Are there pre-Quaternary geological analogues for a future greenhouse warming?

Given the inherent uncertainties in predicting how climate and environments will respond to anthropogenic emissions of greenhouse gases, it would be beneficial to society if science could identify geological analogues to the human race's current grand climate experiment. This has been a focus of the geological and palaeoclimate communities over the last 30 years, with many scientific papers claiming that intervals in Earth history can be used as an analogue for future climate change. Using a coupled ocean-atmosphere modelling approach, we test this assertion for the most probable pre-Quaternary candidates of the last 100 million years: the Mid- and Late Cretaceous, the Palaeocene-Eocene Thermal Maximum (PETM), the Early Eocene, as well as warm intervals within the Miocene and Pliocene epochs. These intervals fail as true direct analogues since they either represent equilibrium climate states to a long-term CO(2) forcing--whereas anthropogenic emissions of greenhouse gases provide a progressive (transient) forcing on climate--or the sensitivity of the climate system itself to CO(2) was different. While no close geological analogue exists, past warm intervals in Earth history provide a unique opportunity to investigate processes that operated during warm (high CO(2)) climate states. Palaeoclimate and environmental reconstruction/modelling are facilitating the assessment and calculation of the response of global temperatures to increasing CO(2) concentrations in the longer term (multiple centuries); this is now referred to as the Earth System Sensitivity, which is critical in identifying CO(2) thresholds in the atmosphere that must not be crossed to avoid dangerous levels of climate change in the long term. Palaeoclimatology also provides a unique and independent way to evaluate the qualities of climate and Earth system models used to predict future climate.     

A new golden age: testing general relativity with cosmology

Gravity drives the evolution of the Universe and is at the heart of its complexity. Einstein's field equations can be used to work out the detailed dynamics of space and time and to calculate the emergence of large-scale structure in the distribution of galaxies and radiation. Over the past few years, it has become clear that cosmological observations can be used not only to constrain different world models within the context of Einstein gravity but also to constrain the theory of gravity itself. In this article, we look at different aspects of this new field in which cosmology is used to test theories of gravity with a wide range of observations.     

Hardware SLE solvers: Efficient building blocks for cryptographic and cryptanalyticapplications

Solving systems of linear equations (SLEs) is a very common computational problem appearing in numerous research disciplines and in particular in the context of cryptographic and cryptanalytic algorithms. In this work, we present highly efficient hardware architectures for solving (small and medium-sized) systems of linear equations over F_2^k. These architectures feature linear or quadratic running times with quadratic space complexities in the size of an SLE, and can be clocked at high frequencies. Among the most promising architectures are one-dimensional and two-dimensional systolic arrays which we call triangular systolic and linear systolic arrays. All designs have been fully implemented for different sizes of SLEs and concrete FPGA implementation results are given. Furthermore, we provide a clear comparison of the presented SLE solvers. The significance of these designs is demonstrated by the fact that they are used in the recent literature as building blocks of efficient architectures for attacking block and stream ciphers (Bogdanov et al., 2007 [5]; Geiselmann et al., 2009 [17]) and for developing cores for multivariate signature schemes (Balasubramanian et al., 2008 [2]; Bogdanov et al., 2008 [6]).     

Fine pitch copper wire bonding in high volume production

Wire bonding is the predominant mode of interconnection in electronic packaging. Gold wire bonding has been refined again and again to retain control of interconnect technology due to its ease of workability and years of reliability data. Economic realities are now enabling fine diameter copper wire to compete with gold wire. It needs to be demonstrated however that known challenges in the assembly process and long term reliability can be managed successfully. Here, a rigorous methodology has been established to introduce copper wire bonding on new as well as converted dice into manufacturing. Manufacturing efficiencies and yields have been driven to be equivalent to gold wires. Reliability testing has passed the usual criteria and has been extended to demonstrate the viability of this technology. Interfacial analysis has confirmed the observations that intermetallic compounds form and grow slowly.     

Postmortem regulation of glycolysis by 6-phosphofructokinase in bovine M. Sternocephalicus pars mandibularis

This experiment addressed the hypothesis that 6-phosphofructokinase (6-PFK) regulates glycolysis in postmortem in M. sternocephalicus pars mandibularis. In two separate experiments, muscle samples were excised from randomly-selected steers that would typically be found on a commercial slaughter floor. In the first experiment, two samples were obtained from each of 6 steers immediately post-exsanguination; one sample was immersed immediately in liquid nitrogen and the other was stored at 4 °C for 4 d, to compare 6-PFK enzyme activity and glycolytic intermediate concentrations between fresh and d 4 postmortem samples. The greatest activity of 6-PFK was measured in fresh muscle extracts at pH 7.4, whereas little activity was detectable at pH 7.0. 6-PFK activity measured at pH 7.4 in d 4 samples also was barely detectable. Hill coefficient values for 6-PFK in fresh samples measured at pH 7.4 or 7.0, and d 4 samples measured at pH 7.4 were 2.9, 0.8, and 0.7, respectively, indicating loss of cooperativity with both lowered pH during assay and with time postmortem. Glycogen concentrations decreased 45% from d 0 to d 4, to 39.6 μmol glycogen/g muscle. Muscle concentrations of free glucose increased (P < 0.001) from 0.84 μmol/g at d 0 to 6.54 μmol/g at d 4. Fructose-6-phosphate and glucose-6-phosphate increased (P < 0.001) from d 0 to d 4 (2.8-fold and 4.7-fold, respectively). Lactate began accumulating immediately (3.33 μmol/g) and was elevated to 45.9 μmol/g by d 4. In the second experiment, conversion of [U-¹⁴C]glucose to lactate, glycogen, and CO₂ was measured in vitro at pH 7.4 and 7.0 in fresh M. sternocephalicus pars mandibularis strips from four steers. Total [U-¹⁴C]glucose was less in muscle strips incubated at pH 7.0 than in those incubated at pH 7.4 (55.5 vs. 123 nmol glucose utilized per 100 mg muscle per h; P = 0.04), due primarily to a reduction in glucose conversion to lactate. The conversion of glucose to glycogen or CO₂ in vitro was unaffected by media pH. These results suggest that the postmortem decline in pH in M. sternocephalicus pars mandibularis ultimately inactivates 6-PFK; this occurs prior to the depletion of glycogen reserves.     

Sources of polycyclic aromatic hydrocarbons and hexachlorobenzene in spruce needles of eastern Alaska

The concentrations of phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, and hexachlorobenzene (HCB) were measured in spruce needles at 36 sites in eastern Alaska during early spring. Concentrations of each polycyclic aromatic hydrocarbon (PAH) varied by an order of magnitude. Samples taken from near the city of Fairbanks had higher concentrations than samples taken from more rural areas. Anthropogenic activities near Fairbanks are most likely a source of PAHs. Variation in the concentration ratios of isomeric PAHs indicates the relative importance of combustion and petrogenic sources. The relative combustion contribution is largest in coastal samples and smallest near Fairbanks. In contrast, the concentration of HCB varied by only a factor of 2. Lipid content of needles and distance from the coast were the major factors correlated with the concentration of HCB.     

Chemotaxis can take plant-parasitic nematodes to the source of a chemo-attractant via the shortest possible routes

It has long been recognized that chemotaxis is the primary means by which nematodes locate host plants. Nonetheless, chemotaxis has received scant attention. We show that chemotaxis is predicted to take nematodes to a source of a chemo-attractant via the shortest possible routes through the labyrinth of air-filled or water-filled channels within a soil through which the attractant diffuses. There are just two provisos: (i) all of the channels through which the attractant diffuses are accessible to the nematodes and (ii) nematodes can resolve all chemical gradients no matter how small. Previously, this remarkable consequence of chemotaxis had gone unnoticed. The predictions are supported by experimental studies of the movement patterns of the root-knot nematodes Meloidogyne incognita and Meloidogyne graminicola in modified Y-chamber olfactometers filled with Pluronic gel. By providing two routes to a source of the attractant, one long and one short, our experiments, the first to demonstrate the routes taken by nematodes to plant roots, serve to test our predictions. Our data show that nematodes take the most direct route to their preferred hosts (as predicted) but often take the longest route towards poor hosts. We hypothesize that a complex of repellent and attractant chemicals influences the interaction between nematodes and their hosts.     

Inactivation of p27Kip1 by the viral E1A oncoprotein in TGFbeta-treated cells

The adenovirus oncoprotein E1A and the simian virus SV40 large T antigen can both reverse the strong growth-inhibitory effect of transforming growth factor(TGF)-beta on mink lung epithelial cells: exposure of TGF-beta causes these cells to arrest late in the G1 phase of the cell cycle (ref. 3). This arrest correlates with an increase in expression of the protein p15Ink4B (ref. 4), inactivation of the cyclin E/A-cdk2 complex by the inhibitory protein p27Kip1 (refs 5-7), and with the accumulation of unphosphorylated retinoblastoma protein. The rescue by E1A of cells from TGF-beta arrest is partly independent of its binding to retinoblastoma protein. Here we show that E1A directly affects the cyclin-dependent kinase inhibitor p27Kip1 in TGF-beta-treated cells by binding to it and blocking its inhibitory effect, thereby restoring the activity of the cyclin-cdk2 kinase complex. In this way, E1A can overcome the effect of TGF-beta and modulate the cell cycle. To our knowledge, E1A provides the first example of a viral oncoprotein that can disable a cellular protein whose function is to inhibit the activity of cyclin-dependent kinases.     

Family rigidity, adolescent problem-solving deficits, and suicidal ideation: a mediational model

Family rigidity and adolescent problem-solving deficits have each been linked to adolescent suicidal behaviors. The objective of the present study was to evaluate the hypothesis that family rigidity has primarily an indirect effect on adolescent suicidal ideation through its effect on adolescent problem-solving deficits. College students and their parents completed the Family Adaptability and Cohesion Evaluation Scale II. Students also completed the Problem-Solving Inventory and the Adult Suicidal ideation Questionnaire. Structural equation models confirmed that family rigidity has an indirect effect on adolescent suicidal ideation through its effect on adolescent problem-solving deficits. Directions for treatment efforts are discussed.