Increase In Frequency Of Occurrence Research Articles

Storylines of weather-induced crop failure events under climate change

Abstract. Unfavourable weather is a common cause for crop failures all over the world. Whilst extreme weather conditions may cause extreme impacts, crop failure commonly is induced by the occurrence of multiple and combined anomalous meteorological drivers. For these cases, the explanation of conditions leading to crop failure is complex, as the links connecting weather and crop yield can be multiple and non-linear. Furthermore, climate change is likely to perturb the meteorological conditions, possibly altering the occurrences of crop failures or leading to unprecedented drivers of extreme impacts. The goal of this study is to identify important meteorological drivers that cause crop failures and to explore changes in crop failures due to global warming. For that, we focus on a historical failure event, the extreme low soybean production during the 2012 season in the midwestern US. We first train a random forest model to identify the most relevant meteorological drivers of historical crop failures and to predict crop failure probabilities. Second, we explore the influence of global warming on crop failures and on the structure of compound drivers. We use large ensembles from the EC-Earth global climate model, corresponding to present-day, pre-industrial +2 and 3 ∘C warming, respectively, to isolate the global warming component. Finally, we explore the meteorological conditions inductive for the 2012 crop failure and construct analogues of these failure conditions in future climate settings. We find that crop failures in the midwestern US are linked to low precipitation levels, and high temperature and diurnal temperature range (DTR) levels during July and August. Results suggest soybean failures are likely to increase with climate change. With more frequent warm years due to global warming, the joint hot–dry conditions leading to crop failures become mostly dependent on precipitation levels, reducing the importance of the relative compound contribution. While event analogues of the 2012 season are rare and not expected to increase, impact analogues show a significant increase in occurrence frequency under global warming, but for different combinations of the meteorological drivers than experienced in 2012. This has implications for assessment of the drivers of extreme impact events.

ВЛИЯНИЕ ФАКТОРОВ ОКРУЖАЮЩЕЙ СРЕДЫ НА ПОПУЛЯЦИОННО- ГЕНЕТИЧЕСКУЮ СТРУКТУРУ ДУБА ЧЕРЕШЧАТОГО (QUERCUS ROBUR L.) В БЕЛАРУСИ

Pedunculate oak (Quercus robur L.) is one of the main forest forming species in the Republic of Belarus. 18 allelic variants were identified by means of microsatellite loci analysis, which are grouped into 17 different combinations (haplotypes). Twelve of them are rare (the total frequency of occurrence is 15 %) and five are widespread (the proportion of occurrence varies from 7 to 48 %). The last of the named groups includes haplotypes No. 1 (μdt189, μdt3123, μdt4142, μcd494, μcd574, μkk4109), No. 2 (μdt190, μdt3120, μdt4141, μcd495, μcd574, μkk4109), No. 3 (μdt189, μdt3120, μdt4141, μcd494, μcd575, μkk4109), No. 8 (μdt189, μdt3121, μdt4142, μcd494, μcd574, μkk4109). It was found that the geographical distribution of the dominant haplotypes from west to east (along the gradient of climate continentality increasing) has the following order No. 8 – No. 7 – No. 3 – No. 1 – No. 2. It was revealed that haplotype No. 3 is predominantly found in oak forests growing on hills. Haplotype No. 8 prones to form forest stands in depressions, while haplotypes No. 1, No. 2 and No. 7 mainly occupied middle relief elements. The actually observed and theoretically expected frequencies of occurrence in different types of oak forests are close to each other only in the case of haplotype No. 2. For haplotypes No. 1 and No. 8 opposite tendencies of distribution were revealed. In those forest types where for haplotype No. 1 there was an increase in the actual frequency of occurrence compared to the expected one, for haplotype No. 8 there was opposite situation. The reverse trend was also true for this pare of haplotypes. The second pair for which opposite tendencies of distribution were also revealed is haplotypes No. 3 and No. 7.

Особенности хориоидального кровотока и их влияние на формирование периферических дегенераций сетчатки у детей школьного возраста с недифференцированной дисплазией соединительной ткани

Purpose. To study choroidal thickness (CT) and assess its effect on frequency of occurrence dangerous types of peripheral retinal degenerations (PRD) in school-age children with myopia associated with undifferentiated connective tissue dysplasia (UCTD). Material and methods. The object of study was 62 children (124 eyes) aged 10–15 years (mean age 12.3±0.8 years) with progressive myopia associated with moderate (48 people, 77.4%) and pronounced (14 people, 22.6%) degree of UCTD. Special ophthalmologic examination included macular imaging by optical coherence tomography (RTVue 100, «Optovue», USA) to measure CT. Diagnostic criteria by T.M. Milkovskaya-Dimitrova et al (1987) were used to identify phenotypic characters of UCTD. Results. Comparative characteristic of CT in macula showed high (p <0.05) relationship between the blood-filled of choroidal vessels and degree of UCTD. Analysis frequency of occurrence of PRD depending on CT demonstrated that against the background accumulation of phenotypic characters of UCTD increase in frequency of occurrence of PRD was observed. Statistical analysis confirmed presence of significant negative correlation between decrease CT and increase in incidence of prognostically dangerous forms of PRD. Conclusion. It was found that in school-age children with myopia with increase degree of UCTD, CT decreases. With choroidal thinning in children with myopia associated with UCTD, the frequency of occurrence dangerous forms of PRD increases. The research results are of clinical importance for the development of rational approaches to clinical examination and treatment children with school myopia with clinical signs of UCTD. Key words: progressive myopia, undifferentiated connective tissue dysplasia, choroidal thickness, peripheral retinal degeneration, rhegmatogenous retinal detachment.

Increased Co-contraction Activity During Push-Off Phase of Walking in Healthy Women

Research purposeThe assessment of possible gender-related differences in co-contraction activity of quadriceps femoris vs. hamstring muscles in able-bodied adults, during straight walking. MethodsStatistical gait analysis was performed on surface-EMG signals from vastus lateralis (VL), rectus femoris (RF), and medial hamstrings (MH) in 15 female (F-group) and 15 male (M-group) age-matched healthy adults. Co-contraction timing and occurrence frequency were provided. Numerous strides (around 450) were considered for each subject. ResultsThe same three co-contractions were found in F and M groups, irrespective of gender: during early stance (ES), push-off (PO) and swing (SW) phase. No relevant differences in co-contraction timing were detected between groups. An increase of occurrence frequency was observed in F-group for VL/MH co-activation during PO phase (21.9±13.6% vs. 11.3±8.6% of strides, p=2.5×10−3). Occurrence-frequency value was higher (p=6.9×10−3) in F-group (25.8±12.1%) than in M-group (17.3±14.2%) also for RF/VL co-activation in PO phase. These differences entailed a 74.1% increase of co-contraction events in females (p<0.05) in PO phase. SignificanceThe present study provides a reference frame for knee-muscle co-contractions during walking, differentiated for women and men. The concomitant analysis of timing and frequency of co-contraction occurrences denotes a significant increase in females of QF/hamstrings co-contraction recruitment in push-off. This suggests a female attempt to augment the level of knee-joint stabilization in the final phase of single support when control of balance is thornier.

Change in strong Eastern Pacific El Niño events dynamics in the warming climate

While there is evidence that ENSO activity will increase in association with the increased vertical stratification due to global warming, the underlying mechanisms remain unclear. Here we investigate this issue using the simulations of the NCAR Community Earth System Model Large Ensemble (CESM-LE) Project focusing on strong El Nino events of the Eastern Pacific (EP) that can be associated to flooding in Northern and Central Peru. It is shown that, in the warmer climate, the duration of strong EP El Nino events peaking in boreal winter is extended by two months, which results in significantly more events peaking in February–March–April (FMA), the season when the climatological Inter-Tropical Convergence Zone is at its southernmost location. This larger persistence of strong EP events is interpreted as resulting from both a stronger recharge process and a more effective thermocline feedback in the eastern equatorial Pacific due to increased mean vertical stratification. A heat budget analysis reveals in particular that the reduction in seasonal upwelling rate is compensated by the increase in anomalous vertical temperature gradient within the surface layer, yielding an overall increase in the effectiveness of the thermocline feedback. In CESM-LE, the appearance of strong EP El Nino events peaking in FMA accounts for one-quarter of the increase in frequency of occurrence of ENSO-induced extreme precipitation events, while one-third results from weak-to-moderate El Nino events that triggers extreme precipitation events because of the warmer mean SST becoming closer to the convective threshold. In CESM-LE, both the increase in mean EP SST and the change in ENSO processes thus contribute to the increase in extreme precipitation events in the warmer climate.

Living with Oxygen.

Work on the electronic structures of metal–oxo complexes began in Copenhagen over 50 years ago. This work led to the prediction that tetragonal multiply bonded transition metal–oxos would not be stable beyond the iron–ruthenium–osmium oxo wall in the periodic table and that triply bonded metal–oxos could not be protonated, even in the strongest Brønsted acids. In this theory, only double bonded metal–oxos could attract protons, with basicities being a function of the electron donating ability of ancillary ligands. Such correlations of electronic structure with reactivity have gained importance in recent years, most notably owing to the widespread recognition that high-valent iron–oxos are intermediates in biological reactions critical to life on Earth.In this Account, we focus attention on the oxygenations of inert organic substrates by cytochromes P450, as these reactions involve multiply bonded iron–oxos. We emphasize that P450 iron–oxos are strong oxidants, so strong that they would destroy nearby amino acids if substrates are not oxygenated rapidly; it is our view that these high-valent iron–oxos are such dangerous reactive oxygen species that Nature surely found ways to disable them. Looking more deeply into this matter, mainly by examining many thousands of structures in the Protein Data Bank, we have found that P450s and other enzymes that require oxygen for function have chains of tyrosines and tryptophans that extend from active-site regions to protein surfaces. Tyrosines are near the heme active sites in bacterial P450s, whereas tryptophan is closest in most human enzymes. High-valent iron–oxo survival times taken from hole hopping maps range from a few nanoseconds to milliseconds, depending on the distance of the closest Trp or Tyr residue to the heme. In our proposed mechanism, multistep hole tunneling (hopping) through Tyr/Trp chains guides the damaging oxidizing hole to the protein surface, where it can be quenched by soluble protein or small molecule reductants. As the Earth’s oxygenic atmosphere is believed to have developed about 2.5 billion years ago, the increase in occurrence frequency of tyrosine and tryptophan since the last universal evolutionary ancestor may be in part a consequence of enzyme protective functions that developed to cope with the environmental toxin, O2.

Meteotsunamis in the Laurentian Great Lakes

The generation mechanism of meteotsunamis, which are meteorologically induced water waves with spatial/temporal characteristics and behavior similar to seismic tsunamis, is poorly understood. We quantify meteotsunamis in terms of seasonality, causes, and occurrence frequency through the analysis of long-term water level records in the Laurentian Great Lakes. The majority of the observed meteotsunamis happen from late-spring to mid-summer and are associated primarily with convective storms. Meteotsunami events of potentially dangerous magnitude (height > 0.3 m) occur an average of 106 times per year throughout the region. These results reveal that meteotsunamis are much more frequent than follow from historic anecdotal reports. Future climate scenarios over the United States show a likely increase in the number of days favorable to severe convective storm formation over the Great Lakes, particularly in the spring season. This would suggest that the convectively associated meteotsunamis in these regions may experience an increase in occurrence frequency or a temporal shift in occurrence to earlier in the warm season. To date, meteotsunamis in the area of the Great Lakes have been an overlooked hazard.

Response of a temperate demersal fish community to global warming

Changes in the distribution of the demersal fish species have been identified in north-European Atlantic waters. The consequence of these changes has been a northward shift of the distribution limits and changes in richness. In this study a notable increase in demersal fish species richness per sampling station was detected in the southern Bay of Biscay. This rise was due to an increase in frequency of occurrence and abundance of the majority of fish species in the area (53% from the total species). A fisheries relate explanation was discarded because the mismatch between the changes in the fishing effort and the augment in frequency of occurrence and abundance. On the contrary, these changes are in agreement with expected response under the increasing temperature of the sea observed over the last three decades, associated to global warming. These changes were positively correlated with an increase in temperature of intermediate waters in the study area. In addition, some of these species showed a notable western displacements of the Centre of Gravity in the study area, which would be expected if temperate water species would be favoured by an increase in water temperature. Our results are consistent with studies in the North Sea, where many of these species showing widened distribution limits towards north. The analysis of the results shows that the studied ecosystem, the Bay of Biscay is under a meridionalization process. On the other hand, only one tropicalization event (Lepidotrigla dieuzeidei), was recorded, maybe due to the conservative restrictions applied in species selection.

The impact of climate change on the global coastal low-level wind jets: EC-EARTH simulations

Coastal low-level jets (CLLJ) are low tropospheric coast-parallel wind features, confined to the marine atmospheric boundary layer, which lay on the east flank of the semi-permanent sub-tropical high-pressure systems, in the mid-latitudes, along equator-ward eastern boundary currents. Coastal jets are of utmost relevance to the regional climate, through their impact on the along coast sea surface temperature, driving the upwelling of cold deep nutrient-rich waters, and by having a decisive impact on the aridity of the mid-latitude western coastal areas. Here the impact of a warmer climate in the CLLJ climate is investigated, through a 2-member ensemble of EC-Earth CMIP5 simulations of future climate, following the RCP8.5 greenhouse gases emissions scenario. Besides the projected changes of the CLLJ, towards the end of the 21st century, the future characteristics of the coastal jets are also presented. No common feature of projected changes in the seven identified CLLJ areas was identified. The Iberian Peninsula and the Oman coastal jets are the ones that presented the highest differences, compared to present climate: highest projected increases in frequency of occurrence, as well as highest projected increases in jet strength (wind speed at the jet height) and jet height. This study presents a step forward towards a larger ensemble of CLLJ projections, required to better assess robustness and uncertainty of potential future climate change.

Trends in mesospheric ice layers in the Northern Hemisphere during 1961–2013

AbstractThe MIMAS ice model is used to study the trend behavior of polar mesospheric clouds (PMCs) responding to long‐term changes in mesospheric temperatures at northern high latitudes for the summer period 1961–2013. This paper presents long‐term PMC variations in terms of ice water content (IWC) at northern high latitudes for monthly July averages that are compared to solar backscatter ultraviolet (SBUV) data available in the period 1979–2013. In general, good agreement is found between long‐term PMC variations from the model and from satellite observations. For example, both model and SBUV data show an increase in ice water content (IWC &gt; 40 g km−2) in the latitude band 74°–82°N with significant IWC trends of 2.8 ± 2.1 g km−2/dec and 2.4 ± 2.0 g km−2/dec, respectively. Modeled trends in IWC are latitudinally dependent. For the entire period 1961–2013 no trend exists at midlatitudes (50°–60°N) but increases poleward to highly significant values of 4.4 ± 0.9 g km−2/dec in the latitude band 74°–82°N. The analysis of trends in extreme PMC events (IWC &gt; 300 g km−2) shows a 23%/dec increase in occurrence frequency at 74°–82°N which is by far the largest trend of all PMC parameters. We discuss the statistical properties of PMC following an exponential distribution. We derive an analytic solution of ice growth from microphysics that allows calculation of ice particle radius as a function of background conditions. As a result, the thermal conditions near 83 km height, with a cooling of −0.58 ± 0.32 K/dec, mainly determine trends in IWC whereas cooling at lower heights, induced by stratospheric ozone, controls to a large extent the long‐term behavior of PMC altitudes.

자연재해로 인한 조경수목 피해 판례 및 제도분석 연구

With the increase in occurrence frequency and severity of natural disasters due to climate changes arising from global warming, damage in the landscaping field is rising. This leads to legal disputes, and is increasing social and economic damage, too. Especially even though landscape trees which are highly affected by external environments, suffer lots of damage from natural disasters, there is no specific scope of disaster criteria and thus it brings plenty of problems of damage restoration and compensation. Therefore, this study aims to suggest that gives ways to improve related criteria for damage of landscape trees from natural disasters. For this objective, this study analyzed damage cases of landscape trees and precedents, and compared Korean and Japanese legal systems and criteria regarding natural disasters with each other. The analysis result showed that opinions of experts have a great deal of influence on judgment results, since there is no definite legal basis on damage from natural disasters in the landscaping field. This implies the need for a professional and objective appraisal process. According to the comparative analysis of Korean and Japanese legal systems and criteria regarding natural disasters, Korea lacked in laws and criteria on natural disasters of landscape plants in Korea, whereas there were concrete disaster assessment standards of landscape trees in Japan. For improving natural disaster-related systems and criteria in the landscaping field, therefore, this study presented `Revision of related laws`, `Revision of appraisal and loss assessment criteria`, `Revision of standard specification of landscaping project`, `Compulsory insuring against disasters`, `Reasonable fulfillment of contract`, and `Compulsory cost estimation for disaster restoration`, as improvement plans.

More frequent occurrence of westerly disturbances in Karakoram up to 2100

The globally averaged mass balance of glaciers and ice caps is negative, but an anomalous gain of mass has been suggested for the Karakoram glaciers of the western Himalaya. Changes in the winter synoptic patterns can influence the amount and seasonality of Himalayan snowfall and consequently influence the mass balance of regional glaciers. We use a clustering method to analyse the sea level pressure patterns which most influence Karakorum snow fall and determine if the frequency of these synoptic patterns changes in future scenarios. A regional climate model is used to assess changes in severity and frequency of snowfall events. A number of weather patterns influence winter precipitation over the western Himalaya, including westerly disturbances, and indicate an increase in frequency of occurrence up to 2100. Thus, the Karakorum glaciers may continue to grow, or decline at a slower rate, compared with those across the rest of the Himalayas.

Phenomenological Description of Tropical Clouds Using CloudSat Cloud Classification

Abstract Two years of tropical oceanic cloud observations are analyzed using the operational CloudSat cloud classification product and Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) lidar. Relationships are examined between cloud types, sea surface temperature (SST), and location during the CloudSat early morning and afternoon overpasses. Based on CloudSat and combined lidar–radar products, the maximum and minimum cloud fractions occur at SSTs near 303 and 299 K, respectively, corresponding to deep convective/detrained cloud populations and the transition from shallow to deep convection. For SSTs below approximately 301 K, low clouds (stratiform and stratocumulus) are dominant (cloud fraction between 0.15 and 0.37) whereas high clouds are dominant for SSTs greater than about 301 K (cloud fraction between 0.18 and 0.28). Consistent with previous studies, most tropical low clouds are associated with lower SSTs, with a strong inverse linear relationship between low cloud frequency and SST. For all cloud types except nimbostratus, stratus, and stratocumulus, a sharp increase in frequency of occurrence is observed for SSTs between 299 and 300.5 K, deduced as the onset of deeper convection. Peak fractions of high, deep convective, altostratus, and altocumulus clouds occur at SSTs close to 303 K, while cumulus clouds, which have lower tops, show a smooth cloud fractional peak about 2° cooler. Deep convective and other high cloud types decrease sharply above SSTs of 303 K, in accordance with previous work suggesting a narrow window of tropical deep convection. Finally, significant cloud frequency differences exist between CloudSat early morning and afternoon overpasses, suggesting a diurnal cycle of some cloud types, particularly stratocumulus, high, and deep convective clouds.

Frequency of occurrence of a set of water-related bird species in an archipelago of remnant marshlands of Central Italy

In an archipelago of marshland fragments in Central Tyrrhenian Italy, we calculated the frequency of occurrence (i.e., the probability that an individual of a sensitive species occurs in a fragment of determined size area) of a set of water-related breeding bird species. Only one species (Cettia cetti) occurred in marshland fragments within the 0–1 size area class while all species were present in larger size classes. Acrocephalus scirpaceus is the only species that showed a significant increase in frequency of occurrence moving from 0–1 to 1–10 ha size area classes. However, our study supports the hypothesis that the frequency of occurrence of several other area-sensitive species (e.g., Tachybaptus ruficollis, Ixobrychus minutus, Gallinula chloropus, Fulica atra) increases toward larger size area classes, although these trends here are not significant. Therefore, the frequency of occurrence of these species should be a focus of further research in a wider range of marshland fragments. These results will be useful in terms of wetland management implications (e.g., selection of suitable fragments for sensitive species).

Daily Rainfall Variability over Northeastern Argentina in the La Plata River Basin

We did a brief description of the climatic behavior and after this we analyzed the temporal variation in the total number of days a year with rainfall and the number of days a year with rainfall above the 100 mm threshold at the rain gauging stations in northeastern Argentina south of the La Plata River basin. The results show an increase both in the frequency of daily rainfall, especially during the winter season, and the frequency of days with heavy rainfall starting in the early 1970s. The increase in frequency of occurrence is more significant in the case of heavy rainfall. The annual maximum rainfall was calculated for periods of 1, 3, 5, 7, and 10 consecutive days at regional rain gauging stations for the respective historical periods, and the rain intensity-duration-return period curves (IDT) were determined on a frequency analysis. The IDT curves were compared with rainfall intensity-duration data of critical storms occurring in the last decades. We noticed that the rain intensities of critical storms (mostly convective) widely exceeded the intensities given by the 100-year IDT curves, particularly for short durations. The increase in both the frequency of heavy rainfall occurrence and rain intensity from the 1970s onward shows an increase in frequency and intensity of the meso-scale convective systems in the region resulting from climatic change. These systems tend to produce rainfall of very high intensity that is spatially concentrated and which generally produces significant floods in the local rivers.

Transition from annular flow to plug/slug flow in condensation of steam in microchannels

A visualization study has been conducted to investigate the transition from annular flow to plug/slug flow in the condensation of steam in two different sets of parallel microchannels, having hydraulic diameters of 90 μm and 136 μm, respectively. The steam in the parallel microchannels was cooled on the bottom by forced convection of water and by natural convection of air from the top. It is found that the location, where the transition from annular flow to plug/slug flow takes place, depends on mass flux and cooling rate of steam. The effects of mass flux and cooling rate on the occurrence frequency of the injection flow in a single microchannel, having a hydraulic diameter of 120 μm and 128 μm, respectively, are investigated. It is found that two different shapes of injection flow occur in the smooth annular flow in microchannels: injection flow with unsteady vapor ligament occurring at low mass flux (or high cooling rate) and injection flow with steady vapor ligament occurring at high mass flux (or low cooling rate). It is also found that increase of steam mass flux, decrease of cooling rate, or decrease of the microchannel diameter tends to enhance instability of the condensate film on the wall, resulting in occurrence of the injection flow further toward the outlet with an increase in occurrence frequency.

Regulation of Hippocampal Sharp Waves by Ca2+-Dependent Slow After Hyperpolarization

In rodent hippocampal pyramidal neurons, repetitive discharges are followed by a slow afterhyperpolarization (sAHP) as a result of activation of a Ca2+-dependent K+ current. The sAHP is sensitive to activation of several G-protein coupled neurotransmitter receptors and downstream signal cascades. Modulations of the sAHP have been shown to be closely associated with synaptic plasticity, learning, and aging processes. However, it is presently unclear whether the sAHP generation is involved in hippocampal network activities. We explored this issue using an in vitro (thick-slice) model of mouse hippocampal sharp waves. Our data show that the sAHP occurs in CA3 pyramidal neurons following each sharp wave event and sAHP suppression is associated with a large increase in occurrence frequency of spontaneous sharp waves. Considering that sharp waves are important for hippocampal-cortical communication and memory processes, we postulate that the sAHP serves as an intrinsic regulatory mechanism of sharp waves and plays a significant role in hippocampus-dependent cognitive functions.

Distribution of population-based indicators across multiple taxa to assess the status of Gulf of Alaska and Bering Sea groundfish communities

Abstract Ecosystem-based approaches to fisheries management require researchers and managers to take into account effects of fishing on other components of the ecosystem, including non-commercial species. Currently, stock assessments in the Northeast Pacific are limited to the most important commercial species, little being known about the status of non-commercial species. Nevertheless, standardized bottom-trawl surveys conducted in the eastern Bering Sea (EBS) and Gulf of Alaska (GoA), although primarily designed to assess commercial species, provide valuable information on the abundance, distribution, and mean weight of numerous taxa. Using a novel statistical approach and survey data for the years 1993–2003, we examined trends in catch per unit effort (cpue), frequency of occurrence, and mean weight of individuals for each taxon. Time trends were computed as the slope of a linear regression of each indicator on year, and were summarized separately for the eastern and western GoA and for the EBS. Within each system, trends were further compared between commercial and non-commercial taxa. Simulations were used to obtain reference distributions for the expected distribution of slopes across many dependent populations. Observed distributions of trends were compared with simulated distributions, suggesting that more taxa than expected showed a decreasing trend in cpue in the EBS, but not in the GoA. These trends likely resulted from low groundfish productivity in the EBS during the 1990s. At the same time, the frequency of occurrence of significantly more taxa than expected increased in the EBS and, to a lesser extent, in the western GoA. Increases in frequency of occurrence were much more common among non-commercial, invertebrate taxa, and may be a response to reductions in trawl fishing effort during the 1990s.

Trends in near-surface ozone concentrations in Switzerland: the 1990s

A time series analysis of ozone monitoring data from several locations in Switzerland from 1991 to 1999 is presented. Different methods are used to address changes in the ozone level during these years and to account for the influence of changing meteorological conditions. The results show a slight decrease of the peaks but a highly significant increase of the mean value of around 0.5–0.9 ppb yr −1. The frequency distribution has changed in the sense that very low values have become less frequent and that there is a strong increase in frequency of occurrence of half-hourly mean values between about 45 and 55 ppb. A selection procedure reveals slight tendencies towards different trends of afternoon ozone peaks in summer depending on weather and pollution situations. Ozone peaks tend to decrease on fair weather days at rural sites (but increase at urban sites) and show a small increase on cloudy and windy days. A non-linear regression model is used to estimate trends of summertime afternoon ozone peaks in the presence of meteorological variability. In the model, the long-term signal is additively split into a linear part and a part which is modulated by global radiation. The coefficients for both terms are statistically significant at many sites, with an increasing linear trend at the sites north of the Alps of around 1 ppb yr −1 and a decrease of ozone peaks under fair weather conditions relative to cloudy conditions. When additionally considering the effect of precursor concentrations in the regression models, both trends are weakened, which means that they can partly be explained by changes in local to regional emissions. However, at the sites north of the Alps remains a tendency towards a positive linear “base trend” of around 0.4 ppb yr −1. This could possibly be due to increasing background ozone concentrations.

Medio-lateral balance adjustments preceding reflexive limb withdrawal are modified by postural demands

We have recently observed medio-lateral balance adjustments (BA) preceding reflexive stepping elicited by noxious stimulation. While task specific modulation is evident for BA prior to voluntary leg movement, it is unclear whether rapid BA reactions (prior to ‘reflexive’ stepping) represent a generic response to evoked limb withdrawal or can be modified to suit task-conditions. This study was designed to establish whether the CNS is able to modify rapid onset latency BAs to match task conditions. Reflexive stepping was evoked by applying a noxious stimulus (50 ms stimulus train, 1 ms pulses, 300 Hz, 4×perceptual threshold) to the plantar surface of the either the left or right foot. Task conditions were varied prior to stimulation by having subjects maintain one of three different static positions: (1) lean left (70% body weight (BW) on left), (2) neutral (50% BW both sides), (3) lean right (70% BW on right). BAs were denoted by centre-of-pressure (CoP) excursions towards the swing foot after the onset of noxious stimulation (average onset latency of 128 ms). There was a significant increase in frequency of occurrence and a significant increase in magnitude of CoP shift when the stimulation was applied to a loaded limb (leaning with 70% BW on the stimulated foot) as compared to an unloaded limb (30%BW). In addition, 78% of loaded trials featured steps taken with the unstimulated foot, which delayed removal of the stimulated foot. Collectively, the results indicate modifiability of the very rapid onset balance adjustments that precede the onset of limb withdrawal revealing complex control of balance exists even over very brief latencies.