Combination Of Proxies Research Articles

The effect of mixing EUV proxies on the correlation with foF2 and on long-term trends estimations

Solar proxies are a valuable tool used in most atmospheric models to simulate or predict the state and variation of the different layers linked to the solar source. In this work, we analyze the performance, through correlation analysis, of six solar EUV proxies, and different combination of them, to reproduce annual ionospheric F2 critical frequency (foF2) from ten different stations. We find that certain combinations of traditional proxies outperform the capacity to reproduce interannual ionospheric foF2 variability, resulting in better statistical correlation and time stability, these new proxies could be a valuable tool to predict the state of the atmosphere and for interpolation in case of missing data. Different combinations of proxies such as F30, MgII, Sn or Lya, creates better indicators than using them alone. These new EUV proxies are also used to estimate long-term trends along the ten stations. As we increase the correlation, the estimated trend decrease as expected by definition. However, a key point is that the average trends, after filtering solar activity, result negative as was predicted by the increase of the greenhouse gases.

Palaeoecological reconstruction of Plio-Pleistocene herbivores from the Ahl al Oughlam site (Casablanca, Morocco): Insights from dental wear and stable isotopes

In this article, we use a multiproxy approach based on stable isotope analyses (δ18O and δ13C), mesowear, and microwear dental analysis to reconstruct the climate, diet, and habitat of Plio-Pleistocene herbivores at the site of Ahl al Oughlam in western Morocco. This study has been conducted on teeth from several taxa (Sivatherium maurusium, Hipparion pomeli, Metridiochoerus phacochoeroides, Gazella sp., Alcelaphini and Anancus osiris), enabling a robust ecological reconstruction. Our isotopic results suggest a predominance of C3 plant consumption for all analyzed species, while dental wear indicates a varied diet, with evidence for both browsing and grazing behavior being present. The combination of proxies indicates a landscape dominated by open C3 grasslands in an arid climate, as supported by the Mean Annual Precipitation (MAP) results. These findings contribute to the ongoing debate on the ecological context that facilitated the Plio-Pleistocene dispersal, occupation, and evolution of mammals and hominins in northern Africa, for which limited information is available.

Impact of Proxies and Prior Estimates on Data Assimilation Using Isotope Ratios for the Climate Reconstruction of the Last Millennium

AbstractClimate reconstructions by data assimilation need to accommodate for sensitivities to proxies and prior estimates because models are uncertain and proxies are spatiotemporally limited. This study examines these sensitivities using multiple climate model simulations and different combinations of proxies (i.e., corals, ice cores, and tree‐ring cellulose). Experiments were conducted using an offline data assimilation approach; the results showed annual variations in the global distribution of surface air temperature and precipitation amount from 850 to 2000. Standard deviations of surface air temperature and precipitation amount during the entire period differed by up to 36% due to prior estimates. Experiments with different types of proxies showed that the El Niño‐like distribution of positive anomalies in the central to eastern tropical Pacific may only be adequately reproduced in experiments with corals, and not experiments without corals. The correlation coefficient of the NINO.3 index from 1971 to 2000 between experiments with corals and the Japanese 55‐year Reanalysis (JRA‐55) was 0.81 at maximum. By contrast, the correlation coefficient between experiments without corals and JRA‐55 was a maximum of 0.19.

A 5000‐year paleoclimate record from Nettilling Lake (Baffin Island) based on diatom assemblages and oxygen isotope composition

ABSTRACTSedimentary diatoms have been used to quantitatively reconstruct climate‐related variables, such as temperature at different timescales. Even though temperature is often less of a key driver of diatom ecology than other environmental parameters (water chemistry), diatom inference models have been shown to be reliable in deducing past temperature trends. In addition, the oxygen isotope composition (δ18Odiatom) preserved in buried diatom frustules has demonstrated its potential to reflect climatic and hydrological conditions at the time of frustule formation. This study combines results from both diatom‐based climate proxies to reconstruct summer water and mean annual air temperatures, and hydrological trends in Nettilling Lake, Baffin Island, from ca. 5000 to 500 cal a bp. Diatom‐inferred temperatures revealed an overall ca. 2 °C cooling throughout the Late‐Holocene. The δ18Odiatom values showed an increasing trend up to ca. 1900 cal a bp, where they reached their highest values (+24.8‰ at 15 cm) and thereafter decreased to their lowest values (+21.4‰ at 4 cm). These trends were linked to meltwater inflows associated with Penny Ice Cap thaw rate that was in turn controlled by regional climatic conditions which went from intensified cooling during the Neoglacial period to slight warming thereafter. Our results suggest that diatom‐ and diatom‐isotope‐based temperature and hydrological reconstructions can identify trends related to the natural climate system variability. The diatom oxygen isotopes are useful for paleoenvironmental studies of terrestrial aquatic ecosystems, but not for all hydrological systems are the ideal temperature proxy. Hence, the combination of proxies helps to disentangle temperature and hydrological effects for paleoclimatic reconstructions and may support future studies of postglacial environmental change in northern lakes.

"Fitness and Fatness" in Children and Adolescents: An Italian Cross-Sectional Study.

Children with obesity tend to have lower level of physical activity compared to non-obese peers. In fact, sedentary behaviors are prevalent in obese children causing difficulties to perform motor tasks and engaging in sport activities. This, in turn, has direct repercussions on adiposity and related comorbidities. The aim of the study was to investigate several components of fitness and their relationship with the degree of fatness in children. We considered 485 Italian schoolchildren (9.5 ± 1.12 years). BMI and prediction modelling outputs of fat mass were employed as markers of body fatness. Physical fitness (PF) was assessed by the 9-item test battery (explosive power, leg muscle power, arm muscle power, upper body power, coordination, agility, speed and endurance). Differences between groups in the PF tests (p < 0.05) were noted. A similar pattern was reflected in both genders. The relationship between anthropometrics’ characteristics and PF tests showed that weight and fat mass had a high level of correlation with different PF tests. Our findings highlight the importance of investigating the degree of fatness in relation with different components of fitness, in children and adolescents. This combination of proxies may cover an unexpectedly helpful screening of the youth population, for both health and performance.

Verbal intelligence is a more robust cross-sectional measure of cognitive reserve than level of education in healthy older adults

BackgroundCognitive reserve is most commonly measured using socio-behavioural proxy variables. These variables are easy to collect, have a straightforward interpretation, and are widely associated with reduced risk of dementia and cognitive decline in epidemiological studies. However, the specific proxies vary across studies and have rarely been assessed in complete models of cognitive reserve (i.e. alongside both a measure of cognitive outcome and a measure of brain structure). Complete models can test independent associations between proxies and cognitive function in addition to the moderation effect of proxies on the brain-cognition relationship. Consequently, there is insufficient empirical evidence guiding the choice of proxy measures of cognitive reserve and poor comparability across studies.MethodIn a cross-sectional study, we assessed the validity of 5 common proxies (education, occupational complexity, verbal intelligence, leisure activities, and exercise) and all possible combinations of these proxies in 2 separate community-dwelling older adult cohorts: The Irish Longitudinal Study on Ageing (TILDA; N = 313, mean age = 68.9 years, range = 54–88) and the Cognitive Reserve/Reference Ability Neural Network Study (CR/RANN; N = 234, mean age = 64.49 years, range = 50–80). Fifteen models were created with 3 brain structure variables (grey matter volume, hippocampal volume, and mean cortical thickness) and 5 cognitive variables (verbal fluency, processing speed, executive function, episodic memory, and global cognition).ResultsNo moderation effects were observed. There were robust positive associations with cognitive function, independent of brain structure, for 2 individual proxies (verbal intelligence and education) and 16 composites (i.e. combinations of proxies). Verbal intelligence was statistically significant in all models. Education was significant only in models with executive function as the cognitive outcome variable. Three robust composites were observed in more than two-thirds of brain-cognition models: the composites of (1) occupational complexity and verbal intelligence, (2) education and verbal intelligence, and (3) education, occupational complexity, and verbal intelligence. However, no composite had larger average effects nor was more robust than verbal intelligence alone.ConclusionThese results support the use of verbal intelligence as a proxy measure of CR in cross-sectional studies of cognitively healthy older adults.

Constructing a banking fragility index for Islamic banks: definition impact on the predictive power of an early warning system

ABSTRACT This study aims to construct a banking sector fragility index for Islamic banks that gives substantial predictive power results. We develop various banking sector fragility indices using different combinations of proxies for credit, liquidity and market risk factors. Apart from the existing literature, we add profitability risk factor into fragility indices. Our results show that the predictive power of an Early Warning System (EWS) is highly sensitive to the proxies and combinations of the risk factors and, profitability risk has a positive impact on the predictive power results for Islamic banks.

A strontium isotope baseline of Cyprus. Assessing the use of soil leachates, plants, groundwater and surface water as proxies for the local range of bioavailable strontium isotope composition

In this study, a strontium isotope baseline for Cyprus is presented. The aim of the study was two-fold; first to provide an environmental multi-proxy-based baseline (water/plants/soil leachates) suitable for archaeological provenance and mobility studies, food source authentication, and forensic investigations; and second, to contribute to the debate around which proxy (or combination of proxies) might be most suitable to define bioavailable fractions of strontium in geologically complex areas also exposed to sea-spray and other Sr-bearing aerosols. Lowest bioavailable strontium isotope signatures range is found within terranes dominated by ophiolites, where 87Sr/86Sr ratios range from 0.7055 to 0.7081, however, results reveal a high degree of variability in bioavailable 87Sr/86Sr ratios, both spatially, along depth profiles and amongst the different proxies. A narrower range of bioavailable Sr isotope signatures is observed within the Circum Troodos Sedimentary Successions (C.T.S.S.), both in spatial distribution and between different proxies. Observed range is 87Sr/86Sr = 0.7079 to 0.7089 in areas dominated by pre-Quaternary C.T.S.S., and 87Sr/86Sr ratios = 0.7076 to 0.7086 in areas covered by Quaternary C.T.S.S., revealing the lithologies to be very homogenous with respect to bioavailable strontium ratios. Intra-site variations in three archaeological sites (multiple samples from each site from within a 500 m radius) within the pre-Quaternary and Quaternary C.T.S.S. are smaller than inter-site variations, suggesting that tracing studies inferred from baselines sampled within a limited spatial area could lead to erroneous conclusions regarding provenance. The study points to the necessity for conducting multi-proxy, spatially extensive sampling to adequately characterize complex geological areas, if these should serve as reliable reference areas in provenance studies.

DETERMINANTS OF THE PERFORMANCE OF MICROFINANCE INSTITUTIONS: A SYSTEMATIC REVIEW

AbstractMicrofinance institutions (MFIs) generally aim at improving the access of the poor to financial services while at the same time being financially sustainable. But what do we know about how MFIs reach and combine these two goals? We carry out a systematic review of close to 170 papers discussing the determinants of the financial and social performance of MFIs. The review shows that the most important determinants addressed in the literature are MFI characteristics (size, age and type of organization), their funding sources, the quality of organizational governance and the MFIs’ external context such as macro‐economic, institutional and political conditions. The evidence on these issues is rather mixed. Moreover, the direction of the relationship between these drivers and MFI performance depends on the context, particularly the country‐specific context. Finally, there is a lack of consensus in the literature on the measurement of financial and social performance. Due to the complexity of the concept, we argue that social performance should only be assessed by using a multidimensional perspective. This can be done either by applying recent and holistic social performance measures such as the SPI4, or at least by using a combination of proxies, such as outreach, gender and rural measures.

Investor Sentiment and Bond Risk Premia: Evidence from China

ABSTRACTThis article shows the statistical significance of a set of variables related to market sentiment and uses them to predict the risk premium embedded in China’s sovereign bonds. We construct a composite index of market-wide investor sentiment as a linear combination of proxies for a degree of market participation and risk appetite of investors. Further, we show that these sentiment-related factors can be summarized in a single-return forecasting factor, similar in a spirit of Cochrane and Piazzesi (2005). Our empirical results show that this sentiment factor has predictive power beyond that contained in the yield curve and macroeconomic variables, and this predictability is robust for out-of-sample testing. In addition, the predictive power of the sentiment factor shows relevance during the 2008 global financial crisis, indicating that the forecasting ability of investor sentiment is mainly derived by a sentiment-induced “flight-to-quality.”

Shallow hypersaline lakes as paleoclimate archives: A case study from the Laguna Salada, Málaga province, southern Spain

Although numerous studies concerning the Holocene climate of the southern Iberian Peninsula were accomplished within the last few decades, the climate history of this region is still poorly understood. Various studies deal with a combination of proxies, which are neither easy to compare nor is their connection easy to explain, e.g., due to spatial patterns and time transgression. Within this study, the suitability of the lacustrine sediments from the Laguna Salada (Andalucía region, southern Spain) as a paleoclimate archive is investigated. The lake sediments were evaluated using a multi-proxy approach including sedimentological, mineralogical, geochemical and biological analyses. The sediments reflect the evolution of the lake from pre-Medieval times onwards and Characeae as well as Ostracod analyses give an indication of paleosalinity. Moreover does the geochemical composition provide profound information concerning changes of elemental and mineralogical composition. Nevertheless, a robust, high-resolution chronology could not be achieved owed to the scarcity of material available for radiocarbon dating and contamination problems. Furthermore, poor preservation of pollen restricted the reconstruction of vegetation history, which could have complemented important information concerning climatic changes and human activity.

An Ethnoarchaeological Study on Anthropic Markers from a Shell-midden in Tierra del Fuego (Southern Argentina): Lanashuaia II

ABSTRACTFor many years the identification of activity areas has been carried out through the spatial distribution of lithics, zooarchaeological remains and specific features such as fireplaces. However, these data are rarely combined and integrated with results from specific analytical techniques such as phytoliths, organic matter, carbonates and multielemental analysis. This research presents the first results of an intrasite spatial analysis on a layer from the site Lanashuaia II, a shell-midden located on the Beagle Channel coast (Tierra del Fuego, Argentina). Ethnoarchaeology is used as a methodological tool to give content to the concept of anthropic markers by means of formulating archaeological hypothesis on the basis of ethnological information. This paper presents the application of specific anthropic markers, which have been designed and applied to identify ashy remains and waste areas through different combinations of proxies. The results show how an approach that integrates different techniques enhances data interpretation and allows to give visibility to activities that may not leave visible evidences.

Review of dated Late Quaternary palaeolimnological records in the Carpathian Region, east-central Europe

The Carpathian Region (including mountains and plains) has for a long time been lacking good palaeoenvironmental and especially palaeolimnological records, particularly for the Late Quaternary. In the last two decades, many new sedimentary sequences were obtained and studied using a wide range of palaeoproxies. This article reviews results from 123 sequences in the Carpathian Region, all dated by radiometric methods. Our aim was to pay attention to the existence of these data; many of them published in national periodicals and journals. Palaeoenvironmental records with at least two proxies and with palaeolimnological interpretation were compiled in both tabular form and on maps. Inspite of the density of examined sites, an assessment of the dataset led us to the following conclusions: (1) very few provide firm hydrological-limnological interpretation, such as lake level and mire water-depth fluctuation, lake productivity changes and pH changes; (2) only 47 of them are real multi-proxy studies (have at least two proxies employed on the same sediment core); (3) glacial lakes in Slovakia and Romania as well as in Ukraine are seriously under-investigated although they would be ideal objects of palaeolimnological works with the many proxies applicable on them; (4) the Hungarian lowland areas are dominated by shallow tectonic lakes or palaeochannels, often with unsatisfactory preservation of certain biological proxies (e.g. diatoms, chironomids, cladocerans). Consequently, palaeolimnological studies from this region have to apply a different combination of proxies and approach than mountain lake studies.

Relative utility of foraminifera, diatoms and macrophytes as high resolution indicators of paleo-sea level in coastal British Columbia, Canada

A multiproxy analysis was carried out on diatom, foraminiferal and macrophyte assemblages across the saltmarsh at Zeballos, Vancouver Island, British Columbia. To determine which group, or combination of groups provided the most accurate elevational zonations, 36 stepwise multiple linear regressions (SMLR) were carried out using a variety of data transformations on an elevational training set. Adjusted R 2 values yielded statistically significant results in all analyses as follows: foraminifera (0.658–0.870); diatoms (0.888–0.974); macrophytes (0.671–0.844); foraminifera/diatoms (0.941–0.981); foraminifera/diatoms/macrophytes (0.958–0.993). The most realistic SMLR results were obtained when data transformations comprised of (ln) normalized fractional abundance data was carried out on species present in statistically significant numbers (NrfaEQ). Of the individual proxies assessed, diatoms yielded the most significant adjusted R 2 results, with the low marsh diatom Achnanthes hauckiana being one of the most important predictor variables (pv's). Amongst the foraminifera, the low marsh species Miliammina fusca and high marsh Balticammina pseudomacrescens were determined to be the most significant pv's. For macrophytes, the low marsh species Carex lyngbyei, the high marsh species Juncus balticus, Shannon–Wiener Diversity Index (SDI) and absence of plant cover on the tidal flat were the most important pv's. As SMLR analysis of all individual groups and combinations of groups yielded statistically significant results, the choice of proxies, or combinations of proxies that are suitable for paleo-sea level research is at the discretion of the researcher.

Short Sale Constraints, Overvaluation, and the Introduction of Options

We investigate whether the existence of traded options represents an economically important relaxation of short sale constraints. Our analysis has three prongs. First, to the extent that option listing relaxes a binding constraint, we would expect to see investors taking synthetic short positions in the newly-listed options. Contrary to this hypothesis, we find that the volume of newly-listed options tends to be very low, and, if anything, signed volume is more bullish that bearish during the first week of trading. Moreover, we find no significant relation between signed option volume and abnormal stock returns surrounding option listing. Second, if options help relax binding short-sale constraints, we might expect bearish option volume to be positively related to proxies for short sale constraints, divergence of opinion, and/or overvaluation. We examine nine different proxies and combinations of proxies, and in each case find either no relation, or a significant negative relation. Third, we demonstrate that prior results in the literature reporting a negative price reaction surrounding option listing are not robust to alternative methodological assumptions. All our evidence suggests that options do not reduce short sale constraints in an economically meaningful way.

Alkenones and multiproxy strategies in paleoceanographic studies

We assess multiproxy strategies involving alkenone‐based and other paleoceanographic indicators in an effort to define uncertainties and to advance understanding of past oceanic and climatic changes. Looking to the future, we recommend a parallel strategy of applying proxies to the geologic record while continuously seeking refinements in methods and understanding of mechanisms that control each proxy. A multiproxy strategy increases confidence in results and provides oceanographic context for more effective interpretation of processes. A combination of proxies allows derivation of additional properties, such as upper ocean paleosalinity or paleo‐pCO2, for a more complete view of the oceanographic and climate mechanisms involved in changing Earth's environment.

On the Long Run Effects of Public Capital and Disaggregated Public Capital on Aggregate Output

We study the cointegration properties of data on aggregate output, five proxies for labor, two proxies for private capital, public capital, and disaggregated public capital for the United States for 1948–1993. We find evidence of multiple cointegrating vectors; we typically find three or four cointegrating vectors depending on which combination of proxies is evaluated. When public capital is disaggregated by type there is less evidence for cointegration. Finally, innovations in public capital have long lasting effects on output, labor, and private capital, and innovations to output, labor, and private capital also have long lasting effects on public capital.