184 research outputs found
Quantifying the behavior of stock correlations under market stress
Understanding correlations in complex systems is crucial in the face of turbulence, such as the ongoing financial crisis. However, in complex systems, such as financial systems, correlations are not constant but instead vary in time. Here we address the question of quantifying state-dependent correlations in stock markets. Reliable estimates of correlations are absolutely necessary to protect a portfolio. We analyze 72 years of daily closing prices of the 30 stocks forming the Dow Jones Industrial Average (DJIA). We find the striking result that the average correlation among these stocks scales linearly with market stress reflected by normalized DJIA index returns on various time scales. Consequently, the diversification effect which should protect a portfolio melts away in times of market losses, just when it would most urgently be needed. Our empirical analysis is consistent with the interesting possibility that one could anticipate diversification breakdowns, guiding the design of protected portfolios
History of oceanic front development in the New Zealand sector of the Southern Ocean during the Cenozoic--a synthesis
The New Zealand sector of the Southern Ocean (NZSSO) has opened about the Indian-Pacific spreading ridge throughout the Cenozoic. Today the NZSSO is characterised by broad zonal belts of antarctic (cold), subantarctic (cool), and subtropical (warm) surface-water masses separated by prominent oceanic fronts: the Subtropical Front (STF) c. 43deg.S, Subantarctic Front (SAF) c. 50deg.S, and Antarctic Polar Front (AAPF) c. 60deg.S. Despite a meagre database, the broad pattern of Cenozoic evolution of these fronts is reviewed from the results of Deep Sea Drilling Project-based studies of sediment facies, microfossil assemblages and diversity, and stable isotope records, as well as from evidence in onland New Zealand Cenozoic sequences. Results are depicted schematically on seven paleogeographic maps covering the NZSSO at 10 m.y. intervals through the Cenozoic.
During the Paleocene and most of the Eocene (65-35 Ma), the entire NZSSO was under the influence of warm to cool subtropical waters, with no detectable oceanic fronts. In the latest Eocene (c. 35 Ma), a proto-STF is shown separating subantarctic and subtropical waters offshore from Antarctica, near 65deg.S paleolatitude. During the earliest Oligocene, this front was displaced northwards by development of an AAPF following major global cooling and biotic turnover associated with ice sheet expansion to sea level on East Antarctica. Early Oligocene full opening (c. 31 Ma) of the Tasmanian gateway initiated vigorous proto-circum-Antarctic flow of cold/cool waters, possibly through a West Antarctic seaway linking the southern Pacific and Atlantic Oceans, including detached northwards "jetting" onto the New Zealand plateau where condensation and unconformity development was widespread in cool-water carbonate facies. Since this time, a broad tripartite division of antarctic, subantarctic, and subtropical waters has existed in the NZSSO, including possible development of a proto-SAF within the subantarctic belt. In the Early-early Middle Miocene (25-15 Ma), warm subtropical waters expanded southwards into the northern NZSSO, possibly associated with reduced ice volume on East Antarctica but particularly with restriction of the Indonesian gateway and redirection of intensified warm surface flows southwards into the Tasman Sea, as well as complete opening of the Drake gateway by 23 Ma allowing more complete decoupling of cool circum-Antarctic flow from the subtropical waters. During the late Middle-Late Miocene (15-5 Ma), both the STF and SAF proper were established in their present relative positions across and about the Campbell Plateau, respectively, accompanying renewed ice buildup on East Antarctica and formation of a permanent ice sheet on West Antarctica, as well as generally more expansive and intensified circum-Antarctic flow.
The ultimate control on the history of oceanic front development in the NZSSO has been plate tectonics through its influence on the paleogeographic changes of the Australian-New Zealand-Antarctic continents and their intervening oceanic basins, the timing of opening and closing of critical seaways, the potential for submarine ridges and plateaus to exert some bathymetric control on the location of fronts, and the evolving ice budget on the Antarctic continent. The broad trends of the Cenozoic climate curve for New Zealand deduced from fossil evidence in the uplifted marine sedimentary record correspond well to the principal paleoceanographic events controlling the evolution and migration of the oceanic fronts in the NZSSO
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Site 502: Colombia Basin, Western Caribbean
Our specific objective at Site 502 was to recover an undisturbed, complete section that could be used as a Neogene and Quaternary reference section. A complete record such as this would allow intercorrelations between (1) paleomagnetic stratigraphy, (2) calcareous biostratigraphy, (3) cyclic accumulation of sediment, (4) paleoceanographic changes, (5) oxygen and carbon isotope stratigraphies, (6) the chronology of Central American volcanism, (7) the timing and effects of the emergence of the Isthmus of Panama, and (8) the timing and effects of the initiation of Northern Hemisphere glaciation
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Site 503: Eastern Equatorial Pacific
Our primary objective at Site 503 (Fig. 1) was to re- cover a complete, undisturbed Neogene and Quaternary section in the eastern equatorial Pacific. Site 503 is located near Site 83 in an area that contains an almost continuous pelagic record of the past 10 m.y. (Hays et al., 1972). Unfortunately, Site 83 was only spot-cored, and the recovered sediment is so badly disturbed by rotary drilling that most of the detailed record is lost. The section has an average sedimentation rate of 2.0 to 2.5 cm/k.y. with good-to-moderate preservation of all the major microfossil groups. We returned to Site 83 to core the same section, using the Hydraulic Piston Corer (HPC) to obtain an undisturbed, continuous section for high-resolution stratigraphic studies
Magnetic intensity loss and core diagenesis in long-core samples from the East Cortez Basin and the San Nicolas Basin (California Borderland)
Determinants of frontline tyrosine kinase inhibitor choice for patients with chronic-phase chronic myeloid leukemia: A study from the Registro Italiano LMC and Campus CML
BackgroundImatinib, dasatinib, and nilotinib are tyrosine kinase inhibitors (TKIs) approved in Italy for frontline treatment of chronic-phase chronic myeloid leukemia (CP-CML). The choice of TKI is based on a combined evaluation of the patient's and the disease characteristics. The aim of this study was to analyze the use of frontline TKI therapy in an unselected cohort of Italian patients with CP-CML to correlate the choice with the patient's features. MethodsA total of 1967 patients with CP-CML diagnosed between 2012 and 2019 at 36 centers throughout Italy were retrospectively evaluated; 1089 patients (55.4%) received imatinib and 878 patients (44.6%) received a second-generation (2G) TKI. ResultsSecond-generation TKIs were chosen for most patients aged <45 years (69.2%), whereas imatinib was used in 76.7% of patients aged >65 years (p < .001). There was a predominant use of imatinib in intermediate/high European long-term survival risk patients (60.0%/66.0% vs. 49.7% in low-risk patients) and a limited use of 2G-TKIs in patients with comorbidities such as hypertension, diabetes, chronic obstructive pulmonary disease, previous neoplasms, ischemic heart disease, or stroke and in those with >3 concomitant drugs. We observed a greater use of imatinib (61.1%) in patients diagnosed in 2018-2019 compared to 2012-2017 (53.2%; p = .002). In multivariable analysis, factors correlated with imatinib use were age > 65 years, spleen size, the presence of comorbidities, and & GE;3 concomitant medications. ConclusionsThis observational study of almost 2000 cases of CML shows that imatinib is the frontline drug of choice in 55% of Italian patients with CP-CML, with 2G-TKIs prevalently used in younger patients and in those with no concomitant clinical conditions. Introduction of the generic formulation in 2018 seems to have fostered imatinib use
Molecular response and quality of life in chronic myeloid leukemia patients treated with intermittent TKIs: First interim analysis of OPTkIMA study
31noBackground: Intermittent treatment with TKIs is an option for the great majority (70%–80%) of CML patients who do not achieve a stable deep molecular response and are not eligible for treatment discontinuation. For these patients, the only alternative is to assume TKI continuously, lifelong. Methods: The Italian phase III multicentric randomized OPTkIMA study started in 2015, with the aim to evaluate if a progressive de-escalation of TKIs (imatinib, nilotinib, and dasatinib) is able to maintain the molecular response (MR3.0) and to improve Health Related Quality of Life (HRQoL). Results: Up to December 2018, 166/185 (90%) elderly CML patients in stable MR3.0/MR4.0 completed the first year of any TKI intermittent schedule 1 month ON and 1 month OFF. The first year probability of maintaining the MR3.0 was 81% and 23.5% of the patients who lost the molecular response regained the MR3.0 after resuming TKI continuously. Patients’ HRQoL at baseline was better than that of matched peers from healthy population. Women was the only factor independently associated with worse baseline HRQoL (p > 0.0001). Overall, global HRQoL worsened at 6 (p < 0.001) but returned to the baseline value at 12 months and it was statistically significantly worse in women (p = 0.001). Conclusions: De-escalation of any TKI by 1 month ON/OFF schedule maintains the MR3.0/MR4.0 in 81% of the patients during the first 12–24 months. No patients progressed to accelerated/blastic phase, all the patients (23.5%) losing MR3.0 regained the MR3.0 and none suffered from TKI withdrawn syndrome. The study firstly report on HRQoL in elderly CML patients moving from a continuous daily therapy to a de-escalated intermittent treatment.openopenMalagola M.; Iurlo A.; Abruzzese E.; Bonifacio M.; Stagno F.; Binotto G.; D'Adda M.; Lunghi M.; Crugnola M.; Ferrari M.L.; Lunghi F.; Castagnetti F.; Rosti G.; Lemoli R.M.; Sancetta R.; Coppi M.R.; Corsetti M.T.; Rege Cambrin G.; Romano A.; Tiribelli M.; Russo Rossi A.; Russo S.; Aprile L.; Gandolfi L.; Farina M.; Bernardi S.; Polverelli N.; Roccaro A.M.; De Vivo A.; Baccarani M.; Russo D.Malagola, M.; Iurlo, A.; Abruzzese, E.; Bonifacio, M.; Stagno, F.; Binotto, G.; D'Adda, M.; Lunghi, M.; Crugnola, M.; Ferrari, M. L.; Lunghi, F.; Castagnetti, F.; Rosti, G.; Lemoli, R. M.; Sancetta, R.; Coppi, M. R.; Corsetti, M. T.; Rege Cambrin, G.; Romano, A.; Tiribelli, M.; Russo Rossi, A.; Russo, S.; Aprile, L.; Gandolfi, L.; Farina, M.; Bernardi, S.; Polverelli, N.; Roccaro, A. M.; De Vivo, A.; Baccarani, M.; Russo, D
Compound-specific radiocarbon dating of the varved Holocene sedimentary record of Saanich Inlet, Canada
Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 19 (2004): PA2012, doi:10.1029/2003PA000927.The radiocarbon contents of various biomarkers extracted from the varve-counted sediments of Saanich Inlet, Canada, were determined to assess their applicability for dating purposes. Calibrated ages obtained from the marine planktonic archaeal biomarker crenarchaeol compared favorably with varve-count ages. The same conclusion could be drawn for a more general archaeal biomarker (GDGT-0), although this biomarker proved to be less reliable due to its less-specific origin. The results also lend support to earlier indications that marine crenarchaeota use dissolved inorganic carbon (DIC) as their carbon source. The average reservoir age offset ΔR of 430 years, determined using the crenarchaeol radiocarbon ages, varied by ±110 years. This may be caused by natural variations in ocean-atmosphere mixing or upwelling at the NE Pacific coast but variability may also be due to an inconsistency in the marine calibration curve when used at sites with high reservoir ages.This work was supported by the Netherlands Organization
for Scientific Research (NWO) and NSF grants OCE-9907129 and
OCE-0137005 (Eglinton)
Late pleistocene sedimentation history of the Shirshov Ridge, Bering Sea
The analysis of the lithology, grain-size distribution, clay minerals, and geochemistry of Upper
Pleistocene sediments from the submarine Shirshov Ridge (Bering Sea) showed that the main source area was
the Yukon–Tanana terrane of Central Alaska. The sedimentary materials were transported by the Yukon
River through Beringia up to the shelf break, where they were entrained by a strong northwestward-flowing
sea current. The lithological data revealed several pulses of ice-rafted debris deposition, roughly synchronous
with Heinrich events, and periods of weaker bottom-current intensity. Based on the geochemical results, we
distinguished intervals of an increase in paleoproductivity and extension of the oxygen minimum zone. The
results suggest that there were three stages of deposition driven by glacioeustatic sea-level fluctuations and
glacial cycles in Alaska
What Happened to Gray Whales during the Pleistocene? The Ecological Impact of Sea-Level Change on Benthic Feeding Areas in the North Pacific Ocean
Gray whales (Eschrichtius robustus) undertake long migrations, from Baja California to Alaska, to feed on seasonally productive benthos of the Bering and Chukchi seas. The invertebrates that form their primary prey are restricted to shallow water environments, but global sea-level changes during the Pleistocene eliminated or reduced this critical habitat multiple times. Because the fossil record of gray whales is coincident with the onset of Northern Hemisphere glaciation, gray whales survived these massive changes to their feeding habitat, but it is unclear how.We reconstructed gray whale carrying capacity fluctuations during the past 120,000 years by quantifying gray whale feeding habitat availability using bathymetric data for the North Pacific Ocean, constrained by their maximum diving depth. We calculated carrying capacity based on modern estimates of metabolic demand, prey availability, and feeding duration; we also constrained our estimates to reflect current population size and account for glaciated and non-glaciated areas in the North Pacific. Our results show that key feeding areas eliminated by sea-level lowstands were not replaced by commensurate areas. Our reconstructions show that such reductions affected carrying capacity, and harmonic means of these fluctuations do not differ dramatically from genetic estimates of carrying capacity.Assuming current carrying capacity estimates, Pleistocene glacial maxima may have created multiple, weak genetic bottlenecks, although the current temporal resolution of genetic datasets does not test for such signals. Our results do not, however, falsify molecular estimates of pre-whaling population size because those abundances would have been sufficient to survive the loss of major benthic feeding areas (i.e., the majority of the Bering Shelf) during glacial maxima. We propose that gray whales survived the disappearance of their primary feeding ground by employing generalist filter-feeding modes, similar to the resident gray whales found between northern Washington State and Vancouver Island
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