Stable isotope ratios of epibenthic foraminifer Cibicidoides wuellerstorfi from sediment profile GeoB9526

Studies of temporal changes of ocean circulation and deep-water ventilation often rely on d13C records of epibenthic foraminifer Cibicidoides wuellerstorfi. However, primary productivity related overprints may distort the signal and simulate a chemical age of ambient water mass that is too old and simulates poorly ventilated ambient bottom waters. To further constrain the use of C. wuellerstorfi d13C records from high-productivity areas, we analyzed a 14CAMS-dated gravity core from the upwelling regime off northwest Africa at 12°N. We compare this new record with 37 radiocarbon dated d13C records from the eastern Atlantic Ocean between 45°N and 25°S that are bathed by the same water mass. Only during Heinrich events 1 and 2, when the investigated core site off northwest Africa experienced year-round, sustained deposition of organic matter, the d13C values at this site faithfully record deep-water ventilation states. During times of predominantly seasonal deposition of fresh phytodetritus, however, d13C values were significantly lower than at the reference sites. This underscores that reconstruction of paleocirculation and deep ocean ventilation using C. wuellerstorfi d13C from regions that experienced seasonal phytodetritus deposition needs to be validated by additional proxies that are not affected by local productivity.

(Table A1) CaCO3 contents and Sr/Ca ratios in ODP Leg 130, 138 and 154

Strontium/calcium (Sr/Ca) ratios in bulk and foraminiferal calcite have been used to constrain the history of Sr/Ca in the oceans and to evaluate calcite diagenetic alteration. However bulk Sr/Ca records also may be influenced by differences in Sr uptake and/or in the diagenetic susceptibility of different calcium carbonate sedimentary components. We present data on the sediment size fraction and calcium carbonate distribution in bulk samples, Sr/Ca in a range of sedimentary size components, and Sr/Ca in bulk sediments. Ocean Drilling Program samples from sites on Ontong Java Plateau and Ceara Rise (in the western equatorial Pacific and Atlantic, respectively) and from sites in the eastern equatorial Pacific were selected to represent progressive stages in the diagenetic pathway from the sea floor through a range of burial depths equivalent to sediment ages of ~5.6, ~9.4, and ~37.1 Ma. Samples were subdivided by size to produce a unique data set of size-specific Sr/Ca ratios. Fine fraction (<45 ?m) Sr/Ca ratios are higher than those of all corresponding coarse fractions, indicating that fine nannofossil-dominated calcite has a Sr partition coefficient 1.3-1.5 times greater than that of coarse foraminifera-dominated calcite. Thus, absolute values of bulk Sr/Ca in contemporaneous samples reflect, in part, the ratio of fine to coarse calcite sedimentary components. Sr/Ca values in fine and coarse components also behave differently in their response to pre-burial dissolution and to recrystallization at depth. Coarse size components are sensitive to bottom water carbonate ion undersaturation, and they lose original Sr/Ca differences among contemporary samples over not, vert, similar10 my. In contrast, fine components recrystallize faster in more deeply buried samples. Interpretation of the historical Sr/Ca record is complicated by post-depositional diagenetic artifacts, and thus our data do not provide clear evidence of specific temporal changes in oceanic Sr/Ca ratios over the past 10 million years. This paper represents the first systematic attempt to examine trends in calcite Sr/Ca as a function of sediment size fraction and age.

Biomarker distributions in surface sediments from the Kara and Laptev Seas (Arctic Ocean)

Studies of spatial and temporal changes in modern and past sea-ice occurrence may help to understand the processes controlling the recent decrease in Arctic sea-ice cover. Here, we determined concentrations of IP25, a novel biomarker proxy for sea ice developed in recent years, phytoplankton-derived biomarkers (brassicasterol and dinosterol) and terrigenous biomarkers (campesterol and ß-sitosterol) in the surface sediments from the Kara and Laptev seas to estimate modern spatial (seasonal) sea-ice variability and organic-matter sources. C25-HBI dienes and trienes were determined as additional paleoenvironmental proxies in the study area. Furthermore, a combined phytoplankton-IP25 biomarker approach (PIP25 index) is used to reconstruct the modern sea-ice distribution more quantitatively. The terrigenous biomarkers reach maximum concentrations in the coastal zones and estuaries, reflecting the huge discharge by the major rivers Ob, Yenisei and Lena. Maxima in phytoplankton biomarkers indicating increased primary productivity were found in the seasonally ice-free central part of the Kara and Laptev seas. Neither IP25 nor PIP25, however, show a clear and simple correlation with satellite sea-ice distribution in our study area due to the complex environmental conditions in our study area and the transportation process of sea-ice diatom in the water column. Differences in the diene/IP25 and triene/IP25 ratios point to different sources of these HBIs and different environmental conditions. The diene/IP25 ratio seems to correlate positively with sea-surface temperature, while negatively with salinity distributions.

Analysis of the Hydrogeological Conditions and the Effects of Development on the Hydraulic Head at Redmond Ridge East

Redmond Ridge East (RRE) is a large-scale master plan community in East King County, WA. In this report, I evaluate the spatial variability of the Quaternary Advance Outwash (Qva) at RRE and the time-series data for 16 water wells with the intent to better understand groundwater below the RRE area. I investigate changes between pre- and post-development conditions through the determination of temporal changes in annual water level, annual water level fluctuations, hydraulic head response to precipitation, and ambient drainage of the aquifer. I also perform a basic analysis of the annual aquifer recharge and a determination for the storage through the implementation of the water table fluctuation (WTF) method. Associated Earth Sciences (AESI) was tasked with monitoring the geological and environmental impacts during the development of RRE and collected the data I use in this report. AESI involvement in monitoring began in 1998 and extends to the present. Sixteen wells were identified in the RRE area with adequate temporal data to conduct the analysis. A comparison of the well logs and aquifer testing data allowed local variations in the Qva to be mapped. The WTF was used to determine a range of reasonable specific yield values for locations where the Qva was unconfined. Yearly average of the seasonal water level high and lows, and the fluctuations were quantified. Temporal relationships were established through linear regression. The average water level was found to be increasing in some locations, and the corresponding fluctuations were found to decrease. However, no clear change between pre- and post-development was observed. The response of hydraulic head to precipitation was investigated through an analysis of hydrographs for ten wells. Periods of consistent response and the corresponding precipitation during each period were delineated. A linear relationship between precipitation and water level change was determined. The threshold precipitation under which there is a positive response in the hydraulic head was established. No observable changes were apparent between pre- and post-development conditions. The ambient drainage for the Qva was calculated using recessional periods on the hydrograph. The transmissivity of Qva varies with thickness of the overlying lodgment till and thickness of the Qva, itself. Water level fluctuations observed in the Qva are consistent with regional observations. Localized areas in the Qva display the large 10 foot fluctuations and these anomalies are likely due to a combination of the local variability in the storativity as well as the concentration and channeling of water due to geographical variations in the Qva and the overlying topography. All trends seen in the RRE area remained relatively constant through time. There was no evidence showing an effect of development on the hydraulic head at RRE. This implies that the style and distribution of infiltration has not changed as a result of development, and that any measures in place are properly mitigating the effects of development on the RRE region.

Spreading and synchronization of intrinsic signals in visual cortex of macaque monkey evoked by a localized visual stimulus

Spatio-temporal maps of the occipital cortex of macaque monkeys were analyzed using optical imaging of intrinsic signals. The images obtained during localized visual stimulation (IS) were compared with the images obtained on presentation of a blank screen (IB). We first investigated spontaneous variations of the intrinsic signals by analyzing the 100 IBs for each of the three cortical areas. Slow periodical activation was observed in alternation over the cortical areas. Cross-correlation analysis indicated that synchronization of spontaneous activation only took place within each cortical area, but not between them. When a small, drifting grating (2degreesX2degrees) was presented on the fovea. a dark spot appeared in the optical image at the cortical representation of this retinal location. It spread bilaterally along the border between V1 and V2, continuing as a number of parallel dark bands covering a large area of the lateral surface of V1. Cross-correlation analysis showed that during visual stimulation the intrinsic signals over all of the three cortical areas were synchronized, with in-phase activation of V1 and V2 and anti-phase activation of V4 and V1/V2. The significance of these extensive synergistic and antagonistic interactions between different cortical areas is discussed. (C) 2003 Elsevier B.V. All rights reserved.

Mining-associated Seismicity in Kolar Gold Mines: Some Case Studies using Multi-fractals

The occurrence of rockbursts was quite common during active mining periods in the Champion reef mines of Kolar gold fields, India. Among the major rockbursts, the ‘area-rockbursts’ were unique both in regard to their spatio-temporal distribution and the extent of damage caused to the mine workings. A detailed study of the spatial clustering of 3 major area-rockbursts (ARB) was carried out using a multi-fractal technique involving generalized correlation integral functions. The spatial distribution analysis of all 3 area-rockbursts showed that they are heterogeneous. The degree of heterogeneity (D2 – D∞) in the cases of ARB-I, II and III were found to be 0.52, 0.37 and 0.41 respectively. These differences in fractal structure indicate that the ARBs of the present study were fully controlled by different heterogeneous stress fields associated with different mining and geological conditions. The present study clearly showed the advantages of the application of multi-fractals to seismic data and to characterise, analyse and examine the area-rockbursts and their causative factors in the Kolar gold mines.

Degradable poly(ethylene glycol)-based hydrogels:synthesis, physico-chemical properties and in vitro characterization

Designing degradable hydrogels is complicated by the structural and temporal complexities of the gel and evolving tissue. A major challenge is to create scaffolds with sufficient mechanical properties to restore initial function while simultaneously controlling temporal changes in the gel structure to facilitate tissue formation. Poly(ethylene glycol) was used in this work, to form biodegradable poly(ethylene glycol)-based hydrogels with hydrolyzable poly-l-lactide segments in the backbone. Non-degradable poly(ethylene glycol) was also introduced in the formulation to obtain control of the degradation profile that encompasses cell growth and new tissue formation. The dependence on polymer composition was observed by higher degradation profiles and decreased mechanical properties as the content of degradable segments was increased in the formulation. Based on in vitro tests, no toxicity of extracts or biomaterial in direct contact with human adipose tissue stem cells was observed, and the ultraviolet light treatment did not affect the proliferation capacity of the cells.

Seeing blur:'Motion sharpening' without motion

It is widely supposed that things tend to look blurred when they are moving fast. Previous work has shown that this is true for sharp edges but, paradoxically, blurred edges look sharper when they are moving than when stationary. This is 'motion sharpening'. We show that blurred edges also look up to 50% sharper when they are presented briefly (8-24 ms) than at longer durations (100-500 ms) without motion. This argues strongly against high-level models of sharpening based specifically on compensation for motion blur. It also argues against a recent, low-level, linear filter model that requires motion to produce sharpening. No linear filter model can explain our finding that sharpening was similar for sinusoidal and non-sinusoidal gratings, since linear filters can never distort sine waves. We also conclude that the idea of a 'default' assumption of sharpness is not supported by experimental evidence. A possible source of sharpening is a nonlinearity in the contrast response of early visual mechanisms to fast or transient temporal changes, perhaps based on the magnocellular (M-cell) pathway. Our finding that sharpening is not diminished at low contrast sets strong constraints on the nature of the nonlinearity.

Role of plasma in femtosecond laser pulse propagation

This paper describes physics of nonlinear ultra-short laser pulse propagation affected by plasma created by the pulse itself. Major applications are also discussed. Nonlinear propagation of the femtosecond laser pulses in gaseous and solid transparent dielectric media is a fundamental physical phenomenon in a wide range of important applications such as laser lidars, laser micro-machining (ablation) and microfabrication etc. These applications require very high intensity of the laser field, typically 1013–1015 TW/cm2. Such high intensity leads to significant ionisation and creation of electron-ion or electron-hole plasma. The presence of plasma results into significant multiphoton and plasma absorption and plasma defocusing. Consequently, the propagation effects appear extremely complex and result from competitive counteraction of the above listed effects and Kerr effect, diffraction and dispersion. The theoretical models used for consistent description of laser-plasma interaction during femtosecond laser pulse propagation are derived and discussed. It turns out that the strongly nonlinear effects such self-focusing followed by the pulse splitting are essential. These phenomena feature extremely complex dynamics of both the electromagnetic field and plasma density with different spatio-temporal structures evolving at the same time. Some numerical approaches capable to handle all these complications are also discussed. ©2006 American Institute of Physics

Spatial aspects of MRSA epidemiology:A case study using stochastic simulation, kernel estimation and SaTScan

The identification of disease clusters in space or space-time is of vital importance for public health policy and action. In the case of methicillin-resistant Staphylococcus aureus (MRSA), it is particularly important to distinguish between community and health care-associated infections, and to identify reservoirs of infection. 832 cases of MRSA in the West Midlands (UK) were tested for clustering and evidence of community transmission, after being geo-located to the centroids of UK unit postcodes (postal areas roughly equivalent to Zip+4 zip code areas). An age-stratified analysis was also carried out at the coarser spatial resolution of UK Census Output Areas. Stochastic simulation and kernel density estimation were combined to identify significant local clusters of MRSA (p<0.025), which were supported by SaTScan spatial and spatio-temporal scan. In order to investigate local sampling effort, a spatial 'random labelling' approach was used, with MRSA as cases and MSSA (methicillin-sensitive S. aureus) as controls. Heavy sampling in general was a response to MRSA outbreaks, which in turn appeared to be associated with medical care environments. The significance of clusters identified by kernel estimation was independently supported by information on the locations and client groups of nursing homes, and by preliminary molecular typing of isolates. In the absence of occupational/ lifestyle data on patients, the assumption was made that an individual's location and consequent risk is adequately represented by their residential postcode. The problems of this assumption are discussed, with recommendations for future data collection.

When do conservation planning methods deliver? Quantifying the consequences of uncertainty

The rapid global loss of biodiversity has led to a proliferation of systematic conservation planning methods. In spite of their utility and mathematical sophistication, these methods only provide approximate solutions to real-world problems where there is uncertainty and temporal change. The consequences of errors in these solutions are seldom characterized or addressed. We propose a conceptual structure for exploring the consequences of input uncertainty and oversimpli?ed approximations to real-world processes for any conservation planning tool or strategy. We then present a computational framework based on this structure to quantitatively model species representation and persistence outcomes across a range of uncertainties. These include factors such as land costs, landscape structure, species composition and distribution, and temporal changes in habitat. We demonstrate the utility of the framework using several reserve selection methods including simple rules of thumb and more sophisticated tools such as Marxan and Zonation. We present new results showing how outcomes can be strongly affected by variation in problem characteristics that are seldom compared across multiple studies. These characteristics include number of species prioritized, distribution of species richness and rarity, and uncertainties in the amount and quality of habitat patches. We also demonstrate how the framework allows comparisons between conservation planning strategies and their response to error under a range of conditions. Using the approach presented here will improve conservation outcomes and resource allocation by making it easier to predict and quantify the consequences of many different uncertainties and assumptions simultaneously. Our results show that without more rigorously generalizable results, it is very dif?cult to predict the amount of error in any conservation plan. These results imply the need for standard practice to include evaluating the effects of multiple real-world complications on the behavior of any conservation planning method.

Neuromagnetic investigations of functional organisation within human visual cortex

This thesis describes a series of experimental investigations into the functional organisation of human visual cortex using neuromagnetometry.This technique combines good spatial and temporal resolution enabling identification of the location and temporal response characteristics of cortical neurones within alert humans. To activate different neuronal populations and cortical areas a range of stimuli were used, the parameters of which were selected to match the known physiological properties of primate cortical neurones. In one series of experiments the evoked magnetic response was recorded to isoluminant red/green gratings. Co-registration of signal and magnetic resonance image data indicated a contribution to the response from visual areas V1, V2 and V4. To investigate the spatio-temporal characteristics of neurones within area V1 the evoked response was recorded for a range of stimulus spatial and temporal frequencies. The response to isoluminant red/green gratings was dominated by a major component which was found to have bandpass spatial frequency tuning with a peak at 1-2 cycles/degree, falling to the level of the noise at 6-8 cycles/degree. The temporal frequency tuning characteristics of the response showed bimodal sensitivity with peaks at 0-1Hz and 4Hz. In a further series of experiments the luminance evoked response was recorded to red/black, yellow/black and achromatic gratings and in all cases was found to be more complex than the isoluminant chromatic response, comprising up to three distinct components. The major response peak showed bandpass spatial frequency tuning characteristics, peaking at 6-8 cycles/degree, falling to the level of the noise at 12-16 cycles/degree. The results provide evidence to suggest that within area V1 the same neuronal population encodes both chromatic and luminance information and has spatial frequency tuning properties consistent with single-opponent cells. Furthermore, the results indicate that cells within area V1 encode chromatic motion information over a wide range of temporal frequencies with temporal response characteristics suggestive of the existence of a sub-population of cells sensitive to high temporal frequencies.

Pooling and suppression in human spatial vision

A distinct feature of several recent models of contrast masking is that detecting mechanisms are divisively inhibited by a broadly tuned ‘gain pool’ of narrow-band spatial pattern mechanisms. The contrast gain control provided by this ‘cross-channel’ architecture achieves contrast normalisation of early pattern mechanisms, which is important for keeping them within the non-saturating part of their biological operating characteristic. These models superseded earlier ‘within-channel’ models, which had supposed that masking arose from direct stimulation of the detecting mechanism by the mask. To reveal the extent of masking, I measured the levels produced with large ranges of pattern spatial relationships that have not been explored before. Substantial interactions between channels tuned to different orientations and spatial frequencies were found. Differences in the masking levels produced with single and multiple component mask patterns provided insights into the summation rules within the gain pool. A widely used cross-channel masking model was tested on these data and was found to perform poorly. The model was developed and a version in which linear summation was allowed between all components within the gain pool but with the exception of the self-suppressing route typically provided the best account of the data. Subsequently, an adaptation paradigm was used to probe the processes underlying pooled responses in masking. This delivered less insight into the pooling than the other studies and areas were identified that require investigation for a new unifying model of masking and adaptation. In further experiments, levels of cross-channel masking were found to be greatly influenced by the spatio-temporal tuning of the channels involved. Old masking experiments and ideas relying on within-channel models were re-elevated in terms of contemporary cross-channel models (e.g. estimations of channel bandwidths from orientation masking functions) and this led to different conclusions than those originally arrived at. The investigation of effects with spatio-temporally superimposed patterns is focussed upon throughout this work, though it is shown how these enquiries might be extended to investigate effects across spatial and temporal position.

Cross-orientation masking is speed invariant between ocular pathways but speed dependent within them

In human (D. H. Baker, T. S. Meese, & R. J. Summers, 2007b) and in cat (B. Li, M. R. Peterson, J. K. Thompson, T. Duong, & R. D. Freeman, 2005; F. Sengpiel & V. Vorobyov, 2005) there are at least two routes to cross-orientation suppression (XOS): a broadband, non-adaptable, monocular (within-eye) pathway and a more narrowband, adaptable interocular (between the eyes) pathway. We further characterized these two routes psychophysically by measuring the weight of suppression across spatio-temporal frequency for cross-oriented pairs of superimposed flickering Gabor patches. Masking functions were normalized to unmasked detection thresholds and fitted by a two-stage model of contrast gain control (T. S. Meese, M. A. Georgeson, & D. H. Baker, 2006) that was developed to accommodate XOS. The weight of monocular suppression was a power function of the scalar quantity ‘speed’ (temporal-frequency/spatial-frequency). This weight can be expressed as the ratio of non-oriented magno- and parvo-like mechanisms, permitting a fast-acting, early locus, as befits the urgency for action associated with high retinal speeds. In contrast, dichoptic-masking functions superimposed. Overall, this (i) provides further evidence for dissociation between the two forms of XOS in humans, and (ii) indicates that the monocular and interocular varieties of XOS are space/time scale-dependent and scale-invariant, respectively. This suggests an image-processing role for interocular XOS that is tailored to natural image statistics—very different from that of the scale-dependent (speed-dependent) monocular variety.

Femtosecond laser microfabrication of subwavelength structures in photonics

This paper describes experimental and numerical results of the plasma-assisted microfabrication of subwavelength structures by means of point-by point femtosecond laser inscription. It is shown that the spatio-temporal evolution of light and plasma patterns critically depend on input power. Subwavelength inscription corresponds to the supercritical propagation regimes when pulse power is several times self-focusing threshold. Experimental and numerical profiles show quantitative agreement.