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Analyzes the resonance Raman depolarization ratios of chlorine dioxide dissolved in cyclohexane. Measurement of the depolarization ratio of the symmetric stretch fundamental transition at several excitation wavelengths spanning the lowest-energy electronic transition; Maximum value of the depolarization ratio.

Despite evidence from a number of Earth systems that abrupt temporal changes known as regime shifts are important, their nature, scale and mechanisms remain poorly documented and understood. Applying principal component analysis, change-point analysis and a sequential t-test analysis of regime shifts to 72 time series, we confirm that the 1980s regime shift represented a major change in the Earth's biophysical systems from the upper atmosphere to the depths of the ocean and from the Arctic to the Antarctic, and occurred at slightly different times around the world. Using historical climate model simulations from the Coupled Model Intercomparison Project Phase 5 ( CMIP5) and statistical modelling of historical temperatures, we then demonstrate that this event was triggered by rapid global warming from anthropogenic plus natural forcing, the latter associated with the recovery from the El Chichón volcanic eruption. The shift in temperature that occurred at this time is hypothesized as the main forcing for a cascade of abrupt environmental changes. Within the context of the last century or more, the 1980s event was unique in terms of its global scope and scale; our observed consequences imply that if unavoidable natural events such as major volcanic eruptions interact with anthropogenic warming unforeseen multiplier effects may occur. [ABSTRACT FROM AUTHOR]

Recent analyses have shown that significant changes have occurred in patterns of sea ice seasonality in West Antarctica since 1979, with wide-ranging climatic, biological and biogeochemical consequences. Here, we provide the first detailed report on long-term change and variability in annual timings of sea ice advance, retreat and resultant ice season duration in East Antarctica. These were calculated from satellite-derived ice concentration data for the period 1979/80 to 2009/10. The pattern of change in sea ice seasonality off East Antarctica comprises mixed signals on regional to local scales, with pockets of strongly positive and negative trends occurring in near juxtaposition in certain regions e.g., Prydz Bay. This pattern strongly reflects change and variability in different elements of the marine “icescape”, including fast ice, polynyas and the marginal ice zone. A trend towards shorter sea-ice duration (of 1 to 3 days per annum) occurs in fairly isolated pockets in the outer pack from∼95–110°E, and in various near-coastal areas that include an area of particularly strong and persistent change near Australia's Davis Station and between the Amery and West Ice Shelves. These areas are largely associated with coastal polynyas that are important as sites of enhanced sea ice production/melt. Areas of positive trend in ice season duration are more extensive, and include an extensive zone from 160–170°E (i.e., the western Ross Sea sector) and the near-coastal zone between 40–100°E. The East Antarctic pattern is considerably more complex than the well-documented trends in West Antarctica e.g., in the Antarctic Peninsula-Bellingshausen Sea and western Ross Sea sectors. [ABSTRACT FROM AUTHOR]

Beaugrand, G. and Reid, P. C. 2012. Relationships between North Atlantic salmon, plankton, and hydroclimatic change in the Northeast Atlantic – ICES Journal of Marine Science, 69: 1549–1562.The abundance of wild salmon (Salmo salar) in the North Atlantic has declined markedly since the late 1980s as a result of increased marine mortality that coincided with a marked rise in sea temperature in oceanic foraging areas. There is substantial evidence to show that temperature governs the growth, survival, and maturation of salmon during their marine migrations through either direct or indirect effects. In an earlier study (2003), long-term changes in three trophic levels (salmon, zooplankton, and phytoplankton) were shown to be correlated significantly with sea surface temperature (SST) and northern hemisphere temperature (NHT). A sequence of trophic changes ending with a stepwise decline in the total nominal catch of North Atlantic salmon (regime shift in ∼1986/1987) was superimposed on a trend to a warmer dynamic regime. Here, the earlier study is updated with catch and abundance data to 2010, confirming earlier results and detecting a new abrupt shift in ∼1996/1997. Although correlations between changes in salmon, plankton, and temperature are reinforced, the significance of the correlations is reduced because the temporal autocorrelation of time-series substantially increased due to a monotonic trend in the time-series, probably related to global warming. This effect may complicate future detection of effects of climate change on natural systems. [ABSTRACT FROM PUBLISHER]

The photochemistry of nitrosyl chloride (ClNO) dissolvedin cyclohexane is investigated using ultrafast time-resolved infrared(TRIR) spectroscopy. Following 266 nm photolysis, the photochemistryis measured by following changes in optical density at frequenciesspanning the NO stretch fundamental transition. A photoinduceddepletion in optical density is observed consistent with the depletionof ground-state ClNO. The depletion in optical density remains constantout to ∼50 ps demonstrating that ClNO photodissociation isnot followed by recombination of the Cl and NO photofragments. Inaddition, no evidence for the formation of the ClON photoisomer isobserved. These results stand in contrast to previous studies in acetonitrilewhere ClNO photolysis is followed by geminate recombination of Cland NO, and by the production of ClON. These differences in ClNO photochemistryare proposed to arise from the population of different excited-statescaused by solvent dependence of the ground-state potential energysurface minimum along the Cl–N stretch coordinate. Solvent-dependentvibrational relaxation and differences in strength of the solventcage are also proposed to contribute to the solvent-dependent photochemistry.Finally, these results are placed in the context of recent modelsof ClNO photochemistry and role of this compound in tropospheric ozoneproduction. [ABSTRACT FROM AUTHOR]

The oceans play a key role in climate regulation especially in part buffering (neutralising) the effects of increasing levels of greenhouse gases in the atmosphere and rising global temperatures. This chapter examines how the regulatory processes performed by the oceans alter as a response to climate change and assesses the extent to which positive feedbacks from the ocean may exacerbate climate change. There is clear evidence for rapid change in the oceans. As the main heat store for the world there has been an accelerating change in sea temperatures over the last few decades, which has contributed to rising sea-level. The oceans are also the main store of carbon dioxide (CO2), and are estimated to have taken up ~40% of anthropogenic-sourced CO2 from the atmosphere since the beginning of the industrial revolution. A proportion of the carbon uptake is exported via the four ocean 'carbon pumps' (Solubility, Biological, Continental Shelf and Carbonate Counter) to the deep ocean reservoir. Increases in sea temperature and changing planktonic systems and ocean currents may lead to a reduction in the uptake of CO2 by the ocean; some evidence suggests a suppression of parts of the marine carbon sink is already underway. While the oceans have buffered climate change through the uptake of CO2 produced by fossil fuel burning this has already had an impact on ocean chemistry through ocean acidification and will continue to do so. Feedbacks to climate change from acidification may result from expected impacts on marine organisms (especially corals and calcareous plankton), ecosystems and biogeochemical cycles. The polar regions of the world are showing the most rapid responses to climate change. As a result of a strong ice-ocean influence, small changes in temperature, salinity and ice cover may trigger large and sudden changes in regional climate with potential downstream feedbacks to the climate of the rest of the world. A warming Arctic Ocean may lead to further releases of the potent greenhouse gas methane from hydrates and permafrost. The Southern Ocean plays a critical role in driving, modifying and regulating global climate change via the carbon cycle and through its impact on adjacent Antarctica. The Antarctic Peninsula has shown some of the most rapid rises in atmospheric and oceanic temperature in the world, with an associated retreat of the majority of glaciers. Parts of the West Antarctic ice sheet are deflating rapidly, very likely due to a change in the flux of oceanic heat to the undersides of the floating ice shelves. The final section on modelling feedbacks from the ocean to climate change identifies limitations and priorities for model development and associated observations. Considering the importance of the oceans to climate change and our limited understanding of climate-related ocean processes, our ability to measure the changes that are taking place are conspicuously inadequate. The chapter highlights the need for a comprehensive, adequately funded and globally extensive ocean observing system to be implemented and sustained as a high priority. Unless feedbacks from the oceans to climate change are adequately included in climate change models, it is possible that the mitigation actions needed to stabilise CO2 and limit temperature rise over the next century will be underestimated. [ABSTRACT FROM AUTHOR]

The Continuous Plankton Recorder survey has monitored plankton in the Northwest Atlantic at monthly intervals since 1962, with an interegnum between 1978 and 1990. In May 1999, large numbers of the Pacific diatom Neodenticula seminae were found in Continuous Plankton Recorder (CPR) samples in the Labrador Sea as the first record in the North Atlantic for more than 800 000 years. The event coincided with modifications in Arctic hydrography and circulation, increased flows of Pacific water into the Northwest Atlantic and in the previous year the exceptional occurrence of extensive ice-free water to the North of Canada. These observations indicate that N. seminae was carried in a pulse of Pacific water in 1998/early 1999 via the Canadian Arctic Archipelago and/or Fram Strait. The species occurred previously in the North Atlantic during the Pleistocene from∼1.2 to∼0.8 Ma as recorded in deep sea sediment cores. The reappearance of N. seminae in the North Atlantic is an indicator of the scale and speed of changes that are taking place in the Arctic and North Atlantic oceans as a consequence of regional climate warming. Because of the unusual nature of the event it appears that a threshold has been passed, marking a change in the circulation between the North Pacific and North Atlantic Oceans via the Arctic. Trans-Arctic migrations from the Pacific into the Atlantic are likely to occur increasingly over the next 100 years as Arctic ice continues to melt affecting Atlantic biodiversity and the biological pump with consequent feedbacks to the carbon cycle. [ABSTRACT FROM AUTHOR]

Abstract Oceanic inflow is estimated to contribute more than 90% of the nutrient input into the North Sea. Variability in the volume, chemical properties, biological content and source of the inflowing water is thus likely to have a considerable effect on North Sea ecosystems. Changes seen in the plankton, and in particular Calanus finmarchicus and Calanus helgolandicus , over the last 40 years as measured by the Continuous Plankton Recorder survey, allow clear periods to be identified that appear to be associated with variability in inflow. Monthly estimates of inflow and outflow across a section between Orkney and Utsira in Norway as well as netflow (sum of Baltic outflow, runoff and Channel inflow), have been derived from runs of the NORWECOM model for two integrated depth intervals: surface to 150 m and >150 m. A comparison is made between the physical model output and plankton results for the period 1958–99. Distinct plankton periods that appear to reflect changing inflow events are discussed in relation to hydrometeorological and earlier plankton studies over approximately the last 100 years. [ABSTRACT FROM AUTHOR]

Abstract Recently, large-scale changes in the biogeography of calanoid copepod crustaceans have been detected in the northeastern North Atlantic Ocean and adjacent seas. Strong biogeographical shifts in all copepod assemblages were found with a northward extension of more than ° in latitude of warm-water species associated with a decrease in the number of colder-water species. These changes were attributed to regional increase in sea surface temperature. Here, we have extended these studies to examine long-term changes in phytoplankton, zooplankton and salmon in relation to hydro-meteorological forcing in the northeast Atlantic Ocean and adjacent seas. We found highly significant relationships between (1) long-term changes in all three trophic levels, (2) sea surface temperature in the northeastern Atlantic, (3) Northern Hemisphere temperature and (4) the North Atlantic Oscillation. The similarities detected between plankton, salmon, temperature and hydro-climatic parameters are also seen in their cyclical variability and in a stepwise shift that started after a pronounced increase in Northern Hemisphere Temperature anomalies at the end of the 1970s. All biological variables show a pronounced change which started after circa 1982 for euphausiids (decline), 1984 for the total abundance of small copepods (increase), 1986 for phytoplankton biomass (increase) and Calanus finmarchicus (decrease) and 1988 for salmon (decrease). This cascade of biological events led to an exceptional period, which is identified after 1986 to present and followed another shift in large-scale hydro-climatic variables and sea surface temperature. This regional temperature increase therefore appears to be an important parameter that is at present governing the dynamic equilibrium of northeast Atlantic pelagic ecosystems with possible consequences for biogeochemical processes and fisheries. [ABSTRACT FROM AUTHOR]

Ultraviolet resonance Raman (UVRR) studies designed to test the utility of fluorinated tyrosines as spectroscopic probes of the local, environment are presented. Specifically, resonance Raman spectra of 2-fluoro-L-tyrosine and 3-fluoro-L-tyrosine (3-Y[sub f]) obtained with 229 nm excitation are reported. In contrast to the modest environmental dependence of the tyrosine resonance Raman spectrum, the spectrum of 3-Y[sub f] is found to be extremely dependent on the hydrogen bonding strength of the surrounding environment. Preliminary ab initio studies suggest that this behavior is due to normal modes having dominant contributions from the C-OH and C-F internal coordinates. Hydrogen bonding to the solvent perturbs the internal coordinate energetics and/or couplings, thereby altering the character of the normal modes and the corresponding transition frequencies and/or intensities. In addition to the solvent studies, 3-Y[sub f] is site specifically incorporated into the influenza hemagglutinin (HA) 100-107 peptide which binds to the F[sub v] fragment of the 17/9 anti-HA(98-108) peptide antibody. These studies demonstrate that the spectrum of 3-Y[sub f] can be monitored in the presence of native tyrosine. In summary, the studies presented here demonstrate that 3-Y[sub f] holds exceptional promise as a probe of the protein environment. [ABSTRACT FROM AUTHOR]

Hypervalent dimethyloxonium radical, (CH3)2O&z.sbnd;H⋅ (1), is formed by collisional electron transfer to protonated dimethyl ether in the gas phase and dissociates rapidly by cleavage of the O&z.sbnd;H and O&z.sbnd;C bonds. Ab initio and density functional theory calculations show that these dissociations originate from different electronic states of 1. The loss of H proceeds from the repulsive ground electronic (X) state of 1 and is 131 kJ mol−1 exothermic to form vibrationally excited (CH3)2O. The loss of methyl proceeds from the first excited electronic (A) state of 1 by crossing to the repulsive part of the X state potential energy surface, yielding vibrationally excited methanol. A substantial fraction of deuterated radicals, (CH3)2O&z.sbnd;D⋅ (1-OD), are metastable on the microsecond time scale. The metastable species result from the population of the B and higher excited states of 1 that are calculated to be bound along both O&z.sbnd;H and O&z.sbnd;C coordinates. The isotope effects on the metastability of 1 are explained by less efficient vibronic coupling between the bound B and dissociative A states in the deuterated radical. [Copyright &y& Elsevier]

The first resonance Raman spectra of nitrosyl chloride (ClNO) in solution obtained with excitation resonant with the A-band are reported. For ClNO dissolved in cyclohexane, intensity is observed for transitions corresponding to all three normal coordinates: the bend, NCl stretch and NO stretch. This observation demonstrates that excited-state structural evolution occurs along these coordinates following photoexcitation resonant with the A-band. Resonance Raman depolarization ratios measured at excitation wavelengths spanning the A-band are reported. The depolarization ratios are found to be less that 1/3 consistent with at least two electronic transitions contributing to the A-band absorption intensity. [Copyright &y& Elsevier]

Trends in basking shark (Cetorhinus maximus ) fishery catches off Achill Island, west Ireland between 1949 and 1975 were examined in relation to zooplankton (total copepod) abundance in four adjacent sea areas over a 27-year period. The numbers of basking sharks caught and copepod abundance showed downward trends and were positively correlated (r -value range, 0.44–0.74). A possible explanation for the downward trend in shark catches was that progressively fewer basking sharks occurred there between 1956 and 1975 because fewer copepods, their food resource, occurred near the surface off west Ireland over the same period. We suggest that the decline in basking sharks may have been due to a distributional shift of sharks to more productive areas, rather than a highly philopatric, localized stock that was over-exploited. [ABSTRACT FROM AUTHOR]

Investigates the photochemistry of chlorine dioxide in aqueous solution via femtosecond transient absorption spectroscopy. Three distinct photochemical pathways available to chlorine dioxide following photoexcitation; Photolytic formation of chlorine and oxygen via isomerization to ClOO; Catalytic destruction of ozone.

In the more than 50 years that the Continuous Plankton Recorder (CPR) survey has operated on a regular monthly basis in the north-east Atlantic and North Sea, large changes have been witnessed in the planktonic ecosystem. These changes have taken the form of long-term trends in abundance for certain species or stepwise changes for others, and in many cases are correlated with a mode of climatic variability in the North Atlantic, either: (1) the North Atlantic Oscillation (NAO), a basin-scale atmospheric alteration of the pressure field between the Azores high pressure cell and the Icelandic Low; or (2) the Gulf Stream Index (GSI), which measures the latitudinal position of the north wall of the Gulf Stream. Recent work has shown that the changes in the GSI are coupled with the NAO and Pacific Southern Oscillation with a 2 year lag. The plankton variability is also possibly linked to changes observed in the distribution and flux of water masses in the surface, intermediate and deep waters of the North Atlantic. For example, in the last two decades, the extent and location of the formation of North Atlantic Deep Water, Labrador Sea Intermediate Water and Norwegian Sea intermediate and upper-layer water has altered considerably. This paper discusses the extent to which observed changes in plankton abundance and distribution may be linked to this basin-scale variability in hydrodynamics. The results are also placed within the context of global climate warming and the possible effects of the observed melting of Arctic permafrost and sea ice on the subpolar North Atlantic. [ABSTRACT FROM AUTHOR]

Objective: The aim of this paper is to report the effect of rapid transcranial magnetic stimulation (rTMS) on the mood and dexamethasone suppression test (DST) of a patient with major depressive disorder (DSM-IV). Clinical picture: A 36-year-old woman with a past history of prolactinoma and recurrent major depressive disorder presented with major depression on three separate occasions over a 3-month period. DST was positive on each occasion. Treatment: During each episode, a course of rTMS was given. Courses varied from seven to 13 once-daily treatment sessions depending on clinical response. These treatment sessions were 20 trains of 10 Hz for 5 s at 100% of motor threshold. Outcome: Remission was achieved, psychiatric rating scales improved and the DST status converted from positive to negative. There were no side effects. Conclusion: DST status in major depressive disorder can be converted from positive to negative by rTMS. This so far unreported observation increases our knowledge of rTMS. [ABSTRACT FROM AUTHOR]

The geographical and seasonal occurrences of dinoflagellate cysts at a depth of 10 m in the North Atlantic and North Sea are described from samples taken by the Continuous Plankton Recorder between June 1973 and December 1975. A special study was made of the large cyst of Polykrikos schwartzii Bütschli in the autumn of 1973 when CPR samples were supplemented by vertical sampling in the upper 500 m with a Longhurst-Hardy Plankton Recorder at Ocean Weather Station, INDIA. Only ten isolated records of cysts were made in the western Atlantic. All others occurred to the east of 30°W in both oceanic and neritic waters and especially in the shallow waters of the North Sea. Cysts were found in the spring plankton but were most abundant in the autumn. They have been recorded down to 500 m but occur most frequently in the top 30 m of the water column. Large aggregations of cysts in bottom sediments probably reflect concentration over many years since they cannot be explained by the low numbers found in the plankton. Generally, the distribution of cysts in the plankton is reflected in bottom sediments but concentrations in sediments may be outside the centres of production, implying movement by currents or sediment transport. [ABSTRACT FROM AUTHOR]

A cluster analysis of the dinoflagellate cyst assemblage of sixty-eight intertidal sediment samples from the British Isles has been used to divide the coastline into eleven regions. The resulting pattern of regions is discussed in relation to hydrography and the distribution of dinoflagellates in the plankton. The subdivision of dinoflagellate regions shows a close relationship to the occurrence of chaetognath indicators of water masses around the British Isles. This suggests that cyst propagation is localized and that each water mass has its own characteristic dinoflagellate population. [ABSTRACT FROM AUTHOR]

Investigates the photoproduct formation, vibrational and conformational relaxation kinetics in the photochemical ring-openings of 1,3-cyclohexadiene and alpha-phellandrene (alpha-PHE). Picosecond, time-resolved UV Stokes and anti-Stokes resonance Raman spectroscopy; Ground-state surfaces; Determination of the molecular temperature of cis-Hexatriene.

Semiconductor nanocrystals or "quantum dots" are attractive materials for exploring quantum confinement effects. For example, band-gap energies of these materials depend on particle size, and this dependence can be explained using simple, quantum mechanical models. We outline here an undergraduate physical chemistry laboratory involving the room-temperature synthesis and absorption spectroscopy of ZnO nanocrystals. The experimental results are compared with the predictions of a three-dimensional quantum confinement (or "particle-in-a-sphere") model. The ease of synthesis and data collection, the common precursors employed, and the simple spectroscopic analysis allow facile incorporation of this experiment into essentially any undergraduate laboratory program. [ABSTRACT FROM AUTHOR]

We provide evidence of large-scale changes in the biogeography of calanoid copepod crustaceans in the eastern North Atlantic Ocean and European shelf seas. We demonstrate that strong biogeogrephical shifts in all copepod assemblages have occurred with a northward extension of more than 10° latitude of warm-water species associated with a decrease in the number of colder-water species. These biogeographical shifts are in agreement with recent changes in the spatial distribution and phenology detected for many taxonomic groups in terrestrial European ecosystems and are related to both the increasing trend in Northern Hemisphere temperature and the North Atlantic Oscillation. [ABSTRACT FROM AUTHOR]

In recent years, the Southern Ocean has experienced extremely low sea ice cover in multiple summers. These low events were preceded by a multidecadal positive trend that culminated in record high ice coverage in 2014. This abrupt transition has led some authors to suggest that Antarctic sea ice has undergone a regime shift. In this study we analyze the satellite sea ice record and atmospheric reanalyses to assess the evidence for such a shift. We find that the standard deviation of the summer sea ice record has doubled from 0.31 million km2 in 1979–2006 to 0.76 million km2 for 2007–22. This increased variance is accompanied by a longer season-to-season sea ice memory. The atmosphere is the primary driver of Antarctic sea ice variability, but using a linear predictive model we show that sea ice changes cannot be explained by the atmosphere alone. Identifying whether a regime shift has occurred is difficult without a complete understanding of the physical mechanism of change. However, the statistical changes that we demonstrate (i.e., increased variance and autocorrelation, and a changed response to atmospheric forcing), as well as the increased spatial coherence noted by previous research, are indicators based on dynamical systems theory of an abrupt critical transition. Thus, our analysis is further evidence in support of a changed Antarctic sea ice system. Significance Statement: In recent years, there have been several summers with extremely low Antarctic sea ice cover, including consecutive record lows in February 2022 and February 2023. Since then, the 2023 winter has seen a remarkably low sea ice growth with an anomaly far below expected climatology. This has led researchers to question whether there has been a regime shift, and we assess the observational evidence for such a shift. In the last decade or so, the variability of summer sea ice has almost doubled, accompanied by a much longer sea ice memory from season to season. These statistical changes, as well an increased spatial coherence noted by other researchers, are consistent with theoretical indicators of a critical transition, or regime shift. [ABSTRACT FROM AUTHOR]

Standard methods for studying the association between two ecologically important variables provide only a small slice of the information content of the association, but statistical approaches are available that provide comprehensive information. In particular, available approaches can reveal tail associations, that is, accentuated or reduced associations between the more extreme values of variables. We here study the nature and causes of tail associations between phenological or population‐density variables of co‐located species, and their ecological importance. We employ a simple method of measuring tail associations which we call the partial Spearman correlation. Using multidecadal, multi‐species spatiotemporal datasets on aphid first flights and marine phytoplankton population densities, we assess the potential for tail association to illuminate two major topics of study in community ecology: the stability or instability of aggregate community measures such as total community biomass and its relationship with the synchronous or compensatory dynamics of the community's constituent species; and the potential for fluctuations and trends in species phenology to result in trophic mismatches. We find that positively associated fluctuations in the population densities of co‐located species commonly show asymmetric tail associations; that is, it is common for two species' densities to be more correlated when large than when small, or vice versa. Ordinary measures of association such as correlation do not take this asymmetry into account. Likewise, positively associated fluctuations in the phenology of co‐located species also commonly show asymmetric tail associations. We provide evidence that tail associations between two or more species' population‐density or phenology time series can be inherited from mutual tail associations of these quantities with an environmental driver. We argue that our understanding of community dynamics and stability, and of phenologies of interacting species, can be meaningfully improved in future work by taking into account tail associations. [ABSTRACT FROM AUTHOR]

We report a series of time-resolved infrared absorption studies on chlorine dioxide (OClO) dissolved in H2O, D2O, and acetonitrile. Following the photoexcitation at 401 nm, the evolution in optical density for frequencies corresponding to asymmetric stretch of OClO is measured with a time resolution of 120±50 fs. The experimentally determined optical-density evolution is compared with theoretical models of OClO vibrational relaxation derived from collisional models as well as classical molecular-dynamics (MD) studies. The vibrational relaxation rates in D2O are reduced by a factor of 3 relative to H2O consistent with the predictions of MD. This difference reflects modification of the frequency-dependent solvent-solute coupling accompanying isotopic substitution of the solvent. Also, the geminate-recombination quantum yield for the primary photofragments resulting in the reformation of ground-state OClO is reduced in D2O relative to H2O. It is proposed that this reduction reflects enhancement of the dissociation rate accompanying vibrational excitation along the asymmetric-stretch coordinate. In contrast to H2O and D2O, the vibrational-relaxation dynamics in acetonitrile are not well described by the theoretical models. Reproduction of the optical-density evolution in acetonitrile requires significant modification of the frequency-dependent solvent-solute coupling derived from MD. It is proposed that this modification reflects vibrational-energy transfer from the asymmetric stretch of OClO to the methyl rock of acetonitrile. In total, the results presented here provide a detailed description of the solvent-dependent geminate-recombination and vibrational-relaxation dynamics of OClO in solution. [ABSTRACT FROM AUTHOR]

Ultrafast time-resolved infrared absorption studies of aqueous chlorine dioxide (OClO) photochemistry are reported. Following photoexcitation at 401 nm, the evolution in optical density at frequencies between 1000 to 1100 cm-1 is monitored to investigate vibrational energy deposition and relaxation along the asymmetric-stretch coordinate following the reformation of ground-state OClO via geminate recombination of the primary photofragments. The measured kinetics are compared to two proposed models for the vibrational-relaxation dynamics along the asymmetric-stretch coordinate. This comparison demonstrates that the perturbation model derived from molecular dynamics studies is capable of qualitatively reproducing the observed kinetics, where the collisional model employed in previous UV-pump, visible probe experiments demonstrates poor agreement with experiment. The ability of the perturbation model to reproduce the optical-density evolution observed in these studies demonstrates that for aqueous OClO, frequency dependence of the solvent–solute coupling is important in defining the level-dependent vibrational relaxation rates along the asymmetric-stretch coordinate. The absence of optical-density evolution corresponding to the population of higher vibrational levels (n>8) along the asymmetric-stretch coordinate suggests that following geminate recombination, energy is initially deposited into a local Cl–O stretch, with the relaxation of vibrational energy from this coordinate providing for delayed vibrational excitation of the asymmetric- and symmetric-stretch coordinates relative to geminate recombination, as previously observed. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The solvation dynamics following photoexcitation of chlorine dioxide (OClO) in different solvents are investigated by classical molecular dynamics. Following previous work on the aqueous response to OClO photoexcitation [J. Chem. Phys. 118, 4563 (2003)], the present study considers the response of chloroform and cyclohexane; these three liquids present unique solvent environments that differ significantly in both polarity and structure. The study is designed to ascertain the origin of the solvent-invariant homogeneous linewidth associated with OClO photoexcitation and to confirm, at the molecular level, whether the relaxation dynamics are similar across dissimilar solvents due to chance or a common relaxation origin. The results obtained here are used to predict the time scale of solvent-induced optical dephasing, and excellent agreement with experiment is observed for all solvents. Analysis demonstrates that the solvation dynamics of OClO are dominated by short-ranged mechanical solute–solvent interactions regardless of the identity and electrostatic properties of the solvent. Low-frequency translational motions dominate the coupling spectrum, and virtually no contribution to energy gap relaxation is achieved through intramolecular solvent motions. The invariant homogeneous linewidth is attributed to the similarity in the primary response of all solvents to OClO photoexcitation. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The solvation dynamics following photoexcitation of aqueous chlorine dioxide (OClO) are investigated by classical molecular dynamics. A total of four OClO/water models are employed, including standard and customized OClO models together with SPC/F and TIP3P water. The simulation results are used to predict the time scale of solvent-induced optical dephasing, and excellent agreement with experiment is observed. The simulations demonstrate that the solvation dynamics of aqueous OClO are dominated by the short-ranged mechanical solute-solvent interactions. When compared to the aqueous solvation of spherical solutes, the solvation dynamics of OClO exhibit a novel effect. The role of the faster translational and librational water motions is suppressed in the dielectric component of the response, but is emphasized in the mechanical response, in stark contrast to the results for other spherical systems. The faster translational motions appear in the mechanical response due to the noncentrosymmetric nature of the OclO-water interaction, enhanced by OclO-water hydrogen bonding. [ABSTRACT FROM AUTHOR]

The production of CIlO following OClO photolysis in water and fluorotrichloromethane (freon-11) is investigated using time-resolved resonance Raman (TRRR) spectroscopy. Stokes spectra are obtained as a function of time following OClO photoexcitation using pump and probe wavelengths of 390 and 260 nm, respectively. Scattering assignable to ClOO is observed, and appears with a time constant of 27.9 ± 4.5 ps in water and 172 ± 30 ps in freon-11. The ClOO intensity decays with a time constant of ∼398 ± 50 ps in water and 864 ± 200 ps in freon-11. Although the production and decay kinetics are solvent dependent, the quantum yield for ClOO production is similar between water and freon-11. Femtosecond pump-probe studies designed to monitor the evolution in optical density at 390 and 260 nm following OClO photoexcitation are also presented. These studies demonstrate that geminate recombination of the primary photoproducts is less efficient in freon-11 relative to water. This result taken in combination with the solvent invariance of the ClOO-production quantum yield indicates that ClOO is not formed via geminate recombination. Instead, the results presented here suggest that OClO photoisomerization results in the production of ClOO. Finally, the vibrational energy content of ClOO upon internal conversion to the ground state is studied through comparison of the ClOO Raman and absorption cross sections to those predicted using computational methods. These studies suggest that ground-state ClOO is produced with minimal excess vibrational energy. The results presented here provide new insight into the mechanism of ClOO formation following OClO photoexcitation. © 2001 American Institute of Physics. [DOI: 10.1063/1.1418733]. [ABSTRACT FROM AUTHOR]

Absolute resonance Raman cross sections for chlorine dioxide (OClO) dissolved in chloroform are obtained at several excitation wavelengths spanning the photochemically relevant [sup 2]B[sub 1]-[sup 2]A[sub 2] optical transition. The absolute scattering cross sections of OClO are determined by reference to the 666 cm[sup -1] transition of chloroform whose absolute scattering cross sections are reported here. The time-dependent theory for Raman and absorption are used to develop a mode-specific description of the [sup 2]A[sub 2] excited state surface. This description demonstrates that photoexcitation of OClO leads to significant structural evolution along the symmetric stretch and bend coordinates, with only limited evolution occurring along the asymmetric stretch. This description is similar to that determined for OClO dissolved in cyclohexane and water demonstrating that the excited-state structural evolution of OClO is similar in these solvents. Analysis of the OClO absolute scattering cross sections establishes that the homogeneous linewidth is 95±15 cm[sup -1] in chloroform, essentially identical to the linewidths in cyclohexane and water. To establish the origin of this linewidth, the fluorescence cross section for OClO dissolved in cyclohexane is measured and found to be consistent with an excited-state lifetime of ∼200 fs. Comparison of this lifetime to the homogeneous linewidth establishes that the homogeneous broadening is dominated by solvent-induced pure dephasing. It is proposed that the apparent solvent independence of the homogeneous linewidth reflects the mechanical response of the solvent to the photoinitiated change in solute geometry. In support of this hypothesis, the homogeneous linewidth is reproduced using the viscoelastic continuum model of nonpolar solvation. Finally, it is argued that the restricted evolution along the asymmetric-stretch coordinate is due to dielectric solvent-solute interactions consistent with the incr... [ABSTRACT FROM AUTHOR]

Large-scale spatial synchrony is ubiquitous in ecology. We examined 56 years of data representing chlorophyll density in 26 areas in British seas monitored by the Continuous Plankton Recorder survey. We used wavelet methods to disaggregate synchronous fluctuations by timescale and determine that drivers of synchrony include both biotic and abiotic variables. We tested these drivers for statistical significance by comparison with spatially synchronous surrogate data. Identification of causes of synchrony is distinct from, and goes beyond, determining drivers of local population dynamics. We generated timescale-specific models, accounting for 61% of long-timescale (> 4yrs) synchrony in a chlorophyll density index, but only 3% of observed short-timescale (< 4yrs) synchrony. Thus synchrony and its causes are timescale-specific. The dominant source of long-timescale chlorophyll synchrony was closely related to sea surface temperature, through a climatic Moran effect, though likely via complex oceanographic mechanisms. The top-down action of Calanus finmarchicus predation enhances this environmental synchronising mechanism and interacts with it non-additively to produce more long-timescale synchrony than top-down and climatic drivers would produce independently. Our principal result is therefore a demonstration of interaction effects between Moran drivers of synchrony, a new mechanism for synchrony that may influence many ecosystems at large spatial scales. [ABSTRACT FROM AUTHOR]

Taylor's law (TL), a commonly observed and applied pattern in ecology, describes variances of population densities as related to mean densities via log(variance) = log(a) + b*log(mean). Variations among datasets in the slope, b, have been associated with multiple factors of central importance in ecology, including strength of competitive interactions and demographic rates. But these associations are not transparent, and the relative importance of these and other factors for TL slope variation is poorly studied. TL is thus a ubiquitously used indicator in ecology, the understanding of which is still opaque.The goal of this study was to provide tools to help fill this gap in understanding by providing proximate determinants of TL slopes, statistical quantities that are correlated to TL slopes but are simpler than the slope itself and are more readily linked to ecological factors.Using numeric simulations and 82 multi‐decadal population datasets, we here propose, test and apply two proximate statistical determinants of TL slopes which we argue can become key tools for understanding the nature and ecological causes of TL slope variation.We find that measures based on population skewness, coefficient of variation and synchrony are effective proximate determinants. We demonstrate their potential for application by using them to help explain covariation in slopes of spatial and temporal TL (two common types of TL).This study provides tools for understanding TL, and demonstrates their usefulness. Using numeric simulations and 82 multi‐decadal population datasets, the authors propose, test and apply two proximate statistical determinants of Taylor's law slopes which they argue can become key tools for understanding the nature and ecological causes of TL slope variation. [ABSTRACT FROM AUTHOR]

Arising from D. G. Boyce, M. R. Lewis & B. Worm 466, 591-596 (2010); Boyce et al. replyPhytoplankton account for approximately 50% of global primary production, form the trophic base of nearly all marine ecosystems, are fundamental in trophic energy transfer and have key roles in climate regulation, carbon sequestration and oxygen production. Boyce et al. compiled a chlorophyll index by combining in situ chlorophyll and Secchi disk depth measurements that spanned a more than 100-year time period and showed a decrease in marine phytoplankton biomass of approximately 1% of the global median per year over the past century. Eight decades of data on phytoplankton biomass collected in the North Atlantic by the Continuous Plankton Recorder (CPR) survey, however, show an increase in an index of chlorophyll (Phytoplankton Colour Index) in both the Northeast and Northwest Atlantic basins (Fig. 1), and other long-term time series, including the Hawaii Ocean Time-series (HOT), the Bermuda Atlantic Time Series (BATS) and the California Cooperative Oceanic Fisheries Investigations (CalCOFI) also indicate increased phytoplankton biomass over the last 20-50 years. These findings, which were not discussed by Boyce et al., are not in accordance with their conclusions and illustrate the importance of using consistent observations when estimating long-term trends. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article “The Coming Arctic invasion,” by G.J. Vermeij and P.D. Roopnarine in the August 8, 2008 issue.

Reports on a medical case of clozapine rechallenge after myocarditis in Australia. Use of clozapine to treat a 23-year old man with deteriorating treatment-resistant schizophrenia; Deterioration of mental state after ceasing clozapine medication; Resumption of clozapine; Factors considered in resuming clozapine treatment; Description of myocarditis.

Climate change is having a dramatic impact on marine animal and plant communities but little is known of its influence on marine prokaryotes, which represent the largest living biomass in the world oceans and play a fundamental role in maintaining life on our planet. In this study, for the first time to our knowledge, experimental evidence is provided on the link between multidecadal climatic variability in the temperate North Atlantic and the presence and spread of an important group of marine prokaryotes, the vibrios, which are responsible for several infections in both humans and animals. Using archived formalin-preserved plankton samples collected by the Continuous Plankton Recorder survey over the past half-century (1958–2011), we assessed retrospectively the relative abundance of vibrios, including human pathogens, in nine areas of the North Atlantic and North Sea and showed correlation with climate and plankton changes. Generalized additive models revealed that long-term increase in Vibrio abundance is promoted by increasing sea surface temperatures (up to ∼1.5 °C over the past 54 y) and is positively correlated with the Northern Hemisphere Temperature (NHT) and Atlantic Multidecadal Oscillation (AMO) climatic indices (P < 0.001). Such increases are associated with an unprecedented occurrence of environmentally acquired Vibrio infections in the human population of Northern Europe and the Atlantic coast of the United States in recent years. [ABSTRACT FROM AUTHOR]

Reports on the medical case of a 22-year-old student in Australia with a four-year history of bilateral facial pain. Treatment with a course of transcranial magnetic stimulation (TMS) for a concurrent major depressive episode; Family history of facial pain; Description of TMS; Decrease in pain in the second week of TMS treatment; Beck Depression Inventory measurement.

During the 1980s, the North Sea plankton community underwent a well-documented ecosystem regime shift, including both spatial changes (northward species range shifts) and temporal changes (increases in the total abundances of warmer water species). This regime shift has been attributed to climate change. Plankton provide a link between climate and higher trophic-level organisms, which can forage on large spatial and temporal scales. It is therefore important to understand not only whether climate change affects purely spatial or temporal aspects of plankton dynamics, but also whether it affects spatiotemporal aspects such as metapopulation synchrony. If plankton synchrony is altered, higher trophic-level feeding patterns may be modified. A second motivation for investigating changes in synchrony is that the possibility of such alterations has been examined for few organisms, in spite of the fact that synchrony is ubiquitous and of major importance in ecology. This study uses correlation coefficients and spectral analysis to investigate whether synchrony changed between the periods 1959-1980 and 1989-2010. Twenty-three plankton taxa, sea surface temperature ( SST), and wind speed were examined. Results revealed that synchrony in SST and plankton was altered. Changes were idiosyncratic, and were not explained by changes in abundance. Changes in the synchrony of Calanus helgolandicus and Para-pseudocalanus spp appeared to be driven by changes in SST synchrony. This study is one of few to document alterations of synchrony and climate-change impacts on synchrony. We discuss why climate-change impacts on synchrony may well be more common and consequential than previously recognized. [ABSTRACT FROM AUTHOR]

New experimental and analysis methods for investigating the role local environment has on photoluminescence intermittency (PI) exhibited by single luminophores are presented. Quasi-single molecule (SM) microscopy provides spatial resolution of dielectric environments within poly(vinylidene fluoride) (PVDF) films, and reveals annealing's effect on the structural phase of PVDF. New analysis methods establish that the PI exhibited by nile red (NR) SMs in PVDF are consistent with photoinduced electron transfer between NR and PVDF, where transfer rates depend on local dielectric environment. These methods should prove useful for SM studies of guest–host materials where elucidating PI contribution from the host is required. [ABSTRACT FROM AUTHOR]

The effect of annealing on the phase transformation and the dielectric properties of poly(vinylidene fluoride) (PVDF) is explored using quasi-single molecule (quasi-SM) microscopy. The solvatochromic properties of nile red (NR) are employed to measure the spatial distribution of the local dielectric constant (ε) in ~30 µm thick PVDF films before and after annealing at 90 °C. The results presented here demonstrate that nonannealed films exhibit much larger ε distributions, both in terms of magnitude and distribution, when compared to annealed films. The polymorphic phase of PVDF before and after annealing is also confirmed using X-ray diffraction. Nonannealed films are found to be in the ɣ-phase with annealing promoting the transition to primarily β-phase. Combining these results, we conclude that the decrease in ε with annealing time is due to the phase transformation from ɣ- to β-phase. Using quasi-SM imaging techniques one can readily visualize the ε environments present within different polymorphic phases of PVDF. [ABSTRACT FROM AUTHOR]

Thedependence of single-molecule photoluminescence intermittency(PI) or “blinking” on the local dielectric constant(ε) is examined for nile red (NR) in thin films of poly(vinylidenefluoride) (PVDF). In previous studies, variation of the local dielectricconstant was accomplished by studying luminophores in chemically andstructurally different hosts. In contrast, the NR/PVDF guest–hostpair allows for the investigation of PI as a function of ε whilekeeping the chemical composition of both the luminophore and hostunchanged. The solvatochromic properties of NR are used to measurethe local ε, while fluctuations in NR emission intensity overtime provide a measure of the PI. PVDF is an ideal host for this studybecause it provides submicron-sized dielectric domains that vary fromnonpolar (ε ≈ 2) to very polar (ε ≈ 70).The results presented here demonstrate that the local dielectric environmentcan have a pronounced effect on PI. We find that the NR emissive eventsincrease 5-fold with an increase in ε from 2.2 to 74. A complexdependence on ε is also observed for NR nonemissive event durations,initially increasing as ε increases from 2.2 to 3.4 but decreasingin duration with further increase in ε. The variation in emissiveevent durations with ε is reproduced using a photoinduced electron-transfermodel involving electron transfer from NR to PVDF. In addition, anincrease in NR photostability with an increase in ε is observed,suggesting that the dielectric environment plays an important rolein defining the photostability of NR in PVDF. [ABSTRACT FROM AUTHOR]

The recently developed technique of femtosecond stimulated Raman spectroscopy, and its variant, femtosecond Raman-induced Kerr effect spectroscopy (FRIKES), offer access to ultrafast excited-state dynamics via structurally specific vibrational spectra. We have used FRIKES to study the photoexcitation dynamics of nickel(II) phthalocyanine with eight butoxy substituents, NiPc(OBu)8. NiPc(OBu)8 is reported to have a relatively long-lived ligandto- metal charge-transfer (LMCT) state, an essential characteristic for efficient electron transfer in photocatalysis. Following photoexcitation, vibrational transitions in the FRIKES spectra, assignable to phthalocyanine ring modes, evolve on the femtosecond to picosecond time scales. Correlation of ring core size with the frequency of the v10 (asymmetric C-N stretching) mode confirms the identity of the LMCT state, which has a ∼500 ps lifetime, as well as that of a precursor d-d excited state. An even earlier (∼0.2 ps) transient is observed and tentatively assigned to a higher-lying Jahn-Teller-active LMCT state. This study illustrates the power of FRIKES spectroscopy in elucidating ultrafast molecular dynamics. [ABSTRACT FROM AUTHOR]

Recent experimental and theoretical studies of photoluminescence intermittency (PI) or "blinking" exhibited by single core/shell quantum dots and single organic luminophores are reviewed. For quantum dots, a discussion of early models describing the origin of PI in these materials and recent challenges to these models are presented. For organic luminophores the role of electron transfer, proton transfer and other photophysical processes in PI are discussed. Finally, new experimental and data analysis methods are outlined that promise to be instrumental in future discoveries regarding the origin(s) of PI exhibited by single emitters. [ABSTRACT FROM AUTHOR]

Abstract: Copepods represent the major part of the dry weight of the mesozooplankton in pelagic ecosystems and therefore have a central role in the secondary production of the North Atlantic Ocean. The calanoid copepod species Calanus finmarchicus is the main large copepod in subarctic waters of the North Atlantic, dominating the dry weight of the mesozooplankton in regions such as the northern North Sea and the Norwegian Sea. The objective of this work was to investigate the relationships between both the fundamental and realised niches of C. finmarchicus in order to better understand the future influence of global climate change on the abundance, the spatial distribution and the phenology of this key-structural species. Based on standardised Principal Component Analyses (PCAs), a macroecological approach was applied to determine factors affecting the spatial distribution of C. finmarchicus and to characterise its realised niche. Second, an ecophysiological model was used to calculate the Potential Egg Production Rate (PEPR) of C. finmarchicus and the centre of its fundamental niche. Relationships between the two niches were then investigated by correlation analysis. We found a close relationship between the fundamental and realised niches of C. finmarchicus at spatial, monthly and decadal scales. While the species is at the centre of its niche in the subarctic gyre, our joint macroecological and macrophysiological analyses show that it is at the edge of its niche in the North Sea, making the species in this region more vulnerable to temperature changes. [Copyright &y& Elsevier]

Abciximab decreases adverse cardiac ischemic events, and in some subgroups, decreases the need for revascularization after percutaneous coronary intervention (PCI). However, abciximab may cause bleeding complications and thrombocytopenia after PCI. We hypothesized that the efficacy and safety of PCI would be maintained, if not improved, when performed using abciximab accompanied by only minimal doses (≤1,000 U) of unfractionated heparin. In this prospectively designed observational study, we assessed 500 consecutive patients who underwent PCI, consisting of either stent deployment or high-speed rotational atherectomy, and who received abciximab accompanied by only a minimal dose of unfractionated heparin, as directed by a novel dosing strategy: (1) if the patient was previously receiving an infusion of heparin, then it was terminated upon arrival to the cardiac catheterization laboratory, and no further heparin was administered; or (2) if the patient was not receiving an infusion of heparin, then a single bolus infusion of 1,000 U was administered after establishment of vascular access. The median activated clotting time for the patients during PCI was 168 seconds (25% quartiles, 153 to 185). The technical success rate was 99.8%. There were no major adverse clinical events during the 24 hours after PCI. The incidence of non–Q-wave myocardial infarction was 1.6%. The incidences of major and minor bleeding complications were 0.2% and 3.6%, respectively, and the incidence of thrombocytopenia was 2.2%. During the 30 days after PCI, there was 1 major adverse clinical event (0.2%). During the 1 year after PCI, among the remaining patients, there were 92 adverse events (18.4%). We conclude that, in the context of historical data, the efficacy and safety of PCI using either stent deployment or high-speed rotational atherectomy is maintained, if not improved, when performed using abciximab accompanied by only minimal doses of unfractionated heparin. [Copyright &y& Elsevier]

Raman and infrared spectra of isopropyl nitrate and isobutyl nitrate are reported. These spectra are used in combination with computational studies employing density functional theory at the B3-LYP/6-31G* level to assign the vibrational transitions to their corresponding normal coordinates. Similar to other alkyl nitrates, the frequency of the NO2 symmetric stretch remains relatively unchanged while the asymmetric stretch shifts to lower frequency with increasing α-carbon substitution. The mode assignments involving the photochemically relevant &z.sbnd;ONO2 chromophore agree well with those from previous infrared work. Raman depolarization ratios are also presented, and provide evidence that the condensed phase, ground-state molecular structure of isobutyl nitrate is of Cs symmetry. In contrast, the minimum energy structure of isopropyl nitrate is predicted to contain a pronounced twist around the C&z.sbnd;O bond relative to the Cs-symmetry structure that lies 2.6 kcal/mol higher in energy. Infrared intensities of isopropyl nitrate are consistent with the twisted geometry, demonstrating that this conformer is favored in solution. [Copyright &y& Elsevier]