqüências é um modo causal encontrado unicamente em coisas vivas ou em máquinas feitas por elas. Foi primeiramente reconhecida na seleção natural, mas explica, também, a modelagem e a manutenção do comportamento do indivíduo e a evolução das culturas. Em todos esses três campos, substitui explicações baseadas nos modos causais da Mecânica Clássica. A substituição é fortemente resistida. A seleção natural é agora reconhecida, mas atrasos similares no reconhecimento do papel da seleção nos outros campos poderiam nos privar de um auxílio valioso na solução dos problemas com os quais somos confrontados.

Seleção por conseqüências / Selection by consequences

A seleção por conseqüências é um modo causal encontrado unicamente em coisas vivas ou em máquinas feitas por elas. Foi primeiramente reconhecida na seleção natural, mas explica, também, a modelagem e a manutenção do comportamento do indivíduo e a evolução das culturas. Em todos esses três campos, substitui explicações baseadas nos modos causais da Mecânica Clássica. A substituição é fortemente resistida. A seleção natural é agora reconhecida, mas atrasos similares no reconhecimento do papel da seleção nos outros campos poderiam nos privar de um auxílio valioso na solução dos problemas com os quais somos confrontados.(AU)