Holocene climate change and past Irish societal response

The extent to which North Atlantic Holocene climatic perturbations influenced past human societies is an area of considerable uncertainty and fierce debate. Ireland is ideally placed to help resolve this issue, being occupied for over 9000 yr and located on the eastern Atlantic seaboard, a region dominated by westerly airflow. Irish bog and lake tree populations provide unambiguous evidence of major shifts in surface moisture through the Holocene similar to cycles recorded in the marine realm of the North Atlantic, indicating significant changes in the latitude and intensity of zonal atmospheric circulation across the region. To test for human response to these cycles we summed the probabilities of 465 radiocarbon ages obtained from Irish archaeological contexts and observe enhanced archaeological visibility during periods of sustained wet conditions. These results suggest either increasing density of human populations in key, often defensive locations, and/or the development of subsistence strategies to overcome changing conditions, the latter recently proposed as a significant factor in avoiding societal collapse. Regardless, we demonstrate environmental change is a significantly more important factor in influencing human activity in the landscape than has hitherto been acknowledged.

Correlated electron-ion dynamics with open boundaries: formalism

We extend a new formalism, which allows correlated electron-ion dynamics to be applied to the problem of open boundary conditions. We implement this at the first moment level (allowing heating of ions by electrons) and observe the expected cooling in the classical part of the ionic kinetic energy and current-induced heating in the quantum contribution. The formalism for open boundaries should be easily extended to higher moments of the correlated electron-ion fluctuations.

On the treatment of singularities of the Watson Hamiltonian for nonlinear molecules

The applicability of the Watson Hamiltonian for the description of nonlinear molecules—especially triatomic ones—has always been questioned, as the Jacobian of the transformation that leads to the Watson Hamiltonian, vanishes at the linear configuration. This results in singular behavior of the Watson Hamiltonian, giving rise to serious numerical problems in the computation of vibrational spectra, with unphysical, spurious vibrational states appearing among the physical vibrations, especially in the region of highly excited states. In this work, we analyze the problem and propose a simple way to confine the nuclear wavefunction in such a way that the spurious solutions are eliminated. We study the water molecule and observe an improvement compared with previous results. We also apply the method to the van der Walls molecule XeHe2.

Ultrafast Electron Dynamics in Phenylalanine Initiated by Attosecond Pulses

In the last decade attosecond technology has opened up the investigation of ultrafast electronic processes in atoms, simple molecules and solids. Here we report the application of isolated attosecond pulses to prompt ionization of the amino acid phenylalanine, and the subsequent detection of ultrafast dynamics on a sub-4.5-fs temporal scale, which is shorter than the vibrational response of the molecule. The ability to initiate and observe such electronic dynamics in polyatomic molecules represents a crucial step forward in attosecond science, which is progressively moving towards the investigation of more and more complex systems.

Simultaneously multiply-configurable or superposed molecular logic systems composed of ICT (internal charge transfer) chromophores and fluorophores integrated with one- or two-ion receptors

Integrated "ICT chromophore-receptor" systems show ion-induced shifts in their electronic absorption spectra. The wavelength of observation can be used to reversibly configure the system to any of the four logic operations permissible with a single input (YES, NOT, PASS 1, PASS 0), under conditions of ion input and transmittance output. We demonstrate these with dyes integrated into Tsien's calcium receptor, 1-2. Applying multiple ion inputs to 1-2 also allows us to perform two- or three-input OR or NOR operations. The weak fluorescence output of 1 also shows YES or NOT logic depending on how it is configured by excitation and emission wavelengths. Integrated "receptor(1)-ICT chromophore-receptor(2)" systems 3-5 selectively target two ions into the receptor terminals. The ion-induced transmittance output of 3-5 can also be configured via wavelength to illustrate several logic types including, most importantly, XOR. The opposite effects of the two ions on the energy of the chromophore excited state is responsible for this behaviour. INHIBIT and REVERSE IMPLICATION are two of the other logic types seen here. Integration of XOR logic with a preceding OR operation can be arranged by using three ion inputs. The fluorescence output of these systems can be configured via wavelength to display INHIBIT or NOR logic under two-input conditions. The superposition or multiplicity of logic gate configurations is an unusual consequence of the ability to simultaneously observe multiple wavelengths.

Properties of SEPT9 Isoforms and the requirement for GTP binding

Members of the evolutionarily conserved septin family of genes are emerging as key components of several cellular processes including membrane trafficking, cytokinesis, and cell-cycle control events. SEPT9 has been shown to have a complex genomic architecture, such that up to 15 different isoforms are possible by the shuffling of five alternate amino termini and three alternate carboxy termini. Genomic and transcriptional alterations of SEPT9 have been associated with neoplasia. The present study has used a Sept9-specific antibody to determine the pattern of isoform expression in a range of tumour cell lines. Western blot analysis indicated considerable variation in the relative amounts and isoform content of Sept9. Immunofluorescence studies showed a range of patterns of cytoplasmic localization ranging from mainly particulate to mainly filamentous. Expression constructs were also generated for each amino terminal isoform to investigate the patterns of localization of individual isoforms and the effects on cells of ectopic expression. The present study shows that the epsilon isoform appears filamentous in this overexpression system while the remaining isoforms are particulate and cytoplasmic. Transient transfection of individual constructs into tumour cell lines results in cell-cycle perturbation with a G2/M arrest and dramatic growth suppression, which was greatest in cell lines with the lowest amounts of endogenous Sept9. Similar phenotypic observations were made with GTP-binding mutants of all five N-terminal variants of Sept9. However, dramatic differences were observed in the kinetics of accumulation of wild-type versus mutant septin protein in transfected cells. In conclusion, the present study shows that the expression patterns of Sept9 protein are very varied in a panel of tumour cell lines and the functional studies are consistent with a model of septin function as a component of a molecular scaffold that contributes to diverse cellular functions. Alterations in the levels of Sept9 protein by overexpression of individual isoforms can clearly perturb cellular behaviour and may thus provide a mechanistic explanation for observations of deranged septin expression in neoplasia. Copyright © 2004 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

RHESSI and SOHO CDS Observations of Explosive Chromospheric Evaporation

Simultaneous observations of explosive chromospheric evaporation are presented using data from the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) and the Coronal Diagnostic Spectrometer (CDS) on board the Solar and Heliospheric Observatory. For the first time, cospatial imaging and spectroscopy have been used to observe explosive evaporation within a hard X-ray emitting region. RHESSI X-ray images and spectra were used to determine the flux of nonthermal electrons accelerated during the impulsive phase of an M2.2 flare. When we assumed a thick-target model, the injected electron spectrum was found to have a spectral index of similar to 7.3, a low-energy cutoff of similar to 20 keV, and a resulting flux of >= 4 x10(10) ergs cm(-2) s(-1). The dynamic response of the atmosphere was determined using CDS spectra; we found a mean upflow velocity of 230 +/- 38 km s(-1) in Fe (XIX) (592.23 angstrom) and associated downflows of 36 +/- 16 and 43 +/- 22 km s(-1) at chromospheric and transition region temperatures, respectively, relative to an averaged quiet- Sun spectra. The errors represent a 1 j dispersion. The properties of the accelerated electron spectrum and the corresponding evaporative velocities were found to be consistent with the predictions of theory.

Post-depositional modification of atmospheric dust on a granite building in central Rio de Janeiro: implications for surface induration and subsequent stone decay

Extensive contour scaling of a 200 year old granite church is associated with the breaching of an apparently iron-rich crust and the widespread deposition of atmospheric dust within the canyon-like streetscape of Rio de Janeiro. Contemporary dust, accumulated dust from within the a depression on the building surface, the surface crust and the underlying granite are examined by a combination of total element analysis and sequential extraction, X-ray diffraction and energy dispersive X-ray fluorescence. Results indicate an increase in total organic carbon and a marked decrease in pH within the accumulated dust, and a rapid mobilization of anions and cations from the water-soluble and carbonate phases. It is considered that the latter is linked to salt accumulation within and eventual salt weathering of the granite. Post-depositional alteration of the dust is also linked with the de-silicification of clay minerals (Illite to kaolinite) and the loss of silica from the amorphous Fe/Mn phase of the accumulated dust under the initially saline and progressively more acidic conditions experienced at the stone - atmosphere interface. This mobilization of silica is associated with the formation of what is, in effect, a thin silica-rich surface crust or glaze. Within the glaze, assessory amounts of extractable iron are concentrated within the amorphous and crystalline Fe/Mn phases at levels that are significantly elevated with respect to the underlying granite, but much lower than the equivalent phases of the accumulated dust from which it is principally assumed to derive. The protection afforded to the stone work by the crust is not, however, permanent and within the last 15 years it has been possible to observe a rapid increase in the surface delamination of the church close to street level.

Molecular Hydrogen Emission from Protoplanetary Disks: Effects of X-ray Irradiation and Dust Evolution

Detailed models for the density and temperature profiles of gas and dust in protoplanetary disks are constructed by taking into account X-ray and UV irradiation from a central T Tauri star, as well as dust size growth and settling toward the disk midplane. The spatial and size distributions of dust grains are numerically computed by solving the coagulation equation for settling dust particles, with the result that the mass and total surface area of dust grains per unit volume of the gas in the disks are very small, except at the midplane. The H2 level populations and line emission are calculated using the derived physical structure of the disks. X-ray irradiation is the dominant heating source of the gas in the inner disk and in the surface layer, while the UV heating dominates otherwise. If the central star has strong X-ray and weak UV radiation, the H2 level populations are controlled by X-ray pumping, and the X-rayinduced transition lines could be observable. If the UV irradiation is strong, the level populations are controlled by thermal collisions or UV pumping, depending on the dust properties. As the dust particles evolve in the disks, the gas temperature at the disk surface drops because the grain photoelectric heating becomes less efficient. This makes the level populations change from LTE to non-LTE distributions, which results in changes to the line ratios. Our results suggest that dust evolution in protoplanetary disks could be observable through the H2 line ratios. The emission lines are strong from disks irradiated by strong UV and X-rays and possessing small dust grains; such disks will be good targets in which to observe H2 emission.

Induction of tetraploidy through loss of p53 and upregulation of Plk1 by Human Papillomavirus type-16 E6

Cancer cells are insensitive to many signals that inhibit growth of untransformed cells. Here, we show that primary human epithelial cells expressing human papillomavirus (HPV) type-16 E6/E7 bypass arrest caused by the DNA-damaging drug adriamycin and become tetraploid. To determine the contribution of E6 in the context of E7 to the resistance of arrest and induction of tetraploidy, we used an E6 mutant unable to degrade p53 or RNAi targeting p53 for knockdown. The E6 mutant fails to generate tetraploidy; however, the presence of E7 is sufficient to bypass arrest while the p53 RNAi permits both arrest insensitivity and tetraploidy. We published previously that polo-like kinase 1 (Plk1) is upregulated in E6/E7-expressing cells. We observe here that abnormal expression of Plk1 protein correlates with tetraploidy. Using the p53 binding-defective mutant of E6 and p53 RNAi, we show that p53 represses Plk1, suggesting that loss of p53 results in tetraploidy through upregulation of Plk1. Consistent with this hypothesis, overexpression of Plk1 in cells generates tetraploidy but does not confer resistance to arrest. These results support a model for transformation caused by HPV-16 where bypass of arrest and tetraploidy are separable consequences of p53 loss with Plk1 required only for the latter effect.

Wide angle crystal spectrometer for angularly and spectrally resolved x-ray scattering experiments

A novel wide angle spectrometer has been implemented with a highly oriented pyrolytic graphite crystal coupled to an image plate. This spectrometer has allowed us to look at the energy resolved spectrum of scattered x rays from a dense plasma over a wide range of angles ( ~ 30°) in a single shot. Using this spectrometer we were able to observe the temporal evolution of the angular scatter cross section from a laser shocked foil. A spectrometer of this type may also be useful in investigations of x-ray line transfer from laser-plasmas experiments.

Dietary glycaemic index, glycaemic load and breast cancer risk: a systematic review and meta-analysis

This systematic review aimed to examine if an association exists between dietary glycaemic index (GI) and glycaemic load (GL) intake and breast cancer risk. A systematic search was conducted in Medline and Embase and identified 14 relevant studies up to May 2008. Adjusted relative risk estimates comparing breast cancer risk for the highest versus the lowest category of GI/GL intake were extracted from relevant studies and combined in meta-analyses using a random-effects model. Combined estimates from six cohort studies show non-significant increased breast cancer risks for premenopausal women (relative risk (RR) 1.14, 95% CI 0.95-1.38) and postmenopausal women (RR 1.11, 95% CI 0.99-1.25) consuming the highest versus the lowest category of GI intake. Evidence of heterogeneity hindered analyses of GL and premenopausal risk, although most studies did not observe any significant association. Pooled cohort study results indicated no association between postmenopausal risk and GL intake (RR 1.03, 95% CI 0.94-1.12). Our findings do not provide strong support of an association between dietary GI and GL and breast cancer risk. © 2008 Cancer Research UK.


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Ca(2+) signals coordinate zygotic polarization and cell cycle progression in the brown alga Fucus serratus

Zygotes of the fucoid brown algae provide excellent models for addressing fundamental questions about zygotic symmetry breaking. Although the acquisition of polarity is tightly coordinated with the timing and orientation of the first asymmetric division-with zygotes having to pass through a G1/S-phase checkpoint before the polarization axis can be fixed -the mechanisms behind the interdependence of polarization and cell cycle progression remain unclear. In this study, we combine in vivo Ca(2+) imaging, single cell monitoring of S-phase progression and multivariate analysis of high-throughput intracellular Ca(2+) buffer loading to demonstrate that Ca(2+) signals coordinate polarization and cell cycle progression in the Fucus serratus zygote. Consistent with earlier studies on this organism, and in contrast to animal models, we observe no fast Ca(2+) wave following fertilization. Rather, we show distinct slow localized Ca(2+) elevations associated with both fertilization and S-phase progression, and we show that both S-phase and zygotic polarization are dependent on pre-S-phase Ca(2+) increases. Surprisingly, this Ca(2+) requirement cannot be explained by co-dependence on a single G1/ S-phase checkpoint, as S phase and zygotic polarization are differentially sensitive to pre-S-phase Ca(2+) elevations and can be uncoupled. Furthermore, subsequent cell cycle progression through M phase is independent of localized actin polymerization and zygotic polarization. This absence of a morphogenesis checkpoint, together with the observed Ca(2+)dependences of S phase and polarization, show that the regulation of zygotic division in the brown algae differs from that in other eukaryotic model systems, such as yeast and Drosophila.