Does the absence of cointegration explain the typical findings in long horizon regressions?

One of the stylized facts in financial and international economics is that of increasing predictability of variables such as exchange rates and stock returns at longer horizons. This fact is based upon applications of long horizon regressions, from which the typical findings are that the point estimates of the regression parameter, the associated t-statistic, and the regression R^2 all tend to increase as the horizon increases. Such long horizon regression analyses implicitly assume the existence of cointegration between the variables involved. In this paper, we investigate the consequences of dropping this assumption. In particular, we look upon the long horizon regression as a conditional error-correction model and interpret the test for long horizon predictability as a single equation test for cointegration. We derive the asymptotic distributions of the estimator of the regression parameter and its t-statistic for arbitrary horizons, under the null hypothesis of no cointegration. It is shown that these distributions provide an alternative explanation for at least part of the typical findings. Furthermore, the distributions are used to derive a Phillips-Perron type correction to the ordinary least-squares t-statistic in order to endow it with a stable size for given, arbitrary, horizon. A local asymptotic power analysis reveals that the power of long horizon regression tests does not increase with the horizon. Exchange rate data are used to demonstrate the empirical relevance of our theoretical results

Does the absence of cointegration explain the typical findings in long horizon regressions?

One of the stylized facts in financial and international economics is that of increasing predictability of variables such as exchangerates and stock returns at longer horizons.This fact is based upon applications of long horizon regressions, from which the typical findings are that the point estimates of the regression parameter, the associated t-statistic, and the regression R^2 all tend to increaseas the horizon increases. Such long horizon regression analyses implicitly assume the existence of cointegration between the variables involved. In this paper, we investigate the consequences of dropping this assumption.In particular, we look upon the long horizon regression as a conditional error-correction model and interpret the test for long horizon predictability as a single equation test for cointegration. We derive the asymptotic distributions of the estimator of the regression parameter and its t-statistic for arbitrary horizons, under the null hypothesis of nocointegration. It is shown that these distributions provide an alternativeexplanation for at least part of the typical findings. Furthermore, the distributions are used to derive a Phillips-Perron type correction to theordinary least-squares t-statistic in order to endow it with a stable size for given, arbitrary, horizon. A local asymptotic power analysis reveals that the power of long horizon regression tests does not increase with the horizon. Exchange rate data are used to demonstratethe empirical relevance of our theoretical results.long horizon regression;regression R^2;t-statistic

Early Holocene Establishment of the Barents Sea Arctic Front

A main feature of the Barents Sea oceanography is the Arctic front. The Arctic front marks the transition between the dominating water masses of the Barents Sea: Atlantic Water in the south and Arctic Water in the north. Presently, the Barents Sea Arctic front is directed by the topography of the Bear Island Trough and to some degree the location of the sea ice boundary. During the last glacial maximum, the Svalbard-Barents Sea and Scandinavian Ice Sheets covered the Barents Sea. Hence, no water entered the Barents Sea, neither from the south nor from the north. Following the deglaciation of the Barents Sea, the present-day ocean circulation developed. The evolution of how the present location of the Barents Sea Arctic front established during the early Holocene is documented by foraminiferal relative assemblage data from six core sites along the western Barents Sea margin and opening. The relative abundance of Arctic front indicator Turborotalita quinqueloba, in combination with the cold, polar Neogloboquadrina pachyderma and warm, Atlantic Neogloboquadrina incompta, are used to infer the location of the Barents Sea Arctic front relative to the individual core sites. Until ca. 11 ka BP, the Barents Sea Arctic front followed the western margin of the Barents Sea. All sites along the Barents Sea margin where still dominated by Arctic Water between ca. 11 and 10.2 ka BP, however, the Barents Sea Arctic front turned eastwards into the southwestern Barents Sea. From ca. 10.2 to 8.8 ka BP, the Barents Sea Arctic front moved eastward and was located right above most sites as it followed the Barents Sea margin. The northwestern Barents Sea Arctic front was close to the present location from ca. 8.8 to 7.4 ka BP, however, it was still confined to the southwestern Barents Sea. From ca. 7.4 ka BP, the Barents Sea Arctic front has been located close to the present position, along the margin southwards from Svalbard, turning eastwards along and beyond the northern Bear Island Trough margin

Insolation and gacial meltwater influence on sea‐ice and circulation variability in the Northeastern Labrador Sea during the last glacial period

The variable amounts of ice rafted debris (IRD) and foraminifers in North Atlantic sediments are related to the abrupt, millennial-scale alteration from Greenland stadials to interstadials during the last glacial period and indicate past ice sheet instabilities, changes in sea-ice cover and productivity. In the Norwegian Sea, Greenland stadials were likely characterized by an extensive, near-perennial sea-ice cover whereas Greenland interstadials were seasonally ice-free. The variability in other areas, such as the Labrador Sea, remains, however, obscure. We therefore investigated deep-sea sediment core GS16-204-22CC retrieved south of Greenland. Using a multiproxy approach, we distinguish two sediment regimes and hence different environmental conditions between ca. 65 and 25 ka b2k. Regime 1 (similar to 65-49 ka b2k) is characterized by the dominance of planktic foraminifers in the sediments. During late MIS4 and early MIS3, the site was covered by near-perennial sea-ice with occasional periods of iceberg discharge. During the younger part of regime 1 the northeastern Labrador Sea was seasonally ice-free with hardly any icebergs melting near the site and long-term environmental conditions were less variable. Regime 2 (similar to 49-25 ka b2k) is characterized by pronounced stadial-interstadial variability of foraminifer and IRD fluxes, suggesting an extensive sea-ice cover during most Greenland stadials and seasonally ice-free conditions during most Greenland interstadials. During MIS2 environmental conditions were very similar to those of the younger part of regime 1. While all Heinrich (H) related Greenland stadials are marked by depleted oxygen isotope values at our core site, only H4 and H3 are associated with pronounced IRD peaks. Plain Language Summary North Atlantic sediments contain variable amounts of sand-sized mineral grains and microorganism shells. Mineral grains indicate iceberg transport from continental ice sheets, like the Greenland ice sheet (more icebergs/melting sea-ice, more grains). If the sea-ice cover is too thick, no light can penetrate and fewer microorganisms live in the water beneath the ice. Using these indicators, we investigated ocean sediments from south of Greenland covering the time period between ca. 65 and 25 thousand years ago. This time period was characterized by several abrupt changes between cold and warm climates on millennial timescales. We find that the ocean south of Greenland was sea-ice covered for most of the year with occasional time periods of iceberg discharge between 65 to 56 thousand years ago. From 56 to 49 thousand years ago the ice-free season was extended and hardly any icebergs melted near the site. From 49 thousand years ago our study area was covered by sea-ice year-round during cold time intervals whereas warm time intervals were only seasonally sea-ice covered. Continental ice sheets were growing during this time interval and we observed two major calving events related to two of the four very cold climate intervals recorded in the analyzed sediment.Fundacao de a Ciencia e a Tecnologia IF/01500/2014 UID/Multi/04326/2019info:eu-repo/semantics/publishedVersio

The characteristics and pre-hospital management of blunt trauma patients with suspected spinal column injuries:a retrospective observational study

Background Pre-hospital spinal immobilisation by emergency medical services (EMS) staff is currently the standard of care in cases of suspected spinal column injuries. There is, however, a lack of data on the characteristics of patients who received spinal immobilisation during the pre-hospital phase and on the adverse effects of immobilisation. The objectives of this study were threefold. First, we determined the pre-hospital characteristics of blunt trauma patients with suspected spinal column injuries who were immobilised by EMS staff. Second, we assessed the choices made by EMS staff regarding spinal immobilisation techniques and reasons for immobilisation. Third, we researched the possible adverse effects of immobilisation. Design A retrospective observational study in a cohort of blunt trauma patients. Study method Data of blunt trauma patients with suspected spinal column injuries were collected from one EMS organisation between January 2008 and January 2013. Coded data and free text notes were analysed. Results A total of 1082 patients were included in this study. Spinal immobilisation was applied in 96.3 % of the patients based on valid pre-hospital criteria. In 2.1 % of the patients immobilisation was not based on valid criteria. Data of 1.6 % patients were missing. Main reasons for spinal immobilisation were posterior midline spinal tenderness (37.2 % of patients) and painful distracting injuries (13.5 % of patients). Spinal cord injury (SCI) was suspected in 5.7 % of the patients with posterior midline spinal tenderness. A total of 15.8 % patients were immobilised using non-standard methods. The reason for departure from the standard method was explained for 3 % of these patients. Reported adverse effects included pain (n = 10, 0.9 %,); shortness of breath (n = 3, 0.3 %); combativeness or anxiety (n = 6, 0.6 %); and worsening of pain when supine (n = 1, 0.1 %). Conclusion/recommendation Spinal immobilisation was applied in 96.3 % of all included patients based on pre-hospital criteria. We found that consensus among EMS staff on how to interpret the criterion 'distracting injury' was lacking. Furthermore, the adverse effects of spinal immobilisation were incompletely documented in pre-hospital care reports. To provide validated information on potential symptoms of SCI, a uniform EMS scoring system for motoric assessment should be developed

A first chronology for the East Greenland Ice-core Project (EGRIP) over the Holocene and last glacial termination

This paper provides the first chronology for the deep ice core from the East Greenland Ice-core Project (EGRIP) over the Holocene and the late last glacial period. We rely mainly on volcanic events and common peak patterns recorded by dielectric profiling (DEP) and electrical conductivity measurement (ECM) for the synchronization between the EGRIP, North Greenland Eemian Ice Drilling (NEEM) and North Greenland Ice Core Project (NGRIP) ice cores in Greenland. We transfer the annual-layer-counted Greenland Ice Core Chronology 2005 (GICC05) from the NGRIP core to the EGRIP ice core by means of 381 match points, typically spaced less than 50 years apart. The NEEM ice core has previously been dated in a similar way and is only included to support the match-point identification. We name our EGRIP timescale GICC05-EGRIP-1. Over the uppermost 1383.84 m, we establish a depth–age relationship dating back to 14 967 years b2k (years before the year 2000 CE). Tephra horizons provide an independent validation of our match points. In addition, we compare the ratio of the annual layer thickness between ice cores in between the match points to assess our results in view of the different ice-flow patterns and accumulation regimes of the different periods and geographical regions. For the next years, this initial timescale will be the basis for climatic reconstructions from EGRIP high-resolution proxy data sets, e.g. stable water isotopes, chemical impurity or dust records

Evidence for Strong Electron Correlations in a Nonsymmorphic Dirac Semimetal

Metallic iridium oxides (iridates) provide a fertile playground to explore new phenomena resulting from the interplay between topological protection, spin-orbit and electron-electron interactions. To date, however, few studies of the low energy electronic excitations exist due to the difficulty in synthesising crystals with sufficiently large carrier mean-free-paths. Here, we report the observation of Shubnikov-de Haas quantum oscillations in high-quality single crystals of monoclinic SrIrO3 in magnetic fields up to 35 T. Analysis of the oscillations reveals a Fermi surface comprising multiple small pockets with effective masses up to 4.5 times larger than the calculated band mass. Ab-initio calculations reveal robust linear band-crossings at the Brillouin zone boundary, due to its non-symmorphic symmetry, and overall we find good agreement between the angular dependence of the oscillations and the theoretical expectations. Further evidence of strong electron correlations is realized through the observation of signatures of non-Fermi liquid transport as well as a large Kadowaki-Woods ratio. These collective findings, coupled with knowledge of the evolution of the electronic state across the Ruddlesden-Popper iridate series, establishes monoclinic SrIrO3 as a topological semimetal on the boundary of the Mott metal-insulator transition. © 2021, The Author(s).We gratefully acknowledge useful discussions with A. Rost and D. F. McMorrow. We would also like to thank G. Stenning and D. Nye for help with the instruments in the Materials Characterisation Laboratory at the ISIS Neutron and Muon Source, Kuang-Yu Samuel Chang and Roos Leenen for technical assistance with the DFT calculations, and Sebastian Bette for XRD characterizations. We acknowledge the support of the HFML-Radboud University (RU)/Netherlands Organisation for Scientific Research (NWO), a member of the European Magnetic Field Laboratory. This work is part of the research program Strange Metals (Grant 16METL01) of the former Foundation for Fundamental Research on Matter, which is financially supported by the NWO and the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant Agreement No. 835279-Catch-22). We gratefully acknowledge support from the UK Engineering and Physical Sciences research council, grant EP/N034694/1. We acknowledge collaborative support from A.S. Gibbs, D. Fortes and the ISIS Crystallography Group for making available the 193Ir for the isotope work. Experiments at the ISIS Neutron and Muon Source were supported by a beamtime allocation RB1990395, DOI:10.5286/ISIS.E.RB1990395, from the Science and Technology Facilities Council. The work of D. P. and V. M. was supported by Act 211 Government of the Russian Federation, contract 02.A03.21.0006

Multilevel factors are associated with immunosuppressant nonadherence in heart transplant recipients: The international BRIGHT study

Factors at the level of family/healthcare worker, organization, and system are neglected in medication nonadherence research in heart transplantation (HTx). The 4-continent, 11-country cross-sectional Building Research Initiative Group: Chronic Illness Management and Adherence in Transplantation (BRIGHT) study used multistaged sampling to examine 36 HTx centers, including 36 HTx directors, 100 clinicians, and 1397 patients. Nonadherence to immunosuppressants\u2014defined as any deviation in taking or timing adherence and/or dose reduction\u2014was assessed using the Basel Assessment of Adherence to Immunosuppressive Medications Scale \ua9 (BAASIS \ua9 ) interview. Guided by the Integrative Model of Behavioral Prediction and Bronfenbrenner's ecological model, we analyzed factors at these multiple levels using sequential logistic regression analysis (6 blocks). The nonadherence prevalence was 34.1%. Six multilevel factors were associated independently (either positively or negatively) with nonadherence: patient level: barriers to taking immunosuppressants (odds ratio [OR]: 11.48); smoking (OR: 2.19); family/healthcare provider level: frequency of having someone to help patients read health-related materials (OR: 0.85); organization level: clinicians reporting nonadherent patients were targeted with adherence interventions (OR: 0.66); pickup of medications at physician's office (OR: 2.31); and policy level: monthly out-of-pocket costs for medication (OR: 1.16). Factors associated with nonadherence are evident at multiple levels. Improving medication nonadherence requires addressing not only the patient, but also family/healthcare provider, organization, and policy levels